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8964d6ec-35b7-4e4f-98ac-b6d7ec8535fb | 8964d6ec-35b7-4e4f-98ac-b6d7ec8535fb | 8964d6ec-35b7-4e4f-98ac-b6d7ec8535fb | human | null | null | none | abstracts | Star Formation in the Bok Globule CB54 | null | We present mid-infrared (10.4 \micron, 11.7 \micron, and 18.3 \micron) imaging intended to locate and characterize the suspected protostellar components within the Bok globule CB54. We detect and confirm the protostellar status for the near-infrared source CB54YC1-II. The mid-infrared luminosity for CB54YC1-II was found to be $L_{midir} \approx 8 L_\sun$, and we estimate a central source mass of $M_* \approx 0.8 M_\sun$ (for a mass accretion rate of ${\dot M}=10^{-6} M_\sun yr^{-1}$). CB54 harbors another near-infrared source (CB54YC1-I), which was not detected by our observations. The non-detection is consistent with CB54YC1-I being a highly extinguished embedded young A or B star or a background G or F giant. An alternative explanation for CB54YC1-I is that the source is an embedded protostar viewed at an extremely high inclination angle, and the near-infrared detections are not of the central protostar, but of light scattered by the accretion disk into our line of sight. In additi |
fc039b38-9eb6-488a-bfd4-f51590c5572d | fc039b38-9eb6-488a-bfd4-f51590c5572d | fc039b38-9eb6-488a-bfd4-f51590c5572d | human | null | null | none | abstracts | Geometrically Engineering the Standard Model: Locally Unfolding Three
Families out of E8 | null | This paper extends and builds upon the results of an earlier paper, in which we described how to use the tools of geometrical engineering to deform geometrically-engineered grand unified models into ones with lower symmetry. This top-down unfolding has the advantage that the relative positions of singularities giving rise to the many `low energy' matter fields are related by only a few parameters which deform the geometry of the unified model. And because the relative positions of singularities are necessary to compute the superpotential, for example, this is a framework in which the arbitrariness of geometrically engineered models can be greatly reduced. In our earlier paper, this picture was made concrete for the case of deforming the representations of an SU(5) model into their Standard Model content. In this paper we continue that discussion to show how a geometrically engineered 16 of SO(10) can be unfolded into the Standard Model, and how the three families of the Standard Mo |
51acacb4-512e-4d76-aedd-5025af29e394 | 51acacb4-512e-4d76-aedd-5025af29e394 | 51acacb4-512e-4d76-aedd-5025af29e394 | human | null | null | none | abstracts | Dramatic Variability of X-ray Absorption Lines in the Black Hole
Candidate Cygnus X-1 | null | We report results from a 30 ks observation of Cygnus X-1 with the High Energy Transmission Grating Spectrometer (HETGS) on board the {\em Chandra X-ray Observatory}. Numerous absorption lines were detected in the HETGS spectrum. The lines are associated with highly ionized Ne, Na, Mg, Al, Si, S, and Fe, some of which have been seen in earlier HETGS observations. Surprisingly, however, we discovered dramatic variability of the lines over the duration of the present observation. For instance, the flux of the Ne X line at 12.14 \AA\ was about $5 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$ in the early part of the observation but became subsequently undetectable, with a 99% upper limit of $0.06 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$ on the flux of the line. This implies that the line weakened by nearly two orders of magnitude on a timescale of hours. The overall X-ray flux of the source did also vary during the observation but only by 20--30%. For Cyg X-1, the absorption lines are gen |
7f9389fc-5240-4ddf-b657-8f62bc1ddd70 | 7f9389fc-5240-4ddf-b657-8f62bc1ddd70 | 7f9389fc-5240-4ddf-b657-8f62bc1ddd70 | human | null | null | none | abstracts | An Extrasolar Planet Census with a Space-based Microlensing Survey | null | A space-based gravitational microlensing exoplanet survey will provide a statistical census of exoplanets with masses down to 0.1 Earth-masses and orbital separations ranging from 0.5AU to infinity. This includes analogs to all the Solar System's planets except for Mercury, as well as most types of planets predicted by planet formation theories. Such a survey will provide results on the frequency of planets around all types of stars except those with short lifetimes. Close-in planets with separations < 0.5 AU are invisible to a space-based microlensing survey, but these can be found by Kepler. Other methods, including ground-based microlensing, cannot approach the comprehensive statistics on the mass and semi-major axis distribution of extrasolar planets that a space-based microlensing survey will provide. The terrestrial planet sensitivity of a ground-based microlensing survey is limited to the vicinity of the Einstein radius at 2-3 AU, and space-based imaging is needed to identify |
ad167abf-46b8-4f74-bc94-8be4f97b9f36 | ad167abf-46b8-4f74-bc94-8be4f97b9f36 | ad167abf-46b8-4f74-bc94-8be4f97b9f36 | human | null | null | none | abstracts | USco1606-1935: An Unusually Wide Low-Mass Triple System? | null | We present photometric, astrometric, and spectroscopic observations of USco160611.9-193532 AB, a candidate ultrawide (~1600 AU), low-mass (M_tot~0.4 M_sun) multiple system in the nearby OB association Upper Scorpius. We conclude that both components are young, comoving members of the association; we also present high-resolution observations which show that the primary is itself a close binary system. If the Aab and B components are gravitationally bound, the system would fall into the small class of young multiple systems which have unusually wide separations as compared to field systems of similar mass. However, we demonstrate that physical association can not be assumed purely on probabilistic grounds for any individual candidate system in this separation range. Analysis of the association's two-point correlation function shows that there is a significant probability (25%) that at least one pair of low-mass association members will be separated in projection by <15", so analysis of |
256b1459-456a-44e2-b6dc-ff36f5d1fb1a | 256b1459-456a-44e2-b6dc-ff36f5d1fb1a | 256b1459-456a-44e2-b6dc-ff36f5d1fb1a | human | null | null | none | abstracts | Rotation Measures of Extragalactic Sources Behind the Southern Galactic
Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky
Way | null | We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253o < l < 356o, |b| < 1.5o), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requries the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius- Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms. In the best-fitting model, the magnetic field in the fourth Galactic quadrant is directed clockwise in the Sagittarius-Carina spir |
cb7fd534-8a53-4113-af55-5a19e6b5c839 | cb7fd534-8a53-4113-af55-5a19e6b5c839 | cb7fd534-8a53-4113-af55-5a19e6b5c839 | human | null | null | none | abstracts | Entanglement increase from local interactions with
not-completely-positive maps | null | Simple examples are constructed that show the entanglement of two qubits being both increased and decreased by interactions on just one of them. One of the two qubits interacts with a third qubit, a control, that is never entangled or correlated with either of the two entangled qubits and is never entangled, but becomes correlated, with the system of those two qubits. The two entangled qubits do not interact, but their state can change from maximally entangled to separable or from separable to maximally entangled. Similar changes for the two qubits are made with a swap operation between one of the qubits and a control; then there are compensating changes of entanglement that involve the control. When the entanglement increases, the map that describes the change of the state of the two entangled qubits is not completely positive. Combination of two independent interactions that individually give exponential decay of the entanglement can cause the entanglement to not decay exponentiall |
8e94e898-bade-412d-8cd4-e6d41cd2b8b0 | 8e94e898-bade-412d-8cd4-e6d41cd2b8b0 | 8e94e898-bade-412d-8cd4-e6d41cd2b8b0 | human | null | null | none | abstracts | Mass and Temperature of the TWA 7 Debris Disk | null | We present photometric detections of dust emission at 850 and 450 micron around the pre-main sequence M1 dwarf TWA 7 using the SCUBA camera on the James Clerk Maxwell Telescope. These data confirm the presence of a cold dust disk around TWA 7, a member of the TW Hydrae Association. Based on the 850 micron flux, we estimate the mass of the disk to be 18 lunar masses (0.2 Earth masses) assuming a mass opacity of 1.7 cm^2/g with a temperature of 45 K. This makes the TWA 7 disk (d=55 pc) an order of magnitude more massive than the disk reported around AU Microscopii (GL 803), the closest (9.9 pc) debris disk detected around an M dwarf. This is consistent with TWA 7 being slightly younger than AU Mic. We find that the mid-IR and submillimeter data require the disk to be comprised of dust at a range of temperatures. A model in which the dust is at a single radius from the star, with a range of temperatures according to grain size, is as effective at fitting the emission spectrum as a model |
b6161eff-ae90-49b8-ac79-7cf52a1d1c43 | b6161eff-ae90-49b8-ac79-7cf52a1d1c43 | b6161eff-ae90-49b8-ac79-7cf52a1d1c43 | human | null | null | none | abstracts | Modeling Accretion Disk X-ray Continuum of Black Hole Candidates | null | We critically examine issues associated with determining the fundamental properties of the black hole and the surrounding accretion disk in an X-ray binary based on modeling the disk X-ray continuum of the source. We base our work mainly on two XMM-Newton observations of GX 339-4, because they provided high-quality data at low energies (below 1 keV) which are critical for reliably modeling the spectrum of the accretion disk. A key issue examined is the determination of the so-called "color correction factor", which is often empirically introduced to account for the deviation of the local disk spectrum from a blackbody (due to electron scattering). This factor cannot be pre-determined theoretically because it may vary with, e.g., mass accretion rate, among a number of important factors. We follow up on an earlier suggestion to estimate the color correction observationally by modeling the disk spectrum with saturated Compton scattering. We show that the spectra can be fitted well and t |
0157689b-1e8a-45f8-babd-9a10c01c3955 | 0157689b-1e8a-45f8-babd-9a10c01c3955 | 0157689b-1e8a-45f8-babd-9a10c01c3955 | human | null | null | none | abstracts | Inapproximability of Maximum Weighted Edge Biclique and Its Applications | null | Given a bipartite graph $G = (V_1,V_2,E)$ where edges take on {\it both} positive and negative weights from set $\mathcal{S}$, the {\it maximum weighted edge biclique} problem, or $\mathcal{S}$-MWEB for short, asks to find a bipartite subgraph whose sum of edge weights is maximized. This problem has various applications in bioinformatics, machine learning and databases and its (in)approximability remains open. In this paper, we show that for a wide range of choices of $\mathcal{S}$, specifically when $| \frac{\min\mathcal{S}} {\max \mathcal{S}} | \in \Omega(\eta^{\delta-1/2}) \cap O(\eta^{1/2-\delta})$ (where $\eta = \max\{|V_1|, |V_2|\}$, and $\delta \in (0,1/2]$), no polynomial time algorithm can approximate $\mathcal{S}$-MWEB within a factor of $n^{\epsilon}$ for some $\epsilon > 0$ unless $\mathsf{RP = NP}$. This hardness result gives justification of the heuristic approaches adopted for various applied problems in the aforementioned areas, and indicates that good approximation a |
19f5462e-0d1e-44a9-b465-08e72546c2b5 | 19f5462e-0d1e-44a9-b465-08e72546c2b5 | 19f5462e-0d1e-44a9-b465-08e72546c2b5 | human | null | null | none | abstracts | Possible non-thermal nature of the soft-excess emission in the cluster
of galaxies Sersic 159-03 | null | We present an analysis of new Suzaku data and archival data from XMM-Newton of the cluster of galaxies Sersic 159-03, which has a strong soft X-ray excess emission component. The Suzaku observation confirms the presence of the soft excess emission, but it does not confirm the presence of redshifted OVII lines in the cluster. Radial profiles and 2D maps derived from XMM-Newton observations show that the soft excess emission has a strong peak at the position of the central cD galaxy and the maps do not show any significant azimuthal variations. Although the soft excess emission can be fitted equally well with both thermal and non-thermal models, its spatial distribution is neither consistent with the models of intercluster warm-hot filaments, nor with models of clumpy warm intracluster gas associated with infalling groups. Using the data obtained by the XMM-Newton Reflection Grating Spectrometers we do not confirm the presence of the warm gas in the cluster centre with the expected pro |
463cf7d9-45c9-4a32-819c-676dbfa2ef91 | 463cf7d9-45c9-4a32-819c-676dbfa2ef91 | 463cf7d9-45c9-4a32-819c-676dbfa2ef91 | human | null | null | none | abstracts | The Transition from the First Stars to the Second Stars in the Early
Universe | null | We observe a sharp transition from a singular, high-mass mode of star formation, to a low-mass dominated mode, in numerical simulations, at a metallicity of 10^-3 Zsolar. We incorporate a new method for including the radiative cooling from metals into adaptive mesh-refinement hydrodynamic simulations. Our results illustrate how metals, produced by the first stars, led to a transition from the high-mass star formation mode of Pop III stars, to the low-mass mode that dominates today. We ran hydrodynamic simulations with cosmological initial conditions in the standard LambdaCDM model, with metallicities, from zero to 10^-2 Zsolar, beginnning at redshift, z = 99. The simulations were run until a dense core forms at the center of a 5 x 10^5 Msolar dark matter halo, at z ~ 18. Analysis of the central 1 Msolar core reveals that the two simulations with the lowest metallicities, Z = 0 and 10^-4 Zsolar, contain one clump with 99% of the mass, while the two with metallicities, Z = 10^-3 and 10 |
ddf750f9-7925-42e0-bc84-f38d6e825b0b | ddf750f9-7925-42e0-bc84-f38d6e825b0b | ddf750f9-7925-42e0-bc84-f38d6e825b0b | human | null | null | none | abstracts | Kinematic Decoupling of Globular Clusters with Extended
Horizontal-Branch | null | About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium enhanced second generation subpopulations, which has raised a possibility that these peculiar GCs might have a unique origin. Here we show that these GCs with extended HB are clearly distinct from other normal GCs in kinematics and mass. The GCs with extended HB are more massive than normal GCs, and are dominated by random motion with no correlation between kinematics and metallicity. Surprisingly, however, when they are excluded, most normal GCs in the inner halo show clear signs of dissipational collapse that apparently led to the formation of the disk. Normal GCs in the outer halo share their kinematic properties with the extended HB GCs, which is consistent with the accretion origin. Our result further suggests heterogeneous origins of GCs, and we anticipate this to be |
68e5ad0d-c00f-4804-ade9-a2677ec6a9ed | 68e5ad0d-c00f-4804-ade9-a2677ec6a9ed | 68e5ad0d-c00f-4804-ade9-a2677ec6a9ed | human | null | null | none | abstracts | Refuting the Pseudo Attack on the REESSE1+ Cryptosystem | null | We illustrate through example 1 and 2 that the condition at theorem 1 in [8] dissatisfies necessity, and the converse proposition of fact 1.1 in [8] does not hold, namely the condition Z/M - L/Ak < 1/(2 Ak^2) is not sufficient for f(i) + f(j) = f(k). Illuminate through an analysis and ex.3 that there is a logic error during deduction of fact 1.2, which causes each of fact 1.2, 1.3, 4 to be invalid. Demonstrate through ex.4 and 5 that each or the combination of qu+1 > qu * D at fact 4 and table 1 at fact 2.2 is not sufficient for f(i) + f(j) = f(k), property 1, 2, 3, 4, 5 each are invalid, and alg.1 based on fact 4 and alg.2 based on table 1 are disordered and wrong logically. Further, manifest through a repeated experiment and ex.5 that the data at table 2 is falsified, and the example in [8] is woven elaborately. We explain why Cx = Ax * W^f(x) (% M) is changed to Cx = (Ax * W^f(x))^d (% M) in REESSE1+ v2.1. To the signature fraud, we point out that [8] misunderstands the existence |
c93a4fe4-5c88-4344-b89f-9bc10caeafb9 | c93a4fe4-5c88-4344-b89f-9bc10caeafb9 | c93a4fe4-5c88-4344-b89f-9bc10caeafb9 | human | null | null | none | abstracts | Phase structure of a surface model on dynamically triangulated spheres
with elastic skeletons | null | We find three distinct phases; a tubular phase, a planar phase, and the spherical phase, in a triangulated fluid surface model. It is also found that these phases are separated by discontinuous transitions. The fluid surface model is investigated within the framework of the conventional curvature model by using the canonical Monte Carlo simulations with dynamical triangulations. The mechanical strength of the surface is given only by skeletons, and no two-dimensional bending energy is assumed in the Hamiltonian. The skeletons are composed of elastic linear-chains and rigid junctions and form a compartmentalized structure on the surface, and for this reason the vertices of triangles can diffuse freely only inside the compartments. As a consequence, an inhomogeneous structure is introduced in the model; the surface strength inside the compartments is different from the surface strength on the compartments. However, the rotational symmetry is not influenced by the elastic skeletons; the |
888dbdb1-3163-4b1b-b2af-f47721dd2a56 | 888dbdb1-3163-4b1b-b2af-f47721dd2a56 | 888dbdb1-3163-4b1b-b2af-f47721dd2a56 | human | null | null | none | abstracts | Vortex Dynamics at the Initial Stage of Resistive Transition in
Superconductors with Fractal Cluster Structure | null | The effect of fractal normal-phase clusters on vortex dynamics in a percolative superconductor is considered. The superconductor contains percolative superconducting cluster carrying a transport current and clusters of a normal phase, acting as pinning centers. A prototype of such a structure is YBCO film, containing clusters of columnar defects, as well as the BSCCO/Ag sheathed tape, which is of practical interest for wire fabrication. Transition of the superconductor into a resistive state corresponds to the percolation transition from a pinned vortex state to a resistive state when the vortices are free to move. The dependencies of the free vortex density on the fractal dimension of the cluster boundary as well as the resistance on the transport current are obtained. It is revealed that a mixed state of the vortex glass type is realized in the superconducting system involved. The current-voltage characteristics of superconductors containing fractal clusters are obtained and their |
26886937-cef0-48d0-9970-b1c1eab6b806 | 26886937-cef0-48d0-9970-b1c1eab6b806 | 26886937-cef0-48d0-9970-b1c1eab6b806 | human | null | null | none | abstracts | Fusion process studied with preequilibrium giant dipole resonance in
time dependent Hartree-Fock theory | null | The equilibration of macroscopic degrees of freedom during the fusion of heavy nuclei, like the charge and the shape, are studied in the Time-Dependent Hartree-Fock theory. The pre-equilibrium Giant Dipole Resonance (GDR) is used to probe the fusion path. It is shown that such isovector collective state is excited in N/Z asymmetric fusion and to a less extent in mass asymmetric systems. The characteristics of this GDR are governed by the structure of the fused system in its preequilibrium phase, like its deformation, rotation and vibration. In particular, we show that a lowering of the pre-equilibrium GDR energy is expected as compared to the statistical one. Revisiting experimental data, we extract an evidence of this lowering for the first time. We also quantify the fusion-evaporation enhancement due to gamma-ray emission from the pre-equilibrium GDR. This cooling mechanism along the fusion path may be suitable to synthesize in the future super heavy elements using radioactive beam |
0e13c7a5-b69b-427d-90dc-3d9d23e6787e | 0e13c7a5-b69b-427d-90dc-3d9d23e6787e | 0e13c7a5-b69b-427d-90dc-3d9d23e6787e | human | null | null | none | abstracts | Optimal Routing for Decode-and-Forward based Cooperation in Wireless
Networks | null | We investigate cooperative wireless relay networks in which the nodes can help each other in data transmission. We study different coding strategies in the single-source single-destination network with many relay nodes. Given the myriad of ways in which nodes can cooperate, there is a natural routing problem, i.e., determining an ordered set of nodes to relay the data from the source to the destination. We find that for a given route, the decode-and-forward strategy, which is an information theoretic cooperative coding strategy, achieves rates significantly higher than that achievable by the usual multi-hop coding strategy, which is a point-to-point non-cooperative coding strategy. We construct an algorithm to find an optimal route (in terms of rate maximizing) for the decode-and-forward strategy. Since the algorithm runs in factorial time in the worst case, we propose a heuristic algorithm that runs in polynomial time. The heuristic algorithm outputs an optimal route when the nodes |
c282539b-03c5-47d4-936f-d64eb388b4b2 | c282539b-03c5-47d4-936f-d64eb388b4b2 | c282539b-03c5-47d4-936f-d64eb388b4b2 | human | null | null | none | abstracts | Stable oscillations of a predator-prey probabilistic cellular automaton:
a mean-field approach | null | We analyze a probabilistic cellular automaton describing the dynamics of coexistence of a predator-prey system. The individuals of each species are localized over the sites of a lattice and the local stochastic updating rules are inspired on the processes of the Lotka-Volterra model. Two levels of mean-field approximations are set up. The simple approximation is equivalent to an extended patch model, a simple metapopulation model with patches colonized by prey, patches colonized by predators and empty patches. This approximation is capable of describing the limited available space for species occupancy. The pair approximation is moreover able to describe two types of coexistence of prey and predators: one where population densities are constant in time and another displaying self-sustained time-oscillations of the population densities. The oscillations are associated with limit cycles and arise through a Hopf bifurcation. They are stable against changes in the initial conditions and, |
97851709-b6a7-4897-a7d4-4459c9c947d7 | 97851709-b6a7-4897-a7d4-4459c9c947d7 | 97851709-b6a7-4897-a7d4-4459c9c947d7 | human | null | null | none | abstracts | SDSS J233325.92+152222.1 and the evolution of intermediate polars | null | Intermediate polars (IPs) are cataclysmic variables which contain magnetic white dwarfs with a rotational period shorter than the binary orbital period. Evolutionary theory predicts that IPs with long orbital periods evolve through the 2-3 hour period gap, but it is very uncertain what the properties of the resulting objects are. Whilst a relatively large number of long-period IPs are known, very few of these have short orbital periods. We present phase-resolved spectroscopy and photometry of SDSS J233325.92+152222.1 and classify it as the IP with the shortest known orbital period (83.12 +/- 0.09 min), which contains a white dwarf with a relatively long spin period (41.66 +/- 0.13 min). We estimate the white dwarf's magnetic moment to be mu(WD) \approx 2 x 10^33 G cm^3, which is not only similar to three of the other four confirmed short-period IPs but also to those of many of the long-period IPs. We suggest that long-period IPs conserve their magnetic moment as they evolve towards s |
6e9f606b-d996-4c23-9aa3-b09d9a2569d2 | 6e9f606b-d996-4c23-9aa3-b09d9a2569d2 | 6e9f606b-d996-4c23-9aa3-b09d9a2569d2 | human | null | null | none | abstracts | Complexity Considerations, cSAT Lower Bound | null | This article discusses completeness of Boolean Algebra as First Order Theory in Goedel's meaning. If Theory is complete then any possible transformation is equivalent to some transformation using axioms, predicates etc. defined for this theory. If formula is to be proved (or disproved) then it has to be reduced to axioms. If every transformation is deducible then also optimal transformation is deducible. If every transformation is exponential then optimal one is too, what allows to define lower bound for discussed problem to be exponential (outside P). Then we show algorithm for NDTM solving the same problem in O(n^c) (so problem is in NP), what proves that P \neq NP. Article proves also that result of relativisation of P=NP question and oracle shown by Baker-Gill-Solovay distinguish between deterministic and non-deterministic calculation models. If there exists oracle A for which P^A=NP^A then A consists of infinite number of algorithms, DTMs, axioms and predicates, or like NDTM i |
a93f01d3-8ca1-4eaa-abfc-3e240e2d3cb8 | a93f01d3-8ca1-4eaa-abfc-3e240e2d3cb8 | a93f01d3-8ca1-4eaa-abfc-3e240e2d3cb8 | human | null | null | none | abstracts | Fractionally charged excitations on frustrated lattices | null | Systems of strongly correlated fermions on certain geometrically frustrated lattices at particular filling factors support excitations with fractional charges $\pm e/2$. We calculate quantum mechanical ground states, low--lying excitations and spectral functions of finite lattices by means of numerical diagonalization. The ground state of the most thoroughfully studied case, the criss-crossed checkerboard lattice, is degenerate and shows long--range order. Static fractional charges are confined by a weak linear force, most probably leading to bound states of large spatial extent. Consequently, the quasi-particle weight is reduced, which reflects the internal dynamics of the fractionally charged excitations. By using an additional parameter, we fine--tune the system to a special point at which fractional charges are manifestly deconfined--the so--called Rokhsar--Kivelson point. For a deeper understanding of the low--energy physics of these models and for numerical advantages, several |
1fd214d2-e35a-4bd8-83f3-425f30944e50 | 1fd214d2-e35a-4bd8-83f3-425f30944e50 | 1fd214d2-e35a-4bd8-83f3-425f30944e50 | human | null | null | none | abstracts | Many-to-One Throughput Capacity of IEEE 802.11 Multi-hop Wireless
Networks | null | This paper investigates the many-to-one throughput capacity (and by symmetry, one-to-many throughput capacity) of IEEE 802.11 multi-hop networks. It has generally been assumed in prior studies that the many-to-one throughput capacity is upper-bounded by the link capacity L. Throughput capacity L is not achievable under 802.11. This paper introduces the notion of "canonical networks", which is a class of regularly-structured networks whose capacities can be analyzed more easily than unstructured networks. We show that the throughput capacity of canonical networks under 802.11 has an analytical upper bound of 3L/4 when the source nodes are two or more hops away from the sink; and simulated throughputs of 0.690L (0.740L) when the source nodes are many hops away. We conjecture that 3L/4 is also the upper bound for general networks. When all links have equal length, 2L/3 can be shown to be the upper bound for general networks. Our simulations show that 802.11 networks with random topologi |
8c43b50d-5a16-4f17-88ea-0056e54bc14a | 8c43b50d-5a16-4f17-88ea-0056e54bc14a | 8c43b50d-5a16-4f17-88ea-0056e54bc14a | human | null | null | none | abstracts | Non-resonant and Resonant X-ray Scattering Studies on Multiferroic
TbMn2O5 | null | Comprehensive x-ray scattering studies, including resonant scattering at Mn L-edge, Tb L- and M-edges, were performed on single crystals of TbMn2O5. X-ray intensities were observed at a forbidden Bragg position in the ferroelectric phases, in addition to the lattice and the magnetic modulation peaks. Temperature dependences of their intensities and the relation between the modulation wave vectors provide direct evidences of exchange striction induced ferroelectricity. Resonant x-ray scattering results demonstrate the presence of multiple magnetic orders by exhibiting their different temperature dependences. The commensurate-to-incommensurate phase transition around 24 K is attributed to discommensuration through phase slipping of the magnetic orders in spin frustrated geometries. We proposed that the low temperature incommensurate phase consists of the commensurate magnetic domains separated by anti-phase domain walls which reduce spontaneous polarizations abruptly at the transition. |
1dd6bc1e-fd15-479c-a865-774953e6c660 | 1dd6bc1e-fd15-479c-a865-774953e6c660 | 1dd6bc1e-fd15-479c-a865-774953e6c660 | human | null | null | none | abstracts | Self-diffusion and Interdiffusion in Al80Ni20 Melts: Simulation and
Experiment | null | A combination of experimental techniques and molecular dynamics (MD) computer simulation is used to investigate the diffusion dynamics in Al80Ni20 melts. Experimentally, the self-diffusion coefficient of Ni is measured by the long-capillary (LC) method and by quasielastic neutron scattering. The LC method yields also the interdiffusion coefficient. Whereas the experiments were done in the normal liquid state, the simulations provided the determination of both self-diffusion and interdiffusion constants in the undercooled regime as well. The simulation results show good agreement with the experimental data. In the temperature range 3000 K >= T >= 715 K, the interdiffusion coefficient is larger than the self-diffusion constants. Furthermore the simulation shows that this difference becomes larger in the undercooled regime. This result can be refered to a relatively strong temperature dependence of the thermodynamic factor \Phi, which describes the thermodynamic driving force for interd |
d233b5c7-6fb9-4397-95f8-43c55dae5272 | d233b5c7-6fb9-4397-95f8-43c55dae5272 | d233b5c7-6fb9-4397-95f8-43c55dae5272 | human | null | null | none | abstracts | The Formation of Globular Cluster Systems in Massive Elliptical
Galaxies: Globular Cluster Multimodality from Radial Variation of Stellar
Populations | null | The most massive elliptical galaxies show a prominent multi-modality in their globular cluster system color distributions. Understanding the mechanisms which lead to multiple globular cluster sub-populations is essential for a complete picture of massive galaxy formation. By assuming that globular cluster formation traces the total star formation and taking into account the radial variations in the composite stellar populations predicted by the Pipino & Matteucci (2004) multi-zone photo-chemical evolution code, we compute the distribution of globular cluster properties as a function of galactocentric radius. We compare our results to the spectroscopic measurements of globular clusters in nearby early-type galaxies by Puzia et al. (2006) and show that the observed multi-modality in globular cluster systems of massive ellipticals can be, at least partly, ascribed to the radial variation in the mix of stellar populations. Our model predicts the presence of a super-metal-rich population |
95cc48a0-d7b8-4fe8-a641-bc1385ca46e0 | 95cc48a0-d7b8-4fe8-a641-bc1385ca46e0 | 95cc48a0-d7b8-4fe8-a641-bc1385ca46e0 | human | null | null | none | abstracts | Spontaneous Lorentz Violation: Non-Abelian Gauge Fields as
Pseudo-Goldstone Vector Bosons | null | We argue that non-Abelian gauge fields can be treated as the pseudo-Goldstone vector bosons caused by spontaneous Lorentz invariance violation (SLIV). To this end, the SLIV which evolves in a general Yang-Mills type theory with the nonlinear vector field constraint $Tr(% \boldsymbol{A}_{\mu }\boldsymbol{A}^{\mu})=\pm M^{2}$ ($M$ is a proposed SLIV scale) imposed is considered in detail. With an internal symmetry group $G$ having $D$ generators not only the pure Lorentz symmetry SO(1,3), but the larger accidental symmetry $SO(D,3D)$ of the SLIV constraint in itself appears to be spontaneously broken as well. As a result, while the pure Lorentz violation still generates only one genuine Goldstone vector boson, the accompanying pseudo-Goldstone vector bosons related to the $SO(D,3D)$ breaking also come into play in the final arrangement of the entire Goldstone vector field multiplet. Remarkably, they remain strictly massless, being protected by gauge invariance of the Yang-Mills theory |
aa5faca1-1bfa-46bc-ba4e-bb50ff06af70 | aa5faca1-1bfa-46bc-ba4e-bb50ff06af70 | aa5faca1-1bfa-46bc-ba4e-bb50ff06af70 | human | null | null | none | abstracts | In-medium effects on particle production in heavy ion collisions | null | The effect of possible in-medium modifications of nucleon-nucleon ($NN$) cross sections on particle production is investigated in heavy ion collisions ($HIC$) at intermediate energies. In particular, using a fully covariant relativistic transport approach, we see that the density dependence of the {\it inelastic} cross sections appreciably affects the pion and kaon yields and their rapidity distributions. However, the $(\pi^{-}/\pi^{+})$- and $(K^{0}/K^{+})$-ratios depend only moderately on the in-medium behavior of the inelastic cross sections. This is particularly true for kaon yield ratios, since kaons are more uniformly produced in high density regions. Kaon potentials are also suitably evaluated in two schemes, a chiral perturbative approach and an effective meson-quark coupling method, with consistent results showing a similar repulsive contribution for $K^{+}$ and $K^{0}$. As a consequence we expect rather reduced effects on the yield ratios. We conclude that particle ratios a |
9769aef3-6c6e-44da-bac4-9f5f5ea4a4ee | 9769aef3-6c6e-44da-bac4-9f5f5ea4a4ee | 9769aef3-6c6e-44da-bac4-9f5f5ea4a4ee | human | null | null | none | abstracts | Effective conservation of energy and momentum algorithm using switching
potentials suitable for molecular dynamics simulation of thermodynamical
systems | null | During a crossover via a switching mechanism from one 2-body potential to another as might be applied in modeling (chemical) reactions in the vicinity of bond formation, energy violations would occur due to finite step size which determines the trajectory of the particles relative to the potential interactions of the unbonded state by numerical (e.g. Verlet) integration. This problem is overcome by an algorithm which preserves the coordinates of the system for each move, but corrects for energy discrepancies by ensuring both energy and momentum conservation in the dynamics. The algorithm is tested for a hysteresis loop reaction model with an without the implementation of the algorithm. The tests involve checking the rate of energy flow out of the MD simulation box; in the equilibrium state, no net rate of flows within experimental error should be observed. The temperature and pressure of the box should also be invariant within the range of fluctuation of these quantities. It is demon |
0d28cf03-b3fb-4422-8a17-5336b33558c8 | 0d28cf03-b3fb-4422-8a17-5336b33558c8 | 0d28cf03-b3fb-4422-8a17-5336b33558c8 | human | null | null | none | abstracts | On the potential of transit surveys in star clusters: Impact of
correlated noise and radial velocity follow-up | null | We present an extension of the formalism recently proposed by Pepper & Gaudi to evaluate the yield of transit surveys in homogeneous stellar systems, incorporating the impact of correlated noise on transit time-scales on the detectability of transits, and simultaneously incorporating the magnitude limits imposed by the need for radial velocity follow-up of transit candidates. New expressions are derived for the different contributions to the noise budget on transit time-scales and the least-squares detection statistic for box-shaped transits, and their behaviour as a function of stellar mass is re-examined. Correlated noise that is constant with apparent stellar magnitude implies a steep decrease in detection probability at the high mass end which, when considered jointly with the radial velocity requirements, can severely limit the potential of otherwise promising surveys in star clusters. However, we find that small-aperture, wide field surveys may detect hot Neptunes whose radial |
1e1e54a9-2250-4ba4-acea-cf0162353e4d | 1e1e54a9-2250-4ba4-acea-cf0162353e4d | 1e1e54a9-2250-4ba4-acea-cf0162353e4d | human | null | null | none | abstracts | 3D photospheric velocity field of a Supergranular cell | null | We investigate the plasma flow properties inside a Supergranular (SG) cell, in particular its interaction with small scale magnetic field structures. The SG cell has been identified using the magnetic network (CaII wing brightness) as proxy, applying the Two-Level Structure Tracking (TST) to high spatial, spectral and temporal resolution observations obtained by IBIS. The full 3D velocity vector field for the SG has been reconstructed at two different photospheric heights. In order to strengthen our findings, we also computed the mean radial flow of the SG by means of cork tracing. We also studied the behaviour of the horizontal and Line of Sight plasma flow cospatial with cluster of bright CaII structures of magnetic origin to better understand the interaction between photospheric convection and small scale magnetic features. The SG cell we investigated seems to be organized with an almost radial flow from its centre to the border. The large scale divergence structure is probably cr |
1ced5f1a-3cb2-4187-af0f-b44899715ac3 | 1ced5f1a-3cb2-4187-af0f-b44899715ac3 | 1ced5f1a-3cb2-4187-af0f-b44899715ac3 | human | null | null | none | abstracts | Substructures in WINGS clusters | null | We search for and characterize substructures in the projected distribution of galaxies observed in the wide field CCD images of the 77 nearby clusters of the WIde-field Nearby Galaxy-cluster Survey (WINGS). This sample is complete in X-ray flux in the redshift range 0.04<z<0.07. We search for substructures in WINGS clusters with DEDICA, an adaptive-kernel procedure. We test the procedure on Monte-Carlo simulations of the observed frames and determine the reliability for the detected structures. DEDICA identifies at least one reliable structure in the field of 55 clusters. 40 of these clusters have a total of 69 substructures at the same redshift of the cluster (redshift estimates of substructures are from color-magnitude diagrams). The fraction of clusters with subclusters (73%) is higher than in most studies. The presence of subclusters affects the relative luminosities of the brightest cluster galaxies (BCGs). Down to L ~ 10^11.2 L_Sun, our observed differential distribution of sub |
9cdaf251-3e54-4230-b4f7-fcfec2c01eee | 9cdaf251-3e54-4230-b4f7-fcfec2c01eee | 9cdaf251-3e54-4230-b4f7-fcfec2c01eee | human | null | null | none | abstracts | Continuous interfaces with disorder: Even strong pinning is too weak in
2 dimensions | null | We consider statistical mechanics models of continuous height effective interfaces in the presence of a delta-pinning at height zero. There is a detailed mathematical understanding of the depinning transition in 2 dimensions without disorder. Then the variance of the interface height w.r.t. the Gibbs measure stays bounded uniformly in the volume for any positive pinning force and diverges like the logarithm of the pinning force when it tends to zero. How does the presence of a quenched disorder term in the Hamiltonian modify this transition? We show that an arbitarily weak random field term is enough to beat an arbitrarily strong delta-pinning in 2 dimensions and will cause delocalization. The proof is based on a rigorous lower bound for the overlap between local magnetizations and random fields in finite volume. In 2 dimensions it implies growth faster than the volume which is a contradiction to localization. We also derive a simple complementary inequality which shows that in hig |
d6c48aca-f9f4-4111-8ec4-9c50f2621384 | d6c48aca-f9f4-4111-8ec4-9c50f2621384 | d6c48aca-f9f4-4111-8ec4-9c50f2621384 | human | null | null | none | abstracts | Dust Formation and Survival in Supernova Ejecta | null | The presence of dust at high redshift requires efficient condensation of grains in SN ejecta, in accordance with current theoretical models. Yet, observations of the few well studied SNe and SN remnants imply condensation efficiencies which are about two orders of magnitude smaller. Motivated by this tension, we have (i) revisited the model of Todini & Ferrara (2001) for dust formation in the ejecta of core collapse SNe and (ii) followed, for the first time, the evolution of newly condensed grains from the time of formation to their survival - through the passage of the reverse shock - in the SN remnant. We find that 0.1 - 0.6 M_sun of dust form in the ejecta of 12 - 40 M_sun stellar progenitors. Depending on the density of the surrounding ISM, between 2-20% of the initial dust mass survives the passage of the reverse shock, on time-scales of about 4-8 x 10^4 yr from the stellar explosion. Sputtering by the hot gas induces a shift of the dust size distribution towards smaller grains. |
638ebd4d-6e94-45fa-a6b3-645f880f8c15 | 638ebd4d-6e94-45fa-a6b3-645f880f8c15 | 638ebd4d-6e94-45fa-a6b3-645f880f8c15 | human | null | null | none | abstracts | Analysis of the real estate market in Las Vegas: Bubble, seasonal
patterns, and prediction of the CSW indexes | null | We analyze 27 house price indexes of Las Vegas from Jun. 1983 to Mar. 2005, corresponding to 27 different zip codes. These analyses confirm the existence of a real-estate bubble, defined as a price acceleration faster than exponential, which is found however to be confined to a rather limited time interval in the recent past from approximately 2003 to mid-2004 and has progressively transformed into a more normal growth rate comparable to pre-bubble levels in 2005. There has been no bubble till 2002 except for a medium-sized surge in 1990. In addition, we have identified a strong yearly periodicity which provides a good potential for fine-tuned prediction from month to month. A monthly monitoring using a model that we have developed could confirm, by testing the intra-year structure, if indeed the market has returned to ``normal'' or if more turbulence is expected ahead. We predict the evolution of the indexes one year ahead, which is validated with new data up to Sep. 2006. The prese |
e222b5ea-2f3f-486a-a95c-4e10915aff68 | e222b5ea-2f3f-486a-a95c-4e10915aff68 | e222b5ea-2f3f-486a-a95c-4e10915aff68 | human | null | null | none | abstracts | Local-field effects in radiatively broadened magneto-dielectric media:
negative refraction and absorption reduction | null | We give a microscopic derivation of the Clausius-Mossotti relations for a homogeneous and isotropic magneto-dielectric medium consisting of radiatively broadened atomic oscillators. To this end the diagram series of electromagnetic propagators is calculated exactly for an infinite bi-cubic lattice of dielectric and magnetic dipoles for a lattice constant small compared to the resonance wavelength $\lambda$. Modifications of transition frequencies and linewidth of the elementary oscillators are taken into account in a selfconsistent way by a proper incorporation of the singular self-interaction terms. We show that in radiatively broadened media sufficiently close to the free-space resonance the real part of the index of refraction approaches the value -2 in the limit of $\rho \lambda^3 \gg 1$, where $\rho$ is the number density of scatterers. Since at the same time the imaginary part vanishes as $1/\rho$ local field effects can have important consequences for realizing low-loss negati |
b796e0ba-3b6c-4b96-abeb-0cc4ba929f9b | b796e0ba-3b6c-4b96-abeb-0cc4ba929f9b | b796e0ba-3b6c-4b96-abeb-0cc4ba929f9b | human | null | null | none | abstracts | Investigation of Colour Reconnection in WW Events with the DELPHI
detector at LEP-2 | null | In the reaction e+e- -> WW -> (q_1 qbar_2)(q_3 qbar_4) the usual hadronization models treat the colour singlets q_1 qbar_2 and q_3 qbar_4 coming from two W bosons independently. However, since the final state partons may coexist in space and time, cross-talk between the two evolving hadronic systems may be possible during fragmentation through soft gluon exchange. This effect is known as Colour Reconnection. In this article the results of the investigation of Colour Reconnection effects in fully hadronic decays of W pairs in DELPHI at LEP are presented. Two complementary analyses were performed, studying the particle flow between jets and W mass estimators, with negligible correlation between them, and the results were combined and compared to models. In the framework of the SK-I model, the value for its kappa parameter most compatible with the data was found to be: kappa_{SK-I} = 2.2^{+2.5}_{-1.3} corresponding to the probability of reconnection P_{reco} to be in the range 0.31 < P_ |
db6ea24e-81e8-4200-82f1-f7358365c649 | db6ea24e-81e8-4200-82f1-f7358365c649 | db6ea24e-81e8-4200-82f1-f7358365c649 | human | null | null | none | abstracts | Evolutionary Neural Gas (ENG): A Model of Self Organizing Network from
Input Categorization | null | Despite their claimed biological plausibility, most self organizing networks have strict topological constraints and consequently they cannot take into account a wide range of external stimuli. Furthermore their evolution is conditioned by deterministic laws which often are not correlated with the structural parameters and the global status of the network, as it should happen in a real biological system. In nature the environmental inputs are noise affected and fuzzy. Which thing sets the problem to investigate the possibility of emergent behaviour in a not strictly constrained net and subjected to different inputs. It is here presented a new model of Evolutionary Neural Gas (ENG) with any topological constraints, trained by probabilistic laws depending on the local distortion errors and the network dimension. The network is considered as a population of nodes that coexist in an ecosystem sharing local and global resources. Those particular features allow the network to quickly adapt |
9fb590d4-194a-467c-a549-6d0e23e6d78f | 9fb590d4-194a-467c-a549-6d0e23e6d78f | 9fb590d4-194a-467c-a549-6d0e23e6d78f | human | null | null | none | abstracts | Solving The High Energy Evolution Equation Including Running Coupling
Corrections | null | We study the solution of the nonlinear BK evolution equation with the recently calculated running coupling corrections [hep-ph/0609105, hep-ph/0609090]. Performing a numerical solution we confirm the earlier result of [hep-ph/0408216] that the high energy evolution with the running coupling leads to a universal scaling behavior for the dipole scattering amplitude. The running coupling corrections calculated recently significantly change the shape of the scaling function as compared to the fixed coupling case leading to a considerable increase in the anomalous dimension and to a slow-down of the evolution with rapidity. The difference between the two recent calculations is due to an extra contribution to the evolution kernel, referred to as the subtraction term, which arises when running coupling corrections are included. These subtraction terms were neglected in both recent calculations. We evaluate numerically the subtraction terms for both calculations, and demonstrate that when th |
6ece21be-f0b6-4cbe-8c6b-6654cf0c9170 | 6ece21be-f0b6-4cbe-8c6b-6654cf0c9170 | 6ece21be-f0b6-4cbe-8c6b-6654cf0c9170 | human | null | null | none | abstracts | Millimeter imaging of HD 163296: probing the disk structure and
kinematics | null | We present new multi-wavelength millimeter interferometric observations of the Herbig Ae star HD 163296 obtained with the IRAM/PBI, SMA and VLA arrays both in continuum and in the 12CO, 13CO and C18O emission lines. Gas and dust properties have been obtained comparing the observations with self-consistent disk models for the dust and CO emission. The circumstellar disk is resolved both in the continuum and in CO. We find strong evidence that the circumstellar material is in Keplerian rotation around a central star of 2.6 Msun. The disk inclination with respect to the line of sight is 46+-4 deg with a position angle of 128+-4 deg. The slope of the dust opacity measured between 0.87 and 7 mm (beta=1) confirms the presence of mm/cm-size grains in the disk midplane. The dust continuum emission is asymmetric and confined inside a radius of 200 AU while the CO emission extends up to 540 AU. The comparison between dust and CO temperature indicates that CO is present only in the disk interio |
43d6dd09-f1a1-483d-a428-c3122cbe2e3e | 43d6dd09-f1a1-483d-a428-c3122cbe2e3e | 43d6dd09-f1a1-483d-a428-c3122cbe2e3e | human | null | null | none | abstracts | Spectropolarimetric observations of the Ca II 8498 A and 8542 A lines in
the quiet Sun | null | The Ca II infrared triplet is one of the few magnetically sensitive chromospheric lines available for ground-based observations. We present spectropolarimetric observations of the 8498 A and 8542 A lines in a quiet Sun region near a decaying active region and compare the results with a simulation of the lines in a high plasma-beta regime. Cluster analysis of Stokes V profile pairs shows that the two lines, despite arguably being formed fairly close, often do not have similar shapes. In the network, the local magnetic topology is more important in determining the shapes of the Stokes V profiles than the phase of the wave, contrary to what our simulations show. We also find that Stokes V asymmetries are very common in the network, and the histograms of the observed amplitude and area asymmetries differ significantly from the simulation. Both the network and internetwork show oscillatory behavior in the Ca II lines. It is stronger in the network, where shocking waves, similar to those i |
39a10090-9f6a-466d-9784-b862249b5a6b | 39a10090-9f6a-466d-9784-b862249b5a6b | 39a10090-9f6a-466d-9784-b862249b5a6b | human | null | null | none | abstracts | Search for Heavy Neutral MSSM Higgs Bosons with CMS: Reach and
Higgs-Mass Precision | null | The search for MSSM Higgs bosons will be an important goal at the LHC. We analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs bosons with an integrated luminosity of 30 or 60 fb^-1. This is done by combining the latest results for the CMS experimental sensitivities based on full simulation studies with state-of-the-art theoretical predictions of MSSM Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios in terms of the parameters tan_beta and the Higgs-boson mass scale, M_A. We study the dependence of the 5 sigma discovery contours in the M_A-tan_beta plane on variations of the other supersymmetric parameters. The largest effects arise from a change in the higgsino mass parameter mu, which enters both via higher-order radiative corrections and via the kinematics of Higgs decays into supersymmetric particles. While the variation of $\mu$ can shift the prospective discovery reach (and correspondingly the ``LHC wedge'' region) by abo |
edeea3b2-f80e-4d6f-bc8c-8ad1dc91258f | edeea3b2-f80e-4d6f-bc8c-8ad1dc91258f | edeea3b2-f80e-4d6f-bc8c-8ad1dc91258f | human | null | null | none | abstracts | Temporal Evolution of Step-Edge Fluctuations Under Electromigration
Conditions | null | The temporal evolution of step-edge fluctuations under electromigration conditions is analysed using a continuum Langevin model. If the electromigration driving force acts in the step up/down direction, and step-edge diffusion is the dominant mass-transport mechanism, we find that significant deviations from the usual $t^{1/4}$ scaling of the terrace-width correlation function occurs for a critical time $\tau$ which is dependent upon the three energy scales in the problem: $k_{B}T$, the step stiffness, $\gamma$, and the bias associated with adatom hopping under the influence of an electromigration force, $\pm \Delta U$. For ($t < \tau$), the correlation function evolves as a superposition of $t^{1/4}$ and $t^{3/4}$ power laws. For $t \ge \tau$ a closed form expression can be derived. This behavior is confirmed by a Monte-Carlo simulation using a discrete model of the step dynamics. It is proposed that the magnitude of the electromigration force acting upon an atom at a step-edge can |
56e037b4-e231-4da3-8357-fc777c11dd0c | 56e037b4-e231-4da3-8357-fc777c11dd0c | 56e037b4-e231-4da3-8357-fc777c11dd0c | human | null | null | none | abstracts | Probing dark energy with steerable wavelets through correlation of WMAP
and NVSS local morphological measures | null | Using local morphological measures on the sphere defined through a steerable wavelet analysis, we examine the three-year WMAP and the NVSS data for correlation induced by the integrated Sachs-Wolfe (ISW) effect. The steerable wavelet constructed from the second derivative of a Gaussian allows one to define three local morphological measures, namely the signed-intensity, orientation and elongation of local features. Detections of correlation between the WMAP and NVSS data are made with each of these morphological measures. The most significant detection is obtained in the correlation of the signed-intensity of local features at a significance of 99.9%. By inspecting signed-intensity sky maps, it is possible for the first time to see the correlation between the WMAP and NVSS data by eye. Foreground contamination and instrumental systematics in the WMAP data are ruled out as the source of all significant detections of correlation. Our results provide new insight on the ISW effect by pro |
c3b02568-e914-4002-ba1a-ac1743b773b3 | c3b02568-e914-4002-ba1a-ac1743b773b3 | c3b02568-e914-4002-ba1a-ac1743b773b3 | human | null | null | none | abstracts | The $e^+ e^-\to K^+ K^- \pi^+\pi^-$, $K^+ K^- \pi^0\pi^0$ and $K^+ K^-
K^+ K^-$ Cross Sections Measured with Initial-State Radiation | null | We study the processes $e^+ e^-\to K^+ K^- \pi^+\pi^-\gamma$, $K^+K^-\pi^0\pi^0\gamma$ and $K^+ K^- K^+ K^-\gamma$, where the photon is radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed events, respectively, are selected from 232 \invfb of \babar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that the $K^+ K^- \pi^+\pi^-\gamma$ data can be compared with direct measurements of the $e^+ e^-\to K^+K^- \pipi$ reaction; no direct measurements exist for the $e^+ e^-\to K^+ K^- \pi^0\pi^0$ or $\epem\to K^+ K^- K^+ K^-$ reactions. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\to\phi(1020) f_{0}(980)$ and study its structure near threshold. In the charmonium region, we observe the $J/\psi$ in all three final states and several intermediate stat |
3f2479b9-c1aa-426c-ac75-4518f7bb70e5 | 3f2479b9-c1aa-426c-ac75-4518f7bb70e5 | 3f2479b9-c1aa-426c-ac75-4518f7bb70e5 | human | null | null | none | abstracts | Detecting and Characterizing Planetary Systems with Transit Timing | null | In the coming decades, research in extrasolar planets aims to advance two goals: 1) detecting and characterizing low-mass planets increasingly similar to the Earth, and 2) improving our understanding of planet formation. We present a new planet detection method that is capable of making large advances towards both of these objectives and describe a modest network of telescopes that is able to make the requisite observations. In a system where a known planet transits its host star, a second planet in that system will cause the time between transits to vary. These transit timing variations can be used to infer the orbital elements and mass of the perturbing planet even if it has a mass that is smaller than the mass of the Earth. This detection technique complements other techniques because it is most sensitive in mean-motion resonances where, due to degeneracies, other techniques have reduced sensitivity. Small ground-based observatories have already exceeded the photometric precision |
ede2d3e5-1da2-4544-82cf-2993da2d2a6e | ede2d3e5-1da2-4544-82cf-2993da2d2a6e | ede2d3e5-1da2-4544-82cf-2993da2d2a6e | human | null | null | none | abstracts | A Finite Element framework for computation of protein normal modes and
mechanical response | null | A coarse-grained computational procedure based on the Finite Element Method is proposed to calculate the normal modes and mechanical response of proteins and their supramolecular assemblies. Motivated by the elastic network model, proteins are modeled as homogeneous isotropic elastic solids with volume defined by their solvent-excluded surface. The discretized Finite Element representation is obtained using a surface simplification algorithm that facilitates the generation of models of arbitrary prescribed spatial resolution. The procedure is applied to compute the normal modes of a mutant of T4 phage lysozyme and of filamentous actin, as well as the critical Euler buckling load of the latter when subject to axial compression. Results compare favorably with all-atom normal mode analysis, the Rotation Translation Blocks procedure, and experiment. The proposed methodology establishes a computational framework for the calculation of protein mechanical response that facilitates the incor |
fcf7a0f3-eb21-4c49-87e0-25a433806c65 | fcf7a0f3-eb21-4c49-87e0-25a433806c65 | fcf7a0f3-eb21-4c49-87e0-25a433806c65 | human | null | null | none | abstracts | Are constant loop widths an artifact of the background and the spatial
resolution? | null | We study the effect of the coronal background in the determination of the diameter of EUV loops, and we analyze the suitability of the procedure followed in a previous paper (L\'opez Fuentes, Klimchuk & D\'emoulin 2006) for characterizing their expansion properties. For the analysis we create different synthetic loops and we place them on real backgrounds from data obtained with the Transition Region and Coronal Explorer (\textit{TRACE}). We apply to these loops the same procedure followed in our previous works, and we compare the results with real loop observations. We demonstrate that the procedure allows us to distinguish constant width loops from loops that expand appreciably with height, as predicted by simple force-free field models. This holds even for loops near the resolution limit. The procedure can easily determine when loops are below resolution limit and therefore not reliably measured. We find that small-scale variations in the measured loop width are likely due to impe |
95c2feea-9b61-402e-8331-29706c0bd2b5 | 95c2feea-9b61-402e-8331-29706c0bd2b5 | 95c2feea-9b61-402e-8331-29706c0bd2b5 | human | null | null | none | abstracts | Mapping the Youngest Galaxies to Redshift One | null | We describe results of a narrow band search for ultra-strong emission line galaxies (USELs) with EW(H beta) > 30 A. 542 candidate galaxies are found in a half square degree survey using two ~100 Angstrom 8150 A and 9140 A filters with Subaru/SuprimeCam. Followup spectroscopy for randomly selected objects in the sample with KeckII/DEIMOS shows they consist of [OIII] 5007, [OII] 3727, and H alpha selected strong-emission line galaxies at intermediate redshifts (z < 1), and Ly alpha emitting galaxies at high-redshift (z >> 5). We determine the H beta luminosity functions and the star formation density of the USELs, which is 5-10% of the value found from ultraviolet continuum objects at z=0-1, suggesting they correspond to a major epoch in galaxy formation at these redshifts. Many USELs show the temperature-sensitive [OIII] 4363 auroral lines and about a dozen have oxygen abundances characteristic of eXtremely Metal Poor Galaxies (XMPGs). These XMPGs are the most distant known today. Our |
268deef1-2681-4edf-97d2-5f4d854fc1ca | 268deef1-2681-4edf-97d2-5f4d854fc1ca | 268deef1-2681-4edf-97d2-5f4d854fc1ca | human | null | null | none | abstracts | Discovery of extreme asymmetry in the debris disk surrounding HD 15115 | null | We report the first scattered light detection of a dusty debris disk surrounding the F2V star HD 15115 using the Hubble Space Telescope in the optical, and Keck adaptive optics in the near-infrared. The most remarkable property of the HD 15115 disk relative to other debris disks is its extreme length asymmetry. The east side of the disk is detected to ~315 AU radius, whereas the west side of the disk has radius >550 AU. We find a blue optical to near-infrared scattered light color relative to the star that indicates grain scattering properties similar to the AU Mic debris disk. The existence of a large debris disk surrounding HD 15115 adds further evidence for membership in the Beta Pic moving group, which was previously argued based on kinematics alone. Here we hypothesize that the extreme disk asymmetry is due to dynamical perturbations from HIP 12545, an M star 0.5 degrees (0.38 pc) east of HD 15115 that shares a common proper motion vector, heliocentric distance, galactic space v |
18a7b7b7-bf2b-49e4-a71b-676106e124c2 | 18a7b7b7-bf2b-49e4-a71b-676106e124c2 | 18a7b7b7-bf2b-49e4-a71b-676106e124c2 | human | null | null | none | abstracts | Testing String Theory with CMB | null | Future detection/non-detection of tensor modes from inflation in CMB observations presents a unique way to test certain features of string theory. Current limit on the ratio of tensor to scalar perturbations, r=T/S, is r < 0.3, future detection may take place for r > 10^{-2}-10^{-3}. At present all known string theory inflation models predict tensor modes well below the level of detection. Therefore a possible experimental discovery of tensor modes may present a challenge to string cosmology. The strongest bound on r in string inflation follows from the observation that in most of the models based on the KKLT construction, the value of the Hubble constant H during inflation must be smaller than the gravitino mass. For the gravitino mass in the usual range, m_{3/2} < O(1) TeV, this leads to an extremely strong bound r < 10^{-24}. A discovery of tensor perturbations with r > 10^{-3} would imply that the gravitinos in this class of models are superheavy, m_{3/2} > 10^{13} GeV. This wo |
2a9cff67-4106-481f-8cf9-04af3c1e130f | 2a9cff67-4106-481f-8cf9-04af3c1e130f | 2a9cff67-4106-481f-8cf9-04af3c1e130f | human | null | null | none | abstracts | Behavioral response to strong aversive stimuli: A neurodynamical model | null | In this paper a theoretical model of functioning of a neural circuit during a behavioral response has been proposed. A neural circuit can be thought of as a directed multigraph whose each vertex is a neuron and each edge is a synapse. It has been assumed in this paper that the behavior of such circuits is manifested through the collective behavior of neurons belonging to that circuit. Behavioral information of each neuron is contained in the coefficients of the fast Fourier transform (FFT) over the output spike train. Those coefficients form a vector in a multidimensional vector space. Behavioral dynamics of a neuronal network in response to strong aversive stimuli has been studied in a vector space in which a suitable pseudometric has been defined. The neurodynamical model of network behavior has been formulated in terms of existing memory, synaptic plasticity and feelings. The model has an analogy in classical electrostatics, by which the notion of force and potential energy has be |
481879ff-66b8-45b8-a431-17a405ea7280 | 481879ff-66b8-45b8-a431-17a405ea7280 | 481879ff-66b8-45b8-a431-17a405ea7280 | human | null | null | none | abstracts | Galactic Wind Signatures around High Redshift Galaxies | null | We carry out cosmological chemodynamical simulations with different strengths of supernova (SN) feedback and study how galactic winds from star-forming galaxies affect the features of hydrogen (HI) and metal (CIV and OVI) absorption systems in the intergalactic medium at high redshift. We find that the outflows tend to escape to low density regions, and hardly affect the dense filaments visible in HI absorption. As a result, the strength of HI absorption near galaxies is not reduced by galactic winds, but even slightly increases. We also find that a lack of HI absorption for lines of sight (LOS) close to galaxies, as found by Adelberger et al., can be created by hot gas around the galaxies induced by accretion shock heating. In contrast to HI, metal absorption systems are sensitive to the presence of winds. The models without feedback can produce the strong CIV and OVI absorption lines in LOS within 50 kpc from galaxies, while strong SN feedback is capable of creating strong CIV and |
e0cf69da-4440-4b4f-aeb8-a938aa2bd0a8 | e0cf69da-4440-4b4f-aeb8-a938aa2bd0a8 | e0cf69da-4440-4b4f-aeb8-a938aa2bd0a8 | human | null | null | none | abstracts | An integral field spectroscopic survey for high redshift damped
Lyman-alpha galaxies | null | We search for galaxy counterparts to damped Lyman-alpha absorbers (DLAs) at z>2 towards nine quasars, which have 14 DLAs and 8 sub-DLAs in their spectra. We use integral field spectroscopy to search for Ly-alpha emission line objects at the redshifts of the absorption systems. Besides recovering two previously confirmed objects, we find six statistically significant candidate Ly-alpha emission line objects. The candidates are identified as having wavelengths close to the DLA line where the background quasar emission is absorbed. In comparison with the six currently known Ly-alpha emitting DLA galaxies the candidates have similar line fluxes and line widths, while velocity offsets between the emission lines and systemic DLA redshifts are larger. The impact parameters are larger than 10 kpc, and lower column density systems are found at larger impact parameters. Assuming that a single gas cloud extends from the QSO line of sight to the location of the candidate emission line, we find t |
694891c7-f9e1-4ffc-bd1c-3d12e8156a8a | 694891c7-f9e1-4ffc-bd1c-3d12e8156a8a | 694891c7-f9e1-4ffc-bd1c-3d12e8156a8a | human | null | null | none | abstracts | Long Gamma-Ray Burst Progenitors: Boundary Conditions and Binary Models | null | The observed association of Long Gamma-Ray Bursts (LGRBs) with peculiar Type Ic supernovae gives support to Woosley`s collapsar/hypernova model, in which the GRB is produced by the collapse of the rapidly rotating core of a massive star to a black hole. The association of LGRBs with small star-forming galaxies suggests low-metallicity to be a condition for a massive star to evolve to the collapsar stage. Both completely-mixed single star models and binary star models are possible. In binary models the progenitor of the GRB is a massive helium star with a close companion. We find that tidal synchronization during core-helium burning is reached on a short timescale (less than a few millennia). However, the strong core-envelope coupling in the subsequent evolutionary stages is likely to rule out helium stars with main-sequence companions as progenitors of hypernovae/GRBs. On the other hand, helium stars in close binaries with a neutron-star or black-hole companion can, despite the stron |
9596c4b3-e60d-451d-820f-fd919677be99 | 9596c4b3-e60d-451d-820f-fd919677be99 | 9596c4b3-e60d-451d-820f-fd919677be99 | human | null | null | none | abstracts | Multiscale model of electronic behavior and localization in stretched
dry DNA | null | When the DNA double helix is subjected to external forces it can stretch elastically to elongations reaching 100% of its natural length. These distortions, imposed at the mesoscopic or macroscopic scales, have a dramatic effect on electronic properties at the atomic scale and on electrical transport along DNA. Accordingly, a multiscale approach is necessary to capture the electronic behavior of the stretched DNA helix. To construct such a model, we begin with accurate density-functional-theory calculations for electronic states in DNA bases and base pairs in various relative configurations encountered in the equilibrium and stretched forms. These results are complemented by semi-empirical quantum mechanical calculations for the states of a small size [18 base pair poly(CG)-poly(CG)] dry, neutral DNA sequence, using previously published models for stretched DNA. The calculated electronic states are then used to parametrize an effective tight-binding model that can describe electron ho |
8b68554f-5bdc-4509-b964-caf246443b29 | 8b68554f-5bdc-4509-b964-caf246443b29 | 8b68554f-5bdc-4509-b964-caf246443b29 | human | null | null | none | abstracts | J/psi Production in an Equilibrating Partonic System | null | Any color singlet or octet ccbar pair is created at short distances and then expands to a full size of J/psi. Such a dynamical evolution process is included here in calculations for the J/psi number distribution as a function of transverse momentum and rapidity in central Au-Au collisions at both RHIC and LHC energies. The ccbar pairs are produced in the initial collision and in the partonic system during the prethermal and thermal stages through the partonic channels ab to ccbar [{2S+1}L_J] and ab to ccbar [{2S+1}L_J]x, and then they dissociate in the latter two stages. Dissociation of ccbar in the medium occurs via two reactions: (a) color singlet ccbar plus a gluon turns to color octet ccbar, (b) color octet ccbar plus a gluon persists as color octet. There are modest yields of ccbar in the prethermal stage at RHIC energy and through the reactions ab to ccbar [{2S+1}L_J] at LHC energy for partons with large average momentum in the prethermal stage at both collider energies and in |
c9602f57-cc77-4914-a627-64e2755516ff | c9602f57-cc77-4914-a627-64e2755516ff | c9602f57-cc77-4914-a627-64e2755516ff | human | null | null | none | abstracts | Hamiltonian formalism in Friedmann cosmology and its quantization | null | We propose a Hamiltonian formalism for a generalized Friedmann-Roberson-Walker cosmology model in the presence of both a variable equation of state (EOS) parameter $w(a)$ and a variable cosmological constant $\Lambda(a)$, where $a$ is the scale factor. This Hamiltonian system containing 1 degree of freedom and without constraint, gives Friedmann equations as the equation of motion, which describes a mechanical system with a variable mass object moving in a potential field. After an appropriate transformation of the scale factor, this system can be further simplified to an object with constant mass moving in an effective potential field. In this framework, the $\Lambda$ cold dark matter model as the current standard model of cosmology corresponds to a harmonic oscillator. We further generalize this formalism to take into account the bulk viscosity and other cases. The Hamiltonian can be quantized straightforwardly, but this is different from the approach of the Wheeler-DeWitt equation |
b0e3a2cd-7cdf-425a-afa3-2e60aca35003 | b0e3a2cd-7cdf-425a-afa3-2e60aca35003 | b0e3a2cd-7cdf-425a-afa3-2e60aca35003 | human | null | null | none | abstracts | Optimal stimulus and noise distributions for information transmission
via suprathreshold stochastic resonance | null | Suprathreshold stochastic resonance (SSR) is a form of noise enhanced signal transmission that occurs in a parallel array of independently noisy identical threshold nonlinearities, including model neurons. Unlike most forms of stochastic resonance, the output response to suprathreshold random input signals of arbitrary magnitude is improved by the presence of even small amounts of noise. In this paper the information transmission performance of SSR in the limit of a large array size is considered. Using a relationship between Shannon's mutual information and Fisher information, a sufficient condition for optimality, i.e. channel capacity, is derived. It is shown that capacity is achieved when the signal distribution is Jeffrey's prior, as formed from the noise distribution, or when the noise distribution depends on the signal distribution via a cosine relationship. These results provide theoretical verification and justification for previous work in both computational neuroscience an |
3cf2db27-6082-46ed-9c11-1cde5022164b | 3cf2db27-6082-46ed-9c11-1cde5022164b | 3cf2db27-6082-46ed-9c11-1cde5022164b | human | null | null | none | abstracts | Three Different Types of Galaxy Alignment within Dark Matter Halos | null | Using a large galaxy group catalogue based on the Sloan Digital Sky Survey Data Release 4 we measure three different types of intrinsic galaxy alignment within groups: halo alignment between the orientation of the brightest group galaxies (BGG) and the distribution of its satellite galaxies, radial alignment between the orientation of a satellite galaxy and the direction towards its BGG, and direct alignment between the orientation of the BGG and that of its satellites. In agreement with previous studies we find that satellite galaxies are preferentially located along the major axis. In addition, on scales r < 0.7 Rvir we find that red satellites are preferentially aligned radially with the direction to the BGG. The orientations of blue satellites, however, are perfectly consistent with being isotropic. Finally, on scales r < 0.1 \Rvir, we find a weak but significant indication for direct alignment between satellites and BGGs. We briefly discuss the implications for weak lensing meas |
723241e6-5ae5-4b29-9185-98bbc46de8b7 | 723241e6-5ae5-4b29-9185-98bbc46de8b7 | 723241e6-5ae5-4b29-9185-98bbc46de8b7 | human | null | null | none | abstracts | A very massive runaway star from Cygnus OB2 | null | Aims: We analyze the available information on the star BD+43 3654 to investigate the possibility that it may have had its origin in the massive OB association Cygnus OB2. Methods: We present new spectroscopic observations allowing a reliable spectral classification of the star, and discuss existing MSX observations of its associated bow shock and astrometric information not previously studied. Results: Our observations reveal that BD+43 3654 is a very early and luminous star of spectral type O4If, with an estimated mass of (70 +/- 15) solar masses and an age of about 1.6 Myr. The high spatial resolution of the MSX observations allows us to determine its direction of motion in the plane of the sky by means of the symmetry axis of the well-defined bow shock, which matches well the orientation expected from the proper motion. Tracing back its path across the sky we find that BD+43 3654 was located near the central, densest region of Cygnus OB2 at a time in the past similar to its es |
0d2a9b05-e995-4896-9208-9f1860b35808 | 0d2a9b05-e995-4896-9208-9f1860b35808 | 0d2a9b05-e995-4896-9208-9f1860b35808 | human | null | null | none | abstracts | Mapping the circumstellar SiO maser emission in R Leo | null | The study of the innermost circumstellar layers around AGB stars is crucial to understand how these envelopes are formed and evolve. The SiO maser emission occurs at a few stellar radii from the central star, providing direct information on the stellar pulsation and on the chemical and physical properties of these regions. Our data also shed light on several aspects of the SiO maser pumping theory that are not well understood yet. We aim to determine} the relative spatial distribution of the 43 GHz and 86 GHz SiO maser lines in the oxygen-rich evolved star R Leo. We have imaged with milliarcsecond resolution, by means of Very Long Baseline Interferometry, the 43 GHz (28SiO v=1, 2 J=1-0 and 29SiO v=0 J=1-0) and 86 GHz (28SiO v=1 J=2-1 and 29SiO v=0 J=2-1) masing regions. We confirm previous results obtained in other oxygen-rich envelopes. In particular, when comparing the 43 GHz emitting regions, the 28SiO v=2 transition is produced in an inner layer, closer to the central star. On th |
82de8f46-b09c-468d-bcfe-d7da254f0303 | 82de8f46-b09c-468d-bcfe-d7da254f0303 | 82de8f46-b09c-468d-bcfe-d7da254f0303 | human | null | null | none | abstracts | Fuzzballs with internal excitations | null | We construct general 2-charge D1-D5 horizon-free non-singular solutions of IIB supergravity on T^4 and K3 describing fuzzballs with excitations in the internal manifold; these excitations are characterized by arbitrary curves. The solutions are obtained via dualities from F1-P solutions of heterotic and type IIB on T^4 for the K3 and T^4 cases, respectively. We compute the holographic data encoded in these solutions, and show that the internal excitations are captured by vevs of chiral primaries associated with the middle cohomology of T^4 or K3. We argue that each geometry is dual to a specific superposition of R ground states determined in terms of the Fourier coefficients of the curves defining the supergravity solution. We compute vevs of chiral primaries associated with the middle cohomology and show that they indeed acquire vevs in the superpositions corresponding to fuzzballs with internal excitations, in accordance with the holographic results. We also address the question of |
1bec0511-4761-418a-8344-4d40784ac6c6 | 1bec0511-4761-418a-8344-4d40784ac6c6 | 1bec0511-4761-418a-8344-4d40784ac6c6 | human | null | null | none | abstracts | CP violation due to multi Froggatt-Nielsen fields | null | We study how to incorporate CP violation in the Froggatt--Nielsen (FN) mechanism. To this end, we introduce non-renormalizable interactions with a flavor democratic structure to the fermion mass generation sector. It is found that at least two iso-singlet scalar fields with imposed a discrete symmetry are necessary to generate CP violation due to the appearance of the relative phase between their vacuum expectation values. In the simplest model, ratios of quark masses and the Cabibbo-Kobayashi-Maskawa (CKM) matrix including the CP violating phase are determined by the CKM element |V_{us}| and the ratio of two vacuum expectation values R=|R|e^{i*alpha} (a magnitude and a phase). It is demonstrated how the angles phi_i (i=1--3) of the unitarity triangle and the CKM off-diagonal elements |V_{ub}| and |V_{cb}| are predicted as a function of |V_{us}|, |R| and \alpha. Although the predicted value of the CP violating phase does not agree with the experimental data within the simplest mode |
360d0fcf-5d91-4156-a004-0b27dad5009f | 360d0fcf-5d91-4156-a004-0b27dad5009f | 360d0fcf-5d91-4156-a004-0b27dad5009f | human | null | null | none | abstracts | Rigorous Results for the Periodic Oscillation of an Adiabatic Piston | null | We study a heavy piston of mass $M$ that moves in one dimension. The piston separates two gas chambers, each of which contains finitely many ideal, unit mass gas particles moving in $d$ dimensions, where $ d\geq 1$. Using averaging techniques, we prove that the actual motions of the piston converge in probability to the predicted averaged behavior on the time scale $M^ {1/2} $ when $M$ tends to infinity while the total energy of the system is bounded and the number of gas particles is fixed. Neishtadt and Sinai previously pointed out that an averaging theorem due to Anosov should extend to this situation. When $ d=1$, the gas particles move in just one dimension, and we prove that the rate of convergence of the actual motions of the piston to its averaged behavior is $\mathcal{O} (M^ {-1/2}) $ on the time scale $M^ {1/2} $. The convergence is uniform over all initial conditions in a compact set. We also investigate the piston system when the particle interactions have been smoothed |
a231dfc4-1558-4a11-82b6-d1f6faa4a2a9 | a231dfc4-1558-4a11-82b6-d1f6faa4a2a9 | a231dfc4-1558-4a11-82b6-d1f6faa4a2a9 | human | null | null | none | abstracts | Detailed kinetic study of the ring opening of cycloalkanes by CBS-QB3
calculations | null | This work reports a theoretical study of the gas phase unimolecular decomposition of cyclobutane, cyclopentane and cyclohexane by means of quantum chemical calculations. A biradical mechanism has been envisaged for each cycloalkane, and the main routes for the decomposition of the biradicals formed have been investigated at the CBS-QB3 level of theory. Thermochemical data (\delta H^0_f, S^0, C^0_p) for all the involved species have been obtained by means of isodesmic reactions. The contribution of hindered rotors has also been included. Activation barriers of each reaction have been analyzed to assess the 1 energetically most favorable pathways for the decomposition of biradicals. Rate constants have been derived for all elementary reactions using transition state theory at 1 atm and temperatures ranging from 600 to 2000 K. Global rate constant for the decomposition of the cyclic alkanes in molecular products have been calculated. Comparison between calculated and experimental result |
784161e7-90ec-455b-9ae5-59514b43a076 | 784161e7-90ec-455b-9ae5-59514b43a076 | 784161e7-90ec-455b-9ae5-59514b43a076 | human | null | null | none | abstracts | On thermal effects in solid state lasers: the case of ytterbium-doped
materials | null | A review of theoretical and experimental studies of thermal effects in solid-state lasers is presented, with a special focus on diode-pumped ytterbium-doped materials. A large part of this review provides however general information applicable to any kind of solid-state laser. Our aim here is not to make a list of the techniques that have been used to minimize thermal effects, but instead to give an overview of the theoretical aspects underneath, and give a state-of-the-art of the tools at the disposal of the laser scientist to measure thermal effects. After a presentation of some general properties of Yb-doped materials, we address the issue of evaluating the temperature map in Yb-doped laser crystals, both theoretically and experimentally. This is the first step before studying the complex problem of thermal lensing (part III). We will focus on some newly discussed aspects, like the definition of the thermo-optic coefficient: we will highlight some misleading interpretations of the |
51badf51-3272-4d44-a98d-acd3b61c97c2 | 51badf51-3272-4d44-a98d-acd3b61c97c2 | 51badf51-3272-4d44-a98d-acd3b61c97c2 | human | null | null | none | abstracts | Transient behavior of surface plasmon polaritons scattered at a
subwavelength groove | null | We present a numerical study and analytical model of the optical near-field diffracted in the vicinity of subwavelength grooves milled in silver surfaces. The Green's tensor approach permits computation of the phase and amplitude dependence of the diffracted wave as a function of the groove geometry. It is shown that the field diffracted along the interface by the groove is equivalent to replacing the groove by an oscillating dipolar line source. An analytic expression is derived from the Green's function formalism, that reproduces well the asymptotic surface plasmon polariton (SPP) wave as well as the transient surface wave in the near-zone close to the groove. The agreement between this model and the full simulation is very good, showing that the transient "near-zone" regime does not depend on the precise shape of the groove. Finally, it is shown that a composite diffractive evanescent wave model that includes the asymptotic SPP can describe the wavelength evolution in this transie |
23e4bdfa-0f53-497c-bdf9-48621778d567 | 23e4bdfa-0f53-497c-bdf9-48621778d567 | 23e4bdfa-0f53-497c-bdf9-48621778d567 | human | null | null | none | abstracts | On second order shape optimization methods for electrical impedance
tomography | null | This paper is devoted to the analysis of a second order method for recovering the \emph{a priori} unknown shape of an inclusion $\omega$ inside a body $\Omega$ from boundary measurement. This inverse problem - known as electrical impedance tomography - has many important practical applications and hence has focussed much attention during the last years. However, to our best knowledge, no work has yet considered a second order approach for this problem. This paper aims to fill that void: we investigate the existence of second order derivative of the state $u$ with respect to perturbations of the shape of the interface $\partial\omega$, then we choose a cost function in order to recover the geometry of $\partial \omega$ and derive the expression of the derivatives needed to implement the corresponding Newton method. We then investigate the stability of the process and explain why this inverse problem is severely ill-posed by proving the compactness of the Hessian at the global minimize |
42e0ff3f-30b2-4a93-9218-bf98b8092edb | 42e0ff3f-30b2-4a93-9218-bf98b8092edb | 42e0ff3f-30b2-4a93-9218-bf98b8092edb | human | null | null | none | abstracts | Maximum solutions of normalized Ricci flows on 4-manifolds | null | We consider maximum solution $g(t)$, $t\in [0, +\infty)$, to the normalized Ricci flow. Among other things, we prove that, if $(M, \omega) $ is a smooth compact symplectic 4-manifold such that $b_2^+(M)>1$ and let $g(t),t\in[0,\infty)$, be a solution to (1.3) on $M$ whose Ricci curvature satisfies that $|\text{Ric}(g(t))|\leq 3$ and additionally $\chi(M)=3 \tau (M)>0$, then there exists an $m\in \mathbb{N}$, and a sequence of points $\{x_{j,k}\in M\}$, $j=1, ..., m$, satisfying that, by passing to a subsequence, $$(M, g(t_{k}+t), x_{1,k},..., x_{m,k}) \stackrel{d_{GH}}\longrightarrow (\coprod_{j=1}^m N_j, g_{\infty}, x_{1,\infty}, ...,, x_{m,\infty}),$$ $t\in [0, \infty)$, in the $m$-pointed Gromov-Hausdorff sense for any sequence $t_{k}\longrightarrow \infty$, where $(N_{j}, g_{\infty})$, $j=1,..., m$, are complete complex hyperbolic orbifolds of complex dimension 2 with at most finitely many isolated orbifold points. Moreover, the convergence is $C^{\infty}$ in the non-singular par |
43623089-bef9-42c1-932a-0d20f761e0ff | 43623089-bef9-42c1-932a-0d20f761e0ff | 43623089-bef9-42c1-932a-0d20f761e0ff | human | null | null | none | abstracts | Gravitational Wave Signals from Chaotic System: A Point Mass with A Disk | null | We study gravitational waves from a particle moving around a system of a point mass with a disk in Newtonian gravitational theory. A particle motion in this system can be chaotic when the gravitational contribution from a surface density of a disk is comparable with that from a point mass. In such an orbit, we sometimes find that there appears a phase of the orbit in which particle motion becomes to be nearly regular (the so-called ``stagnant motion'') for a finite time interval between more strongly chaotic phases. To study how these different chaotic behaviours affect on observation of gravitational waves, we investigate a correlation of the particle motion and the waves. We find that such a difference in chaotic motions reflects on the wave forms and energy spectra. The character of the waves in the stagnant motion is quite different from that either in a regular motion or in a more strongly chaotic motion. This suggests that we may make a distinction between different chaotic beh |
eb8b49c0-f93e-48d6-835f-377cb6e1a58b | eb8b49c0-f93e-48d6-835f-377cb6e1a58b | eb8b49c0-f93e-48d6-835f-377cb6e1a58b | human | null | null | none | abstracts | Revisiting the Issues On Netflow Sample and Export Performance | null | The high volume of packets and packet rates of traffic on some router links makes it exceedingly difficult for routers to examine every packet in order to keep detailed statistics about the traffic which is traversing the router. Sampling is commonly applied on routers in order to limit the load incurred by the collection of information that the router has to undertake when evaluating flow information for monitoring purposes. The sampling process in nearly all cases is a deterministic process of choosing 1 in every N packets on a per-interface basis, and then forming the flow statistics based on the collected sampled statistics. Even though this sampling may not be significant for some statistics, such as packet rate, others can be severely distorted. However, it is important to consider the sampling techniques and their relative accuracy when applied to different traffic patterns. The main disadvantage of sampling is the loss of accuracy in the collected trace when compared to the o |
81eb1893-b25c-4fcb-b6d0-140510357d32 | 81eb1893-b25c-4fcb-b6d0-140510357d32 | 81eb1893-b25c-4fcb-b6d0-140510357d32 | human | null | null | none | abstracts | The tensor part of the Skyrme energy density functional. I. Spherical
nuclei | null | We perform a systematic study of the impact of the J^2 tensor term in the Skyrme energy functional on properties of spherical nuclei. In the Skyrme energy functional, the tensor terms originate both from zero-range central and tensor forces. We build a set of 36 parameterizations, which covers a wide range of the parameter space of the isoscalar and isovector tensor term coupling constants, with a fit protocol very similar to that of the successful SLy parameterizations. We analyze the impact of the tensor terms on a large variety of observables in spherical mean-field calculations, such as the spin-orbit splittings and single-particle spectra of doubly-magic nuclei, the evolution of spin-orbit splittings along chains of semi-magic nuclei, mass residuals of spherical nuclei, and known anomalies of charge radii. Our main conclusion is that the currently used central and spin-orbit parts of the Skyrme energy density functional are not flexible enough to allow for the presence of large |
f1da465b-20f4-4f29-b0e8-c00b3c82584a | f1da465b-20f4-4f29-b0e8-c00b3c82584a | f1da465b-20f4-4f29-b0e8-c00b3c82584a | human | null | null | none | abstracts | The HELLAS2XMM survey. X. The bolometric output of luminous obscured
quasars: The Spitzer perspective | null | Aims: We aim at estimating the spectral energy distributions (SEDs) and the physical parameters related to the black holes harbored in eight high X-ray-to-optical (F_X/F_R>10) obscured quasars at z>0.9 selected in the 2--10 keV band from the HELLAS2XMM survey. Methods: We use IRAC and MIPS 24 micron observations, along with optical and Ks-band photometry, to obtain the SEDs of the sources. The observed SEDs are modeled using a combination of an elliptical template and torus emission (using the phenomenological templates of Silva et al. 2004) for six sources associated with passive galaxies; for two point-like sources, the empirical SEDs of red quasars are adopted. The bolometric luminosities and the M_BH-L_K relation are used to provide an estimate of the masses and Eddington ratios of the black holes residing in these AGN. Results: All of our sources are detected in the IRAC and MIPS (at 24 micron) bands. The SED modeling described above is in good agreement with the observed ne |
8a0c9fa6-b63d-481c-8e2d-0a037ca0fcf3 | 8a0c9fa6-b63d-481c-8e2d-0a037ca0fcf3 | 8a0c9fa6-b63d-481c-8e2d-0a037ca0fcf3 | human | null | null | none | abstracts | Quantifying social group evolution | null | The rich set of interactions between individuals in the society results in complex community structure, capturing highly connected circles of friends, families, or professional cliques in a social network. Thanks to frequent changes in the activity and communication patterns of individuals, the associated social and communication network is subject to constant evolution. Our knowledge of the mechanisms governing the underlying community dynamics is limited, but is essential for a deeper understanding of the development and self-optimisation of the society as a whole. We have developed a new algorithm based on clique percolation, that allows, for the first time, to investigate the time dependence of overlapping communities on a large scale and as such, to uncover basic relationships characterising community evolution. Our focus is on networks capturing the collaboration between scientists and the calls between mobile phone users. We find that large groups persist longer if they are ca |
7e2d5049-6889-4b42-b527-7aef95430dab | 7e2d5049-6889-4b42-b527-7aef95430dab | 7e2d5049-6889-4b42-b527-7aef95430dab | human | null | null | none | abstracts | Local de Broglie-Bohm Trajectories from Entangled Wavefunctions | null | We present a local interpretation of what is usually considered to be a nonlocal de Broglie-Bohm trajectory prescription for an entangled singlet state of massive particles. After reviewing various meanings of the term ``nonlocal'', we show that by using appropriately retarded wavefunctions (i.e., the locality loophole) this local model can violate Bell's inequality, without making any appeal to detector inefficiencies. We analyze a possible experimental configuration appropriate to massive two-particle singlet wavefunctions and find that as long as the particles are not ultra-relativistic, a locality loophole exists and Dirac wave(s) can propagate from Alice or Bob's changing magnetic field, through space, to the other detector, arriving before the particle and thereby allowing a local interpretation to the 2-particle de Broglie-Bohm trajectories. We also propose a physical effect due to changing magnetic fields in a Stern-Gerlach EPR setup that will throw away events and create |
5a0614a8-9ac9-421b-8782-ac877092d039 | 5a0614a8-9ac9-421b-8782-ac877092d039 | 5a0614a8-9ac9-421b-8782-ac877092d039 | human | null | null | none | abstracts | Ground-based Microlensing Surveys | null | Microlensing is a proven extrasolar planet search method that has already yielded the detection of four exoplanets. These detections have changed our understanding of planet formation ``beyond the snowline'' by demonstrating that Neptune-mass planets with separations of several AU are common. Microlensing is sensitive to planets that are generally inaccessible to other methods, in particular cool planets at or beyond the snowline, very low-mass (i.e. terrestrial) planets, planets orbiting low-mass stars, free-floating planets, and even planets in external galaxies. Such planets can provide critical constraints on models of planet formation, and therefore the next generation of extrasolar planet searches should include an aggressive and well-funded microlensing component. When combined with the results from other complementary surveys, next generation microlensing surveys can yield an accurate and complete census of the frequency and properties of planets, and in particular low-mass t |
5a7a33b9-c589-4ef2-a5c3-2a8befc0ad7a | 5a7a33b9-c589-4ef2-a5c3-2a8befc0ad7a | 5a7a33b9-c589-4ef2-a5c3-2a8befc0ad7a | human | null | null | none | abstracts | The luminous infrared composite Seyfert 2 galaxy NGC 7679 through the [O
III] 5007 emission line | null | NGC 7679 is a nearby luminous infrared Sy2 galaxy in which starburst and AGN activities co-exist. The ionization structure is maintained by both the AGN power-law continuum and starburst. The galaxy is a bright X-ray source possessing a low X-ray column density N_H < 4 x 10^20 cm^{-2}. The Compton-thin nature of such unabsorbed objects infers that the simple formulation of the Unified model for SyGs is not applicable in their case. The main goal of this article is to investigate both gas distribution and ionization structure in the circumnuclear region of NGC 7679 in search for the presence of a hidden Sy1 nucleus, using the [O III] 5007 luminosity as a tracer of AGN activity. The [O III] 5007 image of the NGC 7679 shows elliptical isophotes extended along the PA ~ 80 deg in the direction to the counterpart galaxy NGC 7682. The maximum of ionization by the AGN power-law continuum traced by [O III] 5007/Halpha ratio is displaced by ~ 13 arcsec eastward from the nucleus. We conclude th |
0ea1f66b-2ebd-40a8-80b3-7e65f2dfa7b3 | 0ea1f66b-2ebd-40a8-80b3-7e65f2dfa7b3 | 0ea1f66b-2ebd-40a8-80b3-7e65f2dfa7b3 | human | null | null | none | abstracts | Collective behavior of stock price movements in an emerging market | null | To investigate the universality of the structure of interactions in different markets, we analyze the cross-correlation matrix C of stock price fluctuations in the National Stock Exchange (NSE) of India. We find that this emerging market exhibits strong correlations in the movement of stock prices compared to developed markets, such as the New York Stock Exchange (NYSE). This is shown to be due to the dominant influence of a common market mode on the stock prices. By comparison, interactions between related stocks, e.g., those belonging to the same business sector, are much weaker. This lack of distinct sector identity in emerging markets is explicitly shown by reconstructing the network of mutually interacting stocks. Spectral analysis of C for NSE reveals that, the few largest eigenvalues deviate from the bulk of the spectrum predicted by random matrix theory, but they are far fewer in number compared to, e.g., NYSE. We show this to be due to the relative weakness of intra-sector i |
7c5f1c8b-2031-408d-81c7-7a4abecafc60 | 7c5f1c8b-2031-408d-81c7-7a4abecafc60 | 7c5f1c8b-2031-408d-81c7-7a4abecafc60 | human | null | null | none | abstracts | Galaxy morphologies and environment in the Abell 901/902 supercluster
from COMBO-17 | null | We present a morphological study of galaxies in the A901/902 supercluster from the COMBO-17 survey. A total of 570 galaxies with photometric redshifts in the range 0.155 < z_phot < 0.185 are visually classified by three independent classifiers to M_V=-18. These morphological classifications are compared to local galaxy density, distance from the nearest cluster centre, local surface mass density from weak lensing, and photometric classification. At high local galaxy densities, log(Sigma_10 /Mpc^2) > 1.5, a classical morphology-density relation is found. A correlation is also found between morphology and local projected surface mass density, but no trend is observed with distance to the nearest cluster. This supports the finding that local environment is more important to galaxy morphology than global cluster properties. The breakdown of the morphological catalogue by colour shows a dominance of blue galaxies in the galaxies displaying late-type morphologies and a corresponding domina |
d43e4ea3-ee2a-4a51-bddf-36ea6d781e6d | d43e4ea3-ee2a-4a51-bddf-36ea6d781e6d | d43e4ea3-ee2a-4a51-bddf-36ea6d781e6d | human | null | null | none | abstracts | Frobenius splitting and geometry of $G$-Schubert varieties | null | Let $X$ be an equivariant embedding of a connected reductive group $G$ over an algebraically closed field $k$ of positive characteristic. Let $B$ denote a Borel subgroup of $G$. A $G$-Schubert variety in $X$ is a subvariety of the form $\diag(G) \cdot V$, where $V$ is a $B \times B$-orbit closure in $X$. In the case where $X$ is the wonderful compactification of a group of adjoint type, the $G$-Schubert varieties are the closures of Lusztig's $G$-stable pieces. We prove that $X$ admits a Frobenius splitting which is compatible with all $G$-Schubert varieties. Moreover, when $X$ is smooth, projective and toroidal, then any $G$-Schubert variety in $X$ admits a stable Frobenius splitting along an ample divisors. Although this indicates that $G$-Schubert varieties have nice singularities we present an example of a non-normal $G$-Schubert variety in the wonderful compactification of a group of type $G_2$. Finally we also extend the Frobenius splitting results to the more general class of |
3f174f2b-0555-4b1b-86a4-9eedc21e0c47 | 3f174f2b-0555-4b1b-86a4-9eedc21e0c47 | 3f174f2b-0555-4b1b-86a4-9eedc21e0c47 | human | null | null | none | abstracts | Testing outer boundary treatments for the Einstein equations | null | Various methods of treating outer boundaries in numerical relativity are compared using a simple test problem: a Schwarzschild black hole with an outgoing gravitational wave perturbation. Numerical solutions computed using different boundary treatments are compared to a `reference' numerical solution obtained by placing the outer boundary at a very large radius. For each boundary treatment, the full solutions including constraint violations and extracted gravitational waves are compared to those of the reference solution, thereby assessing the reflections caused by the artificial boundary. These tests use a first-order generalized harmonic formulation of the Einstein equations. Constraint-preserving boundary conditions for this system are reviewed, and an improved boundary condition on the gauge degrees of freedom is presented. Alternate boundary conditions evaluated here include freezing the incoming characteristic fields, Sommerfeld boundary conditions, and the constraint-preservin |
3dc8a78b-75df-4b4e-97fb-c9416bfa5750 | 3dc8a78b-75df-4b4e-97fb-c9416bfa5750 | 3dc8a78b-75df-4b4e-97fb-c9416bfa5750 | human | null | null | none | abstracts | New Close Binary Systems from the SDSS-I (Data Release Five) and the
Search for Magnetic White Dwarfs in Cataclysmic Variable Progenitor Systems | null | We present the latest catalog of more than 1200 spectroscopically-selected close binary systems observed with the Sloan Digital Sky Survey through Data Release Five. We use the catalog to search for magnetic white dwarfs in cataclysmic variable progenitor systems. Given that approximately 25% of cataclysmic variables contain a magnetic white dwarf, and that our large sample of close binary systems should contain many progenitors of cataclysmic variables, it is quite surprising that we find only two potential magnetic white dwarfs in this sample. The candidate magnetic white dwarfs, if confirmed, would possess relatively low magnetic field strengths (B_WD < 10 MG) that are similar to those of intermediate-Polars but are much less than the average field strength of the current Polar population. Additional observations of these systems are required to definitively cast the white dwarfs as magnetic. Even if these two systems prove to be the first evidence of detached magnetic white dwarf |
8c0d729c-e384-49e5-9a02-f7e27c8f3731 | 8c0d729c-e384-49e5-9a02-f7e27c8f3731 | 8c0d729c-e384-49e5-9a02-f7e27c8f3731 | human | null | null | none | abstracts | Spectral analysis of Swift long GRBs with known redshift | null | We study the spectral and energetics properties of 47 long-duration gamma-ray bursts (GRBs) with known redshift, all of them detected by the Swift satellite. Due to the narrow energy range (15-150 keV) of the Swift-BAT detector, the spectral fitting is reliable only for fitting models with 2 or 3 parameters. As high uncertainty and correlation among the errors is expected, a careful analysis of the errors is necessary. We fit both the power law (PL, 2 parameters) and cut--off power law (CPL, 3 parameters) models to the time-integrated spectra of the 47 bursts, and present the corresponding parameters, their uncertainties, and the correlations among the uncertainties. The CPL model is reliable only for 29 bursts for which we estimate the nuf_nu peak energy Epk. For these GRBs, we calculate the energy fluence and the rest- frame isotropic-equivalent radiated energy, Eiso, as well as the propagated uncertainties and correlations among them. We explore the distribution of our homogeneous |
9baa293f-b510-4b4e-8019-5e00ef8c03ec | 9baa293f-b510-4b4e-8019-5e00ef8c03ec | 9baa293f-b510-4b4e-8019-5e00ef8c03ec | human | null | null | none | abstracts | Heavy-Light Semileptonic Decays in Staggered Chiral Perturbation Theory | null | We calculate the form factors for the semileptonic decays of heavy-light pseudoscalar mesons in partially quenched staggered chiral perturbation theory (\schpt), working to leading order in $1/m_Q$, where $m_Q$ is the heavy quark mass. We take the light meson in the final state to be a pseudoscalar corresponding to the exact chiral symmetry of staggered quarks. The treatment assumes the validity of the standard prescription for representing the staggered ``fourth root trick'' within \schpt by insertions of factors of 1/4 for each sea quark loop. Our calculation is based on an existing partially quenched continuum chiral perturbation theory calculation with degenerate sea quarks by Becirevic, Prelovsek and Zupan, which we generalize to the staggered (and non-degenerate) case. As a by-product, we obtain the continuum partially quenched results with non-degenerate sea quarks. We analyze the effects of non-leading chiral terms, and find a relation among the coefficients governing the ana |
c55772f7-ea09-4cb2-b000-55b485966d25 | c55772f7-ea09-4cb2-b000-55b485966d25 | c55772f7-ea09-4cb2-b000-55b485966d25 | human | null | null | none | abstracts | Quantum Auctions | null | We present a quantum auction protocol using superpositions to represent bids and distributed search to identify the winner(s). Measuring the final quantum state gives the auction outcome while simultaneously destroying the superposition. Thus non-winning bids are never revealed. Participants can use entanglement to arrange for correlations among their bids, with the assurance that this entanglement is not observable by others. The protocol is useful for information hiding applications, such as partnership bidding with allocative externality or concerns about revealing bidding preferences. The protocol applies to a variety of auction types, e.g., first or second price, and to auctions involving either a single item or arbitrary bundles of items (i.e., combinatorial auctions). We analyze the game-theoretical behavior of the quantum protocol for the simple case of a sealed-bid quantum, and show how a suitably designed adiabatic search reduces the possibilities for bidders to game the au |
fac79504-7e8f-457d-be7b-4c7fcf9870a9 | fac79504-7e8f-457d-be7b-4c7fcf9870a9 | fac79504-7e8f-457d-be7b-4c7fcf9870a9 | human | null | null | none | abstracts | Wide Field Surveys and Astronomical Discovery Space | null | I review the status of science with wide field surveys. For many decades surveys have been the backbone of astronomy, and the main engine of discovery, as we have mapped the sky at every possible wavelength. Surveys are an efficient use of resources. They are important as a fundamental resource; to map intrinsically large structures; to gain the necessary statistics to address some problems; and to find very rare objects. I summarise major recent wide field surveys - 2MASS, SDSS, 2dfGRS, and UKIDSS - and look at examples of the exciting science they have produced, covering the structure of the Milky Way, the measurement of cosmological parameters, the creation of a new field studying substellar objects, and the ionisation history of the Universe. I then look briefly at upcoming projects in the optical-IR survey arena - VISTA, PanSTARRS, WISE, and LSST. Finally I ask, now we have opened up essentially all wavelength windows, whether the exploration of survey discovery space is ended. |
ecb73b33-5e35-4b3f-b1f7-56702d66074c | ecb73b33-5e35-4b3f-b1f7-56702d66074c | ecb73b33-5e35-4b3f-b1f7-56702d66074c | human | null | null | none | abstracts | The Na I D resonance lines in main sequence late-type stars | null | We study the sodium D lines (D1: 5895.92 \AA; D2: 5889.95 \AA) in late-type dwarf stars. The stars have spectral types between F6 and M5.5 (B-V between 0.457 and 1.807) and metallicity between [Fe/H] = -0.82 and 0.6. We obtained medium resolution echelle spectra using the 2.15-m telescope at the argentinian observatory CASLEO. The observations have been performed periodically since 1999. The spectra were calibrated in wavelength and in flux. A definition of the pseudo-continuum level is found for all our observations. We also define a continuum level for calibration purposes. The equivalent width of the D lines is computed in detail for all our spectra and related to the colour index (B-V) of the stars. When possible, we perform a careful comparison with previous studies. Finally, we construct a spectral index (R_D') as the ratio between the flux in the D lines, and the bolometric flux. We find that, once corrected for the photospheric contribution, this index can be used as a chromo |
ffa4ab34-e166-4219-9ea4-44b969db5830 | ffa4ab34-e166-4219-9ea4-44b969db5830 | ffa4ab34-e166-4219-9ea4-44b969db5830 | human | null | null | none | abstracts | Position-Velocity Diagrams for the Maser Emission coming from a
Keplerian Ring | null | We have studied the maser emission from a thin, planar, gaseous ring in Keplerian rotation around a central mass observed edge-on. The absorption coefficient within the ring is assumed to follow a power law dependence with the distance from the central mass as, k=k0r^{-q}. We have calculated position-velocity diagrams for the most intense maser features, for different values of the exponent q. We have found that, depending on the value of q, these diagrams can be qualitatively different. The most intense maser emission at a given velocity can either come mainly from regions close to the inner or outer edges of the amplifying ring or from the line perpendicular to the line of sight and passing through the central mass (as is commonly assumed). Particularly, when q>1 the position-velocity diagram is qualitatively similar to the one observed for the water maser emission in the nucleus of the galaxy NGC 4258. In the context of this simple model, we conclude that in this object the absorp |
59245298-3f7f-4f11-8775-79d5054aa83d | 59245298-3f7f-4f11-8775-79d5054aa83d | 59245298-3f7f-4f11-8775-79d5054aa83d | human | null | null | none | abstracts | 9.7 micrometer Silicate Absorption in a Damped Lyman-alpha Absorber at
z=0.52 | null | We report a detection of the 9.7 micrometer silicate absorption feature in a damped Lyman-alpha (DLA) system at z_{abs} = 0.524 toward AO0235+164, using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope. The feature shows a broad shallow profile over about 8-12 micrometers in the absorber rest frame and appears to be > 15 sigma significant in equivalent width. The feature is fit reasonably well by the silicate absorption profiles for laboratory amorphous olivine or diffuse Galactic interstellar clouds. To our knowledge, this is the first indication of 9.7 micrometer silicate absorption in a DLA. We discuss potential implications of this finding for the nature of the dust in quasar absorbers. Although the feature is relatively shallow (tau_{9.7} = 0.08-0.09), it is about 2 times deeper than expected from extrapolation of the tau_{9.7} vs. E(B-V) relation known for diffuse Galactic interstellar clouds. Further studies of the 9.7 micrometer silicate feature in quasar a |
b9f5493c-091e-4c04-9b70-9b882a55b19b | b9f5493c-091e-4c04-9b70-9b882a55b19b | b9f5493c-091e-4c04-9b70-9b882a55b19b | human | null | null | none | abstracts | Terrestrial and Habitable Planet Formation in Binary and Multi-star
Systems | null | One of the most surprising discoveries of extrasolar planets is the detection of planets in moderately close binary star systems. The Jovian-type planets in the two binaries of Gamma Cephei and GJ 86 have brought to the forefront questions on the formation of giant planets and the possibility of the existence of smaller bodies in such dynamically complex environments. The diverse dynamical characteristics of these objects have made scientists wonder to what extent the current theories of planet formation can be applied to binaries and multiple star systems. At present, the sensitivity of the detection techniques does not allow routine discovery of Earth-sized bodies in binary systems. However, with the advancement of new techniques, and with the recent launch of CoRoT and the launch of Kepler in late 2008, the detection of more planets (possibly terrestrial-class objects) in such systems is on the horizon. Theoretical studies and numerical modeling of terrestrial and habitable planet |
321b3a42-8b92-44f1-a71f-dc15c699e334 | 321b3a42-8b92-44f1-a71f-dc15c699e334 | 321b3a42-8b92-44f1-a71f-dc15c699e334 | human | null | null | none | abstracts | Universal Source Coding for Monotonic and Fast Decaying Monotonic
Distributions | null | We study universal compression of sequences generated by monotonic distributions. We show that for a monotonic distribution over an alphabet of size $k$, each probability parameter costs essentially $0.5 \log (n/k^3)$ bits, where $n$ is the coded sequence length, as long as $k = o(n^{1/3})$. Otherwise, for $k = O(n)$, the total average sequence redundancy is $O(n^{1/3+\epsilon})$ bits overall. We then show that there exists a sub-class of monotonic distributions over infinite alphabets for which redundancy of $O(n^{1/3+\epsilon})$ bits overall is still achievable. This class contains fast decaying distributions, including many distributions over the integers and geometric distributions. For some slower decays, including other distributions over the integers, redundancy of $o(n)$ bits overall is achievable, where a method to compute specific redundancy rates for such distributions is derived. The results are specifically true for finite entropy monotonic distributions. Finally, we stu |
9bbc639e-a78b-4515-a8be-134b777274d5 | 9bbc639e-a78b-4515-a8be-134b777274d5 | 9bbc639e-a78b-4515-a8be-134b777274d5 | human | null | null | none | abstracts | Difermion condensates in vacuum in 2-4D four-fermion interaction models | null | Theoretical analysis of interplay between the condensates $<\bar{q}q>$ and $<qq>$ in vacuum is generally made by relativistic effective potentials in the mean field approximation in 2D, 3D and 4D models with two flavor and $N_c$ color massless fermions. It is found that in ground states of these models, interplay between the two condensates mainly depend on the ratio $G_S/H_S$ for 2D and 4D case or $G_S/H_P$ for 3D case, where $G_S$, $H_S$ and $H_P$ are respectively the coupling constants in a scalar $(\bar{q}q)$, a scalar $(qq)$ and a pseudoscalar $(qq)$ channel. In ground states of all the models, only pure $<\bar{q}q>$ condensates could exist if $G_S/H_S$ or $G_S/H_P$ is bigger than the critical value $2/N_c$, the ratio of the color numbers of the fermions entering into the condensates $<qq>$ and $<\bar{q}q>$. As $G_S/H_S$ or $G_S/H_P$ decreases to the region below $2/N_c$, differences of the models will manifest themselves. Depending on different models, and also on $N_c$ in 3D m |
95431e26-691a-41e0-9510-b9d7660f8aa7 | 95431e26-691a-41e0-9510-b9d7660f8aa7 | 95431e26-691a-41e0-9510-b9d7660f8aa7 | human | null | null | none | abstracts | Availability assessment of SunOS/Solaris Unix Systems based on Syslogd
and wtmpx logfiles : a case study | null | This paper presents a measurement-based availability assessment study using field data collected during a 4-year period from 373 SunOS/Solaris Unix workstations and servers interconnected through a local area network. We focus on the estimation of machine uptimes, downtimes and availability based on the identification of failures that caused total service loss. Data corresponds to syslogd event logs that contain a large amount of information about the normal activity of the studied systems as well as their behavior in the presence of failures. It is widely recognized that the information contained in such event logs might be incomplete or imperfect. The solution investigated in this paper to address this problem is based on the use of auxiliary sources of data obtained from wtmpx files maintained by the SunOS/Solaris Unix operating system. The results obtained suggest that the combined use of wtmpx and syslogd log files provides more complete information on the state of the target sy |
8b68bc50-3ae0-4f9a-937b-2a1af779a80c | 8b68bc50-3ae0-4f9a-937b-2a1af779a80c | 8b68bc50-3ae0-4f9a-937b-2a1af779a80c | human | null | null | none | abstracts | The Low CO Content of the Extremely Metal Poor Galaxy I Zw 18 | null | We present sensitive molecular line observations of the metal-poor blue compact dwarf I Zw 18 obtained with the IRAM Plateau de Bure interferometer. These data constrain the CO J=1-0 luminosity within our 300 pc (FWHM) beam to be L_CO < 1 \times 10^5 K km s^-1 pc^2 (I_CO < 1 K km s^-1), an order of magnitude lower than previous limits. Although I Zw 18 is starbursting, it has a CO luminosity similar to or less than nearby low-mass irregulars (e.g. NGC 1569, the SMC, and NGC 6822). There is less CO in I Zw 18 relative to its B-band luminosity, HI mass, or star formation rate than in spiral or dwarf starburst galaxies (including the nearby dwarf starburst IC 10). Comparing the star formation rate to our CO upper limit reveals that unless molecular gas forms stars much more efficiently in I Zw 18 than in our own galaxy, it must have a very low CO-to-H_2 ratio, \sim 10^-2 times the Galactic value. We detect 3mm continuum emission, presumably due to thermal dust and free-free emission, to |
edf1996c-bd46-465f-a0a8-903cb5e7995f | edf1996c-bd46-465f-a0a8-903cb5e7995f | edf1996c-bd46-465f-a0a8-903cb5e7995f | human | null | null | none | abstracts | A binary model for the UV-upturn of elliptical galaxies (MNRAS version) | null | The discovery of a flux excess in the far-ultraviolet (UV) spectrum of elliptical galaxies was a major surprise in 1969. While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes, rather than young stars, their origin has remained a mystery. Here we show that these stars most likely lost their envelopes because of binary interactions, similar to the hot subdwarf population in our own Galaxy. We have developed an evolutionary population synthesis model for the far-UV excess of elliptical galaxies based on the binary model developed by Han et al (2002, 2003) for the formation of hot subdwarfs in our Galaxy. Despite its simplicity, it successfully reproduces most of the properties of elliptical galaxies with a UV excess: the range of observed UV excesses, both in $(1550-V)$ and $(2000-V)$, and their evolution with redshift. We also present colour-colour diagrams for use as diagnostic tools in the study of e |
5103f159-3882-4067-9e7d-9d01e2968a08 | 5103f159-3882-4067-9e7d-9d01e2968a08 | 5103f159-3882-4067-9e7d-9d01e2968a08 | human | null | null | none | abstracts | Effect of electron-electron interaction on the phonon-mediated spin
relaxation in quantum dots | null | We estimate the spin relaxation rate due to spin-orbit coupling and acoustic phonon scattering in weakly-confined quantum dots with up to five interacting electrons. The Full Configuration Interaction approach is used to account for the inter-electron repulsion, and Rashba and Dresselhaus spin-orbit couplings are exactly diagonalized. We show that electron-electron interaction strongly affects spin-orbit admixture in the sample. Consequently, relaxation rates strongly depend on the number of carriers confined in the dot. We identify the mechanisms which may lead to improved spin stability in few electron (>2) quantum dots as compared to the usual one and two electron devices. Finally, we discuss recent experiments on triplet-singlet transitions in GaAs dots subject to external magnetic fields. Our simulations are in good agreement with the experimental findings, and support the interpretation of the observed spin relaxation as being due to spin-orbit coupling assisted by acoustic pho |
c1a42b76-3661-4452-b6f8-834fb2697ac4 | c1a42b76-3661-4452-b6f8-834fb2697ac4 | c1a42b76-3661-4452-b6f8-834fb2697ac4 | human | null | null | none | abstracts | Structural relaxation around substitutional Cr3+ in MgAl2O4 | null | The structural environment of substitutional Cr3+ ion in MgAl2O4 spinel has been investigated by Cr K-edge Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) spectroscopies. First-principles computations of the structural relaxation and of the XANES spectrum have been performed, with a good agreement to the experiment. The Cr-O distance is close to that in MgCr2O4, indicating a full relaxation of the first neighbors, and the second shell of Al atoms relaxes partially. These observations demonstrate that Vegard's law is not obeyed in the MgAl2O4-MgCr2O4 solid solution. Despite some angular site distortion, the local D3d symmetry of the B-site of the spinel structure is retained during the substitution of Cr for Al. Here, we show that the relaxation is accomodated by strain-induced bond buckling, with angular tilts of the Mg-centred tetrahedra around the Cr-centred octahedron. By contrast, there is no significant alteration of the angles b |
82bfd112-7b53-48d1-af83-edc4415a4266 | 82bfd112-7b53-48d1-af83-edc4415a4266 | 82bfd112-7b53-48d1-af83-edc4415a4266 | human | null | null | none | abstracts | A Hierarchical Approach for Dependability Analysis of a Commercial
Cache-Based RAID Storage Architecture | null | We present a hierarchical simulation approach for the dependability analysis and evaluation of a highly available commercial cache-based RAID storage system. The archi-tecture is complex and includes several layers of overlap-ping error detection and recovery mechanisms. Three ab-straction levels have been developed to model the cache architecture, cache operations, and error detection and recovery mechanism. The impact of faults and errors oc-curring in the cache and in the disks is analyzed at each level of the hierarchy. A simulation submodel is associated with each abstraction level. The models have been devel-oped using DEPEND, a simulation-based environment for system-level dependability analysis, which provides facili-ties to inject faults into a functional behavior model, to simulate error detection and recovery mechanisms, and to evaluate quantitative measures. Several fault models are defined for each submodel to simulate cache component failures, disk failures, transmissio |
3ebb5590-c4e4-4a64-8f1c-ccd9676f6e60 | 3ebb5590-c4e4-4a64-8f1c-ccd9676f6e60 | 3ebb5590-c4e4-4a64-8f1c-ccd9676f6e60 | human | null | null | none | abstracts | On the Origin of Asymmetries in Bilateral Supernova Remnants | null | AIMS: We investigate whether the morphology of bilateral supernova remnants (BSNRs) observed in the radio band is determined mainly either by a non-uniform interstellar medium (ISM) or by a non-uniform ambient magnetic field. METHODS: We perform 3-D MHD simulations of a spherical SNR shock propagating through a magnetized ISM. Two cases of shock propagation are considered: 1) through a gradient of ambient density with a uniform ambient magnetic field; 2) through a homogeneous medium with a gradient of ambient magnetic field strength. From the simulations, we synthesize the synchrotron radio emission, making different assumptions about the details of acceleration and injection of relativistic electrons. RESULTS: We find that asymmetric BSNRs are produced if the line-of-sight is not aligned with the gradient of ambient plasma density or with the gradient of ambient magnetic field strength. We derive useful parameters to quantify the degree of asymmetry of the remnants that may prov |
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