title: Second order Gyrokinetic theory for Particle-In-Cell codes

abstract:
  The main idea of Gyrokinetic dynamical reduction consists in systematical
removing of fastest scale of motion (the gyro motion) from plasma's dynamics,
resulting in a considerable model simplification and gain of computing time.
  Gyrokinetic Maxwell-Vlasov system is broadly implemented in nowadays
numerical experiments for modeling strongly magnetized plasma (both laboratory
and astrophysical). Different versions of reduced set of equations exist
depending on the construction of the Gyrokinetic reduction procedure and
approximations assumed while their derivation.
  The purpose of this paper is to explicitly show the connection between the
general second order gyrokinetic Maxwell-Vlasov system issued from the Modern
Gyrokinetic theory derivation and the model currently implemented in global
electromagnetic Particle in Cell code ORB5.
  Strictly necessary information about the Modern Gyrokinetic formalism is
given together with the consistent derivation of the gyrokinetic Maxwell-Vlasov
equations from the first principle of dynamics. Variational formulation of
dynamics is also used for simultaneously obtaining the corresponding exact
energy conservation law. The result of that explicit derivation is used for
verification of the energy conservation diagnostics currently implemented in
ORB5 code.
  This work subscribes into the context of codes verification project VeriGyro
currently run in IPP Max Planck Institut in collaboration with others European
institutions.


title: Cross-stitch Networks for Multi-task Learning

abstract:
  Multi-task learning in Convolutional Networks has displayed remarkable
success in the field of recognition. This success can be largely attributed to
learning shared representations from multiple supervisory tasks. However,
existing multi-task approaches rely on enumerating multiple network
architectures specific to the tasks at hand, that do not generalize. In this
paper, we propose a principled approach to learn shared representations in
ConvNets using multi-task learning. Specifically, we propose a new sharing
unit: "cross-stitch" unit. These units combine the activations from multiple
networks and can be trained end-to-end. A network with cross-stitch units can
learn an optimal combination of shared and task-specific representations. Our
proposed method generalizes across multiple tasks and shows dramatically
improved performance over baseline methods for categories with few training
examples.


title: Training Region-based Object Detectors with Online Hard Example Mining

abstract:
  The field of object detection has made significant advances riding on the
wave of region-based ConvNets, but their training procedure still includes many
heuristics and hyperparameters that are costly to tune. We present a simple yet
surprisingly effective online hard example mining (OHEM) algorithm for training
region-based ConvNet detectors. Our motivation is the same as it has always
been -- detection datasets contain an overwhelming number of easy examples and
a small number of hard examples. Automatic selection of these hard examples can
make training more effective and efficient. OHEM is a simple and intuitive
algorithm that eliminates several heuristics and hyperparameters in common use.
But more importantly, it yields consistent and significant boosts in detection
performance on benchmarks like PASCAL VOC 2007 and 2012. Its effectiveness
increases as datasets become larger and more difficult, as demonstrated by the
results on the MS COCO dataset. Moreover, combined with complementary advances
in the field, OHEM leads to state-of-the-art results of 78.9% and 76.3% mAP on
PASCAL VOC 2007 and 2012 respectively.


title:
Secure Degrees of Freedom of the Multiple Access Wiretap Channel with
  Multiple Antennas

abstract:
  We consider a two-user multiple-input multiple-output (MIMO) multiple access
wiretap channel with $N$ antennas at each transmitter, $N$ antennas at the
legitimate receiver, and $K$ antennas at the eavesdropper. We determine the
optimal sum secure degrees of freedom (s.d.o.f.) for this model for all values
of $N$ and $K$. We subdivide our problem into several regimes based on the
values of $N$ and $K$, and provide achievable schemes based on real and vector
space alignment techniques for fixed and fading channel gains, respectively. To
prove the optimality of the achievable schemes, we provide matching converses
for each regime. Our results show how the number of eavesdropper antennas
affects the optimal sum s.d.o.f. of the multiple access wiretap channel.


title: Noncommutative principal bundles through twist deformation

abstract:
  We construct noncommutative principal bundles deforming principal bundles
with a Drinfeld twist (2-cocycle). If the twist is associated with the
structure group then we have a deformation of the fibers. If the twist is
associated with the automorphism group of the principal bundle, then we obtain
noncommutative deformations of the base space as well. Combining the two twist
deformations we obtain noncommutative principal bundles with both
noncommutative fibers and base space. More in general, the natural isomorphisms
proving the equivalence of a closed monoidal category of modules and its twist
related one are used to obtain new Hopf-Galois extensions as twists of
Hopf-Galois extensions. A sheaf approach is also considered, and examples
presented.


title: On the time delay between ultra-relativistic particles

abstract:
  The time delay between the receptions of ultra-relativistic particles emitted
simultaneously is a useful observable for both fundamental physics and
cosmology. The expression of the delay when the particles travel through an
arbitrary spacetime has been derived recently by Fanizza et al., using a
particular coordinate system and self-consistent assumptions. The present
article shows that this formula enjoys a simple physical interpretation: the
relative velocity between two ultra-relativistic particles is constant. This
result reveals an interesting kinematical property of general relativity,
namely that the tidal forces experienced by ultra-relativistic particles in the
direction of their motion are much smaller than those experienced orthogonally
to their motion.


title: Ramanujan Graphs in Polynomial Time

abstract:
  The recent work by Marcus, Spielman and Srivastava proves the existence of
bipartite Ramanujan (multi)graphs of all degrees and all sizes. However, that
paper did not provide a polynomial time algorithm to actually compute such
graphs. Here, we provide a polynomial time algorithm to compute certain
expected characteristic polynomials related to this construction. This leads to
a deterministic polynomial time algorithm to compute bipartite Ramanujan
(multi)graphs of all degrees and all sizes.


title:
Sustained phase separation and spin glass in Co-doped
  K$_{x}$Fe$_{2-y}$Se$_{2}$ single crystals

abstract:
  We present Co substitution effects in K$_{x}$Fe$_{2-y-z}$Co$_{z}$Se$_{2}$
(0.06 $\leq$ $z$ $\leq$ 1.73) single crystal alloys. By 3.5\% of Co doping
superconductivity is suppressed whereas phase separation of semiconducting
K$_{2}$Fe$_{4}$Se$_{5}$ and superconducting/metallic K$_{x}$Fe$_{2}$Se$_{2}$ is
still present. We show that the arrangement and distribution of superconducting
phase (stripe phase) is connected with the arrangement of K, Fe and Co atoms.
Semiconducting spin glass is found in proximity to superconducting state,
persisting for large Co concentrations. At high Co concentrations ferromagnetic
metallic state emerges above the spin glass. This is coincident with changes of
the unit cell, arrangement and connectivity of stripe conducting phase.


title:
A search for sub-second radio variability predicted to arise toward 3C
  84 from intergalactic dispersion

abstract:
  We empirically evaluate the scheme proposed by Lieu & Duan (2013) in which
the light curve of a time-steady radio source is predicted to exhibit increased
variability on a characteristic timescale set by the sightline's electron
column density. Application to extragalactic sources is of significant appeal
as it would enable a unique and reliable probe of cosmic baryons. We examine
temporal power spectra for 3C 84 observed at 1.7 GHz with the Karl G. Jansky
Very Large Array and the Robert C. Byrd Green Bank Telescope. These data
constrain the ratio between standard deviation and mean intensity for 3C 84 to
less than 0.05% at temporal frequencies ranging between 0.1-200 Hz. This limit
is 3 orders of magnitude below the variability predicted by Lieu & Duan (2013)
and is in accord with theoretical arguments presented by Hirata & McQuinn
(2014) rebutting electron density dependence. We identify other spectral
features in the data consistent with the slow solar wind, a coronal mass
ejection, and the ionosphere.


title: The S-basis and M-basis Problems for Separable Banach Spaces

abstract:
  This note has two objectives. The first objective is show that, even if a
separable Banach space does not have a Schauder basis (S-basis), there always
exists Hilbert spaces $\mcH_1$ and $\mcH_2$, such that $\mcH_1$ is a continuous
dense embedding in $\mcB$ and $\mcB$ is a continuous dense embedding in
$\mcH_2$. This is the best possible improvement of a theorem due to Mazur (see
\cite{BA} and also \cite{PE1}). The second objective is show how $\mcH_2$
allows us to provide a positive answer to the Marcinkiewicz-basis (M-basis)
problem.


title: Discovery of an extremely wide-angle bipolar outflow in AFGL 5142

abstract:
  Most bipolar outflows are associated with individual young stellar objects
and have small opening angles. Here we report the discovery of an extremely
wide-angle ($\sim$180$\arcdeg$) bipolar outflow ("EWBO") in a cluster forming
region AFGL 5142 from low-velocity emission of the HCN (3-2) and HCO$^{+}$
(3-2) lines. This bipolar outflow is along a north-west to south-east direction
with a line-of-sight flow velocity of about 3 km~s$^{-1}$ and is spatially
connected to the high-velocity jet-like outflows. It seems to be a collection
of low-velocity material entrained by the high-velocity outflows due to
momentum feedback. The total ejected mass and mass loss rate due to both high
velocity jet-like outflows and the "EWBO" are $\sim$24.5 M$_{\sun}$ and
$\sim1.7\times10^{-3}$ M$_{\sun}$~yr$^{-1}$, respectively. Global collapse of
the clump is revealed by the "blue profile" in the HCO$^{+}$ (1-0) line. A
hierarchical network of filaments was identified in NH$_{3}$ (1,1) emission.
Clear velocity gradients of the order of 10 km~s$^{-1}$~pc$^{-1}$ are found
along filaments, indicating gas inflow along the filaments. The sum of the
accretion rate along filaments and mass infall rate along the line of sight is
$\sim$3.1$\times10^{-3}$ M$_{\sun}$~yr$^{-1}$, which exceeds the total mass
loss rate, indicating that the central cluster is probably still gaining mass.
The central cluster is highly fragmented and 22 condensations are identified in
1.1 mm continuum emission. The fragmentation process seems to be determined by
thermal pressure and turbulence. The magnetic field may not play an important
role in fragmentation.


title: The Observer's Guide to the Gamma-Ray Burst-Supernova Connection

abstract:
  In this review we present a progress report of the connection between
long-duration gamma-ray bursts (GRBs) and their accompanying supernovae (SNe).
The analysis is from the point of view of an observer, with much of the
emphasis placed on how observations, and the modelling of observations, have
constrained what we known about GRB-SNe. We discuss their photometric and
spectroscopic properties, their role as cosmological probes, including their
measured luminosity$-$decline relationships, and how they can be used to
measure the Hubble constant. We present a statistical analysis of their
bolometric properties, and use this to determine the properties of the
"average" GRB-SNe: which has a kinetic energy of $E_{\rm K} \approx
2.5\times10^{52}$ erg, an ejecta mass of $M_{\rm ej} \approx 6$ M$_{\odot}$, a
nickel mass of $M_{\rm Ni} \approx 0.4$ M$_{\odot}$, a peak photospheric
velocity of $v_{\rm ph} \approx 21,000$ km s$^{-1}$, a peak bolometric
luminosity of $L_{\rm p} \approx 1\times10^{43}$ erg s$^{-1}$, and it reaches
peak bolometric light in $t_{\rm p} \approx 13$ days. We discuss their
geometry, consider the various physical processes that are thought to power the
luminosity of GRB-SNe, and whether differences exist between GRB-SNe and the
SNe associated with ultra-long duration GRBs. We discuss how observations of
the environments of GRB-SNe further constrain the physical properties of their
progenitor stars, and give an overview of the current theoretical paradigms of
their suspected central engines. We also present an overview of the
radioactively powered transients that have been photometrically associated with
short-duration GRBs. We conclude the review by discussing what additional
research is needed to further our understanding of GRB-SNe, in particular the
role of binary-formation channels and the connection of GRB-SNe with
superluminous SNe (abridged).


title:
Search for associations containing young stars (SACY) VII. New stellar
  and substellar candidate members in the young associations

abstract:
  The young associations offer us one of the best opportunities to study the
properties of young stellar and substellar objects and to directly image
planets thanks to their proximity ($<$200 pc) and age ($\approx$5-150 Myr).
However, many previous works have been limited to identifying the brighter,
more active members ($\approx$1 M$_\odot$) owing to photometric survey
sensitivities limiting the detections of lower mass objects. We search the
field of view of 542 previously identified members of the young associations to
identify wide or extremely wide (1000-100,000 au in physical separation)
companions. We combined 2MASS near-infrared photometry ($J$, $H$, $K$) with
proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the
field of view of known members. We collated further photometry and spectroscopy
from the literature and conducted our own high-resolution spectroscopic
observations for a subsample of candidate members. This complementary
information allowed us to assess the efficiency of our method. We identified 84
targets (45: 0.2-1.3 M$_\odot$, 17: 0.08-0.2 M$_\odot$, 22: $<$0.08 M$_\odot$)
in our analysis, ten of which have been identified from spectroscopic analysis
in previous young association works. For 33 of these 84, we were able to
further assess their membership using a variety of properties (X-ray emission,
UV excess, H$_\alpha$, lithium and K I equivalent widths, radial velocities,
and CaH indices). We derive a success rate of 76-88% for this technique based
on the consistency of these properties. Once confirmed, the targets identified
in this work would significantly improve our knowledge of the lower mass end of
the young associations. Additionally, these targets would make an ideal new
sample for the identification and study of planets around nearby young stars.


title:
Multi-wavelength Observations of the Dissociative Merger in the Galaxy
  Cluster CIZA J0107.7+5408

abstract:
  We present results based on X-ray, optical, and radio observations of the
massive galaxy cluster CIZA J0107.7+5408. We find that this system is a post
core passage, dissociative, binary merger, with the optical galaxy density
peaks of each subcluster leading their associated X-ray emission peaks. This
separation occurs because the diffuse gas experiences ram pressure forces while
the effectively collisionless galaxies (and presumably their associated dark
matter halos) do not. This system contains double peaked diffuse radio
emission, possibly a double radio relic with the relics lying along the merger
axis and also leading the X-ray cores. We find evidence for a temperature peak
associated with the SW relic, likely created by the same merger shock that is
powering the relic radio emission in this region. Thus, this system is a
relatively rare clean example of a dissociative binary merger, which can in
principle be used to place constraints on the self-interaction cross-section of
dark matter. Low frequency radio observations reveal ultra-steep spectrum
diffuse radio emission that is not correlated with the X-ray, optical, or high
frequency radio emission. We suggest that these sources are radio phoenixes,
which are preexisting non-thermal particle populations that have been
re-energized through adiabatic compression by the same merger shocks that power
the radio relics. Finally, we place upper limits on inverse Compton emission
from the SW radio relic.


title:
Phase transitions of an anisotropic N=4 super Yang-Mills plasma via
  holography

abstract:
  Black hole solutions of type IIB supergravity were previously found that are
dual to N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial
deformation. In the zero temperature limit, these black holes approach a
Liftshitz like scaling solution in the IR. It was recently shown that these
black holes are unstable, and at low temperatures there is a new class of black
hole solutions that are thermodynamically preferred. We extend this analysis,
by considering consistent truncations of the Kaluza-Klein reduction of IIB
supergravity on a five-sphere that preserves multiple scalar and $U(1)$ gauge
fields. We show that the previously constructed black holes become unstable at
low temperatures, and construct new classes of exotic black hole solutions. We
study the DC thermo-electric conductivity of these $U(1)$ charged black holes,
and find a diverging DC conductivity at zero temperature due to the divergence
of the gauge field coupling.


title: First order topological phase transition of the Haldane--Hubbard model

abstract:
  We study the interplay of topological band structure and conventional
magnetic long-range order in spinful Haldane model with onsite repulsive
interaction. Using the dynamical cluster approximation with clusters of up to
24 sites we find evidence of a first order phase transition from a Chern
insulator at weak coupling to a topologically trivial antiferromagnetic
insulator at strong coupling. These results call into question a previously
found intermediate state with coexisting topological character and
antiferromagnetic long-range order. Experimentally measurable signatures of the
first order transition include hysteretic behavior of the double occupancy,
single-particle excitation gap and nearest neighbor spin-spin correlations.
This first order transition is contrasted with a continuous phase transition
from the conventional band insulator to the antiferromagnetic insulator in the
ionic Hubbard model on the honeycomb lattice.


title:
Globular clusters hosting intermediate-mass black-holes: no
  mass-segregation based candidates

abstract:
  Recently, both stellar mass-segregation and binary-fractions were uniformly
measured on relatively large samples of Galactic Globular Clusters (GCs).
Simulations show that both sizeable binary-star populations and
Intermediate-Mass Black Holes (IMBHs) quench mass-segregation in relaxed GCs.
Thus mass-segregation in GCs with a reliable binary-fraction measurement is a
valuable probe to constrain IMBHs. In this paper we combine mass-segregation
and binary-fraction measurements from the literature to build a sample of 33
GCs (with measured core-binary fractions), and a sample of 43 GCs (with a
binary fraction measurement in the area between the core radius and the
half-mass radius). Within both samples we try to identify IMBH-host candidates.
These should have relatively low mass-segregation, a low binary fraction (<
5%), and short (< 1 Gyr) relaxation time. Considering the core binary fraction
sample, no suitable candidates emerge. If the binary fraction between the core
and the half-mass radius is considered, two candidates are found, but this is
likely due to statistical fluctuations. We also consider a larger sample of 54
GCs where we obtained an estimate of the core binary fraction using a
predictive relation based on metallicity and integrated absolute magnitude.
Also in this case no suitable candidates are found. Finally, we consider the GC
core- to half-mass radius ratio, that is expected to be larger for GCs
containing either an IMBH or binaries. We find that GCs with large core- to
half-mass radius ratios are less mass-segregated (and show a larger binary
fraction), confirming the theoretical expectation that the energy sources
responsible for the large core are also quenching mass-segregation


title: Mapping the genuine bosonic quartic couplings

abstract:
  The larger center-of-mass energy of the Large Hadron Collider Run 2 opens up
the possibility of a more detailed study of the quartic vertices of the
electroweak gauge bosons. Our goal in this work is to classify all operators
possessing quartic interactions among the electroweak gauge bosons that do not
exhibit triple gauge-boson vertices associated to them. We obtain all relevant
operators in the non-linear and linear realizations of the $SU(2)_L \otimes
U(1)_Y$ gauge symmetry.


title:
Long-term X-Ray Spectral Variability in AGN from the Palomar sample
  observed by Swift

abstract:
  We present X-ray spectral variability of 24 local active galactic nuclei
(AGN) from the Palomar sample of nearby galaxies, as observed mainly by Swift.
From hardness ratio measurements, we find that 18 AGN with low accretion rates
show hardening with increasing count rate, converse to the softer-when-brighter
behaviour normally observed in AGN with higher accretion rates. Two AGN show
softening with increasing count rate, two show more complex behaviour, and two
do not show any simple relationship.
  Sufficient data were available for the spectra of 13 AGN to be summed in
flux-bins. In 9 of these sources, correlated luminosity-dependent changes in
the photon index ($\Gamma$) of a power-law component are found to be the main
cause of hardness variability. For 6 objects, with a low accretion rate as a
fraction of the Eddington rate (\.m$\mathrm{_{Edd}}$), $\Gamma$ is
anticorrelated with \.m$\mathrm{_{Edd}}$, i.e. `harder-when-brighter' behaviour
is observed. The 3 higher-\.m$\mathrm{_{Edd}}$-rate objects show a positive
correlation between $\Gamma$ and \.m$\mathrm{_{Edd}}$. This transition from
harder-when-brighter at low \.m$\mathrm{_{Edd}}$s to softer-when-brighter at
high \.m$\mathrm{_{Edd}}$s can be explained by a change in the dominant source
of seed-photons for X-ray emission from cyclo-synchrotron emission from the
Comptonising corona itself to thermal seed-photons from the accretion disc.
This transition is also seen in the `hard state' of black hole X-ray binaries
(BHXRBs). The results support the idea that LINERs are analogues of BHXRBs in
the hard state and that Seyferts are analogues of BHXRBs in either the
high-accretion-rate end of the hard state or in the hard-intermediate state.


title:
Kondo impurities in the Kitaev spin liquid: Numerical renormalization
  group solution and gauge-flux-driven screening

abstract:
  Kitaev's honeycomb-lattice compass model describes a spin liquid with
emergent fractionalized excitations. Here we study the physics of isolated
magnetic impurities coupled to the Kitaev spin-liquid host. We reformulate this
Kondo-type problem in terms of a many-state quantum impurity coupled to a
multichannel bath of Majorana fermions and present the numerically exact
solution using Wilson's numerical renormalization group technique. Quantum
phase transitions occur as a function of Kondo coupling and locally applied
field. At zero field, the impurity moment is partially screened only when it
binds an emergent gauge flux, and otherwise becomes free at low temperatures.
We show how Majorana degrees of freedom determine the fixed-point properties,
make contact with Kondo screening in pseudogap Fermi systems, and discuss
effects away from the dilute limit.


title: Error Propagation Through a Network With Non-Uniform Failure

abstract:
  A central concern of network operators is to estimate the probability of an
incident that affects a significant part and thus may yield to a breakdown. We
answer this question by modeling how a failure of either a node or an edge will
affect the rest of the network using percolation theory. Our model is general
in the sense that it only needs two inputs: the topology of the network and the
chances of failure of its components. These chances may vary to represent
different types of edges having different tendencies to fail. We illustrate the
approach by an example, for which we can even obtain closed form expressions
for the likelihood of an outbreak remaining bounded or spreading unlimitedly.


title:
Massive black hole binaries from runaway collisions: the impact of
  metallicity

abstract:
  The runaway collision scenario is one of the most promising mechanisms to
explain the formation of intermediate-mass black holes (IMBHs) in young dense
star clusters. On the other hand, the massive stars that participate in the
runaway collisions lose mass by stellar winds. In this paper, we discuss new
N-body simulations of massive (6.5x10^4 Msun) star clusters, in which we added
upgraded recipes for stellar winds and supernova explosion at different
metallicity. We follow the evolution of the principal collision product (PCP),
through dynamics and stellar evolution, till it forms a stellar remnant. At
solar metallicity, the mass of the final merger product spans from few solar
masses up to ~30 Msun. At low metallicity (0.01-0.1 Zsun) the maximum remnant
mass is ~250 Msun, in the range of IMBHs. A large fraction (~0.6) of the PCPs
are not ejected from the parent star cluster and acquire stellar or black hole
(BH) companions. Most of the long-lived binaries hosting a PCP are BH-BH
binaries. We discuss the importance of this result for gravitational wave
detection.


title: F-Theory and N=1 SCFTs in Four Dimensions

abstract:
  Using the F-theory realization, we identify a subclass of 6d (1,0) SCFTs
whose compactification on a Riemann surface leads to N = 1 4d SCFTs where the
moduli space of the Riemann surface is part of the moduli space of the theory.
In particular we argue that for a special case of these theories (dual to M5
branes probing ADE singularities), we obtain 4d N = 1 theories whose space of
marginal deformations is given by the moduli space of flat ADE connections on a
Riemann surface.


title:
Critical O(N) models above four dimensions: Small-N solutions and
  stability

abstract:
  We explore O(N) models in dimensions $4<d<6$. Specifically, we investigate
models of an O(N) vector field coupled to an additional scalar field via a
cubic interaction. Recent results in $d=6-\epsilon$ have uncovered an
interacting ultraviolet fixed point of the renormalization group (RG) if the
number N of components of the vector field is large enough, suggesting that
these models are asymptotically safe. We set up a functional RG analysis of
these systems to address three key issues: Firstly, we find that in $d=5$ the
interacting fixed point exists all the way down to N=1. Secondly, we show that
the standard O(N) universality classes are actually embedded in those of the
cubic models, in that the latter exhibit the same values for (most of) the
critical exponents, but feature an additional third RG relevant direction.
Thirdly, we address the critical question of global stability of the
fixed-point potential to test whether the fixed point can underly a viable
quantum field theory.


title:
Identifying IGR J14091-6108 as a magnetic CV with a massive white dwarf
  using X-ray and optical observations

abstract:
  IGR J14091-6108 is a Galactic X-ray source known to have an iron emission
line, a hard X-ray spectrum, and an optical counterpart. Here, we report on
X-ray observations of the source with XMM-Newton and NuSTAR as well as optical
spectroscopy with ESO/VLT and NOAO/SOAR. In the X-rays, this provides data with
much better statistical quality than the previous observations, and this is the
first report of the optical spectrum. Timing analysis of the XMM data shows a
very significant detection of 576.3+/-0.6 s period. The signal has a pulsed
fraction of 30%+/-3% in the 0.3-12 keV range and shows a strong drop with
energy. The optical spectra show strong emission lines with significant
variability in the lines and continuum, indicating that they come from an
irradiated accretion disk. Based on these measurements, we identify the source
as a magnetic Cataclysmic Variable of Intermediate Polar (IP) type where the
white dwarf spin period is 576.3 s. The X-ray spectrum is consistent with the
continuum emission mechanism being due to thermal Bremsstrahlung, but partial
covering absorption and reflection are also required. In addition, we use the
IP mass (IPM) model, which suggests that the white dwarf in this system has a
high mass, possibly approaching the Chandrasekhar limit.


title: Toward a Science of Autonomy for Physical Systems: Construction

abstract:
  Today, ensuring and improving safety, productivity, quality, and
sustainability in construction, operation, and maintenance of national civil
infrastructure systems through advances in robotics and automation is a
national imperative. By "national civil infrastructure" we refer to the 4.5M
commercial buildings, 3.9M miles of public roads, 2M miles of oil and natural
gas pipelines, 600K bridges, 190K cell phone towers, 120K miles of major
railroads, 100K miles of levees, 84K dams, 50K miles of electrical power lines,
25K miles of commercially navigable waterways, and 5K public-use airports in
the United States, all of which are critical to our national economy and
society. By "ensuring and improving safety, productivity, quality, and
sustainability" we mean to guarantee performance across the entire life cycle
of civil infrastructure, from construction to operation and from maintenance to
disposal. By "advances in robotics and automation" we mean innovative research
and education that will provide tools for systematic and timely execution of
construction, and also collection, analysis, visualization, and operational use
of big data in built environments for project monitoring and control purposes.
In the following, we discuss the current state of construction and operation of
the national civil infrastructure systems in detail and present several
opportunities for improvements through research and education on robotics and
automation.


title:
Star Formation and AGN Activity in Galaxy Clusters from $z=1-2$: a
  Multi-wavelength Analysis Featuring $Herschel$/PACS

abstract:
  We present a detailed, multi-wavelength study of star formation (SF) and AGN
activity in 11 near-infrared (IR) selected, spectroscopically confirmed,
massive ($\gtrsim10^{14}\,\rm{M_{\odot}}$) galaxy clusters at $1<z<1.75$. Using
new, deep $Herschel$/PACS imaging, we characterize the optical to far-IR
spectral energy distributions (SEDs) for IR-luminous cluster galaxies, finding
that they can, on average, be well described by field galaxy templates.
Identification and decomposition of AGN through SED fittings allows us to
include the contribution to cluster SF from AGN host galaxies. We quantify the
star-forming fraction, dust-obscured SF rates (SFRs), and specific-SFRs for
cluster galaxies as a function of cluster-centric radius and redshift. In good
agreement with previous studies, we find that SF in cluster galaxies at
$z\gtrsim1.4$ is largely consistent with field galaxies at similar epochs,
indicating an era before significant quenching in the cluster cores
($r<0.5\,$Mpc). This is followed by a transition to lower SF activity as
environmental quenching dominates by $z\sim1$. Enhanced SFRs are found in lower
mass ($10.1< \log \rm{M_{\star}}/\rm{M_{\odot}}<10.8$) cluster galaxies. We
find significant variation in SF from cluster-to-cluster within our uniformly
selected sample, indicating that caution should be taken when evaluating
individual clusters. We examine AGN in clusters from $z=0.5-2$, finding an
excess AGN fraction at $z\gtrsim1$, suggesting environmental triggering of AGN
during this epoch. We argue that our results $-$ a transition from field-like
to quenched SF, enhanced SF in lower mass galaxies in the cluster cores, and
excess AGN $-$ are consistent with a co-evolution between SF and AGN in
clusters and an increased merger rate in massive haloes at high redshift.


title:
The disappearing momentum of the supercurrent in the superconductor to
  normal phase transformation

abstract:
  A superconductor in a magnetic field has surface currents that prevent the
magnetic field from penetrating its interior. These currents carry kinetic
energy and mechanical momentum. When the temperature is raised and the system
becomes normal the currents disappear. Where do the kinetic energy and
mechanical momentum of the currents go, and how? Here we propose that the
answer to this question reveals a key necessary condition for materials to be
superconductors, that is not part of conventional BCS-London theory:
superconducting materials need to have hole carriers.


title: High Temperature Superconductivity in Iron Pnictides and Chalcogenides

abstract:
  Superconductivity develops in metals upon the formation of a coherent
macroscopic quantum state of electron pairs. Iron pnictides and chalcogenides
are materials that have high superconducting transition temperatures. In this
Review, we describe the advances in the field that have led to higher
superconducting transition temperatures in iron-based superconductors and the
wide range of materials that form them. We summarize both the essential aspects
of the normal state and the mechanism for superconductivity. We emphasize the
degree of electron-electron correlations and their manifestation in properties
of the normal state. We examine the nature of magnetism, analyse its role in
driving the electronic nematicity, and discuss quantum criticality at the
border of magnetism in the phase diagram. Finally, we review the amplitude and
structure of the superconducting pairing, and survey the potential settings for
optimizing superconductivity.


title: On the capillary self-focusing in a microfluidic system

abstract:
  A computational framework is developed to address capillary self-focusing in
Step Emulsification. The microfluidic system consists of a single shallow and
wide microchannel that merges into a deep reservoir. A continuum approach
coupled with a volume of fluid method is used to model the capillary
self-focusing effect. The original governing equations are reduced using the
Hele-Shaw approximation. We show that the interface between the two fluids
takes the shape of a neck narrowing in the flow direction just before entering
the reservoir, in agreement with our experimental observations. Our
computational model relies on the assumption that the pressure at the boundary,
where the fluid exits into the reservoir, is the uniform pressure in the
reservoir. We investigate this hypothesis by comparing the numerical results
with experimental data. We conjecture that the pressure boundary condition
becomes important when the width of the neck is comparable to the depth of the
microchannel. A correction to the exit pressure boundary condition is then
proposed, which is determined by comparison with experimental data. We also
present the experimental observations and the numerical results of the
transitions of breakup regimes.


title: On non-separable growths of omega supporting measures

abstract:
  We present several $\mathsf{ZFC}$ examples of compactifications
$\gamma\omega$ of $\omega$ such that their remainders
$\gamma\omega\backslash\omega$ are nonseparable and carry strictly positive
measures.


title:
An extremely high velocity molecular jet surrounded by an ionized cavity
  in the protostellar source Serpens SMM1

abstract:
  We report ALMA observations of a one-sided, high-velocity ($\sim$80 km
s$^{-1}$) CO($J = 2 \rightarrow 1$) jet powered by the intermediate-mass
protostellar source Serpens SMM1-a. The highly collimated molecular jet is
flanked at the base by a wide-angle cavity; the walls of the cavity can be seen
in both 4 cm free-free emission detected by the VLA and 1.3 mm thermal dust
emission detected by ALMA. This is the first time that ionization of an outflow
cavity has been directly detected via free-free emission in a very young,
embedded Class 0 protostellar source that is still powering a molecular jet.
The cavity walls are ionized either by UV photons escaping from the accreting
protostellar source, or by the precessing molecular jet impacting the walls.
These observations suggest that ionized outflow cavities may be common in Class
0 protostellar sources, shedding further light on the radiation, outflow, and
jet environments in the youngest, most embedded forming stars.


title: BoxLib with Tiling: An AMR Software Framework

abstract:
  In this paper we introduce a block-structured adaptive mesh refinement (AMR)
software framework that incorporates tiling, a well-known loop transformation.
Because the multiscale, multiphysics codes built in BoxLib are designed to
solve complex systems at high resolution, performance on current and next
generation architectures is essential. With the expectation of many more cores
per node on next generation architectures, the ability to effectively utilize
threads within a node is essential, and the current model for parallelization
will not be sufficient. We describe a new version of BoxLib in which the tiling
constructs are embedded so that BoxLib-based applications can easily realize
expected performance gains without extra effort on the part of the application
developer. We also discuss a path forward to enable future versions of BoxLib
to take advantage of NUMA-aware optimizations using the TiDA portable library.


title:
Real time confinement following a quantum quench to a non-integrable
  model

abstract:
  Light cone spreading of correlations and entanglement is a key feature of the
non-equilibrium quench dynamics of many-body quantum systems. First proposed
theoretically, it has been experimentally revealed in cold-atomic gases and it
is expected to be a generic characteristic of any quench in systems with
short-range interactions and no disorder. Conversely, here we propose a
mechanism that, through confinement of the elementary excitations, strongly
suppresses the light-cone spreading. Confinement is a celebrated concept in
particle physics, but it also exists in condensed matter systems, most notably
in one spatial dimension where it has been experimentally observed. Our results
are obtained for the Ising spin chain with transverse and longitudinal magnetic
field, but the proposed mechanism is of general validity since it is based on
the sole concept of confinement and it should be easily observed in cold atom
experiments.


title: Flat surfaces, Bratteli diagrams, and unique ergodicity \`a la Masur

abstract:
  Recalling the construction of a flat surface from a Bratteli diagram, this
paper considers the dynamics of the shift map on the space of all bi-infinite
Bratteli diagrams as the renormalizing dynamics on a moduli space of flat
surfaces of finite area. A criterion of unique ergodicity similar to that of
Masur's for flat surface holds: if there is a subsequence of the renormalizing
dynamical system which has a good accumulation point, the translation flow or
Bratteli-Vershik transformation is uniquely ergodic. Related questions are
explored.


title:
Robust Decentralized Voltage Control of DC-DC Converters with
  Applications to Power Sharing and Ripple Sharing

abstract:
  This paper addresses the problem of output voltage regulation for multiple
DC-DC converters connected to a grid, and prescribes a robust scheme for
sharing power among different sources. Also it develops a method for sharing
120 Hz ripple among DC power sources in a prescribed proportion, which
accommodates the different capabilities of DC power sources to sustain the
ripple. We present a decentralized control architecture, where a nested
(inner-outer) control design is used at every converter. An interesting aspect
of the proposed design is that the analysis and design of the entire
multi-converter system can be done using an equivalent single converter system,
where the multi-converter system inherits the performance and robustness
achieved by a design for the single-converter system. Another key aspect of
this work is that the voltage regulation problem is addressed as a
disturbance-rejection problem, where {\em unknown} load current is viewed as an
external signal, and thus, no prior information is required on the nominal
loading conditions. The control design is obtained using robust optimal-control
framework. Case studies presented show the enhanced performance of prescribed
optimal controllers.


title:
Classical irregular blocks, Hill's equation and PT-symmetric periodic
  complex potentials

abstract:
  The Schroedinger eigenvalue problems for the Whittaker-Hill potential
$Q_{2}(x)=\tfrac{1}{2} h^2\cos4x+4h\mu\cos2x$ and the periodic complex
potential $Q_{1}(x)=\tfrac{1}{4}h^2{\rm e}^{-4ix}+2h^2\cos2x$ are studied using
their realizations in two-dimensional conformal field theory (2dCFT). It is
shown that for the weak coupling (small) $h\in\mathbb{R}$ and non-integer
Floquet parameter $\nu\notin\mathbb{Z}$ spectra of hamiltonians
$H_{i}\!=\!-{\rm d}^2/{\rm d}x^2 + Q_{i}(x)$, $i=1,2$ and corresponding two
linearly independent eigenfunctions are given by the classical limit of the
"single flavor" and "two flavors" ($N_f=1,2$) irregular conformal blocks. It is
known that complex non-hermitian hamiltonians which are PT-symmetric (=
invariant under simultaneous parity P and time reversal T transformations) can
have real eigenvalues. The hamiltonian $H_{1}$ is PT-symmetric for
$h,x\in\mathbb{R}$. It is found that $H_{1}$ has a real spectrum in the weak
coupling region for $\nu\in\mathbb{R}\setminus\mathbb{Z}$. This fact in an
elementary way follows from a definition of the $N_f=1$ classical irregular
block. Thus, $H_{1}$ can serve as yet another new model for testing postulates
of PT-symmetric quantum mechanics.


title: Clustering and the Three-Point Function

abstract:
  We develop analytical methods for computing the structure constant for three
heavy operators, starting from the recently proposed hexagon approach. Such a
structure constant is a semiclassical object, with the scale set by the inverse
length of the operators playing the role of the Planck constant. We reformulate
the hexagon expansion in terms of multiple contour integrals and recast it as a
sum over clusters generated by the residues of the measure of integration. We
test the method on two examples. First, we compute the asymptotic three-point
function of heavy fields at any coupling and show the result in the
semiclassical limit matches both the string theory computation at strong
coupling and the tree-level results obtained before. Second, in the case of one
non-BPS and two BPS operators at strong coupling we sum up all wrapping
corrections associated with the opposite bridge to the non-trivial operator, or
the "bottom" mirror channel. We also give an alternative interpretation of the
results in terms of a gas of fermions and show that they can be expressed
compactly as an operator-valued super-determinant.


title:
Frustration in an exactly solvable mixed-spin Ising model with bilinear
  and three-site four-spin interactions on a decorated square lattice

abstract:
  Competitive effects of so-called three-site four-spin interactions, single
ion anisotropy and bilinear interactions is studied in the mixed spin-1/2 and
spin-1 Ising model on a decorated square lattice. Exploring the
decoration-iteration transformation, we have obtained exact closed-form
expressions for the partition function and other thermodynamic quantities of
the model. From these relations, we have numerically determined ground- state
and finite-temperature phase diagrams of the system. We have also investigated
temperature variations of the correlation functions, internal energy, entropy,
specific heat and Helmholtz free energy of the system. From the physical point
of view, the most interesting result represents our observation of a partially
ordered ferromagnetic or phase in the system with zero bilinear interactions.
It is remarkable, that due to strong frustrations disordered spins survive in
the system even at zero temperature, so that the ground state of the system
becomes macroscopically degenerate with non-zero entropy. Introduction of
arbitrarily small bilinear interaction completely removes degeneracy and the
entropy always goes to zero at the the ground state.


title:
General CPT-even dimension-five nonminimal couplings between fermions
  and photons yielding EDM and MDM

abstract:
  In this letter, we examine a new class of CPT-even nonminimal interactions,
between fermions and photons, deprived of higher order derivatives, that yields
electric dipole moment (EDM) and magnetic dipole moment (MDM) in the context of
the Dirac equation. The couplings are dimension-five CPT-even and
Lorentz-violating nonminimal structures, composed of a rank-2 tensor,
$T_{\mu\nu}$, the electromagnetic tensor, and gamma matrices, being addressed
in its axial and non-axial Hermitian versions, and also comprising general
possibilities. We then use the electron's anomalous magnetic dipole moment and
electron electric dipole moment measurements to reach upper bounds of $1$ part
in $10^{20}$ and $10^{25}$ (eV )$^{-1}$.


title: A model for the LHC diboson excess

abstract:
  The first run of the LHC showed hints of a new resonance with mass near $1.9$
TeV decaying into electroweak gauge boson pairs as well as into dijets. While
Run 2 has neither confirmed nor ruled out such a resonance, it has yielded new
constraints on models attempting to explain these decays. Additionally in $W'$
models where this new resonance is a charged vector boson that is a weak
isospin singlet there is the potential for conflict with the electroweak
precision $T$ parameter. We construct variants of a $W'$ resonance model that
provide an excellent fit to both Run 1 and Run 2 data, as well as electroweak
precision measurements. The model also predicts a neutral vector boson, a $Z'$,
with mass close to $3$ TeV. This $Z'$ is compatible with the intriguing Run 2
observation of a dielectron pair with invariant mass of $2.9$ TeV at CMS.


title: Metrisability of Painlev\'e equations

abstract:
  We solve the metrisability problem for the six Painlev\'e equations, and more
generally for all 2nd order ODEs with Painlev\'e property, and determine for
which of these equations their integral curves are geodesics of a (pseudo)
Riemannian metric on a surface.


title: One Bubble to Rule Them All

abstract:
  We apply the principles of quantum mechanics and quantum cosmology to predict
probabilities for our local observations of a universe undergoing false vacuum
eternal inflation. At a sufficiently fine-grained level, histories of the
universe describe a mosaic of bubble universes separated by inflationary
regions. We show that predictions for local observations can be obtained
directly from sets of much coarser grained histories which only follow a single
bubble. These coarse-grained histories contain neither information about our
unobservable location nor about the unobservable large-scale structure outside
our own bubble. Applied to a landscape of false vacua in the no-boundary state
we predict our local universe emerged from the dominant decay channel of the
lowest energy false vacuum. We compare and contrast this framework for
prediction based on quantum cosmology with traditional approaches to the
measure problem in cosmology.


title: Existentially closed fields with finite group actions

abstract:
  We study algebraic and model-theoretic properties of existentially closed
fields with an action of a fixed finite group. Such fields turn out to be
pseudo-algebraically closed in a rather strong sense. We place this work in a
more general context of the model theory of fields with a (finite) group scheme
action.


title:
Stochastic optimal control of McKean-Vlasov equations with anticipating
  law

abstract:
  In this paper, we generalise Pontryagin's stochastic maximum principle to
controlled McKean-Vlasov equations with anticipating law. The associated new
type of delayed backward equations with implicit terminal condition is studied.


title:
Effortless Data Exploration with zenvisage: An Expressive and
  Interactive Visual Analytics System

abstract:
  Data visualization is by far the most commonly used mechanism to explore
data, especially by novice data analysts and data scientists. And yet, current
visual analytics tools are rather limited in their ability to guide data
scientists to interesting or desired visualizations: the process of visual data
exploration remains cumbersome and time-consuming. We propose zenvisage, a
platform for effortlessly visualizing interesting patterns, trends, or insights
from large datasets. We describe zenvisage's general purpose visual query
language, ZQL ("zee-quel") for specifying the desired visual trend, pattern, or
insight - ZQL draws from use-cases in a variety of domains, including biology,
mechanical engineering, climate science, and commerce. We formalize the
expressiveness of ZQL via a visual exploration algebra, and demonstrate that
ZQL is at least as expressive as that algebra. While analysts are free to use
ZQL directly, we also expose ZQL via a visual specification interface that we
describe in this paper. We then describe our architecture and optimizations,
preliminary experiments in supporting and optimizing for ZQL queries in our
initial zenvisage prototype, and a user study to evaluate whether data
scientists are able to effectively use zenvisage for real applications.


title:
Asynchronous Stochastic Gradient Descent with Variance Reduction for
  Non-Convex Optimization

abstract:
  We provide the first theoretical analysis on the convergence rate of the
asynchronous stochastic variance reduced gradient (SVRG) descent algorithm on
non-convex optimization. Recent studies have shown that the asynchronous
stochastic gradient descent (SGD) based algorithms with variance reduction
converge with a linear convergent rate on convex problems. However, there is no
work to analyze asynchronous SGD with variance reduction technique on
non-convex problem. In this paper, we study two asynchronous parallel
implementations of SVRG: one is on a distributed memory system and the other is
on a shared memory system. We provide the theoretical analysis that both
algorithms can obtain a convergence rate of $O(1/T)$, and linear speed up is
achievable if the number of workers is upper bounded. V1,v2,v3 have been
withdrawn due to reference issue, please refer the newest version v4.


title:
Localization of Temperature Using Plasmonic Hot Spots in Metal
  Nanostructures: The Nano-Optical Antenna Approach and Fano Effect

abstract:
  It is challenging to strongly localize temperature in small volumes because
heat transfer is a diffusive process. Here we show how to overcome this
limitation using electrodynamic hot spots and interference effects in the
regime of continuous-wave (CW) excitation. We introduce a set of figures of
merit for the localization of temperature and for the efficiency of the
plasmonic photo-thermal effect. Our calculations show that the temperature
localization in a trimer nanoparticle assembly is a complex function of the
geometry and sizes. Large nanoparticles in the trimer play the role of the
nano-optical antenna whereas the small nanoparticle in the plasmonic hot spot
acts as a nano-heater. Under the peculiar conditions, the temperature increase
inside a nanoparticle trimer can be localized in a hot spot region at the small
heater nanoparticle and, in this way, a thermal hot spot can be realized.
However, the overall power efficiency of temperature generation in this trimer
is much smaller than that of a single nanoparticle. We can overcome the latter
disadvantage by using a trimer with a nanorod. In the trimer assembly composed
of a nanorod and two spherical nanoparticles, we observe a strong plasmonic
Fano effect that leads to the concertation of optical energy dissipation in the
small heater nanorod. Therefore, the power-absorption efficiency of temperature
generation in the nanorod-based assembly greatly increases due to the strong
plasmonic Fano effect. The Fano heater incorporating a small nanorod in the hot
spot has obviously the best performance compared to both single nanocrystals
and a nanoparticle trimer. The principles of heat localization described here
can be potentially used for thermal photo-catalysis, energy conversion and
bio-related applications.


title:
Late Pop III Star Formation During the Epoch of Reionization: Results
  from the Renaissance Simulations

abstract:
  We present results on the formation of Pop III stars at redshift 7.6 from the
Renaissance Simulations, a suite of extremely high-resolution and physics-rich
radiation transport hydrodynamics cosmological adaptive-mesh refinement
simulations of high redshift galaxy formation performed on the Blue Waters
supercomputer. In a survey volume of about 220 comoving Mpc$^3$, we found 14
Pop III galaxies with recent star formation. The surprisingly late formation of
Pop III stars is possible due to two factors: (i) the metal enrichment process
is local and slow, leaving plenty of pristine gas to exist in the vast volume;
and (ii) strong Lyman-Werner radiation from vigorous metal-enriched star
formation in early galaxies suppresses Pop III formation in ("not so") small
primordial halos with mass less than $\sim$ 3 $\times$ 10$^7$ M$_\odot$. We
quantify the properties of these Pop III galaxies and their Pop III star
formation environments. We look for analogues to the recently discovered
luminous Ly $\alpha$ emitter CR7 (Sobral et al. 2015), which has been
interpreted as a Pop III star cluster within or near a metal-enriched star
forming galaxy. We find and discuss a system similar to this in some respects,
however the Pop III star cluster is far less massive and luminous than CR7 is
inferred to be.


title: FSG: Fast String Graph Construction for De Novo Assembly of Reads Data

abstract:
  The string graph for a collection of next-generation reads is a lossless data
representation that is fundamental for de novo assemblers based on the
overlap-layout-consensus paradigm. In this paper, we explore a novel approach
to compute the string graph, based on the FM-index and Burrows-Wheeler
Transform. We describe a simple algorithm that uses only the FM-index
representation of the collection of reads to construct the string graph,
without accessing the input reads. Our algorithm has been integrated into the
SGA assembler as a standalone module to construct the string graph.
  The new integrated assembler has been assessed on a standard benchmark,
showing that FSG is significantly faster than SGA while maintaining a moderate
use of main memory, and showing practical advantages in running FSG on multiple
threads.


title: Spectrally engineering photonic entanglement with a time lens

abstract:
  In the same manner that free-space propagation and curved glass lenses are
used to shape the spatial properties of light, a combination of chromatic
dispersion and devices known as time lenses may be used to reshape its temporal
properties. These techniques have found extensive application in classical
optical signal processing based on nonlinear optics. A new set of challenges
presents itself when processing quantum signals, including noise suppression
and high fidelity requirements. In this work, we construct a single-photon time
lens based on dispersion and nonlinear sum-frequency generation to image the
spectral waveform of half of an entangled photon pair. We find that the joint
spectrum of the photon pair has strongly negative frequency correlations before
the time lens and strongly positive correlations afterwards, verifying that the
process has an overall negative spectro-temporal magnification. The temporal
imaging of energy-time entangled systems opens up a host of new possible
techniques for distinctly quantum tasks in the frequency domain, including
state engineering, and our results demonstrate that the upconversion time lens
is an essential part of the single-photon waveform manipulation toolkit.


title:
Size and Disorder Effects in Elasticity of Cellular Structures: From
  Discrete Models to Continuum Representations

abstract:
  Open cellular solids usually possess random microstructures that may contain
a characteristic length scale, such as the cell size. This gives rise to size
dependent mechanical properties where large systems behave differently from
small systems. Furthermore, these structures are often irregular, which not
only affects the size dependent behaviour but also leads to significant
property variations among different microstructure realizations. The
computational model for cellular microstructures is based on networks of
Timoshenko beams. It is a computationally efficient approach allowing to obtain
statistically representative averages from computing large numbers of
realizations. For detailed analysis of the underlying deformation mechanisms an
energetically consistent continuization method was developed which links the
forces and displacements of discrete beam networks to equivalent spatially
continuous stress and strain fields. This method is not only useful for
evaluation and visualization purposes but also allows to perform ensemble
averages of, e.g., continuous stress patterns - an analysis approach which is
highly beneficial for comparisons and statistical analysis of microstructures
with respect to different degrees of structural disorder.


title:
Vehicle Routing Problem with Time Windows: A Deterministic Annealing
  approach

abstract:
  The Vehicle Routing Problem with Time-Windows (VRPTW) is an important problem
in allocating resources on networks in time and space. We present in this paper
a Deterministic Annealing (DA)-based approach to solving the VRPTW with its
aspects of routing and scheduling, as well as to model additional constraints
of heterogeneous vehicles and shipments. This is the first time, to our
knowledge, that a DA approach has been used for problems in the class of the
VRPTW. We describe how the DA approach can be adapted to generate an effective
heuristic approach to the VRPTW. Our DA approach is also designed to not get
trapped in local minima, and demonstrates less sensitivity to initial
solutions. The algorithm trades off routing and scheduling in an n-dimensional
space using a tunable parameter that allows us to generate qualitatively good
solutions. These solutions differ in the degree of intersection of the routes,
making the case for transfer points where shipments can be exchanged.
Simulation results on randomly generated instances show that the constraints
are respected and demonstrate near optimal results (when verifiable) in terms
of schedules and tour length of individual tours in each solution.


title:
Protein sequestration versus Hill-type repression in circadian clock
  models

abstract:
  Circadian (~24hr) clocks are self-sustained endogenous oscillators with which
organisms keep track of daily and seasonal time. Circadian clocks frequently
rely on interlocked transcriptional- translational feedback loops to generate
rhythms that are robust against intrinsic and extrinsic perturbations. To
investigate the dynamics and mechanisms of the intracellular feedback loops in
circadian clocks, a number of mathematical models have been developed. The
majority of the models use Hill functions to describe transcriptional
repression in a way that is similar to the Goodwin model. Recently, a new class
of models with protein sequestration-based repression has been introduced.
Here, we discuss how this new class of models differs dramatically from those
based on Hill-type repression in several fundamental aspects: conditions for
rhythm generation, robust network designs and the periods of coupled
oscillators. Consistently, these fundamental properties of circadian clocks
also differ among Neurospora, Drosophila, and mammals depending on their key
transcriptional repression mechanisms (Hill-type repression or protein
sequestration). Based on both theoretical and experimental studies, this review
highlights the importance of careful modeling of transcriptional repression
mechanisms in molecular circadian clocks.


title: Nonlinear consensus protocols with applications to quantized systems

abstract:
  Two types of general nonlinear consensus protocols are considered in this
paper, namely the systems with nonlinear measurement and communication of the
agents' states, respectively. The solutions of the systems are understood in
the sense of Filippov to handle the possible discontinuity of the nonlinear
functions. For each case, we prove the asymptotic stability of the systems
defined on both directed and undirected graphs. Then we reinterpret the results
about the general models for a specific type of systems, i.e., the quantized
consensus protocols, which extend some existing results (e.g., [1,2]) from
undirected graphs to directed ones.


title:
GPz: Non-stationary sparse Gaussian processes for heteroscedastic
  uncertainty estimation in photometric redshifts

abstract:
  The next generation of cosmology experiments will be required to use
photometric redshifts rather than spectroscopic redshifts. Obtaining accurate
and well-characterized photometric redshift distributions is therefore critical
for Euclid, the Large Synoptic Survey Telescope and the Square Kilometre Array.
However, determining accurate variance predictions alongside single point
estimates is crucial, as they can be used to optimize the sample of galaxies
for the specific experiment (e.g. weak lensing, baryon acoustic oscillations,
supernovae), trading off between completeness and reliability in the galaxy
sample. The various sources of uncertainty in measurements of the photometry
and redshifts put a lower bound on the accuracy that any model can hope to
achieve. The intrinsic uncertainty associated with estimates is often
non-uniform and input-dependent, commonly known in statistics as
heteroscedastic noise. However, existing approaches are susceptible to outliers
and do not take into account variance induced by non-uniform data density and
in most cases require manual tuning of many parameters. In this paper, we
present a Bayesian machine learning approach that jointly optimizes the model
with respect to both the predictive mean and variance we refer to as Gaussian
processes for photometric redshifts (GPz). The predictive variance of the model
takes into account both the variance due to data density and photometric noise.
Using the SDSS DR12 data, we show that our approach substantially outperforms
other machine learning methods for photo-z estimation and their associated
variance, such as TPZ and ANNz2. We provide a Matlab and Python implementations
that are available to download at https://github.com/OxfordML/GPz .


title:
On the divisor-class group of monadic submonoids of rings of
  integer-valued polynomials

abstract:
  Let $R$ be a factorial domain. In this work we investigate the connections
between the arithmetic of ${\rm Int}(R)$ (i.e., the ring of integer-valued
polynomials over $R$) and its monadic submonoids (i.e., monoids of the form
$\{g\in {\rm Int}(R)\mid g\mid_{{\rm Int}(R)} f^k$ for some
$k\in\mathbb{N}_0\}$ for some nonzero $f\in {\rm Int}(R)$). Since every monadic
submonoid of ${\rm Int}(R)$ is a Krull monoid it is possible to describe the
arithmetic of these monoids in terms of their divisor-class group. We give an
explicit description of these divisor-class groups in several situations and
provide a few techniques that can be used to determine them. As an application
we show that there are strong connections between ${\rm Int}(R)$ and its
monadic submonoids. If $R=\mathbb{Z}$ or more generally if $R$ has sufficiently
many "nice" atoms, then we prove that the infinitude of the elasticity and the
tame degree of ${\rm Int}(R)$ can be explained by using the structure of
monadic submonoids of ${\rm Int}(R)$.


title:
A Vortex Filament Tracking Method for the Gross-Pitaevskii Model of a
  Superfluid

abstract:
  We present an accurate and robust numerical method to track quantized vortex
lines in a superfluid described by the Gross-Pitaevskii equation. By utilizing
the pseudo-vorticity field of the associated complex scalar order parameter of
the superfluid, we are able to track the topological defects of the superfluid
and reconstruct the vortex lines which correspond to zeros of the field.
Throughout, we assume our field is periodic to allow us to make extensive use
of the Fourier representation of the field and its derivatives in order to
retain spectral accuracy. We present several case studies to test the precision
of the method which include the evaluation of the curvature and torsion of a
torus vortex knot, and the measurement of the Kelvin wave spectrum of a vortex
line and a vortex ring. The method we present makes no a-priori assumptions on
the geometry of the vortices and is therefore applicable to a wide range of
systems such as a superfluid in a turbulent state that is characterised by many
vortex rings coexisting with sound waves. This allows us to track the positions
of the vortex filaments in a dense turbulent vortex tangle and extract
statistical information about the distribution of the size of the vortex rings
and the inter-vortex separations. In principle, the method can be extended to
track similar topological defects arising in other physical systems.


title: Parametrized Homology via Zigzag Persistence

abstract:
  This paper develops the idea of homology for 1-parameter families of
topological spaces. We express parametrized homology as a collection of real
intervals with each corresponding to a homological feature supported over that
interval or, equivalently, as a persistence diagram. By defining persistence in
terms of finite rectangle measures, we classify barcode intervals into four
classes. Each of these conveys how the homological features perish at both ends
of the interval over which they are defined.


title: Highly tunable elastic dielectric metasurface lenses

abstract:
  Dielectric metasurfaces are two-dimensional structures composed of
nano-scatterers that manipulate phase and polarization of optical waves with
subwavelength spatial resolution, enabling ultra-thin components for free-space
optics. While high performance devices with various functionalities, including
some that are difficult to achieve using conventional optical setups have been
shown, most demonstrated components have a fixed functionality. Here we
demonstrate highly tunable metasurface devices based on subwavelength thick
silicon nano-posts encapsulated in a thin transparent elastic polymer. As proof
of concept, we demonstrate a metasurface microlens operating at 915 nm, with
focal distance tuning from 600 $\mu$m to 1400 $\mu$m through radial strain,
while maintaining a diffraction limited focus and a focusing efficiency above
50$\%$. The demonstrated tunable metasurface concept is highly versatile for
developing ultra-slim, multi-functional and tunable optical devices with
widespread applications ranging from consumer electronics to medical devices
and optical communications.


title: 750 GeV Diphotons and Supersymmetric Grand Unification

abstract:
  We investigate the 750 GeV diphoton excess in terms of supersymmetric models
which preserve grand unification in the ultraviolet. We show that minimal
extensions of the MSSM by a singlet and a vector-like 5-plet or 10-plet of
SU(5) can explain the observed signal while remaining perturbative up to the
GUT scale. Different from previous analyses we rely on light sfermions in the
loops which - compared to the analog non-supersymmetric models - enhance the
diphoton cross section by up to a factor of seven. While the resonance decay
width is narrow, mass splitting of the scalar and pseudoscalar components may
result in a double resonance. We perform a likelihood analysis on the ATLAS and
CMS data to show that the significance of the diphoton excess increases from
3.3 sigma (single narrow resonance) to 3.9 sigma for the double resonance. We
also provide signal predictions in other diboson channels to be tested at
LHC-13.


title:
Diffusion in an expanding medium: Fokker-Planck equation, Green's
  function and first-passage properties

abstract:
  We present a classical, mesoscopic derivation of the Fokker-Planck equation
for diffusion in an expanding medium. To this end, we take a conveniently
generalized Chapman-Kolmogorov equation as the starting point. We obtain an
analytical expression for the Green's function (propagator) and investigate
both analytically and numerically how this function and the associated moments
behave. We also study first-passage properties in expanding hyperspherical
geometries. We show that in all cases the behavior is determined to a great
extent by the so-called Brownian conformal time $\tau(t)$, which we define via
the relation $\dot \tau=1/a^2$, where $a(t)$ is the expansion scale factor. If
the medium expansion is driven by a power law [$a(t) \propto t^\gamma$ with
$\gamma>0$], we find interesting crossover effects in the mixing effectiveness
of the diffusion process when the characteristic exponent $\gamma$ is varied.
Crossover effects are also found at the level of the survival probability and
of the moments of the first passage-time distribution with two different
regimes separated by the critical value $\gamma=1/2$. The case of an
exponential scale factor is analyzed separately both for expanding and
contracting media. In the latter situation, a stationary probability
distribution arises in the long time limit.


title:
Suspended InAs nanowire Josephson junctions assembled via
  dielectrophoresis

abstract:
  We present a novel technique for the realization of suspended Josephson
junctions based on InAs semiconductor nanowires. The devices are assembled
using a technique of drop-casting guided by dielectrophoresis that allows to
finely align the nanostructures on top of the electrodes. The proposed
architecture removes the interaction between the nanowire and the substrate
which is known to influence disorder and the orientation of the Rashba vector.
The relevance of this approach in view of the implementation of Josephson
junctions based on High-Temperature Superconductors is discussed.


title: Community Detection with Node Attributes and its Generalization

abstract:
  Community detection algorithms are fundamental tools to understand
organizational principles in social networks. With the increasing power of
social media platforms, when detecting communities there are two possi- ble
sources of information one can use: the structure of social network and node
attributes. However structure of social networks and node attributes are often
interpreted separately in the research of community detection. When these two
sources are interpreted simultaneously, one common as- sumption shared by
previous studies is that nodes attributes are correlated with communities. In
this paper, we present a model that is capable of combining topology
information and nodes attributes information with- out assuming correlation.
This new model can recover communities with higher accuracy even when node
attributes and communities are uncorre- lated. We derive the detectability
threshold for this model and use Belief Propagation (BP) to make inference.
This algorithm is optimal in the sense that it can recover community all the
way down to the threshold. This new model is also with the potential to handle
edge content and dynamic settings.


title:
Origin of low sodium capacity in graphite and generally weak substrate
  binding of Na and Mg among alkali and alkaline earth metals

abstract:
  It is well known that graphite has a low capacity for Na but a high capacity
for other alkali metals. The growing interest in alternative cation batteries
beyond Li makes it particularly important to elucidate the origin of this
behavior, which is not well understood. In examining this question, we find a
quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg
generally have the weakest chemical binding to a given substrate, compared with
the other elements in the same column of the periodic table. We demonstrate
this with quantum mechanics calculations for a wide range of substrate
materials (not limited to C) covering a variety of structures and chemical
compositions. The phenomenon arises from the competition between trends in the
ionization energy and the ion-substrate coupling, down the columns of the
periodic table. Consequently, the cathodic voltage for Na and Mg is expected to
be lower than those for other metals in the same column. This generality
provides a basis for analyzing the binding of alkali and alkaline earth metal
atoms over a broad range of systems.


title: Algorithmic computation of polynomial amoebas

abstract:
  We present algorithms for computation and visualization of amoebas, their
contours, compactified amoebas and sections of three-dimensional amoebas by
two-dimensional planes. We also provide method and an algorithm for the
computation of~polynomials whose amoebas exhibit the most complicated topology
among all polynomials with a fixed Newton polytope. The presented algorithms
are implemented in computer algebra systems Matlab 8 and Mathematica 9.


title:
Quasinormal modes and a new instability of Einstein-Gauss-Bonnet black
  holes in the de Sitter world

abstract:
  Analysis of time-domain profiles for gravitational perturbations shows that
Gauss-Bonnet black holes in a de Sitter world possess a new kind of dynamical
instability which does not take place for asymptotically flat
Einstein-Gauss-Bonnet black holes. The new instability is in the gravitational
perturbations of the scalar type and is due to the nonvanishing cosmological
constant. Analysis of the quasinormal spectrum in the stability sector shows
that although the scalar type of gravitational perturbations alone does not
obey Hod's conjectural bound, connecting the damping rate and the Hawking
temperature, the vector and tensor types (and thereby the gravitational
spectrum as a whole) do obey it.


title: What do different evaluation metrics tell us about saliency models?

abstract:
  How best to evaluate a saliency model's ability to predict where humans look
in images is an open research question. The choice of evaluation metric depends
on how saliency is defined and how the ground truth is represented. Metrics
differ in how they rank saliency models, and this results from how false
positives and false negatives are treated, whether viewing biases are accounted
for, whether spatial deviations are factored in, and how the saliency maps are
pre-processed. In this paper, we provide an analysis of 8 different evaluation
metrics and their properties. With the help of systematic experiments and
visualizations of metric computations, we add interpretability to saliency
scores and more transparency to the evaluation of saliency models. Building off
the differences in metric properties and behaviors, we make recommendations for
metric selections under specific assumptions and for specific applications.


title: M5-branes on S^2 x M_4: Nahm's Equations and 4d Topological Sigma-models

abstract:
  We study the 6d N=(0,2) superconformal field theory, which describes multiple
M5-branes, on the product space S^2 x M_4, and suggest a correspondence between
a 2d N=(0,2) half-twisted gauge theory on S^2 and a topological sigma-model on
the four-manifold M_4. To set up this correspondence, we determine in this
paper the dimensional reduction of the 6d N=(0,2) theory on a two-sphere and
derive that the four-dimensional theory is a sigma-model into the moduli space
of solutions to Nahm's equations, or equivalently the moduli space of
k-centered SU(2) monopoles, where k is the number of M5-branes. We proceed in
three steps: we reduce the 6d abelian theory to a 5d Super-Yang-Mills theory on
I x M_4, with I an interval, then non-abelianize the 5d theory and finally
reduce this to 4d. In the special case, when M_4 is a Hyper-Kahler manifold, we
show that the dimensional reduction gives rise to a topological sigma-model
based on tri-holomorphic maps. Deriving the theory on a general M_4 requires
knowledge of the metric of the target space. For k=2 the target space is the
Atiyah-Hitchin manifold and we twist the theory to obtain a topological
sigma-model, which has both scalar fields and self-dual two-forms.


title: Lara: A Key-Value Algebra underlying Arrays and Relations

abstract:
  Data processing systems roughly group into families such as relational,
array, graph, and key-value. Many data processing tasks exceed the capabilities
of any one family, require data stored across families, or run faster when
partitioned onto multiple families. Discovering ways to execute computation
among multiple available systems, let alone discovering an optimal execution
plan, is challenging given semantic differences between disparate families of
systems. In this paper we introduce a new algebra, Lara, which underlies and
unifies algebras representing the families above in order to facilitate
translation between systems. We describe the operations and objects of
Lara---union, join, and ext on associative tables---and show her properties and
equivalences to other algebras. Multi-system optimization has a bright future,
in which we proffer Lara for the role of universal connector.


title:
Cooperative Network Node Positioning Techniques Using Underwater Radio
  Communications

abstract:
  We analyze the problem of localization algorithms for underwater sensor
networks. We first characterize the underwater channel for radio communications
and adjust a linear model with measurements of real transmissions. We propose
an algorithm where the sensor nodes collaboratively estimate their unknown
positions in the network. In this setting, we assume low connectivity of the
nodes, low data rates, and nonzero probability of lost packets in the
transmission. Finally, we consider the problem of a node estimating it's
position in underwater navigation. We also provide simulations illustrating the
previous proposals.


title: Network Formation Game with Different Cost Value for Players

abstract:
  In Social Networks, it is often interesting to study type of networks formed,
its efficiency with respect to social objective and which networks are stable.
Many work have already been there in this area. Players in network formation
game will incur some cost to form a link. In previous work, all player will
have same cost for forming a link int he network. Here we will the study the
optimal network and Nash equilibrium network when each player have different
cost value for forming the link in the social network.


title: Uniform Value for Recursive Games with Compact Actions

abstract:
  Mertens, Neyman and Rosenberg [MOR, 2009] used the Mertens and Neyman theorem
[IJGT, 1981] to prove the existence of uniform value for absorbing games with
finite state space and compact action sets. We provide an analogous proof for
another class of stochastic games, recursive games with finite state space and
compact action sets. Moreover, both players have stationary epsilon-optimal
strategies.


title: Sequential change-point detection based on nearest neighbors

abstract:
  We propose a new framework for the detection of change-points in online,
sequential data analysis. The approach utilizes nearest neighbor information
and can be applied to sequences of multivariate observations or non-Euclidean
data objects, such as network data. Different stopping rules are explored, and
one specific rule is recommended due to its desirable properties. An accurate
analytic approximation of the average run length is derived for the recommended
rule, making it an easy off-the-shelf approach for real multivariate/object
sequential data monitoring applications. Simulations reveal that the new
approach has better performance than likelihood-based approaches for high
dimensional data. The new approach is illustrated through a real dataset in
detecting global structural changes in social networks.


title: Binary Polar Codes are Optimized Codes for Bitwise Multistage Decoding

abstract:
  Polar codes are considered the latest major breakthrough in coding theory.
Polar codes were introduced by Ar{\i}kan in 2008. In this letter, we show that
the binary polar codes are the same as the optimized codes for bitwise
multistage decoding (OCBM), which have been discovered before by Stolte in
2002. The equivalence between the techniques used for the constructions and
decodings of both codes is established.


title:
Comparison of Volumes of Siegel Sets and Fundamental Domains of
  $\mathrm{SL}_n(\mathbb{Z})$

abstract:
  The purpose of this paper is to calculate explicitly the volumes of Siegel
sets which are coarse fundamental domains for the action of $\mathrm{SL}_n
(\mathbb{Z})$ in $\mathrm{SL}_n (\mathbb{R})$, so that we can compare these
volumes with those of the fundamental domains of $\mathrm{SL}_n (\mathbb{Z})$
in $\mathrm{SL}_n (\mathbb{R})$, which are also computed here, for any $n\geq
2$. An important feature of this computation is that it requires keeping track
of normalization constants of the Haar measures. We conclude that the ratio
between volumes of fundamental domains and volumes of Siegel sets grows
super-exponentially fast as $n$ goes to infinity. As a corollary, we obtained
that this ratio gives a super-exponencial lower bound, depending only on $ n $,
for the number of intersecting Siegel sets. We were also able to give an upper
bound for this number, by applying some results on the heights of intersecting
elements in $ \mathrm{SL}_n (\mathbb{Z}) $.


title: The Market for English Premier League (EPL) Odds

abstract:
  This paper employs a Skellam process to represent real-time betting odds for
English Premier League (EPL) soccer games. Given a matrix of market odds on all
possible score outcomes, we estimate the expected scoring rates for each team.
The expected scoring rates then define the implied volatility of an EPL game.
As events in the game evolve, we re-estimate the expected scoring rates and our
implied volatility measure to provide a dynamic representation of the market's
expectation of the game outcome. Using a dataset of 1520 EPL games from
2012-2016, we show how our model calibrates well to the game outcome. We
illustrate our methodology on real-time market odds data for a game between
Everton and West Ham in the 2015-2016 season. We show how the implied
volatility for the outcome evolves as goals, red cards, and corner kicks occur.
Finally, we conclude with directions for future research.


title: A Nonparametric Bayesian Technique for High-Dimensional Regression

abstract:
  This paper proposes a nonparametric Bayesian framework called VariScan for
simultaneous clustering, variable selection, and prediction in high-throughput
regression settings. Poisson-Dirichlet processes are utilized to detect
lower-dimensional latent clusters of covariates. An adaptive nonlinear
prediction model is constructed for the response, achieving a balance between
model parsimony and flexibility. Contrary to conventional belief, cluster
detection is shown to be aposteriori consistent for a general class of models
as the number of covariates and subjects grows. Simulation studies and data
analyses demonstrate that VariScan often outperforms several well-known
statistical methods.


title:
Heavy-tailed phase-space distributions beyond Boltzmann-Gibbs and
  equipartition: Statistics of confined cold atoms

abstract:
  The Boltzmann-Gibbs density, a central result of equilibrium statistical
mechanics, relates the energy of a system in contact with a thermal bath to its
equilibrium statistics. This relation is lost for non-thermal systems such as
cold atoms in optical lattices, where the heat bath is replaced by the laser
beams of the lattice. We investigate in detail the stationary phase-space
probability for Sisyphus cooling under harmonic confinement. In particular, we
elucidate whether the total energy of the system still describes its stationary
state statistics. We find that this is true for the center part of the
phase-space density for deep lattices, where the Boltzmann-Gibbs density
provides an approximate description. The relation between energy and statistics
also persists for strong confinement and in the limit of high energies, where
the system becomes underdamped. However, the phase-space density now exhibits
heavy power-law tails. In all three cases we find expressions for the leading
order phase-space density and corrections which break the equivalence of
probability and energy and violate energy equipartition. The non-equilibrium
nature of the steady state is confounded by explicit violations of detailed
balance. We complement these analytical results with numerical simulations to
map out the intricate structure of the phase-space density.


title: A note on the duals of skew constacyclic codes

abstract:
  Let $\mathbb{F}_q$ be a finite field with $q$ elements and denote by $\theta
: \mathbb{F}_q\to\mathbb{F}_q$ an automorphism of $\mathbb{F}_q$. In this
paper, we deal with skew constacyclic codes, that is, linear codes of
$\mathbb{F}_q^n$ which are invariant under the action of a semi-linear map
$\Phi_{\alpha,\theta}:\mathbb{F}_q^n\to\mathbb{F}_q^n$, defined by
$\Phi_{\alpha,\theta}(a_0,...,a_{n-2}, a_{n-1}):=(\alpha
\theta(a_{n-1}),\theta(a_0),...,\theta(a_{n-2}))$ for some
$\alpha\in\mathbb{F}_q\setminus\{0\}$ and $n\geq 2$. In particular, we study
some algebraic and geometric properties of their dual codes and we give some
consequences and research results on $1$-generator skew quasi-twisted codes and
on MDS skew constacyclic codes.


title:
The scattering phase shifts of the Hulth\'en-type potential plus Yukawa
  potential

abstract:
  With the aid of an improved short-range approximation, the bound state
energies and the scattering phase shifts for a Hulth\'en- type potential plus
Yukawa potential are calculated within the framework of Nikiforov-Uvarov and
standard methods, respectively. Our numerical calculations show that the
presence of Yukawa potential has a significant influence on bound state
energies and the wave number-dependent phase shifts for any arbitrary values of
the screening parameter {\alpha} and angular momentum l.


title:
Solving the 2-Dimensional Fokker-Planck Equation for Strongly Correlated
  Neurons

abstract:
  Pairs of neurons in brain networks often share much of the input they receive
from other neurons. Due to essential non-linearities of neuronal dynamics, the
consequences for the correlation of the output spike trains are not well
understood in the strongly correlated regime. Here we consider two leaky
integrate-and-fire neurons with correlated white noise input. We analyze this
scenario using a novel non-perturbative approach. Hence our treatment covers
both weakly and strongly correlated dynamics, generalizing previous results
based on linear response theory.


title: Resistivity Minimum in Highly Frustrated Itinerant Magnets

abstract:
  We study the transport properties of frustrated itinerant magnets comprising
localized {\it classical} moments, which interact via exchange with the
conduction electrons. Strong frustration stabilizes a liquidlike spin state,
which extends down to temperatures well below the effective
Ruderman-Kittel-Kasuya-Yosida interaction scale. The crossover into this state
is characterized by spin structure factor enhancement at wave vectors smaller
than twice the Fermi wave vector magnitude. The corresponding enhancement of
electron scattering generates a resistivity upturn at decreasing temperatures.


title:
Magnetic properties and pairing tendencies of the iron-based
  superconducting ladder BaFe$_2$S$_3$: combined ab initio and density matrix
  renormalization group study

abstract:
  The recent discovery of superconductivity under high pressure in the two-leg
ladder compound BaFe$_2$S$_3$ [H. Takahashi et al., Nature Materials 14, 1008
(2015)] opens a broad avenue of research, because it represents the first
report of pairing tendencies in a quasi one-dimensional iron-based high
critical temperature superconductor. Similarly as in the case of the cuprates,
ladders and chains can be far more accurately studied using many-body
techniques and model Hamiltonians than their layered counterparts, particularly
if several orbitals are active. In this publication, we derive a two-orbital
Hubbard model from first principles that describes individual ladders of
BaFe$_2$S$_3$. The model is studied with the density matrix renormalization
group. These first reported results are exciting for two reasons: (i) at
half-filling, ferromagnetic order emerges as the dominant magnetic pattern
along the rungs of the ladder, and antiferromagnetic order along the legs, in
excellent agreement with neutron experiments; (ii) pairs form in the strong
coupling regime, as found by studying the binding energy of two holes doped on
the half-filled system. In addition, Orbital Selective Mott Phase
characteristics develop with doping, with only one Wannier orbital receiving
the hole carriers while the other remains half-filled. These results suggest
that the analysis of models for iron-based two-leg ladders could clarify the
origin of pairing tendencies and other exotic properties of iron-based high
critical temperature superconductors.


title: Kronecker STAP and SAR GMTI

abstract:
  As a high resolution radar imaging modality, SAR detects and localizes
non-moving targets accurately, giving it an advantage over lower resolution
GMTI radars. Moving target detection is more challenging due to target smearing
and masking by clutter. Space-time adaptive processing (STAP) is often used on
multiantenna SAR to remove the stationary clutter and enhance the moving
targets. In (Greenewald et al., 2016) it was shown that the performance of STAP
can be improved by modeling the clutter covariance as a space vs. time
Kronecker product with low rank factors, providing robustness and reducing the
number of training samples required. In this work, we present a massively
parallel algorithm for implementing Kronecker product STAP, enabling
application to very large SAR datasets (such as the 2006 Gotcha data
collection) using GPUs. Finally, we develop an extension of Kronecker STAP that
uses information from multiple passes to improve moving target detection.


title: Pulsar Electrodynamics: an unsolved problem

abstract:
  Pulsar electrodynamics is reviewed emphasizing the role of the inductive
electric field in an oblique rotator and the incomplete screening of its
parallel component by charges, leaving `gaps' with $E_\parallel\ne0$. The
response of the plasma leads to a self-consistent electric field that
complements the inductive electric field with a potential field leading to an
electric drift and a polarization current associated with the total field. The
electrodynamic models determine the charge density, $\rho$, and the current
density, ${\bf J}$, charge starvation refers to situations where the plasma
cannot supply $\rho$, resulting in a gap and associated particle acceleration
and pair creation. It is pointed out that a form of current starvation also
occurs implying a new class of gaps. The properties of gaps are discussed,
emphasizing that static models are unstable, the role of large-amplitude
longitudinal waves, and the azimuthal dependence that arises across a gap in an
oblique rotator. Wave dispersion in a pulsar plasma is reviewed briefly,
emphasizing its role in radio emission. Pulsar radio emission mechanisms are
reviewed, and it is suggested that the most plausible is a form of plasma
emission.


title:
Detection of a turbulent gas component associated with a starless core
  with subthermal turbulence in the Orion A cloud

abstract:
  We report the detection of a wing component in NH$_3$ emission toward the
starless core TUKH122 with subthermal turbulence in the Orion A cloud. This
NH$_3$ core is suggested to be on the verge of star formation because the
turbulence inside the NH$_3$ core is almost completely dissipated, and also
because it is surrounded by CCS, which resembles the prestellar core L1544 in
Taurus showing infall motions. Observations were carried out with the Nobeyama
45 m telescope at 0.05 km s$^{-1}$ velocity resolution. We find that the NH$_3$
line profile consists of two components. The quiescent main component has a
small linewidth of 0.3 km s$^{-1}$ dominated by thermal motions, and the
red-shifted wing component has a large linewidth of 1.36 km s$^{-1}$
representing turbulent motions. These components show kinetic temperatures of
11 K and $<$ 30 K, respectively. Furthermore, there is a clear velocity offset
between the NH$_3$ quiescent gas ($VLSR=3.7$ km s$^{-1}$) and the turbulent gas
($VLSR=4.4$ km s$^{-1}$). The centroid velocity of the turbulent gas
corresponds to that of the surrounding gas traced by the $^{13}$CO ($J=1-0$)
and CS ($J=2-1$) lines. LVG model calculations for CS and CO show that the
turbulent gas has a temperature of $8-13$ K and an H$_2$ density of ~ $10^4$
cm$^{-3}$, suggesting that the temperature of the turbulent component is also ~
10 K. The detections of both NH$_3$ quiescent and wing components may indicate
a sharp transition from the turbulent parent cloud to the quiescent dense core.


title:
Coulomb branches of $3d$ $\mathcal N=4$ quiver gauge theories and slices
  in the affine Grassmannian (with appendices by Alexander Braverman, Michael
  Finkelberg, Joel Kamnitzer, Ryosuke Kodera, Hiraku Nakajima, Ben Webster, and
  Alex Weekes)

abstract:
  This is a companion paper of arXiv:1601.03586. We study Coulomb branches of
unframed and framed quiver gauge theories of type $ADE$. In the unframed case
they are isomorphic to the moduli space of based rational maps from ${\mathbb
C}P^1$ to the flag variety. In the framed case they are slices in the affine
Grassmannian and their generalization. In the appendix, written jointly with
Joel Kamnitzer, Ryosuke Kodera, Ben Webster, and Alex Weekes, we identify the
quantized Coulomb branch with the truncated shifted Yangian.

categories: math.RT hep-th math-ph math.AG math.DG math.MP


title: Privacy & Social Media in the Context of the Arab Gulf

abstract:
  Theories of privacy and how it relates to the use of Information
Communication Technology (ICT) have been a topic of research for decades.
However, little attention has been paid to the perception of privacy from the
perspective of technology users in the Middle East. In this paper, we delve
into interpretations of privacy from the approach of Arab Gulf citizens. We
consider how privacy is practiced and understood in technology-mediated
environments among this population, paying particular attention to the role of
Islam and cultural traditions in constructing norms around privacy. We then
offer culturally sensitive design principles and suggestions for future
research that incorporates previously unexplored characteristics of privacy,
which play a role in how users navigate social media.


title: Dissecting a Social Botnet: Growth, Content and Influence in Twitter

abstract:
  Social botnets have become an important phenomenon on social media. There are
many ways in which social bots can disrupt or influence online discourse, such
as, spam hashtags, scam twitter users, and astroturfing. In this paper we
considered one specific social botnet in Twitter to understand how it grows
over time, how the content of tweets by the social botnet differ from regular
users in the same dataset, and lastly, how the social botnet may have
influenced the relevant discussions. Our analysis is based on a qualitative
coding for approximately 3000 tweets in Arabic and English from the Syrian
social bot that was active for 35 weeks on Twitter before it was shutdown. We
find that the growth, behavior and content of this particular botnet did not
specifically align with common conceptions of botnets. Further we identify
interesting aspects of the botnet that distinguish it from regular users.


title: Joint Unsupervised Learning of Deep Representations and Image Clusters

abstract:
  In this paper, we propose a recurrent framework for Joint Unsupervised
LEarning (JULE) of deep representations and image clusters. In our framework,
successive operations in a clustering algorithm are expressed as steps in a
recurrent process, stacked on top of representations output by a Convolutional
Neural Network (CNN). During training, image clusters and representations are
updated jointly: image clustering is conducted in the forward pass, while
representation learning in the backward pass. Our key idea behind this
framework is that good representations are beneficial to image clustering and
clustering results provide supervisory signals to representation learning. By
integrating two processes into a single model with a unified weighted triplet
loss and optimizing it end-to-end, we can obtain not only more powerful
representations, but also more precise image clusters. Extensive experiments
show that our method outperforms the state-of-the-art on image clustering
across a variety of image datasets. Moreover, the learned representations
generalize well when transferred to other tasks.


title: Quantifying mesoscale neuroanatomy using X-ray microtomography

abstract:
  Methods for resolving the 3D microstructure of the brain typically start by
thinly slicing and staining the brain, and then imaging each individual section
with visible light photons or electrons. In contrast, X-rays can be used to
image thick samples, providing a rapid approach for producing large 3D brain
maps without sectioning. Here we demonstrate the use of synchrotron X-ray
microtomography ($\mu$CT) for producing mesoscale $(1~\mu m^3)$ resolution
brain maps from millimeter-scale volumes of mouse brain. We introduce a
pipeline for $\mu$CT-based brain mapping that combines methods for sample
preparation, imaging, automated segmentation of image volumes into cells and
blood vessels, and statistical analysis of the resulting brain structures. Our
results demonstrate that X-ray tomography promises rapid quantification of
large brain volumes, complementing other brain mapping and connectomics
efforts.