title:
Finite-Temperature Signatures of Spin Liquids in Frustrated Hubbard
  Model

abstract:
  Finite-temperature properties of the frustrated Hubbard model are
theoretically examined by using the recently proposed thermal pure quantum
state, which is an unbiased numerical method for finite-temperature
calculations. By performing systematic calculations for the frustrated Hubbard
model, we show that the geometrical frustration controls the characteristic
energy scale of the metal-insulator transitions. We also find that entropy
remains large even at moderately high temperature around the region where the
quantum spin liquid is expected to appear at zero temperature. We propose that
this is a useful criterion whether the target systems have a chance to be the
quantum spin liquid or the non-magnetic insulator at zero temperature.


title: Timing of 29 Pulsars Discovered in the PALFA Survey

abstract:
  We report on the discovery and timing observations of 29 distant long-period
pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Following
discovery with the Arecibo Telescope, confirmation and timing observations of
these pulsars over several years at Jodrell Bank Observatory have yielded
high-precision positions and measurements of rotation and radiation properties.
We have used multi-frequency data to measure the interstellar scattering
properties of some of these pulsars. Most of the pulsars have properties that
mirror those of the previously known pulsar population, although four show some
notable characteristics. PSRs J1907+0631 and J1925+1720 are young and are
associated with supernova remnants or plerionic nebulae: J1907+0631 lies close
to the center of SNR G40.5-0.5, while J1925+1720 is coincident with a
high-energy Fermi gamma-ray source. One pulsar, J1932+1500, is in a
surprisingly eccentric, 199-day binary orbit with a companion having a minimum
mass of 0.33 solar masses. Several of the sources exhibit timing noise, and
two, PSRs J0611+1436 and J1907+0631, have both suffered large glitches, but
with very different post-glitch rotation properties. In particular, the
rotational period of PSR J0611+1436 will not recover to its pre-glitch value
for about 12 years, a far greater recovery timescale than seen following any
other large glitches.


title: Two long-term intermittent pulsars discovered in the PALFA Survey

abstract:
  We report the discovery of two long-term intermittent radio pulsars in the
ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo
Telescope, extended observations of these pulsars over several years at Jodrell
Bank Observatory have revealed the details of their rotation and radiation
properties. PSRs J1910+0517 and J1929+1357 show long-term extreme bi-modal
intermittency, switching between active (ON) and inactive (OFF) emission states
and indicating the presence of a large, hitherto unrecognised, underlying
population of such objects. For PSR J1929+1357, the initial duty cycle was
fON=0.008, but two years later this changed, quite abruptly, to fON=0.16. This
is the first time that a significant evolution in the activity of an
intermittent pulsar has been seen and we show that the spin-down rate of the
pulsar is proportional to the activity. The spin-down rate of PSR J1929+1357 is
increased by a factor of 1.8 when it is in active mode, similar to the increase
seen in the other three known long-term intermittent pulsars.


title:
Understanding the behavioural difference of PPCA among its homologs in
  C7 family towards recognition of DXCA

abstract:
  Among all the proteins of Periplasmic C type cytochrome A (PPCA) family
obtained from cytochrome C7 found in Geobacter sulfurreducens, PPCA protein can
interact with Deoxycholate (DXCA), while its other homologs do not, as observed
from the crystal structures. Utilizing the concept of 'structure-function
relationship', an effort has been initiated towards understanding the driving
force for recognition of DXCA exclusively by PPCA among its homologs. Further,
a combinatorial analysis of the binding sequences (contiguous sequence of amino
acid residues of binding locations) is performed to build graph-theoretic
models, which show that PPCA differs from its homologues. Analysis of the
results suggests that the underlying impetus of recognition of DXCA by PPCA is
embedded in its primary sequence and 3D conformation.


title: Statistical physics of vaccination

abstract:
  Historically, infectious diseases caused considerable damage to human
societies, and they continue to do so today. To help reduce their impact,
mathematical models of disease transmission have been studied to help
understand disease dynamics and inform prevention strategies. Vaccination - one
of the most important preventive measures of modern times - is of great
interest both theoretically and empirically. And in contrast to traditional
approaches, recent research increasingly explores the pivotal implications of
individual behavior and heterogeneous contact patterns in populations. Our
report reviews the developmental arc of theoretical epidemiology with emphasis
on vaccination, as it led from classical models assuming homogeneously mixing
(mean-field) populations and ignoring human behavior, to recent models that
account for behavioral feedback and/or population spatial/social structure.
Many of the methods used originated in statistical physics, such as lattice and
network models, and their associated analytical frameworks. Similarly, the
feedback loop between vaccinating behavior and disease propagation forms a
coupled nonlinear system with analogs in physics. We also review the new
paradigm of digital epidemiology, wherein sources of digital data such as
online social media are mined for high-resolution information on
epidemiologically relevant individual behavior. Armed with the tools and
concepts of statistical physics, and further assisted by new sources of digital
data, models that capture nonlinear interactions between behavior and disease
dynamics offer a novel way of modeling real-world phenomena, and can help
improve health outcomes. We conclude the review by discussing open problems in
the field and promising directions for future research.

categories: physics.soc-ph cond-mat.stat-mech cs.SI q-bio.PE stat.AP


title:
Confinement in the bulk, deconfinement on the wall: infrared equivalence
  between compactified QCD and quantum magnets

abstract:
  In a spontaneously dimerized quantum antiferromagnet, spin-1/2 excitations
(spinons) are confined in pairs by strings akin to those confining quarks in
non-abelian gauge theories. The system has multiple degenerate ground states
(vacua) and domain walls between regions of different vacua. For two vacua, we
demonstrate that spinons on a domain wall are liberated, in a mechanism
strikingly similar to domain-wall deconfinement of quarks in variants of
quantum chromodynamics. This observation not only establishes a novel
phenomenon in quantum magnetism, but also provides a new direct link between
particle physics and condensed-matter physics. The analogy opens doors to
improving our understanding of particle confinement and deconfinement by
computational and experimental studies in quantum magnetism.


title: Quantum Protocols within Spekkens' Toy Model

abstract:
  Quantum mechanics is known to provide significant improvements in information
processing tasks when compared to classical models. These advantages range from
computational speeds-up to security improvements. A key question is where these
advantages come from. The toy model developed by Spekkens [R. W. Spekkens PRA
75, 032110 (2012)] mimics many of the features of quantum mechanics, such as
entanglement and no-cloning, regarded as being important in this regard,
despite being a local hidden variable theory. In this work we study several
protocols within Spekkens' toy model where we see it can also mimic the
advantages and limitations shown in the quantum case. We first provide explicit
proofs for the impossibility of toy bit-commitment and the existence of a toy
error correction protocol and consequent $k-$threshold secret sharing. Then,
defining a toy computational model based on the quantum one-way computer we
prove the existence of blind and verified protocols. Importantly, these two
last quantum protocols are known to achieve a better-than-classical security.
Our results suggest that such quantum improvements need not arise from any
Bell-type non locality or contextuality, but rather as a consequence of
steering correlations.


title: Continuous generation of delayed light

abstract:
  We use a Raman four-wave mixing process to read-out light from atomic
coherence which is continuously written. The light is continuously generated
after an effective delay, allowing the atomic coherence to evolve during the
process. Contrary to slow-light delay, which depends on the medium optical
depth, here the generation delay is determined solely by the intensive
properties of the system, approaching the atomic coherence lifetime at the weak
driving limit. The generated light is background free. We experimentally probe
these properties utilizing spatial diffusion as an 'internal clock' for the
atomic evolution time.


title:
A Tutorial on Online Supervised Learning with Applications to Node
  Classification in Social Networks

abstract:
  We revisit the elegant observation of T. Cover '65 which, perhaps, is not as
well-known to the broader community as it should be. The first goal of the
tutorial is to explain---through the prism of this elementary result---how to
solve certain sequence prediction problems by modeling sets of solutions rather
than the unknown data-generating mechanism. We extend Cover's observation in
several directions and focus on computational aspects of the proposed
algorithms. The applicability of the methods is illustrated on several
examples, including node classification in a network.
  The second aim of this tutorial is to demonstrate the following phenomenon:
it is possible to predict as well as a combinatorial "benchmark" for which we
have a certain multiplicative approximation algorithm, even if the exact
computation of the benchmark given all the data is NP-hard. The proposed
prediction methods, therefore, circumvent some of the computational
difficulties associated with finding the best model given the data. These
difficulties arise rather quickly when one attempts to develop a probabilistic
model for graph-based or other problems with a combinatorial structure.


title:
Physical consistency of subgrid-scale models for large-eddy simulation
  of incompressible turbulent flows

abstract:
  We study the construction of subgrid-scale models for large-eddy simulation
of incompressible turbulent flows. In particular, we aim to consolidate a
systematic approach of constructing subgrid-scale models, based on the idea
that it is desirable that subgrid-scale models are consistent with the
mathematical and physical properties of the Navier-Stokes equations and the
turbulent stresses. To that end, we first discuss in detail the symmetries of
the Navier-Stokes equations, and the near-wall scaling behavior, realizability
and dissipation properties of the turbulent stresses. We furthermore summarize
the requirements that subgrid-scale models have to satisfy in order to preserve
these important mathematical and physical properties. In this fashion, a
framework of model constraints arises that we apply to analyze the behavior of
a number of existing subgrid-scale models that are based on the local velocity
gradient. We show that these subgrid-scale models do not satisfy all the
desired properties, after which we explain that this is partly due to
incompatibilities between model constraints and limitations of
velocity-gradient-based subgrid-scale models. However, we also reason that the
current framework shows that there is room for improvement in the properties
and, hence, the behavior of existing subgrid-scale models. We furthermore show
how compatible model constraints can be combined to construct new subgrid-scale
models that have desirable properties built into them. We provide a few
examples of such new models, of which a new model of eddy viscosity type, that
is based on the vortex stretching magnitude, is successfully tested in
large-eddy simulations of decaying homogeneous isotropic turbulence and
turbulent plane-channel flow.


title:
Dispersion relations for stationary light in one-dimensional atomic
  ensembles

abstract:
  We investigate the dispersion relations for light coupled to one-dimensional
ensembles of atoms with different level schemes. The unifying feature of all
the considered setups is that the forward and backward propagating quantum
fields are coupled by the applied classical drives such that the group velocity
can vanish in an effect known as "stationary light". We derive the dispersion
relations for all the considered schemes, highlighting the important
differences between them. Furthermore, we show that additional control of
stationary light can be obtained by treating atoms as discrete scatterers and
placing them at well defined positions. For the latter purpose, a multi-mode
transfer matrix theory for light is developed.


title: Criticality or Supersymmetry Breaking ?

abstract:
  In many stochastic dynamical systems, ordinary chaotic behavior is preceded
by a full-dimensional phase that exhibits 1/f-type power-spectra and/or
scale-free statistics of (anti)instantons such as neuroavalanches, earthquakes,
etc. In contrast with the phenomenological concept of self-organized
criticality, the recently developed approximation-free supersymmetric theory of
stochastic differential equations, or stochastics, (STS) identifies this phase
as the noise-induced chaos (N-phase), i.e., the phase where the topological
supersymmetry pertaining to all stochastic dynamical systems is broken
spontaneously by the condensation of the noise-induced (anti-)instantons. Here,
we support this picture in the context of neurodynamics. We study a 1D chain of
neuron-like elements and find that the dynamics in the N-phase is indeed
featured by positive stochastic Lyapunov exponents and dominated by
(anti)instantonic processes of (creation)annihilation of kinks and antikinks,
which can be viewed as predecessors of boundaries of neuroavalanches. We also
construct the phase diagram of emulated stochastic neurodynamics on Spikey
neuromorphic hardware and demonstrate that the width of the N-phase vanishes in
the deterministic limit in accordance with STS. As a first result of the
application of STS to neurodynamics comes the conclusion that a conscious brain
can reside only in the N-phase.


title: A torsion pendulum ground test of the LISA Pathfinder Free-fall mode

abstract:
  LISA Pathfinder is the technological demonstrator space mission for the
future gravitational waves observatory in space eLISA, with the aim of measure
the differential acceleration between free-falling test masses orbiting in the
same apparatus at a level of 30 fm/s-2Hz-1/2 at 1 mHz. Because the satellite
can't follow the two masses at the same time, the second mass must be forced to
follow either the other one or the spacecraft. The actuation force applied to
compensate this effect introduces a dominant source of force noise in the
mission noise budget at frequency near and below the mHz. The free-fall mode
actuation control scheme has been designed to suppress this noise source and
avoid actuation instabilities: actuation is limited to brief periodic impulses,
with test masses in free fall in between two kicks. This actuation-free motion
is then analyzed for the remaining sources of acceleration ultra noise. A
free-fall mode parallel testing has been successfully implemented on torsion
pendulum facility at the University of Trento and the results of the
measurement campaign are ready to be shown and discussed. The implementation of
the data analysis algorithms to estimate the spectrum of the acceleration of
the controlled test mass, and the estimation of system parameters such as the
force gradients, stiffness terms, are also part of this work. The free-fall
mode has been tested at the level of 2 fNm/Hz-1/2, at the frequencies of 1 mHz,
corresponding to an acceleration of about 100 fm /s-2 Hz-1/2. The ground tests
have nevertheless allowed to develop and test quantitatively this innovative
method of noise reduction due to actuation noise, contributing to its
development for the LISA Pathfinder mission.


title: High-resolution Very Large Array observations of 18 MIPSGAL bubbles

abstract:
  We present radio observations of 18 MIPSGAL bubbles performed at 5 GHz (6 cm)
with the Karl G. Jansky Very Large Array in configuration B and BnA. The
observations were aimed at understanding what kind of information
high-resolution and high-sensitivity radio maps can supply on the circumstellar
envelopes of different kinds of evolved stars and what their comparison with
infrared images with similar resolution can tell us. We found that the 18
bubbles can be grouped into five categories according to their radio
morphology. The three bubbles presenting a central point source in the radio
images all correspond to luminous blue variable star candidates. Eleven bubbles
show an elliptical shape and the total lack of a central object in the radio,
and are likely associated with planetary nebulae. Under this assumption we
derive their distance, their ionized mass and their distribution on the
Galactic plane. We discuss the possibility that the MIPSGAL bubbles catalogue
(428 objects) may contain a large fraction of all Galactic planetary nebulae
located at a distance between 1.4 kpc and 6.9 kpc and lying in the MIPSGAL
field of view. Among the remaining bubbles we identify also a H II region and a
proto-planetary nebula candidate.


title:
Importance of intrinsic and non-network contribution in PageRank
  centrality and its effect on PageRank localization

abstract:
  PageRank centrality is used by Google for ranking web-pages to present search
result for a user query. Here, we have shown that PageRank value of a vertex
also depends on its intrinsic, non-network contribution. If the intrinsic,
non-network contributions of the vertices are proportional to their degrees or
zeros, then their PageRank centralities become proportion to their degrees.
Some simulations and empirical data are used to support our study. In addition,
we have shown that localization of PageRank centrality depends upon the same
intrinsic, non-network contribution.


title:
Feinberg-Horodecki States of Time-Dependent Mass Distribution Harmonic
  Oscillator

abstract:
  The solution of the Feinberg-Horodecki (FH) equation for a time-dependent
mass (TDM) harmonic oscillator quantum system is studied. A certain interaction
is applied to a mass to provide a particular spectrum of stationary energies.
The related spectrum of the harmonic oscillator potential acting on the TDM
oscillators is found. We apply the time version of the asymptotic iteration
method (AIM) to calculate analytical expressions of the TDM stationary state
energies and their wave functions. It is shown that the obtained solutions
reduce to those of simple harmonic oscillator as the time-dependent of the mass
reduces to


title: Chiral Floquet Phases of Many-body Localized Bosons

abstract:
  We construct and classify chiral topological phases in driven (Floquet)
systems of strongly interacting bosons, with finite-dimensional site Hilbert
spaces, in two spatial dimensions. The construction proceeds by introducing
exactly soluble models with chiral edges, which in the presence of many-body
localization (MBL) in the bulk are argued to lead to stable chiral phases.
These chiral phases do not require any symmetry, and in fact owe their
existence to the absence of energy conservation in driven systems.
Surprisingly, we show that they are classified by a quantized many-body index,
which is well defined for any MBL Floquet system. The value of this index,
which is always the logarithm of a positive rational number, can be interpreted
as the entropy per Floquet cycle pumped along the edge, formalizing the notion
of quantum-information flow. We explicitly compute this index for specific
models, and show that the nontrivial topology leads to edge thermalization,
which provides an interesting link between bulk topology and chaos at the edge.
We also discuss chiral Floquet phases in interacting fermionic systems and
their relation to chiral bosonic phases.

categories: cond-mat.dis-nn cond-mat.quant-gas cond-mat.str-el quant-ph


title:
Amplitudes and Correlators to Ten Loops Using Simple, Graphical
  Bootstraps

abstract:
  We introduce two new graphical-level relations among possible contributions
to the four-point correlation function and scattering amplitude in planar,
maximally supersymmetric Yang-Mills theory. When combined with the rung rule,
these prove powerful enough to fully determine both functions through ten
loops. This then also yields the full five-point amplitude to eight loops and
the parity-even part to nine loops. We derive these rules, illustrate their
applications, compare their relative strengths for fixing coefficients, and
survey some of the features of the previously unknown nine and ten loop
expressions. Explicit formulae for amplitudes and correlators through ten loops
are available at: http://goo.gl/JH0yEc.


title: Scattering Equations: Real Solutions and Particles on a Line

abstract:
  We find $n(n-3)/2$-dimensional regions of the space of kinematic invariants,
where all the solutions to the scattering equations (the core of the CHY
formulation of amplitudes) for $n$ massless particles are real. On these
regions, the scattering equations are equivalent to the problem of finding
stationary points of $n-3$ mutually repelling particles on a finite real
interval with appropriate boundary conditions. This identification directly
implies that for each of the $(n-3)!$ possible orderings of the $n-3$ particles
on the interval, there exists one stable stationary point. Furthermore,
restricting to four dimensions, we find that the separation of the solutions
into $k\in \{2,3,\ldots ,n-2\}$ sectors naturally matches that of permutations
of $n-3$ labels into those with $k-2$ descents. This leads to a physical
realization of the combinatorial meaning of the Eulerian numbers.


title:
Tidal disruption rates in non-spherical galactic nuclei formed by galaxy
  mergers

abstract:
  We explore the rates of tidal disruption events (TDEs) of stars by
supermassive black holes (SBHs) in galactic nuclei formed in mergers followed
by a formation and coalescence of a binary SBH. Such systems initially have a
deficit of stars on low-angular-momentum orbits caused by the slingshot process
during the binary SBH stage, which tends to reduce the flux of stars into the
SBH compared to the steady-state value. On the other hand, a newly formed
galactic nucleus has a non-spherical shape which enhances the mixing of stars
in angular momentum and thus the TDE rate. In galaxies with relatively low SBH
masses (<10^7 Msun), relaxation times are short enough to wash out the
anisotropy in initial conditions, and for more massive SBH the enhancement of
flux due to non-sphericity turns out to be more important than its suppression
due to initial anisotropy. Therefore, the present-day TDE rates generally
exceed conventional steady-state estimates based on a spherical isotropic
approximation. We thus conjecture that the lower observationally inferred TDE
rates compared to theoretical predictions cannot be attributed to the depletion
of low-angular-momentum stars by SBH binaries.


title: The TDE ASASSN-14li and its host resolved at parsec scales with the EVN

abstract:
  We report European Very Long Baseline Interferometry Network (EVN) radio
continuum observations of ASASSN-14li, one of the best studied tidal disruption
events (TDEs) to date. At 1.7 GHz with ~12x6mas resolution, the emission is
unresolved. At 5.0 GHz with ~3x2mas resolution, the radio emission shows an
extended structure that can be modeled with two components: a core-like
component and a fainter, possibly elongated source 4.3mas (~2pc) away. Our
observations are not conclusive as to the nature of the components, but three
scenarios are discussed. One possibility is a core-jet/outflow morphology, thus
making of ASASSN-14li the first TDE jet/outflow directly imaged. For this case,
the projected separation between the two components can only be explained by
superluminal motion, rather than the lower velocities inferred from
low-resolution radio observations. However, typical fast moving jets have
brightness temperatures ~5 orders of magnitude higher than we find, thus making
this scenario less likely. The second possibility is that we are imaging a
non-relativistic jet from past AGN/TDE activity. In this case a past TDE is
preferred given that the spatial extension and radio luminosity of the
elongated component are consistent with the theoretical predictions for a TDE
outflow. Alternatively, the two sources could indicate the presence of a binary
black hole, which would then naturally explain the enhanced TDE rates of
post-starburst galaxies. Future EVN observations will help us to distinguish
between these scenarios.


title: Duality group actions on fermions

abstract:
  In this short paper we look at the action of T-duality and string duality
groups on fermions, in maximally-supersymmetric theories and related theories.
Briefly, we argue that typical duality groups such as SL(2,Z) have sign
ambiguities in their actions on fermions, and propose that pertinent duality
groups be extended by Z_2, to groups such as the metaplectic group.
Specifically, we look at duality groups arising from mapping class groups of
tori in M theory compactifications, T-duality, ten-dimensional type IIB
S-duality, and (briefly) four-dimensional N=4 super Yang-Mills, and in each
case, propose that the full duality group is a nontrivial Z_2 extension of the
duality group acting on bosonic degrees of freedom, to more accurately describe
possible actions on fermions. We also walk through U-duality groups for
toroidal compactifications to nine, eight, and seven dimensions, which enables
us to perform cross-consistency tests of these proposals.


title:
The COS-Halos Survey: Origins of the Highly Ionized Circumgalactic
  Medium of Star-Forming Galaxies

abstract:
  The total contribution of diffuse halo gas to the galaxy baryon budget
strongly depends on its dominant ionization state. In this paper, we address
the physical conditions in the highly ionized circumgalactic medium (CGM)
traced by OVI absorption lines observed in COS-Halos spectra. We analyze the
observed ionic column densities, absorption-line widths and relative
velocities, along with the ratios of NV/OVI for 39 fitted Voigt profile
components of OVI. We compare these quantities with the predictions given by a
wide range of ionization models. Photoionization models that include only
extragalactic UV background radiation are ruled out; conservatively, the upper
limits to NV/OVI and measurements of N$_{\rm OVI}$ imply unphysically large
path lengths > 100 kpc. Furthermore, very broad OVI absorption (b > 40 km
s$^{-1}$) is a defining characteristic of the CGM of star-forming L* galaxies.
We highlight two possible origins for the bulk of the observed OVI: (1) highly
structured gas clouds photoionized primarily by local high energy sources or
(2) gas radiatively cooling on large scales behind a supersonic wind.
Approximately 20% of circumgalactic OVI does not align with any low-ionization
state gas within $\pm$50 km s$^{-1}$ and is found only in halos with M$_{\rm
halo}$ < 10$^{12}$ M$_{\odot}$. We suggest that this type of unmatched OVI
absorption traces the hot corona itself at a characteristic temperature of
10$^{5.5}$ K. We discuss the implications of these very distinct physical
origins for the dynamical state, gas cooling rates, and total baryonic content
of L* gaseous halos.


title:
MUSE Reveals a Recent Merger in the Post-starburst Host Galaxy of the
  TDE ASASSN-14li

abstract:
  We present MUSE integral field spectroscopic observations of the host galaxy
(PGC 043234) of one of the closest ($z=0.0206$, $D\simeq 90$ Mpc) and
best-studied tidal disruption events (TDE), ASASSN-14li. The MUSE integral
field data reveal asymmetric and filamentary structures that extend up to
$\gtrsim 10$ kpc from the post-starburst host galaxy of ASASSN-14li. The
structures are traced only through the strong nebular [O III] $\lambda$5007, [N
II] $\lambda$6584, and H$\alpha$ emission lines. The total off nuclear [O III]
$\lambda$5007 luminosity is luminosity is $4.7\times 10^{39}$ erg s$^{-1}$ and
the ionized H mass is $\rm \sim 10^4(500/n_e)\,M_{\odot}$. Based on the BPT
diagram, the nebular emission can be driven by either AGN photoionization or
shock excitation, with AGN photoionization favored given the narrow intrinsic
line widths. The emission line ratios and spatial distribution strongly
resemble ionization nebulae around fading AGNs such as IC 2497 (Hanny's
Voorwerp) and ionization "cones" around Seyfert 2 nuclei. The morphology of the
emission line filaments strongly suggest that PGC 043234 is a recent merger,
which likely triggered a strong starburst and AGN activity leading to the
post-starburst spectral signatures and the extended nebular emission line
features we see today. We briefly discuss the implications of these
observations in the context of the strongly enhanced TDE rates observed in
post-starburst galaxies and their connection to enhanced theoretical TDE rates
produced by supermassive black-hole binaries.


title: Thermal States and Wave Packets

abstract:
  The classical and quantum representations of thermal equilibrium are
strikingly different, even for free, non-interacting particles. While the first
involves particles with well-defined positions and momenta, the second usually
involves energy eigenstates that are delocalized over a confining volume. In
this paper, we derive convex decompositions of the density operator for
non-interacting, non-relativistic particles in thermal equilibrium that allow
for a connection between these two descriptions. Associated with each element
of the decomposition of the N-particle thermal state is an N-body wave
function, described as a set of wave packets; the distribution of the average
positions and momenta of the wave packets can be linked to the classical
description of thermal equilibrium, while the different amplitudes in the wave
function capture the statistics relevant for fermions or bosons.


title: Jarzynski-like equality for the out-of-time-ordered correlator

abstract:
  The out-of-time-ordered correlator (OTOC) diagnoses quantum chaos and the
scrambling of quantum information via the spread of entanglement. The OTOC
encodes forward and reverse evolutions and has deep connections with the flow
of time. So do fluctuation relations such as Jarzynski's Equality, derived in
nonequilibrium statistical mechanics. I unite these two powerful, seemingly
disparate tools by deriving a Jarzynski-like equality for the OTOC. The
equality's left-hand side equals the OTOC. The right-hand side suggests a
protocol for measuring the OTOC indirectly. The protocol is
platform-nonspecific and can be performed with weak measurement or with
interference. Time evolution need not be reversed in any interference trial.
The equality opens holography, condensed matter, and quantum information to new
insights from fluctuation relations and vice versa.

categories: quant-ph cond-mat.dis-nn cond-mat.stat-mech hep-th


title: Stellar Companions to the Exoplanet Host Stars HD 2638 and HD 164509

abstract:
  An important aspect of searching for exoplanets is understanding the binarity
of the host stars. It is particularly important because nearly half of the
solar-like stars within our own Milky Way are part of binary or multiple
systems. Moreover, the presence of two or more stars within a system can place
further constraints on planetary formation, evolution, and orbital dynamics. As
part of our survey of almost a hundred host stars, we obtained images at 692 nm
and 880 nm bands using the Differential Speckle Survey Instrument (DSSI) at the
Gemini-North Observatory. From our survey, we detect stellar companions to HD
2638 and HD 164509. The stellar companion to HD 2638 has been previously
detected, but the companion to HD 164509 is a newly discovered companion. The
angular separation for HD 2638 is $0.512 \pm 0.002\arcsec$ and for HD 164509 is
$0.697 \pm 0.002\arcsec$. This corresponds to a projected separation of $25.6
\pm 1.9$ AU and $36.5 \pm 1.9$ AU, respectively. By employing stellar isochrone
models, we estimate the mass of the stellar companions of HD 2638 and HD 164509
to be $0.483 \pm 0.007$ $M_\sun$ and $0.416 \pm 0.007$ $M_\sun$, respectively,
and their effective temperatures to be $3570 \pm 8$~K and $3450 \pm 7$~K,
respectively. These results are consistent with the detected companions being
late-type M dwarfs.


title:
Radiation Search Operations using Scene Understanding with Autonomous
  UAV and UGV

abstract:
  Autonomously searching for hazardous radiation sources requires the ability
of the aerial and ground systems to understand the scene they are scouting. In
this paper, we present systems, algorithms, and experiments to perform
radiation search using unmanned aerial vehicles (UAV) and unmanned ground
vehicles (UGV) by employing semantic scene segmentation. The aerial data is
used to identify radiological points of interest, generate an orthophoto along
with a digital elevation model (DEM) of the scene, and perform semantic
segmentation to assign a category (e.g. road, grass) to each pixel in the
orthophoto. We perform semantic segmentation by training a model on a dataset
of images we collected and annotated, using the model to perform inference on
images of the test area unseen to the model, and then refining the results with
the DEM to better reason about category predictions at each pixel. We then use
all of these outputs to plan a path for a UGV carrying a LiDAR to map the
environment and avoid obstacles not present during the flight, and a radiation
detector to collect more precise radiation measurements from the ground.
Results of the analysis for each scenario tested favorably. We also note that
our approach is general and has the potential to work for a variety of
different sensing tasks.


title:
Can Free-Response Questions Be Approximated by Multiple-Choice
  Equivalents?

abstract:
  We discuss a study to evaluate the extent to which free-response questions
can be approximated by multiple-choice equivalents. Two carefully designed
research-based multiple-choice questions were transformed into a free-response
format and administered on the final exam in a calculus-based introductory
physics course. The original multiple-choice questions were administered in
another, similar introductory physics course on the final exam. Our findings
suggest that carefully designed multiple-choice questions can reflect the
relative performance on the free-response questions while maintaining the
benefits of ease of grading and quantitative analysis, especially if the
different choices in the multiple-choice questions are weighted to reflect the
different levels of understanding that students display.


title:
Baryonic acoustic oscillations from 21cm intensity mapping: the Square
  Kilometre Array case

abstract:
  We quantitatively investigate the possibility of detecting baryonic acoustic
oscillations (BAO) using single-dish 21cm intensity mapping observations in the
post-reionization era. We show that the telescope beam smears out the isotropic
BAO signature and, in the case of the Square Kilometer Array (SKA) instrument,
makes it undetectable at redshifts $z\gtrsim1$. We however demonstrate that the
BAO peak can still be detected in the radial 21cm power spectrum and describe a
method to make this type of measurements. By means of numerical simulations,
containing the 21cm cosmological signal as well as the most relevant Galactic
and extra-Galactic foregrounds and basic instrumental effect, we quantify the
precision with which the radial BAO scale can be measured in the 21cm power
spectrum. We systematically investigate the signal-to-noise and the precision
of the recovered BAO signal as a function of cosmic variance, instrumental
noise, angular resolution and foreground contamination. We find that the
expected noise levels of SKA would degrade the final BAO errors by $\sim5\%$
with respect to the cosmic-variance limited case at low redshifts, but that the
effect grows up to $\sim65\%$ at $z\sim2-3$. Furthermore, we find that the
radial BAO signature is robust against foreground systematics, and that the
main effect is an increase of $\sim20\%$ in the final uncertainty on the
standard ruler caused by the contribution of foreground residuals as well as
the reduction in sky area needed to avoid high-foreground regions. We also find
that it should be possible to detect the radial BAO signature with high
significance in the full redshift range. We conclude that a 21cm experiment
carried out by the SKA should be able to make direct measurements of the
expansion rate $H(z)$ with competitive per-cent level precision on redshifts
$z\lesssim2.5$.


title:
Scaling behaviour and superconducting instability in anisotropic
  non-Fermi liquids

abstract:
  We study the scaling behaviour of the optical conductivity $(\sigma)$, free
energy density $(F)$, and shear viscosity of the quantum critical point
associated with the spin density wave phase transition for a two-dimensional
metallic system with $C_2$ symmetry. A non-Fermi liquid behaviour emerges at
two pairs of isolated points on the Fermi surface, due to the coupling of a
bosonic order parameter to fermionic excitations at those so-called
``hot-spots''. We find that near the hot-spots, $\sigma$ and $F$ obey the
scalings expected for such an anisotropic system, and the direction-dependent
viscosity to entropy density ratio is not a universal number due to the
anisotropy. Lastly, we also estimate the effect of the fermion-boson coupling
at the hot-spots on superconducting instabilities.


title:
Polarized synchrotron emission from the equatorial current sheet in
  gamma-ray pulsars

abstract:
  Polarization is a powerful diagnostic tool to constrain the site of the
high-energy pulsed emission and particle acceleration in gamma-ray pulsars.
Recent particle-in-cell simulations of pulsar magnetosphere suggest that
high-energy emission results from particles accelerated in the equatorial
current sheet emitting synchrotron radiation. In this study, we re-examine the
simulation data to compute the phase-resolved polarization properties. We find
that the emission is mildly polarized and that there is an anticorrelation
between the flux and the degree of linear polarization (on-pulse: ~15%,
off-pulse: ~30%). The decrease of polarization during pulses is mainly
attributed to the formation of caustics in the current sheet. Each pulse of
light is systematically accompanied by a rapid swing of the polarization angle
due to the change of the magnetic polarity when the line of sight passes
through the current sheet. The optical polarization pattern observed in the
Crab can be well-reproduced for a pulsar inclination angle ~60 degrees and an
observer viewing angle ~130 degrees. The predicted high-energy polarization is
a robust feature of the current sheet emitting scenario which can be tested by
future X-ray and gamma-ray polarimetry instruments.


title:
Supernova Progenitors, Their Variability, and the Type IIP Supernova
  ASASSN-16fq in M66

abstract:
  We identify a pre-explosion counterpart to the nearby Type IIP supernova
ASASSN-16fq (SN 2016cok) in archival Hubble Space Telescope (HST) data. The
source appears to be a blend of several stars that prevents obtaining accurate
photometry. However, with reasonable assumptions about the stellar temperature
and extinction, the progenitor almost certainly had an initial mass M<17Msun,
and was most likely in the mass range 8-12Msun. Observations once ASASSN-16fq
has faded will have no difficulty accurately determining the properties of the
progenitor. In 8 years of Large Binocular Telescope (LBT) data, no significant
progenitor variability is detected to RMS limits of roughly 0.03 mag. Of the
six nearby SN with constraints on low level variability, SN 1987A, SN 1993J, SN
2008cn, SN 2011dh, SN 2013ej and ASASSN-16fq, only the slowly fading progenitor
of SN 2011dh showed clear evidence of variability. Excluding SN 1987A, the 90%
confidence limit implied by these sources on the number of outbursts over the
last decade before the SN that last longer than 0.1 years (FWHM) and are
brighter than M_R<-8 mag is approximately N<3. Our continuing LBT monitoring
program will steadily improve constraints on pre-SN progenitor variability at
amplitudes far lower than achievable by SN surveys.


title:
Galaxy Zoo: Evidence for rapid, recent quenching within a population of
  AGN host galaxies

abstract:
  We present a population study of the star formation history of 1244 Type 2
AGN host galaxies, compared to 6107 inactive galaxies. A Bayesian method is
used to determine individual galaxy star formation histories, which are then
collated to visualise the distribution for quenching and quenched galaxies
within each population. We find evidence for some of the Type 2 AGN host
galaxies having undergone a rapid drop in their star formation rate within the
last 2 Gyr. AGN feedback is therefore important at least for this population of
galaxies. This result is not seen for the quenching and quenched inactive
galaxies whose star formation histories are dominated by the effects of
downsizing at earlier epochs, a secondary effect for the AGN host galaxies. We
show that histories of rapid quenching cannot account fully for the quenching
of all the star formation in a galaxy's lifetime across the population of
quenched AGN host galaxies, and that histories of slower quenching, attributed
to secular (non-violent) evolution, are also key in their evolution. This is in
agreement with recent results showing both merger-driven and non-merger
processes are contributing to the co-evolution of galaxies and supermassive
black holes. The availability of gas in the reservoirs of a galaxy, and its
ability to be replenished, appear to be the key drivers behind this
co-evolution.


title:
Thermal chiral vortical and magnetic waves: new excitation modes in
  chiral fluids

abstract:
  In certain circumstances, chiral (parity-violating) medium can be described
hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible
examples of such systems include strongly coupled quark-gluon plasma, liquid
helium 3He-A, neutron stars and the Early Universe. We study first-order
hydrodynamics of a chiral fluid on a vortex background and in an external
magnetic field. We show that there are two previously undiscovered modes
describing heat waves propagating along the vortex and magnetic field. We call
them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also
identify known gapless excitations of density (chiral vortical and chiral
magnetic waves) and transverse velocity (chiral Alfven wave). We demonstrate
that the velocity of the chiral vortical wave is zero, when the full
hydrodynamic framework is applied, and hence the wave is absent and the
excitation reduces to the charge diffusion mode. We also comment on the
frame-dependent contributions to the obtained propagation velocities.


title: A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster

abstract:
  We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm
continuum maps of compact radio sources in the Orion Nebular Cluster. We
mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and
109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and
190 HST-identified proplyds (with significant overlap between those
characterizations). We detected radio emission from 175 compact radio sources
in the ONC, including 26 sources that were detected for the first time at these
wavelengths. For each detected source we fit a simple free-free and dust
emission model to characterize the radio emission. We extrapolate the free-free
emission spectrum model for each source to ALMA bands to illustrate how these
measurements could be used to correctly measure protoplanetary disk dust masses
from sub-millimeter flux measurements. Finally, we compare the fluxes measured
in this survey with previously measured fluxes for our targets, as well as four
separate epochs of 1.3 cm data, to search for and quantify variability of our
sources.


title: Lectures on Gravity and Entanglement

abstract:
  The AdS/CFT correspondence provides quantum theories of gravity in which
spacetime and gravitational physics emerge from ordinary non-gravitational
quantum systems with many degrees of freedom. Recent work in this context has
uncovered fascinating connections between quantum information theory and
quantum gravity, suggesting that spacetime geometry is directly related to the
entanglement structure of the underlying quantum mechanical degrees of freedom
and that aspects of spacetime dynamics (gravitation) can be understood from
basic quantum information theoretic constraints. In these notes, we provide an
elementary introduction to these developments, suitable for readers with some
background in general relativity and quantum field theory. The notes are based
on lectures given at the CERN Spring School 2014, the Jerusalem Winter School
2014, the TASI Summer School 2015, and the Trieste Spring School 2015.


title:
The Riemann zeta function and Gaussian multiplicative chaos: statistics
  on the critical line

abstract:
  We prove that if $\omega$ is uniformly distributed on $[0,1]$, then as
$T\to\infty$, $t\mapsto \zeta(i\omega T+it+1/2)$ converges to a non-trivial
random generalized function, which in turn is identified as a product of a very
well behaved random smooth function and a random generalized function known as
a complex Gaussian multiplicative chaos distribution. This demonstrates a novel
rigorous connection between number theory and the theory of multiplicative
chaos -- the latter is known to be connected to many other areas of
mathematics.
  We also investigate the statistical behavior of the zeta function on the
mesoscopic scale. We prove that if we let $\delta_T$ approach zero slowly
enough as $T\to\infty$, then $t\mapsto \zeta(1/2+i\delta_T t+i\omega T)$ is
asymptotically a product of a divergent scalar quantity suggested by Selberg's
central limit theorem and a strictly Gaussian multiplicative chaos. We also
prove a similar result for the characteristic polynomial of a Haar distributed
random unitary matrix, where the scalar quantity is slightly different but the
multiplicative chaos part is identical. This essentially says that up to scalar
multiples, the zeta function and the characteristic polynomial of a Haar
distributed random unitary matrix have an identical distribution on the
mesoscopic scale.


title: Nonclassical statistics from a polaritonic Josephson junction

abstract:
  We theoretically study the emission statistics of a weakly nonlinear photonic
dimer during coherent oscillations. We show that the phase and population
dynamics allow to periodically meet an optimal intensity squeezing condition
resulting in a strongly nonclassical emission statistics. By considering an
exciton-polariton Josephson junction resonantly driven by a classical source,
we show that a sizeable antibunching should emerge in such semiconductor system
where intrinsic nonclassical signatures have remained elusive to date.


title:
Role of electron-electron interactions in the charge dynamics of
  rare-earth-doped CaFe2As2

abstract:
  We have investigated the charge dynamics and the nature of many-body
interactions in La- and Pr- doped CaFe2As2. From the infrared part of the
optical conductivity, we discover that the scattering rate of mobile carriers
above 200 K exhibits saturation at the Mott-Ioffe-Regel limit of metallic
transport. However, the dc resistivity continues to increase with temperature
above 200 K due to the loss of Drude spectral weight. The loss of Drude
spectral weight with increasing temperature is seen in a wide temperature range
in the uncollapsed tetragonal phase, and this spectral weight is recovered at
energy scales about one order of magnitude larger than the Fermi energy scale
in these semimetals. The phenomena noted above have been observed previously in
other correlated metals in which the dominant interactions are electronic in
origin. Further evidence of significant electron-electron interactions is
obtained from the presence of quadratic temperature and frequency-dependent
terms in the scattering rate at low temperatures and frequencies in the
uncollapsed tetragonal structures of La-doped and Pr-doped CaFe2As2. For
temperatures below the structure collapse transition in Pr-doped CaFe2As2 at 70
K, the scattering rate decreases due to weakening of electronic correlations,
and the Drude spectral weight decreases due to modification of the low-energy
electronic structure.


title: PDDL+ Planning via Constraint Answer Set Programming

abstract:
  PDDL+ is an extension of PDDL that enables modelling planning domains with
mixed discrete-continuous dynamics. In this paper we present a new approach to
PDDL+ planning based on Constraint Answer Set Programming (CASP), i.e. ASP
rules plus numerical constraints. To the best of our knowledge, ours is the
first attempt to link PDDL+ planning and logic programming. We provide an
encoding of PDDL+ models into CASP problems. The encoding can handle non-linear
hybrid domains, and represents a solid basis for applying logic programming to
PDDL+ planning. As a case study, we consider the EZCSP CASP solver and obtain
promising results on a set of PDDL+ benchmark problems.


title:
A Nonparametric Maximum Likelihood Approach for Partially Observed Cured
  Data with Left Truncation and Right-Censoring

abstract:
  Partially observed cured data occur in the analysis of spontaneous abortion
(SAB) in observational studies in pregnancy. In contrast to the traditional
cured data, such data has an observable `cured' portion as women who do not
abort spontaneously. The data is also subject to left truncate in addition to
right-censoring because women may enter or withdraw from a study any time
during their pregnancy. Left truncation in particular causes unique bias in the
presence of a cured portion. In this paper, we study a cure rate model and
develop a conditional nonparametric maximum likelihood approach. To tackle the
computational challenge we adopt an EM algorithm making use of "ghost copies"
of the data, and a closed form variance estimator is derived. Under suitable
assumptions, we prove the consistency of the resulting estimator involving an
unbounded cumulative baseline hazard function, as well as the asymptotic
normality. Simulation results are carried out to evaluate the finite sample
performance. We present the analysis of the motivating SAB study to illustrate
the power of our model addressing both occurrence and timing of SAB, as
compared to existing approaches in practice.


title:
Flexible Metal Oxide/Graphene Oxide Hybrid Neuromorphic Devices on
  Flexible Conducting Graphene Substrates

abstract:
  Flexible metal oxide/graphene oxide hybrid multi-gate neuron transistors were
fabricated on flexible graphene substrates. Dendritic integrations in both
spatial and temporal modes were successfully emulated, and spatiotemporal
correlated logics were obtained. A proof-of-principle visual system model for
emulating lobula giant motion detector neuron was investigated. Our results are
of great interest for flexible neuromorphic cognitive systems.


title:
Overscreened Kondo effect, (color) superconductivity and Shiba states in
  Dirac metals and quark matter

abstract:
  We study the interplay between the Kondo effect and (color) superconductivity
in doped Dirac metals with magnetic impurities and in quark matter with
colorful impurities. We first point out that the overscreened Kondo effect
arises in the normal state of these systems. Next the (color) superconducting
gap is incorporated as a mean field and the phase diagram for a varying gap and
temperature is constructed nonperturbatively. A rich phase structure emerges
from a competition of effects unique to a multichannel system. The
Kondo-screened phase is shown to disappear for a sufficiently large gap.
Peculiarity of quark matter due to the confining property of non-Abelian gauge
fields is noted. We also investigate the spectrum of sub-gap excited states,
called Shiba states. Based on a model calculation and physical reasoning we
predict that, as the coupling of the impurity to the bulk is increased, there
will be more than one quantum phase transition due to level crossing among
overscreened states.

categories: cond-mat.str-el cond-mat.supr-con hep-ph nucl-th


title: Stable Phase Retrieval in Infinite Dimensions

abstract:
  The problem of phase retrieval is to determine a signal $f\in \mathcal{H}$,
with $\mathcal{H}$ a Hilbert space, from intensity measurements $|F(\omega)|$,
where $F(\omega):=\langle f , \varphi_\omega\rangle$ are measurements of $f$
with respect to a measurement system $(\varphi_\omega)_{\omega\in
\Omega}\subset \mathcal{H}$. Although phase retrieval is always stable in the
finite dimensional setting whenever it is possible (i.e. injectivity implies
stability for the inverse problem), the situation is drastically different if
$\mathcal{H}$ is infinite-dimensional: in that case phase retrieval is never
uniformly stable [8, 4]; moreover the stability deteriorates severely in the
dimension of the problem [8]. On the other hand, all empirically observed
instabilities are of a certain type: they occur whenever the function $|F|$ of
intensity measurements is concentrated on disjoint sets $D_j\subset \Omega$,
i.e., when $F= \sum_{j=1}^k F_j$ where each $F_j$ is concentrated on $D_j$ (and
$k \geq 2$). Motivated by these considerations we propose a new paradigm for
stable phase retrieval by considering the problem of reconstructing $F$ up to a
phase factor that is not global, but that can be different for each of the
subsets $D_j$, i.e., recovering $F$ up to the equivalence $$ F \sim
\sum_{j=1}^k e^{i \alpha_j} F_j.$$ We present concrete applications (for
example in audio processing) where this new notion of stability is natural and
meaningful and show that in this setting stable phase retrieval can actually be
achieved, for instance if the measurement system is a Gabor frame or a frame of
Cauchy wavelets.


title:
Instrumentation for the Citizen CATE Experiment: Faroe Islands and
  Indonesia

abstract:
  The inner regions of the solar corona from 1-2.5 Rsun are poorly sampled both
from the ground and space telescopes. A solar eclipse reduces the sky scattered
background intensity by a factor of about 10,000 and opens a window to view
this region directly. The goal of the Citizen {\it Continental-America
Telescopic Eclipse} (CATE) Experiment is to take a 90-minute time sequence of
calibrated white light images of this coronal region using 60 identical
telescopes spread from Oregon to South Carolina during the 21 August 2017 total
solar eclipse. Observations that can address questions of coronal dynamics in
this region can be collected with rather modest telescope equipment, but the
large dynamic range of the coronal brightness requires careful camera control.
The instruments used for test runs on the Faroe Islands in 2015 and at five
sites in Indonesia in 2016 are described. Intensity calibration of the coronal
images is done and compared with previous eclipse measurements from November \&
Koutchmy (1996) and Bazin et al. (2015). The change of coronal brightness with
distance from the Sun seen in the 2016 eclipse agrees with observations from
the 1991 eclipse but differ substantially from the 2010 eclipse. The 2015
observations agree with 2016 and 1991 solar radii near the Sun, but are fainter
at larger distances. Problems encountered during these test runs are discussed
as well the solutions which will be implemented for the 2017 eclipse
experiment.


title: Human Pose Estimation in Space and Time using 3D CNN

abstract:
  This paper explores the capabilities of convolutional neural networks to deal
with a task that is easily manageable for humans: perceiving 3D pose of a human
body from varying angles. However, in our approach, we are restricted to using
a monocular vision system. For this purpose, we apply a convolutional neural
network approach on RGB videos and extend it to three dimensional convolutions.
This is done via encoding the time dimension in videos as the 3\ts{rd}
dimension in convolutional space, and directly regressing to human body joint
positions in 3D coordinate space. This research shows the ability of such a
network to achieve state-of-the-art performance on the selected Human3.6M
dataset, thus demonstrating the possibility of successfully representing
temporal data with an additional dimension in the convolutional operation.


title: Good Enough Practices in Scientific Computing

abstract:
  We present a set of computing tools and techniques that every researcher can
and should adopt. These recommendations synthesize inspiration from our own
work, from the experiences of the thousands of people who have taken part in
Software Carpentry and Data Carpentry workshops over the past six years, and
from a variety of other guides. Unlike some other guides, our recommendations
are aimed specifically at people who are new to research computing.


title:
Nucleation and droplet growth from supersaturated vapor at temperatures
  below the triple point temperature

abstract:
  In 1897 Ostwald formulated his step rule for formation of the most stable
crystal state for a system with crystal polymorphism. The rule describes the
irreversible way a system converts to the crystal with lowest free energy. But
in fact the irreversible way a supercooled gas below the triple point
temperature $T_{tr.p.}$ crystallizes via a liquid droplet is an example of
Ostwald's step rule. The homogeneous nucleation in the supersaturated gas is
not to a crystal, but to a liquid-like critical nucleus. We have for the first
time performed constant energy (NVE) Molecular Dynamics (MD) of homogeneous
nucleation without the use of a thermostat. The simulations of homogeneous
nucleation in a Lennard-Jones system from supersaturated vapor at temperatures
below $T_{tr.p.}$ reveals that the nucleation to a liquid-like critical nucleus
is initiated by a small cold cluster [S. Toxvaerd, J. Chem. Phys. \textbf{143}
154705 (2015)]. The release of latent heat at the subsequent droplet growth
increases the temperature in the liquid-like droplet, which for not deep
supercooling and/or low supersaturation, can exceed $T_{tr.p.}$. The
temperature of the liquid-like droplet increases less for a low supersaturation
and remains below $T_{tr.p.}$, but without a crystallization of the droplet for
long times. The dissipation of the latent heat into the surrounding gas is
affected by a traditional MD thermostat, with the consequence that droplet
growth is different for (NVE) MD and constant temperature (NVT) MD.


title: On continuous causal isomorphisms

abstract:
  It is shown that continuous causal isomorphisms on two-dimensional Minkowski
spacetime can be characterized by the invariance of wave equations.


title: Weak and strong approximation of semigroups on Hilbert spaces

abstract:
  For a sequence of uniformly bounded, degenerate semigroups on a Hilbert
space, we compare various types of convergences to a limit semigroup. Among
others, we show that convergence of the semigroups, or of the resolvents of the
generators, in the weak operator topology, in the strong operator topology or
in certain integral norms are equivalent under certain natural assumptions
which are frequently met in applications.


title:
The "forgotten" pseudomomenta and gauge changes in generalized Landau
  Level problems: spatially nonuniform magnetic and temporally varying electric
  fields

abstract:
  By perceiving gauge invariance as an analytical tool in order to get insight
into the states of the "generalized Landau problem" (a charged quantum particle
moving inside a magnetic, and possibly electric field), and motivated by an
early article that correctly warns against a naive use of gauge transformation
procedures in the usual Landau problem (i.e. with the magnetic field being
static and uniform), we first show how to bypass the complications pointed out
in that article by solving the problem in full generality through gauge
transformation techniques in a more appropriate manner. Our solution provides
in simple and closed analytical forms all Landau Level-wavefunctions without
the need to specify a particular vector potential. This we do by proper
handling of the so-called pseudomomentum K (or of a quantity that we term
pseudoangular momentum Lz), a method that is crucially different from the old
warning argument, but also from standard treatments in textbooks and in
research literature (where the usual Landau wavefunctions are employed -
labeled with canonical momenta quantum numbers). Most importantly, we go
further by showing that a similar procedure can be followed in the more
difficult case of spatially-nonuniform magnetic fields: in such case we define
K and Lz as plausible generalizations of the previous ordinary case, namely as
appropriate line integrals of the inhomogeneous magnetic field - our method
providing closed analytical expressions for all stationary state
wavefunctions.. (see paper) ... also provide explicit Berry's phase
calculations and their connection to probability currents and ...issues in
elementary Quantum Mechanics and Condensed Matter Physics. As an added feature,
we also show how the possible presence of an additional electric field can be
treated through a further generalization of pseudomomenta and their proper
handling.

categories: cond-mat.mes-hall math-ph math.MP quant-ph


title: The status of the Zassenhaus conjecture for small groups

abstract:
  We identify all small groups of order up to 288 in the GAP Library for which
the Zassenhaus conjecture on rational conjugacy of units of finite order in the
integral group ring cannot be established by an existing method. The groups
must first survive all theoretical sieves and all known restrictions on partial
augmentations (the HeLP$^+$ method). Then two new computational methods for
verifying the Zassenhaus conjecture are applied to the unresolved cases, which
we call the quotient method and the partially central unit construction method.
To the cases that remain we attempt an assortment of special arguments
available for units of certain orders and the lattice method. In the end, the
Zassenhaus conjecture is verified for all groups of order less than 144 and we
give a list of all remaining cases among groups of orders 144 to 287.


title:
Relativistic corrections to the algebra of position variables and
  spin-orbital interaction

abstract:
  In the framework of vector model of spin, we discuss the problem of a
covariant formalism \cite{Pomeranskii1998} concerning the discrepancy between
relativistic and Pauli Hamiltonians. We show how the spin-induced non
commutativity of a position accounts the discrepancy on the classical level,
without appeal to the Dirac equation and Foldy-Wouthuysen transformation.


title: Theory of Double Ladder Lumped Circuits With Degenerate Band Edge

abstract:
  A conventional periodic LC ladder circuit forms a transmission line that has
a regular band edge between a pass and a stop band. Here for the first time we
develop the theory of simple yet unconventional double ladder circuit that
exhibits a special degeneracy condition referred to as degenerate band edge
(DBE). The degeneracy occurs when four independent eigenstates coalesce into a
single eigenstate at the DBE frequency. In addition to possible practical
applications, this circuit may provide insight into DBE behavior that is not
clear in more complex systems. We show that double ladder resonators exhibit
unusual behavior of the loaded quality factor near the DBE leading to a stable
resonance frequency against load variations. These two properties in the
proposed circuit are superior to the analogous properties in single ladder
circuits. Our proposed analysis leads to analytic expressions for all circuit
quantities thus providing insight into the very complex behavior near
degeneracy points in periodic circuits. Interestingly, here we show for the
first time that DBE is obtained with unit cells that are symmetric along the
propagation direction. The proposed theory of double ladders presented here has
potential applications in filters, couplers, oscillators, and pulse shaping
networks.


title:
Towards Hybrid Cloud-assisted Crowdsourced Live Streaming: Measurement
  and Analysis

abstract:
  Crowdsourced Live Streaming (CLS), most notably Twitch.tv, has seen explosive
growth in its popularity in the past few years. In such systems, any user can
lively broadcast video content of interest to others, e.g., from a game player
to many online viewers. To fulfill the demands from both massive and
heterogeneous broadcasters and viewers, expensive server clusters have been
deployed to provide video ingesting and transcoding services. Despite the
existence of highly popular channels, a significant portion of the channels is
indeed unpopular. Yet as our measurement shows, these broadcasters are
consuming considerable system resources; in particular, 25% (resp. 30%) of
bandwidth (resp. computation) resources are used by the broadcasters who do not
have any viewers at all. In this paper, we closely examine the challenge of
handling unpopular live-broadcasting channels in CLS systems and present a
comprehensive solution for service partitioning on hybrid cloud. The
trace-driven evaluation shows that our hybrid cloud-assisted design can smartly
assign ingesting and transcoding tasks to the elastic cloud virtual machines,
providing flexible system deployment cost-effectively.


title:
Bayesian Regression Using a Prior on the Model Fit: The R2-D2 Shrinkage
  Prior

abstract:
  Prior distributions for high-dimensional linear regression require specifying
a joint distribution for the unobserved regression coefficients, which is
inherently difficult. We instead propose a new class of shrinkage priors for
linear regression via specifying a prior first on the model fit, in particular,
the coefficient of determination, and then distributing through to the
coefficients in a novel way. The proposed method compares favourably to
previous approaches in terms of both concentration around the origin and tail
behavior, which leads to improved performance both in posterior contraction and
in empirical performance. The limiting behavior of the proposed prior is $1/x$,
both around the origin and in the tails. This behavior is optimal in the sense
that it simultaneously lies on the boundary of being an improper prior both in
the tails and around the origin. None of the existing shrinkage priors obtain
this behavior in both regions simultaneously. We also demonstrate that our
proposed prior leads to the same near-minimax posterior contraction rate as the
spike-and-slab prior.


title: Anisotropic Weyl invariance

abstract:
  We consider a non-relativistic free scalar field theory with a type of
anisotropic scale invariance in which the number of coordinates "scaling like
time" is generically greater than one. We propose the Cartesian product of two
curved spaces, the metric of each space being parameterized by the other space,
as a notion of curved background to which the theory can be extended. We study
this type of geometries, and find a family of extensions of the theory to
curved backgrounds in which the anisotropic scale invariance is promoted to a
local, Weyl-type symmetry.


title: Practical sketching algorithms for low-rank matrix approximation

abstract:
  This paper describes a suite of algorithms for constructing low-rank
approximations of an input matrix from a random linear image of the matrix,
called a sketch. These methods can preserve structural properties of the input
matrix, such as positive-semidefiniteness, and they can produce approximations
with a user-specified rank. The algorithms are simple, accurate, numerically
stable, and provably correct. Moreover, each method is accompanied by an
informative error bound that allows users to select parameters a priori to
achieve a given approximation quality. These claims are supported by numerical
experiments with real and synthetic data.


title:
Reduced Open Gromov-Witten Invariants on K3 Surfaces and Multiple Cover
  Formula

abstract:
  In the paper, we study the wall-crossing phenomenon of reduced open
Gromov-Witten invariants on K3 surfaces with rigid special Lagrangian boundary
condition. As a corollary, we derived the multiple cover formula for the
reduced open Gromov-Witten invariants.


title: Search for Hidden-Charm Pentaquark with CLAS12

abstract:
  LHCb recently announced the discovery of two exotic structures in the $J/\psi
+ p$ decay channel, which have been referred to as charmonium-pentaquark
states. Resolving between the models and clarifying the nature of the
discovered hidden-charm pentaquark peaks, and possibly searching for similar
peaks with other quantum numbers, requires further experimental studies. The
states were observed in the decay mode $J/\psi+p$. Thus, it is natural to
expect that these pentaquarks can be produced in the photoproduction process
$\gamma+p\to P_c\to J/\psi+p$ where these states will appear as s-channel
resonances at photon energy around 10 GeV. The energy and luminosity of the
CLAS12 photon beam permit the detailed studies of the production and decay
properties of the pentaquark resonances. By this reason the pentaquark search
at Jefferson Laboratory looks extremely attractive.


title: Estimation and Control of Quality of Service in Demand Dispatch

abstract:
  It is now well known that flexibility of energy consumption can be harnessed
for the purposes of grid-level ancillary services. In particular, through
distributed control of a collection of loads, a balancing authority regulation
signal can be tracked accurately, while ensuring that the quality of service
(QoS) for each load is acceptable {\it on average}. In this paper it is argued
that a histogram of QoS is approximately Gaussian, and consequently each load
will eventually receive poor service. Statistical techniques are developed to
estimate the mean and variance of QoS as a function of the power spectral
density of the regulation signal. It is also shown that additional local
control can eliminate risk: The histogram of QoS is {\it truncated} through
this local control, so that strict bounds on service quality are guaranteed.
While there is a tradeoff between the grid-level tracking performance (capacity
and accuracy) and the bounds imposed on QoS, it is found that the loss of
capacity is minor in typical cases.


title: The geometry and origin of ultra-diffuse ghost galaxies

abstract:
  The geometry and intrinsic ellipticity distribution of ultra diffuse galaxies
(UDGs) is determined from the line-of-sight distribution of axial ratios q of a
large sample of UDGs, detected by Koda et al. (2015) in the Coma cluster. With
high significance the data rules out an oblate, disk-like geometry,
characterised by major axi a=b>c. The data is however in good agreement with
prolate shapes, corresponding to a=b<c. This indicates that UDGs are not
thickened, rotating, axisymmetric disks, puffed up by violent processes.
Instead they are anisotropic elongated cigar- or bar-like structures, similar
to the prolate dwarf spheroidal galaxy population of the Local Group. The
intrinsic distribution of axial ratios of the Coma UDGs is flat in the range of
0.4 <= a/c <= 0.9 which will provide important constraints for theoretical
models of their origin. Formation scenarios that could explain the extended
prolate nature of UDGs are discussed.


title: Analysis of the Self Projected Matching Pursuit Algorithm

abstract:
  The convergence and numerical analysis of a low memory implementation of the
Orthogonal Matching Pursuit greedy strategy, which is termed Self Projected
Matching Pursuit, is presented. This approach renders an iterative way of
solving the least squares problem with much less storage requirement than
direct linear algebra techniques. Hence, it appropriate for solving large
linear systems. The analysis highlights its suitability within the class of
well posed problems.


title: Speckle-Free Coherence Tomography of Turbid Media

abstract:
  Optical coherence tomography (OCT) is a powerful biomedical imaging
technology that relies on the coherent detection of backscattered light to
image tissue morphology in vivo. As a consequence, OCT is susceptible to
coherent noise (speckle noise), which imposes significant limitations on its
diagnostic capabilities. Here we show a method based purely on light
manipulation that is able to entirely remove the speckle noise originating from
turbid samples without any compromise in resolution. We refer to this method as
Speckle-Free OCT (SFOCT). Using SFOCT, we succeeded in revealing small
structures that are otherwise hidden by speckle noise when using conventional
OCT, including the inner stromal structure of a live mouse cornea, the fine
structures inside the mouse pinna, sweat ducts, and Meissners corpuscle in the
human fingertip skin. SFOCT has the potential to markedly increase OCTs
diagnostic capabilities of various human diseases by revealing minute features
that correlate with early pathology.


title: Reconstruction of Static Black Hole Images Using Simple Geometric Forms

abstract:
  General Relativity predicts that the emission close to a black hole must be
lensed by its strong gravitational field, illuminating the last photon orbit.
This results in a dark circular area known as the black hole 'shadow'. The
Event Horizon Telescope (EHT) is a (sub)mm VLBI network capable of
Schwarzschild-radius resolution on Sagittarius A* (or Sgr A*), the 4 million
solar mass black hole at the Galactic Center. The goals of the Sgr A*
observations include resolving and measuring the details of its morphology.
However, EHT data are sparse in the visibility domain, complicating reliable
detailed image reconstruction. Therefore, direct pixel imaging should be
complemented by other approaches. Using simulated EHT data from a black hole
emission model we consider an approach to Sgr A* image reconstruction based on
a simple and computationally efficient analytical model that produces images
similar to the synthetic ones. The model consists of an eccentric ring with a
brightness gradient and a two-dimensional Gaussian. These elemental forms have
closed functional representations in the visibility domain, which lowers the
computational overhead of fitting the model to the EHT observations. For model
fitting we use a version of the Markov chain Monte-Carlo (MCMC) algorithm based
on the Metropolis-Hastings sampler with replica exchange. Over a series of
simulations we demonstrate that our model can be used for determining geometric
measures of a black hole, thus providing information on the shadow size,
linking General Relativity with accretion theory.


title:
Linear Quadratic Mean Field Teams: Optimal and Approximately Optimal
  Decentralized Solutions

abstract:
  We consider team optimal control of decentralized systems with linear
dynamics, quadratic costs, and arbitrary disturbance that consist of multiple
sub-populations with exchangeable agents (i.e., exchanging two agents within
the same sub-population does not affect the dynamics or the cost). Such a
system is equivalent to one where the dynamics and costs are coupled across
agents through the mean-field (or empirical mean) of the states and actions
(even when the primitive random variables are non-exchangeable). Two
information structures are investigated. In the first, all agents observe their
local state and the mean-field of all sub-populations, in the second, all
agents observe their local state but the mean-field of only a subset of the
sub-populations. Both information structures are non-classical and not
partially nested. Nonetheless, it is shown that linear control strategies are
optimal for the first and approximately optimal for the second, the
approximation error is inversely proportional to the size of the
sub-populations whose mean-fields are not observed. The corresponding gains are
determined by the solution of K+1 decoupled standard Riccati equations, where K
is the number of sub-populations. The dimensions of the Riccati equations do
not depend on the size of the sub-populations, thus the solution complexity is
independent of the number of agents. Generalizations to major-minor agents,
tracking cost, weighted mean-field, and infinite horizon are provided. The
results are illustrated using an example of demand response in smart grids.


title:
Quantification of mixing in vesicle suspensions using numerical
  simulations in two dimensions

abstract:
  We study mixing in Stokesian vesicle suspensions in two dimensions on a
cylindrical Couette apparatus using numerical simulations. The vesicle flow
simulation is done using a boundary integral method and the advection-diffusion
equation for the mixing of the solute is solved using a pseudo-spectral scheme.
We study the effect of the area fraction, the viscosity contrast between the
inside (the vesicles) and the outside (the bulk) fluid, the initial condition
of the solute, and the mixing metric. We compare mixing in the suspension with
mixing in the Couette apparatus without vesicles. On the one hand, the presence
of vesicles in most cases, slightly suppresses mixing. This is because the
solute can be only diffused across the vesicle interface and not advected. On
the other hand, there exist spatial distributions of the solute for which the
unperturbed Couette flow completely fails to mix whereas the presence of
vesicles enables mixing. We derive a simple condition that relates the velocity
and solute and can be used to characterize the cases in which the presence of
vesicles promotes mixing.


title:
Revisiting the zero-temperature phase diagram of stoichiometric SrCoO3
  with first-principles methods

abstract:
  By using first-principles methods based on density functional theory we
revisited the zero-temperature phase diagram of stoichiometric SrCoO3, a
ferromagnetic metallic perovskite that undergoes significant structural,
electronic, and magnetic changes as its content of oxygen is decreased. We
considered both bulk and epitaxial thin film geometries. In the bulk case, we
found that a tetragonal P4/mbm phase with moderate Jahn-Teller distortions and
c/a ratio of ~1/sqrt{2} is consistently predicted to have a lower energy than
the thus far assumed ground-state cubic Pm-3m phase. In thin films, we found
two phase transitions occurring at compressive and tensile epitaxial strains.
However, in contrast to previous theoretical predictions, our results show
that: (i) the phase transition induced by tensile strain is isostructural and
involves only a change in magnetic spin order (that is, not a metallic to
insulator transformation), and (ii) the phase transition induced by compressive
strain comprises simultaneous structural, electronic and magnetic spin order
changes, but the required epitaxial stress is so large (<-6%) that is unlikely
to be observed in practice. Our findings call for a revision of the
crystallographic analysis performed in fully oxidised SrCoO3 samples at low
temperatures, as well as of previous first-principles studies.


title: Generalized solutions of Riccati equalities and inequalities

abstract:
  The Riccati inequality and equality are studied for infinite dimensional
linear discrete time stationary systems with respect to the scattering supply
rate. The results obtained are an addition to and based on our earlier work on
the Kalman-Yakubovich-Popov inequality in [6]. The main theorems are closely
related to the results of Yu. M. Arlinski\u{\i} in [3]. The main difference is
that we do not assume the original system to be a passive scattering system,
and we allow the solutions of the Riccati inequality and equality to satisfy
weaker conditions.


title:
Solving Large-Scale Inverse Magnetostatic Problems using the Adjoint
  Method

abstract:
  An efficient algorithm for the reconstruction of the magnetization state
within magnetic components is presented. The occurring inverse magnetostatic
problem is solved by means of an adjoint approach, based on the Fredkin-Koehler
method for the solution of the forward problem. Due to the use of hybrid
FEM-BEM coupling combined with matrix compression techniques the resulting
algorithm is well suited for large-scale problems. Furthermore the
reconstruction of the magnetization state within a permanent magnet is
demonstrated.


title: Pixel Arrays: A fast and elementary method for solving nonlinear systems

abstract:
  We present a new method, called the pixel array method, for approximating all
solutions in a bounding box for an arbitrary nonlinear system of relations. In
contrast with other solvers, our approach requires that the user must specify
which variables are to be exposed, and which are to be left latent. The entire
solution set is then obtained---in terms of these exposed variables---by
performing a series of array multiplications on the $n_i$-dimensional plots of
the individual relations $R_i$. This procedure introduces no false negatives
and is much faster than Newton-based solvers. The key is the unexposed
variables, which Newton methods can make no use of. In fact, we found that with
even a single unexposed variable our method was more than 10x faster than
Julia's NLsolve. Due to its relative simplicity, the pixel array method is also
applicable to a broader class of systems than Newton-based solvers are. The
purpose of this article is to give an account of this new method.


title:
Full-Duplex Backscatter Interference Networks Based on Time-Hopping
  Spread Spectrum

abstract:
  Future Internet-of-Things (IoT) is expected to wirelessly connect billions of
low-complexity devices. For wireless information transfer (WIT) in IoT, high
density of IoT devices and their ad hoc communication result in strong
interference which acts as a bottleneck on WIT. Furthermore, battery
replacement for the massive number of IoT devices is difficult if not
infeasible, making wireless energy transfer (WET) desirable. This motivates:
(i) the design of full-duplex WIT to reduce latency and enable efficient
spectrum utilization, and (ii) the implementation of passive IoT devices using
backscatter antennas that enable WET from one device (reader) to another (tag).
However, the resultant increase in the density of simultaneous links
exacerbates the interference issue. This issue is addressed in this paper by
proposing the design of full-duplex backscatter communication (BackCom)
networks, where a novel multiple-access scheme based on time-hopping
spread-spectrum (TH-SS) is designed to enable both one-way WET and two-way WIT
in coexisting backscatter reader-tag links. Comprehensive performance analysis
of BackCom networks is presented in this paper, including forward/backward
bit-error rates and WET efficiency and outage probabilities, which accounts for
energy harvesting at tags, non-coherent and coherent detection at tags and
readers, respectively, and the effects of asynchronous transmissions.


title: Mesh Resolution Effect on 3D RANS Turbomachinery Flow Simulations

abstract:
  The paper presents the study of the effect of a mesh refinement on numerical
results of 3D RANS computations of turbomachinery flows. The CFD solver F,
which based on the second-order accurate ENO scheme, is used in this study. The
simplified multigrid algorithm and local time stepping permit decreasing
computational time. The flow computations are performed for a number of turbine
and compressor cascades and stages. In all flow cases, the successively refined
meshes of H-type with an approximate orthogonalization near the solid walls
were generated. The results obtained are compared in order to estimate their
both mesh convergence and ability to resolve the transonic flow pattern. It is
concluded that for thorough studying the fine phenomena of the 3D
turbomachinery flows, it makes sense to use the computational meshes with the
number of cells from several millions up to several hundred millions per a
single turbomachinery blade channel, while for industrial computations, a mesh
of about or less than one million cells per a single turbomachinery blade
channel could be sufficient under certain conditions.


title:
Evidence for Fluorescent Fe II Emission from Extended Low Ionization
  Outflows in Obscured Quasars

abstract:
  Recent studies have shown that outflows in at least some broad absorption
line (BAL) quasars are extended well beyond the putative dusty torus. Such
outflows should be detectable in obscured quasars. We present four WISE
selected infrared red quasars with very strong and peculiar ultraviolet Fe ii
emission lines: strong UV Fe II UV arising from transitions to ground/low
excitation levels, and very weak Fe II at wavelengths longer than 2800 {\AA}.
The spectra of these quasars display strong resonant emission lines, such as C
IV, Al III and Mg II but sometimes, a lack of non-resonant lines such as C
III], S III and He II. We interpret the Fe II lines as resonantly scattered
light from the extended outflows that are viewed nearly edge-on, so that the
accretion disk and broad line region are obscured by the dusty torus, while the
extended outflows are not. We show that dust free gas exposed to strong
radiation longward of 912 {\AA} produces Fe II emission very similar to that
observed. The gas is too cool to collisionally excite Fe II lines, accounting
for the lack of optical emission. The spectral energy distribution from the UV
to the mid-infrared can be modeled as emission from a clumpy dusty torus, with
UV emission being reflected/scattered light either by the dusty torus or the
outflow. Within this scenario, we estimate a minimum covering factor of the
outflows from a few to 20% for the Fe II scattering region, suggesting that Fe
II BAL quasars are at a special stage of quasar evolution.


title: Partitioned Cross-Validation for Divide-and-Conquer Density Estimation

abstract:
  We present an efficient method to estimate cross-validation bandwidth
parameters for kernel density estimation in very large datasets where ordinary
cross-validation is rendered highly inefficient, both statistically and
computationally. Our approach relies on calculating multiple cross-validation
bandwidths on partitions of the data, followed by suitable scaling and
averaging to return a partitioned cross-validation bandwidth for the entire
dataset. The partitioned cross-validation approach produces substantial
computational gains over ordinary cross-validation. We additionally show that
partitioned cross-validation can be statistically efficient compared to
ordinary cross-validation. We derive analytic expressions for the
asymptotically optimal number of partitions and study its finite sample
accuracy through a detailed simulation study. We additionally propose a
permuted version of partitioned cross-validation which attains even higher
efficiency. Theoretical properties of the estimators are studied and the
methodology is applied to the Higgs Boson dataset with 11 million observations


title:
A Review of Multivariate Distributions for Count Data Derived from the
  Poisson Distribution

abstract:
  The Poisson distribution has been widely studied and used for modeling
univariate count-valued data. Multivariate generalizations of the Poisson
distribution that permit dependencies, however, have been far less popular.
Yet, real-world high-dimensional count-valued data found in word counts,
genomics, and crime statistics, for example, exhibit rich dependencies, and
motivate the need for multivariate distributions that can appropriately model
this data. We review multivariate distributions derived from the univariate
Poisson, categorizing these models into three main classes: 1) where the
marginal distributions are Poisson, 2) where the joint distribution is a
mixture of independent multivariate Poisson distributions, and 3) where the
node-conditional distributions are derived from the Poisson. We discuss the
development of multiple instances of these classes and compare the models in
terms of interpretability and theory. Then, we empirically compare multiple
models from each class on three real-world datasets that have varying data
characteristics from different domains, namely traffic accident data,
biological next generation sequencing data, and text data. These empirical
experiments develop intuition about the comparative advantages and
disadvantages of each class of multivariate distribution that was derived from
the Poisson. Finally, we suggest new research directions as explored in the
subsequent discussion section.


title:
Tuning ferromagnetic BaFe$_2$(PO$_4$)$_2$ through a high Chern number
  topological phase

abstract:
  There is strong interest in discovering or designing wide gap Chern
insulators. Here we follow a Chern insulator to trivial Mott insulator
transition versus interaction strength U in a honeycomb lattice Fe-based
transition metal oxide, discovering that a spin-orbit coupling energy scale
$\xi$=40 meV can produce and maintain a topologically entangled Chern
insulating state against large band structure changes arising from an
interaction strength U up to 60 times as large. Within the Chern phase the
minimum gap switches from the zone corner K to the zone center $\Gamma$ while
maintaining the topological structure. At a critical strength $U_c$, the
continuous evolution of the electronic structure encounters a gap closing then
reopening, upon which the system reverts to a trivial Mott insulating phase.
This Chern insulator phase of honeycomb lattice Fe$^{2+}$ BaFe$_2$(PO$_4$)$_2$
corresponds to a large Chern number C=-3 that will provide enhanced anomalous
Hall conductivity due to the associated three edge states threading through the
bulk gap of 80 meV.


title:
Mesa-top quantum dot single photon emitter arrays: growth, optical
  characteristics, and the simulated optical response of integrated dielectric
  nanoantenna-waveguide systems

abstract:
  Nanophotonic quantum information processing systems require spatially
ordered, spectrally uniform single photon sources (SPSs) integrated on-chip
with co-designed light manipulating elements providing emission rate
enhancement, emitted photon guidance, and lossless propagation. Towards this
goal, we consider systems comprising an SPS array with each SPS coupled to a
dielectric building block (DBB) based multifunctional light manipulation unit
(LMU). For the SPS array, we report triggered single photon emission from
GaAs(001)/InGaAs single quantum dots (SQDs) grown selectively on top of
nanomesas using the approach of substrate-encoded size-reducing epitaxy
(SESRE). Systematic temperature and power dependent photoluminescence (PL), PL
excitation, time-resolved PL, and emission statistics studies reveal high
spectral uniformity and single photon emission at 8 K with g(2)(0) of 0.19
plusminus 0.03. The SESRE based SPS arrays, following growth of a planarizing
overlayer, are readily integrable with LMUs fabricated subsequently using
either the 2D photonic crystal approach or, as theoretically examined here, DBB
based LMUs. We report the simulated optical response of SPS embedded in DBB
based nanoantenna-waveguide structures as the multifunctional LMU. The multiple
functions of emission rate enhancement, guiding, and lossless propagation
derive from the behavior of the same collective Mie resonance (dominantly
magnetic) of the interacting DBB based LMU tuned to the SPS targeted emission
wavelength of 980 nm. The simulation utilizes an analytical approach that
provides physical insight to the obtained numerical results. Together, the
combined experimental and modelling demonstrations open a rich approach to
implementing co-designed on-chip integrated SPS-LMU that, in turn, serve as
basic elements of integrated nanophotonic information processing systems.


title: Rainbow Tur\'an problems for paths and forests of stars

abstract:
  For a fixed graph $F$, we would like to determine the maximum number of edges
in a properly edge-colored graph on $n$ vertices which does not contain a
{\emph rainbow copy} of $F$, that is, a copy of $F$ all of whose edges receive
a different color. This maximum, denoted by $ex^*(n,F)$, is the {\emph rainbow
Tur\'an number} of $F$, and its systematic study was initiated by Keevash,
Mubayi, Sudakov and Verstra\"ete in 2007. We determine $ex^*(n,F)$ exactly when
$F$ is a forest of stars, and give bounds on $ex^*(n,F)$ when $F$ is a path
with $k$ edges, disproving a conjecture in Keevash et al.


title:
How Much is 131 Million Dollars? Putting Numbers in Perspective with
  Compositional Descriptions

abstract:
  How much is 131 million US dollars? To help readers put such numbers in
context, we propose a new task of automatically generating short descriptions
known as perspectives, e.g. "$131 million is about the cost to employ everyone
in Texas over a lunch period". First, we collect a dataset of numeric mentions
in news articles, where each mention is labeled with a set of rated
perspectives. We then propose a system to generate these descriptions
consisting of two steps: formula construction and description generation. In
construction, we compose formulae from numeric facts in a knowledge base and
rank the resulting formulas based on familiarity, numeric proximity and
semantic compatibility. In generation, we convert a formula into natural
language using a sequence-to-sequence recurrent neural network. Our system
obtains a 15.2% F1 improvement over a non-compositional baseline at formula
construction and a 12.5 BLEU point improvement over a baseline description
generation.


title: On the essential minimum of Faltings' height

abstract:
  We study the essential minimum of the (stable) Faltings height on the moduli
space of elliptic curves. We prove that, in contrast to the Weil height on a
projective space and the N{\'e}ron-Tate height of an abelian variety, Faltings'
height takes at least two values that are smaller than its essential minimum.
We also provide upper and lower bounds for this quantity that allow us to
compute it up to five decimal places. In addition, we give numerical evidence
that there are at least four isolated values before the essential minimum.
  One of the main ingredients in our analysis is a good approximation of the
hyperbolic Green function associated to the cusp of the modular curve of level
one. To establish this approximation, we make an intensive use of distortion
theorems for univalent functions.
  Our results have been motivated and guided by numerical experiments that are
described in detail in the companion files.


title: Attentional Push: Augmenting Salience with Shared Attention Modeling

abstract:
  We present a novel visual attention tracking technique based on Shared
Attention modeling. Our proposed method models the viewer as a participant in
the activity occurring in the scene. We go beyond image salience and instead of
only computing the power of an image region to pull attention to it, we also
consider the strength with which other regions of the image push attention to
the region in question. We use the term Attentional Push to refer to the power
of image regions to direct and manipulate the attention allocation of the
viewer. An attention model is presented that incorporates the Attentional Push
cues with standard image salience-based attention modeling algorithms to
improve the ability to predict where viewers will fixate. Experimental
evaluation validates significant improvements in predicting viewers' fixations
using the proposed methodology in both static and dynamic imagery.


title:
Modulated Pulses Based High Spatial Resolution Distributed Fiber System
  for Multi-Parameter Sensing

abstract:
  We demonstrate a hybrid distributed fiber sensing system for multi-parameter
detection. The integration of phase-sensitive optical time domain reflectometry
({\Phi}-OTDR) and Brillouin optical time domain reflectometry (B-OTDR) enables
measurement of vibration, temperature and strain. Exploiting the fast changing
property of vibration and the static property of temperature and strain, the
laser pulse width and intensity are modulated and then injected into the
single-mode sensing fiber proportionally, so that the three concerned
parameters can be extracted simultaneously by only one photo-detector and data
acquisition channel. Combining with advanced data processing methods, the
modulation of laser pulse brings additional advantages because of trade and
balance between the backscattering light power and nonlinear effect noise,
which enhances the signal-to-noise ratio, and enables sub-meter level spatial
resolution together with long sensing distance. The proposed method realizes up
to 4.8 kHz vibration sensing with 3 m spatial resolution at 10 km standard
single-mode fiber. And measurements of the distributed temperature and stress
profile along the same fiber with 80 cm spatial resolution are also achieved
concurrently.


title:
Neural Network Architecture Optimization through Submodularity and
  Supermodularity

abstract:
  Deep learning models' architectures, including depth and width, are key
factors influencing models' performance, such as test accuracy and computation
time. This paper solves two problems: given computation time budget, choose an
architecture to maximize accuracy, and given accuracy requirement, choose an
architecture to minimize computation time. We convert this architecture
optimization into a subset selection problem. With accuracy's submodularity and
computation time's supermodularity, we propose efficient greedy optimization
algorithms. The experiments demonstrate our algorithm's ability to find more
accurate models or faster models. By analyzing architecture evolution with
growing time budget, we discuss relationships among accuracy, time and
architecture, and give suggestions on neural network architecture design.