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arxiv_dataset-47001310.4997 | Lindblad equation for a non-interacting fermionic system: full-counting
statistics
cond-mat.mes-hall cond-mat.stat-mech
We develop a method of calculating the full-counting statistics for a
non-interacting fermionic system coupled to the memory-less reservoirs. The
evolution of the system is described by the Lindblad equation. By the basis
change the Liouvillian operator is brought to the quadratic form. This allows
us a straightforward calculation of any observable in the non-equilibrium
steady state. We introduce the counting field in the Lindblad equation which
brings us to the generating function and helps us to obtain all cumulants of
the charge transport. For the two-site system we give the expression for the
generating function. For system longer than two sites we perform numerical
investigations which suggest that it in a uniform system the cumulants of order
$k$ are independent of the size of the system for system sizes larger $k+1$.
The counting statistics from the Lindblad approach does not take into account
interference in the reservoirs which gives a decreased noise in comparison with
the Green function method which describes phase coherent leads. The current
obtained by two methods is the same, which relies on the current conservation.
The Fano factors are different (with a linear relation connecting them) and
allow to distinguish between memory-less and phase coherent reservoirs.
| arxiv topic:cond-mat.mes-hall cond-mat.stat-mech |
arxiv_dataset-47011310.5097 | Cavities in curved spacetimes: the response of particle detectors
quant-ph gr-qc hep-th
We introduce a method to compute particle detector transition probability in
spacetime regions of general curved spacetimes provided that the curvature is
not above a maximum threshold. In particular we use this method to compare the
response of two detectors, one in a spherically symmetric gravitational field
and the other one in Rindler spacetime to compare the Unruh and Hawking
effects: We study the vacuum response of a detector freely falling through a
stationary cavity in a Schwarzschild background as compared with the response
of an equivalently accelerated detector traveling through an inertial cavity in
the absence of curvature. We find that as we set the cavity in further radiuses
from the black hole, the thermal radiation measured by the detector approaches
the quantity recorded by the detector in Rindler background showing in which
way and at what scales the equivalent principle is recovered in the
Hawking-Unruh effect. I.e. when the Hawking effect in a Schwarzschild
background becomes equivalent to the Unruh effect in Rindler spacetime.
| arxiv topic:quant-ph gr-qc hep-th |
arxiv_dataset-47021310.5197 | Vector cross product in n-dimensional vector space
math-ph math.MP
The definition of vector cross product (VCP) introduced by Eckmann only
exists in thethree- and the seven- dimensional vector space. In this paper,
according to the orthogonal completeness, magnitude of basis vector cross
product and all kinds of combinations of basis vector $\hat{e}_i$, the
generalized definition of VCP in the odd n-dimensional vector space is given by
introducing a cross term $X_{AB}$. In addition, the definition is validated by
reducing the generalization definition to the fundamental three- and
seven-dimensional vector space.
| arxiv topic:math-ph math.MP |
arxiv_dataset-47031310.5297 | New solutions with accelerated expansion in string theory
hep-th astro-ph.CO
We present concrete solutions with accelerated expansion in string theory,
requiring a small, tractable list of stress energy sources. We explain how this
construction (and others in progress) evades previous no go theorems for simple
accelerating solutions. Our solutions respect an approximate scaling symmetry
and realize discrete sequences of values for the equation of state, including
one with an accumulation point at w=-1 and another accumulating near w=-1/3
from below. In another class of models, a density of defects generates scaling
solutions with accelerated expansion. We briefly discuss potential applications
to dark energy phenomenology, and to holography for cosmology.
| arxiv topic:hep-th astro-ph.CO |
arxiv_dataset-47041310.5397 | Photometric observation of HAT-P-16b in the near-UV
astro-ph.EP
We present the first primary transit light curve of the hot Jupiter HAT-P-16b
in the near-UV photometric band. We observed this object on December 29,2012 in
order to update the transit ephemeris, constrain its planetary parameters and
search for magnetic field interference. Vidotto et al. (2011a) postulate that
the magnetic field of HAT-P-16b can be constrained if its near-UV light curve
shows an early ingress compared to its optical light curve, while its egress
remains unchanged. However, we did not detect an early ingress in our night of
observing when using a cadence of 60 seconds and an average photometric
precision of 2.26mmag. We find a near-UV planetary radius of
Rp=1.274+-0.057RJup which is consistent with its near-IR radius of
Rp=1.289+-0.066RJup (Buchhave et al., 2010). We developed an automated
reduction pipeline and modeling package to process our data. The data reduction
package synthesizes a set of IRAF scripts to calibrate images and perform
aperture photometry. The modeling package utilizes the Levenberg-Marquardt
minimization algorithm to find a least-squares best fit and a differential
evolution Markov Chain Monte Carlo algorithm to find the best fit to the light
curve. To constrain the red noise in both fitting models we use the residual
permutation (rosary bead) method and time-averaging method.
| arxiv topic:astro-ph.EP |
arxiv_dataset-47051310.5497 | Using CamiTK for rapid prototyping of interactive Computer Assisted
Medical Intervention applications
cs.OH
Computer Assisted Medical Intervention (CAMI hereafter) is a complex
multi-disciplinary field. CAMI research requires the collaboration of experts
in several fields as diverse as medicine, computer science, mathematics,
instrumentation, signal processing, mechanics, modeling, automatics, optics,
etc.
| arxiv topic:cs.OH |
arxiv_dataset-47061310.5597 | CIDS country rankings: comparing documents and citations of USA, UK and
China top researchers
cs.DL cs.IR
This technical report presents a bibliometric analysis of the top 30 cited
researchers from USA, UK and China. The analysis is based on Google Scholar
data using CIDS. The researchers were identified using their email suffix: edu,
uk and cn. This na\"{i}ve approach was able to produce rankings consistent with
the SCImago country rankings using mininal resources in a fully automated way.
| arxiv topic:cs.DL cs.IR |
arxiv_dataset-47071310.5697 | Multivalued Logic Circuit Design for Binary Logic Interface
cs.OH
Binary logic and devices have been in used since inception with advancement
and technology and millennium gate design era. The development in binary logic
has become tedious and cumbersome. Multivalued logic enables significant more
information to be packed within a single digit. The design and development of
logic circuit becomes very compact and easier. Attempts are being made to
fabricate multivalued logic based devices. Since present devices can be
implemented only in binary system,it is necessary to evolve a system that can
built the circuit in multivalued logic system and convert in binary logic
system. In multivalued logic system logic gates differ in different logic
system, a quaternary has become mature in terms of logic algebra and gates.
Hence logic design based on above system can be done using standard procedure.
In this dissertation a logic circuit design entry based on multivalued logic
system has been taken up that can provide the ease of circuit design in
multivalued system and output as binary valued circuit. The named "MVL-DEV"
offers editing, storage and conversion into binary facility.
| arxiv topic:cs.OH |
arxiv_dataset-47081310.5797 | Multi-nucleon bound states in $N_f=2+1$ lattice QCD
hep-lat
We report on our on-going effort to calculate the properties of light nuclei
directly from quarks and gluons based on lattice QCD. After briefly introducing
our motivations and aims, we describe our strategy of fixing the strange quark
mass at its physical value and approaching the physical point for the up and
down quark masses step by step from the region of heavy quark masses. A
successful calculation for the pion mass of 0.51GeV is reviewed, and the status
for a lighter pion mass of 0.30GeV is reported.
| arxiv topic:hep-lat |
arxiv_dataset-47091310.5897 | Regularity of K\"ahler-Ricci flows on Fano manifolds
math.DG
In this paper, we will establish a regularity theory for the K\"ahler-Ricci
flow on Fano $n$-manifolds with Ricci curvature bounded in $L^p$-norm for some
$p > n$. Using this regularity theory, we will also solve a long-standing
conjecture for dimension 3. As an application, we give a new proof of the
Yau-Tian-Donaldson conjecture for Fano 3-manifolds. The results have been
announced in \cite{TiZh12b}.
| arxiv topic:math.DG |
arxiv_dataset-47101310.5997 | Critical behavior of 3D Z(N) lattice gauge theories at zero temperature
hep-lat
Three-dimensional $Z(N)$ lattice gauge theories at zero temperature are
studied for various values of $N$. Using a modified phenomenological
renormalization group, we explore the critical behavior of the generalized
$Z(N)$ model for $N=2,3,4,5,6,8$. Numerical computations are used to simulate
vector models for $N=2,3,4,5,6,8,13,20$ for lattices with linear extension up
to $L=96$. We locate the critical points of phase transitions and establish
their scaling with $N$. The values of the critical indices indicate that the
models with $N>4$ belong to the universality class of the three-dimensional
$XY$ model. However, the exponent $\alpha$ derived from the heat capacity is
consistent with the Ising universality class. We discuss a possible resolution
of this puzzle. We also demonstrate the existence of a rotationally symmetric
region within the ordered phase for all $N\geq 5$ at least in the finite
volume.
| arxiv topic:hep-lat |
arxiv_dataset-47111310.6097 | Electron Correlations and Two-Photon States in Polycyclic Aromatic
Hydrocarbon Molecules: A Peculiar Role of Geometry
cond-mat.str-el
We present numerical studies of one- and two-photon excited states ordering
in a number of polycyclic aromatic hydrocarbon molecules: coronene,
hexa-peri-hexabenzocoronene and circumcoronene, all possessing $D_{6h}$ point
group symmetry versus ovalene with $D_{2h}$ symmetry, within the
Pariser-Parr-Pople model of interacting $\pi$-electrons. The calculated
energies of the two-photon states as well as their relative two-photon
absorption cross-sections within the interacting model are qualitatively
different from single-particle descriptions. More remarkably, a peculiar role
of molecular geometry is found. The consequence of electron correlations is far
stronger for ovalene, where the lowest spin-singlet two-photon state is a
quantum superposition of pairs of lowest spin triplet states, as in the linear
polyenes. The same is not true for $D_{6h}$ group hydrocarbons. Our work
indicates significant covalent character, in valence bond language, of the
ground state, the lowest spin triplet state and a few of the lowest two-photon
states in $D_{2h}$ ovalene but not in those with $D_{6h}$ symmetry.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-47121310.6197 | Extraordinary absorption of decorated undoped graphene
cond-mat.mes-hall
We theoretically study absorption by an undoped graphene layer decorated with
arrays of small particles. We discuss periodic and random arrays within a
common formalism, which predicts a maximum absorption of $50\%$ for suspended
graphene in both cases. The limits of weak and strong scatterers are
investigated and an unusual dependence on particle-graphene separation is found
and explained in terms of the effective number of contributing evanescent
diffraction orders of the array. Our results can be important to boost
absorption by single layer graphene due to its simple setup with potential
applications to light harvesting and photodetection based on energy (F\"orster)
rather than charge transfer.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-47131310.6297 | Abundances and possible diffusion of elements in M67 stars
astro-ph.SR
We present a spectroscopic study at high resolution, R~50,000, of 14 stars
located on the main sequence, at the turn-off point and on the early subgiant
branch in the cluster M67 in order to investigate its detailed chemical
composition, for comparison with the Sun and solar twins in the solar
neighbourhood, and to explore selective atomic diffusion of chemical elements
as predicted by stellar-structure theory. We have obtained VLT/FLAMES-UVES
spectra and analysed these strictly differentially in order to explore
chemical-abundance similarities and differences between the M67 stars and the
Sun, and among the M67 stars themselves. Individual abundances of 19 different
chemical elements are obtained for the stars. They are found to agree very well
with solar abundances, with abundance ratios closer to solar than those of most
solar twins in the solar neighbourhood. An exception is Li which shows a
considerable scatter among the cluster stars. There is a tendency for the
cluster-star abundances to be depleted relative to the abundances in the field
stars in correlation with the condensation temperature of the elements, a
tendency earlier found also for the Sun. The results support the hypothesis
that the gas of the proto-cluster was depleted by formation and cleansing of
dust before the stars formed. They also add support to the proposal that the
Sun was once formed in a dense stellar environment. Moreover, the observed
minor reductions of heavy elements in the atmospheres of the dwarfs and
turn-off point stars relative to our standard star M67-1194 and the subgiants
seem to suggest that diffusion processes are at work in these stars, although
the evidence is not compelling. Based on theoretical models the
diffusion-corrected initial metallicity of M67 is estimated to be [Fe/H]=+0.06.
| arxiv topic:astro-ph.SR |
arxiv_dataset-47141310.6397 | Variance Based Scheduling Algorithm with Relay Selection and Resource
Allocation in Cooperative OFDMA Networks
cs.NI
Nowadays the radio interface of several standards is enhanced with advanced
technologies such as OFDMA and extension technology such as relay. By using
those promising transmission technology for the next generation wireless
communications, scheduling problem becomes more crucial and challenging. In our
work, we aim to maximize the overall system capacity while selecting the most
suitable relay station under fairness constraint among both users and relay
station by proposing a Gap- based scheduling. This one considers the channel
state information and the unbalanced rate capacity of the two hops links.
Simulations results show the effectiveness of our approach in terms of fairness
and the overall system performance.
| arxiv topic:cs.NI |
arxiv_dataset-47151310.6497 | The existence and nature of the interstellar bow shock
astro-ph.SR physics.comp-ph physics.flu-dyn physics.plasm-ph physics.space-ph
We report a new diagnostic between two different states of the local
interstellar medium (LISM) near our solar system using a sensitivity study
constrained by several distinct and complementary observations of the LISM,
solar wind, and inner heliosphere. Assuming the Interstellar Boundary Explorer
(IBEX) He flow parameters for the LISM, we obtain a strength of $\sim
2.7\pm0.2$ $\mu$G and a direction pointing away from galactic coordinates $(28,
52)\pm 3^\circ$ for the interstellar magnetic field as resulting from fitting
Voyager 1 & 2 in situ plasma measurements and IBEX energetic neutral atoms
ribbon}. When using Ulysses parameters for the LISM He flow, we recently
reported the same direction but a strength of $2.2\pm0.1$ $\mu$G. First, we
notice that with Ulysses He flow, our solution is in the expected hydrogen
deflection plane (HDP). In contrast, for the IBEX He flow, the solution is
$\sim 20^{\circ}$ away from the corresponding HDP plane. Second, the long-term
monitoring of the interplanetary H I flow speed shows a value of $\sim 26$ km/s
measured at upwind from the Doppler-shift in the strong Lyman-$\alpha $ sky
background emission line. All elements of diagnostics seem therefore to support
Ulysses He flow parameters for the interstellar state. In that frame, we argue
that reliable discrimination between superfast, subfast, or superslow states of
the interstellar flow should be based on most existing in situ and remote
observations used together with global modelling of the heliosphere. For
commonly accepted LISM ionization rates, we show that a fast interstellar
bow-shock should be standing-off upstream of the heliopause.
| arxiv topic:astro-ph.SR physics.comp-ph physics.flu-dyn physics.plasm-ph physics.space-ph |
arxiv_dataset-47161310.6597 | Rational Quartic Reciprocity II
math.NT
We continue investigating rational quartic reciprocity laws and, at the
suggestion of the editor of AA, provide details of a proof of a remark in the
first article with this title.
| arxiv topic:math.NT |
arxiv_dataset-47171310.6697 | The effect of an ordered azimuthal magnetic field on a migrating planet
in a non-turbulent disc
astro-ph.EP
In this work, we consider the physics of the interaction between a planet and
a magnetized gaseous protoplanetary disc. We investigate the migration of a
planet in a disc that is threaded with an azimuthal magnetic field. We find
that, for a larger magnetic field amplitude, there is an increasingly large
positive torque on the planet from the disc, resulting in slowed and even
outward migration. Our results indicate that magnetic resonances due to a
purely azimuthal, ordered magnetic field can slow or stop the inward migration
of Jupiter-mass, Saturn-mass, and $5 M_{\oplus}$ planets.
| arxiv topic:astro-ph.EP |
arxiv_dataset-47181310.6797 | Focal Conic Flower Textures at Curved Interfaces
cond-mat.soft cond-mat.mtrl-sci
Focal conic domains (FCDs) in smectic-A liquid crystals have drawn much
attention both for their exquisitely structured internal form and for their
ability to direct the assembly of micro- and nanomaterials in a variety of
patterns. A key to directing FCD assembly is control over the eccentricity of
the domain. Here, we demonstrate a new paradigm for creating spatially varying
FCD eccentricity by confining a hybrid-aligned smectic with curved interfaces.
In particular, we manipulate interface behavior with colloidal particles in
order to experimentally produce two examples of what has recently been dubbed
the flower texture, where the focal hyperbolae diverge radially outward from
the center of the texture, rather than inward as in the canonical eventail or
fan texture. We explain how this unconventional assembly can arise from
appropriately curved interfaces. Finally, we present a model for this system
that applies the law of corresponding cones, showing how FCDs may be embedded
smoothly within a "background texture" of large FCDs and concentric spherical
layers, in a manner consistent with the qualitative features of the smectic
flower. Such understanding could potentially lead to disruptive liquid crystal
technologies beyond displays, including patterning, smart surfaces, microlens
arrays, sensors and nanomanufacturing.
| arxiv topic:cond-mat.soft cond-mat.mtrl-sci |
arxiv_dataset-47191310.6897 | Supercurrent multiplet correlators at weak and strong coupling
hep-th
Correlators of gauge invariant operators provide useful information on the
dynamics, phases and spectra of a quantum field theory. In this paper, we
consider N=1 supersymmetric theories and focus our attention on the
supercurrent multiplet. We give a complete characterization of two-point
functions of operators belonging to such multiplet, like the energy-momentum
tensor and the supercurrent, and study the relations between them. We discuss
instances of weakly coupled and strongly coupled theories, in which different
symmetries, like conformal invariance and supersymmetry, may be conserved
and/or spontaneously or explicitly broken. For theories at strong coupling, we
exploit AdS/CFT techniques. We provide a holographic description of different
properties of a strongly coupled theory, including a realization of the
Goldstino mode in a simple illustrative model.
| arxiv topic:hep-th |
arxiv_dataset-47201310.6997 | The Complexity of Online Manipulation of Sequential Elections
cs.GT
Most work on manipulation assumes that all preferences are known to the
manipulators. However, in many settings elections are open and sequential, and
manipulators may know the already cast votes but may not know the future votes.
We introduce a framework, in which manipulators can see the past votes but not
the future ones, to model online coalitional manipulation of sequential
elections, and we show that in this setting manipulation can be extremely
complex even for election systems with simple winner problems. Yet we also show
that for some of the most important election systems such manipulation is
simple in certain settings. This suggests that when using sequential voting,
one should pay great attention to the details of the setting in choosing one's
voting rule.
Among the highlights of our classifications are: We show that, depending on
the size of the manipulative coalition, the online manipulation problem can be
complete for each level of the polynomial hierarchy or even for PSPACE. We
obtain the most dramatic contrast to date between the nonunique-winner and
unique-winner models: Online weighted manipulation for plurality is in P in the
nonunique-winner model, yet is coNP-hard (constructive case) and NP-hard
(destructive case) in the unique-winner model. And we obtain what to the best
of our knowledge are the first PNP[1]-completeness and PNP-completeness results
in the field of computational social choice, in particular proving such
completeness for, respectively, the complexity of 3-candidate and 4-candidate
(and unlimited-candidate) online weighted coalition manipulation of veto
elections.
| arxiv topic:cs.GT |
arxiv_dataset-47211310.7097 | Conformal Transformations and Weak Field Limit of Scalar-Tensor Gravity
gr-qc astro-ph.EP astro-ph.GA
The weak field limit of scalar tensor theories of gravity is discussed in
view of conformal transformations. Specifically, we consider how physical
quantities, like gravitational potentials derived in the Newtonian
approximation for the same scalar-tensor theory, behave in the Jordan and in
the Einstein frame. The approach allows to discriminate features that are
invariant under conformal transformations and gives contributions in the debate
of selecting the true physical frame. As a particular example, the case of
$f(R)$ gravity is considered.
| arxiv topic:gr-qc astro-ph.EP astro-ph.GA |
arxiv_dataset-47221310.7197 | Weak Visibility Queries of Line Segments in Simple Polygons and
Polygonal Domains
cs.CG
In this paper we consider the problem of computing the weak visibility
polygon of any query line segment $pq$ (or $WVP(pq)$) inside a given polygon
$P$. Our first non-trivial algorithm runs in simple polygons and needs $O(n^3
\log n)$ time and $O(n^3)$ space in the preprocessing phase to report $WVP(pq)$
of any query line segment $pq$ in time $O(\log n + |WVP(pq)|)$. We also give an
algorithm to compute the weak visibility polygon of a query line segment in a
non-simple polygon with $h$ pairwise-disjoint polygonal obstacles with a total
of $n$ vertices. Our algorithm needs $O(n^2 \log n)$ time and $O(n^2)$ space in
the preprocessing phase and computes $WVP(pq)$ in query time of $O(n\hbar \log
n + k)$, in which $\hbar$ is an output sensitive parameter of at most
$\min(h,k)$, and $k = O(n^2h^2)$ is the output size. This is the best
query-time result on this problem so far.
| arxiv topic:cs.CG |
arxiv_dataset-47231310.7297 | Scalable Visibility Color Map Construction in Spatial Databases
cs.DB
Recent advances in 3D modeling provide us with real 3D datasets to answer
queries, such as "What is the best position for a new billboard?" and "Which
hotel room has the best view?" in the presence of obstacles. These applications
require measuring and differentiating the visibility of an object (target) from
different viewpoints in a dataspace, e.g., a billboard may be seen from two
viewpoints but is readable only from the viewpoint closer to the target. In
this paper, we formulate the above problem of quantifying the visibility of
(from) a target object from (of) the surrounding area with a visibility color
map (VCM). A VCM is essentially defined as a surface color map of the space,
where each viewpoint of the space is assigned a color value that denotes the
visibility measure of the target from that viewpoint. Measuring the visibility
of a target even from a single viewpoint is an expensive operation, as we need
to consider factors such as distance, angle, and obstacles between the
viewpoint and the target. Hence, a straightforward approach to construct the
VCM that requires visibility computation for every viewpoint of the surrounding
space of the target, is prohibitively expensive in terms of both I/Os and
computation, especially for a real dataset comprising of thousands of
obstacles. We propose an efficient approach to compute the VCM based on a key
property of the human vision that eliminates the necessity of computing the
visibility for a large number of viewpoints of the space. To further reduce the
computational overhead, we propose two approximations; namely, minimum bounding
rectangle and tangential approaches with guaranteed error bounds. Our extensive
experiments demonstrate the effectiveness and efficiency of our solutions to
construct the VCM for real 2D and 3D datasets.
| arxiv topic:cs.DB |
arxiv_dataset-47241310.7397 | Deconstructing Queue-Based Mutual Exclusion
cs.DC
We formulate a modular approach to the design and analysis of a particular
class of mutual exclusion algorithms for shared memory multiprocessor systems.
Specifically, we consider algorithms that organize waiting processes into a
queue. Such algorithms can achieve O(1) remote memory reference (RMR)
complexity, which minimizes (asymptotically) the amount of traffic through the
processor-memory interconnect. We first describe a generic mutual exclusion
algorithm that relies on a linearizable implementation of a particular
queue-like data structure that we call MutexQueue. Next, we show two
implementations of MutexQueue using O(1) RMRs per operation based on
synchronization primitives commonly available in multiprocessors. These
implementations follow closely the queuing code embedded in previously
published mutual exclusion algorithms. We provide rigorous correctness proofs
and RMR complexity analyses of the algorithms we present.
| arxiv topic:cs.DC |
arxiv_dataset-47251310.7497 | Shock-induced $\mathcal{PT}$-symmetric potentials in gas-filled photonic
crystal fibers
physics.optics
We have investigated the interaction between a strong soliton and a weak
probe with certain configurations that allow optical trapping in gas-filled
hollow-core photonic crystal fibers in the presence of the shock effect. We
have shown theoretically and numerically that the shock term can lead to an
unbroken parity-time $ \left(\mathcal{PT}\right) $ symmetry potential in these
kinds of fibers. Reciprocity breaking, a remarkable feature of the $
\mathcal{PT} $ symmetry, is also demonstrated numerically. Our results will
open different configurations and avenues for observing $ \mathcal{PT}
$-symmetry breaking in optical fibers, without the need to resort to cumbersome
dissipative structures.
| arxiv topic:physics.optics |
arxiv_dataset-47261310.7597 | How Fabulous Is Fab 5 Cosmology?
astro-ph.CO gr-qc
Extended gravity origins for cosmic acceleration can solve some fine tuning
issues and have useful characteristics, but generally have little to say
regarding the cosmological constant problem. Fab 5 gravity can be ghost free
and stable, have attractor solutions in the past and future, and possess self
tuning that solves the original cosmological constant problem. Here we show
however it does not possess all these qualities at the same time. We also
demonstrate that the self tuning is so powerful that it not only cancels the
cosmological constant but also all other energy density, and we derive the
scalings of its approach to a renormalized de Sitter cosmology. While this
strong cancellation is bad for the late universe, it greatly eases early
universe inflation.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-47271310.7697 | Linear Convergence of Comparison-based Step-size Adaptive Randomized
Search via Stability of Markov Chains
cs.NA
In this paper, we consider comparison-based adaptive stochastic algorithms
for solving numerical optimisation problems. We consider a specific subclass of
algorithms that we call comparison-based step-size adaptive randomized search
(CB-SARS), where the state variables at a given iteration are a vector of the
search space and a positive parameter, the step-size, typically controlling the
overall standard deviation of the underlying search distribution.We investigate
the linear convergence of CB-SARS on\emph{scaling-invariant} objective
functions. Scaling-invariantfunctions preserve the ordering of points with
respect to their functionvalue when the points are scaled with the same
positive parameter (thescaling is done w.r.t. a fixed reference point). This
class offunctions includes norms composed with strictly increasing functions
aswell as many non quasi-convex and non-continuousfunctions. On
scaling-invariant functions, we show the existence of ahomogeneous Markov
chain, as a consequence of natural invarianceproperties of CB-SARS (essentially
scale-invariance and invariance tostrictly increasing transformation of the
objective function). We thenderive sufficient conditions for \emph{global
linear convergence} ofCB-SARS, expressed in terms of different stability
conditions of thenormalised homogeneous Markov chain (irreducibility,
positivity, Harrisrecurrence, geometric ergodicity) and thus define a general
methodologyfor proving global linear convergence of CB-SARS algorithms
onscaling-invariant functions. As a by-product we provide aconnexion between
comparison-based adaptive stochasticalgorithms and Markov chain Monte Carlo
algorithms.
| arxiv topic:cs.NA |
arxiv_dataset-47281310.7797 | Set-reconstructibility of Post classes
math.CO math.RA
The clones of Boolean functions are classified in regard to
set-reconstructibility via a strong dichotomy result: the clones containing
only affine functions, conjunctions, disjunctions or constant functions are
set-reconstructible, whereas the remaing clones are not weakly reconstructible.
| arxiv topic:math.CO math.RA |
arxiv_dataset-47291310.7897 | Positivity violations in QCD
hep-ph
Both lattice simulations and theoretical studies show that the spectral
function of the gluon propagator of QCD (in various gauges, as well as for the
gauge-invariant Pinch Technique, or PT, propagator) is not non-negative
everywhere, although it should be if it has a physical interpretation as in
QED. Theory says moreover that the non-positive spectral function of the
Landau-gauge or of the PT gluon propagator is further constrained to obey a
superconvergence relation (the integral of the spectral function vanishes). We
review the theoretical and lattice evidence for violation of positivity as well
as various interpretations of this violation, and consider methods for checking
superconvergence on the lattice (so far undone). The most common interpretation
is that positivity violation implies confinement of gluons, so the gluon
propagator does not describe processes with physical gluons. Another more
direct and gauge-invariant interpretation arises from the PT: Asymptotic
freedom alone demands non-positivity and superconvergence.
| arxiv topic:hep-ph |
arxiv_dataset-47301310.7997 | Exponential Convergence of Non-Linear Monotone SPDEs
math.PR
For a Markov semigroup $P_t$ with invariant probability measure $\mu$, a
constant $\ll>0$ is called a lower bound of the ultra-exponential convergence
rate of $P_t$ to $\mu$, if there exists a constant $C\in (0,\infty)$ such that
$$ \sup_{\mu(f^2)\le 1}\|P_tf-\mu(f)\|_\infty \le C \e^{-\ll t},\ \ t\ge 1.$$
By using the coupling by change of measure in the line of [F.-Y. Wang, Ann.
Probab. 35(2007), 1333--1350], explicit lower bounds of the ultra-exponential
convergence rate are derived for a class of non-linear monotone stochastic
partial differential equations. The main result is illustrated by the
stochastic porous medium equation and the stochastic $p$-Laplace equation
respectively. Finally, the $V$-uniformly exponential convergence is
investigated for stochastic fast-diffusion equations.
| arxiv topic:math.PR |
arxiv_dataset-47311310.8097 | Guaranteed Collision Detection With Toleranced Motions
cs.CG cs.RO
We present a method for guaranteed collision detection with toleranced
motions. The basic idea is to consider the motion as a curve in the
12-dimensional space of affine displacements, endowed with an object-oriented
Euclidean metric, and cover it with balls. The associated orbits of points,
lines, planes and polygons have particularly simple shapes that lend themselves
well to exact and fast collision queries. We present formulas for elementary
collision tests with these orbit shapes and we suggest an algorithm, based on
motion subdivision and computation of bounding balls, that can give a
no-collision guarantee. It allows a robust and efficient implementation and
parallelization. At hand of several examples we explore the asymptotic behavior
of the algorithm and compare different implementation strategies.
| arxiv topic:cs.CG cs.RO |
arxiv_dataset-47321310.8197 | Study of forward Z+jet production in pp collisions at $\sqrt{s} = 7$ TeV
hep-ex
A measurement of the $Z(\rightarrow\mu^+\mu^-)$+jet production cross-section
in $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV is presented.
The analysis is based on an integrated luminosity of $1.0\,\text{fb}^{-1}$
recorded by the LHCb experiment. Results are shown with two jet transverse
momentum thresholds, 10 and 20 GeV, for both the overall cross-section within
the fiducial volume, and for six differential cross-section measurements. The
fiducial volume requires that both the jet and the muons from the Z boson decay
are produced in the forward direction ($2.0<\eta<4.5$). The results show good
agreement with theoretical predictions at the second-order expansion in the
coupling of the strong interaction.
| arxiv topic:hep-ex |
arxiv_dataset-47331310.8297 | Constraints on variations of m$_\mathrm{p}$/m$_\mathrm{e}$ based on UVES
observations of H$_2$
astro-ph.CO
This article summarizes the latest results on the proton-to-electron mass
ratio $\mu$ derived from H$_2$ observations at high redshift in the light of
possible variations of fundamental physical constants.
The focus lies on UVES observations of the past years as enormous progress
was achieved since the first positive results on $\Delta\mu/\mu$ were
published. With the better understanding of systematics, dedicated observation
runs, and numerous approaches to improve wavelength calibration accuracy, all
current findings are in reasonable good agreement with no variation and provide
an upper limit of $\Delta\mu/\mu$ $< 1\times 10^{-5}$ for the redshift range of
$2 <$ z $< 3$.
| arxiv topic:astro-ph.CO |
arxiv_dataset-47341310.8397 | Linear Convergence on Positively Homogeneous Functions of a Comparison
Based Step-Size Adaptive Randomized Search: the (1+1) ES with Generalized
One-fifth Success Rule
cs.NA
In the context of unconstraint numerical optimization, this paper
investigates the global linear convergence of a simple probabilistic
derivative-free optimization algorithm (DFO). The algorithm samples a candidate
solution from a standard multivariate normal distribution scaled by a step-size
and centered in the current solution. This solution is accepted if it has a
better objective function value than the current one. Crucial to the algorithm
is the adaptation of the step-size that is done in order to maintain a certain
probability of success. The algorithm, already proposed in the 60's, is a
generalization of the well-known Rechenberg's $(1+1)$ Evolution Strategy (ES)
with one-fifth success rule which was also proposed by Devroye under the name
compound random search or by Schumer and Steiglitz under the name step-size
adaptive random search. In addition to be derivative-free, the algorithm is
function-value-free: it exploits the objective function only through
comparisons. It belongs to the class of comparison-based step-size adaptive
randomized search (CB-SARS). For the convergence analysis, we follow the
methodology developed in a companion paper for investigating linear convergence
of CB-SARS: by exploiting invariance properties of the algorithm, we turn the
study of global linear convergence on scaling-invariant functions into the
study of the stability of an underlying normalized Markov chain (MC). We hence
prove global linear convergence by studying the stability (irreducibility,
recurrence, positivity, geometric ergodicity) of the normalized MC associated
to the $(1+1)$-ES. More precisely, we prove that starting from any initial
solution and any step-size, linear convergence with probability one and in
expectation occurs. Our proof holds on unimodal functions that are the
composite of strictly increasing functions by positively homogeneous functions
with degree $\alpha$ (assumed also to be continuously differentiable). This
function class includes composite of norm functions but also non-quasi convex
functions. Because of the composition by a strictly increasing function, it
includes non continuous functions. We find that a sufficient condition for
global linear convergence is the step-size increase on linear functions, a
condition typically satisfied for standard parameter choices. While introduced
more than 40 years ago, we provide here the first proof of global linear
convergence for the $(1+1)$-ES with generalized one-fifth success rule and the
first proof of linear convergence for a CB-SARS on such a class of functions
that includes non-quasi convex and non-continuous functions. Our proof also
holds on functions where linear convergence of some CB-SARS was previously
proven, namely convex-quadratic functions (including the well-know sphere
function).
| arxiv topic:cs.NA |
arxiv_dataset-47351310.8497 | Counter-gradient heat transport in two-dimensional turbulent
Rayleigh-B\'{e}nard convection
physics.flu-dyn
We present high-resolution numerical investigations of heat transport by
two-dimensional (2D) turbulent Rayleigh-B\'{e}nard (RB) convection over the
Rayleigh number range $10^8 \leqslant Ra\leqslant 10^{10}$ and the Prandtl
number range $0.7\leqslant Pr \leqslant10$. We find that there exist strong
counter-gradient local heat flux with magnitude much larger than the global
Nusselt number $Nu$ of the system. Two mechanisms for generating
counter-gradient heat transport are identified: one is due to the bulk dynamics
and the other is due to the competitions between the corner-flow rolls and the
large-scale circulation (LSC). While the magnitude of the former is found to
increase with increasing Prandtl number, that of the latter maximizes at medium
$Pr$. We further reveal that the corner-LSC competitions lead to the anomalous
$Nu$-$Pr$ relation in 2D RB convection, i.e. $Nu(Pr)$ minimizes, rather than
maximizes as in three-dimensional cylindrical case, at $Pr\approx2\sim3$ for
moderate $Ra$.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-47361310.8597 | Search for $C=+$ charmonium states in $e^+e^-\to \gamma+~X$ at
BEPCII/BESIII
hep-ph
We extend our original study in Ref. [1] on the production of $C=+$
charmonium states $X=\eta_c(1S/2S)$ and $\chi_{cJ}(1P/2P)$ in
$e^+e^-\to\gamma~+~X$ at B factories to the BEPCII/BESIII energy region with
$\sqrt{s}=4.0\mbox{-}5.0$ GeV. In the framework of nonrelativistic QCD
factorization, the cross sections are estimated to be as large as
$0.1\mbox{-}0.9$ pb. The results could be used to search for the missing $2P$
charmonium states or to estimate the continuum backgrounds in the resonance
region.
| arxiv topic:hep-ph |
arxiv_dataset-47371311.0039 | Dilute Magnetism and Spin-Orbital Percolation Effects in Rh-doped
Sr2IrO4
cond-mat.str-el
We have used a combination of resonant magnetic x-ray scattering (RMXS) and
x-ray absorption spectroscopy (XAS) to investigate the properties of the doped
spin-orbital Mott insulator Sr2Ir(1-x)Rh(x)O4 (0.07 < x < 0.70). We show that
Sr2Ir(1-x)Rh(x)O4 represents a unique model system for the study of dilute
magnetism in the presence of strong spin-orbit coupling, and provide evidence
of a doping-induced change in magnetic structure and a suppression of magnetic
order at x_c ~ 0.17. We demonstrate that Rh-doping introduces Rh3+/Ir5+ ions
which effectively hole-dope this material. We propose that the magnetic phase
diagram for this material can be understood in terms of a novel spin-orbital
percolation picture.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-47381311.0139 | Probing a dark matter density spike at the Galactic Center
astro-ph.HE astro-ph.CO hep-ph
The dark matter halo profile in the inner Galaxy is very uncertain. Yet its
radial dependence toward the Galactic Center is of crucial importance for the
determination of the gamma-ray and radio fluxes originating from dark matter
annihilations. Here we use synchrotron emission to probe the dark matter energy
distribution in the inner Galaxy. We first solve the problem of the cosmic ray
diffusion on very small scales, typically smaller than 10^{-3} pc, by using a
Green's function approach and use this technique to quantify the effect of a
spiky profile (rho(r) ~ r^{-7/3}) on the morphology and intensity of the
synchrotron emission expected from dark matter. We illustrate our results using
10 and 800 GeV candidate weakly interacting dark matter particles annihilating
directly into e+ e-. Our most critical assumptions are that the dark matter is
heavier than a few GeV and directly produces a reasonable amount of electrons
and positrons in the Galaxy. We conclude that dark matter indirect detection
techniques (including the Planck experiment) could be used to shed light on the
dark matter halo profile on scales that lie beyond the capability of any
current numerical simulations.
| arxiv topic:astro-ph.HE astro-ph.CO hep-ph |
arxiv_dataset-47391311.0239 | Mass of a Black Hole Firewall
gr-qc hep-th
Quantum entanglement of Hawking radiation has been supposed to give rise to a
Planck density "firewall" near the event horizon of old black holes. We show
that Planck density firewalls are excluded by Einstein's equations for black
holes of mass exceeding the Planck mass. We find an upper limit of $1/(8\pi M)$
to the surface density of a firewall in a Schwarzschild black hole of mass $M$,
translating for astrophysical black holes into a firewall density smaller than
Planck density by more than 30 orders of magnitude. A strict upper limit on the
firewall density is given by the Planck density times the ratio $M_{\rm
Pl}/(8\pi M)$.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-47401311.0339 | A Novel Term Weighing Scheme Towards Efficient Crawl of Textual
Databases
cs.IR
The Hidden Web is the vast repository of informational databases available
only through search form interfaces, accessible by therein typing a set of
keywords in the search forms. Typically, a Hidden Web crawler is employed to
autonomously discover and download pages from the Hidden Web. Traditional
hidden web crawlers do not provide the search engines with an optimal search
experience because of the excessive number of search requests posed through the
form interface so as to exhaustively crawl and retrieve the contents of the
target hidden web database. Here in our work, we provide a framework to
investigate the problem of optimal search and curtail it by proposing an
effective query term selection approach based on the frequency & distribution
of terms in the document database. The paper focuses on developing a
term-weighing scheme called VarDF (acronym for variable document frequency)
that can ease the identification of optimal terms to be used as queries on the
interface for maximizing the achieved coverage of the crawler which in turn
will facilitate the search engine to have a diversified and expanded index. We
experimentally evaluate the effectiveness of our approach on a manually created
database of documents in the area of Information Retrieval.
| arxiv topic:cs.IR |
arxiv_dataset-47411311.0439 | The role of $N^*(2120)$ nucleon resonance in $K\Lambda(1520)$ photon and
hadronic productions
nucl-th
The associate $K\Lambda(1520)$ photon and hadronic production in the $\gamma
p \to K^+\Lambda(1520)$, $p p \to p K^+ \Lambda(1520)$ and $\pi^- p \to K^0
\Lambda(1520)$ reactions are investigated within the effective Lagrangian
approach and the isobar model. We are interested in the contribution from the
$N^*(2120)$ (previously called $N^*(2080)$) resonance, which has a significant
coupling to the $K\Lambda(1520)$ channel. The theoretical results show that the
current experimental data for the $\gamma p \to K^+\Lambda(1520)$ reaction
favor the existence of the $N^*(2120)$ resonance, and that these measurements
can be used to further constrain its properties. We present results, including
the $N^*(2120)$ contribution, for total cross sections of the $\gamma p \to
K^+\Lambda(1520)$, $\pi^- p \to K^0 \Lambda(1520)$, and $p p \to p K^+
\Lambda(1520)$ reactions. For this latter one, we also calculate invariant mass
and Dalitz plot distributions.
| arxiv topic:nucl-th |
arxiv_dataset-47421311.0539 | Online and size anti-Ramsey numbers
math.CO
A graph is properly edge-colored if no two adjacent edges have the same
color. The smallest number of edges in a graph any of whose proper edge
colorings contains a totally multicolored copy of a graph H is the size
anti-Ramsey number AR_s(H) of H. This number in offline and online setting is
investigated here.
| arxiv topic:math.CO |
arxiv_dataset-47431311.0639 | Kinetics of the elementary act of electrochemical reactions at the
semiconductor--electrolyte solution interface
physics.chem-ph cond-mat.mtrl-sci
In the framework of the quantum-mechanical theory of elementary act of
non-adiabatic electrochemical reactions, it is carried out the calculation of
the discharge current of ions at the semiconductor--electrolyte solution
interface using the model of isotropic spherically symmetric band. It is shown
that our results generalize the well-known formulae for the current density
obtained by Dogonadze, Kuznetsov, and Chizmadzhev [R.R. Dogonadze, A.M.
Kuznetsov, and Yu.A. Chizmadzhev, The kinetics of some heterogeneous reactions
at semiconductor--electrolyte interface, Zhur. Fiz. Khim. 38 (1964)
1195--1202]. The average densities of states in the valence band and the
conduction band of the semiconductor electrode in the heterogeneous charge
transfer are found.
| arxiv topic:physics.chem-ph cond-mat.mtrl-sci |
arxiv_dataset-47441311.0739 | Alignment of vorticity and rods with Lagrangian fluid stretching in
turbulence
physics.flu-dyn
Stretching in continuum mechanics is naturally described using the
Cauchy-Green strain tensors. These tensors quantify the Lagrangian stretching
experienced by a material element, and provide a powerful way to study
processes in turbulent fluid flows that involve stretching such as vortex
stretching and alignment of anisotropic particles. Analyzing data from a
simulation of isotropic turbulence, we observe preferential alignment between
anisotropic particles and vorticity. We show that this alignment arises because
both of these quantities independently tend to align with the strongest
Lagrangian stretching direction, as defined by the maximum eigenvector of the
left Cauchy-Green strain tensor. In particular, anisotropic particles approach
almost perfect alignment with the strongest stretching direction. The alignment
of vorticity with stretching is weaker, but still much stronger than previously
observed alignment of vorticity with the eigenvectors of the Eulerian strain
rate tensor. The alignment of strong vorticity is almost the same as that of
rods that have experienced the same stretching.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-47451311.0839 | Computation of hyperspherical Bessel functions
astro-ph.IM astro-ph.CO physics.comp-ph
In this paper we present a fast and accurate numerical algorithm for the
computation of hyperspherical Bessel functions of large order and real
arguments. For the hyperspherical Bessel functions of closed type, no stable
algorithm existed so far due to the lack of a backwards recurrence. We solved
this problem by establishing a relation to Gegenbauer polynomials. All our
algorithms are written in C and are publicly available at Github
[https://github.com/lesgourg/class_public]. A Python wrapper is available upon
request.
| arxiv topic:astro-ph.IM astro-ph.CO physics.comp-ph |
arxiv_dataset-47461311.0939 | An application of liaison theory to the Eisenbud-Green-Harris conjecture
math.AC math.AG
In this paper, we apply liaison theory to the Eisenbud-Green-Harris
conjecture and prove that the conjecture holds for a certain subclass of
homogeneous ideals in the linkage class of a complete intersection ideal. In
the case of three variables, we prove that the conjecture holds for Gorenstein
ideals.
| arxiv topic:math.AC math.AG |
arxiv_dataset-47471311.1039 | Maximum penalized likelihood estimation in semiparametric
capture-recapture models
stat.AP q-bio.QM stat.ME
We discuss the semiparametric modeling of mark-recapture-recovery data where
the temporal and/or individual variation of model parameters is explained via
covariates. Typically, in such analyses a fixed (or mixed) effects parametric
model is specified for the relationship between the model parameters and the
covariates of interest. In this paper, we discuss the modeling of the
relationship via the use of penalized splines, to allow for considerably more
flexible functional forms. Corresponding models can be fitted via numerical
maximum penalized likelihood estimation, employing cross-validation to choose
the smoothing parameters in a data-driven way. Our contribution builds on and
extends the existing literature, providing a unified inferential framework for
semiparametric mark-recapture-recovery models for open populations, where the
interest typically lies in the estimation of survival probabilities. The
approach is applied to two real datasets, corresponding to grey herons (Ardea
Cinerea), where we model the survival probability as a function of
environmental condition (a time-varying global covariate), and Soay sheep (Ovis
Aries), where we model the survival probability as a function of individual
weight (a time-varying individual-specific covariate). The proposed
semiparametric approach is compared to a standard parametric (logistic)
regression and new interesting underlying dynamics are observed in both cases.
| arxiv topic:stat.AP q-bio.QM stat.ME |
arxiv_dataset-47481311.1139 | Hysteresis and Relaxation Effects in the Spin-Ice Compound
Dy$_2$Ti$_2$O$_7$ studied by Heat Transport
cond-mat.str-el
The low-temperature thermal conductivity $\kappa$ of the spin-ice compound
Dy$_2$Ti$_2$O$_7$ shows pronounced hysteresis as a function of magnetic field.
Here, we investigate how these hysteresis effects depend on temperature, the
magnetic-field direction, the rate of magnetic-field change, and on the
direction of the heat current. In addition, the time-dependent relaxation of
the heat conductivity is investigated. These measurements yield information
about possible equilibrium states and reveal that in the low-field and
low-temperature region extremely slow relaxation processes occur.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-47491311.1239 | Quantum criticality and Lifshitz transition in the Ising system
CeRu2Si2: Comparison with YbRh2Si2
cond-mat.str-el
New thermoelectric power (TEP) measurements on prototype heavy-fermion
compounds close to magnetic quantum criticality are presented. The highly
sensitive technique of TEP is an unique tool to reveal Fermi surface
instabilities, referred here as Lifshitz transitions. The first focus is on the
Ising CeRu2Si2 series. Doping CeRu2Si2 with Rh produces a decoupling between
the first order metamagnetic transition and the pseudo-metamagnetism observed
in the pure compound. Comparison is made with the case of YbRh2Si2 which is
often considered as the archetype of local quantum criticality by contrast to
CeRu2Si2, taken as an example of spin-density wave criticality. Up to now for
ferromagnetic materials showing ferromagnetic wings, no simple case appears
where the Fermi surface is preserved between the ferromagnetic and paramagnetic
phases. An open issue is the consequence of Lifshitz transitions on
superconductivity in these multiband systems.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-47501311.1339 | Zero-Error Capacity of a Class of Timing Channels
cs.IT cs.DM math.IT
We analyze the problem of zero-error communication through timing channels
that can be interpreted as discrete-time queues with bounded waiting times. The
channel model includes the following assumptions: 1) Time is slotted, 2) at
most $ N $ "particles" are sent in each time slot, 3) every particle is delayed
in the channel for a number of slots chosen randomly from the set $ \{0, 1,
\ldots, K\} $, and 4) the particles are identical. It is shown that the
zero-error capacity of this channel is $ \log r $, where $ r $ is the unique
positive real root of the polynomial $ x^{K+1} - x^{K} - N $.
Capacity-achieving codes are explicitly constructed, and a linear-time decoding
algorithm for these codes devised. In the particular case $ N = 1 $, $ K = 1 $,
the capacity is equal to $ \log \phi $, where $ \phi = (1 + \sqrt{5}) / 2 $ is
the golden ratio, and the constructed codes give another interpretation of the
Fibonacci sequence.
| arxiv topic:cs.IT cs.DM math.IT |
arxiv_dataset-47511311.1439 | Magnetoresistance of granular Pt-C nanostructures close to the
metal-insulator-transition
cond-mat.mes-hall
We investigate the electrical and magneto-transport properties of Pt-C
granular metals prepared by focused-electron-beam induced deposition. In
particular, we consider samples close to the metal-insulator-transition
obtained from as-grown deposits by means of a low- energy electron irradiation
treatment. The temperature dependence of the conductivity shows a lnT behavior
with a transition to square root of T at low temperature, as expected for
systems in the strong-coupling tunneling regime. The magnetoresistance is
positive and is described within the wave-function shrinkage model, normally
used for disordered system in the weak-coupling regime. In order to fit the
experimental data spin-dependent tunneling has to be taken into account. In the
discussion we attribute the origin of the spin-dependency to confinement
effects of Pt nano-grains embedded in the carbon matrix.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-47521311.1539 | Category-Theoretic Quantitative Compositional Distributional Models of
Natural Language Semantics
cs.CL cs.LG math.CT math.LO
This thesis is about the problem of compositionality in distributional
semantics. Distributional semantics presupposes that the meanings of words are
a function of their occurrences in textual contexts. It models words as
distributions over these contexts and represents them as vectors in high
dimensional spaces. The problem of compositionality for such models concerns
itself with how to produce representations for larger units of text by
composing the representations of smaller units of text.
This thesis focuses on a particular approach to this compositionality
problem, namely using the categorical framework developed by Coecke, Sadrzadeh,
and Clark, which combines syntactic analysis formalisms with distributional
semantic representations of meaning to produce syntactically motivated
composition operations. This thesis shows how this approach can be
theoretically extended and practically implemented to produce concrete
compositional distributional models of natural language semantics. It
furthermore demonstrates that such models can perform on par with, or better
than, other competing approaches in the field of natural language processing.
There are three principal contributions to computational linguistics in this
thesis. The first is to extend the DisCoCat framework on the syntactic front
and semantic front, incorporating a number of syntactic analysis formalisms and
providing learning procedures allowing for the generation of concrete
compositional distributional models. The second contribution is to evaluate the
models developed from the procedures presented here, showing that they
outperform other compositional distributional models present in the literature.
The third contribution is to show how using category theory to solve linguistic
problems forms a sound basis for research, illustrated by examples of work on
this topic, that also suggest directions for future research.
| arxiv topic:cs.CL cs.LG math.CT math.LO |
arxiv_dataset-47531311.1639 | GIANO-TNG spectroscopy of red supergiants in the young star cluster
RSGC2
astro-ph.GA astro-ph.SR
The inner disk of the Galaxy has a number of young star clusters dominated by
red supergiants that are heavily obscured by dust extinction and observable
only at infrared wavelengths. These clusters are important tracers of the
recent star formation and chemical enrichment history in the inner Galaxy.
During the technical commissioning and as a first science verification of the
GIANO spectrograph at the Telescopio Nazionale Galileo, we secured
high-resolution (R~50,000) near-infrared spectra of three red supergiants in
the young Scutum cluster RSGC2. Taking advantage of the full YJHK spectral
coverage of GIANO in a single exposure, we were able to identify several tens
of atomic and molecular lines suitable for chemical abundance determinations.
By means of spectral synthesis and line equivalent width measurements, we
obtained abundances of Fe and other iron-peak elements such as V, Cr, Ni, of
alpha (O, Mg, Si, Ca and Ti) and other light elements (C, N, Na, Al, K, Sc),
and of some s-process elements (Y, Sr). We found iron abundances between half
and one third solar and solar-scaled [X/Fe] abundance patterns of iron-peak,
alpha and most of the light elements, consistent with a thin-disk chemistry. We
found a depletion of [C/Fe] and enhancement of [N/Fe], consistent with CN
burning, and low 12C/13C abundance ratios (between 9 and 11), requiring
extra-mixing processes in the stellar interiors during the post-main sequence
evolution. Finally, we found a slight [Sr/Fe] enhancement and a slight [Y/Fe]
depletion (by a factor of <=2), with respect to solar.
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-47541311.1739 | General model for simulation of the measurement-device independent
quantum key distribution
quant-ph
We present a general model on the simulation of the measurement-device
independent quantum key distribution (MDI-QKD). It can be used to predict
experimental observations of a MDI-QKD with linear channel loss, simulating
corresponding values for the gains, the error rates in different basis, and
also the final key rates. Our model can be applicable to the MDI-QKDs with
whatever convex source states or using whatever coding schemes. Therefore, it
is useful in characterizing and evaluating the performance of any MDI-QKD
protocols, making it a valuable tool in studying the quantum key distributions.
| arxiv topic:quant-ph |
arxiv_dataset-47551311.1839 | An Efficiently Solvable Quadratic Program for Stabilizing Dynamic
Locomotion
cs.RO
We describe a whole-body dynamic walking controller implemented as a convex
quadratic program. The controller solves an optimal control problem using an
approximate value function derived from a simple walking model while respecting
the dynamic, input, and contact constraints of the full robot dynamics. By
exploiting sparsity and temporal structure in the optimization with a custom
active-set algorithm, we surpass the performance of the best available
off-the-shelf solvers and achieve 1kHz control rates for a 34-DOF humanoid. We
describe applications to balancing and walking tasks using the simulated Atlas
robot in the DARPA Virtual Robotics Challenge.
| arxiv topic:cs.RO |
arxiv_dataset-47561311.1939 | Fast Tracking via Spatio-Temporal Context Learning
cs.CV
In this paper, we present a simple yet fast and robust algorithm which
exploits the spatio-temporal context for visual tracking. Our approach
formulates the spatio-temporal relationships between the object of interest and
its local context based on a Bayesian framework, which models the statistical
correlation between the low-level features (i.e., image intensity and position)
from the target and its surrounding regions. The tracking problem is posed by
computing a confidence map, and obtaining the best target location by
maximizing an object location likelihood function. The Fast Fourier Transform
is adopted for fast learning and detection in this work. Implemented in MATLAB
without code optimization, the proposed tracker runs at 350 frames per second
on an i7 machine. Extensive experimental results show that the proposed
algorithm performs favorably against state-of-the-art methods in terms of
efficiency, accuracy and robustness.
| arxiv topic:cs.CV |
arxiv_dataset-47571311.2039 | Recent VERITAS Results
astro-ph.HE
VERITAS is an array of four imaging atmospheric Cherenkov telescopes near
Tucson, Arizona and is one of the world's most sensitive detectors of very high
energy (VHE: >100 GeV) gamma rays. The scientific reach of VERITAS covers the
study of both extragalactic and Galactic objects as well as the search for
astrophysical dark matter. In these proceedings we will discuss the status of
VERITAS operations and upgrades and present a selection of recent results.
| arxiv topic:astro-ph.HE |
arxiv_dataset-47581311.2139 | Large Margin Semi-supervised Structured Output Learning
cs.LG
In structured output learning, obtaining labelled data for real-world
applications is usually costly, while unlabelled examples are available in
abundance. Semi-supervised structured classification has been developed to
handle large amounts of unlabelled structured data. In this work, we consider
semi-supervised structural SVMs with domain constraints. The optimization
problem, which in general is not convex, contains the loss terms associated
with the labelled and unlabelled examples along with the domain constraints. We
propose a simple optimization approach, which alternates between solving a
supervised learning problem and a constraint matching problem. Solving the
constraint matching problem is difficult for structured prediction, and we
propose an efficient and effective hill-climbing method to solve it. The
alternating optimization is carried out within a deterministic annealing
framework, which helps in effective constraint matching, and avoiding local
minima which are not very useful. The algorithm is simple to implement and
achieves comparable generalization performance on benchmark datasets.
| arxiv topic:cs.LG |
arxiv_dataset-47591311.2239 | On the linear operation of cloned dynamical systems and its Lyapunov
exponents
nlin.CD physics.ao-ph
The cloned dynamical system theory is introduced and the Lyapunov exponents
of this system are qualitatively proven to be same as the original dynamical
system. This property indicates that these two systems have the same error
propagation speed in the phase space, and thus we can interpret the phenomenon
as why the ensemble mean method sometimes is not effective.
| arxiv topic:nlin.CD physics.ao-ph |
arxiv_dataset-47601311.2339 | Non-formal deformation quantization and star-exponential of the Poincare
Group
math.QA math-ph math.DG math.FA math.MP
We recall the construction of non-formal deformation quantization of the
Poincare Group ISO(1,1) on its coadjoint orbit and exhibit the associated
non-formal star-exponentials.
| arxiv topic:math.QA math-ph math.DG math.FA math.MP |
arxiv_dataset-47611311.2439 | Derivations and Alberti representations
math.MG math.DG
We relate generalized Lebesgue decompositions of measures in terms of curve
fragments (Alberti representations) and Weaver derivations. This correspondence
leads to a geometric characterization of the local norm on the Weaver cotangent
bundle of a metric measure space $(X,\mu)$: the local norm of a form $df$ sees
how fast $f$ grows on curve fragments seen by $\mu$. This implies a new
characterization of differentiability spaces in terms of the
$\mu$-a.e.~equality of the local norm of $df$ and the local Lipschitz constant
of $f$. As a consequence, the Lip-lip inequality of Keith must be an equality.
We also provide dimensional bounds for the module of derivations in terms of
the Assouad dimension of $X$.
| arxiv topic:math.MG math.DG |
arxiv_dataset-47621311.2539 | Field independent cosmic evolution
gr-qc
It has been shown earlier that Noether symmetry does not admit a form of F(R)
corresponding to an action in which F(R) is coupled to scalar-tensor action for
gravity or even for pure F(R) gravity taking anisotropic model into account.
Here, we prove that F(R) theory of gravity does not admit Noether symmetry even
if it is coupled to Tachyonic field and considering a gauge in addition. To
handle such a theory, a general conserved current has been constructed under a
condition which decouples higher order curvature part from the field part. This
condition in principle, solves for the scale factor, independently. Thus
cosmological evolution remains independent of the form of the chosen field,
whether it be a scalar or a tachyon.
| arxiv topic:gr-qc |
arxiv_dataset-47631311.2639 | Texture and Cofactor Zeros of the Neutrino Mass Matrix
hep-ph
We study Majorana neutrino mass matrices that have two texture zeros, or two
cofactor zeros, or one texture zero and one cofactor zero. The two
texture/cofactor zero conditions give four constraints, which in conjunction
with the five measured oscillation parameters completely determine the nine
independent real parameters of the neutrino mass matrix. We also study the
implications that future measurements of neutrinoless double beta decay and the
Dirac CP phase will have on these cases.
| arxiv topic:hep-ph |
arxiv_dataset-47641311.2739 | Effects of the symmetry energy on the kaon condensates in the QMC Model
nucl-th astro-ph.HE
In this work we investigate protoneutron star properties within a modified
version of the quark coupling model (QMC) that incorporates a omega-rho
interaction plus kaon condensed matter at finite temperature. Fixed entropy and
trapped neutrinos are taken into account. Our results are compared with the
ones obtained with the GM1 parametrization of the non-linear Walecka model for
similar values of the symmetry energy slope. Contrary to GM1, within the QMC
the formation of low mass black-holes during cooling are not probable. It is
shown that the evolution of the protoneutron star may include the melting of
the kaon condensate driven by the neutrino diffusion, followed by the formation
of a second condensate after cooling. The signature of this complex proccess
could be a neutrino signal followed by a gamma ray burst. We have seen that
both models can, in general, describe very massive stars.
| arxiv topic:nucl-th astro-ph.HE |
arxiv_dataset-47651311.2839 | Gossip vs. Markov Chains, and Randomness-Efficient Rumor Spreading
cs.DC cs.CC cs.DS math.PR
We study gossip algorithms for the rumor spreading problem which asks one
node to deliver a rumor to all nodes in an unknown network. We present the
first protocol for any expander graph $G$ with $n$ nodes such that, the
protocol informs every node in $O(\log n)$ rounds with high probability, and
uses $\tilde{O}(\log n)$ random bits in total. The runtime of our protocol is
tight, and the randomness requirement of $\tilde{O}(\log n)$ random bits almost
matches the lower bound of $\Omega(\log n)$ random bits for dense graphs. We
further show that, for many graph families, polylogarithmic number of random
bits in total suffice to spread the rumor in $O(\mathrm{poly}\log n)$ rounds.
These results together give us an almost complete understanding of the
randomness requirement of this fundamental gossip process.
Our analysis relies on unexpectedly tight connections among gossip processes,
Markov chains, and branching programs. First, we establish a connection between
rumor spreading processes and Markov chains, which is used to approximate the
rumor spreading time by the mixing time of Markov chains. Second, we show a
reduction from rumor spreading processes to branching programs, and this
reduction provides a general framework to derandomize gossip processes. In
addition to designing rumor spreading protocols, these novel techniques may
have applications in studying parallel and multiple random walks, and
randomness complexity of distributed algorithms.
| arxiv topic:cs.DC cs.CC cs.DS math.PR |
arxiv_dataset-47661311.2939 | Topological energy bounds in generalized Skyrme models
hep-th math-ph math.MP
The Skyrme model has a natural generalization amenable to a standard
hamiltonian treatment, consisting of the standard sigma model and the Skyrme
terms, a potential, and a certain term sextic in first derivatives. Here we
demonstrate that, in this theory, each pair of terms in the static energy
functional which may support topological solitons according to the Derrick
criterion (i.e., each pair of terms with opposite Derrick scaling) separately
posesses a topological energy bound. As a consequence, there exists a
four-parameter family of topological bounds for the full generalized Skyrme
model. The optimal bounds, i.e., the optimal values of the parameters, depend
both on the form of the potential and on the relative strength of the different
terms. It also follows that various submodels of the generalized Skyrme model
have one-parameter families of topological energy bounds. We also consider the
case of topological bounds for the generalized Skyrme model on a compact base
space as well as generalizations to higher dimensions.
| arxiv topic:hep-th math-ph math.MP |
arxiv_dataset-47671311.3039 | On the radius of habitable planets
astro-ph.EP
The conditions that a planet must fulfill to be habitable are not precisely
known. However, it is comparatively easier to define conditions under which a
planet is very likely not habitable. Finding such conditions is important as it
can help select, in an ensemble of potentially observable planets, which ones
should be observed in greater detail for characterization studies. Assuming, as
in the Earth, that the presence of a C-cycle is a necessary condition for
long-term habitability, we derive, as a function of the planetary mass, a
radius above which a planet is likely not habitable. We compute the maximum
radius a planet can have to fulfill two constraints: surface conditions
compatible with the existence of liquid water, and no ice layer at the bottom
of a putative global ocean. We demonstrate that, above a given radius, these
two constraints cannot be met. We compute internal structure models of planets,
using a five-layer model (core, inner mantle, outer mantle, ocean, and
atmosphere), for different masses and composition of the planets (in
particular, the Fe/Si ratio of the planet). Our results show that for planets
in the Super-Earth mass range (1-12 Mearth), the maximum that a planet, with a
composition similar to that of the Earth, can have varies between 1.7 and 2.2
Rearth. This radius is reduced when considering planets with higher Fe/Si
ratios and taking radiation into account when computing the gas envelope
structure. These results can be used to infer, from radius and mass
determinations using high-precision transit observations like those that will
soon be performed by the CHaracterizing ExOPlanet Satellite (CHEOPS), which
planets are very likely not habitable, and therefore which ones should be
considered as best targets for further habitability studies.}
| arxiv topic:astro-ph.EP |
arxiv_dataset-47681311.3139 | Entropy Assessment of Windows OS Performance Counters
cs.CR
The security of many cryptographic constructions depends on random number
generators for providing unpredictable keys, nonces, initialization vectors and
other parameters. Modern operating systems implement cryptographic
pseudo-random number generators (PRNGs) to fulfill this need. Performance
counters and other system parameters are often used as a low-entropy source to
initialize (seed) the generators. We perform an experiment to analyze all
performance counters in standard installation of Microsoft Windows 7 operating
system, and assess their suitability as entropy sources. Besides selecting top
19 counters, we analyze their mutual information (independence) as well as
robustness in the virtual environment. Final selection contains 14 counters
with sufficient overall entropy for practical applications.
| arxiv topic:cs.CR |
arxiv_dataset-47691311.3239 | On free stochastic processes and their derivatives
math.OA math.FA math.PR
We study a family of free stochastic processes whose covariance kernels $K$
may be derived as a transform of a tempered measure $\sigma$. These processes
arise, for example, in consideration non-commutative analysis involving free
probability. Hence our use of semi-circle distributions, as opposed to
Gaussians. In this setting we find an orthonormal bases in the corresponding
non-commutative $L^2$ of sample-space. We define a stochastic integral for our
family of free processes.
| arxiv topic:math.OA math.FA math.PR |
arxiv_dataset-47701311.3339 | Untwisting algebras with van den Bergh duality into Calabi-Yau algebras
math.KT
Jake Goodman and Ulrich Kr\"ahmer have recently shown that a twisted
Calabi-Yau algebra $A$ with modular automorphism $\sigma$ and dimension $d$ can
be "untwisted," in the sense that the Ore extensions $A[X;\sigma]$ and
$A[X^{\pm1};\sigma]$ are Calabi-Yau algebras of dimension $d+1$. In this note
we show that this in fact extends more generally to the case where we start
with an algebra with van den Bergh duality.
| arxiv topic:math.KT |
arxiv_dataset-47711311.3439 | Helical multiferroics for electric field controlled quantum information
processing
cond-mat.str-el
Magnetoelectric coupling in helical multiferroics allows to steer spin order
with electric fields. Here we show theoretically that in a helical multiferroic
chain quantum information processing as well as quantum phases are highly
sensitive to electric (E) field. Applying E-field, the quantum state transfer
fidelity can be increased and made directionally dependent.
We also show that E field transforms the spin-density-wave/nematic or
multipolar phases of frustrated ferromagnetic spin-1/2 chain in chiral phase
with a strong magnetoelectric coupling. We find sharp reorganization of the
entanglement spectrum as well as a large enhancement of fidelity susceptibility
at Ising quantum phase transition from nematic to chiral states driven by
electric field. These findings point to a new tool for quantum information with
low power consumption.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-47721311.3539 | What Mathematical Theories of Truth Should be Like (and Can be)
math.LO
Hannes Leitgeb formulated eight norms for theories of truth in his paper:
`What Theories of Truth Should be Like (but Cannot be'). We shall present in
this paper a theory of truth for suitably constructed languages which contain
the first-order language of set theory, and prove that it satisfies all those
norms.
| arxiv topic:math.LO |
arxiv_dataset-47731311.3639 | Dynamical evolution of star forming regions
astro-ph.GA
We model the dynamical evolution of star forming regions with a wide range of
initial properties. We follow the evolution of the regions' substructure using
the Q-parameter, we search for dynamical mass segregation using the Lambda_MSR
technique, and we also quantify the evolution of local density around stars as
a function of mass using the Sigma_LDR method.
The amount of dynamical mass segregation measured by Lambda_MSR is generally
only significant for subvirial and virialised, substructured regions - which
usually evolve to form bound clusters. The Sigma_LDR method shows that massive
stars attain higher local densities than the median value in all regions, even
those that are supervirial and evolve to form (unbound) associations.
We also introduce the Q-Sigma_LDR plot, which describes the evolution of
spatial structure as a function of mass-weighted local density in a star
forming region. Initially dense (>1000 stars pc^{-2}), bound regions always
have Q >1, Sigma_LDR > 2 after 5Myr, whereas dense unbound regions always have
Q < 1, Sigma_LDR > 2 after 5Myr. Less dense regions (<100 stars pc^{-2}) do not
usually exhibit Sigma_LDR > 2 values, and if relatively high local density
around massive stars arises purely from dynamics, then the Q-Sigma_LDR plot can
be used to estimate the initial density of a star forming region.
| arxiv topic:astro-ph.GA |
arxiv_dataset-47741311.3739 | An Enriched Constitutive Model for Fracture Propagation Analysis using
the Material Point Method
physics.comp-ph cond-mat.soft
We develop a novel constitutive modeling approach for the analysis of
fracture propagation in quasi-brittle materials using the Material Point
Method. The kinematics of constitutive models is enriched with an additional
mode of localized deformation to take into account the strain discontinuity
once cracking has occurred. The crack details therefore can be stored at
material point level and there is no need to enrich the kinematics of finite
elements to capture the localization caused by fracturing processes. This
enhancement also removes the drawback of classical smeared crack approach in
producing unphysical snapping back constitutive responses when the spatial
resolution is not fine enough. All these facilitate the implementation of the
new approach in the Material Point Method for analysis of large scale problems.
Numerical examples of fracture propagation are used to demonstrate the
effectiveness and potentials of the new approach.
| arxiv topic:physics.comp-ph cond-mat.soft |
arxiv_dataset-47751311.3839 | Plane-wave scattering by self-complementary metasurfaces in terms of
electromagnetic duality and Babinet's principle
physics.optics
We investigate theoretically electromagnetic plane-wave scattering by
self-complementary metasurfaces. By using Babinet's principle extended to
metasurfaces with resistive elements, we show that the frequency-independent
transmission and reflection are realized for normal incidence of a circularly
polarized plane wave onto a self-complementary metasurface, even if there is
diffraction. Next, we consider two special classes of self-complementary
metasurfaces. We show that self-complementary metasurfaces with rotational
symmetry can act as coherent perfect absorbers, and those with translational
symmetry compatible with their self-complementarity can split the incident
power equally, even for oblique incidences.
| arxiv topic:physics.optics |
arxiv_dataset-47761311.3939 | Local computation mechanism design
cs.GT
We introduce the notion of Local Computation Mechanism Design - designing
game theoretic mechanisms which run in polylogarithmic time and space. Local
computation mechanisms reply to each query in polylogarithmic time and space,
and the replies to different queries are consistent with the same global
feasible solution. In addition, the computation of the payments is also done in
polylogarithmic time and space. Furthermore, the mechanisms need to maintain
incentive compatibility with respect to the allocation and payments.
We present local computation mechanisms for a variety of classical
game-theoretical problems: 1. stable matching, 2. job scheduling, 3.
combinatorial auctions for unit-demand and k-minded bidders, and 4. the housing
allocation problem.
For stable matching, some of our techniques may have general implications.
Specifically, we show that when the men's preference lists are bounded, we can
achieve an arbitrarily good approximation to the stable matching within a fixed
number of iterations of the Gale-Shapley algorithm.
| arxiv topic:cs.GT |
arxiv_dataset-47771311.4039 | Fourier-Mukai transformation on algebraic cobordism
math.AG math.KT
We define a notion of Fourier-Mukai transform on algebraic cobordism cycles
with $\mathbb{Q}$-coefficients on an abelian variety. We use this to produce a
Beauville decomposition of algebraic cobordism and study its consequences,
including a decomposition of the cobordism motive of an abelian variety.
| arxiv topic:math.AG math.KT |
arxiv_dataset-47781311.4139 | First-principle study of octahedral tilting and Ferroelectric like
transition in metallic LiOsO3
cond-mat.mtrl-sci
The octahedral tilting and ferroelectric-like structural transition of LiOsO3
metallic perovskite [Nature Materials 12, 1024 (2013)] was examined using
first-principles density-functional theory. In LiOsO3, a-a-a- octahedral
titling mode is responsible for the cubic to rhombohedral structural
transition, which is stable phase at room temperature. At low temperatures, a
non-centrosymmetric transition to a rhombohedra phase was realized due to zone
center phonon softening. The phase transition behavior of LiOsO3 can be
explained fully by density functional calculations and phonon calculations. The
electronic structure and Fermi surface changes due to the electron lattice
coupling effect are also presented. The carrier density of state across the
phase transition is associated with the resistivity, heat capacity, and
susceptibility.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-47791311.4239 | Hypermodular Distributed Solar Power Satellites -- Exploring a
Technology Option for Near-Term LEO Demonstration and GLPO Full-Scale Plants
physics.space-ph astro-ph.IM
This paper presents a new and innovative design for scaleable space solar
power systems based on satellite self-assembly and microwave spatial power
combination. Lower system cost of utility-scale space solar power is achieved
by independence of yet-to-be-built in-space assembly and transportation
infrastructure. Using current and expected near-term technology, this study
explores a design for near-term space solar power low-Earth orbit demonstrators
and for mid-term utility-scale power plants in geosynchronous Laplace plane
orbits. High-level economic considerations in the context of current and
expected future launch costs are given as well.
| arxiv topic:physics.space-ph astro-ph.IM |
arxiv_dataset-47801311.4339 | BOKS 45906: a CV with an orbital period of 56.6 min in the Kepler field?
astro-ph.GA astro-ph.SR
BOKS 45906 was found to be a blue source in the Burrell-Optical-Kepler-Survey
which showed a 3 mag outburst lasting ~5 d. We present the Kepler light curve
of this source which covers nearly 3 years. We find that it is in a faint
optical state for approximately half the time and shows a series of outbursts
separated by distinct dips in flux. Using data with 1 min sampling, we find
clear evidence that in its low state BOKS 45906 shows a flux variability on a
period of 56.5574+/-0.0014 min and a semi-amplitude of ~3 percent. Since we can
phase all the 1 min cadence data on a common ephemeris using this period, it is
probable that 56.56 min is the binary orbital period. Optical spectra of BOKS
45906 show the presence of Balmer lines in emission indicating it is not an AM
CVn (pure Helium) binary. Swift data show that it is a weak X-ray source and is
weakly detected in the bluest of the UVOT filters. We conclude that BOKS 45906
is a cataclysmic variable with a period shorter than the `period-bounce'
systems and therefore BOKS 45906 could be the first helium-rich cataclysmic
variable detected in the Kepler field.
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-47811311.4439 | 60 GHz Wireless Link Within Metal Enclosures: Channel Measurements and
System Analysis
cs.IT math.IT
Wireless channel measurement results for 60 GHz within a closed metal cabinet
are provided. A metal cabinet is chosen to emulate the environment within a
mechatronic system, which have metal enclosures in general. A frequency domain
sounding technique is used to measure the wireless channel for different
volumes of the metal enclosure, considering both line-of-sight (LOS) and
non-line-of-sight (NLOS) scenarios. Large-scale and small-scale characteristics
of the wireless channel are extracted in order to build a comprehensive channel
model. In contrast to conventional indoor channels at 60 GHz, the channel in
the metal enclosure is highly reflective resulting in a rich scattering
environment with a significantly large root-mean-square (RMS) delay spread.
Based on the obtained measurement results, the bit error rate (BER) performance
is evaluated for a wideband orthogonal frequency division multiplexing (OFDM)
system.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-47821311.4539 | On the Marginally Relevant Operator in z=2 Lifshitz Holography
hep-th
We study holographic renormalization and RG flow in a strongly-coupled
Lifshitz-type theory in 2+1 dimensions with dynamical exponent z=2. The
bottom-up gravity dual we use is 3+1 dimensional Einstein gravity coupled to a
massive vector field. This model contains a marginally relevant operator around
the Lifshitz fixed point. We show how holographic renormalization works in the
presence of this marginally relevant operator without the need to introduce
explicitly cutoff-dependent counterterms. A simple closed-form expression is
found for the renormalized on-shell action. We also discuss how asymptotically
Lifshitz geometries flow to AdS in the interior due to the marginally relevant
operator. We study the behavior of the renormalized entanglement entropy and
confirm that it decreases monotonically along the Lifshitz-to-AdS RG flow.
| arxiv topic:hep-th |
arxiv_dataset-47831311.4639 | Post-Proceedings of the First International Workshop on Learning and
Nonmonotonic Reasoning
cs.AI cs.LG cs.LO
Knowledge Representation and Reasoning and Machine Learning are two important
fields in AI. Nonmonotonic logic programming (NMLP) and Answer Set Programming
(ASP) provide formal languages for representing and reasoning with commonsense
knowledge and realize declarative problem solving in AI. On the other side,
Inductive Logic Programming (ILP) realizes Machine Learning in logic
programming, which provides a formal background to inductive learning and the
techniques have been applied to the fields of relational learning and data
mining. Generally speaking, NMLP and ASP realize nonmonotonic reasoning while
lack the ability of learning. By contrast, ILP realizes inductive learning
while most techniques have been developed under the classical monotonic logic.
With this background, some researchers attempt to combine techniques in the
context of nonmonotonic ILP. Such combination will introduce a learning
mechanism to programs and would exploit new applications on the NMLP side,
while on the ILP side it will extend the representation language and enable us
to use existing solvers. Cross-fertilization between learning and nonmonotonic
reasoning can also occur in such as the use of answer set solvers for ILP,
speed-up learning while running answer set solvers, learning action theories,
learning transition rules in dynamical systems, abductive learning, learning
biological networks with inhibition, and applications involving default and
negation. This workshop is the first attempt to provide an open forum for the
identification of problems and discussion of possible collaborations among
researchers with complementary expertise. The workshop was held on September
15th of 2013 in Corunna, Spain. This post-proceedings contains five technical
papers (out of six accepted papers) and the abstract of the invited talk by Luc
De Raedt.
| arxiv topic:cs.AI cs.LG cs.LO |
arxiv_dataset-47841311.4739 | A new view of the Lindemann criterion
cond-mat.dis-nn cond-mat.soft
The Lindemann criterion is reformulated in terms of the average shear modulus
$G_c$ of the melting crystal, indicating a critical melting shear strain which
is necessary to form the many different inherent states of the liquid. In glass
formers with covalent bonds, one has to distinguish between soft and hard
degrees of freedom to reach agreement. The temperature dependence of the
picosecond mean square displacements of liquid and crystal shows that there are
two separate contributions to the divergence of the viscosity with decreasing
temperature: the anharmonic increase of the shear modulus and a diverging
correlation length .
| arxiv topic:cond-mat.dis-nn cond-mat.soft |
arxiv_dataset-47851311.4839 | Ferromagnetic Potts Model: Refined #BIS-hardness and Related Results
cs.CC math-ph math.MP math.PR
Recent results establish for 2-spin antiferromagnetic systems that the
computational complexity of approximating the partition function on graphs of
maximum degree D undergoes a phase transition that coincides with the
uniqueness phase transition on the infinite D-regular tree. For the
ferromagnetic Potts model we investigate whether analogous hardness results
hold. Goldberg and Jerrum showed that approximating the partition function of
the ferromagnetic Potts model is at least as hard as approximating the number
of independent sets in bipartite graphs (#BIS-hardness). We improve this
hardness result by establishing it for bipartite graphs of maximum degree D. We
first present a detailed picture for the phase diagram for the infinite
D-regular tree, giving a refined picture of its first-order phase transition
and establishing the critical temperature for the coexistence of the disordered
and ordered phases. We then prove for all temperatures below this critical
temperature that it is #BIS-hard to approximate the partition function on
bipartite graphs of maximum degree D. As a corollary, it is #BIS-hard to
approximate the number of k-colorings on bipartite graphs of maximum degree D
when k <= D/(2 ln D).
The #BIS-hardness result for the ferromagnetic Potts model uses random
bipartite regular graphs as a gadget in the reduction. The analysis of these
random graphs relies on recent connections between the maxima of the
expectation of their partition function, attractive fixpoints of the associated
tree recursions, and induced matrix norms. We extend these connections to
random regular graphs for all ferromagnetic models and establish the Bethe
prediction for every ferromagnetic spin system on random regular graphs. We
also prove for the ferromagnetic Potts model that the Swendsen-Wang algorithm
is torpidly mixing on random D-regular graphs at the critical temperature for
large q.
| arxiv topic:cs.CC math-ph math.MP math.PR |
arxiv_dataset-47861311.4939 | Geometrical perspective on quantum states and quantum computation
quant-ph
We interpret quantum computing as a geometric evolution process by
reformulating finite quantum systems via Connes' noncommutative geometry. In
this formulation, quantum states are represented as noncommutative connections,
while gauge transformations on the connections play a role of unitary quantum
operations. Thereby, a geometrical model for quantum computation is presented,
which is equivalent to the quantum circuit model. This result shows a geometric
way of realizing quantum computing and as such, provides an alternative
proposal of building a quantum computer.
| arxiv topic:quant-ph |
arxiv_dataset-47871311.5039 | Face numbers of down-sets
math.CO
We compare various viewpoints on down-sets (simplicial complexes),
illustrating how the combinatorial inclusion-exclusion principle may serve as
an alternative to more advanced methods of studying their face numbers.
| arxiv topic:math.CO |
arxiv_dataset-47881311.5139 | Uniform self-diffusion in a granular gas
cond-mat.stat-mech
A granular gas composed of inelastic hard spheres or disks in the homogeneous
cooling state is considered. Some of the particles are labeled and their number
density exhibits a time-independent linear profile along a given direction. As
a consequence, there is a uniform flux of labeled particles in that direction.
It is shown that the inelastic Boltzmann-Enskog kinetic equation has a solution
describing this self-diffusion state. Approximate expressions for the transport
equation and the distribution function of labeled particles are derived. The
theoretical predictions are compared with simulation results obtained using the
direct Monte Carlo method to generate solutions of the kinetic equation. A
fairly good agreement is found.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-47891311.5239 | General aspects of the vapor growth of semiconductor crystals - a study
based on DFT simulations of the NH3/NH2 covered GaN(0001) surface in hydrogen
ambient
cond-mat.mtrl-sci
Vapor growth of semiconductors is analyzed using recently obtained dependence
of the adsorption energy on the electron charge transfer between the surface
adsorbed species and the bulk [Krukowski et al. J. Appl. Phys. 114 (2013)
063507, Kempisty et al. ArXiv 1307.5778 (2013)]. Ab initio calculations were
performed to study the physical properties of GaN(0001) surface in ammonia-rich
conditions, i.e. covered by mixture of NH3 molecules and NH2 radicals. The
Fermi level is pinned at valence band maximum (VBM) and conduction band minimum
(CBM) for full coverage by NH3 molecules and NH2 radicals, respectively. For
the crossover content of ammonia of about 25% monolayer (ML), the Fermi level
is unpinned. It was shown that hydrogen adsorption energy depends on the doping
in the bulk for the unpinned Fermi level, i.e. for this coverage. Surface
structure thermodynamic and mechanical stability criteria are defined and
compared. Mechanical stability of the coverage of such surfaces was checked by
determination of the desorption energy of hydrogen molecules. Thermodynamic
stability analysis indicates that initally equilibrium hydrogen vapor partial
pressure steeply increases with NH3 content to attain the crossover NH3/NH2
coverage, i.e. the unpinned Fermi level condition. For such condition the
entire range of experimentally accessible pressures belongs showing that vapor
growth of semiconductor crystals occurs predominantly for unpinned Fermi level
at the surface, i.e. for flat bands. Accordingly, adsorption energy of most
species depends on the doping in the bulk that is basis of the possible
molecular scenario explaining dependence of the growth and the doping of
semiconductor crystals on the doping in the bulk
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-47901311.5339 | Constraining models of initial conditions with elliptic and triangular
flow data
nucl-th hep-ph nucl-ex
We carry out a combined analysis of elliptic and triangular flow data using
viscous relativistic hydrodynamics. We show that these data allow to put tight
constraints on models of the early dynamics of a nucleus-nucleus collision.
Specifically, the rms values of the initial ellipticity $\varepsilon_2$ and the
initial triangularity $\varepsilon_3$ are constrained to lie within a narrow
band for each centrality. We use these constraints as a filter for existing
Monte-Carlo models of initial state, and provide a simple test that can be
performed on any candidate model to determine its compatibility with data.
| arxiv topic:nucl-th hep-ph nucl-ex |
arxiv_dataset-47911311.5439 | Nanostructured epoxies based on the self-assembly of block copolymers: a
new miscible block that can be tailored to different epoxy formulations
cond-mat.soft cond-mat.mtrl-sci
Nanostructured thermosets may be obtained by self-assembly of amphiphilic
block copolymers in a reactive solvent and fixation of the morphologies by the
cross-linking reaction. Nanostructuration requires the presence of a bock that
remains miscible in the polymer during polymerization. The selection of the
miscible block depends on the particular system and in some cases (e.g., for
epoxy-amine network based on diglycidyl ether of bisphenol A, and 4,4'-
diaminodiphenylsulfone) it is very difficult to find such a block. In this
manuscript it is shown that random copolymers of methyl methacrylate (MMA) and
N,N-dimethylacrylamide (DMA) containing different molar fractions of DMA, can
be used as a miscible block for the nanostructuration of epoxies. The
miscibility of the random copolymer during formation of the epoxy network was
first analyzed determining cloud-point conversions as a function of the molar
fraction of DMA in the copolymer. A thermodynamic model of the phase separation
was performed using the Flory-Huggins model and taking the polydispersities of
both polymers into account. A single expression of the interaction parameter
based on the theory of random copolymers provided a reasonable fitting of the
experimental cloud-point curves. The significant increase in the miscibility
produced by using small DMA molar fractions in the copolymer was explained by
the high negative value of the binary interaction energy between DMA and the
epoxy-amine solvent, associated to the positive value of the interaction energy
between DMA and MMA units. Block copolymers with poly(n-butyl acrylate) as the
immiscible block and the random copolymer P(MMA-co-DMA) as the miscible block
were used for the nanostructuration of epoxy networks. The necessary molar
fraction of DMA in the miscible block to stabilize a dispersion of nanosize
domains depended on the fraction of the immiscible block.
| arxiv topic:cond-mat.soft cond-mat.mtrl-sci |
arxiv_dataset-47921311.5539 | Universal symmetry-protected topological invariants for
symmetry-protected topological states
cond-mat.str-el hep-th
Symmetry-protected topological (SPT) states are short-range entangled states
with a symmetry G. They belong to a new class of quantum states of matter which
are classified by the group cohomology $H^{d+1}(G,\mathbb{R}/\mathbb{Z})$ in
d-dimensional space. In this paper, we propose a class of symmetry- protected
topological invariants that may allow us to fully characterize SPT states with
a symmetry group G (ie allow us to measure the cocycles in
$H^{d+1}(G,\mathbb{R}/\mathbb{Z})$ that characterize the SPT states). We give
an explicit and detailed construction of symmetry-protected topological
invariants for 2+1D SPT states. Such a construction can be directly generalized
to other dimensions.
| arxiv topic:cond-mat.str-el hep-th |
arxiv_dataset-47931311.5639 | Classification of ST and Q Type MI variant using thresholding and
neighbourhood estimation method after cross wavelet based analysis
cs.OH
This paper proposes a cross wavelet transform based method for
Electrocardiogram signal analysis where parameters are identified from wavelet
cross spectrum and wavelet cross coherence of ECG patterns. Most of the ECG
analysing systems use explicit time plane features for cardiac pattern
classification. Application of this proposed technique for classification
eliminates the need for extraction of various explicit time plane features and
hence reduces the complexity of the system. The cross-correlation is the
measure of similarity between two waveforms or two time series and the cross
examination reveals localized similarities in time and scale. Parameters
extracted from Wavelet Cross Spectrum (WCS) and Wavelet Coherence (WCOH) is
used for classification. A pathologically varying pattern in QT zone of
inferior lead III shows the presence of Inferior Myocardial Infarction (IMI).
The Cross Wavelet Transform and Wavelet Coherence is used for the cross
examination of single normal and abnormal (IMI) beats. A normal template beat
is selected as the absolute normal pattern. Computation of the WCS and WCOH of
the selected normal template and various other normal and abnormal beats
reveals the existence of variation among patterns under study. The Wavelet
cross spectrum and Wavelet coherence of various ECG patterns shows
distinguishing characteristics over two specific regions R1 and R2, where R1 is
the QRS complex location and R2 is the T wave region. Parameters are identified
for classification of Type 1 IMI (non Q type, with ST elevation and attenuated
QRS complex) and Type 2 IMI (Q type MI with deep Q and inverted T) and normal
subjects. Accuracy of the proposed classification method is obtained as 99.43%
for normal and abnormal class and 88.5% and 87.02% for Type I and Type II
respectively.
| arxiv topic:cs.OH |
arxiv_dataset-47941311.5739 | Explicit constructions of Vandermonde sequences using global function
fields
math.NT
The authors recently introduced so-called Vandermonde nets. These digital
nets share properties with the well-known polynomial lattices. For example,
both can be constructed via component-by-component search algorithms. A
striking characteristic of the Vandermonde nets is that for fixed $m$ an
explicit construction of $m \times m$ generating matrices over the finite field
$F_q$ is known for dimensions $s \le q+1$. This paper extends this explicit
construction in two directions. We give a maximal extension in terms of $m$ by
introducing a construction algorithm for $\infty \times \infty$ generating
matrices for digital sequences over $F_q$, which works in the rational function
field over $F_q$. Furthermore, we generalize this method to global function
fields of positive genus, which leads to extensions in the dimension $s$.
| arxiv topic:math.NT |
arxiv_dataset-47951311.5839 | Exceptional sequences of maximal length on some surfaces isogenous to a
higher product
math.AG
Let $S=(C \times D)/G$ be a surface isogenous to a higher product of unmixed
type with $p_g=q=0$, $G=(\mathbb{Z}/2)^3$ or $(\mathbb{Z}/2)^4$. We construct
exceptional sequences of maximal length and quasiphantom categories on $S$.
| arxiv topic:math.AG |
arxiv_dataset-47961311.5939 | Hypergeometric tail inequalities: ending the insanity
math.PR stat.OT
The hypergeometric distribution is briefly and informally surveyed, including
popular notation, symmetries, and the tail inequalities $Pr[i \ge E[i]+tn] \le
e^{-2t^2n}$ and $Pr[i \le E[i]-tn] \le e^{-2t^2n}$.
| arxiv topic:math.PR stat.OT |
arxiv_dataset-47971311.6039 | Variable density sampling with continuous trajectories. Application to
MRI
stat.AP
Reducing acquisition time is a crucial challenge for many imaging techniques.
Compressed Sensing (CS) theory offers an appealing framework to address this
issue since it provides theoretical guarantees on the reconstruction of sparse
signals by projection on a low dimensional linear subspace. In this paper, we
focus on a setting where the imaging device allows to sense a fixed set of
measurements. We first discuss the choice of an optimal sampling subspace
(smallest subset) allowing perfect reconstruction of sparse signals. Its
standard design relies on the random drawing of independent measurements. We
discuss how to select the drawing distribution and show that a mixed strategy
involving partial deterministic sampling and independent drawings can help
breaking the so-called "coherence barrier". Unfortunately, independent random
sampling is irrelevant for many acquisition devices owing to acquisition
constraints. To overcome this limitation, the notion of Variable Density
Samplers (VDS) is introduced and defined as a stochastic process with a
prescribed limit empirical measure. It encompasses samplers based on
independent measurements or continuous curves. The latter are crucial to extend
CS results to actual applications. Our main contribution lies in two original
continuous VDS. The first one relies on random walks over the acquisition space
whereas the second one is heuristically driven and rests on the approximate
solution of a Traveling Salesman Problem. Theoretical analysis and
retrospective CS simulations in magnetic resonance imaging highlight that the
TSP-based solution provides improved reconstructed images in terms of
signal-to-noise ratio compared to standard sampling schemes (spiral, radial, 3D
iid...).
| arxiv topic:stat.AP |
arxiv_dataset-47981311.6139 | Distributed multinomial regression
stat.AP
This article introduces a model-based approach to distributed computing for
multinomial logistic (softmax) regression. We treat counts for each response
category as independent Poisson regressions via plug-in estimates for fixed
effects shared across categories. The work is driven by the
high-dimensional-response multinomial models that are used in analysis of a
large number of random counts. Our motivating applications are in text
analysis, where documents are tokenized and the token counts are modeled as
arising from a multinomial dependent upon document attributes. We estimate such
models for a publicly available data set of reviews from Yelp, with text
regressed onto a large set of explanatory variables (user, business, and rating
information). The fitted models serve as a basis for exploring the connection
between words and variables of interest, for reducing dimension into supervised
factor scores, and for prediction. We argue that the approach herein provides
an attractive option for social scientists and other text analysts who wish to
bring familiar regression tools to bear on text data.
| arxiv topic:stat.AP |
arxiv_dataset-47991311.6239 | Fundamental performance limits for ideal decoders in high-dimensional
linear inverse problems
cs.IT math.IT
This paper focuses on characterizing the fundamental performance limits that
can be expected from an ideal decoder given a general model, ie, a general
subset of "simple" vectors of interest. First, we extend the so-called notion
of instance optimality of a decoder to settings where one only wishes to
reconstruct some part of the original high dimensional vector from a
low-dimensional observation. This covers practical settings such as medical
imaging of a region of interest, or audio source separation when one is only
interested in estimating the contribution of a specific instrument to a musical
recording. We define instance optimality relatively to a model much beyond the
traditional framework of sparse recovery, and characterize the existence of an
instance optimal decoder in terms of joint properties of the model and the
considered linear operator. Noiseless and noise-robust settings are both
considered. We show somewhat surprisingly that the existence of noise-aware
instance optimal decoders for all noise levels implies the existence of a
noise-blind decoder. A consequence of our results is that for models that are
rich enough to contain an orthonormal basis, the existence of an L2/L2 instance
optimal decoder is only possible when the linear operator is not substantially
dimension-reducing. This covers well-known cases (sparse vectors, low-rank
matrices) as well as a number of seemingly new situations (structured sparsity
and sparse inverse covariance matrices for instance). We exhibit an
operator-dependent norm which, under a model-specific generalization of the
Restricted Isometry Property (RIP), always yields a feasible instance
optimality property. This norm can be upper bounded by an atomic norm relative
to the considered model.
| arxiv topic:cs.IT math.IT |
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