title: Axial-Current Matrix Elements in Light Nuclei from Lattice QCD

abstract:
  I present results from the first lattice QCD calculations of axial-current
matrix elements in light nuclei, performed by the NPLQCD collaboration.
Precision calculations of these matrix elements, and the subsequent extraction
of multi-nucleon axial-current operators, are essential in refining theoretical
predictions of the proton-proton fusion cross section, neutrino-nucleus cross
sections and $\beta\beta$-decay rates of nuclei. In addition, they are expected
to shed light on the phenomenological quenching of $g_A$ that is required in
nuclear many-body calculations.


title: Fracture of a model cohesive granular material

abstract:
  We study experimentally the fracture mechanisms of a model cohesive granular
medium consisting of glass beads held together by solidified polymer bridges.
The elastic response of this material can be controlled by changing the
cross-linking of the polymer phase, for example. Here we show that its fracture
toughness can be tuned over an order of magnitude by adjusting the stiffness
and size of the polymer bridges. We extract a well-defined fracture energy from
fracture testing under a range of material preparations. This energy is found
to scale linearly with the cross-sectional area of the bridges. Finally, X-ray
microcomputed tomography shows that crack propagation is driven by adhesive
failure of about one polymer bridge per bead located at the interface, along
with microcracks in the vicinity of the failure plane. Our findings provide
insight to the fracture mechanisms of this model material, and the mechanical
properties of disordered cohesive granular media in general.


title:
A JVLA survey of the high frequency radio emission of the massive
  magnetic B- and O-type stars

abstract:
  We conducted a survey of seven magnetic O and eleven B-type stars with masses
above $8M_{\odot}$ using the Very Large Array in the 1cm, 3cm and 13cm bands.
The survey resulted in a detection of two O and two B-type stars. While the
detected O-type stars - HD 37742 and HD 47129 - are in binary systems, the
detected B-type stars, HD 156424 and ALS 9522, are not known to be in binaries.
All four stars were detected at 3cm, whereas three were detected at 1cm and
only one star was detected at 13cm. The detected B-type stars are significantly
more radio luminous than the non-detected ones, which is not the case for
O-type stars. The non-detections at 13cm are interpreted as due to thermal
free-free absorption. Mass-loss rates were estimated using 3cm flux densities
and were compared with theoretical mass-loss rates, which assume free-free
emission. For HD 37742, the two values of the mass-loss rates were in good
agreement, possibly suggesting that the radio emission for this star is mainly
thermal. For the other three stars, the estimated mass-loss rates from radio
observations were much higher than those expected from theory, suggesting
either a possible contribution from non- thermal emission from the magnetic
star or thermal or non-thermal emission due to interacting winds of the binary
system, especially for HD 47129. All the detected stars are predicted to host
centrifugal magnetospheres except HD 37742, which is likely to host a dynamical
magnetosphere. This suggests that non-thermal radio emission is favoured in
stars with centrifugal magnetospheres.


title:
Surpassing Gradient Descent Provably: A Cyclic Incremental Method with
  Linear Convergence Rate

abstract:
  Recently, there has been growing interest in developing optimization methods
for solving large-scale machine learning problems. Most of these problems boil
down to the problem of minimizing an average of a finite set of smooth and
strongly convex functions where the number of functions $n$ is large. Gradient
descent method (GD) is successful in minimizing convex problems at a fast
linear rate; however, it is not applicable to the considered large-scale
optimization setting because of the high computational complexity. Incremental
methods resolve this drawback of gradient methods by replacing the required
gradient for the descent direction with an incremental gradient approximation.
They operate by evaluating one gradient per iteration and executing the average
of the $n$ available gradients as a gradient approximate. Although, incremental
methods reduce the computational cost of GD, their convergence rates do not
justify their advantage relative to GD in terms of the total number of gradient
evaluations until convergence. In this paper, we introduce a Double Incremental
Aggregated Gradient method (DIAG) that computes the gradient of only one
function at each iteration, which is chosen based on a cyclic scheme, and uses
the aggregated average gradient of all the functions to approximate the full
gradient. The iterates of the proposed DIAG method uses averages of both
iterates and gradients in oppose to classic incremental methods that utilize
gradient averages but do not utilize iterate averages. We prove that not only
the proposed DIAG method converges linearly to the optimal solution, but also
its linear convergence factor justifies the advantage of incremental methods on
GD. In particular, we prove that the worst case performance of DIAG is better
than the worst case performance of GD.


title: $Q Q \bar Q \bar Q$ states: masses, production, and decays

abstract:
  The question of whether there exist bound states of two heavy quarks
$Q=(c,b)$ and antiquarks $\bar Q = (\bar c, \bar b)$, distinct from a pair of
quark-antiquark mesons, has been debated for more than forty years. We suggest
some means of producing and observing $Q_1 Q_2 \bar Q_3 \bar Q_4$ resonant
states, concentrating on the $c c \bar c \bar c$ channel which is most easily
produced and the $b b \bar b \bar b$ channel which has a better chance of being
relatively narrow. We obtain $M_{(cc)(\bar c \bar c)} = 6,192 \pm 25$ MeV and
$M_{(bb)(\bar b \bar b)} = 18,826 \pm 25$ MeV, for the charmed and bottom
tetraquarks, respectively. Experimental search for these states in the relevant
mass region is highly desirable.


title:
Collective Transport for Active Matter Run and Tumble Disk Systems on a
  Traveling Wave Substrate

abstract:
  We numerically examine the transport of an assembly of active run-and-tumble
disks interacting with a traveling wave substrate. We show that as a function
of substrate strength, wave speed, disk activity, and disk density, a variety
of dynamical phases arise that are correlated with the structure and net flux
of disks. We find that there is a sharp transition into a state where the disks
are only partially coupled to the substrate and form a phase separated cluster
state. This transition is associated with a drop in the net disk flux and can
occur as a function of the substrate speed, maximum substrate force, disk run
time, and disk density. Since variation of the disk activity parameters
produces different disk drift rates for a fixed traveling wave speed on the
substrate, the system we consider could be used as an efficient method for
active matter species separation. Within the cluster phase, we find that in
some regimes the motion of the cluster center of mass is in the opposite
direction to that of the traveling wave, while when the maximum substrate force
is increased, the cluster drifts in the direction of the traveling wave. This
suggests that swarming or clustering motion can serve as a method by which an
active system can collectively move against an external drift.


title: Adversarial Influence Maximization

abstract:
  We consider the problem of influence maximization in fixed networks for
contagion models in an adversarial setting. The goal is to select an optimal
set of nodes to seed the influence process, such that the number of influenced
nodes at the conclusion of the campaign is as large as possible. We formulate
the problem as a repeated game between a player and adversary, where the
adversary specifies the edges along which the contagion may spread, and the
player chooses sets of nodes to influence in an online fashion. We establish
upper and lower bounds on the minimax pseudo-regret in both undirected and
directed networks.


title:
Intrinsic isoperimetry of the giant component of supercritical bond
  percolation in dimension two

abstract:
  We study the isoperimetric subgraphs of the giant component $\textbf{C}_n$ of
supercritical bond percolation on the square lattice. These are subgraphs of
$\textbf{C}_n$ having minimal edge boundary to volume ratio. In contrast to the
work of Biskup, Louidor, Procaccia and Rosenthal, the edge boundary is taken
only within $\textbf{C}_n$ instead of the full infinite cluster. The
isoperimetric subgraphs are shown to converge almost surely, after rescaling,
to the collection of optimizers of a continuum isoperimetric problem emerging
naturally from the model. We also show that the Cheeger constant of
$\textbf{C}_n$ scales to a deterministic constant, which is itself an
isoperimetric ratio, settling a conjecture of Benjamini in dimension two.


title: Device-independent randomness generation from several Bell estimators

abstract:
  Device-independent randomness generation and quantum key distribution
protocols rely on a fundamental relation between the non-locality of quantum
theory and its random character. This relation is usually expressed in terms of
a trade-off between the probability of guessing correctly the outcomes of
measurements performed on quantum systems and the amount of violation of a
given Bell inequality. However, a more accurate assessment of the randomness
produced in Bell experiments can be obtained if the value of several Bell
expressions is simultaneously taken into account, or if the full set of
probabilities characterizing the behavior of the device is considered. We
introduce protocols for device-independent randomness generation, secure
against classical side information, that rely on the estimation of an arbitrary
number of Bell expressions or even directly on the experimental frequencies of
measurement outcomes. Asymptotically, this results in an optimal generation of
randomness from experimental data (as measured by the min-entropy), without
having to assume beforehand that the devices violate a specific Bell
inequality.


title:
Thermoelectric properties of a ferromagnet-superconductor hybrid
  junction: Role of interfacial Rashba spin-orbit interaction

abstract:
  We investigate thermoelectric properties of a ferromagnet-superconductor
hybrid structure with Rashba spin-orbit interaction and delta function
potential barrier at the interfacial layer. The exponential rise of thermal
conductance with temperature manifests a cross-over temperature scale
separating two opposite behaviors of it with the change of polarization in the
ferromagnet whereas the inclusion of interfacial Rashba spin-orbit field
results in a non-monotonic behavior of it with the strength of Rashba field. We
employ scattering matrix approach to determine the amplitudes of all the
scattering processes possible at the interface to explain the thermoelectric
properties of the device. We examine Seebeck effect and show that higher
thermopower can be achieved when the polarization of the ferromagnet tends
towards the half-metallic limit. It can be enhanced even for lower polarization
in presence of the finite potential barrier. In presence of interfacial Rashba
spin-orbit interaction, Seebeck coefficient rises with the increase of barrier
strength and polarization at weak or moderate interfacial Rashba field. From
the application perspective, we compute the figure of merit and show that
$zT\sim 4-5$ with higher polarization of the ferromagnet both in absence and
presence of weak or moderate Rashba spin-orbit interaction along with the
scalar potential barrier.


title:
Faster decoding for subword level Phrase-based SMT between related
  languages

abstract:
  A common and effective way to train translation systems between related
languages is to consider sub-word level basic units. However, this increases
the length of the sentences resulting in increased decoding time. The increase
in length is also impacted by the specific choice of data format for
representing the sentences as subwords. In a phrase-based SMT framework, we
investigate different choices of decoder parameters as well as data format and
their impact on decoding time and translation accuracy. We suggest best options
for these settings that significantly improve decoding time with little impact
on the translation accuracy.


title: Reply to Comment on "Anomalous Edge State in a Non-Hermitian Lattice"

abstract:
  The Comment by Xiong et al. (arXiv:1610.06275) criticizing my Letter [Phys.
Rev. Lett. 116, 133903 (2016)] was rejected by Physical Review Letters. In this
Reply, I show that all their claims are wrong.


title: Using Artificial Intelligence to Identify State Secrets

abstract:
  Whether officials can be trusted to protect national security information has
become a matter of great public controversy, reigniting a long-standing debate
about the scope and nature of official secrecy. The declassification of
millions of electronic records has made it possible to analyze these issues
with greater rigor and precision. Using machine-learning methods, we examined
nearly a million State Department cables from the 1970s to identify features of
records that are more likely to be classified, such as international
negotiations, military operations, and high-level communications. Even with
incomplete data, algorithms can use such features to identify 90% of classified
cables with <11% false positives. But our results also show that there are
longstanding problems in the identification of sensitive information. Error
analysis reveals many examples of both overclassification and
underclassification. This indicates both the need for research on inter-coder
reliability among officials as to what constitutes classified material and the
opportunity to develop recommender systems to better manage both classification
and declassification.


title: An Extension of the Chen-Beurling-Helson-Lowdenslager Theorem

abstract:
  Yanni Chen extended the classical Beurling-Helson-Lowdenslager Theorem for
Hardy spaces on the unit circle $\mathbb{T}$ defined in terms of continuous
gauge norms on $L^{\infty}$ that dominate $\Vert\cdot\Vert_{1}$. We extend
Chen's result to a much larger class of continuous gauge norms. A key
ingredient is our result that if $\alpha$ is a continuous normalized gauge norm
on $L^{\infty}$, then there is a probability measure $\lambda$, mutually
absolutely continuous with respect to Lebesgue measure on $\mathbb{T}$, such
that $\alpha\geq c\Vert\cdot\Vert_{1,\lambda}$ for some $0<c\leq1.$


title:
Shannon entropy of brain functional complex networks under the influence
  of the psychedelic Ayahuasca

abstract:
  The entropic brain hypothesis holds that the key facts concerning
psychedelics are partially explained in terms of increased entropy of the
brain's functional connectivity. Ayahuasca is a psychedelic beverage of
Amazonian indigenous origin with legal status in Brazil in religious and
scientific settings. In this context, we use tools and concepts from the theory
of complex networks to analyze resting state fMRI data of the brains of human
subjects under two distinct conditions: (i) under ordinary waking state and
(ii) in an altered state of consciousness induced by ingestion of Ayahuasca. We
report an increase in the Shannon entropy of the degree distribution of the
networks subsequent to Ayahuasca ingestion. We also find increased local and
decreased global network integration. Our results are broadly consistent with
the entropic brain hypothesis. Finally, we discuss our findings in the context
of descriptions of "mind-expansion" frequently seen in self-reports of users of
psychedelic drugs.


title:
Model-independent estimations for the curvature from standard candles
  and clocks

abstract:
  Model-independent estimations for the spatial curvature not only provide a
test for the fundamental Copernican principle assumption, but also can
effectively break the degeneracy between curvature and dark energy properties.
In this paper, we propose to achieve model-independent constraints on the
spatial curvature from observations of standard candles and standard clocks,
without assuming any fiducial cosmology and other priors. We find that, for the
popular Union2.1 type Ia supernovae (SNe Ia ) observations, the spatial
curvature is constrained to be $\Omega_K=-0.045_{-0.172}^{+0.176}$. For the
latest joint light-curve analysis (JLA) of SNe Ia observations, we obtain
$\Omega_K=-0.140_{-0.158}^{+0.161}$. It is suggested that these results are in
excellent agreement with the spatially flat Universe. Moreover, compared to
other approaches aiming for model-independent estimations of spatial curvature,
this method also achieves constraints with competitive precision.


title: de Sitter as a Resonance

abstract:
  A quantum mechanical formulation of de Sitter cosmological spacetimes still
eludes string theory. In this paper we conjecture a potentially rigorous
framework in which the status of de Sitter space is the same as that of a
resonance in a scattering process. We conjecture that transition amplitudes
between certain states with asymptotically supersymmetric flat vacua contain
resonant poles characteristic metastable intermediate states. A calculation
employing constrained instantons illustrates this idea.


title:
Off-Shell Spinor-Helicity Amplitudes from Light-Cone Deformation
  Procedure

abstract:
  We study the consistency conditions for interactions of massless fields of
any spin in four-dimensional flat space using the light-cone approach. We show
that they can be equivalently rewritten as the Ward identities for the
off-shell light-cone amplitudes built from the light-cone Hamiltonian in the
standard way. Then we find a general solution of these Ward identities. The
solution admits a compact representation when written in the spinor-helicity
form and is given by an arbitrary function of spinor products, satisfying
well-known homogeneity constraints. Thus, we show that the light-cone
consistent deformation procedure inevitably leads to a certain off-shell
version of the spinor-helicity approach. We discuss how the relation between
the two approaches can be employed to facilitate the search of consistent
interaction of massless higher-spin fields.


title: Kaluza-Klein Reduction of Massive and Partially Massless Spin-2 Fields

abstract:
  We describe the dimensional reduction of massive and partially massless
spin-2 fields on general Einstein direct product manifolds. As with massless
fields, the higher-dimensional gauge symmetry of the partially massless field
displays itself upon dimensional reduction as a tower of St\"uckelberg
symmetries for the massive modes of the tower. Unlike the massless case, the
zero mode of the gauge symmetry does not display itself as a lower-dimensional
non-Stuckelberg gauge symmetry enforcing partial masslessness on the zero mode.
Partial masslessness is destroyed by the dimensional reduction and the zero
mode gauge symmetry instead serves to eliminate the radion. In addition, we
study the fully non-linear dimensional reduction of dRGT massive gravity on a
circle, which results in a massive scalar-tensor-vector theory which we expect
to be ghost-free, and whose scalar-tensor sector is a special case of
mass-varying massive gravity.


title:
EmpiriciSN: Re-sampling Observed Supernova/Host Galaxy Populations using
  an XD Gaussian Mixture Model

abstract:
  We describe two new open source tools written in Python for performing
extreme deconvolution Gaussian mixture modeling (XDGMM) and using a conditioned
model to re-sample observed supernova and host galaxy populations. XDGMM is new
program for using Gaussian mixtures to do density estimation of noisy data
using extreme deconvolution (XD) algorithms that has functionality not
available in other XD tools. It allows the user to select between the AstroML
(Vanderplas et al. 2012; Ivezic et al. 2015) and Bovy et al. (2011) fitting
methods and is compatible with scikit-learn machine learning algorithms
(Pedregosa et al. 2011). Most crucially, it allows the user to condition a
model based on the known values of a subset of parameters. This gives the user
the ability to produce a tool that can predict unknown parameters based on a
model conditioned on known values of other parameters. EmpiriciSN is an example
application of this functionality that can be used for fitting an XDGMM model
to observed supernova/host datasets and predicting likely supernova parameters
using on a model conditioned on observed host properties. It is primarily
intended for simulating realistic supernovae for LSST data simulations based on
empirical galaxy properties.


title:
Planets Around Low-Mass Stars (PALMS). VI. Discovery of a Remarkably Red
  Planetary-Mass Companion to the AB Dor Moving Group Candidate 2MASS
  J22362452+4751425

abstract:
  We report the discovery of an extremely red planetary-mass companion to 2MASS
J22362452+4751425, a $\approx$0.6 $M_{\odot}$ late-K dwarf likely belonging to
the $\sim$120 Myr AB Doradus moving group. 2M2236+4751 b was identified in
multi-epoch NIRC2 adaptive optics imaging at Keck Observatory at a separation
of 3.7$"$, or 230 $\pm$ 20 AU in projection at the kinematic distance of 63
$\pm$ 5 pc to its host star. Assuming membership in the AB Dor group, as
suggested from its kinematics, the inferred mass of 2M2236+4751 b is 11-14
$M_\mathrm{Jup}$. Follow-up Keck/OSIRIS $K$-band spectroscopy of the companion
reveals strong CO absorption similar to other faint red L dwarfs and lacks
signs of methane absorption despite having an effective temperature of
$\approx$900-1200 K. With a ($J$-$K$)$_\mathrm{MKO}$ color of 2.69 $\pm$ 0.12
mag, the near-infrared slope of 2M2236+4751 b is redder than all of the HR 8799
planets and instead resembles the $\approx$23 Myr isolated planetary-mass
object PSO J318.5-22, implying that similarly thick photospheric clouds can
persist in the atmospheres of giant planets at ages beyond 100 Myr. In
near-infrared color-magnitude diagrams, 2M2236+4751 b is located at the tip of
the red L dwarf sequence and appears to define the "elbow" of the AB Dor
substellar isochrone separating low-gravity L dwarfs from the cooler young T
dwarf track. 2M2236+4751 b is the reddest substellar companion to a star and
will be a valuable benchmark to study the shared atmospheric properties of
young low-mass brown dwarfs and extrasolar giant planets.


title: Multicomponent Dark Matter from Gauge Symmetry

abstract:
  The composition of Dark Matter (DM) remains an important open question. The
current data do not distinguish between single- and multi-component DM, while
in theory constructions it is often assumed that DM is composed of a single
field. In this work, we study a hidden sector which naturally entails
multicomponent DM consisting of spin-1 and spin-0 states. This UV complete
set-up is based on SU(3) hidden gauge symmetry with the minimal scalar field
content to break it spontaneously. The presence of multiple DM components is a
result of a residual Z_2 x Z'_2 symmetry which is part of an unbroken global
U(1) x Z'_2 inherent in the Yang-Mills systems. We find that the model exhibits
various parametric regimes with drastically different DM detection prospects.
In particular, we find that the direct detection cross section is much
suppressed in large regions of parameter space as long as the Standard Model
Higgs mixes predominantly with a single scalar from the hidden sector. The
resulting scattering rate is often beyond the level of sensitivity of XENON1T,
while still being consistent with the thermal WIMP paradigm.


title: On the Level of Cluster Assembly Bias in SDSS

abstract:
  Recently, several studies have discovered a strong discrepancy between the
large-scale clustering biases of two subsamples of galaxy clusters at the same
halo mass, split by their average projected membership distances
$R_{\mathrm{mem}}$. The level of this discrepancy significantly exceeds the
maximum halo assembly bias signal predicted by LCDM. In this study, we explore
whether some of the clustering bias differences could be caused by biases in
$R_{\mathrm{mem}}$ due to projection effects from other systems along the
line-of-sight. We thoroughly investigate the halo assembly bias of the
photometrically-detected redMaPPer clusters in SDSS, by defining a new variant
of the average membership distance estimator $\tilde{R}_{\mathrm{mem}}$ that is
more robust against projection effects in the cluster membership
identification. Using the angular mark correlation functions of clusters, we
show that the large-scale bias differences when splitting by $R_{\mathrm{mem}}$
can be largely attributed to such projection effects. After splitting by
$\tilde{R}_{\mathrm{mem}}$, the anomalously large signal is reduced, giving a
ratio of $1.02\pm0.14$ between the two clustering biases as measured from weak
lensing. Using a realistic mock cluster catalog, we predict that the bias ratio
between two $\tilde{R}_{\mathrm{mem}}$-split subsamples should be $<1.10$,
which is at least 60% weaker than the maximum halo assembly bias signal (1.24)
when split by halo concentration. Therefore, our results demonstrate that the
level of halo assembly bias exhibited by redMaPPer clusters in SDSS is
consistent with the LCDM prediction. With a ten-fold increase in cluster
numbers, deeper ongoing surveys will enable a more robust detection of halo
assembly bias. Our findings also have important implications for how projection
effects and their impact on cluster cosmology can be quantified in photometric
cluster catalogs.


title: The Galaxy End Sequence

abstract:
  A common assumption is that galaxies fall in two distinct regions on a plot
of specific star-formation rate (SSFR) versus galaxy stellar mass: a
star-forming Galaxy Main Sequence (GMS) and a separate region of `passive' or
`red and dead galaxies'. Starting from a volume-limited sample of nearby
galaxies designed to contain most of the stellar mass in this volume, and thus
being a fair representation of the Universe at the end of 12 billion years of
galaxy evolution, we investigate the distribution of galaxies in this diagram
today. We show that galaxies follow a strongly curved extended GMS with a steep
negative slope at high galaxy stellar masses. There is a gradual change in the
morphologies of the galaxies along this distribution, but there is no clear
break between early-type and late-type galaxies. Examining the other evidence
that there are two distinct populations, we argue that the `red sequence' is
the result of the colours of galaxies changing very little below a critical
value of the SSFR, rather than implying a distinct population of galaxies, and
that Herschel observations, which show at least half of early-type galaxies
contain a cool interstellar medium, also imply continuity between early-type
and late-type galaxies. This picture of a unitary population of galaxies
requires more gradual evolutionary processes than the rapid quenching processes
needed to to explain two distinct populations. We challenge theorists to
reproduce the properties of this `Galaxy End Sequence'.


title: Chiral Effective Theory of Dark Matter Direct Detection

abstract:
  We present the effective field theory for dark matter interactions with the
visible sector that is valid at scales of O(1 GeV). Starting with an effective
theory describing the interactions of fermionic and scalar dark matter with
quarks, gluons and photons via higher dimension operators that would arise from
dimension-five and dimension-six operators above electroweak scale, we perform
a nonperturbative matching onto a heavy baryon chiral perturbation theory that
describes dark matter interactions with light mesons and nucleons. This is then
used to obtain the coefficients of the nuclear response functions using a
chiral effective theory description of nuclear forces. Our results consistently
keep the leading contributions in chiral counting for each of the initial
Wilson coefficients.


title:
The Candidate Progenitor of the Type IIn SN 2010jl is Not an Optically
  Luminous Star

abstract:
  The nature of the progenitor star (or system) for the Type IIn supernova (SN)
subclass remains uncertain. While there are direct imaging constraints on the
progenitors of at least four Type IIn supernovae, one of them being SN 2010jl,
ambiguities remain in the interpretation of the unstable progenitors and the
explosive events themselves. A blue source in pre-explosion HST/WFPC2 images
falls within the 5 sigma astrometric error circle derived from post-explosion
ground-based imaging of SN 2010jl. At the time the ground-based astrometry was
published, however, the SN had not faded sufficiently for post-explosion HST
follow-up observations to determine a more precise astrometric solution and/or
confirm if the pre-explosion source had disappeared, both of which are
necessary to ultimately disentangle the possible progenitor scenarios. Here we
present HST/WFC3 imaging of the SN 2010jl field obtained in 2014 and 2015, when
the SN had faded sufficiently to allow for new constraints on the progenitor.
The SN, which is still detected in the new images, is offset by 0."099 +/-
0."008 (24 +/- 2 pc) from the underlying and extended source of emission that
contributes at least partially, if not entirely, to the blue source previously
suggested as the candidate progenitor in the WFPC2 data. This point alone rules
out the possibility that the blue source in the pre-explosion images is the
exploding star, but may instead suggest an association with a young (<5-6 Myr)
cluster and still argues for a massive (>30 solar masses) progenitor. We obtain
new upper limits on the flux from a single star at the SN position in the
pre-explosion WFPC2 and Spitzer/IRAC images that may ultimately be used to
constrain the progenitor properties.


title:
Critical success factors for m-commerce in Saudi Arabia's private sector
  -- a multiple case study analysis

abstract:
  Many developing country firms are investing huge money in the sector of
mobile commerce m commerce Simplifying and understanding the factors which can
impact on m commerce success enables the organisations managers to focus their
efforts on the key areas of their m commerce businesses thereby contributing to
the successful implementation of m commerce This study provides a clear
understanding of m commerce in the private sector in the Kingdom of Saudi
Arabia and identifies the critical success factors of implementing m commerce
within the local business environment A case study approach will be used for
five Saudi companies which use mcommerce represented by Alrajhi Bank Souqcom
Saudi Electricity Company Saudi telecom company STC and Saudi Airlines This
study represents a research in progress and interviews based on the literature
to identify the key success factors for these companies in particular and in
Saudi Arabia s private sector in general


title:
Energetics of H$_2$ clusters from density functional and coupled cluster
  theories

abstract:
  We use coupled-cluster quantum chemical methods to calculate the energetics
of molecular clusters cut out of periodic molecular hydrogen structures that
model observed phases of solid hydrogen. The hydrogen structures are obtained
from Kohn-Sham density functional theory (DFT) calculations at pressures of
150, 250 and 350 GPa, which are within the pressure range in which phases II,
III and IV are found to be stable. The calculated deviations in the DFT
energies from the coupled-cluster data are reported for different functionals,
and optimized functionals are generated which provide reduced errors. We give
recommendations for semi-local and hybrid density functionals that are expected
to accurately describe hydrogen at high pressures.


title:
The Impact of Unresolved Turbulence on the Escape Fraction of Lyman
  Continuum Photons

abstract:
  We investigate the relation between the turbulent Mach number (\mach) and the
escape fraction of Lyman continuum photons ($f_{\rm esc}$) in high-redshift
galaxies. Approximating the turbulence as isothermal and isotropic, we show
that the increase in the variance in column densities from $\mathcal{M}=1$ to
$\mathcal{M}=10$ causes $f_{\rm esc}$ to increase by $\approx 25$\%, and the
increase from $\mathcal{M}=1$ to $\mathcal{M}=20$ causes $f_{\rm esc}$ to
increases by $\approx 50$\% for a medium with opacity $\tau\approx1$. At a
fixed Mach number, the correction factor for escape fraction relative to a
constant column density case scales exponentially with the opacity in the cell,
which has a large impact for simulated star forming regions. Furthermore, in
simulations of isotropic turbulence with full atomic/ionic cooling and
chemistry, the fraction of HI drops by a factor of $\approx 2.5$ at
$\mathcal{M}\approx10$ even when the mean temperature is $\approx5\times10^3
K$. If turbulence is unresolved, these effects together enhance $f_{\rm esc}$
by a factor $>3$ at Mach numbers above 10. Such Mach numbers are common at
high-redshifts where vigorous turbulence is driven by supernovae, gravitational
instabilities, and merger activity, as shown both by numerical simulations and
observations. These results, if implemented in the current hydrodynamical
cosmological simulations to account for unresolved turbulence, can boost the
theoretical predictions of the Lyman Continuum photon escape fraction and
further constrain the sources of reionization.


title: Neutrino Interactions and Long-Baseline Experiments

abstract:
  The extraction of neutrino mixing parameters and the CP-violating phase
requires knowledge of the neutrino energy. This energy must be reconstructed
from the final state of a neutrino-nucleus reaction since all long-baseline
experiments use nuclear targets. This reconstruction requires detailed
knowledge of the neutrino reactions with bound nucleons and of the final state
interactions of hadrons with the nuclear environment. Quantum-kinetic transport
theory can be used to build an event generator for this reconstruction that
takes basic nuclear properties, such as binding, into account. Some examples
are discussed that show the effects of nuclear interactions on observables in
long-baseline experiments


title:
A secure service provisioning framework for cyber physical cloud
  computing systems

abstract:
  Cyber physical systems (CPS) are mission critical systems engineered by
combination of cyber and physical systems respectively. These systems are
tightly coupled, resource constrained systems and have dynamic real time
applications. Due to the limitation of resources, and in order to improve the
efficiency of the CPS systems, they are combined with cloud computing
architecture, and are called as Cyber Physical Cloud Computing Systems (CPCCS).
These CPCCS have critical care applications where security of the systems is a
major concern. Therefore, we propose a Secure Service provisioning architecture
for Cyber Physical Cloud Computing Systems (CPCCS), which includes the
combination of technologies such as CPS, Cloud Computing and Wireless Sensor
Networks. In addition to this, we also highlight various threats/attacks;
security requirements and mechanisms that are applicable to CPCCS at different
layers and propose two security models that can be adapted in a layered
architectural format.


title: The SLH framework for modeling quantum input-output networks

abstract:
  Many emerging quantum technologies demand precise engineering and control
over networks consisting of quantum mechanical degrees of freedom connected by
propagating electromagnetic fields, or quantum input-output networks. Here we
review recent progress in theory and experiment related to such quantum
input-output networks, with a focus on the SLH framework, a powerful modeling
framework for networked quantum systems that is naturally endowed with
properties such as modularity and hierarchy. We begin by explaining the
physical approximations required to represent any individual node of a network,
eg. atoms in cavity or a mechanical oscillator, and its coupling to quantum
fields by an operator triple $(S,L,H)$. Then we explain how these nodes can be
composed into a network with arbitrary connectivity, including coherent
feedback channels, using algebraic rules, and how to derive the dynamics of
network components and output fields. The second part of the review discusses
several extensions to the basic SLH framework that expand its modeling
capabilities, and the prospects for modeling integrated implementations of
quantum input-output networks. In addition to summarizing major results and
recent literature, we discuss the potential applications and limitations of the
SLH framework and quantum input-output networks, with the intention of
providing context to a reader unfamiliar with the field.


title: Early Cosmology Constrained

abstract:
  We investigate our knowledge of early universe cosmology by exploring how
much additional energy density can be placed in different components beyond
those in the $\Lambda$CDM model. To do this we use a method to separate early-
and late-universe information enclosed in observational data, thus markedly
reducing the model-dependency of the conclusions. We find that the 95\%
credibility regions for extra energy components of the early universe at
recombination are: non-accelerating additional fluid density parameter
$\Omega_{\rm MR} < 0.006$ and extra radiation parameterised as extra effective
neutrino species $2.3 < N_{\rm eff} < 3.2$ when imposing flatness. Our
constraints thus show that even when analyzing the data in this largely
model-independent way, the possibility of hiding extra energy components beyond
$\Lambda$CDM in the early universe is seriously constrained by current
observations. We also find that the standard ruler, the sound horizon at
radiation drag, can be well determined in a way that does not depend on
late-time Universe assumptions, but depends strongly on early-time physics and
in particular on additional components that behave like radiation. We find that
the standard ruler length determined in this way is $r_{\rm s} = 147.4 \pm 0.7$
Mpc if the radiation and neutrino components are standard, but the uncertainty
increases by an order of magnitude when non-standard dark radiation components
are allowed, to $r_{\rm s} = 150 \pm 5$ Mpc.


title: Collaboration Networks in the Music Industry

abstract:
  Recording an album brings singers, producers, musicians, audio engineers, and
many other professions together. We know from the press that a few
"super"-producers work with many artists. But how does the large-scale social
structure of the music industry look like? What is the social network behind
the finest albums of all time? In this paper we studied the large-scale
structure of music collaborations using the tools of network science. We
considered all albums in Rolling Stone Magazine's list of '500 Greatest Albums
of All Time' and the '1001 Albums You Must Hear Before You Die' by Robert
Dimery. We found that the existing research on collaboration networks is
corroborated by the particular collaboration network in the music industry.
Furthermore, it has been found that the most important professions of the music
industry in terms of connectivity were main artists and engineers.


title: Phenomenology of hard diffraction at high energies

abstract:
  We present some of the topics covered in two lectures under the same title
that were given at the "Summer School on High Energy Physics at the LHC: New
trends in HEP" in Natal, Brazil. In this contribution we give a brief review on
the application of perturbative QCD to the hard diffractive processes. Some
examples of phenomenology for the diffractive production of $W/Z$, heavy
$Q\bar{Q}$ and quarkonium in hadron-hadron reactions are presented. It is also
discussed the exclusive diffractive processes in $ep$ interactions. They are in
general driven by the gluon content of proton which is strongly subject to
parton saturation effects in the very high energy limit. These saturation
effects are well described within the color dipole formalism. We present some
examples of corresponding phenomenology as the elastic vector meson production
and the DVCS relying on the color dipole approach.


title: The Machine Learning Algorithm as Creative Musical Tool

abstract:
  Machine learning is the capacity of a computational system to learn
structures from datasets in order to make predictions on newly seen data. Such
an approach offers a significant advantage in music scenarios in which
musicians can teach the system to learn an idiosyncratic style, or can break
the rules to explore the system's capacity in unexpected ways. In this chapter
we draw on music, machine learning, and human-computer interaction to elucidate
an understanding of machine learning algorithms as creative tools for music and
the sonic arts. We motivate a new understanding of learning algorithms as
human-computer interfaces. We show that, like other interfaces, learning
algorithms can be characterised by the ways their affordances intersect with
goals of human users. We also argue that the nature of interaction between
users and algorithms impacts the usability and usefulness of those algorithms
in profound ways. This human-centred view of machine learning motivates our
concluding discussion of what it means to employ machine learning as a creative
tool.


title: Cardy Formula for 4d SUSY Theories and Localization

abstract:
  We study 4d $\mathcal{N}=1$ supersymmetric theories on a compact Euclidean
manifold of the form $S^1 \times\mathcal{M}_3$. Partition functions of gauge
theories on this background can be computed using localization, and explicit
formulas have been derived for different choices of the compact manifold
$\mathcal{M}_3$. Taking the limit of shrinking $S^1$, we present a general
formula for the limit of the localization integrand, derived by simple
effective theory considerations, generalizing the result of arXiv:1512.03376.
The limit is given in terms of an effective potential for the holonomies around
the $S^1$, whose minima determine the asymptotic behavior of the partition
function. If the potential is minimized in the origin, where it vanishes, the
partition function has a Cardy-like behavior fixed by $\mathrm{Tr}(R)$, while a
nontrivial minimum gives a shift in the coefficient. In all the examples that
we consider, the origin is a minimum if $\mathrm{Tr}(R) \leq 0$.


title: Comments on an image encryption scheme based on a chaotic Tent map

abstract:
  Recently an image encryption scheme based on a chaotic Tent map has been
proposed by Li et al. This comment shows that this scheme is broken and no
secure application can be found for it.


title: Motivic Homotopical Galois Extensions

abstract:
  We establish a formal framework for Rognes's homotopical Galois theory and
adapt it to the context of motivic spaces and spectra. We discuss examples of
Galois extensions between Eilenberg-MacLane motivic spectra and between the
Hermitian and algebraic K-theory spectra.


title:
Self-healing properties of 1-amino, 2,4-dibromo anthraquinone dye doped
  in PMMA polymer

abstract:
  We used fluorescence spectroscopic measurements as a probe to study the
self-healing properties of anthraquinone derivative molecules doped in
poly(methyl methacrylate) (PMMA). 2,4-dibromo anthraquinone dye doped in PMMA
recovers after photodegradation. Its dynamics differs from other anthraquinone
derivative molecules. This could be due to the relatively heavier bromine atom
attached to one of the carbon atoms of the benzene ring. In this paper, we will
discuss the self-healing properties of 2,4-dibromo anthraquinone doped in PMMA
matrix. We also tested the correlated chromophore domain model (CCrDM) and have
characterized the self-healing properties by determining the CCrDM parameters.
We also estimated the self-absorption of fluorescence signal by the dye
molecule without which the analysis of the self-recovery of the molecule would
be incomplete.


title:
CB2CF: A Neural Multiview Content-to-Collaborative Filtering Model for
  Completely Cold Item Recommendations

abstract:
  In Recommender Systems research, algorithms are often characterized as either
Collaborative Filtering (CF) or Content Based (CB). CF algorithms are trained
using a dataset of user preferences while CB algorithms are typically based on
item profiles. These approaches harness different data sources and therefore
the resulting recommended items are generally very different. This paper
presents the CB2CF, a deep neural multiview model that serves as a bridge from
items content into their CF representations. CB2CF is a real-world algorithm
designed for Microsoft Store services that handle around a billion users
worldwide. CB2CF is demonstrated on movies and apps recommendations, where it
is shown to outperform an alternative CB model on completely cold items.


title:
Magnetically Localizing Heat or Enhancing Equilibration in a Quasi 1D
  Magnetic Fluid

abstract:
  Using two different configurations of temperature and magnetic field
gradients, we observed that, in a quasi one-dimensional magnetic fluid,
magnetic force either reduces the temperature difference across the sample when
the two gradients are parallel to each other (PL), or increase the temperature
difference when the two gradients are antiparallel (AP), where the single
convection roll in zero field was replaced by two localized flows at the two
ends of the sample cell. This flow structure stops the heat flow of approaching
to thermal equilibrium in the system, causing the temperature at hot side of
the sample cell getting hotter and cold side becoming colder. None of these
phenomena can be described by the existing theories of magnetically-induced
instabilities. The underlying physics for observed results for AP configuration
has been proposed as the mechanism to drive a new type of heat engines that has
much higher efficiency than Carnot engines and has no pollution to the
environment, our results point to the potential feasibility of this proposed
mechanism.


title: Folding kinetics of a polymer [corrigendum]

abstract:
  In our original article (Phys. Chem. Chem. Phys., 2012, 14, 60446053) a
convergence problem resulted in an averaging error in computing the entropy
from a set of Wang-Landau Monte-Carlo simulations. Here we report corrected
results for the freezing temperature of the homopolymer chain as a function of
the range of the non-bonded interaction. We find that the previously reported
forward-flux sampling (FFS) and brute-force (BF) simulation results are in
agreement with the revised Wang-Landau (WL) calculations. This confirms the
utility of FFS for computing crystallisation rates in systems of this kind.


title:
Comparison theorems for summability methods of sequences of fuzzy
  numbers

abstract:
  In this study we compare Ces\`{a}ro and Euler weighted mean methods of
summability of sequences of fuzzy numbers with Abel and Borel power series
methods of summability of sequences of fuzzy numbers. Also some results dealing
with series of fuzzy numbers are obtained.


title: Automated scalable segmentation of neurons from multispectral images

abstract:
  Reconstruction of neuroanatomy is a fundamental problem in neuroscience.
Stochastic expression of colors in individual cells is a promising tool,
although its use in the nervous system has been limited due to various sources
of variability in expression. Moreover, the intermingled anatomy of neuronal
trees is challenging for existing segmentation algorithms. Here, we propose a
method to automate the segmentation of neurons in such (potentially
pseudo-colored) images. The method uses spatio-color relations between the
voxels, generates supervoxels to reduce the problem size by four orders of
magnitude before the final segmentation, and is parallelizable over the
supervoxels. To quantify performance and gain insight, we generate simulated
images, where the noise level and characteristics, the density of expression,
and the number of fluorophore types are variable. We also present segmentations
of real Brainbow images of the mouse hippocampus, which reveal many of the
dendritic segments.


title: Option pricing in exponential L\'evy models with transaction costs

abstract:
  We present an approach for pricing European call options in presence of
proportional transaction costs, when the stock price follows a general
exponential L\'{e}vy process. The model is a generalization of the celebrated
work of Davis, Panas and Zariphopoulou (1993), where the value of the option is
defined as the utility indifference price. This approach requires the solution
of two stochastic singular control problems in finite horizon, satisfying the
same Hamilton-Jacobi-Bellman equation, with different terminal conditions. We
introduce a general formulation for these portfolio selection problems, and
then we focus on the special case in which the probability of default is
ignored. We solve numerically the optimization problems using the Markov chain
approximation method and show results for diffusion, Merton and Variance Gamma
processes. Option prices are computed for both the writer and the buyer.


title:
Films, layers and droplets: The effect of near-wall fluid structure on
  spreading dynamics

abstract:
  We present a study of the spreading of liquid droplets on a solid substrate
at very small scales. We focus on the regime where effective wetting energy
(binding potential) and surface tension effects significantly influence steady
and spreading droplets. In particular, we focus on strong packing and layering
effects in the liquid near the substrate due to underlying density oscillations
in the fluid caused by attractive substrate-liquid interactions. We show that
such phenomena can be described by a thin-film (or long-wave or lubrication)
model including an oscillatory Derjaguin (or disjoining/conjoining) pressure,
and explore the effects it has on steady droplet shapes and the spreading
dynamics of droplets on both, an adsorption (or precursor) layer and completely
dry substrates. At the molecular scale, commonly used two-term binding
potentials with a single preferred minimum controlling the adsorption layer
height are inadequate to capture the rich behaviour caused by the near-wall
layered molecular packing. The adsorption layer is often sub-monolayer in
thickness, i.e., the dynamics along the layer consists of single-particle
hopping, leading to a diffusive dynamics, rather than the collective
hydrodynamic motion implicit in standard thin-film models. We therefore modify
the model in such a way that for thicker films the standard hydrodynamic theory
is realised, but for very thin layers a diffusion equation is recovered.


title: Branes through finite group actions

abstract:
  Mid-dimensional $(A,B,A)$ and $(B,B,B)$-branes in the moduli space of flat
$G_{\mathbb C}$-connections appearing from finite group actions on compact
Riemann surfaces are studied. The geometry and topology of these spaces is then
described via the corresponding Higgs bundles and Hitchin fibrations.


title:
Cosmological perturbations in an effective and genuinely phantom dark
  energy Universe

abstract:
  We carry out an analysis of the cosmological perturbations in general
relativity for three different models which are good candidates to describe the
current acceleration of the Universe. These three set-ups are described
classically by perfect fluids with a phantom nature and represent deviations
from the most widely accepted $\Lambda$CDM model. In addition, each of the
models under study induce different future singularities or abrupt events known
as (i) Big Rip, (ii) Little Rip and (iii) Little Sibling of the Big Rip. Only
the first one is regarded as a true singularity since it occurs at a finite
cosmic time. For this reason, we refer to the others as abrupt events. With the
aim to find possible footprints of this scenario in the Universe matter
distribution, we not only obtain the evolution of the cosmological scalar
perturbations but also calculate the matter power spectrum for each model. We
have carried the perturbations in the absence of any anisotropic stress and
within a phenomenological approach for the speed of sound. We constrain
observationally these models using several measurements of the growth rate
function, more precisely $f\sigma_8$, and compare our results with the
observational ones.


title: Combining Multiple Cues for Visual Madlibs Question Answering

abstract:
  This paper presents an approach for answering fill-in-the-blank multiple
choice questions from the Visual Madlibs dataset. Instead of generic and
commonly used representations trained on the ImageNet classification task, our
approach employs a combination of networks trained for specialized tasks such
as scene recognition, person activity classification, and attribute prediction.
We also present a method for localizing phrases from candidate answers in order
to provide spatial support for feature extraction. We map each of these
features, together with candidate answers, to a joint embedding space through
normalized canonical correlation analysis (nCCA). Finally, we solve an
optimization problem to learn to combine scores from nCCA models trained on
multiple cues to select the best answer. Extensive experimental results show a
significant improvement over the previous state of the art and confirm that
answering questions from a wide range of types benefits from examining a
variety of image cues and carefully choosing the spatial support for feature
extraction.


title: Backreaction Issues in Axion Monodromy and Minkowski 4-forms

abstract:
  We clarify the differences between the usual Kaloper-Sorbo description of
axion monodromy and the effective axionic potential in terms of Minkowski
4-forms derived in string compactifications. The fact that the metric of the
3-form fields coming from string theory is field dependent (unlike in
Kaloper-Sorbo) leads to the backreaction issues recently studied in axion
monodromy models within string theory. We reanalyse these problems in terms of
the 4-forms focusing on the case in which the non-periodic scalars backreact on
the Kahler metric of the inflaton reducing the physical field range. In the
closed string sector of Type II Calabi-Yau compactifications with fluxes the
metric becomes field dependent precisely when $\Delta\phi\sim M_p$,
independently of the choice of fluxes. We propose, however, some
counter-examples to this universal behaviour by including open string fields.


title: Finite temperature quantum embedding theories for correlated systems

abstract:
  The cost of the exact solution of the many-electron problem is believed to be
exponential in the number of degrees of freedom, necessitating approximations
that are controlled and accurate but numerically tractable. In this paper, we
show that one of these approximations, the self-energy embedding theory (SEET),
is derivable from a universal functional and therefore implicitly satisfies
conservation laws and thermodynamic consistency. We also show how other
approximations, such as the dynamical mean field theory (DMFT) and its
combinations with many-body perturbation theory, can be understood as a special
case of SEET and discuss how the additional freedom present in SEET can be used
to obtain systematic convergence of results.


title: Parity-time-symmetric quantum critical phenomena

abstract:
  Synthetic nonconservative systems with parity-time (PT) symmetric gain-loss
structures can exhibit unusual spontaneous symmetry breaking that accompanies
spectral singularity. Recent studies on PT symmetry in optics and weakly
interacting open quantum systems have revealed intriguing physical properties,
yet many-body correlations still play no role. Here by extending the idea of PT
symmetry to strongly correlated many-body systems, we report that a combination
of spectral singularity and quantum criticality yields an exotic universality
class which has no counterpart in known critical phenomena. Moreover, we find
unconventional low-dimensional quantum criticality, where superfluid
correlation is anomalously enhanced owing to non-monotonic renormalization
group flows in a PT-symmetry-broken quantum critical phase, in stark contrast
to the Berezinskii-Kosterlitz-Thouless paradigm. Our findings can be
experimentally tested in ultracold atoms and predict critical phenomena beyond
the Hermitian paradigm of quantum many-body physics.

categories: cond-mat.stat-mech cond-mat.quant-gas physics.optics quant-ph


title:
Ultra Short Period Planets in K2 with companions: a double transiting
  system for EPIC 220674823

abstract:
  Two transiting planets have been identified orbiting K2 target EPIC
220674823. One object is an ultra-short-period planet (USP) with a period of
just 0.57 days (13.7 hours), while the other has a period of 13.3 days. Both
planets are small, with the former having a radius of R_p1=1.5 R_E and the
latter R_p2=2.5 R_E. Follow-up observations, including radial velocity (with
uncertainties of 110 m/s) and high-resolution adaptive optics imagery, show no
signs of stellar companions. EPIC 220674823 is the 12th confirmed or validated
planetary system in which an ultra-short-period planet (i.e., having an orbital
period less than 1 day) is accompanied by at least one additional planet,
suggesting that such systems may be common and must be accounted for in models
for the formation and evolution of such extreme systems.


title: Orthogonal samples for estimators in time series

abstract:
  Inference for statistics of a stationary time series often involve nuisance
parameters and sampling distributions that are difficult to estimate. In this
paper, we propose the method of orthogonal samples, which can be used to
address some of these issues. For a broad class of statistics, an orthogonal
sample is constructed through a slight modification of the original statistic,
such that it shares similar distributional properties as the centralised
statistic of interest. We use the orthogonal sample to estimate nuisance
parameters of weighted average periodogram estimators and $L_{2}$-type spectral
statistics. Further, the orthogonal sample is utilized to estimate the finite
sampling distribution of various test statistics under the null hypothesis. The
proposed method is simple and computationally fast to implement. The viability
of the method is illustrated with various simulations.


title: Black hole shadows in fourth-order conformal Weyl gravity

abstract:
  We calculate the characteristics of the "black hole shadow" for a rotating,
neutral black hole in fourth-order conformal Weyl gravity. It is shown that the
morphology is not significantly affected by the underlying framework, except
for very large masses. Conformal gravity black hole shadows would also
significantly differ from their general relativistic counterparts if the values
of the main conformal gravity parameters, $\gamma$ and $\kappa$, were increased
by several orders of magnitude. Such increased values for $\gamma$ and $\kappa$
are currently ruled out by gravitational phenomenology. Therefore, it is
unlikely that these differences in black hole shadows will be detected in
future observations, carried out by the Event Horizon Telescope or other such
experiments.


title: Minimum Average Deviance Estimation for Sufficient Dimension Reduction

abstract:
  Sufficient dimension reduction reduces the dimensionality of data while
preserving relevant regression information. In this article, we develop Minimum
Average Deviance Estimation (MADE) methodology for sufficient dimension
reduction. It extends the Minimum Average Variance Estimation (MAVE) approach
of Xia et al. (2002) from continuous responses to exponential family
distributions to include Binomial and Poisson responses. Local likelihood
regression is used to learn the form of the regression function from the data.
The main parameter of interest is a dimension reduction subspace which projects
the covariates to a lower dimension while preserving their relationship with
the outcome. To estimate this parameter within its natural space, we consider
an iterative algorithm where one step utilizes a Stiefel manifold optimizer. We
empirically evaluate the performance of three prediction methods, two that are
intrinsic to local likelihood estimation and one that is based on the
Nadaraya-Watson estimator. Initial results show that, as expected, MADE can
outperform MAVE when there is a departure from the assumption of additive
errors.


title: Games for Bisimulations and Abstraction

abstract:
  Weak bisimulations are typically used in process algebras where silent steps
are used to abstract from internal behaviours. They facilitate relating
implementations to specifications. When an implementation fails to conform to
its specification, pinpointing the root cause can be challenging. In this paper
we provide a generic characterisation of branching-, delayed-, $\eta$- and
weak-bisimulation as a game between Spoiler and Duplicator, offering an
operational understanding of the relations. We show how such games can be used
to assist in diagnosing non-conformance between implementation and
specification. Moreover, we show how these games can be extended to distinguish
divergences.


title:
OVI Emission From the Supernovae-regulated Interstellar Medium:
  Simulation Vs Observation

abstract:
  The OVI $\lambda\lambda$1032, 1038\AA\ doublet emission traces collisionally
ionized gas with $T\approx 10^{5.5}$ K, where the cooling curve peaks for
metal-enriched plasma. This warm-hot phase is usually not well-resolved in
numerical simulations of the multiphase interstellar medium (ISM), but can be
responsible for a significant fraction of the emitted energy. Comparing
simulated OVI emission to observations is therefore a valuable test of whether
simulations predict reasonable cooling rates from this phase. We calculate OVI
$\lambda$1032\AA\ emission, assuming collisional ionization equilibrium, for
our small-box simulations of the stratified ISM regulated by supernovae. We
find that the agreement is very good for our solar neighborhood model, both in
terms of emission flux and mean OVI density seen in absorption. We explore runs
with higher surface densities and find that, in our simulations, the OVI
emission from the disk scales roughly linearly with the star formation rate.
Observations of OVI emission are rare for external galaxies, but our results do
not show obvious inconsistency with the existing data. Assuming the solar
metallicity, OVI emission from the galaxy disk in our simulations accounts for
roughly 0.5\% of supernovae heating.


title:
An Experimental Investigation of Hyperbolic Routing with a Smart
  Forwarding Plane in NDN

abstract:
  Routing in NDN networks must scale in terms of forwarding table size and
routing protocol overhead. Hyperbolic routing (HR) presents a potential
solution to address the routing scalability problem, because it does not use
traditional forwarding tables or exchange routing updates upon changes in
network topologies. Although HR has the drawbacks of producing sub-optimal
routes or local minima for some destinations, these issues can be mitigated by
NDN's intelligent data forwarding plane. However, HR's viability still depends
on both the quality of the routes HR provides and the overhead incurred at the
forwarding plane due to HR's sub-optimal behavior. We designed a new forwarding
strategy called Adaptive Smoothed RTT-based Forwarding (ASF) to mitigate HR's
sub-optimal path selection. This paper describes our experimental investigation
into the packet delivery delay and overhead under HR as compared with
Named-Data Link State Routing (NLSR), which calculates shortest paths. We run
emulation experiments using various topologies with different failure
scenarios, probing intervals, and maximum number of next hops for a name
prefix. Our results show that HR's delay stretch has a median close to 1 and a
95th-percentile around or below 2, which does not grow with the network size.
HR's message overhead in dynamic topologies is nearly independent of the
network size, while NLSR's overhead grows polynomially at least. These results
suggest that HR offers a more scalable routing solution with little impact on
the optimality of routing paths.


title:
Per-Server Dominant-Share Fairness (PS-DSF): A Multi-Resource Fair
  Allocation Mechanism for Heterogeneous Servers

abstract:
  Users of cloud computing platforms pose different types of demands for
multiple resources on servers (physical or virtual machines). Besides
differences in their resource capacities, servers may be additionally
heterogeneous in their ability to service users - certain users' tasks may only
be serviced by a subset of the servers. We identify important shortcomings in
existing multi-resource fair allocation mechanisms - Dominant Resource Fairness
(DRF) and its follow up work - when used in such environments. We develop a new
fair allocation mechanism called Per-Server Dominant-Share Fairness (PS-DSF)
which we show offers all desirable sharing properties that DRF is able to offer
in the case of a single "resource pool" (i.e., if the resources of all servers
were pooled together into one hypothetical server). We evaluate the performance
of PS-DSF through simulations. Our evaluation shows the enhanced efficiency of
PS-DSF compared to the existing allocation mechanisms. We argue how our
proposed allocation mechanism is applicable in cloud computing networks and
especially large scale data-centers.


title:
Hubbard pair cluster in the external fields. Studies of the chemical
  potential

abstract:
  The chemical potential of the two-site Hubbard cluster (pair) embedded in the
external electric and magnetic fields is studied by exact diagonalization of
the Hamiltonian. The formalism of the grand canonical ensemble is adopted. The
influence of temperature, Hubbard on-site Coulombic energy $U$ and electron
concentration on the chemical potential is investigated and illustrated in
figures. In particular, a discontinuous behaviour of the chemical potential (or
electron concentration) in the ground state is discussed.


title: Photodetectors and front-end electronics for the LHCb RICH upgrade

abstract:
  The RICH detectors of the LHCb experiment provide identification of hadrons
produced in high energy proton-proton collisions in the LHC at CERN over a wide
momentum range (2 to 100 GeV/c). Cherenkov light is collected on photon
detector planes sensitive to single photons. The RICH will be upgraded (in
2019) to read out every bunch crossing, at a rate of 40 MHz. The current hybrid
photon detectors (HPD) will be replaced with multi-anode photomultiplier tubes
(customisations of the Hamamatsu R11265 and the H12699 MaPMTs). These
8$\times$8 pixel devices meet the experimental requirements thanks to their
small pixel size, high gain, negligible dark count rate ($\sim$50 Hz/cm$^2$)
and moderate cross-talk. The measured performance of several tubes is reported,
together with their long-term stability. A new 8-channel front-end chip, named
CLARO, has been designed in 0.35 $\mu$m CMOS AMS technology for the MaPMT
readout. The CLARO chip operates in binary mode and combines low power
consumption (\hbox{$\sim$1 mW/Ch}), wide bandwidth (baseline restored in
$\leq$25 ns) and radiation hardness. A 12-bit digital register permits the
optimisation of the dynamic range and the threshold level for each channel and
provides tools for the on-site calibration. The design choices and the
characterization of the electronics are presented.


title:
Synthetic absorption lines for a clumpy medium: a spectral signature for
  cloud acceleration in AGN?

abstract:
  There is increasing evidence that the highly ionized multiphase components of
AGN disk winds may be due to thermal instability. The ions responsible for
forming the observed X-ray absorption lines may only exist in relatively cold
clumps that can be identified with the so-called 'warm absorbers'. Here we
calculate synthetic absorption lines for such warm absorbers from first
principles by combining 2D hydrodynamic solutions of a two-phase medium with a
dense grid of photoionization models to determine the detailed ionization
structure of the gas. Our calculations reveal that cloud disruption, which
leads to a highly complicated velocity field (i.e. a clumpy flow), will only
mildly affect line shapes and strengths when the cold gas becomes highly mixed
but not depleted. Prior to complete disruption, clouds which are optically thin
to the driving UV resonance lines will cause absorption at an increasingly
blueshifted line of sight velocity as they are accelerated. This behavior will
imprint an identifiable signature on the line profile if warm absorbers are
enshrouded in an even broader absorption line produced by a high column of
intercloud gas. Interestingly, we show that it is possible to develop a
spectral diagnostic for cloud acceleration by differencing the absorption
components of a doublet line, a result which can be qualitatively understood
using a simple partial covering model. Our calculations also permit us to
comment on the spectral differences between cloud disruption and ionization
changes driven by flux variability. Notably, cloud disruption offers another
possibility for explaining absorption line variability.


title:
Momentum-driven outflow emission from an O-type YSO: Comparing the radio
  jet with the molecular outflow

abstract:
  Aims: We want to study the physical properties of the ionized jet emission in
the vicinity of an O-type young stellar object (YSO), and estimate how
efficient is the transfer of energy and momentum from small- to large-scale
outflows. Methods: We conducted Karl G. Jansky Very Large Array (VLA)
observations, at both 22 and 45 GHz, of the compact and faint radio continuum
emission in the high-mass star-forming region G023.01-00.41, with an angular
resolution between 0.3" and 0.1", and a thermal rms of the order of 10
uJy/beam. Results: We discovered a collimated thermal (bremsstrahlung) jet
emission, with a radio luminosity (L_rad) of 24 mJy kpc^2 at 45 GHz, in the
inner 1000 AU from an O-type YSO. The radio thermal jet has an opening angle of
44 degrees and brings a momentum rate of 8 10^-3 M_sun yr^-1 km/s. By combining
the new data with previous observations of the molecular outflow and water
maser shocks, we can trace the outflow emission from its driving source through
the molecular clump, across more than two order of magnitude in length (500
AU-0.2 pc). We find that the momentum-transfer efficiency, between the inner
jet emission and the extended outflow of entrained ambient gas, is near unity.
This result suggests that the large-scale flow is swept-up by the mechanical
force of the radio jet emission, which originates in the inner 1000 AU from the
high-mass YSO.


title: Blurred stochastic chains

abstract:
  Assume we have two stochastic chains taking values in a finite alphabet.
These chains may be of infinite order. Assume also that these chains are
coupled in such a way that given the past of both chains they have a not too
large probability of differing. This is the case when we observe a chain
through a noisy channel. This situation presumably also occurs in models for
the brain activity when a chain of stimuli is presented to a volunteer and we
observe a corresponding chain of neurophysiological recordings. The question is
how these two chains are quantitatively related. Under suitable conditions, we
obtain upper-bounds for the differences between the marginal conditional
distributions of the two chains and between the probability of the next symbol
of each chain, given the past of the past of one of them.


title: Drinfeld Orbifold Algebras for Symmetric Groups

abstract:
  Drinfeld orbifold algebras are a type of deformation of skew group algebras
generalizing graded Hecke algebras of interest in representation theory,
algebraic combinatorics, and noncommutative geometry. In this article, we
classify all Drinfeld orbifold algebras for symmetric groups acting by the
natural permutation representation. This provides, for nonabelian groups,
infinite families of examples of Drinfeld orbifold algebras that are not graded
Hecke algebras. We include explicit descriptions of the maps recording
commutator relations and show there is a one-parameter family of such maps
supported only on the identity and a three-parameter family of maps supported
only on 3-cycles and 5-cycles. Each commutator map must satisfy properties
arising from a Poincar\'{e}-Birkhoff-Witt condition on the algebra, and our
analysis of the properties illustrates reduction techniques using orbits of
group element factorizations and intersections of fixed point spaces.


title: Laplacian growth, sandpiles and scaling limits

abstract:
  Laplacian growth is the study of interfaces that move in proportion to
harmonic measure. Physically, it arises in fluid flow and electrical problems
involving a moving boundary. We survey progress over the last decade on
discrete models of (internal) Laplacian growth, including the abelian sandpile,
internal DLA, rotor aggregation, and the scaling limits of these models on the
lattice Z^d as the mesh size goes to zero. These models provide a window into
the tools of discrete potential theory: harmonic functions, martingales,
obstacle problems, quadrature domains, Green functions, smoothing. We also
present one new result: rotor aggregation in Z^d has O(log r) fluctuations
around a Euclidean ball, improving a previous power-law bound. We highlight
several open questions, including whether these fluctuations are O(1).


title: A nonlinear free boundary problem with a self-driven Bernoulli condition

abstract:
  We study a Bernoulli type free boundary problem with two phases
$$J[u]=\int_{\Omega}|\nabla u(x)|^2\,dx+\Phi\big({\mathcal M}_-(u),
{\mathcal{M}}_+(u)\big), \quad u-\bar u\in W^{1,2}_0(\Omega), $$ where $\bar
u\in W^{1,2}(\Omega)$ is a given boundary datum. Here, ${\mathcal M}_1$ and
${\mathcal M}_2$ are weighted volumes of $\{u\le 0\}\cap \Omega$ and
$\{u>0\}\cap \Omega$, respectively, and $\Phi$ is a nonnegative function of two
real variables.
  We show that, for this problem, the Bernoulli constant, which determines the
gradient jump condition across the free boundary, is of global type and it is
indeed determined by the weighted volumes of the phases.
  In particular, the Bernoulli condition that we obtain can be seen as a
pressure prescription in terms of the volume of the two phases of the minimizer
itself (and therefore it depends on the minimizer itself and not only on the
structural constants of the problem).
  Another property of this type of problems is that the minimizer in $\Omega$
is not necessarily a minimizer in a smaller subdomain, due to the nonlinear
structure of the problem.
  Due to these features, this problem is highly unstable as opposed to the
classical case studied by Alt, Caffarelli and Friedman. It also interpolates
the classical case, in the sense that the blow-up limits of $u$ are minimizers
of the Alt-Caffarelli-Friedman functional. Namely, the energy of the problem
somehow linearizes in the blow-up limit.
  As a special case, we can deal with the energy levels generated by the volume
term $\Phi(0, r_2)=r_2^{\frac{n-1}n}$, which interpolates the
Athanasopoulos-Caffarelli-Kenig-Salsa energy, thanks to the isoperimetric
inequality.
  In particular, we develop a detailed optimal regularity theory for the
minimizers and for their free boundaries.


title: Discordlike correlation of bipartite coherence

abstract:
  Quantum discord has been studied extensively as a measure of non-classical
correlations which includes entanglement as a subset. Although it is well known
that non-zero discord can exist without entanglement, the origin of quantum
discord is not well understood as compared to entanglement, which manifests
itself more simply as inseparable higher dimensional quantum superposition. In
this paper we establish the discordlike correlation of bipartite coherence and
then compare it to quantum discord. Consequently, we show that the minimum of
the discordlike correlation of coherence coincides with the original quantum
discord. This demonstrates quantum discord as the irreducible correlated
bipartite coherence. In addition, the discordlike correlated coherence is shown
to admit the postulates of the quantum resource theory (QRT), although the
original quantum discord is not a "good" candidate under the QRT. We also find
that the relative entropy measure induced from the discordlike coherence is a
well-defined coherence measure for bipartite states.


title:
Effective Mass in Bilayer Graphene at Low Carrier Densities: the Role of
  Potential Disorder and Electron-Electron Interaction

abstract:
  In a two-dimensional electron gas, the electron-electron interaction
generally becomes stronger at lower carrier densities and renormalizes the
Fermi liquid parameters such as the effective mass of carriers. We combine
experiment and theory to study the effective masses of electrons and holes
$m^*_e$ and $m^*_h$ in bilayer graphene in the low carrier density regime of
order 1 * 10^11 cm^-2. Measurements use temperature-dependent low-field
Shubnikov-de Haas (SdH) oscillations are observed in high-mobility hexagonal
boron nitride (h-BN) supported samples. We find that while $m^*_e$ follows a
tight-binding description in the whole density range, $m^*_h$ starts to drop
rapidly below the tight-binding description at carrier density n = 6 * 10^11
cm^-2 and exhibits a strong suppression of 30% when n reaches 2 * 10^11 cm^-2.
Contributions from electron-electron interaction alone, evaluated using several
different approximations, cannot explain the experimental trend. Instead, the
effect of potential fluctuation and the resulting electron-hole puddles play a
crucial role. Calculations including both the electron-electron interaction and
disorder effects explain the experimental data qualitatively and
quantitatively. This study reveals an unusual disorder effect unique to
two-dimensional semi-metallic systems.


title: Regularity and cohomology of determinantal thickenings

abstract:
  We consider the ring S=C[x_ij] of polynomial functions on the vector space
C^(m x n) of complex m x n matrices. We let GL= GL_m x GL_n and consider its
action via row and column operations on C^(m x n) (and the induced action on
S). For every GL-invariant ideal I in S and every j>=0, we describe the
decomposition of the modules Ext^j_S(S/I,S) into irreducible
GL-representations. For any inclusion I into J of GL-invariant ideals we
determine the kernels and cokernels of the induced maps Ext^j_S(S/I,S) ->
Ext^j_S(S/J,S). As a consequence of our work, we give a formula for the
regularity of the powers and symbolic powers of generic determinantal ideals,
and in particular we determine which powers have a linear minimal free
resolution. As another consequence, we characterize the GL-invariant ideals I
in S for which the induced maps Ext^j_S(S/I,S) -> H_I^j(S) are injective. In a
different direction we verify that Kodaira vanishing, as described in work of
Bhatt-Blickle-Lyubeznik-Singh-Zhang, holds for determinantal thickenings.


title:
On the characteristic foliation on a smooth hypersurface in a
  holomorphic symplectic fourfold

abstract:
  Let $X$ be an irreducible holomorphic symplectic fourfold and $D$ a smooth
hypersurface in $X$. It follows from a result by Amerik and Campana that the
characteristic foliation (that is the foliation given by the kernel of the
restriction of the symplectic form to $D$) is not algebraic unless $D$ is
uniruled. Suppose now that the Zariski closure of its general leaf is a
surface. We prove that $X$ has a lagrangian fibration and $D$ is the inverse
image of a curve on its base.


title: On Nov\'ak numbers

abstract:
  In this work, we obtain some new lower bounds for the number $\mathcal
N_B(x)$ of Nov\'ak numbers less than or equal to $x$. We also prove,
conditionally on Generalized Riemann Hypothesis, the upper estimates for the
number of primes dividing at least one Nov\'ak number and give description for
the prime factors of Nov\'ak numbers $N$, such that $2N$ is a
Nov\'ak-Carmichael number.


title:
The Cosmic Microwave Background And Pseudo-Nambu-Goldstone Bosons:
  Searching For Lorentz Violations In The Cosmos

abstract:
  One of the most powerful probes of new physics is the polarized Cosmic
Microwave Background (CMB). The detection of a nonzero polarization angle
rotation between the CMB surface of last scattering and today could provide
evidence of Lorentz-violating physics. The purpose of this paper is twofold.
First we review one popular mechanism for polarization rotation of CMB photons:
the pseudo-Nambu-Goldstone boson. Second, we propose a method to use the
Polarbear experiment to constrain Lorentz-violating physics in the context of
the Standard-Model Extension, a framework to standardize a large class of
potential Lorentz-violating terms in particle physics.


title: The progenitor and early evolution of the Type IIb SN 2016gkg

abstract:
  We report initial observations and analysis on the Type IIb SN~2016gkg in the
nearby galaxy NGC~613. SN~2016gkg exhibited a clear double-peaked light curve
during its early evolution, as evidenced by our intensive photometric follow-up
campaign. SN~2016gkg shows strong similarities with other Type IIb SNe, in
particular with respect to the \he~emission features observed in both the
optical and near infrared. SN~2016gkg evolved faster than the prototypical
Type~IIb SN~1993J, with a decline similar to that of SN~2011dh after the first
peak. The analysis of archival {\it Hubble Space Telescope} images indicate a
pre-explosion source at SN~2016gkg's position, suggesting a progenitor star
with a $\sim$mid F spectral type and initial mass $15-20$\msun, depending on
the distance modulus adopted for NGC~613. Modeling the temperature evolution
within $5\,\rm{days}$ of explosion, we obtain a progenitor radius of
$\sim\,48-124$\rsun, smaller than that obtained from the analysis of the
pre-explosion images ($240-320$\rsun).


title: Noncircular Outer Disks in Unbarred S0 Galaxies: NGC 502 and NGC 5485

abstract:
  Strongly noncircular outer stellar disks have been found in two unbarred SA0
galaxies by analyzing spectroscopic data on the rotation of stars and
photometric data on the shape and orientation of the isophotes. In NGC 502, the
oval distortion of the disk is manifested as two elliptical rings, the inner
and the outer ones, covering wide radial zones between the bulge and the disk
and at the outer edge of the stellar disk. Such a structure may be a
consequence of the so-called "dry" minor merger - multiple accretion of
gas-free satellites. In NGC 5485, the kinematical major axis does not coincide
with the orientation of isophotes in the disk-dominated region, and for this
galaxy the conclusion about its global triaxial structure is unavoidable.


title: Flood-Filling Networks

abstract:
  State-of-the-art image segmentation algorithms generally consist of at least
two successive and distinct computations: a boundary detection process that
uses local image information to classify image locations as boundaries between
objects, followed by a pixel grouping step such as watershed or connected
components that clusters pixels into segments. Prior work has varied the
complexity and approach employed in these two steps, including the
incorporation of multi-layer neural networks to perform boundary prediction,
and the use of global optimizations during pixel clustering. We propose a
unified and end-to-end trainable machine learning approach, flood-filling
networks, in which a recurrent 3d convolutional network directly produces
individual segments from a raw image. The proposed approach robustly segments
images with an unknown and variable number of objects as well as highly
variable object sizes. We demonstrate the approach on a challenging 3d image
segmentation task, connectomic reconstruction from volume electron microscopy
data, on which flood-filling neural networks substantially improve accuracy
over other state-of-the-art methods. The proposed approach can replace complex
multi-step segmentation pipelines with a single neural network that is learned
end-to-end.


title:
Optimal stellar photometry for multi-conjugate adaptive optics systems
  using science-based metrics

abstract:
  We present a detailed discussion of how to obtain precise stellar photometry
in crowded fields using images from multi-conjugate adaptive optics (MCAO)
systems, with the intent of informing the scientific development of this key
technology for the Extremely Large Telescopes. We use deep J and K_s exposures
of NGC 1851 taken with the Gemini Multi-Conjugate Adaptive Optics System (GeMS)
on Gemini South to quantify the performance of the instrument and to develop an
optimal strategy for stellar photometry using PSF-fitting techniques. We judge
the success of the various methods we employ by using science-based metrics,
particularly the width of the main sequence turn-off region. We also compare
the GeMS photometry with the exquisite HST data in the visible of the same
target. We show that the PSF produced by GeMS possesses significant spatial and
temporal variability that must be accounted for during the analysis. We show
that the majority of the variation of the PSF occurs within the "control
radius" of the MCAO system and that the best photometry is obtained when the
PSF radius is chosen to closely match this spatial scale. We identify
photometric calibration as a critical issue for next generation MCAO systems
such as those on TMT and E-ELT. Our final CMDs reach K_s~22---below the main
sequence knee---making it one of the deepest for a globular cluster available
from the ground. Theoretical isochrones are in remarkable agreement with the
stellar locus in our data from below the main sequence knee to the upper red
giant branch.


title: Computing Skylines on Distributed Data

abstract:
  In this paper we study skyline queries in the distributed computational
model, where we have $s$ remote sites and a central coordinator (the query
node); each site holds a piece of data, and the coordinator wants to compute
the skyline of the union of the $s$ datasets. The computation is in terms of
rounds, and the goal is to minimize both the total communication cost and the
round cost.
  Viewing data objects as points in the Euclidean space, we consider both the
horizontal data partition case where each site holds a subset of points, and
the vertical data partition case where each site holds one coordinate of all
the points. We give a set of algorithms that have provable theoretical
guarantees, and complement them with information theoretical lower bounds. We
also demonstrate the superiority of our algorithms over existing heuristics by
an extensive set of experiments on both synthetic and real world datasets.


title:
Stability of the Phase Transition of Critical-Field Ising Model on
  Cayley trees under Inhomogeneous External Fields

abstract:
  We consider the ferromagnetic Ising model with spatially dependent external
fields on a Cayley tree, and we investigate the conditions for the existence of
the phase transition for a class of external fields, asymptotically approaching
a homogeneous critical external field. Our results extend earlier results by
Rozikov and Ganikhodjaev.

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


title:
Combining configuration interaction with perturbation theory for atoms
  with large number of valence electrons

abstract:
  A version of the configuration interaction (CI) method is developed which
treats highly excited many-electron basis states perturbatively, so that their
inclusion does not affect the size of the CI matrix. This removes, at least in
principle, the main limitation of the CI method in dealing with many-electron
atoms or ions. We perform calculations of the spectra of iodine and its ions,
tungsten, and ytterbium as examples of atoms with open $s$, $p$, $d$ and
$f$-shells. Good agreement of the calculated data with experiment illustrates
the power of the method. Its advantages and limitations are discussed.


title:
Observation of Quantum Criticality and Luttinger Liquid in
  One-dimensional Bose Gases

abstract:
  We experimentally investigate the quantum criticality and Tomonaga-Luttinger
liquid (TLL) behavior within one-dimensional (1D) ultracold atomic gases. Based
on the measured density profiles at different temperatures, the universal
scaling laws of thermodynamic quantities are observed. The quantum critical
regime and the relevant crossover temperatures are determined through the
double-peak structure of the specific heat. In the TLL regime, we obtain the
Luttinger parameter by probing sound propagation. Furthermore, a characteristic
power-law behavior emerges in the measured momentum distributions of the 1D
ultracold gas, confirming the existence of the TLL.


title:
Efficient charge separation in organic photovoltaics through incoherent
  hopping

abstract:
  We demonstrate that efficient and nearly field-independent charge separation
in organic planar heterojunction solar cells can be described by an incoherent
hopping mechanism. We model the separation efficiency of electron-hole pairs
created at donor-acceptor organic interfaces. By using kinetic Monte Carlo
simulations that include the effect of on-chain delocalization we show that
efficient charge extraction to the electrodes requires bipolar transport and
increased dimensionality. This model explains experimental results of almost
field independent charge separation in some molecular systems and provides
important guidelines at the molecular level for maximizing the efficiencies of
organic solar cells.


title: Metastable dark energy

abstract:
  We build a model of metastable dark energy, in which the observed vacuum
energy is the value of the scalar potential at the false vacuum. The scalar
potential is given by a sum of even self-interactions up to order six. The
deviation from the Minkowski vacuum is due to a term suppressed by the Planck
scale. The decay time of the metastable vacuum can easily accommodate a mean
life time compatible with the age of the universe. The metastable dark energy
is also embedded into a model with $SU(2)_R$ symmetry. The dark energy doublet
and the dark matter doublet naturally interact with each other. A three-body
decay of the dark energy particle into (cold and warm) dark matter can be as
long as large fraction of the age of the universe, if the mediator is massive
enough, the lower bound being at intermediate energy level some orders below
the grand unification scale. Such a decay shows a different form of interaction
between dark matter and dark energy, and the model opens a new window to
investigate the dark sector from the point-of-view of particle physics.


title: Distributed Mean Estimation with Limited Communication

abstract:
  Motivated by the need for distributed learning and optimization algorithms
with low communication cost, we study communication efficient algorithms for
distributed mean estimation. Unlike previous works, we make no probabilistic
assumptions on the data. We first show that for $d$ dimensional data with $n$
clients, a naive stochastic binary rounding approach yields a mean squared
error (MSE) of $\Theta(d/n)$ and uses a constant number of bits per dimension
per client. We then extend this naive algorithm in two ways: we show that
applying a structured random rotation before quantization reduces the error to
$\mathcal{O}((\log d)/n)$ and a better coding strategy further reduces the
error to $\mathcal{O}(1/n)$ and uses a constant number of bits per dimension
per client. We also show that the latter coding strategy is optimal up to a
constant in the minimax sense i.e., it achieves the best MSE for a given
communication cost. We finally demonstrate the practicality of our algorithms
by applying them to distributed Lloyd's algorithm for k-means and power
iteration for PCA.


title:
On Quasinormal Modes for Scalar Perturbations of Static Spherically
  Symmetric Black Holes in Nash Embedding Framework

abstract:
  In this paper we investigate scalar perturbations of black holes embedded in
a five dimensional bulk space. It is calculated the quasinormal frequencies of
a such black holes using the third order of Wentzel, Kramers, Brillouin (WKB)
approximation for scalar perturbations. The results are presented in tables
along the text.


title: RN-AdS Nontopoligical Solitons in Broken Einstein-Maxwell-Higgs Theory

abstract:
  Results are presented from numerical simulations of the
Einstein-Maxwell-Higgs equations with a broken U(1) symmetry. Coherent
nontopological soliton solutions are shown to exist that separate an Anti-de
Sitter (AdS) true vacuum interior from a Reissner-Nordstrom (RN) false vacuum
exterior. The stability of these bubble solutions is tested by perturbing the
charge of the coherent solution and evolving the time-dependent equations of
motion. In the weak gravitational limit, the short-term stability depends on
the sign of $(\omega/ Q) \, \partial_\omega Q$, similar to q-balls. The
long-term end state of the perturbed solutions demonstrates a rich structure
and is visualized using "phase diagrams." Regions of both stability and
instability are shown to exist for $\kappa_g \lesssim 0.015$, while solutions
with $\kappa_g \gtrsim 0.015$ were observed to be entirely unstable. Threshold
solutions are shown to demonstrate time-scaling laws, and the space separating
true and false vacuum end states is shown to be fractal in nature, similar to
oscillons. Coherent states with superextremal charge-to-mass ratios are shown
to exist and observed to collapse or expand, depending on the sign of the
charge perturbation. Expanding superextremal bubbles induce a phase transition
to the true AdS vacuum, while collapsing superextremal bubbles can form
nonsingular strongly gravitating solutions with superextremal RN exteriors.


title: Group actions, Teichm\"uller spaces and cobordisms

abstract:
  We discuss how the global geometry and topology of manifolds depend on
different group actions of their fundamental groups, and in particular, how
properties of a non-trivial compact 4-dimensional cobordism $M$ whose interior
has a complete hyperbolic structure depend on properties of the variety of
discrete representations of the fundamental group of its 3-dimensional boundary
$\partial M$. In addition to the standard conformal ergodic action of a uniform
hyperbolic lattice on the round sphere $S^{n-1}$ and its quasiconformal
deformations in $S^n$, we present several constructions of unusual actions of
such lattices on everywhere wild spheres (boundaries of quasisymmetric
embeddings of the closed $n$-ball into $S^n$), on non-trivial $(n-1)$-knots in
$S^{n+1}$, as well as actions defining non-trivial compact cobordisms with
complete hyperbolic structures in its interiors. We show that such unusual
actions always correspond to discrete representations of a given hyperbolic
lattice from "non-standard" components of its varieties of representations
(faithful or with large kernels of defining homomorphisms).


title: The Neumann Problem on Ellipsoids

abstract:
  The Neumann problem on an ellipsoid in R^n asks for a function harmonic
inside the ellipsoid whose normal derivative is some specified function on the
ellipsoid. We solve this problem when the specified function on the ellipsoid
is a normalized polynomial (a polynomial divided by the norm of the normal
vector arising from the definition of the ellipsoid). Specifically, we give a
necessary and sufficient condition for a solution to exist, and we show that if
a solution exists then it is a polynomial whose degree is at most the degree of
the polynomial giving the specified function. Furthermore, we give an algorithm
for computing this solution. We also solve the corresponding generalized
Neumann problem and give an algorithm for computing its solution.


title: Intermittent many-body dynamics at equilibrium

abstract:
  The equilibrium value of an observable defines a manifold in the phase space
of an ergodic and equipartitioned many-body system. A typical trajectory
pierces that manifold infinitely often as time goes to infinity. We use these
piercings to measure both the relaxation time of the lowest frequency eigenmode
of the Fermi-Pasta-Ulam chain (FPU), as well as the fluctuations of the
subsequent dynamics in equilibrium. The dynamics in equilibrium is
characterized by a power-law distribution of excursion times far off
equilibrium, with diverging variance. Long excursions arise from sticky
dynamics close to q-breathers localized in normal mode space. Measuring the
exponent allows to predict the transition into nonergodic dynamics. We
generalize our method to Klein-Gordon lattices (KG) where the sticky dynamics
is due to discrete breathers localized in real space.


title:
Bounds for the $l_1$-distance of $q$-ary lattices obtained via
  Constructions D, D$^{'}$ and $\overline{D}$

abstract:
  Lattices have been used in several problems in coding theory and
cryptography. In this paper we approach $q$-ary lattices obtained via
Constructions D, $\D'$ and $\overline{D}$. It is shown connections between
Constructions D and $\D'$. Bounds for the minimum $l_1$-distance of lattices
$\Lambda_{D}$, $\Lambda_{D'}$ and $\Lambda_{\overline{D}}$ and, under certain
conditions, a generator matrix for $\Lambda_{D'}$ are presented. In addition,
when the chain of codes used is closed under the zero-one addition, we derive
explicit expressions for the minimum $l_1$-distances of the lattices
$\Lambda_{D}$ and $\Lambda_{\overline{D}}$ attached to the distances of the
codes used in these constructions.


title: Vortex Mechanics in Thin Ferromagnetic Nanodisks

abstract:
  The magnetostatic energy is calculated for a magnetic vortex in a noncircular
elliptical nanodisk. It is well-known that the energy of a vortex in the
circular disk is minimized though an ansatz that eliminates the magnetostatic
charge at the disk edge. Beginning with this ansatz for the circular disk, a
conformal mapping of a circle interior onto the interior of an ellipse results
in the magnetization of the elliptical disk. This magnetization in the interior
of an ellipse also has no magnetostatic charge at the disk edge also minimizing
the magnetostatic energy. As expected the energy has a quadratic dependence on
the displacement of the vortex core from the ellipse center, but reflecting the
lower symmetry of the ellipse. Through numerical integration of the
magnetostatic integral a general expression for the energy is obtained for
ellipticity values from 1.0 to about 0.3. Finally a general expression for the
gyrotropic frequency as described by the Thiele equation is obtained.