title: Stability of Riemannian manifolds with Killing spinors

abstract:
  Riemannian manifolds with non-zero Killing spinors are Einstein manifolds.
Klaus Kr\"{o}ncke proved that all complete Riemannian manifolds with imaginary
Killing spinors are (linearly) strictly stable in \cite{Kro15}. In this paper,
we obtain a new proof for this stability result by using a Bochner type formula
in \cite{DWW05} and \cite{Wan91}. Moreover, existence of real Killing spinors
is closely related to the Sasaki-Einstein structure. A regular Sasaki-Einstein
manifold is essentially the total space of a certain principal $S^{1}$-bundle
over a K\"{a}hler-Einstein manifold. We prove that if the base space is a
product of two K\"{a}hler-Einstein manifolds then the regular Sasaki-Einstein
manifold is unstable. This provides us many new examples of unstable manifolds
with real Killing spinors.


title: Analog Optical Computing Based on Dielectric Meta-reflect-array

abstract:
  In this paper, we realize the concept of analog computing using an array of
engineered gradient dielectric meta-reflect-array. The proposed configuration
consists of individual subwavelength silicon nanobricks in combination with
fused silica spacer and silver ground plane realizing a reflection beam with
full phase coverage $2\pi$ degrees as well as amplitude range $0$ to $1$.
Spectrally overlapping electric and magnetic dipole resonances, such high-index
dielectric metasurfaces can locally and independently manipulate the amplitude
and phase of the incident electromagnetic wave. This practically feasible
structure overcomes substantial limitations imposed by plasmonic metasurfaces
such as absorption losses and low polarization conversion efficiency in the
visible range. Using such CMOS-compatible and easily integrable platforms
promises highly efficient ultrathin planar wave-based computing systems which
circumvent the drawbacks of conventional bulky lens-based signal processors.
Based on these key properties and general concept of spatial Fourier
transformation, we design and realize broadband mathematical operators such as
differentiator and integrator in the telecommunication wavelengths.


title: Shotgun edge assembly of random jigsaw puzzles

abstract:
  In recent work by Mossel and Ross, it was asked how large $q$ has to be for a
random jigsaw puzzle with $q$ different shapes of "jigs" to have exactly one
solution. The jigs are assumed symmetric in the sense that two jigs of the same
type always fit together. They showed that for $q=o(n^{2/3})$ there are a.a.s.
multiple solutions, and for $q=\omega(n^2)$ there is a.a.s. exactly one. The
latter bound has since been improved to $q\geq n^{1+\varepsilon}$ independently
by Nenadov, Pfister and Steger, and by Bordernave, Feige and Mossel. Both
groups further remark that for $q=o(n)$ there are a.a.s. duplicate pieces in
the puzzle. In this paper, we show that such puzzle a.a.s. has multiple
solutions whenever $q\leq \frac{2}{\sqrt{e}}\,n - \omega(\log_2 n)$, even if
permuting identical pieces is not considered changing the solution. We further
give some remarks about the number of solutions, and the probability of a
unique solution in this regime.


title:
Optical Reciprocity Induced Symmetry of the Scattering Eigenstates in
  Non-$\cal PT$-Symmetric Heterostructures

abstract:
  The scattering matrix $S$ obeys the unitary relation $S^\dagger S=1$ in a
Hermitian system and the symmetry property ${\cal PT}S{\cal PT}=S^{-1}$ in a
Parity-Time (${\cal PT}$) symmetric system. Here we report a different symmetry
relation of the $S$ matrix in a one-dimensional heterostructure, which is given
by the amplitude ratio of the incident waves in the scattering eigenstates. It
originates from the optical reciprocity and holds independent of the
Hermiticity or $\cal PT$ symmetry of the system. Using this symmetry relation,
we probe a quasi-transition that is reminiscent of the spontaneous symmetry
breaking of a $\cal PT$-symmetric $S$ matrix, now with unbalanced gain and loss
and even in the absence of gain. We show that the additional symmetry relation
provides a clear evidence of an exceptional point, even when all other
signatures of the $\cal PT$ symmetry breaking are completely erased. We also
discuss the existence of a final exceptional point in this correspondence,
which is attributed to asymmetric reflections from the two sides of the
heterostructure.


title:
Functional neuroimaging of psychedelic experience: An overview of
  psychological and neural effects and their relevance to research on
  creativity, daydreaming, and dreaming

abstract:
  Humans have employed an incredible variety of plant-derived substances over
the millennia in order to alter consciousness and perception. Among the
innumerable narcotics, analgesics, 'ordeal' drugs, and other psychoactive
substances discovered and used in ritualistic contexts by cultures around the
world, one class in particular stands out not only for its radical
psychological effects, but also for the highly charged political and legal
atmosphere that has surrounded it since its widespread adoption about 50 years
ago: so-called psychedelic substances. We review functional neuroimaging
investigations of the neural correlates of the psychedelic experience, and
highlight relationships with the psychological and neural bases of creativity,
daydreaming, and dreaming.


title:
Path-Normalized Optimization of Recurrent Neural Networks with ReLU
  Activations

abstract:
  We investigate the parameter-space geometry of recurrent neural networks
(RNNs), and develop an adaptation of path-SGD optimization method, attuned to
this geometry, that can learn plain RNNs with ReLU activations. On several
datasets that require capturing long-term dependency structure, we show that
path-SGD can significantly improve trainability of ReLU RNNs compared to RNNs
trained with SGD, even with various recently suggested initialization schemes.


title:
Direct comparison of current-induced spin polarization in topological
  insulator Bi2Se3 and InAs Rashba states

abstract:
  Three-dimensional topological insulators (TIs) exhibit time-reversal symmetry
protected, linearly dispersing Dirac surface states. Band bending at the TI
surface may also lead to coexisting trivial two-dimensional electron gas (2DEG)
states with parabolic energy dispersion that exist as spin-split pairs due to
Rashba spin-orbit coupling (SOC). A bias current is expected to generate spin
polarization in both systems arising from their helical spin-momentum locking.
However, their induced spin polarization is expected to be different in both
magnitude and sign. Here, we compare spin potentiometric measurements of bias
current-generated spin polarization in Bi2Se3(111) films where Dirac surface
states coexist with trivial 2DEG states, with identical measurements on
InAs(001) samples where only trivial 2DEG states are present. We observe spin
polarization arising from spin-momentum locking in both cases, with opposite
signs of the spin voltage. We present a model based on spin dependent
electrochemical potentials to directly derive the signs expected for the TI
surface states, and unambiguously show that the dominant contribution to the
current-generated spin polarization measured in the TI is from the Dirac
surface states. This direct electrical access of the helical spin texture of
Dirac and Rashba 2DEG states is an enabling step towards the electrical
manipulation of spins in next generation TI and SOC based quantum devices.


title:
Genetic Architect: Discovering Genomic Structure with Learned Neural
  Architectures

abstract:
  Each human genome is a 3 billion base pair set of encoding instructions.
Decoding the genome using deep learning fundamentally differs from most tasks,
as we do not know the full structure of the data and therefore cannot design
architectures to suit it. As such, architectures that fit the structure of
genomics should be learned not prescribed. Here, we develop a novel search
algorithm, applicable across domains, that discovers an optimal architecture
which simultaneously learns general genomic patterns and identifies the most
important sequence motifs in predicting functional genomic outcomes. The
architectures we find using this algorithm succeed at using only RNA expression
data to predict gene regulatory structure, learn human-interpretable
visualizations of key sequence motifs, and surpass state-of-the-art results on
benchmark genomics challenges.


title: Unsupervised Learning for Physical Interaction through Video Prediction

abstract:
  A core challenge for an agent learning to interact with the world is to
predict how its actions affect objects in its environment. Many existing
methods for learning the dynamics of physical interactions require labeled
object information. However, to scale real-world interaction learning to a
variety of scenes and objects, acquiring labeled data becomes increasingly
impractical. To learn about physical object motion without labels, we develop
an action-conditioned video prediction model that explicitly models pixel
motion, by predicting a distribution over pixel motion from previous frames.
Because our model explicitly predicts motion, it is partially invariant to
object appearance, enabling it to generalize to previously unseen objects. To
explore video prediction for real-world interactive agents, we also introduce a
dataset of 59,000 robot interactions involving pushing motions, including a
test set with novel objects. In this dataset, accurate prediction of videos
conditioned on the robot's future actions amounts to learning a "visual
imagination" of different futures based on different courses of action. Our
experiments show that our proposed method produces more accurate video
predictions both quantitatively and qualitatively, when compared to prior
methods.


title: 3-D Glasma initial state for relativistic heavy ion collisions

abstract:
  We extend the impact parameter dependent Glasma model (IP-Glasma) to three
dimensions using explicit small x evolution of the two incoming nuclear gluon
distributions. We compute rapidity distributions of produced gluons and the
early time energy momentum tensor as a function of space-time rapidity and
transverse coordinates. We study rapidity correlations and fluctuations of the
initial geometry and multiplicity distributions and compare to existing models
for the three dimensional initial state.


title:
Complexity of Consistent Query Answering in Databases under
  Cardinality-Based and Incremental Repair Semantics (extended version)

abstract:
  A database D may be inconsistent wrt a given set IC of integrity constraints.
Consistent Query Answering (CQA) is the problem of computing from D the answers
to a query that are consistent wrt IC . Consistent answers are invariant under
all the repairs of D, i.e. the consistent instances that minimally depart from
D. Three classes of repair have been considered in the literature: those that
minimize set-theoretically the set of tuples in the symmetric difference; those
that minimize the changes of attribute values, and those that minimize the
cardinality of the set of tuples in the symmetric difference. The latter class
has not been systematically investigated. In this paper we obtain algorithmic
and complexity theoretic results for CQA under this cardinality-based repair
semantics. We do this in the usual, static setting, but also in a dynamic
framework where a consistent database is affected by a sequence of updates,
which may make it inconsistent. We also establish comparative results with the
other two kinds of repairs in the dynamic case.


title:
Self-assembly of a space-tessellating structure in the binary system of
  hard tetrahedra and octahedra

abstract:
  We report the formation of a binary crystal of hard polyhedra due solely to
entropic forces. Although the alternating arrangement of octahedra and
tetrahedra is a known space-tessellation, it had not previously been observed
in self-assembly simulations. Both known one-component phases - the dodecagonal
quasicrystal of tetrahedra and the densest-packing of octahedra in the
Minkowski lattice - are found to coexist with the binary phase. No additional
crystalline phases were observed.


title: Photoproduction of leptophobic bosons

abstract:
  We propose a search for photoproduction of leptophobic bosons that couple to
quarks at the GlueX experiment at Jefferson Lab. We study in detail a new gauge
boson that couples to baryon number $B$, and estimate that $\gamma p \to p B$
will provide the best sensitivity for $B$ masses above 0.5 GeV. This search
will also provide sensitivity to other proposed dark-sector states that couple
to quarks. Finally, our results motivate a similar search for $B$ boson
electroproduction at the CLAS experiment.


title: Pure Exploration of Multi-armed Bandit Under Matroid Constraints

abstract:
  We study the pure exploration problem subject to a matroid constraint
(Best-Basis) in a stochastic multi-armed bandit game. In a Best-Basis instance,
we are given $n$ stochastic arms with unknown reward distributions, as well as
a matroid $\mathcal{M}$ over the arms. Let the weight of an arm be the mean of
its reward distribution. Our goal is to identify a basis of $\mathcal{M}$ with
the maximum total weight, using as few samples as possible.
  The problem is a significant generalization of the best arm identification
problem and the top-$k$ arm identification problem, which have attracted
significant attentions in recent years. We study both the exact and PAC
versions of Best-Basis, and provide algorithms with nearly-optimal sample
complexities for these versions. Our results generalize and/or improve on
several previous results for the top-$k$ arm identification problem and the
combinatorial pure exploration problem when the combinatorial constraint is a
matroid.


title:
Quantum critical dynamics for a prototype class of insulating
  antiferromagnets

abstract:
  Quantum criticality is a fundamental organizing principle for studying
strongly correlated systems. Nevertheless, understanding quantum critical
dynamics at nonzero temperatures is a major challenge of condensed matter
physics due to the intricate interplay between quantum and thermal
fluctuations. The recent experiments in the quantum spin dimer material
TlCuCl$_3$ provide an unprecedented opportunity to test the theories of quantum
criticality. We investigate the nonzero temperature quantum critical spin
dynamics by employing an effective $O(N)$ field theory. The on-shell mass and
the damping rate of quantum critical spin excitations as functions of
temperature are calculated based on the renormalized coupling strength, which
are in excellent agreements with experiment observations. Their $T\ln T$
dependence is predicted to be dominant at very low temperatures, which is to be
tested in future experiments. Our work provides confidence that quantum
criticality as a theoretical framework, being considered in so many different
contexts of condensed matter physics and beyond, is indeed grounded in
materials and experiments accurately. It is also expected to motivate further
experimental investigations on the applicability of the field theory to related
quantum critical systems.


title: One loop contributions to neutral Higgs decay h-->mu tau

abstract:
  In calculating one-loop contributions to amplitudes of the lepton-flavor
violating decays of the neutral Higgses (LFVHD) to different flavor charged
leptons, the analytic expressions can be written in term of Passarino-Veltman
functions. Then, they can be computed numerically by Looptools [1]. Another
approach is using suitable analytic expressions established for just this
particular case. We compare numerical results obtained from Looptools and those
computed by different expressions that have been applied recently. Then we
derive the preferable ones that are applicable for the large ranges of free
parameters introduced in the models beyond the Standard Model (SM). For
illustration, the LFVHD in a simple model, which has been discussed recently,
will be investigated more precisely.


title:
Topologically Twisted SUSY Gauge Theory, Gauge-Bethe Correspondence and
  Quantum Cohomology

abstract:
  We calculate partition function and correlation functions in A-twisted 2d
$\mathcal{N}=(2,2)$ theories and topologically twisted 3d $\mathcal{N}=2$
theories containing adjoint chiral multiplet with particular choices of
$R$-charges and the magnetic fluxes for flavor symmetries. According to
Gauge-Bethe correspondence, they correspond to Heisenberg XXX and XXZ spin
chain models. We identify the partition function as the inverse of the norm of
the Bethe eigenstates. Correlation functions are identified as the coefficients
of the expectation value of Baxter $Q$-operators. In addition, we consider
correlation functions of 2d $\mathcal{N}=(2,2)^*$ theory and their relation to
equivariant quantum cohomology and equivariant integration of cotangent bundle
of Grassmann manifolds. Also, we study the ring relations of supersymmetric
Wilson loops in 3d $\mathcal{N}=2^*$ theory and Bethe subalgebra of XXZ spin
chain model.


title: P-Type Tunnel FETs With Triple Heterojunctions

abstract:
  A triple-heterojunction (3HJ) design is employed to improve p-type InAs/GaSb
heterojunction (HJ) tunnel FETs. The added two HJs (AlInAsSb/InAs in the source
and GaSb/AlSb in the channel) significantly shorten the tunnel distance and
create two resonant states, greatly improving the ON state tunneling
probability. Moreover, the source Fermi degeneracy is reduced by the increased
source (AlInAsSb) density of states and the OFF state leakage is reduced by the
heavier channel (AlSb) hole effective masses. Quantum ballistic transport
simulations show, that with V_{DD} = 0.3V and I_{OFF} = 10^{-3}A/m, I_{ON} of
582A=m (488A=m) is obtained at 30nm (15nm) channel length, which is comparable
to n-type 3HJ counterpart and significantly exceeding p-type silicon MOSFET.
Simultaneously, the nonlinear turn on and delayed saturation in the output
characteristics are also greatly improved.


title:
On Web User Tracking: How Third-Party Http Requests Track Users'
  Browsing Patterns for Personalised Advertising

abstract:
  On today's Web, users trade access to their private data for content and
services. Advertising sustains the business model of many websites and
applications. Efficient and successful advertising relies on predicting users'
actions and tastes to suggest a range of products to buy. It follows that,
while surfing the Web users leave traces regarding their identity in the form
of activity patterns and unstructured data. We analyse how advertising networks
build user footprints and how the suggested advertising reacts to changes in
the user behaviour.


title:
A Miniature CCA2 Public key Encryption scheme based on non-Abelian
  factorization problems in Lie Groups

abstract:
  Since 1870s, scientists have been taking deep insight into Lie groups and Lie
algebras. With the development of Lie theory, Lie groups have got profound
significance in many branches of mathematics and physics. In Lie theory,
exponential mapping between Lie groups and Lie algebras plays a crucial role.
Exponential mapping is the mechanism for passing information from Lie algebras
to Lie groups. Since many computations are performed much more easily by
employing Lie algebras, exponential mapping is indispensable while studying Lie
groups. In this paper, we first put forward a novel idea of designing
cryptosystem based on Lie groups and Lie algebras. Besides, combing with
discrete logarithm problem(DLP) and factorization problem(FP), we propose some
new intractable assumptions based on exponential mapping. Moreover, in analog
with Boyen's sceme(AsiaCrypt 2007), we disign a public key encryption scheme
based on non-Abelian factorization problems in Lie Groups. Finally, our
proposal is proved to be IND-CCA2 secure in the random oracle model.


title: Fe2O3/ Co3O4 composite nanoparticle ethanol sensor

abstract:
  In this study Fe2O3/Co3O4 nanocomposites were synthesized by using a simple
hydrothermal route. The X-ray diffraction analysis results showed that
synthesized powders were pure, and nanocrystalline in nature. Moreover,
Scanning electron microscopy revealed that Fe2O3 nanoparticles had spherical
shapes while Co3O4 particles had a rod-like morphology. Ethanol sensing
properties of Fe2O3/Co3O4 nanocomposites were examined and compared with those
of pristine Fe2O3 nanoparticles. It was shown that the gas sensing properties
of Fe2O3/Co3O4 nanocomposites were superior to those of pristine Fe2O3
nanoparticles and for all concentrations of ethanol, the response of the
nanocomposite sensor was higher than the pristine Fe2O3 nanoparticle sensor. In
detail, the response of Fe2O3/Co3O4 nanocomposite sensor to 200 ppm of ethanol
at 300{\deg}C was about 3 times higher than pristine one. Also in general, the
response and recovery times of Fe2O3/Co3O4 nanocomposite sensor were shorter
than those of the pristine one. The improved sensing characteristics of the
Fe2O3/Co3O4 sensor were attributed to a combination of several effects: the
formation of a potential barrier at the Fe2O3-Co3O4 interface, the enhanced
modulation of the conduction channel width accompanying the adsorption and
desorption of ethanol gas, the catalytic activity of Co3O4 for the oxidation of
ethanol, the stronger oxygen adsorption of p-type Co3O4, and the formation of
preferential adsorption sites.


title: A remark on A+B and A-A for compact sets in R^n

abstract:
  We prove in particular that if A be a compact convex subset of R^n, and B
from R^n be an arbitrary compact set then \mu (A-A) \ll \mu(A+B)^2 / (\sqrt{n}
\mu (A)), provided that \mu(B)\ge \mu(A).


title: The bitwise operations in relation to obtaining Latin squares

abstract:
  The main thrust of the article is to provide interesting example, useful for
students of using bitwise operations in the programming languages C ++ and
Java. As an example, we describe an algorithm for obtaining a Latin square of
arbitrary order. We will outline some techniques for the use of bitwise
operations.


title: Submodular Maximization using Test Scores

abstract:
  We study the canonical problem of maximizing a stochastic submodular function
subject to a cardinality constraint, where the goal is to select a subset from
a ground set of items with uncertain individual performances to maximize their
expected group value. Although near-optimal algorithms have been proposed for
this problem, practical concerns regarding scalability, compatibility with
distributed implementation, and expensive oracle queries persist in large-scale
applications. Motivated by online platforms that rely on individual item scores
for content recommendation and team selection, we propose a special class of
algorithms that select items based solely on individual performance measures
known as test scores. The central contribution of this work is a novel and
systematic framework for designing test score based algorithms for a broad
class of naturally occurring utility functions. We introduce a new scoring
mechanism that we refer to as replication test scores and prove that as long as
the objective function satisfies a diminishing returns property, one can
leverage these scores to compute solutions that are within a constant factor of
the optimum. We then extend our results to the more general stochastic
submodular welfare maximization problem, where the goal is to select items and
assign them to multiple groups to maximize the sum of the expected group
values. For this more difficult problem, we show that replication test scores
can be used to develop an algorithm that approximates the optimum solution up
to a logarithmic factor. The techniques presented in this work bridge the gap
between the rigorous theoretical work on submodular optimization and simple,
scalable heuristics that are useful in certain domains.


title: Nonnegative rank depends on the field II

abstract:
  We provide an example of a $21\times 21$ matrix with nonnegative integer
entries which can be written as a sum of $19$ nonnegative rank-one matrices but
not as a sum of $19$ rational nonnegative rank-one matrices. This gives a
solution for a problem posed by Cohen and Rothblum in 1993.


title: Kernel-based Reconstruction of Graph Signals

abstract:
  A number of applications in engineering, social sciences, physics, and
biology involve inference over networks. In this context, graph signals are
widely encountered as descriptors of vertex attributes or features in
graph-structured data. Estimating such signals in all vertices given noisy
observations of their values on a subset of vertices has been extensively
analyzed in the literature of signal processing on graphs (SPoG). This paper
advocates kernel regression as a framework generalizing popular SPoG modeling
and reconstruction and expanding their capabilities. Formulating signal
reconstruction as a regression task on reproducing kernel Hilbert spaces of
graph signals permeates benefits from statistical learning, offers fresh
insights, and allows for estimators to leverage richer forms of prior
information than existing alternatives. A number of SPoG notions such as
bandlimitedness, graph filters, and the graph Fourier transform are naturally
accommodated in the kernel framework. Additionally, this paper capitalizes on
the so-called representer theorem to devise simpler versions of existing
Thikhonov regularized estimators, and offers a novel probabilistic
interpretation of kernel methods on graphs based on graphical models. Motivated
by the challenges of selecting the bandwidth parameter in SPoG estimators or
the kernel map in kernel-based methods, the present paper further proposes two
multi-kernel approaches with complementary strengths. Whereas the first enables
estimation of the unknown bandwidth of bandlimited signals, the second allows
for efficient graph filter selection. Numerical tests with synthetic as well as
real data demonstrate the merits of the proposed methods relative to
state-of-the-art alternatives.


title:
Next-to-leading order transverse momentum broadening for Drell-Yan
  production in p+A collisions

abstract:
  We present the nuclear transverse momentum broadening for Drell-Yan lepton
pair production in p+A collisions at next-to-leading order (NLO) in powers of
strong coupling constant $\alpha_s$. We verify that the transverse momentum
weighted differential cross section in NLO perturbative QCD (pQCD) at twist-4
can be factorized into the convolution of parton distribution function of an
active parton in the projectile proton, a twist-4 multiparton correlation
function of the target nucleus, and perturbatively calculable hard coefficient
function. We identify a QCD evolution equation for such a twist-4 nuclear
gluon-quark correlation function, and verify its universality -- its process
independence. This finding demonstrates the prediction power of pQCD
factorization approach for studying parton multiple scattering in nuclear
medium.


title: Large scale structure around a z=2.1 cluster

abstract:
  The most prodigious starburst galaxies are absent in massive galaxy clusters
today, but their connection with large scale environments is less clear at
$z\gtrsim2$. We present a search of large scale structure around a galaxy
cluster core at $z=2.095$ using a set of spectroscopically confirmed galaxies.
We find that both color-selected star-forming galaxies (SFGs) and dusty
star-forming galaxies (DSFGs) show significant overdensities around the
$z=2.095$ cluster. A total of 8 DSFGs (including 3 X-ray luminous active
galactic nuclei, AGNs) and 34 SFGs are found within a 10 arcmin radius
(corresponds to $\sim$15 cMpc at $z\sim2.1$) from the cluster center and within
a redshift range of $\Delta z=0.02$, which leads to galaxy overdensities of
$\delta_{\rm DSFG}\sim12.3$ and $\delta_{\rm SFG}\sim2.8$. The cluster core and
the extended DSFG- and SFG-rich structure together demonstrate an active
cluster formation phase, in which the cluster is accreting a significant amount
of material from large scale structure while the more mature core may begin to
virialize. Our finding of this DSFG-rich structure, along with a number of
other protoclusters with excess DSFGs and AGNs found to date, suggest that the
overdensities of these rare sources indeed trace significant mass
overdensities. However, it remains puzzling how these intense star formers are
triggered concurrently. Although an increased probability of galaxy
interactions and/or enhanced gas supply can trigger the excess of DSFGs, our
stacking analysis based on 850 $\mu$m images and morphological analysis based
on rest-frame optical imaging do not show such enhancements of merger fraction
and gas content in this structure.


title:
High-Precision Radio and Infrared Astrometry of LSPM J1314+1320AB - I:
  Parallax, Proper Motions, and Limits on Planets

abstract:
  We present multi-epoch astrometric radio observations with the Very Long
Baseline Array (VLBA) of the young ultracool-dwarf binary LSPM J1314+1320AB .
The radio emission comes from the secondary star. Combining the VLBA data with
Keck near-infrared adaptive-optics observations of both components, a full
astrometric fit of parallax ($\pi_{\rm abs}=57.975\pm0.045$ mas, corresponding
to a distance of $d=17.249\pm0.013$ pc), proper motion ($\mu_{\rm \alpha cos
\delta}=-247.99\pm0.10$ mas yr$^{-1}$, $\mu_{\delta}=-183.58\pm0.22$ mas
yr$^{-1}$), and orbital motion is obtained. Despite the fact that the two
components have nearly identical masses to within $\pm2$%, the secondary's
radio emission exceeds that of the primary by a factor of $\gtrsim$30,
suggesting a difference in stellar rotation history, which could result in
different magnetic field configurations. Alternatively, the emission could be
anisotropic and beamed toward us for the secondary but not for the primary.
Using only reflex motion, we exclude planets of mass 0.7 to 10 $M_{\rm jup}$
with orbital periods of 600 to 10 days, respectively. Additionally, we use the
full orbital solution of the binary to derive an upper limit for the semi-major
axis of 0.23 AU for stable planetary orbits within this system. These limits
cover a parameter space that is inaccessible with, and complementary to,
near-infrared radial velocity surveys of ultracool dwarfs. Our absolute
astrometry will constitute an important test for the astrometric calibration of
Gaia.


title: How isotropic is the Universe?

abstract:
  A fundamental assumption in the standard model of cosmology is that the
Universe is isotropic on large scales. Breaking this assumption leads to a set
of solutions to Einstein's field equations, known as Bianchi cosmologies, only
a subset of which have ever been tested against data. For the first time, we
consider all degrees of freedom in these solutions to conduct a general test of
isotropy using cosmic microwave background temperature and polarization data
from Planck. For the vector mode (associated with vorticity), we obtain a limit
on the anisotropic expansion of $(\sigma_V/H)_0 < 4.7 \times 10^{-11}$ (95%
CI), which is an order of magnitude tighter than previous Planck results that
used CMB temperature only. We also place upper limits on other modes of
anisotropic expansion, with the weakest limit arising from the regular tensor
mode, $(\sigma_{T,\rm reg}/H)_0<1.0 \times 10^{-6}$ (95% CI). Including all
degrees of freedom simultaneously for the first time, anisotropic expansion of
the Universe is strongly disfavoured, with odds of 121,000:1 against.


title:
No-go theorem for a time-reversal invariant topological phase in
  noninteracting systems coupled to conventional superconductors

abstract:
  We prove that a system of non-interacting electrons proximity coupled to a
conventional s-wave superconductor cannot realize a time reversal invariant
topological phase. This is done by showing that for such a system, in either
one or two dimensions, the topological invariant of the corresponding symmetry
class (DIII) is always trivial. Our results suggest that the pursuit of
Majorana bound states in time-reversal invariant systems should be aimed at
interacting systems or at proximity to unconventional superconductors.


title:
Entanglement harvesting from the electromagnetic vacuum with
  hydrogenlike atoms

abstract:
  We study how two fully-featured hydrogenlike atoms harvest entanglement from
the electromagnetic field vacuum, even when the atoms are spacelike separated.
We compare the electromagnetic case ---qualitatively and quantitatively--- with
previous results that used scalar fields and featureless, idealized atomic
models. Our study reveals the new traits that emerge when we relax these
idealizations, such as anisotropies in entanglement harvesting and the effect
of exchange of angular momentum. We show that, under certain circumstances,
relaxing previous idealizations makes vacuum entanglement harvesting more
efficient.


title:
Free Energy of a Heavy Quark-Antiquark Pair in a Thermal Medium from
  AdS/CFT

abstract:
  We study the free energy of a heavy quark-antiquark pair in a thermal medium
using the AdS/CFT correspondence. We point out that a commonly used
prescription for calculating this quantity leads to a temperature dependence in
conflict with general properties of the free energy. The problem originates
from a particular way of subtracting divergences. We argue that the commonly
used prescription gives rise to the binding energy rather than the free energy.
We consider a different subtraction procedure and show that the resulting free
energy is well-behaved and in qualitative agreement with results from lattice
QCD. The free energy and the binding energy of the quark pair are computed for
N = 4 supersymmetric Yang-Mills theory and several non-conformal theories. We
also calculate the entropy and the internal energy of the pair in these
theories. Using the consistent subtraction, we further study the free energy,
entropy, and internal energy of a single heavy quark in the thermal medium for
various theories. Also here the results are found to be in qualitative
agreement with lattice QCD results.


title:
High-Precision Radio and Infrared Astrometry of LSPM J1314+1320AB - II:
  Testing Pre--Main-Sequence Models at the Lithium Depletion Boundary with
  Dynamical Masses

abstract:
  We present novel tests of pre$-$main-sequence models based on individual
dynamical masses for the M7 binary LSPM J1314+1320AB. Joint analysis of our
Keck adaptive optics astrometric monitoring along with Very Long Baseline Array
radio data from a companion paper yield component masses of $0.0885\pm0.0006$
$M_{\odot}$ and $0.0875\pm0.0010$ $M_{\odot}$ and a parallactic distance of
$17.249\pm0.013$ pc. We also derive component luminosities that are consistent
with the system being coeval at an age of $80.8\pm2.5$ Myr, according to BHAC15
evolutionary models. The presence of lithium is consistent with model
predictions, marking the first time the theoretical lithium depletion boundary
has been tested with ultracool dwarfs of known mass. However, we find that the
average evolutionary model-derived effective temperature ($2950\pm5$ K) is 180
K hotter than we derive from a spectral type$-$$T_{\rm eff}$ relation based on
BT-Settl models ($2770\pm100$ K). We suggest that the dominant source of this
discrepancy is model radii being too small by $\approx$13%. In a test that
mimics the typical application of evolutionary models by observers, we derive
masses on the H-R diagram using the luminosity and BT-Settl temperature. The
estimated masses are $46^{+16}_{-19}$% (2.0$\sigma$) lower than we measure
dynamically and would imply that this is a system of $\approx$50 $M_{\rm Jup}$
brown dwarfs, highlighting the large systematic errors possible when inferring
masses from the H-R diagram. This is first time masses have been measured for
ultracool ($\geq$M6) dwarfs displaying spectral signatures of low gravity.
Based on features in the infrared, LSPM J1314+1320AB appears higher gravity
than typical Pleiades and AB Dor members, opposite the expectation given its
younger age. The components of LSPM J1314+1320AB are now the nearest, lowest
mass pre$-$main-sequence stars with direct mass measurements.


title: Phenomenology of Strongly Coupled Chiral Gauge Theories

abstract:
  A sector with QCD-like strong dynamics is common in models of non-standard
physics. Such a model could be accessible in LHC searches if both confinement
and big-quarks charged under the confining group are at the TeV scale.
Big-quark masses at this scale can be explained if the new fermions are chiral
under a new $U(1)^\prime$ gauge symmetry such that their bare masses are
related to the $U(1)^\prime$-breaking and new confinement scales. Here we
present a study of a minimal GUT-motivated and gauge anomaly-free model with
implications for the LHC Run 2 searches. We find that the first signatures of
such models could appear as two gauge boson resonances. The chiral nature of
the model could be confirmed by observation of a $Z^\prime \gamma$ resonance,
where the $Z^\prime$ naturally has a large leptonic branching ratio because of
its kinetic mixing with the hypercharge gauge boson.


title:
Simulating collisions of thick nuclei in the color glass condensate
  framework

abstract:
  We present our work on the simulation of the early stages of heavy-ion
collisions with finite longitudinal thickness in the laboratory frame in 3+1
dimensions. In particular we study the effects of nuclear thickness on the
production of a glasma state in the McLerran-Venugopalan model within the color
glass condensate framework. A finite thickness enables us to describe nuclei at
lower energies, but forces us to abandon boost-invariance. As a consequence,
random classical color sources within the nuclei have to be included in the
simulation, which is achieved by using the colored particle-in-cell (CPIC)
method. We show that the description in the laboratory frame agrees with
boost-invariant approaches as a limiting case. Furthermore we investigate
collisions beyond boost-invariance, in particular the pressure anisotropy in
the glasma.


title:
Raman Scattering by Molecular Hydrogen and Nitrogen in Exoplanetary
  Atmospheres

abstract:
  An important source of opacity in exoplanet atmospheres at short visible and
near-UV wavelengths is Rayleigh scattering of light on molecules. It is
accompanied by a related, albeit weaker process -- Raman scattering. We analyze
the signatures of Raman scattering imprinted in the reflected light and the
geometric albedo of exoplanets, which could provide information about
atmospheric properties. Raman scattering affects the geometric albedo spectra
of planets in following ways. Firstly, it causes filling-in of strong
absorption lines in the incident radiation, thus producing sharp peaks in the
albedo. Secondly, it shifts the wavelengths of spectral features in the
reflected light causing the so-called Raman ghost lines. Raman scattering can
also cause a broadband reduction of the albedo due to wavelength shifting of a
stellar spectrum with red spectral index. Observing the Raman peaks in the
albedo could be used to measure the column density of gas, thus providing
constrains on the presence of clouds in the atmosphere. Observing the Raman
ghost lines could be used to spectroscopically identify the main scatterer in
the atmosphere, even molecules like H$_2$ or N$_2$ that do not have prominent
spectral signatures in the optical wavelength range. If detected, ghost lines
could also provide information about the temperature of the atmosphere. In this
paper we investigate the effects of Raman scattering in hydrogen- and
nitrogen-dominated atmospheres. We analyze the feasibility of detecting the
signatures of Raman scattering with the existing and future observational
facilities, and of using these signatures as probes of exoplanetary
atmospheres.


title: Reconciling the Stellar and Nebular Spectra of High Redshift Galaxies

abstract:
  We present a combined analysis of rest-frame far-UV (1000-2000 A) and
rest-frame optical (3600-7000 A) composite spectra formed from very deep
observations of a sample of 30 star-forming galaxies with z=2.4+/-0.1, selected
to be representative of the full KBSS-MOSFIRE spectroscopic survey. Since the
same massive stars are responsible for the observed FUV continuum and the
excitation of the observed nebular emission, a self-consistent stellar
population synthesis model must simultaneously match the details of the far-UV
stellar+nebular continuum and-- when inserted as the excitation source in
photoionization models-- account for all observed nebular emission line ratios.
We find that only models including massive star binaries, having low stellar
metallicity (Z_*/Z_{sun} ~ 0.1) but relatively high ionized gas-phase oxygen
abundances (Z_{neb}/Z_{sun} ~ 0.5), can successfully match all of the
observational constraints. We argue that this apparent discrepancy is naturally
explained by highly super-solar O/Fe [4-5 times (O/Fe)_{sun}], expected for gas
whose enrichment is dominated by the products of core-collapse supernovae. Once
the correct ionizing spectrum is identified, photoionization models reproduce
all of the observed strong emission line ratios, the direct T_e measurement of
O/H, and allow accurate measurement of the gas-phase abundance ratios of N/O
and C/O -- both of which are significantly sub-solar but, as for O/Fe, are in
remarkable agreement with abundance patterns observed in Galactic thick disk,
bulge, and halo stars with similar O/H. High nebular excitation is the rule at
high-z (and rare at low-z) because of systematically shorter enrichment
timescales (<<1 Gyr): low Fe/O environments produce harder (and longer-lived)
stellar EUV spectra at a given O/H, enhanced by dramatic effects on the
evolution of massive star binaries.


title: The formation and physical origin of highly ionized cooling gas

abstract:
  We present a simple model that explains the origin of warm diffuse gas seen
primarily as highly ionized absorption line systems in the spectra of
background sources. We predict the observed column densities of several highly
ionized transitions such as OVI, OVIII, NeVIII, NV, and MgX; and present a
unified comparison of the model predictions with absorption lines seen in the
Milky Way disk, Milky Way halo,starburst galaxies, the circumgalactic medium
and the intergalactic medium at low and high redshifts. We show that diffuse
gas seen in such diverse environments can be simultaneously explained by a
simple model of radiatively cooling gas. We show that most of such absorption
line systems are consistent with being collisionally ionized, and estimate the
maximum likelihood temperature of the gas in each observation. This model
satisfactorily explains why OVI is regularly observed around star-forming low-z
L* galaxies, and why NV is rarely seen around the same galaxies. We further
present some consequences of this model in quantifying the dynamics of the
cooling gas around galaxies and predict the shock velocities associated with
such flows. A unique strength of this model is that while it has only one free
(but physically well-constrained) parameter, it nevertheless successfully
reproduces the available data on O VI absorbers in the interstellar,
circumgalactic, intra-group, and intergalactic media, as well as the available
data on other absorption-line from highly ionized species.


title:
Sharing but not Caring: Dark Matter and the Baryon Asymmetry of the
  Universe

abstract:
  We consider scenarios where Dark Matter (DM) particles carry baryon and/or
lepton numbers, which can be defined if there exist operators connecting the
dark to the visible sector. As a result, the DM fields become intimately linked
to the Standard Model (SM) ones and can be maximally asymmetric just like the
ordinary matter. In particular, we discuss minimal scenarios where the DM is a
complex scalar or a Dirac fermion coupled to operators with nonzero baryon
and/or lepton numbers, and that consist of only SM fields. We consider an
initial asymmetry stored in either the SM or the DM sector; the main role of
these operators is to properly $share$ the asymmetry between the two sectors,
in accordance with observations. After the chemical decoupling, the DM and SM
sectors do $not$ $care$ about each other as there is only an ineffective
communication between them. Once the DM mass is specified, the Wilson
coefficients of these operators are fixed by the requirement of the correct
transfer of the asymmetry. We study the phenomenology of this framework at
colliders, direct detection and indirect detection experiments. In particular,
the LHC phenomenology is very rich and can be tested in different channels such
as the two same-sign leptons with two jets, monojet and monojet with a
monolepton.


title:
SDSS IV MaNGA - Spatially resolved diagnostic diagrams: A proof that
  many galaxies are LIERs

abstract:
  We study the spatially resolved excitation properties of the ionised gas in a
sample of 646 galaxies using integral field spectroscopy data from SDSS-IV
MaNGA. Making use of Baldwin-Philips-Terlevich diagnostic diagrams we
demonstrate the ubiquitous presence of extended (kpc scale) low ionisation
emission-line regions (LIERs) in both star forming and quiescent galaxies. In
star forming galaxies LIER emission can be associated with diffuse ionised gas,
most evident as extra-planar emission in edge-on systems. In addition, we
identify two main classes of galaxies displaying LIER emission: `central LIER'
(cLIER) galaxies, where central LIER emission is spatially extended, but
accompanied by star formation at larger galactocentric distances, and `extended
LIER' (eLIER) galaxies, where LIER emission is extended throughout the whole
galaxy. In eLIER and cLIER galaxies, LIER emission is associated with radially
flat, low H$\alpha$ equivalent width of line emission ($<$ 3 \AA) and stellar
population indices demonstrating the lack of young stellar populations,
implying that line emission follows tightly the continuum due to the underlying
old stellar population. The H$\alpha$ surface brightness radial profiles are
always shallower than $\rm 1/r^{2}$ and the line ratio
[OIII]$\lambda$5007/[OII]$\lambda$3727,29 (a tracer of the ionisation parameter
of the gas) shows a flat gradient. This combined evidence strongly supports the
scenario in which LIER emission is not due to a central point source but to
diffuse stellar sources, the most likely candidates being hot, evolved
(post-asymptotic giant branch) stars. Shocks are observed to play a significant
role in the ionisation of the gas only in rare merging and interacting systems.


title:
Sharp peaks in the conductance of double quantum dot and quantum dot
  spin-valve systems at high temperatures: A hierarchical quantum master
  equation approach

abstract:
  We study sharp peaks in the conductance-voltage characteristics of a double
quantum dot and a quantum dot spin-valve that are located around zero bias. The
peaks share similarities with a Kondo peak but can be clearly distinguished, in
particular as they occur at high temperatures. The underlying physical
mechanism is a strong current suppression that is quenched in bias-voltage
dependent ways by exchange interactions. Our theoretical results are based on
the quantum master equation methodology, including the Born-Markov
approximation and a numerically exact, hierarchical scheme, which we extend
here to the spin-valve case. The comparison of exact and approximate results
allows us to reveal the underlying physical mechanisms, the role of first-,
second- and beyond-second-order processes and the robustness of the effect.


title:
Correlating new physics signals in $B \to D^{(*)} \tau \nu_{\tau}$ with
  $B \to \tau \nu_{\tau}$

abstract:
  Semileptonic and purely leptonic decays of B meson to $\tau$, such as $B\to
D^{(\ast)}\tau\nu_{\tau}$ and $B\to\tau\nu_\tau$ are studied. Recognizing that
there already were some weak hints of possible deviations from the SM in the
measurements of $\mathcal{B}(B\to\tau\nu_\tau)$ by \Babar~and Belle and the
fact that detection of the $\tau$ also occurs in the measurements of $B\to
D^{(\ast)}\tau\nu_{\tau}$, we stress the importance of joint studies of these
processes, whenever possible. For this purpose, as an illustration, we
introduce the observable, $\mathcal{R}(D^{(*)})/\mathcal{B}(B\to\tau\nu_\tau)$
where, for one thing, the unknown systematics due to $\tau$ identification are
expected to largely cancel. We show that all measurements of this observable
are consistent with the existing data, within somewhat largish experimental
errors, with the predictions of the SM. We stress that precise experimental
measurement and comparison with theory of the branching ratio for $B \to \tau
\nu_\tau$ is extremely important for a reliable search of new physics.
Furthermore, in view of the anticipated improved precision in experiments in
the next few years, in addition to $\mathcal{R}(D^{(*)})$, host of other ratios
analogous to $\mathcal{R}(D^{(*)})/\mathcal{B}(B \to \tau \nu_{\tau})$ in the
SM are suggested for lattice calculations as well, so that for more stringent
tests of the SM, correlations in lattice calculations can be properly taken
into account to enhance precision.


title:
Underlying event sensitive observables in Drell-Yan production using
  GENEVA

abstract:
  We present an extension of the GENEVA Monte Carlo framework to include
multiple parton interactions (MPI) provided by PYTHIA8. This allows us to
obtain predictions for underlying-event sensitive measurements in Drell-Yan
production, in conjunction with GENEVA's fully-differential NNLO calculation,
NNLL' resummation for the 0-jet resolution variable (beam thrust), and NLL
resummation for the 1-jet resolution variable. We describe the interface with
the parton shower algorithm and MPI model of PYTHIA8, which preserves both the
precision of partonic N-jet cross sections in GENEVA as well as the shower
accuracy and good description of soft hadronic physics of PYTHIA8. We present
results for several underlying-event sensitive observables and compare to data
from ATLAS and CMS as well as to standalone PYTHIA8 predictions. This includes
a comparison with the recent ATLAS measurement of the beam thrust spectrum,
which provides a potential avenue to fully disentangle the physical effects
from the primary hard interaction, primary soft radiation, multiple parton
interactions, and nonperturbative hadronization.


title: Stable photon orbits in stationary axisymmetric electrovacuum spacetimes

abstract:
  We investigate the existence and phenomenology of stable photon orbits (SPOs)
in stationary axisymmetric electrovacuum spacetimes in four dimensions. First,
we review the classification of equatorial circular photon orbits on
Kerr-Newman spacetimes in the charge-spin plane. Second, using a Hamiltonian
formulation, we show that Reissner-Nordstr\"om di-holes (a family encompassing
the Majumdar-Papapetrou and Weyl-Bach special cases) admit SPOs, in a certain
parameter regime that we investigate. Third, we explore the transition from
order to chaos for typical SPOs bounded within a toroidal region around a
di-hole, via a selection of Poincar\'e sections. Finally, for general
axisymmetric stationary spacetimes, we show that the Einstein-Maxwell field
equations allow for the existence of SPOs in electrovacuum; but not in pure
vacuum.


title:
Signatures of broken parity and time-reversal symmetry in generalized
  string-net models

abstract:
  We study indicators of broken time-reversal and parity symmetries in gapped
topological phases of matter. We focus on phases realized by Levin-Wen
string-net models, and generalize the string-net model to describe phases which
break parity and time-reversal symmetries. We do this by introducing an extra
degree of freedom into the string-net graphical calculus, which takes the form
of a branch cut located at each vertex of the underlying string-net lattice. We
also work with string-net graphs defined on arbitrary (non-trivalent) graphs,
which reveals otherwise hidden information about certain configurations of
anyons in the string-net graph. Most significantly, we show that objects known
as higher Frobenius-Schur indicators can provide several efficient ways to
detect whether or not a given topological phase breaks parity or time-reversal
symmetry.


title: Cosmological Constraints on Decoupled Dark Photons and Dark Higgs

abstract:
  Any neutral boson such as a dark photon or dark Higgs that is part of a
non-standard sector of particles can mix with its standard model counterpart.
When very weakly mixed with the Standard Model, these particles are produced in
the early Universe via the freeze-in mechanism and subsequently decay back to
standard model particles. In this work, we place constraints on such mediator
decays by considering bounds from Big Bang nucleosynthesis and the cosmic
microwave background radiation. We find both nucleosynthesis and CMB can
constrain dark photons with a kinetic mixing parameter between log {\epsilon} ~
-10 to -17 for masses between 1 MeV and 100 GeV. Similarly, the dark Higgs
mixing angle {\epsilon} with the Standard Model Higgs is constrained between
log {\epsilon} ~ -6 to -15. Dramatic improvement on the bounds from CMB
spectral distortions can be achieved with proposed experiments such as PIXIE.


title: Balls and Funnels: Energy Efficient Group-to-Group Anycasts

abstract:
  We introduce group-to-group anycast (g2g-anycast), a network design problem
of substantial practical importance and considerable generality. Given a
collection of groups and requirements for directed connectivity from source
groups to destination groups, the solution network must contain, for each
requirement, an omni-directional down-link broadcast, centered at any node of
the source group, called the ball; the ball must contain some node from the
destination group in the requirement and all such destination nodes in the ball
must aggregate into a tree directed towards the source, called the funnel-tree.
The solution network is a collection of balls along with the funnel-trees they
contain. g2g-anycast models DBS (Digital Broadcast Satellite), Cable TV systems
and drone swarms. It generalizes several well known network design problems
including minimum energy unicast, multicast, broadcast, Steiner-tree,
Steiner-forest and Group-Steiner tree. Our main achievement is an $O(\log^4 n)$
approximation, counterbalanced by an $\log^{(2-\epsilon)}n$ hardness of
approximation, for general weights. Given the applicability to wireless
communication, we present a scalable and easily implemented $O(\log n)$
approximation algorithm, Cover-and-Grow for fixed-dimensional Euclidean space
with path-loss exponent at least 2.


title: Quantum computation with realistic magic state factories

abstract:
  Leading approaches to fault-tolerant quantum computation dedicate a
significant portion of the hardware to computational factories that churn out
high-fidelity ancillas called magic states. Consequently, efficient and
realistic factory design is of paramount importance. Here we present the most
detailed resource assessment to date of magic state factories within a surface
code quantum computer, along the way introducing a number of new techniques. We
show that the block codes of Bravyi and Haah [Phys. Rev. A 86, 052329 (2012)]
have been systematically undervalued; we track correlated errors both
numerically and analytically, providing fidelity estimates without appeal to
the union bound. We also introduce a subsystem code realisation of these
protocols with constant time and low ancilla cost. Additionally, we confirm
that magic state factories have space-time costs that scale as a constant
factor of surface code costs. We find that the magic state factory required for
post-classical factoring can be as small as 6.3 million data qubits, ignoring
ancilla qubits, assuming $10^{-4}$ error gates, and the availability of long
range interactions.


title:
Efficient preconditioners for saddle point systems with trace
  constraints coupling 2D and 1D domains

abstract:
  We study preconditioners for a model problem describing the coupling of two
elliptic subproblems posed over domains with different topological dimension by
a parameter dependent constraint. A pair of parameter robust and efficient
preconditioners is proposed and analyzed. Robustness and efficiency of the
preconditioners is demonstrated by numerical experiments.


title: Holographic Entanglement Renormalization of Topological Insulators

abstract:
  We study the real-space entanglement renormalization group flows of
topological band insulators in (2+1) dimensions by using the continuum
multi-scale entanglement renormalization ansatz (cMERA). Given the ground state
of a Chern insulator, we construct and study its cMERA by paying attention, in
particular, to how the bulk holographic geometry and the Berry curvature depend
on the topological properties of the ground state. It is found that each state
defined at different energy scale of cMERA carries a nonzero Berry flux, which
is emanated from the UV layer of cMERA, and flows towards the IR. Hence, a
topologically nontrivial UV state flows under the RG to an IR state, which is
also topologically nontrivial. On the other hand, we found that there is an
obstruction to construct the exact ground state of a topological insulator with
a topologically trivial IR state. I.e., if we try to construct a cMERA for the
ground state of a Chern insulator by taking a topologically trivial IR state,
the resulting cMERA does not faithfully reproduce the exact ground state at all
length scales.


title: A new generalisation of Macdonald polynomials

abstract:
  We introduce a new family of symmetric multivariate polynomials, whose
coefficients are meromorphic functions of two parameters $(q,t)$ and polynomial
in a further two parameters $(u,v)$. We evaluate these polynomials explicitly
as a matrix product. At $u=v=0$ they reduce to Macdonald polynomials, while at
$q=0$, $u=v=s$ they recover a family of inhomogeneous symmetric functions
originally introduced by Borodin.


title: Robust determination of maximally-localized Wannier functions

abstract:
  We propose an algorithm to determine Maximally Localized Wannier Functions
(MLWFs). This algorithm, based on recent theoretical developments, does not
require any physical input such as initial guesses for the Wannier functions,
unlike popular schemes based on the projection method. We discuss how the
projection method can fail on fine grids when the initial guesses are too far
from MLWFs. We demonstrate that our algorithm is able to find localized Wannier
functions through tests on two-dimensional systems, simplified models of
semiconductors, and realistic DFT systems by interfacing with the Wannier90
code. We also test our algorithm on the Haldane and Kane-Mele models to examine
how it fails in the presence of topological obstructions.

categories: cond-mat.mtrl-sci cond-mat.mes-hall math-ph math.MP


title: Entanglement and extreme spin squeezing of unpolarized states

abstract:
  We present criteria to detect the depth of entanglement in macroscopic
ensembles of spin-j particles using the variance and second moments of the
collective spin components. The class of states detected goes beyond
traditional spin-squeezed states by including Dicke states and other
unpolarized states. The criteria derived are easy to evaluate numerically even
for systems of very many particles and outperform past approaches, especially
in practical situations where noise is present. We also derive analytic lower
bounds based on the linearization of our criteria, which make it possible to
define spin-squeezing parameters for Dicke states. In addition, we obtain spin
squeezing parameters also from the condition derived in [A. S. Sorensen and K.
Molmer, Phys. Rev. Lett. 86, 4431 (2001)]. We also extend our results to
systems with fluctuating number of particles.


title: Computing torus-equivariant K-theory of singular varieties

abstract:
  This expository note surveys some results on equivariant K-theory of
varieties with a torus action, focusing on recent work with Sam Payne and
Richard Gonzales. It is based on my contribution to the Clifford Lectures at
Tulane University in March 2015.


title: Most edge-orderings of $K_n$ have maximal altitude

abstract:
  Suppose the edges of the complete graph on $n$ vertices are assigned a
uniformly chosen random ordering. Let $X$ denote the corresponding number of
Hamiltonian paths that are increasing in this ordering. It was shown in a
recent paper by Lavrov and Loh that this quantity is non-zero with probability
at least $1/e-o(1)$, and conjectured that $X$ is asymptotically almost surely
non-zero. In this paper, we prove their conjecture. We further prove a partial
result regarding the limiting behaviour of $X$, suggesting that $X/n$ is
log-normal in the limit as $n\rightarrow\infty$. A key idea of our proof is to
show a certain relation between $X$ and its size-biased distribution. This
relies heavily on estimates for the third moment of $X$.


title:
Initial-data contribution to the error budget of gravitational waves
  from neutron-star binaries

abstract:
  As numerical calculations of inspiralling neutron-star binaries reach values
of accuracy that are comparable with those of binary black holes, a fine
budgeting of the various sources of error becomes increasingly important. Among
such sources, the initial data is normally not accounted for, the rationale
being that the error on the initial spacelike hypersurface is always far
smaller than the one gained during the evolution. We here consider critically
this assumption and perform a comparative analysis of the gravitational
waveforms relative to essentially the same physical binary configuration when
computed with two different initial-data codes, and then evolved with the same
evolution code. More specifically, we consider the evolution of irrotational
neutron-star binaries computed either with the pseudo-spectral code \lorene{},
or with the newly developed finite-difference code \cocal{}; both sets of
initial data are subsequently evolved with the high-order evolution code
\whiskythc{}. In this way we find that despite the initial data shows global
(local) differences that are $\lesssim 0.02\%\ (1\%)$, the gravitational-wave
phase at the merger time differs by $\sim 0.5$ radians after $\sim 3$ orbits, a
surprisingly large value. Our results highlight the highly nonlinear impact
that errors in the initial data can have on the subsequent evolution and the
importance of using exactly the same initial data when comparative studies are
done.


title: On the space of non-Gaussian fields with single-clock bispectra

abstract:
  We develop a mathematical construction of non-Gaussian fields whose bispectra
satisfy the single-clock inflation consistency relation. At the same order that
our basis for bispectra recovers the two simplest single clock templates, we
also find a third orthogonal template which has the single clock squeezed
limit, peaks in folded configurations, and has very small coupling in the
equilateral limit. We explore the map between templates and operators in a very
general Lagrangian for single-clock fluctuations and find no significant
overlap between the new template and models in the literature. We comment on
the physical implications of this conclusion. Our findings add support for the
idea that both theory and data driven considerations will be best served if
next generation non-Gaussianity constraints are made in a basis that uses the
degree of coupling between long and short wavelength modes as an organizing
principle.


title: Quantized gravitoelectromagnetism theory at finite temperature

abstract:
  The Gravitoelectromagnetism (GEM) theory is considered in a lagrangian
formulation using the Weyl tensor components. A perturbative approach to
calculate processes at zero temperature has been used. Here the GEM at finite
temperature is analyzed using Thermo Field Dynamics, real time finite
temperature quantum field theory. Transition amplitudes involving gravitons,
fermions and photons are calculated for various processes. These amplitudes are
likely of interest in astrophysics.


title:
Broadband, Polarization-insensitive and Wide-angle Optical Absorber
  based on Fractal Plasmonics

abstract:
  In this paper, a plasmonic absorber consisting of a metal-dielectric-metal
stack with a top layer of Sierpinski nanocarpet is theoretically investigated.
Such compact absorber depicts broadband angle-independent behavior over a wide
optical wavelength range ($400-700$ nm) and a broad range of angles of light
incidence ($0-80^{\circ}$). Including several feature sizes, such fractal-like
structure shows widely strong extinction ($85-99$%) response for either
transverse electric or magnetic polarization states under normal incidence.
Underlying mechanisms of absorbance due to excited surface plasmon modes as
well as electric/magnetic dipole resonances are well revealed by investigating
electric field, magnetic field and current distributions. The proposed absorber
opens a path to realize high-performance ultrathin light trapping devices.


title:
Beyond the Interface Limit: Structural and Magnetic Depth Profiles of
  Voltage-Controlled Magneto-Ionic Heterostructures

abstract:
  Electric-field control of magnetism provides a promising route towards
ultralow power information storage and sensor technologies. The effects of
magneto-ionic motion have so far been prominently featured in the direct
modification of interface chemical and physical characteristics. Here we
demonstrate magnetoelectric coupling moderated by voltage-driven oxygen
migration beyond the interface limit in relatively thick AlOx/GdOx/Co (15 nm)
films. Oxygen migration and its ramifications on the Co magnetization are
quantitatively mapped with polarized neutron reflectometry under thermal and
electro-thermal conditionings. The depth-resolved profiles uniquely identify
interfacial and bulk behaviors and a semi-reversible suppression and recovery
of the magnetization. Magnetometry measurements show that the conditioning
changes the microstructure so as to disrupt long-range ferromagnetic ordering,
resulting in an additional magnetically soft phase. X-ray spectroscopy confirms
electric field induced changes in the Co oxidation state but not in the Gd,
suggesting that the GdOx transmits oxygen but does not source or sink it. These
results together provide crucial insight into controlling magnetic
heterostructures via magneto-ionic motion, not only at the interface, but also
throughout the bulk of the films.


title:
Boson Stars in a Theory of Complex Scalar Fields coupled to $U(1)$ Gauge
  Field and Gravity

abstract:
  We study boson shells and boson stars in a theory of complex scalar field
coupled to the $U(1)$ gauge field $A_{\mu}$ and Einstein gravity with the
potential: $V(|\Phi|) := \frac{1}{2} m^{2} \left(|\Phi|+ a \right)^2$. This
could be considered either as a theory of massive complex scalar field coupled
to electromagnetic field and gravity in a conical potential or as a theory in
the presence of a potential which is an overlap of a parabolic and a conical
potential. Our theory has a positive cosmological constant $(\Lambda := 4 \pi G
m^2 a^2)$. Boson stars are found to come in two types, having either ball-like
or shell-like charge density. We have studied the properties of these solutions
and have also determined their domains of existence for some specific values of
the parameters of the theory. Similar solutions have also been obtained by
Kleihaus, Kunz, Laemmerzahl and List, in a V-shaped scalar potential.


title: Temperate Earth-sized planets transiting a nearby ultracool dwarf star

abstract:
  Star-like objects with effective temperatures of less than 2,700 kelvin are
referred to as ultracool dwarfs. This heterogeneous group includes stars of
extremely low mass as well as brown dwarfs (substellar objects not massive
enough to sustain hydrogen fusion), and represents about 15 per cent of the
population of astronomical objects near the Sun. Core-accretion theory predicts
that, given the small masses of these ultracool dwarfs, and the small sizes of
their protoplanetary disk, there should be a large but hitherto undetected
population of terrestrial planets orbiting them - ranging from metal-rich
Mercury-sized planets to more hospitable volatile-rich Earth-sized planets.
Here we report observations of three short-period Earth-sized planets
transiting an ultracool dwarf star only 12 parsecs away. The inner two planets
receive four times and two times the irradiation of Earth, respectively,
placing them close to the inner edge of the habitable zone of the star. Our
data suggest that 11 orbits remain possible for the third planet, the most
likely resulting in irradiation significantly less than that received by Earth.
The infrared brightness of the host star, combined with its Jupiter-like size,
offers the possibility of thoroughly characterizing the components of this
nearby planetary system.


title: On Calabi's diastasis function of the cigar metric

abstract:
  We show that the Cigar metric on $\mathbb{C}$ is an example of real analytic
K\"ahler manifold with globally defined and positive Calabi's diastasis
function which cannot be K\"ahler immersed into any (finite or infinite
dimensional) complex space form.


title: Linear $\sigma$ model for the Goldstone Higgs - Experimental tests

abstract:
  In order to explore a possible dynamical nature for the Higgs field (such as
its being a pseudo-Goldstone boson) we develop a renormalizable Lagrangian
based on the minimal $SO(5)$ linear $\sigma$-model with the symmetry softly
broken to $SO(4)$, including gauge bosons and fermions. We then present the
phenomenological implications and constraints from precision observables and
the impact on present and future LHC data.


title:
Topological states and phase transitions in Sb$_2$Te$_3$-GeTe
  multilayers

abstract:
  Topological insulators (TIs) are bulk insulators with exotic 'topologically
protected' surface conducting modes. It has recently been pointed out that when
stacked together, interactions between surface modes can induce diverse phases
including the TI, Dirac semimetal, and Weyl semimetal. However, currently a
full experimental understanding of the conditions under which topological modes
interact is lacking. Here, working with multilayers of the TI Sb$_2$Te$_3$ and
the band insulator GeTe, we provide experimental evidence of a multiple
topological modes in a single Sb$_2$Te$_3$-GeTe-Sb$_2$Te$_3$ structure.
Furthermore, we show that reducing the thickness of the GeTe layer induces a
phase transition from a Dirac-like phase to a gapped phase. By comparing
different multilayer structures we demonstrate that this transition occurs due
to the hybridisation of states associated with different TI films. Our results
demonstrate that the Sb$_2$Te$_3$-GeTe system offers strong potential towards
manipulating topological states as well as towards controlledly inducing
various topological phases.


title:
An in-depth spectroscopic examination of molecular bands from 3D
  hydrodynamical model atmospheres I. Formation of the G-band in metal-poor
  dwarf stars

abstract:
  Recent developments in the three-dimensional (3D) spectral synthesis code
Linfor3D have meant that, for the first time, large spectral wavelength
regions, such as molecular bands, can be synthesised with it in a short amount
of time. A detailed spectral analysis of the synthetic G-band for several dwarf
turn-off-type 3D atmospheres (5850 <= T_eff [K] <= 6550, 4.0 <= log g <= 4.5,
-3.0 <= [Fe/H] <= -1.0) was conducted, under the assumption of local
thermodynamic equilibrium. We also examine carbon and oxygen molecule formation
at various metallicity regimes and discuss the impact it has on the G-band.
Using a qualitative approach, we describe the different behaviours between the
3D atmospheres and the traditional one-dimensional (1D) atmospheres and how the
different physics involved inevitably leads to abundance corrections, which
differ over varying metallicities. Spectra computed in 1D were fit to every 3D
spectrum to determine the 3D abundance correction. Early analysis revealed that
the CH molecules that make up the G-band exhibited an oxygen abundance
dependency; a higher oxygen abundance leads to weaker CH features. Nitrogen
abundances showed zero impact to CH formation. The 3D corrections are also
stronger at lower metallicity. Analysis of the 3D corrections to the G-band
allows us to assign estimations of the 3D abundance correction to most dwarf
stars presented in the literature. The 3D corrections suggest that A(C) in CEMP
stars with high A(C) would remain unchanged, but would decrease in CEMP stars
with lower A(C). It was found that the C/O ratio is an important parameter to
the G-band in 3D. Additional testing confirmed that the C/O ratio is an equally
important parameter for OH transitions under 3D. This presents a clear
interrelation between the carbon and oxygen abundances in 3D atmospheres
through their molecular species, which is not seen in 1D.


title:
Geometric syntomic cohomology and vector bundles on the Fargues-Fontaine
  curve

abstract:
  We show that geometric syntomic cohomology lifts canonically to the category
of Banach-Colmez spaces and study its relation to extensions of modifications
of vector bundles on the Fargues-Fontaine curve. We include some computations
of geometric syntomic cohomology Spaces: they are finite rank $Q_p$-vector
spaces for ordinary varieties, but in the nonordinary case, these cohomology
Spaces carry much more information, in particular they can have a non-trivial
$C$-rank. This dichotomy is reminiscent of the Hodge-Tate period map for
$p$-divisible groups.


title: Cross-Section Fluctuations in Chaotic Scattering Systems

abstract:
  Exact analytical expressions for the cross-section correlation functions of
chaotic scattering sys- tems have hitherto been derived only under special
conditions. The objective of the present article is to provide expressions that
are applicable beyond these restrictions. The derivation is based on a
statistical model of Breit-Wigner type for chaotic scattering amplitudes which
has been shown to describe the exact analytical results for the scattering
(S)-matrix correlation functions accurately. Our results are given in the
energy and in the time representations and apply in the whole range from
isolated to overlapping resonances. The S-matrix contributions to the
cross-section correla- tions are obtained in terms of explicit irreducible and
reducible correlation functions. Consequently, the model can be used for a
detailed exploration of the key features of the cross-section correlations and
the underlying physical mechanisms. In the region of isolated resonances, the
cross-section correlations contain a dominant contribution from the
self-correlation term. For narrow states the self-correlations originate
predominantly from widely spaced states with exceptionally large partial width.
In the asymptotic region of well-overlapping resonances, the cross-section
autocorrelation functions are given in terms of the S-matrix autocorrelation
functions. For inelastic correlations, in particular, the Ericson fluctuations
rapidly dominate in that region. Agreement with known analytical and with
experimental results is excellent.


title:
Radioactivity and thermalization in the ejecta of compact object mergers
  and their impact on kilonova light curves

abstract:
  One of the most promising electromagnetic signatures of compact object
mergers are kilonovae: approximately isotropic radioactively-powered transients
that peak days to weeks post-merger. Key uncertainties in modeling kilonovae
include the emission profiles of the radioactive decay products---non-thermal
beta- and alpha-particles, fission fragments, and gamma-rays---and the
efficiency with which they deposit their energy in the ejecta. The total
radioactive energy and the efficiency of its thermalization sets the luminosity
budget and is therefore necessary for predicting kilonova light curves. We
outline the uncertainties in r-process decay, describe the physical processes
by which the energy of the decay products is absorbed in the ejecta, and
present time-dependent thermalization efficiencies for each particle type. We
determine the net heating efficiency and explore its dependence on r-process
yields---in particular, the production of translead nuclei that undergo
alpha-decay---and on the ejecta's mass, velocity, composition, and magnetic
field configuration. We incorporate our results into new time-dependent,
multi-wavelength radiation transport simulations, and calculate updated
predictions of kilonova light curves. Thermalization has a substantial effect
on kilonova photometry, reducing the luminosity by a factor of roughly 2 at
peak, and by an order of magnitude or more at later times (15 days or more
after explosion). We present simple analytic fits to time-dependent net
thermalization efficiencies, which can easily be used to improve light curve
models. We briefly revisit the putative kilonova that accompanied gamma ray
burst 130603B, and offer new estimates of the mass ejected in that event. We
find that later-time kilonova light curves can be significantly impacted by
alpha-decay from translead isotopes; data at these times may therefore be
diagnostic of ejecta abundances.


title: Non-topological Vortex Configurations in the ABJM Model

abstract:
  In this paper we study the existence of vortex-type solutions for a system of
self-dual equations deduced from the mass-deformed
Aharony--Bergman--Jafferis--Maldacena (ABJM) model. The governing equations,
derived by Mohammed, Murugan, and Nastse under suitable ansatz involving fuzzy
sphere matrices, have the new feature that they can support only
non-topological vortex solutions. After transforming the self-dual equations
into a nonlinear elliptic $2\times 2$ system we prove first an existence result
by means of a perturbation argument based on a new and appropriate scaling for
the solutions. Subsequently, we prove a more complete existence result by using
a dynamical analysis together with a blow-up argument. In this way we establish
that, any positive energy level is attained by a 1-parameter family of vortex
solutions which also correspond to (constraint) energy minimizers. In other
words, we register the exceptional fact in a BPS-setting that, neither a
"quantization" effect nor an energy gap is induced upon the system by the rigid
"critical" coupling of the self-dual regime.


title:
Canonical Number and NutCracker: Heuristic Algorithms for the Graph
  Isomorphism Problem using Free Energy

abstract:
  This paper develops two heuristic algorithms to solve graph isomorphism,
using free energy encoding. The first algorithm uses four types of encoding
refinement techniques such that every graph can be distinguished by a canonical
number computed by the algorithm. The second algorithm injects energy into the
graph to conduct individualization such that the correspondence relation
between a pair of isomorphic graphs can be found. The core principle behind the
two algorithms is encoding discrete structures as real numbers. A large set of
experiments demonstrated the effectiveness of our algorithms.


title: Global Optimality of Local Search for Low Rank Matrix Recovery

abstract:
  We show that there are no spurious local minima in the non-convex factorized
parametrization of low-rank matrix recovery from incoherent linear
measurements. With noisy measurements we show all local minima are very close
to a global optimum. Together with a curvature bound at saddle points, this
yields a polynomial time global convergence guarantee for stochastic gradient
descent {\em from random initialization}.


title: Mechanisms of vortices termination in the cardiac muscle

abstract:
  We propose a solution to a long standing problem: how to terminate multiple
vortices in the heart, when the locations of their cores and their critical
time windows are unknown. We scan the phases of all pinned vortices in parallel
with electric field pulses (E-pulses). We specify a condition on pacing
parameters that guarantees termination of one vortex. For more than one vortex
with significantly different frequencies, the success of scanning depends on
chance, and all vortices are terminated with a success rate of less than one.
We found that a similar mechanism terminates also a free (not pinned) vortex. A
series of about 500 experiments with termination of ventricular fibrillation by
E-pulses in pig isolated hearts is evidence that pinned vortices, hidden from
direct observation, are significant in fibrillation. These results form a
physical basis needed for the creation of new effective low energy
defibrillation methods based on the termination of vortices underlying
fibrillation.


title:
Twisted representations of vertex operator algebras associated to affine
  Lie algebras

abstract:
  In this paper, we prove the categories of lower bounded twisted modules of
positive integer levels for simple vertex operator algebras associated with
affine Lie algebras and general automorphisms are semisimple, using the twisted
generalization of Zhu's algebra for these vertex operator algebras, constructed
in \cite{HY}. We also show that the category of lower bounded twisted modules
for a general automorphism is equivalent to the category of lower bounded
twisted modules for the corresponding diagram automorphism.


title:
A Free Energy Foundation of Semantic Similarity in Automata and
  Languages

abstract:
  This paper develops a free energy theory from physics including the
variational principles for automata and languages and also provides algorithms
to compute the energy as well as efficient algorithms for estimating the
nondeterminism in a nondeterministic finite automaton. This theory is then used
as a foundation to define a semantic similarity metric for automata and
languages. Since automata are a fundamental model for all modern programs while
languages are a fundamental model for the programs' behaviors, we believe that
the theory and the metric developed in this paper can be further used for
real-word programs as well.


title:
A linear dispersion relation for the hybrid kinetic-ion/fluid-electron
  model of plasma physics

abstract:
  A dispersion relation for a commonly used hybrid model of plasma physics is
developed, which combines fully kinetic ions and a massless-electron fluid
description. Although this model and variations of it have been used to
describe plasma phenomena for about 40 years, to date there exists no general
dispersion relation to describe the linear wave physics contained in the model.
Previous efforts along these lines are extended here to retain arbitrary wave
propagation angles, temperature anisotropy effects, as well as additional terms
in the generalized Ohm's law which determines the electric field. A numerical
solver for the dispersion relation is developed, and linear wave physics is
benchmarked against solutions of a full Vlasov-Maxwell dispersion relation
solver. This work opens the door to a more accurate interpretation of existing
and future wave and turbulence simulations using this type of hybrid model.


title: Role of Genome in the Formation of Conical Retroviral Shells

abstract:
  Human immunodeficiency virus (HIV) capsid proteins spontaneously assemble
around the genome into a protective protein shell called the capsid, which can
take on a variety of shapes broadly classified as conical, cylindrical and
irregular. The majority of capsids seen in in vivo studies are conical in
shape, while in vitro experiments have shown a preference for cylindrical
capsids. The factors involved in the selection of the unique shape of HIV
capsids are not well understood, and in particular the impact of RNA on the
formation of the capsid is not known. In this work, we study the role of the
genome and its interaction with the capsid protein by modeling the genomic RNA
through a mean-field theory. Our results show that the confinement free energy
for a homopolymeric model genome confined in a conical capsid is lower than
that in a cylindrical capsid, at least when the genome does not interact with
the capsid, which seems to be the case in in vivo experiments. Conversely, the
confinement free energy for the cylinder is lower than for a conical capsid if
the genome is attracted to the capsid proteins as the in vitro experiments.
Understanding the factors that contribute to the formation of conical capsids
may shed light on the infectivity of HIV particles.


title:
Flux states and topological phases from spontaneous time-reversal
  symmetry breaking in CrSi(Ge)Te$_3$-based systems

abstract:
  We study adatom-covered single layers of CrSiTe$_3$ and CrGeTe$_3$ using
first-principles calculations based on hybrid functionals. We find that the
insulating ground state of a monolayer of La (Lu) deposited on single-layer
CrSiTe$_3$ (CrGeTe$_3$) carries spontaneously generated current loops around
the Cr sites, These "flux states" induce antiferromagnetically ordered orbital
moments on the Cr sites and are also associated with nontrivial topological
properties. The calculated Chern numbers for these systems are predicted to be
$\pm 1$ even in the absence of spin-orbit coupling, with sizable gaps on the
order of 100 meV. The flux states and the associated topological phases result
from spontaneous time-reversal symmetry breaking due to the presence of
nonlocal Coulomb interactions.


title: A note concerning Primary Source Knowledge

abstract:
  We add a small increment to understanding the notion of Primary Source
Knowledge, knowledge that the non-expert and the citizen can acquire by
assiduously reading the primary scientific journal literature without being
embedded in the cultural life of the corresponding technical specialty. This
comes from exposing four papers to the automated computer filters used by the
physics preprint server arXiv. These filters are used to flag papers in need of
further review by human assessors before being promulgated on the server;
papers not flagged by the algorithm are generally posted on arXiv without
further review. After the filtering, human moderators decide whether papers
should be posted based on a relatively low bar of whether they are of interest,
relevance and value to the research communities that populate arXiv.


title:
Fibre Products of Supersingular Curves and the Enumeration of
  Irreducible Polynomials with Prescribed Coefficients

abstract:
  For any positive integers $n\geq 3, r\geq 1$ we present formulae for the
number of irreducible polynomials of degree $n$ over the finite field
$\mathbb{F}_{2^r}$ where the coefficients of $x^{n-1}$, $x^{n-2}$ and $x^{n-3}$
are zero. Our proofs involve counting the number of points on certain algebraic
curves over finite fields, a technique which arose from Fourier-analysing the
known formulae for the $\mathbb{F}_2$ base field cases, reverse-engineering an
economical new proof and then extending it. This approach gives rise to fibre
products of supersingular curves and makes explicit why the formulae have
period $24$ in $n$.


title: Deep Portfolio Theory

abstract:
  We construct a deep portfolio theory. By building on Markowitz's classic
risk-return trade-off, we develop a self-contained four-step routine of encode,
calibrate, validate and verify to formulate an automated and general portfolio
selection process. At the heart of our algorithm are deep hierarchical
compositions of portfolios constructed in the encoding step. The calibration
step then provides multivariate payouts in the form of deep hierarchical
portfolios that are designed to target a variety of objective functions. The
validate step trades-off the amount of regularization used in the encode and
calibrate steps. The verification step uses a cross validation approach to
trace out an ex post deep portfolio efficient frontier. We demonstrate all four
steps of our portfolio theory numerically.


title:
Application of a Regional Model to Astronomical Site Testing in Western
  Antarctica

abstract:
  The quality of ground based astronomical observations are significantly
affected by telluric conditions, and the search for best sites has led to the
construction of observatories at remote locations, including recent initiatives
on the high plateaus of E Antarctica where the calm, dry and cloud free
conditions during winter are recognized as amongst the best. Site selection is
an important phase of any observatory development project, and candidate sites
must be tested with specialized equipment, a process both time consuming and
costly. A potential screening of site locations before embarking on field
testing is through the use of climate models. Here, we describe the application
of the Polar version of the Weather Research and Forecast (WRF) model to the
preliminary site suitability assessment of an unstudied region in W Antarctica.
Numerical simulations with WRF were carried out for the winter of 2011 at 3 km
and 1 km spatial resolution over a region centered on the Ellsworth mountain
range. Comparison with observations of surface wind speed and direction,
temperature and specific humidity at nine automatic weather stations indicate
that the model succeed in capturing the mean and time variability of these
variables. Credible features shown by the model include zones of high winds
over the southernmost part of the Ellsworth Mntns, a deep thermal inversion
over the Ronne-Fincher Ice Shelf and strong west to east moisture gradient
across the entire study area. Comparison of simulated cloud fraction with a
spacebourne Lidar climatology indicates that the model may underestimate cloud
occurrence, a problem that has been noted in previous studies. A simple scoring
system was applied to reveal the most promising locations. The results of this
study indicate that the WRF model is capable of providing useful guidance
during the initial site selection stage of project development.


title:
Large time behaivor of global solutions to nonlinear wave equations with
  frictional and viscoelastic damping terms

abstract:
  In this paper, we study the Cauchy problem for a nonlinear wave equation with
frictional and viscoelastic damping terms. As is pointed out by [8], in this
combination, the frictional damping term is dominant for the viscoelastic one
for the global dynamics of the linear equation. In this note we observe that if
the initial data is small, the frictional damping term is again dominant even
in the nonlinear equation case. In other words, our main result is diffusion
phenomena: the solution is approximated by the heat kernel with a suitable
constant. Our proof is based on several estimates for the corresponding linear
equations.


title: An interpolation proof of Ehrhard's inequality

abstract:
  We prove Ehrhard's inequality using interpolation along the
Ornstein-Uhlenbeck semi-group. We also provide an improved Jensen inequality
for Gaussian variables that might be of independent interest.


title:
The Bilinear Assignment Problem: Complexity and polynomially solvable
  special cases

abstract:
  In this paper we study the {\it bilinear assignment problem} (BAP) with size
parameters $m$ and $n$, $m\leq n$. BAP is a generalization of the well known
quadratic assignment problem and the three dimensional assignment problem and
hence NP-hard. We show that BAP cannot be approximated within a constant factor
unless P=NP even if the associated quadratic cost matrix $Q$ is diagonal.
Further, we show that BAP remains NP-hard if $m = O(\sqrt[r]{n})$, for some
fixed $r$, but is solvable in polynomial time if $m = O(\sqrt{\log n})$. When
the rank of $Q$ is fixed, BAP is observed to admit FPTAS and when this rank is
one, it is solvable in polynomial time under some additional restrictions. We
then provide a necessary and sufficient condition for BAP to be equivalent to
two linear assignment problems. A closed form expression to compute the average
of the objective function values of all solutions is presented, whereas the
median of the solution values cannot be identified in polynomial time, unless
P=NP. We then provide polynomial time heuristic algorithms that find a solution
with objective function value no worse than that of $(m-1)!(n-1)!$ solutions.
However, computing a solution whose objective function value is no worse than
that of $m!n!-\lceil\frac{m}{\beta}\rceil !\lceil\frac{n}{\beta}\rceil !$
solutions is NP-hard for any fixed rational number $\beta>1$.


title: Kilonova/Macronova Emission from Compact Binary Mergers

abstract:
  We review current understanding of kilonova/macronova emission from compact
binary mergers (mergers of two neutron stars or a neutron star and a black
hole). Kilonova/macronova is optical and near-infrared emission powered by
radioactive decays of r-process nuclei. Emission from the dynamical ejecta with
~0.01 Msun is likely to have a luminosity of ~10^{40}-10^{41} erg s^{-1} with a
characteristic timescale of about 1 week. The spectral peak is located in red
optical or near-infrared wavelengths. A subsequent accretion disk wind may
provide an additional luminosity, or an earlier/bluer emission if it is not
absorbed by the precedent dynamical ejecta. The detection of near-infrared
excess in the afterglow of short GRB 130603B and possible optical excess in GRB
060614 supports the concept of the kilonova/macronova scenario. At 200 Mpc
distance, a typical brightness of kilonova/macronova with 0.01 Msun ejecta is
expected to be about 22 mag and the emission rapidly fades to >24 mag within
~10 days after the merger. Kilonova/macronova candidates can be distinguished
from supernovae by (1) the faster time evolution, (2) fainter absolute
magnitudes, and (3) redder colors. To effectively search for such objects,
follow-up survey observations with multiple visits within <10 days and with
multiple filters will be important. Since the high expansion velocity (v ~
0.1-0.2c) is a robust outcome of compact binary mergers, the detection of
smooth spectra will be the smoking gun to conclusively identify the GW source.


title: Toward $ab\,initio$ extremely metal poor stars

abstract:
  Extremely metal poor stars have been the focus of much recent attention owing
to the expectation that their chemical abundances can shed light on the metal
and dust yields of the earliest supernovae. We present our most realistic
simulation to date of the astrophysical pathway to the first metal enriched
stars. We simulate the radiative and supernova hydrodynamic feedback of a
$60\,M_\odot$ Population III star starting from cosmological initial conditions
realizing Gaussian density fluctuations. We follow the gravitational
hydrodynamics of the supernova remnant at high spatial resolution through its
freely-expanding, adiabatic, and radiative phases, until gas, now
metal-enriched, has resumed runaway gravitational collapse. Our findings are
surprising: while the Population III progenitor exploded with a low energy of
$10^{51}\,\text{erg}$ and injected an ample metal mass of $6\,M_\odot$, the
first cloud to collapse after the supernova explosion is a dense surviving
primordial cloud on which the supernova blastwave deposited metals only
superficially, in a thin, unresolved layer. The first metal-enriched stars can
form at a very low metallicity, of only $2-5\times10^{-4}\,Z_\odot$, and can
inherit the parent cloud's highly elliptical, radially extended orbit in the
dark matter gravitational potential.


title: Adding random edges to dense graphs

abstract:
  This paper investigates the addition of random edges to arbitrary dense
graphs; in particular, we determine the number of random edges required to
ensure various monotone properties including the appearance of a fixed size
clique, small diameter and $k$-connectivity.


title: Escape and Finite-Size Scaling in Diffusion-Controlled Annihilation

abstract:
  We study diffusion-controlled single-species annihilation with a finite
number of particles. In this reaction-diffusion process, each particle
undergoes ordinary diffusion, and when two particles meet, they annihilate. We
focus on spatial dimensions $d>2$ where a finite number of particles typically
survive the annihilation process. Using the rate equation approach and scaling
techniques we investigate the average number of surviving particles, $M$, as a
function of the initial number of particles, $N$. In three dimensions, for
instance, we find the scaling law $M\sim N^{1/3}$ in the asymptotic regime
$N\gg 1$. We show that two time scales govern the reaction kinetics: the
diffusion time scale, $T\sim N^{2/3}$, and the escape time scale, $\tau\sim
N^{4/3}$. The vast majority of annihilation events occur on the diffusion time
scale, while no annihilation events occur beyond the escape time scale.


title: Optimizing Gershgorin for Symmetric Matrices

abstract:
  The Gershgorin Circle Theorem is a well-known and efficient method for
bounding the eigenvalues of a matrix in terms of its entries. If $A$ is a
symmetric matrix, by writing $A = B + x{\bf 1}$, where ${\bf 1}$ is the matrix
with unit entries, we consider the problem of choosing $x$ to give the optimal
Gershgorin bound on the eigenvalues of $B$, which then leads to one-sided
bounds on the eigenvalues of $A$. We show that this $x$ can be found by an
efficient linear program (whose solution can in may cases be written in closed
form), and we show that for large classes of matrices, this shifting method
beats all existing piecewise linear or quadratic bounds on the eigenvalues. We
also apply this shifting paradigm to some nonlinear estimators and show that
under certain symmetries this also gives rise to a tractable linear program. As
an application, we give a novel bound on the lowest eigenvalue of a adjacency
matrix in terms of the "top two" or "bottom two" degrees of the corresponding
graph, and study the efficacy of this method in obtaining sharp eigenvalue
estimates for certain classes of matrices.


title:
Constructions involving interaction of Markov process's with a random
  environment

abstract:
  Recently Belopolskaya and Suhov studied Markov process's in a random
environment, where the environment changes in likeness to a Markov process.
Constructions were made to allow the process to "interact with the
environment", this was done in such a manner that the combined process could be
studied by studying the individual ones. A new construction is made which has
similar properties. This construction can be carried out with more relaxed
conditions than the ones previously done.