id stringlengths 16 29 | text stringlengths 86 3.49k | source stringlengths 14 112 |
|---|---|---|
arxiv_dataset-60001502.0534 | Sieved Enumeration of Interval Orders and Other Fishburn Structures
math.CO
Following a result of Eriksen and Sj\"{o}strand (2014) we detail a technique
to construct structures following the Fishburn distribution from appropriate
Mahonian structures.
This technique is introduced on a bivincular pattern of Bousquet-M\'elou et
al. (2010) and then used to introduce a previously unconsidered class of
matchings; explicitly, zero alignment matchings according to the number of arcs
which are both right-crossed and left nesting.
We then define a statistic on the factorial posets of Claesson and Linusson
(2011) counting the number of features which we refer to as mislabelings and
demonstrate that according to the number of mislabelings that factorial posets
follow the Fishburn distribution.
As a consequence of our approach we find an identity for the Fishburn numbers
in terms of the Mahonian numbers.
| arxiv topic:math.CO |
arxiv_dataset-60011502.0544 | Connectivity of Soft Random Geometric Graphs Over Annuli
math.CO cond-mat.stat-mech
Nodes are randomly distributed within an annulus (and then a shell) to form a
point pattern of communication terminals which are linked stochastically
according to the Rayleigh fading of radio-frequency data signals. We then
present analytic formulas for the connection probability of these spatially
embedded graphs, describing the connectivity behaviour as a dense-network limit
is approached. This extends recent work modelling ad hoc networks in non-convex
domains.
| arxiv topic:math.CO cond-mat.stat-mech |
arxiv_dataset-60021502.0554 | Demonstration of a highly-sensitive tunable beam displacer with no
movable elements based on the concept of weak value amplification
quant-ph
We report the implementation of a highly sensitive beam displacer based on
the concept of weak value amplification that allows to displace the centroid of
a Gaussian beam a distance much smaller than its beam width without the need to
use movable optical elements. The beam's centroid position can be displaced by
controlling the linear polarization of the output beam, and the dependence
between the centroid's position and the angle of polarization is linear.
| arxiv topic:quant-ph |
arxiv_dataset-60031502.0564 | A Motivic Grothendieck-Teichm\"uller Group
math.KT math.AG
This paper proves the Beilinson-Soul{\'e} vanishing conjecture for motives
attached to the moduli spaces of curves of genus 0 with n marked points. As
part of the proof, it is also proved that these motives are mixed Tate. As a
consequence of Levine's work, one obtains then well defined categories of mixed
Tate motives over the moduli spaces of curves . It is shown that morphisms
between moduli spaces forgetting marked points and embedding as boundary
components induce functors between those categories and how tangential bases
points fit in these functorialities. Tannakian formalism attaches groups to
these categories and morphisms reflecting the functorialities leading to the
definition of a motivic Grothendieck-Teichm{\"u}ller group. Proofs of the above
properties rely on the geometry of the tower of the moduli spaces . This allows
us to treat the general case of motives over Spec(Z) with integral coefficients
working in Spitzweck's category of motives. From there, passing to
Q-coefficients we deal with the classical tannakian formalism and explain how
working over Spec(Q) allows a more concrete description of the tannakian group.
| arxiv topic:math.KT math.AG |
arxiv_dataset-60041502.0574 | Ultra-Close Encounters of Stars With Massive Black Holes: Tidal
Disruption Events With Prompt Hyperaccretion
astro-ph.GA astro-ph.HE gr-qc
A bright flare from a galactic nucleus followed at late times by a $t^{-5/3}$
decay in luminosity is often considered the signature of the complete tidal
disruption of a star by a massive black hole. The flare and power-law decay are
produced when the stream of bound debris returns to the black hole,
self-intersects, and eventually forms an accretion disk or torus. In the
canonical scenario of a solar-type star disrupted by a $10^{6}\; M_\odot$ black
hole, the time between the disruption of the star and the formation of the
accretion torus could be years. We present fully general relativistic
simulations of a new class of tidal disruption events involving ultra-close
encounters of solar-type stars with intermediate mass black holes. In these
encounters, a thick disk forms promptly after disruption, on timescales of
hours. After a brief initial flare, the accretion rate remains steady and
highly super-Eddington for a few days at $\sim 10^2\,M_\odot\,{\rm yr}^{-1}$.
| arxiv topic:astro-ph.GA astro-ph.HE gr-qc |
arxiv_dataset-60051502.0584 | A General Multi-Graph Matching Approach via Graduated
Consistency-regularized Boosting
cs.CV
This paper addresses the problem of matching $N$ weighted graphs referring to
an identical object or category. More specifically, matching the common node
correspondences among graphs. This multi-graph matching problem involves two
ingredients affecting the overall accuracy: i) the local pairwise matching
affinity score among graphs; ii) the global matching consistency that measures
the uniqueness of the pairwise matching results by different chaining orders.
Previous studies typically either enforce the matching consistency constraints
in the beginning of iterative optimization, which may propagate matching error
both over iterations and across graph pairs; or separate affinity optimizing
and consistency regularization in two steps. This paper is motivated by the
observation that matching consistency can serve as a regularizer in the
affinity objective function when the function is biased due to noises or
inappropriate modeling. We propose multi-graph matching methods to incorporate
the two aspects by boosting the affinity score, meanwhile gradually infusing
the consistency as a regularizer. Furthermore, we propose a node-wise
consistency/affinity-driven mechanism to elicit the common inlier nodes out of
the irrelevant outliers. Extensive results on both synthetic and public image
datasets demonstrate the competency of the proposed algorithms.
| arxiv topic:cs.CV |
arxiv_dataset-60061502.0594 | Beyond Thomas--Fermi analysis of the density profiles of a miscible
two-component Bose--Einstein condensate
cond-mat.quant-gas
We investigate a harmonically trapped two-component Bose--Einstein condensate
within the miscible regime, close to its boundaries, for different ratios of
effective intra- and inter-species interactions. We derive analytically a
universal equation for the density around the different boundaries in one, two
and three dimensions, for both the coexisting and spatially separated regimes.
We also present a general procedure to solve the Thomas--Fermi approximation in
all three spatial dimensionalities, reducing the complexity of the
Thomas--Fermi problem for the spatially separated case in one and three
dimensions to a single numerical inversion. Finally, we analytically determine
the frontier between the two different regimes of the system.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-60071502.0604 | Sea ice floes dissipate the energy of steep ocean waves
physics.flu-dyn physics.ao-ph
Wave attenuation by ice floes is an important parameter for modelling the
Arctic Oceans. At present, attenuation coefficients are extracted from linear
models as a function of the incident wave period and floe thickness. Recent
explorations in the Antarctic Mixed Ice Zone (MIZ) revealed a further
dependence on wave amplitude, suggesting that nonlinear contributions are
non-negligible. An experimental model for wave attenuation by a single ice floe
in a wave flume is here presented. Observations are compared with linear
predictions based on wave scattering. Results indicate that linear models
perform well under the effect of gently sloping waves. For more energetic wave
fields, however, transmitted wave height is normally over predicted. Deviations
from linearity appear to be related to an enhancement of wave dissipation
induced by unaccounted wave-ice interaction processes, including the floe over
wash.
| arxiv topic:physics.flu-dyn physics.ao-ph |
arxiv_dataset-60081502.0614 | Observation of Discrete Oscillations in a Model-independent Plot of
Cosmological Scale Factor vs. Lookback Time and a Scalar Field Model
astro-ph.CO
We have observed damped longitudinal cosmological-scale oscillations in a
unique model-independent plot of scale factor against cosmological time for
Type Ia supernovae data. We found several first-derivative relative
maxima/minima spanning the range of reported transition-redshifts. These
extrema comprise 2 full cycles with a period of approximately 0.15 Hubble times
(H0=68 km/s/Mpc). This period corresponds to a fundamental frequency of
approximately 7 cycles over the Hubble time. Transition-z values quoted in the
literature generally fall near these minima and may explain the reported wide
spread up to the predicted LCDM value of approximately z = 0.77. We also
observe second and third harmonics of the fundamental. The scale factor data is
analyzed several different ways including smoothing, Fourier transform and
autocorrelation. We propose a cosmological scalar field harmonic oscillator
model for the observation. On this time scale, for a quantum scalar field, the
scalar field mass is extraordinarily small at 3x10-32 eV. Our scalar field
density parameter precisely replaces the LCDM dark matter density parameter in
the Friedmann equations, resulting in essentially identical data fits, and its
present value matches the Planck value. Thus the wave is fundamentally a dark
matter wave. We therefore posit that this scalar field manifests itself as the
dark matter.
| arxiv topic:astro-ph.CO |
arxiv_dataset-60091502.0624 | On some strong convergence results of a new Halpern-type iterative
process for quasi-nonexpansive mappings and accretive operators in Banach
spaces
math.FA
In this study, we introduce a new iterative processes to approximate common
fixed points of an infinite family of quasi-nonexpansive mappings and obtain a
strongly convergent iterative sequence to the common fixed points of these
mappings in a uniformly convex Banach space. Also we prove that this process to
approximate zeros of an infinite family of accretive operators and we obtain a
strong convergence result for these operators. Our results improve and
generalize many known results in the current literature.
| arxiv topic:math.FA |
arxiv_dataset-60101502.0634 | Video Analysis and Modeling Performance Task to promote becoming like
scientists in classrooms
physics.ed-ph physics.class-ph physics.comp-ph
This paper aims to share the use of Tracker a free open source video analysis
and modeling tool that is increasingly used as a pedagogical tool for the
effective learning and teaching of Physics for Grade 9 Secondary 3 students in
Singapore schools to make physics relevant to the real world. We discuss the
pedagogical use of Tracker, guided by the Framework for K-12 Science Education
by National Research Council, USA to help students to be more like scientists.
For a period of 6 to 10 weeks, students use a video analysis coupled with the 8
practices of sciences such as 1. Ask question, 2. Use models, 3. Plan and carry
out investigation, 4. Analyse and interpret data, 5. Use mathematical and
computational thinking, 6. Construct explanations, 7. Argue from evidence and
8. Communicate information. This papers focus in on discussing some of the
performance task design ideas such as 3.1 flip video, 3.2 starting with simple
classroom activities, 3.3 primer science activity, 3.4 integrative dynamics and
kinematics lesson flow using Tracker progressing from video analysis to video
modeling, 3.5 motivating performance task, 3.6 assessment rubrics and lastly
3.7 close mentorship. Initial research findings using pre and post perception
survey, triangulated with student interviews suggest an increased level of
students enjoyment. Most importantly, the artefacts of the students performance
task in terms of the research report and Tracker .TRZ files, further suggest
that the use of the Tracker for performance tasks, guided by the Framework for
K-12 Science Education by National Research Council, USA, can be an innovative
way to mentor authentic and meaningful learning that empowers students to be
more like scientists as defined in the K-12 Science Education Framework in
classrooms.
| arxiv topic:physics.ed-ph physics.class-ph physics.comp-ph |
arxiv_dataset-60111502.0644 | Improved Laplace Approximation for Marginal Likelihoods
stat.CO stat.ME
Statistical applications often involve the calculation of intractable
multidimensional integrals. The Laplace formula is widely used to approximate
such integrals. However, in high-dimensional or small sample size problems, the
shape of the integrand function may be far from that of the Gaussian density,
and thus the standard Laplace approximation can be inaccurate. We propose an
improved Laplace approximation that reduces the asymptotic error of the
standard Laplace formula by one order of magnitude, thus leading to third-order
accuracy. We also show, by means of practical examples of various complexity,
that the proposed method is extremely accurate, even in high dimensions,
improving over the standard Laplace formula. Such examples also demonstrate
that the accuracy of the proposed method is comparable with that of other
existing methods, which are computationally more demanding. An R implementation
of the improved Laplace approximation is also provided through the R package
iLaplace available on CRAN.
| arxiv topic:stat.CO stat.ME |
arxiv_dataset-60121502.0654 | Symmetries, Symmetry Breaking, Gauge Symmetries
physics.hist-ph hep-th
The concepts of symmetry, symmetry breaking and gauge symmetries are
discussed, their operational meaning being displayed by the observables {\em
and} the (physical) states. For infinitely extended systems the states fall
into physically disjoint {\em phases} characterized by their behavior at
infinity or boundary conditions, encoded in the ground state, which provide the
cause of symmetry breaking without contradicting Curie Principle. Global gauge
symmetries, not seen by the observables, are nevertheless displayed by
detectable properties of the states (superselected quantum numbers and
parastatistics). Local gauge symmetries are not seen also by the physical
states; they appear only in non-positive representations of field algebras.
Their role at the Lagrangian level is merely to ensure the validity on the
physical states of local Gauss laws, obeyed by the currents which generate the
corresponding global gauge symmetries; they are responsible for most
distinctive physical properties of gauge quantum field theories. The
topological invariants of a local gauge group define superselected quantum
numbers, which account for the $\theta$ vacua.
| arxiv topic:physics.hist-ph hep-th |
arxiv_dataset-60131502.0664 | Joint statistics of quantum transport in chaotic cavities
cond-mat.stat-mech math-ph math.MP
We study the joint statistics of conductance $G$ and shot noise $P$ in
chaotic cavities supporting a large number $N$ of open electronic channels in
the two attached leads. We determine the full phase diagram in the $(G,P)$
plane, employing a Coulomb gas technique on the joint density of transmission
eigenvalues, as dictated by Random Matrix Theory. We find that in the region of
typical fluctuations, conductance and shot noise are uncorrelated and jointly
Gaussian, and away from it they fluctuate according to a different joint rate
function in each phase of the $(G,P)$ plane. Different functional forms of the
rate function in different regions emerge as a direct consequence of third
order phase transitions in the associated Coulomb gas problem.
| arxiv topic:cond-mat.stat-mech math-ph math.MP |
arxiv_dataset-60141502.0674 | Observations on gaussian upper bounds for Neumann heat kernels
math.AP
Given a domain $\Omega$ of a complete Riemannian manifold $\mathcal{M}$ and
define $\mathcal{A}$ to be the Laplacian with Neumann boundary condition on
$\Omega$. We prove that, under appropriate conditions, the corresponding heat
kernel satisfies the Gaussian upper bound $$ h(t,x,y)\leq
\frac{C}{\left[V\_\Omega(x,\sqrt{t})V\_\Omega (y,\sqrt{t})\right]^{1/2}}\left(
1+\frac{d^2(x,y)}{4t}\right)^{\delta}e^{-\frac{d^2(x,y)}{4t}},\;\;
t\textgreater{}0,\; x,y\in \Omega . $$ Here $d$ is the geodesic distance on
$\mathcal{M}$, $V\_\Omega (x,r)$ is the Riemannian volume of $B(x,r)\cap
\Omega$, where $B(x,r)$ is the geodesic ball of center $x$ and radius $r$, and
$\delta$ is a constant related to the doubling property of $\Omega$.
As a consequence we obtain analyticity of the semigroup $e^{-t {\mathcal A}}$
on $L^p(\Omega)$ for all $p \in [1, \infty)$ as well as a spectral multiplier
result.
| arxiv topic:math.AP |
arxiv_dataset-60151502.0684 | Maximal subgroups of finite soluble groups in general position
math.GR
For a finite group $G$ we investigate the difference between the maximum size
MaxDim$(G)$ of an "independent" family of maximal subgroups of $G$ and maximum
size $m(G)$ of an irredundant sequence of generators of $G$. We prove that
MaxDim$(G)=m(G)$ if the derived subgroup of $G$ is nilpotent. However
MaxDim$(G)-m(G)$ can be arbitrarily large: for any odd prime $p,$ we construct
a finite soluble group with Fitting length 2 satisfying $m(G)=3$ and
MaxDim$(G)=p.$
| arxiv topic:math.GR |
arxiv_dataset-60161502.0694 | Georg Cantor from St. Petersburg. Childhood and history of the family.
Archival research
math.HO
Georg Cantor (1845-1918) was born, and spent the first 11 years of his life
in St. Petersburg. The present lecture is devoted to his childhood and his
family. Most of these documents were not available before and are now published
for the first time.
| arxiv topic:math.HO |
arxiv_dataset-60171502.0704 | P-MaNGA: Gradients in Recent Star Formation Histories as Diagnostics for
Galaxy Growth and Death
astro-ph.GA astro-ph.CO
We present an analysis of the data produced by the MaNGA prototype run
(P-MaNGA), aiming to test how the radial gradients in recent star formation
histories, as indicated by the 4000AA-break (D4000), Hdelta absorption
(EW(Hd_A)) and Halpha emission (EW(Ha)) indices, can be useful for
understanding disk growth and star formation cessation in local galaxies. We
classify 12 galaxies observed on two P-MaNGA plates as either centrally
quiescent (CQ) or centrally star-forming (CSF), according to whether D4000
measured in the central spaxel of each datacube exceeds 1.6. For each galaxy we
generate both 2D maps and radial profiles of D4000, EW(Hd_A) and EW(Ha). We
find that CSF galaxies generally show very weak or no radial variation in these
diagnostics. In contrast, CQ galaxies present significant radial gradients, in
the sense that D4000 decreases, while both EW(Hd_A) and EW(Ha) increase from
the galactic center outward. The outer regions of the galaxies show greater
scatter on diagrams relating the three parameters than their central parts. In
particular, the clear separation between centrally-measured quiescent and
star-forming galaxies in these diagnostic planes is largely filled in by the
outer parts of galaxies whose global colors place them in the green valley,
supporting the idea that the green valley represents a transition between
blue-cloud and red-sequence phases, at least in our small sample. These results
are consistent with a picture in which the cessation of star formation
propagates from the center of a galaxy outwards as it moves to the red
sequence.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-60181502.0714 | Conformally K\"ahler geometry and quasi-Einstein metrics
math.DG
We prove that the quasi-Einstein metrics found by L\"u, Page and Pope on
$\mathbb{C}P^{1}$-bundles over Fano K\"ahler-Einstein bases are conformally
K\"ahler and that the K\"ahler class of the conformal metric is a multiple of
the first Chern class. A detailed study of the lowest-dimensional example of
such metrics on $\mathbb{C}P^{2}\sharp \overline{\mathbb{C}P}^{2}$ using the
methods developed by Abreu and Guillemin for studying toric K\"ahler metrics is
given. Our methods yield, in a unified framework, proofs of the existence of
the Page, Koiso-Cao and L\"u-Page-Pope metrics on $\mathbb{C}P^{2}\sharp
\overline{\mathbb{C}P}^{2}$. Finally, we investigate the properties that
similar quasi-Einstein metrics would have if they also exist on the toric
surface $\mathbb{C}P^{2}\sharp 2 \overline{\mathbb{C}P}^{2}$.
| arxiv topic:math.DG |
arxiv_dataset-60191502.0724 | Two-Color Magneto-Optical Trap with Small Magnetic Field for Ytterbium
physics.atom-ph
We report a two-color magneto-optical trap (MOT) for ytterbium atoms
operating at a low magnetic field gradient down to 2 G/cm where a conventional
MOT using the singlet transition (6s^2 1S0 -> 6s6p 1P1) is unable to trap
atoms. By simultaneously applying laser light on both the broad-linewidth
singlet transition and the narrow-linewidth triplet transition (6s^2 1S0 ->
6s6p 3P1), we load and trap 4.0 x 10^5 atoms directly from an atomic beam at
700 K. In the two-color MOT, the slowing and trapping functions are separately
performed by the singlet transition light and the triplet transition light,
respectively. The two-color MOT is highly robust against laser power imbalance
even at very low magnetic field gradients.
| arxiv topic:physics.atom-ph |
arxiv_dataset-60201502.0734 | The Dynamical Composite Higgs
hep-ph
We present a simple microscopic realization of a pseudo-Nambu-Goldstone
(pNGB) boson Higgs scenario arising from the breaking of $SO(5) \rightarrow
SO(4)$. The Higgs constituents are explicitly identified as well as the
interactions responsible for forming the bound state and breaking the
electroweak symmetry. This outcome follows from the presence of four-fermion
interactions with a super-critical coupling, and uses the Nambu-Jona-Lasinio
mechanism to break the global $SO(5)$ symmetry. The Higgs potential is found to
be insensitive to high energy scales due to the existence of an approximate
infrared fixed point. The appearance of vector resonances is described and the
correspondence with other proposals in the literature established. The model
described here is significantly simpler than other recent ultraviolet
completions of pNGB scenarios. The observed Higgs mass can be accommodated, and
agreement with electroweak precision tests achieved in certain regions of
parameter space. There are also new vector-like fermions, some of which may lie
within reach of the LHC. In addition, we predict a heavy standard model singlet
scalar in the multi-TeV range. The amount of fine-tuning required in the model
is studied. Finally, we show that such a scheme can be completed in the
ultraviolet by a renormalizable theory.
| arxiv topic:hep-ph |
arxiv_dataset-60211502.0744 | Scaling limit of the corrector in stochastic homogenization
math.AP math.PR
In the homogenization of divergence-form equations with random coefficients,
a central role is played by the corrector. We focus on a discrete space setting
and on dimension 3 and more. Completing the argument started in previous work,
we identify the scaling limit of the corrector, which is akin to a Gaussian
free field.
| arxiv topic:math.AP math.PR |
arxiv_dataset-60221502.0754 | A hypothesize-and-verify framework for Text Recognition using Deep
Recurrent Neural Networks
cs.CV
Deep LSTM is an ideal candidate for text recognition. However text
recognition involves some initial image processing steps like segmentation of
lines and words which can induce error to the recognition system. Without
segmentation, learning very long range context is difficult and becomes
computationally intractable. Therefore, alternative soft decisions are needed
at the pre-processing level. This paper proposes a hybrid text recognizer using
a deep recurrent neural network with multiple layers of abstraction and long
range context along with a language model to verify the performance of the deep
neural network. In this paper we construct a multi-hypotheses tree architecture
with candidate segments of line sequences from different segmentation
algorithms at its different branches. The deep neural network is trained on
perfectly segmented data and tests each of the candidate segments, generating
unicode sequences. In the verification step, these unicode sequences are
validated using a sub-string match with the language model and best first
search is used to find the best possible combination of alternative hypothesis
from the tree structure. Thus the verification framework using language models
eliminates wrong segmentation outputs and filters recognition errors.
| arxiv topic:cs.CV |
arxiv_dataset-60231502.0764 | Phase diagram of the Quantum Electrodynamics of 2D and 3D Dirac
semimetals
cond-mat.mes-hall cond-mat.str-el
We study the Quantum Electrodynamics of 2D and 3D Dirac semimetals by means
of a self-consistent resolution of the Schwinger-Dyson equations, aiming to
obtain the respective phase diagrams in terms of the relative strength of the
Coulomb interaction and the number N of Dirac fermions. In this framework, 2D
Dirac semimetals have just a strong-coupling instability characterized by
exciton condensation (and dynamical generation of mass) that we find at a
critical coupling well above previous theoretical estimates, thus explaining
the absence of that instability in free-standing graphene samples. On the other
hand, we show that 3D Dirac semimetals have a richer phase diagram, with a
strong-coupling instability leading to dynamical mass generation up to N = 4
and a line of critical points for larger values of N characterized by the
vanishing of the electron quasiparticle weight in the low-energy limit. Such a
critical behavior signals the transition to a strongly correlated liquid,
characterized by noninteger scaling dimensions that imply the absence of a pole
in the electron propagator and are the signature of non-Fermi liquid behavior
with no stable electron quasiparticles.
| arxiv topic:cond-mat.mes-hall cond-mat.str-el |
arxiv_dataset-60241502.0774 | The Contribution of Faint Galaxy Wings to Source-subtracted
Near-infrared Background Fluctuations
astro-ph.GA astro-ph.CO
The source-subtracted, 1.1 and 1.6 {\mu}m NICMOS images used in earlier
analyses of the near-infrared Hubble Ultra Deep Field contained residual flux
in extended wings of identified sources that contributed an unknown amount to
fluctuation power. When compared to the original results, a reanalysis after
subtracting this residual flux shows that mean-square and rms fluctuations
decrease a maximum of 52 and 31 per cent at 1.6 {\mu}m and 50 and 30 per cent
at 1.1 {\mu}m. However, total mean-square fluctuations above 0.5 arcsec only
decrease 6.5 and 1.4 per cent at 1.6 and 1.1 {\mu}m, respectively. These
changes would not affect any published conclusions based on the prior analyses.
These results exclude previous suggestions that extended wings of detected
galaxies may be a major contributor to the source-subtracted near-infrared
background and confirm that most fluctuation power in these images must be
explained by other means.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-60251502.0784 | A simple finite element method for the boundary value problem with a
Riemann-Liouville derivative
math.NA
We consider a boundary value problem involving a Riemann-Liouville fractional
derivative of order $\alpha\in (3/2,2)$ on the unit interval $(0,1)$. The
standard Galerkin finite element approximation converges slowly due to the
presence of singularity term $x^{\alpha-1}$ in the solution representation. In
this work, we develop a simple technique, by transforming it into a
second-order two-point boundary value problem with nonlocal low order terms,
whose solution can reconstruct directly the solution to the original problem.
The stability of the variational formulation, and the optimal regularity pickup
of the solution are analyzed. A novel Galerkin finite element method with
piecewise linear or quadratic finite elements is developed, and $L^2(D)$ error
estimates are provided. The approach is then applied to the corresponding
fractional Sturm-Liouville problem, and error estimates of the eigenvalue
approximations are given. Extensive numerical results fully confirm our
theoretical study.
| arxiv topic:math.NA |
arxiv_dataset-60261502.0794 | A study of final-state radiation in decays of Z bosons produced in pp
collisions at 7 TeV
hep-ex
The differential cross sections for the production of photons in Z to mu+ mu-
gamma decays are presented as a function of the transverse energy of the photon
and its separation from the nearest muon. The data for these measurements were
collected with the CMS detector and correspond to an integrated luminosity of
4.7 inverse femtobarns of pp collisions at sqrt(s) = 7 TeV delivered by the
CERN LHC. The cross sections are compared to simulations with POWHEG and
PYTHIA, where PYTHIA is used to simulate parton showers and final-state
photons. These simulations match the data to better than 5%.
| arxiv topic:hep-ex |
arxiv_dataset-60271502.0804 | DistancePPG: Robust non-contact vital signs monitoring using a camera
cs.CV
Vital signs such as pulse rate and breathing rate are currently measured
using contact probes. But, non-contact methods for measuring vital signs are
desirable both in hospital settings (e.g. in NICU) and for ubiquitous in-situ
health tracking (e.g. on mobile phone and computers with webcams). Recently,
camera-based non-contact vital sign monitoring have been shown to be feasible.
However, camera-based vital sign monitoring is challenging for people with
darker skin tone, under low lighting conditions, and/or during movement of an
individual in front of the camera. In this paper, we propose distancePPG, a new
camera-based vital sign estimation algorithm which addresses these challenges.
DistancePPG proposes a new method of combining skin-color change signals from
different tracked regions of the face using a weighted average, where the
weights depend on the blood perfusion and incident light intensity in the
region, to improve the signal-to-noise ratio (SNR) of camera-based estimate.
One of our key contributions is a new automatic method for determining the
weights based only on the video recording of the subject. The gains in SNR of
camera-based PPG estimated using distancePPG translate into reduction of the
error in vital sign estimation, and thus expand the scope of camera-based vital
sign monitoring to potentially challenging scenarios. Further, a dataset will
be released, comprising of synchronized video recordings of face and pulse
oximeter based ground truth recordings from the earlobe for people with
different skin tones, under different lighting conditions and for various
motion scenarios.
| arxiv topic:cs.CV |
arxiv_dataset-60281503.00086 | A finite variant of the Toom Model
cond-mat.stat-mech math.CO math.PR
We present results for a finite variant of the one-dimensional Toom model
with closed boundaries. We show that the steady state distribution is not of
product form, but is nonetheless simple. In particular, we give explicit
formulas for the densities and some nearest neighbour correlation functions. We
also give exact results for eigenvalues and multiplicities of the transition
matrix using the theory of ${\mathscr R}$-trivial monoids in joint work with A.
Schilling, B. Steinberg and N. M. Thi\'ery.
| arxiv topic:cond-mat.stat-mech math.CO math.PR |
arxiv_dataset-60291503.00186 | Short-period X-ray oscillations in super-soft novae and persistent SSS
astro-ph.HE astro-ph.SR
Transient short-period <100s oscillations have been found in the X-ray light
curves of three novae during their SSS phase and in one persistent SSS. We
pursue an observational approach to determine possible driving mechanisms and
relations to fundamental system parameters such as the white dwarf mass.
We performed a systematic search for short-period oscillations in all
available XMM-Newton and Chandra X-ray light curves of persistent SSS and novae
during their SSS phase. To study time evolution, we divided each light curve
into short time segments and computed power spectra. We then constructed
dynamic power spectra from which we identified transient periodic signals even
when only present for a short time. From all time segments of each system, we
computed fractions of time when periodic signals were detected.
In addition to the previously known systems with short-period oscillations,
RS Oph (35s), KT Eri (35s), V339 Del (54s), and Cal 83 (67s), we found one
additional system, LMC 2009a (33s), and also confirm the 35s period from
Chandra data of KT Eri. The amplitudes of oscillations are of order <15% of the
respective count rates and vary without any clear dependence on the X-ray count
rate. The fractions of the time when the respective periods were detected at
2-sigma significance (duty cycle) are 11.3%, 38.8%, 16.9%, 49.2%, and 18.7% for
LMC 2009a, RS Oph, KT Eri, V339 Del, and Cal 83, respectively. The respective
highest duty cycles found in a single observation are 38.1%, 74.5%, 61.4%,
67.8%, and 61.8%.
| arxiv topic:astro-ph.HE astro-ph.SR |
arxiv_dataset-60301503.00286 | Magnetic-dipolar-mode Fano resonances for microwave spectroscopy of high
absorption matter
physics.optics cond-mat.mtrl-sci
Study of interaction between high absorption matter and microwave radiated
energy is a subject of great importance. Especially, this concerns microwave
spectroscopic characterization of biological liquids. Use of effective testing
methods to obtain information about physical properties of different liquids on
the molecular level is one of the most important problems in biophysics.
However, the standard methods based on the microwave resonant techniques are
not sufficiently suitable for biological liquids because the resonance peak in
a resonator with high-loss liquids is so broad that the material parameters
cannot be measured correctly. Although molecular vibrations of biomolecules may
have microwave frequencies, it is not thought that such resonant coupling is
significant due to their low energy compared with thermal energy and the
strongly dampening aqueous environment. This paper presents an innovative
microwave sensing technique for different types of lossy materials, including
biological liquids. The technique is based on the combination of the microwave
perturbation method and the Fano-resonance effects observed recently in
microwave structures with embedded magnetic-dipolar quantum dots. When
frequency of the magnetic-dipolar-mode (MDM) resonance is not equal to the
cavity resonance frequency, one gets Fano transmission intensity. With tuning,
by a bias magnetic field, the MDM resonance frequency to the cavity resonance
frequency, one observes a Lorentz line shape. Use of an extremely narrow
Lorentzian peak allows exact probing the resonant frequency of a cavity loaded
by a high-lossy-material sample. For different kinds of samples, one has
different frequencies of Lorentzian peaks. This gives a picture for precise
spectroscopic characterization of high absorption matter in microwaves.
| arxiv topic:physics.optics cond-mat.mtrl-sci |
arxiv_dataset-60311503.00386 | Transient evolution of solitary electron holes in low pressure
laboratory plasma
physics.plasm-ph
Solitary electrons holes (SEHs) are localized electrostatic positive
potential structures in collisionless plasmas. These are vortex-like structures
in the electron phase space. Its existence is cause of distortion of the
electron distribution in the resonant region. These are explained theoretically
first time by Schamel et.al [Phys. Scr. 20, 336 (1979) and Phys. Plasmas 19,
020501 (2012)]. Propagating solitary electron holes can also be formed in a
laboratory plasma when a fast rising high positive voltage pulse is applied to
a metallic electrode [Kar et. al., Phys. Plasmas 17, 102113 (2010)] immersed in
a low pressure plasma. The temporal evolution of these structures can be
studied by measuring the transient electron distribution function (EDF). In the
present work, transient EDF is measured after formation of a solitary electron
hole in nearly uniform, unmagnetized, and collisionless plasma for applied
pulse width and, where and are applied pulse width and inverse of ion plasma
frequency respectively. For both type of pulse widths, double hump like profile
of transient EDF is observed, indicating that solitary electron hole exists in
the system for time periods longer than the applied pulse duration. The beam
(or free) electrons along with trapped (or bulk) electrons gives the solution
of SEHs in the plasma. Without free or beam electrons, no SEHs exist. Transient
EDF measurements reveal the existence and evolution of SEHs in the plasma.
Measurements show that these structures live in system for longer time in the
low pressure range. In high pressure cases, only single hump like transient EDF
is observed i.e. only trapped or bulk electrons. In this situation, SEH does
not exist in the plasma during evolution of plasma after the end of applied
pulse.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-60321503.00486 | HetFHMM: A novel approach to infer tumor heterogeneity using factorial
Hidden Markov model
q-bio.GN
Cancer arises from successive rounds of mutations which generate tumor cells
with different genomic variation i.e. clones. For drug responsiveness and
therapeutics, it is necessary to identify the clones in tumor sample
accurately. Many methods are developed to infer tumor heterogeneity by either
computing cellular prevalence and tumor phylogeny or predicting genotype of
mutations. All methods suffer some problems e.g. inaccurate computation of
clonal frequencies, discarding clone specific genotypes etc. In the paper, we
propose a method, called- HetFHMM to infer tumor heterogeneity by predicting
clone specific genotypes and cellular prevalence. To infer clone specific
genotype, we consider the presence of multiple mutations at any genomic
location. We also tested our model on different simulated data. The results
shows that HetFHMM outperforms recent methods which infer tumor heterogeneity.
Therefore, HetFHMM is a novel approach in tumor heterogeneity research area.
| arxiv topic:q-bio.GN |
arxiv_dataset-60331503.00586 | Evaluation of spatial audio reproduction schemes for application in
hearing aid research
cs.SD
Loudspeaker-based spatial audio reproduction schemes are increasingly used
for evaluating hearing aids in complex acoustic conditions. To further
establish the feasibility of this approach, this study investigated the
interaction between spatial resolution of different reproduction methods and
technical and perceptual hearing aid performance measures using computer
simulations. Three spatial audio reproduction methods -- discrete speakers,
vector base amplitude panning and higher order ambisonics -- were compared in
regular circular loudspeaker arrays with 4 to 72 channels. The influence of
reproduction method and array size on performance measures of representative
multi-microphone hearing aid algorithm classes with spatially distributed
microphones and a representative single channel noise-reduction algorithm was
analyzed. Algorithm classes differed in their way of analyzing and exploiting
spatial properties of the sound field, requiring different accuracy of sound
field reproduction. Performance measures included beam pattern analysis,
signal-to-noise ratio analysis, perceptual localization prediction, and quality
modeling. The results show performance differences and interaction effects
between reproduction method and algorithm class that may be used for guidance
when selecting the appropriate method and number of speakers for specific tasks
in hearing aid research.
| arxiv topic:cs.SD |
arxiv_dataset-60341503.00686 | Semigroup approach to diffusion and transport problems on networks
math.DS
Models describing transport and diffusion processes occurring along the edges
of a graph and interlinked by its vertices have been recently receiving a
considerable attention. In this paper we generalize such models and consider a
network of transport or diffusion operators defined on one dimensional domains
and connected through boundary conditions linking the end-points of these
domains in an arbitrary way (not necessarily as the edges of a graph are
connected). We prove the existence of $C_0$-semigroups solving such problems
and provide conditions fully characterizing when they are positive.
| arxiv topic:math.DS |
arxiv_dataset-60351503.00786 | The Solution of the Relativistic Schrodinger Equation for the
$\delta'$-Function Potential in 1-dimension Using Cutoff Regularization
hep-th
We study the relativistic version of Schr\"odinger equation for a point
particle in 1-d with potential of the first derivative of the delta function.
The momentum cutoff regularization is used to study the bound state and
scattering states. The initial calculations show that the reciprocal of the
bare coupling constant is ultra-violet divergent, and the resultant expression
cannot be renormalized in the usual sense. Therefore a general procedure has
been developed to derive different physical properties of the system. The
procedure is used first on the non-relativistic case for the purpose of
clarification and comparisons. The results from the relativistic case show that
this system behaves exactly like the delta function potential, which means it
also shares the same features with quantum field theories, like being
asymptotically free, and in the massless limit, it undergoes dimensional
transmutation and it possesses an infrared conformal fixed point.
| arxiv topic:hep-th |
arxiv_dataset-60361503.00886 | On Geometry of Interaction for Polarized Linear Logic
cs.LO
We present Geometry of Interaction (GoI) models for Multiplicative Polarized
Linear Logic, MLLP, which is the multiplicative fragment of Olivier Laurent's
Polarized Linear Logic. This is done by uniformly adding multipoints to various
categorical models of GoI. Multipoints are shown to play an essential role in
semantically characterizing the dynamics of proof networks in polarized proof
theory. For example, they permit us to characterize the key feature of
polarization, focusing, as well as being fundamental to our construction of
concrete polarized GoI models.
Our approach to polarized GoI involves two independent studies, based on
different categorical perspectives of GoI.
(i) Inspired by the work of Abramsky, Haghverdi, and Scott, a polarized GoI
situation is defined in which multipoints are added to a traced monoidal
category equipped with a reflexive object $U$. Using this framework,
categorical versions of Girard's Execution formula are defined, as well as the
GoI interpretation of MLLP, proofs. Running the Execution formula is shown to
characterize the focusing property (and thus polarities) as well as the
dynamics of cut-elimination.
(ii) The Int construction of Joyal-Street-Verity is another fundamental
categorical structure for modelling GoI. Here, we investigate it in a
multipointed setting. Our presentation yields a compact version of
Hamano-Scott's polarized categories, and thus denotational models of MLLP.
These arise from a contravariant duality between monoidal categories of
positive and negative objects, along with an appropriate bimodule structure
(representing "non-focused proofs") between them.
Finally, as a special case of (ii) above, a compact model of MLLP is also
presented based on Rel (the category of sets and relations) equipped with
multi-points.
| arxiv topic:cs.LO |
arxiv_dataset-60371503.00986 | Van der Waals interactions between excited atoms in generic environments
quant-ph
We consider the the van der Waals force involving excited atoms in general
environments, constituted by magnetodielectric bodies. We develop a dynamical
approach studying the dynamics of the atoms and the field, mutually coupled.
When only one atom is excited, our dynamical theory suggests that for large
distances the van der Waals force acting on the ground-state atom is monotonic,
while the force acting in the excited atom is spatially oscillating. We show
how this latter force can be related to the known oscillating Casimir--Polder
force on an excited atom near a (ground-state) body. Our force also reveals a
population-induced dynamics: for times much larger that the atomic lifetime the
atoms will decay to their ground-states leading to the van der Waals
interaction between ground-state atoms.
| arxiv topic:quant-ph |
arxiv_dataset-60381503.01086 | Some properties of a sequence defined with the aid of prime numbers
math.NT
For every integer $n\ge 1$ let $a_n$ be the smallest positive integer such
that $n+a_n$ is prime. We investigate the behavior of the sequence $(a_n)_{n\ge
1}$, and prove asymptotic results for the sums $\sum_{n\le x} a_n$, $\sum_{n\le
x} 1/a_n$ and $\sum_{n\le x} \log a_n$.
| arxiv topic:math.NT |
arxiv_dataset-60391503.01186 | Automated detection and classification of cryptographic algorithms in
binary programs through machine learning
cs.CR
Threats from the internet, particularly malicious software (i.e., malware)
often use cryptographic algorithms to disguise their actions and even to take
control of a victim's system (as in the case of ransomware). Malware and other
threats proliferate too quickly for the time-consuming traditional methods of
binary analysis to be effective. By automating detection and classification of
cryptographic algorithms, we can speed program analysis and more efficiently
combat malware.
This thesis will present several methods of leveraging machine learning to
automatically discover and classify cryptographic algorithms in compiled binary
programs.
While further work is necessary to fully evaluate these methods on real-world
binary programs, the results in this paper suggest that machine learning can be
used successfully to detect and identify cryptographic primitives in compiled
code. Currently, these techniques successfully detect and classify
cryptographic algorithms in small single-purpose programs, and further work is
proposed to apply them to real-world examples.
| arxiv topic:cs.CR |
arxiv_dataset-60401503.01286 | Hamilton--Jacobi meet M\"obius
hep-th
Adaptation of the Hamilton--Jacobi formalism to quantum mechanics leads to a
cocycle condition, which is invariant under $D$--dimensional M\"obius
transformations with Euclidean or Minkowski metrics. In this paper we aim to
provide a pedagogical presentation of the proof of the M\"obius symmetry
underlying the cocycle condition. The M\"obius symmetry implies energy
quantization and undefinability of quantum trajectories, without assigning any
prior interpretation to the wave function. As such, the Hamilton--Jacobi
formalism, augmented with the global M\"obius symmetry, provides an alternative
starting point, to the axiomatic probability interpretation of the wave
function, for the formulation of quantum mechanics and the quantum spacetime.
The M\"obius symmetry can only be implemented consistently if spatial space is
compact, and correspondingly if there exist a finite ultraviolet length scale.
Evidence for non--trivial space topology may exist in the cosmic microwave
background radiation.
| arxiv topic:hep-th |
arxiv_dataset-60411503.01386 | Saturated simple and 2-simple topological graphs with few edges
cs.CG math.CO
A simple topological graph is a topological graph in which any two edges have
at most one common point, which is either their common endpoint or a proper
crossing. More generally, in a k-simple topological graph, every pair of edges
has at most k common points of this kind. We construct saturated simple and
2-simple graphs with few edges. These are k-simple graphs in which no further
edge can be added. We improve the previous upper bounds of Kyn\v{c}l, Pach,
Radoi\v{c}i\'c, and T\'oth and show that there are saturated simple graphs on n
vertices with only 7n edges and saturated 2-simple graphs on n vertices with
14.5n edges. As a consequence, 14.5n edges is also a new upper bound for
k-simple graphs (considering all values of k). We also construct saturated
simple and 2-simple graphs that have some vertices with low degree.
| arxiv topic:cs.CG math.CO |
arxiv_dataset-60421503.01486 | Electromagnetic Torques, Precession and Evolution of Magnetic
Inclination of Pulsars
astro-ph.SR astro-ph.HE
We present analytic calculations of the electromagnetic torques acting on a
magnetic neutron star rotating in vacuum, including near-zone torques
associated with the inertia of dipole and quadrupole magnetic fields. We
incorporate these torques into the rotational dynamics of a rigid-body neutron
star, and show that the effects of the inertial torque can be understood as a
modification of the moment of inertia tensor of the star. We apply our
rotational dynamics equation to the Crab pulsar, including intrinsic
distortions of the star and various electromagnetic torques, to investigate the
possibility that the counter-alignment of the magnetic inclination angle, as
suggested by recent observations, could be explained by pulsar precession. We
find that if the effective principal axis of the pulsar is nearly aligned with
either the magnetic dipole axis or the rotation axis, then precession may
account for the observed counter-alignment over decade timescales. Over the
spindown timescale of the pulsar, the magnetic inclination angle always
decreases.
| arxiv topic:astro-ph.SR astro-ph.HE |
arxiv_dataset-60431503.01586 | Giant cross section for molecular ion formation in ultracold Rydberg
gases
physics.atom-ph cond-mat.quant-gas physics.chem-ph physics.plasm-ph
We have studied the associative ionization of a Rydberg atom and a ground
state atom in an ultracold Rydberg gas. The measured scattering cross section
is three orders of magnitude larger than the geometrical size of the produced
molecule. This giant enhancement of the reaction kinetics is due to an
efficient directed mass transport which is mediated by the Rydberg electron. We
also find that the total inelastic scattering cross section is given by the
geometrical size of the Rydberg electron's wavefunction.
| arxiv topic:physics.atom-ph cond-mat.quant-gas physics.chem-ph physics.plasm-ph |
arxiv_dataset-60441503.01686 | Lepton number violation and neutrino masses in 3-3-1 models
hep-ph
Lepton number violation and its relation to neutrino masses is investigated
in several versions of the $SU(3)_c\otimes SU(3)_L\otimes U(1)_x$ model.
Spontaneous and explicit violation and conservation of the lepton number are
considered. In one of the models (the so-called economical one), the lepton
number is spontaneously violated and it is found that the would be Majoron is
not present because it is gauged away, poviding in this way the longitudinal
polarization component to a now massive gauge field.
| arxiv topic:hep-ph |
arxiv_dataset-60451503.01786 | Protected quasi-locality in quantum systems with long-range interactions
cond-mat.quant-gas
We study the out-of-equilibrium dynamics of quantum systems with long-range
interactions. Two different models describing, respectively, interacting
lattice bosons and spins are considered. Our study relies on a combined
approach based on accurate many-body numerical calculations as well as on a
quasiparticle microscopic theory. For sufficiently fast decaying long-range
potentials, we find that the quantum speed limit set by the long-range
Lieb-Robinson bounds is never attained and a purely ballistic behavior is
found. For slowly decaying potentials, a radically different scenario is
observed. In the bosonic case, a remarkable local spreading of correlations is
still observed, despite the existence of infinitely fast traveling excitations
in the system. This is in marked contrast to the spin case, where locality is
broken. We finally provide a microscopic justification of the different regimes
observed and of the origin of the protected locality in the bosonic model.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-60461503.01886 | Visual Survey of 18020 Objects from the 2MFGC Catalog
astro-ph.GA
We conducted a continuous survey of infrared and visual images of 18020 2MFGC
galaxies which were selected on an automatic basis from 1.64 mln extended
objects of the 2MASS XSC catalog based on the ratio of the infrared axes
a/b>=3. This work aims to exclude "false" objects from the list of flat
galaxies. Having observed more than 80 thousand images in different filters, we
were able to detect 1512 such objects (8.4% of the total number). We found 23
galaxies duplicated in 2MASS, which have two 2MFGC numbers correspondingly, and
three flat galaxies which are not included in other catalogs and are located
close to three "false" galaxies. Galaxies with magnitudes fainter than K_s =13
mag compose the main part of the excluded objects. They show small angular
sizes, low surface brightnesses and concentration ratios. The results of the
work in the form of the 2MFGC table with notes are given in the astronomical
databases VizieR, NED, HyperLeda.
| arxiv topic:astro-ph.GA |
arxiv_dataset-60471503.01986 | Convex Color Image Segmentation with Optimal Transport Distances
cs.CV
This work is about the use of regularized optimal-transport distances for
convex, histogram-based image segmentation. In the considered framework, fixed
exemplar histograms define a prior on the statistical features of the two
regions in competition. In this paper, we investigate the use of various
transport-based cost functions as discrepancy measures and rely on a
primal-dual algorithm to solve the obtained convex optimization problem.
| arxiv topic:cs.CV |
arxiv_dataset-60481503.02086 | Gender-Based Violence in 140 Characters or Fewer: A #BigData Case Study
of Twitter
cs.SI cs.CY
Public institutions are increasingly reliant on data from social media sites
to measure public attitude and provide timely public engagement. Such reliance
includes the exploration of public views on important social issues such as
gender-based violence (GBV). In this study, we examine big (social) data
consisting of nearly fourteen million tweets collected from Twitter over a
period of ten months to analyze public opinion regarding GBV, highlighting the
nature of tweeting practices by geographical location and gender. We
demonstrate the utility of Computational Social Science to mine insight from
the corpus while accounting for the influence of both transient events and
sociocultural factors. We reveal public awareness regarding GBV tolerance and
suggest opportunities for intervention and the measurement of intervention
effectiveness assisting both governmental and non-governmental organizations in
policy development.
| arxiv topic:cs.SI cs.CY |
arxiv_dataset-60491503.02186 | Homogeneous space with non virtually abelian discontinuous groups but
without any proper SL(2,R)-action
math.DG math.RT
In the study of discontinuous groups for non-Riemannian homogeneous spaces,
the idea of "continuous analogue" gives a powerful method (T. Kobayashi [Math.
Ann. 1989]). For example, a semisimple symmetric space G/H admits a
discontinuous group which is not virtually abelian if and only if G/H admits a
proper SL(2,R)-action (T. Okuda [J. Differential Geom. 2013]). However, the
action of discrete subgroups is not always approximated by that of connected
groups. In this paper, we show that the theorem cannot be extended to general
homogeneous spaces G/H of reductive type. We give a counterexample in the case
G = SL(5,R).
| arxiv topic:math.DG math.RT |
arxiv_dataset-60501503.02286 | Three-Source Extractors for Polylogarithmic Min-Entropy
cs.CC cs.IT math.IT
We continue the study of constructing explicit extractors for independent
general weak random sources. The ultimate goal is to give a construction that
matches what is given by the probabilistic method --- an extractor for two
independent $n$-bit weak random sources with min-entropy as small as $\log
n+O(1)$. Previously, the best known result in the two-source case is an
extractor by Bourgain \cite{Bourgain05}, which works for min-entropy $0.49n$;
and the best known result in the general case is an earlier work of the author
\cite{Li13b}, which gives an extractor for a constant number of independent
sources with min-entropy $\mathsf{polylog(n)}$. However, the constant in the
construction of \cite{Li13b} depends on the hidden constant in the best known
seeded extractor, and can be large; moreover the error in that construction is
only $1/\mathsf{poly(n)}$.
In this paper, we make two important improvements over the result in
\cite{Li13b}. First, we construct an explicit extractor for \emph{three}
independent sources on $n$ bits with min-entropy $k \geq \mathsf{polylog(n)}$.
In fact, our extractor works for one independent source with poly-logarithmic
min-entropy and another independent block source with two blocks each having
poly-logarithmic min-entropy. Thus, our result is nearly optimal, and the next
step would be to break the $0.49n$ barrier in two-source extractors. Second, we
improve the error of the extractor from $1/\mathsf{poly(n)}$ to
$2^{-k^{\Omega(1)}}$, which is almost optimal and crucial for cryptographic
applications. Some of the techniques developed here may be of independent
interests.
| arxiv topic:cs.CC cs.IT math.IT |
arxiv_dataset-60511503.02386 | Riemann-Roch Spaces and Linear Network Codes
cs.IT math.IT
We construct linear network codes utilizing algebraic curves over finite
fields and certain associated Riemann-Roch spaces and present methods to obtain
their parameters.
In particular we treat the Hermitian curve and the curves associated with the
Suzuki and Ree groups all having the maximal number of points for curves of
their respective genera.
Linear network coding transmits information in terms of a basis of a vector
space and the information is received as a basis of a possibly altered vector
space. Ralf Koetter and Frank R. Kschischang
%\cite{DBLP:journals/tit/KoetterK08} introduced a metric on the set of vector
spaces and showed that a minimal distance decoder for this metric achieves
correct decoding if the dimension of the intersection of the transmitted and
received vector space is sufficiently large.
The vector spaces in our construction have minimal distance bounded from
below in the above metric making them suitable for linear network coding.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-60521503.02486 | Performance of the VLT Planet Finder SPHERE II. Data analysis and
Results for IFS in laboratory
astro-ph.IM
We present the performance of the Integral Field Spectrograph (IFS) of
SPHERE, the high-contrast imager for the ESO VLT telescope designed to perform
imaging and spectroscopy of extrasolar planets, obtained from tests performed
at the Institute de Plan\'etologie et d'Astrophysique de Grenoble facility
during the integration phase of the instrument.} {The tests were performed
using the instrument software purposely prepared for SPHERE. The output data
were reduced applying the SPHERE data reduction and handling software, adding
an improved spectral deconvolution procedure. To this aim, we prepared an
alternative procedure for the spectral subtraction exploiting the principal
components analysis algorithm. Moreover, a simulated angular differential
imaging procedure was also implemented to estimate how the instrument performed
once this procedure was applied at telescope. The capability of the IFS to
faithfully retrieve the spectra of the detected faint companions was also
considered.} {We found that the application of the updated version of the
spectral deconvolution procedure alone, when the algorithm throughput is
properly taken into account, gives us a $5\sigma$ limiting contrast of the
order of 5$\times$$10^{-6}$ or slightly better. The further application of the
angular differential imaging procedure on these data should allow us to improve
the contrast by one order of magnitude down to around 7$\times$$10^{-7}$ at a
separation of 0.3 arcsec. The application of a principal components analysis
procedure that simultaneously uses spectral and angular data gives comparable
results. Finally, we found that the reproducibility of the spectra of the
detected faint companions is greatly improved when angular differential imaging
is applied in addition to the spectral deconvolution.
| arxiv topic:astro-ph.IM |
arxiv_dataset-60531503.02586 | On stability of electroweak vacuum during inflation
hep-ph
We study Coleman-De Luccia tunneling of the Standard Model Higgs field during
inflation in the case when the electroweak vacuum is metastable. We verify that
the tunneling rate is exponentially suppressed. The main contribution to the
suppression is the same as in flat space-time. We analytically estimate the
corrections due to the expansion of the universe and an effective mass term in
the Higgs potential that can be present at inflation.
| arxiv topic:hep-ph |
arxiv_dataset-60541503.02686 | Electrical and optical studies of GaMnAs/GaAs(001) thin films grown by
molecular beam epitaxy
cond-mat.mes-hall
GaMnAs/GaAs films were grown via molecular beam epitaxy using both low and
high substrate temperatures. The films were investigated using Hall effect and
photoluminescence (PL) measurements from 8 to 300 K. The carrier concentrations
in the samples grown at a low substrate temperature are greater than those in
the samples grown at a high substrate temperature. The PL spectra show a GaAs
exciton peak, a peak involving a carbon acceptor, a substitutional Mn
acceptor-related peak and an optical phonon-related peak.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-60551503.02786 | J and H-band Imaging of AKARI North Ecliptic Pole Survey Field
astro-ph.GA
We present the J and H-band source catalog covering the AKARI North Ecliptic
Pole field. Filling the gap between the optical data from other follow-up
observations and mid-infrared (MIR) data from AKARI, our near-infrared (NIR)
data provides contiguous wavelength coverage from optical to MIR. For the J and
H-band imaging, we used the FLoridA Multi-object Imaging Near-ir Grism
Observational Spectrometer (FLAMINGOS) on the Kitt Peak National Observatory
2.1m telescope covering a 5.1 deg2 area down to a 5 sigma depth of ~21.6 mag
and ~21.3 mag (AB) for J and H-band with an astrometric accuracy of 0.14" and
0.17" for 1 sigma in R.A. and Decl. directions, respectively. We detected
208,020 sources for J-band and 203,832 sources for H-band. This NIR data is
being used for studies including analysis of the physical properties of
infrared sources such as stellar mass and photometric redshifts, and will be a
valuable dataset for various future missions.
| arxiv topic:astro-ph.GA |
arxiv_dataset-60561503.02886 | Calibrated submanifolds in neck manifolds
math.DG
We find calibrated submanifolds in neck manifolds. Particularly, we obtain a
calibrated submanifold in the Lagrangian self-expander constructed by Joyce,
Lee and Tsui.
| arxiv topic:math.DG |
arxiv_dataset-60571503.02986 | Strategies for High-Throughput FPGA-based QC-LDPC Decoder Architecture
cs.AR cs.IT math.IT
We propose without loss of generality strategies to achieve a high-throughput
FPGA-based architecture for a QC-LDPC code based on a circulant-1 identity
matrix construction. We present a novel representation of the parity-check
matrix (PCM) providing a multi-fold throughput gain. Splitting of the node
processing algorithm enables us to achieve pipelining of blocks and hence
layers. By partitioning the PCM into not only layers but superlayers we derive
an upper bound on the pipelining depth for the compact representation. To
validate the architecture, a decoder for the IEEE 802.11n (2012) QC-LDPC is
implemented on the Xilinx Kintex-7 FPGA with the help of the FPGA IP compiler
[2] available in the NI LabVIEW Communication System Design Suite (CSDS) which
offers an automated and systematic compilation flow where an optimized hardware
implementation from the LDPC algorithm was generated in approximately 3
minutes, achieving an overall throughput of 608Mb/s (at 260MHz). As per our
knowledge this is the fastest implementation of the IEEE 802.11n QC-LDPC
decoder using an algorithmic compiler.
| arxiv topic:cs.AR cs.IT math.IT |
arxiv_dataset-60581503.03086 | Calculation of the Electroelastic Green's Function of the Hexagonal
Infinite Medium
math-ph math.MP physics.class-ph
The electroelastic 4 $\times$ 4 Green's function of a piezoelectric hexagonal
(transversely isotropic) infinitely extended medium is calculated explicitly in
closed compact form (eqs. (73) ff. and (88) ff., respectively) by using residue
calculation. The results can also be derived from Fredholm's method [2]. In the
case of vanishing piezoelectric coupling the derived Green's function coincides
with two well known results: Kr{\"o}ner 's expressions for the elastic Green's
function tensor [4] is reproduced and the electric part then coincides with the
electric potential (solution of Poisson equation) which is caused by a unit
point charge. The obtained electroelastic Green's function is useful for the
calculation of the electroelastic Eshelby tensor [16].
| arxiv topic:math-ph math.MP physics.class-ph |
arxiv_dataset-60591503.03186 | Continuum excitations of $^{26}$O in a three-body model: $0^+$ and $2^+$
states
nucl-th
The structure and decay dynamics for $0^+$ and $2^+$ continuum excitations of
$^{26}$O are investigated in a three-body $^{24}$O+$n$+$n$ model. The validity
of a simple approximation for the cross section profile for long-lived $2n$
emission is demonstrated. A sequence of three $0^+$ monopole ("breathing mode"
type) excited states is predicted. These states could probably be interpreted
as analogues of Efimov states pushed in the continuum due to insufficient
binding. The calculated energies of the $2^+$ states are related to the
excitation spectrum of $^{25}$O. We discuss the correlation between the
predicted $^{26}$O spectrum and experimental observations.
| arxiv topic:nucl-th |
arxiv_dataset-60601503.03286 | Correlation of sequences and of measures, generic points for joinings
and ergodicity of certain cocycles
math.DS
The main subject of the paper, motivated by a question raised by
Boshernitzan, is to give criteria for a bounded complex-valued sequence to be
uncorrelated to any strictly ergodic sequence. As a tool developed to study
this problem we introduce the notion of correlation between two shift-invariant
measures supported by the symbolic space with complex symbols. We also prove a
"lifting lemma" for generic points: given a joining $\xi$ of two
shift-invariant measures $\mu$ and $\nu$, every point $x$ generic for $\mu$
lifts to a pair $(x,y)$ generic for $\xi$ (such $y$ exists in the full symbolic
space). This lemma allows us to translate correlation between bounded sequences
to the language of correlation of measures. Finally, to establish that the
property of an invariant measure being uncorrelated to any ergodic measure is
essentially weaker than the property of being disjoint from any ergodic
measure, we develop and apply criteria for ergodicity of four-jump cocycles
over irrational rotations. We believe that apart from the applications to
studying the notion of correlation, the two developed tools: the lifting lemma
and the criteria for ergodicity of four-jump cocycles, are of independent
interest. This is why we announce them also in the title. In the Appendix we
also introduce the notion of conditional disjointness.
| arxiv topic:math.DS |
arxiv_dataset-60611503.03386 | Phase modulated multiphoton microscopy
physics.optics
We show that the modulation of the phases of the laser beams of ultra-short
pulses leads to modulation of the two photon fluorescence intensity. The phase
modulation technique when used in multi-photon microscopy can improve the
signal to noise ratio. The technique can also be used in multiplexing the
signals in the frequency domain in multi-focal raster scanning microscopy. As
the technique avoids the use of array detectors as well as elaborate
spatiotemporal multiplexing schemes it provides a convenient means to
multi-focal scanning in axial direction. We show examples of such uses. Similar
methodology can be used in other non-linear scanning microscopies, such as
second or third harmonic generation microscopy.
| arxiv topic:physics.optics |
arxiv_dataset-60621503.03486 | Gromov compactness for squiggly strip shrinking in pseudoholomorphic
quilts
math.SG
We establish a Gromov compactness theorem for strip shrinking in
pseudoholomorphic quilts when composition of Lagrangian correspondences is
immersed. In particular, we show that figure eight bubbling occurs in the
limit, argue that this is a codimension-$0$ effect, and predict its algebraic
consequences -- geometric composition extends to a curved $A_\infty$-bifunctor,
in particular the associated Floer complexes are isomorphic after a figure
eight correction of the bounding cochain. An appendix with Felix Schm\"{a}schke
provides examples of nontrivial figure eight bubbles.
| arxiv topic:math.SG |
arxiv_dataset-60631503.03586 | Development of nanowire devices with quantum functionalities
cond-mat.mtrl-sci cond-mat.mes-hall
Silicon has dominated the microelectronics industry for the last 50 years.
With its zero nuclear spin isotope (28Si) and low spin orbit coupling, it is
believed that silicon can become an excellent host material for an entirely new
generation of devices that operate under the laws of quantum mechanics [1}.
Semiconductor nanowires however, offer huge potential as the next building
blocks of nano-devices due to their one-dimensional structure and properties
[2]. We describe a fabrication process to prepare doped vapor-liquid-solid
(VLS) grown silicon nanowire samples in a 2- and 4-terminal measurement setup
for electrical characterisation.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-60641503.03686 | Simple water-like lattice models in one dimension
cond-mat.stat-mech
In this contribution we review a series of simple one dimensional lattice
models that with an appropriate choice of parameters can account for various
anomalous features of the behaviour of complex systems such as water. In
particular, we will focus on the presence of $p-T$ fluid-solid coexistence
lines with negative slope (i.e. solids that melt upon compression), solid
phases less dense than the liquid phase, and the existence of temperatures of
maximum density. We will see how a simple two-parameter model can reproduce the
phase behaviour of a range of systems well known for their anomalous behaviour
regarding the temperature and pressure dependence of properties such as
density, diffusivity or viscosity.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-60651503.03786 | Complementary upper bounds for fourth central moment with extensions and
applications
math.ST stat.TH
We prove some inequalities involving fourth central moment of a random
variable that takes values in a given finite interval. Both discrete and
continuous cases are considered. Bounds for the spread are obtained when a
given nxn complex matrix has real eigenvalues. Likewise, we discuss bounds for
the spans of polynomial equations.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-60661503.03886 | Transplanckian axions !?
hep-th astro-ph.CO hep-ph
We discuss quantum gravitational effects in Einstein theory coupled to
periodic axion scalars to analyze the viability of several proposals to achieve
superplanckian axion periods (aka decay constants) and their possible
application to large field inflation models. The effects we study correspond to
the nucleation of euclidean gravitational instantons charged under the axion,
and our results are essentially compatible with (but independent of) the Weak
Gravity Conjecture, as follows: Single axion theories with superplanckian
periods contain gravitational instantons inducing sizable higher harmonics in
the axion potential, which spoil superplanckian inflaton field range. A similar
result holds for multi-axion models with lattice alignment (like the
Kim-Nilles-Peloso model). Finally, theories with $N$ axions can still achieve a
moderately superplanckian periodicity (by a $\sqrt{N}$ factor) with no higher
harmonics in the axion potential. The Weak Gravity Conjecture fails to hold in
this case due to the absence of some instantons, which are forbidden by a
discrete $\mathbf{Z}_N$ gauge symmetry. Finally we discuss the realization of
these instantons as euclidean D-branes in string compactifications.
| arxiv topic:hep-th astro-ph.CO hep-ph |
arxiv_dataset-60671503.03986 | Measuring switching processes in financial markets with the
Mean-Variance spin glass approach
q-fin.RM physics.soc-ph q-fin.PM
In this article we use the Mean-Variance Model in order to measure the
current market state. In our study we take the approach of detecting the
overall alignment of portfolios in the spin picture. The projection to the
ground-states enables us to use physical observables in order to describe the
current state of the explored market. The defined magnetization of portfolios
shows cursor effects, which we use to detect turmoils.
| arxiv topic:q-fin.RM physics.soc-ph q-fin.PM |
arxiv_dataset-60681503.04086 | Schwartz operators
math-ph math.FA math.MP quant-ph
In this paper we introduce Schwartz operators as a non-commutative analog of
Schwartz functions and provide a detailed discussion of their properties. We
equip them in particular with a number of different (but equivalent) families
of seminorms which turns the space of Schwartz operators into a Frechet space.
The study of the topological dual leads to non-commutative tempered
distributions which are discussed in detail as well. We show in particular that
the latter can be identified with a certain class of quadratic forms, therefore
making operations like products with bounded (and also some unbounded)
operators and quantum harmonic analysis available to objects which are
otherwise too singular for being a Hilbert space operator. Finally we show how
the new methods can be applied by studying operator moment problems and
convergence properties of fluctuation operators.
| arxiv topic:math-ph math.FA math.MP quant-ph |
arxiv_dataset-60691503.04186 | (2+1)-Dimensional Gravity in Weyl Integrable Spacetime
gr-qc
We investigate (2+1)-dimensional gravity in a Weyl integrable spacetime
(WIST). We show that, unlike general relativity, this scalar-tensor theory has
a Newtonian limit for any dimension and that in three dimensions the congruence
of world lines of particles of a pressureless fluid has a non-vanishing
geodesic deviation. We present and discuss a class of static vacuum solutions
generated by a circularly symmetric matter distribution that for certain values
of the parameter w corresponds to a space-time with a naked singularity at the
center of the matter distribution. We interpret all these results as being a
direct consequence of the space-time geometry.
| arxiv topic:gr-qc |
arxiv_dataset-60701503.04286 | ICT and RFID in Education: Some Practical Aspects in Campus Life
cs.CY
The paper summarizes our preliminary findings regarding the development and
implementation of a newly proposed system based on ICT and RFID (Radio
Frequency Identification) technologies for campus access and facility usage. It
is generally acknowledged that any educational environment is highly dependent
upon a wide range of resources or variables such as teaching staff, research
and study areas, meeting and accommodation facilities, library services,
restaurant and leisure facilities, etc. The system we have devised using ICT
and RFID technologies supports not only authentic transactions among all
university departments, but also interconnects all levels of academic life and
activity. Thus, the utility of the system ranges from access control (student/
staff/ visitor identification), attendance tracking, library check-out services
and voting to grade book consulting, inventory, cashless vending, parking,
laundry and copying services. Physically, the system consists of several RFID
gates/readers, a data server and some network stations, all of them requiring
specific structuring and integration solutions. The system is quite different
from already existing ones in that it proposes an innovative access solution.
Thus, the search of the ID card holder in a database has been replaced by local
processing. Since one and the same card is employed to perform a variety of
operations, the system has immediate and numerous utilizations.
| arxiv topic:cs.CY |
arxiv_dataset-60711503.04386 | A duality between a dark state and a quasi-dark state
quant-ph
We consider the optomechanical system consisting of an atom-cavity system
coupled with a mechanical resonator, and expand the notion of quasi-dark state
to the optomechanical system. We theoretically prove that even if both the
one-mode light of the cavity and the one-mode Bose field of the mechanical
resonator interact with the atom, each of a dark state and a quasi-dark state
has an individual chance to appear when an interaction between the one-mode
light and the one-mode Bose field exists. We then come up with a duality
between the dark state and the quasi-dark state.
| arxiv topic:quant-ph |
arxiv_dataset-60721503.04486 | The complexity of computing the minimum rank of a sign pattern matrix
cs.CC math.CO
We show that computing the minimum rank of a sign pattern matrix is NP hard.
Our proof is based on a simple but useful connection between minimum ranks of
sign pattern matrices and the stretchability problem for pseudolines
arrangements. In fact, our hardness result shows that it is already hard to
determine if the minimum rank of a sign pattern matrix is $\leq 3$. We
complement this by giving a polynomial time algorithm for determining if a
given sign pattern matrix has minimum rank $\leq 2$.
Our result answers one of the open problems from Linial et al.
[Combinatorica, 27(4):439--463, 2007].
| arxiv topic:cs.CC math.CO |
arxiv_dataset-60731503.04586 | Numerical schemes for kinetic equations in the diffusion and anomalous
diffusion limits. Part I: the case of heavy-tailed equilibrium
math.NA
In this work, we propose some numerical schemes for linear kinetic equations
in the diffusion and anomalous diffusion limit. When the equilibrium
distribution function is a Maxwellian distribution, it is well known that for
an appropriate time scale, the small mean free path limit gives rise to a
diffusion type equation. However, when a heavy-tailed distribution is
considered, another time scale is required and the small mean free path limit
leads to a fractional anomalous diffusion equation. Our aim is to develop
numerical schemes for the original kinetic model which works for the different
regimes, without being restricted by stability conditions of standard explicit
time integrators. First, we propose some numerical schemes for the diffusion
asymptotics; then, their extension to the anomalous diffusion limit is studied.
In this case, it is crucial to capture the effect of the large velocities of
the heavy-tailed equilibrium, so that some important transformations of the
schemes derived for the diffusion asymptotics are needed. As a result, we
obtain numerical schemes which enjoy the Asymptotic Preserving property in the
anomalous diffusion limit, that is: they do not suffer from the restriction on
the time step and they degenerate towards the fractional diffusion limit when
the mean free path goes to zero. We also numerically investigate the uniform
accuracy and construct a class of numerical schemes satisfying this property.
Finally, the efficiency of the different numerical schemes is shown through
numerical experiments.
| arxiv topic:math.NA |
arxiv_dataset-60741503.04686 | Quarter-BPS Black Holes in AdS$_4$-NUT from $N=2$ Gauged Supergravity
hep-th
We study $N=2$ gauged supergravity with $U(1)$ gauge group coupled to $n_v$
vector multiplets and find quite general analytic solutions for quarter-BPS
black holes with mass, NUT and dyonic Maxwell charges. The solutions we find
have running scalar fields and flow in the IR region to a horizon geometry of
the form AdS$_2\times \Sigma_g$.
| arxiv topic:hep-th |
arxiv_dataset-60751503.04786 | Darboux transformations for multivariate orthogonal polynomials
math.CA math-ph math.AG math.MP math.RA nlin.SI
Darboux transformations for polynomial perturbations of a real multivariate
measure are found. The 1D Christoffel formula is extended to the
multidimensional realm: multivariate orthogonal polynomials are expressed in
terms of last quasi-determinants and sample matrices. The coefficients of these
matrices are the original orthogonal polynomials evaluated at a set of nodes,
which is supposed to be poised. A discussion for the existence of poised sets
is given in terms of algebraic hypersufaces in the complex affine space.
| arxiv topic:math.CA math-ph math.AG math.MP math.RA nlin.SI |
arxiv_dataset-60761503.04886 | Inexact Shift-and-Invert Arnoldi for Toeplitz Matrix Exponential
math.NA
We revisit the shift-and-invert Arnoldi method proposed in [S. Lee, H. Pang,
and H. Sun. {\it Shift-invert Arnoldi approximation to the Toeplitz matrix
exponential}, SIAM J. Sci. Comput., 32: 774--792, 2010] for numerical
approximation to the product of Toeplitz matrix exponential with a vector. In
this approach, one has to solve two large scale Toeplitz linear systems in
advance. However, if the desired accuracy is high, the cost will be
prohibitive. Therefore, it is interesting to investigate how to solve the
Toeplitz systems inexactly in this method. The contribution of this paper is in
three regards. First, we give a new stability analysis on the Gohberg-Semencul
formula (GSF) and define the GSF condition number of a Toeplitz matrix. It is
shown that, when the size of the Toeplitz matrix is large, our result is
sharper than the one given in [M. Gutknecht and M. Hochbruck. {\it The
stability of inversion formulas for Toeplitz matrices}, Linear Algebra Appl.,
223/224: 307--324, 1995]. Second, we establish a relation between the error of
Toeplitz systems and the residual of Toeplitz matrix exponential. We show that
if the GSF condition number of the Toeplitz matrix is medium sized, then the
Toeplitz systems can be solved in a low accuracy. Third, based on this
relationship, we present a practical stopping criterion for relaxing the
accuracy of the Toeplitz systems, and propose an inexact shift-and-invert
Arnoldi algorithm for the Toeplitz matrix exponential problem. Numerical
experiments illustrate the numerical behavior of the new algorithm, and show
the effectiveness of our theoretical results.
| arxiv topic:math.NA |
arxiv_dataset-60771503.04986 | Entanglement entropy in the Hamming networks
quant-ph
We investigate the Hamming networks that their nodes are considered as
quantum harmonic oscillators. The entanglement of the ground state can be used
to quantify the amount of information each part of a network shares with the
rest of the system via quantum fluctuations. Therefore, the Schmidt numbers and
entanglement entropy between two special parts of Hamming network, can be
calculated. To this aim, first we use the stratification method to rewrite the
adjacency matrix of the network in the stratification basis. Then the
entanglement entropy and Schmidt number for special partitions are calculated
analytically by using the generalized Schur complement method. Also, we
calculate the entanglement entropy between two arbitrary subsets (two equal
subsets have the same number of vertices) in H(2; 3) and H(2; 4) numerically,
and we give the minimum and maximum values of entanglement entropy in these two
Hamming network.
| arxiv topic:quant-ph |
arxiv_dataset-60781503.05086 | Mechanical Flip-Chip for Ultra-High Electron Mobility Devices
cond-mat.mes-hall
Electrostatic gates are of paramount importance for the physics of devices
based on high-mobility two-dimensional electron gas (2DEG) since they allow
depletion of electrons in selected areas. This field-effect gating enables the
fabrication of a wide range of devices such as, for example, quantum point
contacts (QPC), electron interferometers and quantum dots. To fabricate these
gates, processing is usually performed on the 2DEG material, which is in many
cases detrimental to its electron mobility. Here we propose an alternative
process which does not require any processing of the 2DEG material other than
for the ohmic contacts. This approach relies on processing a separate wafer
that is then mechanically mounted on the 2DEG material in a flip-chip fashion.
This technique proved successful to fabricate quantum point contacts on both
GaAs/AlGaAs materials with both moderate and ultra-high electron mobility.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-60791503.05186 | The threshold for jigsaw percolation on random graphs
math.PR math.CO
Jigsaw percolation is a model for the process of solving puzzles within a
social network, which was recently proposed by Brummitt, Chatterjee, Dey and
Sivakoff. In the model there are two graphs on a single vertex set (the
`people' graph and the `puzzle' graph), and vertices merge to form components
if they are joined by an edge of each graph. These components then merge to
form larger components if again there is an edge of each graph joining them,
and so on. Percolation is said to occur if the process terminates with a single
component containing every vertex. In this note we determine the threshold for
percolation up to a constant factor, in the case where both graphs are
Erd\H{o}s--R\'enyi random graphs.
| arxiv topic:math.PR math.CO |
arxiv_dataset-60801503.05286 | Robust Collimation Control of Laser-Generated Ion Beam
physics.plasm-ph
The robustness of a structured collimation device is discussed for an
intense-laser-produced ion beam. In this paper the ion beam collimation is
realized by the solid structured collimation device, which produces the
transverse electric field; the electric field contributes to reduce the ion
beam transverse velocity and collimate the ion beam. Our 2.5 dimensional
particle-in cell simulations demonstrate that the collimation device is rather
robust against the changes in the laser parameters and the collimation target
sizes. The intense short-pulse lasers are now available, and are used to
generate an ion beam. The issues in the laser ion acceleration include an ion
beam collimation, ion energy spectrum control, ion production efficiency, ion
energy control, ion beam bunching, etc. The laser-produced ion beam tends to
expand in the transverse and longitudinal directions during the ion beam
propagation. The ion beam collimation is focused in this paper.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-60811503.05386 | A connection between flat fronts in hyperbolic space and minimal
surfaces in euclidean space
math.DG
A geometric construction is provided that associates to a given flat front in
$\mathbb{H}^3$ a pair of minimal surfaces in $\mathbb{R}^3$ which are related
by a Ribaucour transformation. This construction is generalized associating to
a given frontal in $\mathbb{H}^3$ , a pair of frontals in $\mathbb{R}^3$ that
are envelopes of a smooth congruence of spheres. The theory of Ribaucour
transformations for minimal surfaces is reformulated in terms of a complex
Riccati ordinary differential equation for a holomorphic function. This enables
one to simplify and extend the classical theory, that in principle only works
for umbilic free and simply connected surfaces, to surfaces with umbilic points
and non trivial topology. Explicit examples are included.
| arxiv topic:math.DG |
arxiv_dataset-60821503.05486 | Molecular recognition by van der Waals interaction between polymers with
sequence-specific polarizabilities
cond-mat.soft cond-mat.dis-nn cond-mat.stat-mech physics.bio-ph physics.chem-ph
We analyze van der Waals interactions between two rigid polymers with
sequence-specific, anisotropic polarizabilities along the polymer backbones, so
that the dipole moments fluctuate parallel to the polymer backbones. Assuming
that each polymer has a quenched-in polarizability sequence which reflects, for
example, the polynucleotide sequence of a double-stranded DNA molecule, we
study the van der Waals interaction energy between a pair of such polymers with
rod-like structure for the cases where their respective polarizability
sequences are (i) distinct and (ii) identical, with both zero and non-zero
correlation length of the polarizability correlator along the polymer backbones
in the latter case. For identical polymers, we find a novel $r^{-5}$ scaling
behavior of the van der Waals interaction energy for small inter-polymer
separation $r$, in contradistinction to the $r^{-4}$ scaling behavior of
distinct polymers, with furthermore a pronounced angular dependence favoring
attraction between sufficiently aligned identical polymers. Such behavior can
assist the molecular recognition between polymers.
| arxiv topic:cond-mat.soft cond-mat.dis-nn cond-mat.stat-mech physics.bio-ph physics.chem-ph |
arxiv_dataset-60831503.05586 | Topological transition in a nanowire medium and its radiative
implication
cond-mat.mes-hall physics.optics
We reveal and study the topological transition in a metamaterial formed by
parallel nanowires of polaritonic material. When the dispersion transits from
the elliptic (epsilon-positive) to hyperbolic (epsilon-indefinite) regime, a
very specific isofrequency surface arises which implies an extraordinary
Purcell factor in spite of noticeable optical losses.
| arxiv topic:cond-mat.mes-hall physics.optics |
arxiv_dataset-60841503.05686 | Around distance-squared mappings
math.DG
This is a survey article on distance-squared mappings and related topics.
| arxiv topic:math.DG |
arxiv_dataset-60851503.05786 | A General Framework for Multi-focal Image Classification and
Authentication: Application to Microscope Pollen Images
cs.CV
In this article, we propose a general framework for multi-focal image
classification and authentication, the methodology being demonstrated on
microscope pollen images. The framework is meant to be generic and based on a
brute force-like approach aimed to be efficient not only on any kind, and any
number, of pollen images (regardless of the pollen type), but also on any kind
of multi-focal images. All stages of the framework's pipeline are designed to
be used in an automatic fashion. First, the optimal focus is selected using the
absolute gradient method. Then, pollen grains are extracted using a
coarse-to-fine approach involving both clustering and morphological techniques
(coarse stage), and a snake-based segmentation (fine stage). Finally, features
are extracted and selected using a generalized approach, and their
classification is tested with four classifiers: Weighted Neighbor Distance,
Neural Network, Decision Tree and Random Forest. The latter method, which has
shown the best and more robust classification accuracy results (above 97\% for
any number of pollen types), is finally used for the authentication stage.
| arxiv topic:cs.CV |
arxiv_dataset-60861503.05886 | Holomorphic triples and the prescribed curvature problem on $S^2$
math.DG
We prove new results on existence of solutions for the prescribed gaussian
curvature problem on the euclidean sphere S^2. Those results are achieved by
relating this problem with the holomorphic triples theory on Riemann surfaces.
We think this approach might be applied to study some other semi-linear
elliptic equations of 2nd order on the sphere.
| arxiv topic:math.DG |
arxiv_dataset-60871503.05986 | Cellular automaton model with dynamical 2D speed-gap relation reproduces
empirical and experimental features of traffic flow
nlin.CG physics.soc-ph
This paper proposes an improved cellular automaton traffic flow model based
on the brake light model, which takes into account that the desired time gap of
vehicles is remarkably larger than one second. Although the hypothetical steady
state of vehicles in the deterministic limit corresponds to a unique
relationship between speeds and gaps in the proposed model, the traffic states
of vehicles dynamically span a two-dimensional region in the plane of speed
versus gap, due to the various randomizations. It is shown that the model is
able to well reproduce (i) the free flow, synchronized flow, jam as well as the
transitions among the three phases; (ii) the evolution features of disturbances
and the spatiotemporal patterns in a car-following platoon; (iii) the empirical
time series of traffic speed obtained from NGSIM data. Therefore, we argue that
a model can potentially reproduce the empirical and experimental features of
traffic flow, provided that the traffic states are able to dynamically span a
2D speed-gap region.
| arxiv topic:nlin.CG physics.soc-ph |
arxiv_dataset-60881503.06086 | Intrinsic ionic screening of the ferroelectric polarization of KTP
cond-mat.mtrl-sci
Mobile charges and lattice polarization interact in ferroelectric materials
because of the Coulomb interaction between the mobile free charges and the
fixed lattice dipoles. We have investigated this mutual screening in KTiOPO4, a
ferroelectric/superionic single crystal in which the mobile charges are K+
ions. The ionic accumulation close to the crystal surfaces leads to orders of
magnitude increase of the Second Harmonic Generation. This ionic space charge
model is supported by the absence of such an effect in non-ionic conductor but
ferroelectric BaTiO3, by its temperature dependence in KTiOPO4 and by its broad
depletion at domain walls.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-60891503.06186 | Probing the hyperbolic branch/focus point region of the constrained
minimal supersymmetric standard model with generalized Yukawa
quasi-unification
hep-ph astro-ph.CO
We analyze the parametric space of the constrained minimal supersymmetric
standard model with mu>0 supplemented by a generalized asymptotic Yukawa
coupling quasi-unification condition which yields acceptable masses for the
fermions of the third family. We impose constraints from the cold dark matter
abundance in the universe and its direct detection experiments, the B-physics,
as well as the masses of the sparticles and the lightest neutral CP-even Higgs
boson. Fixing the mass of the latter to its central value from the LHC and
taking 40<=tanbeta<=50, we find a relatively wide allowed parameter space with
-11<=A_0/M_{1/2}<=15 and mass of the lightest sparticle in the range (0.09-1.1)
TeV. This sparticle is possibly detectable by the present cold dark matter
direct search experiments. The required fine-tuning for the electroweak
symmetry breaking is much milder than the one needed in the neutralino-stau
coannihilation region of the same model.
| arxiv topic:hep-ph astro-ph.CO |
arxiv_dataset-60901503.06286 | Maximizing the order of a regular graph of given valency and second
eigenvalue
math.CO cs.DM
From Alon and Boppana, and Serre, we know that for any given integer $k\geq
3$ and real number $\lambda<2\sqrt{k-1}$, there are finitely many $k$-regular
graphs whose second largest eigenvalue is at most $\lambda$. In this paper, we
investigate the largest number of vertices of such graphs.
| arxiv topic:math.CO cs.DM |
arxiv_dataset-60911503.06386 | Collisional Penrose Process in Rotating Wormhole Spacetime
gr-qc
In a collisional Penrose process, two particles coming from the
asymptotically flat region collide in the ergosphere of a compact object. The
collision produces two new particles, one with positive energy and one with
negative energy. When the particle with positive energy escapes to infinity,
the process extracts energy from the compact object. In this paper, we study
the collisional Penrose process in a rotating wormhole spacetime. We consider
the simple case of a head-on collision at the throat of a Teo wormhole. We find
that the process of energy extraction from a Teo wormhole can be substantially
more efficient than the collisional Penrose process in the Kerr black hole
spacetime.
| arxiv topic:gr-qc |
arxiv_dataset-60921503.06486 | A fractional counting process and its connection with the Poisson
process
math.PR
We consider a fractional counting process with jumps of amplitude
$1,2,\ldots,k$, with $k\in \mathbb{N}$, whose probabilities satisfy a suitable
system of fractional difference-differential equations. We obtain the moment
generating function and the probability law of the resulting process in terms
of generalized Mittag-Leffler functions. We also discuss two equivalent
representations both in terms of a compound fractional Poisson process and of a
subordinator governed by a suitable fractional Cauchy problem. The first
occurrence time of a jump of fixed amplitude is proved to have the same
distribution as the waiting time of the first event of a classical fractional
Poisson process, this extending a well-known property of the Poisson process.
When $k=2$ we also express the distribution of the first passage time of the
fractional counting process in an integral form. Finally, we show that the
ratios given by the powers of the fractional Poisson process and of the
counting process over their means tend to 1 in probability.
| arxiv topic:math.PR |
arxiv_dataset-60931503.06586 | APEX observations of non-stationary magneto-hydrodynamical shocks in W44
astro-ph.GA astro-ph.HE
Supernova remnants (SNRs) are considered as being the sources of galactic
cosmic rays. In order to understand the origin, acceleration, and composition
of these cosmic rays, detailed knowledge of the physical conditions in the
local interstellar medium is needed. The shock interaction of SNRs with
molecular clouds that gives rise to strong molecular emission in the far-IR and
sub-mm wavelength regimes can be used as a highly valuable tracer of these
conditions. The application of MHD shock models in the interpretation of the
resulting line emission can yield information on the energetic and chemical
impact of supernova remnants. We have mapped two regions in the supernova
remnant W44 with the APEX telescope in ${}^{12}$CO (3-2), (4-3), (6-5), (7-6)
and ${}^{13}$CO (3-2). The extraction of integrated intensities on five
different positions, corresponding to local maxima of CO emission, allows to
compare these intensities to the outputs of a grid of models, which combine an
MHD shock code with a radiative transfer module based on the 'large velocity
gradient' approximation. We find that the observed CO line emission is
compatible with non-stationary shocks and a pre-shock density of $10^4$
cm${}^{-3}$. Our models furthermore allow to constrain shock ages, velocities,
the pre-shock magnetic field strength components perpendicular to the
line-of-sight, and the full ladder of CO transitions. Finally, our analysis can
be used to estimate the contribution of such SNRs to, e.g. the galactic energy
balance and the momentum-injection into the surrounding interstellar medium.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-60941503.06686 | On rational functions with monodromy group $M_{11}$
math.NT
We compute new polynomials with Galois group $M_{11}$ over $\mathbb{Q}(t)$.
These polynomials stem from various families of covers of
$\mathbb{P}^1\mathbb{C}$ ramified over at least 4 points. Each of these
families has features that make a detailed study interesting. Some of the
polynomials lead, via specialization, to number fields with very small
discriminant or few ramified primes.
| arxiv topic:math.NT |
arxiv_dataset-60951503.06786 | Applicability of point dipoles approximation to all-dielectric
metamaterials
physics.optics
All-dielectric metamaterials consisting of high-dielectric inclusions in a
low-dielectric matrix are considered as a low-loss alternative to resonant
metal-based metamaterials. In this contribution we investigate the
applicability of the point electric and magnetic dipoles approximation to
dielectric meta-atoms on the example of a dielectric ring metamaterial. Despite
the large electrical size of high-dielectric meta-atoms, the dipole
approximation allows for accurate prediction of the metamaterials properties
for the rings with diameters up to ~0.8 of the lattice constant. The results
provide important guidelines for design and optimization of all-dielectric
metamaterials.
| arxiv topic:physics.optics |
arxiv_dataset-60961503.06886 | Search for ultralight scalar dark matter with atomic spectroscopy
physics.atom-ph hep-ex hep-ph
We report new limits on ultralight scalar dark matter (DM) with dilaton-like
couplings to photons that can induce oscillations in the fine-structure
constant alpha. Atomic dysprosium exhibits an electronic structure with two
nearly degenerate levels whose energy splitting is sensitive to changes in
alpha. Spectroscopy data for two isotopes of dysprosium over a two-year span is
analyzed for coherent oscillations with angular frequencies below 1 rad/s. No
signal consistent with a DM coupling is identified, leading to new constraints
on dilaton-like photon couplings over a wide mass range. Under the assumption
that the scalar field comprises all of the DM, our limits on the coupling
exceed those from equivalence-principle tests by up to 4 orders of magnitude
for masses below 3 * 10^-18 eV. Excess oscillatory power, inconsistent with
fine-structure variation, is detected in a control channel, and is likely due
to a systematic effect. Our atomic spectroscopy limits on DM are the first of
their kind, and leave substantial room for improvement with state-of-the-art
atomic clocks.
| arxiv topic:physics.atom-ph hep-ex hep-ph |
arxiv_dataset-60971503.06986 | Hadronic "flow" in p--Pb collisions at the Large Hadron Collider?
nucl-th nucl-ex
Using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, we
investigate azimuthal correlations in p--Pb collisions at $\sqrt{s_{_{\rm
NN}}}=5.02$ TeV. Comparison with the experimental data shows that UrQMD can not
reproduce the multiplicity dependence of 2- and 4-particle cumulants,
especially the transition from positive to negative values of $c_{2}\{4\}$ in
high multiplicity events, which has been taken as experimental evidence of
collectivity in p--Pb collisions. Meanwhile, UrQMD can not qualitatively
describe the differential elliptic flow, $v_{2}(p_{\rm T})$, of all charged
hadrons at various multiplicity classes. These discrepancies show that the
simulated hadronic p--Pb systems can not generate enough collective flow as
observed in experiment, the associated hadron emissions are largely influenced
by non-flow effects. However, the characteristic $v_{2}(p_{\rm T})$
mass-ordering of pions, kaons and protons is observed in UrQMD, which is the
consequence of hadronic interactions and not necessarily associated with strong
fluid-like expansions.
| arxiv topic:nucl-th nucl-ex |
arxiv_dataset-60981503.07086 | Global minima for semilinear optimal control problems
math.OC
We consider an optimal control problem subject to a semilinear elliptic PDE
together with its variational discretization. We provide a condition which
allows to decide whether a solution of the necessary first order conditions is
a global minimum. This condition can be explicitly evaluated at the discrete
level. Furthermore, we prove that if the above condition holds uniformly with
respect to the discretization parameter the sequence of discrete solutions
converges to a global solution of the corresponding limit problem. Numerical
examples with unique global solutions are presented.
| arxiv topic:math.OC |
arxiv_dataset-60991503.07186 | On the Central Charge of Spacetime Current Algebras and Correlators in
String Theory on AdS3
hep-th
Spacetime Virasoro and affine Lie algebras for strings propagating in AdS3
are known to all orders in $\alpha'$. The central extension of such algebras is
a string vertex, whose expectation value can depend on the number of long
strings present in the background but should be otherwise state-independent. In
hep-th/0106004, on the other hand, a state-dependent expectation value was
found. Another puzzling feature of the theory is lack of cluster decomposition
property in certain connected correlators. This note shows that both problems
can be removed by defining the free energy of the spacetime boundary conformal
field theory as the Legendre transform of the formula proposed in the
literature. This corresponds to pass from a canonical ensemble, where the
number of fundamental strings that create the background can fluctuate, to a
microcanonical one, where it is fixed.
| arxiv topic:hep-th |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.