title: A bridge between Sobolev and Escobar inequalities and beyond

abstract:
  The classical Sobolev and Escobar inequalities are embedded into the same
one-parameter family of sharp trace-Sobolev inequalities on half-spaces.
Equality cases are characterized for each inequality in this family by tweaking
a well-known mass transportation argument and lead to a new comparison theorem
for trace Sobolev inequalities. The case $p=2$ corresponds to a family of
variational problems on conformally flat metrics which was previously settled
by Carlen and Loss with their method of competing symmetries. In this case
minimizers interpolate between conformally flat spherical and hyperbolic
geometries, passing through the Euclidean geometry defined by the fundamental
solution of the Laplacian.


title:
Exact-dimensional property of density of states measure of Sturm
  Hamiltonian

abstract:
  For frequency $\alpha$ of bounded type and coupling $\lambda>20$, we show
that the density of states measure $\NN_{\alpha,\lambda}$ of the related Sturm
Hamiltonian is exact upper and lower dimensional, however, in general it is not
exact-dimensional.


title:
Automorphisms of Salem degree 22 on supersingular K3 surfaces of higher
  Artin invariant

abstract:
  We give a short proof that every supersingular K3 surface (except possibly in
characteristic $2$ with Artin invariant $\sigma=10$) has an automorphism of
Salem degree 22. In particular an infinite subgroup of the automorphism group
does not lift to characteristic zero. The proof relies on the case $\sigma=1$
and the cone conjecture for K3 surfaces.


title: A superhedging approach to stochastic integration

abstract:
  Using Vovk's outer measure, which corresponds to a minimal superhedging
price, the existence of quadratic variation is shown for "typical price paths"
in the space of c\`adl\`ag functions possessing a mild restriction on the jumps
directed downwards. In particular, this result includes the existence of
quadratic variation of "typical price paths" in the space of non-negative
c\`adl\`ag paths and implies the existence of quadratic variation in the sense
of F\"ollmer quasi surely under all martingale measures. Based on the robust
existence of the quadratic variation, a model-free It\^o integration is
developed.


title: The Fermi Large Area Telescope as a Galactic Supernovae Axionscope

abstract:
  In a Galactic core-collapse supernova (SN), axionlike particles (ALPs) could
be emitted via the Primakoff process and eventually convert into $\gamma$ rays
in the magnetic field of the Milky Way. From a data-driven sensitivity
estimate, we find that, for a SN exploding in our Galaxy, the Fermi Large Area
Telescope (LAT) would be able to explore the photon-ALP coupling down to
$g_{a\gamma} \simeq 2 \times 10^{-13}\,$GeV$^{-1}$ for an ALP mass $m_a
\lesssim 10^{-9}\,$eV. These values are out of reach of next generation
laboratory experiments. In this event, the Fermi LAT would probe large regions
of the ALP parameter space invoked to explain the anomalous transparency of the
Universe to $\gamma$ rays, stellar cooling anomalies, and cold dark matter. If
no $\gamma$-ray emission were to be detected, Fermi-LAT observations would
improve current bounds derived from SN1987A by more than one order of
magnitude.


title: Rainbow connection of bridgeless outerplanar graphs with small diameters

abstract:
  In this paper, we investigate rainbow connection number $rc(G)$ of bridgeless
outerplanar graphs $G$ with diameter 2 or 3. We proved the following results:
If $G$ has diameter $2,$ then $rc(G)=3$ for fan graphs $F_{n}$ with $n\geq 7$
or $C_5,$ otherwise $rc(G)=2;$ if $G$ has diameter $3,$ then $rc(G)\leq 4$ and
the bound is sharp.


title: Quantum Magnetism with Mesoscopic Bose-Einstein Condensates

abstract:
  Lattice gases in the strongly correlated regime have been proven to simulate
quantum magnetic models under certain conditions: the mapping of the
double-well system onto the Lipkin-Meshkov-Glick spin model is a paradigmatic
case. A suitable definition of the length in the Hilbert space of the system
leads to the concept of a correlation length, whose divergence is a
characteristic property of continuous quantum phase transitions. We calculate
the finite-size scaling of some observables like e.g. the magnetization or the
population imbalance, as well as of the Schmidt gap, obtaining in this way the
critical exponents associated to such transitions. The systematic definition of
the Schmidt gap in extended Hamiltonians provides a good tool to analyze the
set of critical exponents associated to transitions in systems formed by a
larger number of traps. This demonstrates, thus, the potential use of
mesoscopic Bose-Einstein condensates as quantum simulators of condensed matter
systems.


title: 9-1-1 DDoS: Threat, Analysis and Mitigation

abstract:
  The 911 emergency service belongs to one of the 16 critical infrastructure
sectors in the United States. Distributed denial of service (DDoS) attacks
launched from a mobile phone botnet pose a significant threat to the
availability of this vital service. In this paper we show how attackers can
exploit the cellular network protocols in order to launch an anonymized DDoS
attack on 911. The current FCC regulations require that all emergency calls be
immediately routed regardless of the caller's identifiers (e.g., IMSI and
IMEI). A rootkit placed within the baseband firmware of a mobile phone can mask
and randomize all cellular identifiers, causing the device to have no genuine
identification within the cellular network. Such anonymized phones can issue
repeated emergency calls that cannot be blocked by the network or the emergency
call centers, technically or legally. We explore the 911 infrastructure and
discuss why it is susceptible to this kind of attack. We then implement
different forms of the attack and test our implementation on a small cellular
network. Finally, we simulate and analyze anonymous attacks on a model of
current 911 infrastructure in order to measure the severity of their impact. We
found that with less than 6K bots (or $100K hardware), attackers can block
emergency services in an entire state (e.g., North Carolina) for days. We
believe that this paper will assist the respective organizations, lawmakers,
and security professionals in understanding the scope of this issue in order to
prevent possible 911-DDoS attacks in the future.


title: Generalized Autoregressive Score Models in R: The GAS Package

abstract:
  This paper presents the R package GAS for the analysis of time series under
the Generalized Autoregressive Score (GAS) framework of Creal et al. (2013) and
Harvey (2013). The distinctive feature of the GAS approach is the use of the
score function as the driver of time-variation in the parameters of nonlinear
models. The GAS package provides functions to simulate univariate and
multivariate GAS processes, estimate the GAS parameters and to make time series
forecasts. We illustrate the use of the GAS package with a detailed case study
on estimating the time-varying conditional densities of a set of financial
assets.


title:
Influence of classic noise on entangled state formation in parametric
  systems

abstract:
  A study of "high temperature" entangled states in a system of two
parametrically coupled quantum oscillators placed into independent thermal
baths is performed taking into account partially coherent parametric pump.
Processes in an open system are considered based on the Heisenberg-Langevin
formalism. We obtain a closed system of equations for the averaged quadratic
correlation functions in quantum stochastic problem as a result of Markov
processes approximation. On the basis of numerical calculations the dynamics of
the logarithmic negativity, which is the measure of entanglement in the system,
is investigated. It is shown that the partial coherence of the parametric pump
makes the lifetime of the entangled states finite. The threshold
characteristics of the formation and existence of these states are specified.


title:
Adaptive Regularization in Convex Composite Optimization for Variational
  Imaging Problems

abstract:
  We propose an adaptive regularization scheme in a variational framework where
a convex composite energy functional is optimized. We consider a number of
imaging problems including denoising, segmentation and motion estimation, which
are considered as optimal solutions of the energy functionals that mainly
consist of data fidelity, regularization and a control parameter for their
trade-off. We presents an algorithm to determine the relative weight between
data fidelity and regularization based on the residual that measures how well
the observation fits the model. Our adaptive regularization scheme is designed
to locally control the regularization at each pixel based on the assumption
that the diversity of the residual of a given imaging model spatially varies.
The energy optimization is presented in the alternating direction method of
multipliers (ADMM) framework where the adaptive regularization is iteratively
applied along with mathematical analysis of the proposed algorithm. We
demonstrate the robustness and effectiveness of our adaptive regularization
through experimental results presenting that the qualitative and quantitative
evaluation results of each imaging task are superior to the results with a
constant regularization scheme. The desired properties, robustness and
effectiveness, of the regularization parameter selection in a variational
framework for imaging problems are achieved by merely replacing the static
regularization parameter with our adaptive one.


title: 4-colored graphs and knot/link complements

abstract:
  A representation for compact 3-manifolds with non-empty non-spherical
boundary via 4-colored graphs (i.e., 4-regular graphs endowed with a proper
edge-coloration with four colors) has been recently introduced by two of the
authors, and an initial classification of such manifolds has been obtained up
to 8 vertices of the representing graphs. Computer experiments show that the
number of graphs/manifolds grows very quickly as the number of vertices
increases. As a consequence, we have focused on the case of orientable
3-manifolds with toric boundary, which contains the important case of
complements of knots and links in the 3-sphere. In this paper we obtain the
complete catalogation/classification of these 3-manifolds up to 12 vertices of
the associated graphs, showing the diagrams of the involved knots and links.
For the particular case of complements of knots, the research has been extended
up to 16 vertices.


title: The HI content of extremely metal-deficient blue compact dwarf galaxies

abstract:
  We have obtained new HI observations with the 100m Green Bank Telescope (GBT)
for a sample of 29 extremely metal-deficient star-forming Blue Compact Dwarf
(BCD) galaxies, selected from the Sloan Digital Sky Survey spectral data base
to be extremely metal-deficient (12+logO/H<7.6). Neutral hydrogen was detected
in 28 galaxies, a 97% detection rate. Combining the HI data with SDSS optical
spectra for the BCD sample and adding complementary galaxy samples from the
literature to extend the metallicity and mass ranges, we have studied how the
HI content of a galaxy varies with various global galaxian properties. There is
a clear trend of increasing gas mass fraction with decreasing metallicity, mass
and luminosity. We obtain the relation M(HI)/L(g)~L(g)^{-0.3}, in agreement
with previous studies based on samples with a smaller luminosity range. The
median gas mass fraction f(gas) for the GBT sample is equal to 0.94 while the
mean gas mass fraction is 0.90+/-0.15, with a lower limit of ~0.65. The HI
depletion time is independent of metallicity, with a large scatter around the
median value of 3.4 Gyr. The ratio of the baryonic mass to the dynamical mass
of the metal-deficient BCDs varies from 0.05 to 0.80, with a median value of
~0.2. About 65% of the BCDs in our sample have an effective yield larger than
the true yield, implying that the neutral gas envelope in BCDs is more
metal-deficient by a factor of 1.5-20, as compared to the ionized gas.


title:
Multistability of Phase-Locking in Equal-Frequency Kuramoto Models on
  Planar Graphs

abstract:
  The number $\mathcal{N}$ of stable fixed points of locally coupled Kuramoto
models depends on the topology of the network on which the model is defined. It
has been shown that cycles in meshed networks play a crucial role in
determining $\mathcal{N}$, because any two different stable fixed points differ
by a collection of loop flows on those cycles. Since the number of different
loop flows increases with the length of the cycle that carries them, one
expects $\mathcal{N}$ to be larger in meshed networks with longer cycles.
Simultaneously, the existence of more cycles in a network means more freedom to
choose the location of loop flows differentiating between two stable fixed
points. Therefore, $\mathcal{N}$ should also be larger in networks with more
cycles. We derive an algebraic upper bound for the number of stable fixed
points of the Kuramoto model with identical frequencies, under the assumption
that angle differences between connected nodes do not exceed $\pi/2$. We obtain
$\mathcal{N}\leq\prod_{k=1}^c\left[2\cdot{\rm Int}(n_k/4)+1\right]$, which
depends both on the number $c$ of cycles and on the spectrum of their lengths
$\{n_k\}$. We further identify network topologies carrying stable fixed points
with angle differences larger than $\pi/2$, which leads us to conjecture an
upper bound for the number of stable fixed points for Kuramoto models on any
planar network. Compared to earlier approaches that give exponential upper
bounds in the total number of vertices, our bounds are much lower and therefore
much closer to the true number of stable fixed points.


title: Canonical syzygies of smooth curves on toric surfaces

abstract:
  In a first part of this paper, we prove constancy of the canonical graded
Betti table among the smooth curves in linear systems on Gorenstein weak Fano
toric surfaces. In a second part, we show that Green's canonical syzygy
conjecture holds for all smooth curves of genus at most 32 or Clifford index at
most 6 on arbitrary toric surfaces. Conversely we use known results on Green's
conjecture (due to Lelli-Chiesa) to obtain new facts about graded Betti tables
of projectively embedded toric surfaces.


title: Top-squark in natural SUSY under current LHC run-2 data

abstract:
  We utilize the recent LHC-13 TeV data to study the lower mass bound on
top-squark (stop) in natural supersymmetry. We recast the LHC sparticle
inclusive search of $(\ge 1){\rm jets} + E^{miss}_T$ with $\alpha_T$ variable,
the direct stop pair search (1-lepton channel and all-hadronic channel) and the
monojet analyses. We find that these searches are complementary depending on
stop and higgsino masses: for a heavy stop the all-hadronic stop pair search
provides the strongest bound, for an intermediate stop the inclusive SUSY
analysis with $\alpha_T$ variable is most efficient, while for a compressed
stop-higgsino scenario the monojet search plays the key role. Finally, the
lower mass bound on a stop is: (i) 320 GeV for compressed stop-higgsino
scenario (mass splitting less than 20 GeV); (ii) 765 (860) GeV for higgsinos
lighter than 300 (100) GeV.


title:
The lower limit for time resolution in frequency modulation atomic force
  microscopy

abstract:
  Atomic force microscopy (AFM) routinely achieves structural information in
the sub-nm length scale. Measuring time resolved properties on this length
scale to understand kinetics at the nm scale remains an elusive goal. We
present a general analysis of the lower limit for time resolution in AFM. Our
finding suggests the time resolution in AFM is ultimately limited by the
well-known thermal limit of AFM and not as often proposed by the mechanical
response time of the force sensing cantilever. We demonstrate a general
pump-probe approach using the cantilever as a detector responding to the
averaged signal. This method can be applied to any excitation signal such as
electrical, thermal, magnetic or optical. Experimental implementation of this
method allows us to measure a photocarrier decay time of ~1 ps in low
temperature grown GaAs using a cantilever with a resonance frequency of 280
kHz.


title: Kondo resonance of a Co atom exchange coupled to a ferromagnetic tip

abstract:
  The Kondo effect of a Co atom on Cu(100) was investigated with a
low-temperature scanning tunneling microscope using a monoatomically sharp
nickel tip. Upon a tip-Co contact, the differential conductance spectra exhibit
a spin-split asymmetric Kondo resonance. The computed ab initio value of the
exchange coupling is too small to suppress the Kondo effect, but sufficiently
large to produce the splitting observed. A quantitative analysis of the line
shape using the numerical renormalization group technique indicates that the
junction spin polarization is weak.


title:
A general computational method for electron emission and thermal effects
  in field emitting nanotips

abstract:
  Electron emission from nanometric size emitters becomes of increasing
interest due to its involvement to sharp electron sources, vacuum breakdown
phenomena and various other vacuum nanoelectronics applications. The most
commonly used theoretical tools for the calculation of electron emission are
still nowadays the Fowler-Nordheim and the Richardson-Laue-Dushman equations
although it has been shown since the 1990's that they are inadequate for
nanometrically sharp emitters or in the intermediate thermal-field regime. In
this paper we develop a computational method for the calculation of emission
currents and Nottingham heat, which automatically distinguishes among different
emission regimes, and implements the appropriate calculation method for each.
Our method covers all electron emission regimes (thermal, field and
intermediate), aiming to maximize the calculation accuracy while minimizing the
computational time. As an example, we implemented it in atomistic simulations
of the thermal evolution of Cu nanotips under strong electric fields and found
that the predicted behaviour of such nanotips by the developed technique
differs significantly from estimations obtained based on the Fowler-Nordheim
equation. Finally, we show that our tool can be also successfully applied in
the analysis of experimental I-V data.


title:
Clumpy and Extended Starbursts in the Brightest Unlensed Submillimeter
  Galaxies

abstract:
  The central structure in three of the brightest unlensed z=3-4 submillimeter
galaxies are investigated through 0.015" - 0.05" (120 -- 360~pc) 860 micron
continuum images obtained using the Atacama Large Millimeter/submillimeter
Array (ALMA). The distribution in the central kpc in AzTEC1 and AzTEC8 are
extremely complex, and they are composed of multiple ~200 pc clumps. AzTEC4
consists of two sources that are separated by ~1.5 kpc, indicating a mid-stage
merger. The peak star formation rate densities in the central clumps are ~300 -
3000 Msun/yr/kpc^2, suggesting regions with extreme star formation near the
Eddington Limit. By comparing the flux obtained by ALMA and Submillimeter Array
(SMA), we find that 68-90% of the emission is extended (> 1 kpc) in AzTEC 4 and
8. For AzTEC1, we identify at least 11 additional compact (~200 pc) clumps in
the extended 3 - 4 kpc region. Overall, the data presented here suggest that
the luminosity surface densities observed at < 150 pc scales are roughly
similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220.
Between 10 to 30% of the 860 micron continuum is concentrated in clumpy
structures in the central kpc while the remaining flux is distributed over > 1
kpc regions, some of which could also be clumpy. These sources can be explained
by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by
extended and clumpy starbursts. However, the cold mode accretion model is not
ruled out.


title: The CMS trigger system

abstract:
  This paper describes the CMS trigger system and its performance during Run 1
of the LHC. The trigger system consists of two levels designed to select events
of potential physics interest from a GHz (MHz) interaction rate of
proton-proton (heavy ion) collisions. The first level of the trigger is
implemented in hardware, and selects events containing detector signals
consistent with an electron, photon, muon, tau lepton, jet, or missing
transverse energy. A programmable menu of up to 128 object-based algorithms is
used to select events for subsequent processing. The trigger thresholds are
adjusted to the LHC instantaneous luminosity during data taking in order to
restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout
electronics. The second level, implemented in software, further refines the
purity of the output stream, selecting an average rate of 400 Hz for offline
event storage. The objectives, strategy and performance of the trigger system
during the LHC Run 1 are described.


title:
Formation of globular clusters induced by external ultraviolet radiation
  II: Three-dimensional radiation hydrodynamics simulations

abstract:
  We explore the possibility of the formation of globular clusters under
ultraviolet (UV) background radiation. One-dimensional spherical symmetric
radiation hydrodynamics (RHD) simulations by Hasegawa et al. have demonstrated
that the collapse of low-mass (10^6-10^7 solar masses) gas clouds exposed to
intense UV radiation can lead to the formation of compact star clusters like
globular clusters (GCs) if gas clouds contract with supersonic infall
velocities. However, three-dimensional effects, such as the anisotropy of
background radiation and the inhomogeneity in gas clouds, have not been studied
so far. In this paper, we perform three-dimensional RHD simulations in a
semi-cosmological context, and reconsider the formation of compact star
clusters in strong UV radiation fields. As a result, we find that although
anisotropic radiation fields bring an elongated shadow of neutral gas, almost
spherical compact star clusters can be procreated from a "supersonic infall"
cloud, since photo-dissociating radiation suppresses the formation of hydrogen
molecules in the shadowed regions and the regions are compressed by UV heated
ambient gas. The properties of resultant star clusters match those of GCs. On
the other hand, in weak UV radiation fields, dark matter-dominated star
clusters with low stellar density form due to the self-shielding effect as well
as the positive feedback by ionizing photons. Thus, we conclude that the
"supersonic infall" under a strong UV background is a potential mechanism to
form GCs.


title: Ear-to-ear Capture of Facial Intrinsics

abstract:
  We present a practical approach to capturing ear-to-ear face models
comprising both 3D meshes and intrinsic textures (i.e. diffuse and specular
albedo). Our approach is a hybrid of geometric and photometric methods and
requires no geometric calibration. Photometric measurements made in a
lightstage are used to estimate view dependent high resolution normal maps. We
overcome the problem of having a single photometric viewpoint by capturing in
multiple poses. We use uncalibrated multiview stereo to estimate a coarse base
mesh to which the photometric views are registered. We propose a novel approach
to robustly stitching surface normal and intrinsic texture data into a
seamless, complete and highly detailed face model. The resulting relightable
models provide photorealistic renderings in any view.


title: Stochastic Tail Exponent For Asymmetric Power Laws

abstract:
  We examine random variables in the power law/regularly varying class with
stochastic tail exponent, the exponent $\alpha$ having its own distribution. We
show the effect of stochasticity of $\alpha$ on the expectation and higher
moments of the random variable. For instance, the moments of a right-tailed or
right-asymmetric variable, when finite, increase with the variance of $\alpha$;
those of a left-asymmetric one decreases. The same applies to conditional
shortfall (CVar), or mean-excess functions. We prove the general case and
examine the specific situation of lognormally distributed $\alpha \in
[b,\infty), b>1$. The stochasticity of the exponent induces a significant bias
in the estimation of the mean and higher moments in the presence of data
uncertainty. This has consequences on sampling error as uncertainty about
$\alpha$ translates into a higher expected mean. The bias is conserved under
summation, even upon large enough a number of summands to warrant convergence
to the stable distribution. We establish inequalities related to the asymmetry.
We also consider the situation of capped power laws (i.e. with compact
support), and apply it to the study of violence by Cirillo and Taleb (2016). We
show that uncertainty concerning the historical data increases the true mean.


title: A Single Zone Synchrotron Model for Flares of PKS 1510-089

abstract:
  PKS 1510-089 is one of the most variable blazars. Very high energy gamma ray
emission from this source was observed by H.E.S.S. during March-April 2009 and
by MAGIC from February 3 to April 3, 2012 quasi-simultaneously with
multi-wavelength flares. The spectral energy distributions of these flares have
been modeled earlier with the external Compton mechanism which depends on our
knowledge of the densities of the seed photons in the broad line region, the
dusty infrared torus or a hypothetical slow sheath surrounding the jet around
the radio core. Here we show that to explain the multi-wavelength data with
synchrotron emission of electrons and protons the jet power should be of the
order of 10^48 ergs/sec.


title: Conformal Walker metrics and linear Fefferman-Graham equations

abstract:
  The conformal Fefferman-Graham ambient metric construction is one of the most
fundamental constructions in conformal geometry. It embeds a manifold with a
conformal structure into a pseudo-Riemannian manifold whose Ricci tensor
vanishes up to a certain order along the original manifold. Despite the general
existence result of such ambient metrics by Fefferman and Graham, not many
examples of conformal structures with Ricci-flat ambient metrics are known.
Motivated by previous examples, for which the Fefferman-Graham equations for
the ambient metric to be Ricci-flat reduce to a system of linear PDEs, in the
present article we develop a method to find ambient metrics for conformal
classes of metrics with two-step nilpotent Schouten tensor. Using this method,
for metrics for which the image of the Schouten tensor is invariant under
parallel transport, i.e., certain types of Walker metrics, we obtain explicit
ambient metrics. This includes certain left-invariant Walker metrics as well as
pp-waves.


title: Scaling regimes in spherical shell rotating convection

abstract:
  Rayleigh-B\'enard convection in rotating spherical shells can be considered
as a simplified analogue of many astrophysical and geophysical fluid flows.
Here, we use three-dimensional direct numerical simulations to study this
physical process. We construct a dataset of more than 200 numerical models that
cover a broad parameter range with Ekman numbers spanning $3\times 10^{-7} \leq
E \leq 10^{-1}$, Rayleigh numbers within the range $10^3 < Ra < 2\times
10^{10}$ and a Prandtl number unity. We investigate the scaling behaviours of
both local (length scales, boundary layers) and global (Nusselt and Reynolds
numbers) properties across various physical regimes from onset of rotating
convection to weakly-rotating convection. Close to critical, the convective
flow is dominated by a triple force balance between viscosity, Coriolis force
and buoyancy. For larger supercriticalities, a subset of our numerical data
approaches the asymptotic diffusivity-free scaling of rotating convection
$Nu\sim Ra^{3/2}E^{2}$ in a narrow fraction of the parameter space delimited by
$6\,Ra_c \leq Ra \leq 0.4\,E^{-8/5}$. Using a decomposition of the viscous
dissipation rate into bulk and boundary layer contributions, we establish a
theoretical scaling of the flow velocity that accurately describes the
numerical data. In rapidly-rotating turbulent convection, the fluid bulk is
controlled by a triple force balance between Coriolis, inertia and buoyancy,
while the remaining fraction of the dissipation can be attributed to the
viscous friction in the Ekman layers. Beyond $Ra \simeq E^{-8/5}$, the
rotational constraint on the convective flow is gradually lost and the flow
properties vary to match the regime changes between rotation-dominated and
non-rotating convection. The quantity $Ra E^{12/7}$ provides an accurate
transition parameter to separate rotating and non-rotating convection.

categories: physics.flu-dyn astro-ph.EP astro-ph.SR physics.geo-ph


title:
Inward Diffusion and Acceleration of Particles Driven by Turbulent
  Fluctuations in Magnetosphere

abstract:
  Charged particles in a magnetosphere are spontaneously attracted to a planet
while increasing their kinetic energy via inward diffusion process. A
constraint on particles' micro-scale adiabatic invariants restricts the class
of motions available to the system, giving rise to a proper frame on which
particle diffusion occurs. We investigate the inward diffusion process by
numerical simulation of particles on constrained phase space. The results
reveal the emergence of inhomogeneous density gradient and anisotropic heating,
which is consistent with spacecraft observations, experimental observations,
and the recently formulated diffusion model on the constrained phase space.


title:
Extraction of Skin Lesions from Non-Dermoscopic Images Using Deep
  Learning

abstract:
  Melanoma is amongst most aggressive types of cancer. However, it is highly
curable if detected in its early stages. Prescreening of suspicious moles and
lesions for malignancy is of great importance. Detection can be done by images
captured by standard cameras, which are more preferable due to low cost and
availability. One important step in computerized evaluation of skin lesions is
accurate detection of lesion region, i.e. segmentation of an image into two
regions as lesion and normal skin. Accurate segmentation can be challenging due
to burdens such as illumination variation and low contrast between lesion and
healthy skin. In this paper, a method based on deep neural networks is proposed
for accurate extraction of a lesion region. The input image is preprocessed and
then its patches are fed to a convolutional neural network (CNN). Local texture
and global structure of the patches are processed in order to assign pixels to
lesion or normal classes. A method for effective selection of training patches
is used for more accurate detection of a lesion border. The output segmentation
mask is refined by some post processing operations. The experimental results of
qualitative and quantitative evaluations demonstrate that our method can
outperform other state-of-the-art algorithms exist in the literature.


title:
Feasibility Study on Disaster Management with Hybrid Network of LTE and
  Satellite Links

abstract:
  We are highly vulnerable to either natural or artificial catastrophes and
therefore, Public Protection and Disaster Relief (PPDR) operators need reliable
wireless communications for successful operations especially in critical rescue
missions. PPDR dedicated or commercial terrestrial networks have always been
used which at most times lead to unsuccessful operations. This is due to the
fact these networks are all infrastructure-based which can be destroyed, fail
to deliver the required service or the networks are not able to support and
sustain the sudden traffic surge. Long-Term Evolution (LTE) is earmarked as the
future candidate technology for PPDR purpose and so much have been put into it
in terms of research, perhaps suitable architecture that will meet
mission-critical requirements can be developed. This can only work if
terrestrial networks will always be available. Unfortunately, in worst case
scenarios, infrastructures might get damaged totally or might be destroyed by
subsequent disasters. As a result, adequate guarantees can only be possible in
the hypothesis of very high financial involvement. Fortunately, considering
availability, coverage ubiquity and reliability, satellite technologies have
lately proven good. So, to maximize the high channel performance of terrestrial
networks and the availability and reliability of non-terrestrial networks, the
solution lies in a hybrid system. It is on this ground that this work deals
with the integration of LTE and satellite networks in both infrastructure-based
and infrastructure-less topologies for PPDR purpose. It is aim at providing
people trapped in disaster and field operators with a transparent accessibility
and guaranteed coverage even when infrastructures are damaged. The requirements
are defined and the model simulated. The network is able to provide network
coverage, enhanced capacity and promised greater resilience.


title:
Observing the PTPS Sample of Evolved Exoplanet Host Candidates Using the
  NPOI

abstract:
  We plan to measure the angular diameters of a sample of Penn State-Torun
Planet Search (PTPS) giant exoplanet host star candidates using the Navy
Precision Optical Interferometer. The radii of evolved giant stars obtained
using spectroscopy are usually ill-defined because of the method's indirect
nature and evolutionary model dependency. The star's radius is a critical
parameter used to calculate luminosity and mass, which are often not well known
for giant stars. Therefore, this problem also affects the orbital period, mass,
and surface temperature of the planet. Our interferometric observations will
significantly decrease the errors for these parameters. We present preliminary
results from NPOI observations of six stars in the PTPS sample.


title: Boundaries of Kleinian groups

abstract:
  We review the theory of splittings of hyperbolic groups, as determined by the
topology of the boundary. We give explicit examples of certain phenomena and
then use this to describe limit sets of Kleinian groups up to homeomorphism.


title:
Highly bright photon-pair generation in Doppler-broadened ladder-type
  atomic system

abstract:
  We report a bright photon-pair source with a coincidence counting rate per
input power (cps/mW) of tens of thousands, obtained via spontaneous four-wave
mixing from a Doppler-broadened atomic ensemble of the 5S1/2-5P3/2-5D5/2
transition of 87Rb. The photon-pair generation rate is enhanced by the
two-photon coherence contributions from almost all the atomic velocity groups
in the Doppler-broadened ladder-type atomic system. We obtained the violation
of the Cauchy-Schwarz inequality by a factor of 2370(150). We believe that our
scheme for highly bright paired photons is important as a useful quantum light
source for quantum entanglement swapping between completely autonomous sources.


title: Spectroscopic and Interferometric Measurements of Nine K Giant Stars

abstract:
  We present spectroscopic and interferometric measurements for a sample of
nine K giant stars. These targets are of particular interest because they are
slated for stellar oscillation observations. Our improved parameters will
directly translate into reduced errors in the final masses for these stars when
interferometric radii and asteroseismic densities are combined. Here we
determine each star's limb-darkened angular diameter, physical radius,
luminosity, bolometric flux, effective temperature, surface gravity,
metallicity, and mass. When we compare our interferometric and spectroscopic
results, we find no systematic offsets in the diameters and the values
generally agree within the errors. Our interferometric temperatures for seven
of the nine stars are hotter than those determined from spectroscopy with an
average difference of about 380 K.


title: Automorphisms of K-groups II

abstract:
  This work is a continuation of Automorphisms of $K$-groups I, P. Flavell,
preprint.
  The main object of study is a finite $K$-group $G$ that admits an elementary
abelian group $A$ acting coprimely. For certain group theoretic properties
$\mathcal P$, we study the $AC_{G}(A)$-invariant $\mathcal P$-subgroups of $G$.
  A number of results of McBride, 'Near solvable signalizer functors on finite
groups' J. Algebra {\bf 78}(1) (1982) 181-214 and 'Nonsolvable signalizer
functors on finite groups', J. Algebra {\bf 78}(1) (1982) 215-238 are extended.
  One purpose of this work is to build a general theory of automorphisms, one
of whose applications will be a new proof of the Nonsolvable Signalizer Functor
Theorem.
  As an illustration, this work concludes with a new proof of a special case of
that theorem due to Gorenstein and Lyons.


title: Morse-Bott inequalities for manifolds with boundary

abstract:
  In the present paper, we define Morse-Bott functions on manifolds with
boundary which are generalizations of Morse functions and show Morse-Bott
inequalities for these manifolds.


title: Heavy-Meson Decay Constants: QCD Sum-Rule Glance at Isospin Breaking

abstract:
  QCD sum rules for decay constants of heavy mesons with $u$ or $d$ quark yield
for $B$ mesons much less isospin breaking than lattice QCD but good agreement
for $D$ mesons.


title: Improved Optimistic Mirror Descent for Sparsity and Curvature

abstract:
  Online Convex Optimization plays a key role in large scale machine learning.
Early approaches to this problem were conservative, in which the main focus was
protection against the worst case scenario. But recently several algorithms
have been developed for tightening the regret bounds in easy data instances
such as sparsity, predictable sequences, and curved losses. In this work we
unify some of these existing techniques to obtain new update rules for the
cases when these easy instances occur together. First we analyse an adaptive
and optimistic update rule which achieves tighter regret bound when the loss
sequence is sparse and predictable. Then we explain an update rule that
dynamically adapts to the curvature of the loss function and utilizes the
predictable nature of the loss sequence as well. Finally we extend these
results to composite losses.


title: Multiple elliptic gamma functions associated to cones

abstract:
  We define generalizations of the multiple elliptic gamma functions and the
multiple sine functions, associated to good rational cones. We explain how good
cones are related to collections of $SL_r(\mathbb{Z})$-elements and prove that
the generalized multiple sine and multiple elliptic gamma functions enjoy
infinite product representations and modular properties determined by the cone.
This generalizes the modular properties of the elliptic gamma function studied
by Felder and Varchenko, and the results about the usual multiple sine and
elliptic gamma functions found by Narukawa.


title: Experimental Study of a Triode Reflex Geometry Vircator

abstract:
  Triode reflex geometry vircator operating within 3.0 - 4.2 GHz range with
efficiency up to 6% is developed and experimentally investigated. Shiftable
reflectors are shown to enable frequency tuning and output power control.
Radiation frequency and power are analyzed for different cathode-anode gap
values and varied reflector positions.


title: Solar neutrinos: Oscillations or No-oscillations?

abstract:
  The Nobel prize in physics 2015 has been awarded "... for the discovery of
neutrino oscillations which show that neutrinos have mass". While
SuperKamiokande (SK), indeed, has discovered oscillations, SNO observed effect
of the adiabatic (almost non-oscillatory) flavor conversion of neutrinos in the
matter of the Sun. Oscillations are irrelevant for solar neutrinos apart from
small $\nu_e$ regeneration inside the Earth. Both oscillations and adiabatic
conversion do not imply masses uniquely and further studies were required to
show that non-zero neutrino masses are behind the SNO results. Phenomena of
oscillations (phase effect) and adiabatic conversion (the MSW effect driven by
the change of mixing in matter) are described in pedagogical way.


title:
Electronic Structures of Ferromagnetic CeAgSb$_2$:Soft X-ray Absorption,
  Magnetic Circular Dichroism and Angle-Resolved Photoemission Spectroscopies

abstract:
  We report a combined study for the electronic structures of ferromagnetic
CeAgSb$_2$ using soft X-ray absorption (XAS), magnetic circular dichroism
(XMCD), and angle-resolved photoemission (ARPES) spectroscopies. The Ce $M_{4,
5}$ XAS spectra show very small satellite structures, reflecting a strongly
localized character of the Ce $4f$ electrons. The linear dichroism effects in
the Ce $M_{4, 5}$ XAS spectra demonstrate the ground state Ce $4f$ symmetry of
$\Gamma{_6}$, the spatial distribution of which is directed along the $c$-axis.
The XMCD results give support to the picture of local-moment magnetism in
CeAgSb$_2$. Moreover it is also found that the theoretical band dispersions for
LaAgSb$_2$ provides better description of the ARPES band structures than those
for CeAgSb$_2$. Nevertheless, ARPES spectra at the Ce $3d$-$4f$ resonance show
the momentum dependence for the intensity ratio between Ce $4f^{1}_{5/2}$ and
$4f^{1}_{7/2}$ peaks in a part of the Brillouin zone, suggesting the
non-negligible momentum dependent hybridization effect between the Ce $4f$ and
the conduction electrons. This is associated with the moderate mass enhancement
in CeAgSb$_2$.


title:
Detection of Possible Quasi-periodic Oscillations in the Long-term
  Optical Light Curve of the BL Lac Object OJ 287

abstract:
  Detection of periodicity in the broad-band non-thermal emission of blazars
has so far been proven to be elusive. However, there are a number of scenarios
which could lead to quasi-periodic variations in blazar light curves. For
example, orbital or thermal/viscous period of accreting matter around central
supermassive black holes could, in principle, be imprinted in the
multi-wavelength emission of small-scale blazar jets, carrying as such crucial
information about plasma conditions within the jet launching regions. In this
paper, we present the results of our time series analysis of $\sim 9.2$
year-long, and exceptionally well-sampled optical light curve of the BL Lac OJ
287. The study primarily uses the data from our own observations performed at
the Mt. Suhora and Krak\'ow Observatories in Poland, and at the Athens
Observatory in Greece. Additionally, SMARTS observations were used to fill in
some of the gaps in the data. The Lomb-Scargle Periodogram and the Weighted
Wavelet Z-transform methods were employed to search for the possible QPOs in
the resulting optical light curve of the source. Both the methods consistently
yielded possible quasi-periodic signal around the periods of $\sim 400$ and
$\sim 800$ days, the former one with a significance (over the underlying
colored noise) of $\geq 99\%$. A number of likely explanations for such are
discussed, with a preference given to a modulation of the jet production
efficiency by highly magnetized accretion disks. This supports the previous
findings and the interpretation reported recently in the literature for OJ 287
and other blazar sources.


title:
Quasielectrons as inverse quasiholes in lattice fractional quantum Hall
  models

abstract:
  From an experimental point of view, quasielectrons and quasiholes play very
similar roles in the fractional quantum Hall effect. Nevertheless, the
theoretical description of quasielectrons is known to be much harder than the
one of quasiholes. The problem is that one obtains a singularity in the
wavefunction if one tries to naively construct the quasielectron as the inverse
of the quasihole. Here, we demonstrate that the same problem does not arise in
lattice fractional quantum Hall models. This result allows us to make detailed
investigations of the properties of quasielectrons, including their braiding
statistics and density distribution on lattices on the plane and on the torus.
We show that some of the states considered have high overlap with certain
fractional Chern insulator states. We also derive few-body Hamiltonians, for
which various states containing quasielectrons are exact ground states.


title: Superconductivity of niobium thin films in the BiOCl/Nb heterostructures

abstract:
  In the current paper, electrical transport properties of 25 nm thick Nb films
sputtered on the photosensitive semiconductor BiOCl were investigated in the
temperature range 7.5 K $\leq T \leq$ 8.5 K. The influence of green (532 nm)
and red (640 nm) laser excitations on resistive superconducting transitions of
the niobium thin films on a silicon glass and BiOCl single crystal substrates
were studied. The temperature dependences of the resistivity for Nb are in good
agreement with the McMillan model which indicates the strong influence of the
inverse proximity effect induced by the interface. The increased influence of
the BiOCl/Nb interface under laser excitation corresponds to the raising the
ratio of the density of normal to superconductivity carriers in the
$T\rightarrow 0$ limit and this observation is in agreement with the
photoconductivity study of BiOCl single crystals.


title:
Request Patterns and Caching for VoD Services with Recommendation
  Systems

abstract:
  Video on Demand (VoD) services like Netflix and YouTube account for ever
increasing fractions of Internet traffic. It is estimated that this fraction
will cross 80% in the next three years. Most popular VoD services have
recommendation engines which recommend videos to users based on their viewing
history, thus introducing time-correlation in user requests. Understanding and
modeling this time-correlation in user requests is critical for network traffic
engineering. The primary goal of this work is to use empirically observed
properties of user requests to model the effect of recommendation engines on
the request patterns in VoD services. We propose a Markovian request model to
capture the time-correlation in user requests and show that our model is
consistent with the observations of existing empirical studies.
  Most large-scale VoD services deliver content to users via a distributed
network of servers as serving users requests via geographically co-located
servers reduces latency and network bandwidth consumption. The content
replication policy, i.e., determining which contents to cache on the servers is
a key resource allocation problem for VoD services. Recent studies show that
low start-up delay is a key Quality of Service (QoS) requirement of users of
VoD services. This motivates the need to pre-fetch (fetch before contents are
requested) and cache content likely to be request in the near future. Since
pre-fetching leads to an increase in the network bandwidth usage, we use our
Markovian model to explore the trade-offs and feasibility of implementing
recommendation based pre-fetching.


title: Characters and Brauer trees of the covering group of $^2E_6(2)$

abstract:
  Let $G$ be the finite simple Chevalley group of type $^2E_6(2)$. It has a
Schur multiplier of type $C_2^2 \times C_3$. We determine the ordinary
character tables of the central extensions $3.G$, $6.G$, $(2^2\times 3).G$ of
$G$ and their extensions by an automorphism of order $2$, that is $3.G.2$,
$6.G.2$ and $(2^2\times 3).G.2$.
  Furthermore we determine all Brauer trees of all groups of type $Z.G.A$
(where $Z$ is central in $Z.G \lhd Z.G.A$ and $A \cong Z.G.A/Z.G$) for which
the ordinary character table is known.


title:
Analysis of Artificial Dissipation of Explicit and Implicit
  Time-Integration Methods

abstract:
  Stability is an important aspect of numerical methods for hyperbolic
conservation laws and has received much interest. However, continuity in time
is often assumed and only semidiscrete stability is studied. Thus, it is
interesting to investigate the influence of explicit and implicit time
integration methods on the stability of numerical schemes. If an explicit time
integration method is applied, spacially stable numerical schemes for
hyperbolic conservation laws can result in unstable fully discrete schemes.
Focusing on the explicit Euler method (and convex combinations thereof),
undesired terms in the energy balance trigger this phenomenon and introduce an
erroneous growth of the energy over time. In this work, we study the influence
of artificial dissipation and modal filtering in the context of discontinuous
spectral element methods to remedy these issues. In particular, lower bounds on
the strength of both artificial dissipation and modal filtering operators are
given and an adaptive procedure to conserve the (discrete) $\mathbf{L}_2$ norm
of the numerical solution in time is derived. This might be beneficial in
regions where the solution is smooth and for long time simulations. Moreover,
this approach is used to study the connections between explicit and implicit
time integration methods and the associated energy production. By adjusting the
adaptive procedure, we demonstrate that filtering in explicit time integration
methods is able to mimic the dissipative behavior inherent in implicit time
integration methods. This contribution leads to a better understanding of
existing algorithms and numerical techniques, in particular the application of
artificial dissipation as well as modal filtering in the context of numerical
methods for hyperbolic conservation laws together with the selection of
explicit or implicit time integration methods.


title:
Slice regular Besov spaces of hyperholomorphic functions and composition
  operators

abstract:
  In this paper we investigate some basic results on the slice regular Besov
spaces of hyperholomorphic functions on the unit ball $\mathbb{B}.$ We also
characterize the boundedness, compactness and find the essential norm estimates
of composition operators between these spaces.


title: Dissecting cross-impact on stock markets: An empirical analysis

abstract:
  The vast majority of market impact studies assess each product individually,
and the interactions between the different order flows are disregarded. This
strong approximation may lead to an underestimation of trading costs and
possible contagion effects. Transactions in fact mediate a significant part of
the correlation between different instruments. In turn, liquidity shares the
sectorial structure of market correlations, which can be encoded as a set of
eigenvalues and eigenvectors. We introduce a multivariate linear propagator
model that successfully describes such a structure, and accounts for a
significant fraction of the covariance of stock returns. We dissect the various
dynamical mechanisms that contribute to the joint dynamics of assets. We also
define two simplified models with substantially less parameters in order to
reduce overfitting, and show that they have superior out-of-sample performance.


title:
Ring Formation around Giant Planets by Tidal Disruption of a Single
  Passing Large Kuiper Belt Object

abstract:
  The origin of rings around giant planets remains elusive. Saturn's rings are
massive and made of 90-95% of water ice. In contrast, the much less massive
rings of Uranus and Neptune are dark and likely to have higher rock fraction.
Here we investigate, for the first time, the tidal disruption of a passing
object, including the subsequent formation of planetary rings. First, we
perform SPH simulations of the tidal destruction of big differentiated objects
($M_{\rm body}=10^{21-23}$) that experience close encounters with Saturn or
Uranus. We find that about $0.1-10$% of the mass of the passing body is
gravitationally captured around the planet. However, these fragments are
initially big chunks and have highly eccentric orbits around the planet. Then,
we perform N-body simulations including the planet's oblateness, starting with
data obtained from the SPH simulations. Our N-body simulations show that the
chunks are tidally destroyed during their next several orbits. Their individual
orbits then start to precess incoherently around the planet's equator, which
enhances their encounter velocities on longer-term evolution, resulting in more
destructive impacts. These collisions would damp their eccentricities resulting
in a progressive collapse of the debris cloud into a thin equatorial and
low-eccentricity ring. These high energy impacts are expected to be
catastrophic enough to produce small particles. Our numerical results also show
that the mass of formed rings is large enough to explain current rings
including inner regular satellites around Saturn and Uranus. In the case of
Uranus, a body can go deeper inside the planet's Roche limit resulting in a
more efficient capture of rocky material compared to Saturn's case in which
mostly ice is captured. Thus, our results can naturally explain the
compositional difference between the rings of Saturn, Uranus and Neptune.


title: Relative Loday constructions and applications to higher THH-calculations

abstract:
  We define a relative version of the Loday construction for a sequence of
commutative S-algebras $A \rightarrow B \rightarrow C$ and a pointed simplicial
subset $Y \subset X$. We use this to construct several spectral sequences for
the calculation of higher topological Hochschild homology and apply those for
calculations in some examples that could not be treated before.


title: Reduced-Rank Channel Estimation for Large-Scale MIMO Systems

abstract:
  We present two reduced-rank channel estimators for large-scale
multiple-input, multiple-output (MIMO) systems and analyze their mean square
error (MSE) performance. Taking advantage of the channel's transform domain
sparseness, the estimators yield outstanding performance and may offer
additional mean angle-of-arrival (AoA) information. It is shown that, for the
estimators to be effective, one has to select a proper predetermined unitary
basis (transform) and be able to determine the dominant channel rank and the
associated subspace. Further MSE analysis reveals the relations among the array
size, channel rank, signal-to-noise ratio (SNR), and the estimators'
performance. It provides rationales for the proposed rank determination and
mean AoA estimation algorithms as well.
  An angle alignment operation included in one of our channel models is proved
to be effective in further reducing the required rank, shifting the dominant
basis vectors' range (channel spectrum) and improving the estimator's
performance when a suitable basis is used. We also draw insightful analogies
among MIMO channel modeling, transform coding, parallel spatial search, and
receive beamforming. Computer experiment results are provided to examine the
numerical effects of various estimator parameters and the advantages of the
proposed channel estimators and rank determination method.


title:
An Explicit Formula for the Eigenvectors of Acyclic Matrices and
  Weighted Trees

abstract:
  Let $A$ be an acyclic symmetric matrix of order $n$. There is a weighted
forest $F$ whose adjacency matrix is $A$. In this paper, using some results on
matching polynomials, we provide an explicit formula for eigenvectors of $A$.


title:
A Massive Dense Gas Cloud close to the Nucleus of the Seyfert galaxy NGC
  1068

abstract:
  Using the ALMA archival data of both CO(6--5) line and 689 GHz continuum
emission towards the archetypical Seyfert galaxy, NGC 1068, we identified a
distinct continuum peak separated by 14 pc from the nuclear radio component S1
in projection. The continuum flux gives a gas mass of ~2x10^5 Msun and
bolometric luminosity of ~10^8 Lsun, leading to a star formation rate of ~0.1
Msun/yr. Subsequent analysis on the line data suggest that the gas has a size
of ~10 pc, yielding to mean H2 number density of ~10^5 cm^{-3}. We therefore
refer to the gas as "massive dense gas cloud": the gas density is high enough
to form a "proto starcluster" whose stellar mass of ~10^4 Msun. We found that
the gas stands a unique position between galactic and extraglactic clouds in
the diagrams of start formation rate (SFR) vs. gas mass proposed by Lada et al.
and surface density of gas vs. SFR density by Krumholz and McKee. All the
gaseous and star-formation properties may be understood in terms of the
turbulence-regulated star formation scenario. Since there are two stellar
populations with the ages of 300 Myr and 30 Myr in the 100 pc-scale
circumnulear region, we discuss that NGC1068 has experienced at least three
episodic star formation events with a tendency that the inner star-forming
region is the younger. Together with several lines of evidence that the
dynamics of the nuclear region is decoupled from that of the entire galactic
disk, we discuss that the gas inflow towards the nuclear region of NGC 1068 may
be driven by a past minor merger.


title:
Evolution of intermediate mass and massive binary stars: physics, mass
  loss, and rotation

abstract:
  In the present review we discuss the past and present status of the
interacting OB-type binary frequency. We critically examine the popular idea
that Be-stars and supergiant sgB[e] stars are binary evolutionary products. The
effects of rotation on stellar evolution in general, stellar population studies
in particular, and the link with binaries will be evaluated. Finally a
discussion is presented of massive double compact star binary mergers as
possible major sites of chemical enrichment of r-process elements and as the
origin of recent aLIGO GW events.


title: Radiation length imaging with high resolution telescopes

abstract:
  The construction of low mass vertex detectors with a high level of system
integration is of great interest for next generation collider experiments.
Radiation length images with a sufficient spatial resolution can be used to
measure and disentangle complex radiation length $X$/$X_0$ profiles and
contribute to the understanding of vertex detector systems. Test beam
experiments with multi GeV particle beams and high-resolution tracking
telescopes provide an opportunity to obtain precise 2D images of the radiation
length of thin planar objects. At the heart of the $X$/$X_0$ imaging is a
spatially resolved measurement of the scattering angles of particles traversing
the object under study. The main challenges are the alignment of the reference
telescope and the calibration of its angular resolution. In order to
demonstrate the capabilities of $X$/$X_0$ imaging, a test beam experiment has
been conducted. The devices under test were two mechanical prototype modules of
the Belle II vertex detector. A data sample of 100 million tracks at $4\,
\mathrm{GeV}$ has been collected, which is sufficient to resolve complex
material profiles on the $30\,\mu$m scale.


title:
Realization and application of parity-time-symmetric oscillators in
  quantum regime

abstract:
  Although people have already artificially formed parity--time
($\mathcal{PT}$) symmetry with gain and loss in a balanced manner, it is still
a defect that the gain is restricted to semi--classical but not full quantum.
Here we propose and analyze a theoretical scheme to realize full quantum
oscillator $\mathcal{PT}$--symmetry. The quantum gain is provided by a
dissipation optical cavity with blue detuned laser field. After adiabatically
eliminating the cavity modes, we give an effective master equation, which is a
more complete quantum description compared with non--Hermitian Hamiltonian, to
reveal the quantum behaviors of such a gain oscillator. This kind of
$\mathcal{PT}$--symmetry can eliminate the dissipation effect in quantum
regime. As examples, we finally apply $\mathcal{PT}$--symmetric oscillators to
enhance optomechanically induced transparency and to preserve oscillator
non--classical state.


title: ITect: Scalable Information Theoretic Similarity for Malware Detection

abstract:
  Malware creators have been getting their way for too long now. String-based
similarity measures can leverage ground truth in a scalable way and can operate
at a level of abstraction that is difficult to combat from the code level. We
introduce ITect, a scalable approach to malware similarity detection based on
information theory. ITect targets file entropy patterns in different ways to
achieve 100% precision with 90% accuracy but it could target 100% recall
instead. It outperforms VirusTotal for precision and accuracy on combined
Kaggle and VirusShare malware.


title:
Reversal and amplification of zonal flows by boundary enforced thermal
  wind

abstract:
  Zonal flows in rapidly-rotating celestial objects such as the Sun, gas or ice
giants form in a variety of surface patterns and amplitudes. Whereas the
differential rotation on the Sun, Jupiter and Saturn features a super-rotating
equatorial region, the ice giants, Neptune and Uranus harbour an equatorial jet
slower than the planetary rotation. Global numerical models covering the
optically thick, deep-reaching and rapidly rotating convective envelopes of gas
giants reproduce successfully the prograde jet at the equator. In such models,
convective columns shaped by the dominant Coriolis force typically exhibit a
consistent prograde tilt. Hence angular momentum is pumped away from the
rotation axis via Reynolds stresses. Those models are found to be strongly
geostrophic, hence a modulation of the zonal flow structure along the axis of
rotation, e.g. introduced by persistent latitudinal temperature gradients,
seems of minor importance. Within our study we stimulate these thermal
gradients and the resulting ageostrophic flows by applying an axisymmetric and
equatorially symmetric outer boundary heat flux anomaly ($Y_{20}$) with
variable amplitude and sign. Such a forcing pattern mimics the thermal effect
of intense solar or stellar irradiation. Our results suggest that the
ageostrophic flows are linearly amplified with the forcing amplitude $q^\star$
leading to a more pronounced dimple of the equatorial jet (alike Jupiter). The
geostrophic flow contributions, however, are suppressed for weak $q^\star$, but
inverted and re-amplified once $q^\star$ exceeds a critical value. The inverse
geostrophic differential rotation is consistently maintained by now also
inversely tilted columns and reminiscent of zonal flow profiles observed for
the ice giants. Analysis of the main force balance and parameter studies
further foster these results.


title: Cosmological Constant Implementing Mach Principle in General Relativity

abstract:
  We consider the fact that noticing on the operational meaning of the physical
concepts played an impetus role in the appearance of general relativity (GR).
Thus, we have paid more attention to the operational definition of the
gravitational coupling constant in this theory as a dimensional constant which
is gained through an experiment. However, as all available experiments just
provide the value of this constant locally, this coupling constant can
operationally be meaningful only in a local area. Regarding this point, to
obtain an extension of GR for the large scale, we replace it by a conformal
invariant model and then, reduce this model to a theory for the cosmological
scale via breaking down the conformal symmetry through singling out a specific
conformal frame which is characterized by the large scale characteristics of
the universe. Finally, we come to the same field equations that historically
were proposed by Einstein for the cosmological scale (GR plus the cosmological
constant) as the result of his endeavor for making GR consistent with the Mach
principle. However, we declare that the obtained field equations in this
alternative approach do~not carry the problem of the field equations proposed
by Einstein for being consistent with Mach's principle (i.e., the existence of
de Sitter solution), and can also be considered compatible with this principle
in the Sciama view.


title: Fault Detection and Identification - a Filter Investigation

abstract:
  This paper develops a new active fault tolerant control system based on the
concept of analytical redundancy. The novel design consists of an observation
filter based fault detection and identification system integrated with a
nonlinear model predictive controller. A number of observation filters were
designed, integrated with the nonlinear controller and tested before reaching
the final design which comprises an unscented Kalman filter for fault detection
and identification together with a nonlinear model predictive controller to
form an active fault tolerant control system design.


title: Sprague-Grundy theory in bounded arithmetic

abstract:
  In this paper, we formalize Sprague-Grundy theory for combinatorial games in
bounded arithmetic. We show that in the presence of Sprague-Grundy numbers, a
fairly weak axioms capture PSPACE.


title: Comparison of several short-term traffic speed forecasting models

abstract:
  The widespread adoption of smartphones in recent years has made it possible
for us to collect large amounts of traffic data. Special software installed on
the phones of drivers allow us to gather GPS trajectories of their vehicles on
the road network. In this paper, we simulate the trajectories of multiple
agents on a road network and use various models to forecast the short-term
traffic speed of various links. Our results show that traditional techniques
like multiple regression and artificial neural networks work well but simpler
adaptive models that do not require prior training also perform comparatively
well.


title: Practical Demonstration of a Memristive Fuse

abstract:
  Since its inception the memristive fuse has been a good example of how small
numbers of memristors can be combined to obtain useful behaviours unachievable
by individual devices. In this work, we link the memristive fuse concept with
that of the Complementary Resistive Switch (CRS), exploit that link to
experimentally demonstrate a practical memristive fuse using TiOx-based ReRAM
cells and explain its basic operational principles. The fuse is stimulated by
trains of identical pulses where successive pulse trains feature opposite
polarities. In response, we observe a gradual (analogue) drop in resistive
state followed by a gradual recovery phase regardless of input stimulus
polarity; echoing traditional, binary CRS behaviour. This analogue switching
property opens the possibility of operating the memristive fuse as a
single-component step change detector. Moreover, we discover that the
characteristics of the individual memristors used to demonstrate the memristive
fuse concept in this work allow our fuse to be operated in a regime where one
of the two constituent devices can be switched largely independently from the
other. This property, not present in the traditional CRS, indicates that the
inherently analogue memristive fuse architecture may support additional
operational flexibility through e.g. allowing finer control over its resistive
state.


title: Velocity-Aware Handover Management in Two-Tier Cellular Networks

abstract:
  While network densification is considered an important solution to cater the
ever-increasing capacity demand, its effect on the handover (HO) rate is
overlooked. In dense 5G networks, HO delays may neutralize or even negate the
gains offered by network densification. Hence, user mobility imposes a
nontrivial challenge to harvest capacity gains via network densification. In
this paper, we propose a velocity-aware HO management scheme for two-tier
downlink cellular network to mitigate the HO effect on the foreseen
densification throughput gains. The proposed HO scheme sacrifices the best BS
connectivity, by skipping HO to some BSs along the user's trajectory, to
maintain longer connection durations and reduce HO rates. Furthermore, the
proposed scheme enables cooperative BS service and strongest interference
cancellation to compensate for skipping the best connectivity. To this end, we
consider different HO skipping scenarios and develop a velocity-aware
mathematical model, via stochastic geometry, to quantify the performance of the
proposed HO scheme in terms of the coverage probability and user throughput.
The results highlight the HO rate problem in dense cellular environments and
show the importance of the proposed HO schemes. Finally, the value of BS
cooperation along with handover skipping is quantified for different user
mobility profiles.


title:
Quantum-enhanced metrology without entanglement based on optical
  cavities with feedback

abstract:
  There are a number of different strategies to measure the phase shift between
two pathways of light more efficiently than suggested by the standard quantum
limit. One way is to use highly entangled photons. Another way is to expose
photons to a non-linear or interacting Hamiltonian. This paper emphasises that
the conditional dynamics of open quantum systems provides an interesting
additional tool for quantum-enhanced metrology. As a concrete example, we
review a recent scheme which exploits the conditional dynamics of a
laser-driven optical cavity with spontaneous photon emission inside a quantum
feedback loop. Deducing information from second-order photon correlation
measurements requires neither optical non-linearities nor entangled photons and
should therefore be of immediate practical interest.


title:
Macroscopic evolution of mechanical and thermal energy in a harmonic
  chain with random flip of velocities

abstract:
  We consider an unpinned chain of harmonic oscillators with periodic boundary
conditions, whose dynamics is perturbed by a random flip of the sign of the
velocities. The dynamics conserves the total volume (or elongation) and the
total energy of the system. We prove that in a diffusive space-time scaling
limit the profiles corresponding to the two conserved quantities converge to
the solution of a diffusive system of differential equations. While the
elongation follows a simple autonomous linear diffusive equation, the evolution
of the energy depends on the gradient of the square of the elongation.

categories: math.PR cond-mat.stat-mech math-ph math.MP


title: A Probabilistic Look at Conservative Growth-Fragmentation Equations

abstract:
  In this note, we consider general growth-fragmentation equations from a
probabilistic point of view. Using Foster-Lyapunov techniques, we study the
recurrence of the associated Markov process depending on the growth and
fragmentation rates. We prove the existence and uniqueness of its stationary
distribution, and we are able to derive precise bounds for its tails in the
neighborhoods of both $0$ and $+\infty$. This study is systematically compared
to the results obtained so far in the literature for this class of
integro-differential equations.


title:
A family of compact strictly pseudoconvex hypersurfaces in $\mathbb C^2$
  without umbilical points

abstract:
  We prove the following: For $\epsilon>0$, let $D_\epsilon$ be the bounded
strictly pseudoconvex domain in $\mathbb C^2$ given by \begin{equation*}
(\log|z|)^2+(\log|w|)^2<\epsilon^2. \end{equation*} The boundary
$M_\epsilon:=\partial D_\epsilon\subset \mathbb C^2$ is a compact strictly
pseudoconvex CR manifold without umbilical points. This resolves a
long-standing question in complex analysis that goes back to the work of S.-S.
Chern and J. K. Moser in 1974.


title:
A quantum-inspired algorithm for estimating the permanent of positive
  semidefinite matrices

abstract:
  We construct a quantum-inspired classical algorithm for computing the
permanent of Hermitian positive semidefinite matrices, by exploiting a
connection between these mathematical structures and the boson sampling model.
Specifically, the permanent of a Hermitian positive semidefinite matrix can be
expressed in terms of the expected value of a random variable, which stands for
a specific photon-counting probability when measuring a linear-optically
evolved random multimode coherent state. Our algorithm then approximates the
matrix permanent from the corresponding sample mean and is shown to run in
polynomial time for various sets of Hermitian positive semidefinite matrices,
achieving a precision that improves over known techniques. This work
illustrates how quantum optics may benefit algorithms development.


title: Discovery of a pseudobulge galaxy launching powerful relativistic jets

abstract:
  Supermassive black holes launching plasma jets at close to speed of light,
producing gamma-rays, have ubiquitously been found to be hosted by massive
elliptical galaxies. Since elliptical galaxies are generally believed to be
built through galaxy mergers, active galactic nuclei (AGN) launching
relativistic jets are associated to the latest stages of galaxy evolution. We
have discovered a pseudo-bulge morphology in the host galaxy of the gamma-ray
AGN PKS 2004-447. This is the first gamma-ray emitter radio loud AGN found to
be launched from a system where both black hole and host galaxy have been
actively growing via secular processes. This is evidence for an alternative
black hole-galaxy co-evolutionary path to develop powerful relativistic jets
that is not merger-driven.


title: On the Origin of Non-Saturating Linear Magnetoresistivity

abstract:
  The observation of non-saturating classical linear magnetoresistivity has
been an enigmatic phenomenon in solid state physics. We present a study of a
two-dimensional ohmic conductor, including local Hall effect and a
self-consistent consideration of the environment. An equivalent-circuit scheme
delivers a simple and convincing argument why the magnetoresistivity is linear
in strong magnetic field, provided that current and biasing electric field are
misaligned by a nonlocal mechanism. A finite-element model of a two-dimensional
conductor is suited to display the situations that create such deviating
currents. Besides edge effects next to electrodes, charge carrier density
fluctuations are efficiently generating this effect. However, mobility
fluctuations that have frequently been related to linear magnetoresistivity are
barely relevant. Despite its rare observation, linear magnetoresitivity is
rather the rule than the exception in a regime of low charge carrier densities,
misaligned current pathways and strong magnetic field.


title: A local factorization of the fermion determinant in lattice QCD

abstract:
  We introduce a factorization of the fermion determinant in lattice QCD with
Wilson-type fermions that leads to a bosonic action which is local in the block
fields. The interaction among gauge fields on distant blocks is mediated by
multiboson fields located on the boundaries of the blocks. The resultant
multiboson domain-decomposed hybrid Monte Carlo passes extensive numerical
tests carried out by measuring standard gluonic observables. The combination of
the determinant factorization and of the one of the propagator, that we put
forward recently, paves the way for multilevel Monte Carlo integration in the
presence of fermions. We test this possibility by computing the disconnected
correlator of two flavor-diagonal pseudoscalar densities, and we observe a
significant increase of the signal-to-noise ratio due to a two-level
integration.


title: Non-holomorphic Lefschetz fibrations with $(-1)$-sections

abstract:
  We construct two types of non-holomorphic Lefschetz fibrations over $S^2$
with $(-1)$-sections ---hence, they are fiber sum indecomposable--- by giving
the corresponding positive relators. One type of the two does not satisfy the
slope inequality (a necessary condition for a fibration to be holomorphic) and
has a simply-connected total space, and the other has a total space that cannot
admit any complex structure in the first place. These give an alternative
existence proof for non-holomorphic Lefschetz pencils without Donaldson's
theorem.


title:
Statistical Mechanical Model for a closed loop plectoneme with weak
  helix specific forces

abstract:
  We develop a statistical mechanical framework, based on a variational
approximation, to describe closed loop plectonemes. This framework incorporates
weak helix structure dependent forces into the determination of the free energy
and average structure of a plectoneme. Notably, due to their chiral nature,
helix structure dependent forces break the symmetry between left and right
handed supercoiling. The theoretical approach, presented here, also provides a
systematic way of enforcing the topological constraint of closed loop
supercoiling in the variational approximation. At large plectoneme lengths, by
considering correlation functions in an expansion in terms of the spatial mean
twist density about its thermally averaged value, it can be argued that
topological constraint may be approximated with by replacing twist and writhe
by their thermal averages. A Lagrange Multiplier, containing the sum of average
twist and writhe, can be added to the free energy to conveniently inforce this
result. The average writhe can be calculated through the thermal average of
Gauss integral in the variational approximation. Furthermore, this approach
allows for a possible way to calculate finite size corrections due to the
topological constraint. Using interaction energy terms from the mean-field
Kornyshev-Leikin theory, for parameter values that correspond to weak helix
dependent forces, we calculate the free energy, fluctuation magnitudes and mean
geometric parameters for the plectoneme. We see a slight asymmetry, where
interestingly enough left handed supercoils have looser structure than right
handed ones, although a lower free energy, unlike what previous ground state
calculations would suggest.


title: What can (partition) logic contribute to information theory?

abstract:
  Logical probability theory was developed as a quantitative measure based on
Boole's logic of subsets. But information theory was developed into a mature
theory by Claude Shannon with no such connection to logic. A recent development
in logic changes this situation. In category theory, the notion of a subset is
dual to the notion of a quotient set or partition, and recently the logic of
partitions has been developed in a parallel relationship to the Boolean logic
of subsets (subset logic is usually mis-specified as the special case of
propositional logic). What then is the quantitative measure based on partition
logic in the same sense that logical probability theory is based on subset
logic? It is a measure of information that is named "logical entropy" in view
of that logical basis. This paper develops the notion of logical entropy and
the basic notions of the resulting logical information theory. Then an
extensive comparison is made with the corresponding notions based on Shannon
entropy.


title: The Incentive Ratio in Exchange Economies

abstract:
  The incentive ratio measures the utility gains from strategic behaviour.
Without any restrictions on the setup, ratios for linear, Leontief and
Cobb-Douglas exchange markets are unbounded, showing that manipulating the
equilibrium is a worthwhile endeavour, even if it is computationally
challenging. Such unbounded improvements can be achieved even if agents only
misreport their utility functions. This provides a sharp contrast with previous
results from Fisher markets. When the Cobb-Douglas setup is more restrictive,
the maximum utility gain is bounded by the number of commodities. By means of
an example, we show that it is possible to exceed a known upper bound for
Fisher markets in exchange economies.


title: Dark matter in GUT inspired $Z^\prime$ portal scenarios

abstract:
  We consider simple dark matter extensions of the standard model in $Z^\prime$
portal scenarios inspired by grand unification theory constructions and we
study the phenomenology of such models by considering Spin Dependent and Spin
Independent direct detection constraints, confronting the canonical thermally
produced dark matter scenario and we show that in this simple framework the
combination and the complementary of these constraints is a powerful tool to
derive stringent bounds and to reduce the viable parameter space of the model.


title:
The limit distribution in the $q$-CLT for $q \ge 1$ is unique and can
  not have a compact support

abstract:
  In a paper by Umarov, Tsallis and Steinberg (2008), a generalization of the
Fourier transform, called the $q$-Fourier transform, was introduced and applied
for the proof of a $q$-generalized central limit theorem ($q$-CLT).
Subsequently, Hilhorst illustrated (2009 and 2010) that the $q$-Fourier
transform for $q>1$ is not invertible in the space of density functions.
Indeed, using an invariance principle, he constructed a family of densities
with the same $q$-Fourier transform and noted that "as a consequence, the
$q$-central limit theorem falls short of achieving its stated goal". The
distributions constructed there have compact support. We prove now that the
limit distribution in the $q$-CLT is unique and can not have a compact support.
This result excludes all the possible counterexamples which can be constructed
using the invariance principle and fills the gap mentioned by Hilhorst.


title: Extension of the General Thermal Field Equation for nanosized emitters

abstract:
  During the previous decade, K.L. Jensen et. al. developed a general
analytical model that successfully describes electron emission from metals both
in the field and thermionic regimes, as well as in the transition region. In
that development, the standard image corrected triangular potential barrier was
used. This barrier model is valid only for planar surfaces and therefore cannot
be used in general for modern nanometric emitters. In a recent publication the
authors showed that the standard Fowler-Nordheim theory can be generalized for
highly curved emitters if a quadratic term is included to the potential model.
In this paper we extend this generalization for high temperatures and include
both the thermal and intermediate regimes. This is achieved by applying the
general method developed by Jensen to the quadratic barrier model of our
previous publication. We obtain results that are in good agreement with fully
numerical calculations for radii $R>4nm$, while our calculated current density
differs by a factor up to 27 from the one predicted by the Jensen's standard
General-Thermal-Field (GTF) equation. Our extended GTF equation has application
to modern sharp electron sources, beam simulation models and vacuum breakdown
theory.


title: Waveform Candidates for 5G Networks: Analysis and Comparison

abstract:
  As the next generation cellular system, 5G network is required to provide a
large variety of services for different kinds of terminals, from traditional
voice and data services over mobile phones to small packet transmission over
massive machine-type terminals. Although orthogonal-subcarrier based waveform
has been widely used nowadays in many practical systems, it can hardly meet the
future requirements in the coming 5G networks. Therefore, more flexible
waveforms have been proposed to address the unprecedented challenges. In this
article, we will provide comprehensive analysis and comparison for the typical
waveform candidates. To obtain insightful analysis, we will not only introduce
the basic principles of the waveforms but also reveal the underlying
characteristics of each waveform. Moreover, a comprehensive comparison in terms
of different performance metrics will be also presented in this article, which
provide an overall understanding of the new waveforms.


title: Quantum dimensions from local operator excitations in the Ising model

abstract:
  We compare the time evolution of entanglement measures after local operator
excitation in the critical Ising model with predictions from conformal field
theory. For the spin operator and its descendants we find that Renyi entropies
of a block of spins increase by a constant that matches the logarithm of the
quantum dimension of the conformal family. However, for the energy operator we
find a small constant contribution that differs from the conformal field theory
answer equal to zero. We argue that the mismatch is caused by the subtleties in
the identification between the local operators in conformal field theory and
their lattice counterpart. Our results indicate that evolution of entanglement
measures in locally excited states not only constraints this identification,
but also can be used to extract non-trivial data about the conformal field
theory that governs the critical point. We generalize our analysis to the Ising
model away from the critical point, states with multiple local excitations, as
well as the evolution of the relative entropy after local operator excitation
and discuss universal features that emerge from numerics.

categories: cond-mat.str-el cond-mat.stat-mech hep-th quant-ph


title: Coarse graining flow of spin foam intertwiners

abstract:
  Simplicity constraints play a crucial role in the construction of spin foam
models, yet their effective behaviour on larger scales is scarcely explored. In
this article we introduce intertwiner and spin net models for the quantum group
$\text{SU}(2)_k \times \text{SU}(2)_k$, which implement the simplicity
constraints analogous to 4D Euclidean spin foam models, namely the
Barrett-Crane (BC) and the Engle-Pereira-Rovelli-Livine/Freidel-Krasnov
(EPRL/FK) model. These models are numerically coarse grained via tensor network
renormalization, allowing us to trace the flow of simplicity constraints to
larger scales. In order to perform these simulations we have substantially
adapted tensor network algorithms, which we discuss in detail.
  The BC and the EPRL/FK model behave very differently under coarse graining:
While the unique BC intertwiner model is a fixed point and therefore
constitutes a 2D topological phase, BC spin net models flow away from the
initial simplicity constraints and converge to several different topological
phases. Most of these phases correspond to decoupling spin foam vertices,
however we find also a new phase in which this is not the case, and in which a
non-trivial version of the simplicity constraints holds. The coarse graining
flow of the BC spin net models indicates furthermore that the phase transitions
are not of second order. The EPRL/FK model by contrast reveals a far more
intricate and complex dynamics. We observe an immediate flow away from the
original simplicity constraints, however, with the truncation employed here,
the models generically do not converge to a fixed point.
  The results show that the imposition of simplicity constraints can indeed
lead to interesting and complex dynamics. Thus we will need to further develop
coarse graining tools to efficiently study the large scale behaviour of spin
foam models, in particular for the EPRL/FK model.


title: Exact Solutions and Conserved Quantities in f(R,T) Gravity

abstract:
  This paper explores Noether and Noether gauge symmetries of anisotropic
universe model in $f(R,T)$ gravity. We consider two particular models of this
gravity and evaluate their symmetry generators as well as associated conserved
quantities. We also find exact solution by using cyclic variable and
investigate its behavior via cosmological parameters. The behavior of
cosmological parameters turns out to be consistent with recent observations
which indicates accelerated expansion of the universe. Next we study Noether
gauge symmetry and corresponding conserved quantities for both isotropic and
anisotropic universe models. We conclude that symmetry generators and the
associated conserved quantities appear in all cases.


title:
Quench dynamics of the three-dimensional U(1) complex field theory:
  geometric and scaling characterisation of the vortex tangle

abstract:
  We present a detailed study of the equilibrium properties and stochastic
dynamic evolution of the U(1)-invariant relativistic complex field theory in
three dimensions. This model has been used to describe, in various limits,
properties of relativistic bosons at finite chemical potential, type II su-
perconductors, magnetic materials and aspects of cosmology. We characterise the
thermodynamic second-order phase transition in different ways. We study the
equilibrium vortex configurations and their statistical and geometrical
properties in equilibrium at all temperatures. We show that at very high
temperature the statistics of the filaments is the one of fully-packed loop
models. We identify the temperature, within the ordered phase, at which the
number density of vortex lengths falls-off algebraically and we associate it to
a geometric percolation transition that we characterise in various ways. We
measure the fractal properties of the vortex tangle at this threshold. Next, we
perform infinite rate quenches from equilibrium in the disordered phase, across
the thermo- dynamic critical point, and deep into the ordered phase. We show
that three time regimes can be distinguished: a first approach towards a state
that, within numerical accuracy, shares many features with the one at the
percolation threshold, a later coarsening process that does not alter, at
sufficiently low temperature, the fractal properties of the long vortex loops,
and a final approach to equilibrium. These features are independent of the
reconnection rule used to build the vortex lines. In each of these regimes we
identify the various length-scales of the vortices in the system. We also study
the scaling properties of the ordering process and the progressive annihilation
of topological defects and we prove that the time-dependence of the
time-evolving vortex tangle can be described within the dynamic scaling
framework.


title: Topological order of mixed states in quantum many-body systems

abstract:
  Topological order has become a new paradigm to distinguish ground states of
interacting many-body systems without conventional long-range order. Here we
discuss possible extensions of this concept to density matrices describing
statistical ensembles. For a large class of quasi-thermal states, which can be
realized as thermal states of some quasi-local Hamiltonian, we generalize
earlier definitions of density matrix topology to generic many-body systems
with strong correlations. We point out that the robustness of topological
order, defined as a pattern of long-range entanglement, depends crucially on
the perturbations under consideration. While it is intrinsically protected
against local perturbations of arbitrary strength in an infinite closed quantum
system, purely local perturbations can destroy topological order in open
systems coupled to baths if the coupling is sufficiently strong. We discuss our
classification scheme using the finite-temperature quantum Hall states and
point out that the classical Hall effect can be understood as a finite
temperature topological phase.


title: Binary simple homogeneous structures

abstract:
  We describe all binary simple homogeneous structures M in terms of
0-definable equivalence relations on M, which "coordinatize" M and control
dividing, and extension properties that respect these equivalence relations.


title: Incremental Consistency Guarantees for Replicated Objects

abstract:
  Programming with replicated objects is difficult. Developers must face the
fundamental trade-off between consistency and performance head on, while
struggling with the complexity of distributed storage stacks. We introduce
Correctables, a novel abstraction that hides most of this complexity, allowing
developers to focus on the task of balancing consistency and performance. To
aid developers with this task, Correctables provide incremental consistency
guarantees, which capture successive refinements on the result of an ongoing
operation on a replicated object. In short, applications receive both a
preliminary---fast, possibly inconsistent---result, as well as a
final---consistent---result that arrives later.
  We show how to leverage incremental consistency guarantees by speculating on
preliminary values, trading throughput and bandwidth for improved latency. We
experiment with two popular storage systems (Cassandra and ZooKeeper) and three
applications: a Twissandra-based microblogging service, an ad serving system,
and a ticket selling system. Our evaluation on the Amazon EC2 platform with
YCSB workloads A, B, and C shows that we can reduce the latency of strongly
consistent operations by up to 40% (from 100ms to 60ms) at little cost (10%
bandwidth increase, 6% throughput drop) in the ad system. Even if the
preliminary result is frequently inconsistent (25% of accesses), incremental
consistency incurs a bandwidth overhead of only 27%.


title: Lattice effects on Laughlin wave functions and parent Hamiltonians

abstract:
  We investigate lattice effects on wave functions that are lattice analogues
of bosonic and fermionic Laughlin wave functions with number of particles per
flux $\nu=1/q$ in the Landau levels. These wave functions are defined
analytically on lattices with $\mu$ particles per lattice site, where $\mu$ may
be different than $\nu$. We give numerical evidence that these states have the
same topological properties as the corresponding continuum Laughlin states for
different values of $q$ and for different fillings $\mu$. These states define,
in particular, particle-hole symmetric lattice Fractional Quantum Hall states
when the lattice is half-filled. On the square lattice it is observed that for
$q\leq 4$ this particle-hole symmetric state displays the topological
properties of the continuum Laughlin state at filling fraction $\nu=1/q$, while
for larger $q$ there is a transition towards long-range ordered
anti-ferromagnets. This effect does not persist if the lattice is deformed from
a square to a triangular lattice, or on the Kagome lattice, in which case the
topological properties of the state are recovered. We then show that changing
the number of particles while keeping the expression of these wave functions
identical gives rise to edge states that have the same correlations in the bulk
as the reference lattice Laughlin states but a different density at the edge.
We derive an exact parent Hamiltonian for which all these edge states are
ground states with different number of particles. In addition this Hamiltonian
admits the reference lattice Laughlin state as its unique ground state of
filling factor $1/q$. Parent Hamiltonians are also derived for the lattice
Laughlin states at other fillings of the lattice, when $\mu\leq 1/q$ or
$\mu\geq 1-1/q$ and when $q=4$ also at half-filling.


title:
Ageing of a space-based CCD: photometric performance development of the
  low Earth orbiting detectors of the CoRoT mission

abstract:
  In this thesis we have analysed the time evolution of the photometric
precision achieved by the space-based exoplanet-hunting mission CoRoT during
its flight phase (2007-2012). This study of the noise level of CoRoT light
curves has been based on a previous paper by Aigrain et al. 2009, where they
found a gradual degradation of the photometric performance over time for the
first 14 months of data. Here we have analysed the anti-center runs IRa01
(2007), LRa01 (2008), LRa03 (2010) and LRa06 (2012). The two first runs were
studied by Aigrain as well, so we are able to compare our results. The two last
runs allowed us to evaluate the trend of photometric degradation over more than
5 years. We obtain low observational point-to-point noise, although a factor 3
bigger than the source photon noise. We find effects showing the ageing of the
CoRoT CCDs. On 2h time scales we notice a receding photometric performance,
with a noise increase of about 2.1 times across the four analysed runs,
corresponding to a 15% increase per year. Correlated noise becomes more
important than white uncorrelated noise for the two last studied runs, LRa03
and LRa06. The strongest degradation, however, occurs during the first year of
operations, with a 30% noise increase, opening up a two-ageing-timescales
scenario.


title: Constant curvature surfaces in a pseudo-isotropic space

abstract:
  In this study, we deal with the local structure of curves and surfaces
immersed in a pseudo-isotropic space I_{p}^{3} that is a particular
Cayley-Klein space. We provide the formulas of curvature, torsion and Frenet
trihedron in order for spacelike and timelike curves. The causal character of
all admissible surfaces in I_{p}^{3} has to be timelike or lightlike up to its
absolute. We introduce the formulas of Gaussian and mean curvature for timelike
surfaces in I_{p}^{3}. As applications, we describe the surfaces of revolution
which are the orbits of a plane curve under a hyperbolic rotation with constant
Gaussian and mean curvature.


title: Integration by parts on the law of the modulus of the Brownian bridge

abstract:
  We prove an infinite dimensional integration by parts formula on the law of
the modulus of the Brownian bridge $BB=(BB_t)_{0 \leq t \leq 1}$ from $0$ to
$0$ in use of methods from white noise analysis and Dirichlet form theory.
Additionally to the usual drift term, this formula contains a distribution
which is constructed in the space of Hida distributions by means of a Wick
product with Donsker's delta (which correlates with the local time of $|BB|$ at
zero). This additional distribution corresponds to the reflection at zero
caused by the modulus.


title: Quantum Coherence as a Resource

abstract:
  The coherent superposition of states, in combination with the quantization of
observables, represents one of the most fundamental features that mark the
departure of quantum mechanics from the classical realm. Quantum coherence in
many-body systems embodies the essence of entanglement and is an essential
ingredient for a plethora of physical phenomena in quantum optics, quantum
information, solid state physics, and nanoscale thermodynamics. In recent
years, research on the presence and functional role of quantum coherence in
biological systems has also attracted a considerable interest. Despite the
fundamental importance of quantum coherence, the development of a rigorous
theory of quantum coherence as a physical resource has only been initiated
recently. In this Colloquium we discuss and review the development of this
rapidly growing research field that encompasses the characterization,
quantification, manipulation, dynamical evolution, and operational application
of quantum coherence.

categories: quant-ph cond-mat.mes-hall hep-th math-ph math.MP physics.optics