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1807.02425 | Beamforming in Millimeter Wave Systems: Prototyping and Measurement
Results | Demonstrating the feasibility of large antenna array beamforming is essential
for realizing mmWave communication systems. This is due to the dependency of
these systems on the large array beamforming gains to provide sufficient
received signal power. In this paper, the design of a proof-of-concept
prototype that demonstrates these gains in practice is explained in detail. We
develop a mmWave system with digitally controlled analog front-end. The
developed prototype uses 60 GHz phased arrays and universal software radio
peripheral (USRP) controllers. The software interface of our design is easily
reproducible and can be leveraged for future mmWave prototypes and
demonstrations.
| cs.IT math.IT |
1807.02426 | On the Cauchy Problem for Weyl-Geometric Scalar-Tensor Theories of
Gravity | In this paper, we analyse the well-posedness of the initial value formulation
for particular kinds of geometric scalar-tensor theories of gravity, which are
based on a Weyl integrable space-time. We will show that, within a
frame-invariant interpretation for the theory, the Cauchy problem in vacuum is
well-posed. We will analyse the global in space problem, and, furthermore, we
will show that geometric uniqueness holds for the solutions. We make contact
with Brans-Dicke theory, and by analysing the similarities with such models, we
highlight how some of our results can be translated to this well-known context,
where not all of these problems have been previously addressed.
| gr-qc |
1807.02427 | The mincut graph of a graph | In this paper we introduce an intersection graph of a graph $G$, with vertex
set the minimum edge-cuts of $G$. We find the minimum cut-set graphs of some
well-known families of graphs and show that every graph is a minimum cut-set
graph, henceforth called a \emph{mincut graph}. Furthermore, we show that
non-isomorphic graphs can have isomorphic mincut graphs and ask the question
whether there are sufficient conditions for two graphs to have isomorphic
mincut graphs. We introduce the $r$-intersection number of a graph $G$, the
smallest number of elements we need in $S$ in order to have a family $F=\{S_1,
S_2 \ldots , S_i\}$ of subsets, such that $|S_i|=r$ for each subset. Finally we
investigate the effect of certain graph operations on the mincut graphs of some
families of graphs.
| math.CO |
1807.02428 | Effect of wall thermal inertia upon transient thermoacoustic dynamics of
a swirl-stabilized flame | This paper shows the importance of considering the thermal state of a
combustor to investigate or predict its thermoacoustic stability. This aspect
is often neglected or regarded as less important than the effect of the
operating parameters, such as thermal power or equivalence ratio, but under
certain circumstances it can have a dramatic influence on the development of
the instabilities. The paper presents experimental results collected from a
combustor featuring a lean swirl-stabilized flame exhibiting thermoacoustic
instability at some operating conditions. It is shown that this instability is
caused by a change of the flame topology that is induced by the progressive
increase of the wall temperature with the thermal power. This dependence of the
instability on wall temperature leads to inertial effects and hysteresis when
the operating condition is changed dynamically. A low-order model of the system
reproducing this remarkable dynamics is proposed and validated against the
experimental data.
| physics.flu-dyn |
1807.02429 | Profinite groups in which centralizers are abelian | The article deals with profinite groups in which the centralizers are abelian
(CA-groups), that is, with profinite commutativity-transitive groups. It is
shown that such groups are virtually pronilpotent. More precisely, let G be a
profinite CA-group. It is shown that G has a normal open subgroup N which is
either abelian or pro-p. Further, a rather detailed information about the
finite quotient G/N is obtained.
| math.GR |
1807.02430 | Simply connected indefinite homogeneous spaces of finite volume | Let $M$ be a simply connected pseudo-Riemannian homogeneous space of finite
volume with isometry group $G$. We show that $M$ is compact and that the
solvable radical of $G$ is abelian and the Levi factor is a compact semisimple
Lie group acting transitively on $M$. For metric index less than three, we find
that the isometry group of $M$ is compact itself. Examples demonstrate that $G$
is not necessarily compact for higher indices. To prepare these results, we
study Lie algebras with abelian solvable radical and a nil-invariant symmetric
bilinear form. For these, we derive an orthogonal decomposition into three
distinct types of metric Lie algebras.
| math.DG |
1807.02431 | gen.parRep: a first implementation of the Generalized Parallel Replica
dynamics for the long time simulation of metastable biochemical systems | Metastability is one of the major encountered obstacle when performing long
molecular dynamics simulations, and many methods were developed to address this
challenge. The "Parallel Replica" (ParRep) dynamics is known for allowing to
simulate very long trajectories of metastable Langevin dynamics in the
materials science community, but it relies on assumptions that can hardly be
transposed to the world of biochemical simulations. The later developed
"Generalized ParRep" variant solves those issues, but it was not applied to
significant systems of interest so far.
In this article, we present the program gen.parRep, the first publicly
available implementation of the Generalized Parallel Replica method (BSD
3-Clause license), targeting frequently encountered metastable biochemical
systems, such as conformational equilibria or dissociation of protein-ligand
complexes. It will be shown that the resulting C++ implementation exhibits a
strong linear scalability, providing up to 70 % of the maximum possible speedup
on several hundreds of CPUs.
| physics.chem-ph physics.comp-ph |
1807.02432 | Freeness of Hyperplane Arrangements between Boolean Arrangements and
Weyl Arrangements of Type $ B_{\ell} $ | Every subarrangement of Weyl arrangements of type $ B_{\ell} $ is represented
by a signed graph. Edelman and Reiner characterized freeness of subarrangements
between type $ A_{\ell-1} $ and type $ B_{\ell} $ in terms of graphs. Recently,
Suyama and the authors characterized freeness for subarrangements containing
Boolean arrangements satisfying a certain condition. This article is a sequel
to the previous work. Namely, we give a complete characterization for freeness
of arrangements between Boolean arrangements and Weyl arrangements of type $
B_{\ell} $ in terms of graphs.
| math.CO |
1807.02433 | Implementation of a Volume-of-Fluid Method in a Finite Element Code with
Applications to Thermochemical Convection in a Density Stratified Fluid in
the Earth's Mantle | We describe the implementation of a second-order accurate volume-of-fluid
interface tracking algorithm in the open source finite element code ASPECT,
which is designed to model convection in the Earth's mantle. This involves the
solution of the incompressible Stokes equations coupled to an advection
diffusion equation for the temperature, a Boussinesq approximation that governs
the dependence of the density on the temperature, and an advection equation for
a marker indicating the two initial density states. The volume-of-fluid method
is fully parallelized and is integrated with the adaptive mesh refinement
algorithm in ASPECT. We present the results of several standard interface
tracking benchmarks in order to demonstrate the accuracy of the method as well
as the results of several benchmarks commonly used in the computational mantle
convection community. Finally, we present the results of computations with and
without adaptive mesh refinement of a model problem involving thermochemical
convection in a computationally stratified fluid designed to provide insight
into how thermal plumes, that eventually reach the Earth's surface as ocean
island basalts, originate at structures on the core-mantle boundary known as
Large Low Shear wave Velocity Provinces.
| math.NA |
1807.02434 | Ultrastrong coupling regime of non-dipolar light-matter interactions | We present a circuit-QED scheme which allows to reach the ultrastrong
coupling regime of a nondipolar interaction between a single qubit and a
quantum resonator. We show that the system Hamiltonian is well approximated by
a two-photon quantum Rabi model and propose a simple scattering experiment to
probe its fundamental properties. In particular, we identify a driving scheme
that reveals the change in selection rules characterizing the breakdown of the
rotating-wave approximation and the transition from strong to ultrastrong
two-photon interactions. Finally, we show that a frequency crowding in a narrow
spectral region is observable in the output fluoresce spectrum as the coupling
strength approaches the collapse point, paving the way to the direct
observation of the onset of the spectral collapse in a solid-state device.
| quant-ph cond-mat.mes-hall |
1807.02435 | Precision Charge Control for Isolated Free-Falling Test Masses: LISA
Pathfinder Results | The LISA Pathfinder charge management device was responsible for neutralising
the cosmic ray induced electric charge that inevitably accumulated on the
free-falling test masses at the heart of the experiment. We present
measurements made on ground and in-flight that quantify the performance of this
contactless discharge system which was based on photo-emission under UV
illumination. In addition, a two-part simulation is described that was
developed alongside the hardware. Modelling of the absorbed UV light within the
Pathfinder sensor was carried out with the GEANT4 software toolkit and a
separate MATLAB charge transfer model calculated the net photocurrent between
the test masses and surrounding housing in the presence of AC and DC electric
fields. We confront the results of these models with observations and draw
conclusions for the design of discharge systems for future experiments like
LISA that will also employ free-falling test masses.
| physics.ins-det |
1807.02436 | Disorder perturbed Flat Bands II: a search for criticality | We seek the possibility of a disorder driven transition in a tight-binding
lattice with a flat band using complexity parameter approach. Our results
indicate the existence of a localized to extended states transition with
increasing disorder, insensitive to disorder strength, in weak disorder limit;
the spectral statistics at the critical point corresponds to a critical
Brownian ensemble, a non-equilibrium universality class of random matrix
ensembles, intermediate to Poisson and Gaussian orthogonal ensemble. With
increasing disorder, the statistics again approaches Poisson limit indicating a
localization -> extended -> localization transition of the wave-dynamics. Our
analysis also reveals a hidden connection of weakly disordered flat bands to a
wide-range of other complex systems including standard Anderson Hamiltonian.
| cond-mat.stat-mech |
1807.02437 | Deep Sequential Segmentation of Organs in Volumetric Medical Scans | Segmentation in 3D scans is playing an increasingly important role in current
clinical practice supporting diagnosis, tissue quantification, or treatment
planning. The current 3D approaches based on convolutional neural networks
usually suffer from at least three main issues caused predominantly by
implementation constraints - first, they require resizing the volume to the
lower-resolutional reference dimensions, second, the capacity of such
approaches is very limited due to memory restrictions, and third, all slices of
volumes have to be available at any given training or testing time. We address
these problems by a U-Net-like architecture consisting of bidirectional
convolutional LSTM and convolutional, pooling, upsampling and concatenation
layers enclosed into time-distributed wrappers. Our network can either process
the full volumes in a sequential manner, or segment slabs of slices on demand.
We demonstrate performance of our architecture on vertebrae and liver
segmentation tasks in 3D CT scans.
| cs.CV |
1807.02438 | Towards topological Hochschild homology of Johnson-Wilson spectra | We offer a complete description of $THH(E(2))$ under the assumption that the
Johnson-Wilson spectrum $E(2)$ at a chosen odd prime carries an
$E_\infty$-structure. We also place $THH(E(2))$ in a cofiber sequence $E(2)
\rightarrow THH(E(2))\rightarrow \overline{THH}(E(2))$ and describe
$\overline{THH}(E(2))$ under the assumption that $E(2)$ is an $E_3$-ring
spectrum. We state general results about the $K(i)$-local behaviour of
$THH(E(n))$ for all $n$ and $0 \leq i \leq n$. In particular, we compute
$K(i)_*THH(E(n))$.
| math.AT |
1807.02439 | Nonplanar graphs in boundaries of CAT(0) groups | Croke and Kleiner constructed two homeomorphic locally CAT(0) complexes whose
universal covers have visual boundaries that are not homeomorphic. We construct
two homeomorphic locally CAT(0) complexes so that the visual boundary of one
universal cover contains a nonplanar graph, while the visual boundary of the
other does not. In contrast, we prove for any two locally CAT(0) metrics on the
Croke-Kleiner complex, if a finite graph embeds in the visual boundary of one
universal cover, then the graph embeds in the visual boundary of the other.
| math.GT math.GR |
1807.02440 | Equivalent description of Hom-Lie algebroids | In this paper, we study representations of Hom-Lie algebroids, give some
properties of Hom-Lie algebroids and discuss equivalent statements of Hom-Lie
algebroids. Then, we prove that two known definitions of Hom-Lie algebroids can
be transformed into each other under some conditions.
| math.RA math-ph math.MP |
1807.02441 | Top-Quark Physics at the CLIC Electron-Positron Linear Collider | The Compact Linear Collider (CLIC) is a proposed future high-luminosity
linear electron-positron collider operating at three energy stages, with
nominal centre-of-mass energies: 380 GeV, 1.5 TeV, and 3 TeV. Its aim is to
explore the energy frontier, providing sensitivity to physics beyond the
Standard Model (BSM) and precision measurements of Standard Model processes
with an emphasis on Higgs boson and top-quark physics. The opportunities for
top-quark physics at CLIC are discussed in this paper. The initial stage of
operation focuses on top-quark pair production measurements, as well as the
search for rare flavour-changing neutral current (FCNC) top-quark decays. It
also includes a top-quark pair production threshold scan around 350 GeV which
provides a precise measurement of the top-quark mass in a well-defined
theoretical framework. At the higher-energy stages, studies are made of
top-quark pairs produced in association with other particles. A study of ttH
production including the extraction of the top Yukawa coupling is presented as
well as a study of vector boson fusion (VBF) production, which gives direct
access to high-energy electroweak interactions. Operation above 1 TeV leads to
more highly collimated jet environments where dedicated methods are used to
analyse the jet constituents. These techniques enable studies of the top-quark
pair production, and hence the sensitivity to BSM physics, to be extended to
higher energies. This paper also includes phenomenological interpretations that
may be performed using the results from the extensive top-quark physics
programme at CLIC.
| hep-ex hep-ph |
1807.02442 | Multi-Task Learning with Incomplete Data for Healthcare | Multi-task learning is a type of transfer learning that trains multiple tasks
simultaneously and leverages the shared information between related tasks to
improve the generalization performance. However, missing features in the input
matrix is a much more difficult problem which needs to be carefully addressed.
Removing records with missing values can significantly reduce the sample size,
which is impractical for datasets with large percentage of missing values.
Popular imputation methods often distort the covariance structure of the data,
which causes inaccurate inference. In this paper we propose using plug-in
covariance matrix estimators to tackle the challenge of missing features.
Specifically, we analyze the plug-in estimators under the framework of robust
multi-task learning with LASSO and graph regularization, which captures the
relatedness between tasks via graph regularization. We use the Alzheimer's
disease progression dataset as an example to show how the proposed framework is
effective for prediction and model estimation when missing data is present.
| stat.ML cs.LG |
1807.02443 | Tangent Convolutions for Dense Prediction in 3D | We present an approach to semantic scene analysis using deep convolutional
networks. Our approach is based on tangent convolutions - a new construction
for convolutional networks on 3D data. In contrast to volumetric approaches,
our method operates directly on surface geometry. Crucially, the construction
is applicable to unstructured point clouds and other noisy real-world data. We
show that tangent convolutions can be evaluated efficiently on large-scale
point clouds with millions of points. Using tangent convolutions, we design a
deep fully-convolutional network for semantic segmentation of 3D point clouds,
and apply it to challenging real-world datasets of indoor and outdoor 3D
environments. Experimental results show that the presented approach outperforms
other recent deep network constructions in detailed analysis of large 3D
scenes.
| cs.CV |
1807.02444 | Multi-modal Non-line-of-sight Passive Imaging | We consider the non-line-of-sight (NLOS) imaging of an object using the light
reflected off a diffusive wall. The wall scatters incident light such that a
lens is no longer useful to form an image. Instead, we exploit the 4D spatial
coherence function to reconstruct a 2D projection of the obscured object. The
approach is completely passive in the sense that no control over the light
illuminating the object is assumed and is compatible with the partially
coherent fields ubiquitous in both the indoor and outdoor environments. We
formulate a multi-criteria convex optimization problem for reconstruction,
which fuses the reflected field's intensity and spatial coherence information
at different scales. Our formulation leverages established optics models of
light propagation and scattering and exploits the sparsity common to many
images in different bases. We also develop an algorithm based on the
alternating direction method of multipliers to efficiently solve the convex
program proposed. A means for analyzing the null space of the measurement
matrices is provided as well as a means for weighting the contribution of
individual measurements to the reconstruction. This paper holds promise to
advance passive imaging in the challenging NLOS regimes in which the intensity
does not necessarily retain distinguishable features and provides a framework
for multi-modal information fusion for efficient scene reconstruction.
| cs.CV physics.optics |
1807.02445 | Spin-torque-induced magnetization dynamics in ferrimagnets based on
Landau-Lifshitz-Bloch Equation | A theoretical model based on the Landau-Lifshitz-Bloch equation is developed
to study the spin-torque effect in ferrimagnets. Experimental findings, such as
the temperature dependence, the peak in spin torque, and the angular-momentum
compensation, can be well captured. In contrast to the ferromagnet system, the
switching trajectory in ferrimagnets is found to be precession free. The two
sublattices are not always collinear, which produces large exchange field
affecting the magnetization dynamics. The study of material composition shows
the existence of an oscillation region at intermediate current density, induced
by the nondeterministic switching. Compared to the Landau-Lifshitz-Gilbert
model, our developed model based on the Landau-Lifshitz-Bloch equation enables
the systematic study of spin-torque effect and the evaluation of
ferrimagnet-based devices.
| cond-mat.mtrl-sci |
1807.02446 | The evenness conjecture in equivariant unitary bordism | The evenness conjecture for the equivariant unitary bordism groups states
that these bordism groups are free modules over the unitary bordism ring on
even-dimensional generators. In this paper we review the cases in which the
conjecture is known to hold and we highlight the properties that permit one to
prove the conjecture in these cases.
| math.AT |
1807.02447 | Random band matrices in the delocalized phase, III: Averaging
fluctuations | We consider a general class of symmetric or Hermitian random band matrices
$H=(h_{xy})_{x,y \in \llbracket 1,N\rrbracket^d}$ in any dimension $d\ge 1$,
where the entries are independent, centered random variables with variances
$s_{xy}=\mathbb E|h_{xy}|^2$. We assume that $s_{xy}$ vanishes if $|x-y|$
exceeds the band width $W$, and we are interested in the mesoscopic scale with
$1\ll W\ll N$. Define the {\it{generalized resolvent}} of $H$ as $G(H,Z):=(H -
Z)^{-1}$, where $Z$ is a deterministic diagonal matrix with entries $Z_{xx}\in
\mathbb C_+$ for all $x$. Then we establish a precise high-probability bound on
certain averages of polynomials of the resolvent entries. As an application of
this fluctuation averaging result, we give a self-contained proof for the
delocalization of random band matrices in dimensions $d\ge 2$. More precisely,
for any fixed $d\ge 2$, we prove that the bulk eigenvectors of $H$ are
delocalized in certain averaged sense if $N\le W^{1+\frac{d}{2}}$. This
improves the corresponding results in \cite{HeMa2018} under the assumption
$N\ll W^{1+\frac{d}{d+1}}$, and in \cite{ErdKno2013,ErdKno2011} under the
assumption $N\ll W^{1+\frac{d}{6}}$. For 1D random band matrices, our
fluctuation averaging result was used in \cite{PartII,PartI} to prove the
delocalization conjecture and bulk universality for random band matrices with
$N\ll W^{4/3}$.
| math.PR |
1807.02448 | Stability and metastability of trapless Bose-Einstein condensates and
quantum liquids | Various kinds of Bose-Einstein condensates are considered, which evolve
without any geometric constraints or external trap potentials including
gravitational. For studies of their collective oscillations and stability,
including the metastability and macroscopic tunneling phenomena, both the
variational approach and the Vakhitov-Kolokolov criterion are employed,
calculations are done for condensates of an arbitrary spatial dimension. It is
determined that that the trapless condensate described by the logarithmic wave
equation is essentially stable, regardless of its dimensionality, while the
trapless condensates described by wave equations of a polynomial type with
respect to the wavefunction, such as the Gross-Pitaevskii (cubic),
cubic-quintic, and so on, are at best metastable. This means that trapless
"polynomial" condensates are unstable against spontaneous delocalization caused
by fluctuations of their width, density and energy, leading to a finite
lifetime.
| cond-mat.quant-gas physics.atm-clus physics.flu-dyn |
1807.02449 | A Bayesian Approach to Forced Oscillation Source Location Given
Uncertain Generator Parameters | Since forced oscillations are exogenous to dynamic power system models, the
models by themselves cannot predict when or where a forced oscillation will
occur. Locating the sources of these oscillations, therefore, is a challenging
problem which requires analytical methods capable of using real time power
system data to trace an observed oscillation back to its source. The difficulty
of this problem is exacerbated by the fact that the parameters associated with
a given power system model can range from slightly uncertain to entirely
unknown. In this paper, a Bayesian framework, via a two-stage Maximum A
Posteriori optimization routine, is employed in order to locate the most
probable source of a forced oscillation given an uncertain prior model. The
approach leverages an equivalent circuit representation of the system in the
frequency domain and employs a numerical procedure which makes the problem
suitable for real time application. The derived framework lends itself to
successful performance in the presence of PMU measurement noise, high generator
parameter uncertainty, and multiple forced oscillations occurring
simultaneously. The approach is tested on a 4-bus system with a single forced
oscillation source and on the WECC 179-bus system with multiple oscillation
sources.
| cs.SY |
1807.02450 | Gravitationally produced Top Quarks and the Stability of the Electroweak
Vacuum During Inflation | In the standard model the (Brout-Englert-)Higgs quartic coupling becomes
negative at high energies rendering our current electroweak vacuum metastable,
but with an instability timescale much longer than the age of the Current
Universe. During cosmological Inflation, unless there is a non-minimal coupling
to gravity, the Higgs field is pushed away from the origin of its potential due
to quantum fluctuations. It is therefore a mystery how we have remained in our
current vacuum if we went through such a period of Inflation. In this work we
study the effect of top quarks created gravitationally during Inflation and
their effect upon the Higgs potential using only General Relativity with
minimal couplings and Standard Model particle physics. We show how the
evolution of the Higgs field during Inflation is modified coming to the
conclusion that this effect is non negligible for scales of Inflation close to
or larger than the stability scale but small for scales where the Higgs is
stable. Also, we briefly discuss the effect of other fermions to the Higgs
instability.
| hep-ph gr-qc hep-th |
1807.02451 | Evolution of natural patterns from random fields | In the article a transition from pattern evolution equation of
reaction-diffusion type to a cellular automaton (CA) is described. The
applicability of CA is demonstrated by generating patterns of complex irregular
structure on a hexagonal and quadratic lattice. With this aim a random initial
field is transformed by a sequence of CA actions into a new pattern. On the
hexagonal lattice this pattern resembles a lizard skin. The properties of CA
are specified by the most simple majority rule that adapts selected cell state
to the most frequent state of cells in its surrounding. The method could be of
interest for manufacturing of textiles as well as for modeling of patterns on
skin of various animals.
| cs.GR nlin.CG |
1807.02452 | MRPC3b mass production for CBM-TOF and eTOF at STAR | The Compressed Baryonic Matter (CBM) spectrometer aims to study strongly
interacting matter under extreme conditions. The key element providing hadron
identification at incident energies between 2 and 11 AGeV in heavy-ion
collisions at the SIS100 accelerator is a Time-of-Flight (TOF) wall covering
the polar angular range from $2.5^0$ --$25^0$ and full azimuth. CBM is expected
to be operational in the year 2024 at the Facility for Anti-proton and Ion
Research (FAIR) in Darmstadt, Germany. The existing conceptual design foresees
a 120 m^2 TOF-wall composed of Multi-gap Resistive Plate Chambers (MRPC) which
is subdivided into a high rate region, a middle rate region and a low rate
region. The MRPC3b Multistrip-MRPCs, foreseen to be integrated in the low rate
region, have to cope with charged particle fluxes up to 1 kHz/cm2 and therefore
will be constructed with thin float glass (0.28 mm thickness) as resistive
electrode material. In the scope of the FAIR phase 0 program it is planned to
install about 36 \% of the MRPC3b counters in the east endcap region of the
STAR experiment at BNL as an upgrade for the Beam Energy Scan campaign (BESII)
in 2019/2020.
| physics.ins-det |
1807.02453 | Stein's method and Papangelou intensity for Poisson or Cox process
approximation | In this paper, we apply the Stein's method in the context of point processes,
namely when the target measure is the distribution of a finite Poisson point
process. We show that the so-called Kantorovich-Rubinstein distance between
such a measure and another finite point process is bounded by the
$L^1$-distance between their respective Papangelou intensities. Then, we deduce
some convergence rates for sequences of point processes approaching a Poisson
or a Cox point process.
| math.PR |
1807.02454 | Rationality and p-adic properties of reduced forms of half-integral
weight | In this paper we study special bases of certain spaces of half-integral
weight weakly holomorphic modular forms. We establish a criterion for the
integrality of Fourier coefficients of such bases. By using recursive relations
between Hecke operators, we derive relations of Fourier coefficients of each
basis element and obtain congruences of the Fourier coefficients, which extend
known congruences for traces of singular moduli.
| math.NT |
1807.02455 | On the non-existence of local Birkhoff coordinates for the focusing NLS
equation | We prove that there exist potentials so that near them the focusing
non-linear Schr\"odinger equation does not admit local Birkhoff coordinates.
The proof is based on the construction of a local normal form of the
linearization of the equation at such potentials.
| math.AP |
1807.02456 | A retrospective look at Regge poles | The theoretical motivations that led Tullio Regge to investigate the
analytical properties of the scattering amplitude of the collision process
between two particles in terms of complex energy and complex angular momentum
are briefly reviewed and set in the context of the S-matrix theory that was
developed in the late Fifties and early Sixties of the last century, in an
attempt to unravel the properties of the strong interaction.
| physics.hist-ph hep-ph hep-th |
1807.02457 | Few-electron atomic ions in non-relativistic QED: the Ground state
energy | Following detailed analysis of relativistic, QED and mass corrections for
helium-like and lithium-like ions with static nuclei for $Z \leq 20$ the domain
of applicability of Non-Relativistic QED (NRQED) is localized for ground state
energy. It is demonstrated that for both helium-like and lithium-like ions with
$Z \leq 20$ the finite nuclear mass effects do not change 4-5 significant
digits (s.d.), and the leading relativistic and QED effects leave unchanged 3-4
s.d. in the ground state energy. It is shown that the non-relativistic ground
state energy can be interpolated with accuracy not less than 13 s.d. for $Z
\leq 12$, and not less than 12 s.d. for $Z \leq 50$ for helium-like as well as
for $Z \leq 20$ for lithium-like ions by a compact meromorphic function in
${\lambda}=\sqrt{Z-{Z_B}}$ ($Z_B$ is the 2nd critical charge, see {TLO:2016}),
$P_9(\lambda)/Q_5(\lambda)$. It is found that the Majorana formula - a second
degree polynomial in $Z$ with two free parameters - and a fourth degree
polynomial in ${\lambda}$ (a generalization of the Majorana formula) reproduce
the ground state energy of the helium-like and lithium-like ions for $Z \leq
20$ in the domain of applicability of NRQED, thus, at least, 3 s.d. It is noted
that $\gtrsim 99.9\%$ of the ground state energy is given by the variational
energy for properly optimized trial function of the form of (anti)-symmetrized
product of three (six) screened Coulomb orbitals for two-(three) electron
system with 3 (7) free parameters for $Z \leq 20$, respectively. It may imply
that these trial functions are, in fact, {\it exact} wavefunctions in
non-relativistic QED, thus, the NRQED effective potential can be derived. It is
shown that the sum of relativistic and QED effects in leading approximation - 3
s.d. - for both 2 and 3 electron systems is interpolated by 4th degree
polynomial in $Z$ for $Z \leq 20$.
| physics.atom-ph quant-ph |
1807.02458 | A Practical Approach to the Automatic Classification of
Security-Relevant Commits | The lack of reliable sources of detailed information on the vulnerabilities
of open-source software (OSS) components is a major obstacle to maintaining a
secure software supply chain and an effective vulnerability management process.
Standard sources of advisories and vulnerability data, such as the National
Vulnerability Database (NVD), are known to suffer from poor coverage and
inconsistent quality.
To reduce our dependency on these sources, we propose an approach that uses
machine-learning to analyze source code repositories and to automatically
identify commits that are security-relevant (i.e., that are likely to fix a
vulnerability). We treat the source code changes introduced by commits as
documents written in natural language, classifying them using standard document
classification methods.
Combining independent classifiers that use information from different facets
of commits, our method can yield high precision (80%) while ensuring acceptable
recall (43%). In particular, the use of information extracted from the source
code changes yields a substantial improvement over the best known approach in
state of the art, while requiring a significantly smaller amount of training
data and employing a simpler architecture.
| cs.CR |
1807.02459 | Discrete Scale Invariance in Topological Semimetals | The discovery of Weyl and Dirac semimetals has produced a number of dramatic
physical effects, including the chiral anomaly and topological Fermi arc
surface states. We point out that a very different but no less dramatic
physical effect is also to be found in these materials: discrete scale
invariance. This invariance leads to bound state spectra for Coulomb impurities
that repeat when the binding energy is changed by a fixed factor, reminiscent
of fractal behavior. We show that this effect follows from the peculiar
dispersion relation in Weyl and Dirac semimetals. It is observed when such a
material is placed in very strong magnetic field B: there are oscillations in
the magnetoresistivity somewhat similar to Shubnikov-de Haas oscillations but
with a periodicity in ln B rather than 1/B. These oscillations should be
present in other thermodynamic and transport properties. The oscillations have
now been seen in three topological semimetals: ZrTe$_{5}$, TaAs, and Bi.
| cond-mat.mtrl-sci |
1807.02460 | $P$-partitions and $p$-positivity | Using the combinatorics of $\alpha$-unimodal sets, we establish two new
results in the theory of quasisymmetric functions. First, we obtain the
expansion of the fundamental basis into quasisymmetric power sums. Secondly, we
prove that generating functions of reverse $P$-partitions expand positively
into quasisymmetric power sums. Consequently any nonnegative linear combination
of such functions is $p$-positive whenever it is symmetric. As an application
we derive positivity results for chromatic quasisymmetric functions,
unicellular and vertical strip LLT polynomials, multivariate Tutte polynomials
and the more general $B$-polynomials, matroid quasisymmetric functions, and
certain Eulerian quasisymmetric functions, thus reproving and improving on
numerous results in the literature.
| math.CO |
1807.02461 | Quantum Mechanics of the Interior of the Russo-Susskind-Thorlacius Black
Hole | We study the quantum mechanics of homogeneous black hole interiors in the RST
model of 2D gravity. The model, which contains a dilaton and metric, includes
radiation back-reaction terms and is exactly solvable classically. The reduced
phase space is four dimensional. The equations for one pair of variables can be
trivially solved. The dynamics of the remaining degree of freedom, namely the
dilaton, is more interesting and corresponds to that of a particle on the half
line in a linear potential with time dependent coupling. We construct the
self-adjoint extension of the corresponding quantized Hamiltonian and
numerically solve the time dependent Schr$\ddot{\mbox{o}}$dinger equation for
Gaussian initial data. As expected the singularity is resolved and the
expectation value of the dilaton oscillates between a minimum and maximum,
which both gradually decrease with time due to the time dependence in the
potential. In the classical black hole spacetime, the maximum value of the
dilaton corresponds to the size of the horizon while the minimum is the
singularity. The quantum dynamics, therefore, corresponds at the semi-classical
level to an evaporating black hole. The rate of quantum fluctuations increases
as the system evolves but intriguingly, at longer times the expectation value
of the radius undergoes "revivals" in which the amplitude of oscillations
between minimum and maximum temporarily increases. These revivals are also
characteristic of the quantum dynamics of the {\it time independent} quantum
linear potential.
| gr-qc |
1807.02462 | Instabilities in a combustion model with two free interfaces | We study in a strip of $\mathbb R^2$ a combustion model of flame propagation
with stepwise temperature kinetics and zero-order reaction, characterized by
two free interfaces, respectively the ignition and the trailing fronts. The
latter interface presents an additional difficulty because the non-degeneracy
condition is not met. We turn the system to a fully nonlinear problem which is
thoroughly investigated. When the width $\ell$ of the strip is sufficiently
large, we prove the existence of a critical value $Le_c$ of the Lewis number
$Le$, such that the one-dimensional, planar, solution is unstable for
$0<Le<Le_c$. Some numerical simulations confirm the analysis.
| math.AP |
1807.02463 | Giant planet effects on terrestrial planet formation and system
architecture | The giant planets of the solar system likely played a large role in shaping
the architecture of the terrestrial planets. Using an updated collision model,
we conduct a suite of high resolution N-body integrations to probe the
relationship between giant planet mass, and terrestrial planet formation and
system architecture. We vary the mass of the planets that reside at Jupiter's
and Saturn's orbit and examine the effects on the interior terrestrial system.
We find a correlation between the mass of the exterior giant planets and the
collision history of the resulting planets, which holds implications for the
planet's properties. More massive giants also produce terrestrial planets that
are on smaller, more circular orbits. We do not find a strong correlation
between exterior giant planet mass and the number of Earth-analogs (analogous
in mass and semi-major axis) produced in the system. These results allow us to
make predictions on the nature of terrestrial planets orbiting distant Sun-like
star systems that harbor giant planet companions on long orbits---systems which
will be a priority for NASA's upcoming Wide-Field Infrared Space Telescope
(WFIRST) mission.
| astro-ph.EP |
1807.02464 | Optimal sustainable harvesting of populations in random environments | We study the optimal sustainable harvesting of a population that lives in a
random environment. The novelty of our setting is that we maximize the
asymptotic harvesting yield, both in an expected value and almost sure sense,
for a large class of harvesting strategies and unstructured population models.
We prove under relatively weak assumptions that there exists a unique optimal
harvesting strategy characterized by an optimal threshold below which the
population is maintained at all times by utilizing a local time push-type
policy. We also discuss, through Abelian limits, how our results are related to
the optimal harvesting strategies when one maximizes the expected cumulative
present value of the harvesting yield and establish a simple connection and
ordering between the values and optimal boundaries. Finally, we explicitly
characterize the optimal harvesting strategies in two different cases, one of
which is the celebrated stochastic Verhulst Pearl logistic model of population
growth.
| math.PR q-bio.PE |
1807.02465 | Tone Recognition Using Lifters and CTC | In this paper, we present a new method for recognizing tones in continuous
speech for tonal languages. The method works by converting the speech signal to
a cepstrogram, extracting a sequence of cepstral features using a convolutional
neural network, and predicting the underlying sequence of tones using a
connectionist temporal classification (CTC) network. The performance of the
proposed method is evaluated on a freely available Mandarin Chinese speech
corpus, AISHELL-1, and is shown to outperform the existing techniques in the
literature in terms of tone error rate (TER).
| eess.AS cs.SD |
1807.02466 | A polynomial automorphism with a wandering Fatou component | We construct polynomial automorphisms with wandering Fatou components. The
four-dimensional automorphisms $H$ lie in a one-parameter family, depending on
the parameter $\delta \in \mathbb C \setminus \{0\}$, and as $\delta
\rightarrow 0$ the automorphisms degenerate to the two-dimensional polynomial
map $P$ constructed in Astorg et al (Ann. of Math., 2016). Our main result
states that if $P$ has a wandering domain, then $H$ does too for $\delta$
sufficiently small.
| math.DS |
1807.02467 | Error-mitigated digital quantum simulation | Variational algorithms may enable classically intractable simulations on
near-future quantum computers. However, their potential is limited by hardware
errors. It is therefore crucial to develop efficient ways to mitigate these
errors. Here, we propose a stabiliser-like method which enables the detection
of up to 60 - 80 % of depolarising errors. Our method is suitable for near-term
quantum hardware. Simulations show that our method can significantly benefit
calculations subject to both stochastic and correlated noise, especially when
combined with existing error mitigation techniques.
| quant-ph |
1807.02468 | Interpretable machine learning for inferring the phase boundaries in a
nonequilibrium system | Still under debate is the question of whether machine learning is capable of
going beyond black-box modeling for complex physical systems. We investigate
the generalizing and interpretability properties of learning algorithms. To
this end, we use supervised and unsupervised learning to infer the phase
boundaries of the active Ising model, starting from an ensemble of
configurations of the system. We illustrate that unsupervised learning
techniques are powerful at identifying the phase boundaries in the control
parameter space, even in situations of phase coexistence. It is demonstrated
that supervised learning with neural networks is capable of learning the
characteristics of the phase diagram, such that the knowledge obtained at a
limited set of control variables can be used to determine the phase boundaries
across the phase diagram. In this way, we show that properly designed
supervised learning provides predictive power to regions in the phase diagram
that are not included in the training phase of the algorithm. We stress the
importance of introducing interpretability methods in order to perform a
physically relevant classification of the phases with deep learning.
| cond-mat.stat-mech |
1807.02469 | Astrometric Detection of Intermediate-Mass Black Holes At the Galactic
Centre | We assess the astrometric detectability of intermediate-mass black holes
populating the inner parsec of the Milky Way Galaxy. The presence of these
objects induces dynamical effects on Sgr A* and the star S2, which could be
detected by next generation astrometric instruments that enable micro-arcsecond
astrometry. An allowed population of ten $10^4~M_{\odot}$ IMBHs within one
parsec induces an angular shift of about 65 $\mu$as yr$^{-1}$ on the position
of Sgr A*, corresponding to a perpendicular velocity component magnitude of 1.6
km s$^{-1}$. It also induces changes in the orbit of S2 that surpass those
induced by general relativity but lie within observational constraints,
generating a mean angular shift in periapse and apoapse of 62 $\mu$as and 970
$\mu$as respectively.
| astro-ph.GA |
1807.02470 | Cluster-void degeneracy breaking: Neutrino properties and dark energy | Future large-scale spectroscopic astronomical surveys, e.g. Euclid, will
enable the compilation of vast new catalogues of clusters and voids in the
galaxy distribution. By combining the constraining power of both cluster and
void number counts, such surveys could place stringent simultaneous limits on
the sum of neutrino masses $M_\nu$ and the dark energy equation of state $w(z)
= w_0 + w_a z/(1+z)$. For minimal normal-hierarchy neutrino masses, we forecast
that Euclid clusters + voids ideally could reach uncertainties $\sigma(M_\nu)
\lesssim 15$ meV, $\sigma(w_0) \lesssim~0.02$, $\sigma(w_a) \lesssim 0.07$,
independent of other data. Such precision is competitive with expectations for
e.g. galaxy clustering and weak lensing in future cosmological surveys, and
could reject an inverted neutrino mass hierarchy at $\gtrsim 99\%$ confidence.
| astro-ph.CO hep-ex hep-th |
1807.02471 | A Review of Different Word Embeddings for Sentiment Classification using
Deep Learning | The web is loaded with textual content, and Natural Language Processing is a
standout amongst the most vital fields in Machine Learning. But when data is
huge simple Machine Learning algorithms are not able to handle it and that is
when Deep Learning comes into play which based on Neural Networks. However
since neural networks cannot process raw text, we have to change over them
through some diverse strategies of word embedding. This paper demonstrates
those distinctive word embedding strategies implemented on an Amazon Review
Dataset, which has two sentiments to be classified: Happy and Unhappy based on
numerous customer reviews. Moreover we demonstrate the distinction in accuracy
with a discourse about which word embedding to apply when.
| cs.IR cs.CL cs.LG stat.ML |
1807.02472 | Typical Phone Use Habits: Intense Use Does Not Predict Negative
Well-Being | Not all smartphone owners use their device in the same way. In this work, we
uncover broad, latent patterns of mobile phone use behavior. We conducted a
study where, via a dedicated logging app, we collected daily mobile phone
activity data from a sample of 340 participants for a period of four weeks.
Through an unsupervised learning approach and a methodologically rigorous
analysis, we reveal five generic phone use profiles which describe at least 10%
of the participants each: limited use, business use, power use, and
personality- & externally induced problematic use. We provide evidence that
intense mobile phone use alone does not predict negative well-being. Instead,
our approach automatically revealed two groups with tendencies for lower
well-being, which are characterized by nightly phone use sessions.
| cs.HC |
1807.02473 | Self-Similar Approach for Rotating Magnetohydrodynamic Solar and
Astrophysical Structures | Rotating magnetic structures are common in astrophysics, from vortex tubes
and tornados in the Sun all the way to jets in different astrophysical systems.
The physics of these objects often combine inertial, magnetic, gas pressure and
gravitational terms. Also, they often show approximate symmetries that help
simplify the otherwise rather intractable equations governing their morphology
and evolution. Here we propose a general formulation of the equations assuming
axisymmetry and a self-similar form for all variables: in spherical coordinates
$(r,\theta,\phi)$, the magnetic field and plasma velocity are taken to be of
the form: ${\bf B}={\bf f}(\theta)/r^n$ and
${\bf v}={\bf g}(\theta)/r^m$, with corresponding expressions for the scalar
variables like pressure and density. Solutions are obtained for potential,
force-free, and non-force-free magnetic configurations. Potential-field
solutions can be found for all values of~$n$. Non-potential force-free
solutions possess an azimuthal component $B_\phi$ and exist only for $n\ge2$;
the resulting structures are twisted and have closed field lines but are not
collimated around the system axis. In the non-force free case, including gas
pressure, the magnetic field lines acquire an additional curvature to
compensate for an outward pointing pressure gradient force. We have also
considered a pure rotation situation with no gravity, in the zero-$\beta$
limit: the solution has cylindrical geometry and twisted magnetic field lines.
The latter solutions can be helpful in producing a collimated magnetic field
structure; but they exist only when $n<0$ and $m<0$: for applications they must
be matched to an external system at a finite distance from the origin.
| astro-ph.SR |
1807.02474 | Close evaluation of layer potentials in three dimensions | We present a simple and effective method for evaluating double-and
single-layer potentials for Laplace's equation in three dimensions close to the
boundary. The close evaluation of these layer potentials is challenging because
they are nearly singular integrals. The method we propose is based on writing
these layer potentials in spherical coordinates where the point at which their
kernels are peaked maps to the north pole. An N-point Gauss-Legendre quadrature
rule is used for integration with respect to the the polar angle rather than
the cosine of the polar angle. A 2N-point periodic trapezoid rule is used to
compute the integral with respect to the azimuthal angle which acts as a
natural and effective averaging operation in this coordinate system. The
numerical method resulting from combining these two quadrature rules in this
rotated coordinate system yields results that are consistent with asymptotic
behaviors of the double- and single-layer potentials at close evaluation
distances. In particular, we show that the error in computing the double-layer
potential, after applying a subtraction method, is quadratic with respect to
the evaluation distance from the boundary, and the error is linear for the
single-layer potential. We improve upon the single-layer potential by
introducing an alternate approximation based on a perturbation expansion and
obtain an error that is quadratic with respect to the evaluation distance from
the boundary.
| math.NA cs.NA |
1807.02475 | ${\tilde{J}}$-pseudospin states and the crystal field of cubic systems | Theory of $\tilde{J}$-pseudospin for $f$ element in cubic environment is
developed. By fulfilling the symmetry requirements and the adiabatic connection
to atomic limit, the crystal-field states are uniquely transformed into
$\tilde{J}$-pseudospin states. In terms of the pseudospin operators, both the
total angular momentum and the crystal-field Hamiltonian contain higher-rank
tensor terms than the traditional ones do, which means the present framework
naturally include the effects such as the covalency and $J$-mixing beyond the
$f$-shell model. Combining the developed theory with {\it ab initio}
calculations, the $\tilde{J}$-pseudospin states for Nd$^{3+}$ and Np$^{4+}$
ions in octahedral sites of insulators are derived.
| cond-mat.str-el cond-mat.mtrl-sci physics.chem-ph |
1807.02476 | An Alternative Explicit Expression of the Kernel of the One Dimensional
Heat Equation with Dirichlet Conditions | This paper is devoted to the study of the one dimensional non homogeneous
heat equation coupled to Dirichlet Boundary Conditions.
We obtain the explicit expression of the solution of the linear equation by
means of a direct integral in an unbounded domain. The main novelty of this
expression relies in the fact that the solution is not given as a series of
infinity terms. On our expression the solution is given as a sum of two
integrals with a finite number of terms on the kernel.
The main novelty is that, on the contrary to the classical method, where the
solutions are derived by a direct application of the separation of variables
method, on the basis of the spectral theory and the Fourier Series expansion,
the solution is obtained by means of the application of the Laplace Transform
with respect to the time variable. As a consequence, for any $t \ge 0$ fixed,
we must solve an Ordinary Differential Equation on the spatial variable,
coupled to Dirichlet Boundary conditions. The solution of such a problem is
given by the construction of the related Green's function.
| math.AP |
1807.02477 | Development of a sensory-neural network for medical diagnosing | Performance of a sensory-neural network developed for diagnosing of diseases
is described. Information about patient's condition is provided by answers to
the questionnaire. Questions correspond to sensors generating signals when
patients acknowledge symptoms. These signals excite neurons in which
characteristics of the diseases are represented by synaptic weights associated
with indicators of symptoms. The disease corresponding to the most excited
neuron is proposed as the result of diagnosing. Its reliability is estimated by
the likelihood defined by the ratio of excitation of the most excited neuron
and the complete neural network.
| cs.NE |
1807.02478 | CAIL2018: A Large-Scale Legal Dataset for Judgment Prediction | In this paper, we introduce the \textbf{C}hinese \textbf{AI} and \textbf{L}aw
challenge dataset (CAIL2018), the first large-scale Chinese legal dataset for
judgment prediction. \dataset contains more than $2.6$ million criminal cases
published by the Supreme People's Court of China, which are several times
larger than other datasets in existing works on judgment prediction. Moreover,
the annotations of judgment results are more detailed and rich. It consists of
applicable law articles, charges, and prison terms, which are expected to be
inferred according to the fact descriptions of cases. For comparison, we
implement several conventional text classification baselines for judgment
prediction and experimental results show that it is still a challenge for
current models to predict the judgment results of legal cases, especially on
prison terms. To help the researchers make improvements on legal judgment
prediction, both \dataset and baselines will be released after the CAIL
competition\footnote{http://cail.cipsc.org.cn/}.
| cs.CL |
1807.02479 | A metric model for the functional architecture of the visual cortex | The purpose of this work is to construct a model for the functional
architecture of the primary visual cortex (V1), based on a structure of metric
measure space induced by the underlying organization of receptive profiles
(RPs) of visual cells. In order to account for the horizontal connectivity of
V1 in such a context, a diffusion process compatible with the geometry of the
space is defined following the classical approach of K.-T. Sturm. The
construction of our distance function does neither require any group
parameterization of the family of RPs, nor involve any differential structure.
As such, it adapts to non-parameterized sets of RPs, possibly obtained through
numerical procedures; it also allows to model the lateral connectivity arising
from non-differential metrics such as the one induced on a pinwheel surface by
a family of filters of vanishing scale. On the other hand, when applied to the
classical framework of Gabor filters, this construction yields a distance
approximating the sub-Riemannian structure proposed as a model for V1 by G.
Citti and A. Sarti [J Math Imaging Vis 24: 307 (2006)], thus showing itself to
be consistent with existing cortex models.
| math.MG q-bio.NC |
1807.02480 | A Fully Convolutional Two-Stream Fusion Network for Interactive Image
Segmentation | In this paper, we propose a novel fully convolutional two-stream fusion
network (FCTSFN) for interactive image segmentation. The proposed network
includes two sub-networks: a two-stream late fusion network (TSLFN) that
predicts the foreground at a reduced resolution, and a multi-scale refining
network (MSRN) that refines the foreground at full resolution. The TSLFN
includes two distinct deep streams followed by a fusion network. The intuition
is that, since user interactions are more direct information on
foreground/background than the image itself, the two-stream structure of the
TSLFN reduces the number of layers between the pure user interaction features
and the network output, allowing the user interactions to have a more direct
impact on the segmentation result. The MSRN fuses the features from different
layers of TSLFN with different scales, in order to seek the local to global
information on the foreground to refine the segmentation result at full
resolution. We conduct comprehensive experiments on four benchmark datasets.
The results show that the proposed network achieves competitive performance
compared to current state-of-the-art interactive image segmentation methods
| cs.CV |
1807.02481 | Design of Low-Complexity Convolutional Codes over GF(q) | This paper proposes a new family of recursive systematic convolutional codes,
defined in the non-binary domain over different Galois fields GF(q) and
intended to be used as component codes for the design of non-binary turbo
codes. A general framework for the design of the best codes over different
GF(q) is described. The designed codes offer better performance than the
non-binary convolutional codes found in the literature. They also outperform
their binary counterparts when combined with their corresponding QAM modulation
or with lower order modulations.
| cs.IT math.IT |
1807.02482 | Weak solutions to the quaternionic Monge-Amp\`ere equation | We solve the Dirichlet problem for the quaternionic Monge-Amp\`ere equation
with a continuous boundary data and the right hand side in $L^p$ for $p>2$.
This is the optimal bound on $p$. We prove also that the local integrability
exponent of quaternionic plurisubharmonic functions is two which turns out to
be less than an integrability exponent of the fundamental solution.
| math.CV math.AP |
1807.02483 | Minimizing the bias in exoplanet detection - application to radial
velocities of LHS 1140 | A rocky planet orbiting LHS 1140 with a period of 24.7d has been found based
on the discovery of transits in its light and high precision radial velocity
data (Dittmann et al. 2017). This discovery by two independent methods is an
observational tour-de-force, however, we find that a conservative analysis of
the data gives a different solution. A three planet system is apparent in the
radial velocity data based on our diagnosis of stellar activity. We encourage
further targeted photometric and radial velocity observations in order to
constrain the mini-Neptune and super-Earth mass objects apparently causing the
3.8 and 90 day radial velocity signals. We use our package Agatha
(https://phillippro.shinyapps.io/Agatha/) to provide a comprehensive strategy
to disentangle planetary signals from stellar activity in radial velocity data.
| astro-ph.EP |
1807.02484 | Quadratic estimator for CMB cross-correlation | The Quadratic Maximum Likelihood estimator can be used to reconstruct the
Cosmic Microwave Background (CMB) power spectra with minimal error bars. Still,
it requires an accurate estimate of the datasets noise covariance matrix in
order to be corrected for spurious bias. We describe an extension of this
method to cross-correlation, thus removing noise bias and mitigating the impact
of systematic effects, providing they are uncorrelated. This estimator is
tested on two simulation surveys at large and intermediate angular scales,
respectively corresponding to satellite and ground-based CMB experiments. The
analysis focuses on polarization maps, over a wide range of noise levels from
0.1 to 50 muK.arcmin. We show how this estimator minimizes the increase of
variance due to polarization leakage between E and B modes. We compare this
method with the pure pseudo-spectrum formalism which is computationally faster
but less optimal, especially on large angular scales.
| astro-ph.CO |
1807.02485 | Deployment Strategies of Multiple Aerial BSs for User Coverage and Power
Efficiency Maximization | Unmanned aerial vehicle (UAV) based aerial base stations (BSs) can provide
rapid communication services to ground users and are thus promising for future
communication systems. In this paper, we consider a scenario where no
functional terrestrial BSs are available and the aim is deploying multiple
aerial BSs to cover a maximum number of users within a certain target area. To
this end, we first propose a naive successive deployment method, which converts
the non-convex constraints in the involved optimization into a combination of
linear constraints through geometrical relaxation. Then we investigate a
deployment method based on K-means clustering. The method divides the target
area into K convex subareas, where within each subarea, a mixed integer
non-linear problem (MINLP) is solved. An iterative power efficient technique is
further proposed to improve coverage probability with reduced power. Finally,
we propose a robust technique for compensating the loss of coverage probability
in the existence of inaccurate user location information (ULI). Our simulation
results show that, the proposed techniques achieve an up to 30% higher coverage
probability when users are not distributed uniformly. In addition, the proposed
simultaneous deployment techniques, especially the one using iterative
algorithm improve power-efficiency by up to 15% compared to the benchmark
circle packing theory.
| eess.SP |
1807.02486 | Gravity as Gauge Theory Squared: A Ghost Story | The Becchi-Rouet-Stora-Tyutin (BRST) transformations and equations of motion
of a gravity-two-form-dilaton system are derived from the product of two
Yang-Mills theories in a BRST covariant form, to linear approximation. The
inclusion of ghost fields facilitates the separation of the graviton and
dilaton. The gravitational gauge fixing term is uniquely determined by those of
the Yang-Mills factors which can be freely chosen. Moreover, the resulting
gravity-two-form-dilaton Lagrangian is anti-BRST invariant and the BRST and
anti-BRST charges anti commute as a direct consequence of the formalism.
| hep-th gr-qc |
1807.02487 | Single-shot energetic-based estimator for entanglement in a half-parity
measurement setup | Producing and certifying entanglement between distant qubits is a highly
desirable skill for quantum information technologies. Here we propose a new
strategy to monitor and characterize entanglement genesis in a half parity
measurement setup, that relies on the continuous readout of an energetic
observable which is the half-parity observable itself. Based on a
quantum-trajectory approach, we theoretically analyze the statistics of
energetic fluctuations for a pair of continuously monitored qubits. We
quantitatively relate these energetic fluctuations to the rate of entanglement
produced between the qubits, and build an energetic-based estimator to assess
the presence of entanglement in the circuit. Remarkably, this estimator is
valid at the single-trajectory level and shows to be robust against finite
detection efficiency. Our work paves the road towards a fundamental
understanding of the stochastic energetic processes associated with
entanglement genesis, and opens new perspectives for witnessing quantum
correlations thanks to quantum thermodynamic quantities.
| quant-ph |
1807.02488 | Enabling Covariance-Based Feedback in Massive MIMO: A User
Classification Approach | In this paper, we propose a novel channel feedback scheme for frequency
division duplexing massive multi-input multi-output systems. The concept uses
the notion of user statistical separability which was hinted in several prior
works in the massive antenna regime but not fully exploited so far. We here
propose a hybrid statistical-instantaneous feedback scheme based on a user
classification mechanism where the classification metric derives from a rate
bound analysis. According to classification results, a user either operates on
a statistical feedback mode or instantaneous mode. Our results illustrate the
sum rate advantages of our scheme under a global feedback overhead constraint.
| cs.IT math.IT |
1807.02489 | Parity-mixing superconducting phase in the Rashba-Hubbard model and its
topological properties from dynamical mean field theory | We investigate parity-mixing superconductivity in the two-dimensional Hubbard
model with Rashba spin-orbit coupling, using Cellular Dynamical Mean-Field
Theory (CDMFT). A superconducting state with mixed singlet $d$-wave and triplet
$p$-wave character is found in a wide range of doping. The singlet component
decreases with the amplitude of the Rashba spin-orbit coupling, whereas the
triplet component increases, but both disappear at about 20\% doping. The
effect of a Zeeman field is also investigated; it tends to suppress both types
of superconductivity, but induces nontrivial topological properties: the
computed bulk Chern number is nonzero in the mixed superconductivity phase, at
least in the underdoped region. A strong suppression of the excitation gap
occurs slightly after optimal doping; this might be the sign of a topological
transition within the superconducting dome.
| cond-mat.supr-con |
1807.02490 | Deep Multiple Instance Feature Learning via Variational Autoencoder | We describe a novel weakly supervised deep learning framework that combines
both the discriminative and generative models to learn meaningful
representation in the multiple instance learning (MIL) setting. MIL is a weakly
supervised learning problem where labels are associated with groups of
instances (referred as bags) instead of individual instances. To address the
essential challenge in MIL problems raised from the uncertainty of positive
instances label, we use a discriminative model regularized by variational
autoencoders (VAEs) to maximize the differences between latent representations
of all instances and negative instances. As a result, the hidden layer of the
variational autoencoder learns meaningful representation. This representation
can effectively be used for MIL problems as illustrated by better performance
on the standard benchmark datasets comparing to the state-of-the-art
approaches. More importantly, unlike most related studies, the proposed
framework can be easily scaled to large dataset problems, as illustrated by the
audio event detection and segmentation task. Visualization also confirms the
effectiveness of the latent representation in discriminating positive and
negative classes.
| cs.LG cs.AI stat.ML |
1807.02491 | Koszulity of finitely semi-graded algebras | In this paper, we introduce the class of finitely semi-graded algebras which
extends the connected graded algebras finitely generated in degree one. The
Koszul behavior of finitely semi-graded algebras is investigated by the
distributivity of some associated lattice of ideals. The Hilbert series, the
Poincar\'e series and the Yoneda algebra are defined for this class of
algebras. Finitely semi-graded algebras include many important examples of non
$\mathbb{N}$-graded algebras finitely generated in degree one coming from
mathematical physics, and for these concrete examples the Koszulity will be
established, as well as, the explicit computation of its Hilbert and Poincar\'e
series.
| math.RA |
1807.02492 | Dynamic Load Balancing for Compressible Multiphase Turbulence | CMT-nek is a new scientific application for performing high fidelity
predictive simulations of particle laden explosively dispersed turbulent flows.
CMT-nek involves detailed simulations, is compute intensive and is targeted to
be deployed on exascale platforms. The moving particles are the main source of
load imbalance as the application is executed on parallel processors. In a
demonstration problem, all the particles are initially in a closed container
until a detonation occurs and the particles move apart. If all processors get
an equal share of the fluid domain, then only some of the processors get
sections of the domain that are initially laden with particles, leading to
disparate load on the processors. In order to eliminate load imbalance in
different processors and to speedup the makespan, we present different load
balancing algorithms for CMT-nek on large scale multi-core platforms consisting
of hundred of thousands of cores. The detailed process of the load balancing
algorithms are presented. The performance of the different load balancing
algorithms are compared and the associated overheads are analyzed. Evaluations
on the application with and without load balancing are conducted and these show
that with load balancing, simulation time becomes faster by a factor of up to
$9.97$.
| cs.DC |
1807.02493 | Characterization theorems for the spaces of derivations of evolution
algebras associated to graphs | It is well-known that the space of derivations of $n$-dimensional evolution
algebras with non-singular matrices is zero. On the other hand, the space of
derivations of evolution algebras with matrices of rank $n-1$ has also been
completely described in the literature. In this work we provide a complete
description of the space of derivations of evolution algebras associated to
graphs, depending on the twin partition of the graph. For graphs without twin
classes with at least three elements we prove that the space of derivations of
the associated evolution algebra is zero. Moreover, we describe the spaces of
derivations for evolution algebras associated to the remaining families of
finite graphs. It is worth pointing out that our analysis includes examples of
finite dimensional evolution algebras with matrices of any rank.
| math.RA |
1807.02494 | Joint Channel-Estimation/Decoding with Frequency-Selective Channels and
Few-Bit ADCs | We propose a fast and near-optimal approach to joint channel-estimation,
equalization, and decoding of coded single-carrier (SC) transmissions over
frequency-selective channels with few-bit analog-to-digital converters (ADCs).
Our approach leverages parametric bilinear generalized approximate message
passing (PBiGAMP) to reduce the implementation complexity of joint channel
estimation and (soft) symbol decoding to that of a few fast Fourier transforms
(FFTs). Furthermore, it learns and exploits sparsity in the channel impulse
response. Our work is motivated by millimeter-wave systems with bandwidths on
the order of Gsamples/sec, where few-bit ADCs, SC transmissions, and fast
processing all lead to significant reductions in power consumption and
implementation cost. We numerically demonstrate our approach using signals and
channels generated according to the IEEE 802.11ad wireless local area network
(LAN) standard, in the case that the receiver uses analog beamforming and a
single ADC.
| cs.IT math.IT |
1807.02495 | Nitric Oxide in Climatological Global Energy Budget During 1982-2013 | Over the past decades, temperature and density of the upper atmosphere show
negative trends and decrease of the upper atmospheric temperature is attributed
to the declining neutral density. Specifically, nitric oxide (NO) and carbon
dioxide (CO2) govern thermospheric cooling at 5.3 and 15 micron, respectively.
While a lot of efforts have focused on the CO2 effects on the long-term trends,
relatively less attention has been paid to the impacts by NO, which responds to
solar and geomagnetic activities dynamically. In this study, we investigate the
role of NO in climatological global energy budget for the recent three solar
cycles using the Global Ionosphere Thermosphere Model. From 1982 to 2013, the
F10.7 and Ap indices showed a decadal decrease of ~8% and ~20%, respectively.
By imposing temporal-varying F10.7 and Ap values in the simulations, we find a
decadal change of -0.28x1011 W or -17.3% in total NO cooling power, which
agrees well with that (-0.34x1011 W or -17.2%) from the empirical Thermosphere
Climate Index derived from the TIMED/SABER data. Neutral density decreases by
10-20% at 200-450km and Tex decreases by 25.3 K per decade. The deduced-decadal
change of NO cooling reaches ~25% of the sum of total heating at ~130 km and
its significance decreases with altitude.
| physics.space-ph |
1807.02496 | Particle creation and energy conditions for a quantized scalar field in
the presence of an external, time-dependent, Mamev-Trunov potential | We study the behavior of a massless, quantized, scalar field on a
two-dimensional cylinder spacetime as it responds to the time-dependent
evolution of a Mamev-Trunov potential of the form $V(x,t) = 2 \xi \delta(x)
\theta(-t)$. We begin by constructing mode solutions to the classical
Klein-Gordon-Fock equation with potential on the whole spacetime. For a given
eigen-mode solution of the IN region of the spacetime ($t<0$), we determine its
evolution into the OUT region ($t>0$) through the use of a Fourier
decomposition in terms of the OUT region eigen-modes. The classical system is
then second quantized in the canonical quantization scheme. On the OUT region,
there is a unitarily equivalent representation of the quantized field in terms
of the OUT region eigen-modes, including zero-frequency modes which we also
quantize in a manner which allows for their interpretation as particles in the
typical sense. After determining the Bogolubov coefficients between the two
representations, we study the production of quanta out of the vacuum when the
potential turns off. We find that the number of "particles" created on the OUT
region is finite for the standard modes, and with the usual ambiguity in the
number of particles created in the zero frequency modes. We then look at the
renormalized expectation value of the stress-energy-tensor on the IN and OUT
regions for the IN vacuum state. We find that the resulting stress-tensor can
violate the null, weak, strong, and dominant energy conditions because the
standard Casimir energy-density of the cylinder spacetime is negative. Finally,
we show that the same stress-tensor satisfies a quantum inequality on the OUT
region.
| math-ph math.MP |
1807.02497 | Creep dynamics of athermal amorphous materials: a mesoscopic approach | Yield stress fluids display complex dynamics, in particular when driven into
the transient regime between the solid and the flowing state. Inspired by creep
experiments on dense amorphous materials, we implement mesocale elasto-plastic
descriptions to analyze such transient dynamics in athermal systems. Both our
mean-field and space-dependent approaches consistently reproduce the typical
experimental strain rate responses to different applied steps in stress.
Moreover, they allow us to understand basic processes involved in the strain
rate slowing down (creep) and the strain rate acceleration (fluidization)
phases. The fluidization time increases in a power-law fashion as the applied
external stress approaches a static yield stress. This stress value is related
to the stress over-shoot in shear start-up experiments, and it is known to
depend on sample preparation and age. By calculating correlations of the
accumulated plasticity in the spatially resolved model, we reveal different
modes of cooperative motion during the creep dynamics.
| cond-mat.soft cond-mat.dis-nn cond-mat.mtrl-sci cond-mat.stat-mech |
1807.02498 | Microwave and Hard X-Ray Observations of the 2017 September 10 Solar
Limb Flare | We report the first science results from the newly completed Expanded Owens
Valley Solar Array (EOVSA), which obtained excellent microwave imaging
spectroscopy observations of SOL2017-09-10, a classic partially-occulted solar
limb flare associated with an erupting flux rope. This event is also
well-covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI) in hard X-rays (HXRs). We present an overview of this event focusing
on microwave and HXR data, both associated with high-energy nonthermal
electrons, and discuss them within the context of the flare geometry and
evolution revealed by extreme ultraviolet (EUV) observations from the
Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory (SDO/AIA).
The EOVSA and RHESSI data reveal the evolving spatial and energy distribution
of high-energy electrons throughout the entire flaring region. The results
suggest that the microwave and HXR sources largely arise from a common
nonthermal electron population, although the microwave imaging spectroscopy
provides information over a much larger volume of the corona.
| astro-ph.SR |
1807.02499 | Class groups and local indecomposability for non-CM forms | In the late 1990's, R. Coleman and R. Greenberg (independently) asked for a
global property characterizing those $p$-ordinary cuspidal eigenforms whose
associated Galois representation becomes decomposable upon restriction to a
decomposition group at $p$. It is expected that such $p$-ordinary eigenforms
are precisely those with complex multiplication. In this paper, we study
Coleman-Greenberg's question using Galois deformation theory. In particular,
for $p$-ordinary eigenforms which are congruent to one with complex
multiplication, we prove that the conjectured answer follows from the
$p$-indivisibility of a certain class group.
| math.NT |
1807.02500 | Overview and Comparison of Gate Level Quantum Software Platforms | Quantum computers are available to use over the cloud, but the recent
explosion of quantum software platforms can be overwhelming for those deciding
on which to use. In this paper, we provide a current picture of the rapidly
evolving quantum computing landscape by comparing four software
platforms---Forest (pyQuil), Qiskit, ProjectQ, and the Quantum Developer Kit
(Q\#)---that enable researchers to use real and simulated quantum devices. Our
analysis covers requirements and installation, language syntax through example
programs, library support, and quantum simulator capabilities for each
platform. For platforms that have quantum computer support, we compare
hardware, quantum assembly languages, and quantum compilers. We conclude by
covering features of each and briefly mentioning other quantum computing
software packages.
| quant-ph cs.ET |
1807.02501 | Tensor networks as path integral geometry | In the context of a quantum critical spin chain whose low energy physics
corresponds to a conformal field theory (CFT), it was recently demonstrated [A.
Milsted G. Vidal, arXiv:1805.12524] that certain classes of tensor networks
used for numerically describing the ground state of the spin chain can also be
used to implement (discrete, approximate versions of) conformal transformations
on the lattice. In the continuum, the same conformal transformations can be
implemented through a CFT path integral on some curved spacetime. Based on this
observation, in this paper we propose to interpret the tensor networks
themselves as a path integrals on curved spacetime. This perspective assigns (a
discrete, approximate version of) a geometry to the tensor network, namely that
of the underlying curved spacetime.
| cond-mat.str-el hep-lat |
1807.02502 | Maximizing Welfare in Social Networks under a Utility Driven Influence
Diffusion Model | Motivated by applications such as viral marketing, the problem of influence
maximization (IM) has been extensively studied in the literature. The goal is
to select a small number of users to adopt an item such that it results in a
large cascade of adoptions by others. Existing works have three key
limitations. (1) They do not account for economic considerations of a user in
buying/adopting items. (2) Most studies on multiple items focus on competition,
with complementary items receiving limited attention. (3) For the network
owner, maximizing social welfare is important to ensure customer loyalty, which
is not addressed in prior work in the IM literature. In this paper, we address
all three limitations and propose a novel model called UIC that combines
utility-driven item adoption with influence propagation over networks. Focusing
on the mutually complementary setting, we formulate the problem of social
welfare maximization in this novel setting. We show that while the objective
function is neither submodular nor supermodular, surprisingly a simple greedy
allocation algorithm achieves a factor of $(1-1/e-\epsilon)$ of the optimum
expected social welfare. We develop \textsf{bundleGRD}, a scalable version of
this approximation algorithm, and demonstrate, with comprehensive experiments
on real and synthetic datasets, that it significantly outperforms all
baselines.
| cs.SI econ.EM |
1807.02503 | Phenomenological Constraints on Anomaly-Free Dark Matter Models | We study minimal benchmark models of dark matter with an extra anomaly-free
U(1)' gauge boson Z'. We find model parameters that give rise to the correct
cosmological dark matter density while evading the latest direct detection
searches for dark matter scattering produced by the XENON1T experiment,
including the effects of Z-Z' mixing. We also find regions of parameter space
that evade the constraints from LHC measurements of dileptons and dijets,
precision electroweak measurements, and LHC searches for monojet events with
missing transverse energy. We study two benchmark Z' models with Y-sequential
couplings to quarks and leptons, one with a vector-like coupling to the dark
matter particle and one with an axial dark matter coupling. The vector-like
model is extremely tightly constrained, with only a narrow allowed strip where
$m_\chi \simeq M_{Z'}/2$, and the axial model is excluded within the parameter
range studied. We also consider two leptophobic Z$^\prime$ benchmark models,
finding again narrow allowed strips where $m_\chi \simeq M_{Z'}/2$ as well as
more extended regions where $\log_{10} (m_\chi/ {\rm GeV}) \gtrsim 3.2$.
| hep-ph hep-ex |
1807.02504 | From Rank Estimation to Rank Approximation: Rank Residual Constraint for
Image Restoration | In this paper, we propose a novel approach to the rank minimization problem,
termed rank residual constraint (RRC) model. Different from existing low-rank
based approaches, such as the well-known nuclear norm minimization (NNM) and
the weighted nuclear norm minimization (WNNM), which estimate the underlying
low-rank matrix directly from the corrupted observations, we progressively
approximate the underlying low-rank matrix via minimizing the rank residual.
Through integrating the image nonlocal self-similarity (NSS) prior with the
proposed RRC model, we apply it to image restoration tasks, including image
denoising and image compression artifacts reduction. Towards this end, we first
obtain a good reference of the original image groups by using the image NSS
prior, and then the rank residual of the image groups between this reference
and the degraded image is minimized to achieve a better estimate to the desired
image. In this manner, both the reference and the estimated image are updated
gradually and jointly in each iteration. Based on the group-based sparse
representation model, we further provide a theoretical analysis on the
feasibility of the proposed RRC model. Experimental results demonstrate that
the proposed RRC model outperforms many state-of-the-art schemes in both the
objective and perceptual quality.
| cs.CV |
1807.02505 | Parsec-scale radio structure of 14 Fanaroff-Riley type 0 radio galaxies | Recently a population of compact radio galaxies were classified as
Fanaroff-Riley type 0 radio galaxies (FR 0s). The physical nature of FR 0s and
the connection with the classical FR I and II galaxies are not currently well
understood. Here, we report the radio properties of fourteen FR 0s on parsec
(pc) scales derived from their very long baseline interferometry (VLBI) imaging
observations. All sources show compact structures. Four sources show
relativistic beaming with Doppler boosting factors ranging from 1.7 to 6. The
brightness temperatures of the other ten are below the equilibrium limit. Jet
proper motions are determined in two sources which have multiple epoch data,
between 0.23 c and 0.49 c, implying mildly relativistic jet flow. Low-amplitude
flux density variation is found in J0943+3614 over a time period of 10 years.
No significant variability are detected in three other sources over time scales
of a few years. The radio properties of the FR 0s inferred from the VLBI data
resemble GHz-peaked spectrum or compact steep-spectrum sources. Moreover, the
diversity of their relativistic beaming indicators (brightness temperature,
variability, jet proper motion) also imply that FR 0s might not be a
homogeneous population of radio sources. Detailed studies of the low-power FR 0
sources in the local Universe additionally offer a promising opportunity to
understand their connection to the FR Is.
| astro-ph.HE |
1807.02506 | Shifted convolutions and a conjecture by Mazur, Rubin and Stein | In this paper, a conjecture of Mazur, Rubin and Stein concerning certain
averages of modular symbols is proved.
| math.NT |
1807.02507 | Unexpected behaviour of the crystal growth velocity at the hypercooling
limit | The crystal growth velocity is one thermodynamic parameter of solidification
experiments of undercooled melts under non-equilibrium conditions, which is
directly accessible to observation. We applied the electrostatic levitation
technique in order to study the crystal growth velocity $v$ as a function of
the undercooling $\Delta T$ for the intermetallic, congruently melting binary
alloy NiTi and the glass forming alloy Cu--Zr, as well as for the Zr-based
ternary alloys (Cu$_{\mathrm{x}}$Ni$_{\mathrm{1-x}}$)Zr ($x= 0.7, 0.6$) and the
Ni-based ternary alloy Ni(Zr$_{\mathrm{x}}$Ti$_{\mathrm{1-x}}) (x= 0.5)$. All
investigated systems within this work, except the eutectics $Cu_{56}Zr_{44}$
and $Cu_{46}Zr_{54}$, exceeded the hypercooling limit $\Delta T_{\mathrm{hyp}}$
and, remarkably, every $v(\Delta T)$ relation changed significantly at $\Delta
T_{\mathrm{hyp}}$. Our results for glass forming CuZr indicate that the
influence of the diffusion coefficient $D(T)$ on $v(\Delta T)$ at high
undercoolings, as claimed in literature, cannot be the sole reason for the
existence of a maximum in the $v(\Delta T)$ behaviour. These observations could
make a valuable contribution concerning an extension of growth theories to
undercooling temperatures $\Delta T > \Delta T_{\mathrm{hyp}}$. Nevertheless,
our finding has direct consequences to various disciplines, as our earth and
all living beings are examples for non-equilibrium systems. The scatter of our
velocity data is at least two orders of magnitude smaller than measurements
performed by former works due to our experimental setup, which allowed precise
contactless triggering at a specific undercooling, and our analysis method,
which considered the respective solidification morphologies.
| cond-mat.mtrl-sci physics.app-ph physics.chem-ph |
1807.02508 | Multi-wavelength observations of a new redback millisecond pulsar
candidate: 3FGL J0954.8-3948 | We present a multi-wavelength study of the unassociated Fermi-LAT source,
3FGL J0954.8-3948, which is likely the gamma-ray counterpart of a 9.3-hour
binary in the field. With more than 9 years of Pass 8 LAT data, we updated the
gamma-ray spectral properties and the LAT localization of the gamma-ray source.
While the binary lies outside the cataloged 95% error ellipse, the optimized
LAT ellipse is 0.1 degrees closer and encloses the binary. The system is likely
spectrally hard in X-rays (photon index ~ 1.4) with orbital modulations
detected in optical, UV, and possibly X-rays. A steep spectrum radio
counterpart (spectral index ~ -1.6) is also found in the TIFR GMRT Sky Survey
(TGSS), implying that it is a pulsar system. We obtained a series of SOAR and
Gemini spectroscopic observations in 2017/2018, which show a low-mass secondary
orbiting in a close circular orbit with K2 = 272 km/s under strong irradiation
by the primary compact object. All the observations as well as the modelling of
the X/gamma-ray high-energy emission suggest that 3FGL J0954.8-3948 is a
redback millisecond pulsar in a rotation-powered state.
| astro-ph.HE |
1807.02509 | Kelvin knots in superconducting state | The failed "vortex-atoms" theory of matter by Kelvin and Tait had a profound
impact on mathematics and physics. Building on the understanding of vorticity
by Helmholtz, and observing stability of smoke rings, they hypothesised that
elementary particles (at that time atoms) are indestructible knotted vortices
in luminiferous aether: the hypothetical ideal fluid filling the universe. The
vortex-atoms theory identified chemical elements as topologically different
vortex knots, and matter was interpreted as bound states of these knotted
vortices. This work initiated the field of knot theory in mathematics. It also
influenced modern physics, where a close although incomplete analogy exists
with the theory of superfluidity, which started with Onsager's and Feynman's
introduction of quantum vortices. Indeed many macroscopic properties of
superconductors and superfluids are indeed determined by vortex lines forming
different "aggregate states", such as vortex crystals and liquids. While
crucial importance of knots was understood for many physical systems in the
recent years, there is no known physical realization of the central element of
Kelvin theory: the stable particle-like vortex knot. Indeed, vortex loops and
knots in superfluids and ordinary superconductors form as dynamical excitations
and are unstable by Derrick theorem. This instability in fact dictates many of
the universal macroscopic properties of superfluids. Here we show that there
are superconducting states with principally different properties of the
vorticity: where vortex knots are intrinsically stable. We demonstrate that
such features should be realised near certain critical points, where the
hydro-magneto-statics of superconducting states yields stables vortex knots
which behave similar to those envisaged in Kelvin and Tait's theory of
vortex-atoms in luminiferous aether.
| cond-mat.supr-con hep-th nlin.PS |
1807.02510 | Denoting and Comparing Leadership Attributes and Behaviors in Group Work | Projects and Practices in Physics (P$^3$) is an introductory physics class at
Michigan State University that replaces lectures with a problem based learning
environment. To promote the development of group based practices, students all
receive group and individual feedback at the end of each week. The groups are
comprised of four students, one of which often takes on the role of being the
group's "leader." Developing leadership based skills is a specific learning
goal of the P$^3$ learning environment and the goal of this research is to
examine what leadership-specific actions/traits students in P$^3$ demonstrate
while working in their group. The initial phase of this study examined multiple
pieces of literature to identify possible characteristics and behaviors that
may present themselves in potential leaders -- creating a codebook. This phase
of the study applies the codebook to in-class data to compare two tutor-labeled
leaders and their leadership styles.
| physics.ed-ph |
1807.02511 | Evaluating Black Hole Detectability with LISA | We conduct an analysis of the measurement abilities of distinctive LISA
detector designs, examining the influence of LISA's low-frequency performance
on the detection and characterization of massive black hole binaries. We are
particularly interested in LISA's ability to measure massive black holes
merging at frequencies near the low-frequency band edge, with masses in the
range of $\sim 10^6-10^{10}M_\odot$. We examine the signal-to-noise ratio (SNR)
using phenomenological waveforms for inspiral, merger, and ringdown over a wide
range of massive black hole binary parameters. We employ a broad palette of
possible LISA configurations with different sensitivities at low frequencies.
For this analysis, we created a tool (github.com/mikekatz04/BOWIE) that
evaluates the change in SNR between two parameterized situations. The shifts in
SNR are computed as gains or losses as a function of binary parameters, and
graphically displayed across a two dimensional grid of parameter values. We
illustrate the use of this technique for both parameterized LISA mission
designs, as well as for considering the influence of astrophysical parameters
on gravitational wave signal models. In terms of low-frequency sensitivity,
acceleration noise or armlength is found to be the most important factor in
observing the largest massive black hole binaries, followed by break frequency
and then spectral index. LISA's ability to probe the astrophysical population
of $\sim10^7-10^9M_\odot$ black holes is greatly influenced by these aspects of
its sensitivity. The importance of the constituent black hole spins is also
highlighted.
| gr-qc |
1807.02512 | Transversal Modes and Higgs Bosons in Electroweak Vector-Boson
Scattering at the LHC | Processes where $W$ and $Z$ bosons scatter into pairs of electroweak bosons
$W$, $Z$, and Higgs, are sensitive probes of new physics in the electroweak
sector. We study simplified models that describe typical scenarios of new
physics and parameterize the range of possible LHC results between the
Standard-Model prediction and unitarity limits. Extending the study beyond
purely longitudinal scattering, we investigate the role of transversally
polarized gauge bosons. Unitarity becomes an essential factor, and limits on
parameters matched to the naive perturbative low-energy effective theory turn
out to be necessarily model-dependent. We discuss the implications of our
approach for the interpretation of LHC data on vector-boson scattering and
Higgs-pair production.
| hep-ph hep-ex |
1807.02513 | On Algorithms for and Computing with the Tensor Ring Decomposition | Tensor decompositions such as the canonical format and the tensor train
format have been widely utilized to reduce storage costs and operational
complexities for high-dimensional data, achieving linear scaling with the input
dimension instead of exponential scaling. In this paper, we investigate even
lower storage-cost representations in the tensor ring format, which is an
extension of the tensor train format with variable end-ranks. Firstly, we
introduce two algorithms for converting a tensor in full format to tensor ring
format with low storage cost. Secondly, we detail a rounding operation for
tensor rings and show how this requires new definitions of common linear
algebra operations in the format to obtain storage-cost savings. Lastly, we
introduce algorithms for transforming the graph structure of graph-based tensor
formats, with orders of magnitude lower complexity than existing literature.
The efficiency of all algorithms is demonstrated on a number of numerical
examples, and in certain cases, we demonstrate significantly higher compression
ratios when compared to previous approaches to using the tensor ring format.
| math.NA cs.NA |
1807.02514 | A Neural-Astrocytic Network Architecture: Astrocytic calcium waves
modulate synchronous neuronal activity | Understanding the role of astrocytes in brain computation is a nascent
challenge, promising immense rewards, in terms of new neurobiological knowledge
that can be translated into artificial intelligence. In our ongoing effort to
identify principles endow-ing the astrocyte with unique functions in brain
computation, and translate them into neural-astrocytic networks (NANs), we
propose a biophysically realistic model of an astrocyte that preserves the
experimentally observed spatial allocation of its distinct subcellular
compartments. We show how our model may encode, and modu-late, the extent of
synchronous neural activity via calcium waves that propagate intracellularly
across the astrocytic compartments. This relationship between neural activity
and astrocytic calcium waves has long been speculated but it is still lacking a
mechanistic explanation. Our model suggests an astrocytic "calcium cascade"
mechanism for neuronal synchronization, which may empower NANs by imposing
periodic neural modulation known to reduce coding errors. By expanding our
notions of information processing in astrocytes, our work aims to solidify a
computational role for non-neuronal cells and incorporate them into artificial
networks.
| q-bio.NC |
1807.02515 | Blockchain as a Service: A Decentralized and Secure Computing Paradigm | Thanks to the advances in machine learning, data-driven analysis tools have
become valuable solutions for various applications. However, there still remain
essential challenges to develop effective data-driven methods because of the
need to acquire a large amount of data and to have sufficient computing power
to handle the data. In many instances these challenges are addressed by relying
on a dominant cloud computing vendor, but, although commercial cloud vendors
provide valuable platforms for data analytics, they can suffer from a lack of
transparency, security, and privacy-perservation. Furthermore, reliance on
cloud servers prevents applying big data analytics in environments where the
computing power is scattered. To address these challenges, a decentralize,
secure, and privacy-preserving computing paradigm is proposed to enable an
asynchronized cooperative computing process amongst scattered and untrustworthy
computing nodes that may have limited computing power and computing
intelligence. This paradigm is designed by exploring blockchain, decentralized
learning, homomorphic encryption, and software defined networking(SDN)
techniques. The performance of the proposed paradigm is evaluated via different
scenarios in the simulation section.
| cs.CR cs.CY cs.DC cs.LG stat.ML |
1807.02516 | Element history of the Laplace resonance: a dynamical approach | We consider the three-body mean motion resonance defined by the Jovian moons
Io, Europa, and Ganymede, which is commonly known as the Laplace resonance. In
particular, we construct approximate models for the evolution of the librating
argument over the period of 100 years, focusing on its principal amplitude and
frequency, and on the observed mean motion combinations associated with the
quasi-resonant interactions. First, we numerically propagated the Cartesian
equations of motion of the Jovian system for the period under examination, and
by comparing the results with a suitable set of ephemerides, we derived the
main dynamical effects on the target quantities. Using these effects, we built
an alternative Hamiltonian formulation and used the normal forms theory to
locate the resonance and to compute its main amplitude and frequency. From the
Cartesian model we observe that on the timescale considered and with
ephemerides as initial conditions, both the librating argument and the
diagnostics are well approximated by considering the mutual gravitational
interactions of Jupiter and the Galilean moons (including Callisto), and the
effect of Jupiter's J2 harmonic. Under the same initial conditions, the
Hamiltonian formulation in which Callisto and J2 are reduced to their secular
contributions achieves larger errors for the quantities above, particularly for
the librating argument. By introducing appropriate resonant variables, we show
that these errors can be reduced by moving in a certain action-angle phase
plane, which in turn implies the necessity of a tradeoff in the selection of
the initial conditions. In addition to being a good starting point for a deeper
understanding of the Laplace resonance, the models and methods described are
easily generalizable to different types of multi-body mean motion resonances.
They are also prime tools for studying the dynamics of extrasolar systems.
| astro-ph.EP math-ph math.MP nlin.CD |
1807.02517 | Some remarks on Dupont contraction | We present an alternative equivalent description of Dupont's simplicial
contraction: it is an explicit example of a simplicial contraction between the
simplicial differential graded algebra of polynomial differential forms on
standard simplices and the space of Whitney elementary forms.
| math.AG math.CT |
1807.02518 | Mean field and beyond description of nuclear structure with the Gogny
force: A review | Nowadays, the Gogny force is a referent in the theoretical description of
nuclear structure phenomena. Its phenomenological character manifests in a
simple analytical form that allows for implementations of techniques both at
the mean field and beyond all over the nuclide chart. Over the years, multiple
applications of the standard many-body techniques in an assorted set of nuclear
structure applications have produced results which are in a rather good
agreement with experimental data. The agreement allows for a simple
interpretation of those intriguing phenomena in simple terms and gives
confidence on the predictability of the interaction. The present status on the
implementation of different many body techniques with the Gogny force is
reviewed with a special emphasis on symmetry restoration and large amplitude
collective motion.
| nucl-th nucl-ex |
1807.02519 | Inferred Evidence For Dark Matter Kinematic Substructure with SDSS-Gaia | We use the distribution of accreted stars in SDSS-Gaia DR2 to demonstrate
that a non-trivial fraction of the dark matter halo within Galactocentric radii
of 7.5-10 kpc and $|z| > 2.5$ kpc is in substructure, and thus may not be in
equilibrium. Using a mixture likelihood analysis, we separate the contributions
of an old, isotropic stellar halo and a younger anisotropic population. The
latter dominates and is uniform within the region studied. It can be explained
as the tidal debris of a disrupted massive satellite on a highly radial orbit,
and is consistent with mounting evidence from recent studies. Simulations that
track the tidal debris from such mergers find that the dark matter traces the
kinematics of its stellar counterpart. If so, our results indicate that a
component of the nearby dark matter halo that is sourced by luminous satellites
is in kinematic substructure referred to as debris flow. These results
challenge the Standard Halo Model, which is discrepant with the distribution
recovered from the stellar data, and have important ramifications for the
interpretation of direct detection experiments.
| astro-ph.GA astro-ph.CO hep-ph |
1807.02520 | Master formula for $\varepsilon'/\varepsilon$ beyond the Standard Model | We present for the first time a master formula for
$\varepsilon'/\varepsilon$, the ratio probing direct CP violation in $K \to
\pi\pi$ decays, valid in any theory beyond the Standard Model (BSM). The
formula makes use of hadronic matrix elements of BSM operators calculated
recently in the Dual QCD approach and the ones of the SM operators from lattice
QCD. We emphasize the large impact of several scalar and tensor BSM operators
in the context of the emerging $\varepsilon'/\varepsilon$ anomaly. We have
implemented the results in the open source code flavio.
| hep-ph hep-ex hep-lat |
1807.02521 | Quiver Theories and Formulae for Slodowy Slices of Classical Algebras | We utilise SUSY quiver gauge theories to compute properties of Slodowy
slices; these are spaces transverse to the nilpotent orbits of a Lie algebra
$\mathfrak g$. We analyse classes of quiver theories, with Classical gauge and
flavour groups, whose Higgs branch Hilbert series are the intersections between
Slodowy slices and the nilpotent cone $\mathcal S\cap \mathcal N$ of
$\mathfrak{g}$. We calculate refined Hilbert series for Classical algebras up
to rank $4$ (and $A_5$), and find descriptions of their representation matrix
generators as algebraic varieties encoding the relations of the chiral ring. We
also analyse a class of dual quiver theories, whose Coulomb branches are
intersections $\mathcal S\cap \mathcal N$; such dual quiver theories exist for
the Slodowy slices of $A$ algebras, but are limited to a subset of the Slodowy
slices of $BCD$ algebras. The analysis opens new questions about the extent of
$3d$ mirror symmetry within the class of SCFTs known as $T_\sigma^\rho(G)$
theories. We also give simple group theoretic formulae for the Hilbert series
of Slodowy slices; these draw directly on the $SU(2)$ embedding into $G$ of the
associated nilpotent orbit, and the Hilbert series of the nilpotent cone.
| hep-th |
1807.02522 | Spinning operators and defects in conformal field theory | We study the kinematics of correlation functions of local and extended
operators in a conformal field theory. We present a new method for constructing
the tensor structures associated to primary operators in an arbitrary bosonic
representation of the Lorentz group. The recipe yields the explicit structures
in embedding space, and can be applied to any correlator of local operators,
with or without a defect. We then focus on the two-point function of traceless
symmetric primaries in the presence of a conformal defect, and explain how to
compute the conformal blocks. In particular, we illustrate various techniques
to generate the bulk channel blocks either from a radial expansion or by acting
with differential operators on simpler seed blocks. For the defect channel, we
detail a method to compute the blocks in closed form, in terms of projectors
into mixed symmetry representations of the orthogonal group.
| hep-th |
1807.02523 | Near infrared spectroscopy and star-formation histories of 3<z<4
quiescent galaxies | We present Keck-MOSFIRE H and K spectra for a sample of 24 candidate
quiescent galaxies (QGs) at 3<z<4, identified from UVJ colors and photometric
redshifts in the ZFOURGE and 3DHST surveys. We obtain spectroscopic redshifts
for half of the sample, using absorption or emission lines, and confirm the
high accuracy of the photometric redshifts with a median error of 1.2%. Two
galaxies turn out to be dusty objects at lower redshifts (z<2.5), and are the
only two detected in the sub-mm with ALMA. High equivalent-width [OIII] was
observed in two galaxies, contributing up to 30% of the K-band flux and
mimicking the colors of an old stellar population. This implies a failure rate
of only 20% for the UVJ selection at these redshifts. Balmer absorption was
identified in 4 of the brighest galaxies, confirming the absence of OB stars.
Modeling all QGs with a wide range of star-formation histories, we find sSFR a
factor of 10 below the main sequence (MS) for all but one galaxy, and less than
0.01 Gyr$^{-1}$ for half of the sample. This is consistent with the H$\beta$
and [OII] luminosities, and the ALMA non-detections. We then find that these
QGs have quenched on average 300 Myr before observation, between z=3.5 and 5,
and that they formed at z~5.5 with a mean SFR~300 Msun/yr. Considering an
alternative selection of QGs based solely on the sSFR from SED modeling, we
find that galaxies a factor 10 below the MS are 40% more numerous than
UVJ-quiescent galaxies, implying that the UVJ selection is pure but incomplete.
Current models fail at reproducing our observations and underestimate either
the number density of QGs by more than an order of magnitude or the duration of
their quiescence by a factor two. Overall, these results confirm the existence
of an unexpected population of QGs at z>3, and offer the first insights on
their formation history. [abridged]
| astro-ph.GA |
1807.02524 | Exact renormalization group for quantum spin systems | We show that the diagrammatic approach to quantum spin systems developed in a
seminal work by Vaks, Larkin, and Pikin [Sov. Phys. JETP 26, 188 (1968)] can be
embedded in the framework of the functional renormalization group. The crucial
insight is that the generating functional of the time-ordered connected spin
correlation functions of an arbitrary quantum spin system satisfies an exact
renormalization group flow equation which resembles the corresponding flow
equation of a system of interacting bosons. The $SU (2)$ spin algebra is
implemented via a non-trivial initial condition for the renormalization group
flow. Our method is rather general and offers a new non-perturbative approach
to quantum spin systems.
| cond-mat.str-el cond-mat.stat-mech |
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