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arxiv_dataset-73001605.01885 | Minimising movements for oscillating energies: the critical regime
math.AP math.DS
Minimising movements are investigated for an energy which is the
superposition of a convex functional and fast small oscillations. Thus a
minimising movement scheme involves a temporal parameter $\tau$ and a spatial
parameter $\epsilon$, with $\tau$ describing the time step and the frequency of
the oscillations being proportional to $\frac 1 \epsilon$. The extreme cases of
fast time scales $\tau << \epsilon$ and slow time scales $\epsilon << \tau$
have been investigated in Braides, Springer Lecture Notes 2094 (2014). In this
article, the intermediate (critical) case of finite ratio $\epsilon/\tau>0$ is
studied. It is shown that a pinning threshold exists, with initial data below
the threshold being a fixed point of the dynamics. A characterisation of the
pinning threshold is given. For initial data above the pinning threshold, the
equation and velocity describing the homogenised motion are determined.
| arxiv topic:math.AP math.DS |
arxiv_dataset-73011605.01985 | CW-resolutions of monomial ideals that are supported on face posets
math.AC math.CO
Given a monomial ideal $I$ with minimal free resolution $\mathcal{F}$
supported in characteristic $p>0$ on a CW-complex $X$ with regular
$2$-skeleton, we construct a CW-complex $Y$ that also supports~$\mathcal{F}$
and such that the face poset $P(Y)$ also supports $\mathcal{F}$ in the sense of
Clark and Tchernev.
| arxiv topic:math.AC math.CO |
arxiv_dataset-73021605.02085 | X-ray-induced photoemission yield for surface studies of solids beyond
the photoelectron escape depth
physics.ins-det
X-ray-induced photoemission in materials research is commonly acknowledged as
a method with a probing depth limited by the escape depth of the
photoelectrons. This general statement should be complemented with exceptions
arising from the distribution of the X-ray wavefield in the material. Here we
show that the integral hard-X-ray-induced photoemission yield is modulated by
the Fresnel reflectivity of a multilayer structure with the signal originating
well below the photoelectron escape depth. A simple electric self-detection of
the integral photoemission yield and Fourier data analysis permit extraction of
thicknesses of individual layers. The approach does not require detection of
the reflected radiation and can be considered as a framework for non-invasive
evaluation of buried layers with hard X-rays under grazing incidence.
| arxiv topic:physics.ins-det |
arxiv_dataset-73031605.02185 | Stateless Model Checking for POWER
cs.LO
We present the first framework for efficient application of stateless model
checking (SMC) to programs running under the relaxed memory model of POWER. The
framework combines several contributions. The first contribution is that we
develop a scheme for systematically deriving operational execution models from
existing axiomatic ones. The scheme is such that the derived execution models
are well suited for efficient SMC. We apply our scheme to an axiomatic model of
POWER. Our main contribution is a technique for efficient SMC, called Relaxed
Stateless Model Checking (RSMC), which systematically explores the possible
inequivalent executions of a program. RSMC is suitable for execution models
obtained using our scheme. We prove that RSMC is sound and optimal for the
POWER memory model, in the sense that each complete program behavior is
explored exactly once. We show the feasibility of our technique by providing an
implementation for programs written in C/pthreads.
| arxiv topic:cs.LO |
arxiv_dataset-73041605.02285 | Goodness-of-fit analysis of the Cosmicflows-2 database of velocities
astro-ph.CO
The goodness-of-fit (GoF) of the Cosmicflows-2 (CF2) database of peculiar
velocities with the LCDM standard model of cosmology is presented. Standard
application of the Chi^2 statistics of the full database, of its 4,838 data
points, is hampered by the small scale nonlinear dynamics which is not
accounted for by the (linear regime) velocity power spectrum. The bulk velocity
constitutes a highly compressed representation of the data which filters out
the small scales non-linear modes. Hence the statistics of the bulk flow
provides an efficient tool for assessing the GoF of the data given a model. The
particular approach introduced here is to use the (spherical top-hat window)
bulk velocity extracted from the Wiener filter reconstruction of the 3D
velocity field as a linear low pass filtered highly compressed representation
of the CF2 data. An ensemble 2250 random linear realizations of the WMAP/LCDM
model has been used to calculate the bulk velocity auto-covariance matrix. We
find that the CF2 data is consistent with the WMAP/LCDM model to better than
the 2 sigma confidence limits. This provides a further validation that the CF2
database is consistent with the standard model of cosmology.
| arxiv topic:astro-ph.CO |
arxiv_dataset-73051605.02385 | Forbidden Iron Lines and Dust Destruction in Supernova Remnant Shocks:
The Case of N49 in the Large Magellanic Cloud
astro-ph.GA
We present results of a complete integral field survey of the bright SNR N49
in the LMC, obtained with the WiFeS instrument mounted on the ANU 2.3m
telescope at Siding Spring Observatory. From theoretical shock modelling with
the new MAPPINGS 5.1 code we have, for the first time, subjected the optical Fe
emission line spectrum of a supernova remnant to a detailed abundance and
dynamical analysis covering 8 separate stages of ionisation. This allows us to
derive the dust depletion factors as a function of ionisation stage. We have
shown that there is substantial (30% - 90%) destruction of Fe-bearing dust
grains in these fast shocks ($v_s \sim 250$ km/s), and we have confirmed that
the dominant dust destruction is through the non-thermal sputtering and
grain-grain collision mechanisms developed in a number of theoretical works.
| arxiv topic:astro-ph.GA |
arxiv_dataset-73061605.02485 | On the local boundedness of maximal H--monotone operators
math.FA
In this paper we prove that maximal H-monotone operators
$T:H^n\rightrightarrows V_1$ whose domain is all the Heisenberg group $H^n$ are
locally bounded. This implies that they are upper semicontinuous. As a
consequence, maximal H-monotonicity of an operator on $H^n$ can be
characterized by a suitable version of Minty's type theorem.
| arxiv topic:math.FA |
arxiv_dataset-73071605.02585 | System Intelligence: Model, Bounds and Algorithms
math.OC
We present a general framework for understanding system intelligence, i.e.,
the level of system smartness perceived by users, and propose a novel metric
for measuring intelligence levels of dynamical human-in-the-loop systems,
defined to be the maximum average reward obtained by proactively serving user
demands, subject to a resource constraint. Our metric captures two important
elements of smartness, i.e., being able to know what users want and pre-serve
them, and achieving good resource management while doing so. We provide an
explicit characterization of the system intelligence, and show that it is
jointly determined by user demand volume (opportunity to impress), demand
correlation (user predictability), and system resource and action costs
(flexibility to pre-serve).
We then propose an online learning-aided control algorithm called
Learning-aided Budget-limited Intelligent System Control (\mtt{LBISC}). We show
that \lbisc{} achieves an intelligence level that is within
$O(N(T)^{-\frac{1}{2}}+\epsilon)$ of the highest level, where $N(T)$ represents
the number of data samples collected within a learning period $T$ and is
proportional to the user population size in the system, while guaranteeing an
$O(\max( N(T)^{-\frac{1}{2}}/\epsilon, \log(1/\epsilon)^2))$ average resource
deficit. Moreover, we show that \lbisc{} possesses an $O(\max(
N(T)^{-\frac{1}{2}}/\epsilon$, $ \log(1/\epsilon)^2)+T)$ convergence time,
which is much smaller compared to the $\Theta(1/\epsilon)$ time required for
non-learning based algorithms. The analysis of \lbisc{} rigorously quantifies
the impacts of data and user population (captured by $N(T)$), learning
(captured by our learning method), and control (captured by \lbisc) on
achievable system intelligence, and provides novel insight and guideline into
designing future smart systems.
| arxiv topic:math.OC |
arxiv_dataset-73081605.02685 | HII Region Ionization of the Interstellar Medium: A Case Study of NGC
7538
astro-ph.GA
Using data from the Green Bank Telescope, we analyze the radio continuum
(free-free) and radio recombination line (RRL) emission of the compact HII
region NGC 7538 (Sharpless 158). We detect extended radio continuum and
hydrogen RRL emission beyond the photodissociation region (PDR) toward the
north and east, but a sharp decrease in emission toward the south and west.
This indicates that a non-uniform PDR morphology is affecting the amount of
radiation "leaking" through the PDR. The strongest carbon RRL emission is found
in the western PDR that appears to be dense. We compute a leaking fraction $f_R
= 15 \pm 5$ % of the radio continuum emission measured in the plane of the sky
which represents a lower limit when accounting for the three-dimensional
geometry of the region. We detect an average $^4\textrm{He}^+/\textrm{H}^+$
abundance ratio by number of $0.088 \pm 0.003$ inside the HII region and a
decrease in this ratio with increasing distance from the region beyond the PDR.
Using Herschel Space Observatory data, we show that small dust temperature
enhancements to the north and east of NGC 7538 coincide with extended radio
emission, but that the dust temperature enhancements are mostly contained
within a second PDR to the east. Unlike the giant HII region W43, the radiation
leaking from NGC 7538 seems to only affect the local ambient medium. This
suggests that giant HII regions may have a large effect in maintaining the
ionization of the interstellar medium.
| arxiv topic:astro-ph.GA |
arxiv_dataset-73091605.02785 | Hagedorn temperature and physics of black holes
hep-th
A mini-review devoted to some implications of the Hagedorn temperature for
black hole physics. The existence of a limiting temperature is a generic
feature of string models. The Hagedorn temperature was introduced first in the
context of hadronic physics. Nowadays, the emphasis is shifted to fundamental
strings which might be a necessary ingredient to obtain a consistent theory of
black holes. The point is that, in field theory, the local temperature close to
the horizon could be arbitrarily high, and this observation is difficult to
reconcile with the finiteness of the entropy of black holes. After preliminary
remarks, we review our recent attempt to evaluate the entropy of large black
holes in terms of fundamental strings. We also speculate on implications for
dynamics of large-N gauge theories arising within holographic models.
| arxiv topic:hep-th |
arxiv_dataset-73101605.02885 | Separating Topological Noise from Features using Persistent Entropy
cs.IT math.IT
In this paper, we derive a simple method for separating topological noise
from topological features using a novel measure for comparing persistence
barcodes called persistent entropy.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-73111605.02985 | Planck intermediate results. XLVI. Reduction of large-scale systematic
effects in HFI polarization maps and estimation of the reionization optical
depth
astro-ph.CO
This paper describes the identification, modelling, and removal of previously
unexplained systematic effects in the polarization data of the Planck High
Frequency Instrument (HFI) on large angular scales, including new mapmaking and
calibration procedures, new and more complete end-to-end simulations, and a set
of robust internal consistency checks on the resulting maps. These maps, at
100, 143, 217, and 353 GHz, are early versions of those that will be released
in final form later in 2016.
The improvements allow us to determine the cosmic reionization optical depth
$\tau$ using, for the first time, the low-multipole $EE$ data from HFI,
reducing significantly the central value and uncertainty, and hence the upper
limit. Two different likelihood procedures are used to constrain $\tau$ from
two estimators of the CMB $E$- and $B$-mode angular power spectra at 100 and
143 GHz, after debiasing the spectra from a small remaining systematic
contamination. These all give fully consistent results.
A further consistency test is performed using cross-correlations derived from
the Low Frequency Instrument maps of the Planck 2015 data release and the new
HFI data. For this purpose, end-to-end analyses of systematic effects from the
two instruments are used to demonstrate the near independence of their dominant
systematic error residuals.
The tightest result comes from the HFI-based $\tau$ posterior distribution
using the maximum likelihood power spectrum estimator from $EE$ data only,
giving a value $0.055\pm 0.009$. In a companion paper these results are
discussed in the context of the best-fit Planck $\Lambda$CDM cosmological model
and recent models of reionization.
| arxiv topic:astro-ph.CO |
arxiv_dataset-73121605.03085 | Minimax rational approximation of the Fermi-Dirac distribution
physics.comp-ph cond-mat.mtrl-sci physics.chem-ph
Accurate rational approximations of the Fermi-Dirac distribution are a useful
component in many numerical algorithms for electronic structure calculations.
The best known approximations use $O( \log (\beta \Delta) \log
(\epsilon^{-1}))$ poles to achieve an error tolerance $\epsilon$ at temperature
$\beta^{-1}$ over an energy interval $\Delta$. We apply minimax approximation
to reduce the number of poles by a factor of four and replace $\Delta$ with
$\Delta_{\mathrm{occ}}$, the occupied energy interval. This is particularly
beneficial when $\Delta \gg \Delta_{\mathrm{occ}}$, such as in electronic
structure calculations that use a large basis set.
| arxiv topic:physics.comp-ph cond-mat.mtrl-sci physics.chem-ph |
arxiv_dataset-73131605.03185 | Simulating the timescale dependent color variation in quasars with a
revised inhomogeneous disk model
astro-ph.GA astro-ph.CO
The UV/optical variability of active galactic nuclei and quasars is useful
for understanding the physics of the accretion disk and is gradually attributed
to the stochastic fluctuations over the accretion disk. Quasars generally
appear bluer when they brighten in the UV/optical, the nature of which remains
controversial. Recently \citeauthor{Sun2014} discovered that the color
variation of quasars is timescale dependent, in the way that faster variations
are even bluer than longer term ones. While this discovery can directly rule
out models that simply attribute the color variation to contamination from the
host galaxies, or to changes in the global accretion rates, it favors the
stochastic disk fluctuation model as fluctuations in the innermost hotter disk
could dominate the short-term variations. In this work, we show that a revised
inhomogeneous disk model, where the characteristic timescales of thermal
fluctuations in the disk are radius-dependent (i.e., $\tau \sim r$; based on
the one originally proposed by \citeauthor{DexterAgol2011}), can well reproduce
a timescale dependent color variation pattern, similar to the observed one and
unaffected by the un-even sampling and photometric error. This demonstrates
that one may statistically use variation emission at different timescales to
spatially resolve the accretion disk in quasars, thus opens a new window to
probe and test the accretion disk physics in the era of time domain astronomy.
Caveats of the current model, which ought to be addressed in future
simulations, are discussed.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-73141605.03285 | Carrier mediated reduction of stiffness in nanoindented crystalline
Si(100)
cond-mat.mtrl-sci
We report the observation of carrier mediated decrease in the stiffness of
crystalline (c)-Si(100) under nanoindentation. The apparent elastic modulii of
heavily dopes (1E21 cm-3) p- and n-type c-Si are observed to be lower by 5.-7.5
percent that the estimated value for intrinsic (1E14 cm-3) c-Si. The deviation
observed with respect to elastic modulus remarkably matches with the estimated
value while considering the electronic elastic strain effect on carrier
concentration as an influence of negative pressure coefficient of band gap for
Si. The value is predominantly higher than the reported value of a decrease of
1-3 percent in stiffness as an effect of impurity in c-Si.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-73151605.03385 | Discrete symmetries and Lieb-Schultz-Mattis theorem
cond-mat.stat-mech
In this study, we consider one-dimension (1D) quantum spin systems with the
translation and discrete symmetries (spin reversal, space inversion and time
reversal symmetries). By combining the continuous U(1) symmetry with the
discrete symmetries and using the extended Lieb-Schultz-Mattis theorem
\cite{Lieb-Schultz-Mattis-1961}\cite{Nomura-Morishige-Isoyama-2015}, we
investigate the relation between the ground states, energy spectra and
symmetries. For half-integer spin cases, we generalize the dimer and N\'eel
concepts using the discrete symmetries, and we can reconcile the LSM theorem
with the dimer or N\'eel states, since there was a subtle dilemma. Furthermore,
a part of discrete symmetries is enough to classify possible phases. Thus we
can deepen our understanding of the relation between the LSM theorem and the
discrete symmetries.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-73161605.03485 | Investigating the opportunities of using mobile learning by young
children in Bulgaria
cs.CY
This paper provides an analysis of literature related to the use of mobile
devices in teaching young children. For this purpose, the most popular mobile
operating systems in Bulgaria are considered and the functionality of the
existing mobile applications with Bulgarian interface is discussed. The results
of a survey of parents' views regarding the mobile devices as a learning tool
are presented and the ensuing conclusions are provided.
| arxiv topic:cs.CY |
arxiv_dataset-73171605.03585 | 750 GeV Diphotons: Implications for Supersymmetric Unification II
hep-ph hep-ex
Perturbative supersymmetric gauge coupling unification is possible in six
theories where complete SU(5) TeV-scale multiplets of vector matter account for
the size of the reported $750~{\rm GeV}$ diphoton resonance, interpreted as a
singlet multiplet $S = (s+ia)/\sqrt{2}$. One of these has a full generation of
vector matter and a unified gauge coupling $\alpha_G \sim 1$. The diphoton
signal rate is enhanced by loops of vector squarks and sleptons, especially
when the trilinear $A$ couplings are large. If the $SH_u H_d$ coupling is
absent, both $s$ and $a$ can contribute to the resonance, which may then have a
large apparent width if the mass splitting from $s$ and $a$ arises from loops
of vector matter. The width depends sensitively on $A$ parameters and phases of
the vector squark and slepton masses. Vector quarks and/or squarks are expected
to be in reach of the LHC. If the $SH_uH_d$ coupling is present, $a$ leads to a
narrow diphoton resonance, while a second resonance with decays $s \rightarrow
hh, W^+ W^-,ZZ$ is likely to be discovered at future LHC runs. In some of the
theories a non-standard origin or running of the soft parameters is required,
for example involving conformal hidden sector interactions.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-73181605.03685 | No-enclave percolation corresponds to holes in the cluster backbone
cond-mat.dis-nn
The no-enclave percolation (NEP) model introduced recently by Sheinman et al.
can be mapped to a problem of holes within a standard percolation backbone, and
numerical measurements of these holes gives the size-distribution exponent
$\tau = 1.82(1)$ of the NEP model. An argument is given that $\tau=1 + d_B/2
\approx 1.822$ where $d_B$ is the backbone dimension. On the other hand, a
model of simple holes within a percolation cluster implies $\tau = 1 + d_f/2 =
187/96 \approx 1.948$, where $d_f$ is the fractal dimension of the cluster, and
this value is consistent with Sheinman et al.'s experimental results of gel
collapse which gives $\tau = 1.91(6)$. Both models yield a discontinuous
maximum hole size at $p_c$, signifying explosive percolation behavior. At
$p_c$, the largest hole fills exactly half the system, due to symmetry.
Extensive numerical simulations confirm our results.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-73191605.03785 | Variable-length Non-overlapping Codes
cs.IT cs.DM math.IT
We define a variable-length code having the property that no (non-empty)
prefix of each its codeword is a suffix of any other one, and vice versa. This
kind of code can be seen as an extension of two well-known codes in literature,
called respectively fix-free code and non-overlapping code. In this paper, some
constructive algorithms for such codes are presented as well as numerical
results about their cardinality.
| arxiv topic:cs.IT cs.DM math.IT |
arxiv_dataset-73201605.03885 | Gone with the heat: A fundamental constraint on the imaging of dust and
molecular gas in the early Universe
astro-ph.GA astro-ph.CO
Images of dust continuum and carbon monoxide (CO) line emission are powerful
tools for deducing structural characteristics of galaxies, such as disk sizes,
H$_2$ gas velocity fields and enclosed H$_2$ and dynamical masses. We report on
a fundamental constraint set by the cosmic microwave background (CMB) on the
observed structural and dynamical characteristics of galaxies, as deduced from
dust continuum and CO-line imaging at high redshifts. As the CMB temperature
rises in the distant Universe, the ensuing thermal equilibrium between the CMB
and the cold dust and H$_2$ gas progressively erases all spatial and spectral
contrasts between their brightness distributions and the CMB. For high-redshift
galaxies, this strongly biases the recoverable H$_2$ gas and dust mass
distributions, scale lengths, gas velocity fields and dynamical mass estimates.
This limitation is unique to mm/submm wavelengths and unlike its known effect
on the global dust continuum and molecular line emission of galaxies, it cannot
be addressed simply. We nevertheless identify a unique signature of
CMB-affected continuum brightness distributions, namely an increasing rather
than diminishing contrast between such brightness distributions and the CMB
when the cold dust in distant galaxies is imaged at frequencies beyond the
Raleigh-Jeans limit. For the molecular gas tracers, the same effect makes the
atomic carbon (CI) lines maintain a larger contrast than the CO lines against
the CMB.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-73211605.03985 | Dippers and Dusty Disks Edges: A Unified Model
astro-ph.SR
We revisit the nature of large dips in flux from extinction by dusty
circumstellar material that is observed by Kepler for many young stars in the
Upper Sco and $\rho$ Oph star formation regions. These young, low-mass "dipper"
stars are known to have low accretion rates and primarily host moderately
evolved dusty circumstellar disks. Young low mass stars often exhibit rotating
star spots that cause quasi-periodic photometric variations. We found no
evidence for periods associated with the dips that are different from the star
spot rotation period in spectrograms constructed from the light curves. The
material causing the dips in most of these light curves must be approximately
corotating with the star. We find that disk temperatures computed at the disk
corotation radius are cool enough that dust should not sublime. Crude estimates
for stellar magnetic field strengths and accretion rates are consistent with
magnetospheric truncation near the corotation radius. Magnetospheric truncation
models can explain why the dips are associated with material near corotation
and how dusty material is lifted out of the midplane to obscure the star which
would account for the large fraction of young low mass stars that are dippers.
We propose that variations in disk orientation angle, stellar magnetic field
dipole tilt axis, and disk accretion rate are underlying parameters accounting
for differences in the dipper light curves.
| arxiv topic:astro-ph.SR |
arxiv_dataset-73221605.04085 | Higher order unfitted FEM for Stokes interface problems
math.NA
We consider the discretization of a stationary Stokes interface problem in a
velocity-pressure formulation. The interface is described implicitly as the
zero level of a scalar function as it is common in level set based methods.
Hence, the interface is not aligned with the mesh. An unfitted finite element
discretization based on a Taylor-Hood velocity-pressure pair and an XFEM (or
CutFEM) modification is used for the approximation of the solution. This allows
for the accurate approximation of solutions which have strong or weak
discontinuities across interfaces which are not aligned with the mesh. To
arrive at a consistent, stable and accurate formulation we require several
additional techniques. First, a Nitsche-type formulation is used to implement
interface conditions in a weak sense. Secondly, we use the ghost penalty
stabilization to obtain an inf-sup stable variational formulation. Finally, for
the highly accurate approximation of the implicitly described geometry, we use
a combination of a piecewise linear interface reconstruction and a parametric
mapping of the underlying mesh. We introduce the method and discuss results of
numerical examples.
| arxiv topic:math.NA |
arxiv_dataset-73231605.04185 | Pinning down neutrino oscillation parameters in the 2-3 sector with a
mgnetised atmospheric neutrino detector: a new study
hep-ph
We determine the sensitivity to neutrino oscillation parameters from a study
of atmospheric neutrinos in a magnetised detector such as the ICAL at the
proposed India-based Neutrino Observatory. In such a detector that can {\em
separately} count $\nu_\mu$ and $\overline{\nu}_\mu$-induced events, the
relatively smaller (about 5\%) uncertainties on the neutrino--anti-neutrino
flux ratios translate to a constraint in the $\chi^2$ analysis that results in
a significant improvement in the precision with which neutrino oscillation
parameters such as $\sin^2\theta_{23}$ can be determined. Such an effect is
unique to all magnetisable detectors and constitutes a great advantage in
determining neutrino oscillation parameters using such detectors. Such a study
has been performed for the first time here. Along with an increase in the
kinematic range compared to earlier analyses, this results in sensitivities to
oscillation parameters in the 2--3 sector that are comparable to or better than
those from accelerator experiments where the fluxes are significantly higher.
For example, the $1\sigma$ precisions on $\sin^2\theta_{23}$ and
$|\Delta{m^2_{32(31)}}|$ achievable for 500 kTon yr exposure of ICAL are
$\sim9\%$ and $\sim2.5\%$ respectively for both normal and inverted
hierarchies. The mass hierarchy sensitivity achievable with this combination
when the true hierarchy is normal (inverted) for the same exposure is
$\Delta\chi^2\approx8.5$ ($\Delta\chi^2\approx9.5$).
| arxiv topic:hep-ph |
arxiv_dataset-73241605.04285 | Search for gluinos in events with an isolated lepton, jets and missing
transverse momentum at $\sqrt{s}$ = 13 TeV with the ATLAS detector
hep-ex
The results of a search for gluinos in final states with an isolated electron
or muon, multiple jets and large missing transverse momentum using
proton--proton collision data at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV
are presented. The dataset used was recorded in 2015 by the ATLAS experiment at
the Large Hadron Collider and corresponds to an integrated luminosity of 3.2
fb$^{-1}$. Six signal selections are defined that best exploit the signal
characteristics. The data agree with the Standard Model background expectation
in all six signal selections, and the largest deviation is a 2.1 standard
deviation excess. The results are interpreted in a simplified model where
pair-produced gluinos decay via the lightest chargino to the lightest
neutralino. In this model, gluinos are excluded up to masses of approximately
1.6 TeV depending on the mass spectrum of the simplified model, thus surpassing
the limits of previous searches.
| arxiv topic:hep-ex |
arxiv_dataset-73251605.04385 | Knight--Walras Equilibria
q-fin.EC
Knightian uncertainty leads naturally to nonlinear expectations. We introduce
a corresponding equilibrium concept with sublinear prices and establish their
existence. In general, such equilibria lead to Pareto inefficiency and coincide
with Arrow--Debreu equilibria only if the values of net trades are
ambiguity--free in the mean. Without aggregate uncertainty, inefficiencies
arise generically.
We introduce a constrained efficiency concept, uncertainty--neutral
efficiency and show that Knight--Walras equilibrium allocations are efficient
in this constrained sense. Arrow--Debreu equilibria turn out to be non--robust
with respect to the introduction of Knightian uncertainty.
| arxiv topic:q-fin.EC |
arxiv_dataset-73261605.04485 | Equilibration and aging of liquids of non-spherically interacting
particles
cond-mat.soft cond-mat.stat-mech
The non-equilibrium self-consistent generalized Langevin equation theory of
irreversible processes in liquids is extended to describe the positional and
orientational thermal fluctuations of the instantaneous local concentration
profile $n(\mathbf{r},\Omega,t)$ of a suddenly-quenched colloidal liquid of
particles interacting through non spherically-symmetric pairwise interactions,
whose mean value $\overline{n}(\mathbf{r},\Omega,t)$ is constrained to remain
uniform and isotropic, $\overline{n}(\mathbf{r},\Omega,t)=\overline{n}(t)$.
Such self-consistent theory is cast in terms of the time-evolution equation of
the covariance $\sigma(t)=\overline{\delta n_{lm}(\mathbf{k};t) \delta
n^{\dagger}_{lm}(\mathbf{k};t)}$ of the fluctuations $\delta
n_{lm}(\mathbf{k};t)=n_{lm}(\mathbf{k};t) -\overline{n_{lm}}(\mathbf{k};t)$ of
the spherical harmonics projections $n_{lm}(\mathbf{k};t)$ of the Fourier
transform of $n(\mathbf{r},\Omega,t)$. The resulting theory describes the
non-equilibrium evolution after a sudden temperature quench of both, the static
structure factor projections $S_{lm}(k,t)$ and the two-time correlation
function $F_{lm}(k,\tau;t)\equiv\overline{\delta n_{lm}(\mathbf{k},t)\delta
n_{lm}(\mathbf{k},t+\tau)}$, where $\tau$ is the correlation \emph{delay} time
and $t$ is the \emph{evolution} or \emph{waiting} time after the quench. As a
concrete and illustrative application we use the resulting self-consistent
equations to describe the irreversible processes of equilibration or aging of
the orientational degrees of freedom of a system of strongly interacting
classical dipoles with quenched positional disorder.
| arxiv topic:cond-mat.soft cond-mat.stat-mech |
arxiv_dataset-73271605.04585 | Small subgraphs in the trace of a random walk
math.CO
We consider the combinatorial properties of the trace of a random walk on the
complete graph and on the random graph $G(n,p)$. In particular, we study the
appearance of a fixed subgraph in the trace. We prove that for a subgraph
containing a cycle, the threshold for its appearance in the trace of a random
walk of length $m$ is essentially equal to the threshold for its appearance in
the random graph drawn from $G(n,m)$. In the case where the base graph is the
complete graph, we show that a fixed forest appears in the trace typically much
earlier than it appears in $G(n,m)$.
| arxiv topic:math.CO |
arxiv_dataset-73281605.04685 | Spin-polarization in the vicinity of quantum point contact with
spin-orbit interaction
cond-mat.mes-hall
We have developed a novel technique for detection of spin polarization with a
quantum dot weakly coupled to the objective device. The disturbance to the
object in this technique is very small since the detection is performed through
sampling of single electrons in the object with very slow rate. We have applied
the method to a quantum point contact (QPC) under a spin-orbit interaction. A
high degree of spin polarization in the vicinity of the QPC was detected when
the conductance stayed on a plateau at a half of the unit conductance quantum
($G_{\rm q}/2\equiv e^2/h$), and also on another plateau at $2e^2/h$. On the
half-quantum plateau, the degree of polarization $P$ decreased with the bias
source-drain voltage of the QPC while $P$ increased on the single-quantum
plateau, manifesting that different mechanisms of polarization were working on
these plateaus. Very long spin relaxation times in the detector quantum dot
probably due to dynamical nuclear spin polarization were observed. Anomalous
decrease of $P$ around zero-bias was observed at a Kondo-like resonance peak.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-73291605.04785 | An Alternative Matting Laplacian
cs.CV
Cutting out and object and estimate its transparency mask is a key task in
many applications. We take on the work on closed-form matting by Levin et al.,
that is used at the core of many matting techniques, and propose an alternative
formulation that offers more flexible controls over the matting priors. We also
show that this new approach is efficient at upscaling transparency maps from
coarse estimates.
| arxiv topic:cs.CV |
arxiv_dataset-73301605.04885 | Doubly cvharged vector leptons and the Higgs portal
hep-ph
Using a bottom up phenomenological approach we constructed a simple doubly
charged vector lepton $E^{\pm\pm}$ model for the possible 750 GeV diphoton
resonance $\Phi$ at the LHC assuming it to be a scalar particle. Since no
stable doubly charged leptons are seen, to facilitate their decays we complete
the model by adding a charged SM electroweak scalar $S^\pm$. $\Phi$ is a SM
singlet and can be either an inert scalar or a Higgs field. In the inert case
more than one vector lepton are required to account for the photon fusion
production of the resonance if the model is to remain perturbative. For a
Higgssed case $S^\pm$ can assist the production mechanism without using more
than one such lepton. We also found that precision measurements constrain the
couplings of $E^{\pm\pm}$ and $S^\pm$ to SM particles to be small. This raises
the possibility that they can be fairly long lived and can give rise to
displaced vertices if produced at the LHC.
| arxiv topic:hep-ph |
arxiv_dataset-73311605.04985 | On a group-theoretical approach to the curl operator
math-ph math.MP
We utilize group-theoretical methods to develop a matrix representation of
differential operators that act on tensors of any rank. In particular, we
concentrate on the matrix formulation of the curl operator. A self-adjoint
matrix of the curl operator is constructed and its action is extended to a
complex plane. This scheme allows us to obtain properties, similar to those of
the traditional curl operator.
| arxiv topic:math-ph math.MP |
arxiv_dataset-73321605.05085 | Tuning the receding contact angle on hydrogels by addition of particles
cond-mat.soft
Control of the swelling, chemical functionalization, and adhesivity of
hydrogels are finding new applications in a wide range of material systems. We
investigate experimentally the effect of adsorbed particles on hydrogels on the
depinning of contact lines. In our experiments, a water drop containing
polystyrene microspheres is deposited on a swelling hydrogel, which leads to
the drop absorption and particle deposition. Two regimes are observed: a
decreasing drop height with a pinned contact line followed by a receding
contact line. We show that increasing the particles concentration increases the
duration of the first regime and significantly decreases the total absorption
time. The adsorbed particles increase the pinning force at the contact line.
Finally, we develop a method to measure the receding contact angle with the
consideration of the hydrogel swelling.
| arxiv topic:cond-mat.soft |
arxiv_dataset-73331605.05185 | How to calculate dark matter direct detection exclusion limits that are
consistent with gamma rays from annihilation in the Milky Way halo
astro-ph.CO hep-ph
When comparing constraints on the Weakly Interacting Massive Particle (WIMP)
properties from direct and indirect detection experiments it is crucial that
the assumptions made about the dark matter (DM) distribution are realistic and
consistent. For instance, if the Fermi-LAT Galactic centre GeV gamma-ray excess
was due to WIMP annihilation, its morphology would be incompatible with the
Standard Halo Model that is usually used to interpret data from direct
detection experiments. In this article, we calculate exclusion limits from
direct detection experiments using self-consistent velocity distributions,
derived from mass models of the Milky Way where the DM halo has a generalized
NFW profile. We use two different methods to make the mass model compatible
with a DM interpretation of the Galactic centre gamma-ray excess. Firstly, we
fix the inner slope of the DM density profile to the value that best fits the
morphology of the excess. Secondly, we allow the inner slope to vary and
include the morphology of the excess in the data sets used to constrain the
gravitational potential of the Milky Way. The resulting direct detection limits
differ significantly from those derived using the Standard Halo Model, in
particular for light WIMPs, due to the differences in both the local DM density
and velocity distribution.
| arxiv topic:astro-ph.CO hep-ph |
arxiv_dataset-73341605.05285 | Variational Convergence of Discrete Minimal Surfaces
math.NA
Building on and extending tools from variational analysis, we prove
Kuratowski convergence of sets of simplicial area minimizers to minimizers of
the smooth Douglas-Plateau problem under simplicial refinement. This
convergence is with respect to a topology that is stronger than uniform
convergence of both positions and surface normals.
| arxiv topic:math.NA |
arxiv_dataset-73351605.05385 | Residues in group completions and the Cech cohomology of BG
math.GT math.AG
Let $G$ be a connected affine algebraic group over $\mathbb{C}$, $G \to X$ be
an open immersion of $G$-varieties, $Z = X-G$ and $i: Z \to X$ be the
inclusion. Let $\alpha \in H^*(G,\mathbb{C})$ be primitive. We give a method to
compute the image of $\alpha$ in $H^*(Z, i^!\mathbb{C}_X)$, using a lift of
$\alpha$ along the first edge map of the \v{C}ech spectral sequence for
$H^*(BG, \mathbb{C})$. We apply it to the wonderful compactification of a
centerless semisimple group $G$.
| arxiv topic:math.GT math.AG |
arxiv_dataset-73361605.05485 | Strong Correlations, Strong Coupling and s-wave Superconductivity in
Hole-doped BaFe2As2 Single Crystals
cond-mat.supr-con cond-mat.str-el
We present a comprehensive study of the low-temperature heat capacity and
thermal expansion of single crystals of the hole-doped Ba1-xKxFe2As2 series
(0<x<1) and the end-members RbFe2As2 and CsFe2As2. A large increase of the
Sommerfeld coefficient is observed with both decreasing band filling and
isovalent substitution (K, Rb, Cs) revealing a strong enhancement of electron
correlations and the possible proximity of these materials to a Mott insulator.
This trend is well reproduced theoretically by our Density-Functional Theory +
Slave-Spin (DFT+SS) calculations, confirming that 122-iron pnictides are
effectively Hund metals, in which sizable Hund's coupling and orbital
selectivity are the key ingredients for tuning correlations. We also find
direct evidence for the existence of a coherence-incoherence crossover between
a low-temperature heavy Fermi liquid and a highly incoherent high-temperature
regime similar to heavy fermion systems. In the superconducting state, clear
signatures of multiband superconductivity are observed with no evidence for
nodes in the energy gaps, ruling out the existence of a doping-induced change
of symmetry (from s to d-wave). We argue that the disappearance of the electron
band in the range 0.4<x<1.0 is accompanied by a strong-to-weak coupling
crossover and that this shallow band remains involved in the superconducting
pairing, although its contribution to the normal state fades away. Differences
between hole- and electron-doped BaFe2As2 series are emphasized and discussed
in terms of strong pair breaking by potential scatterers beyond the Born limit.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-73371605.05585 | EFTfitter---A tool for interpreting measurements in the context of
effective field theories
hep-ex hep-ph
Over the past years, the interpretation of measurements in the context of
effective field theories has attracted much attention in the field of particle
physics. We present a tool for interpreting sets of measurements in such models
using a Bayesian ansatz by calculating the posterior probabilities of the
corresponding free parameters numerically. An example is given, in which
top-quark measurements are used to constrain anomalous couplings at the
Wtb-vertex.
| arxiv topic:hep-ex hep-ph |
arxiv_dataset-73381605.05685 | First direct evidence of two stages in free recall and three
corresponding estimates of working memory capacity
q-bio.OT
I find that exactly two stages can be seen directly in sequential free recall
distributions. These distributions show that the first three recalls come from
the emptying of working memory, recalls 6 and above come from a second stage
and the 4th and 5th recalls are mixtures of the two. A discontinuity, a rounded
step function, is shown to exist in the fitted linear slope of the recall
distributions as the recall shifts from the emptying of working memory
(positive slope) to the second stage (negative slope). The discontinuity leads
to a first estimate of the capacity of working memory at 4-4.5 items. Working
memory accounts for the recency effect. The primacy effect comes from the
second stage with a contribution also from working memory for short lists (the
first item). The different slopes of the working memory and secondary stages,
and that the two have different functional forms, accounts for the u-shaped
serial position curve. The total recall is shown to be a linear combination of
the content of working memory and items recalled in the second stage with
3.0-3.9 items coming from working memory, a second estimate of the capacity of
working memory. A third, separate upper limit on the capacity of working memory
is found (3.06 items), corresponding to the requirement that the content of
working memory cannot exceed the total recall, item by item. This third limit
presumably corresponds to the least chunked item. This is the best limit on the
capacity of unchunked working memory.
| arxiv topic:q-bio.OT |
arxiv_dataset-73391605.05785 | Efficient Nonparametric Smoothness Estimation
math.ST cs.IT math.IT stat.ML stat.TH
Sobolev quantities (norms, inner products, and distances) of probability
density functions are important in the theory of nonparametric statistics, but
have rarely been used in practice, partly due to a lack of practical
estimators. They also include, as special cases, $L^2$ quantities which are
used in many applications. We propose and analyze a family of estimators for
Sobolev quantities of unknown probability density functions. We bound the bias
and variance of our estimators over finite samples, finding that they are
generally minimax rate-optimal. Our estimators are significantly more
computationally tractable than previous estimators, and exhibit a
statistical/computational trade-off allowing them to adapt to computational
constraints. We also draw theoretical connections to recent work on fast
two-sample testing. Finally, we empirically validate our estimators on
synthetic data.
| arxiv topic:math.ST cs.IT math.IT stat.ML stat.TH |
arxiv_dataset-73401605.05885 | Convection-driven spherical shell dynamos at varying Prandtl numbers
astro-ph.SR
(abidged) Context: Stellar convection zones are characterized by vigorous
high-Reynolds number turbulence at low Prandtl numbers. Aims: We study the
dynamo and differential rotation regimes at varying levels of viscous, thermal,
and magnetic diffusion. Methods: We perform three-dimensional simulations of
stratified fully compressible magnetohydrodynamic convection in rotating
spherical wedges at various thermal and magnetic Prandtl numbers (from 0.25 to
2 and 5, respectively). Results: We find that the rotation profiles for high
thermal diffusivity show a monotonically increasing angular velocity from the
bottom of the convection zone to the top and from the poles toward the equator.
For sufficiently rapid rotation, a region of negative radial shear develops at
mid-latitudes as the thermal diffusivity is decreased. This coincides with a
change in the dynamo mode from poleward propagating activity belts to
equatorward propagating ones. Furthermore, the cyclic solutions disappear at
the highest magnetic Reynolds numbers. The total magnetic energy increases with
the magnetic Reynolds number in the range studied here ($5-151$), but the
energies of the mean magnetic fields level off at high magnetic Reynolds
numbers. The differential rotation is strongly affected by the magnetic fields
and almost vanishes at the highest magnetic Reynolds numbers. In some of our
most turbulent cases we find that two regimes are possible where either
differential rotation is strong and mean magnetic fields relatively weak or
vice versa. Conclusions: Our simulations indicate a strong non-linear feedback
of magnetic fields on differential rotation, leading to qualitative changes in
the behaviors of large-scale dynamos at high magnetic Reynolds numbers.
Furthermore, we do not find indications of the simulations approaching an
asymptotic regime where the results would be independent of diffusion
coefficients.
| arxiv topic:astro-ph.SR |
arxiv_dataset-73411605.05985 | Pivotal Quantities with Arbitrary Small Skewness
stat.ME
In this paper we present randomization methods to enhance the accuracy of the
central limit theorem (CLT) based inferences about the population mean $\mu$.
We introduce a broad class of randomized versions of the Student $t$-statistic,
the classical pivot for $\mu$, that continue to possess the pivotal property
for $\mu$ and their skewness can be made arbitrarily small, for each fixed
sample size $n$. Consequently, these randomized pivots admit CLTs with smaller
errors. The randomization framework in this paper also provides an explicit
relation between the precision of the CLTs for the randomized pivots and the
volume of their associated confidence regions for the mean for both univariate
and multivariate data. This property allows regulating the trade-off between
the accuracy and the volume of the randomized confidence regions discussed in
this paper.
| arxiv topic:stat.ME |
arxiv_dataset-73421605.06085 | A minimal coupled fluid-discrete element model for bedload transport
physics.geo-ph
A minimal Lagragian two-phase model to study turbulent bedload transport
focusing on the granular phase is presented, and validated with experiments.
The model intends to describe bedload transport of massive particles in fully
rough flows at relatively low Shields numbers, for which no suspension occurs.
A discrete element method for the granular phase is coupled with a one
dimensional volume-averaged two-phase momentum equation for the fluid phase.
The coupling between the discrete granular phase and the continuous fluid phase
is discussed, and a consistent averaging formulation adapted to bedload
transport is introduced. An original simple discrete random walk model is
proposed to account for the fluid velocity fluctuations. The model is compared
with experiments considering both classical sediment transport rate as a
function of the Shields number, and depth profiles of solid velocity, volume
fraction, and transport rate density, from existing bedload transport
experiments in inclined flume. The results successfully reproduce the classical
3/2 power law, and more importantly describe well the depth profiles of the
granular phase, showing that the model is able to reproduce the particle scale
mechanisms. From a sensitivity analysis, it is shown that the fluctuation model
allows to reproduce a realistic critical Shields number, and that the influence
of the granular parameters on the macroscopic results are weak. Nevertheless,
the analysis of the corresponding depth profiles reveals an evolution of the
depth structure of the granular phase with varying restitution and friction
coefficients, which denotes the non-trivial underlying physical mechanisms.
| arxiv topic:physics.geo-ph |
arxiv_dataset-73431605.06185 | The Generality of a Section of a Curve
math.AG
Let f: C --> P^3 be a general curve of genus g, mapped to P^3 via a general
linear series of degree d; and let Q be a general (and thus smooth) quadric. In
this paper, we show that the points of intersection f(C) \cap Q give a general
collection of 2d points on Q, except for exactly six exceptional cases. We also
prove similar theorems for every other pair (r, n) for which, except for only
finitely many pairs (d, g), the intersection of a general curve of genus g
mapped to P^r via a general linear series of degree d, with a general
hypersurface S of degree n, is a general collection of dn points on S.
As explained in arXiv:1809.05980, these results play a key role in the
author's proof of the Maximal Rank Conjecture
| arxiv topic:math.AG |
arxiv_dataset-73441605.06285 | On-the-Fly TCP Acceleration with Miniproxy
cs.NI
TCP proxies are basic building blocks for many advanced middleboxes. In this
paper we present Miniproxy, a TCP proxy built on top of a specialized
minimalistic cloud operating system. Miniproxy's connection handling
performance is comparable to that of full-fledged GNU/Linux TCP proxy
implementations, but its minimalistic footprint enables new use cases.
Specifically, Miniproxy requires as little as 6 MB to run and boots in tens of
milliseconds, enabling massive consolidation, on-the-fly instantiation and edge
cloud computing scenarios. We demonstrate the benefits of Miniproxy by
implementing and evaluating a TCP acceleration use case.
| arxiv topic:cs.NI |
arxiv_dataset-73451605.06385 | Spinors, Lagrangians and rank 2 Higgs bundles
math.AG
The paper considers the Dirac operator on a Riemann surface coupled to a
symplectic holomorphic vector bundle W. Each spinor in the null-space generates
through the moment map a Higgs bundle, and varying W one obtains a holomorphic
Lagrangian subvariety in the moduli space of Higgs bundles. Applying this to
the irreducible symplectic representations of SL(2) we obtain Lagrangian
submanifolds of the rank 2 moduli space which link up with m-period points on
the Prym variety of the spectral curve as well as Brill-Noether loci on the
moduli space of semistable bundles. The case of genus 2 is investigated in some
detail.
| arxiv topic:math.AG |
arxiv_dataset-73461605.06485 | Multicolour Poisson Matching
math.PR
Consider several independent Poisson point processes on R^d, each with a
different colour and perhaps a different intensity, and suppose we are given a
set of allowed family types, each of which is a multiset of colours such as
red-blue or red-red-green. We study translation-invariant schemes for
partitioning the points into families of allowed types. This generalizes the
1-colour and 2-colour matching schemes studied previously (where the sets of
allowed family types are the singletons {red-red} and {red-blue} respectively).
We characterize when such a scheme exists, as well as the optimal tail
behaviour of a typical family diameter. The latter has two different regimes
that are analogous to the 1-colour and 2-colour cases, and correspond to the
intensity vector lying in the interior and boundary of the existence region
respectively.
We also address the effect of requiring the partition to be a deterministic
function (i.e. a factor) of the points. Here we find the optimal tail behaviour
in dimension 1. There is a further separation into two regimes, governed by
algebraic properties of the allowed family types.
| arxiv topic:math.PR |
arxiv_dataset-73471605.06585 | Bayesian Analysis of Modified Weibull distribution under progressively
censored competing risk model
stat.CO stat.ME
In this paper we study bayesian analysis of Modified Weibull distribution
under progressively censored competing risk model. This study is made for
progressively censored data. We use deterministic scan Gibbs sampling combined
with slice sampling to generate from the posterior distribution. Posterior
distribution is formed by taking prior distribution as reference prior. A real
life data analysis is shown for illustrative purpose.
| arxiv topic:stat.CO stat.ME |
arxiv_dataset-73481605.06685 | Analysis of High Power Behavior in Piezoelectric Ceramics from a
Mechanical Energy Density Perspective
cond-mat.mtrl-sci
In this work, a new methodology for comparing high power performance of
different piezoelectric materials is presented. When comparing high power
performance of piezoelectric materials of varying compositions and vibration
modes, there exists an inherent problem in comparing the mechanical quality
factor directly. Typically the behavior of the mechanical quality factor is
reported as a function of tip vibration velocity of the sample. This paper
shows why this approach can be inherently problematic and proposes an energy
approach to characterize the mechanical quality factor as the solution. By
utilizing mechanical energy density ($u_{e}$), the mass density of the material
system ($\rho$), and the vibration mode shape (e.g. $k_{31}$ and $k_{p}$) of
the sample are accounted for. Therefore, a better method to compare high power
performance of varying piezoelectric compositions is introduced. Furthermore,
the new method is applied to various compositions by using data available in
the literature. As a result, the high power behavior of the materials appear to
be significantly different when the new "energy density approach" is used to
compare the mechanical quality factor rather than vibration velocity. Also, the
technique's ability to be utilized to consolidate data from different
resonators to determine anisotropic loss factors is demonstrated on hard and
soft PZT samples of $k_{31}$ and $k_{p}$ geometries.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-73491605.06785 | Fractal snowflake domain diffusion with boundary and interior drifts
math.AP math.FA
We study a parabolic Ventsell problem for a second order differential
operator in divergence form and with interior and boundary drift terms on the
snowflake domain. We prove that under standard conditions a related Cauchy
problem possesses a unique classical solution and explain in which sense it
solves a rigorous formulation of the initial Ventsell problem. As a second
result we prove that functions that are intrinsically Lipschitz on the
snowflake boundary admit Euclidean Lipschitz extensions to the closure of the
entire domain. Our methods combine the fractal membrane analysis, the vector
analysis for local Dirichlet forms and PDE on fractals, coercive closed forms,
and the analysis of Lipschitz functions.
| arxiv topic:math.AP math.FA |
arxiv_dataset-73501605.06885 | Bridging Category-level and Instance-level Semantic Image Segmentation
cs.CV
We propose an approach to instance-level image segmentation that is built on
top of category-level segmentation. Specifically, for each pixel in a semantic
category mask, its corresponding instance bounding box is predicted using a
deep fully convolutional regression network. Thus it follows a different
pipeline to the popular detect-then-segment approaches that first predict
instances' bounding boxes, which are the current state-of-the-art in instance
segmentation. We show that, by leveraging the strength of our state-of-the-art
semantic segmentation models, the proposed method can achieve comparable or
even better results to detect-then-segment approaches. We make the following
contributions. (i) First, we propose a simple yet effective approach to
semantic instance segmentation. (ii) Second, we propose an online bootstrapping
method during training, which is critically important for achieving good
performance for both semantic category segmentation and instance-level
segmentation. (iii) As the performance of semantic category segmentation has a
significant impact on the instance-level segmentation, which is the second step
of our approach, we train fully convolutional residual networks to achieve the
best semantic category segmentation accuracy. On the PASCAL VOC 2012 dataset,
we obtain the currently best mean intersection-over-union score of 79.1%. (iv)
We also achieve state-of-the-art results for instance-level segmentation.
| arxiv topic:cs.CV |
arxiv_dataset-73511605.06985 | Zero sets of functions in the Nevanlinna class and the
$\bar\partial_b$-equation on convex domains of general type in $\mathbb{C}^2$
math.CV
The purpose of this paper is to characterize the zero sets of holomorphic
functions in the Nevanlinna class on a class of convex domains of infinite type
in $\mathbb{C}^2$. Moreover, we also obtain $L^p$ estimates, $1 \leq p \leq
\infty$, for a particular solution of the tangential Cauchy-Riemann equation on
the boundaries of these domains.
| arxiv topic:math.CV |
arxiv_dataset-73521605.07085 | The entanglement spectrum and R\'enyi entropies of non-relativistic
conformal fermions
cond-mat.quant-gas hep-lat hep-th nucl-th quant-ph
We characterize non-perturbatively the R\'enyi entropies of degree n=2,3,4,
and 5 of three-dimensional, strongly coupled many-fermion systems in the
scale-invariant regime of short interaction range and large scattering length,
i.e. in the unitary limit. We carry out our calculations using lattice methods
devised recently by us. Our results show the effect of strong pairing
correlations on the entanglement entropy, which modify the sub-leading behavior
for large subsystem sizes (as characterized by the dimensionless parameter x=kF
L_A, where kF is the Fermi momentum and L_A the linear subsystem size), but
leave the leading order unchanged relative to the non-interacting case.
Moreover, we find that the onset of the sub-leading asymptotic regime is at
surprisingly small x=2-4. We provide further insight into the entanglement
properties of this system by analyzing the spectrum of the entanglement
Hamiltonian of the two-body problem from weak to strong coupling. The low-lying
entanglement spectrum displays clear features as the strength of the coupling
is varied, such as eigenvalue crossing, a sharp change in the Schmidt gap, and
scale invariance at unitarity. Beyond the low-lying component, the spectrum
appears as a quasi-continuum distribution, for which we present a statistical
characterization; we find, in particular, that the mean shifts to infinity as
the coupling is turned off, which indicates that that part of the spectrum
represents non-perturbative contributions to the entanglement Hamiltonian. In
contrast, the low-lying entanglement spectrum evolves to finite values in the
noninteracting limit. The scale invariance of the unitary regime guarantees
that our results are universal features intrinsic to 3D quantum mechanics and
represent a well-defined prediction for ultracold atom experiments, which were
recently shown to have direct access to the entanglement entropy.
| arxiv topic:cond-mat.quant-gas hep-lat hep-th nucl-th quant-ph |
arxiv_dataset-73531605.07185 | Raman Scattering by Molecular Hydrogen and Nitrogen in Exoplanetary
Atmospheres
astro-ph.EP
An important source of opacity in exoplanet atmospheres at short visible and
near-UV wavelengths is Rayleigh scattering of light on molecules. It is
accompanied by a related, albeit weaker process -- Raman scattering. We analyze
the signatures of Raman scattering imprinted in the reflected light and the
geometric albedo of exoplanets, which could provide information about
atmospheric properties. Raman scattering affects the geometric albedo spectra
of planets in following ways. Firstly, it causes filling-in of strong
absorption lines in the incident radiation, thus producing sharp peaks in the
albedo. Secondly, it shifts the wavelengths of spectral features in the
reflected light causing the so-called Raman ghost lines. Raman scattering can
also cause a broadband reduction of the albedo due to wavelength shifting of a
stellar spectrum with red spectral index. Observing the Raman peaks in the
albedo could be used to measure the column density of gas, thus providing
constrains on the presence of clouds in the atmosphere. Observing the Raman
ghost lines could be used to spectroscopically identify the main scatterer in
the atmosphere, even molecules like H$_2$ or N$_2$ that do not have prominent
spectral signatures in the optical wavelength range. If detected, ghost lines
could also provide information about the temperature of the atmosphere. In this
paper we investigate the effects of Raman scattering in hydrogen- and
nitrogen-dominated atmospheres. We analyze the feasibility of detecting the
signatures of Raman scattering with the existing and future observational
facilities, and of using these signatures as probes of exoplanetary
atmospheres.
| arxiv topic:astro-ph.EP |
arxiv_dataset-73541605.07285 | Deterministic Time-Space Tradeoffs for k-SUM
cs.DS
Given a set of numbers, the $k$-SUM problem asks for a subset of $k$ numbers
that sums to zero. When the numbers are integers, the time and space complexity
of $k$-SUM is generally studied in the word-RAM model; when the numbers are
reals, the complexity is studied in the real-RAM model, and space is measured
by the number of reals held in memory at any point.
We present a time and space efficient deterministic self-reduction for the
$k$-SUM problem which holds for both models, and has many interesting
consequences. To illustrate:
* $3$-SUM is in deterministic time $O(n^2 \lg\lg(n)/\lg(n))$ and space
$O\left(\sqrt{\frac{n \lg(n)}{\lg\lg(n)}}\right)$. In general, any
polylogarithmic-time improvement over quadratic time for $3$-SUM can be
converted into an algorithm with an identical time improvement but low space
complexity as well. * $3$-SUM is in deterministic time $O(n^2)$ and space
$O(\sqrt n)$, derandomizing an algorithm of Wang.
* A popular conjecture states that 3-SUM requires $n^{2-o(1)}$ time on the
word-RAM. We show that the 3-SUM Conjecture is in fact equivalent to the
(seemingly weaker) conjecture that every $O(n^{.51})$-space algorithm for
$3$-SUM requires at least $n^{2-o(1)}$ time on the word-RAM.
* For $k \ge 4$, $k$-SUM is in deterministic $O(n^{k - 2 + 2/k})$ time and
$O(\sqrt{n})$ space.
| arxiv topic:cs.DS |
arxiv_dataset-73551605.07385 | Local efficiency of integrated goodness-of-fit tests under skew
alternatives
math.ST stat.TH
The efficiency of distribution-free {\it integrated} goodness-of-fit tests
was studied by Henze and Nikitin (2000, 2002) under location alternatives. We
calculate local Bahadur efficiencies of these tests under more realistic
generalized skew alternatives. They turn out to be unexpectedly high.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-73561605.07485 | Measurement of the relative width difference of the $B^0$-$\bar B^0$
system with the ATLAS detector
hep-ex
This paper presents the measurement of the relative width difference $\Delta
\Gamma_d / \Gamma_d$ of the $B^0$-$\bar B^0$ system using the data collected by
the ATLAS experiment at the LHC in $p p$ collisions at $\sqrt{s} = 7$ TeV and
$\sqrt{s} = 8$ TeV and corresponding to an integrated luminosity of 25.2
fb$^{-1}$. The value of $\Delta \Gamma_d / \Gamma_d$ is obtained by comparing
the decay-time distributions of $B^0 \to J/\psi K_S$ and $B^0 \to J/\psi
K^{*0}(892)$ decays. The result is $\Delta \Gamma_d / \Gamma_d = (-0.1 \pm
1.1~\mbox{(stat.)} \pm 0.9~\mbox{(syst.)}) \times 10^{-2}$. Currently, this is
the most precise single measurement of $\Delta \Gamma_d / \Gamma_d$. It agrees
with the Standard Model prediction and the measurements by other experiments.
| arxiv topic:hep-ex |
arxiv_dataset-73571605.07585 | Ultradilute low-dimensional liquids
cond-mat.quant-gas
We calculate the energy of one- and two-dimensional weakly interacting
Bose-Bose mixtures analytically in the Bogoliubov approximation and by using
the diffusion Monte Carlo technique. We show that in the case of attractive
inter- and repulsive intraspecies interactions the energy per particle has a
minimum at a finite density corresponding to a liquid state. We derive the
Gross-Pitaevskii equation to describe droplets of such liquids and solve it
analytically in the one-dimensional case.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-73581605.07685 | Characterizing and Avoiding Routing Detours Through Surveillance States
cs.NI
An increasing number of countries are passing laws that facilitate the mass
surveillance of Internet traffic. In response, governments and citizens are
increasingly paying attention to the countries that their Internet traffic
traverses. In some cases, countries are taking extreme steps, such as building
new Internet Exchange Points (IXPs), which allow networks to interconnect
directly, and encouraging local interconnection to keep local traffic local. We
find that although many of these efforts are extensive, they are often futile,
due to the inherent lack of hosting and route diversity for many popular sites.
By measuring the country-level paths to popular domains, we characterize
transnational routing detours. We find that traffic is traversing known
surveillance states, even when the traffic originates and ends in a country
that does not conduct mass surveillance. Then, we investigate how clients can
use overlay network relays and the open DNS resolver infrastructure to prevent
their traffic from traversing certain jurisdictions. We find that 84\% of paths
originating in Brazil traverse the United States, but when relays are used for
country avoidance, only 37\% of Brazilian paths traverse the United States.
Using the open DNS resolver infrastructure allows Kenyan clients to avoid the
United States on 17\% more paths. Unfortunately, we find that some of the more
prominent surveillance states (e.g., the U.S.) are also some of the least
avoidable countries.
| arxiv topic:cs.NI |
arxiv_dataset-73591605.07785 | Geometry-aware stationary subspace analysis
cs.LG
In many real-world applications data exhibits non-stationarity, i.e., its
distribution changes over time. One approach to handling non-stationarity is to
remove or minimize it before attempting to analyze the data. In the context of
brain computer interface (BCI) data analysis this may be done by means of
stationary subspace analysis (SSA). The classic SSA method finds a matrix that
projects the data onto a stationary subspace by optimizing a cost function
based on a matrix divergence. In this work we present an alternative method for
SSA based on a symmetrized version of this matrix divergence. We show that this
frames the problem in terms of distances between symmetric positive definite
(SPD) matrices, suggesting a geometric interpretation of the problem. Stemming
from this geometric viewpoint, we introduce and analyze a method which utilizes
the geometry of the SPD matrix manifold and the invariance properties of its
metrics. Most notably we show that these invariances alleviate the need to
whiten the input matrices, a common step in many SSA methods which often
introduces errors. We demonstrate the usefulness of our technique in
experiments on both synthesized and real-world data.
| arxiv topic:cs.LG |
arxiv_dataset-73601605.07885 | Radii and binding energies in oxygen isotopes: a puzzle for nuclear
forces
nucl-ex nucl-th
We present a systematic study of both nuclear radii and binding energies in
(even) oxygen isotopes from the valley of stability to the neutron drip line.
Both charge and matter radii are compared to state-of-the-art {\it ab initio}
calculations along with binding energy systematics. Experimental matter radii
are obtained through a complete evaluation of the available elastic proton
scattering data of oxygen isotopes. We show that, in spite of a good
reproduction of binding energies, {\it ab initio} calculations with
conventional nuclear interactions derived within chiral effective field theory
fail to provide a realistic description of charge and matter radii. A novel
version of two- and three-nucleon forces leads to considerable improvement of
the simultaneous description of the three observables for stable isotopes, but
shows deficiencies for the most neutron-rich systems. Thus, crucial challenges
related to the development of nuclear interactions remain.
| arxiv topic:nucl-ex nucl-th |
arxiv_dataset-73611605.07985 | Compressed sensing for real measurements of quaternion signals
math.FA
The article concerns compressed sensing methods in the quaternion algebra. We
prove that it is possible to uniquely reconstruct - by $\ell_1$ norm
minimization - a sparse quaternion signal from a limited number of its real
linear measurements, provided the measurement matrix satisfies so-called
restricted isometry property with a sufficiently small constant. We also
provide error estimates for the reconstruction of a non-sparse quaternion
signal in the noisy and noiseless cases.
| arxiv topic:math.FA |
arxiv_dataset-73621605.08085 | Impact of galactic and intergalactic dust on the stellar EBL
astro-ph.GA astro-ph.CO
Current theories assume that the low intensity of the stellar extragalactic
background light (stellar EBL) is caused primarily by finite age of the
Universe because the finite age limits the number of photons pumped into the
space by galaxies and thus the sky is dark in the night. We oppose this opinion
and show that two main factors are responsible for the extremely low intensity
of the observed stellar EBL: (1) a low mean surface brightness of galaxies,
which causes a low luminosity density in the local Universe, and (2) light
extinction due to absorption by galactic and intergalactic dust. Dust produces
a partial opacity of galaxies and of the Universe. The galactic opacity reduces
the intensity of light from more distant background galaxies obscured by
foreground galaxies. The effective extinction AV for light passing through a
galaxy is 0.2 mag. This causes that distant background galaxies do not
contribute to the EBL significantly. In addition, light of distant galaxies is
dimmed due to absorption by intergalactic dust. Even a minute intergalactic
opacity of 1x10^(-2) mag per Gpc is high enough to produce significant effects
on the EBL. The absorbed starlight heats up the galactic and intergalactic dust
and is further re-radiated at the IR, FIR and micro-wave spectrum. Assuming
static infinite universe with no galactic and intergalactic dust, the stellar
EBL should be as high as the surface brightness of stars. However, if dust is
considered, the predicted stellar EBL is about 290 nWm^(-2)sr^(-1), which is
only 5 times higher than the observed value. Hence, the presence of dust has
higher impact on the EBL than currently assumed. In the expanding universe, the
calculated value of the EBL is further decreased, because the obscuration
effect and intergalactic absorption become more pronounced at high redshifts
when the matter was concentrated at smaller volume than at present.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-73631605.08185 | Ruling Out Static Latent Homophily in Citation Networks
cs.DL
Citation and coauthor networks offer an insight into the dynamics of
scientific progress. We can also view them as representations of a causal
structure, a logical process captured in a graph. From a causal perspective, we
can ask questions such as whether authors form groups primarily due to their
prior shared interest, or if their favourite topics are 'contagious' and spread
through co-authorship. Such networks have been widely studied by the artificial
intelligence community, and recently a connection has been made to nonlocal
correlations produced by entangled particles in quantum physics -- the impact
of latent hidden variables can be analyzed by the same algebraic geometric
methodology that relies on a sequence of semidefinite programming (SDP)
relaxations. Following this trail, we treat our sample coauthor network as a
causal graph and, using SDP relaxations, rule out latent homophily as a
manifestation of prior shared interest leading to the observed patternedness.
By introducing algebraic geometry to citation studies, we add a new tool to
existing methods for the analysis of content-related social influences.
| arxiv topic:cs.DL |
arxiv_dataset-73641605.08285 | Solving Systems of Random Quadratic Equations via Truncated Amplitude
Flow
stat.ML cs.IT math.IT math.OC
This paper presents a new algorithm, termed \emph{truncated amplitude flow}
(TAF), to recover an unknown vector $\bm{x}$ from a system of quadratic
equations of the form $y_i=|\langle\bm{a}_i,\bm{x}\rangle|^2$, where
$\bm{a}_i$'s are given random measurement vectors. This problem is known to be
\emph{NP-hard} in general. We prove that as soon as the number of equations is
on the order of the number of unknowns, TAF recovers the solution exactly (up
to a global unimodular constant) with high probability and complexity growing
linearly with both the number of unknowns and the number of equations. Our TAF
approach adopts the \emph{amplitude-based} empirical loss function, and
proceeds in two stages. In the first stage, we introduce an
\emph{orthogonality-promoting} initialization that can be obtained with a few
power iterations. Stage two refines the initial estimate by successive updates
of scalable \emph{truncated generalized gradient iterations}, which are able to
handle the rather challenging nonconvex and nonsmooth amplitude-based objective
function. In particular, when vectors $\bm{x}$ and $\bm{a}_i$'s are
real-valued, our gradient truncation rule provably eliminates erroneously
estimated signs with high probability to markedly improve upon its untruncated
version. Numerical tests using synthetic data and real images demonstrate that
our initialization returns more accurate and robust estimates relative to
spectral initializations. Furthermore, even under the same initialization, the
proposed amplitude-based refinement outperforms existing Wirtinger flow
variants, corroborating the superior performance of TAF over state-of-the-art
algorithms.
| arxiv topic:stat.ML cs.IT math.IT math.OC |
arxiv_dataset-73651605.08385 | Comparative study of gyrokinetic, hybrid-kinetic and fully kinetic wave
physics for space plasmas
physics.plasm-ph physics.space-ph
A set of numerical solvers for the linear dispersion relations of the
gyrokinetic, the hybrid-kinetic, and the fully kinetic model is employed to
study the physics of the kinetic Alfv\'en wave and the fast magnetosonic mode
in these models. In particular, we focus on parameters that are relevant for
solar wind oriented applications (using a homogeneous, isotropic background),
which are characterized by wave propagation angles averaging close to 90{\deg}.
It is found that the gyrokinetic model, while lacking high-frequency solutions
and cyclotron effects, faithfully reproduces the fully kinetic Alfv\'en wave
physics close to, and sometimes significantly beyond, the boundaries of its
range of validity. The hybrid-kinetic model, on the other hand, is much more
complete in terms of high-frequency waves, but owing to its simple electron
model it is found to severely underpredict wave damping rates even on ion
spatial scales across a large range of parameters, despite containing full
kinetic ion physics.
| arxiv topic:physics.plasm-ph physics.space-ph |
arxiv_dataset-73661605.08485 | The State of the Art in Cartograms
cs.HC
Cartograms combine statistical and geographical information in thematic maps,
where areas of geographical regions (e.g., countries, states) are scaled in
proportion to some statistic (e.g., population, income). Cartograms make it
possible to gain insight into patterns and trends in the world around us and
have been very popular visualizations for geo-referenced data for over a
century. This work surveys cartogram research in visualization, cartography and
geometry, covering a broad spectrum of different cartogram types: from the
traditional rectangular and table cartograms, to Dorling and diffusion
cartograms. A particular focus is the study of the major cartogram dimensions:
statistical accuracy, geographical accuracy, and topological accuracy. We
review the history of cartograms, describe the algorithms for generating them,
and consider task taxonomies. We also review quantitative and qualitative
evaluations, and we use these to arrive at design guidelines and research
challenges.
| arxiv topic:cs.HC |
arxiv_dataset-73671605.08585 | Simultaneous analysis of matter radii, transition probabilities, and
excitation energies of Mg isotopes by angular-momentum-projected
configuration-mixing calculations
nucl-th
We perform simultaneous analysis of (1) matter radii, (2) $B(E2; 0^+
\rightarrow 2^+ )$ transition probabilities, and (3) excitation energies,
$E(2^+)$ and $E(4^+)$, for $^{24-40}$Mg by using the beyond mean-field (BMF)
framework with angular-momentum-projected configuration mixing with respect to
the axially symmetric $\beta_2$ deformation with infinitesimal cranking. The
BMF calculations successfully reproduce all of the data for $r_{\rm m}$,
$B(E2)$, and $E(2^+)$ and $E(4^+)$, indicating that it is quite useful for data
analysis, particularly for low-lying states. We also discuss the absolute value
of the deformation parameter $\beta_2$ deduced from measured values of $B(E2)$
and $r_{\rm m}$. This framework makes it possible to investigate the effects of
$\beta_2$ deformation, the change in $\beta_2$ due to restoration of rotational
symmetry, $\beta_2$ configuration mixing, and the inclusion of time-odd
components by infinitesimal cranking. Under the assumption of axial deformation
and parity conservation, we clarify which effect is important for each of the
three measurements, and propose the kinds of BMF calculations that are
practical for each of the three kinds of observables.
| arxiv topic:nucl-th |
arxiv_dataset-73681605.08685 | Modelling turbulent stellar convection zones: sub-grid scales effects
astro-ph.SR
The impressive development of global numerical simulations of turbulent
stellar interiors unveiled a variety of possible differential rotation (solar
or anti-solar), meridional circulation (single or multi-cellular), and dynamo
states (stable large scale toroidal field or periodically reversing magnetic
fields). Various numerical schemes, based on the so-called anelastic set of
equations, were used to obtain these results. It appears today mandatory to
assess their robustness with respect to the details of the numerics, and in
particular to the treatment of turbulent sub-grid scales. We report on an
ongoing comparison between two global models, the ASH and EULAG codes. In EULAG
the sub-grid scales are treated implicitly by the numerical scheme, while in
ASH their effect is generally modelled by using enhanced dissipation
coefficients. We characterize the sub-grid scales effect in a turbulent
convection simulation with EULAG. We assess their effect at each resolved scale
with a detailed energy budget. We derive equivalent eddy-diffusion coefficients
and use the derived diffusivities in twin ASH numerical simulations. We find a
good agreement between the large-scale flows developing in the two codes in the
hydrodynamic regime, which encourages further investigation in the
magnetohydrodynamic regime for various dynamo solutions.
| arxiv topic:astro-ph.SR |
arxiv_dataset-73691605.08785 | Examining Tatooine: Atmospheric Models of Neptune-Like Circumbinary
Planets
astro-ph.EP
Circumbinary planets experience a time varying irradiation pattern as they
orbit their two host stars. In this work, we present the first detailed study
of the atmospheric effects of this irradiation pattern on known and
hypothetical gaseous circumbinary planets. Using both a one-dimensional Energy
Balance Model and a three-dimensional General Circulation Model, we look at the
temperature differences between circumbinary planets and their equivalent
single-star cases in order to determine the nature of the atmospheres of these
planets. We find that for circumbinary planets on stable orbits around their
host stars, temperature differences are on average no more than 1.0% in the
most extreme cases. Based on detailed modeling with the General Circulation
Model, we find that these temperature differences are not large enough to
excite circulation differences between the two cases. We conclude that gaseous
circumbinary planets can be treated as their equivalent single-star case in
future atmospheric modeling efforts.
| arxiv topic:astro-ph.EP |
arxiv_dataset-73701605.08885 | Gromov-Witten Theory of Quotient of Fermat Calabi-Yau varieties
math.AG hep-th
We construct a global B-model for weighted homogeneous polynomials based on
K. Saito's theory of primitive forms. Our main motivation is to give a rigorous
statement of the so called global mirror symmetry conjecture relating
Gromov-Witten invariants and Fan--Jarvis--Ruan--Witten invariants. Furthermore,
our construction allows us to generalize the notion of a quasi-modular form and
holomorphic anomaly equations. Finally, we prove the global mirror symmetry
conjecture for the Fermat polynomials.
| arxiv topic:math.AG hep-th |
arxiv_dataset-73711605.08985 | Liquid-liquid transition in supercooled aqueous solution involving a
low-temperature phase similar to low-density amorphous water
physics.chem-ph
The striking anomalies in physical properties of supercooled water that were
discovered in the 1960-70s, remain incompletely understood and so provide both
a source of controversy amongst theoreticians, and a stimulus to
experimentalists and simulators to find new ways of penetrating the
"crystallization curtain" that effectively shields the problem from solution.
Recently a new door on the problem was opened by showing that, in ideal
solutions, made using ionic liquid solutes, water anomalies are not destroyed
as earlier found for common salt and most molecular solutes, but instead are
enhanced to the point of precipitating an apparently first order liquid-liquid
transition. The evidence was a spike in apparent heat capacity during cooling
that could be fully reversed during reheating before any sign of ice
crystallization appeared. Here, we use decoupled-oscillator infrared
spectroscopy to define the structural character of this phenomenon using
similar down and upscan rates as in the calorimetric study. Thin-film samples
also permit slow scans (1 K/min) in which the transition has a width of less
than 1 K, and is fully reversible. The OH spectrum changes discontinuously at
the phase-transition temperature, indicating a discrete change in hydrogen-bond
structure. The spectral changes show that the low-temperature liquid is more
strongly hydrogen bonded and less disordered as compared to the
high-temperature liquid. The spectrum of the low-temperature liquid is
essentially that seen in low-density amorphous water. This similarity suggests
that the liquid-liquid transition observed here also exists in neat undercooled
water, providing a unified explanation for many of its anomalies.
| arxiv topic:physics.chem-ph |
arxiv_dataset-73721605.09085 | Stochastic Function Norm Regularization of Deep Networks
cs.LG cs.CV stat.ML
Deep neural networks have had an enormous impact on image analysis.
State-of-the-art training methods, based on weight decay and DropOut, result in
impressive performance when a very large training set is available. However,
they tend to have large problems overfitting to small data sets. Indeed, the
available regularization methods deal with the complexity of the network
function only indirectly. In this paper, we study the feasibility of directly
using the $L_2$ function norm for regularization. Two methods to integrate this
new regularization in the stochastic backpropagation are proposed. Moreover,
the convergence of these new algorithms is studied. We finally show that they
outperform the state-of-the-art methods in the low sample regime on benchmark
datasets (MNIST and CIFAR10). The obtained results demonstrate very clear
improvement, especially in the context of small sample regimes with data laying
in a low dimensional manifold. Source code of the method can be found at
\url{https://github.com/AmalRT/DNN_Reg}.
| arxiv topic:cs.LG cs.CV stat.ML |
arxiv_dataset-73731605.09185 | RAFCON: a Graphical Tool for Task Programming and Mission Control
cs.RO
There are many application fields for robotic systems including service
robotics, search and rescue missions, industry and space robotics. As the
scenarios in these areas grow more and more complex, there is a high demand for
powerful tools to efficiently program heterogeneous robotic systems. Therefore,
we created RAFCON, a graphical tool to develop robotic tasks and to be used for
mission control by remotely monitoring the execution of the tasks. To define
the tasks, we use state machines which support hierarchies and concurrency.
Together with a library concept, even complex scenarios can be handled
gracefully. RAFCON supports sophisticated debugging functionality and tightly
integrates error handling and recovery mechanisms. A GUI with a powerful state
machine editor makes intuitive, visual programming and fast prototyping
possible. We demonstrated the capabilities of our tool in the SpaceBotCamp
national robotic competition, in which our mobile robot solved all exploration
and assembly challenges fully autonomously. It is therefore also a promising
tool for various RoboCup leagues.
| arxiv topic:cs.RO |
arxiv_dataset-73741605.09285 | A semi-classical recipe for wobbly limp noodles in partonic soup
hep-th hep-ph nucl-th
We compute the average squared distance, $s^2(t)$, travelled by a
light-flavour off-mass-shell coloured parton in a strongly-coupled
$\mathcal{N}=4$ $SU(N_c)$ super-symmetric Yang Mills plasma using the
gauge/string duality. In fact, we derive a closed integral expression for
$s^2(t;a)$ in $AdS_3$-Schwarzschild, which interpolates between a heavy quark
when $a = 0$ and a light quark when $a = 1$, that we evaluate analytically for
small virtualities - labelled $s_\text{small}^2(t;a)$. For arbitrary
virtualities, we show that for asymptotically early times the motion is
ballistic, $\left.s^2(t;a)\right|_{t\ll\beta}\sim t^2$, while at asymptotically
late times the motion is diffusive, $\left. s^2(t;a) \right|_{t\gg\beta} =
s_\text{small}^2(t;a) \sim 2D(a) t$, from which we are able to extract the
diffusion coefficient $D(a)$. Motivated by the apparent universality of the
late time behaviour, we compute $s_{\text{small}}^2(t;a,d)$ and $D(a,d)$ for an
arbitrary $AdS_d$-Schwarzschild geometry. From $D(a,d)$ we then compute for the
first time the dynamic, time-dependent transverse momentum squared per unit
path length picked up by a high momentum light quark in a strongly-coupled
plasma, the transport coefficient $\hat{q}(t)$, which is critically important
for phenomenology in heavy ion collisions.
| arxiv topic:hep-th hep-ph nucl-th |
arxiv_dataset-73751605.09385 | Interaction-driven topological superconductivity in one dimension
cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con
We study one-dimensional topological superconductivity in the presence of
time-reversal symmetry. This phase is characterized by having a bulk gap, while
supporting a Kramers' pair of zero-energy Majorana bound states at each of its
ends. We present a general simple model which is driven into this topological
phase in the presence of repulsive electron-electron interactions. We further
propose two experimental setups and show that they realize this model at low
energies. The first setup is a narrow two-dimensional topological insulator
partially covered by a conventional s-wave superconductor, and the second is a
semiconductor wire in proximity to an s-wave superconductor. These systems can
therefore be used to realize and probe the time-reversal invariant topological
superconducting phase. The effect of interactions is studied using both a
mean-field approach and a renormalization group analysis.
| arxiv topic:cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-73761605.09485 | Band Structure and Topological Properties of Graphene in a Superlattice
Spin Exchange Field
cond-mat.mes-hall cond-mat.mtrl-sci
We analyze the energy spectrum of graphene in the presence of spin-orbit
coupling and a unidirectionally periodic Zeeman field, focusing on the
stability and location of Dirac points it may support. It is found that the
Dirac points at the $K$ and $K'$ points are generically moved to other
locations in the Brillouin zone, but that they remain present when the Zeeman
field $\vec{\Delta}(x)$ integrates to zero within a unit cell. A large variety
of locations for the Dirac points is shown to be possible: when $\vec\Delta
\parallel \hat{z}$ they are shifted from their original locations along the
direction perpendicular to the superlattice axis, while realizations of
$\vec\Delta(x)$ that rotate periodically move the Dirac points to locations
that can reflect the orbit of the rotating electron spin as it moves through a
unit cell. When a uniform Zeeman field is applied in addition to a periodic
$\vec\Delta \parallel \hat{z}$ integrating to zero, the system can be brought
into a metallic, Dirac semimetal, or insulating state, depending on the
direction of the uniform field. The latter is shown to be an anomalous quantum
Hall insulator.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-73771605.09585 | Free Subalgebras of Graded Algebras
math.RA
Let $k$ be a field and let $A=\bigoplus_{n\ge 1}A_n$ be a positively graded
$k$-algebra. We recall that $A$ is graded nilpotent if for every $d\ge 1$, the
subalgebra of $A$ generated by elements of degree $d$ is nilpotent. We give a
method of producing grading nilpotent algebras and use this to prove that over
any base field $k$ there exists a finitely generated graded nilpotent algebra
that contains a free $k$-subalgebra on two generators.
| arxiv topic:math.RA |
arxiv_dataset-73781605.09685 | Opto acoustical gravitational bar detector with cryogenic mirrors
gr-qc physics.ins-det
Enhancing of sensitivity of the opto-acoustical gravitational wave (GW)
antenna OGRAN installed in the underground facilities of Baksan Neutrino
Observatory is analyzed. Calculations are presented showing a sensitivity
improving on two orders of value after a cooling the solid body acoustical part
of the antenna to the nitrogen temperature. A possibility of keeping of the
same optical scheme of the antenna at low temperature is discussed. Design of
modernized construction for cryogenic version of the antenna OGRAN is
described. Test experiments with cooled pilot model carrying cryogenic mirrors
illuminated by the optical pump up to 0.5 W are presented.
| arxiv topic:gr-qc physics.ins-det |
arxiv_dataset-73791605.09785 | Enabling Distributed Optimization in Large-Scale Power Systems
cs.DC math.OC
Distributed optimization for solving non-convex Optimal Power Flow (OPF)
problems in power systems has attracted tremendous attention in the last
decade. Most studies are based on the geographical decomposition of IEEE test
systems for verifying the feasibility of the proposed approaches. However, it
is not clear if one can extrapolate from these studies that those approaches
can be applied to very large-scale real-world systems. In this paper, we show,
for the first time, that distributed optimization can be effectively applied to
a large-scale real transmission network, namely, the Polish 2383-bus system for
which no pre-defined partitions exist, by using a recently developed
partitioning technique. More specifically, the problem solved is the AC OPF
problem with geographical decomposition of the network using the Alternating
Direction Method of Multipliers (ADMM) method in conjunction with the
partitioning technique. Through extensive experimental results and analytical
studies, we show that with the presented partitioning technique the convergence
performance of ADMM can be improved substantially, which enables the
application of distributed approaches on very large-scale systems.
| arxiv topic:cs.DC math.OC |
arxiv_dataset-73801606.00093 | ExTASY: Scalable and Flexible Coupling of MD Simulations and Advanced
Sampling Techniques
cs.CE
For many macromolecular systems the accurate sampling of the relevant regions
on the potential energy surface cannot be obtained by a single, long Molecular
Dynamics (MD) trajectory. New approaches are required to promote more efficient
sampling. We present the design and implementation of the Extensible Toolkit
for Advanced Sampling and analYsis (ExTASY) for building and executing advanced
sampling workflows on HPC systems. ExTASY provides Python based "templated
scripts" that interface to an interoperable and high-performance pilot-based
run time system, which abstracts the complexity of managing multiple
simulations. ExTASY supports the use of existing highly-optimised parallel MD
code and their coupling to analysis tools based upon collective coordinates
which do not require a priori knowledge of the system to bias. We describe two
workflows which both couple large "ensembles" of relatively short MD
simulations with analysis tools to automatically analyse the generated
trajectories and identify molecular conformational structures that will be used
on-the-fly as new starting points for further "simulation-analysis" iterations.
One of the workflows leverages the Locally Scaled Diffusion Maps technique; the
other makes use of Complementary Coordinates techniques to enhance sampling and
generate start-points for the next generation of MD simulations. We show that
the ExTASY tools have been deployed on a range of HPC systems including ARCHER
(Cray CX30), Blue Waters (Cray XE6/XK7), and Stampede (Linux cluster), and that
good strong scaling can be obtained up to 1000s of MD simulations, independent
of the size of each simulation. We discuss how ExTASY can be easily extended or
modified by end-users to build their own workflows, and ongoing work to improve
the usability and robustness of ExTASY.
| arxiv topic:cs.CE |
arxiv_dataset-73811606.00193 | Not dead, just resting: The practical value of per publication citation
indicators
cs.DL
In the final analysis citation-based indicators are inferior to effective
peer review and even peer review is flawed. It is impossible to accurately
measure the value or impact of scientific research and a key task of
scientometricians should be to produce figures for policy makers and others
that are as informative as it is practical to make them and to ensure that
users are fully aware of their limitations. Although the Abramo and D'Angelo
(2016) suggestions make a lot of theoretical sense and so are a goal that is
worth aiming for, it is unrealistic in practice to advocate their universal use
in the contexts discussed above. This is because the indicators would still
have flaws in addition to the generic limitations of citation-based indicators
and would still be inadequate for replacing peer review. Thus, the expense of
the data gathering does not always justify the value in practice of the extra
accuracy. In the longer term, the restructuring of education needed in order to
get the homogeneity necessary for genuinely comparable statistics would be too
expensive and probably damaging to the research mission, in addition to being
out of proportion to the likely value of any citation-based indicator.
| arxiv topic:cs.DL |
arxiv_dataset-73821606.00293 | Ergodic measures on infinite skew-symmetric matrices over
non-Archimedean local fields
math.DS math.PR
Let $F$ be a non-discrete non-Archimedean locally compact field such that the
characteristic $\mathrm{ch}(F)\ne 2$ and let $\mathcal{O}_F$ be the ring of
integers in $F$. The main results of this paper are Theorem 1.2 that classifies
ergodic probability measures on the space $\mathrm{Skew}(\mathbb{N}, F)$ of
infinite skew-symmetric matrices with respect to the natural action of the
group $\mathrm{GL}(\infty,\mathcal{O}_F)$ and Theorem 1.4, that gives an
unexpected natural correspondence between the set of
$\mathrm{GL}(\infty,\mathcal{O}_F)$-invariant Borel probability measures on
$\mathrm{Sym}(\mathbb{N}, F)$ with the set of
$\mathrm{GL}(\infty,\mathcal{O}_F) \times
\mathrm{GL}(\infty,\mathcal{O}_F)$-invariant Borel probability measures on the
space $\mathrm{Mat}(\mathbb{N}, F)$ of infinite matrices over $F$.
| arxiv topic:math.DS math.PR |
arxiv_dataset-73831606.00393 | GammaLib and ctools: A software framework for the analysis of
astronomical gamma-ray data
astro-ph.IM astro-ph.HE
The field of gamma-ray astronomy has seen important progress during the last
decade, yet there exists so far no common software framework for the scientific
analysis of gamma-ray telescope data. We propose to fill this gap by means of
the GammaLib software, a generic library that we have developed to support the
analysis of gamma-ray event data. GammaLib has been written in C++ and all
functionality is available in Python through an extension module. On top of
this framework we have developed the ctools software package, a suite of
software tools that enables building of flexible workflows for the analysis of
Imaging Air Cherenkov Telescope event data. The ctools are inspired by science
analysis software available for existing high-energy astronomy instruments, and
they follow the modular ftools model developed by the High Energy Astrophysics
Science Archive Research Center. The ctools have been written in Python and
C++, and can be either used from the command line, via shell scripts, or
directly from Python. In this paper we present the GammaLib and ctools software
versions 1.0 that have been released end of 2015. GammaLib and ctools are ready
for the science analysis of Imaging Air Cherenkov Telescope event data, and
also support the analysis of Fermi-LAT data and the exploitation of the COMPTEL
legacy data archive. We propose to use ctools as the Science Tools software for
the Cherenkov Telescope Array Observatory.
| arxiv topic:astro-ph.IM astro-ph.HE |
arxiv_dataset-73841606.00493 | Minimal positive design for self-assembly of the Archimedean tilings
cond-mat.stat-mech cond-mat.soft
A challenge of molecular self-assembly is to understand how to design
particles that self-assemble into a desired structure and not any of a
potentially large number of undesired structures. Here we use simulation to
show that a strategy of minimal positive design allows the self-assembly of
networks equivalent to the 8 semiregular Archimedean tilings of the plane,
structures not previously realized in simulation. This strategy consists of
identifying the fewest distinct types of interparticle interaction that appear
in the desired structure, and does not require enumeration of the many possible
undesired structures. The resulting particles, which self-assemble into the
desired networks, possess DNA-like selectivity of their interactions. Assembly
of certain molecular networks may therefore require such selectivity.
| arxiv topic:cond-mat.stat-mech cond-mat.soft |
arxiv_dataset-73851606.00593 | Aging and percolation dynamics in a Non-Poissonian temporal network
model
cond-mat.dis-nn physics.soc-ph
We present an exhaustive mathematical analysis of the recently proposed
Non-Poissonian Ac- tivity Driven (NoPAD) model [Moinet et al. Phys. Rev. Lett.,
114 (2015)], a temporal network model incorporating the empirically observed
bursty nature of social interactions. We focus on the aging effects emerging
from the Non-Poissonian dynamics of link activation, and on their effects on
the topological properties of time-integrated networks, such as the degree
distribution. Analytic expressions for the degree distribution of integrated
networks as a function of time are derived, ex- ploring both limits of
vanishing and strong aging. We also address the percolation process occurring
on these temporal networks, by computing the threshold for the emergence of a
giant connected component, highlighting the aging dependence. Our analytic
predictions are checked by means of extensive numerical simulations of the
NoPAD model.
| arxiv topic:cond-mat.dis-nn physics.soc-ph |
arxiv_dataset-73861606.00693 | Thermodynamics of acoustic black holes in two dimensions
hep-th gr-qc
It is well-known that the thermal Hawking-like radiation can be emitted from
the acoustic horizon, but the thermodynamic-like understanding for acoustic
black holes was rarely made. In this paper, we will show that the kinematic
connection can lead to the dynamic connection at the horizon between the fluid
and gravitational models in two dimension, which implies that there exists the
thermodynamic-like description for acoustic black holes. Then, we discuss the
first law of thermodynamics for the acoustic black hole via an intriguing
connection between the gravitational-like dynamics of the acoustic horizon and
thermodynamics. We obtain a universal form for the entropy of acoustic black
holes, which has an interpretation similar to the entropic gravity. We also
discuss the specific heat, and find that the derivative of the velocity of
background fluid can be regarded as a novel acoustic analogue of the
two-dimensional dilaton potential, which interprets why the two-dimensional
fluid dynamics can be connected to the gravitational dynamics but difficult for
four-dimensional case. In particular, when a constraint is added for the fluid,
the analogue of a Schwarzschild black hole can be realized.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-73871606.00793 | Exact solution of the $D_3$ non-Abelian anyon chain
cond-mat.str-el hep-th math-ph math.MP
Commuting transfer matrices for linear chains of interacting non-Abelian
anyons from the two-dimensional irreducible representation of the dihedral
group $D_3$ (or, equivalently, the integer sector of the $su(2)_4$ spin-$1$
chain) are constructed using the spin-anyon correspondence to a $D_3$-symmetric
formulation of the XXZ Heisenberg spin chain. The spectral problem is solved
using discrete inversion identities satisfied by these transfer matrices and
functional Bethe ansatz methods. The resulting spectrum can be related to that
of the XXZ spin-$1/2$ Heisenberg chain with boundary conditions depending on
the topological sector of the anyon chain. The properties of this model in the
critical regime are studied by finite size analysis of the spectrum. In
particular, points in the phase diagram where the anyon chain realizes some of
the rational $\mathbb{Z}_2$ orbifold theories are identified.
| arxiv topic:cond-mat.str-el hep-th math-ph math.MP |
arxiv_dataset-73881606.00893 | Evaluating the Business Value of CPOE for Cancer Care in Australia: A
Resource Based View Perspective
cs.CY
Today, cancer is one of the leading causes of death throughout the world.
This threatening disease has huge negative impacts, not only on quality of
life, but also on the healthcare industry, whose resources are already scarce.
Thus, finding new approaches for cancer care has been a central point of
interest during the last few decades. One of these approaches is the use of
computerised physician order entry (CPOE) systems. This systems have the
potential to provide more effective and efficient patient-centric cancer care.
This paper serves to examine the business value of an American CPOE in an
Australian context. This is achieved by using our specifically designed tool to
evaluate the business value of IT in the healthcare, in combination with a
resource based view perspective. Our results show that the system has a number
of enabling resources to generate business value subject to having other
resources.
| arxiv topic:cs.CY |
arxiv_dataset-73891606.00993 | High rate, fast timing Glass RPC for the high $\eta$ CMS muon detectors
physics.ins-det hep-ex
The HL-LHC phase is designed to increase by an order of magnitude the amount
of data to be collected by the LHC experiments. To achieve this goal in a
reasonable time scale the instantaneous luminosity would also increase by an
order of magnitude up to $6 \cdot 10^{34}$ cm$^{-2}$s$^{-1}$. The region of the
forward muon spectrometer ($|\eta| > 1.6$) is not equipped with RPC stations.
The increase of the expected particles rate up to 2 kHz/cm$^2$ ( including a
safety factor 3 ) motivates the installation of RPC chambers to guarantee
redundancy with the CSC chambers already present. The actual RPC technology of
CMS cannot sustain the expected background level. A new generation Glass-RPC
(GRPC) using low resistivity glass (LR) is proposed to equip at least the two
most far away of the four high eta muon stations of CMS. The design of small
size prototypes and the studies of their performances under high rate particles
flux is presented.
| arxiv topic:physics.ins-det hep-ex |
arxiv_dataset-73901606.01093 | Extraction of clinical information from the non-invasive fetal
electrocardiogram
cs.CV
Estimation of the fetal heart rate (FHR) has gained interest in the last
century, low heart rate variability has been studied to identify intrauterine
growth restricted fetuses (prepartum), and abnormal FHR patterns have been
associated with fetal distress during delivery (intrapartum). Several
monitoring techniques have been proposed for FHR estimation, including
auscultation and Doppler ultrasound. This thesis focuses on the extraction of
the non-invasive fetal electrocardiogram (NI-FECG) recorded from a limited set
of abdominal sensors. The main challenge with NI-FECG extraction techniques is
the low signal-to-noise ratio of the FECG signal on the abdominal mixture
signal which consists of a dominant maternal ECG component, FECG and noise.
However the NI-FECG offers many advantages over the alternative fetal
monitoring techniques, the most important one being the opportunity to enable
morphological analysis of the FECG which is vital for determining whether an
observed FHR event is normal or pathological. In order to advance the field of
NI-FECG signal processing, the development of standardised public databases and
benchmarking of a number of published and novel algorithms was necessary.
| arxiv topic:cs.CV |
arxiv_dataset-73911606.01193 | Homogeneity degree of some symmetric products
math.GN
For a metric continuum $X$, we consider the $n^{\tiny\textrm{th}}$-symmetric
product $F_{n}(X)$ defined as the hyperspace of all nonempty subsets of $X$
with at most $n$ points. The homogeneity degree $hd(X)$ of a continuum $X$ is
the number of orbits for the action of the group of homeomorphisms of $X$ onto
itself. In this paper we determine $hd(F_{n}(X))$ for every manifold without
boundary and $n\in \mathbb{N}$. We also compute $hd(F_{n}[0,1])$ for all $n\in
\mathbb{N}$.
| arxiv topic:math.GN |
arxiv_dataset-73921606.01293 | Robust Inversion Methods for Aerosol Spectroscopy
math.NA
The Fast Aerosol Spectrometer (FASP) is a device for spectral aerosol
measurements. Its purpose is to safely monitor the atmosphere inside a reactor
containment. First we describe the FASP and explain its basic physical laws.
Then we introduce our reconstruction methods for aerosol particle size
distributions designed for the FASP. We extend known existence results for
constrained Tikhonov regularization by uniqueness criteria and use those to
generate reasonable models for the size distributions. We apply a Bayesian
model-selection framework on these pre-generated models. We compare our
algorithm with classical inversion methods using simulated measurements. We
then extend our reconstruction algorithm for two-component aerosols, so that we
can simultaneously retrieve their particle-size distributions and unknown
volume fractions of their two components. Finally we present the results of a
numerical study for the extended algorithm.
| arxiv topic:math.NA |
arxiv_dataset-73931606.01393 | Automated Image Captioning for Rapid Prototyping and Resource
Constrained Environments
cs.CV
Significant performance gains in deep learning coupled with the exponential
growth of image and video data on the Internet have resulted in the recent
emergence of automated image captioning systems. Ensuring scalability of
automated image captioning systems with respect to the ever increasing volume
of image and video data is a significant challenge. This paper provides a
valuable insight in that the detection of a few significant (top) objects in an
image allows one to extract other relevant information such as actions (verbs)
in the image. We expect this insight to be useful in the design of scalable
image captioning systems. We address two parameters by which the scalability of
image captioning systems could be quantified, i.e., the traditional algorithmic
time complexity which is important given the resource limitations of the user
device and the system development time since the programmers' time is a
critical resource constraint in many real-world scenarios. Additionally, we
address the issue of how word embeddings could be used to infer the verb
(action) from the nouns (objects) in a given image in a zero-shot manner. Our
results show that it is possible to attain reasonably good performance on
predicting actions and captioning images using our approaches with the added
advantage of simplicity of implementation.
| arxiv topic:cs.CV |
arxiv_dataset-73941606.01493 | A note on the order of the Schur multiplier of p-groups
math.GR
Let $G$ be a finite $p$-group of order $p^n$ with $|G'| = p^k$. Let $M(G)$
denotes the Schur multiplier of $G$. A classical result of Green states that
$|M(G)| \leq p^{\frac{1}{2}n(n-1)}$. In 2009, Niroomand, improving Green's and
other bounds on $|M(G)|$ for a non-abelain $p$-group $G$, proved that $|M(G)|
\leq p^{\frac{1}{2}(n-k-1)(n+k-2)+1}$. In this article we note that a bound,
obtained earlier, by Ellis and Weigold is more general than the bound of
Niroomand. We derive from the bound of Ellis and Weigold that $|M(G)| \leq
p^{\frac{1}{2}(d(G)-1)(n+k-2)+1}$ for a non-abelain $p$-group $G$. Moreover, we
sharpen the bound of Ellis and Weigold and as a consequence derive that if
$G^{ab}$ is not homocyclic then $|M(G)| \leq p^{\frac{1}{2}(d(G)-1)(n+k-3)+1}$.
We further note an improvement in an old bound given by Vermani. Finally we
note, for a $p$-group of coclass $r$, that $|M(G)| \leq
p^{\frac{1}{2}(r^2-r)+kr+1}$. This improves a bound by Moravec.
| arxiv topic:math.GR |
arxiv_dataset-73951606.01593 | Generalized Suffix Tree based Multiple Sequence Alignment for Service
Virtualization
cs.SE
Assuring quality of contemporary software systems is a very challenging task
due to the often large complexity of the deployment environments in which they
will operate. Service virtualization is an approach to this challenge where
services within the deployment environment are emulated by synthesising service
response messages from models or by recording and then replaying service
interaction messages with the system. Record-and-replay techniques require an
approach where (i) message prototypes can be derived from recorded system
interactions (i.e. request-response sequences), (ii) a scheme to match incoming
request messages against message prototypes, and (iii) the synthesis of
response messages based on similarities between incoming messages and the
recorded system interactions. Previous approaches in service virtualization
have required a multiple sequence alignment (MSA) algorithm as a means of
finding common patterns of similarities and differences between messages
required by all three steps.
In this paper, we present a novel MSA algorithm based on Generalized Suffix
Trees (GSTs). We evaluated the accuracy and efficiency of the proposed
algorithm against six enterprise service message trace datasets, with the
proposed algorithm performing up to 50 times faster than standard MSA
approaches. Furthermore, the algorithm has applicability to other domains
beyond service virtualization.
| arxiv topic:cs.SE |
arxiv_dataset-73961606.01693 | Polyhedra with few 3-cuts are hamiltonian
math.CO
In 1956, Tutte showed that every planar 4-connected graph is hamiltonian. In
this article, we will generalize this result and prove that polyhedra with at
most three 3-cuts are hamiltonian. In 2002 Jackson and Yu have shown this
result for the subclass of triangulations. We also prove that polyhedra with at
most four 3-cuts have a hamiltonian path. It is well known that for each $k \ge
6$ non-hamiltonian polyhedra with $k$ 3-cuts exist. We give computational
results on lower bounds on the order of a possible non-hamiltonian polyhedron
for the remaining open cases of polyhedra with four or five 3-cuts.
| arxiv topic:math.CO |
arxiv_dataset-73971606.01793 | Low-rank Optimization with Convex Constraints
math.OC cs.LG stat.ML
The problem of low-rank approximation with convex constraints, which appears
in data analysis, system identification, model order reduction, low-order
controller design and low-complexity modelling is considered. Given a matrix,
the objective is to find a low-rank approximation that meets rank and convex
constraints, while minimizing the distance to the matrix in the squared
Frobenius norm. In many situations, this non-convex problem is convexified by
nuclear norm regularization. However, we will see that the approximations
obtained by this method may be far from optimal. In this paper, we propose an
alternative convex relaxation that uses the convex envelope of the squared
Frobenius norm and the rank constraint. With this approach, easily verifiable
conditions are obtained under which the solutions to the convex relaxation and
the original non-convex problem coincide. An SDP representation of the convex
envelope is derived, which allows us to apply this approach to several known
problems. Our example on optimal low-rank Hankel approximation/model reduction
illustrates that the proposed convex relaxation performs consistently better
than nuclear norm regularization and may outperform balanced truncation.
| arxiv topic:math.OC cs.LG stat.ML |
arxiv_dataset-73981606.01893 | Particle-Vortex Duality from 3d Bosonization
hep-th cond-mat.str-el
We provide a simple derivation of particle-vortex duality in d=2+1
dimensions. Our starting point is a relativistic form of flux attachment,
designed to transmute the statistics of particles. From this seed, we derive a
web of new dualities. These include particle-vortex duality for bosons as well
as the recently discovered counterpart for fermions.
| arxiv topic:hep-th cond-mat.str-el |
arxiv_dataset-73991606.01993 | Asynchronous Multi-Agent Primal-Dual Optimization
math.OC
We present a framework for asynchronously solving convex optimization
problems over networks of agents which are augmented by the presence of a
centralized cloud computer. This framework uses a Tikhonov-regularized
primal-dual approach in which the agents update the system's primal variables
and the cloud updates its dual variables. To minimize coordination requirements
placed upon the system, the times of communications and computations among the
agents are allowed to be arbitrary, provided they satisfy mild conditions.
Communications from the agents to the cloud are likewise carried out without
any coordination in their timing. However, we require that the cloud keep the
dual variable's value synchronized across the agents, and a counterexample is
provided that demonstrates that this level of synchrony is indeed necessary for
convergence. Convergence rate estimates are provided in both the primal and
dual spaces, and simulation results are presented that demonstrate the
operation and convergence of the proposed algorithm.
| arxiv topic:math.OC |
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