title:
The connection between stellar activity cycles and magnetic field
  topology

abstract:
  Zeeman Doppler imaging has successfully mapped the large-scale magnetic
fields of stars over a large range of spectral types, rotation periods and
ages. When observed over multiple epochs, some stars show polarity reversals in
their global magnetic fields. On the Sun, polarity reversals are a feature of
its activity cycle. In this paper, we examine the magnetic properties of stars
with existing chromospherically determined cycle periods. Previous authors have
suggested that cycle periods lie on multiple branches, either in the cycle
period-Rossby number plane or the cycle period-rotation period plane. We find
some evidence that stars along the active branch show significant average
toroidal fields that exhibit large temporal variations while stars exclusively
on the inactive branch remain dominantly poloidal throughout their entire
cycle. This lends credence to the idea that different shear layers are in
operation along each branch. There is also evidence that the short magnetic
polarity switches observed on some stars are characteristic of the inactive
branch while the longer chromospherically determined periods are characteristic
of the active branch. This may explain the discrepancy between the magnetic and
chromospheric cycle periods found on some stars. These results represent a
first attempt at linking global magnetic field properties obtained form ZDI and
activity cycles.


title:
Exploring the Entire Regularization Path for the Asymmetric Cost Linear
  Support Vector Machine

abstract:
  We propose an algorithm for exploring the entire regularization path of
asymmetric-cost linear support vector machines. Empirical evidence suggests the
predictive power of support vector machines depends on the regularization
parameters of the training algorithms. The algorithms exploring the entire
regularization paths have been proposed for single-cost support vector machines
thereby providing the complete knowledge on the behavior of the trained model
over the hyperparameter space. Considering the problem in two-dimensional
hyperparameter space though enables our algorithm to maintain greater
flexibility in dealing with special cases and sheds light on problems
encountered by algorithms building the paths in one-dimensional spaces. We
demonstrate two-dimensional regularization paths for linear support vector
machines that we train on synthetic and real data.


title: MeV electron acceleration at 1 kHz with <10mJ laser pulses

abstract:
  We demonstrate laser driven acceleration of electrons to MeV-scale energies
at 1kHz repetition rate using <10mJ pulses focused on near-critical density He
and H2 gas jets. Using the H2 gas jet, electron acceleration to ~0.5MeV in
~10fC bunches was observed with laser pulse energy as low as 1.3mJ. Increasing
the pulse energy to 10mJ, we measure ~1pC charge bunches with >1MeV energy for
both He and H2 gas jets.


title:
Extensions of almost faithful prime ideals in virtually nilpotent
  mod-$p$ Iwasawa algebras

abstract:
  Let $G$ be a nilpotent-by-finite compact $p$-adic analytic group for some
$p>2$, and $H = \mathbf{FN}_p(G)$ its finite-by-(nilpotent $p$-valuable)
radical. Fix a finite field $k$ of characteristic $p$, and write $kG$ for the
completed group ring of $G$ over $k$. We show that almost faithful $G$-stable
prime ideals $P$ of $kH$ extend to prime ideals $PkG$ of $kG$.


title:
Helium at white dwarf photospheric conditions: preliminary laboratory
  results

abstract:
  We present preliminary results of an experimental study exploring helium at
photospheric conditions of white dwarf stars. These data were collected at
Sandia National Laboratories' Z-machine, the largest x-ray source on earth. Our
helium results could have many applications ranging from validating current DB
white dwarf model atmospheres to providing accurate He pressure shifts at
varying temperatures and densities. In a much broader context, these helium
data can be used to guide theoretical developments in new continuum-lowering
models for two-electron atoms. We also discuss future applications of our
updated experimental design, which enables us to sample a greater range of
densities, temperatures, and gas compositions.


title: Helicoidal Graphene Nanoribbons: Chiraltronics

abstract:
  We present a calculation of the effective geometry-induced quantum potential
for the carriers in graphene shaped as a helicoidal nanoribbon. In this
geometry the twist of the nanoribbon plays the role of an effective transverse
electric field in graphene and this is reminiscent of the Hall effect. However,
this effective electric field has a different sign for the two iso-spin states
and translates into a mechanism to separate the two chiral species on the
opposing rims of the nanoribbon. Iso-spin transitions are expected with the
emission or absorption of microwave radiation which could be adjusted to be in
the THz region.


title: High Efficiency Raman Memory by Suppressing Radiation Trapping

abstract:
  Raman interactions in alkali vapours are used in applications such as atomic
clocks, optical signal processing, generation of squeezed light and Raman
quantum memories for temporal multiplexing. To achieve a strong interaction the
alkali ensemble needs both a large optical depth and a high level of
spin-polarisation. We implement a technique known as quenching using a
molecular buffer gas which allows near-perfect spin-polarisation of over
$99.5\%$ in caesium vapour at high optical depths of up to $\sim 2 \times
10^5$; a factor of 4 higher than can be achieved without quenching. We use this
system to explore efficient light storage with high gain in a GHz bandwidth
Raman memory.


title: A fractional generalization of the classical lattice dynamics approach

abstract:
  We develop physically admissible lattice models in the harmonic approximation
which define by Hamilton's variational principle fractional Laplacian matrices
of the forms of power law matrix functions on the n -dimensional periodic and
infinite lattice in n=1,2,3,..n=1,2,3,.. dimensions. The present model which is
based on Hamilton's variational principle is confined to conservative
non-dissipative isolated systems. The present approach yields the discrete
analogue of the continuous space fractional Laplacian kernel. As continuous
fractional calculus generalizes differential operators such as the Laplacian to
non-integer powers of Laplacian operators, the fractional lattice approach
developed in this paper generalized difference operators such as second
difference operators to their fractional (non-integer) powers. Whereas
differential operators and difference operators constitute local operations,
their fractional generalizations introduce nonlocal long-range features. This
is true for discrete and continuous fractional operators. The nonlocality
property of the lattice fractional Laplacian matrix allows to describe numerous
anomalous transport phenomena such as anomalous fractional diffusion and random
walks on lattices. We deduce explicit results for the fractional Laplacian
matrix in 1D for finite periodic and infinite linear chains and their Riesz
fractional derivative continuum limit kernels.


title: Dividing goods and bads under additive utilities

abstract:
  When utilities are additive, we uncovered in our previous paper (Bogomolnaia
et al. "Dividing Goods or Bads under Additive Utilities") many similarities but
also surprising differences in the behavior of the familiar Competitive rule
(with equal incomes), when we divide (private) goods or bads. The rule picks in
both cases the critical points of the product of utilities (or disutilities) on
the efficiency frontier, but there is only one such point if we share goods,
while there can be exponentially many in the case of bads.
  We extend this analysis to the fair division of mixed items: each item can be
viewed by some participants as a good and by others as a bad, with
corresponding positive or negative marginal utilities. We find that the
division of mixed items boils down, normatively as well as computationally, to
a variant of an all goods problem, or of an all bads problem: in particular the
task of dividing the non disposable items must be either good news for
everyone, or bad news for everyone.
  If at least one feasible utility profile is positive, the Competitive rule
picks the unique maximum of the product of (positive) utilities. If no feasible
utility profile is positive, this rule picks all critical points of the product
of disutilities on the efficient frontier.


title:
Effect of Electron Count and Chemical Complexity in the Ta-Nb-Hf-Zr-Ti
  High-Entropy Alloy Superconductor

abstract:
  High-entropy alloys are made from random mixtures of principal elements on
simple lattices, stabilized by a high mixing entropy. The recently discovered
BCC Ta-Nb-Hf-Zr-Ti high entropy alloy superconductor appears to display
properties of both simple crystalline intermetallics and amorphous materials,
e.g. it has a well defined superconducting transition along with an exceptional
robustness against disorder. Here we show that the valence-electron count
dependence of the superconducting transition temperature in the high entropy
alloy falls between those of analogous simple solid solutions and amorphous
materials, and test the effect of alloy complexity on the superconductivity. We
propose high-entropy alloys as excellent intermediate systems for studying
superconductivity as it evolves between crystalline and amorphous materials.


title: Two-loop $gg \to Hg$ amplitude mediated by a nearly massless quark

abstract:
  We analytically compute the two-loop scattering amplitude $gg \to Hg$
assuming that the mass of the quark, that mediates the ggH interaction, is
vanishingly small. Our computation provides an important ingredient required to
improve the theoretical description of the top-bottom interference effect in
Higgs boson production in gluon fusion, and to elucidate its impact on the
Higgs boson transverse momentum distribution.


title: Sedimentation of Inertialess Particles in Stokes Flows

abstract:
  We investigate the sedimentation of a cloud of rigid, spherical particles of
identical radii under gravity in a Stokes fluid. Both inertia and rotation of
particles are neglected. We consider the homogenization limit of many small
particles in the case of a dilute system in which interactions between
particles are still important. In the relevant time scale, we rigorously prove
convergence of the dynamics to the solution of a macroscopic equation. This
macroscopic equation resembles the Stokes equations for a fluid of variable
density subject to gravitation.


title: Acoustic Coherent Perfect Absorbers as Sensitive Null Detectors

abstract:
  We report the experimental realization of acoustic coherent perfect
absorption (CPA) of four symmetric scatterers of very different structures. The
only conditions necessary for these scatterers to exhibit CPA are that both the
reflection and transmission amplitudes of the scatterers are 0.5 under one
incident wave, and there are two collinear and counter-propagating incident
waves with appropriate relative amplitude and phase. Nearly 1000 times in the
modulation of output power has been demonstrated by changing the relative phase
of the incident waves over 180{\deg}. We further demonstrate that these
scatterers are sensitive devices to detect the small differences between two
nearly equal incident waves. A 27 % change in the strength of the scattering
wave has been demonstrated for every degree of phase deviation from the optimum
condition between the incident waves.


title:
Semi-supervised Discovery of Informative Tweets During the Emerging
  Disasters

abstract:
  The first objective towards the effective use of microblogging services such
as Twitter for situational awareness during the emerging disasters is discovery
of the disaster-related postings. Given the wide range of possible disasters,
using a pre-selected set of disaster-related keywords for the discovery is
suboptimal. An alternative that we focus on in this work is to train a
classifier using a small set of labeled postings that are becoming available as
a disaster is emerging. Our hypothesis is that utilizing large quantities of
historical microblogs could improve the quality of classification, as compared
to training a classifier only on the labeled data. We propose to use unlabeled
microblogs to cluster words into a limited number of clusters and use the word
clusters as features for classification. To evaluate the proposed
semi-supervised approach, we used Twitter data from 6 different disasters. Our
results indicate that when the number of labeled tweets is 100 or less, the
proposed approach is superior to the standard classification based on the bag
or words feature representation. Our results also reveal that the choice of the
unlabeled corpus, the choice of word clustering algorithm, and the choice of
hyperparameters can have a significant impact on the classification accuracy.


title:
A Decade of TeV Observations of the Gamma-ray Binary HESSJ0632+057 with
  VERITAS

abstract:
  The gamma-ray binary HESSJ0632+057 (VERJ0633+057) has been observed at
very-high energies for a decade by all major systems of imaging atmospheric
Cherenkov telescopes. We present here new observations taken by the VERITAS
observatory during the season 2015-2016. The observations cover now all phases
of the binary orbit (with its period of about 315 days), showing clearly
enhancements around phases 0.35 and 0.75. The results are discussed along with
simultaneous observations with Swift's X-Ray Telescope.


title:
Influence of the surface symmetry breaking on the magnetism, collapsing
  and three dimensional dispersion of Co pnictides ACo2As2 (A=Ba, Sr, Ca)

abstract:
  We use angle-resolved photoemission to study the three dimensional (3D)
electronic structure of Co pnictides ACo2As2 with A=Ba, Sr, Ca or a mixture of
Sr and Ca. These compounds are isostructural to Fe based superconductors, but
have one more electron in the Co $3d$ orbitals. Going from Ba to Ca, they
become more and more 3D, eventually forming a 'collapsed' tetragonal phase,
where the distance between CoAs layers is markedly reduced. The observed
periodicity of the 3D electronic structure matches in each case that expected
from the distance between the planes in the bulk. However, the electronic
structure is better fitted by a calculation corresponding to a slab with 2 CoAs
layers than to the bulk structure. We attribute this to subtle modifications of
the 2D electronic structure induced by the truncation of the 3D dispersion at
the surface in the ARPES measurement. We further study how this affects the
electronic properties. We show that, despite this distortion, the electronic
structure of CaCo2As2 is essentially that expected for a collapsed phase.
Electronic correlations produce a renormalization of the electronic structure
by a factor 1.4, which is not affected by the transition to the collapsed
state. On the other hand, a small shift of the Fermi level reduces the density
of states in the eg bands and suppresses the magnetic transition expected in
CaCo2As2. Our study evidences that observing the bulk periodicity is not
sufficient to ensure bulk sensitivity. It further gives direct information on
the role of 3D interactions, mostly governed by Co-As hybridization, among eg
and t2g orbitals. It is also useful to better understand the electronic
structure of Fe superconductors and the range of validity of ARPES
measurements.


title:
Evidence for a spinon Fermi surface in the triangular S=1 quantum spin
  liquid Ba$_3$NiSb$_2$O$_9$

abstract:
  Inelastic neutron scattering is used to study the low-energy magnetic
excitations in the spin-1 triangular lattice of the 6H-B phase of
Ba$_3$NiSb$_2$O$_9$. We study two powder samples: Ba$_3$NiSb$_2$O$_9$
synthesized under high pressure and Ba$_{2.5}$Sr$_{0.5}$NiSb$_2$O$_9$ in which
chemical pressure stabilizes the 6H-B structure. The measured excitation
spectra show broad gapless and nondispersive continua at characteristic wave
vectors. Our data rules out most theoretical scenarios that have previously
been proposed for this phase, and we find that it is well described by an
exotic quantum spin liquid with three flavors of unpaired fermionic spinons,
forming a large spinon Fermi surface.


title:
Hybrid membrane resonators for multiple frequency asymmetric absorption
  and reflection in large waveguide

abstract:
  We report that Hybrid membrane resonators (HMRs) made of a decorated membrane
resonator backed by a shallow cavity can function as Helmholtz resonators (HRs)
when mounted on the sidewall of a clear waveguide for air ventilation. When two
single-frequency HMRs are used in the same scheme as two frequency-detuned HRs,
asymmetric total absorption/reflection is demonstrated at 286.7 Hz with
absorption coefficient over 97 % in a waveguide 9 cm x 9 cm in cross section.
When two multiple-frequency HMRs are used, absorption in the range of near 60 %
to above 80 % is observed at 403 Hz, 450 Hz, 688 Hz, 863 Hz and 945 Hz.
Theoretical predictions agree well with the experimental data. The HMRs may
replace HRs in duct noise reduction applications in that at a single operation
frequency they have stronger strength to cover a much larger cross section area
than that of HRs with similar cavity volume, and they can be designed to
provide multiple frequency absorption band.


title: Signatures of Chaos in Thermal Switching of Nanomagnets

abstract:
  Thermally-activated magnetization dynamics of small nanoparticles subject to
microwave (AC) external fields is studied. It is shown that, under sufficiently
strong microwave excitations, chaotic magnetization dynamics may occur close to
saddle-type heteroclinic connections, and this heteroclinic chaos is
responsible for the erosion of the safe basin around stable magnetization
states. The erosion phenomenon is then connected to the escape problem from the
energy well surrounding a stable equilibrium. It is shown that escape times
follow a generalized Arrhenius' law governed by temperature, microwave field
amplitude, frequency and heteroclinic chaos threshold.


title:
Lattice Dynamics Calculations based on Density-functional Perturbation
  Theory in Real Space

abstract:
  A real-space formalism for density-functional perturbation theory (DFPT) is
derived and applied for the computation of harmonic vibrational properties in
molecules and solids. The practical implementation using numeric atom-centered
orbitals as basis functions is demonstrated exemplarily for the all-electron
Fritz Haber Institute ab initio molecular simulations (FHI-aims) package. The
convergence of the calculations with respect to numerical parameters is
carefully investigated and a systematic comparison with finite-difference
approaches is performed both for finite (molecules) and extended (periodic)
systems. Finally, the scaling tests and scalability tests on massively parallel
computer systems demonstrate the computational efficiency.


title:
Interaction of CME/ICME with HSS solar wind from coronal holes: case
  study

abstract:
  In this paper we look for traces of interaction of CME/ICME with high-speed
stream (HSS) of solar wind from coronal hole (CH) for two serial Carrington
rotations (CRs) during December 2011 - January 2012. We analyze two cases. (1)
In CR 2118 instead of predicted arrival of HSS the signatures of ICME with
modified back side and compressed slow stream were observed. (2) In CR 2119 the
predicted HSS was observed in time, and after arrival of preceding ICME. Our
analysis shows that difference of these cases can be explained by different
interactions between HSS and CME, which in the first case result in significant
deflection of HSS of solar wind from the Sun-Earth line. Thus, the CH passage
through the central meridian with simultaneous occurrence of CMEs in the nearby
located sources can result in interaction between HSS and CME streams,
deflection of the HSS stream aside of the ecliptic and changes in parameters of
the solar wind.


title: Sturmian bases for two-electron systems in hyperspherical coordinates

abstract:
  We give a detailed account of an $\it{ab}$ $\it{initio}$ spectral approach
for the calculation of energy spectra of two active electron atoms in a system
of hyperspherical coordinates. In this system of coordinates, the Hamiltonian
has the same structure as the one of atomic hydrogen with the Coulomb potential
expressed in terms of a hyperradius and the nuclear charge replaced by an angle
dependent effective charge. The simplest spectral approach consists in
expanding the hyperangular wave function in a basis of hyperspherical
harmonics. This expansion however, is known to be very slowly converging.
Instead, we introduce new hyperangular sturmian functions. These functions do
not have an analytical expression but they treat the first term of the
multipole expansion of the electron-electron interaction potential, namely the
radial electron correlation, exactly. The properties of these new functions are
discussed in detail. For the basis functions of the hyperradius, several
choices are possible. In the present case, we use Coulomb sturmian functions of
half integer angular momentum. We show that, in the case of H$^-$, the accuracy
of the energy and the width of the resonance states obtained through a single
diagonalization of the Hamiltonian, is comparable to the values given by
state-of-the-art methods while using a much smaller basis set. In addition, we
show that precise values of the electric-dipole oscillator strengths for
$S\rightarrow P$ transitions in helium are obtained thereby confirming the
accuracy of the bound state wave functions generated with the present method.


title: Language Models with Pre-Trained (GloVe) Word Embeddings

abstract:
  In this work we implement a training of a Language Model (LM), using
Recurrent Neural Network (RNN) and GloVe word embeddings, introduced by
Pennigton et al. in [1]. The implementation is following the general idea of
training RNNs for LM tasks presented in [2], but is rather using Gated
Recurrent Unit (GRU) [3] for a memory cell, and not the more commonly used LSTM
[4].


title:
Thermal Anisotropy Enhanced by Phonon Size Effects in Nanoporous
  Materials

abstract:
  While thermal anisotropicity is a desirable materials property for many
applications, including transverse thermoelectrics and thermal management in
electronic devices, it remains elusive in practical natural compounds. In this
work, we show how nanoporous materials with anisotropic pore lattices can be
used as a platform for inducing strong heat transport directionality in
isotropic materials. Using density functional theory and the phonon Boltzmann
transport equation, we calculate the phonon-size effects and thermal
conductivity of nanoporous silicon with different anisotropicpore lattices. Our
calculations predict a strong directionality in the thermal conductivity,
dictated by the difference in the pore-pore distances along the two Cartesian
axes. As the space between pores along the direction of the applied temperature
gradient represents the phonon bottleneck, an anisotropic pores lattice
distortion induces directionality in heat transport. Using Fourier's law, we
also compute diffusive heat transport for the same geometries obtaining
significantly smaller anisotropicity, revealing the crucial role of phonon-size
effects in tuning thermal transport directionality. Besides enhancing our
understanding of nanoscale heat transport, our results demonstrate the promise
of nanoporous materials for modulating anisotropy in thermal conductivity.


title:
Detecting Unseen Falls from Wearable Devices using Channel-wise Ensemble
  of Autoencoders

abstract:
  A fall is an abnormal activity that occurs rarely, so it is hard to collect
real data for falls. It is, therefore, difficult to use supervised learning
methods to automatically detect falls. Another challenge in using machine
learning methods to automatically detect falls is the choice of engineered
features. In this paper, we propose to use an ensemble of autoencoders to
extract features from different channels of wearable sensor data trained only
on normal activities. We show that the traditional approach of choosing a
threshold as the maximum of the reconstruction error on the training normal
data is not the right way to identify unseen falls. We propose two methods for
automatic tightening of reconstruction error from only the normal activities
for better identification of unseen falls. We present our results on two
activity recognition datasets and show the efficacy of our proposed method
against traditional autoencoder models and two standard one-class
classification methods.


title: Large subgraphs in pseudo-random graphs

abstract:
  We consider classes of pseudo-random graphs on $n$ vertices for which the
degree of every vertex and the co-degree between every pair of vertices are in
the intervals $(np - Cn^\delta,np+Cn^\delta)$ and $(np^2- C n^\delta, np^2 +C
n^\delta)$ respectively, for some absolute constant $C$, and $p, \delta \in
(0,1)$. We show that for such pseudo-random graphs the number of induced
isomorphic copies of subgraphs of size $s$ are approximately same as that of an
Erd\H{o}s-R\'{e}yni random graph with edge connectivity probability $p$ as long
as $s \le (((1-\delta)\wedge \frac{1}{2})-o(1))\log n/\log (1/p)$, when $p \in
(0,1/2]$. When $p \in (1/2,1)$ we obtain a similar result. Our result is
applicable for a large class of random and deterministic graphs including
exponential random graph models (ERGMs), thresholded graphs from
high-dimensional correlation networks, Erd\H{o}s-R\'{e}yni random graphs
conditioned on large cliques, random $d$-regular graphs and graphs obtained
from vector spaces over binary fields. In the context of the last example, the
results obtained are optimal. Straight-forward extensions using the proof
techniques in this paper imply strengthening of the above results in the
context of larger motifs if a model allows control over higher co-degree type
functionals.


title:
Gravitational waves at interferometer scales and primordial black holes
  in axion inflation

abstract:
  We study the prospects of detection at terrestrial and space interferometers,
as well as at pulsar timing array experiments, of a stochastic gravitational
wave background which can be produced in models of axion inflation. This
potential signal, and the development of these experiments, open a new window
on inflation on scales much smaller than those currently probed with Cosmic
Microwave Background and Large Scale Structure measurements. The sourced signal
generated in axion inflation is an ideal candidate for such searches, since it
naturally grows at small scales, and it has specific properties (chirality and
non-gaussianity) that can distinguish it from an astrophysical background. We
study under which conditions such a signal can be produced at an observable
level, without the simultaneous overproduction of scalar perturbations in
excess of what is allowed by the primordial black hole limits. We also explore
the possibility that scalar perturbations generated in a modified version of
this model may provide a distribution of primordial black holes compatible with
the current bounds, that can act as a seeds of the present black holes in the
universe.


title:
Technical Report: Improved Fourier Reconstruction using Jump Information
  with Applications to MRI

abstract:
  Certain applications such as Magnetic Resonance Imaging (MRI) require the
reconstruction of functions from Fourier spectral data. When the underlying
functions are piecewise-smooth, standard Fourier approximation methods suffer
from the Gibbs phenomenon - with associated oscillatory artifacts in the
vicinity of edges and an overall reduced order of convergence in the
approximation. This paper proposes an edge-augmented Fourier reconstruction
procedure which uses only the first few Fourier coefficients of an underlying
piecewise-smooth function to accurately estimate jump information and then
incorporate it into a Fourier partial sum approximation. We provide both
theoretical and empirical results showing the improved accuracy of the proposed
method, as well as comparisons demonstrating superior performance over existing
state-of-the-art sparse optimization-based methods. Extensions of the proposed
techniques to functions of several variables are also addressed preliminarily.
All code used to generate the results in this report are made publicly
available.


title: Biderivations of finite dimensional complex simple Lie algebras

abstract:
  In this paper, we prove that a biderivation of a finite dimensional complex
simple Lie algebra without the restriction of skewsymmetric is inner. As an
application, the biderivation of a general linear Lie algebra is presented. In
particular, we find a class of a non-inner and non-skewsymmetric biderivations.
Furthermore, we also get the forms of linear commuting maps on the finite
dimensional complex simple Lie algebra or general linear Lie algebra.


title: Independent Set Reconfiguration Thresholds of Hereditary Graph Classes

abstract:
  Traditionally, reconfiguration problems ask the question whether a given
solution of an optimization problem can be transformed to a target solution in
a sequence of small steps that preserve feasibility of the intermediate
solutions. In this paper, rather than asking this question from an algorithmic
perspective, we analyze the combinatorial structure behind it. We consider the
problem of reconfiguring one independent set into another, using two different
processes: (1) exchanging exactly $k$ vertices in each step, or (2) removing or
adding one vertex in each step while ensuring the intermediate sets contain at
most $k$ fewer vertices than the initial solution. We are interested in
determining the minimum value of $k$ for which this reconfiguration is
possible, and bound these threshold values in terms of several structural graph
parameters. For hereditary graph classes we identify structures that cause the
reconfiguration threshold to be large.


title: Primordial Universe Inside the Black Hole and Inflation

abstract:
  We speculate that the early Universe was inside a primordial black hole. The
interior of the the black hole is a dS background and the two spacetimes are
separated on the surface of black hole's event horizon. We argue that this
picture provides a natural realization of inflation without invoking the
inflaton field. The black hole evaporation by Hawking radiation provides a
natural mechanism for terminating inflation so reheating and the hot big bang
cosmology starts from the evaporation of black hole to relativistic particles.
The quantum gravitational fluctuations at the boundary of black hole generate
the nearly scale invariant scalar and tensor perturbations with the ratio of
tensor to scalar power spectra at the order of $10^{-3}$. As the black hole
evaporates, the radius of its event horizon shrinks and the Hubble expansion
rate during inflation increases slowly so the quantum Hawking radiation
provides a novel mechanism for the violation of null energy condition in
cosmology.


title:
The high-dimensional cohomology of the moduli space of curves with level
  structures

abstract:
  We prove that the moduli space of curves with level structures has an
enormous amount of rational cohomology in its cohomological dimension. As an
application, we prove that the coherent cohomological dimension of the moduli
space of curves is at least g-2. Well known conjectures of Looijenga would
imply that this is sharp.


title: On Origins of Bubbles

abstract:
  We discuss - in what is intended to be a pedagogical fashion - a criterion,
which is a lower bound on a certain ratio, for when a stock (or a similar
instrument) is not a good investment in the long term, which can happen even if
the expected return is positive. The root cause is that prices are positive and
have skewed, long-tailed distributions, which coupled with volatility results
in a long-run asymmetry. This relates to bubbles in stock prices, which we
discuss using a simple binomial tree model, without resorting to the stochastic
calculus machinery. We illustrate empirical properties of the aforesaid ratio.
Log of market cap and sectors appear to be relevant explanatory variables for
this ratio, while price-to-book ratio (or its log) is not. We also discuss a
short-term effect of volatility, to wit, the analog of Heisenberg's uncertainty
principle in finance and a simple derivation thereof using a binary tree.


title: $N$-Scaling of Timescales in Long-Range $N$-Body Quantum Systems

abstract:
  Long-range interacting many-body systems exhibit a number of peculiar and
intriguing properties. One of those is the scaling of relaxation times with the
number $N$ of particles in a system. In this paper I give a survey of results
on long-range quantum spin models that illustrate this scaling behaviour, and
provide indications for its common occurrence by making use of Lieb-Robinson
bounds. I argue that these findings may help in understanding the
extraordinarily short equilibration timescales predicted by typicality
techniques.


title:
SentiHood: Targeted Aspect Based Sentiment Analysis Dataset for Urban
  Neighbourhoods

abstract:
  In this paper, we introduce the task of targeted aspect-based sentiment
analysis. The goal is to extract fine-grained information with respect to
entities mentioned in user comments. This work extends both aspect-based
sentiment analysis that assumes a single entity per document and targeted
sentiment analysis that assumes a single sentiment towards a target entity. In
particular, we identify the sentiment towards each aspect of one or more
entities. As a testbed for this task, we introduce the SentiHood dataset,
extracted from a question answering (QA) platform where urban neighbourhoods
are discussed by users. In this context units of text often mention several
aspects of one or more neighbourhoods. This is the first time that a generic
social media platform in this case a QA platform, is used for fine-grained
opinion mining. Text coming from QA platforms is far less constrained compared
to text from review specific platforms which current datasets are based on. We
develop several strong baselines, relying on logistic regression and
state-of-the-art recurrent neural networks.


title:
RAVEN X High Performance Data Mining Toolbox for Bioacoustic Data
  Analysis

abstract:
  Objective of this work is to integrate high performance computing (HPC)
technologies and bioacoustics data-mining capabilities by offering a
MATLAB-based toolbox called Raven-X. Raven-X will provide a
hardware-independent solution, for processing large acoustic datasets - the
toolkit will be available to the community at no cost. This goal will be
achieved by leveraging prior work done which successfully deployed MATLAB based
HPC tools within Cornell University's Bioacoustics Research Program (BRP).
These tools enabled commonly available multi-core computers to process data at
accelerated rates to detect and classify whale sounds in large multi-channel
sound archives. Through this collaboration, we will expand on this effort which
was featured through Mathworks research and industry forums incorporate new
cutting-edge detectors and classifiers, and disseminate Raven-X to the broader
bioacoustics community.


title:
Resolving the blazar CGRaBS J0809+5341 in the presence of telescope
  systematics

abstract:
  We analyse Very Long Baseline Interferometry (VLBI) observations of the
blazar CGRaBS J0809+5341 using Bayesian inference methods. The observation was
carried out at 5 GHz using 8 telescopes that form part of the European VLBI
Network. Imaging and deconvolution using traditional methods imply that the
blazar is unresolved. To search for source structure beyond the diffraction
limit, we perform Bayesian model selection between three source models (point,
elliptical Gaussian, and circular Gaussian). Our modelling jointly accounts for
antenna-dependent gains and system equivalent flux densities. We obtain
posterior distributions for the various source and instrumental parameters
along with the corresponding uncertainties and correlations between them. We
find that there is very strong evidence (>1e9 :1) in favour of elliptical
Gaussian structure and using this model derive the apparent brightness
temperature distribution of the blazar, accounting for uncertainties in the
shape estimates. To test the integrity of our method, we also perform model
selection on synthetic observations and use this to develop a Bayesian
criterion for the minimum resolvable source size and consequently the maximum
measurable brightness temperature for a given interferometer, dependent on the
signal-to-noise ratio (SNR) of the data incorporating the aforementioned
systematics. We find that calibration errors play an increasingly important
role in determining the over-resolution limit for SNR>>100. We show that it is
possible to exploit the resolving power of future VLBI arrays down to about 5
per cent of the size of the naturally-weighted restoring beam, if the gain
calibration is precise to 1 per cent or less.


title:
Parallelizing Stochastic Gradient Descent for Least Squares Regression:
  mini-batching, averaging, and model misspecification

abstract:
  This work characterizes the benefits of averaging schemes widely used in
conjunction with stochastic gradient descent (SGD). In particular, this work
provides a sharp analysis of: (1) mini-batching, a method of averaging many
samples of a stochastic gradient to both reduce the variance of the stochastic
gradient estimate and for parallelizing SGD and (2) tail-averaging, a method
involving averaging the final few iterates of SGD to decrease the variance in
SGD's final iterate. This work presents non-asymptotic excess risk bounds for
these schemes for the stochastic approximation problem of least squares
regression.
  Furthermore, this work establishes a precise problem-dependent extent to
which mini-batch SGD yields provable near-linear parallelization speedups over
SGD with batch size one. This allows for understanding learning rate versus
batch size tradeoffs for the final iterate of an SGD method. These results are
then utilized in providing a highly parallelizable SGD method that obtains the
minimax risk with nearly the same number of serial updates as batch gradient
descent, improving significantly over existing SGD methods. A non-asymptotic
analysis of communication efficient parallelization schemes such as
model-averaging/parameter mixing methods is then provided.
  Finally, this work sheds light on some fundamental differences in SGD's
behavior when dealing with agnostic noise in the (non-realizable) least squares
regression problem. In particular, the work shows that the stepsizes that
ensure minimax risk for the agnostic case must be a function of the noise
properties.
  This paper builds on the operator view of analyzing SGD methods, introduced
by Defossez and Bach (2015), followed by developing a novel analysis in
bounding these operators to characterize the excess risk. These techniques are
of broader interest in analyzing computational aspects of stochastic
approximation.


title: Optical Properties Of Nanometer-Scale Structures

abstract:
  Two approaches (micro- and macro- investigations) are used to determine the
dimension dependences of the optical parameters of the nanometer-scale layers
of materials. It is shown that both an index of refraction and coefficient of
absorption depend strongly on the thickness of the layer. In this region of
thicknesses, the dimension resonance occurs, where an index of refraction has a
maximum and a coefficient of absorption has a minimum. The numerical
calculation of the optical parameters of some materials (Ag, Al, Fe, Ge, Si,
Se, Te) have been carried out with the use of the experimental data of
reflection and transparency of thin layers, obtained in a series of works, and
with our formulas for the wave amplitudes and the laws of refractions. The
analogues of the Fresnel formulas and the Snell law have been derived from the
Maxwell boundary conditions where the absorption and conductivity of media were
taken into account. The use of our formulas for the wave amplitudes leads to
the fulfillment of the conservation law of energy both for the TE- and TM-
polarizations of light. The reemission of light is possible for the
thicknesses, which is equal to the wavelength of light in a medium, divisible
by integer:
$\frac{2{\pi}d_{res}}{2}={\lambda}_m{\cdot}m=\frac{{\lambda}_0}{n}{\cdot}m$,
where m=1,2,3... The visible luminescence of the porous silicon, silicon
whiskers and other nanometer-scale structures can be explained by their
emission in the case of dimension resonance because in this region of
thicknesses, layers have a big negative coefficient of absorption and little -
of a damping. It is also shown that in the case of the TM-polarization, in a
material with a high conductivity, light refracts in a "wrong" direction (at
all positive optical parameters) due to a surface current. In the case of the
TE-polarization, light refracts only in a "right" direction.


title:
Sharp exponential inequalities in survey sampling: conditional Poisson
  sampling schemes

abstract:
  This paper is devoted to establishing exponential bounds for the
probabilities of deviation of a sample sum from its expectation, when the
variables involved in the summation are obtained by sampling in a finite
population according to a rejective scheme, generalizing sampling without
replacement, and by using an appropriate normalization. In contrast to Poisson
sampling, classical deviation inequalities in the i.i.d. setting do not
straightforwardly apply to sample sums related to rejective schemes, due to the
inherent dependence structure of the sampled points. We show here how to
overcome this difficulty, by combining the formulation of rejective sampling as
Poisson sampling conditioned upon the sample size with the Escher
transformation. In particular, the Bennett/Bernstein type bounds established
highlight the effect of the asymptotic variance of the (properly standardized)
sample weighted sum and are shown to be much more accurate than those based on
the negative association property shared by the terms involved in the
summation. Beyond its interest in itself, such a result for rejective sampling
is crucial, insofar as it can be extended to many other sampling schemes,
namely those that can be accurately approximated by rejective plans in the
sense of the total variation distance.


title: Deep disentangled representations for volumetric reconstruction

abstract:
  We introduce a convolutional neural network for inferring a compact
disentangled graphical description of objects from 2D images that can be used
for volumetric reconstruction. The network comprises an encoder and a
twin-tailed decoder. The encoder generates a disentangled graphics code. The
first decoder generates a volume, and the second decoder reconstructs the input
image using a novel training regime that allows the graphics code to learn a
separate representation of the 3D object and a description of its lighting and
pose conditions. We demonstrate this method by generating volumes and
disentangled graphical descriptions from images and videos of faces and chairs.


title:
Photoionization Models for the Semi-Forbidden C III] 1909 Emission in
  Star-Forming Galaxies

abstract:
  The increasing neutrality of the intergalactic medium at z>6 suppresses
Ly-alpha emission, and spectroscopic confirmation of galaxy redshifts requires
detecting alternative UV lines. The strong [C III] 1907 + C III] 1909 doublet
frequently observed in low-metallicity, actively star-forming galaxies is a
promising emission feature. We present CLOUDY photoionization model predictions
for C III] equivalent widths (EWs) and line ratios as a function of starburst
age, metallicity, and ionization parameter. Our models include a range of C/O
abundances, dust content, and gas density. We also examine the effects of
varying the nebular geometry and optical depth. Only the stellar models that
incorporate binary interaction effects reproduce the highest observed C III]
EWs. The spectral energy distributions from the binary stellar population
models also generate observable C III] over a longer timescale relative to
single-star models. We show that diagnostics using C III] and nebular He II
1640 can separate star-forming regions from shock-ionized gas. We also find
that density-bounded systems should exhibit weaker C III] EWs at a given
ionization parameter, and C III] EWs could therefore select candidate Lyman
continuum-leaking systems. In almost all models, C III] is the next strongest
line at < 2700 Angstroms after Ly-alpha, and C III] reaches detectable levels
for a wide range of conditions at low metallicity. C III] may therefore serve
as an important diagnostic for characterizing galaxies at z>6.


title:
Generating Clustered Journal Maps: An Automated System for Hierarchical
  Classification

abstract:
  Journal maps and classifications for 11,359 journals listed in the combined
Journal Citation Reports 2015 of the Science and Social Sciences Citation
Indexes are provided at http://www.leydesdorff.net/jcr15. A routine using
VOSviewer for integrating the journal mapping and their hierarchical clustering
is also made available. In this short communication, we provide background on
the journal mapping/clustering and an explanation and instructions about the
routine. We compare 2015 journal maps with those for 2014 and show the
delineations among fields and subfields to be sensitive to fluctuations. Labels
for fields and sub-fields are not provided by the routine, but can be added by
an analyst for pragmatic or intellectual reasons. The routine provides a means
for testing one's assumptions against a baseline without claiming authority,
clusters of related journals can be visualized to understand communities. The
routine is generic and can be used for any 1-mode network.


title: The innermost astronomical unit of protoplanetary disks

abstract:
  Circumstellar disks around young stars are the birthsites of planets. It is
thus fundamental to study the disks in which they form, their structure and the
physical conditions therein. The first astronomical unit is of great interest
because this is where the terrestrial-planets form and the angular momentum is
controled via massloss through winds/jets. With its milli-arcsecond resolution,
optical interferometry is the only technic able to spatially resolve the first
few astronomical units of the disk. In this review, we will present a broad
overview of studies of young stellar objects with interferometry, and discuss
prospects for the future.


title:
Measurement of the ratio of the sixth order to the second order cumulant
  of net-proton multiplicity distributions in relativistic heavy-ion collisions

abstract:
  We investigate the measurement of the sixth order cumulant and its ratio to
the second order cumulant ($C_6/C_2$) in relativistic heavy-ion collisions. The
influence of statistics and different methods of centrality bin width
correction on $C_6/C_2$ of net-proton multiplicity distributions is
demonstrated. There is no satisfactory method to extract $C_6/C_2$ with the
current statistics recorded at lower energies by STAR at RHIC. With statistics
comparable to the expected statistics at the planned future RHIC Beam Energy
Scan II (BES II), no energy dependence of $C_6/C_2$ is observed in central
collisions using the UrQMD model. We find if the transition signal is as strong
as predicted by the PQM model, then it is hopefully observed at the upcoming
RHIC BES II.


title: Video Depth-From-Defocus

abstract:
  Many compelling video post-processing effects, in particular aesthetic focus
editing and refocusing effects, are feasible if per-frame depth information is
available. Existing computational methods to capture RGB and depth either
purposefully modify the optics (coded aperture, light-field imaging), or employ
active RGB-D cameras. Since these methods are less practical for users with
normal cameras, we present an algorithm to capture all-in-focus RGB-D video of
dynamic scenes with an unmodified commodity video camera. Our algorithm turns
the often unwanted defocus blur into a valuable signal. The input to our method
is a video in which the focus plane is continuously moving back and forth
during capture, and thus defocus blur is provoked and strongly visible. This
can be achieved by manually turning the focus ring of the lens during
recording. The core algorithmic ingredient is a new video-based
depth-from-defocus algorithm that computes space-time-coherent depth maps,
deblurred all-in-focus video, and the focus distance for each frame. We
extensively evaluate our approach, and show that it enables compelling video
post-processing effects, such as different types of refocusing.


title: Change-point detection in high-dimensional covariance structure

abstract:
  In this paper we introduce a novel approach for an important problem of break
detection. Specifically, we are interested in detection of an abrupt change in
the covariance structure of a high-dimensional random process -- a problem,
which has applications in many areas e.g., neuroimaging and finance. The
developed approach is essentially a testing procedure involving a choice of a
critical level. To that end a non-standard bootstrap scheme is proposed and
theoretically justified under mild assumptions. Theoretical study features a
result providing guaranties for break detection. All the theoretical results
are established in a high-dimensional setting (dimensionality $p \gg n$).
Multiscale nature of the approach allows for a trade-off between sensitivity of
break detection and localization. The approach can be naturally employed in an
on-line setting. Simulation study demonstrates that the approach matches the
nominal level of false alarm probability and exhibits high power, outperforming
a recent approach.


title:
Fine regularity results for Mumford-Shah minimizers: porosity, higher
  integrability and the Mumford-Shah conjecture

abstract:
  We review some classical results and more recent insights about the
regularity theory for local minimizers of the Mumford and Shah energy and their
connections with the Mumford and Shah conjecture. We discuss in details the
links among the latter, the porosity of the jump set and the higher
integrability of the approximate gradient. In particular, higher integrability
turns out to be related with an explicit estimate on the Hausdorff dimension of
the singular set and an energetic characterization of the conjecture itself.


title:
On the limits to mobility in InAs quantum wells with nearly
  lattice-matched barriers

abstract:
  The growth and the density dependence of the low temperature mobility of a
series of two-dimensional electron systems confined to un-intentionally doped,
low extended defect density InAs quantum wells with Al$_{1-x}$Ga$_{x}$Sb
barriers are reported. The electron mobility limiting scattering mechanisms
were determined by utilizing dual-gated devices to study the dependence of
mobility on carrier density and electric field independently. Analysis of the
possible scattering mechanisms indicate the mobility was limited primarily by
rough interfaces in narrow quantum wells and a combination of alloy disorder
and interface roughness in wide wells at high carrier density within the first
occupied electronic sub-band. At low carrier density the functional dependence
of the mobility on carrier density provided evidence of coulombic scattering
from charged defects. A gate-tuned electron mobility exceeding 750,000
cm$^{2}$/Vs was achieved at a sample temperature of 2 K.


title:
MI-Sim: A MATLAB Package for the Numerical Analysis of Microbial
  Ecological Interactions

abstract:
  Food-webs and other classes of ecological network motifs, are a means of
describing feeding relationships between consumers and producers in an
ecosystem. They have application across scales where they differ only in the
underlying characteristics of the organisms and substrates describing the
system. Mathematical modelling, using mechanistic approaches to describe the
dynamic behaviour and properties of the system through sets of ordinary
differential equations, has been used extensively in ecology. Models allow
simulation of the dynamics of the various motifs and their numerical analysis
provides a greater understanding of the interplay between the system components
and their intrinsic properties. We have developed the MI-Sim software for use
with MATLAB to allow a rigorous and rapid numerical analysis of several common
ecological motifs. MI-Sim contains a series of the most commonly used motifs
such as cooperation, competition and predation. It does not require detailed
knowledge of mathematical analytical techniques and is offered as a single
graphical user interface containing all input and output options. The tools
available in the current version of MI-Sim include model simulation, steady-
state existence and stability analysis, and basin of attraction analysis. The
software includes seven ecological interaction motifs and seven growth function
models. Unlike other system analysis tools, MI-Sim is designed as a simple and
user-friendly tool specific to ecological population type models, allowing for
rapid assessment of their dynamical and behavioural properties.


title: Tight contact structures on hyperbolic three-manifolds

abstract:
  We show the existence of tight contact structures on infinitely many
hyperbolic three-manifolds obtained via Dehn surgeries along sections of
hyperbolic surface bundles over circle.


title: Computing the Expected Value and Variance of Geometric Measures

abstract:
  Let P be a set of points in R^d, and let M be a function that maps any subset
of P to a positive real number. We examine the problem of computing the exact
mean and variance of M when a subset of points in P is selected according to a
well-defined random distribution. We consider two distributions; in the first
distribution (which we call the Bernoulli distribution), each point p in P is
included in the random subset independently, with probability pi(p). In the
second distribution (the fixed-size distribution), a subset of exactly s points
is selected uniformly at random among all possible subsets of s points in P.
  This problem is a crucial part of modern ecological analyses; each point in P
represents a species in d-dimensional trait space, and the goal is to compute
the statistics of a geometric measure on this trait space, when subsets of
species are selected under random processes.
  We present efficient exact algorithms for computing the mean and variance of
several geometric measures when point sets are selected under one of the
described random distributions. More specifically, we provide algorithms for
the following measures: the bounding box volume, the convex hull volume, the
mean pairwise distance (MPD), the squared Euclidean distance from the centroid,
and the diameter of the minimum enclosing disk. We also describe an efficient
(1-e)-approximation algorithm for computing the mean and variance of the mean
pairwise distance. We implemented three of our algorithms and we show that our
implementations can provide major speedups compared to the existing imprecise
approaches.


title: Suprathermal electron distributions in the solar transition region

abstract:
  Suprathermal tails are a common feature of solar wind electron velocity
distributions, and are expected in the solar corona. From the corona,
suprathermal electrons can propagate through the steep temperature gradient of
the transition region towards the chromosphere, and lead to non-Maxwellian
electron velocity distribution functions (VDFs) with pronounced suprathermal
tails. We calculate the evolution of a coronal electron distribution through
the transition region in order to quantify the suprathermal electron population
there. A kinetic model for electrons is used which is based on solving the
Boltzmann-Vlasov equation for electrons including Coulomb collisions with both
ions and electrons. Initial and chromospheric boundary conditions are
Maxwellian VDFs with densities and temperatures based on a background fluid
model. The coronal boundary condition has been adopted from earlier studies of
suprathermal electron formation in coronal loops. The model results show the
presence of strong suprathermal tails in transition region electron VDFs,
starting at energies of a few 10 eV. Above electron energies of 600 eV,
electrons can traverse the transition region essentially collision-free. The
presence of strong suprathermal tails in transition region electron VDFs shows
that the assumption of local thermodynamic equilibrium is not justified there.
This has a significant impact on ionization dynamics, as is shown in a
companion paper.


title: Quantum-enhanced phase estimation using optical spin squeezing

abstract:
  Quantum metrology enables estimation of optical phase shifts with precision
beyond the shot-noise limit. One way to exceed this limit is to use squeezed
states, where the quantum noise of one observable is reduced at the expense of
increased quantum noise for its complementary partner. Because shot-noise
limits the phase sensitivity of all classical states, reduced noise in the
average value for the observable being measured allows for improved phase
sensitivity. However, additional phase sensitivity can be achieved using phase
estimation strategies that account for the full distribution of measurement
outcomes. Here we experimentally investigate the phase sensitivity of a
five-particle optical spin-squeezed state generated by photon subtraction from
a parametric downconversion photon source. The Fisher information for all
photon-number outcomes shows it is possible to obtain a quantum advantage of
1.58 compared to the shot-noise limit, even though due to experimental
imperfection, the average noise for the relevant spin-observable does not
achieve sub-shot-noise precision. Our demonstration implies improved
performance of spin squeezing for applications to quantum metrology.


title: $\mathbb{A}^1$-curves on affine complete intersections

abstract:
  We generalize the results of Clemens, Ein, and Voisin regarding rational
curves and zero cycles on generic projective complete intersections to the
logarithmic setup.


title: Decentralized Coded Caching with Distinct Cache Capacities

abstract:
  Decentralized coded caching is studied for a content server with $N$ files,
each of size $F$ bits, serving $K$ active users, each equipped with a cache of
distinct capacity. It is assumed that the users' caches are filled in advance
during the off-peak traffic period without the knowledge of the number of
active users, their identities, or the particular demands. User demands are
revealed during the peak traffic period, and are served simultaneously through
an error-free shared link. A new decentralized coded caching scheme is proposed
for this scenario, and it is shown to improve upon the state-of-the-art in
terms of the required delivery rate over the shared link, when there are more
users in the system than the number of files. Numerical results indicate that
the improvement becomes more significant as the cache capacities of the users
become more skewed.


title: Introduction to the "Industrial Benchmark"

abstract:
  A novel reinforcement learning benchmark, called Industrial Benchmark, is
introduced. The Industrial Benchmark aims at being be realistic in the sense,
that it includes a variety of aspects that we found to be vital in industrial
applications. It is not designed to be an approximation of any real system, but
to pose the same hardness and complexity.


title: Heralded temporal shaping of single photons enabled by entanglement

abstract:
  We propose a method to produce pure single photons with an arbitrary designed
temporal shape in a heralded, lossless and scalable way. As the indispensable
resource, the method uses pairs of time-energy entangled photons. To accomplish
the shaping, one photon of a pair undergoes temporal modulation according to
the desired shape. Subsequent frequency-resolving detection of the photon
heralds its entangled counterpart in a pure quantum state with a temporal shape
non-locally affected by the modulation. We found conditions for the shape of
the heralded photon to reproduce the modulation function. The method can be
implemented with various sources of time-energy entangled photons. In
particular, using entangled photons from the parametric down-conversion the
method enables generation of pure photons with tunable shape within
unprecedentedly broad range of temporal durations - from tenths of femtoseconds
to microseconds. Proposed shaping of single photons will push forward
implementation of scalable multidimensional quantum information protocols,
efficient photon-matter coupling and quantum control at the level of single
quanta.


title:
Anticipating Non-Resonant New Physics in Dilepton Angular Spectra at the
  LHC

abstract:
  At the LHC, dileptonic events may turn up new physics interacting with quarks
and leptons. The poster child for this scenario is a resonant $Z'$, much
anticipated in $\ell^+ \ell^-$ invariant mass spectra. However, angular spectra
of dileptons may play an equal or stronger role in discovering a non-resonant
species. This paper avails of their LHC measurements to corner the couplings
and masses of leptoquarks (LQs), that can mediate $q \bar{q} \rightarrow \ell^+
\ell^-$ in the $t$-channel and dramatically alter Standard Model angular
spectra. Also derived are constraints from alterations to $m_{\ell \ell}$
distributions. These dilepton probes, exploiting the high rates and small
uncertainties of the Drell-Yan process, rival or outdo dedicated LHC searches
for LQs in single and pair production modes. The couplings of LQs with
electronic interactions are best bound today by low-energy measurements of
atomic parity violation, but can be probed better by $\ell^+ \ell^-$
measurements in the high luminosity runs of the LHC, with the angular spectra
leading the way. This work also advocates the experimental presentation of
boost-invariant angular asymmetries that vanish in the SM.


title:
A local uniqueness theorem for minimizers of Petty's conjectured
  projection inequality

abstract:
  Employing the inverse function theorem on Banach spaces, we prove that in a
$C^{2}(S^{n-1})$-neighborhood of the unit ball, the only solutions of
$\Pi^2K=cK$ are origin-centered ellipsoids. Here $K$ is an $n$-dimensional
convex body, $\Pi K$ is the projection body of $K$ and $\Pi^2K=\Pi(\Pi K).$


title:
Spin injection and detection up to room temperature in
  Heusler~alloy/$n$-GaAs spin valves

abstract:
  We have measured the spin injection efficiency and spin lifetime in
Co$_2$FeSi/$n$-GaAs lateral nonlocal spin valves from 20 to 300 K. We observe
large ($\sim$40 $\mu$V) spin valve signals at room temperature and injector
currents of $10^3~$A/cm$^2$, facilitated by fabricating spin valve separations
smaller than the 1 $\mu$m spin diffusion length and applying a forward bias to
the detector contact. The spin transport parameters are measured by comparing
the injector-detector contact separation dependence of the spin valve signal
with a numerical model accounting for spin drift and diffusion. The apparent
suppression of the spin injection efficiency at the lowest temperatures
reflects a breakdown of the ordinary drift-diffusion model in the regime of
large spin accumulation. A theoretical calculation of the D'yakonov-Perel spin
lifetime agrees well with the measured $n$-GaAs spin lifetime over the entire
temperature range.


title: On Probabilistic Checking in Perfect Zero Knowledge

abstract:
  We present the first constructions of single-prover proof systems that
achieve perfect zero knowledge (PZK) for languages beyond NP, under no
intractability assumptions:
  1. The complexity class #P has PZK proofs in the model of Interactive PCPs
(IPCPs) [KR08], where the verifier first receives from the prover a PCP and
then engages with the prover in an Interactive Proof (IP).
  2. The complexity class NEXP has PZK proofs in the model of Interactive
Oracle Proofs (IOPs) [BCS16,RRR16], where the verifier, in every round of
interaction, receives a PCP from the prover.
  Our constructions rely on succinct simulators that enable us to "simulate
beyond NP", achieving exponential savings in efficiency over [BCGV16]. These
simulators crucially rely on solving a problem that lies at the intersection of
coding theory, linear algebra, and computational complexity, which we call the
succinct constraint detection problem, and consists of detecting dual
constraints with polynomial support size for codes of exponential block length.
Our two results rely on solutions to this problem for fundamental classes of
linear codes:
  * An algorithm to detect constraints for Reed--Muller codes of exponential
length.
  * An algorithm to detect constraints for PCPs of Proximity of Reed--Solomon
codes [BS08] of exponential degree.
  The first algorithm exploits the Raz--Shpilka [RS05] deterministic polynomial
identity testing algorithm, and shows, to our knowledge, a first connection of
algebraic complexity theory with zero knowledge. Along the way, we give a
perfect zero knowledge analogue of the celebrated sumcheck protocol [LFKN92],
by leveraging both succinct constraint detection and low-degree testing. The
second algorithm exploits the recursive structure of the PCPs of Proximity to
show that small-support constraints are "locally" spanned by a small number of
small-support constraints.


title: Some supercongruences on truncated ${}_3F_2$ hypergeometric series

abstract:
  In 2003, Rodriguez-Villegas conjectured four supercongruences on the
truncated ${}_3F_2$ hypergeometric series for certain modular K3 surfaces,
which were gradually proved by several authors. Motivated by some
supercongruences on combinatorial numbers such as Ap\'ery numbers and Domb
numbers, we establish some new supercongruences on the truncated ${}_3F_2$
hypergeometric series, which extend the four Rodriguez-Villegas
supercongruences.


title: A new prescription for the mass-loss rates of WC and WO stars

abstract:
  We present a new empirical prescription for the mass-loss rates of carbon and
oxygen sequence Wolf-Rayet stars as a function of their luminosity, surface
chemical composition, and initial metallicity. The new prescription is based on
results of detailed spectral analyses of WC and WO stars, and improves the
often applied Nugis & Lamers (2000) relation. We find that the mass-loss rates
of WC and WO stars (with $X=0$ and $Y < 0.98$) can be expressed as
$\log{\dot{M}} = -9.20 + 0.85\log{(L/L_{\odot})} + 0.44\log{Y} +
0.25\log{(Z_{\mathrm{Fe}}/Z_{\mathrm{Fe}, \odot})}$. This relation is based on
mass-loss determinations that assume a volume-filling factor of 0.1, but the
prescription can easily be scaled to account for other volume-filling factors.
The residual of the fit is $\sigma = 0.06$ dex. We investigated whether the
relation can also describe the mass loss of hydrogen-free WN stars and showed
that it can when an adjustement of the metallicty dependence ($\log{\dot{M}}
\propto 1.3\log{(Z_{\mathrm{Fe}}/Z_{\mathrm{Fe}, \odot})}$) is applied.
Compared to Nugis & Lamers (2000), $\dot{M}$ is less sensitive to the
luminosity and the surface abundance, implying a stronger mass loss of massive
stars in their late stages of evolution. The modest metallicity dependence
implies that if WC or WO stars are formed in metal deficient environments,
their mass-loss rates are higher than currently anticipated. These effects may
result in a larger number of type Ic supernovae and less black holes to be
formed, and may favour the production of superluminous type Ic supernovae
through interaction with C and O rich circumstellar material or the dense
stellar wind.


title: A selection rule for transitions in PT-symmetric quantum theory

abstract:
  Carl Bender and collaborators have developed a quantum theory governed by
Hamiltonians that are PT-symmetric rather than Hermitian. To implement this
theory, the inner product was redefined to guarantee positive norms of
eigenstates of the Hamiltonian. In the general case, which includes arbitrary
time-dependence in the Hamiltonian, a modification of the Schrodinger equation
is necessary as shown by Gong and Wang to conserve probability. In this paper,
we derive the following selection rule: transitions induced by time dependence
in a PT-symmetric Hamiltonian cannot occur between normalized states of
differing PT-norm. We show three examples of this selection rule in action: two
matrix models and one in the continuum.


title: Skew Closed Structure of Gray-Categories

abstract:
  We define a skew-closed structure for Gray-categories extending the mapping
space construction of the author.


title: Robust Scheduling for Flexible Processing Networks

abstract:
  Modern processing networks often consist of heterogeneous servers with widely
varying capabilities, and process job flows with complex structure and
requirements. A major challenge in designing efficient scheduling policies in
these networks is the lack of reliable estimates of system parameters, and an
attractive approach for addressing this challenge is to design robust policies,
i.e., policies that do not use system parameters such as arrival and/or service
rates for making scheduling decisions. In this paper, we propose a general
framework for the design of robust policies. The main technical novelty is the
use of a stochastic gradient projection method that reacts to queue-length
changes in order to find a balanced allocation of service resources to incoming
tasks. We illustrate our approach on two broad classes of processing systems,
namely the flexible fork-join networks and the flexible queueing networks, and
prove the rate stability of our proposed policies for these networks under
non-restrictive assumptions.


title: Small Sets containing any Pattern

abstract:
  Given any dimension function $h$, we construct a perfect set $E \subseteq
\mathbb{R}$ of zero $h$-Hausdorff measure, that contains any finite polynomial
pattern.
  This is achieved as a special case of a more general construction in which we
have a family of functions $\mathcal{F}$ that satisfy certain conditions and we
construct a perfect set $E$ in $\mathbb{R}^N$, of $h$-Hausdorff measure zero,
such that for any finite set $\{ f_1,\ldots,f_n\}\subseteq \mathcal{F}$, $E$
satisfies that $\bigcap_{i=1}^n f^{-1}_i(E)\neq\emptyset$.
  We also obtain an analogous result for the images of functions. Additionally
we prove some related results for countable (not necessarily finite)
intersections, obtaining, instead of a perfect set, an $\mathcal{F}_{\sigma}$
set without isolated points.


title: The initial value problem as it relates to numerical relativity

abstract:
  Spacetime is foliated by spatial hypersurfaces in the 3+1 split of General
Relativity. The initial value problem then consists of specifying initial data
for all relevant fields on one such a spatial hypersurface. These fields are
the 3-metric and extrinsic curvature together with matter fields such as fluid
velocity, energy density and rest mass density. There is a lot of freedom in
choosing such initial data. This freedom corresponds to the physical state of
the system at the initial time. At the same time the initial data have to
satisfy the Hamiltonian and momentum constraint equations of General Relativity
and can thus not be chosen completely freely. We discuss the conformal
transverse traceless and conformal thin sandwich decompositions that are
commonly used in the construction of constraint satisfying initial data. These
decompositions allow us to specify certain free data that describe the physical
nature of the system. The remaining metric fields are then determined by
solving elliptic equations derived from the constraint equations. We describe
initial data for single black holes and single neutron stars, and how we can
use conformal decompositions to construct initial data for binaries made up of
black holes or neutron stars. Orbiting binaries will emit gravitational
radiation and thus lose energy. Since the emitted radiation tends to
circularize the orbits over time, one can thus expect that the objects in a
typical binary move on almost circular orbits with slowly shrinking radii. This
leads us to the concept of quasi-equilibrium which essentially assumes that
time derivatives are negligible in corotating coordinates, for binaries on
almost circular orbits. We review how quasi-equilibrium assumptions can be used
to make physically well motivated approximations that simplify the elliptic
equations we have to solve.


title: Controlling mechanical properties of a polymeric glass

abstract:
  In this work we use molecular simulations to examine methods of controlling
mechanical properties of polymeric glass materials such as elastic moduli,
mechanical heterogeneity as well as their glass transition temperature. We
study filled and unfilled polymers and examine the effect of particle size,
volume fraction and polymer-particle interactions. We identify a relationship
between mobility and dynamic heterogeneity with elastic moduli and glass
transition temperature.


title: Question Generation from a Knowledge Base with Web Exploration

abstract:
  Question generation from a knowledge base (KB) is the task of generating
questions related to the domain of the input KB. We propose a system for
generating fluent and natural questions from a KB, which significantly reduces
the human effort by leveraging massive web resources. In more detail, a seed
question set is first generated by applying a small number of hand-crafted
templates on the input KB, then more questions are retrieved by iteratively
forming already obtained questions as search queries into a standard search
engine, before finally questions are selected by estimating their fluency and
domain relevance. Evaluated by human graders on 500 random-selected triples
from Freebase, questions generated by our system are judged to be more fluent
than those of \newcite{serban-EtAl:2016:P16-1} by human graders.


title: Lyndon word decompositions and pseudo orbits on q-nary graphs

abstract:
  A foundational result in the theory of Lyndon words (words that are strictly
earlier in lexicographic order than their cyclic permutations) is the
Chen-Fox-Lyndon theorem which states that every word has a unique
non-increasing decomposition into Lyndon words. This article extends this
factorization theorem, obtaining the proportion of these decompositions that
are strictly decreasing. This result is then used to count primitive pseudo
orbits (sets of primitive periodic orbits) on q-nary graphs. As an application
we obtain a diagonal approximation to the variance of the characteristic
polynomial coefficients q-nary quantum graphs.


title: A Continuous Model of Cortical Connectivity

abstract:
  We present a continuous model for structural brain connectivity based on the
Poisson point process. The model treats each streamline curve in a tractography
as an observed event in connectome space, here a product space of cortical
white matter boundaries. We approximate the model parameter via kernel density
estimation. To deal with the heavy computational burden, we develop a fast
parameter estimation method by pre-computing associated Legendre products of
the data, leveraging properties of the spherical heat kernel. We show how our
approach can be used to assess the quality of cortical parcellations with
respect to connectivty. We further present empirical results that suggest the
discrete connectomes derived from our model have substantially higher
test-retest reliability compared to standard methods.


title:
Cocycle deformations and Galois objects for semisimple Hopf algebras of
  dimension $p^3$ and $pq^2$

abstract:
  Let $p$ and $q$ be distinct prime numbers. We study the Galois objects and
cocycle deformations of the noncommutative, noncocommutative, semisimple Hopf
algebras of odd dimension $p^3$ and of dimension $pq^2$. We obtain that the
$p+1$ non-isomorphic self-dual semisimple Hopf algebras of dimension $p^3$
classified by Masuoka have no non-trivial cocycle deformations, extending his
previous results for the 8-dimensional Kac-Paljutkin Hopf algebra. This is done
as a consequence of the classification of categorical Morita equivalence
classes among semisimple Hopf algebras of odd dimension $p^3$, established by
the third-named author in an appendix.


title:
Next-to-leading order corrections to the spin-dependent energy spectrum
  of hadrons from polarized top quark decay in the general two Higgs doublet
  model

abstract:
  In recent years, searches for the light and heavy charged Higgs bosons have
been done by the ATLAS and the CMS collaborations at the Large Hadron Collider
(LHC) in proton-proton collision. Nevertheless, a definitive search is a
program that still has to be carried out at the LHC. The experimental
observation of charged Higgs bosons would indicate physics beyond the Standard
Model. In the present work, we study the scaled-energy distribution of
bottom-flavored mesons ($B$) inclusively produced in polarized top quark decays
into a light charged Higgs boson and a massless bottom quark at next-to-leading
order in the two-Higgs-doublet model; $t(\uparrow)\to bH^+\to BH^++X$. This
spin-dependent energy distribution is studied in a specific helicity coordinate
system where the polarization vector of the top quark is measured with respect
to the direction of the Higgs momentum. The study of these energy distributions
could be considered as a new channel to search for the charged Higgs bosons at
the LHC. For our numerical analysis and phenomenological predictions, we
restrict ourselves to the unexcluded regions of the MSSM $m_{H^+}-\tan\beta$
parameter space determined by the recent results of the CMS \cite{CMS:2014cdp}
and ATLAS \cite{TheATLAScollaboration:2013wia} collaborations.


title:
Finding Small Hitting Sets in Infinite Range Spaces of Bounded
  VC-dimension

abstract:
  We consider the problem of finding a small hitting set in an {\it infinite}
range space $\cF=(Q,\cR)$ of bounded VC-dimension. We show that, under
reasonably general assumptions, the infinite dimensional convex relaxation can
be solved (approximately) efficiently by multiplicative weight updates. As a
consequence, we get an algorithm that finds, for any $\delta>0$, a set of size
$O(s_{\cF}(z^*_\cF))$ that hits $(1-\delta)$-fraction of $\cR$ (with respect to
a given measure) in time proportional to $\log(\frac{1}{\delta})$, where
$s_{\cF}(\frac{1}{\epsilon})$ is the size of the smallest $\epsilon$-net the
range space admits, and $z^*_{\cF}$ is the value of the {\it fractional}
optimal solution. This {\it exponentially} improves upon previous results which
achieve the same approximation guarantees with running time proportional to
$\poly(\frac{1}{\delta})$. Our assumptions hold, for instance, in the case when
the range space represents the {\it visibility} regions of a polygon in
$\RR^2$, giving thus a deterministic polynomial time $O(\log
z^*_{\cF})$-approximation algorithm for guarding $(1-\delta)$-fraction of the
area of any given simple polygon, with running time proportional to
$\polylog(\frac{1}{\delta})$.


title:
Effective temperature and radial velocity of the small-amplitude Cepheid
  Polaris (alpha UMi) in 2015

abstract:
  We present the results of an analysis of 21 spectra of alpha UMi (Polaris)
obtained in September - December 2015. Frequency analysis shows an increase of
the pulsation period up to 8.6 min in comparison to the 2007 observational set.
The radial velocity amplitude comes to 4.16 km s^-1, and it approximately twice
the one found in 2007. The average Teff = 6017 K, and it is close to the value
determined for the 2001-2004 set. Therefore Polaris moves to the red edge of
the Cepheid instability strip (CIS)


title: The Triple Lattice PETs

abstract:
  Polytope exchange transformations (PETs) are higher dimensional
generalizations of interval exchange transformations (IETs) which have been
well-studied for more than 40 years. A general method of constructing PETs
based on multigraphs was described by R. Schwartz in 2013. In this paper, we
describe a one-parameter family of multigraph PETs called the triple lattice
PETs.
  We show that there exists a renormalization scheme of the triple lattice PETs
in the interval $(0,1)$. We analyze the the limit set $\Lambda_\phi$ with
respect to the parameter $\phi=\frac{-1+\sqrt 5}{2}$. By renormalization, we
show that $\Lambda_\phi$ is the limit of embedded polygons in $\mathbb R^2$ and
its Hausdorff dimension satisfies the inequality $1< \dim_H(\Lambda_\phi) =
\log(\sqrt 2-1)/\log(\phi)<2$ so that $\Lambda_\phi$ has Lebesgue measure zero.


title:
Electronic structure of graphene: (nearly) free electrons bands vs.
  tight-binding bands

abstract:
  In our previous paper (Phys. Rev. B {\bf 89}, 165430 (2014)) we have found
that in graphene, in distinction to the four occupied bands, which can be
described by the simple tight-binding model (TBM) with four atomic orbitals per
atom, the two lowest lying at the $\Gamma$-point unoccupied bands (one of them
of a $\sigma$ type and the other of a $\pi$ type) can not be described by such
model. In the present work we suggest a minimalistic model for these two bands,
based on (nearly) free electrons model (FEM), which correctly describes the
symmetry of these bands, their dispersion law and their localization with
respect to the graphene plane.


title: Spectral and thermodynamic properties of the Sachdev-Ye-Kitaev model

abstract:
  We study spectral and thermodynamic properties of the Sachdev-Ye-Kitaev
model, a variant of the $k$-body embedded random ensembles studied for several
decades in the context of nuclear physics and quantum chaos. We show
analytically that the fourth and sixth order energy cumulants vanish in the
limit of large number of particles $N \to \infty$ which is consistent with a
Gaussian spectral density. However, for finite $N$, the tail of the average
spectral density is well approximated by a semi-circle law. The specific heat
coefficient, determined numerically from the low temperature behavior of the
partition function, is consistent with the value obtained by previous
analytical calculations. For energy scales of the order of the mean level
spacing we show that level statistics are well described by random matrix
theory. Due to the underlying Clifford algebra of the model, the universality
class of the spectral correlations depends on $N$. For larger energy
separations we identify an energy scale that grows with $N$, reminiscent of the
Thouless energy in mesoscopic physics, where deviations from random matrix
theory are observed. Our results are a further confirmation that the
Sachdev-Ye-Kitaev model is quantum chaotic for all time scales. According to
recent claims in the literature, this is an expected feature in field theories
with a gravity-dual.


title: Disparity of clustering coefficients in the Holme-Kim network model

abstract:
  The Holme-Kim random graph processes is a variant of the Barabasi-Albert
scale-free graph that was designed to exhibit clustering. In this paper we show
that whether the model does indeed exhibit clustering depends on how we define
the clustering coefficient. In fact, we find that local clustering coefficient
remains typically positive whereas global clustering tends to 0 at a slow rate.
These and other results are proven via martingale techniques, such as
Freedman's concentration inequality combined with a bootstrapping argument.


title: Arrow of Time for Continuous Quantum Measurement

abstract:
  We investigate the statistical arrow of time for a quantum system being
monitored by a sequence of measurements. For a continuous qubit measurement
example, we demonstrate that time-reversed evolution is always physically
possible, provided that the measurement record is also negated. Despite this
restoration of dynamical reversibility, a statistical arrow of time emerges,
and may be quantified by the log-likelihood difference between forward and
backward propagation hypotheses. We then show that such reversibility is a
universal feature of non-projective measurements, with forward or backward
Janus measurement sequences that are time-reversed inverses of each other.


title: Recursive Diffeomorphism-Based Regression for Shape Functions

abstract:
  This paper proposes a recursive diffeomorphism based regression method for
one-dimensional generalized mode decomposition problem that aims at extracting
generalized modes $\alpha_k(t)s_k(2\pi N_k\phi_k(t))$ from their superposition
$\sum_{k=1}^K \alpha_k(t)s_k(2\pi N_k\phi_k(t))$. First, a one-dimensional
synchrosqueezed transform is applied to estimate instantaneous information,
e.g., $\alpha_k(t)$ and $N_k\phi_k(t)$. Second, a novel approach based on
diffeomorphisms and nonparametric regression is proposed to estimate wave shape
functions $s_k(t)$. These two methods lead to a framework for the generalized
mode decomposition problem under a weak well-separation condition. Numerical
examples of synthetic and real data are provided to demonstrate the fruitful
applications of these methods.


title:
Implicitization of tensor product surfaces in the presence of a generic
  set of basepoints

abstract:
  Given a $4$-dimensional vector subspace $U=\{ f_{0},\ldots,f_{3}\}$ of
$H^{0}(\mathbb{P}^1 \times \mathbb{P}^1,\mathcal{O}(a,b))$, a tensor product
surface, denoted by $X_{U}$, is the closure of the image of the rational map
$\lambda_{U}:\mathbb{P}^1 \times \mathbb{P}^1 -\!\to \mathbb{P}^{3}$ determined
by $U$. These surfaces arise in geometric modeling and in this context it is
useful to know the implicit equation of $X_{U}$ in $\mathbb{P}^{3}$. In this
paper we show that if $U\subseteq H^{0}(\mathbb{P}^1 \times
\mathbb{P}^1,\mathcal{O}(a,1))$ has a finite set of $r$ basepoints in generic
position, then the implicit equation of $X_{U}$ is determined by two syzygies
of $I_{U}=\langle f_{0},\ldots,f_{3} \rangle$ in bidegrees $\left(
a-\lceil\frac{r}{2}\rceil,0 \right)$ and $\left( a-\lfloor\frac{r}{2}\rfloor,0
\right)$. This result is proved by understanding the geometry of the basepoints
of $U$ in $\mathbb{P}^1 \times \mathbb{P}^1$. The proof techniques for the main
theorem also apply when $U$ is basepoint free.


title: Wilson loop expectations in $SU(N)$ lattice gauge theory

abstract:
  This article gives a rigorous formulation and proof of the $1/N$ expansion
for Wilson loop expectations in strongly coupled $SU(N)$ lattice gauge theory
in any dimension. The coefficients of the expansion are represented as
absolutely convergent sums over trajectories in a string theory on the lattice,
establishing a kind of gauge-string duality. Moreover, it is shown that in
large $N$ limit, calculations in $SU(N)$ lattice gauge theory with coupling
strength $2\beta$ corresponds to those in $SO(N)$ lattice gauge theory with
coupling strength $\beta$ when $|\beta|$ is sufficiently small.


title: Confronting SUSY models with LHC data via electroweakino production

abstract:
  We investigate multi-lepton signals produced by ElectroWeakino (EWino) decays
in the MSSM and the TMSSM scenarios with sfermions, gluinos and non Standard
Model Higgses at the TeV scale, being the Bino electroweak-scale dark matter.
We recast the present LHC constraints on EWinos for these models and we find
that wide MSSM and TMSSM parameter regions prove to be allowed. We forecast the
number of events expected in the signal regions of the experimental
multi-lepton analyses in the next LHC runs. The correlations among these
numbers will help to determine whether future deviations in multi-lepton data
are ascribable to the EWinos, as well as the supersymmetric model they
originate from.


title: All-optical hyperpolarization of electron and nuclear spins in diamond

abstract:
  Low thermal polarization of nuclear spins is a primary sensitivity limitation
for nuclear magnetic resonance. Here we demonstrate optically pumped
(microwave-free) nuclear spin polarization of $^{13}\mathrm{C}$ and
$^{15}\mathrm{N}$ in $^{15}\mathrm{N}$-doped diamond. $^{15}\mathrm{N}$
polarization enhancements up to $-2000$ above thermal equilibrium are observed
in the paramagnetic system $\mathrm{N_s}^{0}$. Nuclear spin polarization is
shown to diffuse to bulk $^{13}\mathrm{C}$ with NMR enhancements of $-200$ at
room temperature and $-500$ at $\mathrm{240~K}$, enabling a route to
microwave-free high-sensitivity NMR study of biological samples in ambient
conditions.


title:
Effective dynamics of the nonlinear Schr\"odinger equation on large
  domains

abstract:
  We consider the nonlinear Schr\"odinger (NLS) equation posed on the box
$[0,L]^d$ with periodic boundary conditions. The aim is to describe the
long-time dynamics by deriving effective equations for it when $L$ is large and
the characteristic size $\epsilon$ of the data is small. Such questions arise
naturally when studying dispersive equations that are posed on large domains
(like water waves in the ocean), and also in theory of statistical physics of
dispersive waves, that goes by the name of "wave turbulence". Our main result
is deriving a new equation, the continuous resonant (CR) equation, that
describes the effective dynamics for large $L$ and small $\epsilon$ over very
large time-scales. Such time-scales are well beyond the (a) nonlinear
time-scale of the equation, and (b) the Euclidean time-scale at which the
effective dynamics are given by (NLS) on $\mathbb R^d$. The proof relies
heavily on tools from analytic number theory, such as a relatively modern
version of the Hardy-Littlewood circle method, which are modified and extended
to be applicable in a PDE setting.


title: Finite-type Invariants of Long and Framed Virtual Knots

abstract:
  We generalize three invariants, first discovered by A. Henrich, to the long
and/or framed virtual knot case. These invariants are all finite-type
invariants of order one, and include a universal one. The generalization will
require us to extend the notion of a based matrix of a virtual string, first
introduced by V. Turaev and later generalized by Henrich, to the long and
framed cases.


title:
Quantum to classical transition in the ground state of a spin-$S$
  quantum antiferromagnet

abstract:
  We study a frustrated spin-$S$ staggered-dimer Heisenberg model on square
lattice by using the bond-operator representation for quantum spins, and
investigate the emergence of classical magnetic order from the quantum
mechanical (staggered-dimer singlet) ground state for increasing $S$. Using
triplon analysis, we find the critical couplings for this quantum phase
transition to scale as $1/S(S+1)$. We extend the triplon analysis to include
the effect of quintet dimer-states, which proves to be essential for
establishing the classical order (N\'eel or collinear in the present study) for
large $S$, both in the purely Heisenberg case and also in the model with
single-ion anisotropy.


title:
Study of the performance of the NA62 Small-Angle Calorimeter at the
  DA$\Phi$NE Linac

abstract:
  The measurement of $BR(K^+\to\pi^+\nu\bar{\nu})$ with 10% precision by the
NA62 experiment requires extreme background suppression. The Small Angle
Calorimeter aims to provide an efficient veto for photons flying at angles down
to zero with respect to the kaon flight direction. The initial prototype was
upgraded and tested at the Beam Test Facility of the DA$\Phi$NE Linac at
Frascati. The energy resolution and the efficiency were measured and are
presented.


title: Linking structure and activity in nonlinear spiking networks

abstract:
  Recent experimental advances are producing an avalanche of data on both
neural connectivity and neural activity. To take full advantage of these two
emerging datasets we need a framework that links them, revealing how collective
neural activity arises from the structure of neural connectivity and intrinsic
neural dynamics. This problem of {\it structure-driven activity} has drawn
major interest in computational neuroscience. Existing methods for relating
activity and architecture in spiking networks rely on linearizing activity
around a central operating point and thus fail to capture the nonlinear
responses of individual neurons that are the hallmark of neural information
processing. Here, we overcome this limitation and present a new relationship
between connectivity and activity in networks of nonlinear spiking neurons by
developing a diagrammatic fluctuation expansion based on statistical field
theory. We explicitly show how recurrent network structure produces pairwise
and higher-order correlated activity, and how nonlinearities impact the
networks' spiking activity. Our findings open new avenues to investigating how
single-neuron nonlinearities---including those of different cell
types---combine with connectivity to shape population activity and function.


title: Stabilization of the Gear-Grimshaw system with weak damping

abstract:
  The aim of this work is to consider the internal stabilization of a nonlinear
coupled system of two Korteweg--de Vries equations in a finite interval under
the effect of a very weak localized damping. The system was introduced by Gear
and Grimshaw to model the interactions of two-dimensional, long, internal
gravity waves propagation in a stratified fluid. Considering feedback controls
laws and using Compactness--Uniqueness Argument, which reduce the problem to
use a unique continuation property, we establish the exponential stability of
the weak solutions when the exponent in the nonlinear term ranges over the
interval $[1,4)$.


title: Bipyramid Decompositions of Multi-crossing Link Complements

abstract:
  Generalizing previous constructions, we present a dual pair of decompositions
of the complement of a link L into bipyramids, given any multi-crossing
projection of L. When L is hyperbolic, this gives new upper bounds on the
volume of L given its multi-crossing projection. These bounds are realized by
three closely related infinite tiling weaves.


title: R-Linear Convergence of Limited Memory Steepest Descent

abstract:
  The limited memory steepest descent method (LMSD) proposed by Fletcher is an
extension of the Barzilai-Borwein "two-point step size" strategy for steepest
descent methods for solving unconstrained optimization problems. It is known
that the Barzilai-Borwein strategy yields a method with an R-linear rate of
convergence when it is employed to minimize a strongly convex quadratic. This
paper extends this analysis for LMSD, also for strongly convex quadratics. In
particular, it is shown that the method is R-linearly convergent for any choice
of the history length parameter. The results of numerical experiments are
provided to illustrate behaviors of the method that are revealed through the
theoretical analysis.


title: Phase shift in atom interferometry due to spacetime curvature

abstract:
  We present a single-source dual atom interferometer and utilize it as a
gradiometer for precise gravitational measurements. The macroscopic separation
between interfering atomic wave packets (as large as 16 cm) reveals the
interplay of recoil effects and gravitational curvature from a nearby Pb source
mass. The gradiometer baseline is set by the laser wavelength and pulse
timings, which can be measured to high precision. Using a long drift time and
large momentum transfer atom optics, the gradiometer reaches a resolution of $3
\times 10^{-9}$ s$^{-2}$ per shot and measures a 1 rad phase shift induced by
the source mass.


title:
Rigorous cubical approximation and persistent homology of continuous
  functions

abstract:
  The interaction between discrete and continuous mathematics lies at the heart
of many fundamental problems in applied mathematics and computational sciences.
In this paper we discuss the problem of discretizing vector-valued functions
defined on finite-dimensional Euclidean spaces in such a way that the
discretization error is bounded by a pre-specified small constant. While the
approximation scheme has a number of potential applications, we consider its
usefulness in the context of computational homology. More precisely, we
demonstrate that our approximation procedure can be used to rigorously compute
the persistent homology of the original continuous function on a compact
domain, up to small explicitly known and verified errors. In contrast to other
work in this area, our approach requires minimal smoothness assumptions on the
underlying function.


title:
MAC Rate Adaptation and Cross Layer Behavior for Vehicular WiFi Access:
  An Experimental Study

abstract:
  Vehicular WiFi is different from conventional WiFi access. Firstly, as the
connections arise opportunistically, they are short lived and intermittent.
Secondly, at vehicular speeds channel conditions change rapidly. Under these
conditions, the MAC bit rate adaptation plays a critical role to ensure that
devices can maximize throughput performance. The goal of this work is to gain a
deeper understanding of current MAC bit rate adaptation algorithms and their
interaction with higher layer protocols under vehicular settings. Towards this
end, we evaluate the performance of four MAC bit rate adaptation algorithms;
SampleRate, AMRR, Minstrel, and RRAA, and their interactions with transport
layer protocols such as TCP in real world vehicular settings. Our experimental
study reveals that in general these algorithm perform poorly in vehicular
settings, and can have an extremely adverse impact on TCP performance.


title: Cooperation driven by success-driven group formation

abstract:
  In the traditional setup of public goods game all players are involved in
every available groups and the mutual benefit is shared among competing
cooperator and defector strategies. But in real life situations the group
formation of players could be more sophisticated because not all players are
attractive enough for others to participate in a joint venture. What if only
those players can initiate a group formation and establish a game who are
successful enough to the neighbors? To elaborate this idea we employ a modified
protocol and demonstrate that a carefully chosen threshold to establish joint
venture could efficiently improve the cooperation level even if the synergy
factor would suggest a full defector state otherwise. The microscopic mechanism
which is responsible for this effect is based on the asymmetric consequences of
competing strategies: while the success of a cooperator provides a long-time
well-being for the neighborhood, the temporary advantage of defection cannot be
maintained if the protocol is based on the success of leaders.