title:
Spacetime-Free Approach to Quantum Theory and Effective Spacetime
  Structure

abstract:
  Motivated by hints of the effective emergent nature of spacetime structure,
we formulate a spacetime-free algebraic framework for quantum theory, in which
no a priori background geometric structure is required. Such a framework is
necessary in order to study the emergence of effective spacetime structure in a
consistent manner, without assuming a background geometry from the outset.
Instead, the background geometry is conjectured to arise as an effective
structure of the algebraic and dynamical relations between observables that are
imposed by the background statistics of the system. Namely, we suggest that
quantum reference states on an extended observable algebra, the free algebra
generated by the observables, may give rise to effective spacetime structures.
Accordingly, perturbations of the reference state lead to perturbations of the
induced effective spacetime geometry. We initiate the study of these
perturbations, and their relation to gravitational phenomena.


title: Digit permutations revisited

abstract:
  We discuss here characteristic $p$ $L$-series as well as the group $S_{(q)}$
which appears to act as symmetries of these functions. We explain various
actions of $S_{(q)}$ that arise naturally in the theory as well as extensions
of these actions. In general such extensions appear to be highly arbitrary but
in the case where the zeroes are unramified, the extension is unique (and it is
reasonable to expect it is unique only in this case). Having unramified zeroes
is the best one could hope for in finite characteristic and appears to be an
avatar of the Riemann hypothesis in this setting; see Section [8] for a more
detailed discussion.


title: Detection of low energy antimatter with emulsions

abstract:
  Emulsion detectors feature a very high position resolution and consequently
represent an ideal device when particle detection is required at the
micrometric scale. This is the case of quantum interferometry studies with
antimatter, where micrometric fringes have to be measured. In this framework,
we designed and realized a new emulsion based detector characterized by a gel
enriched in terms of silver bromide crystal contents poured on a glass plate.
We tested the sensitivity of such a detector to low energy positrons in the
range 10-20 keV. The obtained results prove that nuclear emulsions are highly
efficient at detecting positrons at these energies. This achievement paves the
way to perform matter-wave interferometry with positrons using this technology.


title: Fundamental Limits of Optical Force and Torque

abstract:
  Optical force and torque provide unprecedented control on the spatial motion
of small particles. A valid scientific question, that has many practical
implications, concerns the existence of fundamental upper bounds for the
achievable force and torque exerted by a plane wave illumination with a given
intensity. Here, while studying isotropic particles, we show that different
light-matter interaction channels contribute to the exerted force and torque;
and analytically derive upper bounds for each of the contributions. Specific
examples for particles that achieve those upper bounds are provided. We study
how and to which extent different contributions can add up to result in the
maximum optical force and torque. Our insights are important for applications
ranging from molecular sorting, particle manipulation, nanorobotics up to
ambitious projects such as laser-propelled spaceships.


title:
Lattices of double-quanta vortices and chirality inversion in $p_x+ip_y$
  superconductors

abstract:
  We investigate the magnetization processes of a standard Ginzburg-Landau
model for chiral p-wave superconducting states in an applied magnetic field. We
find that the phase diagram is dominated by triangular lattices of doubly
quantized vortices. Only in close vicinity to the upper critical field, the
lattice starts to dissociate into a structure of single-quanta vortices. The
degeneracy between states with opposite chirality is broken in a nonzero field.
If the magnetization starts with an energetically unfavorable chirality, the
process of chirality-inversion induced by the external magnetic field results
in the formation of a sequence of metastable states with characteristic
magnetic signatures that can be probed by standard experimental techniques.


title:
Testing consistency of general relativity with kinematic and dynamical
  probes

abstract:
  In this work, we test consistency relations between a kinematic probe, the
observational Hubble data, and a dynamical probe, the growth rates for cosmic
large scale structure, which should hold if general relativity is the correct
theory of gravity on cosmological scales. Moreover, we summarize the
development history of parametrization in testings and make an improvement of
it. Taking advantage of the Hubble parameter given from both parametric and
non-parametric methods, we propose three equations and test two of them
performed by means of two-dimensional parameterizations, including one using
trigonometric functions we propose. As a result, it is found that the
consistency relations satisfies well at $1\sigma$ CL and trigonometric
functions turn out to be efficient tools in parameterizations. Furthermore, in
order to confirm the validity of our test, we introduce a model of modified
gravity, DGP model and compare the testing results in the cases of
$\Lambda$CDM, "DGP in GR" and DGP model with mock data. It can be seen that it
is the establishing of consistency relations which dominates the results of the
testing. Overall, the present observational Hubble data and growth rate data
favor convincingly that the general relativity is the correct theory of gravity
on cosmological scales.


title:
A fresh view of cosmological models describing very early Universe:
  general solution of the dynamical equations

abstract:
  The dynamics of any spherical cosmology with a scalar field (`scalaron')
coupling to gravity is described by the nonlinear second-order differential
equations for two metric functions and the scalaron depending on the `time'
parameter. The equations depend on the scalaron potential and on the arbitrary
gauge function that describes time parameterizations. This dynamical system can
be integrated for flat, isotropic models with very special potentials. But,
somewhat unexpectedly, replacing the `time' variable by one of the metric
functions allows us to completely integrate the general spherical theory in any
gauge and with apparently arbitrary potentials. The main restrictions on the
potential arise from positivity of the derived analytic expressions for the
solutions, which are essentially the squared canonical momenta. An interesting
consequence is emerging of classically forbidden regions for these analytic
solutions. It is also shown that in this rather general model the inflationary
solutions can be identified, explicitly derived, and compared to the standard
approximate expressions. This approach can be applied to intrinsically
anisotropic models with a massive vector field (`vecton') as well as to some
non-inflationary models.


title: Efficient Similarity Search in Dynamic Data Streams

abstract:
  The Jaccard index is an important similarity measure for item sets and
Boolean data. On large datasets, an exact similarity computation is often
infeasible for all item pairs both due to time and space constraints, giving
rise to faster approximate methods. The algorithm of choice used to quickly
compute the Jaccard index $\frac{\vert A \cap B \vert}{\vert A\cup B\vert}$ of
two item sets $A$ and $B$ is usually a form of min-hashing. Most min-hashing
schemes are maintainable in data streams processing only additions, but none
are known to work when facing item-wise deletions. In this paper, we
investigate scalable approximation algorithms for rational set similarities, a
broad class of similarity measures including Jaccard. Motivated by a result of
Chierichetti and Kumar [J. ACM 2015] who showed any rational set similarity $S$
admits a locality sensitive hashing (LSH) scheme if and only if the
corresponding distance $1-S$ is a metric, we can show that there exists a space
efficient summary maintaining a $(1\pm \varepsilon)$ multiplicative
approximation to $1-S$ in dynamic data streams. This in turn also yields a
$\varepsilon$ additive approximation of the similarity. The existence of these
approximations hints at, but does not directly imply a LSH scheme in dynamic
data streams. Our second and main contribution now lies in the design of such a
LSH scheme maintainable in dynamic data streams. The scheme is space efficient,
easy to implement and to the best of our knowledge the first of its kind able
to process deletions.


title: The contraction principle in extended context

abstract:
  There are several extensions of the classical Banach Fixed Point Theorem in
technical literature. A branch of generalizations replaces usual contractivity
by weaker but still effective assumptions. Our note follows this stream,
presenting an elementary proof for a known fixed point result. Some
applications are also considered.


title:
ASASSN-15lh: A Superluminous Ultraviolet Rebrightening Observed by Swift
  and Hubble

abstract:
  We present and discuss ultraviolet and optical photometry from the
Ultraviolet/Optical Telescope and X-ray limits from the X-Ray Telescope on
Swift and imaging polarimetry and ultraviolet/optical spectroscopy with the
Hubble Space Telescope of ASASSN-15lh. It has been classified as a
hydrogen-poor superluminous supernova (SLSN I) more luminous than any other
supernova observed. ASASSN-15lh is not detected in the X-rays in individual or
coadded observations. From the polarimetry we determine that the explosion was
only mildly asymmetric. We find the flux of ASASSN-15lh to increase strongly
into the ultraviolet, with a ultraviolet luminosity a hundred times greater
than the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find objects
as bright as ASASSN-15lh are easily detectable beyond redshifts of ~4 with the
single-visit depths planned for the Large Synoptic Survey Telescope. Deep
near-infrared surveys could detect such objects past a redshift of ~20 enabling
a probe of the earliest star formation. A late rebrightening -- most prominent
at shorter wavelengths -- is seen about two months after the peak brightness,
which is itself as bright as a superluminous supernova. The ultraviolet spectra
during the rebrightening are dominated by the continuum without the broad
absorption or emission lines seen in SLSNe or tidal disruption events and the
early optical spectra of ASASSN-15lh. Our spectra show no strong hydrogen
emission, showing only LyA absorption near the redshift previously found by
optical absorption lines of the presumed host. The properties of ASASSN-15lh
are extreme when compared to either SLSNe or tidal disruption events.


title:
Estimating the dimensionality of neural responses with fMRI Repetition
  Suppression

abstract:
  We propose a novel method that exploits fMRI Repetition Suppression (RS-fMRI)
to measure the dimensionality of the set response vectors, i.e. the dimension
of the space of linear combinations of neural population activity patterns in
response to specific task conditions. RS-fMRI measures the overlap between
response vectors even in brain areas displaying no discernible average
differential BOLD signal. We show how this property can be used to estimate the
neural response dimensionality in areas lacking macroscopic spatial patterning.
The importance of dimensionality derives from how it relates to a neural
circuit's functionality. As we show, the dimensionality of the response vectors
is predicted to be high in areas involved in multi-stream integration, while it
is low in areas where inputs from independent sources do not interact or merely
overlap linearly. Our method can be used to identify and functionally
characterize cortical circuits that integrate multiple independent information
pathways.


title:
Chapman-Enskog expansion for the Vicsek model of self-propelled
  particles

abstract:
  Using the standard Vicsek model, I show how the macroscopic transport
equations can be systematically derived from microscopic collision rules. The
approach starts with the exact evolution equation for the N-particle
probability distribution, and after making the mean-field assumption of
Molecular Chaos leads to a multi-particle Enskog-type equation. This equation
is treated by a non-standard Chapman-Enskog expansion to extract the
macroscopic behavior. The expansion includes terms up to third order in a
formal expansion parameter $\epsilon$, and involves a fast time scale. A
self-consistent closure of the moment equations is presented that leads to a
continuity equation for the particle density and a Navier-Stokes-like equation
for the momentum density. Expressions for all transport coefficients in these
macroscopic equations are given explicitly in terms of microscopic parameters
of the model. The transport coefficients depend on specific angular integrals
which are evaluated asymptotically in the limit of infinitely many collision
partners, using an analogy to a random walk. The consistency of the
Chapman-Enskog approach is checked by an independent calculation of the shear
viscosity using a Green-Kubo relation.

categories: cond-mat.stat-mech cond-mat.soft physics.bio-ph physics.flu-dyn


title:
Applying Bayesian parameter estimation to relativistic heavy-ion
  collisions: simultaneous characterization of the initial state and
  quark-gluon plasma medium

abstract:
  We quantitatively estimate properties of the quark-gluon plasma created in
ultra-relativistic heavy-ion collisions utilizing Bayesian statistics and a
multi-parameter model-to-data comparison. The study is performed using a
recently developed parametric initial condition model, TRENTO, which
interpolates among a general class of particle production schemes, and a modern
hybrid model which couples viscous hydrodynamics to a hadronic cascade. We
calibrate the model to multiplicity, transverse momentum, and flow data and
report constraints on the parametrized initial conditions and the
temperature-dependent transport coefficients of the quark-gluon plasma. We show
that initial entropy deposition is consistent with a saturation-based picture,
extract a relation between the minimum value and slope of the
temperature-dependent specific shear viscosity, and find a clear signal for a
nonzero bulk viscosity.


title:
Amplitude modulation in $\delta$ Sct stars: statistics from an ensemble
  study of Kepler targets

abstract:
  We present the results of a search for amplitude modulation of pulsation mode
frequencies in 983 $\delta$ Sct stars, which have effective temperatures
between 6400 $\leq T_{\rm eff} \leq$ 10 000 K in the Kepler Input Catalogue and
were continuously observed by the Kepler Space Telescope for 4 yr. We
demonstrate the diversity in pulsational behaviour observed, in particular
nonlinearity, which is predicted for $\delta$ Sct stars. We analyse and discuss
examples of $\delta$ Sct stars with constant amplitudes and phases; those that
exhibit amplitude modulation caused by beating of close-frequency pulsation
modes; those that exhibit pure amplitude modulation (with no associated phase
variation); those that exhibit phase modulation caused by binarity; and those
that exhibit amplitude modulation caused by nonlinearity. Using models and
examples of individual stars, we demonstrate that observations of the changes
in amplitude and phase of pulsation modes can be used to distinguish among the
different scenarios. We find that 603 $\delta$ Sct stars (61.3 per cent)
exhibit at least one pulsation mode that varies significantly in amplitude over
4 yr. Conversely, many $\delta$ Sct stars have constant pulsation amplitudes so
short-length observations can be used to determine precise frequencies,
amplitudes and phases for the most coherent and periodic $\delta$ Sct stars. It
is shown that amplitude modulation is not restricted to a small region on the
HR diagram, therefore not necessarily dependent on stellar parameters such as
$T_{\rm eff}$ or $\log\,g$. Our catalogue of 983 $\delta$ Sct stars will be
useful for comparisons to similar stars observed by K2 and TESS, because the
length of the 4-yr Kepler data set will not be surpassed for some time.


title: On the Convergent Properties of Word Embedding Methods

abstract:
  Do word embeddings converge to learn similar things over different
initializations? How repeatable are experiments with word embeddings? Are all
word embedding techniques equally reliable? In this paper we propose evaluating
methods for learning word representations by their consistency across
initializations. We propose a measure to quantify the similarity of the learned
word representations under this setting (where they are subject to different
random initializations). Our preliminary results illustrate that our metric not
only measures a intrinsic property of word embedding methods but also
correlates well with other evaluation metrics on downstream tasks. We believe
our methods are is useful in characterizing robustness -- an important property
to consider when developing new word embedding methods.


title:
Exploratory investigation of the HIPPO gas-jet target fluid dynamic
  properties

abstract:
  In order to optimize the performance of gas-jet targets for future nuclear
reaction measurements, a detailed understanding of the dependence of the
gas-jet properties on experiment design parameters is required. Common methods
of gas-jet characterization rely on measuring the effective thickness using
nuclear elastic scattering and energy loss techniques; however, these tests are
time intensive and limit the range of design modifications which can be
explored to improve the properties of the jet as a nuclear reaction target.
Thus, a more rapid jet-characterization method is desired. We performed the
first steps towards characterizing the gas-jet density distribution of the
HIPPO gas-jet target at the University of Notre Dame's Nuclear Science
Laboratory by reproducing results from
$^{20}\rm{Ne}(\alpha,\alpha)^{20}\rm{Ne}$ elastic scattering measurements with
computational fluid dynamics (CFD) simulations performed with the
state-of-the-art CFD software ANSYS Fluent. We find a strong sensitivity to
experimental design parameters of the gas-jet target, such as the jet nozzle
geometry and ambient pressure of the target chamber. We argue that improved
predictive power will require moving to three-dimensional simulations and
additional benchmarking with experimental data.


title:
OpenMP Fortran and C programs for solving the time-dependent
  Gross-Pitaevskii equation in an anisotropic trap

abstract:
  We present new version of previously published Fortran and C programs for
solving the Gross-Pitaevskii equation for a Bose-Einstein condensate with
contact interaction in one, two and three spatial dimensions in imaginary and
real time, yielding both stationary and non-stationary solutions. To reduce the
execution time on multicore processors, new versions of parallelized programs
are developed using Open Multi-Processing (OpenMP) interface. The input in the
previous versions of programs was the mathematical quantity nonlinearity for
dimensionless form of Gross-Pitaevskii equation, whereas in the present
programs the inputs are quantities of experimental interest, such as, number of
atoms, scattering length, oscillator length for the trap, etc. New output files
for some integrated one- and two-dimensional densities of experimental interest
are given. We also present speedup test results for the new programs.

categories: cond-mat.quant-gas nlin.PS physics.comp-ph quant-ph


title: The ABC (in any D) of Logarithmic CFT

abstract:
  Logarithmic conformal field theories have a vast range of applications, from
critical percolation to systems with quenched disorder. In this paper we
thoroughly examine the structure of these theories based on their symmetry
properties. Our analysis is model-independent and holds for any spacetime
dimension. Our results include a determination of the general form of
correlation functions and conformal block decompositions, clearing the path for
future bootstrap applications. Several examples are discussed in detail,
including logarithmic generalized free fields, holographic models,
self-avoiding random walks and critical percolation.


title:
Inferring the evolutionary stages of the internal structures of NGC 7538
  S and IRS1 from chemistry

abstract:
  To unambiguously diagnose the detailed physical mechanisms and the
evolutionary status of high-mass star-forming regions (HMSFRs), we have
performed 0.4" ($\sim1000$ AU) resolution observations towards NGC7538S and
IRS1, using the Plateau de Bure Interferometer (PdBI). This paper presents a
joint analysis of the 1.37 mm continuum emission and the line intensity of 15
molecular species. Assuming local thermal equilibrium, we derived molecular
column densities and molecular abundances for each internal gas substructure
which is spatially resolved. These derived quantities are compared with a suite
of 1-D gas-grain models.
  NGC7538S is resolved into at least three dense gas condensations. Despite the
comparable continuum intensity of these condensations, their differing
molecular line emission is suggestive of an overall chemical evolutionary trend
from the northeast to the southeast. Since these condensations are embedded
within the same parent gas core, their differing chemical properties are the
most likely due to the different warm-up histories, rather than the different
dynamic timescales. Despite remaining spatially unresolved, in IRS1 we detect
abundant complex organic molecules, indicating that IRS1 is the most chemically
evolved hot molecular core presented here. We observe a continuum that is
dominated by absorption features with at least three strong emission lines,
potentially from $\rm CH_3OH$. The $\rm CH_3OH$ lines which are purely in
emission have higher excitation than the ones showing purely absorption.
Potential reasons for that difference are discussed.
  This is the first comprehensive comparison of observations of the high-mass
cores NGC7538S and IRS1 and a chemical model. We have found that different
chemical evolutionary stages can coexist in the same natal gas core. Our
achievement illustrates the strength of chemical analysis for understanding
HMSFRs.


title: Constrained superfields from an anti-D3-brane in KKLT

abstract:
  The KKLT construction of dS vacua relies on an uplift term that arises from
an anti-D3-brane. It was argued by Kachru, Pearson and Verlinde that this
anti-D3-brane is an excited state in a supersymmetric theory since it can decay
to a supersymmetric ground state. Hence the anti-D3-brane breaks supersymmetry
spontaneously and one should be able to package all the world-volume fields on
the anti-D3-brane into a four dimensional $\cal{N}=1$ supersymmetric action.
Here we extend previous results and identify the constrained superfields that
correspond to all the degrees of freedom on the anti-D3-brane. In particular,
we show explicitly that the four 4D worldvolume spinors give rise to
constrained chiral multiplets $S$ and $Y^i$, $i=1,2,3$ that satisfy
$S^2=SY^i=0$. We also conjecture (and provide evidence in a forthcoming
publication) that the vector field $A_\mu$ and the three scalars $\phi^i$ give
rise to a field strength multiplet $W_\alpha$ and three chiral multiplets $H^i$
that satisfy the constraints $S W_\alpha= \bar{D}_{\dot \alpha} (S \bar
H^i)=0$. This is the first time that such constrained multiplets appear in
string theory constructions.


title:
SPOTS: The Search for Planets Orbiting Two Stars: II. First constraints
  on the frequency of sub-stellar companions on wide circumbinary orbits

abstract:
  A large number of direct imaging surveys for exoplanets have been performed
in recent years, yielding the first directly imaged planets and providing
constraints on the prevalence and distribution of wide planetary systems.
However, like most of the radial velocity ones, these surveys generally focus
on single stars, hence binaries and higher-order multiples have not been
studied to the same level of scrutiny. This motivated the SPOTS (Search for
Planets Orbiting Two Stars) survey, which is an ongoing direct imaging study of
a large sample of close binaries, started with VLT/NACO and now continuing with
VLT/SPHERE. To complement this survey, we have identified the close binary
targets in 24 published direct imaging surveys. Here we present our statistical
analysis of this combined body of data. We analysed a sample of 117 tight
binary systems, using a combined Monte Carlo and Bayesian approach to derive
the expected values of the frequency of companions, for different values of the
companion's semi-major axis. Our analysis suggest that the frequency of
sub-stellar companions in wide orbit is moderately low ($\lesssim $13% with a
best value of 6% at 95% confidence level) and not significantly different
between single stars and tight binaries. One implication of this result is that
the very high frequency of circumbinary planets in wide orbits around
post-common envelope binaries, implied by eclipse timing (up to 90% according
to Zorotovic & Schreiber 2013), can not be uniquely due to planets formed
before the common-envelope phase (first generation planets), supporting instead
the second generation planet formation or a non-Keplerian origin of the timing
variations.


title: Gas-to-dust ratio in massive star-forming galaxies at z~1.4

abstract:
  We present results of 12CO(J=2-1) observations toward four massive
star-forming galaxies at z~1.4 with the Nobeyama 45~m radio telescope. The
galaxies are detected with Spitzer/MIPS in 24 um, Herschel/SPIRE in 250 um, and
350 um and they mostly reside in the main sequence. Their gas-phase
metallicities derived with N2 method by using the Ha and [NII]6584 emission
lines are near the solar value. CO lines are detected toward three galaxies.
The molecular gas masses obtained are (9.6-35) x 10^{10} Msun by adopting the
Galactic CO-to-H2 conversion factor and the CO(2-1)/CO(1-0) flux ratio of 3.
The dust masses derived with the modified blackbody model (assuming the dust
temperature of 35 K and the emissivity index of 1.5) are (2.4-5.4) x 10^{8}
Msun. The resulting gas-to-dust ratios (not accounting for HI mass) at z~1.4
are 220-1450, which are several times larger than those in local star-forming
galaxies. A dependence of the gas-to-dust ratio on the far-infrared luminosity
density is not clearly seen.


title:
The gap of stellar mass in galaxy groups: another perspective of the
  Too-big-To-Fail problem in the Milky Way

abstract:
  The Milky Way presents the too-big-to-fail (TBTF) problem that there are two
observed satellite galaxies with maximum circular velocity larger than 55km/s,
and others have velocity less than 25km/s, but the cold dark matter model
predicts there should be more than 10 subhaloes with velocity larger than
25km/s. Those massive subhaloes with $25km/s<V_{max}<55km/s$ should not have
failed to form stars. The TBTF problem severely challenges the CDM model. Most
efforts are seeking the effects of baryonic feedback, decreasing the mass of
the Milky Way, changing the properties of dark matter, so as to assign the
observed low-velocity satellites into the massive subhaloes found in
simulations. However, the TBTF problem can be avoided if the MW have not
accreted subhaloes with velocity between $25km/s<V_{max}<55km/s$ although the
probability of such a gap is lower as $\sim 1\%$ and can not be tested against
observations. In this work we study the gap in stellar mass of satellite
galaxies using the SDSS group catalogue and a semi-analytical model. We find
that there are 1-2\% of galaxy groups with a large gap in the stellar mass of
their satellites. These 'big gap' groups have accreted less massive subhaloes
in their formation history and naturally display a gap between their satellite
galaxies. If extrapolating our results to the Milky Way is appropriate, we
conclude that it is very likely that our Milky Way has not accreted enough
massive subhaloes to host those low-velocity satellites, and the TBTF problem
is naturally avoided.


title:
Validating estimates of the growth rate of structure with modified
  gravity simulations

abstract:
  We perform a validation of estimates of the growth rate of structure,
described by the parameter combination $f\sigma_8$, in modified gravity
cosmologies. We consider an analysis pipeline based on the redshift-space
distortion modelling of the clustering wedges statistic of the galaxy
correlation function and apply it to mock catalogues of $\Lambda{\rm CDM}$ and
the normal branch of DGP cosmologies. We employ a halo occupation distribution
approach to construct our mocks, which we ensure resemble the CMASS sample from
BOSS in terms of the total galaxy number density and large scale amplitude of
the power spectrum monopole. We show that the clustering wedges model
successfully recovers the true growth rate difference between DGP and
$\Lambda{\rm CDM}$, even for cases with over 40\% enhancement in $f\sigma_8$
compared to $\Lambda{\rm CDM}$. The unbiased performance of the clustering
wedges model allows us to use the growth rate values estimated from the BOSS
DR12 data to constrain the cross-over scale $r_c$ of DGP gravity to
$\left[r_cH_0\right]^{-1} < 0.97$ ($2\sigma$) or $r_c > 3090\ {\rm Mpc}/h$,
cutting into the interesting region of parameter space with $r_c \sim H_0^{-1}$
using constraints from the growth of structure alone.


title:
The Soft State of Cygnus X-1 Observed with NuSTAR: A Variable Corona and
  a Stable Inner Disk

abstract:
  We present a multi-epoch hard X-ray analysis of Cygnus X-1 in its soft state
based on four observations with NuSTAR. Despite the basic similarity of the
observed spectra, there is clear spectral variability between epochs. To
investigate this variability, we construct a model incorporating both the
standard disk-corona continuum and relativistic reflection from the accretion
disk, based on prior NuSTAR work on Cygnus X-1, and apply this model to each
epoch independently. We find excellent consistency for the black hole spin, and
the iron abundance of the accretion disk, which are expected to remain constant
on observational timescales. In particular, we confirm that Cygnus X-1 hosts a
rapidly rotating black hole, 0.93<a*<0.96, in broad agreement with the majority
of prior studies of the relativistic disk reflection and constraints on the
spin obtained through studies of the thermal accretion disk continuum. Our work
also confirms the apparent misalignment between the inner disk and the orbital
plane of the binary system reported previously, finding the magnitude of this
warp to be ~10-15deg. This level of misalignment does not significantly change
(and may even improve) the agreement between our reflection results and the
thermal continuum results regarding the black hole spin. The spectral
variability observed by NuSTAR is dominated by the primary continuum, implying
variability in the temperature of the scattering electron plasma. Finally, we
consistently observe absorption from ionized iron at ~6.7 keV, which varies in
strength as a function of orbital phase in a manner consistent with the
absorbing material being an ionized phase of the focused stellar wind from the
supergiant companion star.


title:
New Surface Brightness Fluctuations Spectroscopic Technique: NGC4449 and
  its Stellar Tidal Stream

abstract:
  We present a new spectroscopic technique based in part on targeting the
upward fluctuations of the surface brightness for studying the internal stellar
kinematics and metallicities of low surface brightness galaxies and streams
beyond the Local Group. The distance to these systems makes them unsuitable for
targeting individual red giant branch (RGB) stars (tip of RGB at
$I\gtrsim24$~mag) and their surface brightness is too low ($\mu_r\gtrsim
25$~mag~arcsec$^{-2}$) for integrated light spectroscopic measurements. This
technique overcomes these two problems by targeting individual objects that are
brighter than the tip of the RGB. We apply this technique to the star-forming
dwarf galaxy NGC 4449 and its stellar stream. We use Keck/DEIMOS data to
measure the line-of-sight radial velocity out to $\sim7$~kpc in the East side
of the galaxy and $\sim8$~kpc along the stream. We find that the two systems
are likely gravitationally bound to each other and have heliocentric radial
velocities of $227.3\pm10.7$~km/s and $225.8\pm16.0$~km/s, respectively.
Neither the stream nor the near half of the galaxy shows a significant velocity
gradient. We estimate the stellar metallicity of the stream based on the
equivalent width of its Calcium triplet lines and find [Fe/H]~$=-1.37\pm0.41$,
which is consistent with the metallicity-luminosity relation for Local Group
dwarf galaxies. Whether the stream's progenitor was moderately or severely
stripped cannot be constrained with this metallicity uncertainty. We
demonstrate that this new technique can be used to measure the kinematics and
(possibly) the metallicity of the numerous faint satellites and stellar streams
in the halos of nearby ($\sim 4$~Mpc) galaxies.


title:
Detection of Phosphorus, Sulphur, and Zinc in the Carbon-Enhanced
  Metal-Poor Star BD+44 493

abstract:
  The carbon-enhanced metal-poor star BD+44 493 ([Fe/H]=-3.9) has been proposed
as a candidate second-generation star enriched by metals from a single Pop III
star. We report the first detections of P and S and the second detection of Zn
in any extremely metal-poor carbon-enhanced star, using new spectra of BD+44
493 collected by the Cosmic Origins Spectrograph on the Hubble Space Telescope.
We derive [P/Fe]=-0.34 +/- 0.21, [S/Fe]=+0.07 +/- 0.41, and [Zn/Fe]=-0.10 +/-
0.24. We increase by ten-fold the number of Si I lines detected in BD+44 493,
yielding [Si/Fe]=+0.15 +/- 0.22. The solar [S/Fe] and [Zn/Fe] ratios exclude
the hypothesis that the abundance pattern in BD+44 493 results from depletion
of refractory elements onto dust grains. Comparison with zero-metallicity
supernova models suggests that the stellar progenitor that enriched BD+44 493
was massive and ejected much less than 0.07 Msun of Ni-56, characteristic of a
faint supernova.


title:
Crossover From Strong to Weak Pairing States in $t-J-U$ Model Studied by
  A Slave Spin Method

abstract:
  We investigate the superconductivity in the $t-J-U$ model within a slave-spin
formalism. We show that the BCS mean-field theory implemented with the slave
spin formalism naturally predicts two distinct gaps which are the pairing gap
of the spinons $\Delta_f$ and the Cooper pairing gap of the electrons
$\Delta_{SC} = Z\Delta_f$, where $Z$ is the quasiparticle weight. Furthermore,
we find that the nature of the superconducting state depends crucially on the
interaction providing the pairing mechanism. For spin interactions, the
bandwidth of the spinon hopping term is renormalized by $Z$ but the its pairing
term is not. As a result, if $U$ exceeds the critical value for the Mott
insulating state at half-filling, $Z$ develops a strong doping dependence,
leading to a doping-driven crossover from strong to weak pairing states. In the
strong pairing state, while $\Delta_f$ is enhanced as $x\to 0$,
$\Delta_{SC}\sim x$ due to the renormalization of $Z$. In the weak pairing
state, $Z$ does not change with $x$ significantly. Therefore, $\Delta_{SC}$ is
mainly controlled by $\Delta_f$, and both of them go to zero at larger doping.
The crossover from strong to weak pairing states is well captured by the slave
spin formalism within reasonable range of parameters just at the mean-field
level, indicating the slave spin formalism is a powerful tool to study
correlated materials. For charge interactions, we find that the bandwidth of
the spinon hopping term and its pairing term are renormalized by $Z$ and $Z^2$
respectively. Consequently, both $\Delta_f$ and $\Delta_{SC}$ are suppressed at
small $x$ in large U, and no crossover will occur. The implication of our
results for the superconducting states in correlated materials will be
discussed.


title:
Reconstructing the redshift evolution of escaped ionizing flux from
  early galaxies with Planck and HST observations

abstract:
  While galaxies at $6 \lesssim z \lesssim 10$ are believed to dominate the
epoch of cosmic reionization, the escape fraction of ionizing flux
$f_\mathrm{esc}$ and the photon production rate $\dot n_\gamma$ from these
galaxies must vary with redshift to simultaneously match CMB and low-redshift
observations. We constrain $f_\mathrm{esc}(z)$ and $\dot n_\gamma(z)$ with
Planck 2015 measurements of the Thomson optical depth $\tau$, recent low
multipole E-mode polarization measurements from Planck 2016, SDSS BAO data, and
$3 \lesssim z \lesssim 10$ galaxy observations. We compare different galaxy
luminosity functions that are calibrated to HST observations, using both
parametric and non-parametric statistical methods that marginalize over the
effective clumping factor $C_\mathrm{HII}$, the LyC production efficiency
$\xi_\mathrm{ion}$, and the time-evolution of the UV limiting magnitude
$dM_\mathrm{SF}/dz$. Using a power-law model, we find $f_\mathrm{esc} \lesssim
0.5$ at $z=8$ with slope $\beta \gtrsim 2.0$ at $68\%$ confidence with little
dependence on the galaxy luminosity function or data, although there is
non-negligible probability for no redshift evolution $\beta \sim 0$ or small
escape fraction $f_\mathrm{esc} \sim 10^{-2}$. A non-parametric form for
$f_\mathrm{esc}(z)$ evolves significantly with redshift, yielding
$f_\mathrm{esc} \sim 0.2, 0.3, 0.6$ at $z=6,9,12$, respectively. However, a
model-independent reconstruction of $\dot n_\gamma(z)$ predicts a suppressed
escaped photon production rate at $z=9$ for the latest Planck data compared to
the other models, implying a quicker period of reionization. We find evidence
for redshift evolution in the limiting magnitude of the galaxy luminosity
function for empirical models of the galaxy luminosity function.


title:
COPSS II: The Molecular Gas Content of Ten Million Cubic Megaparsecs at
  $z\sim3$

abstract:
  We present a measurement of the abundance of carbon monoxide in the early
Universe, utilizing the final results from the CO Power Spectrum Survey
(COPSS). Between 2013 and 2015, we performed observations with the
Sunyaev-Zel'dovich Array (SZA) to measure the aggregate CO emission from
$z\sim3$ galaxies with the intensity mapping technique. Data were collected on
19 fields, covering an area of 0.7 square degrees, over a frequency range of 27
to 35 GHz. With these data, along with data analyzed in COPSS I, we are able to
observe the CO(1-0) transition in the redshift range of $z=2.3-3.3$ for spatial
frequencies between $k=0.5-10\ h\,\textrm{Mpc}^{-1}$, spanning a comoving
volume of $4.9\times10^{6}\ h^{-3}\,\textrm{Mpc}^{3}$. We present estimates of
contributions from continuum sources and ground illumination within our
measurement. We constrain the amplitude of the CO power spectrum to be
$P_{\textrm{CO}}=3.0_{-1.3}^{+1.3}\times10^{3}\ \mu\textrm{K}^{2}
(h^{-1}\,\textrm{Mpc})^{3}$, or $\Delta^{2}_{\textrm{CO}}(k\!=\!1\
h\,\textrm{Mpc}^{-1})=1.5^{+0.7}_{-0.7} \times10^{3}\ \mu\textrm{K}^{2}$, at
68% confidence, and $P_{\textrm{CO}}>0$ at 98.9% confidence. These results are
a factor of 10 improvement in sensitivity compared to the previous limits set
in COPSS I. We use this measurement to place constraints on the CO(1-0) galaxy
luminosity function at $z\sim3$. We constrain the ratio of CO(1-0) luminosity
to host halo mass to $A_{\textrm{CO}}=6.3_{-2.1}^{+1.4}\times10^{-7}\
L_{\odot}\ M_{\odot}^{-1}$, and estimate a mass fraction of molecular gas of
$f_{\textrm{H}_{2}}=5.5^{+3.4}_{-2.2}\times10^{-2}$ for halos with masses of
order $10^{12}M_{\odot}$. Using simple theoretical estimates for the scaling of
molecular gas mass fraction and halo mass, we estimate the global density of
molecular gas to be
$\rho_{z\sim3}(\textrm{H}_{2})=1.1_{-0.4}^{+0.7}\times10^{8}\ M_{\odot}\
\textrm{Mpc}^{-3}$.


title:
Improved Contacts to MoS2 Transistors by Ultra-High Vacuum Metal
  Deposition

abstract:
  The scaling of transistors to sub-10 nm dimensions is strongly limited by
their contact resistance (Rc). Here we present a systematic study of scaling
MoS2 devices and contacts with varying electrode metals and controlled
deposition conditions, over a wide range of temperatures (80 to 500 K), carrier
densities (10^12 to 10^13 1/cm^2), and contact dimensions (20 to 500 nm). We
uncover that Au deposited in ultra-high vacuum (~10^-9 Torr) yields three times
lower Rc than under normal conditions, reaching 740 Ohm-um and specific contact
resistivity 3x10^-7 Ohm.cm2, stable for over four months. Modeling reveals
separate Rc contributions from the Schottky barrier and the series access
resistance, providing key insights on how to further improve scaling of MoS2
contacts and transistor dimensions. The contact transfer length is ~35 nm at
300 K, which is verified experimentally using devices with 20 nm contacts and
70 nm contact pitch (CP), equivalent to the "14 nm" technology node.


title: Low energy signatures of nonlocal field theories

abstract:
  The response of inertial particle detectors coupled to a scalar field
satisfying nonlocal dynamics described by nonanalytic functions of the
d'Alembertian operator $\Box$ is studied. We show that spontaneous emission
processes of a low energy particle detector are very sensitive to high-energy
nonlocality scales. This allows us to suggest a nuclear physics experiment
($\sim$ MeV energy scales) that outperforms the sensitivity of LHC experiments
by many orders of magnitude. This may have implications for the falsifiability
of theoretical proposals of quantum gravity.


title: Mirror quintic vacua: hierarchies and inflation

abstract:
  We study the moduli space of type IIB string theory flux compactifications on
the mirror of the CY quintic 3-fold in P4. We focus on the dynamics of the four
dimensional moduli space, defined by the axio-dilaton {\tau} and the complex
structure modulus z. The z-plane has critical points, the conifold, the
orbifold and the large complex structure with non trivial monodromies. We find
the solutions to the Picard-Fuchs equations obeyed by the periods of the CY in
the full z-plane as a series expansion in z around the critical points to
arbitrary order. This allows us to discard fake vacua, which appear as a result
of keeping only the leading order term in the series expansions. Due to
monodromies vacua are located at a given sheet in the z-plane. A dS vacuum
appears for a set of fluxes. We revisit vacua with hierarchies among the 4D and
6D physical scales close to the conifold point and compare them with those
found at leading order in [1, 2]. We explore slow-roll inflationary directions
of the scalar potential by looking at regions where the multi-field slow-roll
parameters {\epsilon} and {\eta} are smaller than one. The value of {\epsilon}
depends strongly on the approximation of the periods and to achieve a stable
value, several orders in the expansion are needed. We do not find realisations
of single field axion monodromy inflation. Instead, we find that inflationary
regions appear along linear combinations of the four real field directions and
for certain configurations of fluxes.


title:
Equivariant Perturbation in Gomory and Johnson's Infinite Group Problem.
  VI. The curious case of two-sided discontinuous minimal valid functions

abstract:
  We construct a two-sided discontinuous piecewise linear minimal valid
function for the 1-row Gomory--Johnson model which is not extreme, but which is
not a convex combination of other piecewise linear minimal valid functions. The
new function only admits piecewise microperiodic perturbations. We present an
algorithm for computations with a restricted class of such perturbations.


title: Convergence of the Bernstein-Durrmeyer operators in variation seminorm

abstract:
  The aim of this paper is to study variation detracting property and con-
vergence in variation of the Bernstein-Durrmeyer modifications of the classical
Bernstein operators in the space of functions of bounded variation. These
problems are studied with respect to the variation seminorm. Moreover we also
study the problem of the rate of approximation.


title:
Large-surface-area diamond (111) crystal plates for applications in
  high-heat-load wavefront-preserving x-ray crystal optics

abstract:
  We report fabrication and results of high-resolution X-ray topography
characterization of diamond single crystal plates with a large surface area
(10$\times$10 mm$^2$) and (111) crystal surface orientation for applications in
high-heat-load X-ray crystal optics. The plates were fabricated by laser
cutting of the (111) facets of diamond crystals grown using high-pressure
high-temperature method. The intrinsic crystal quality of a selected
3$\times$7~mm$^2$ crystal region of one of the studied samples was found to be
suitable for applications in wavefront-preserving high-heat-load crystal
optics. The wavefront characterization was performed using sequential X-ray
diffraction topography in the pseudo plane wave configuration and data analysis
using rocking curve topography. The variation of the rocking curve width and
peak position measured with a spatial resolution of 13$\times$13 $\mu m^2$ over
the selected region were found to be less than one microradian.


title: Background Rejection of n$^+$ Surface Events in GERDA Phase II

abstract:
  The GERDA experiment searches for neutrinoless double beta ($0\nu\beta\beta$)
decay in $^{76}$Ge using an array of high purity germanium (HPGe) detectors
immersed in liquid argon (LAr). Phase II of the experiment uses 30 new broad
energy germanium (BEGe) detectors with superior pulse shape discrimination
capabilities compared to the previously used semi-coaxial detector design. By
far the largest background component for BEGe detectors in GERDA are
n$^+$-surface events from $^{42}$K $\beta$ decays which are intrinsic in LAr.
The $\beta$ particles with up to 3.5 MeV can traverse the 0.5 to 0.9 mm thick
electrode and deposit energy within the region of interest for the
$0\nu\beta\beta$ decay. However, those events have particular pulse shape
features allowing for a strong discrimination. The understanding and simulation
of this background, showing a reduction by up to a factor 145 with pulse shape
discrimination alone, is presented in this work.


title: Saving Moore's Law Down To 1nm Channels With Anisotropic Effective Mass

abstract:
  Scaling transistors' dimensions has been the thrust for the semiconductor
industry in the last 4 decades. However, scaling channel lengths beyond 10 nm
has become exceptionally challenging due to the direct tunneling between source
and drain which degrades gate control, switching functionality, and worsens
power dissipation. Fortunately, the emergence of novel classes of materials
with exotic properties in recent times has opened up new avenues in device
design. Here, we show that by using channel materials with an anisotropic
effective mass, the channel can be scaled down to 1nm and still provide an
excellent switching performance in both MOSFETs and TFETs. In the case of
TFETs, a novel design has been proposed to take advantage of anisotropic mass
in both ON- and OFF-state of the TFETs. Full-band atomistic quantum transport
simulations of phosphorene nanoribbon MOSFETs and TFETs based on the new design
have been performed as a proof.


title:
Brute-Force Mapmaking with Compact Interferometers: A MITEoR Northern
  Sky Map from 128 MHz to 175 MHz

abstract:
  We present a new method for interferometric imaging that is ideal for the
large fields of view and compact arrays common in 21 cm cosmology. We first
demonstrate the method with simulations for two very different low frequency
interferometers, the Murchison Widefield Array (MWA) and the MIT Epoch of
Reionization (MITEoR) Experiment. We then apply the method to the MITEoR data
set collected in July 2013 to obtain the first northern sky map from 128 MHz to
175 MHz at about 2 degree resolution, and find an overall spectral index of
-2.73+/-0.11. The success of this imaging method bodes well for upcoming
compact redundant low-frequency arrays such as HERA. Both the MITEoR
interferometric data and the 150 MHz sky map are publicly available at
http://space.mit.edu/home/tegmark/omniscope.html.


title: Scope ambiguities, monads and strengths

abstract:
  In this paper, we will discuss three semantically distinct scope assignment
strategies: traditional movement strategy, polyadic approach, and
continuation-based approach. As a generalized quantifier on a set X is an
element of C(X), the value of continuation monad C on X, in all three
approaches QPs are interpreted as C-computations. The main goal of this paper
is to relate the three strategies to the computational machinery connected to
the monad C (strength and derived operations). As will be shown, both the
polyadic approach and the continuation-based approach make heavy use of monad
constructs. In the traditional movement strategy, monad constructs are not used
but we still need them to explain how the three strategies are related and what
can be expected of them wrt handling scopal ambiguities in simple sentences.


title:
Cosmic Voids and Void Lensing in the Dark Energy Survey Science
  Verification Data

abstract:
  Galaxies and their dark matter halos populate a complicated filamentary
network around large, nearly empty regions known as cosmic voids. Cosmic voids
are usually identified in spectroscopic galaxy surveys, where 3D information
about the large-scale structure of the Universe is available. Although an
increasing amount of photometric data is being produced, its potential for void
studies is limited since photometric redshifts induce line-of-sight position
errors of $\sim50$ Mpc/$h$ or more that can render many voids undetectable. In
this paper we present a new void finder designed for photometric surveys,
validate it using simulations, and apply it to the high-quality photo-$z$
redMaGiC galaxy sample of the Dark Energy Survey Science Verification (DES-SV)
data. The algorithm works by projecting galaxies into 2D slices and finding
voids in the smoothed 2D galaxy density field of the slice. Fixing the
line-of-sight size of the slices to be at least twice the photo-$z$ scatter,
the number of voids found in these projected slices of simulated spectroscopic
and photometric galaxy catalogs is within 20% for all transverse void sizes,
and indistinguishable for the largest voids of radius $\sim 70$ Mpc/$h$ and
larger. The positions, radii, and projected galaxy profiles of photometric
voids also accurately match the spectroscopic void sample. Applying the
algorithm to the DES-SV data in the redshift range $0.2<z<0.8$, we identify 87
voids with comoving radii spanning the range 18-120 Mpc/$h$, and carry out a
stacked weak lensing measurement. With a significance of $4.4\sigma$, the
lensing measurement confirms the voids are truly underdense in the matter field
and hence not a product of Poisson noise, tracer density effects or systematics
in the data. It also demonstrates, for the first time in real data, the
viability of void lensing studies in photometric surveys.


title: Data Acquisition System for Segmented Reactor Antineutrino Detector

abstract:
  This paper describes the data acquisition system used for data readout from a
segmented detector of reactor antineutrinos with active shielding. Theoretical
approach to the data acquisition is described and two possible solutions using
QDCs and digitizers are discussed. Also described are the results of the DAQ
performance during routine data taking operation of DANSS. DANSS (Detector of
the reactor AntiNeutrino based on Solid Scintillator) is a project aiming to
measure a spectrum of reactor antineutrinos using inverse beta decay (IBD) in a
plastic scintillator. The detector is located close to an industrial nuclear
reactor core and is covered by passive and active shielding. It is expected to
have about 15000 IBD interactions per day. Light from the detector is sensed by
PMT and SiPM.


title: Polarimetry and flux distribution in the debris disk around HD 32297

abstract:
  We present high-contrast angular differential imaging (ADI) observations of
the debris disk around HD 32297 in H-band, as well as the first polarimetric
images for this system in polarized differential imaging (PDI) mode with
Subaru/HICIAO. In ADI, we detect the nearly edge-on disk at >5sigma levels from
~0.45 arcsec to ~1.7 arcsec (50-192 AU) from the star and recover the spine
deviation from the midplane already found in previous works. We also find for
the first time imaging and surface brightness (SB) indications for the presence
of a gapped structure on both sides of the disk at distances of ~0.75 arcsec
(NE side) and ~0.65 arcsec (SW side). Global forward-modelling work delivers a
best-fit model disk and well-fitting parameter intervals that essentially match
previous results, with high-forward scattering grains and a ring located at 110
AU. However, this single ring model cannot account for the gapped structure
seen in our SB profiles. We create simple double ring models and achieve a
satisfactory fit with two rings located at 60 and 95 AU, respectively,
low-forward scattering grains and very sharp inner slopes. In polarized light
we retrieve the disk extending from ~0.25-1.6 arcsec, although the central
region is quite noisy and high S/N are only found in the range ~0.75-1.2
arcsec. The disk is polarized in the azimuthal direction, as expected, and the
departure from the midplane is also clearly observed. Evidence for a gapped
scenario is not found in the PDI data. We obtain a linear polarization degree
of the grains that increases from ~10% at 0.55 arcsec to ~25% at 1.6 arcsec.
The maximum is found at scattering angles of ~90degrees, either from the main
components of the disk or from dust grains blown out to larger radii.


title: Dippers and Dusty Disks Edges: A Unified Model

abstract:
  We revisit the nature of large dips in flux from extinction by dusty
circumstellar material that is observed by Kepler for many young stars in the
Upper Sco and $\rho$ Oph star formation regions. These young, low-mass "dipper"
stars are known to have low accretion rates and primarily host moderately
evolved dusty circumstellar disks. Young low mass stars often exhibit rotating
star spots that cause quasi-periodic photometric variations. We found no
evidence for periods associated with the dips that are different from the star
spot rotation period in spectrograms constructed from the light curves. The
material causing the dips in most of these light curves must be approximately
corotating with the star. We find that disk temperatures computed at the disk
corotation radius are cool enough that dust should not sublime. Crude estimates
for stellar magnetic field strengths and accretion rates are consistent with
magnetospheric truncation near the corotation radius. Magnetospheric truncation
models can explain why the dips are associated with material near corotation
and how dusty material is lifted out of the midplane to obscure the star which
would account for the large fraction of young low mass stars that are dippers.
We propose that variations in disk orientation angle, stellar magnetic field
dipole tilt axis, and disk accretion rate are underlying parameters accounting
for differences in the dipper light curves.


title: Unification of Gauge Couplings in Radiative Neutrino Mass Models

abstract:
  We investigate the possibility of gauge coupling unification in various
radiative neutrino mass models, which generate neutrino masses at one- and/or
two-loop level. Renormalization group running of gauge couplings is performed
analytically and numerically at one- and two-loop order, respectively. We study
three different classes of neutrino mass models: (I) minimal ultraviolet
completions of the dimension-7 $\Delta L=2$ operators which generate neutrino
masses at one- and/or two-loop level without and with dark matter candidates,
(II) models with dark matter which lead to neutrino masses at one-loop level
and (III) models with particles in the adjoint representation of
$\mathrm{SU}(3)$. In class (I), gauge couplings unify in a few models and
adding dark matter amplifies the chances for unification. In class (II), about
a quarter of the models admit gauge coupling unification. In class (III), none
of the models leads to gauge coupling unification. Regarding the scale of
unification, we find values between $10^{14}$ GeV and $10^{16}$ GeV for models
belonging to class (I) without dark matter, whereas models in class (I) with
dark matter as well as models of class (II) prefer values in the range $5 \cdot
10^{10}-5 \cdot 10^{14}$ GeV.


title:
Cell contractility facilitates alignment of cells and tissues to static
  uniaxial stretch

abstract:
  During animal development and homeostasis, the structure of tissues,
including muscles, blood vessels and connective tissues adapts to mechanical
strains in the extracellular matrix (ECM). These strains originate from the
differential growth of tissues or forces due to muscle contraction or gravity.
Here we show using a computational model that by amplifying local strain cues,
active cell contractility can facilitate and accelerate the reorientation of
single cells to static strains. At the collective cell level, the model
simulations show that active cell contractility can facilitate the formation of
strings along the orientation of stretch. The computational model is based on a
hybrid cellular Potts and finite-element simulation framework describing a
mechanical cell-substrate feedback, where: 1) cells apply forces on the ECM,
such that 2) local strains are generated in the ECM, and 3) cells
preferentially extend protrusions along the strain orientation. In accordance
with experimental observations, simulated cells align and form string-like
structures parallel to static uniaxial stretch. Our model simulations predict
that the magnitude of the uniaxial stretch and the strength of the contractile
forces regulate a gradual transition between string-like patterns and vascular
network-like patterns. Our simulations also suggest that at high population
densities, less cell cohesion promotes string formation.

categories: q-bio.CB cond-mat.soft physics.bio-ph q-bio.TO


title: Modular curves of prime-power level with infinitely many rational points

abstract:
  For each open subgroup $G$ of ${\rm GL}_2(\hat{\mathbb{Z}})$ containing $-I$
with full determinant, let $X_G/\mathbb{Q}$ denote the modular curve that
loosely parametrizes elliptic curves whose Galois representation, which arises
from the Galois action on its torsion points, has image contained in $G$. Up to
conjugacy, we determine a complete list of the $248$ such groups $G$ of prime
power level for which $X_G(\mathbb{Q})$ is infinite. For each $G$, we also
construct explicit maps from each $X_G$ to the $j$-line. This list consists of
$220$ modular curves of genus $0$ and $28$ modular curves of genus $1$. For
each prime $\ell$, these results provide an explicit classification of the
possible images of the $\ell$-adic Galois representations arising from elliptic
curves over $\mathbb{Q}$ that is complete except for a finite set of
exceptional $j$-invariants.


title:
Some new results on sample path optimality in ergodic control of
  diffusions

abstract:
  We present some new results on sample path optimality for the ergodic control
problem of a class of non-degenerate diffusions controlled through the drift.
The hypothesis most often used in the literature to ensure the existence of an
a.s. sample path optimal stationary Markov control requires finite second
moments of the first hitting times $\tau$ of bounded domains over all
admissible controls. We show that this can be considerably weakened: ${\mathrm
E}[\tau^2]$ may be replaced with ${\mathrm E}[\tau\ln^+(\tau)]$, thus reducing
the required rate of convergence of averages from polynomial to logarithmic. A
Foster-Lyapunov condition which guarantees this is also exhibited. Moreover, we
study a large class of models that are neither uniformly stable, nor have a
near-monotone running cost, and we exhibit sufficient conditions for the
existence of a sample path optimal stationary Markov control.


title: Torsional optomechanics of a levitated nonspherical nanoparticle

abstract:
  An optically levitated nanoparticle in vacuum is a paradigm optomechanical
system for sensing and studying macroscopic quantum mechanics. While its
center-of-mass motion has been investigated intensively, its torsional
vibration has only been studied theoretically in limited cases. Here we report
the first experimental observation of the torsional vibration of an optically
levitated nonspherical nanoparticle in vacuum. We achieve this by utilizing the
coupling between the spin angular momentum of photons and the torsional
vibration of a nonspherical nanoparticle whose polarizability is a tensor. The
torsional vibration frequency can be one order of magnitude higher than its
center-of-mass motion frequency, which is promising for ground state cooling.
We propose a simple yet novel scheme to achieve ground state cooling of its
torsional vibration with a linearly-polarized Gaussian cavity mode. A levitated
nonspherical nanoparticle in vacuum will also be an ultrasensitive nanoscale
torsion balance with a torque detection sensitivity on the order of $10^{-29}
~\mathrm{N}\cdot \mathrm{m}/\sqrt{\mathrm{ Hz}}$ under realistic conditions.


title:
First survey of Wolf-Rayet star populations over the full extension of
  nearby galaxies observed with CALIFA

abstract:
  The search of extragalactic regions with conspicuous presence of Wolf-Rayet
(WR) stars outside the Local Group is challenging task due to the difficulties
in detecting their faint spectral features. In this exploratory work, we
develop a methodology to perform an automated search of WR signatures through a
pixel-by-pixel analysis of integral field spectroscopy (IFS) data belonging to
the Calar Alto Legacy Integral Field Area survey, CALIFA. This technique
allowed us to build the first catalogue of Wolf-Rayet rich regions with
spatially-resolved information, allowing to study the properties of these
complexes in a 2D context. The detection technique is based on the
identification of the blue WR bump (around He II 4686 {\AA}, mainly associated
to nitrogen-rich WR stars, WN) and the red WR bump (around C IV 5808 {\AA} and
associated to carbon-rich WR stars, WC) using a pixel-by-pixel analysis. We
identified 44 WR-rich regions with blue bumps distributed in 25 galaxies of a
total of 558. The red WR bump was identified only in 5 of those regions. We
found that the majority of the galaxies hosting WR populations in our sample
are involved in some kind of interaction process. Half of the host galaxies
share some properties with gamma-ray burst (GRB) hosts where WR stars, as
potential candidates to being the progenitors of GRBs, are found. We also
compared the WR properties derived from the CALIFA data with stellar population
synthesis models, and confirm that simple star models are generally not able to
reproduce the observations. We conclude that other effects, such as the binary
star channel (which could extend the WR phase up to 10 Myr), fast rotation or
other physical processes that causes the loss of observed Lyman continuum
photons, are very likely affecting the derived WR properties, and hence should
be considered when modelling the evolution of massive stars.


title:
Fast Approximation of Small p-values in Permutation Tests by
  Partitioning the Permutations

abstract:
  Researchers in genetics and other life sciences commonly use permutation
tests to evaluate differences between groups. Permutation tests have desirable
properties, including exactness if data are exchangeable, and are applicable
even when the distribution of the test statistic is analytically intractable.
However, permutation tests can be computationally intensive. We propose both an
asymptotic approximation and a resampling algorithm for quickly estimating
small permutation p-values (e.g. $<10^{-6}$) for the difference and ratio of
means in two-sample tests. Our methods are based on the distribution of test
statistics within and across partitions of the permutations, which we define.
In this article, we present our methods and demonstrate their use through
simulations and an application to cancer genomic data. Through simulations, we
find that our resampling algorithm is more computationally efficient than
another leading alternative, particularly for extremely small p-values (e.g.
$<10^{-30}$). Through application to cancer genomic data, we find that our
methods can successfully identify up- and down-regulated genes. While we focus
on the difference and ratio of means, we speculate that our approaches may work
in other settings.


title: Rho resonance parameters from lattice QCD

abstract:
  We perform a high-precision calculation of the phase shifts for $\pi$-$\pi$
scattering in the I = 1, J = 1 channel in the elastic region using elongated
lattices with two mass-degenerate quark favors ($N_f = 2$). We extract the
$\rho$ resonance parameters using a Breit-Wigner fit at two different quark
masses, corresponding to $m_{\pi} = 226$MeV and $m_{\pi} = 315$MeV, and perform
an extrapolation to the physical point. The extrapolation is based on a
unitarized chiral perturbation theory model that describes well the
phase-shifts around the resonance for both quark masses. We find that the
extrapolated value, $m_{\rho} = 720(1)(15)$MeV, is significantly lower that the
physical rho mass and we argue that this shift could be due to the absence of
the strange quark in our calculation.


title:
Asymmetries in SN 2014J Near Maximum Light Revealed Through
  Spectropolarimetry

abstract:
  We present spectropolarimetric observations of the nearby Type Ia SN 2014J in
M82 over six epochs: +0, +7, +23, +51, +77, +109, and +111 days with respect to
B-band maximum. The strong continuum polarization, which is constant with time,
shows a wavelength dependence unlike that produced by linear dichroism in Milky
Way dust. The observed polarization may be due entirely to interstellar dust or
include a circumstellar scattering component. We find that the polarization
angle aligns with the magnetic field of the host galaxy, arguing for an
interstellar origin. Additionally, we confirm a peak in polarization at short
wavelengths that would imply $R_V < 2 $ along the light of sight, in agreement
with earlier polarization measurements. For illustrative purposes, we include a
two component fit to the continuum polarization of our +51 day epoch that
combines a circumstellar scattering component with interstellar dust where
scattering can account for over half of the polarization at $4000$ \AA. Upon
removal of the interstellar polarization signal, SN 2014J exhibits very low
levels of continuum polarization. Asymmetries in the distribution of elements
within the ejecta are visible through moderate levels of time-variable
polarization in accordance with the Si II 6355 \AA absorption line. At maximum
light, the line polarization reaches $\sim0.6$% and decreases to $\sim0.4\%$
one week later. This feature also forms a loop on the $q_{RSP}$-$u_{RSP}$ plane
illustrating that the ion does not have an axisymmetric distribution. The
observed polarization properties suggest the explosion geometry of SN 2014J is
generally spheroidal with a clumpy distribution of silicon.


title: On Hopf Algebras over quantum subgroups

abstract:
  Using the standard filtration associated with a generalized lifting method,
we determine all finite-dimensional Hopf algebras over an algebraically closed
field of characteristic zero whose coradical generates a Hopf subalgebra
isomorphic to the smallest non-pointed non-cosemisimple Hopf algebra
${\mathcal{K}}$ and the corresponding infinitesimal module is an indecomposable
object in ${}^{{\mathcal{K}}}_{{\mathcal{K}}}\mathcal{YD}$ (we assume that the
diagrams are Nichols algebras). As a byproduct, we obtain new Nichols algebras
of dimension 8 and new Hopf algebras of dimension 64.


title: Classical limit of Rabi nutations in spins of ferromagnets

abstract:
  Rabi oscillations describe the interaction of a two-level system with a
rotating electromagnetic field. As such, they serve as the principle method for
manipulating quantum bits. By using a combination of femtosecond laser pulses
and microwave excitations, we have observed the classical form of Rabi
nutations in a ferromagnetic system whose equations of motion mirror the case
of a precessing quantum two-level system. Key to our experiments is the
selection of a subset of spins that is in resonance with the microwave
excitation and whose coherence time is thereby extended. Taking advantage of
Gilbert damping, the relaxation times are further increased such that
mode-locking takes place. The observation of such Rabi nutations is the first
step towards potential applications based on phase-coherent spin manipulation
in ferromagnets.


title: Toda Theory From Six Dimensions

abstract:
  We describe a compactification of the six-dimensional (2,0) theory on a
four-sphere which gives rise to a two-dimensional Toda theory at long
distances. This construction realizes chiral Toda fields as edge modes trapped
near the poles of the sphere. We relate our setup to compactifications of the
(2,0) theory on the five and six-sphere. In this way, we explain a connection
between half-BPS operators of the (2,0) theory and two-dimensional W-algebras,
and derive an equality between their conformal anomalies. As we explain, all
such relationships between the six-dimensional (2,0) theory and Toda field
theory can be interpreted as statements about the edge modes of complex
Chern-Simons on various three-manifolds with boundary.


title:
An adaptive $O(\log n)$-optimal policy for the online selection of a
  monotone subsequence from a random sample

abstract:
  Given a sequence of $n$ independent random variables with common continuous
distribution, we propose a simple adaptive online policy that selects a
monotone increasing subsequence. We show that the expected number of monotone
increasing selections made by such a policy is within $O(\log n)$ of optimal.
Our construction provides a direct and natural way for proving the $O(\log
n)$-optimality gap. An earlier proof of the same result made crucial use of a
key inequality of Bruss and Delbaen (2001) and of de-Poissonization.


title: Yarrp'ing the Internet: Randomized High-Speed Active Topology Discovery

abstract:
  Obtaining a "snapshot" of the Internet topology remains an elusive task.
Existing active topology discovery techniques and systems require significant
probing time -- time during which the underlying network may experience
transient dynamics. This work considers how active probing can gather the
Internet topology in minutes rather than days. Conventional approaches to
active topology mapping face two primary speed and scale impediments: i)
per-trace state maintenance; and ii) a low-degree of parallelism. Based on this
observation, we develop Yarrp (Yelling at Random Routers Progressively), a new
traceroute technique designed for high-rate, Internet-scale probing. Yarrp is
stateless, reconstituting all necessary information from ICMP replies as they
arrive asynchronously. To avoid overloading routers or links with probe
traffic, Yarrp randomly permutes an input IP x TTL space. We run Yarrp at
100Kpps, a rate at which the paths to all /24's on the IPv4 Internet can be
mapped in approximately one hour from a single vantage point. We compare Yarrp
against existing systems, and present examples of topological dynamics exposed
via the high sampling rates Yarrp enables.


title: The nonnegative rank of a matrix: Hard problems, easy solutions

abstract:
  Using elementary linear algebra, we develop a technique that leads to
solutions of two widely known problems on nonnegative matrices. First, we give
a short proof of the result by Vavasis stating that the nonnegative rank of a
matrix is NP-hard to compute. This proof is essentially contained in the paper
by Jiang and Ravikumar, who discussed this topic in different terms fifteen
years before the work of Vavasis. Secondly, we present a solution of the
problem of Cohen and Rothblum on rational nonnegative factorizations, which was
posed in 1993 and remained open.


title: Hermitian ranks of compact complex manifolds

abstract:
  We investigate degenerate special-Hermitian metrics on compact complex
manifolds, in particular, degenerate K\"ahler and locally conformally K\"ahler
metrics on special classes of non-K\"ahler manifolds.


title:
Which Learning Algorithms Can Generalize Identity-Based Rules to Novel
  Inputs?

abstract:
  We propose a novel framework for the analysis of learning algorithms that
allows us to say when such algorithms can and cannot generalize certain
patterns from training data to test data. In particular we focus on situations
where the rule that must be learned concerns two components of a stimulus being
identical. We call such a basis for discrimination an identity-based rule.
Identity-based rules have proven to be difficult or impossible for certain
types of learning algorithms to acquire from limited datasets. This is in
contrast to human behaviour on similar tasks. Here we provide a framework for
rigorously establishing which learning algorithms will fail at generalizing
identity-based rules to novel stimuli. We use this framework to show that such
algorithms are unable to generalize identity-based rules to novel inputs unless
trained on virtually all possible inputs. We demonstrate these results
computationally with a multilayer feedforward neural network.


title:
Black holes in nonlinear electrodynamics: quasi-normal spectra and
  parity splitting

abstract:
  We discuss the quasi-normal oscillations of black holes which are sourced by
a nonlinear electrodynamic field. While previous studies have focused on the
computation of quasi-normal frequencies for the wave or higher spin equation on
a fixed background geometry described by such black holes, here we compute for
the first time the quasi-normal frequencies for the coupled
electromagnetic-gravitational linear perturbations.
  To this purpose, we consider a parametrized family of Lagrangians for the
electromagnetic field which contains the Maxwell Lagrangian as a special case.
In the Maxwell case, the unique spherically symmetric black hole solutions are
described by the Reissner-Nordstr\"om family and in this case it is well-known
that the quasi-normal spectra in the even- and odd-parity sectors are identical
to each other. However, when moving away from the Maxwell case, we obtain
deformed Reissner-Nordstr\"om black holes, and we show that in this case there
is a parity splitting in the quasi-normal mode spectra. A partial explanation
for this phenomena is provided by considering the eikonal (high-frequency)
limit.


title: Price of Competition and Dueling Games

abstract:
  We study competition in a general framework introduced by Immorlica et al.
and answer their main open question. Immorlica et al. considered classic
optimization problems in terms of competition and introduced a general class of
games called dueling games. They model this competition as a zero-sum game,
where two players are competing for a user's satisfaction. In their main and
most natural game, the ranking duel, a user requests a webpage by submitting a
query and players output an ordering over all possible webpages based on the
submitted query. The user tends to choose the ordering which displays her
requested webpage in a higher rank. The goal of both players is to maximize the
probability that her ordering beats that of her opponent and gets the user's
attention. Immorlica et al. show this game directs both players to provide
suboptimal search results. However, they leave the following as their main open
question: "does competition between algorithms improve or degrade expected
performance?" In this paper, we resolve this question for the ranking duel and
a more general class of dueling games.
  More precisely, we study the quality of orderings in a competition between
two players. This game is a zero-sum game, and thus any Nash equilibrium of the
game can be described by minimax strategies. Let the value of the user for an
ordering be a function of the position of her requested item in the
corresponding ordering, and the social welfare for an ordering be the expected
value of the corresponding ordering for the user. We propose the price of
competition which is the ratio of the social welfare for the worst minimax
strategy to the social welfare obtained by a social planner. We use this
criterion for analyzing the quality of orderings in the ranking duel. We prove
the quality of minimax results is surprisingly close to that of the optimum
solution.


title: A Wavelet Based Approach to Solar--Terrestrial Coupling

abstract:
  Transient and recurrent solar activity drive geomagnetic disturbances; these
are quantified (amongst others) by DST, AE indices time-series. Transient
disturbances are related to the Interplanetary Coronal Mass Ejections (ICMEs)
while recurrent disturbances are related to corotating interaction regions
(CIR). We study the relationship of the geomagnetic disturbances to the solar
wind drivers within solar Cycle 23 where the drivers are represented by ICMEs
and CIRs occurrence rate and compared to the DST and AE as follows: terms with
common periodicity in both the geomagnetic disturbances and the solar drivers
are, firstly, detected using continuous wavelet transform (CWT). Then, common
power and phase coherence of these periodic terms are calculated from the
cross-wavelet spectra (XWT) and waveletcoherence (WTC) respectively. In
time-scales of about 27 days our results indicate an anti-correlation of the
effects of ICMEs and CIRs on the geomagnetic disturbances. The former modulates
the DST and AE time series during the cycle maximum the latter during periods
of reduced solar activity. The phase relationship of these modulation is highly
non-linear. Only the annual frequency component of the ICMEs is phase-locked
with DST and AE. In time-scales of about 1.3-1.7 years the CIR seem to be the
dominant driver for both geomagnetic indices throughout the whole solar cycle
23.


title:
A Gaussian Mixture MRF for Model-Based Iterative Reconstruction with
  Applications to Low-Dose X-ray CT

abstract:
  Markov random fields (MRFs) have been widely used as prior models in various
inverse problems such as tomographic reconstruction. While MRFs provide a
simple and often effective way to model the spatial dependencies in images,
they suffer from the fact that parameter estimation is difficult. In practice,
this means that MRFs typically have very simple structure that cannot
completely capture the subtle characteristics of complex images.
  In this paper, we present a novel Gaussian mixture Markov random field model
(GM-MRF) that can be used as a very expressive prior model for inverse problems
such as denoising and reconstruction. The GM-MRF forms a global image model by
merging together individual Gaussian-mixture models (GMMs) for image patches.
In addition, we present a novel analytical framework for computing MAP
estimates using the GM-MRF prior model through the construction of surrogate
functions that result in a sequence of quadratic optimizations. We also
introduce a simple but effective method to adjust the GM-MRF so as to control
the sharpness in low- and high-contrast regions of the reconstruction
separately. We demonstrate the value of the model with experiments including
image denoising and low-dose CT reconstruction.


title: Ordered set partition statistics and the Delta Conjecture

abstract:
  The Delta Conjecture of Haglund, Remmel, and Wilson is a recent
generalization of the Shuffle Conjecture in the field of diagonal harmonics. In
this paper we give evidence for the Delta Conjecture by proving a pair of
conjectures of Wilson and Haglund-Remmel-Wilson which give equidistribution
results for statistics related to inversion count and major index on objects
related to ordered set partitions. Our results generalize the famous result of
MacMahon that major index and inversion number share the same distribution on
permutations.


title:
Finding Planted Subgraphs with Few Eigenvalues using the Schur-Horn
  Relaxation

abstract:
  Extracting structured subgraphs inside large graphs - often known as the
planted subgraph problem - is a fundamental question that arises in a range of
application domains. This problem is NP-hard in general, and as a result,
significant efforts have been directed towards the development of tractable
procedures that succeed on specific families of problem instances. We propose a
new computationally efficient convex relaxation for solving the planted
subgraph problem; our approach is based on tractable semidefinite descriptions
of majorization inequalities on the spectrum of a symmetric matrix. This
procedure is effective at finding planted subgraphs that consist of few
distinct eigenvalues, and it generalizes previous convex relaxation techniques
for finding planted cliques. Our analysis relies prominently on the notion of
spectrally comonotone matrices, which are pairs of symmetric matrices that can
be transformed to diagonal matrices with sorted diagonal entries upon
conjugation by the same orthogonal matrix.


title:
Synchronization of heterogeneous oscillators under network
  modifications: Perturbation and optimization of the synchrony alignment
  function

abstract:
  Synchronization is central to many complex systems in engineering physics
(e.g., the power-grid, Josephson junction circuits, and electro-chemical
oscillators) and biology (e.g., neuronal, circadian, and cardiac rhythms).
Despite these widespread applications---for which proper functionality depends
sensitively on the extent of synchronization---there remains a lack of
understanding for how systems evolve and adapt to enhance or inhibit
synchronization. We study how network modifications affect the synchronization
properties of network-coupled dynamical systems that have heterogeneous node
dynamics (e.g., phase oscillators with non-identical frequencies), which is
often the case for real-world systems. Our approach relies on a synchrony
alignment function (SAF) that quantifies the interplay between heterogeneity of
the network and of the oscillators and provides an objective measure for a
system's ability to synchronize. We conduct a spectral perturbation analysis of
the SAF for structural network modifications including the addition and removal
of edges, which subsequently ranks the edges according to their importance to
synchronization. Based on this analysis, we develop gradient-descent algorithms
to efficiently solve optimization problems that aim to maximize phase
synchronization via network modifications. We support these and other results
with numerical experiments.


title: Eigenvalue dynamics in the presence of non-uniform gain and loss

abstract:
  Loss-induced transmission in waveguides, and reversed pump dependence in
lasers, are two prominent examples of counter-intuitive effects in
non-Hermitian systems with patterned gain and loss. By analyzing the eigenvalue
dynamics of complex symmetric matrices when a system parameter is varied, we
introduce a general set of theoretical conditions for these two effects. We
show that these effects arise in any irreducible system where the gain or loss
is added to a subset of the elements of the system, without the need for
parity-time symmetry or for the system to be near an exceptional point. These
results are confirmed using full-wave numerical simulations. The conditions
presented here vastly expand the design space for observing these effects. We
also show that a similarly broad class of systems exhibit a loss-induced
narrowing of the density of states.


title:
Liouville first-passage percolation: subsequential scaling limits at
  high temperature

abstract:
  Let $\{Y_{\mathfrak{B}}(x)\,:\,x\in\mathfrak{B}\}$ be a discrete Gaussian
free field in a two-dimensional box $\mathfrak{B}$ of side length $S$ with
Dirichlet boundary conditions. We study Liouville first-passage percolation:
the shortest-path metric in which each vertex $x$ is given a weight of
$e^{\gamma Y_{\mathfrak{B}}(x)}$ for some $\gamma>0$. We show that for
sufficiently small but fixed $\gamma>0$, for any sequence of scales $\{S_{k}\}$
there exists a subsequence along which the appropriately scaled and
interpolated Liouville FPP metric converges in the Gromov--Hausdorff sense to a
random metric on the unit square in $\mathbf{R}^{2}$. In addition, all possible
(conjecturally unique) scaling limits are homeomorphic by
bi-H\"older-continuous homeomorphisms to the unit square with the Euclidean
metric.


title: Global properties of the symmetrized $s$-divergence

abstract:
  In this paper we give a study of the symmetrized divergences
$U_s(p,q)=K_s(p||q)+K_s(q||p)$ and $V_s(p,q)=K_s(p||q)K_s(q||p)$, where $K_s$
is the relative divergence of type $s, s\in\mathbb R$. Some basic properties as
symmetry, monotonicity and log-convexity are established. An important result
from the Convexity Theory is also proved.


title: A Corpus-based Toy Model for DisCoCat

abstract:
  The categorical compositional distributional (DisCoCat) model of meaning
rigorously connects distributional semantics and pregroup grammars, and has
found a variety of applications in computational linguistics. From a more
abstract standpoint, the DisCoCat paradigm predicates the construction of a
mapping from syntax to categorical semantics. In this work we present a
concrete construction of one such mapping, from a toy model of syntax for
corpora annotated with constituent structure trees, to categorical semantics
taking place in a category of free R-semimodules over an involutive commutative
semiring R.


title: On a convexity property

abstract:
  In this article we proved an interesting property of the class of continuous
convex functions. This leads to the form of pre-Hermite-Hadamard inequality
which in turn admits a generalization of the famous Hermite-Hadamard
inequality. Some further discussion is also given.


title: A spin pump characterized by entanglement Chern numbers

abstract:
  We study a spin pump on a two-leg ladder chain of the Rice--Mele model. To
characterize the spin pump, we propose the Chern number for the many-body
ground state of the entanglement Hamiltonian, which is referred to as the
entanglement Chern number. We show that this model has two phases distinguished
by the entanglement Chern numbers. These two phases can be experimentally
verified in cold atoms.


title:
Coarsening and thermalisation properties of a quenched ferromagnetic
  spin-1 condensate

abstract:
  We examine the dynamics of a quasi-two-dimensional spin-1 condensate in which
the quadratic Zeeman energy q is suddenly quenched to a value where the system
has a ferromagnetic ground state. There are two distinct types of ferromagnetic
phases, i.e. a range of q values where the magnetization prefers to be in the
direction of the external field (easy-axis), and a range of q values where it
prefers to be transverse to the field (easy-plane). We study the quench
dynamics for a variety of q values and show that there is a single dynamical
critical exponent to characterize the scale invariant domain growth for each
ferromagnetic phase. For both quenches we give simple analytic models that
capture the essential scale invariant dynamics, and correctly predict the
exponents. Because the order parameter for each phase is different, the natures
of the domains and the relevant topological defects in each type of coarsening
is also different. To explore these differences we characterize the fractal
dimension of the domain walls, and the relationship of polar-core spin vortices
to the domains in the easy-plane phase. Finally, we consider how the energy
liberated from the quench thermalizes in the easy-axis quench. We show that
local equilibrium is established in the spin waves on moderate time scales, but
continues to evolve as the domains anneal.


title: Variance of Resistance of "Line-Circle-Line" Graphs

abstract:
  We find the order of the variance of the growth model $X_{n+1} = X_n+X'_n +
f(X''_n,X'''_n)$, where all the variables $X_n,X'_n,X''_n$ and $X'''_n$ are
i.i.d., $X_0$ takes the values $1$ and $2$ with equal probability and $f$ is
positive, monotone non-decreasing and satisfies conditions which, roughly
speaking, pertain to its first and second order partial derivatives. For an
appropriate choice of $f$ we obtain that the variance of the effective
resistance between the endpoints of the "line-circle-line" graph $G_n$ is of
order $\bigl(2 + \frac{1}{8} + {\scriptscriptstyle\mathcal{O}} (1)\bigr)^n$.


title:
On the exponential decay of the characteristic function of the quicksort
  distribution

abstract:
  We prove that the characteristic function of the quicksort distribution is
exponentially decreasing at infinity. As a consequence it follows that the
density of the quicksort distribution can be analytically extended to the
vicinity of the real line.


title: Bounding Stability Constants for Affinely Parameter-Dependent Operators

abstract:
  In this article we introduce new possibilities of bounding the stability
constants that play a vital role in the reduced basis method. By bounding
stability constants over a neighborhood we make it possible to guarantee
stability at more than a finite number of points and to do that in the offline
stage. We additionally show that Lyapunov stability of dynamical systems can be
handled in the same framework.


title: A Hull with No Nontrivial Gleason Parts

abstract:
  The existence of a nontrivial polynomially convex hull with every point a
one-point Gleason part and with no nonzero bounded point derivations is
established. This strengthens the \hbox{celebrated} result of Stolzenberg that
there exists a nontrivial polynomially convex hull that contains no analytic
discs. A doubly generated counterexample to the peak point conjecture is also
presented.


title:
Redundancy Elimination Might Be Overrated: A Quantitative Study on
  Real-World Wireless Traffic

abstract:
  With significant increases in mobile device traffic slated for the
foreseeable future, numerous technologies must be embraced to satisfy such
demand. Notably, one of the more intriguing approaches has been blending
on-device caching and device-to-device (D2D) communications. While various past
research has pointed to potentially significant gains (30%+) via redundancy
elimination (RE), some skepticism has emerged to whether or not such gains are
truly harnessable in practice. The premise of this paper is to explore whether
or not significant potential for redundancy elimination exists and whether the
rise of video and encryption might blunt said efforts. Critically, we find that
absent significant synchronized interests of mobile users, the actual
redundancy falls well short of the promising values from the literature. In our
paper, we investigate the roots for said shortcomings by exploring RE savings
with regards to cache hit characteristics and to what extent client and domain
diversity contribute to the realized redundancy savings.


title: Particle Acceleration in Solar Flares and Associated CME Shocks

abstract:
  Observations relating the characteristics of electrons seen near Earth (SEPs)
and those producing flare radiation show that in certain (prompt) events the
origin of both population appears to be the flare site, which show strong
correlation between the number and spectral index of SEP and hard X-ray
radiating electrons, but in others(delayed), which are associated with fast
CMEs, this relation is complex and SEPs tend to be harder. Prompt event
spectral relation disagrees with that expected in thick or thin target models.
We show that using a a more accurate treatment of the transport of the
accelerated electrons to the footpoints and to the Earth can account for this
discrepancy. Our results are consistent with those found by Chen and Petrosian
(2013) for two flares using non-parametric inversion methods, according to
which we have weak diffusion conditions, and trapping mediated by magnetic
field convergence. The weaker correlations and harder spectra of delayed events
can come about by re-acceleration of electrons in the CME shock environment. We
describe under what conditions such a hardening can be achieved. Using this
(acceleration at the flare and re-acceleration in the CME) scenario we show
that we can describe the similar dichotomy that exists between the so called
impulsive, highly enriched ($^3$He and heavy ions) and softer SEP events, and
stronger more gradual SEP events with near normal ionic abundances and harder
spectra. These methods can be used to distinguish the acceleration mechanisms
and to constrain their characteristics.


title:
LIGO gravitational wave detection, primordial black holes and the
  near-IR cosmic infrared background anisotropies

abstract:
  LIGO's discovery of a gravitational wave from two merging black holes (BHs)
of similar masses rekindled suggestions that primordial BHs (PBHs) make up the
dark matter (DM). If so, PBHs would add a Poissonian isocurvature density
fluctuation component to the inflation-produced adiabatic density fluctuations.
For LIGO's BH parameters, this extra component would dominate the small-scale
power responsible for collapse of early DM halos at z>10, where first luminous
sources formed. We quantify the resultant increase in high-z abundances of
collapsed halos that are suitable for producing the first generation of stars
and luminous sources. The significantly increased abundance of the early halos
would naturally explain the observed source-subtracted near-IR cosmic infrared
background (CIB) fluctuations, which cannot be accounted for by known galaxy
populations. For LIGO's BH parameters this increase is such that the observed
CIB fluctuation levels at 2 to 5 micron can be produced if only a tiny fraction
of baryons in the collapsed DM halos forms luminous sources. Gas accretion onto
these PBHs in collapsed halos, where first stars should also form, would
straightforwardly account for the observed high coherence between the CIB and
unresolved cosmic X-ray background in soft X-rays. We discuss modifications
possibly required in the processes of first star formation if LIGO-type BHs
indeed make up the bulk or all of DM. The arguments are valid only if the PBHs
make up all, or at least most, of DM, but at the same time the mechanism
appears inevitable if DM is made of PBHs.


title:
Vortical fluid and $\Lambda$ spin correlations in high-energy heavy-ion
  collisions

abstract:
  Fermions become polarized in a vortical fluid due to spin-vorticity coupling.
The spin polarization density is proportional to the local fluid vorticity at
the next-to-leading order of a gradient expansion in a quantum kinetic theory.
Spin correlations of two $\Lambda$-hyperons can therefore reveal the vortical
structure of the dense matter in high-energy heavy-ion collisions. We employ a
(3+1)D viscous hydrodynamic model with event-by-event fluctuating initial
conditions from A MultiPhase Transport (AMPT) model to calculate the vorticity
distributions and $\Lambda$ spin correlations. The azimuthal correlation of the
transverse spin is shown to have a cosine form plus an offset due to a circular
structure of the transverse vorticity around the beam direction and global spin
polarization. The longitudinal spin correlation shows a structure of
vortex-pairing in the transverse plane due to the convective flow of hot spots
in the radial direction. The dependence on colliding energy, rapidity,
centrality and sensitivity to the shear viscosity are also investigated.


title:
FlowIntent: Detecting Privacy Leakage from User Intention to Network
  Traffic Mapping

abstract:
  The exponential growth of mobile devices has raised concerns about sensitive
data leakage. In this paper, we make the first attempt to identify suspicious
location-related HTTP transmission flows from the user's perspective, by
answering the question: Is the transmission user-intended? In contrast to
previous network-level detection schemes that mainly rely on a given set of
suspicious hostnames, our approach can better adapt to the fast growth of app
market and the constantly evolving leakage patterns. On the other hand,
compared to existing system-level detection schemes built upon program taint
analysis, where all sensitive transmissions as treated as illegal, our approach
better meets the user needs and is easier to deploy. In particular, our
proof-of-concept implementation (FlowIntent) captures sensitive transmissions
missed by TaintDroid, the state-of-the-art dynamic taint analysis system on
Android platforms. Evaluation using 1002 location sharing instances collected
from more than 20,000 apps shows that our approach achieves about 91% accuracy
in detecting illegitimate location transmissions.


title: On Truthful Mechanisms for Maximin Share Allocations

abstract:
  We study a fair division problem with indivisible items, namely the
computation of maximin share allocations. Given a set of $n$ players, the
maximin share of a single player is the best she can guarantee to herself, if
she would partition the items in any way she prefers, into $n$ bundles, and
then receive her least desirable bundle. The objective then is to find an
allocation, so that each player is guaranteed her maximin share. Previous works
have studied this problem mostly algorithmically, providing constant factor
approximation algorithms. In this work we embark on a mechanism design approach
and investigate the existence of truthful mechanisms. We propose three models
regarding the information that the mechanism attempts to elicit from the
players, based on the cardinal and ordinal representation of preferences. We
establish positive and negative (impossibility) results for each model and
highlight the limitations imposed by truthfulness on the approximability of the
problem. Finally, we pay particular attention to the case of two players, which
already leads to challenging questions.