title:
Cosmological Constraints from Galaxy Clusters in the 2500 square-degree
  SPT-SZ Survey

abstract:
  (abridged) We present cosmological constraints obtained from galaxy clusters
identified by their Sunyaev-Zel'dovich effect signature in the 2500 square
degree South Pole Telescope Sunyaev Zel'dovich survey. We consider the 377
cluster candidates identified at z>0.25 with a detection significance greater
than five, corresponding to the 95% purity threshold for the survey. We compute
constraints on cosmological models using the measured cluster abundance as a
function of mass and redshift. We include additional constraints from
multi-wavelength observations, including Chandra X-ray data for 82 clusters and
a weak lensing-based prior on the normalization of the mass-observable scaling
relations. Assuming a LCDM cosmology, where the species-summed neutrino mass
has the minimum allowed value (mnu = 0.06 eV) from neutrino oscillation
experiments, we combine the cluster data with a prior on H0 and find sigma_8 =
0.797+-0.031 and Omega_m = 0.289+-0.042, with the parameter combination
sigma_8(Omega_m/0.27)^0.3 = 0.784+-0.039. These results are in good agreement
with constraints from the CMB from SPT, WMAP, and Planck, as well as with
constraints from other cluster datasets. Adding mnu as a free parameter, we
find mnu = 0.14+-0.08 eV when combining the SPT cluster data with Planck CMB
data and BAO data, consistent with the minimum allowed value. Finally, we
consider a cosmology where mnu and N_eff are fixed to the LCDM values, but the
dark energy equation of state parameter w is free. Using the SPT cluster data
in combination with an H0 prior, we measure w = -1.28+-0.31, a constraint
consistent with the LCDM cosmological model and derived from the combination of
growth of structure and geometry. When combined with primarily geometrical
constraints from Planck CMB, H0, BAO and SNe, adding the SPT cluster data
improves the w constraint from the geometrical data alone by 14%, to w =
-1.023+-0.042.


title:
Investigating the peculiar emission from the new VHE gamma-ray source
  H1722+119

abstract:
  The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes observed
the BL Lac object H1722+119 (redshift unknown) for six consecutive nights
between 2013 May 17 and 22, for a total of 12.5 h. The observations were
triggered by high activity in the optical band measured by the KVA (Kungliga
Vetenskapsakademien) telescope. The source was for the first time detected in
the very high energy (VHE, $E > 100$ GeV) $\gamma$-ray band with a statistical
significance of 5.9 $\sigma$. The integral flux above 150 GeV is estimated to
be $(2.0\pm 0.5)$ per cent of the Crab Nebula flux. We used contemporaneous
high energy (HE, 100 MeV $ < E < 100$ GeV) $\gamma$-ray observations from
Fermi-LAT (Large Area Telescope) to estimate the redshift of the source. Within
the framework of the current extragalactic background light models, we estimate
the redshift to be $z = 0.34 \pm 0.15$. Additionally, we used contemporaneous
X-ray to radio data collected by the instruments on board the Swift satellite,
the KVA, and the OVRO (Owens Valley Radio Observatory) telescope to study
multifrequency characteristics of the source. We found no significant temporal
variability of the flux in the HE and VHE bands. The flux in the optical and
radio wavebands, on the other hand, did vary with different patterns. The
spectral energy distribution (SED) of H1722+119 shows surprising behaviour in
the $\sim 3\times10^{14} - 10^{18}$ Hz frequency range. It can be modelled
using an inhomogeneous helical jet synchrotron self-Compton model.


title: Kerr-Schild--Kundt Metrics are Universal

abstract:
  We define (non-Einsteinian) universal metrics as the metrics that solve the
source-free covariant field equations of generic gravity theories. Here,
extending the rather scarce family of universal metrics known in the
literature, we show that the Kerr-Schild--Kundt class of metrics are universal.
Besides being interesting on their own, these metrics can provide consistent
backgrounds for quantum field theory at extremely high energies.


title:
Metal-insulator transition in correlated two-dimensional systems with
  disorder

abstract:
  Experimental evidence for the possible universality classes of the
metal-insulator transition (MIT) in two dimensions (2D) is discussed.
Sufficiently strong disorder, in particular, changes the nature of the
transition. Comprehensive studies of the charge dynamics are also reviewed,
describing evidence that the MIT in a 2D electron system in silicon should be
viewed as the melting of the Coulomb glass. Comparisons are made to recent
results on novel 2D materials and quasi-2D strongly correlated systems, such as
cuprates.


title: Speciation and Dissolution of Hydrogen in the Proto-Lunar Disk

abstract:
  Despite very high temperatures accompanying lunar origin, indigenous water in
the form of OH has been unambiguously observed in Apollo samples in recent
years. Such observations have prompted questions about the abundance and
distribution of lunar hydrogen. Here, we investigate the related question of
the origin of lunar H: is the hydrogen observed a remnant of a much larger
initial inventory that was inherited from a wet Earth but partly depleted
during the process of origin, or was hydrogen quantitatively lost from the
lunar material, with water being delivered to lunar reservoirs via subsequent
impacts after the origins sequence? Motivated by recent results pointing to a
limited extent of hydrogen escape from the gravity field of the Earth during
lunar origin, we apply a newly developed thermodynamic model of liquid-vapor
silicates to the proto-lunar disk to interrogate the behavior of H as a trace
element in the energetic aftermath of the giant impact. We find that: (1)
pre-existing H-bearing molecules are rapidly dissociated at the temperatures
considered (3,100-4,200 K) and vaporized hydrogen predominantly exists as
OH(v), H(v) and MgOH(v) for nearly the full range of thermal states encountered
in the proto-lunar disk, (2) despite such a diversity in the vapor speciation,
which reduces the water fugacity and favors hydrogen exsolution from
co-existing liquids, the equilibration of the vapor atmosphere with the disk
liquid results in significant dissolution of H into proto-lunar magmas, and (3)
equilibrium H isotopic fractionation in this setting is limited to < 10 per mil
and the terrestrial character of lunar D/H recently inferred should extend to
such a precision if liquid-vapor equilibration in the proto-lunar disk is the
process that gave rise to lunar hydrogen. Taken together, these results
implicate dissolution as the process responsible for establishing lunar H
abundances.


title:
The number of linear transformations defined on a subspace with given
  invariant factors

abstract:
  Given a finite-dimensional vector space $V$ over the finite field
$\mathbb{F}_q$ and a subspace $W$ of $V$, we consider the problem of counting
linear transformations $T:W\to V$ which have prescribed invariant factors. The
case $W=V$ is a well-studied problem that is essentially equivalent to counting
the number of square matrices over $\mathbb{F}_q$ in a conjugacy class and an
explicit formula is known in this case. On the other hand, the case of general
$W$ is also an interesting problem and there hasn't been substantive progress
in this case for over two decades, barring a special case where all the
invariant factors of $T$ are of degree zero. We extend this result to the case
of arbitrary $W$ by giving an explicit counting formula. As an application of
our results, we give new proofs of some recent enumerative results in linear
control theory and derive an extension of the Gerstenhaber-Reiner formula for
the number of square matrices over $\mathbb{F}_q$ with given characteristic
polynomial.


title:
Invariant metrics on homogeneous spaces with equivalent isotropy
  summands

abstract:
  The space of $G$-invariant metrics on a homogeneous space $G/H$ is in
one-to-one correspondence with the set of inner products on the tangent space
$\fr{m}\cong T_{{\it o}}(G/H)$, which are invariant under the isotropy
representation. When all the isotropy summands are inequivalent to each other,
then the metric is called diagonal. We will describe a special class of
$G$-invariant metrics %with additional symmetries. in the case where the
isotropy representation of $G/H$ contains some equivalent isotropy summands.
Even though this problem has been considered sporadically in the bibliography,
in the present article we provide a more systematic and organized description
of such metrics. This will enable us to simplify the problem of finding
$G$-invariant Einstein metrics for homogeneous spaces. We also provide some
applications.


title: Universal Strangeness Production in Hadronic and Nuclear Collisions

abstract:
  We show that strangeness suppression in hadronic and nuclear collisions is
fully determined by the initial energy density of the collision. The
suppression factor $\gamma_s(s)$, with $\sqrt s$ denoting the collision energy,
can be expressed as a universal function of the initial energy density
$\epsilon_0(s)$, and the resulting pattern is in excellent agreement with data
from $p-p,~p-Pb,~Cu-Cu,~Au-Au$ and $Pb-Pb$ data over a wide range of energies
and for different centralities.


title: Torsion type invariants of singularities

abstract:
  Inspired by the LG/CY correspondence, we study the local index theory of the
Schr\"odinger operator associated to a singularity defined on ${\mathbb C}^n$
by a quasi-homogeneous polynomial $f$. Under some mild assumption on $f$, we
show that the small time heat kernel expansion of the corresponding
Schr\"odinger operator exists and is a series of fractional powers of time $t$.
Then we prove a local index formula which expresses the Milnor number of $f$ by
a Gaussian type integral. Furthermore, the heat kernel expansion provides
spectral invariants of $f$. Especially, we define torsion type invariants
associated to a singularity. These spectral invariants provide a new direction
to study the singularity.


title: Deep video gesture recognition using illumination invariants

abstract:
  In this paper we present architectures based on deep neural nets for gesture
recognition in videos, which are invariant to local scaling. We amalgamate
autoencoder and predictor architectures using an adaptive weighting scheme
coping with a reduced size labeled dataset, while enriching our models from
enormous unlabeled sets. We further improve robustness to lighting conditions
by introducing a new adaptive filer based on temporal local scale
normalization. We provide superior results over known methods, including recent
reported approaches based on neural nets.


title: Shear and depth-averaged Stokes drift under a Phillips-type spectrum

abstract:
  The transport and shear under a Phillips-type spectrum are presented. A
combined profile for monochromatic swell and a Phillips-type wind sea spectrum
which can be used to investigate the shear under crossing seas is then
presented.


title:
Superharmonicity of Logarithm of Jacobian of harmonic mappings between
  surfaces

abstract:
  We prove that the Logarithm of the Jacobian of a sense preserving harmonic
mappings between surfaces is superharmonic, provided that the Gaussian
curvature of the image domain is non-negative.


title:
Dynamics of entanglement among the environment oscillators of many-body
  systems

abstract:
  In this work we extend the discussion that was began in the Ref. [A. L. de
Paula Jr., J. G. G. de Oliveira Jr., J. G. Peixoto de Faria, Dagoberto S.
Freitas and M. C. Nemes, {\it Phys. Rev.} {\bf A89}, (2014) 022303] to deal
with the dynamics of the concurrence of a many-body system. In that previous
paper, the discussion was focused in the residual entanglement between the
partitions of the system. The purpose of the present contribution is to shed
some light on the dynamical properties of entanglement among the environment
oscillators. We consider a system consisting of a harmonic oscillator linearly
coupled to N others and solve the corresponding dynamical problem analytically.
We divide the environment in arbitrary two partitions and the entanglement
dynamics between any of these partitions is quantified and it shows that in the
case that excitations in each partitions are equal, the concurrence reaches the
value one and the two partition of the environment are maximally entangled. For
long times the excitations of the main oscillator are completely transferred to
environment and the environment oscillators are found entangled.


title: Splash Detail Due to Grain Incident on Granular Bed

abstract:
  Using the discrete element method (DEM), we study the splash processes
induced by the impact of a grain on two types of granular beds, namely,
randomly packed and FCC-structured beds.Good correspondence is obtained between
our numerical results and the findings of previous experiments, and it is
demonstrated that the packing structure of the granular bed strongly affects
the splash process.The mean ejection angle for the randomly packed bed is
consistent with previous experimental results. The FCC-structured bed yields a
larger mean ejection angle; however, the latter result has not been confirmed
experimentally. Furthermore, the ejection angle distributions and the vertical
ejection speeds for individual grains vary depending on the relative timing at
which the grains are ejected after the initial impact. Obvious differences are
observed between the distributions of grains ejected during the earlier and
later splash periods: the form of the vertical ejection speed distribution
varies from a power-law form to a lognormal form with time, and more than 80\%
of the kinetic energy of all ejected grains is used for earlier ejected grains.


title:
Measurement of the top quark mass using charged particles in pp
  collisions at sqrt(s) = 8 TeV

abstract:
  A novel technique for measuring the mass of the top quark that uses only the
kinematic properties of its charged decay products is presented. Top quark pair
events with final states with one or two charged leptons and hadronic jets are
selected from the data set of 8 TeV proton-proton collisions, corresponding to
an integrated luminosity of 19.7 inverse femtobarns. By reconstructing
secondary vertices inside the selected jets and computing the invariant mass of
the system formed by the secondary vertex and an isolated lepton, an observable
is constructed that is sensitive to the top quark mass that is expected to be
robust against the energy scale of hadronic jets. The main theoretical
systematic uncertainties, concerning the modeling of the fragmentation and
hadronization of b quarks and the reconstruction of secondary vertices from the
decays of b hadrons, are studied. A top quark mass of 173.68 +/- 0.20 (stat)
+1.58 -0.97 (syst) GeV is measured. The overall systematic uncertainty is
dominated by the uncertainty in the b quark fragmentation and the modeling of
kinematic properties of the top quark.


title: Critical Test Of Gamma Ray Burst Theories

abstract:
  Very long and precise follow-up measurements of the X-ray afterglow of very
intense gamma ray bursts (GRBs) allow a critical test of GRB theories. Here we
show that the single power-law decay with time of the X-ray afterglow of GRB
130427A, the record long and most accurately measured X-ray afterglow of an
intense GRB by the Swift, Chandra and XMM Newton space observatories, and of
all other known intense GRBs, is that predicted by the cannonball (CB) model of
GRBs from their measured spectral index, while it disagrees with that predicted
by the widely accepted fireball (FB) models of GRBs.


title: Natural site-directed mutagenesis might exist in eukaryotic cells

abstract:
  Site-directed mutagenesis refers to a man-made molecular biology method that
is used to make genetic alterations in the DNA sequence of a gene of interest.
But based on our recently published experimental findings, we propose that
natural site-directed mutagenesis might exist in the eukaryotic cells, which is
triggered by harmful agents and co-directed by special transcription hotspots
and mutation-contained intranuclear primers.


title: The index of shrinkers of the mean curvature flow

abstract:
  We introduce a notion of index for shrinkers of the mean curvature flow. We
then prove a gap theorem for the index of rotationally symmetric immersed
shrinkers in R^3, namely, that such shrinkers have index at least 3, unless
they are one of the stable ones: the sphere, the cylinder, or the plane. We
also provide a generalization of the result to higher dimensions.


title:
Improvement of Spectroscopic Performance using a Charge-sensitive
  Amplifier Circuit for an X-Ray Astronomical SOI Pixel Detector

abstract:
  We have been developing monolithic active pixel sensors series, named
"XRPIX," based on the silicon-on-insulator (SOI) pixel technology, for future
X-ray astronomical satellites. The XRPIX series offers high coincidence time
resolution ({\rm \sim}1 {\rm \mu}s), superior readout time ({\rm \sim}10 {\rm
\mu}s), and a wide energy range (0.5--40 keV). In the previous study, we
successfully demonstrated X-ray detection by event-driven readout of XRPIX2b.
We here report recent improvements in spectroscopic performance. We
successfully increased the gain and reduced the readout noise in XRPIX2b by
decreasing the parasitic capacitance of the sense-node originated in the buried
p-well (BPW). On the other hand, we found significant tail structures in the
spectral response due to the loss of the charge collection efficiency when a
small BPW is employed. Thus, we increased the gain in XRPIX3b by introducing
in-pixel charge sensitive amplifiers instead of having even smaller BPW. We
finally achieved the readout noise of 35 e{\rm ^{-}} (rms) and the energy
resolution of 320 eV (FWHM) at 6 keV without significant loss of the charge
collection efficiency.


title: A Comparison Study of Nonlinear Kernels

abstract:
  In this paper, we compare 5 different nonlinear kernels: min-max, RBF, fRBF
(folded RBF), acos, and acos-$\chi^2$, on a wide range of publicly available
datasets. The proposed fRBF kernel performs very similarly to the RBF kernel.
Both RBF and fRBF kernels require an important tuning parameter ($\gamma$).
Interestingly, for a significant portion of the datasets, the min-max kernel
outperforms the best-tuned RBF/fRBF kernels. The acos kernel and acos-$\chi^2$
kernel also perform well in general and in some datasets achieve the best
accuracies.
  One crucial issue with the use of nonlinear kernels is the excessive
computational and memory cost. These days, one increasingly popular strategy is
to linearize the kernels through various randomization algorithms. In our
study, the randomization method for the min-max kernel demonstrates excellent
performance compared to the randomization methods for other types of nonlinear
kernels, measured in terms of the number of nonzero terms in the transformed
dataset.
  Our study provides evidence for supporting the use of the min-max kernel and
the corresponding randomized linearization method (i.e., the so-called "0-bit
CWS"). Furthermore, the results motivate at least two directions for future
research: (i) To develop new (and linearizable) nonlinear kernels for better
accuracies; and (ii) To develop better linearization algorithms for improving
the current linearization methods for the RBF kernel, the acos kernel, and the
acos-$\chi^2$ kernel. One attempt is to combine the min-max kernel with the
acos kernel or the acos-$\chi^2$ kernel. The advantages of these two new and
tuning-free nonlinear kernels are demonstrated vias our extensive experiments.


title: Forensic Acquisition of Cloud Drives

abstract:
  Cloud computing and cloud storage services, in particular, pose a new
challenge to digital forensic investigations. Currently, evidence acquisition
for such services still follows the traditional method of collecting artifacts
on a client device. This approach requires labor-intensive reverse engineering
efforts, and ultimately results in an acquisition that is inherently
incomplete. Specifically, it makes the incorrect assumption that all storage
content for an account is fully replicated on the client; further, there are no
means to acquire historical data in the form of document revisions, nor is
there a way to acquire cloud-native artifacts, such as Google Docs.
  In this work, we introduce the concept of API-based evidence acquisition for
cloud services, which addresses these concerns by utilizing the officially
supported API of the service. To demonstrate the utility of this approach, we
present a proof-of-concept acquisition tool, kumodd, which can acquire evidence
from four major cloud drive providers: Google Drive, Microsoft OneDrive,
Dropbox, and Box. The implementation provides both command-line and web user
interfaces, and can be readily incorporated into established forensic
processes.


title:
On the co-orbital motion in the planar restricted three-body problem:
  the quasi-satellite motion revisited

abstract:
  In the framework of the planar and circular restricted three-body problem, we
consider an asteroid that orbits the Sun in quasi-satellite motion with a
planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital
resonance with the planet, characterized by a non zero eccentricity and a
resonant angle that librates around zero. Likewise, in the rotating frame with
the planet it describes the same trajectory as the one of a retrograde
satellite even though the planet acts as a perturbator. In the last few years,
the discoveries of asteroids in this type of motion made the term
"quasi-satellite" more and more present in the literature. However, some
authors rather use the term "retrograde satellite" when referring to this kind
of motion in the studies of the restricted problem in the rotating frame. In
this paper we intend to clarify the terminology to use, in order to bridge the
gap between the perturbative co-orbital point of view and the more general
approach in the rotating frame. Through a numerical exploration of the
co-orbital phase space, we describe the quasi-satellite domain and highlight
that it is not reachable by low eccentricities by averaging process. We will
show that the quasi-satellite domain is effectively included in the domain of
the retrograde satellites and neatly defined in terms of frequencies.
Eventually, we highlight a remarkable high eccentric quasi-satellite orbit
corresponding to a frozen ellipse in the heliocentric frame. We extend this
result to the eccentric case (planet on an eccentric motion) and show that two
families of frozen ellipses originate from this remarkable orbit.


title: Nearest Points on Toric Varieties

abstract:
  We determine the Euclidean distance degree of a projective toric variety.
This extends the formula of Matsui and Takeuchi for the degree of the
$A$-discriminant in terms of Euler obstructions. Our primary goal is the
development of reliable algorithmic tools for computing the points on a real
toric variety that are closest to a given data point.


title: Ricci de Turck flow on singular manifolds

abstract:
  In this paper we prove local existence of a Ricci de Turck flow starting at a
space with incomplete edge singularities and flowing for a short time within a
class of incomplete edge manifolds. We derive regularity properties for the
corresponding family of Riemannian metrics and discuss boundedness of the Ricci
curvature along the flow. For Riemannian metrics that are sufficiently close to
a flat incomplete edge metric, we prove long time existence of the Ricci de
Turck flow. Under certain conditions, our results yield existence of Ricci flow
on spaces with incomplete edge singularities. The proof works by a careful
analysis of the Lichnerowicz Laplacian and the Ricci de Turck flow equation.


title: Search for the decay B0 -> phi gamma

abstract:
  We have searched for the decay B0 -> phi gamma using the full Belle data set
of 772 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle
detector at the KEKB e+e- collider. No signal is observed, and we set an upper
limit on the branching fraction of B(B0 -> phi gamma) < 1.0 x 10^{-7} at 90%
confidence level. This is the most stringent limit on this decay mode to date.


title: Constructive canonicity for lattice-based fixed point logics

abstract:
  We prove the algorithmic canonicity of two classes of $\mu$-inequalities in a
constructive meta-theory of normal lattice expansions. This result
simultaneously generalizes Conradie and Craig's canonicity for
$\mu$-inequalities based on a bi-intuitionistic bi-modal language, and Conradie
and Palmigiano's constructive canonicity for inductive inequalities (restricted
to normal lattice expansions to keep the page limit). Besides the greater
generality, the unification of these strands smoothes the existing treatments
for the canonicity of $\mu$-formulas and inequalities. In particular, the rules
of the algorithm ALBA used for this result have exactly the same formulation as
those of Conradie and Palmigiano, with no additional rule added specifically to
handle the fixed point binders. Rather, fixed points are accounted for by
certain restrictions on the application of the rules, concerning the
order-theoretic properties of the term functions associated with the formulas
to which the rules are applied.


title: Gluon TMD in particle production from low to moderate x

abstract:
  We study the rapidity evolution of gluon transverse momentum dependent
distributions appearing in processes of particle production and show how this
evolution changes from small to moderate Bjorken x.


title: Consistently faster and smaller compressed bitmaps with Roaring

abstract:
  Compressed bitmap indexes are used in databases and search engines. Many
bitmap compression techniques have been proposed, almost all relying primarily
on run-length encoding (RLE). However, on unsorted data, we can get superior
performance with a hybrid compression technique that uses both uncompressed
bitmaps and packed arrays inside a two-level tree. An instance of this
technique, Roaring, has recently been proposed. Due to its good performance, it
has been adopted by several production platforms (e.g., Apache Lucene, Apache
Spark, Apache Kylin and Druid).
  Yet there are cases where run-length encoded bitmaps are smaller than the
original Roaring bitmaps---typically when the data is sorted so that the
bitmaps contain long compressible runs. To better handle these cases, we build
a new Roaring hybrid that combines uncompressed bitmaps, packed arrays and RLE
compressed segments. The result is a new Roaring format that compresses better.
  Overall, our new implementation of Roaring can be several times faster (up to
two orders of magnitude) than the implementations of traditional RLE-based
alternatives (WAH, Concise, EWAH) while compressing better. We review the
design choices and optimizations that make these good results possible.


title:
Excess current in ferromagnet-superconductor structures with fully
  polarized triplet component

abstract:
  We study the $I$-$V$ characteristics of S$_{\text{T}}$/n/N contacts, where
S$_{\text{T}}$ is a BCS superconductor S with a built-in exchange field $h$, n
represents a normal metal wire, and N---a normal metal reservoir. The
superconductor S$_{\text{T}}$ is separated from the n-wire by a spin filter
which allows the passage of electrons with a certain spin direction so that
only fully polarized triplet Cooper pairs penetrate into the n-wire. We show
that both the subgap conductance $\sigma_{\text{sg}}$ and the excess current
$I_{\text{exc}}$, which occur in conventional S/n/N contacts due to Andreev
reflection (AR), exist also in the considered system. In our case, they are
caused by unconventional AR that is not accompanied by spin flip. The excess
current $I_{\text{exc}}$ exists only if $h$ exceeds a certain magnitude
$h_{\text{c}}$. At ${h < h_{\text{c}}}$ the excess current is converted into a
deficit current $I_\text{{def}}$. The dependencies of the differential
conductance and the current $I_{\text{exc}}$ are presented as a function of
voltage and $h$.


title: Finite soluble groups with nilpotent wide subgroups

abstract:
  A subgroup of a finite group is wide if each prime divisor of the group order
divides the subgroup order. We obtain the description of finite soluble groups
with no wide subgroups. We also prove that a finite soluble group with
nilpotent wide subgroups has the quotient group by its hypercenter with no wide
subgroups.


title: Hereditary Konig Egervary Collections

abstract:
  Let $G$ be a simple graph with vertex set $V(G)$. A subset $S$ of $V(G)$ is
independent if no two vertices from $S$ are adjacent. The graph $G$ is known to
be a Konig-Egervary (KE in short) graph if $\alpha(G) + \mu(G)= |V(G)|$, where
$\alpha(G)$ denotes the size of a maximum independent set and $\mu(G)$ is the
cardinality of a maximum matching. Let $\Omega(G)$ denote the family of all
maximum independent sets. A collection $F$ of sets is an hke collection if
$|\bigcup \Gamma|+|\bigcap \Gamma|=2\alpha$ holds for every subcollection
$\Gamma$ of $F$. We characterize an hke collection and invoke new
characterizations of a KE graph. We prove the existence and uniqueness of a
graph $G$ such that $\Omega(G)$ is a maximal hke collection. It is a bipartite
graph. As a result, we solve a problem of Jarden, Levit and Mandrescu
\cite{jlm}, proving that $F$ is an hke collection if and only if it is a subset
of $\Omega(G)$ for some graph $G$ and $|\bigcup F|+|\bigcap F|=2\alpha(F)$.
Finally, we show that the maximal cardinality of an hke collection $F$ with
$\alpha(F)=\alpha$ and $|\bigcup F|=n$ is $2^{n-\alpha}$.


title: On Asymptotic Approximate Groups of Integers

abstract:
  Let $r$ be a positive integer, and let $A$ be a nonempty finite set of at
least two integers. We let $\tilde{C}_r(A)$ denote the {\em asymptotic
$r$-covering number} of $A$, that is, the smallest integer value of $l$ for
which, for all sufficiently large positive integers $h$, the $rh$-fold sumset
of $A$ is contained in at most $l$ translates of the $h$-fold sumset of $A$.
Nathanson proved that $\tilde{C}_r(A)$ is always at most $r+1$; here we extend
this result to prove that $\tilde{C}_r(A)$ is always at least $r$, and
determine all sets $A$ for which $\tilde{C}_r(A)=r$.


title:
Action-Affect Classification and Morphing using Multi-Task
  Representation Learning

abstract:
  Most recent work focused on affect from facial expressions, and not as much
on body. This work focuses on body affect analysis. Affect does not occur in
isolation. Humans usually couple affect with an action in natural interactions;
for example, a person could be talking and smiling. Recognizing body affect in
sequences requires efficient algorithms to capture both the micro movements
that differentiate between happy and sad and the macro variations between
different actions. We depart from traditional approaches for time-series data
analytics by proposing a multi-task learning model that learns a shared
representation that is well-suited for action-affect classification as well as
generation. For this paper we choose Conditional Restricted Boltzmann Machines
to be our building block. We propose a new model that enhances the CRBM model
with a factored multi-task component to become Multi-Task Conditional
Restricted Boltzmann Machines (MTCRBMs). We evaluate our approach on two
publicly available datasets, the Body Affect dataset and the Tower Game
dataset, and show superior classification performance improvement over the
state-of-the-art, as well as the generative abilities of our model.


title:
Thermoelectric Transport in Graphene/$h$-BN/Graphene Heterostructures: A
  Computational Study

abstract:
  We present first principles study of thermoelectric transport properties of
sandwiched heterostructure of Graphene (G)/hexagonal Boron Nitride (BN)/G,
based on Boltzmann transport theory for band electrons using the bandstructure
calculated from the Density Functional Theory (DFT) based plane-wave method.
Calculations were carried out for three, four and five BN layers sandwiched
between Graphene layers with three different arrangements to obtain the Seebeck
coefficient and Power factor in $T\sim 25-400$K range. Moreover, using
Molecular Dynamics (MD) simulations with very large simulation cell we obtained
the thermal conductance ($K$) of these heterostructures and obtained finally
the Figure-of-Merit ($ZT$). These results are in agreement with recently
reported experimental measurements.


title: Weighted sampling without replacement

abstract:
  Comparing concentration properties of uniform sampling with and without
replacement has a long history which can be traced back to the pioneer work of
Hoeffding (1963). The goal of this short note is to extend this comparison to
the case of non-uniform weights, using a coupling between the two samples. When
the items' weights are arranged in the same order as their values, we show that
the induced coupling for the cumulative values is a submartingale coupling. As
a consequence, the powerful Chernoff-type upper-tail estimates known for
sampling with replacement automatically transfer to the case of sampling
without replacement. For general weights, we use the same coupling to establish
a sub-Gaussian concentration inequality. We also construct another martingale
coupling which allows us to answer a question raised by Luh and Pippenger
(2014) on sampling in Polya urns with different replacement numbers.


title: Homotopy in Exact Categories

abstract:
  In this monograph we develop various aspects of the homotopy theory of exact
categories. We introduce different notions of compactness and generation in
exact categories $E$, and use these to study model structures on categories of
chain complexes $Ch_{*}(E)$ which are induced by cotorsion pairs on $E$. As a
special case we show that under very general conditions the categories
$Ch_{+}(E)$, $Ch_{\ge0}(E)$, and $Ch(E)$ are equipped with the projective model
structure, and that a generalisation of the Dold-Kan correspondence holds. We
also establish conditions under which categories of filtered objects in exact
categories are equipped with natural model structures. When $E$ is monoidal we
also examine when these model structures are monoidal and conclude by studying
some homotopical algebra in such categories. In particular we provide
conditions under which $Ch(E)$ and $Ch_{\ge0}(E)$ are homotopical algebra
contexts, thus making them suitable settings for derived geometry.


title: Universal trading under proportional transaction costs

abstract:
  The theory of optimal trading under proportional transaction costs has been
considered from a variety of perspectives. In this paper, we show that all the
results can be interpreted using a universal law, illustrating the results in
trading algorithm design.


title: Kauffman states, bordered algebras, and a bigraded knot invariant

abstract:
  We define and study a bigraded knot invariant whose Euler characteristic is
the Alexander polynomial, closely connected to knot Floer homology. The
invariant is the homology of a chain complex whose generators correspond to
Kauffman states for a knot diagram. The definition uses decompositions of knot
diagrams: to a collection of points on the line, we associate a differential
graded algebra; to a partial knot diagram, we associate modules over the
algebra. The knot invariant is obtained from these modules by an appropriate
tensor product.


title: Hyperband: A Novel Bandit-Based Approach to Hyperparameter Optimization

abstract:
  Performance of machine learning algorithms depends critically on identifying
a good set of hyperparameters. While recent approaches use Bayesian
optimization to adaptively select configurations, we focus on speeding up
random search through adaptive resource allocation and early-stopping. We
formulate hyperparameter optimization as a pure-exploration non-stochastic
infinite-armed bandit problem where a predefined resource like iterations, data
samples, or features is allocated to randomly sampled configurations. We
introduce a novel algorithm, Hyperband, for this framework and analyze its
theoretical properties, providing several desirable guarantees. Furthermore, we
compare Hyperband with popular Bayesian optimization methods on a suite of
hyperparameter optimization problems. We observe that Hyperband can provide
over an order-of-magnitude speedup over our competitor set on a variety of
deep-learning and kernel-based learning problems.


title:
Modified spin-wave theory and spin liquid behavior of cold bosons on an
  inhomogeneous triangular lattice

abstract:
  Ultracold bosons in a triangular lattice are a promising candidate for
observing quantum spin liquid behavior. Here we investigate, for such system,
the role of a harmonic trap giving rise to an inhomogeneous density. We
construct a modified spin-wave theory for arbitrary filling, and predict the
breakdown of order for certain values of the lattice anisotropy. These regimes,
identified with the spin liquid phases, are found to be quite robust upon
changes in the filling factor. This result is backed by an exact
diagonalization study on a small lattice.


title:
A natural extension of the universal enveloping algebra functor to
  crossed modules of Leibniz algebras

abstract:
  The universal enveloping algebra functor between Leibniz and associative
algebras defined by Loday and Pirashvili is extended to crossed modules. We
prove that the universal enveloping crossed module of algebras of a crossed
module of Leibniz algebras is its natural generalization. Then we construct an
isomorphism between the category of representations of a Leibniz crossed module
and the category of left modules over its universal enveloping crossed module
of algebras. Our approach is particularly interesting since the actor in the
category of Leibniz crossed modules does not exist in general, so the technique
used in the proof for the Lie case cannot be applied. Finally we move on to the
framework of the Loday-Pirashvili category $\mathcal{LM}$ in order to
comprehend this universal enveloping crossed module in terms of the Lie crossed
modules case.


title:
Bayesian comparison of nonstandard cosmologies using type Ia supernovae
  and BAO data

abstract:
  We use the most recent type Ia supernovae (SNe Ia) observations to perform a
statistical comparison between the standard $\Lambda$CDM model and its
extensions [$w$CDM and $w(z)$CDM] and some alternative cosmologies: namely, the
Dvali--Gabadadze--Porrati (DGP) model, a power-law $f(R)$ scenario in the
metric formalism and an example of vacuum decay [$\Lambda(t)$CDM] cosmology in
which the dilution of pressureless matter is attenuated with respect to the
usual $a^{-3}$ scaling due to the interaction of the dark matter and dark
energy fields. We perform a Bayesian model selection analysis using the
\textsc{MultiNest} algorithm. To obtain the posterior distribution for the
parameters of each model, we use the joint light-curve analysis (JLA) SNe Ia
compilation containing 740 events in the interval $0.01 < z < 1.3$ along with
current measurements of baryon acoustic oscillations (BAO). The JLA data are
analyzed with the SALT2 light-curve fitter and the model selection is then
performed by computing the Bayesian evidence of each model and the Bayes factor
of the $\Lambda$CDM cosmology related to the other models. The results indicate
that the JLA data alone are unable to distinguish the standard $\Lambda$CDM
model from some of its alternatives but its combination with current
measurements of baryon acoustic oscillations shows up an ability to distinguish
them. In particular, the DGP model is practically not supported by both the BAO
and the joint JLA + BAO data sets compared to the standard scenario. Finally,
we provide a rank order for the models considered.


title:
Weak limits for the largest subpopulations in Yule processes with high
  mutation probabilities

abstract:
  We consider a Yule process until the total population reaches size $n\gg 1$,
and assume that neutral mutations occur with high probability $1-p$ (in the
sense that each child is a new mutant with probability $1-p$, independently of
the other children), where $p=p_n\ll 1$. We establish a general strategy for
obtaining Poisson limit laws for the number of subpopulations exceeding a given
size and apply this to some mutation regimes of particular interest. Finally,
we give an application to subcritical Bernoulli bond percolation on random
recursive trees with percolation parameter $p_n$ tending to zero.


title:
Systematic construction of density functionals based on matrix product
  state computations

abstract:
  We propose a systematic procedure for the approximation of density
functionals in density functional theory that consists of two parts. First, for
the efficient approximation of a general density functional, we introduce an
efficient ansatz whose non-locality can be increased systematically. Second, we
present a fitting strategy that is based on systematically increasing a
reasonably chosen set of training densities. We investigate our procedure in
the context of strongly correlated fermions on a one-dimensional lattice in
which we compute accurate training densities with the help of matrix product
states. Focusing on the exchange-correlation energy, we demonstrate how an
efficient approximation can be found that includes and systematically improves
beyond the local density approximation. Importantly, this systematic
improvement is shown for target densities that are quite different from the
training densities.


title:
Comments on the diphoton excess: critical reappraisal of effective field
  theory interpretations

abstract:
  We consider the diphoton excess observed by ATLAS and CMS using the most
up-to-date data and estimate the preferred enhancement in the production rate
between 8 TeV and 13 TeV. Within the framework of effective field theory (EFT),
we then show that for both spin-0 and spin-2 Standard Model (SM) gauge-singlet
resonances, two of the three processes S to ZZ, S to Z gamma, and S to WW must
occur with a non-zero rate. Moreover, we demonstrate that these branching
ratios are highly correlated in the EFT. Couplings of S to additional SM states
may be constrained and differentiated by comparing the S production rates with
and without the vector-boson fusion (VBF) cuts. We find that for a given VBF to
inclusive production ratio there is maximum rate of S to gauge bosons, b b-bar,
and lighter quark anti-quark pairs. Simultaneous measurements of the width and
the VBF ratio may be able to point towards the existence of hidden decays.


title: Spin Hall effects in mesoscopic Pt films with high resistivity

abstract:
  The energy efficiency of the spin Hall effects (SHE) can be enhanced if the
electrical conductivity is decreased without sacrificing the spin Hall
conductivity. The resistivity of Pt films can be increased to 150-300
{\mu}{\Omega}*cm by mesoscopic lateral confinement, thereby decreasing the
conductivity. The SHE and inverse spin Hall effects (ISHE) in these mesoscopic
Pt films are explored at 10 K by using the nonlocal spin injection/detection
method. All relevant physical quantities are determined in-situ on the same
substrate, and a quantitative approach is developed to characterize all
processes effectively. Extensive measurements with various Pt thickness values
reveal an upper limit for the Pt spin diffusion length: {\lambda}_pt<0.8 nm.
The average product of {\lambda}_pt and the Pt spin Hall angle {\alpha}_H is
substantial: {\alpha}_H*{\lambda}_pt=(0.142 +/- 0.040)nm for 4 nm thick Pt,
though a gradual decrease is observed at larger Pt thickness. The results
suggest enhanced spin Hall effects in resistive mesoscopic Pt films.


title:
Modelling Temporal Information Using Discrete Fourier Transform for
  Recognizing Emotions in User-generated Videos

abstract:
  With the widespread of user-generated Internet videos, emotion recognition in
those videos attracts increasing research efforts. However, most existing works
are based on framelevel visual features and/or audio features, which might fail
to model the temporal information, e.g. characteristics accumulated along time.
In order to capture video temporal information, in this paper, we propose to
analyse features in frequency domain transformed by discrete Fourier transform
(DFT features). Frame-level features are firstly extract by a pre-trained deep
convolutional neural network (CNN). Then, time domain features are transferred
and interpolated into DFT features. CNN and DFT features are further encoded
and fused for emotion classification. By this way, static image features
extracted from a pre-trained deep CNN and temporal information represented by
DFT features are jointly considered for video emotion recognition. Experimental
results demonstrate that combining DFT features can effectively capture
temporal information and therefore improve emotion recognition performance. Our
approach has achieved a state-of-the-art performance on the largest video
emotion dataset (VideoEmotion-8 dataset), improving accuracy from 51.1% to
62.6%.


title:
Classification of joint numerical ranges of three hermitian matrices of
  size three

abstract:
  The joint numerical range $W(F)$ of three hermitian $3$-by-$3$ matrices
$F=(F_1,F_2,F_3)$ is a convex and compact subset in $\mathbb{R}^3$. Generically
we find that $W(F)$ is a three-dimensional oval. Assuming $\dim(W(F))=3$, every
one- or two-dimensional face of $W(F)$ is a segment or a filled ellipse. We
prove that only ten configurations of these segments and ellipses are possible.
We identify a triple $F$ for each class and illustrate $W(F)$ using random
matrices and dual varieties.

categories: math.FA math-ph math.MG math.MP quant-ph


title:
Magnetic Field Evolution in Giant Radio Relics using the example of CIZA
  J2242.8+5301

abstract:
  Giant radio relics are the arc-shaped diffuse radio emission regions observed
in the outskirts of some merging galaxy clusters. They are believed to trace
shock-waves in the intra-cluster medium. Recent observations demonstrated that
some prominent radio relics exhibit a steepening above 2 GHz in their radio
spectrum. This challenges standard theoretical models because shock
acceleration is expected to accelerate electrons to very high energies with a
power-law distribution in momentum. In this work we attempt to reconcile these
data with the shock-acceleration scenario. We propose that the spectral
steepening may be caused by the highest energy electrons emitting
preferentially in lower magnetic fields than the bulk of synchrotron bright
electrons in relics. Here, we focus on a model with an increasing mag- netic
field behind the shock front, which quickly saturates and then declines. We
derive the time-evolution of cosmic-ray electron spectra in time variable
magnetic fields and an expanding medium. We then apply the formalism on the
large radio relic in the cluster CIZA J2242.8+5301 (the Sausage relic). We show
that under favourable circumstances of magnetic field amplification downstream,
our model can explain the observed radio spectrum, the brightness profile and
the spectral index profile of the relic. A possible interpretation for the
required amplification of the magnetic field downstream is a dynamo acting
behind the shock with an injection scale of magnetic turbulence of about 10
kpc. Our models require injection efficiencies of CRe - which are in tension
with simple diffusive shock acceleration from the thermal pool. We show that
this problem can likely be alleviated considering pre-existing CRe.


title: Bayesian Neural Word Embedding

abstract:
  Recently, several works in the domain of natural language processing
presented successful methods for word embedding. Among them, the Skip-Gram with
negative sampling, known also as word2vec, advanced the state-of-the-art of
various linguistics tasks. In this paper, we propose a scalable Bayesian neural
word embedding algorithm. The algorithm relies on a Variational Bayes solution
for the Skip-Gram objective and a detailed step by step description is
provided. We present experimental results that demonstrate the performance of
the proposed algorithm for word analogy and similarity tasks on six different
datasets and show it is competitive with the original Skip-Gram method.


title:
soLenoid and time projectioN chAmber for neutron lifetime measurement --
  LINA

abstract:
  Among measurements of the neutron lifetime, there is a 1% difference between
proton-counting methods and neutron-counting methods. In this paper, a new
electron-counting method with a magnetic field aiming for a 0.1% accuracy is
proposed, which would have a possibility to probe the discrepancy.


title: Search for Sphalerons: IceCube vs. LHC

abstract:
  We discuss the observability of neutrino-induced sphaleron transitions in the
IceCube detector, encouraged by a recent paper by Tye and Wong (TW), which
argued on the basis of a Bloch wave function in the periodic sphaleron
potential that such transitions should be enhanced compared to most previous
calculations. We calculate the dependence on neutrino energy of the sphaleron
transition rate, comparing it to that for conventional neutrino interactions,
and we discuss the observability of tau and multi-muon production in
sphaleron-induced transitions. We use IceCube 4-year data to constrain the
sphaleron rate, finding that it is comparable to the upper limit inferred
previously from a recast of an ATLAS search for microscopic black holes at the
LHC with $\sim 3$/fb of collisions at 13 TeV. The IceCube constraint is
stronger for a sphaleron barrier height $E_{\rm Sph} \gtrsim 9$ TeV, and would
be comparable with the prospective LHC sensitivity with 300/fb of data at 14
TeV if $E_{\rm Sph} \sim 11$ TeV.


title: Constructing Polynomial Spectral Models for Stars

abstract:
  Stellar spectra depend on the stellar parameters and on dozens of
photospheric elemental abundances. Simultaneous fitting of these
$\mathcal{N}\sim 10-40$ model labels to observed spectra has been deemed
unfeasible, because the number of ab initio spectral model grid calculations
scales exponentially with $\mathcal{N}$. We suggest instead the construction of
a polynomial spectral model (PSM) of order $\mathcal{O}$ for the model flux at
each wavelength. Building this approximation requires a minimum of only
${\mathcal{N}+\mathcal{O}\choose\mathcal{O}}$ calculations: e.g. a quadratic
spectral model ($\mathcal{O}=2$) to fit $\mathcal{N}=20$ labels simultaneously,
can be constructed from as few as $231$ ab initio spectral model calculations;
in practice, a somewhat larger number ($\sim 300-1000$) of randomly chosen
models lead to a better performing PSM. Such a PSM can be a good approximation
only over a portion of label space, which will vary case by case. Yet, taking
the APOGEE survey as an example, a single quadratic PSM provides a remarkably
good approximation to the exact ab initio spectral models across much of this
survey: for random labels within that survey the PSM approximates the flux to
within $10^{-3}$, and recovers the abundances to within $\sim 0.02$ dex rms of
the exact models. This enormous speed-up enables the simultaneous many-label
fitting of spectra with computationally expensive ab initio models for stellar
spectra, such as non-LTE models. A PSM also enables the simultaneous fitting of
observational parameters, such as the spectrum's continuum or line-spread
function.


title: Dust dynamics in 2D gravito-turbulent disks

abstract:
  The dynamics of solid bodies in protoplanetary disks are subject to the
properties of any underlying gas turbulence. Turbulence driven by disk
self-gravity shows features distinct from those driven by the magnetorotational
instability (MRI). We study the dynamics of solids in gravito-turbulent disks
with two-dimensional (in the disk plane), hybrid (particle and gas)
simulations. Gravito-turbulent disks can exhibit stronger gravitational
stirring than MRI-active disks, resulting in greater radial diffusion and
larger eccentricities and relative speeds for large particles (those with
dimensionless stopping times $t_{stop} \Omega > 1$, where $\Omega$ is the
orbital frequency). The agglomeration of large particles into planetesimals by
pairwise collisions is therefore disfavored in gravito-turbulent disks.
However, the relative speeds of intermediate-size particles $t_{stop} \Omega
\sim 1$ are significantly reduced as such particles are collected by gas drag
and gas gravity into coherent filament-like structures with densities high
enough to trigger gravitational collapse. First-generation planetesimals may
form via gravitational instability of dust in marginally gravitationally
unstable gas disks.


title: A new 6d fixed point from holography

abstract:
  We propose a stringy construction giving rise to a class of interacting and
non-supersymmetric CFT's in six dimensions. Such theories may be obtained as an
IR conformal fixed point of an RG flow ending up in a $(1, 0)$ theory in the
UV. We provide the due holographic evidence in the context of massive type IIA
on $\textrm {AdS}_{7}\times M_3$, where $M_3$ is topologically an $S^3$. In
particular, in this paper we present a 10d flow solution which may be
interpreted as a non-BPS bound state of NS5, D6 and $\overline{\textrm{D6}}$
branes. Moreover, by adopting its 7d effective description, we are able to
holographically compute the free energy and the operator spectrum in the novel
IR conformal fixed point.


title:
Constraints on Black Hole/Host Galaxy Co-evolution and Binary Stalling
  Using Pulsar Timing Arrays

abstract:
  Pulsar timing arrays are now setting increasingly tight limits on the
gravitational wave background from binary supermassive black holes. But as
upper limits grow more constraining, what can be implied about galaxy
evolution? We investigate which astrophysical parameters have the largest
impact on strain spectrum predictions and provide a simple framework to
directly translate between measured values for the parameters of galaxy
evolution and PTA limits on the gravitational wave background of binary
supermassive black holes. We find that the most influential observable is the
relation between a host galaxy's central bulge and its central black hole,
$\mbox{$M_{\bullet}$-$M_{\rm bulge}$}$, which has the largest effect on the
mean value of the characteristic strain amplitude. However, the variance of
each prediction is dominated by uncertainties in the galaxy stellar mass
function. Using this framework with the best published PTA limit, we can set
limits on the shape and scatter of the $\mbox{$M_{\bullet}$-$M_{\rm bulge}$}$
relation. We find our limits to be in contention with strain predictions using
two leading measurements of this relation. We investigate several possible
reasons for this disagreement. If we take the $\mbox{$M_{\bullet}$-$M_{\rm
bulge}$}$ relations to be correct within a simple power-law model for the
gravitational wave background, then the inconsistency is reconcilable by
allowing for an additional "stalling" time between a galaxy merger and
evolution of a binary supermassive black hole to sub-parsec scales, with lower
limits on this timescale of $\sim 1-2$ Gyr.


title:
Before the Bar: Kinematic Detection of A Spheroidal Metal-Poor Bulge
  Component

abstract:
  We present 947 radial velocities of RR Lyrae variable stars in four fields
located toward the Galactic bulge, observed within the data from the ongoing
Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR). We show that these RR Lyrae
stars exhibit hot kinematics and null or negligible rotation and are therefore
members of a separate population from the bar/pseudobulge that currently
dominates the mass and luminosity of the inner Galaxy. Our RR Lyrae stars
predate these structures, and have metallicities, kinematics, and spatial
distribution that are consistent with a "classical" bulge, although we cannot
yet completely rule out the possibility that they are the metal-poor tail of a
more metal rich ([Fe/H] ~ -1 dex) halo-bulge population. The complete catalog
of radial velocities for the BRAVA-RR stars is also published electronically.


title: Exact results for ABJ Wilson loops and open-closed duality

abstract:
  We find new exact relations between the partition function and vacuum
expectation values (VEVs) of 1/2 BPS Wilson loops in ABJ theory, which allow us
to predict the large N expansions of the 1/2 BPS Wilson loops from known
results of the partition function. These relations are interpreted as an
open-closed duality where the closed string background is shifted by the
insertion of Wilson loops due to a back-reaction. Using the connection between
ABJ theory and the topological string on local P1 x P1, we explicitly write
down non-trivial relations between open and closed string amplitudes.


title: Ultralight Repulsive Dark Matter and BEC

abstract:
  Ultralight scalar dark matter with mass at or below the eV scale and pressure
from repulsive self-interaction could form a Bose-Einstein condensate in the
early Universe and maybe in galaxies as well. It has been suggested to be a
possible solution to the cusp/core problem or even to explain MOND
phenomenology. In this paper, I initiate a study of possible self-interactions
of ultralight scalar dark matter from the particle physics point of view. To
protect its mass, the scalar dark matter is identified as a pseudo
Nambu-Goldstone boson (pNGB). Quite a few pNGB models with different potentials
such as the QCD axion and the dilaton lead to attractive self-interactions. Yet
if an axion is a remnant of a 5D gauged U(1) symmetry, its self-interactions
could be repulsive provided the masses and charges of the 5D matter
contributing to its potential satisfy certain constraints. Collective symmetry
breaking could also lead to a repulsive self-interaction yet with too large a
strength that is ruled out by Bullet Cluster constraints. I also discuss
cosmological and astrophysical constraints on ultralight repulsive dark matter
in terms of a parametrization motivated by particle physics considerations.


title:
CoMaLit-V. Mass forecasting with proxies. Method and application to weak
  lensing calibrated samples

abstract:
  Mass measurements of astronomical objects are most wanted but still elusive.
We need them to trace the formation and evolution of cosmic structure but we
can get direct measurements only for a minority. This lack can be circumvented
with a proxy and a scaling relation. The twofold goal of estimating the
unbiased relation and finding the right proxy value to plug in can be hampered
by systematics, selection effects, Eddington/Malmquist biases and time
evolution. We present a Bayesian hierarchical method which deals with these
issues. Masses to be predicted are treated as missing data in the regression
and are estimated together with the scaling parameters. The calibration
subsample with measured masses does not need to be representative of the full
sample as far as it follows the same scaling relation. We apply the method to
forecast weak lensing calibrated masses of the Planck, redMaPPer and MCXC
clusters. Planck masses are biased low with respect to weak lensing calibrated
masses, with a bias more pronounced for high redshift clusters. MCXC masses are
under-estimated by ~20 per cent, which may be ascribed to hydrostatic bias.
Packages and catalogs are made available with the paper.


title:
A Latitude-Dependent Analysis of the Leptonic Hypothesis for the Fermi
  Bubbles

abstract:
  The Fermi Bubbles are giant Galactic structures observed in both gamma-rays
and microwaves. Recent studies have found support for the hypothesis that the
gamma-ray and microwave emission can both be understood as arising from a hard
cosmic-ray electron population within the volume of the Bubbles, via inverse
Compton scattering and synchrotron radiation respectively. The relative rates
of these processes are set by the relative energy density of the interstellar
radiation field and the magnetic field within the Bubbles; consequently, under
the hypothesis of a common origin, the combination of the gamma-ray and
microwave measurements can be used to estimate the magnetic field within the
Bubbles. We revisit the consistency of this hypothesis on a
latitude-by-latitude basis, using data from Fermi, WMAP and Planck; estimate
the variation of the electron spectrum within the Bubbles; and infer bounds on
the magnetic field within the Bubbles as a function of distance from the
Galactic plane. We find that while the microwave and gamma-ray spectra are
generally consistent with the leptonic hypothesis for few-microGauss magnetic
fields, there appears to be a preference for spectral hardening in the
microwaves at mid-latitudes (especially in the |b|~ 25-35 degree range) that is
not mirrored in the gamma rays. This result may hint at a non-leptonic
contribution to the gamma-ray spectra; however, the discrepancy can be
reconciled in purely leptonic models if the cutoff energy for the electrons is
lower in this latitude range and the spectrum below the cutoff is harder.


title: Catalogs of Compact Groups of Galaxies from the Enhanced SDSS DR12

abstract:
  We apply a friends-of-friends algorithm to an enhanced SDSS DR12
spectroscopic catalog including redshift from literature to construct a catalog
of $1588~N\ge3$ compact groups of galaxies containing 5179 member galaxies and
covering the redshift range $0.01 < z < 0.19$. This catalog contains 18 times
as many systems and reaches 3 times the depth of similar catalog of Barton et
al. (1996). We construct catalogs from both magnitude-limited and
volume-limited galaxy samples. Like Barton et al. (1996) we omit the frequently
applied isolation criterion in the compact group selection algorithm. Thus the
groups selected by fixed projected spatial and rest frame line-of-sight
velocity separation produce a catalog of groups with a redshift independent
median size. In contrast with previous catalogs, the enhanced SDSS DR12 catalog
(including galaxies with $r < 14.5$) includes many systems with $z\leq 0.05$.
The volume-limited samples are unique to this study. The compact group
candidates in these samples have a median stellar mass independent of redshift.
Groups with velocity dispersion $\leq 100$ km s$^{-1}$ show abundant evidence
for ongoing dynamical interactions among the members. The number density of the
volume-limited catalogs agrees with previous catalogs at the lowest redshifts
but decreases as the redshift increases. The SDSS fiber placement constraints
limit the catalog completeness. In spite of this issue the volume-limited
catalogs provide a promising basis for detailed spatially resolved probes of
the impact of galaxy-galaxy interactions within similar dense systems over a
broad redshift range.


title:
Improved Cosmic-Ray Injection Models and the Galactic Center Gamma-Ray
  Excess

abstract:
  Fermi-LAT observations of the Galactic Center (GC) have revealed a
spherically- symmetric excess of GeV gamma rays extending to at least 10 deg
from the dynamical center of the Galaxy. A critical uncertainty in extracting
the intensity, spectrum, and morphology of this excess concerns the accuracy of
astrophysical diffuse gamma-ray emission models near the GC. Recently, it has
been noted that many diffuse emission models utilize a cosmic-ray injection
rate far below that predicted based on the observed star formation rate in the
Central Molecular Zone. In this study, we add a cosmic-ray injection component
which non-linearly traces the Galactic H2 density determined in
three-dimensions, and find that the associated gamma-ray emission is degenerate
with many properties of the GC gamma-ray excess. In models that utilize a large
sideband (40x40 deg surrounding the GC) to normalize the best-fitting diffuse
emission models, the intensity of the GC excess decreases by a factor of 2, and
the morphology of the excess becomes less peaked and less spherically
symmetric. In models which utilize a smaller region of interest (15x15 deg) the
addition of an excess template instead suppresses the intensity of the best-fit
astrophysical diffuse emission, and the GC excess is rather resilient to
changes in the details of the astrophysical diffuse modeling. In both analyses,
the addition of a GC excess template still provides a statistically significant
improvement to the overall fit to the gamma-ray data. We also implement
advective winds at the GC, and find that the Fermi-LAT data strongly prefer
outflows of order several hundred km/s, whose role is to efficiently advect
low-energy cosmic rays from the Galactic center. Finally, we perform numerous
tests of our models, and conclude that they significantly improve our
understanding of multi-wavelength non-thermal emission from the GC.


title:
XMM-Newton Slew Survey observations of the gravitational wave event
  GW150914

abstract:
  The detection of the first gravitational wave (GW) transient GW150914
prompted an extensive campaign of follow-up observations at all wavelengths.
Although no dedicated XMM-Newton observations have been performed, the
satellite passed through the GW150914 error box during normal operations. Here
we report the analysis of the data taken during these satellite slews performed
two hours and two weeks after the GW event. Our data cover 1.1 square degrees
and 4.8 square degrees of the final GW localization region. No credible X-ray
counterpart to GW150914 is found down to a sensitivity of 6E-13 erg/cm2/s in
the 0.2-2 keV band. Nevertheless, these observations show the great potential
of XMM-Newton slew observations for the search of the electromagnetic
counterparts of GW events. A series of adjacent slews performed in response to
a GW trigger would take <1.5 days to cover most of the typical GW credible
region. We discuss this scenario and its prospects for detecting the X-ray
counterpart of future GW detections.


title:
Peeling off the late Universe: Reconstructing the ISW map with galaxy
  surveys

abstract:
  The Integrated Sachs-Wolfe (ISW) effect is a large-angle modulation of the
cosmic microwave background (CMB), generated when CMB photons traverse evolving
potential wells associated with large scale structure (LSS). Recent efforts
have been made to reconstruct maps of the ISW signal using information from
surveys of galaxies and other LSS tracers, but investigation into how survey
systematics affect their reliability has so far been limited. Using simulated
ISW and LSS maps, we study the impact of galaxy survey properties and
systematic errors on the accuracy of reconstructed ISW signal. We find that
systematics that affect the observed distribution of galaxies along the line of
sight, such as photo-z and bias-evolution related errors, have a relatively
minor impact on reconstruction quality. In contrast, however, we find that
direction-dependent calibration errors can be very harmful. Specifically, we
find that in order to avoid significant degradation of our reconstruction
quality statistics, direction-dependent number density fluctuations due to
systematics must be controlled so that their variance is smaller than $10^{-6}$
(which corresponds to a 0.1% calibration). Additionally, we explore the
implications of our results for attempts to use reconstructed ISW maps to shed
light on the origin of large-angle CMB alignments. We find that there is only a
weak correlation between the true and reconstructed angular momentum
dispersion, which quantifies alignment, even for reconstructed ISW maps which
are fairly accurate overall.


title: Chameleon Dark Energy and Atom Interferometry

abstract:
  Atom interferometry experiments are searching for evidence of chameleon
scalar fields with ever-increasing precision. As experiments become more
precise, so too must theoretical predictions. Previous work has made numerous
approximations to simplify the calculation, which in general requires solving a
3-dimensional nonlinear partial differential equation (PDE). In this paper, we
introduce a new technique for calculating the chameleonic force, using a
numerical relaxation scheme on a uniform grid. This technique is more general
than previous work, which assumed spherical symmetry to reduce the PDE to a
1-dimensional ordinary differential equation (ODE). We examine the effects of
approximations made in previous efforts on this subject, and calculate the
chameleonic force in a set-up that closely mimics the recent experiment of
Hamilton et al. Specifically, we simulate the vacuum chamber as a cylinder with
dimensions matching those of the experiment, taking into account the
backreaction of the source mass, its offset from the center, and the effects of
the chamber walls. Remarkably, the acceleration on a test atomic particle is
found to differ by only 20% from the approximate analytical treatment. These
results allow us to place rigorous constraints on the parameter space of
chameleon field theories, although ultimately the constraint we find is the
same as the one we reported in Hamilton et al. because we had slightly
underestimated the size of the vacuum chamber. This new computational technique
will continue to be useful as experiments become even more precise, and will
also be a valuable tool in optimizing future searches for chameleon fields and
related theories.


title:
Spin transport of weakly disordered Heisenberg chain at infinite
  temperature

abstract:
  We study the disordered Heisenberg spin chain, which exhibits many body
localization at strong disorder, in the weak to moderate disorder regime. A
continued fraction calculation of dynamical correlations is devised, using a
variational extrapolation of recurrents. Good convergence for the infinite
chain limit is shown. We find that the local spin correlations decay at long
times as $C \sim t^{-\beta}$, while the conductivity exhibits a low frequency
power law $\sigma \sim \omega^{\alpha}$. The exponents depict sub-diffusive
behavior $ \beta < 1/2, \alpha> 0 $ at all finite disorders, and convergence to
the scaling result, $\alpha+2\beta = 1$, at large disorders.


title:
A Tale of Two Narrow-Line Regions: Ionization, Kinematics, and Spectral
  Energy Distributions for a Local Pair of Merging Obscured Active Galaxies

abstract:
  We explore the gas ionization and kinematics, as well as the optical--IR
spectral energy distributions for UGC 11185, a nearby pair of merging galaxies
hosting obscured active galactic nuclei (AGNs), also known as SDSS
J181611.72+423941.6 and J181609.37+423923.0 (J1816NE and J1816SW, $z \approx
0.04$). Due to the wide separation between these interacting galaxies ($\sim
23$ kpc), observations of these objects provide a rare glimpse of the
concurrent growth of supermassive black holes at an early merger stage. We use
BPT line diagnostics to show that the full extent of the narrow line emission
in both galaxies is photoionized by an AGN and confirm the existence of a
10-kpc-scale ionization cone in J1816NE, while in J1816SW the AGN narrow-line
region is much more compact (1--2 kpc) and relatively undisturbed. Our
observations also reveal the presence of ionized gas that nearly spans the
entire distance between the galaxies which is likely in a merger-induced tidal
stream. In addition, we carry out a spectral analysis of the X-ray emission
using data from {\em XMM-Newton}. These galaxies represent a useful pair to
explore how the [\ion{O}{3}] luminosity of an AGN is dependent on the size of
the region used to explore the extended emission. Given the growing evidence
for AGN "flickering" over short timescales, we speculate that the appearances
and impact of these AGNs may change multiple times over the course of the
galaxy merger, which is especially important given that these objects are
likely the progenitors of the types of systems commonly classified as "dual
AGNs."


title: Strongly interacting photons in one-dimensional continuum

abstract:
  Photon-photon scattering in vacuum is extremely weak. However, strong
effective interactions between single photons can be realized by employing
strong light-matter coupling. These interactions are a fundamental building
block for quantum optics, bringing many-body physics to the photonic world and
providing important resources for quantum photonic devices and for optical
metrology. In this Colloquium, we review the physics of strongly-interacting
photons in one-dimensional systems with no optical confinement along the
propagation direction. We focus on two recently-demonstrated experimental
realizations: superconducting qubits coupled to open transmission lines, and
interacting Rydberg atoms in a cold gas. Advancements in the theoretical
understanding of these systems are presented in complementary formalisms and
compared to experimental results. The experimental achievements are summarized
alongside a description of the quantum optical effects and quantum devices
emerging from them.

categories: quant-ph cond-mat.mes-hall cond-mat.quant-gas cond-mat.supr-con physics.atom-ph


title:
A plethora of diffuse steep spectrum radio sources in Abell 2034
  revealed by LOFAR

abstract:
  With Low-Frequency Array (LOFAR) observations, we have discovered a diverse
assembly of steep spectrum emission that is apparently associated with the
intra cluster medium (ICM) of the merging galaxy cluster Abell 2034. Such a
rich variety of complex emission associated with the ICM has been observed in
few other clusters. This not only indicates that Abell 2034 is a more
interesting and complex system than previously thought but it also demonstrates
the importance of sensitive and high-resolution, low-frequency observations.
These observations can reveal emission from relativistic particles which have
been accelerated to sufficient energy to produce observable emission or have
had their high energy maintained by mechanisms in the ICM. The most prominent
feature in our maps is a bright bulb of emission connected to two steep
spectrum filamentary structures, the longest of which extends perpendicular to
the merger axis for 0.5Mpc across the south of the cluster. The origin of these
objects is unclear, with no shock detected in the X-ray images and no obvious
connection with cluster galaxies or AGNs. We also find that the X-ray bright
region of the cluster coincides with a giant radio halo with an irregular
morphology and a very steep spectrum. In addition, the cluster hosts up to
three possible radio relics, which are misaligned with the cluster X-ray
emission. Finally, we have identified multiple regions of emission with a very
steep spectral index that seem to be associated with either tailed radio
galaxies or a shock.


title:
Orbital evolution of mass-transferring eccentric binary systems. I.
  Phase-dependent evolution

abstract:
  Observations reveal that mass-transferring binary systems may have non-zero
orbital eccentricities. The time-evolution of the orbital semi-major axis and
eccentricity of mass-transferring eccentric binary systems is an important part
of binary evolution theory and has been widely studied. However, various
different approaches and assumptions on the subject have made the literature
difficult to comprehend and comparisons between different orbital element
time-evolution equations not easy to make. Consequently, no self-consistent
treatment of this phase has been ever included in binary population synthesis
codes. In this paper, we present a general formalism to derive the
time-evolution equations of the binary orbital elements, treating mass-loss and
mass-transfer as perturbations to the general two-body problem. We present the
self-consistent form of the perturbing acceleration and the phase-dependent
time-evolution equations for the orbital elements under different
mass-loss/transfer processes. First, we study the cases of isotropic and
anisotropic wind mass-loss. Then, we proceed with the non-isotropic ejection
and accretion in conservative as well as non-conservative manner for both point
masses and extended bodies. Comparison of the derived equations with similar
work in the literature is made and explanation of the existing discrepancies is
provided.


title:
Orbital evolution of mass-transferring eccentric binary systems. II.
  Secular Evolution

abstract:
  Finite eccentricities in mass-transferring eccentric binary systems can be
explained by taking into account mass-loss and mass-transfer processes that
often occur in these systems. These processes can be treated as perturbations
to the general two-body problem. The time-evolution equations for the
semi-major axis and the eccentricity derived from perturbative methods are in
general phase-dependent. The osculating semi-major axis and eccentricity change
over the orbital timescale and they are not easy to implement in binary
evolution codes like MESA. However, the secular orbital element evolution
equations can be simplified averaging over the rapidly varying true anomalies.
In this paper, we derive the secular time-evolution equations for the
semi-major axis and the eccentricity for various mass-loss/transfer processes
using either the adiabatic approximation or the assumption of delta-function
mass-loss/transfer at periastron. We begin with the cases of isotropic and
anisotropic wind mass-loss. We continue with conservative and non-conservative
non-isotropic mass ejection/accretion (including RLOF) for both point-masses
and extended bodies. We conclude with the case of phase-dependent mass
accretion. Comparison of the derived equations with similar work in the
literature is included and explanation of the existing discrepancies is
provided.


title:
Model-Independent Inference of Neutron Star Radii from Moment of Inertia
  Measurements

abstract:
  A precise moment of inertia measurement for PSR J0737-3039A in the double
pulsar system is expected within the next five years. We present here a new
method of mapping the anticipated measurement of the moment of inertia directly
into the neutron star structure. We determine the maximum and minimum values
possible for the moment of inertia of a neutron star of a given radius based on
physical stability arguments, assuming knowledge of the equation of state only
at densities below the nuclear saturation density. If the equation of state is
trusted up to the nuclear saturation density, we find that a measurement of the
moment of inertia will place absolute bounds on the radius of PSR J0737-3039A
to within $\pm$1 km. The resulting combination of moment of inertia, mass, and
radius measurements for a single source will allow for new, stringent
constraints on the dense-matter equation of state.


title: The different baryonic Tully-Fisher relations at low masses

abstract:
  We compare the Baryonic Tully-Fisher relation (BTFR) of simulations and
observations of galaxies ranging from dwarfs to spirals, using various measures
of rotational velocity Vrot. We explore the BTFR when measuring Vrot at the
flat part of the rotation curve, Vflat, at the extent of HI gas, Vlast, and
using 20% (W20) and 50% (W50) of the width of HI line profiles. We also compare
with the maximum circular velocity of the parent halo, Vmax, within dark matter
only simulations. The different BTFRs increasingly diverge as galaxy mass
decreases. Using Vlast one obtains a power law over four orders of magnitude in
baryonic mass, with slope similar to the observed BTFR. Measuring Vflat gives
similar results as Vlast when galaxies with rising rotation curves are
excluded. However, higher rotation velocities would be found for low mass
galaxies if the cold gas extended far enough for Vrot to reach a maximum. W20
gives a similar slope as Vlast but with slightly lower values of Vrot for low
mass galaxies, although this may depend on the extent of the gas in your galaxy
sample. W50 bends away from these other relations toward low velocities at low
masses. By contrast, Vmax bends toward high velocities for low mass galaxies,
as cold gas does not extend out to the radius at which halos reach Vmax. Our
study highlights the need for careful comparisons between observations and
models: one needs to be consistent about the particular method of measuring
Vrot, and precise about the radius at which velocities are measured.


title: Evolutionary Analysis of Gaseous Sub-Neptune-Mass Planets with MESA

abstract:
  Sub-Neptune-sized exoplanets represent one of the most common types of
planets in the Milky Way, yet many of their properties are unknown. Here, we
present a prescription to adapt the capabilities of the stellar evolution
toolkit Modules for Experiments in Stellar Astrophysics (MESA) to model
sub-Neptune mass planets with H/He envelopes. With the addition of routines
treating the planet core luminosity, heavy element enrichment, atmospheric
boundary condition, and mass loss due to hydrodynamic winds, the evolutionary
pathways of planets with diverse starting conditions are more accurately
constrained. Using these dynamical models, we construct mass-composition
relationships of planets from 1 to 400 $M_{\oplus}$ and investigate how
mass-loss impacts their composition and evolution history. We demonstrate that
planet radii are typically insensitive to the evolution pathway that brought
the planet to its instantaneous mass, composition and age, with variations from
hysteresis. We find that planet envelope mass loss timescales, $\tau_{\rm
env}$, vary non-monotonically with H/He envelope mass fractions (at fixed
planet mass). In our simulations of young (100~Myr) low-mass
($M_p\lesssim10~M_\oplus$) planets with rocky cores, $\tau_{\rm env}$ is
maximized at $M_{\rm env}/M_p=1\%$ to $3\%$. The resulting convergent mass loss
evolution could potentially imprint itself on the close-in planet population as
a preferred H/He mass fraction of ${\sim}1\%$. Looking ahead, we anticipate
that this numerical code will see widespread applications complementing both
3-D models and observational exoplanet surveys.


title:
Evaluating the Security of a DNS Query Obfuscation Scheme for Private
  Web Surfing

abstract:
  The Domain Name System (DNS) does not provide query privacy. Query
obfuscation schemes have been proposed to overcome this limitation, but, so
far, they have not been evaluated in a realistic setting. In this paper we
evaluate the security of a random set range query scheme in a real-world web
surfing scenario. We demonstrate that the scheme does not sufficiently
obfuscate characteristic query patterns, which can be used by an adversary to
determine the visited websites. We also illustrate how to thwart the attack and
discuss practical challenges. Our results suggest that previously published
evaluations of range queries may give a false sense of the attainable security,
because they do not account for any interdependencies between queries.


title: Stack-propagation: Improved Representation Learning for Syntax

abstract:
  Traditional syntax models typically leverage part-of-speech (POS) information
by constructing features from hand-tuned templates. We demonstrate that a
better approach is to utilize POS tags as a regularizer of learned
representations. We propose a simple method for learning a stacked pipeline of
models which we call "stack-propagation". We apply this to dependency parsing
and tagging, where we use the hidden layer of the tagger network as a
representation of the input tokens for the parser. At test time, our parser
does not require predicted POS tags. On 19 languages from the Universal
Dependencies, our method is 1.3% (absolute) more accurate than a
state-of-the-art graph-based approach and 2.7% more accurate than the most
comparable greedy model.


title:
Extended degeneracy and order by disorder in the square lattice
  J$_1$-J$_2$-J$_3$ model

abstract:
  The square lattice antiferromagnet with frustrating next nearest neighbour
coupling continues to generate tremendous interest, with an elusive quantum
disordered phase in the vicinity of $J_2$ = $J_1$/2. At this precise value of
frustration, the classical model has a very large degeneracy which makes the
problem difficult to handle. We show that introducing a ferromagnetic $J_3$
coupling partially lifts this degeneracy. It gives rise to a four-site magnetic
unit cell with the constraint that the spins on every square must add to zero.
This leads to a two-parameter family of ground states and an emergent vector
order parameter. We reinterpret this family of ground states as coexistence
states of three spirals. Using spin wave analysis, we show that thermal and
quantum fluctuations break this degeneracy differently. Thermal fluctuations
break it down to a threefold degeneracy with a N\'eel phase and two stripe
phases. This threefold symmetry is restored via a $Z_3$ thermal transition, as
we demonstrate using classical Monte Carlo simulations. On the other hand,
quantum fluctuations select the N\'eel state. In the extreme quantum limit of
spin-$1/2$, we use exact diagonalization to demonstrate N\'eel ordering beyond
a critical $J_3$ coupling. For weak $J_3$, a variational approach suggests an
$s$-wave plaquette-RVB state. Away from the $J_2 = J_1/2$ line, we show that
quantum fluctuations favour N\'eel ordering strongly enough to stabilize it
within the classical stripe region. Our results shed light on the origin of the
quantum disordered phase in the $J_1$-$J_2$ model.


title:
Dispersive estimates for rational symbols and local well-posedness of
  the nonzero energy NV equation. II

abstract:
  In this paper we continue our study on the Cauchy problem for the
two-dimensional Novikov-Veselov (NV) equation, integrable via the inverse
scattering transform for the two dimensional Schr\"odinger operator at a fixed
energy parameter. This work is concerned with the case of positive energy. For
the solution of the linearized equation we derive smoothing and Strichartz
estimates by combining two different frequency regimes. At non-low frequencies
we also derive improved smoothing estimates with gain of almost one derivative.
We combine the linear estimates with the Fourier decomposition method and $
X^{s,b} $ spaces to obtain local well-posedness of NV at positive energy in
$H^s$, $s>\frac12$. Our result implies, in particular, that {\it at least} for
$s>\frac12$, NV does not change its behavior from semilinear to quasilinear as
energy changes sign, in contrast to the closely related Kadomtsev-Petviashvili
equations. As a supplement, we provide some new explicit solutions of NV at
zero energy which exhibit an interesting behavior at large times.


title: Origins and Interpretation of Tidal Debris

abstract:
  The stellar debris structures that have been discovered around the Milky Way
and other galaxies are thought to be formed from the disruption of satellite
stellar systems --- dwarf galaxies or globular clusters --- by galactic tidal
fields. The total stellar mass in these structures is typically tiny compared
to the galaxy around which they are found, and it is hence easy to dismiss them
as inconsequential. However, they are remarkably useful as probes of a galaxy's
history (as described in this chapter) and mass distribution (covered in a
companion chapter in this volume). This power is actually a consequence of
their apparent insignificance: their low contribution to the overall mass makes
the physics that describes them both elegant and simple and this means that
their observed properties are relatively easy to understand and interpret.


title: Tidal Debris as a Dark Matter Probe

abstract:
  Tidal debris streams from galaxy satellites can provide insight into the dark
matter distribution in halos. This is because we have more information about
stars in a debris structure than about a purely random population of stars: we
know that in the past they were all bound to the same dwarf galaxy; and we know
that they form a dynamically cold population moving on similar orbits. They
also probe a different region of the matter distribution in a galaxy than many
other methods of mass determination, as their orbits take them far beyond the
typical extent of those for the bulk of stars. Although conclusive results from
this information have yet to be obtained, significant progress has been made in
developing the methodologies for determining both the global mass distribution
of the Milky Way's dark matter halo and the amount of dark matter substructure
within it. Methods for measuring the halo shape are divided into "predictive
methods," which predict the tidal debris properties from the progenitor
satellite's mass and orbit, given an assumed parent galaxy mass distribution;
and "fundamental methods," which exploit properties fundamental to the nature
of tidal debris as global potential constraints. Methods for quantifying the
prevalence of dark matter subhalos within halos through the analysis of the
gaps left in tidal streams after these substructures pass through them are
reviewed.


title: The Quaternions and Bott Periodicity Are Quantum Hamiltonian Reductions

abstract:
  We show that the Morita equivalences $\mathrm{Cliff}(4) \simeq {\mathbb H}$,
$\mathrm{Cliff}(7) \simeq \mathrm{Cliff}(-1)$, and $\mathrm{Cliff}(8) \simeq
{\mathbb R}$ arise from quantizing the Hamiltonian reductions ${\mathbb
R}^{0|4} // \mathrm{Spin}(3)$, ${\mathbb R}^{0|7} // G_2$, and ${\mathbb
R}^{0|8} // \mathrm{Spin}(7)$, respectively.


title: The dynamics of radiation driven, optically thick winds

abstract:
  Recent observation of some luminous transient sources with low color
temperatures suggests that the emission is dominated by optically thick winds
driven by super-Eddington accretion. We present a general analytical theory of
the dynamics of radiation pressure-driven, optically thick winds. Unlike the
classical adiabatic stellar wind solution whose dynamics are solely determined
by the sonic radius, here the loss of the radiation pressure due to photon
diffusion also plays an important role. We identify two high mass loss rate
regimes ($\dot{M} > L_{\rm Edd\,}/c^2$). In the large total luminosity regime
the solution resembles an adiabatic wind solution. Both the radiative
luminosity, $L$, and the kinetic luminosity, $L_k$, are super-Eddington with $L
< L_k$ and $L \propto L_k^{1/3}$. In the lower total luminosity regime most of
the energy is carried out by the radiation with $L_k < L \approx L_{\rm
Edd\,}$. In a third, low mass loss regime ($\dot{M} < L_{\rm Edd\,}/c^2$), the
wind becomes optically thin early on and, unless gas pressure is important at
this stage, the solution is very different from the adiabatic one. The results
are independent from the energy generation mechanism at the foot of the wind,
therefore they are applicable to a wide range of mass ejection systems, from
black hole accretion, to planetary nebulae, and to classical novae.


title:
Improved Optimization for the Cluster Jastrow Antisymmetric Geminal
  Power and Tests on Triple-Bond Dissociations

abstract:
  We present a novel specialization of the variational Monte Carlo linear
method for the optimization of the recently introduced cluster Jastrow
antisymmetric geminal power ansatz, achieving a lower-order polynomial cost
scaling than would be possible with a naive application of the linear method
and greatly improving optimization performance relative to the previously
employed quasi-Newton approach. We test the methodology on highly
multi-reference triple-bond stretches, achieving accuracies superior to
traditional coupled cluster theory and multi-reference perturbation theory in
both the typical example of N$_2$ and the transition-metal-oxide example of
[ScO]$^+$.


title:
Accurate feeding of nano antenna by polarization singularities for
  lateral and rotational displacement sensing

abstract:
  Addressing subwavelength object and displacement is crucial in optical
nanometrology. We show in this Letter that nano antennas with subwavelength
structures can be addressed precisely by incident beams with singularity. This
accurate feeding beyond the diffraction limit can lead to dynamic control of
the unidirectional scattering in the far field. The combination of polarization
discontinuity of the incoming singular beam, along with the rapid phase
variation near the antenna leads to remarkable sensitivity of the far field
scattering to displacement at deep subwavelength scale. This opens a far field
deep subwavelength postion detection method based on the interaction of
singular optics with nano antennas.


title:
Consequences of high-$x$ proton size fluctuations in small collision
  systems at RHIC

abstract:
  Recent measurements of jet production rates at large transverse momentum
($p_T$) in the collisions of small projectiles with large nuclei at RHIC and
the LHC indicate that they have an unexpected relationship with estimates of
the collision centrality. One compelling interpretation of the data is that it
captures an $x_p$-dependent decrease in the average interaction strength of the
nucleon in the projectile undergoing a hard scattering. A weakly interacting or
"shrinking" nucleon in the projectile strikes fewer nucleons in the nucleus,
resulting in a particular pattern of centrality-dependent modifications to
high-$p_T$ processes. We describe a simple one-parameter geometric
implementation of this picture within a modified Monte Carlo Glauber model
tuned to $d$$+$Au jet data, and explore two of its major consequences. First,
the model predicts a particular projectile-species dependence to the centrality
dependence at high-$x_p$, opposite to that expected from an energy loss effect.
Second, we find that some of the large centrality dependence observed for
forward di-hadron production in $d$$+$Au collisions at RHIC may arise from the
physics of the "shrinking" projectile nucleon, in addition to impact
parameter-dependent shadowing or saturation effects at low nuclear-$x$. We
conclude that analogous measurements in recently collected $p$$+$Au and
$^3$He$+$Au collision data at RHIC can provide a unique test of these
predictions.


title: Warm Ekpyrosis

abstract:
  We propose a mechanism to generate a nearly scale-invariant spectrum of
adiabatic scalar perturbations about a stable, ekpyrotic background. The key
ingredient is a coupling between a single ekpyrotic field and a perfect fluid
of ultra-relativistic matter. This coupling introduces a friction term into the
equation of motion for the field, opposing the Hubble anti-friction, which can
be chosen such that an exactly scale-invariant (or nearly scale-invariant)
spectrum of adiabatic density perturbations is continuously produced throughout
the ekpyrotic phase. This mechanism eliminates the need for a second (entropic)
scalar field and hence any need for introducing a second phase for converting
entropic into curvature fluctuations. It also reduces the constraints on the
equation of state during the ekpyrotic phase and, thereby, the need for
parametric fine-tuning.


title: Flavor hierarchies from dynamical scales

abstract:
  One main obstacle for any beyond the SM (BSM) scenario solving the hierarchy
problem is its potentially large contributions to electric dipole moments. An
elegant way to avoid this problem is to have the light SM fermions couple to
the BSM sector only through bilinears, $\bar ff$. This possibility can be
neatly implemented in composite Higgs models. We study the implications of
dynamically generating the fermion Yukawa couplings at different scales,
relating larger scales to lighter SM fermions. We show that all flavor and
CP-violating constraints can be easily accommodated for a BSM scale of few TeV,
without requiring any extra symmetry. Contributions to B physics are mainly
mediated by the top, giving a predictive pattern of deviations in $\Delta F=2$
and $\Delta F=1$ flavor observables that could be seen in future experiments.


title: Guarantees of Riemannian Optimization for Low Rank Matrix Completion

abstract:
  We study the Riemannian optimization methods on the embedded manifold of low
rank matrices for the problem of matrix completion, which is about recovering a
low rank matrix from its partial entries. Assume $m$ entries of an $n\times n$
rank $r$ matrix are sampled independently and uniformly with replacement. We
first prove that with high probability the Riemannian gradient descent and
conjugate gradient descent algorithms initialized by one step hard thresholding
are guaranteed to converge linearly to the measured matrix provided
\begin{align*} m\geq C_\kappa n^{1.5}r\log^{1.5}(n), \end{align*} where
$C_\kappa$ is a numerical constant depending on the condition number of the
underlying matrix. The sampling complexity has been further improved to
\begin{align*} m\geq C_\kappa nr^2\log^{2}(n) \end{align*} via the resampled
Riemannian gradient descent initialization. The analysis of the new
initialization procedure relies on an asymmetric restricted isometry property
of the sampling operator and the curvature of the low rank matrix manifold.
Numerical simulation shows that the algorithms are able to recover a low rank
matrix from nearly the minimum number of measurements.


title:
Searching for electromagnetic counterpart of LIGO gravitational waves in
  the Fermi GBM data with ADWO

abstract:
  The Fermi collaboration identified a possible electromagnetic counterpart of
the gravitational wave event of September 14, 2015. Our goal is to provide an
unsupervised data analysis algorithm to identify similar events in Fermi's
Gamma-ray Burst Monitor CTTE data stream. We are looking for signals that are
typically weak. Therefore, they can only be found by a careful analysis of
count rates of all detectors and energy channels simultaneously. Our
Automatized Detector Weight Optimization (ADWO) method consists of a search for
the signal, and a test of its significance. We developed ADWO, a virtual
detector analysis tool for multi-channel multi-detector signals, and performed
successful searches for short transients in the data-streams. We have
identified GRB150522B, as well as possible electromagnetic candidates of the
transients GW150914 and LVT151012. ADWO is an independently developed,
unsupervised data analysis tool that only relies on the raw data of the Fermi
satellite. It can therefore provide a strong, independent test to any
electromagnetic signal accompanying future gravitational wave observations.

categories: astro-ph.HE astro-ph.IM gr-qc physics.data-an