title: Oscillations in a flexible channel flow of a generalized Newtonian fluid

abstract:
  We study the flow of a generalized Newtonian fluid, characterized by a
power-law model, through a channel consisting of a wall with a flexible
membrane under longitudinal tension. It is assumed that at steady state the
flow through the channel admits a constant flux unidirectional flow profile,
while for the unsteady case, we employ the long wave approximation and use a
set of reduced equations to describe the variation of the shape of the membrane
(assumed to be massless and elastic) and the variation of the fluid-flux. By
means of asymptotic expansion, multiscale analysis and full numerical solutions
of the pertinent governing equations, we show that depending upon the Reynolds
number and the membrane stress, the flow behaviour for a shear-thinning,
shear-thickening and Newtonian fluid may be markedly different, being
oscillatory for one while chaotic for the other. The results presented herein
hold practical relevance for several biologically relevant processes involving
transport of rheologically complex biofluids through flexible domains.


title: PIR schemes with small download complexity and low storage requirements

abstract:
  In the classical model for (information theoretically secure) Private
Information Retrieval (PIR), a user wishes to retrieve one bit of a database
that is stored on a set of $n$ servers, in such a way that no individual server
gains information about which bit the user is interested in. The aim is to
design schemes that minimise communication between the user and the servers.
More recently, there have been moves to consider more realistic models where
the total storage of the set of servers, or the per server storage, should be
minimised (possibly using techniques from distributed storage), and where the
database is divided into $R$-bit records with $R>1$, and the user wishes to
retrieve one record rather than one bit. When $R$ is large, downloads from the
servers to the user dominate the communication complexity and so the aim is to
minimise the total number of downloaded bits. Shah, Rashmi and Ramchandran show
that at least $R+1$ bits must be downloaded from servers in the worst case, and
provide PIR schemes meeting this bound. Sun and Jafar determine the best
asymptotic download cost of a PIR scheme (as $R\rightarrow\infty$), where this
cost is defined as the ratio of the message length $R$ and the total number of
bits downloaded.
  This paper provides various bounds on the download complexity of a PIR
scheme, generalising those of Shah et al. to the case when the number $n$ of
servers is bounded, and providing links with classical techniques due to Chor
et al. The paper also provides a range of constructions for PIR schemes that
are either simpler or perform better than previously known schemes, including
explicit schemes that achieve the best asymptotic download complexity of Sun
and Jafar with significantly lower upload complexity, and general techniques
for constructing a scheme with good worst case download complexity from a
scheme with good download complexity on average.


abstract:
  Entity images could provide significant visual information for knowledge
representation learning. Most conventional methods learn knowledge
representations merely from structured triples, ignoring rich visual
information extracted from entity images. In this paper, we propose a novel
Image-embodied Knowledge Representation Learning model (IKRL), where knowledge
representations are learned with both triple facts and images. More
specifically, we first construct representations for all images of an entity
with a neural image encoder. These image representations are then integrated
into an aggregated image-based representation via an attention-based method. We
evaluate our IKRL models on knowledge graph completion and triple
classification. Experimental results demonstrate that our models outperform all
baselines on both tasks, which indicates the significance of visual information
for knowledge representations and the capability of our models in learning
knowledge representations with images.


title:
Leading Impulse Response Identification via the Weighted Elastic Net
  Criterion

abstract:
  This paper deals with the problem of finding a low-complexity estimate of the
impulse response of a linear time-invariant discrete-time dynamic system from
noise-corrupted input-output data. To this purpose, we introduce an
identification criterion formed by the average (over the input perturbations)
of a standard prediction error cost, plus a weighted l1 regularization term
which promotes sparse solutions. While it is well known that such criteria do
provide solutions with many zeros, a critical issue in our identification
context is where these zeros are located, since sensible low-order models
should be zero in the tail of the impulse response. The flavor of the key
results in this paper is that, under quite standard assumptions (such as i.i.d.
input and noise sequences and system stability), the estimate of the impulse
response resulting from the proposed criterion is indeed identically zero from
a certain time index (named the leading order) onwards, with arbitrarily high
probability, for a sufficiently large data cardinality. Numerical experiments
are reported that support the theoretical results, and comparisons are made
with some other state-of-the-art methodologies.


title: Chiral Shock Waves

abstract:
  We study the shock waves in relativistic chiral matter. We argue that the
conventional Rankine-Hugoinot relations are modified due to the presence of
chiral transport phenomena. We show that the entropy discontinuity in a weak
shock wave is quadratic in the pressure discontinuity when the effect of chiral
transport becomes sufficiently large. We also show that rarefaction shock
waves, which do not exist in usual nonchiral fluids, can appear in chiral
matter. The direction of shock wave propagation in a vorticity is found to be
completely determined by the direction of the vorticity and the chirality of
fermions. These features are exemplified by shock propagation in dense neutrino
matter in the hydrodynamic regime.

categories: hep-th astro-ph.CO cond-mat.mes-hall hep-ph


title:
Exponential moments for numerical approximations of stochastic partial
  differential equations

abstract:
  Stochastic partial differential equations (SPDEs) have become a crucial
ingredient in a number of models from economics and the natural sciences. Many
SPDEs that appear in such applications include non-globally monotone
nonlinearities. Solutions of SPDEs with non-globally monotone nonlinearities
are in nearly all cases not known explicitly. Such SPDEs can thus only be
solved approximatively and it is an important research problem to construct and
analyze discrete numerical approximation schemes which converge with positive
strong convergence rates to the solutions of such infinite dimensional SPDEs.
In the case of finite dimensional stochastic ordinary differential equations
(SODEs) with non-globally monotone nonlinearities it has recently been revealed
that exponential integrability properties of the discrete numerical
approximation scheme are a key instrument to establish positive strong
convergence rates for the considered approximation scheme. To the best of our
knowledge, there exists no result in the scientific literature which proves
exponential integrability properties for a time discrete approximation scheme
in the case of an infinite dimensional SPDE. In this paper we propose a new
class of tamed space-time-noise discrete exponential Euler approximation
schemes that admit exponential integrability properties in the case of infinite
dimensional SPDEs. In particular, we establish exponential moment bounds for
the proposed approximation schemes in the case of stochastic Burgers equations,
stochastic Kuramoto-Sivashinsky equations, and two-dimensional stochastic
Navier-Stokes equations.


title:
Interference Mitigation Using Asynchronous Transmission and Sampling
  Diversity

abstract:
  In this paper, we show that by investigating inherent time delays between
different users in a multiuser scenario, we are able to cancel interference
more efficiently. Time asynchrony provides another tool to cancel interference
which results in preserving other resources like frequency, time and code.
Therefore, we can save the invaluable resource of frequency band and also
increase spectral efficiency. A sampling method is presented which results in
independent noise samples and obviates the need for the complex process of
noise whitening. By taking advantage of this sampling method and its unique
structure, we implement maximum-likelihood sequence detection which outperforms
synchronous maximum-likelihood detection. We also present successive
interference cancellation with hard decision passing which gives rise to a
novel forward-backward belief propagation method. Next, the performance of zero
forcing detection is analyzed. Simulation results are also presented to verify
our analysis.


title: Generating Abstractive Summaries from Meeting Transcripts

abstract:
  Summaries of meetings are very important as they convey the essential content
of discussions in a concise form. Generally, it is time consuming to read and
understand the whole documents. Therefore, summaries play an important role as
the readers are interested in only the important context of discussions. In
this work, we address the task of meeting document summarization. Automatic
summarization systems on meeting conversations developed so far have been
primarily extractive, resulting in unacceptable summaries that are hard to
read. The extracted utterances contain disfluencies that affect the quality of
the extractive summaries. To make summaries much more readable, we propose an
approach to generating abstractive summaries by fusing important content from
several utterances. We first separate meeting transcripts into various topic
segments, and then identify the important utterances in each segment using a
supervised learning approach. The important utterances are then combined
together to generate a one-sentence summary. In the text generation step, the
dependency parses of the utterances in each segment are combined together to
create a directed graph. The most informative and well-formed sub-graph
obtained by integer linear programming (ILP) is selected to generate a
one-sentence summary for each topic segment. The ILP formulation reduces
disfluencies by leveraging grammatical relations that are more prominent in
non-conversational style of text, and therefore generates summaries that is
comparable to human-written abstractive summaries. Experimental results show
that our method can generate more informative summaries than the baselines. In
addition, readability assessments by human judges as well as log-likelihood
estimates obtained from the dependency parser show that our generated summaries
are significantly readable and well-formed.


title:
Multi-document abstractive summarization using ILP based multi-sentence
  compression

abstract:
  Abstractive summarization is an ideal form of summarization since it can
synthesize information from multiple documents to create concise informative
summaries. In this work, we aim at developing an abstractive summarizer. First,
our proposed approach identifies the most important document in the
multi-document set. The sentences in the most important document are aligned to
sentences in other documents to generate clusters of similar sentences. Second,
we generate K-shortest paths from the sentences in each cluster using a
word-graph structure. Finally, we select sentences from the set of shortest
paths generated from all the clusters employing a novel integer linear
programming (ILP) model with the objective of maximizing information content
and readability of the final summary. Our ILP model represents the shortest
paths as binary variables and considers the length of the path, information
score and linguistic quality score in the objective function. Experimental
results on the DUC 2004 and 2005 multi-document summarization datasets show
that our proposed approach outperforms all the baselines and state-of-the-art
extractive summarizers as measured by the ROUGE scores. Our method also
outperforms a recent abstractive summarization technique. In manual evaluation,
our approach also achieves promising results on informativeness and
readability.


title: Abstractive Meeting Summarization UsingDependency Graph Fusion

abstract:
  Automatic summarization techniques on meeting conversations developed so far
have been primarily extractive, resulting in poor summaries. To improve this,
we propose an approach to generate abstractive summaries by fusing important
content from several utterances. Any meeting is generally comprised of several
discussion topic segments. For each topic segment within a meeting
conversation, we aim to generate a one sentence summary from the most important
utterances using an integer linear programming-based sentence fusion approach.
Experimental results show that our method can generate more informative
summaries than the baselines.


title:
Indirect to direct bandgap transition in methylammonium lead halide
  perovskite

abstract:
  Methylammonium lead iodide perovskites are considered direct bandgap
semiconductors. Here we show that in fact they present a weakly indirect
bandgap 60 meV below the direct bandgap transition. This is a consequence of
spin-orbit coupling resulting in Rashba-splitting of the conduction band. The
indirect nature of the bandgap explains the apparent contradiction of strong
absorption and long charge carrier lifetime. Under hydrostatic pressure from
ambient to 325 MPa, Rashba splitting is reduced due to a pressure induced
ordering of the crystal structure. The nature of the bandgap becomes
increasingly more direct, resulting in five times faster charge carrier
recombination, and a doubling of the radiative efficiency. At hydrostatic
pressures above 325 MPa, MAPI undergoes a reversible phase transition resulting
in a purely direct bandgap semiconductor. The pressure-induced changes suggest
epitaxial and synthetic routes to higher efficiency optoelectronic devices.


title: Recommendations for PDF usage in LHC predictions

abstract:
  A short review of the currently available modern parton distribution
functions (PDFs)and the theory predictions obtained using those PDFs for
several benchmark processes at LHC, including Higgs boson production, is
presented in this write-up. It includes the discussion on theory assumptions
made in the determination procedure of PDFs and an impact on the differences in
the obtained predictions, followed by the alternative to PDF4LHC
recommendations for the usage of PDF sets for theory predictions at the LHC.


title:
Simultaneous Intermittent Communication Control and Path Optimization in
  Networks of Mobile Robots

abstract:
  In this paper, we propose an intermittent communication framework for mobile
robot networks. Specifically, we consider robots that move along the edges of a
connected mobility graph and communicate only when they meet at the nodes of
that graph giving rise to a dynamic communication network. Our proposed
distributed controllers ensure intermittent connectivity of the network and
path optimization, simultaneously. We show that the intermittent connectivity
requirement can be encapsulated by a global Linear Temporal Logic (LTL)
formula. Then we approximately decompose it into local LTL expressions which
are then assigned to the robots. To avoid conflicting robot behaviors that can
occur due to this approximate decomposition, we develop a distributed conflict
resolution scheme that generates non-conflicting discrete motion plans for
every robot, based on the assigned local LTL expressions, whose composition
satisfies the global LTL formula. By appropriately introducing delays in the
execution of the generated motion plans we also show that the proposed
controllers can be executed asynchronously.


title: Irradiation induced vacancy creation in single walled carbon nanotubes

abstract:
  Single walled carbon nanotubes of 2 nm diameter and 3 to 13 micro meter
length were compressed in Cu bullets and irradiated with positive ions of Cs
with energies from 0.2 to 2.0 keV and subjected to successively increasing Cs
dose. From the mass spectra of the sputtered carbon atoms and clusters as a
function of Cs energy the monitoring of trend of the relative number densities
of the fragmenting species indicates the accumulating damage. Irradiation
induced fragmentation provide clues to the structural changes as a result of
creation of vacancies due to the sputtering of monatomic, diatomic, triatomic
and higher species. Monitoring of the the irradiated target electrical
conductivity provides information of the sequences of the transformation that
may be occurring in the structures of the single walled carbon nanotube as a
function of Cs energy and dose.


title: Temperature effects in deep-water hydrate foam

abstract:
  This study focuses on heat and mass exchange processes in hydrate foam during
its formation from methane bubbles in gas hydrate stability zone (GHSZ) of the
Lake Baikal and following delivery of it in open container to the lake surface.
The foam was formed as a result of methane bubble collection with a
trap/container. The trap was inverted glass beaker of diameter of 70 mm and 360
mm long. Open bottom end of the beaker used as enter for bubbles ascended from
the lakebed. At a depth of 1400 m all bubbles which fed to the trap were
transformed here into solid hydrate foam. The sensitive thermometer was mounted
in the middle of the trap and recorded the temperature inside trap. The fate of
the bubbles in the trap was recorded by video-camera. During ascend within GHSZ
with velocity of about 0.375 m/s we observed the continuous decrease of the
temperature in the foam up to a level of negative magnitude in a depth interval
of 1400 - 750 meters. Above 750 m temperature decrease was changed by small
growth. However once the trap ascended above top boundary of GHSZ at a depth of
380 m, the temperature fell sharply. Falling to a negative values -0.25 oC, the
temperature sharply stabilized and did not changed further until the trap
reached the surface. The decreasing of the temperature during the ascent is due
to the cooling of gas as a result of the performing of the work against the
forces of hydrostatic pressure. The temperature drop at the boundary of the
GHSZ is due to the absorption of heat by the decomposition of hydrate.


title: Primordial density and BAO reconstruction

abstract:
  We present a new method to reconstruct the primordial (linear) density field
using the estimated nonlinear displacement field. The divergence of the
displacement field gives the reconstructed density field. We solve the
nonlinear displacement field in the 1D cosmology and show the reconstruction
results. The new reconstruction algorithm recovers a lot of linear modes and
reduces the nonlinear damping scale significantly. The successful 1D
reconstruction results imply the new algorithm should also be a promising
technique in the 3D case.


title: Pose-Selective Max Pooling for Measuring Similarity

abstract:
  In this paper, we deal with two challenges for measuring the similarity of
the subject identities in practical video-based face recognition - the
variation of the head pose in uncontrolled environments and the computational
expense of processing videos. Since the frame-wise feature mean is unable to
characterize the pose diversity among frames, we define and preserve the
overall pose diversity and closeness in a video. Then, identity will be the
only source of variation across videos since the pose varies even within a
single video. Instead of simply using all the frames, we select those faces
whose pose point is closest to the centroid of the K-means cluster containing
that pose point. Then, we represent a video as a bag of frame-wise deep face
features while the number of features has been reduced from hundreds to K.
Since the video representation can well represent the identity, now we measure
the subject similarity between two videos as the max correlation among all
possible pairs in the two bags of features. On the official 5,000 video-pairs
of the YouTube Face dataset for face verification, our algorithm achieves a
comparable performance with VGG-face that averages over deep features of all
frames. Other vision tasks can also benefit from the generic idea of employing
geometric cues to improve the descriptiveness of deep features.


title: On percolation critical probabilities and unimodular random graphs

abstract:
  We investigate generalisations of the classical percolation critical
probabilities $p_c$, $p_T$ and the critical probability $\tilde{p_c}$ defined
by Duminil-Copin and Tassion (2015) to bounded degree unimodular random graphs.
We further examine Schramm's conjecture in the case of unimodular random
graphs: does $p_c(G_n)$ converge to $p_c(G)$ if $G_n\to G$ in the local weak
sense? Among our results are the following:
  1. $p_c=\tilde{p_c}$ holds for bounded degree unimodular graphs. However,
there are unimodular graphs with sub-exponential volume growth and $p_T < p_c$;
i.e., the classical sharpness of phase transition does not hold.
  2. We give conditions which imply $\lim p_c(G_n) = p_c(\lim G_n)$.
  3. There are sequences of unimodular graphs such that $G_n\to G$ but
$p_c(G)>\lim p_c(G_n)$ or $p_c(G)<\lim p_c(G_n)<1$.
  As a corollary to our positive results, we show that for any transitive graph
with sub-exponential volume growth there is a sequence $T_n$ of large girth
bi-Lipschitz invariant subgraphs such that $p_c(T_n)\to 1$. It remains open
whether this holds whenever the transitive graph has cost 1.


title:
Adaptation of the Alicki-Fannes-Winter method for the set of states with
  bounded energy and its use

abstract:
  We describe a modification of the Alicki-Fannes-Winter method which allows to
prove uniform continuity on the set of quantum states with bounded energy of
any locally almost affine function having limited growth with increasing
energy.
  Some applications in quantum information theory are considered. The
asymptotic continuity of the relative entropy of entanglement and of its
regularization under the energy constraint on one subsystem is proved.
Channel-independent continuity bounds for the quantum mutual information at the
output of a local channel and for the output Holevo quantity under the input
energy constraint are obtained.


title:
Measurement of $W$ boson angular distributions in events with high
  transverse momentum jets at $\sqrt{s}=$ 8 TeV using the ATLAS detector

abstract:
  The $W$ boson angular distribution in events with high transverse momentum
jets is measured using data collected by the ATLAS experiment from
proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 8 TeV at the
Large Hadron Collider, corresponding to an integrated luminosity of 20.3
fb$^{-1}$. The focus is on the contributions to $W$ + jets processes from real
$W$ emission, which is achieved by studying events where a muon is observed
close to a high transverse momentum jet. At small angular separations, these
contributions are expected to be large. Various theoretical models of this
process are compared to the data in terms of the absolute cross-section and the
angular distributions of the muon from the leptonic $W$ decay.


title:
Optimal boundary control of a nonstandard viscous Cahn-Hilliard system
  with dynamic boundary condition

abstract:
  In this paper, we study an optimal boundary control problem for a model for
phase separation taking place in a spatial domain that was introduced by
Podio-Guidugli in Ric. Mat. 55 (2006), pp. 105-118. The model consists of a
strongly coupled system of nonlinear parabolic differential equations, in which
products between the unknown functions and their time derivatives occur that
are difficult to handle analytically. In contrast to the existing control
literature about this PDE system, we consider here a dynamic boundary condition
involving the Laplace-Beltrami operator for the order parameter of the system,
which models an additional nonconserving phase transition occurring on the
surface of the domain. We show the Fr\'echet differentiability of the
associated control-to-state operator in appropriate Banach spaces and derive
results on the existence of optimal controls and on first-order necessary
optimality conditions in terms of a variational inequality and the adjoint
state system.


title:
Lifetimes and Oscillator Strengths for Ultraviolet Transitions in
  Singly-Ionized Tin

abstract:
  Lifetime measurements using beam foil techniques for the $5s5p^{2}$
$^{2}D_{3/2,5/2}$ levels in Sn II are presented. The resulting oscillator
strengths for transitions at 1699.4, 1831.8 and 1811.2 \AA{} are reported. We
also studied these levels with multi-configuration Dirac Hartree-Fock (MCDHF)
calculations using a development version of the GRASP2K package. Our
experimental and theoretical results are compared with other available studies.


title: Minkowski games

abstract:
  We introduce and study Minkowski games. These are two player games, where the
players take turns to chose positions in $\mathbb{R}^d$ based on some rules.
Variants include boundedness games, where one player wants to keep the
positions bounded, and the other wants to escape to infinity; as well as safety
games, where one player wants to stay within a prescribed set, while the other
wants to leave it.
  We provide some general characterizations of which player can win such games,
and explore the computational complexity of the associated decision problems. A
natural representation of boundedness games yields coNP-completeness, whereas
the safety games are undecidable.


title: Customized Facial Constant Positive Air Pressure (CPAP) Masks

abstract:
  Sleep apnea is a syndrome that is characterized by sudden breathing halts
while sleeping. One of the common treatments involves wearing a mask that
delivers continuous air flow into the nostrils so as to maintain a steady air
pressure. These masks are designed for an average facial model and are often
difficult to adjust due to poor fit to the actual patient. The incompatibility
is characterized by gaps between the mask and the face, which deteriorates the
impermeability of the mask and leads to air leakage. We suggest a fully
automatic approach for designing a personalized nasal mask interface using a
facial depth scan. The interfaces generated by the proposed method accurately
fit the geometry of the scanned face, and are easy to manufacture. The proposed
method utilizes cheap commodity depth sensors and 3D printing technologies to
efficiently design and manufacture customized masks for patients suffering from
sleep apnea.


title: A gap theorem for the complex geometry of convex domains

abstract:
  In this paper we establish a gap theorem for the complex geometry of smoothly
bounded convex domains which informally says that if the complex geometry near
the boundary is close to the complex geometry of the unit ball, then the domain
must be strongly pseudoconvex.
  One consequence of our general result is the following: for any dimension
there exists some $\epsilon > 0$ so that if the squeezing function on a
smoothly bounded convex domain is greater than $1-\epsilon$ outside a compact
set, then the domain is strongly pseudoconvex (and hence the squeezing function
limits to one on the boundary). Another consequence is the following: for any
dimension $d$ there exists some $\epsilon > 0$ so that if the holomorphic
sectional curvature of the Bergman metric on a smoothly bounded convex domain
is within $\epsilon$ of $-4/(d+1)$ outside a compact set, then the domain is
strongly pseudoconvex (and hence the holomorphic sectional curvature limits to
$-4/(d+1)$ on the boundary).


title: Multivariate Garch with dynamic beta

abstract:
  We investigate a solution for the problems related to the application of
multivariate GARCH models to markets with a large number of stocks by
restricting the form of the conditional covariance matrix. The model is a
factor model and uses only six free GARCH parameters. One factor can be
interpreted as the market component, the remaining factors are equal. This
allow the analytical calculation of the inverse covariance matrix. The
time-dependence of the factors enables the determination of dynamical beta
coefficients. We compare the results from our model with the results of other
GARCH models for the daily returns from the S\&P500 market and find that they
are competitive. As applications we use the daily values of beta coefficients
to confirm a transition of the market in 2006. Furthermore we discuss the
relationship of our model with the leverage effect.


title:
The role of pebble fragmentation in planetesimal formation II. Numerical
  simulations

abstract:
  Some scenarios for planetesimal formation go through a phase of collapse of
gravitationally bound clouds of mm-cm-sized pebbles. Such clouds can form for
example through the streaming instability in protoplanetary disks. We model the
collapse process with a statistical model to obtain the internal structure of
planetesimals with solid radii between 10 and 1,000 km. In the collapse,
pebbles collide and, depending on relative speed, collisions have different
outcomes. A mixture of particle sizes inside a planetesimal leads to better
packing capabilities and higher densities. In this paper we apply results from
new laboratory experiments of dust aggregate collisions (presented in a
companion paper) to model collision outcomes. We find that the internal
structure of a planetesimal is strongly dependent on both its mass and the
applied fragmentation model. Low-mass planetesimals have no/few fragmenting
pebble collisions in the collapse phase and end up as porous pebble-piles. The
amount of fragmenting collisions increases with increasing cloud mass,
resulting in wider particle size distributions and higher density. The collapse
is nevertheless "cold" in the sense that collision speeds are damped by the
high collision frequency. This ensures that a significant fraction of large
pebbles survive the collapse in all but the most massive clouds. Our results
are in broad agreement with the observed increase in density of Kuiper belt
objects with increasing size as exemplified by the recent characterization of
the highly porous comet 67P/Churyumov-Gerasimenko.


title: Semantic Tagging with Deep Residual Networks

abstract:
  We propose a novel semantic tagging task, sem-tagging, tailored for the
purpose of multilingual semantic parsing, and present the first tagger using
deep residual networks (ResNets). Our tagger uses both word and character
representations and includes a novel residual bypass architecture. We evaluate
the tagset both intrinsically on the new task of semantic tagging, as well as
on Part-of-Speech (POS) tagging. Our system, consisting of a ResNet and an
auxiliary loss function predicting our semantic tags, significantly outperforms
prior results on English Universal Dependencies POS tagging (95.71% accuracy on
UD v1.2 and 95.67% accuracy on UD v1.3).


title: Scaling Theory for the Frictionless Unjamming Transition

abstract:
  We develop a scaling theory of the unjamming transition of soft frictionless
disks in two dimensions by defining local areas, which can be uniquely assigned
to each contact. These serve to define local order parameters, whose
distribution exhibits divergences as the unjamming transition is approached. We
derive scaling forms for these divergences from a mean-field approach that
treats the local areas as non interacting entities, and demonstrate that these
results agree remarkably well with numerical simulations. We find that the
asymptotic behaviour of the scaling functions arises from the geometrical
structure of the packing while the overall scaling with the compression energy
depends on the force law. We use the scaling forms of the distributions to
determine the scaling of the total grain area $A_G$, and the total number of
contacts $N_C$.


title: On yielding and jointly yielding entries of Euclidean distance matrices

abstract:
  An $n \times n$ matrix D is a Euclidean distance matrix (EDM) if there exist
$p^1, \ldots, p^n$ in some Euclidean space such that $d_{ij} = || p^i -
p^j||^2$ for all $i,j=1,\ldots,n$. Let D be an EDM and let $E^{ij}$ be the $n
\times n$ symmetric matrix with 1's in the $ij$th and $ji$th entries and 0's
elsewhere. We say that $[l_{ij},u_{ij}]$ is the yielding interval of entry
$d_{ij}$ if it holds that $D+t E^{ij}$ is an EDM iff $l_{ij} \leq t \leq
u_{ij}$. If the yielding interval of entry $d_{ij}$ has length 0, i.e., if
$l_{ij}=u_{ij}$, then $d_{ij}$ is said to be unyielding. Otherwise, if $l_{ij}
\neq u_{ij}$, then $d_{ij}$ is said to be yielding. Let $d_{ij}$ and $d_{ik}$
be two unyielding entries of $D$. We say that $d_{ij}$ and $d_{ik}$ are jointly
yielding if $D+t_1 E^{ij} + t_2 E^{ik}$ is an EDM for some nonzero scalars
$t_1$ and $t_2$. In this paper, we characterize the yielding and the jointly
yielding entries of an EDM D in terms of Gale transform of $p^1,\ldots,p^n$.
Moreover, for each yielding entry, we present explicit formulae of its yielding
interval. Finally, we specialize our results to the case where $p^1,\ldots,p^n$
are in general position.


title: Nash Social Welfare, Matrix Permanent, and Stable Polynomials

abstract:
  We study the problem of allocating $m$ items to $n$ agents subject to
maximizing the Nash social welfare (NSW) objective. We write a novel convex
programming relaxation for this problem, and we show that a simple randomized
rounding algorithm gives a $1/e$ approximation factor of the objective.
  Our main technical contribution is an extension of Gurvits's lower bound on
the coefficient of the square-free monomial of a degree $m$-homogeneous stable
polynomial on $m$ variables to all homogeneous polynomials. We use this
extension to analyze the expected welfare of the allocation returned by our
randomized rounding algorithm.


title:
Multiplexing Superconducting Qubit Circuit for Single Microwave Photon
  Generation

abstract:
  We report on a device that integrates eight superconducting transmon qubits
in lambda/4 superconducting coplanar waveguide resonators fed from a common
feedline. Using this multiplexing architecture, each resonator and qubit can be
addressed individually thus reducing the required hardware resources and
allowing their individual characterisation by spectroscopic methods. The
measured device parameters agree with the designed values and the resonators
and qubits exhibit excellent coherence properties and strong coupling, with the
qubit relaxation rate dominated by the Purcell effect when brought in resonance
with the resonator. Our analysis shows that the circuit is suitable for
generation of single microwave photons on demand with an efficiency exceeding
80%.


title: Presentations of generalisations of Thompson's group $V$

abstract:
  We consider generalisations of Thompson's group $V$, denoted by
$V_r(\Sigma)$, which also include the groups of Higman, Stein and Brin. It was
shown by the authors in [20] that under some mild conditions these groups and
centralisers of their finite subgroups are of type $\mathrm{F}_\infty$. Under
more general conditions we show that the groups $V_r(\Sigma)$ are finitely
generated and, under the mild conditions mentioned above, we see that they are
finitely presented and give a recipe to find explicit presentations. For the
centralisers of finite subgroups we find a suitable infinite presentation and
then apply a general procedure to shorten this presentation. In the appendix,
we give a proof of this general shortening procedure.


title: Streaming Communication Protocols

abstract:
  We define the Streaming Communication model that combines the main aspects of
communication complexity and streaming. We consider two agents that want to
compute some function that depends on inputs that are distributed to each
agent. The inputs arrive as data streams and each agent has a bounded memory.
Agents are allowed to communicate with each other and also update their memory
based on the input bit they read and the previous message they received.
  We provide tight tradeoffs between the necessary resources, i.e.
communication and memory, for some of the canonical problems from communication
complexity by proving a strong general lower bound technique. Second, we
analyze the Approximate Matching problem and show that the complexity of this
problem (i.e. the achievable approximation ratio) in the one-way variant of our
model is strictly different both from the streaming complexity and the one-way
communication complexity thereof.


title:
An equivalence between high dimensional Bayes optimal inference and
  M-estimation

abstract:
  When recovering an unknown signal from noisy measurements, the computational
difficulty of performing optimal Bayesian MMSE (minimum mean squared error)
inference often necessitates the use of maximum a posteriori (MAP) inference, a
special case of regularized M-estimation, as a surrogate. However, MAP is
suboptimal in high dimensions, when the number of unknown signal components is
similar to the number of measurements. In this work we demonstrate, when the
signal distribution and the likelihood function associated with the noise are
both log-concave, that optimal MMSE performance is asymptotically achievable
via another M-estimation procedure. This procedure involves minimizing convex
loss and regularizer functions that are nonlinearly smoothed versions of the
widely applied MAP optimization problem. Our findings provide a new heuristic
derivation and interpretation for recent optimal M-estimators found in the
setting of linear measurements and additive noise, and further extend these
results to nonlinear measurements with non-additive noise. We numerically
demonstrate superior performance of our optimal M-estimators relative to MAP.
Overall, at the heart of our work is the revelation of a remarkable equivalence
between two seemingly very different computational problems: namely that of
high dimensional Bayesian integration underlying MMSE inference, and high
dimensional convex optimization underlying M-estimation. In essence we show
that the former difficult integral may be computed by solving the latter,
simpler optimization problem.

categories: stat.ML cond-mat.dis-nn math.ST q-bio.NC stat.TH


title:
Quantized Neural Networks: Training Neural Networks with Low Precision
  Weights and Activations

abstract:
  We introduce a method to train Quantized Neural Networks (QNNs) --- neural
networks with extremely low precision (e.g., 1-bit) weights and activations, at
run-time. At train-time the quantized weights and activations are used for
computing the parameter gradients. During the forward pass, QNNs drastically
reduce memory size and accesses, and replace most arithmetic operations with
bit-wise operations. As a result, power consumption is expected to be
drastically reduced. We trained QNNs over the MNIST, CIFAR-10, SVHN and
ImageNet datasets. The resulting QNNs achieve prediction accuracy comparable to
their 32-bit counterparts. For example, our quantized version of AlexNet with
1-bit weights and 2-bit activations achieves $51\%$ top-1 accuracy. Moreover,
we quantize the parameter gradients to 6-bits as well which enables gradients
computation using only bit-wise operation. Quantized recurrent neural networks
were tested over the Penn Treebank dataset, and achieved comparable accuracy as
their 32-bit counterparts using only 4-bits. Last but not least, we programmed
a binary matrix multiplication GPU kernel with which it is possible to run our
MNIST QNN 7 times faster than with an unoptimized GPU kernel, without suffering
any loss in classification accuracy. The QNN code is available online.


title:
Spectral energy distribution of M-subdwarfs: A study of their
  atmospheric properties

abstract:
  Context. M-type subdwarfs are metal-poor low-mass stars and probe for the old
populations in our Galaxy. Accurate knowledge of their atmospheric parameters
and especially the composition is essential for understanding the chemical
history of our Galaxy. Aims. The purpose of this work is to perform a detailed
study of M-subdwarf spectra covering the full wavelength range from the optical
to the near-infrared. It allows to do a more detailed analysis of the
atmospheric composition in order to determine the stellar parameters, and to
constrain the atmospheric models. The study will allow us to further understand
physical and chemical processes such as increasing condensation of gas into
dust, to point out the missing continuum opacities and see how the main band
features are reproduced by the models. The spectral resolution and the large
wavelength coverage used is a unique combination to constrain the process that
occur in cool atmosphere. Methods. We obtained medium-resolution (R =
5000-7000) spectra over the wavelength range 0.3-2.5 {\mu}m of ten M-type
subdwarfs with X-SHOOTER at VLT. These data constitute an unique atlas of
M-subdwarfs from optical to near-infrared. We performed spectral synthesis
analysis using a full grid of synthetic spectra computed from BT-Settl models
and obtained consistent stellar parameters such as effective temperature,
surface gravity and metallicity. Results. We show that state-of the-art
atmospheric models correctly represent the overall shape of their spectral
energy distribution, as well as atomic and molecular line profiles both in the
optical and near-infrared. We found that the actual fitted gravities of almost
all our sample are consistent with old objects, except for LHS 73 where it is
found surprisingly low.


title:
A Hartree-Fock study of the $\nu=0$ quantum Hall state of monolayer
  graphene with short range interactions

abstract:
  Recent experiments involving tilted graphene samples have shown evidence of a
continuous phase transition in the $\nu=0$ quantum Hall bulk state. We present
here a simple model that supports such a transition. In addition to a long
range SU(4) symmetric Coulomb interaction, we include Hubbard on-site and
nearest neighbor interactions with tunable coupling strengths, and perform a
self-consistent Hartree-Fock analysis. A large sea of negative energy Landau
levels is retained, and is shown to have important qualitative and quantitative
effects. Phase diagrams are constructed within the space of physically relevant
parameters, yielding results consistent with experimental observation.


title: Quantum key distribution by phase flipping of coherent states of light

abstract:
  In this paper we present quantum key distribution protocol that, instead of
single qubits, uses mesoscopic coherent states of light $|\alpha\rangle$ to
encode bit values of a randomly generated key. Given the reference value
$\alpha\in\mathbb C$, and a string of phase rotations each randomly taken from
a set of $2M$ equidistant phases, Alice prepares a quantum state given by a
product of coherent states of light, such that a complex phase of each pulse is
rotated by the corresponding phase rotation. The encoding of $i$-th bit of the
key $r=r_1 \dots r_\ell$ is done by further performing phase rotation $r_i \pi$
(with $r_i = 0,1$) on the $i$-th coherent state pulse. In order to protect the
protocol against the man-in-the-middle attack, we introduce a verification
procedure, and analyse the protocol's security using the Holevo bound. We also
analyse the possibility of beam splitting-like and of collective attacks,
showing the impossibility of the former and, in the case of our protocol, the
inadequacy of the latter. While we cannot prove full perfect security against
the most general attacks allowed by the laws of quantum mechanics, our protocol
achieves faster quantum key distribution, over larger distances and with lower
costs, than the single-photon counterparts, maintaining at least practical
security against the current and the near future technologies.


title:
Termination of Cycle Rewriting by Transformation and Matrix
  Interpretation

abstract:
  We present techniques to prove termination of cycle rewriting, that is,
string rewriting on cycles, which are strings in which the start and end are
connected. Our main technique is to transform cycle rewriting into string
rewriting and then apply state of the art techniques to prove termination of
the string rewrite system. We present three such transformations, and prove for
all of them that they are sound and complete. In this way not only termination
of string rewriting of the transformed system implies termination of the
original cycle rewrite system, a similar conclusion can be drawn for
non-termination. Apart from this transformational approach, we present a
uniform framework of matrix interpretations, covering most of the earlier
approaches to automatically proving termination of cycle rewriting. All our
techniques serve both for proving termination and relative termination. We
present several experiments showing the power of our techniques.


title: Random walks in non homogeneous Poissonian environment

abstract:
  We consider the moving particle process in Rd which is defined in the
following way. There are two independent sequences (Tk) and (dk) of random
variables. The variables Tk are non negative and form an increasing sequence,
while variables dk form an i.i.d sequence with common distribution concentrated
on the unit sphere. The values dk are interpreted as the directions, and Tk as
the moments of change of directions. A particle starts from zero and moves in
the direction d1 up to the moment T1 . It then changes direction to d2 and
moves on within the time interval T2 minus T1 , etc. The speed is constant at
all sites. The position of the particle at time t is denoted by X(t). We
suppose that the points (Tk) form a non homogeneous Poisson point process and
we are interested in the global behavior of the process (X(t)), namely, we are
looking for conditions under which the processes (Y(T,t), T is non negative),
Y(T,t) is X(tT) normalized by B(T), t in (0, 1), weakly converges in C(0, 1) to
some process Y when T tends to infinity. In the second part of the paper the
process X(t) is considered as a Markov chain. We construct diffusion
approximations for this process and investigate their accuracy. The main tool
in this part is the paramertix method.


title:
Incommensurate charge ordered states in the $\mathit{t-t^{\prime}-J}$
  model

abstract:
  We study the incommensurate charge ordered states in the
$\mathit{t-t^{\prime}-J}$ model using the Gutzwiller mean field theory on large
systems. In particular, we explore the properties of incommensurate charge
modulated states referred to as nodal pair density waves (nPDW) in the
literature. nPDW states intertwine site and bond charge order with modulated
$d$-wave pair order, and are characterized by a nonzero amplitude of uniform
pairing; they also manifest a dominant intra-unit cell $d$-density wave form
factor. To compare with a recent scanning tunneling microscopy (STM) study
[Hamidian \textit{et al.}, Nat. Phys. 3519 (2015)] of the cuprate
superconductor BSCCO-2212, we compute the continuum local density of states
(LDOS) at a typical STM tip height using the Wannier function based approach.
By Fourier transforming Cu and O sub-lattice LDOS we also obtain bias-dependent
intra-unit cell form factors and spatial phase difference. We find that in the
nPDW state the behavior of form factors and spatial phase difference as a
function of energy agrees remarkably well with the experiment. This is in
contrast to commensurate charge modulated states, which we show do not agree
with experiment. We propose that the nPDW states are good candidates for the
charge density wave phase observed in the superconducting state of underdoped
cuprates.


title: Mechanisms underlying different onset patterns of focal seizures

abstract:
  Focal seizures are episodes of pathological brain activity that appear to
arise from a localised area of the brain. The onset patterns of focal seizure
activity have been studied intensively, and they have largely been
distinguished into two types - low amplitude fast oscillations (LAF), or high
amplitude spikes (HAS). Here we explore whether these two patterns arise from
fundamentally different mechanisms. Here, we use a previously established
computational model of neocortical tissue, and validate it as an adequate model
using clinical recordings of focal seizures. We then reproduce the two onset
patterns in their most defining properties and investigate the possible
mechanisms underlying the different focal seizure onset patterns in the model.
We show that the two patterns are associated with different mechanisms at the
spatial scale of a single ECoG electrode. The LAF onset is initiated by
independent patches of localised activity, which slowly invade the surrounding
tissue and coalesce over time. In contrast, the HAS onset is a global, systemic
transition to a coexisting seizure state triggered by a local event. We find
that such a global transition is enabled by an increase in the excitability of
the "healthy" surrounding tissue, which by itself does not generate seizures,
but can support seizure activity when incited. In our simulations, the
difference in surrounding tissue excitability also offers a simple explanation
of the clinically reported difference in surgical outcomes. Finally, we
demonstrate in the model how changes in tissue excitability could be
elucidated, in principle, using active stimulation. Taken together, our
modelling results suggest that the excitability of the tissue surrounding the
seizure core may play a determining role in the seizure onset pattern, as well
as in the surgical outcome.


title: Origin of chaos in 3-d Bohmian trajectories

abstract:
  We study the 3-d Bohmian trajectories of a quantum system of three harmonic
oscillators. We focus on the mechanism responsible for the generation of
chaotic trajectories. We demonstrate the existence of a 3-d analogue of the
mechanism found in earlier studies of 2-d systems, based on moving 2-d `nodal
point - X-point complexes'. In the 3-d case, we observe a foliation of nodal
point - X-point complexes, forming a `3-d structure of nodal and X-points'.
Chaos is generated when the Bohmian trajectories are scattered at one or more
close encounters with such a structure.


title: PIR Array Codes with Optimal PIR Rates

abstract:
  There has been much recent interest in Private information Retrieval (PIR) in
models where a database is stored across several servers using coding
techniques from distributed storage, rather than being simply replicated. In
particular, a recent breakthrough result of Fazelli, Vardy and Yaakobi
introduces the notion of a PIR code and a PIR array code, and uses this notion
to produce efficient protocols.
  In this paper we are interested in designing PIR array codes. We consider the
case when we have $m$ servers, with each server storing a fraction
$(1/\omegaR)$ of the bits of the database; here $\omegaR$ is a fixed rational
number with $\omegaR > 1$. We study the maximum PIR rate of a PIR array code
with the $k$-PIR property (which enables a $k$-server PIR protocol to be
emulated on the $m$ servers), where the PIR rate is defined to be $k/m$. We
present upper bounds on the achievable rate, some constructions, and ideas how
to obtain PIR array codes with the highest possible PIR rate. In particular, we
present constructions that asymptotically meet our upper bounds, and the exact
largest PIR rate is obtained when $1 < \omegaR \leq 2$.


title:
Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein
  condensate

abstract:
  Dynamics of vortex clusters is essential for understanding diverse superfluid
phenomena. In this paper, we examine the dynamics of vortex quadrupoles in a
trapped two-dimensional (2D) Bose-Einstein condensate. We find that the
movement of these vortex-clusters fall into three distinct regimes which are
fully described by the radial positions of the vortices in a 2D isotropic
harmonic trap, or by the major radius (minor radius) of the elliptical
equipotential lines decided by the vortex positions in a 2D anisotropic
harmonic trap. In the "recombination" and "exchange" regimes the quadrupole
structure maintains, while the vortices annihilate each other permanently in
the "annihilation" regime. We find that the mechanism of the charge flipping in
the "exchange" regime and the disappearance of the quadrupole structure in the
"annihilation" regime are both through an intermediate state where two vortex
dipoles connected through a soliton ring. We give the parameter ranges for
these three regimes in coordinate space for a specific initial configuration
and phase diagram of the vortex positions with respect to the Thomas-Fermi
radius of the condensate. We show that the results are also applicable to
systems with quantum fluctuations for the short-time evolution.


title: The Many-Body Expansion Combined with Neural Networks

abstract:
  Fragmentation methods such as the many-body expansion (MBE) are a common
strategy to model large systems by partitioning energies into a hierarchy of
decreasingly significant contributions. The number of fragments required for
chemical accuracy is still prohibitively expensive for ab-initio MBE to compete
with force field approximations for applications beyond single-point energies.
Alongside the MBE, empirical models of ab-initio potential energy surfaces have
improved, especially non-linear models based on neural networks (NN) which can
reproduce ab-initio potential energy surfaces rapidly and accurately. Although
they are fast, NNs suffer from their own curse of dimensionality; they must be
trained on a representative sample of chemical space. In this paper we examine
the synergy of the MBE and NN's, and explore their complementarity. The MBE
offers a systematic way to treat systems of arbitrary size and intelligently
sample chemical space. NN's reduce, by a factor in excess of $10^6$ the
computational overhead of the MBE and reproduce the accuracy of ab-initio
calculations without specialized force fields. We show they are remarkably
general, providing comparable accuracy with drastically different chemical
embeddings. To assess this we test a new chemical embedding which can be
inverted to predict molecules with desired properties.


title:
Unattainability of Carnot efficiency in thermal motors: Coarse-graining
  and entropy production of Feynman-Smoluchowski ratchet

abstract:
  We revisit and analyze the thermodynamic efficiency of the
Feynman-Smoluchowski (FS) ratchet, a classical thought experiment describing an
autonomous heat-work converter. Starting from the full kinetics of the FS
ratchet and deriving the exact forms of the hidden dissipations resulting from
coarse-graining, we restate the historical controversy over its thermodynamic
efficiency. The existence of hidden entropy productions implies that the
standard framework of stochastic thermodynamics applied to the coarse-grained
descriptions fails in capturing the dissipative feature of the system. In
response to this problem, we explore an extended framework of stochastic
thermodynamics to reconstruct the hidden entropy production from the
coarse-grained dynamics. The approach serves as a key example of how we can
systematically address the problem of thermodynamic efficiency in a
multi-variable fluctuating non-equilibrium system.


title: Regularization by noise for stochastic Hamilton-Jacobi equations

abstract:
  We study regularizing effects of nonlinear stochastic perturbations for fully
nonlinear PDE. More precisely, path-by-path $L^{\infty}$ bounds for the second
derivative of solutions to such PDE are shown. These bounds are expressed as
solutions to reflected SDE and are shown to be optimal.


title:
Knowledge Representation via Joint Learning of Sequential Text and
  Knowledge Graphs

abstract:
  Textual information is considered as significant supplement to knowledge
representation learning (KRL). There are two main challenges for constructing
knowledge representations from plain texts: (1) How to take full advantages of
sequential contexts of entities in plain texts for KRL. (2) How to dynamically
select those informative sentences of the corresponding entities for KRL. In
this paper, we propose the Sequential Text-embodied Knowledge Representation
Learning to build knowledge representations from multiple sentences. Given each
reference sentence of an entity, we first utilize recurrent neural network with
pooling or long short-term memory network to encode the semantic information of
the sentence with respect to the entity. Then we further design an attention
model to measure the informativeness of each sentence, and build text-based
representations of entities. We evaluate our method on two tasks, including
triple classification and link prediction. Experimental results demonstrate
that our method outperforms other baselines on both tasks, which indicates that
our method is capable of selecting informative sentences and encoding the
textual information well into knowledge representations.


title: Rational approximations of the exponential function at rational points

abstract:
  We give explicit and asymptotic lower bounds for the quantity $|e^{s/t}-M/N|$
by studying a generalized continued fraction expansion of $e^{s/t}$. In cases
$|s|\geq 3$ we improve existing results by extracting a large common factor
from the numerators and the denominators of the convergents of that generalized
continued fraction.


title: Suppressing spin relaxation in silicon

abstract:
  Uniaxial compressive strain along the [001] direction strongly suppresses the
spin relaxation in silicon. When the strain level is large enough so that
electrons are redistributed only in the two valleys along the strain axis, the
dominant scattering mechanisms are quenched and electrons mainly experience
intra-axis scattering processes (intravalley or intervalley scattering within
valleys on the same crystal axis). We first derive the spin-flip matrix
elements due to intra-axis electron scattering off impurities, and then provide
a comprehensive model of the spin relaxation time due to all possible
interactions of conduction-band electrons with impurities and phonons. We
predict nearly three orders of magnitude improvement in the spin relaxation
time of $\sim10^{19}\text{cm}^{-3}$ antimony-doped silicon (Si:Sb) at low
temperatures.


title:
Non-abelian $Z$-theory: Berends-Giele recursion for the
  $\alpha'$-expansion of disk integrals

abstract:
  We present a recursive method to calculate the $\alpha'$-expansion of disk
integrals arising in tree-level scattering of open strings which resembles the
approach of Berends and Giele to gluon amplitudes. Following an earlier
interpretation of disk integrals as doubly partial amplitudes of an effective
theory of scalars dubbed as $Z$-theory, we pinpoint the equation of motion of
$Z$-theory from the Berends-Giele recursion for its tree amplitudes. A computer
implementation of this method including explicit results for the recursion up
to order $\alpha'^7$ is made available on the website
http://repo.or.cz/BGap.git


title: A gap for PPT entanglement

abstract:
  Let $W$ be a finite dimensional vector space over a field with characteristic
not equal to 2. Denote by $\text{Sym}(V)$ and $\text{Skew-Sym}(V)$ the
subspaces of symmetric and skew-symmetric tensors of a subspace $V$ of
$W\otimes W$, respectively. In this paper we show that if $V$ is generated by
tensors with tensor rank 1, $V=\text{Sym}(V)\oplus\text{Skew-Sym}(V)$ and $W$
is the smallest vector space such that $V\subset W\otimes W$ then
$\dim(\text{Sym}(V))\geq\max\{\frac{2\dim(\text{Skew-Sym}(V))}{\dim(W)},
\frac{\dim(W)}{2}\}$.
  This result has a straightforward application to the separability problem in
Quantum Information Theory: If $\rho\in M_k\otimes M_k\simeq M_{k^2}$ is
separable then $\text{rank}(Id+F)\rho(Id+F)\geq\text{max}\{
\frac{2}{r}\text{rank}(Id-F)\rho(Id-F), \frac{r}{2}\},$ where $F\in M_k\otimes
M_k$ is the flip operator, $Id\in M_k\otimes M_k$ is the identity and $r$ is
the marginal rank of $\rho+F\rho F$. We prove the sharpness of this inequality.
  Moreover, we show that if $\rho\in M_k\otimes M_k$ is positive under partial
transposition (PPT) and $\text{rank }(Id+F)\rho(Id+F)=1$ then $\rho$ is
separable. This result follows from Perron-Frobenius theory. We also present a
large family of PPT matrices satisfying $\text{rank}(Id+F)\rho(Id+F)\geq r\geq
\frac{2}{r-1} \text{rank}(Id-F)\rho(Id-F)$.
  There is a possibility that an entangled PPT matrix $\rho\in M_k\otimes M_k$
satisfying $1<\text{rank}(Id+F)\rho (Id+F)<\frac{2}{r} \text{rank}(Id-F)\rho
(Id-F)$ exists. However, the family referenced above shows that finding one
shall not be trivial.


title:
Mechanism of unconfined dust explosions: turbulent clustering and
  radiation-induced ignition

abstract:
  It is known that unconfined dust explosions typically starts off with a
relatively weak primary flame followed by a severe secondary explosion. We show
that clustering of dust particles in a temperature stratified turbulent flow
ahead of the primary flame may give rise to a significant increase in the
radiation penetration length. These particle clusters, even far ahead of the
flame, are sufficiently exposed and heated by the radiation from the flame to
become ignition kernels capable to ignite a large volume of fuel-air mixtures.
This efficiently increases the total flame surface area and the effective
combustion speed, defined as the rate of reactant consumption of a given
volume. We show that this mechanism explains the high rate of combustion and
overpressures required to account for the observed level of damage in
unconfined dust explosions, e.g., at the 2005 Buncefield vapor-cloud explosion.
The effect of the strong increase of radiation transparency due to turbulent
clustering of particles goes beyond the state-of-the-art of the application to
dust explosions and has many implications in atmospheric physics and
astrophysics.


title: Implication of Sterile Fermions in Particle Physics and Cosmology

abstract:
  The neutrino mass generation mechanism, the nature of dark matter and the
origin of the baryon asymmetry of the Universe are three compelling questions
that cannot be accounted for in the Standard Model of particle physics. In this
thesis we focus on all these issues by providing a possible solution in terms
of a minimal extension of the Standard Model, consisting in the addition of a
set of sterile fermions to the field content of the theory. Sterile fermions
are gauge singlet fields, that can interact via mixing with the active
neutrinos. We focus on the Inverse Seesaw mechanism, which is characterised by
a low (TeV or lower) new physics scale and that can be tested in current and
future experimental facilities. We present the model building analysis that
points towards the minimal realisations of the mechanism, and the
phenomenological study in order to accommodate light neutrino masses and to
impose all the relevant experimental constraints in the model, as well as the
expected experimental signatures. We show the viability of the sterile neutrino
hypothesis as dark matter component, together with the characteristic features
of this scenario in the minimal Inverse Seesaw mechanism. The possibility of
successfully accounting for the baryon asymmetry in a testable realisation of
the leptogenesis mechanism is also addressed. On the other hand it is important
to look for manifestations of sterile fermions in laboratory experiments. We
address this point by making predictions for the expected rates of rare lepton
number violating decays of vector bosons, that can be mediated by sterile
fermions, as well as by studying the impact of sterile fermions on global fit
of electroweak precision data.


title:
Large Margin Nearest Neighbor Classification using Curved Mahalanobis
  Distances

abstract:
  We consider the supervised classification problem of machine learning in
Cayley-Klein projective geometries: We show how to learn a curved Mahalanobis
metric distance corresponding to either the hyperbolic geometry or the elliptic
geometry using the Large Margin Nearest Neighbor (LMNN) framework. We report on
our experimental results, and further consider the case of learning a mixed
curved Mahalanobis distance. Besides, we show that the Cayley-Klein Voronoi
diagrams are affine, and can be built from an equivalent (clipped) power
diagrams, and that Cayley-Klein balls have Mahalanobis shapes with displaced
centers.


abstract:
  In this work, we adapt Sinkhorn-Knopp theorem for rectangular positive maps
$(T:M_k\rightarrow M_m)$. We extend their concepts of support and total support
to these maps. We show that a positive map $T:M_k\rightarrow M_m$ is equivalent
to a doubly stochastic map if and only if $T:M_k\rightarrow M_m$ is equivalent
to a positive map with total support.
  Moreover, if $k$ and $m$ are coprime then $T:M_k\rightarrow M_m$ is
equivalent to a doubly stochastic map if and only if $T:M_k\rightarrow M_m$ has
support.
  This result provides a necessary and sufficient condition for the filter
normal form, which is commonly used in Quantum Information Theory in order to
simplify the task of detecting entanglement. Let $A=\sum_{i=1}^nA_i\otimes
B_i\in M_k\otimes M_m$ be a state and $G_A: M_k\rightarrow M_m$ be the positive
map $G_A(X)=\sum_{i=1}^nB_itr(A_iX)$. We show that $A$ can be put in the filter
normal form if and only if $G_A: M_k\rightarrow M_m$ is equivalent to a
positive map with total support. We prove that any state $A\in M_k\otimes
M_m\simeq M_{km}$ such that $\dim(\ker(A))<k-1$, if $k=m$, and
$\dim(\ker(A))<\min\{k,m\}$, if $k\neq m$, can be put in the filter normal
form.
  Recently, a connection between the capacity of a rectangular positive map
$T:M_k\rightarrow M_m$ and the capacity of a certain square positive map
$\widetilde{T}:M_{mk}\rightarrow M_{mk}$ was noticed. Here, we obtain a deeper
connection between these maps. As a corollary of our main results, we prove
that $T:M_k\rightarrow M_m$ is equivalent to a doubly stochastic map if and
only if $\widetilde{T}:M_{mk}\rightarrow M_{mk}$ is equivalent to a doubly
stochastic map.


title: Directed Polymers and Interfaces in Disordered Media

abstract:
  We consider field theory formulation for directed polymers and interfaces in
the presence of quenched disorder. We write a series representation for the
averaged free energy, where all the integer moments of the partition function
of the model contribute. The structure of field space is analysed for polymers
and interfaces at finite temperature using the saddle-point equations derived
from each integer moments of the partition function. For the case of an
interface we obtain the wandering exponent $\xi= (4-d)/2$, also obtained by the
conventional replica method for the replica symmetric scenario.


title: Local well-posedness of the contact line problem in 2-D Stokes flow

abstract:
  We consider the evolution of contact lines for viscous fluids in a
two-dimensional open-top vessel. The domain is bounded above by a free moving
boundary and otherwise by the solid wall of a vessel. The dynamics of the fluid
are governed by the incompressible Stokes equations under the influence of
gravity, and the interface between fluid and air is under the effect of
capillary forces. Here we develop a local well-posedness theory of the problem
in the framework of nonlinear energy methods. We utilize several techniques,
including: energy estimates of a geometric formulation of the Stokes equations,
a Galerkin method with a time-dependent basis for an $\epsilon$--perturbed
linear Stokes problem in moving domains, the contraction mapping principle for
the $\epsilon$--perturbed nonlinear full contact line problem, and a continuity
argument for uniform energy estimates.


title: A Randomized Tensor Singular Value Decomposition based on the t-product

abstract:
  The tensor Singular Value Decomposition (t-SVD) for third order tensors that
was proposed by Kilmer and Martin~\cite{2011kilmer} has been applied
successfully in many fields, such as computed tomography, facial recognition,
and video completion. In this paper, we propose a method that extends a
well-known randomized matrix method to the t-SVD. This method can produce a
factorization with similar properties to the t-SVD, but is more computationally
efficient on very large datasets. We present details of the algorithm,
theoretical results, and provide numerical results that show the promise of our
approach for compressing and analyzing datasets. We also present an improved
analysis of the randomized subspace iteration for matrices, which may be of
independent interest to the scientific community.


title: (Bandit) Convex Optimization with Biased Noisy Gradient Oracles

abstract:
  Algorithms for bandit convex optimization and online learning often rely on
constructing noisy gradient estimates, which are then used in appropriately
adjusted first-order algorithms, replacing actual gradients. Depending on the
properties of the function to be optimized and the nature of ``noise'' in the
bandit feedback, the bias and variance of gradient estimates exhibit various
tradeoffs. In this paper we propose a novel framework that replaces the
specific gradient estimation methods with an abstract oracle. With the help of
the new framework we unify previous works, reproducing their results in a clean
and concise fashion, while, perhaps more importantly, the framework also allows
us to formally show that to achieve the optimal root-$n$ rate either the
algorithms that use existing gradient estimators, or the proof techniques used
to analyze them have to go beyond what exists today.


title:
Learning Modular Neural Network Policies for Multi-Task and Multi-Robot
  Transfer

abstract:
  Reinforcement learning (RL) can automate a wide variety of robotic skills,
but learning each new skill requires considerable real-world data collection
and manual representation engineering to design policy classes or features.
Using deep reinforcement learning to train general purpose neural network
policies alleviates some of the burden of manual representation engineering by
using expressive policy classes, but exacerbates the challenge of data
collection, since such methods tend to be less efficient than RL with
low-dimensional, hand-designed representations. Transfer learning can mitigate
this problem by enabling us to transfer information from one skill to another
and even from one robot to another. We show that neural network policies can be
decomposed into "task-specific" and "robot-specific" modules, where the
task-specific modules are shared across robots, and the robot-specific modules
are shared across all tasks on that robot. This allows for sharing task
information, such as perception, between robots and sharing robot information,
such as dynamics and kinematics, between tasks. We exploit this decomposition
to train mix-and-match modules that can solve new robot-task combinations that
were not seen during training. Using a novel neural network architecture, we
demonstrate the effectiveness of our transfer method for enabling zero-shot
generalization with a variety of robots and tasks in simulation for both visual
and non-visual tasks.


title:
First measurement of surface nuclear recoil background for argon dark
  matter searches

abstract:
  One major background in direct searches for weakly interacting massive
particles (WIMPs) comes from the deposition of radon progeny on detector
surfaces. The most dangerous surface background is the $^{206}$Pb recoils
produced by $^{210}$Po decays. In this letter, we report the first
characterization of this background in liquid argon. The scintillation signal
of low energy Pb recoils is measured to be highly quenched in argon, and we
estimate that the 103keV $^{206}$Pb recoil background will produce a signal
equal to that of a ~5keV (30keV) electron recoil ($^{40}$Ar recoil). In
addition, we demonstrate that this dangerous $^{210}$Po surface background can
be suppressed by a factor of ~100 or higher using pulse shape discrimination
methods, which can make argon dark matter detectors near background-free and
enhance their potential for discovery of medium- and high-mass WIMPs. We also
discuss the impact on other low background experiments.


title: Skeletons of stable maps II: Superabundant geometries

abstract:
  We implement new techniques involving Artin fans to study the realizability
of tropical stable maps in superabundant combinatorial types. Our approach is
to understand the skeleton of a fundamental object in logarithmic
Gromov--Witten theory -- the stack of prestable maps to the Artin fan. This is
used to examine the structure of the locus of realizable tropical curves and
derive 3 principal consequences. First, we prove a realizability theorem for
limits of families of tropical stable maps. Second, we extend the sufficiency
of Speyer's well-spacedness condition to the case of curves with good
reduction. Finally, we demonstrate the existence of liftable genus 1
superabundant tropical curves that violate the well-spacedness condition.


title:
Identification of an inclusion in Multifrequency Electric Impedance
  Tomography

abstract:
  The multifrequency electrical impedance tomography is considered in order to
image a conductivity inclusion inside a homogeneous background medium by
injecting one current. An original spectral decomposition of the solution of
the forward conductivity problem is used to retrieve the Cauchy data
corresponding to the extreme case of perfect conductor. Using results based on
the unique continuation we then prove the uniqueness of multifrequency
electrical impedance tomography and obtain rigorous stability estimates. Our
results in this paper are quite surprising in inverse conductivity problem
since in general infinitely many input currents are needed in order to obtain
the uniqueness in the determination of the conductivity.


title:
A fast algorithm for Earth Mover's Distance based on optimal transport
  and L1 type Regularization

abstract:
  We propose a new algorithm to approximate the Earth Mover's distance (EMD).
Our main idea is motivated by the theory of optimal transport, in which EMD can
be reformulated as a familiar $L_1$ type minimization. We use a regularization
which gives us a unique solution for this $L_1$ type problem. The new
regularized minimization is very similar to problems which have been solved in
the fields of compressed sensing and image processing, where several fast
methods are available. In this paper, we adopt a primal-dual algorithm designed
there, which uses very simple updates at each iteration and is shown to
converge very rapidly. Several numerical examples are provided.


title: Neural Photo Editing with Introspective Adversarial Networks

abstract:
  The increasingly photorealistic sample quality of generative image models
suggests their feasibility in applications beyond image generation. We present
the Neural Photo Editor, an interface that leverages the power of generative
neural networks to make large, semantically coherent changes to existing
images. To tackle the challenge of achieving accurate reconstructions without
loss of feature quality, we introduce the Introspective Adversarial Network, a
novel hybridization of the VAE and GAN. Our model efficiently captures
long-range dependencies through use of a computational block based on
weight-shared dilated convolutions, and improves generalization performance
with Orthogonal Regularization, a novel weight regularization method. We
validate our contributions on CelebA, SVHN, and CIFAR-100, and produce samples
and reconstructions with high visual fidelity.


title:
Effect of Non Unitarity on Neutrino Mass Hierarchy determination at
  DUNE, NO$\nu$A and T2K

abstract:
  The neutrino mass ordering is one of the principal unknowns in the neutrino
sector. Long baseline neutrino experiments have the potential of resolving this
issue as they are sensitive to large matter effects. The superbeam experiment
DUNE is one of the most promising candidates to study the neutrino mass
hierarchy, along with NO$\nu$A and T2K. But in the presence of non unitarity of
the leptonic mixing matrix, the capability of such experiments to discriminate
between the two hierarchies gets suppressed. The mass hierarchy sensitivity of
DUNE decreases in the presence of new physics. In this paper we analyze the
origin and extent of this loss of sensitivity at the level of oscillation
probabilities, events, mass hierarchy sensitivity and the discovery reach of
DUNE, NO$\nu$A and T2K.


title: Symmetries of Massive and Massless Neutrinos

abstract:
  Wigner's little groups are subgroups of the Lorentz group dictating the
internal space-time symmetries of massive and massless particles. These little
groups are like O(3) and E(2) for massive and massless particles respectively.
While the geometry of the O(3) symmetry is familiar to us, the geometry of the
flat plane cannot explain the E(2)-like symmetry for massless particles.
However, the geometry of a circular cylinder can explain the symmetry with the
helicity and gauge degrees of freedom. It is shown further that the symmetry of
the massless particle can be obtained as a zero-mass limit of O(3)-like
symmetry for massive particles. It is shown further that the polarization of
massless neutrinos is a consequence of gauge invariance, while the symmetry of
massive neutrinos is still like O(3).


title:
Scale-invariant puddles in Graphene: Geometric properties of
  electron-hole distribution at the Dirac point

abstract:
  We characterize the carrier density profile of the ground state of graphene
in the presence of particle-particle interaction and random charged impurity
for zero gate voltage. We provide detailed analysis on the resulting spatially
inhomogeneous electron gas taking into account the particle-particle
interaction and the remote coulomb disorder on an equal footing within the
Thomas-Fermi-Dirac theory. We present some general features of the carrier
density probability measure of the graphene sheet. We also show that, when
viewed as a random surface, the resulting electron-hole puddles at zero
chemical potential show peculiar self-similar statistical properties. Although
the disorder potential is chosen to be Gaussian, we show that the charge field
is non-Gaussian with unusual Kondev relations which can be regarded as a new
class of two-dimensional (2D) random-field surfaces.


title:
Non-linear transport in an out-of-equilibrium single-site Bose Hubbard
  model: scaling, rectification and time dynamics

abstract:
  Recent experiments in hybrid-quantum systems facilitate the potential
realization of one of the most fundamental interacting Hamiltonian-Reservoir
system, namely, the single-site Bose-Hubbard model coupled to two reservoirs at
different temperatures. Using Redfield equations in Born-Markov approximation,
we compute non-equilibrium average particle number, energy and currents beyond
linear response regime, both time-dynamics and steady state and investigate its
dependence on various tunable parameters analytically. We find interesting
scaling laws in high temperature regimes that are independent of choice of bath
spectral functions. We also demonstrate that the system shows very interesting
particle and energy current rectification properties which can be controlled
via the relative strength of interaction and temperatures, as well as via the
degree of asymmetry in system-bath coupling. Specifically, we find inversion of
direction of thermal rectification as a function of the relative strength of
the interaction strength and the temperatures. We also show that, in the limit
of low-temperature and high interaction strength our results are consistent
with the non-equilibrium spin-Boson model. Our results are experimentally
relevant not only to hybrid quantum systems, but also in other areas such as
molecular junctions.


title:
Resonant enhancement of thermoelectric properties by correlated hopping
  for the Falicov-Kimball model on Bethe lattice

abstract:
  The effect of correlated hopping on the charge and heat transport of strongly
correlated particles is studied for the Falicov-Kimball model on the Bethe
lattice. Exact solutions for the one particle density of states (DOS) and two
particle transport function (the "quasiparticle" scattering time) are derived
using dynamical mean field theory. For a wide range of the correlated hopping,
the transport function exhibits singularities due to the resonant two-particle
contribution, whereas the one particle DOS does not show any anomalous
features. By tuning the number of itinerant electrons, so as to bring the Fermi
level close to the resonant frequency, we get a large increase of the
electrical and thermal conductivities, and the thermoelectric power. When the
hopping amplitude between the occupied sites is reduced sufficiently, the
itinerant electrons localize in the clusters of sites occupied by $f$
electrons. This gives rise to an additional narrow band in the DOS between the
lower and upper Hubbard bands, but has only a minor effect on the
thermoelectric properties.


title: Angular Momentum Distribution in the Transverse Plane

abstract:
  Several possibilities to relate the $t$-dependence of Generalized Parton
Distributions (GPDs) to the distribution of angular momentum in the transverse
plane are discussed. Using a simple spectator model we demonstrate that non of
them correctly describes the orbital angular momentum distribution that for a
longitudinally polarized nucleon obtained directly from light-front
wavefunctions.


title:
Hyperbolicity and near hyperbolicity of quadratic forms over function
  fields of quadrics

abstract:
  Let $p$ and $q$ be anisotropic quadratic forms over a field $F$ of
characteristic $\neq 2$, let $s$ be the unique non-negative integer such that
$2^s < \mathrm{dim}(p) \leq 2^{s+1}$, and let $k$ denote the dimension of the
anisotropic part of $q$ after scalar extension to the function field $F(p)$ of
$p$. We conjecture that $\mathrm{dim}(q)$ must lie within $k$ of a multiple of
$2^{s+1}$. This can be viewed as a direct generalization of Hoffmann's
separation theorem. Among other cases, we prove that the conjecture is true if
$k<2^{s-1}$. When $k=0$, this shows that any anisotropic form representing an
element of the kernel of the natural restriction homomorphism $W(F)\rightarrow
W(F(p))$ has dimension divisible by $2^{s+1}$.


title: Superstability from categoricity in abstract elementary classes

abstract:
  Starting from an abstract elementary class with no maximal models, Shelah and
Villaveces have shown (assuming instances of diamond) that categoricity implies
a superstability-like property for a certain independence relation called
nonsplitting. We generalize their result as follows: given an abstract notion
of independence for Galois (orbital) types over models, we derive that the
notion satisfies a superstability property provided that the class is
categorical and satisfies a weakening of amalgamation. This extends the
Shelah-Villaveces result (the independence notion there was splitting) as well
as a result of the first and second author where the independence notion was
coheir. The argument is in ZFC and fills a gap in the Shelah-Villaveces proof.


title: NdFluents: A Multi-dimensional Contexts Ontology

abstract:
  Annotating semantic data with metadata is becoming more and more important to
provide information about the statements being asserted. While initial
solutions proposed a data model to represent a specific dimension of
meta-information (such as time or provenance), the need for a general
annotation framework which allows representing different context dimensions is
needed. In this paper, we extend the 4dFluents ontology by Welty and Fikes---on
associating temporal validity to statements---to any dimension of context, and
discuss possible issues that multidimensional context representations have to
face and how we address them.


title:
Stability of synchronization under stochastic perturbations in leaky
  integrate and fire neural networks of finite size

abstract:
  We study the synchronization of fully-connected and totally excitatory
integrate and fire neural networks in presence of Gaussian white noises. Using
a large deviation principle, we prove the stability of the synchronized state
under stochastic perturbations. Then, we give a lower bound on the probability
of synchronization for networks which are not initially synchronized. This
bound shows the robustness of the emergence of synchronization in presence of
small stochastic perturbations.


title:
Measurement of the production of high-$p_{\rm T}$ electrons from
  heavy-flavour hadron decays in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76
  TeV

abstract:
  Electrons from heavy-flavour hadron decays (charm and beauty) were measured
with the ALICE detector in Pb-Pb collisions at a centre-of-mass of energy
$\sqrt{s_{\rm NN}}=2.76$ TeV. The transverse momentum ($p_{\rm T}$)
differential production yields at mid-rapidity were used to calculate the
nuclear modification factor $R_{\rm AA}$ in the interval $3<p_{\rm T}< 18$
GeV/$c$. The $R_{\rm AA}$ shows a strong suppression compared to binary scaling
of pp collisions at the same energy (up to a factor of 4) in the 10% most
central Pb-Pb collisions. There is a centrality trend of suppression, and a
weaker suppression (down to a factor of 2) in semi-peripheral (50-80%)
collisions is observed. The suppression of electrons in this broad $p_{\rm T}$
interval indicates that both charm and beauty quarks lose energy when they
traverse the hot medium formed in Pb-Pb collisions at LHC.


title:
Quantum meets classical phase transition: Low-temperature anomaly in
  disordered superconductors near $B_{c2}$

abstract:
  Strongly disordered superconductors in a magnetic field display many
characteristic properties of type-II superconductivity--- except at low
temperatures where an anomalous linear $T$-dependence of the resistive critical
field $B_{c2}$ is routinely observed. This behavior violates the conventional
theory of superconductivity, and its origin remains a long-standing puzzle.
Here we report on systematic measurements of the critical magnetic field and
current on amorphous indium oxide films of various levels of disorder.
Surprisingly, our measurements show that the $B_{c2}$ anomaly near
zero-temperature is accompanied by a clear mean-field like scaling behavior of
the critical current. We demonstrate theoretically that these are consequences
of the vortex-glass ground state and its thermal fluctuations. This theory
further predicts the linear-$T$ anomaly to occur in films as well as bulk
superconductors with a slope that depends on the normal-state sheet
resistance---in agreement with experimental data. Thus, our combined
experimental and theoretical study reveals universal low-temperature behavior
of $B_{c2}$ in a large class of disordered superconductors.


title: Gravity-Darkened Seasons: Insolation Around Rapid Rotators

abstract:
  I model the effect of rapid stellar rotation on a planet's insolation.
Fast-rotating stars have induced pole-to-equator temperature gradients (known
as gravity-darkening) of up to several thousand Kelvin that affect the star's
luminosity and peak emission wavelength as a function of latitude. When
orbiting such a star, a planet's annual insolation can strongly vary depending
on its orbit inclination. Specifically, inclined orbits result in temporary
exposure to the star's hotter poles. I find that gravity-darkening can drive
changes in a planet's equilibrium temperature of up to $\sim15\%$ due to
increased irradiance near the stellar poles. This effect can also vary a
planet's exposure to UV radiation by up to $\sim80\%$ throughout its orbit as
it is exposed to an irradiance spectrum corresponding to different stellar
effective temperatures over time.


title:
Structure, Dynamics and Deuterium Fractionation of Massive Pre-Stellar
  Cores

abstract:
  High levels of deuterium fraction in N$_2$H$^+$ are observed in some
pre-stellar cores. Single-zone chemical models find that the timescale required
to reach observed values ($D_{\rm frac}^{{\rm N}_2{\rm H}^+} \equiv {\rm
N}_2{\rm D}^+/{\rm N}_2{\rm H}^+ \gtrsim 0.1$) is longer than the free-fall
time, possibly ten times longer. Here, we explore the deuteration of turbulent,
magnetized cores with 3D magnetohydrodynamics simulations. We use an
approximate chemical model to follow the growth in abundances of N$_2$H$^+$ and
N$_2$D$^+$. We then examine the dynamics of the core using each tracer for
comparison to observations. We find that the velocity dispersion of the core as
traced by N$_2$D$^+$ appears slightly sub-virial compared to predictions of the
Turbulent Core Model of McKee & Tan, except at late times just before the onset
of protostar formation. By varying the initial mass surface density, the
magnetic energy, the chemical age, and the ortho-to-para ratio of H$_2$, we
also determine the physical and temporal properties required for high
deuteration. We find that low initial ortho-to-para ratios ($\lesssim 0.01$)
and/or multiple free-fall times ($\gtrsim 3$) of prior chemical evolution are
necessary to reach the observed values of deuterium fraction in pre-stellar
cores.


title: A Web API ecosystem through feature-based reuse

abstract:
  The fast-growing Web API landscape brings clients more options than ever
before---in theory. In practice, they cannot easily switch between different
providers offering similar functionality. We discuss a vision for developing
Web APIs based on reuse of interface parts called features. Through the
introduction of 5 design principles, we investigate the impact of feature-based
reuse on Web APIs. Applying these principles enables a granular reuse of client
and server code, documentation, and tools. Together, they can foster a
measurable ecosystem with cross-API compatibility, opening the door to a more
flexible generation of Web clients.


title: Partial restoration of chiral symmetry in hot and dense neutron matter

abstract:
  We review efforts to describe the approach to chiral symmetry restoration in
neutron matter from the low-energy realization of QCD, chiral effective field
theory.


title: How bright are the gaps in circumbinary disk systems?

abstract:
  When a circumbinary disk surrounds a binary whose secondary's mass is at
least $\sim 10^{-2}\times$ the primary's mass, a nearly empty cavity with
radius a few times the binary separation is carved out of the disk. Narrow
streams of material pass from the inner edge of the circumbinary disk into the
domain of the binary itself, where they eventually join onto the small disks
orbiting the members of the binary. Using data from 3-d MHD simulations of this
process, we determine the luminosity of these streams; it is mostly due to weak
laminar shocks, and is in general only a few percent of the luminosity of
adjacent regions of either the circumbinary disk or the "mini-disks". This
luminosity therefore hardly affects the deficit in the thermal continuum
predicted on the basis of a perfectly dark gap region.


title: Organized Complexity: is Big History a Big Computation?

abstract:
  The concept of "logical depth" introduced by Charles H. Bennett (1988) seems
to capture, at least partially, the notion of organized complexity, so central
in big history. More precisely, the increase in organized complexity refers
here to the wealth, variety and intricacy of structures, and should not be
confused with the increase of random complexity, formalized by Kolmogorov
(1965). If Bennett is right in proposing to assimilate organized complexity
with "computational content", then the fundamental cause of the increase of
complexity in the universe is the existence of computing mechanisms with
memory, and able to cumulatively create and preserve computational contents. In
this view, the universe computes, remembers its calculations, and reuses them
to conduct further computations. Evolutionary mechanisms are such forms of
cumulative computation with memory and we owe them the organized complexity of
life. Language, writing, culture, science and technology can also be analyzed
as computation mechanisms generating, preserving and accelerating the increase
in organized complexity. The main unifying theme for big history is the energy
rate density, a metric based on thermodynamics. However useful, this metric
does not provide much insight into the role that information and computation
play in our universe. The concept of "logical depth" provides a new lens to
examine the increase of organized complexity. We argue in this paper that
organized complexity is a valid and useful way to make sense of big history.
Additionally, logical depth has a rigorous formal definition in theoretical
computer science that hints at a broader research program to quantify
complexity in the universe.
  Keywords: organized complexity, Kolmogorov complexity, logical depth, big
history, cosmic evolution, evolution, complexity, complexification,
computation, artificial life, philosophy of information


title: Semi-inclusive jet cross sections within SCET

abstract:
  We review the definition of semi-inclusive jet functions within Soft
Collinear Effective Theory (SCET) and their application to inclusive jet cross
sections. As an example, we consider both the inclusive production of jets and
the jet fragmentation function in proton-proton collisions. The semi-inclusive
jet functions satisfy renormalization group (RG) equations which take the form
of standard timelike DGLAP evolution equations, analogous to collinear
fragmentation functions. By solving these RG equations, the resummation of
potentially large single logarithms $(\alpha_s \ln R)^n$ can be achieved. We
present numerical results at NLO+NLL$_R$ accuracy and compare to existing data
from the LHC.


title:
Breaking news from the HST: The central star of the Stingray Nebula is
  now returning towards the AGB

abstract:
  SAO244567 is a rare example of a star that allows us to witness stellar
evolution in real time. Between 1971 and 1990 it changed from a B-type star
into the hot central star of the Stingray Nebula. This observed rapid heating
has been a mystery for decades, since it is in strong contradiction with the
low mass of the star and canonical post-asymptotic giant branch (AGB)
evolution. We speculated that SAO244567 might have suffered from a late thermal
pulse (LTP) and obtained new observations with HST/COS to follow the evolution
of the surface properties of SAO244567 and to verify the LTP hypothesis. Our
non-LTE spectral analysis reveals that the star cooled significantly since 2002
and that its envelope is now expanding. Therefore, we conclude that SAO244567
is currently on its way back towards the AGB, which strongly supports the LTP
hypothesis. A comparison with state-of-the-art LTP evolutionary calculations
shows that these models cannot fully reproduce the evolution of all surface
parameters simultaneously, pointing out possible shortcomings of stellar
evolution models. Thereby, SAO244567 keeps on challenging stellar evolution
theory and we highly encourage further investigations.


title: A Stable FDTD Method with Embedded Reduced-Order Models

abstract:
  The computational efficiency of the Finite-Difference Time-Domain (FDTD)
method can be significantly reduced by the presence of complex objects with
fine features. Small geometrical details impose a fine mesh and a reduced time
step, significantly increasing computational cost. Model order reduction has
been proposed as a systematic way to generate compact models for complex
objects, that one can then instantiate into a main FDTD mesh. However, the
stability of FDTD with embedded reduced models remains an open problem. We
propose a systematic method to generate reduced models for FDTD domains, and
embed them into a main FDTD mesh with guaranteed stability up to the
Courant-Friedrichs-Lewy (CFL) limit of the fine mesh. With a simple
perturbation technique, the CFL of the whole scheme can be further extended
beyond the fine grid's CFL limit. Reduced models can be created for arbitrary
domains containing inhomogeneous and lossy materials. Numerical tests confirm
the stability of the proposed method, and its potential to accelerate
multiscale FDTD simulations.


title:
Numerical study of tree-level improved lattice gradient flows in pure
  Yang-Mills theory

abstract:
  We study several types of tree-level improvement in the Yang-Mills gradient
flow method in order to reduce the lattice discretization errors in line with
Fodor et al. [arXiv:1406.0827]. The tree-level $\mathcal{O}(a^2)$ improvement
can be achieved in a simple manner, where an appropriate weighted average is
computed between two definitions of the action density $\langle E(t)\rangle$
measured at every flow time $t$. We further develop the idea of achieving the
tree-level $\mathcal{O}(a^4)$ improvement. For testing our proposal, we present
numerical results for $\langle E(t) \rangle$ obtained on gauge configurations
generated with the Wilson and Iwasaki gauge actions at three lattice spacings
($a\approx 0.1, 0.07,$ and 0.05 fm). Our results show that tree-level improved
flows significantly eliminate the discretization corrections on $t^2\langle
E(t)\rangle$ in the relatively small-$t$ regime. To demonstrate the feasibility
of our tree-level improvement proposal, we also study the scaling behavior of
the dimensionless combinations of the $\Lambda_{\overline{\textrm{MS}}}$
parameter and the new reference scale $t_X$, which is defined through
$t_X^2\langle E(t_X)\rangle=X$ for the smaller $X$, e.g., $X= 0.15$. It is
found that $\sqrt{t_{0.15}}\Lambda_{\overline{\textrm{MS}}}$ shows a nearly
perfect scaling behavior as a function of $a^2$ regardless of the types of
gauge action and flow, after tree-level improvement is achieved up to
$\mathcal{O}(a^4)$. Further detailed study of the scaling behavior exposes the
presence of the remnant $\mathcal{O}(g^{2n} a^2)$ corrections, which are beyond
the tree level. Although our proposal is not enough to eliminate all
$\mathcal{O}(a^2)$ effects, we show that the $\mathcal{O}(g^{2n} a^2)$
corrections can be well under control even by the simplest tree-level
$\mathcal{O}(a^2)$ improved flow.