title: Delocalization at small energy for heavy-tailed random matrices

abstract:
  We prove that the eigenvectors associated to small enough eigenvalues of an
heavy-tailed symmetric random matrix are delocalized with probability tending
to one as the size of the matrix grows to infinity. The delocalization is
measured thanks to a simple criterion related to the inverse participation
ratio which computes an average ratio of L4 and L2-norms of vectors. In
contrast, as a consequence of a previous result, for random matrices with
sufficiently heavy tails, the eigenvectors associated to large enough
eigenvalues are localized according to the same criterion. The proof is based
on a new analysis of the fixed point equation satisfied asymptotically by the
law of a diagonal entry of the resolvent of this matrix.


title: Chiral Quasiparticles at the Fermi Surface of the Weyl Semimetal TaAs

abstract:
  Tantalum arsenide is a member of the non-centrosymmetric monopnictides, which
are putative Weyl semimetals. In these materials, three-dimensional chiral
massless quasiparticles, the so-called Weyl fermions, are predicted to induce
novel quantum mechanical phenomena, such as the chiral anomaly and topological
surface states. However, their chirality is only well-defined if the Fermi
level is close enough to the Weyl points that separate Fermi surface pockets of
opposite chirality exist. In this article, we present the bulk Fermi surface
topology of high quality single crystals of TaAs, as determined by
angle-dependent Shubnikov-de Haas and de Haas-van Alphen measurements combined
with ab-initio band-structure calculations. Quantum oscillations originating
from three different types of Fermi surface pocket were found in magnetization,
magnetic torque, and mag- netoresistance measurements performed in magnetic
fields up to 14 T and temperatures down to 1.8 K. Of these Fermi pockets, two
are pairs of topologically non-trivial electron pockets around the Weyl points
and one is a trivial hole pocket. Unlike the other members of the
non-centrosymmetric monopnictides, TaAs is the first Weyl semimetal candidate
with the Fermi energy suffciently close to both types of Weyl points to
generate chiral quasiparticles at the Fermi surface.


title: High pressure research using muons at the Paul Scherrer Institute

abstract:
  Pressure, together with temperature and magnetic field, is an important
thermodynamical parameter in physics. Investigating the response of a compound
or of a material to pressure allows to elucidate ground states, investigate
their interplay and interactions and determine microscopic parameters. Pressure
tuning is used to establish phase diagrams, study phase transitions and
identify critical points. Muon spin rotation/relaxation (muSR) is now a
standard technique making increasing significant contribution in condensed
matter physics, material science research and other fields. In this review, we
will discuss specific requirements and challenges to perform muSR experiments
under pressure, introduce the high-pressure muon facility at the Paul Scherrer
Institute (PSI, Switzerland) and present selected results obtained by combining
the sensitivity of the muSR technique with pressure.

categories: cond-mat.mtrl-sci cond-mat.other cond-mat.str-el cond-mat.supr-con


title:
Mass Spectra of Heavy-Light Mesons in Heavy Hadron Chiral Perturbation
  Theory

abstract:
  We study the masses of the low-lying charm and bottom mesons within the
framework of heavy- hadron chiral perturbation theory (HHChPT). We work to
third order in the chiral expansion, where meson loops contribute. In contrast
to previous approaches, we use physical meson masses in evaluating these loops.
This ensures that their imaginary parts are consistent with the observed widths
of the D-mesons. The lowest odd- and even-parity, strange and nonstrange charm
mesons provide enough constraints to determine only certain linear combinations
of the low-energy constants (LECs) in the effective Lagrangian. We comment on
how lattice QCD could provide further information to disentangle these
constants. Then we use the results from the charm sector to predict the
spectrum of odd- and even-parity of the bottom mesons. The predicted masses
from our theory are in good agreement with experimentally measured masses for
the case of the odd-parity sector. For the even-parity sector, the B-meson
states have not yet been observed; thus, our results provide useful information
for experimentalists investigating such states. The near degeneracy of
nonstrange and strange scalar B mesons is confirmed in our predictions using
HHChPT. We show why previous approaches of using HHChPT in studying the mass
degeneracy in the scalar states of charm and bottom meson sectors gave
unsatisfactory results.


title:
Role of nonlocal probes of thermalization for a strongly interacting
  non-Abelian plasma

abstract:
  We use a holographic method to investigate thermalization of a
boost-invariant strongly interacting non-Abelian plasma. Boundary sourcing, a
distorsion of the boundary metric, is employed to drive the system far from
equilibrium. Thermalization is analyzed through nonlocal probes: the equal-time
two-point correlation function of large conformal dimension operators in the
boundary theory, and Wilson loops of different shapes. We study the dependence
of the thermalization time on the size of the probes, and compare the results
to the ones obtained using local observables: the onset of thermalization is
first observed at short distances.


title: Realizations of Gromov-Hausdorff Distance

abstract:
  It is shown that for any two compact metric spaces there exists an "optimal"
correspondence which the Gromov-Hausdorff distance is attained at. Each such
correspondence generates isometric embeddings of these spaces into a compact
metric space such that the Gromov-Hausdorff distance between the initial spaces
is equal to the Hausdorff distance between their images. Also, the optimal
correspondences could be used for constructing the shortest curves in the
Gromov-Hausdorff space in exactly the same way as it was done by Alexander
Ivanov, Nadezhda Nikolaeva, and Alexey Tuzhilin in arXiv:1504.03830, where it
is proved that the Gromov-Hausdorff space is geodesic. Notice that all proofs
in the present paper are elementary and use no more than the idea of
compactness.


title: Rigorous constraint satisfaction for sampled linear systems

abstract:
  We address a specific but recurring problem related to sampled linear
systems. In particular, we provide a numerical method for the rigorous
verification of constraint satisfaction for linear continuous-time systems
between sampling instances. The proposed algorithm combines elements of
classical branch and bound schemes from global optimization with a recently
published procedure to bound the exponential of interval matrices.


title:
Positive Matrices in the Hardy Space with Prescribed Boundary
  Representations via the Kaczmarz Algorithm

abstract:
  For a singular probability measure $\mu$ on the circle, we show the existence
of positive matrices on the unit disc which admit a boundary representation on
the unit circle with respect to $\mu$. These positive matrices are constructed
in several different ways using the Kaczmarz algorithm. Some of these positive
matrices correspond to the projection of the Szeg\H{o} kernel on the disc to
certain subspaces of the Hardy space corresponding to the normalized Cauchy
transform of $\mu$. Other positive matrices are obtained which correspond to
subspaces of the Hardy space after a renormalization, and so are not
projections of the Szeg\H{o} kernel. We show that these positive matrices are a
generalization of a spectrum or Fourier frame for $\mu$, and the existence of
such a positive matrix does not require $\mu$ to be spectral.


title: Effects of Information Heterogeneity in Bayesian Routing Games

abstract:
  This article studies the value of information in route choice decisions when
a fraction of players have access to high accuracy information about traffic
incidents relative to others. To model such environments, we introduce a
Bayesian congestion game, in which players have private information about
incidents, and each player chooses her route on a network of parallel links.
The links are prone to incidents that occur with an ex-ante known probability.
The demand is comprised of two player populations: one with access to high
accuracy incident information and another with low accuracy information, i.e.
the populations differ only by their access to information. The common
knowledge includes: (i) the demand and route cost functions, (ii) the fraction
of highly-informed players, (iii) the incident probability, and (iv) the
marginal type distributions induced by the information structure of the game.
We present a full characterization of the Bayesian Wardrop Equilibrium of this
game under the assumption that low information players receive no additional
information beyond common knowledge. We also compute the cost to individual
players and the social cost as a function of the fraction of highly-informed
players when they receive perfectly accurate information. Our first result
suggests that below a certain threshold of highly-informed players, both
populations experience a reduction in individual cost, with the highly-informed
players receiving a greater reduction. However, above this threshold, both
populations realize the same equilibrium cost. Secondly, there exists another
(lower or equal) threshold above which a further increase in the fraction of
highly-informed players does not reduce the expected social costs. Thus, once a
sufficiently large number of players are highly informed, wider distribution of
more accurate information is ineffective at best, and otherwise socially
harmful.


title:
The $\beta$-function of $SU(3)$ gauge theory with $ N_f = 10 $ massless
  fermions in the fundamental representation

abstract:
  We present the first study of the discrete $\beta$-function of the $ SU(3) $
gauge theory with 10 massless domain-wall fermions in the fundamental
representation. The renormalized coupling is obtained by the finite-volume
gradient flow scheme, and the discrete $\beta$-function is extrapolated to the
continuum limit by the step-scaling method. Our result of the discrete
$\beta$-function (with $ s = 2 $) suggests that this theory possesses an
infrared fixed point around $ g_c^2 \sim 7.0 $ for $ c = \sqrt{8t}/L = 0.3 $.


title: Commutative hairy graphs and representations of $Out(F_r)$

abstract:
  We express the hairy graph complexes computing the rational homotopy groups
of long embeddings (modulo immersion) of R^m in R^n as "decorated" graph
complexes associated to certain representations of the outer automorphism
groups of free groups. This interpretation gives rise to a natural spectral
sequence, which allows us to shed some light on the structure of the hairy
graph cohomology. We also explain briefly the connection to the deformation
theory of the little discs operads and some conclusions that this brings.


title: Brill-Noether varieties of k-gonal curves

abstract:
  We consider a general curve of fixed gonality k and genus g. We propose an
estimate for the dimension of the variety $W^r_d(C)$ of special linear series
on C, by solving an analogous problem in tropical geometry. Using work of
Coppens and Martens, we prove that this estimate is exactly correct if k is at
least g/5 + 2, and is an upper bound in all other cases. We also completely
characterize the cases in which $W^r_d(C)$ has the same dimension as for a
general curve of genus g.


title:
Self-consistent Monte Carlo simulations of proton acceleration in
  coronal shocks: Effect of anisotropic pitch-angle scattering of particles

abstract:
  Context. Solar energetic particles observed in association with coronal mass
ejections (CMEs) are produced by the CME-driven shock waves. The acceleration
of particles is considered to be due to diffusive shock acceleration (DSA).
Aims. We aim at a better understanding of DSA in the case of quasi-parallel
shocks, in which self-generated turbulence in the shock vicinity plays a key
role. Methods. We have developed and applied a new Monte Carlo simulation code
for acceleration of protons in parallel coronal shocks. The code performs a
self-consistent calculation of resonant interactions of particles with Alfv\'en
waves based on the quasi-linear theory. In contrast to the existing Monte Carlo
codes of DSA, the new code features the full quasi-linear resonance condition
of particle pitch-angle scattering. This allows us to take anisotropy of
particle pitch-angle scattering into account, while the older codes implement
an approximate resonance condition leading to isotropic scattering.We performed
simulations with the new code and with an old code, applying the same initial
and boundary conditions, and have compared the results provided by both codes
with each other, and with the predictions of the steady-state theory. Results.
We have found that anisotropic pitch-angle scattering leads to less efficient
acceleration of particles than isotropic. However, extrapolations to particle
injection rates higher than those we were able to use suggest the capability of
DSA to produce relativistic particles. The particle and wave distributions in
the foreshock as well as their time evolution, provided by our new simulation
code, are significantly different from the previous results and from the
steady-state theory. Specifically, the mean free path in the simulations with
the new code is increasing with energy, in contrast to the theoretical result.


title:
A multi-modes Monte Carlo finite element method for elliptic partial
  differential equations with random coefficients

abstract:
  This paper develops and analyzes an efficient numerical method for solving
elliptic partial differential equations, where the diffusion coefficients are
random perturbations of deterministic diffusion coefficients. The method is
based upon a multi-modes representation of the solution as a power series of
the perturbation parameter, and the Monte Carlo technique for sampling the
probability space. One key feature of the proposed method is that the governing
equations for all the expanded mode functions share the same deterministic
diffusion coefficients, thus an efficient direct solver by repeated use of the
$LU$ decomposition matrices can be employed for solving the finite element
discretized linear systems. It is shown that the computational complexity of
the whole algorithm is comparable to that of solving a few deterministic
elliptic partial differential equations using the $LU$ director solver. Error
estimates are derived for the method, and numerical experiments are provided to
test the efficiency of the algorithm and validate the theoretical results.


title: Effects of quantum deformation on the integer quantum Hall effect

abstract:
  In this work an application of the $\kappa$--deformed algebra in condensed
matter physics is presented. Starting by the $\kappa$--deformed Dirac equation
we study the relativistic generalization of the $\kappa$--deformed Landau
levels as well as the consequences of the deformation on the Hall conductivity.
By comparing the $\kappa$--deformed Landau levels in the nonrelativistic regime
with the energy levels of a two-dimensional electron gas (2DEG) in the presence
of a normal magnetic field, upper bounds for the deformation parameter in
different materials are established. An expression for the $\kappa$--deformed
Hall conductivity of a 2DEG is obtained as well. The expression recovers the
well-known result for the usual Hall conductivity in the limit
$\varepsilon=\kappa^{-1}\to 0$. The deformation parameter breaks the Landau
levels degeneracy and due to this, it is observed that deformation gives rise
to new plateaus of conductivity in a such way that the plateaus widths of the
$\kappa$--deformed Hall conductivity are less than the usual one. By studying
the temperature dependence of the $\kappa$--deformed Hall conductivity, we show
that an increase of the temperature causes the smearing of the plateaus and a
diminution of the effect of the deformation, whilst an increase in the magnetic
field enhances the effect of the deformation.

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


title: Quasi-local energy in presence of gravitational radiation

abstract:
  We discuss our recent work [4] in which gravitational radiation was studied
by evaluating the Wang-Yau quasi-local mass of surfaces of fixed size at the
infinity of both axial and polar perturbations of the Schwarzschild spacetime,
\`{a} la Chandrasekhar [1].


title: Revisiting Semi-Supervised Learning with Graph Embeddings

abstract:
  We present a semi-supervised learning framework based on graph embeddings.
Given a graph between instances, we train an embedding for each instance to
jointly predict the class label and the neighborhood context in the graph. We
develop both transductive and inductive variants of our method. In the
transductive variant of our method, the class labels are determined by both the
learned embeddings and input feature vectors, while in the inductive variant,
the embeddings are defined as a parametric function of the feature vectors, so
predictions can be made on instances not seen during training. On a large and
diverse set of benchmark tasks, including text classification, distantly
supervised entity extraction, and entity classification, we show improved
performance over many of the existing models.


title:
On the numerical range of generators of symmetric $L_\infty$-contractive
  semigroups

abstract:
  A result by Liskevich and Perelmuter from 1995 yields the optimal angle of
analyticity for symmetric submarkovian semigroups on $L_p$, $1<p<\infty$.
C.~Kriegler showed in 2011 that the result remains true without the assumption
of positivity of the semigroup. Here we give an elementary proof of Kriegler's
result.


title:
Ground level observations of relativistic solar particles on Oct 29th,
  2015: Is it a new GLE on the current solar cycle?

abstract:
  On Oct. 29th, 2015, the Earth crossed through a fold in the heliospheric
current sheet. This is called a "solar sector boundary crossing". Under this
circumstances, a large coronal mass ejection (CME) occurred at 2:24 UT, behind
the west limb on the sun. Therefore, the boundary crossing occurred when in the
blast's nearby environment was filled with energetic particles accelerated by
the CME shock waves, spacecraft measurements (ACE and GOES) have shown that in
such a case, protons with energies at least up to 30 MeV were stored within the
range of the sector boundary. Thus, a fraction of the solar energetic particles
(SEP) from CME, reached Earth around 03:00 UT in the aftermath of the solar
blast, reaching the condition of an S1 (minor) radiation storm level. The
effect at ground level was a small increase in the counting rate in some ground
based detectors, such as the South Pole Neutron Monitor (NM) and a sharp peak
observed in the counting rate in the New-Tupi detector in Rio de Janeiro,
Brazil and Thule NM. The event is being classified as a new GLE (Ground Level
Enhancement) in the current solar cycle, as the GLE 73. However, in all cases,
the counting rate increase is smaller or near than 2\%. The Earth crossed
through a fold in the heliospheric current sheet also caused a geomagnetic
disturbance, below the minor geomagnetic storm threshold, observed in the ACE
spacecraft and a small decrease in the counting rates of some ground level
detectors, such as the New-Tupi detector and Thuly NM. Details of these
observations are reported.


title: Scaling laws in chiral hydrodynamic turbulence

abstract:
  We study the turbulent regime of chiral (magneto)hydrodynamics for charged
and neutral matter with chirality imbalance. We find that the chiral
magnetohydrodynamics for charged plasmas possesses a unique scaling symmetry,
only without fluid helicity under the local charge neutrality. We also find a
different type of unique scaling symmetry in the chiral hydrodynamics for
neutral matter with fluid helicity in the inertial range. We show that these
symmetries dictate the self-similar inverse cascade of the magnetic and kinetic
energies. Our results imply the possible inverse energy cascade in
core-collapse supernovae due to the chiral transport of neutrinos.


title: Compilation as a Typed EDSL-to-EDSL Transformation

abstract:
  This article is about an implementation and compilation technique that is
used in RAW-Feldspar which is a complete rewrite of the Feldspar embedded
domain-specific language (EDSL) (Axelsson et al. 2010). Feldspar is high-level
functional language that generates efficient C code to run on embedded targets.
The gist of the technique presented in this post is the following: rather
writing a back end that converts pure Feldspar expressions directly to C, we
translate them to a low-level monadic EDSL. From the low-level EDSL, C code is
then generated. This approach has several advantages:
  1. The translation is simpler to write than a complete C back end.
  2. The translation is between two typed EDSLs, which rules out many potential
errors.
  3. The low-level EDSL is reusable and can be shared between several
high-level EDSLs.
  Although the article contains a lot of code, most of it is in fact reusable.
As mentioned in Discussion, we can write the same implementation in less than
50 lines of code using generic libraries that we have developed to support
Feldspar.


title: Tight Reference Frame--Independent Quantum Teleportation

abstract:
  We give a tight scheme for teleporting a quantum state between two parties
whose reference frames are misaligned by an action of a finite symmetry group.
Unlike previously proposed schemes, ours requires no additional tokens or data
to be passed between the participants; the same amount of classical information
is transferred as for ordinary quantum teleportation, and the Hilbert space of
the entangled resource is of the same size. In the terminology of Peres and
Scudo, our protocol relies on classical communication of unspeakable
information.


title: Gravitational-Wave Constraints on the Progenitors of Fast Radio Bursts

abstract:
  The nature of fast radio bursts (FRBs) remains enigmatic. Highly energetic
radio pulses of millisecond duration, FRBs are observed with dispersion
measures consistent with an extragalactic source. A variety of models have been
proposed to explain their origin. One popular class of theorized FRB progenitor
is the coalescence of compact binaries composed of neutron stars and/or black
holes. Such coalescence events are strong gravitational-wave emitters. We
demonstrate that measurements made by the LIGO and Virgo gravitational-wave
observatories can be leveraged to severely constrain the validity of FRB binary
coalescence models. Existing measurements constrain the binary black hole rate
to approximately $5\%$ of the FRB rate, and results from Advanced LIGO's O1 and
O2 observing runs may place similarly strong constraints on the fraction of
FRBs due to binary neutron star and neutron star--black hole progenitors.


title:
A Readable Read: Automatic Assessment of Language Learning Materials
  based on Linguistic Complexity

abstract:
  Corpora and web texts can become a rich language learning resource if we have
a means of assessing whether they are linguistically appropriate for learners
at a given proficiency level. In this paper, we aim at addressing this issue by
presenting the first approach for predicting linguistic complexity for Swedish
second language learning material on a 5-point scale. After showing that the
traditional Swedish readability measure, L\"asbarhetsindex (LIX), is not
suitable for this task, we propose a supervised machine learning model, based
on a range of linguistic features, that can reliably classify texts according
to their difficulty level. Our model obtained an accuracy of 81.3% and an
F-score of 0.8, which is comparable to the state of the art in English and is
considerably higher than previously reported results for other languages. We
further studied the utility of our features with single sentences instead of
full texts since sentences are a common linguistic unit in language learning
exercises. We trained a separate model on sentence-level data with five
classes, which yielded 63.4% accuracy. Although this is lower than the document
level performance, we achieved an adjacent accuracy of 92%. Furthermore, we
found that using a combination of different features, compared to using lexical
features alone, resulted in 7% improvement in classification accuracy at the
sentence level, whereas at the document level, lexical features were more
dominant. Our models are intended for use in a freely accessible web-based
language learning platform for the automatic generation of exercises.


title: Algorithms for Batch Hierarchical Reinforcement Learning

abstract:
  Hierarchical Reinforcement Learning (HRL) exploits temporal abstraction to
solve large Markov Decision Processes (MDP) and provide transferable subtask
policies. In this paper, we introduce an off-policy HRL algorithm: Hierarchical
Q-value Iteration (HQI). We show that it is possible to effectively learn
recursive optimal policies for any valid hierarchical decomposition of the
original MDP, given a fixed dataset collected from a flat stochastic behavioral
policy. We first formally prove the convergence of the algorithm for tabular
MDP. Then our experiments on the Taxi domain show that HQI converges faster
than a flat Q-value Iteration and enjoys easy state abstraction. Also, we
demonstrate that our algorithm is able to learn optimal policies for different
hierarchical structures from the same fixed dataset, which enables model
comparison without recollecting data.


title: Tropical Graph Curves

abstract:
  We study tropical line arrangements associated to a three-regular graph $G$
that we refer to as \emph{tropical graph curves}. Roughly speaking, the
tropical graph curve associated to $G$, whose genus is $g$, is an arrangement
of $2g-2$ lines in tropical projective space that contains $G$ (more precisely,
the topological space associated to $G$) as a deformation retract. We show the
existence of tropical graph curves when the underlying graph is a
three-regular, three-vertex-connected planar graph. Our method involves
explicitly constructing an arrangement of lines in projective space, i.e. a
graph curve whose tropicalisation yields the corresponding tropical graph curve
and in this case, solves a topological version of the tropical lifting problem
associated to canonically embedded graph curves. We also show that the set of
tropical graph curves that we construct are connected via certain local
operations. These local operations are inspired by Steinitz' theorem in
polytope theory.


title:
A substructure inside spiral arms, and a mirror image across the
  Galactic Meridian

abstract:
  While the galactic density wave theory is over 50 years old and well known in
science, whether it fits our own Milky Way disk has been difficult to say. Here
we show a substructure inside the spiral arms. This substructure is reversing
with respect to the Galactic Meridian (longitude zero), and crosscuts of the
arms at negative longitudes appear as mirror images of crosscuts of the arms at
positive longitudes. Four lanes are delineated: mid-arm (extended 12CO gas at
mid arm, HI atoms), in-between offset by about 100 pc (synchrotron, radio
recombination lines), in between offset by about 200 pc (masers, colder dust),
and inner edge (hotter dust seen in Mid-IR and Near-IR).


title: Equivariant Kodaira embedding of CR manifolds with circle action

abstract:
  We consider a compact CR manifold with a transversal CR locally free circle
action endowed with a rigid positive CR line bundle. We prove that a certain
weighted Fourier-Szeg\H{o} kernel of the CR sections in the high tensor powers
admits a full asymptotic expansion. As a consequence, we establish an
equivariant Kodaira embedding theorem.


title:
Orbital engineering in nickelate heterostructures driven by anisotropic
  oxygen hybridization rather than orbital energy levels

abstract:
  Resonant inelastic x-ray scattering is used to investigate the electronic
origin of orbital polarization in nickelate heterostructures taking
$\mathrm{LaTiO_3-LaNiO_3-3x(LaAlO_3)}$, a system with exceptionally large
polarization, as a model system. We find that heterostructuring generates only
minor changes in the Ni $3d$ orbital energy levels, contradicting the
often-invoked picture in which changes in orbital energy levels generate
orbital polarization. Instead, O $K$-edge x-ray absorption spectroscopy
demonstrates that orbital polarization is caused by an anisotropic
reconstruction of the oxygen ligand hole states. This provides an explanation
for the limited success of theoretical predictions based on tuning orbital
energy levels and implies that future theories should focus on anisotropic
hybridization as the most effective means to drive large changes in electronic
structure and realize novel emergent phenomena.


title: Non-deterministic self-assembly with asymmetric interactions

abstract:
  We investigate general properties of non-deterministic self-assembly with
asymmetric interactions, using a computational model and DNA tile assembly
experiments. By contrasting symmetric and asymmetric interactions we show that
the latter can lead to self-limiting cluster growth. Furthermore, by adjusting
the relative abundance of self-assembly particles in a two-particle mixture, we
are able to tune the final sizes of these clusters. We show that this is a
fundamental property of asymmetric interactions, which has potential
applications in bioengineering, and provides new insights into the study of
diseases caused by protein aggregation.


title:
A Burst in a Wind Bubble and the Impact on Baryonic Ejecta: High-Energy
  Gamma-Ray Flashes and Afterglows from Fast Radio Bursts and Pulsar-Driven
  Supernova Remnants

abstract:
  Tenuous wind bubbles, which are formed by the spin-down activity of central
compact remnants, are relevant in some models of fast radio bursts (FRBs) and
super-luminous supernovae. We study their high-energy signatures, focusing on
the role of pair-enriched bubbles produced by young magnetars, rapidly-rotating
neutron stars, and magnetized white dwarfs. (i) First, we study the nebular
properties and the conditions allowing for escape of high-energy gamma-rays and
radio waves, showing that their escape is possible for nebulae with ages of
>10-100 yr. In the rapidly-rotating neutron star scenario, we find that radio
emission from the quasi-steady nebula itself may be bright enough to be
detected especially at sub-mm frequencies, which is relevant as a possible
counterpart of pulsar-driven SNe and FRBs. (ii) Second, we consider the fate of
bursting emission in the nebulae. We suggest that an impulsive burst may lead
to a highly relativistic flow, which would interact with the nebula. If the
shocked nebula is still relativistic, pre-existing non-thermal particles in the
nebula can be significantly boosted by the forward shock, leading to
short-duration (maybe millisecond or longer) high-energy gamma-ray flashes.
Possible dissipation at the reverse shock may also lead to gamma-ray emission.
(iii) After such flares, interactions with the baryonic ejecta may lead to
afterglow emission with a duration of days to weeks. In the magnetar scenario,
this burst-in-bubble model leads to the expectation that nearby (<10-100 Mpc)
high-energy gamma-ray flashes may be detected by HAWC and CTA, and the
subsequent afterglow emission may be seen by radio telescopes such as VLA. (iv)
Finally, we discuss several implications specific to FRBs, including
constraints on the emission regions and limits on soft gamma-ray counterparts.


title: Locally recoverable codes on algebraic curves

abstract:
  A code over a finite alphabet is called locally recoverable (LRC code) if
every symbol in the encoding is a function of a small number (at most $r$)
other symbols of the codeword. In this paper we introduce a construction of LRC
codes on algebraic curves, extending a recent construction of Reed-Solomon like
codes with locality. We treat the following situations: local recovery of a
single erasure, local recovery of multiple erasures, and codes with several
disjoint recovery sets for every coordinate (the {\em availability problem}).
For each of these three problems we describe a general construction of codes on
curves and construct several families of LRC codes. We also describe a
construction of codes with availability that relies on automorphism groups of
curves.


title: Semigroups of L-space knots and nonalgebraic iterated torus knots

abstract:
  Algebraic knots are known to be iterated torus knots and to admit L-space
surgeries. However, Hedden proved that there are iterated torus knots that
admit L-space surgeries but are not algebraic. We present an infinite family of
such examples, with the additional property that no nontrivial linear
combination of knots in this family is concordant to a linear combination of
algebraic knots. The proof uses the Ozsvath-Stipsicz-Szabo Upsilon function,
and also introduces a new invariant of L-space knots, the formal semigroup.


title:
Cyclic LRC Codes, binary LRC codes, and upper bounds on the distance of
  cyclic codes

abstract:
  We consider linear cyclic codes with the locality property, or locally
recoverable codes (LRC codes). A family of LRC codes that generalize the
classical construction of Reed-Solomon codes was constructed in a recent paper
by I. Tamo and A. Barg (IEEE Trans. Inform. Theory, no. 8, 2014). In this paper
we focus on optimal cyclic codes that arise from this construction. We give a
characterization of these codes in terms of their zeros, and observe that there
are many equivalent ways of constructing optimal cyclic LRC codes over a given
field. We also study subfield subcodes of cyclic LRC codes (BCH-like LRC codes)
and establish several results about their locality and minimum distance. The
locality parameter of a cyclic code is related to the dual distance of this
code, and we phrase our results in terms of upper bounds on the dual distance.


title: Energy-momentum mapping of d-derived Au(111) states in a thin film

abstract:
  The quantum well states of a film can be used to sample the electronic
structure of the parent bulk material and determine its band parameters. We
highlight the benefits of two-dimensional film band mapping, with respect to
complex bulk analysis, in an angle-resolved photoemission spectroscopy study of
the 5d states of Au(111). Discrete 5d-derived quantum well states of various
orbital characters form in Au(111) films and span the width of the
corresponding bulk bands. For sufficiently thick films, the dispersion of these
states samples the bulk band edges, as confirmed by first-principles
calculations, thus providing the positions of the critical points of bulk Au in
agreement with previously determined values. In turn, this analysis identifies
several d-like surface states and resonances with large spin-splittings that
originate from the strong spin-orbit coupling of the Au 5d atomic levels.


title:
The repeating Fast Radio Burst FRB 121102: Multi-wavelength observations
  and additional bursts

abstract:
  We report on radio and X-ray observations of the only known repeating Fast
Radio Burst (FRB) source, FRB 121102. We have detected six additional radio
bursts from this source: five with the Green Bank Telescope at 2 GHz, and one
at 1.4 GHz at the Arecibo Observatory for a total of 17 bursts from this
source. All have dispersion measures consistent with a single value ($\sim559$
pc cm$^{-3}$) that is three times the predicted maximum Galactic value. The
2-GHz bursts have highly variable spectra like those at 1.4 GHz, indicating
that the frequency structure seen across the individual 1.4 and 2-GHz
bandpasses is part of a wideband process. X-ray observations of the FRB 121102
field with the Swift and Chandra observatories show at least one possible
counterpart; however, the probability of chance superposition is high. A radio
imaging observation of the field with the Jansky Very Large Array at 1.6 GHz
yields a 5$\sigma$ upper limit of 0.3 mJy on any point-source continuum
emission. This upper limit, combined with archival WISE 22-$\mu$m and IPHAS
H$\alpha$ surveys, rules out the presence of an intervening Galactic HII
region. We update our estimate of the FRB detection rate in the PALFA survey to
be 1.1$^{+3.7}_{-1.0} \times 10^4$ FRBs sky$^{-1}$ day$^{-1}$ (95% confidence)
for peak flux density at 1.4 GHz above 300 mJy. We find that the intrinsic
widths of the 12 FRB 121102 bursts from Arecibo are, on average, significantly
longer than the intrinsic widths of the 13 single-component FRBs detected with
the Parkes telescope.


title:
Light-front representation of chiral dynamics with Delta isobar and
  large-N_c relations

abstract:
  Transverse densities describe the spatial distribution of electromagnetic
current in the nucleon at fixed light-front time. At peripheral distances b =
O(M_pi^{-1}) the densities are governed by chiral dynamics and can be
calculated model-independently using chiral effective field theory (EFT).
Recent work has shown that the EFT results can be represented in
first-quantized form, as overlap integrals of chiral light-front wave functions
describing the transition of the nucleon to soft-pion-nucleon intermediate
states, resulting in a quantum-mechanical picture of the peripheral transverse
densities. We now extend this representation to include intermediate states
with Delta isobars and implement relations based on the large-N_c limit of QCD.
We derive the wave function overlap formulas for the Delta contributions to the
peripheral transverse densities by way of a three-dimensional reduction of
relativistic chiral EFT expressions. Our procedure effectively maintains
rotational invariance and avoids the ambiguities with higher-spin particles in
the light-front time-ordered approach. We study the interplay of pi-N and
pi-Delta intermediate states in the quantum-mechanical picture of the densities
in a transversely polarized nucleon. We show that the correct N_c-scaling of
the charge and magnetization densities emerges as the result of the particular
combination of currents generated by intermediate states with degenerate N and
Delta. The off-shell behavior of the chiral EFT is summarized in contact terms
and can be studied easily. The methods developed here can be applied to other
peripheral densities and to moments of the nucleon's generalized parton
distributions.


title: Cold Fronts: Probes of Plasma Astrophysics in Galaxy Clusters

abstract:
  The most massive baryonic component of galaxy clusters is the "intracluster
medium" (ICM), a diffuse, hot, weakly magnetized plasma that is most easily
observed in the X-ray band. Despite being observed for decades, the macroscopic
transport properties of the ICM are still not well-constrained. A path to
determine macroscopic ICM properties opened up with the discovery of "cold
fronts". These were observed as sharp discontinuities in surface brightness and
temperature in the ICM, with the property that the brighter (and denser) side
of the discontinuity is the colder one. The high spatial resolution of the
Chandra X-ray Observatory revealed two puzzles about the cold fronts. First,
they should be subject to Kelvin-Helmholtz instabilites, yet in many cases they
appear relatively smooth and undisturbed. Second, the width of the interface
between the two gas phases is typically narrower than the mean free path of the
particles in the plasma, indicating negligible thermal conduction. From the
time of their discovery, it was realized that these special characteristics of
cold fronts may be used to probe the physical properties of the cluster plasma.
In this review, we will discuss the recent simulations of cold front formation
and evolution in galaxy clusters, with a focus on those which have attempted to
use these features to constrain the physics of the ICM. In particular, we will
focus on the effects of magnetic fields, viscosity, and thermal conductivity on
the stability properties and long-term evolution of cold fronts. We conclude
with a discussion on what important questions remain unanswered, and the future
role of simulations and the next generation of X-ray observatories.


title: Network dismantling

abstract:
  We study the network dismantling problem, which consists in determining a
minimal set of vertices whose removal leaves the network broken into connected
components of sub-extensive size. For a large class of random graphs, this
problem is tightly connected to the decycling problem (the removal of vertices
leaving the graph acyclic). Exploiting this connection and recent works on
epidemic spreading we present precise predictions for the minimal size of a
dismantling set in a large random graph with a prescribed (light-tailed) degree
distribution. Building on the statistical mechanics perspective we propose a
three-stage Min-Sum algorithm for efficiently dismantling networks, including
heavy-tailed ones for which the dismantling and decycling problems are not
equivalent. We also provide further insights into the dismantling problem
concluding that it is an intrinsically collective problem and that optimal
dismantling sets cannot be viewed as a collection of individually well
performing nodes.


title: A Parallel-Hierarchical Model for Machine Comprehension on Sparse Data

abstract:
  Understanding unstructured text is a major goal within natural language
processing. Comprehension tests pose questions based on short text passages to
evaluate such understanding. In this work, we investigate machine comprehension
on the challenging {\it MCTest} benchmark. Partly because of its limited size,
prior work on {\it MCTest} has focused mainly on engineering better features.
We tackle the dataset with a neural approach, harnessing simple neural networks
arranged in a parallel hierarchy. The parallel hierarchy enables our model to
compare the passage, question, and answer from a variety of trainable
perspectives, as opposed to using a manually designed, rigid feature set.
Perspectives range from the word level to sentence fragments to sequences of
sentences; the networks operate only on word-embedding representations of text.
When trained with a methodology designed to help cope with limited training
data, our Parallel-Hierarchical model sets a new state of the art for {\it
MCTest}, outperforming previous feature-engineered approaches slightly and
previous neural approaches by a significant margin (over 15\% absolute).


title: On the Performance of Delay Aware Shared Access with Priorities

abstract:
  In this paper, we analyze a shared access network with a fixed primary node
and randomly distributed secondary nodes whose distribution follows a Poisson
point process (PPP). The secondaries use a random access protocol allowing them
to access the channel with probabilities that depend on the queue size of the
primary. Assuming a system with multipacket reception (MPR) receivers having
bursty packet arrivals at the primary and saturation at the secondaries, our
protocol can be tuned to alleviate congestion at the primary. We study the
throughput of the secondary network and the primary average delay, as well as
the impact of the secondary node access probability and transmit power. We
formulate an optimization problem to maximize the throughput of the secondary
network under delay constraints for the primary node, which in the case that no
congestion control is performed has a closed form expression providing the
optimal access probability. Our numerical results illustrate the impact of
network operating parameters on the performance of the proposed priority-based
shared access protocol.


title:
The influence of mergers and ram-pressure stripping on black hole-bulge
  correlations

abstract:
  We analyse the scatter in the correlation between super-massive black hole
(SMBH) mass and bulge stellar mass of the host galaxy, and infer that it cannot
be accounted for by mergers alone. The merger-only scenario, where small
galaxies merge to establish a proportionality relation between the SMBH and
bulge masses, leads to a scatter around the linear proportionality line that
increases with the square root of the SMBH (or bulge) mass. By examining a
sample of 103 galaxies we find that the intrinsic scatter increases more
rapidly than expected from the merger-only scenario. The correlation between
SMBH masses and their host galaxy properties is therefore more likely to be
determined by a negative feedback mechanism that is driven by an active
galactic nucleus. We find a hint that some galaxies with missing stellar mass
reside close to the centre of clusters and speculate that ram-pressure
stripping of gas off the young galaxy as it moves near the cluster centre,
might explain the missing stellar mass at later times.


title:
Learning-Based Single-Document Summarization with Compression and
  Anaphoricity Constraints

abstract:
  We present a discriminative model for single-document summarization that
integrally combines compression and anaphoricity constraints. Our model selects
textual units to include in the summary based on a rich set of sparse features
whose weights are learned on a large corpus. We allow for the deletion of
content within a sentence when that deletion is licensed by compression rules;
in our framework, these are implemented as dependencies between subsentential
units of text. Anaphoricity constraints then improve cross-sentence coherence
by guaranteeing that, for each pronoun included in the summary, the pronoun's
antecedent is included as well or the pronoun is rewritten as a full mention.
When trained end-to-end, our final system outperforms prior work on both ROUGE
as well as on human judgments of linguistic quality.


title: Center manifolds of coupled cell networks

abstract:
  Dynamical systems with a network structure can display anomalous bifurcations
as a generic phenomenon. As an explanation for this it has been noted that
homogeneous networks can be realized as quotient networks of so-called
fundamental networks. The class of admissible vector fields for these
fundamental networks is equal to the class of equivariant vector fields of the
regular representation of a monoid. Using this insight, we set up a framework
for center manifold reduction in fundamental networks and their quotients. We
then use this machinery to explain the difference in generic bifurcations
between three example networks with identical spectral properties and identical
robust synchrony spaces.


title:
Technical Note: Proximal Ordered Subsets Algorithms for TV Constrained
  Optimization in CT Image Reconstruction

abstract:
  This article is intended to supplement our 2015 paper in Medical Physics
titled "Noise properties of CT images reconstructed by use of constrained
total-variation, data-discrepancy minimization", in which ordered subsets
methods were employed to perform total-variation constrained data-discrepancy
minimization for image reconstruction in X-ray computed tomography. Here we
provide details regarding implementation of the ordered subsets algorithms and
suggestions for selection of algorithm parameters. Detailed pseudo-code is
included for every algorithm implemented in the original manuscript.


title:
Impact of photon cross section systematic uncertainties on Monte
  Carlo-determined depth-dose distributions

abstract:
  This work studies the impact of systematic uncertainties associated to
interaction cross sections on depth dose curves determined by Monte Carlo
simulations. The corresponding sensitivity factors are quantified by changing
cross sections in a given amount and determining the variation in the dose. The
influence of total cross sections for all particles, photons and only for
Compton scattering is addressed. The PENELOPE code was used in all simulations.
It was found that photon cross section sensitivity factors depend on depth. In
addition, they are positive and negative for depths below and above an
equilibrium depth, respectively. At this depth, sensitivity factors are null.
The equilibrium depths found in this work agree very well with the mean free
path of the corresponding incident photon energy. Using the sensitivity factors
reported here, it is possible to estimate the impact of photon cross section
uncertainties on the uncertainty of Monte Carlo-determined depth dose curves.


title:
First-principles investigation of MnP magnetic states precursors of
  superconductivity under high pressure

abstract:
  The discovery of a superconducting dome in the proximity of the magnetic to
paramagnetic transition in the electronic phase diagram of MnP as a function of
hydrostatic pressure has renewed the interest in the magnetic properties of
this binary pnictide. Here we present an ab initio study obtained with Density
Functional Theory (DFT) simulations as a function of pressure. We show that the
itinerant-electron magnetism of MnP is well characterized by the mean-field
Kohn-Sham method which correctly describes the ambient pressure magnetic
states, the anomalous trend of the lattice parameters as a function of pressure
and the critical pressure for the disappearance of the magnetic order. We are
finally able to confirm the nature of the new helical structure observed at
high pressure.


title:
Spitzer observations of extragalactic H II regions - III. NGC 6822 and
  the hot star, H II region connection

abstract:
  Using the short-high module of the Infrared Spectrograph on the Spitzer Space
Telescope, we have measured the [S IV] 10.51, [Ne II] 12.81, [Ne III] 15.56,
and [S III] 18.71-micron emission lines in nine H II regions in the dwarf
irregular galaxy NGC 6822. These lines arise from the dominant ionization
states of the elements neon (Ne$^{++}$, Ne$^+$) and sulphur (S$^{3+}$,
S$^{++}$), thereby allowing an analysis of the neon to sulphur abundance ratio
as well as the ionic abundance ratios Ne$^+$/Ne$^{++}$ and S$^{3+}$/S$^{++}$.
By extending our studies of H II regions in M83 and M33 to the lower
metallicity NGC 6822, we increase the reliability of the estimated Ne/S ratio.
We find that the Ne/S ratio appears to be fairly universal, with not much
variation about the ratio found for NGC 6822: the median (average) Ne/S ratio
equals 11.6 (12.2$\pm$0.8). This value is in contrast to Asplund et al.'s
currently best estimated value for the Sun: Ne/S = 6.5. In addition, we
continue to test the predicted ionizing spectral energy distributions (SEDs)
from various stellar atmosphere models by comparing model nebulae computed with
these SEDs as inputs to our observational data, changing just the stellar
atmosphere model abundances. Here we employ a new grid of SEDs computed with
different metallicities: Solar, 0.4 Solar, and 0.1 Solar. As expected, these
changes to the SED show similar trends to those seen upon changing just the
nebular gas metallicities in our plasma simulations: lower metallicity results
in higher ionization. This trend agrees with the observations.


title: Finite strain FFT-based non-linear solvers made simple

abstract:
  Computational micromechanics and homogenization require the solution of the
mechanical equilibrium of a periodic cell that comprises a (generally complex)
microstructure. Techniques that apply the Fast Fourier Transform have attracted
much attention as they outperform other methods in terms of speed and memory
footprint. Moreover, the Fast Fourier Transform is a natural companion of
pixel-based digital images which often serve as input. In its original form,
one of the biggest challenges for the method is the treatment of
(geometrically) non-linear problems, partially due to the need for a uniform
linear reference problem. In a geometrically linear setting, the problem has
recently been treated in a variational form resulting in an unconditionally
stable scheme that combines Newton iterations with an iterative linear solver,
and therefore exhibits robust and quadratic convergence behavior. Through this
approach, well-known key ingredients were recovered in terms of discretization,
numerical quadrature, consistent linearization of the material model, and the
iterative solution of the resulting linear system. As a result, the extension
to finite strains, using arbitrary constitutive models, is at hand. Because of
the application of the Fast Fourier Transform, the implementation is
substantially easier than that of other (Finite Element) methods. Both claims
are demonstrated in this paper and substantiated with a simple code in Python
of just 59 lines (without comments). The aim is to render the method
transparent and accessible, whereby researchers that are new to this method
should be able to implement it efficiently. The potential of this method is
demonstrated using two examples, each with a different material model.


title: Persisting correlations of a central spin coupled to large spin baths

abstract:
  The decohering environment of a quantum bit is often described by the
coupling to a large bath of spins. The quantum bit itself can be seen as a spin
$S=1/2$ which is commonly called the central spin. The resulting central spin
model describes an important mechanism of decoherence. We provide
mathematically rigorous bounds for a persisting magnetization of the central
spin in this model with and without magnetic field. In particular, we show that
there is a well defined limit of infinite number of bath spins. Only if the
fraction of very weakly coupled bath spins tends to 100\% does no magnetization
persist.


title: Latent Embeddings for Zero-shot Classification

abstract:
  We present a novel latent embedding model for learning a compatibility
function between image and class embeddings, in the context of zero-shot
classification. The proposed method augments the state-of-the-art bilinear
compatibility model by incorporating latent variables. Instead of learning a
single bilinear map, it learns a collection of maps with the selection, of
which map to use, being a latent variable for the current image-class pair. We
train the model with a ranking based objective function which penalizes
incorrect rankings of the true class for a given image. We empirically
demonstrate that our model improves the state-of-the-art for various class
embeddings consistently on three challenging publicly available datasets for
the zero-shot setting. Moreover, our method leads to visually highly
interpretable results with clear clusters of different fine-grained object
properties that correspond to different latent variable maps.


title:
Quantum phase diagram of $J_1-J_2$ Heisenberg $S=1/2$ antiferromagnet in
  honeycomb lattice: a modified spin wave study

abstract:
  Using modified spin wave (MSW) method, we study the $J_1-J_2$ Heisenberg
model with first and second neighbor antiferromagnetic exchange interactions.
For symmetric $S=1/2$ model, with the same couplings for all the equivalent
neighbors, we find three phase in terms of frustration parameter
${\bar\alpha=J_2/J_1}$: (1) a commensurate collinear ordering with staggered
magnetization (N{\'e}el.I state) for $0\leq{\bar\alpha}\lesssim 0.207$ , (2) a
magnetically gapped disordered state for $0.207\lesssim{\bar\alpha}\lesssim
0.369$, preserving all the symmetries of the Hamiltonian and lattice, hence by
definition is a quantum spin liquid (QSL) state and (3) a commensurate
collinear ordering in which two out of three nearest neighbor magnetizations
are antiparallel and the remaining pair are parallel (N{\'e}el.II state), for
$0.396\lesssim{\bar\alpha}\leq 1$. We also explore the phase diagram of
distorted $J_1-J_2$ model with $S=1/2$. Distortion is introduced as an
inequality of one nearest neighbor coupling with the other two. This yields a
richer phase diagram by the appearance of a new gapped QSL, a gapless QSL and
also a valence bond crystal (VBC) phase in addition to the previously three
phases found for undistorted model.


title:
Inverse correlation between quasiparticle mass and Tc in a cuprate
  high-Tc superconductor

abstract:
  Close to a zero temperature transition between ordered and disordered
electronic phases, quantum fluctuations can lead to a strong enhancement of the
electron mass and to the emergence of competing phases such as
superconductivity. A correlation between the existence of such a quantum phase
transition and superconductivity is quite well established in some heavy
fermion and iron-based superconductors and there have been suggestions that
high temperature superconductivity in the copper oxide materials (cuprates) may
also be driven by the same mechanism. Close to optimal doping, where the
superconducting transition temperature $T_c$ is maximum in the cuprates, two
different phases are known to compete with superconductivity: a poorly
understood pseudogap phase and a charge ordered phase. Recent experiments have
shown a strong increase in quasiparticle mass $m^*$ in the cuprate
YBa$_2$Cu$_3$O$_{7-\delta}$ as optimal doping is approached suggesting that
quantum fluctuations of the charge ordered phase may be responsible for the
high-$T_c$ superconductivity. We have tested the robustness of this correlation
between $m^*$ and $T_c$ by performing quantum oscillation studies on the
stoichiometric compound YBa$_2$Cu$_4$O$_8$ under hydrostatic pressure. In
contrast to the results for YBa$_2$Cu$_3$O$_{7-\delta}$, we find that in
YBa$_2$Cu$_4$O$_8$ the mass decreases as $T_c$ increases under pressure. This
inverse correlation between $m^*$ and $T_c$ suggests that quantum fluctuations
of the charge order enhance $m^*$ but do not enhance $T_c$.


title:
Fracture initiation in multi-phase materials: a statistical
  characterization of microstructural damage sites

abstract:
  Understanding the microstructural influence on the failure mechanisms in
multi-phase materials calls for the identification of the worst-case scenario.
This necessitates a statistical approach. By performing simulations directly
based on micrographs, such an approach becomes feasible. This is applied here
to extract the average microstructure around damage sites.


title: Thermoelasticity of Fe$^{3+}$- and Al-bearing bridgmanite

abstract:
  We report \textit{ab initio} (LDA + U$_{sc}$) calculations of thermoelastic
properties of ferric iron (Fe$^{3+}$)- and aluminum (Al)-bearing bridgmanite
(MgSiO$_3$ perovskite), the main Earth forming phase, at relevant pressure and
temperature conditions and compositions. Three coupled substitutions, namely,
[Al]$_{Mg}$-[Al]$_{Si}$, [Fe$^{3+}$]$_{Mg}$-[Fe$^{3+}$]$_{Si}$, and
[Fe$^{3+}$]$_{Mg}$-[Al]$_{Si}$ have been investigated. Aggregate elastic moduli
and sound velocities are successfully compared with limited experimental data
available. In the case of the [Fe$^{3+}$]$_{Mg}$-[Fe$^{3+}$]$_{Si}$
substitution, the high-spin (S=5/2) to low-spin (S=1/2) crossover in
[Fe$^{3+}$]$_{Si}$ induces a volume collapse and elastic anomalies across the
transition region. However, the associated anomalies should disappear in the
presence of aluminum in the most favorable substitution, i.e.,
[Fe$^{3+}$]$_{Mg}$-[Al]$_{Si}$. Calculated elastic properties along a lower
mantle model geotherm suggest that the elastic behavior of bridgmanite with
simultaneous substitution of Fe$_{2}$O$_3$ and Al$_{2}$O$_3$ in equal
proportions or with Al$_{2}$O$_3$ in excess should be similar to that of
(Mg,Fe$^{2+}$)SiO$_3$ bridgmanite. Excess Fe$_{2}$O$_3$ should produce elastic
anomalies though.


title: Thermoelectrics with Coulomb coupled quantum dots

abstract:
  In this article we review the thermoelectric properties of three terminal
devices with Coulomb coupled quantum dots (QDs) as observed in recent
experiments [1,2]. The system we consider consists of two Coulomb-blockade QDs
one of which can exchange electrons with only a single reservoir (heat
reservoir) while the other dot is tunnel coupled to two reservoirs at a lower
temperature (conductor). The heat reservoir and the conductor interact only via
the Coulomb-coupling of the quantum dots. It has been found that two regimes
have to be considered. In the first one heat flow between the two systems is
small. In this regime thermally driven occupation fluctuations of the hot QD
modify the transport properties of the conductor system. This leads to an
effect called thermal gating. Experiment have shown how this can be used to
control charge flow in the conductor by means of temperature in a remote
reservoir. We further substantiate the observations with model calculations and
implications for the realization of an all-thermal transistor are discussed. In
the second regime, heat flow between the two systems is relevant. Here the
system works as a nano scale heat engine, as proposed recently [3]. We review
the conceptual idea, its experimental realization and the novel features
arising in this new kind of thermoelectric device such as decoupling of heat
and charge flow.


title: Perfect powers that are sums of consecutive cubes

abstract:
  Euler noted the relation $6^3=3^3+4^3+5^3$ and asked for other instances of
cubes that are sums of consecutive cubes. Similar problems have been studied by
Cunningham, Catalan, Gennochi, Lucas, Pagliani, Cassels, Uchiyama, Stroeker and
Zhongfeng Zhang. In particular Stroeker determined all squares that can be
written as a sum of at most $50$ consecutive cubes. We generalize Stroeker's
work by determining all perfect powers that are sums of at most $50$
consecutive cubes. Our methods include descent, linear forms in two logarithms,
and Frey-Hellegouarch curves.


title: The Lexington Benchmarks for Numerical Simulations of Nebulae

abstract:
  We present the results of a meeting on numerical simulations of ionized
nebulae held at the University of Kentucky in conjunction with the celebration
of the 70th birthdays of Profs. Donald Osterbrock and Michael Seaton.


title:
Many-electron effects on the x-ray Rayleigh scattering by highly charged
  He-like ions

abstract:
  The Rayleigh scattering of x-rays by many-electron highly charged ions is
studied theoretically. The many-electron perturbation theory, based on a
rigorous quantum electrodynamics approach, is developed and implemented for the
case of the elastic scattering of (high-energetic) photons by helium-like ion.
Using this elaborate approach, we here investigate the many-electron effects
beyond the independent-particle approximation (IPA) as conventionally employed
for describing the Rayleigh scattering. The total and angle-differential cross
sections are evaluated for the x-ray scattering by helium-like Ni$^{26+}$,
Xe$^{52+}$, and Au$^{77+}$ ions in their ground state. The obtained results
show that, for high-energetic photons, the effects beyond the IPA do not exceed
2% for the scattering by a closed $K$-shell.


title: Mathematical Harmony Analysis

abstract:
  Musical chords, harmonies or melodies in Just Intonation have note
frequencies which are described by a base frequency multiplied by rational
numbers. For any local section, these notes can be converted to some base
frequency multiplied by whole positive numbers. The structure of the chord can
be analysed mathematically by finding functions which are unchanged upon chord
transposition. These functions are are denoted invariant, and are important for
understanding the structure of harmony. Each chord described by whole numbers
has a greatest common divisor, GCD, and a lowest common multiple, LCM. The
ratio of these is denoted Complexity which is a positive whole number. The set
of divisors of Complexity give a subset of a p limit tone lattice and have both
a natural ordering and a multiplicative structure. The position and orientation
of the original chord, on the ordered set or on the lattice, give rise to many
other invariant functions including measures for otonality and utonality. Other
invariant functions can be constructed from: ratios between note pairs, prime
projections, weighted chords which incorporate loudness. Given a set of
conditions described by invariant functions, algorithms can be developed to
find all scales or chords meeting those conditions, allowing the classification
of consonant harmonies up to specified limits.


title:
The Limit Spectral Graph in the Semi-Classical Approximation for the
  Sturm-Liouville Problem With a Complex Polynomial Potential

abstract:
  The limit distribution of the discrete spectrum of the Sturm-Liouville
problem with complex-valued polynomial potential on an interval, on a
half-axis, and on the entire axis is studied. It is shown that at large
parameter values, the eigenvalues are concentrated along the so-called limit
spectral graph; the curves forming this graph are classified. Asymptotics of
eigenvalues along curves of various types in the graph are calculated.


title: A Critical Appraisal and Evaluation of Modern PDFs

abstract:
  We review the present status of the determination of parton distribution
functions (PDFs) in the light of the precision requirements for the LHC in Run
2 and other future hadron colliders. We provide brief reviews of all currently
available PDF sets and use them to compute cross sections for a number of
benchmark processes, including Higgs boson production in gluon-gluon fusion at
the LHC. We show that the differences in the predictions obtained with the
various PDFs are due to particular theory assumptions made in the fits of those
PDFs. We discuss PDF uncertainties in the kinematic region covered by the LHC
and on averaging procedures for PDFs, such as advocated by the PDF4LHC15 sets,
and provide recommendations for the usage of PDF sets for theory predictions at
the LHC.


title: Cross-modal Supervision for Learning Active Speaker Detection in Video

abstract:
  In this paper, we show how to use audio to supervise the learning of active
speaker detection in video. Voice Activity Detection (VAD) guides the learning
of the vision-based classifier in a weakly supervised manner. The classifier
uses spatio-temporal features to encode upper body motion - facial expressions
and gesticulations associated with speaking. We further improve a generic model
for active speaker detection by learning person specific models. Finally, we
demonstrate the online adaptation of generic models learnt on one dataset, to
previously unseen people in a new dataset, again using audio (VAD) for weak
supervision. The use of temporal continuity overcomes the lack of clean
training data. We are the first to present an active speaker detection system
that learns on one audio-visual dataset and automatically adapts to speakers in
a new dataset. This work can be seen as an example of how the availability of
multi-modal data allows us to learn a model without the need for supervision,
by transferring knowledge from one modality to another.


title:
An $L_p$-estimate for the stochastic heat equation on an angular domain
  in $\mathbb{R}^2$

abstract:
  We prove a weighted $L_p$-estimate for the stochastic convolution associated
to the stochastic heat equation with zero Dirichlet boundary condition on a
planar angular domain $\mathcal{D}_{\kappa_0}\subset\mathbb{R}^2$ with angle
$\kappa_0\in(0,2\pi)$. Furthermore, we use this estimate to establish existence
and uniqueness of a solution to the corresponding equation in suitable weighted
$L_p$-Sobolev spaces. In order to capture the singular behaviour of the
solution and its derivatives at the vertex, we use powers of the distance to
the vertex as weight functions. The admissible range of weight parameters
depends explicitly on the angle $\kappa_0$.


title:
Yu-Shiba-Rusinov states and topological superconductivity in Ising
  paired superconductors

abstract:
  An unusual form of superconductivity, called Ising superconductivity, has
recently been uncovered in mono- and few-layered transition metal
dichalcogenides. This 2D superconducting state is characterized by the
so-called Ising spin-orbit coupling (SOC), which produces strong oppositely
oriented effective Zeeman fields perpendicular to the 2D layer in opposite
momentum space valleys. We examine the Yu-Shiba-Rusinov (YSR) bound states
localized at magnetic impurities in Ising superconductors and show that the
unusual SOC manifests itself in unusually strong anisotropy in magnetic field
response of zero bias conductance peaks observable in STM experiments on
impurity sites. For a chain of magnetic impurities with moments parallel to the
plane of Ising superconductors we show that the low energy YSR band can host
topological superconductivity and Majorana fermions as a direct manifestation
of Ising spin-orbit coupling induced topological effects.


title:
Fracture in multi-phase materials: why some microstructures are more
  critical than others

abstract:
  Our goal is to unravel the mechanisms that lead to failure of a ductile
two-phase material - that consists of a ductile soft phase and a relatively
brittle hard phase. An idealized microstructural model is used to study damage
propagation systematically and transparently. The analysis uncovers distinct
microstructural features around early voids, whereby regions of the hard phase
are aligned with the tensile axis and regions of the soft phase are aligned
with the shear directions. These features are consistently found in regions
exhibiting damage propagation, whereby the damage remains initiation driven,
i.e. voids nucleate independently of each other. Upon localization, damage is
controlled on a longer length-scale relying on a critical relative position of
'initiation hot-spots'. The damage rapidly increases in bands of the soft phase
wherein several voids are aligned with the shear directions. The relative
arrangement of the voids determines whether the microstructure fails early, or
at a substantially higher strain. Although much research is needed to refine
these findings for real or more realistic microstructures, in particular in
three-dimensions, this paper opens a route to a deeper understanding of the
ultimate failure of multi-phase materials.


title: Pinning down electroweak dipole operators of the top quark

abstract:
  We consider hadronic top quark pair production and pair production in
association with a photon or a $Z$ boson to probe electroweak dipole couplings
in $t\bar{b}W$, $t\bar{t}\gamma$ and $t\bar{t}Z$ interactions. We demonstrate
how measurements of these processes at the 13 TeV LHC can be combined to
disentangle and constrain anomalous dipole operators. The construction of cross
section ratios allows us to significantly reduce various uncertainties and
exploit orthogonal sensitivity between the $t\bar{t}\gamma$ and $t\bar{t}Z$
couplings. In addition, we show that angular correlations in $t\bar{t}$
production can be used to constrain the remaining $t\bar{b}W$ dipole operator.
Our approach yields excellent sensitivity to the anomalous couplings and can be
a further step towards precise and direct measurements of the top quark
electroweak interactions.


title:
The focusing cubic NLS with inverse-square potential in three space
  dimensions

abstract:
  We consider the focusing cubic nonlinear Schr\"odinger equation with
inverse-square potential in three space dimensions. We identify a sharp
threshold between scattering and blowup, establishing a result analogous to
that of Duyckaerts, Holmer, and Roudenko for the standard focusing cubic NLS.
We also prove failure of uniform space-time bounds at the threshold.


title: A 750 GeV graviton from holographic composite dark sectors

abstract:
  We show that the 750 GeV di-photon excess can be interpreted as a spin-2
resonance arising from a strongly interacting dark sector featuring some
departure from conformality. This spin-2 resonance has negligible couplings to
the SM particles, with the exception of the SM gauge bosons which mediate
between the two sectors. We have explicitly studied the collider constraints as
well as some theoretical bounds in a holographic five dimensional model with a
warp factor that deviates from AdS$_5$. In particular, we have shown that it is
not possible to decouple the vector resonances arising from the strong sector
while explaining the di-photon anomaly and keeping the five dimensional gravity
theory under perturbative control. However, vector resonances with masses
around the TeV scale can be present while all experimental constraints are met.


title:
Search for dark matter particles in proton-proton collisions at sqrt(s)
  = 8 TeV using the razor variables

abstract:
  A search for dark matter particles directly produced in proton-proton
collisions recorded by the CMS experiment at the LHC is presented. The data
correspond to an integrated luminosity of 18.8 inverse femtobarns, at a
center-of-mass energy of 8 TeV. The event selection requires at least two jets
and no isolated leptons. The razor variables are used to quantify the
transverse momentum balance in the jet momenta. The study is performed
separately for events with and without jets originating from b quarks. The
observed yields are consistent with the expected backgrounds and, depending on
the nature of the production mechanism, dark matter production at the LHC is
excluded at 90% confidence level for a mediator mass scale Lambda below 1 TeV.
The use of razor variables yields results that complement those previously
published.


title:
Several realizations of Fock modules for quantum toroidal algebras of
  sl(n)

abstract:
  In this paper, we relate the well-known Fock representations of the quantum
toroidal algebra of sl(n) to the vertex, shuffle, and L-operator
representations of the same algebra. These identifications generalize those for
the quantum toroidal algebra of gl(1), which were recently established by
Feigin-Jimbo-Miwa-Mukhin.


title: The new axiom of set theory and Bell inequality

abstract:
  The new axiom in set theory, axiom of the empty sets, allows another way to
formulate Bell inequality in quantum mechanics. The new axiom emerges from the
historical and philosophical analysis of set theory.


title: On the Firoozbakht's conjecture

abstract:
  This paper proves Firoozbakht's conjecture using Rosser and Schoenfelds'
inequality on the distribution of primes. This inequality is valid for all
natural numbers ${n\geq 21}$. Firoozbakht's conjecture states that if $
{p_{n}}$ and ${p_{(n+1)}}$ are consecutive prime numbers, then
${p_{(n+1)}^{1/(n+1)}< p_{n}^{1/n}}$ for every ${n\geq 1}$. Rosser's inequality
for the ${n}$th and ${(n+1)}$th roots, changes from strictly increasing to
strictly decreasing for ${n\geq 21}$. The inequality is considered for
${n>e^{e^{3/2}}}$, i.e., ${n\geq 89}$, but since the inequalities for ${n\geq
195340>e^{e^{5/2}}}$, are also required, these inequalities are explicitly
proven as well. Silva has already verified Firoozbakht's conjecture up to
${p_{n}<4 \times 10^{18}}$, and the additional theorem is proven here that
there is the smallest natural number, ${m>n\geq 1}$ and ${p_{m}^{1/m}<
p_{n}^{1/n}}$. It is also shown that there is a unique one to one function,
which maps each element ${p_n}$ to each element ${p_{n}^{1/n}}$ for every
${n\geq 1}$ and ${1<p_{n}^{1/n}\leq 2}$. Finally, it is proved that there is a
strictly decreasing sequence and Firoozbakht's conjecture would be true for all
${n\geq 1}$.


title:
Analysis of the ground level enhancements on 14 July 2000 and on 13
  December 2006 using neutron monitor data

abstract:
  On the basis of neutron monitor data we estimate the energy spectrum,
anisotropy axis direction and pitch-angle distribution of solar energetic
particles during two major ground level enhancements (GLE 59 on 14 July 2000
and GLE 70 on 13 December 2006). For the analysis we use a newly computed
neutron monitor yield function. The method consists of several consecutive
steps: definition of the asymptotic viewing cones of neutron monitor stations
considered for the data analysis by computations of cosmic ray particles
propagation in a model magnetosphere with the MAGNETOCOSMICS code; computation
of the neutron monitor model responses and derivation of the solar energetic
particle characteristics on the basis of inverse problem solution. The
pitch-angle distribution and rigidity spectrum of high-energy protons are
obtained as function of time in the course of ground level enhancements. A
comparison with previously reported results is performed and reasonable
agreement is achieved. A discussion of the obtained results is included as well
their possible application is included.


title:
Enhanced tidal stripping of satellites in the galactic halo from dark
  matter self-interactions

abstract:
  We investigate the effects of self-interacting dark matter (SIDM) on the
tidal stripping and evaporation of satellite galaxies in a Milky Way-like host.
We use a suite of five zoom-in, dark-matter-only simulations, two with
velocity-independent SIDM cross sections, two with velocity-dependent SIDM
cross sections, and one cold dark matter simulation for comparison. After
carefully assigning stellar mass to satellites at infall, we find that stars
are stripped at a higher rate in SIDM than in CDM. In contrast, the total bound
dark matter mass loss rate is minimally affected, with subhalo evaporation
having negligible effects on satellites for viable SIDM models. Centrally
located stars in SIDM haloes disperse out to larger radii as cores grow.
Consequently, the half-light radius of satellites increases, stars become more
vulnerable to tidal stripping, and the stellar mass function is suppressed. We
find that the ratio of core radius to tidal radius accurately predicts the
relative strength of enhanced SIDM stellar stripping. Velocity-independent SIDM
models show a modest increase in the stellar stripping effect with satellite
mass, whereas velocity-dependent SIDM models show a large increase in this
effect towards lower masses, making observations of ultra-faint dwarfs prime
targets for distinguishing between and constraining SIDM models. Due to small
cores in the largest satellites of velocity-dependent SIDM, no identifiable
imprint is left on the all-sky properties of the stellar halo. While our
results focus on SIDM, the main physical mechanism of enhanced tidal stripping
of stars apply similarly to satellites with cores formed via other means.


title:
Mass ratio determination from Halpha lines in Black-Hole X-ray
  transients

abstract:
  We find that the mass ratio q in quiescent black hole (BH) X-ray transients
is tightly correlated with the ratio of the double peak separation (DP) to the
full-width-half maximum (FWHM) of the Halpha emission line, log q = -6.88 -23.2
log (DP/FWHM). The correlation is explained through the efficient truncation of
the outer disc radius by the 3:1 resonance with the companion star. This is the
dominant tidal interaction for extreme mass ratios q=M2/M1<~0.25, the realm of
BH (and some neutron star) X-ray transients. Mass ratios can thus be estimated
with a typical uncertainty of ~32%, provided that the Halpha profile used to
measure DP/FWHM is an orbital phase average. We apply the DP/FWHM-q relation to
the three faint BH transients XTE J1650-500, XTE J1859+226 and Swift J1357-0933
and predict q=0.026 (+0.038-0.007), 0.049 (+0.023-0.012) and 0.040
(+0.003-0.005), respectively. This new relation, together with the FWHM-K2
correlation presented in Paper I (casares 2015) allows the extraction of
fundamental parameters from very faint targets and, therefore, the extension of
dynamical BH studies to much deeper limits than was previously possible. As an
example, we combine our mass ratio determination for Swift J1357-0933 with
previous results to yield a BH mass of 12.4+-3.6 Msun. This confirms Swift
J1357-0933 as one of the most massive BH low-mass X-ray binaries in the Galaxy.


title: Turbulent Chemical Diffusion in Convectively Bounded Carbon Flames

abstract:
  It has been proposed that mixing induced by convective overshoot can disrupt
the inward propagation of carbon deflagrations in super-asymptotic giant branch
stars. To test this theory, we study an idealized model of convectively bounded
carbon flames with 3D hydrodynamic simulations of the Boussinesq equations
using the pseudospectral code Dedalus. Because the flame propagation timescale
is much longer than the convection timescale, we approximate the flame as fixed
in space, and only consider its effects on the buoyancy of the fluid. By
evolving a passive scalar field, we derive a {\it turbulent} chemical
diffusivity produced by the convection as a function of height, $D_{\rm t}(z)$.
Convection can stall a flame if the chemical mixing timescale, set by the
turbulent chemical diffusivity, $D_{\rm t}$, is shorter than the flame
propagation timescale, set by the thermal diffusivity, $\kappa$, i.e., when
$D_{\rm t}>\kappa$. However, we find $D_{\rm t}<\kappa$ for most of the flame
because convective plumes are not dense enough to penetrate into the flame.
Extrapolating to realistic stellar conditions, this implies that convective
mixing cannot stall a carbon flame and that "hybrid carbon-oxygen-neon" white
dwarfs are not a typical product of stellar evolution.


title:
Stray, swing and scatter: angular momentum evolution of orbits and
  streams in aspherical potentials

abstract:
  In aspherical potentials orbital planes continuously evolve. The
gravitational torques impel the angular momentum vector to precess, that is to
slowly stray around the symmetry axis, and nutate, i.e. swing up and down
periodically in the perpendicular direction. This familiar orbital pole motion
- if detected and measured - can reveal the shape of the underlying
gravitational potential, the quantity only crudely gauged in the Galaxy so far.
Here we demonstrate that the debris poles of stellar tidal streams show a very
similar straying and swinging behavior, and give analytic expressions to link
the amplitude and the frequency of the pole evolution to the flattening of the
dark matter distribution. While these results are derived for near-circular
orbits, we show they are also valid for eccentric orbits. Most importantly, we
explain how the differential orbital plane precession leads to the broadening
of the stream and show that streams on polar orbits ought to scatter faster. We
provide expressions for the stream width evolution as a function of the
axisymmetric potential flattening and the angle from the symmetry plane and
prove that our models are in good agreement with streams produced in N-body
simulations. Interestingly, the same intuition applies to streams whose
progenitors are on short or long-axis loops in a triaxial potential. Finally,
we present a compilation of the Galactic cold stream data, and discuss how the
simple picture developed here, along with stream modelling, can be used to
constrain the symmetry axes and flattening of the Milky Way.


title:
Cosmological Simulations of Early Blackhole Formation: Halo Mergers,
  Tidal Disruption, and the Conditions for Direct Collapse

abstract:
  Gravitational collapse of a massive primordial gas cloud is thought to be a
promising path for the formation of supermassive blackholes in the early
universe. We study conditions for the so-called direct collapse (DC) blackhole
formation in a fully cosmological context. We combine a semianalytic model of
early galaxy formation with halo merger trees constructed from dark matter
$N$-body simulations. We locate a total of 68 possible DC sites in a volume of
$20\;h^{-1}\;\mathrm{Mpc}$ on a side. We then perform hydrodynamics simulations
for 42 selected halos to study in detail the evolution of the massive clouds
within them. We find only two successful cases where the gas clouds rapidly
collapse to form stars. In the other cases, gravitational collapse is prevented
by the tidal force exerted by a nearby massive halo, which otherwise should
serve as a radiation source necessary for DC. Ram pressure stripping disturbs
the cloud approaching the source. In many cases, a DC halo and its nearby light
source halo merge before the onset of cloud collapse. Only when the DC halo is
assembled through major mergers, the gas density increases rapidly to trigger
gravitational instability. Based on our cosmological simulations, we conclude
that the event rate of DC is an order of magnitude smaller than reported in
previous studies, although the absolute rate is still poorly constrained. It is
necessary to follow the dynamical evolution of a DC cloud and its nearby
halo(s) in order to determine the critical radiation flux for DC.


title:
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Exploring the
  dependence of the three-point correlation function on stellar mass and
  luminosity at 0.5<z<1.1

abstract:
  The three-point correlation function (3PCF) is a powerful probe to
investigate the clustering of matter in the Universe in a complementary way
with respect to lower-order statistics, providing additional information with
respect to the two-point correlation function and allowing us to shed light on
biasing, nonlinear processes, and deviations from Gaussian statistics. In this
paper, we analyse the first data release of the VIMOS Public Extragalactic
Redshift Survey (VIPERS), determining the dependence of the three-point
correlation function on luminosity and stellar mass at $z=[0.5,1.1]$. We
exploit the VIPERS Public Data Release 1, consisting of more than 50,000
galaxies with B-band magnitudes in the range $-21.6\lesssim M_{\rm
B}-5\log(h)\lesssim-19.9$ and stellar masses in the range
$9.8\lesssim\log(M_\star[h^{-2}\,M_\odot])\lesssim 10.7$. We measure both the
connected 3PCF and the reduced 3PCF in redshift space, probing different
configurations and scales, in the range $2.5<r\,$[Mpc/h]$<20$. We find a
significant dependence of the reduced 3PCF on scales and triangle shapes, with
stronger anisotropy at larger scales ($r\sim10$ Mpc/h) and an almost flat trend
at smaller scales, $r\sim2.5$ Mpc/h. Massive and luminous galaxies present a
larger connected 3PCF, while the reduced 3PCF is remarkably insensitive to
magnitude and stellar masses in the range we explored. These trends, already
observed at low redshifts, are confirmed for the first time to be still valid
up to $z=1.1$, providing support to the hierarchical scenario for which massive
and bright systems are expected to be more clustered. The possibility of using
the measured 3PCF to provide independent constraints on the linear galaxy bias
$b$ has also been explored, showing promising results in agreement with other
probes.


title: On Information Loss in AdS$_3$/CFT$_2$

abstract:
  We discuss information loss from black hole physics in AdS$_3$, focusing on
two sharp signatures infecting CFT$_2$ correlators at large central charge $c$:
'forbidden singularities' arising from Euclidean-time periodicity due to the
effective Hawking temperature, and late-time exponential decay in the
Lorentzian region. We study an infinite class of examples where forbidden
singularities can be resolved by non-perturbative effects at finite $c$, and we
show that the resolution has certain universal features that also apply in the
general case. Analytically continuing to the Lorentzian regime, we find that
the non-perturbative effects that resolve forbidden singularities qualitatively
change the behavior of correlators at times $t \sim S_{BH}$, the black hole
entropy. This may resolve the exponential decay of correlators at late times in
black hole backgrounds. By Borel resumming the $1/c$ expansion of exact
examples, we explicitly identify 'information-restoring' effects from heavy
states that should correspond to classical solutions in AdS$_3$. Our results
suggest a line of inquiry towards a more precise formulation of the
gravitational path integral in AdS$_3$.


title: Inclusive Dark Photon Search at LHCb

abstract:
  We propose an inclusive search for dark photons $A'$ at the LHCb experiment
based on both prompt and displaced di-muon resonances. Because the couplings of
the dark photon are inherited from the photon via kinetic mixing, the dark
photon $A' \to \mu^+ \mu^-$ rate can be directly inferred from the off-shell
photon $\gamma^* \to \mu^+ \mu^-$ rate, making this a fully data-driven search.
For Run 3 of the LHC, we estimate that LHCb will have sensitivity to large
regions of the unexplored dark-photon parameter space, especially in the
210-520 MeV and 10-40 GeV mass ranges. This search leverages the excellent
invariant-mass and vertex resolution of LHCb, along with its unique
particle-identification and real-time data-analysis capabilities.


title:
Three-jet production in electron-positron collisions using the
  CoLoRFulNNLO method

abstract:
  We introduce a subtraction method for jet cross sections at
next-to-next-to-leading order (NNLO) accuracy in the strong coupling and use it
to compute event shapes in three-jet production in electron-positron
collisions. We validate our method on two event shapes, thrust and C-parameter,
which are already known in the literature at NNLO accuracy and compute for the
first time oblateness and the energy-energy correlation at the same accuracy.


title: A Cloaking Device for Transiting Planets

abstract:
  The transit method is presently the most successful planet discovery and
characterization tool at our disposal. Other advanced civilizations would
surely be aware of this technique and appreciate that their home planet's
existence and habitability is essentially broadcast to all stars lying along
their ecliptic plane. We suggest that advanced civilizations could cloak their
presence, or deliberately broadcast it, through controlled laser emission. Such
emission could distort the apparent shape of their transit light curves with
relatively little energy, due to the collimated beam and relatively infrequent
nature of transits. We estimate that humanity could cloak the Earth from
Kepler-like broadband surveys using an optical monochromatic laser array
emitting a peak power of about 30 MW for roughly 10 hours per year. A chromatic
cloak, effective at all wavelengths, is more challenging requiring a large
array of tunable lasers with a total power of approximately 250 MW.
Alternatively, a civilization could cloak only the atmospheric signatures
associated with biological activity on their world, such as oxygen, which is
achievable with a peak laser power of just around 160 kW per transit. Finally,
we suggest that the time of transit for optical SETI is analogous to the
water-hole in radio SETI, providing a clear window in which observers may
expect to communicate. Accordingly, we propose that a civilization may
deliberately broadcast their technological capabilities by distorting their
transit to an artificial shape, which serves as both a SETI beacon and a medium
for data transmission. Such signatures could be readily searched in the
archival data of transit surveys.


title: Flavor-changing decays of the top quark in 5D warped models

abstract:
  We study flavor changing neutral current decays of the top quark in the
context of general warped extra dimensions, where the five dimensional metric
is slightly modified from 5D anti-de-Sitter (AdS$_5$). These models address the
Planck-electroweak hierarchies of the Standard Model $and$ can obey all the low
energy flavor bounds and electroweak precision tests, while allowing the scale
of new physics to be at the TeV level, and thus within the reach of the LHC at
Run II. We perform the calculation of these exotic top decay rates for the case
of a bulk Higgs, and thus include in particular the effect of the additional
Kaluza-Klein (KK) Higgs modes running in the loops, along with the usual KK
fermions and KK gluons.


title: Probing Planet Forming Zones with Rare CO Isotopologues

abstract:
  The gas near the midplanes of planet-forming protostellar disks remains
largely unprobed by observations due to the high optical depth of commonly
observed molecules such as CO and H$_2$O. However, rotational emission lines
from rare molecules may have optical depths near unity in the vertical
direction, so that the lines are strong enough to be detected, yet remain
transparent enough to trace the disk midplane. Here we present a chemical model
of an evolving T-Tauri disk and predict the optical depths of rotational
transitions of $^{12}$C$^{16}$O, $^{13}$C$^{16}$O, $^{12}$C$^{17}$O and
$^{12}$C$^{18}$O. The MRI-active disk is primarily heated by the central star
due to the formation of the dead zone. CO does not freeze out in our modeled
region within $70$AU around a sunlike star. However, the abundance of CO
decreases because of the formation of complex organic molecules (COM),
producing an effect that can be misinterpreted as the "snow line". These
results are robust to variations in our assumptions about the evolution of the
gas to dust ratio. The optical depths of low-order rotational lines of
C$^{17}$O are around unity, making it possible to see into the disk midplane
using C$^{17}$O. Combining observations with modeled C$^{17}$O$/$H$_2$ ratios,
like those we provide, can yield estimates of protoplanetary disks' gas masses.


title: Diagnostic of the unstable envelopes of Wolf-Rayet stars

abstract:
  The envelopes of stars near the Eddington limit are prone to various
instabilities. A high Eddington factor in connection with the Fe opacity peak
leads to convective instability, and a corresponding envelope inflation may
induce pulsational instability. Here, we investigate the occurrence and
consequences of both instabilities in models of Wolf-Rayet stars. We determine
the convective velocities in the sub-surface convective zones to estimate the
amplitude of the turbulent velocity at the base of the wind that potentially
leads to the formation of small-scale wind structures, as observed in several
WR stars. We also investigate the effect of mass loss on the pulsations of our
models. We approximated solar metallicity WR stars by models of mass-losing
helium stars, and we characterized the properties of convection in the envelope
adopting the standard MLT. Our results show the occurrence of sub-surface
convective regions in all studied models. Small surface velocity amplitudes are
predicted for models with masses below 10Msun. For models with M>10Msun, the
surface velocity amplitudes are of the order of 10km/s. Moreover we find the
occurrence of pulsations for stars in the mass range 9-14Msun, while mass loss
appears to stabilize the more massive WR stars. We confront our results with
observationally derived line variabilities of 17 WN stars. The data suggest
variability to occur for stars above 10Msun, which is increasing linearly with
mass above this value, in agreement with our results. We further find some of
our models to be unstable to radial pulsations, and predict local magnetic
fields of the order of hundreds of Gauss in WR stars more massive than 10Msun.
Our study relates the surface velocity fluctuations induced by sub-surface
convection to the formation of clumping in the inner part of the wind. From
this mechanism, we expect a stronger variability in more massive WR stars.


title: Diphotons from an Electroweak Triplet-Singlet

abstract:
  The neutral component of a real pseudoscalar electroweak (EW) triplet can
produce a diphoton excess at 750 GeV, if it is somewhat mixed with an EW
singlet pseudoscalar. This triplet-singlet mixing allows for greater freedom in
the diboson branching ratios than the singlet-only case, but it is still
possible to probe the parameter space extensively with 300 fb$^{-1}$. The
charged component of the triplet is pair-produced at the LHC, which results in
a striking signal in the form of a pair of $W\gamma$ resonances with an
irreducible rate of 0.27 fb. Other signatures include multiboson final states
from cascade decays of the triplet-singlet neutral states. A large class of
composite models feature both EW singlet and triplet pseudo-Nambu Goldstone
bosons in their spectrum, with the diboson couplings generated by axial
anomalies.


title:
Spin-catalyzed hopping conductivity in disordered strongly interacting
  quantum wires

abstract:
  In one-dimensional electronic systems with strong repulsive interactions,
charge excitations propagate much faster than spin excitations. Such systems
therefore have an intermediate temperature range [termed the "spin-incoherent
Luttinger liquid'" (SILL) regime] where charge excitations are "cold" (i.e.,
have low entropy) whereas spin excitations are "hot." We explore the effects of
charge-sector disorder in the SILL regime in the absence of external sources of
equilibration. We argue that the disorder localizes all charge-sector
excitations; however, spin excitations are protected against full localization,
and act as a heat bath facilitating charge and energy transport on
asymptotically long timescales. The charge, spin, and energy conductivities are
widely separated from one another. The dominant carriers of energy are neither
charge nor spin excitations, but neutral "phonon" modes, which undergo an
unconventional form of hopping transport that we discuss. We comment on the
applicability of these ideas to experiments and numerical simulations.

categories: cond-mat.dis-nn cond-mat.mes-hall cond-mat.stat-mech cond-mat.str-el


title: Covariant effective action for a Galilean invariant quantum Hall system

abstract:
  We construct effective field theories for gapped quantum Hall systems coupled
to background geometries with local Galilean invariance i.e. Bargmann
spacetimes. Along with an electromagnetic field, these backgrounds include the
effects of curved Galilean spacetimes, including torsion and a gravitational
field, allowing us to study charge, energy, stress and mass currents within a
unified framework. A shift symmetry specific to single constituent theories
constraints the effective action to couple to an effective background gauge
field and spin connection that is solved for by a self-consistent equation,
providing a manifestly covariant extension of Hoyos and Son's improvement terms
to arbitrary order in $m$.


title: Relevant deformations and c-extremization

abstract:
  We consider RG flows obtained by a relevant deformation from unitary and
compact two-dimensional (0,2) SCFTs. We point out that an N=2 super-Kac-Moody
algebra present in the UV is preserved by the flow and does not mix with the
R-current. On the other hand, a direct sum of N=2 algebras in the UV theory
leads to a few complications in determining the IR R-symmetry; nevertheless, in
flows without accidental IR symmetries, we determine the IR R-symmetry and show
that it maximizes the IR central charge.