title: Critical dynamics on a large human Open Connectome network

abstract:
  Extended numerical simulations of threshold models have been performed on a
human brain network with N=836733 connected nodes available from the Open
Connectome project. While in case of simple threshold models a sharp
discontinuous phase transition without any critical dynamics arises, variable
thresholds models exhibit extended power-law scaling regions. This is
attributed to fact that Griffiths effects, stemming from the
topological/interaction heterogeneity of the network, can become relevant if
the input sensitivity of nodes is equalized. I have studied the effects effects
of link directness, as well as the consequence of inhibitory connections.
Non-universal power-law avalanche size and time distributions have been found
with exponents agreeing with the values obtained in electrode experiments of
the human brain. The dynamical critical region occurs in an extended control
parameter space without the assumption of self organized criticality.


title:
Cryptompress: A Symmetric Cryptography algorithm to deny Bruteforce
  Attack

abstract:
  Cryptompress, a new 128-bit (initial) private-key cryptography algorithm is
proposed. It uses a block size of at least 30 bits and increments prior key
size to additional 32 bits on each unsuccessful attempt of any means, including
bruteforcing, further changing a specific portion of the cyphertext using the
reformed Feistel network. Encryption process results from a proposed
compression sequence developed using lookup table and shift operations followed
by key generation. Eventually, four matrixes named add-sub matrix, reduced
matrix, sequence matrix and term matrix are obtained which ultimately forms a
cyphertext.


title: Horizon Lines in the Wild

abstract:
  The horizon line is an important contextual attribute for a wide variety of
image understanding tasks. As such, many methods have been proposed to estimate
its location from a single image. These methods typically require the image to
contain specific cues, such as vanishing points, coplanar circles, and regular
textures, thus limiting their real-world applicability. We introduce a large,
realistic evaluation dataset, Horizon Lines in the Wild (HLW), containing
natural images with labeled horizon lines. Using this dataset, we investigate
the application of convolutional neural networks for directly estimating the
horizon line, without requiring any explicit geometric constraints or other
special cues. An extensive evaluation shows that using our CNNs, either in
isolation or in conjunction with a previous geometric approach, we achieve
state-of-the-art results on the challenging HLW dataset and two existing
benchmark datasets.


title: Quantile Processes for Semi and Nonparametric Regression

abstract:
  A collection of quantile curves provides a complete picture of conditional
distributions. Properly centered and scaled versions of estimated curves at
various quantile levels give rise to the so-called quantile regression process
(QRP). In this paper, we establish weak convergence of QRP in a general series
approximation framework, which includes linear models with increasing
dimension, nonparametric models and partial linear models. An interesting
consequence is obtained in the last class of models, where parametric and
non-parametric estimators are shown to be asymptotically independent.
Applications of our general process convergence results include the
construction of non-crossing quantile curves and the estimation of conditional
distribution functions. As a result of independent interest, we obtain a series
of Bahadur representations with exponential bounds for tail probabilities of
all remainder terms. Bounds of this kind are potentially useful in analyzing
statistical inference procedures under divide-and-conquer setup.


title:
Towards rational design of carbon nitride photocatalysts: Identification
  of cyanamide "defects" as catalytically relevant sites

abstract:
  The heptazine-based polymer melon (also known as graphitic carbon nitride,
g-C3N4), is a promising photocatalyst for hydrogen evolution. Nonetheless,
attempts to improve its inherently low activity are rarely based on rational
approaches due to a lack of fundamental understanding of its mechanistic
operation. Here, we employ molecular heptazine-based model catalysts to
identify the cyanamide moiety as a photocatalytically relevant "defect". We
exploit this knowledge for the rational design of a carbon nitride polymer
populated with cyanamide groups, yielding a material with 12- and 16-times the
hydrogen evolution rate and apparent quantum efficiency (400 nm), respectively,
compared to the benchmark melon. Computational modelling and material
characterization suggest this moiety improves co-ordination (and, in turn,
charge transfer kinetics) to the platinum co-catalyst and enhances the
separation of the photo-generated charge carriers. The demonstrated knowledge
transfer for rational catalyst design presented here provides the conceptual
framework for engineering high performance heptazine-based photocatalysts.


title: The Ricci flow on a cylinder

abstract:
  In this paper we study the Ricci flow on surfaces homeomorphic to a cylinder
(that is, a product of the circle with a compact interval). We prove longtime
existence results, results on the asymptotic behavior of the flow, and we
report on an interesting phenomenon: convergence to constant curvature in the
normalised flow,under certain assumptions on the initial data, cannot be
exponential.


title: Revising Incompletely Specified Convex Probabilistic Belief Bases

abstract:
  We propose a method for an agent to revise its incomplete probabilistic
beliefs when a new piece of propositional information is observed. In this
work, an agent's beliefs are represented by a set of probabilistic formulae --
a belief base. The method involves determining a representative set of
'boundary' probability distributions consistent with the current belief base,
revising each of these probability distributions and then translating the
revised information into a new belief base. We use a version of Lewis Imaging
as the revision operation. The correctness of the approach is proved. The
expressivity of the belief bases under consideration are rather restricted, but
has some applications. We also discuss methods of belief base revision
employing the notion of optimum entropy, and point out some of the benefits and
difficulties in those methods. Both the boundary distribution method and the
optimum entropy method are reasonable, yet yield different results.


title:
Topological Yu-Shiba-Rusinov chain in monolayer transition-metal
  dichalcogenide superconductors

abstract:
  Monolayers of transition-metal dichalcogenides (TMDs) are two-dimensional
materials whose low energy sector consists of two inequivalent valleys. The
valence bands have a large spin splitting due to strong spin-orbit coupling.
Furthermore the spin is polarized up in one valley and down in the other (in
directions perpendicular to the two-dimensional crystal). We focus on lightly
hole-doped systems where the Fermi surface consists of two disconnected circles
with opposite spins. For both proximity induced and intrinsic local attractive
interaction induced superconductivity, a fully gapped intervalley pairing state
is favored in this system, which is an equal superposition of the singlet and
the m=0 triplet for the lack of centrosymmetry. We show that a
ferromagnetically ordered magnetic-adatom chain placed on a monolayer TMD
superconductor provides a platform to realize one-dimensional topological
superconducting state characterized by the presence of Majorana zero modes at
its ends. We obtain the topological phase diagram and show that the topological
superconducting phase is affected not only by the adatom spacing and the
direction of the magnetic moment, but also by the orientation of the chain
relative to the crystal.


title: A MultiPath Network for Object Detection

abstract:
  The recent COCO object detection dataset presents several new challenges for
object detection. In particular, it contains objects at a broad range of
scales, less prototypical images, and requires more precise localization. To
address these challenges, we test three modifications to the standard Fast
R-CNN object detector: (1) skip connections that give the detector access to
features at multiple network layers, (2) a foveal structure to exploit object
context at multiple object resolutions, and (3) an integral loss function and
corresponding network adjustment that improve localization. The result of these
modifications is that information can flow along multiple paths in our network,
including through features from multiple network layers and from multiple
object views. We refer to our modified classifier as a "MultiPath" network. We
couple our MultiPath network with DeepMask object proposals, which are well
suited for localization and small objects, and adapt our pipeline to predict
segmentation masks in addition to bounding boxes. The combined system improves
results over the baseline Fast R-CNN detector with Selective Search by 66%
overall and by 4x on small objects. It placed second in both the COCO 2015
detection and segmentation challenges.


title: Cauchy-Davenport type inequalities, I

abstract:
  Let $\mathbb G = (G, +)$ be a group (either abelian or not). Given $X, Y
\subseteq G$, we denote by $\langle Y \rangle$ the subsemigroup of $\mathbb G$
generated by $Y$, and we set $$\gamma(Y) := \sup_{y_0 \in Y} \inf_{y_0 \ne y
\in Y} {\rm ord}(y - y_0)$$ if $|Y| \ge 2$ and $\gamma(Y) := |Y|$ otherwise. We
prove that if $\langle Y \rangle$ is commutative, $Y$ is non-empty, and $X+2Y
\neq X + Y + y$ for some $y \in Y$, then $$ |X+Y| \ge |X|+\min(\gamma(Y), |Y| -
1). $$ Actually, this is obtained from a more general result, which improves on
previous work of the author on sumsets in cancellative semigroups, and yields a
comprehensive generalization, and in some cases a considerable strengthening,
of various additive theorems, notably including the Chowla-Pillai theorem (on
sumsets in finite cyclic groups) and the specialization to abelian groups of
the Hamidoune-Shatrowsky theorem.


title: Online Learning of Feasible Strategies in Unknown Environments

abstract:
  Define an environment as a set of convex constraint functions that vary
arbitrarily over time and consider a cost function that is also convex and
arbitrarily varying. Agents that operate in this environment intend to select
actions that are feasible for all times while minimizing the cost's time
average. Such action is said optimal and can be computed offline if the cost
and the environment are known a priori. An online policy is one that depends
causally on the cost and the environment. To compare online policies to the
optimal offline action define the fit of a trajectory as a vector that
integrates the constraint violations over time and its regret as the cost
difference with the optimal action accumulated over time. Fit measures the
extent to which an online policy succeeds in learning feasible actions while
regret measures its success in learning optimal actions. This paper proposes
the use of online policies computed from a saddle point controller which are
shown to have fit and regret that are either bounded or grow at a sublinear
rate. These properties provide an indication that the controller finds
trajectories that are feasible and optimal in a relaxed sense. Concepts are
illustrated throughout with the problem of a shepherd that wants to stay close
to all sheep in a herd. Numerical experiments show that the saddle point
controller allows the shepherd to do so.


title: Boundary Anomalies and Correlation Functions

abstract:
  It was shown recently that boundary terms of conformal anomalies recover the
universal contribution to the entanglement entropy and also play an important
role in the boundary monotonicity theorem of odd-dimensional quantum field
theories. Motivated by these results, we investigate relationships between
boundary anomalies and the stress tensor correlation functions in conformal
field theories. In particular, we focus on how the conformal Ward identity and
the renormalization group equation are modified by boundary central charges.
Renormalized stress tensors induced by boundary Weyl invariants are also
discussed, with examples in spherical and cylindrical geometries.


title: Electronic Griffiths Phase in the Te - Doped Semiconductor FeSb$_{2}$

abstract:
  We report on the emergence of an Electronic Griffiths Phase (EGP) in the
doped semiconductor FeSb$_{2}$, predicted for disordered insulators with random
localized moments in the vicinity of a metal-insulator transition (MIT).
Magnetic, transport, and thermodynamic measurements of
Fe(Sb$_{1-x}$Te$_{x}$)$_{2}$ single crystals show signatures of
disorder-induced non-Fermi liquid behavior and a Wilson ratio expected for
strong electronic correlations. The EGP states are found on the metallic
boundary, between the insulating state ($x = 0$) and a long-range albeit weak
magnetic order ($x \geq 0.075$).


title:
Quasinormal modes and Hawking radiation of a Reissner-Nordstr\"om black
  hole surrounded by quintessence

abstract:
  We investigate quasinormal modes (QNMs) and Hawking radiation of a
Reissner-Nordstr\"om black hole sur-rounded by quintessence. The
Wentzel-Kramers-Brillouin (WKB) method is used to evaluate the QNMs and the
rate of radiation. The results show that due to the interaction of the
quintessence with the background metric, the QNMs of the black hole damp more
slowly when increasing the density of quintessence and the black hole radiates
at slower rate.


title:
Workshop on Physics with Neutral Kaon Beam at JLab (KL2016)
  Mini-Proceedings

abstract:
  The KL2016 Workshop is following the Letter of Intent LoI12-15-001 "Physics
Opportunities with Secondary KL beam at JLab" submitted to PAC43 with the main
focus on the physics of excited hyperons produced by the Kaon beam on
unpolarized and polarized targets with GlueX setup in Hall D. Such studies will
broaden a physics program of hadron spectroscopy extending it to the strange
sector. The Workshop was organized to get a feedback from the community to
strengthen physics motivation of the LoI and prepare a full proposal.
  Further details about the Workshop can be found on the web page of the
conference: http://www.jlab.org/conferences/kl2016/index.html .


title:
Geometric Quantization of the moduli space of the vortex equations on a
  Riemann surface

abstract:
  In this note we quantize the usual symplectic (K\"{a}hler) form on the vortex
moduli space by modifying the Quillen metric of the Quillen determinant line
bundle.


title: Duality and scale invariant magnetic fields from bouncing universes

abstract:
  Recently, we had numerically shown that, for a non-minimal coupling that is a
simple power of the scale factor, scale invariant magnetic fields arise in a
class of bouncing universes. In this work, we {\it analytically} evaluate the
spectrum of magnetic and electric fields generated in a sub-class of such
models. We illustrate that, for cosmological scales which have wavenumbers much
smaller than the wavenumber associated with the bounce, the shape of the
spectrum is preserved across the bounce. Using the analytic solutions obtained,
we also illustrate that the problem of backreaction is severe at the bounce.
Finally, we show that the power spectrum of the magnetic field remains
invariant under a two parameter family of transformations of the non-minimal
coupling function.


title:
Predominantly Low Metallicities Measured in a Stratified Sample of Lyman
  Limit Systems at z=3.7

abstract:
  We measured metallicities for 33 z=3.4-4.2 absorption line systems drawn from
a sample of H I-selected-Lyman limit systems (LLSs) identified in Sloan Digital
Sky Survey (SDSS) quasar spectra and stratified based on metal line features.
We obtained higher-resolution spectra with the Keck Echellette Spectrograph and
Imager, selecting targets according to our stratification scheme in an effort
to fully sample the LLS population metallicity distribution. We established a
plausible range of H I column densities and measured column densities (or
limits) for ions of carbon, silicon, and aluminum, finding ionization-corrected
metallicities or upper limits. Interestingly, our ionization models were better
constrained with enhanced $\alpha$-to-aluminum abundances, with a median
abundance ratio of [$\alpha$/Al]=0.3. Measured metallicities were generally
low, ranging from [M/H]=-3 to -1.68, with even lower metallicities likely for
some systems with upper limits. Using survival statistics to incorporate
limits, we constructed the cumulative distribution function (CDF) for LLS
metallicities. Recent models of galaxy evolution propose that galaxies
replenish their gas from the low-metallicity intergalactic medium (IGM) via
high-density H I "flows" and eject enriched interstellar gas via outflows.
Thus, there has been some expectation that LLSs at the peak of cosmic star
formation ($z\approx3$) might have a bimodal metallicity distribution. We
modeled our CDF as a mix of two Gaussian distributions, one reflecting the
metallicity of the IGM and the other representative of the interstellar medium
of star-forming galaxies. This bimodal distribution yielded a poor fit. A
single Gaussian distribution better represented the sample with a low mean
metallicity of [M/H] $\approx -2.5$.


title:
Discrete spin structures and commuting projector models for 2d fermionic
  symmetry protected topological phases

abstract:
  We construct exactly solved commuting projector Hamiltonian lattice models
for all known 2+1d fermionic symmetry protected topological phases (SPTs) with
on-site unitary symmetry group $G_f = G \times \mathbb{Z}_2^f$, where $G$ is
finite and $\mathbb{Z}_2^f$ is the fermion parity symmetry. In particular, our
models transcend the class of group supercohomology models, which realize some,
but not all, fermionic SPTs in 2+1d. A natural ingredient in our construction
is a discrete form of the spin structure of the 2d spatial surface $M$ on which
our model is defined, namely a `Kasteleyn' orientation of a certain graph
associated with the lattice. As a special case, our construction yields
commuting projector models for all $8$ members of the $\mathbb{Z}_8$
classification of 2d fermionic SPTs with $G = \mathbb{Z}_2$.

categories: cond-mat.str-el math-ph math.MP quant-ph


title: Kepler K2 Observations of the Intermediate Polar FO Aquarii

abstract:
  We present photometry of the intermediate polar FO Aquarii obtained as part
of the K2 mission using the Kepler space telescope. The amplitude spectrum of
the data confirms the orbital period of 4.8508(4) h, and the shape of the light
curve is consistent with the outer edge of the accretion disk being eclipsed
when folded on this period. The average flux of FO Aquarii changed during the
observations, suggesting a change in the mass accretion rate. There is no
evidence in the amplitude spectrum of a longer period that would suggest disk
precession. The amplitude spectrum also shows the white dwarf spin period of
1254.3401(4) s, the beat period of 1351.329(2) s, and 31 other spin and orbital
harmonics. The detected period is longer than the last reported period of
1254.284(16) s, suggesting that FO Aqr is now spinning down, and has a positive
$\dot{P}$. There is no detectable variation in the spin period over the course
of the K2 observations, but the phase of the spin cycle is correlated with the
system brightness. We also find the amplitude of the beat signal is correlated
with the system brightness.


title:
Achieving Convergence in Galaxy Formation Models by Augmenting N-body
  Merger Trees

abstract:
  Accurate modeling of galaxy formation in a hierarchical, cold dark matter
universe requires the use of sufficiently high-resolution merger trees to
obtain convergence in the predicted properties of galaxies. When semi-analytic
galaxy formation models are applied to cosmological N-body simulation merger
trees, it is often the case that those trees have insufficient resolution to
give converged galaxy properties. We demonstrate a method to augment the
resolution of N-body merger trees by grafting in branches of Monte Carlo merger
trees with higher resolution, but which are consistent with the pre-existing
branches in the N-body tree. We show that this approach leads to converged
galaxy properties.


title: Detecting triple systems with gravitational wave observations

abstract:
  The Laser Interferometer Gravitational Wave Observatory (LIGO) has recently
discovered gravitational waves (GWs) emitted by merging black hole binaries. We
examine whether future GW detections may identify triple companions of merging
binaries. Such a triple companion causes variations in the GW signal due to (1)
the varying path length along the line of sight during the orbit around the
center of mass, (2) relativistic beaming, Doppler, and gravitational redshift,
(3) the variation of the "light"-travel time in the gravitational field of the
triple companion, and (4) secular variations of the orbital elements. We find
that the prospects for detecting the triple companion are the highest for
low-mass compact object binaries which spend the longest time in the LIGO
frequency band. In particular, for merging neutron star binaries, LIGO may
detect a white dwarf or M-dwarf perturber at signal to noise ratio of 8, if it
is within 0.4 solar radius distance from the binary and the system is within a
distance of 100 Mpc. Stellar mass (supermassive) black hole perturbers may be
detected at a factor 5x (1000x) larger separations. Such pertubers in orbit
around the merging binary emit GWs at frequencies above 1 mHz detectable by the
Laser Interferometer Space Antenna (LISA) in coincidence.


title:
Dissecting galaxy triplets in the Sloan Digital Sky Survey Data Release
  10: I. Stellar populations and emission line analysis

abstract:
  We identify isolated galaxy triplets in a volume-limited sample from the
Sloan Digital Sky Survey Data Release 10. Our final sample has 80 galaxy
systems in the redshift range 0.04$\le$z$\le$0.1, brighter than $M_r = -20.5 +
5\log h_{70}$. Spectral synthesis results and WHAN and BPT diagnostic diagrams
were employed to classify the galaxies in these systems as star-forming, active
nuclei, or passive/retired.
  Our results suggest that the brightest galaxies drive the triplet evolution,
as evidenced by the strong correlations between properties as mass assembly and
mean stellar population age with triplet properties. Galaxies with intermediate
luminosity or the faintest one within the triplet seem to play a secondary
role. Moreover, the relation between age and stellar mass of galaxies is
similar for these galaxies but different for the brightest galaxy in the
system. Most of the triplet galaxies are passive or retired, according to the
WHAN classification. Low mass triplets present different fractions of WHAN
classes when compared to higher mass triplets. A census of WHAN class
combinations shows the dominance of star-forming galaxies in low mass triplets
while retired and passive galaxies prevail in high-mass systems. We argue that
these results suggest that the local environment, through galaxy interactions
driven by the brightest galaxy, is playing a major role in triplet evolution.


title:
On the connection between the metal-enriched intergalactic medium and
  galaxies: an OVI-galaxy cross-correlation study at $z < 1$

abstract:
  We present new results on the auto- and cross-correlation functions of
galaxies and OVI absorbers in a $\sim 18~\textrm{Gpc}^3$ comoving volume at $z
< 1$. We use a sample of 51,296 galaxies and 140 OVI absorbers in the column
density range $13 \lesssim \log N \lesssim 15$ to measure two-point correlation
functions in the two dimensions transverse and orthogonal to the line-of-sight
$\xi(r_{\perp}, r_{\parallel})$. We furthermore infer the corresponding
'real-space' correlation functions, $\xi(r)$, by projecting $\xi(r_{\perp},
r_{\parallel})$ along $r_{\parallel}$, and assuming a power-law form, $\xi(r) =
(r / r_0)^{-\gamma}$. Comparing the results from the absorber-galaxy
cross-correlation function, $\xi_{\textrm{ag}}$, the galaxy auto-correlation
function, $\xi_{\textrm{gg}}$, and the absorber auto-correlation function,
$\xi_{\textrm{aa}}$, we constrain the statistical connection between galaxies
and the metal-enriched intergalactic medium as a function of star-formation
activity. We also compare these results to predictions from the EAGLE
cosmological hydrodynamical simulation and find a reasonable agreement. We find
that: (i) OVI absorbers show very little velocity dispersion with respect to
galaxies on $\sim$ Mpc scales, likely $\lesssim$ 100 \kms; (ii) OVI absorbers
and galaxies may not linearly trace the same underlying distribution of matter
in general. In particular, our results demonstrate that OVI absorbers are less
clustered, and potentially more extended around galaxies than galaxies are
around themselves; (iii) On $\gtrsim 100$ kpc scales, the likelihood of finding
OVI absorbers around star-forming galaxies is similar to the likelihood of
finding OVI absorbers around non star-forming galaxies (abridged)


title:
GRB off-axis afterglows and the emission from the accompanying
  supernovae

abstract:
  Gamma-ray burst (GRB) afterglows are likely produced in the shock that is
driven as the GRB jet interacts with the external medium. Long-duration GRBs
are also associated with powerful supernovae (SNe). We consider the optical and
radio afterglows of long GRBs for both blasts viewed along the jet axis
("on-axis" afterglows) and misaligned observes ("off-axis" afterglows).
Comparing the optical emission from the afterglow with that of the accompanying
SN, using SN 1998bw as an archetype, we find that only a few percent of
afterglows viewed off-axis are brighter than the SN. For observable optical
off-axis afterglows, the viewing angle is at most twice the half-opening angle
of the GRB jet. Radio off-axis afterglows should be detected with upcoming
radio surveys within a few hundred Mpc. We propose that these surveys will act
as "radio triggers", and that dedicated radio facilities should follow-up these
sources. Follow-ups can unveil the presence of the radio SN remnant, if
present. In addition, they can probe the presence of a mildly relativistic
component, either associated with the GRB jet or the SN ejecta, expected in
these sources.


title:
A dipole amplifier for electric dipole moments, axion-like particles and
  a dense dark matter hairs detector

abstract:
  A tool that can constrain, in minutes, beyond-the-standard-model parameters
like electric dipole moments (EDM) down to a lower-bound
$d_\text{e}^{\cal{N}}<10^{-37}\text{e}\cdot\text{cm}$ in bulk materials, or the
coupling of axion-like particles (ALP) to photons down to
$|G_{a\gamma\gamma}|<10^{-16}$~GeV$^{-1}$, is described. Best limits are
$d^n_e<3\cdot10^{-26}\text{e}\cdot\text{cm}$ for neutron EDM and
$|G_{a\gamma\gamma}|<6.6\cdot10^{-11}$~GeV$^{-1}$. The {\it dipole amplifier}
is built from a superconducting loop immersed in a toroidal magnetic field,
$\vec{B}$. When nuclear magnetic moments in the London penetration depth align
with $\vec{B}$, the bulk magnetization is always accompanied by an EDM-induced
bulk electric field $\vec{E}\propto\vec{B}$ that generates detectable
oscillatory supercurrents with a characteristic frequency
$\omega_{\text{D}}\propto d_\text{e}^{\cal{N}}$. Cold dark matter (CDM) ALP are
formally similar where $\omega_\text{D}\propto
|G_{a\gamma\gamma}|\sqrt{n_a/(2m_a)}$ with $m_a$ the ALP mass and $n_a$ its
number density. A space probe traversing a dark matter hair with a dipole
amplifier is sensitive enough to detect ALP density variations if
$|G_{a\gamma\gamma}|\sqrt{n_h/(2m_a)}>4.9\cdot10^{-27}$ where $n_h$ is the ALP
number density in the hair.

categories: astro-ph.IM astro-ph.CO hep-ex nucl-ex physics.ins-det


title:
A Semi-Lagrangian two-level preconditioned Newton-Krylov solver for
  constrained diffeomorphic image registration

abstract:
  We propose an efficient numerical algorithm for the solution of diffeomorphic
image registration problems. We use a variational formulation constrained by a
partial differential equation (PDE), where the constraints are a scalar
transport equation.
  We use a pseudospectral discretization in space and second-order accurate
semi-Lagrangian time stepping scheme for the transport equations. We solve for
a stationary velocity field using a preconditioned, globalized, matrix-free
Newton-Krylov scheme. We propose and test a two-level Hessian preconditioner.
We consider two strategies for inverting the preconditioner on the coarse grid:
a nested preconditioned conjugate gradient method (exact solve) and a nested
Chebyshev iterative method (inexact solve) with a fixed number of iterations.
  We test the performance of our solver in different synthetic and real-world
two-dimensional application scenarios. We study grid convergence and
computational efficiency of our new scheme. We compare the performance of our
solver against our initial implementation that uses the same spatial
discretization but a standard, explicit, second-order Runge-Kutta scheme for
the numerical time integration of the transport equations and a single-level
preconditioner. Our improved scheme delivers significant speedups over our
original implementation. As a highlight, we observe a 20$\times$ speedup for a
two dimensional, real world multi-subject medical image registration problem.


title:
Radiation from a D-dimensional collision of shock waves: Two dimensional
  reduction and Carter-Penrose diagram

abstract:
  We analyse the causal structure of the two dimensional (2D) reduced
background used in the perturbative treatment of a head-on collision of two
$D$-dimensional Aichelburg-Sexl gravitational shock waves. After defining all
causal boundaries, namely the future light-cone of the collision and the past
light-cone of a future observer, we obtain characteristic coordinates using two
independent methods. The first is a geometrical construction of the null rays
which define the various light cones, using a parametric representation. The
second is a transformation of the 2D reduced wave operator for the problem into
a hyperbolic form. The characteristic coordinates are then compactified
allowing us to represent all causal light rays in a conformal Carter-Penrose
diagram. Our construction holds to all orders in perturbation theory. In
particular, we can easily identify the singularities of the source functions
and of the Green's functions appearing in the perturbative expansion, at each
order, which is crucial for a successful numerical evaluation of any higher
order corrections using this method.


title: Chiral algebra of Argyres-Douglas theory from M5 brane

abstract:
  We study chiral algebras associated with Argyres-Douglas theories engineered
from M5 brane. For the theory engineered using 6d $(2,0)$ type $J$ theory on a
sphere with a single irregular singularity (without mass parameter), its chiral
algebra is the minimal model of W algebra of $J$ type. For the theory
engineered using an irregular singularity and a regular full singularity, its
chiral algebra is the affine Kac-Moody algebra of $J$ type. We can obtain the
Schur index of these theories by computing the vacua character of the
corresponding chiral algebra.


title: Bottom-Tau Unification in Supersymmetric Model with Anomaly-Mediation

abstract:
  We study the Yukawa unification, in particular, the unification of the Yukawa
coupling constants of $b$ and $\tau$, in the framework of supersymmetric (SUSY)
model. We concentrate on the model in which the SUSY breaking scalar masses are
of the order of the gravitino mass while the gaugino masses originate from the
effect of anomaly mediation and hence are one-loop suppressed relative to the
gravitino mass. We perform an accurate calculation of the Yukawa coupling
constants of $b$ and $\tau$ at the grand unified theory (GUT) scale, including
relevant renormalization group effects and threshold corrections. In
particular, we study the renormalization group effects, taking into account the
mass splittings among sfermions, gauginos, and the standard model particles. We
found that the Yukawa coupling constant of $b$ at the GUT scale is about $70\
\%$ of that of $\tau$ if there is no hierarchy between the sfermion masses and
the gravitino mass. Our results suggest sizable threshold corrections to the
Yukawa coupling constants at the GUT scale or significant suppressions of the
sfermion masses relative to the gravitino mass.


title: Diphoton Resonances in the Renormalizable Coloron Model

abstract:
  The renormalizable coloron model, which has previously been shown in the
literature to be consistent with a wide array of theoretical and precision
electroweak constraints, includes a pair of spinless bosons (one scalar, one
pseudoscalar). We show that either of them, or both together if they are
degenerate, could be responsible for the diphoton resonance signal for which
both CMS and ATLAS have seen evidence. Because either of these bosons would be
produced and decay through loops of spectator fermions, the absence of signals
in dijet, $t\bar{t}$, and electroweak boson pair channels is not a surprise.


title:
Structured Correlation Detection with Application to Colocalization
  Analysis in Dual-Channel Fluorescence Microscopic Imaging

abstract:
  Motivated by the problem of colocalization analysis in fluorescence
microscopic imaging, we study in this paper structured detection of correlated
regions between two random processes observed on a common domain. We argue that
although intuitive, direct use of the maximum log-likelihood statistic suffers
from potential bias and substantially reduced power, and introduce a simple
size-based normalization to overcome this problem. We show that scanning with
the proposed size-corrected likelihood ratio statistics leads to optimal
correlation detection over a large collection of structured correlation
detection problems.


title: Involution and commutator length for complex hyperbolic isometries

abstract:
  We study decompositions of complex hyperbolic isometries as products of
involutions. We show that PU(2,1) has involution length 4 and commutator length
1, and that for all $n \geqslant 3$ PU($n$,1) has involution length at most 8.


title: Stability versions of Erd\H{o}s-Ko-Rado type theorems, via isoperimetry

abstract:
  Erd\H{o}s-Ko-Rado (EKR) type theorems yield upper bounds on the sizes of
families of sets, subject to various intersection requirements on the sets in
the family. Stability versions of such theorems assert that if the size of a
family is close to the maximum possible size, then the family itself must be
close (in some appropriate sense) to a maximum-sized family.
  In this paper, we present an approach to obtaining stability versions of
EKR-type theorems, via isoperimetric inequalities for subsets of the hypercube.
Our approach is rather general, and allows the leveraging of a wide variety of
exact EKR-type results into strong stability versions of these results, without
going into the proofs of the original results.
  We use this approach to obtain tight stability versions of the EKR theorem
itself and of the Ahlswede-Khachatrian theorem on $t$-intersecting families of
$k$-element subsets of $\{1,2,\ldots.n\}$ (for $k < \frac{n}{t+1}$), and to
show that, somewhat surprisingly, all these results hold when the intersection
requirement is replaced by a much weaker requirement.
  Other examples include stability versions of Frankl's recent result on the
Erd\H{o}s matching conjecture, the Ellis-Filmus-Friedgut proof of the
Simonovits-S\'{o}s conjecture, and various EKR-type results on $r$-wise
(cross)-$t$-intersecting families.


title: Quasiconformal mappings on the Grushin plane

abstract:
  We prove that a self-homeomorphism of the Grushin plane is quasisymmetric if
and only if it is metrically quasiconformal and if and only if it is
geometrically quasiconformal. As the main step in our argument, we show that a
quasisymmetric parametrization of the Grushin plane by the Euclidean plane must
also be geometrically quasiconformal. We also discuss some aspects of the
Euclidean theory of quasiconformal maps, such as absolute continuity on almost
every compact curve, not satisfied in the Grushin case.


title:
GW Librae: A unique laboratory for pulsations in an accreting white
  dwarf

abstract:
  Non-radial pulsations have been identified in a number of accreting white
dwarfs in cataclysmic variables. These stars offer insight into the excitation
of pulsation modes in atmospheres with mixed compositions of hydrogen, helium,
and metals, and the response of these modes to changes in the white dwarf
temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae
stands out by having a well-established observational record of three
independent pulsation modes that disappeared when the white dwarf temperature
rose dramatically following its 2007 accretion outburst. Our analysis of HST
ultraviolet spectroscopy taken in 2002, 2010 and 2011, showed that pulsations
produce variations in the white dwarf effective temperature as predicted by
theory. Additionally in May~2013, we obtained new HST/COS ultraviolet
observations that displayed unexpected behaviour: besides showing variability
at ~275s, which is close to the post-outburst pulsations detected with HST in
2010 and 2011, the white dwarf exhibits high-amplitude variability on a ~4.4h
time-scale. We demonstrate that this variability is produced by an increase of
the temperature of a region on white dwarf covering up to ~30 per cent of the
visible white dwarf surface. We argue against a short-lived accretion episode
as the explanation of such heating, and discuss this event in the context of
non-radial pulsations on a rapidly rotating star


title:
The relation between mass and concentration in X-ray galaxy clusters at
  high redshift

abstract:
  Galaxy clusters are the most recent, gravitationally-bound products of the
hierarchical mass accretion over cosmological scales. How the mass is
concentrated is predicted to correlate with the total mass in the cluster's
halo, with systems at higher mass being less concentrated at given redshift and
for any given mass, systems with lower concentration are found at higher
redshifts. Through a spatial and spectral X-ray analysis, we reconstruct the
total mass profile of 47 galaxy clusters observed with Chandra in the redshift
range $0.4<z<1.2$, selected to have no major mergers, to investigate the
relation between the mass and the dark matter concentration, and the evolution
of this relation with redshift. The sample in exam is the largest one
investigated so far at $z>0.4$, and is well suited to provide the first
constraint on the concentration--mass relation at $z>0.7$ from X-ray analysis.
Under the assumptions that the distribution of the X-ray emitting gas is
spherically symmetric and in hydrostatic equilibrium, we combine the
deprojected gas density and spectral temperature profiles through the
hydrostatic equilibrium equation to recover the parameters that describe a NFW
total mass distribution. The comparison with results from weak lensing analysis
reveals a very good agreement both for masses and concentrations. Uncertainties
are however too large to make any robust conclusion on the hydrostatic bias of
these systems. The relation is well described by the form $c \propto M^B
(1+z)^C$, with $B=-0.50 \pm 0.20$, $C=0.12 \pm 0.61$ (at 68.3\% confidence), it
is slightly steeper than the one predicted by numerical simulations
($B\sim-0.1$) and does not show any evident redshift evolution. We obtain the
first constraints on the properties of the concentration--mass relation at $z >
0.7$ from X-ray data, showing a reasonable good agreement with recent numerical
predictions.


title: Varieties of Characters

abstract:
  Let G be a connected reductive affine algebraic group. In this short note we
define the "variety of G-characters" of a finitely generated group F and show
that the quotient of the G-character variety of F by the action of the trace
preserving outer automorphisms of G normalizes the variety of G-characters when
F is a free group, free abelian group, or a surface group.


title: The Manin-Stevens constant in the semistable case

abstract:
  Stevens conjectured that for every optimal parametrization $\phi\colon X_1(n)
\rightarrow E$ of an elliptic curve $E$ over $\mathbb{Q}$ of conductor $n$, the
pullback of some N\'eron differential on $E$ is the differential associated to
the normalized new eigenform that corresponds to the isogeny class of $E$. We
prove this conjecture under the assumption that $E$ is semistable, the key
novelty lying in the $2$-primary analysis when $n$ is even. For this analysis,
we first relate the general case of the conjecture to a divisibility relation
between $\mathrm{deg}\, \phi$ and a certain congruence number and then reduce
the semistable case to a question of exhibiting enough suitably constrained
oldforms. Our methods also apply to parametrizations by $X_0(n)$ and prove new
cases of the Manin conjecture.


title: Smooth Rational Curves on Singular Rational Surfaces

abstract:
  We classify all complex surfaces with quotient singularities that do not
contain any smooth rational curves, under the assumption that the canonical
divisor of the surface is not pseudo-effective. As a corollary we show that if
$X$ is a log del Pezzo surface such that for every closed point $p\in X$, there
is a smooth curve (locally analytically) passing through $p$, then $X$ contains
at least one smooth rational curve.


title:
Decidability of multiset, set and numerically decipherable directed
  figure codes

abstract:
  Codes with various kinds of decipherability, weaker than the usual unique
decipherability, have been studied since multiset decipherability was
introduced in mid-1980s. We consider decipherability of directed figure codes,
where directed figures are defined as labelled polyominoes with designated
start and end points, equipped with catenation operation that may use a merging
function to resolve possible conflicts. This is one of possible extensions
generalizing words and variable-length codes to planar structures. Here,
verification whether a given set is a code is no longer decidable in general.
We study the decidability status of figure codes depending on catenation type
(with or without a merging function), decipherability kind (unique, multiset,
set or numeric) and code geometry (several classes determined by relative
positions of start and end points of figures). We give decidability or
undecidability proofs in all but two cases that remain open.


title: A Universal Density Structure for Circum-Galactic Gas

abstract:
  We develop a new method to constrain the physical conditions in the cool
(~10^4 K) circumgalactic medium (CGM) from measurements of ionic column
densities, by assuming that the cool CGM spans a large range of gas densities
and that small high-density clouds are hierarchically embedded in large
low-density clouds. The new method combines the information available from
different sightlines during the photoionization modeling, thus yielding tighter
constraints on CGM properties compared to traditional methods which model each
sightline individually. Applying this new technique to the COS-Halos survey of
low-redshift ~L* galaxies, we find that we can reproduce all observed ion
columns in all 44 galaxies in the sample, from the low-ions to OVI, with a
single universal density structure for the cool CGM. The gas densities span the
range 50 < \rho/\rho_mean < 5x10^5 (\rho_mean is the cosmic mean), while the
physical size of individual clouds scales as ~\rho^-1, from ~35 kpc of the low
density OVI clouds to ~6 pc of the highest density low-ion clouds. The deduced
cloud sizes are too small for this density structure to be driven by
self-gravity, thus its physical origin is unclear. The implied cool CGM mass
within the virial radius is 1.3x10^10 M_sun (~1% of the halo mass), distributed
rather uniformly over the four decades in density. The mean cool gas density
profile scales as R^-1.0, where R is the distance from the galaxy center. We
construct a 3D model of the cool CGM based on our results, which we argue
provides a benchmark for the CGM structure in hydrodynamic simulations. Our
results can be tested by measuring the coherence scales of different ions.


title:
Discrete and continuous fractional persistence problems - the positivity
  property and applications

abstract:
  In this article, we study the continuous and discrete fractional persistence
problem which looks for the persistence of properties of a given classical
($\alpha=1$) differential equation in the fractional case (here using
fractional Caputo's derivatives) and the numerical scheme which are associated
(here with discrete Gr\"unwald-Letnikov derivatives). Our main concerns are
positivity, order preserving ,equilibrium points and stability of these points.
We formulate explicit conditions under which a fractional system preserves
positivity. We deduce also sufficient conditions to ensure order preserving. We
deduce from these results a fractional persistence theorem which ensures that
positivity, order preserving, equilibrium points and stability is preserved
under a Caputo fractional embedding of a given differential equation. At the
discrete level, the problem is more complicated. Following a strategy initiated
by R. Mickens dealing with non local approximations, we define a non standard
finite difference scheme for fractional differential equations based on
discrete Gr\"unwald-Letnikov derivatives, which preserves positivity
unconditionally on the discretization increment. We deduce a discrete version
of the fractional persistence theorem for what concerns positivity and
equilibrium points. We then apply our results to study a fractional
prey-predator model introduced by Javidi and al.


title:
Steiner Problem in Gromov-Hausdorff Space: the Case of Finite Metric
  Spaces

abstract:
  It is shown that each finite family of finite metric spaces, being considered
as a subset of Gromov--Hausdorff space, can be connected by a Steiner minimal
tree.


title: Aware: Controlling App Access to I/O Devices on Mobile Platforms

abstract:
  Smartphones' cameras, microphones, and device displays enable users to
capture and view memorable moments of their lives. However, adversaries can
trick users into authorizing malicious apps that exploit weaknesses in current
mobile platforms to misuse such on-board I/O devices to stealthily capture
photos, videos, and screen content without the users' consent. Contemporary
mobile operating systems fail to prevent such misuse of I/O devices by
authorized apps due to lack of binding between users' interactions and accesses
to I/O devices performed by these apps. In this paper, we propose Aware, a
security framework for authorizing app requests to perform operations using I/O
devices, which binds app requests with user intentions to make all uses of
certain I/O devices explicit. We evaluate our defense mechanisms through
laboratory-based experimentation and a user study, involving 74 human subjects,
whose ability to identify undesired operations targeting I/O devices increased
significantly. Without Aware, only 18% of the participants were able to
identify attacks from tested RAT apps. Aware systematically blocks all the
attacks in absence of user consent and supports users in identifying 82% of
social-engineering attacks tested to hijack approved requests, including some
more sophisticated forms of social engineering not yet present in available
RATs. Aware introduces only 4.79% maximum performance overhead over operations
targeting I/O devices. Aware shows that a combination of system defenses and
user interface can significantly strengthen defenses for controlling the use of
on-board I/O devices.


title: SPN graphs: when copositive=SPN

abstract:
  A real symmetric matrix $A$ is copositive if $x^TAx\ge 0$ for every
nonnegative vector $x$. A matrix is SPN if it is a sum of a real positive
semidefinite matrix and a nonnegative one. Every SPN matrix is copositive, but
the converse does not hold for matrices of order greater than $4$. A graph $G$
is an SPN graph if every copositive matrix whose graph is $G$ is SPN. In this
paper we present sufficient conditions for a graph to be SPN (in terms of its
possible blocks) and necessary conditions for a graph to be SPN (in terms of
forbidden subgraphs). We also discuss the remaining gap between these two sets
of conditions, and make a conjecture regarding the complete characterization of
SPN graphs.


title: Compact Group Actions on Topological and Noncommutative Joins

abstract:
  We consider the Type 1 and Type 2 noncommutative Borsuk-Ulam conjectures of
Baum, D$\k{a}$browski, and Hajac: there are no equivariant morphisms $A \to A
\circledast_\delta H$ or $H \to A \circledast_\delta H$, respectively, when $H$
is a nontrivial compact quantum group acting freely on a unital $C^*$-algebra
$A$. Here $A \circledast_\delta H$ denotes the equivariant noncommutative join
of $A$ and $H$; this join procedure is a modification of the topological join
that allows a free action of $H$ on $A$ to produce a free action of $H$ on $A
\circledast_\delta H$. For the classical case $H = \mathcal{C}(G)$, $G$ a
compact group, we present a reduction of the Type 1 conjecture and
counterexamples to the Type 2 conjecture. We also present some examples and
conditions under which the Type 2 conjecture does hold.


title: Squircular Calculations

abstract:
  The Fernandez-Guasti squircle is a plane algebraic curve that is an
intermediate shape between the circle and the square. In this paper, we will
analyze this curve and derive formulas for its area and polar form. We will
also provide several parametric equations of the squircle. Finally, we extend
the squircle to three dimensions by coming up with an analogous surface that is
an intermediate shape between the sphere and the cube.


title:
GEMFsim: A Stochastic Simulator for the Generalized Epidemic Modeling
  Framework

abstract:
  The recently proposed generalized epidemic modeling framework (GEMF)
\cite{sahneh2013generalized} lays the groundwork for systematically
constructing a broad spectrum of stochastic spreading processes over complex
networks. This article builds an algorithm for exact, continuous-time numerical
simulation of GEMF-based processes. Moreover the implementation of this
algorithm, GEMFsim, is available in popular scientific programming platforms
such as MATLAB, R, Python, and C; GEMFsim facilitates simulating stochastic
spreading models that fit in GEMF framework. Using these simulations one can
examine the accuracy of mean-field-type approximations that are commonly used
for analytical study of spreading processes on complex networks.


title:
The Age of the Directly-Imaged Planet Host Star $\kappa$ Andromedae
  Determined From Interferometric Observations

abstract:
  $\kappa$ Andromedae, an early type star that hosts a directly imaged low mass
companion, is expected to be oblate due to its rapid rotational velocity
($v\sin i$ = $\sim$162 $\mathrm{km~s^{-1}}$). We observed the star with the
CHARA Array's optical beam combiner, PAVO, measuring its size at multiple
orientations and determining its oblateness. The interferometric measurements,
combined with photometry and this $v\sin i$ value are used to constrain an
oblate star model that yields the fundamental properties of the star and finds
a rotation speed that is $\sim$85\% of the critical rate and a low inclination
of $\sim$30$^\circ$. Three modeled properties (the average radius, bolometric
luminosity, and equatorial velocity) are compared to MESA evolution models to
determine an age and mass for the star. In doing so, we determine an age for
the system of 47$^{+27}_{-40}$ Myr. Based on this age and previous measurements
of the companion's temperature, the BHAC15 evolution models imply a mass for
the companion of 22$^{+8}_{-9}$ M$_\mathrm{J}$.


title: Integral homology of real isotropic and odd orthogonal Grassmannians

abstract:
  We obtain a combinatorial expression for the coefficients of the boundary map
of real isotropic and odd orthogonal Grassmannians providing a natural
generalization of the formulas already obtained for Lagrangian and maximal
isotropic Grassmannians. The results are given in terms of the classification
into four types of covering pairs among the Schubert cells when identified with
signed $k$-Grassmannian permutations. It turns out that these coefficients only
depend on the positions changed over each pair of permutations. As an
application, we give an orientability criterion, exhibit a symmetry of these
coefficients and, compute low-dimensional homology groups.


title: Stellar yields from metal-rich asymptotic giant branch models

abstract:
  We present new theoretical stellar yields and surface abundances for three
grids of metal-rich asymptotic giant branch (AGB) models. Post-processing
nucleosynthesis results are presented for stellar models with initial masses
between 1$M_{\odot}$ and 7.5$M_{\odot}$ for $Z=0.007$, and 1$M_{\odot}$ and
8$M_{\odot}$ for $Z=0.014$ (solar) and $Z=0.03$. We include stellar surface
abundances as a function of thermal pulse on the AGB for elements from C to Bi
and for a selection of isotopic ratios for elements up to Fe and Ni (e.g.,
$^{12}$C/$^{13}$C), which can be obtained from observations of molecules in
stars and from the laboratory analysis of meteoritic stardust grains. Ratios of
elemental abundances of He/H, C/O, and N/O are also included, which are useful
for direct comparison to observations of AGB stars and their progeny including
planetary nebulae. The integrated elemental stellar yields are presented for
each model in the grid for hydrogen, helium and all stable elements from C to
Bi. Yields of Li are also included for intermediate-mass models with hot bottom
burning. We present the first $slow$ neutron-capture ($s$-process) yields for
super-solar metallicity AGB stars with $Z=0.03$, and the first complete
$s$-process yields for models more massive than 6$M_{\odot}$ at all three
metallicities.


title:
Limits of the circles-in-the-sky searches in the determination of cosmic
  topology of nearly flat universes

abstract:
  [Abridged] An observable signature of a detectable nontrivial spatial
topology of the Universe is the circles-in-the-sky in the CMB sky. In the most
general search, pairs of circles with deviation from antipodality $0^\circ \leq
\theta \leq 169^\circ$ and radii $10^\circ \leq \lambda \leq 90^\circ$ were
investigated, but no matching circles were found. Assuming this negative
result, we examine the question as to whether there are nearly flat universes
with compact topology that would give rise to circles whose observable
parameters $\lambda$ and $\theta$ fall o outside the ranges covered by this
search. We derive the expressions for the deviation from antipodality and for
the radius of the circles associated to a pair elements
($\gamma\,$,$\gamma^{-1}$) of the holonomy group $\Gamma$ which define the
spatial section of any positively curved universe with a nontrivial topology.
We show that there is a critical position that maximizes the deviation from
antipodality, and prove that no matter how nearly flat the Universe is, it can
always have a nontrivial spatial topology that gives rise to circles whose
deviation from antipodality $\theta$ is larger than $169^\circ$, and whose
radii of the circles $\lambda$ are smaller than $10^\circ$ for some observers.
This makes apparent that slightly positively curved universes with cosmological
parameters within Planck bounds can be endowed with a nontrivial spatial
topology with values of the parameters $\lambda$ and $\theta$ outside the
ranges covered by the searches for circles carried out so far. Thus, these
circles searches so far undertaken are not sufficient to exclude the
possibility of a universe with a detectable nontrivial cosmic topology. We
present concrete examples of such nearly flat universes, and discuss the
implications of our results in view of unavoidable practical limits of the
circles-in-the-sky method.


title:
Service Chain and Virtual Network Embeddings: Approximations using
  Randomized Rounding

abstract:
  The SDN and NFV paradigms enable novel network services which can be realized
and embedded in a flexible and rapid manner. For example, SDN can be used to
flexibly steer traffic from a source to a destination through a sequence of
virtualized middleboxes, in order to realize so-called service chains. The
service chain embedding problem consists of three tasks: admission control,
finding suitable locations to allocate the virtualized middleboxes and
computing corresponding routing paths. This paper considers the offline batch
embedding of multiple service chains. Concretely, we consider the objectives of
maximizing the profit by embedding an optimal subset of requests or minimizing
the costs when all requests need to be embedded. Interestingly, while the
service chain embedding problem has recently received much attention, so far,
only non- polynomial time algorithms (based on integer programming) as well as
heuristics (which do not provide any formal guarantees) are known. This paper
presents the first polynomial time service chain approximation algorithms both
for the case with admission and without admission control. Our algorithm is
based on a novel extension of the classic linear programming and randomized
rounding technique, which may be of independent interest. In particular, we
show that our approach can also be extended to more complex service graphs,
containing cycles or sub-chains, hence also providing new insights into the
classic virtual network embedding problem.


title:
A Unified Framework for Sparse Non-Negative Least Squares using
  Multiplicative Updates and the Non-Negative Matrix Factorization Problem

abstract:
  We study the sparse non-negative least squares (S-NNLS) problem. S-NNLS
occurs naturally in a wide variety of applications where an unknown,
non-negative quantity must be recovered from linear measurements. We present a
unified framework for S-NNLS based on a rectified power exponential scale
mixture prior on the sparse codes. We show that the proposed framework
encompasses a large class of S-NNLS algorithms and provide a computationally
efficient inference procedure based on multiplicative update rules. Such update
rules are convenient for solving large sets of S-NNLS problems simultaneously,
which is required in contexts like sparse non-negative matrix factorization
(S-NMF). We provide theoretical justification for the proposed approach by
showing that the local minima of the objective function being optimized are
sparse and the S-NNLS algorithms presented are guaranteed to converge to a set
of stationary points of the objective function. We then extend our framework to
S-NMF, showing that our framework leads to many well known S-NMF algorithms
under specific choices of prior and providing a guarantee that a popular
subclass of the proposed algorithms converges to a set of stationary points of
the objective function. Finally, we study the performance of the proposed
approaches on synthetic and real-world data.


title:
Families in the Wild (FIW): Large-Scale Kinship Image Database and
  Benchmarks

abstract:
  We present the largest kinship recognition dataset to date, Families in the
Wild (FIW). Motivated by the lack of a single, unified dataset for kinship
recognition, we aim to provide a dataset that captivates the interest of the
research community. With only a small team, we were able to collect, organize,
and label over 10,000 family photos of 1,000 families with our annotation tool
designed to mark complex hierarchical relationships and local label information
in a quick and efficient manner. We include several benchmarks for two
image-based tasks, kinship verification and family recognition. For this, we
incorporate several visual features and metric learning methods as baselines.
Also, we demonstrate that a pre-trained Convolutional Neural Network (CNN) as
an off-the-shelf feature extractor outperforms the other feature types. Then,
results were further boosted by fine-tuning two deep CNNs on FIW data: (1) for
kinship verification, a triplet loss function was learned on top of the network
of pre-trained weights; (2) for family recognition, a family-specific softmax
classifier was added to the network.


title:
Toward an improved control of the fixed-node error in quantum Monte
  Carlo: The case of the water molecule

abstract:
  All-electron Fixed-node Diffusion Monte Carlo (FN-DMC) calculations for the
nonrelativistic ground-state energy of the water molecule at equilibrium
geometry are presented. The determinantal part of the trial wavefunction is
obtained from a perturbatively selected Configuration Interaction calculation
(CIPSI method) including up to about 1.4 million of determinants. Calculations
are made using the cc-pCV$n$Z family of basis sets, with $n$=2 to 5. In
contrast with most QMC works no re-optimization of the determinantal part in
presence of a Jastrow is performed. For the largest cc-pCV5Z basis set the
lowest upper bound for the ground-state energy reported so far of -76.43744(18)
is obtained. The fixed-node energy is found to decrease regularly as a function
of the cardinal number $n$ and the Complete Basis Set limit (CBS) associated
with {\it exact nodes} is easily extracted. The resulting energy of
-76.43894(12) -in perfect agreement with the best experimentally derived value-
is the most accurate theoretical estimate reported so far. We emphasize that
employing selected CI nodes of increasing quality in a given family of basis
sets may represent a simple, deterministic, reproducible, and systematic way of
controlling the fixed-node error in DMC.


title:
A Polyhedral Study of the Integrated Minimum-Up/-Down Time and Ramping
  Polytope

abstract:
  In this paper, we study the polyhedral structure of an integrated
minimum-up/-down time and ramping polytope, which has broad applications in
variant industries. The polytope we studied includes minimum-up/-down time,
generation ramp-up/-down rate, logical, and generation upper/lower bound
constraints. By exploring its specialized structures, we derive strong valid
inequalities and explore a new proof technique to prove these inequalities are
sufficient to provide convex hull descriptions for variant two-period and
three-period polytopes, under different parameter settings. For multi-period
cases, we derive generalized strong valid inequalities (including one, two, and
three continuous variables, respectively) and further prove that these
inequalities are facet-defining under mild conditions. Moreover, we discover
efficient polynomial time separation algorithms for these inequalities to
improve the computational efficiency. Finally, extensive computational
experiments are conducted to verify the effectiveness of our proposed strong
valid inequalities by testing the applications of these inequalities to solve
both self-scheduling and network-constrained unit commitment problems, for
which our derived approach outperforms the default CPLEX significantly.


title:
Possible Existence of Superconductivity in the Quasi-One-Dimensional
  Conductor Li$_{0.9}$Mo${_6}$O$_{17}$ at Ultrahigh Magnetic Fields, $H \geq 45
  \ T$

abstract:
  We derive a so-called gap equation for superconductivity in a
quasi-one-dimensional (Q1D) layered conductor in a magnetic field, which is
parallel to both its conducting plane and its conducting axis. This equation
demonstrates that the orbital destructive effects against superconductivity
cannot destroy it, if the perpendicular to the plane coherence length is less
than the inter-plane distance. On the basis of our results, we suggest
arguments that some triplet superconducting phase was indeed discovered in
ultrahigh magnetic fields in the Q1D superconductor Li$_{0.9}$Mo$_6$O$_{17}$
[see Xiaofeng Xu et al., Phys. Rev. Lett., $\bf{102}$, 206602 (2009).] We also
discuss a possibility that the above-mentioned superconducting phase can be
stable at arbitrary high magnetic fields.


title: How to form asteroids from mm-sized grains

abstract:
  The size distribution of asteroids in the solar system suggests that they
formed top-down, with 100-1000 km bodies forming from the gravitational
collapse of dense clumps of small solid particles. We investigate the
conditions under which solid particles can form dense clumps in a
protoplanetary disc. We used a hydrodynamic code to model the solid-gas
interaction in disc. We found that particles down to millimeter size can form
dense clumps, but only in regions where solids make $\sim$ 8% of the local
surface density. More generally, we mapped the range of particle sizes and
concentrations that is consistent with the formation of particle clumps.


title:
Two robust nonconforming H$^2-$elements for linear strain gradient
  elasticity

abstract:
  We propose two nonconforming finite elements to approximate a boundary value
problem arising from strain gradient elasticity, which is a higher-order
perturbation of the linearized elastic system. Our elements are
H$^2-$nonconforming while H$^1-$conforming. We show both elements converges in
the energy norm uniformly with respect to the perturbation parameter.


title: Simultaneous Nearest Neighbor Search

abstract:
  Motivated by applications in computer vision and databases, we introduce and
study the Simultaneous Nearest Neighbor Search (SNN) problem. Given a set of
data points, the goal of SNN is to design a data structure that, given a
collection of queries, finds a collection of close points that are compatible
with each other. Formally, we are given $k$ query points $Q=q_1,\cdots,q_k$,
and a compatibility graph $G$ with vertices in $Q$, and the goal is to return
data points $p_1,\cdots,p_k$ that minimize (i) the weighted sum of the
distances from $q_i$ to $p_i$ and (ii) the weighted sum, over all edges $(i,j)$
in the compatibility graph $G$, of the distances between $p_i$ and $p_j$. The
problem has several applications, where one wants to return a set of consistent
answers to multiple related queries. This generalizes well-studied
computational problems, including NN, Aggregate NN and the 0-extension problem.
  In this paper we propose and analyze the following general two-step method
for designing efficient data structures for SNN. In the first step, for each
query point $q_i$ we find its (approximate) nearest neighbor point $\hat{p}_i$;
this can be done efficiently using existing approximate nearest neighbor
structures. In the second step, we solve an off-line optimization problem over
sets $q_1,\cdots,q_k$ and $\hat{p}_1,\cdots,\hat{p}_k$; this can be done
efficiently given that $k$ is much smaller than $n$. Even though
$\hat{p}_1,\cdots,\hat{p}_k$ might not constitute the optimal answers to
queries $q_1,\cdots,q_k$, we show that, for the unweighted case, the resulting
algorithm is $O(\log k/\log \log k)$-approximation. Also, we show that the
approximation factor can be in fact reduced to a constant for compatibility
graphs frequently occurring in practice.
  Finally, we show that the "empirical approximation factor" provided by the
above approach is very close to 1.


title: Should Entanglement Measures be Monogamous or Faithful?

abstract:
  "Is entanglement monogamous?" asks the title of a popular article [B. Terhal,
IBM J. Res. Dev. 48, 71 (2004)], celebrating C. H. Bennett's legacy on quantum
information theory. While the answer is affirmative in the qualitative sense,
the situation is less clear if monogamy is intended as a quantitative
limitation on the distribution of bipartite entanglement in a multipartite
system, given some particular measure of entanglement. Here, we formalize what
it takes for a bipartite measure of entanglement to obey a general quantitative
monogamy relation on all quantum states. We then prove that an important class
of entanglement measures fail to be monogamous in this general sense of the
term, with monogamy violations becoming generic with increasing dimension. In
particular, we show that every additive and suitably normalized entanglement
measure cannot satisfy any nontrivial general monogamy relation while at the
same time faithfully capturing the geometric entanglement structure of the
fully antisymmetric state in arbitrary dimension. Nevertheless, monogamy of
such entanglement measures can be recovered if one allows for
dimension-dependent relations, as we show explicitly with relevant examples.

categories: quant-ph cond-mat.stat-mech hep-th math-ph math.MP


title:
Generalizations of $Q$-systems and Orthogonal Polynomials from
  Representation Theory

abstract:
  We briefly describe what tau-functions in integrable systems are. We then
define a collection of tau-functions given as matrix elements for the action of
$\widehat{GL_2}$ on two-component Fermionic Fock space. These tau-functions are
solutions to a discrete integrable system called a $Q$-system.
  We can prove that our tau-functions satisfy $Q$-system relations by applying
the famous "Desnanot-Jacobi identity" or by using "connection matrices", the
latter of which gives rise to orthogonal polynomials. In this paper, we will
provide the background information required for computing these tau-functions
and obtaining the connection matrices and will then use the connection matrices
to derive our difference relations and to find orthogonal polynomials.
  We generalize the above by considering tau-functions that are matrix elements
for the action of $\widehat{GL_3}$ on three-component Fermionic Fock space, and
discuss the new system of discrete equations that they satisfy. We will show
how to use the connection matrices in this case to obtain "multiple orthogonal
polynomials of type II".


title: A new approach to the Higgs transverse-momentum resummation at NNLL+NNLO

abstract:
  We propose a new approach to the resummation of the transverse-momentum
distribution of a high-mass colour-singlet system in hadronic collisions. The
resummation is performed in momentum space and is free of kinematic
singularities at small transverse momentum. We derive a formula accurate at the
next-to-next-to-leading-logarithmic level, and present the first matched
predictions to next-to-next-to-leading order for Higgs-boson production in
gluon fusion at the LHC. This method can be adapted to all observables
featuring kinematic cancellations in the infrared region.


title:
The growth of disks and bulges during hierarchical galaxy formation. I:
  fast evolution vs secular processes

abstract:
  We present a theoretical model for the evolution of mass, angular momentum
and size of galaxy disks and bulges, and we implement it into the semi-analytic
galaxy formation code SAGE. The model follows both secular and violent
evolutionary channels, including smooth accretion, disk instabilities, minor
and major mergers. We find that the combination of our recipe with hierarchical
clustering produces two distinct populations of bulges: merger-driven bulges,
akin to classical bulges and ellipticals, and instability-driven bulges, akin
to secular (or pseudo-)bulges. The model mostly reproduces the mass-size
relation of gaseous and stellar disks, the evolution of the mass-size relation
of ellipticals, the Faber-Jackson relation, and the magnitude-colour diagram of
classical and secular bulges. The model predicts only a small overlap of
merger-driven and instability-driven components in the same galaxy, and
predicts different bulge types as a function of galaxy mass and disk fraction.
Bulge type also affects the star formation rate and colour at a given
luminosity. The model predicts a population of merger-driven red ellipticals
that dominate both the low-mass and high-mass ends of the galaxy population,
and span all dynamical ages; merger-driven bulges in disk galaxies are
dynamically old and do not interfere with subsequent evolution of the
star-forming component. Instability-driven bulges dominate the population at
intermediate galaxy masses, especially thriving in massive disks. The model
green valley is exclusively populated by instability-driven bulge hosts.
Through the present implementation the mass accretion history is perceivable in
the galaxy structure, morphology and colours.


title: New algorithmic challenges of adaptive immune repertoire construction

abstract:
  Motivation: The analysis of antibodies and T-cell receptors (TCRs)
concentrations in serum is a fundamental problem in immunoinformatics.
Repertoire construction is a preliminary step of analysis of clonal lineages,
understanding of immune response dynamics, population analysis of
immunoglobulin and TCR loci. Emergence of MiSeq Illumina sequencing machine in
2013 opened horizons of investigation of adaptive immune repertoires using
highly accurate reads. Reads produced by MiSeq are able to cover repertoires of
moderate size. At the same time, throughput of sequencing machines increases
from year to year. This will enable ultra deep scanning of adaptive immune
repertoires and analysis of their diversity. Such data requires both efficient
and highly accurate repertoire construction tools. In 2015 Safonova et al.
presented IgRepertoireConstructor, a tool for accurate construction of antibody
repertoire and immunoproteogenomics analysis. Unfortunately, proposed algorithm
was very time and memory consuming and could be a bottleneck of processing
large immunosequencing libraries. In this paper we overcome this challenge and
present IgReC, a novel algorithm for adaptive repertoire construction problem.
IgReC reconstructs a repertoire with high precision even if each input read
contains sequencing errors and performs well on contemporary datasets. Results
of computational experiments show that IgReC improves state-of-the-art in the
field. Availability: IgReC is an open source and freely available program
running on Linux platforms. The source code is available at GitHub:
yana-safonova.github.io/ig_repertoire_constructor. Contact:
safonova.yana@gmail.com


title:
Dynamical indicators for the prediction of bursting phenomena in
  high-dimensional systems

abstract:
  Drawing upon the bursting mechanism in slow-fast systems, we propose
indicators for the prediction of such rare extreme events which do not require
a priori known slow and fast coordinates. The indicators are associated with
functionals defined in terms of Optimally Time Dependent (OTD) modes. One such
functional has the form of the largest eigenvalue of the symmetric part of the
linearized dynamics reduced to these modes. In contrast to other choices of
subspaces, the proposed modes are flow invariant and therefore a projection
onto them is dynamically meaningful. We illustrate the application of these
indicators on three examples: a prototype low-dimensional model, a body forced
turbulent fluid flow, and a unidirectional model of nonlinear water waves. We
use Bayesian statistics to quantify the predictive power of the proposed
indicators.

categories: math.DS nlin.CD physics.comp-ph physics.flu-dyn


title:
Existence of a Not Necessarily Symmetric Matrix with Given Distinct
  Eigenvalues and Graph

abstract:
  For given k distinct complex conjugate pairs, l distinct real numbers, and a
given graph G on 2k+l vertices with a matching of size at least k, we will show
that there is a real matrix whose eigenvalues are the given numbers and its
graph is G. In particular, this implies that any real matrix with distinct
eigenvalues is similar to a real, irreducible, tridiagonal matrix.


title: Fine's Theorem on First-Order Complete Modal Logics

abstract:
  Fine's influential Canonicity Theorem states that if a modal logic is
determined by a first-order definable class of Kripke frames, then it is valid
in its canonical frames. This article reviews the background and context of
this result, and the history of its impact on further research. It then
develops a new characterisation of when a logic is canonically valid, providing
a precise point of distinction with the property of first-order completeness.
The ultimate point is that the construction of the canonical frame of a modal
algebra does not commute with the ultrapower construction.


title: Understanding weak values without new probability theory

abstract:
  The physical meaning of weak values and measurements can be completely
understood with Born rule and the general probability theory. It is known that
the weak value of an observable $\hat A$ with post-selection $\langle F|$ may
be out of the eigenvalue range of $\hat A$. This is because the weak value of
$\hat A$ with the post-selection is, in general, not the expectation value of
$\hat A$, but the expectation value of $\hat A| F\rangle\langle F|$ boosted by
the post-selection.


title: Interference at the tunnel ionization from double-center potential

abstract:
  The tunnel ionization of an electron bounded by two delta potentials under
the influence of a constant electric field is considered. The equations for the
electron current density for two different initial states are obtained. The
dependence of the emission current on the orientation of the potential with
respect to the field direction and the distance between them is studied.
Appropriate conditions for observation essential interference effects are
defined.


title:
Distributionally Robust Stochastic Optimization with Wasserstein
  Distance

abstract:
  Distributionally robust stochastic optimization (DRSO) is an approach to
optimization under uncertainty in which, instead of assuming that there is a
known true underlying probability distribution, one hedges against a chosen set
of distributions. In this paper we first point out that the set of
distributions should be chosen to be appropriate for the application at hand,
and that some of the choices that have been popular until recently are, for
many applications, not good choices. We next consider sets of distributions
that are within a chosen Wasserstein distance from a nominal distribution. Such
a choice of sets has two advantages: (1) The resulting distributions hedged
against are more reasonable than those resulting from other popular choices of
sets. (2) The problem of determining the worst-case expectation over the
resulting set of distributions has desirable tractability properties. We derive
a strong duality reformulation of the corresponding DRSO problem and construct
approximate worst-case distributions explicitly via the first-order optimality
conditions of the dual problem.
  Our contributions are four-fold. (i) We identify necessary and sufficient
conditions for the existence of a worst-case distribution, which are naturally
related to the growth rate of the objective function. (ii) We show that the
worst-case distributions resulting from an appropriate Wasserstein distance
have a concise structure and a clear interpretation. (iii) Using this
structure, we show that data-driven DRSO problems can be approximated to any
accuracy by robust optimization problems, and thereby many DRSO problems become
tractable by using tools from robust optimization. (iv) Our strong duality
result holds in a very general setting. As examples, we show that it can be
applied to infinite-dimensional process control and intensity estimation for
point processes.


title:
Apsidal motions of 90 eccentric binary systems in the Small Magellanic
  Cloud

abstract:
  We examined light curves of 1138 stars brighter than 18.0 mag in the $I$ band
and less than a mean magnitude error of 0.1 mag in the $V$ band from the
OGLE-III eclipsing binary catalogue, and found 90 new binary systems exhibiting
apsidal motion. In this study, the samples of apsidal motion stars in the SMC
were increased by a factor of about 3 than previously known. In order to
determine the period of the apsidal motion for the binaries, we analysed in
detail both the light curves and eclipse timings using the MACHO and OGLE
photometric database. For the eclipse timing diagrams of the systems, new times
of minimum light were derived from the full light curve combined at intervals
of one year from the survey data. The new 90 binaries have apsidal motion
periods in the range of 12$-$897 years. An additional short-term oscillation
was detected in four systems (OGLE-SMC-ECL-1634, 1947, 3035, and 4946), which
most likely arises from the existence of a third body orbiting each eclipsing
binary. Since the systems presented here are based on homogeneous data and have
been analysed in the same way, they are suitable for further statistical
analysis.


title: Transfer Learning for Low-Resource Neural Machine Translation

abstract:
  The encoder-decoder framework for neural machine translation (NMT) has been
shown effective in large data scenarios, but is much less effective for
low-resource languages. We present a transfer learning method that
significantly improves Bleu scores across a range of low-resource languages.
Our key idea is to first train a high-resource language pair (the parent
model), then transfer some of the learned parameters to the low-resource pair
(the child model) to initialize and constrain training. Using our transfer
learning method we improve baseline NMT models by an average of 5.6 Bleu on
four low-resource language pairs. Ensembling and unknown word replacement add
another 2 Bleu which brings the NMT performance on low-resource machine
translation close to a strong syntax based machine translation (SBMT) system,
exceeding its performance on one language pair. Additionally, using the
transfer learning model for re-scoring, we can improve the SBMT system by an
average of 1.3 Bleu, improving the state-of-the-art on low-resource machine
translation.


title:
Measurable genuine tripartite entanglement of ($2\otimes 2\otimes
  n$)-dimensional quantum states via only two simultaneous copies

abstract:
  Usually, the three-tangle of a tripartite pure state of qubits can be
directly measured with the simultaneous preparation of a
not-less-than-four-fold copy of the state. We show that the exact genuine
tripartite entanglement for ($2\otimes2\otimes n$)-dimensional pure quantum
states can be measured in a similar manner, provided that only two simultaneous
copies of the state are available. Lower bounds are also proposed for more
convenient experimental operations. As an example, a comprehensive
demonstration of the scheme is provided for the three-tangle of a three-qubit
state.


title: Photon statistics on the extreme entanglement

abstract:
  The effects of photon bunching and antibunching correspond to the classical
and quantum features of the electromagnetic field, respectively. No direct
evidence suggests whether these effects can be potentially related to quantum
entanglement. Here we design a cavity quantum electrodynamics model with two
atoms trapped in to demonstrate the connections between the steady-state photon
statistics and the two-atom entanglement . It is found that within the weak
dissipations and to some good approximation, the local maximal two-atom
entanglements perfectly correspond to not only the quantum feature of the
electromagnetic field---the optimal photon antibunching, but also the classical
feature---the optimal photon bunching. We also analyze the influence of strong
dissipations and pure dephasing. An intuitive physical understanding is also
given finally.


title:
Scaled up low-mass star formation in massive star-forming cores in the
  G333 giant molecular cloud

abstract:
  Three bright molecular line sources in G333 have recently been shown to
exhibit signatures of infall. We describe a molecular line radiative transfer
modelling process which is required to extract the infall signature from Mopra
and Nanten2 data. The observed line profiles differ greatly between individual
sources but are reproduced well by variations upon a common unified model where
the outflow viewing angle is the most significant difference between the
sources. The models and data together suggest that the observed properties of
the high-mass star-forming regions such as infall, turbulence, and mass are
consistent with scaled-up versions of the low-mass case with turbulent
velocities that are supersonic and an order of magnitude larger than those
found in low-mass star-forming regions. Using detailed radiative transfer
modeling, we show that the G333 cores are essentially undergoing a scaled-up
version of low mass star formation. This is an extension of earlier work in
that the degree of infall and the chemical abundances are constrained by the RT
modeling in a way that is not practical with a standard analysis of
observational data. We also find high velocity infall and high infall mass
rates, possibly suggesting accelerated collapse due to external pressure.
Molecular depletion due to freeze-out onto dust grains in central regions of
the cores is suggested by low molecular abundances of several species. Strong
evidence for a local enhancement of 13C-bearing species towards the outflow
cloud cores is discussed, consistent with the presence of shocks caused by the
supersonic motions within them.


title:
Intrinsic rotation drive by collisionless trapped electron mode
  turbulence

abstract:
  Both the parallel residual stress and parallel turbulent acceleration driven
by electrostatic collisionsless trapped electron mode (CTEM) turbulence are
calculated analytically using gyrokinetic theory. Quasilinear results show that
the parallel residual stress contributes an outward flux of co-current rotation
for normal magnetic shear and turbulence intensity profile increasing outward.
This may induce intrinsic counter-current rotation or flattening of the
co-current rotation profile. The parallel turbulent acceleration driven by CTEM
turbulence vanishes, due to the absence of a phase shift between density
fluctuation and ion pressure fluctuation. This is different from the case of
ion temperature gradient (ITG) turbulence, for which the turbulent acceleration
can provide co-current drive for normal magnetic shear and turbulence intensity
profile increasing outward. Its order of magnitude is predicted to be the same
as that of the divergence of the residual stress [Lu Wang and P.H. Diamond,
Phys. Rev. Lett. {\bf 110}, 265006 (2013)]. A possible connection of these
theoretical results to experimental observations of electron cyclotron heating
effects on toroidal rotation is discussed.


title: A Yang-Baxter equation for metaplectic ice

abstract:
  We will give new applications of quantum groups to the study of spherical
Whittaker functions on the metaplectic $n$-fold cover of $GL(r,F)$, where $F$
is a nonarchimedean local field. Earlier Brubaker, Bump, Friedberg, Chinta and
Gunnells had shown that these Whittaker functions can be identified with the
partition functions of statistical mechanical systems. They postulated that a
Yang-Baxter equation underlies the properties of these Whittaker functions. We
confirm this, and identify the corresponding Yang-Baxter equation with that of
the quantum affine Lie superalgebra
$U_{\sqrt{v}}(\widehat{\mathfrak{gl}}(1|n))$, modified by Drinfeld twisting to
introduce Gauss sums. (The deformation parameter $v$ is specialized to the
inverse of the residue field cardinality.) For principal series representations
of metaplectic groups, the Whittaker models are not unique. The scattering
matrix for the standard intertwining operators is vector valued. For a simple
reflection, it was computed by Kazhdan and Patterson, who applied it to
generalized theta series. We will show that the scattering matrix on the space
of Whittaker functions for a simple reflection coincides with the twisted
$R$-matrix of the quantum group $U_{\sqrt{v}}(\widehat{\mathfrak{gl}}(n))$.
This is a piece of the twisted $R$-matrix for
$U_{\sqrt{v}}(\widehat{\mathfrak{gl}}(1|n))$, mentioned above.


title: Acceleration of Compact Radio Jets on Sub-parsec Scales

abstract:
  Jets of compact radio sources are highly relativistic and Doppler boosted,
making studies of their intrinsic properties difficult. Observed brightness
temperatures can be used to study the intrinsic physical properties of the
relativistic jets, and constrain models of jet formation in the inner jet
region. We aim to observationally test such inner jet models. The very long
baseline interferometry (VLBI) cores of compact radio sources are optically
thick at a given frequency. The distance of the core from the central engine is
inversely proportional to the frequency. Under the equipartition condition
between the magnetic field energy and particle energy densities, the absolute
distance of the VLBI core can be predicted. We compiled the brightness
temperatures of VLBI cores at various radio frequencies of 2, 8, 15, and
86~GHz. We derive the brightness temperature on sub-parsec scales in the rest
frame of the compact radio sources. We find that the brightness temperature
increases with increasing distance from the central engine, indicating that the
intrinsic jet speed (the Lorentz-factor) increases along the jet. This implies
that the jets are accelerated in the (sub-)parsec regions from the central
engine.


title:
Dynamic network and epigenetic landscape model of a regulatory core
  underlying spontaneous immortalization and epithelial carcinogenesis

abstract:
  Tumorigenic transformation of human epithelial cells in vitro has been
described experimentally as the potential result of a process known as
spontaneous immortalization. In this process a generic series of cell state
transitions occur in which normal epithelial cells acquire a senescent state,
later surpassed to attain first a mesenchymal state and then a final
mesenchymal stem-like phenotype, with potential tumorigenic behavior. In this
paper we integrate published data on the molecular components and interactions
that have been described as key regulators of such cell states and transitions.
A large network, that is provided, is constructed and then reduced with the aim
of recovering a minimal regulatory core incorporating the necessary and
sufficient restrictions to recover the observed cell states and their generic
progression patterns in epithelial-mesenchymal transition. Data is formalized
into logical regulatory rules that govern the dynamics of each of the network's
components as a function of the states of its regulators. The proposed core
gene regulatory network attains only three steady-state gene expression
configurations that correspond to the profiles characteristic of normal
epithelial, senescent, and mesenchymal stem-like cells. Interestingly,
epigenetic landscape analyses of the uncovered network shows that it also
recovers the generic time-ordered transitions documented during tumorigenic
transformation in vitro of epithelial cells. The latter strongly correlate with
the patterns observed during the progressive pathological description of
epithelial carcinogenesis in vivo.


title: Three-dimensional non-equilibrium Potts systems with magnetic friction

abstract:
  We study the non-equilibrium steady states that emerge when two interacting
three-dimensional Potts blocks slide on each other. As at equilibrium the Potts
model exhibits different types of phase transitions for different numbers $q$
of spin states, we consider the following three cases: $q=2$ (i.e. the Ising
case), $q=3$, and $q=9$, which at equilibrium yield respectively a second order
phase transition, a weak first order transition and a strong first order
transition. In our study we focus on the anisotropic character of the steady
states that result from the relative motion and discuss the change in
finite-size signatures when changing the number $q$ of spin states.


title: Solar system tests for massive conformal gravity

abstract:
  We find the linearized gravitational field of a static spherically symmetric
mass distribution in massive conformal gravity and test it with some solar
system experiments. The result is that the theory agrees with the general
relativistic observations in the solar system for a determined lower bound on
the graviton mass.


title: Fluctuation Diamagnetism in Two-Band Superconductors

abstract:
  Anomalously large fluctuation diamagnetism around the superconducting
critical temperature has been recently observed on iron selenide (FeSe) [S.
Kasahara et al., unpublished]. This indicates that superconducting fluctuations
(SCFs) play a more significant role in FeSe, which supposedly has two-band
structure, than in the familiar single-band superconductors. Motivated by the
data in FeSe, SCF-induced diamagnetism is examined in a two-band system, on the
basis of a phenomenological approach with a Ginzburg-Landau functional. The
obtained results indicate that the SCF-induced diamagnetism may be more
enhanced than that in a single-band system due to the existence of two distinct
fluctuation modes. Such enhancement of diamagnetism unique to a two-band system
seems consistent with the large diamagnetism observed on FeSe, though still far
from a quantitative agreement.


title: On the Ball-Constrained Weighted Maximin Dispersion Problem

abstract:
  The ball-constrained weighted maximin dispersion problem $(\rm P_{ball})$ is
to find a point in an $n$-dimensional Euclidean ball such that the minimum of
the weighted Euclidean distance from given $m$ points is maximized. We propose
a new second-order cone programming relaxation for $(\rm P_{ball})$. Under the
condition $m\le n$, $(\rm P_{ball})$ is polynomial-time solvable since the new
relaxation is shown to be tight. In general, we prove that $({\rm P_{ball}})$
is NP-hard. Then, we propose a new randomized approximation algorithm for
solving $({\rm P_{ball}})$, which provides a new approximation bound of
$\frac{1-O(\sqrt{\ln(m)/n})}{2}$.


title:
Nuclear chiral and magnetic rotation in covariant density functional
  theory

abstract:
  Excitations of chiral rotation observed in triaxial nuclei and magnetic
and/or antimagnetic rotations seen in near-spherical nuclei have attracted a
lot of attention. Unlike conventional rotation in well-deformed or
superdeformed nuclei, here the rotational axis is not necessary coinciding with
any principal axis of the nuclear density distribution. Thus, tilted axis
cranking is mandatory to describe these excitations self-consistently in the
framework of covariant density functional theory (CDFT). We will briefly
introduce the formalism of tilted axis cranking CDFT and its application for
magnetic and antimagnetic rotation phenomena. Configuration-fixed CDFT and its
predictions for nuclear chiral configurations and for favorable triaxial
deformation parameters are also presented, and the discoveries of the multiple
chiral doublets (M\c{hi}D) in 133Ce and 103Rh are discussed.


title:
A New Constraint on the Ly$\alpha$ Fraction of UV Very Bright Galaxies
  at Redshift 7

abstract:
  We study the extent to which very bright (-23.0 < MUV < -21.75) Lyman-break
selected galaxies at redshifts z~7 display detectable Lya emission. To explore
this issue, we have obtained follow-up optical spectroscopy of 9 z~7 galaxies
from a parent sample of 24 z~7 galaxy candidates selected from the 1.65 sq.deg
COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared
public survey data, and new ultra-deep Subaru z'-band imaging (which we also
present and describe in this paper). Our spectroscopy has yielded only one
possible detection of Lya at z=7.168 with a rest-frame equivalent width EW_0 =
3.7 (+1.7/-1.1) Angstrom. The relative weakness of this line, combined with our
failure to detect Lya emission from the other spectroscopic targets allows us
to place a new upper limit on the prevalence of strong Lya emission at these
redshifts. For conservative calculation and to facilitate comparison with
previous studies at lower redshifts, we derive a 1-sigma upper limit on the
fraction of UV bright galaxies at z~7 that display EW_0 > 50 Angstrom, which we
estimate to be < 0.23. This result may indicate a weak trend where the fraction
of strong Lya emitters ceases to rise, and possibly falls between z~6 and z~7.
Our results also leave open the possibility that strong Lya may still be more
prevalent in the brightest galaxies in the reionization era than their fainter
counterparts. A larger spectroscopic sample of galaxies is required to derive a
more reliable constraint on the neutral hydrogen fraction at z~7 based on the
Lya fraction in the bright galaxies.


title: Cross sections of Borel flows with restrictions on the distance set

abstract:
  Given a set of positive reals, we provide a necessary and sufficient
condition for a free Borel flow to admit a cross section with all distances
between adjacent points coming from this set.


title:
A Primal-Dual Type Algorithm with the $O(1/t)$ Convergence Rate for
  Large Scale Constrained Convex Programs

abstract:
  This paper considers large scale constrained convex programs, which are
usually not solvable by interior point methods or other Newton-type methods due
to the prohibitive computation and storage complexity for Hessians and matrix
inversions. Instead, large scale constrained convex programs are often solved
by gradient based methods or decomposition based methods. The conventional
primal-dual subgradient method, aka, Arrow-Hurwicz-Uzawa subgradient method, is
a low complexity algorithm with the $O(1/\sqrt{t})$ convergence rate, where $t$
is the number of iterations. If the objective and constraint functions are
separable, the Lagrangian dual type method can decompose a large scale convex
program into multiple parallel small scale convex programs. The classical dual
gradient algorithm is an example of Lagrangian dual type methods and has
convergence rate $O(1/\sqrt{t})$. Recently, a new Lagrangian dual type
algorithm with faster $O(1/t)$ convergence is proposed in Yu and Neely (2015).
However, if the objective or constraint functions are not separable, each
iteration of the Lagrangian dual type method in Yu and Neely (2015) requires to
solve a large scale unconstrained convex program, which can have huge
complexity. This paper proposes a new primal-dual type algorithm, which only
involves simple gradient updates at each iteration and has the $O(1/t)$
convergence rate.


title: Chudnovsky's Conjecture for very general points in $\mathbb{P}_k^{N}$

abstract:
  We prove a long-standing conjecture of Chudnovsky for very general and
generic points in $\mathbb{P}_k^N$, where $k$ is an algebraically closed field
of characteristic zero, and for any finite set of points lying on a quadric,
without any assumptions on $k$. We also prove that for any homogeneous ideal
$I$ in the homogeneous coordinate ring $R=k[x_0, \ldots, x_N]$, Chudnovsky's
conjecture holds for large enough symbolic powers of $I$.