title: The Franks-Misiurewicz conjecture for extensions of irrational rotations

abstract:
  We show that a toral homeomorphism which is homotopic to the identity and
topologically semiconjugate to an irrational rotation of the circle is always a
pseudo-rotation (i.e. its rotation set is a single point). In combination with
recent results, this allows us to complete the study of the Franks-Misiurewicz
conjecture in the minimal case.


title: Enumeration of Commuting Pairs in Lie Algebras over Finite Fields

abstract:
  Feit and Fine derived a generating function for the number of ordered pairs
of commuting n by n matrices over the finite field F_q. This has been reproved
and studied by Bryan and Morrison from the viewpoint of motivic
Donaldson-Thomas theory. In this note we give a new proof of the Feit-Fine
result, and generalize it to the Lie algebra of finite unitary groups and to
the Lie algebra of odd characteristic finite symplectic groups. We extract some
asymptotic information from these generating functions. Finally, we derive
generating functions for the number of commuting nilpotent elements for the Lie
algebras of the finite general linear and unitary groups, and of odd
characteristic symplectic groups.


title: Non-ergodic Banach spaces are near Hilbert

abstract:
  We prove that a non ergodic Banach space must be near Hilbert. In particular,
$\ell_p$ ($2<p<\infty$) is ergodic. This reinforces the conjecture that
$\ell_2$ is the only non ergodic Banach space. As an application of our
criterion for ergodicity, we prove that there is no separable Banach space
which is complementably universal for the class of all subspaces of $\ell_p$,
for $1\leq p <2$. This solves a question left open by W. B. Johnson and A.
Szankowski in 1976.


title:
The puzzling case of the radio-loud QSO 3C 186: a gravitational wave
  recoiling black hole in a young radio source?

abstract:
  Context. Radio-loud AGNs with powerful relativistic jets are thought to be
associated with rapidly spinning black holes (BHs). BH spin-up may result from
a number of processes, including accretion of matter onto the BH itself, and
catastrophic events such as BH-BH mergers. Aims. We study the intriguing
properties of the powerful (L_bol ~ 10^47 erg s^-1) radio-loud quasar 3C 186.
This object shows peculiar features both in the images and in the spectra.
Methods. We utilize near-IR Hubble Space Telescope (HST) images to study the
properties of the host galaxy, and HST UV and Sloan Digital Sky Survey optical
spectra to study the kinematics of the source. Chandra X-ray data are also used
to better constrain the physical interpretation. Results. HST imaging shows
that the active nucleus is offset by 1.3 +- 0.1 arcsec (i.e. ~11 kpc) with
respect to the center of the host galaxy. Spectroscopic data show that the
broad emission lines are offset by -2140 +-390 km/s with respect to the narrow
lines. Velocity shifts are often seen in QSO spectra, in particular in
high-ionization broad emission lines. The host galaxy of the quasar displays a
distorted morphology with possible tidal features that are typical of the late
stages of a galaxy merger. Conclusions. A number of scenarios can be envisaged
to account for the observed features. While the presence of a peculiar outflow
cannot be completely ruled out, all of the observed features are consistent
with those expected if the QSO is associated with a gravitational wave (GW)
recoiling BH. Future detailed studies of this object will allow us to confirm
this type of scenario and will enable a better understanding of both the
physics of BH-BH mergers and the phenomena associated with the emission of GW
from astrophysical sources.


title:
Spin-1 diquark contributing to the formation of tetraquarks in light
  mesons

abstract:
  We apply a mixing framework to the light meson systems and examine tetraquark
possibility in the scalar channel. In the diquark-antidiquark model, a scalar
diquark is a compact object when its color and flavor structures are in
($\bar{\bm{3}}_c$, $\bar{\bm{3}}_f$). Assuming that all the quarks are in an
$S$-wave, the spin-0 tetraquark formed out of this scalar diquark has only one
spin configuration, $|J,J_{12},J_{34}\rangle=|000\rangle$, where $J$ is the
spin of the tetraquark, $J_{12}$ the diquark spin, $J_{34}$ the antidiquark
spin. In this construction of the scalar tetraquark, we notice that another
compact diquark with spin-1 in ($\bm{6}_c$, $\bar{\bm{3}}_f$) can be used
although it is less compact than the scalar diquark. The spin-0 tetraquark
constructed from this vector diquark leads to the spin configuration
$|J,J_{12},J_{34}\rangle=|011\rangle$. The two configurations, $|000\rangle$
and $|011\rangle$, are found to mix strongly through the color-spin
interaction. The physical states can be identified with certain mixtures of the
two configurations which diagonalize the hyperfine masses of the color-spin
interaction. Matching these states to two scalar resonances $a_0(980),
a_0(1450)$ or to $K^*_0(800), K^*_0(1430)$ depending on the isospin channel, we
find that their mass splittings are qualitatively consistent with the hyperfine
mass splittings which can support their tetraquark structure. To test our
mixing scheme further, we also construct the tetraquarks for $J=1,J=2$ with the
spin configurations, $|111\rangle$ and $|211\rangle$, and discuss possible
candidates in the physical spectrum.


title:
On the Exploration of Convolutional Fusion Networks for Visual
  Recognition

abstract:
  Despite recent advances in multi-scale deep representations, their
limitations are attributed to expensive parameters and weak fusion modules.
Hence, we propose an efficient approach to fuse multi-scale deep
representations, called convolutional fusion networks (CFN). Owing to using
1$\times$1 convolution and global average pooling, CFN can efficiently generate
the side branches while adding few parameters. In addition, we present a
locally-connected fusion module, which can learn adaptive weights for the side
branches and form a discriminatively fused feature. CFN models trained on the
CIFAR and ImageNet datasets demonstrate remarkable improvements over the plain
CNNs. Furthermore, we generalize CFN to three new tasks, including scene
recognition, fine-grained recognition and image retrieval. Our experiments show
that it can obtain consistent improvements towards the transferring tasks.


title:
Gaia TGAS search for Large Magellanic Cloud runaway supergiant
  stars:Candidate hypervelocity star discovery, and the nature of R71

abstract:
  We search for runaway stars in the Large Magellanic Cloud (LMC) by computing
the space velocities of the visually brightest stars in the LMC that are
included in the Gaia TGAS proper motion catalog. We compare with predictions
from stellar dynamical models to obtain (peculiar) velocities relative to their
local stellar environment. Two of the 31 stars have unusually high proper
motions. Of the remaining 29 stars we find that most objects in this sample
have velocities in very good agreement with model predictions of a circularly
rotating disk model. Indeed the excellent fit to the model implies that the
TGAS uncertainty estimates are likely overestimated. The fastest outliers in
this subsample contain the LBV R71 and a few other well known emission line
objects though in no case do we derive velocities consistent with fast (~100
km/s) runaways. Our results imply that R 71 in particular has a moderate
deviation from the local stellar velocity field (40 km/s) lending support to
the proposition that this object cannot have evolved as a normal single star
since it lies too far from massive star forming complexes to have arrived at
its current position during its lifetime. Our findings therefore strengthen the
case for this LBV being the result of binary evolution. Of the two stars with
unusually high proper motions we find that one, the isolated B1.5 Ia+
supergiant Sk-67 2 (HIP 22237), is a candidate hypervelocity star, the TGAS
proper motion implying a very large peculiar transverse velocity (~360 km/s)
directed radially away from the LMC centre. If confirmed, for example by Gaia
Data Release 2, it would imply that this massive supergiant, on the periphery
of the LMC, is leaving the galaxy where it will explode as a supernova.


title: Understanding the Physical Nature of Coronal "EIT Waves"

abstract:
  For almost 20 years the physical nature of globally propagating waves in the
solar corona (commonly called "EIT waves") has been controversial and subject
to debate. Additional theories have been proposed over the years to explain
observations that did not fit with the originally proposed fast-mode wave
interpretation. However, the incompatibility of observations made using the
Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric
Observatory with the fast-mode wave interpretation was challenged by differing
viewpoints from the twin Solar Terrestrial Relations Observatory spacecraft and
higher spatial/temporal resolution data from the Solar Dynamics Observatory. In
this article, we reexamine the theories proposed to explain "EIT waves" to
identify measurable properties and behaviours that can be compared to current
and future observations. Most of us conclude that "EIT waves" are best
described as fast-mode large-amplitude waves/shocks that are initially driven
by the impulsive expansion of an erupting coronal mass ejection in the low
corona.


title:
Mapping the Polarization of the Radio-Loud Ly$\alpha$ Nebula B3
  J2330+3927

abstract:
  Lya nebulae, or "Lya blobs", are extended (up to ~100 kpc), bright (L[Lya] >
10^43 erg/s) clouds of Lya emitting gas that tend to lie in overdense regions
at z ~ 2--5. The origin of the Lya emission remains unknown, but recent
theoretical work suggests that measuring the polarization might discriminate
among powering mechanisms. Here we present the first narrowband, imaging
polarimetry of a radio-loud Lya nebula, B3 J2330+3927 at z=3.09, with an
embedded active galactic nucleus (AGN). The AGN lies near the blob's Lya
emission peak and its radio lobes align roughly with the blob's major axis.
With the SPOL polarimeter on the 6.5m MMT telescope, we map the total (Lya +
continuum) polarization in a grid of circular apertures of radius 0.6"
(4.4kpc), detecting a significant (>2sigma) polarization fraction P in nine
apertures and achieving strong upper-limits (as low as 2%) elsewhere. P
increases from <2% at ~5kpc from the blob center to ~17% at ~15-25kpc. The
detections are distributed asymmetrically, roughly along the nebula's major
axis. The polarization angles theta are mostly perpendicular to this axis.
Comparing the Lya flux to that of the continuum, and conservatively assuming
that the continuum is highly polarized (20-100%) and aligned with the total
polarization, we place lower limits on the polarization of the Lya emission
P(Lya) ranging from no significant polarization at ~5 kpc from the blob center
to ~ 3--17% at 10--25kpc. Like the total polarization, the Lya polarization
detections occur more often along the blob's major axis.


title: Deep Feature Interpolation for Image Content Changes

abstract:
  We propose Deep Feature Interpolation (DFI), a new data-driven baseline for
automatic high-resolution image transformation. As the name suggests, it relies
only on simple linear interpolation of deep convolutional features from
pre-trained convnets. We show that despite its simplicity, DFI can perform
high-level semantic transformations like "make older/younger", "make
bespectacled", "add smile", among others, surprisingly well - sometimes even
matching or outperforming the state-of-the-art. This is particularly unexpected
as DFI requires no specialized network architecture or even any deep network to
be trained for these tasks. DFI therefore can be used as a new baseline to
evaluate more complex algorithms and provides a practical answer to the
question of which image transformation tasks are still challenging in the rise
of deep learning.


title: Geometry over the tropical dual numbers

abstract:
  We introduce tropical dual numbers as an extension of tropical semiring. By
this innovation, one can work with honest ideals, instead of congruences, and
recover the Euclidean topology on affine tropical spaces similar to Zariski's
approach in classical algebraic geometry. The bend loci of an ideal over
tropical dual numbers coincides with the bend loci of a congruence over
tropical semiring and this enables tropical dual numbers to serve as an
algebraic structure for tropical geometry. Tropical Zariski topology on affine
tropical spaces whose closed sets are non-linear loci of ideals over tropical
dual numbers offers an alternative point of view to strong Zariski topology
defined by Giansiracusa.


title: Bayesian Semiparametric Mixed Effects Markov Chains

abstract:
  Studying the neurological, genetic and evolutionary basis of human vocal
communication mechanisms using animal vocalization models is an important field
of neuroscience. The data sets typically comprise structured sequences of
syllables or `songs' produced by animals from different genotypes under
different social contexts. We develop a novel Bayesian semiparametric framework
for inference in such data sets. Our approach is built on a novel class of
mixed effects Markov transition models for the songs that accommodates
exogenous influences of genotype and context as well as animal-specific
heterogeneity. We design efficient Markov chain Monte Carlo algorithms for
posterior computation. Crucial advantages of the proposed approach include its
ability to provide insights into key scientific queries related to global and
local influences of the exogenous predictors on the transition dynamics via
automated tests of hypotheses. The methodology is illustrated using simulation
experiments and the aforementioned motivating application in neuroscience.


title:
Regularization of singularities in the weighted summation of Dirac-delta
  functions for the spectral solution of hyperbolic conservation laws?

abstract:
  Singular source terms expressed as weighted summations of Dirac-delta
functions are regularized through approximation theory with convolution
operators. We consider the numerical solution of scalar and one-dimensional
hyperbolic conservation laws with the singular source by spectral Chebyshev
collocation methods. The regularization is obtained by convolution with a
high-order compactly supported Dirac-delta approximation whose overall accuracy
is controlled by the number of vanishing moments, degree of smoothness and
length of the support (scaling parameter). An optimal scaling parameter that
leads to a high-order accurate representation of the singular source at smooth
parts and full convergence order away from the singularities in the spectral
solution is derived. The accuracy of the regularization and the spectral
solution is assessed by solving an advection and Burgers equation with smooth
initial data. Nu- merical results illustrate the enhanced accuracy of the
spectral method through the proposed regularization.


title: Planetesimal collisions as a chondrule forming event

abstract:
  Chondritic meteorites contain unique spherical materials named chondrules:
sub-mm sized silicate grains once melted in a high temperature condition in the
solar nebula. We numerically explore one of chondrule forming processes,
planetesimal collisions. Previous studies found that impact jetting via
protoplanet-planetesimal collisions make chondrules with an amount of 1 % of
impactors' mass, when impact velocity exceeds 2.5 km s$^{-1}$. Based on the
mineralogical data of chondrules, undifferentiated planetesimals would be more
suitable for chondrule-forming collisions than potentially differentiated
protoplanets. We examine planetesimal-planetesimal collisions using a shock
physics code and find two things: one is that planetesimal-planetesimal
collisions produce the nearly same amount of chondrules as
protoplanet-planetesimal collisions ($\sim$ 1 %). The other is that the amount
of produced chondrules becomes larger as the impact velocity increases when two
planetesimals collide with each other. We also find that progenitors of
chondrules can be ejected from deeper regions of large targets (planetesimals
or protoplanets) than small impactors (planetesimals). The composition of
targets is therefore important to fully account for the mineralogical data of
currently sampled chondrules.


title:
Unmatched Perturbation Accommodation for an Aerospace Launch Vehicle
  Autopilot Using Dynamic Sliding Manifolds

abstract:
  Sliding mode control of a launch vehicle during its atmospheric flight phase
is studied in the presence of unmatched disturbances. Linear time-varying
dynamics of the aerospace vehicle is converted into a systematic formula and
then dynamic sliding manifold as an advanced method is used in order to
overcome the limited capability of conventional sliding manifolds in minimizing
the undesired effects of unmatched perturbations on the control system. At the
end, simulation results are evaluated and the performance of two approaches are
compared in terms of stability and robustness of the autopilot.


title: Dilated Floor Functions That Commute

abstract:
  We determine all pairs of real numbers $(\alpha, \beta)$ such that the
dilated floor functions $\lfloor \alpha x\rfloor$ and $\lfloor \beta x\rfloor$
commute under composition, i.e., such that $\lfloor \alpha \lfloor \beta
x\rfloor\rfloor = \lfloor \beta \lfloor \alpha x\rfloor\rfloor$ holds for all
real $x$.


title: Cylinders in rational surfaces

abstract:
  We answer a question of Ciro Ciliberto about cylinders in rational surfaces
which are obtained by blowing up the plane at points in general position.


title: Self-interacting scalar fields at high-temperature

abstract:
  We study two self-interacting scalar field theories in their high-temperature
limit using path integrals on a lattice. We first discuss the formalism and
recover known potentials to validate the method. We then discuss how these
theories can model, in the high-temperature limit, the strong interaction and
General Relativity. For the strong interaction, the model recovers the known
phenomenology of the nearly static regime of heavy quarkonia. The model also
exposes a possible origin for the emergence of the confinement scale from the
approximately conformal Lagrangian. Aside from such possible insights, the main
purpose of addressing the strong interaction here --given that more
sophisticated approaches already exist-- is mostly to further verify the
pertinence of the model in the more complex case of General Relativity for
which non-perturbative methods are not as developed. The results have important
implications on the nature of Dark Matter. In particular, non-perturbative
effects naturally provide flat rotation curves for disk galaxies, without need
for non-baryonic matter, and explain as well other observations involving Dark
Matter such as cluster dynamics or the dark mass of elliptical galaxies.


title: Draining the Local Void

abstract:
  Two galaxies that lie deep within the Local Void provide a test of the
expectation that voids expand. The modest (M_B~-14) HI bearing dwarf galaxies
ALFAZOAJ1952+1428 and KK246 have been imaged with Hubble Space Telescope in
order to study the stellar populations and determine distances from the
luminosities of stars at the tip of the red giant branch. The mixed age systems
have respective distances of 8.39 Mpc and 6.95 Mpc and inferred line-of-sight
peculiar velocities of -114 km/s and -66 km/s toward us and away from the void
center. These motions compound on the Milky Way motion of ~230 km/s away from
the void. The orbits of the two galaxies are reasonably constrained by a
numerical action model encompassing an extensive region that embraces the Local
Void. It is unambiguously confirmed that these two void galaxies are moving
away from the void center at several hundred km/s.


title:
Lifting linear preferential attachment trees yields the arcsine
  coalescent

abstract:
  We consider linear preferential attachment trees which are specific
scale-free trees also known as (random) plane-oriented recursive trees.
Starting with a linear preferential attachment tree of size $n$ we show that
repeatedly applying a so-called lifting yields a continuous-time Markov chain
on linear preferential attachment trees. Each such tree induces a partition of
$\{1, \ldots, n\}$ by placing labels in the same block if and only if they are
attached to the same node in the tree. Our main result is that this Markov
chain on linear preferential attachment trees induces a partition valued
process which is equal in distribution (up to a random time-change) to the
arcsine $n$-coalescent, that is the multiple merger coalescent whose $\Lambda$
measure is the arcsine distribution.


title: Robust Trading of Implied Skew

abstract:
  In this paper, we present a method for constructing a (static) portfolio of
co-maturing European options whose price sign is determined by the skewness
level of the associated implied volatility. This property holds regardless of
the validity of a specific model - i.e. the method is robust. The strategy is
given explicitly and depends only on beliefs about the future values of implied
skewness, which is an observable market indicator. As such, our method allows
to use the existing statistical tools to formulate the beliefs, providing a
practical interpretation of the more abstract mathematical setting, in which
the belies are understood as a family of probability measures. One of the
applications of our results is a method for trading views on the future changes
in implied skew, largely independently of other market factors. Another
application provides a concrete improvement of the existing model-independent
super- and sub- replication strategies for barrier options, which exploits a
given set of beliefs on the implied skew. Our theoretical results are tested
empirically, using the historical prices of SP500 options.


title:
Theoretical constraints on properties of low-mass neutron stars from EOS
  of inner crust matters

abstract:
  By employing four typical equation of states (EOSs) of the inner crust
matters, the constraint on properties of low-mass neutron stars are
theoretically investigated. Based on the well known fact that there is a big
gap between the neutron stars and white dwarfs in the mass-radius sequence of
compact stars, here we explicitly point out the forbidden region for the
central density and stellar radius to form a compact stars, that is, there is
no compact star in the nature having central density in the region from about
$10^{12}~kg/m^3$ to $10^{17}~kg/m^3$, and there is also no compact star having
a radius in the region from about 400 km to 2000 km. It is found that for a
low-mass neutron star with central densities at subnuclear densities, the
stellar mass is mainly determined by the softness of the EOS at the higher
density region ($ > 10^{16}~\textrm{kg.m}^{-3}$) while the stellar radius is
dependent on the softness of the EOS at lower density region ($ <
10^{16}~\textrm{kg.m}^{-3}$). For a stable neutron star with stellar mass near
the minimum mass, the Keplerian period is several hundred millisecond, the
moment of inertia is in an order of $10^{37} kg\cdot m^{2}$, and the surface
gravitational redshift is in an order of $10^{-4}$.


title:
Deep Action- and Context-Aware Sequence Learning for Activity
  Recognition and Anticipation

abstract:
  Action recognition and anticipation are key to the success of many computer
vision applications. Existing methods can roughly be grouped into those that
extract global, context-aware representations of the entire image or sequence,
and those that aim at focusing on the regions where the action occurs. While
the former may suffer from the fact that context is not always reliable, the
latter completely ignore this source of information, which can nonetheless be
helpful in many situations. In this paper, we aim at making the best of both
worlds by developing an approach that leverages both context-aware and
action-aware features. At the core of our method lies a novel multi-stage
recurrent architecture that allows us to effectively combine these two sources
of information throughout a video. This architecture first exploits the global,
context-aware features, and merges the resulting representation with the
localized, action-aware ones. Our experiments on standard datasets evidence the
benefits of our approach over methods that use each information type
separately. We outperform the state-of-the-art methods that, as us, rely only
on RGB frames as input for both action recognition and anticipation.


title:
Robust Hashing for Multi-View Data: Jointly Learning Low-Rank Kernelized
  Similarity Consensus and Hash Functions

abstract:
  Learning hash functions/codes for similarity search over multi-view data is
attracting increasing attention, where similar hash codes are assigned to the
data objects characterizing consistently neighborhood relationship across
views. Traditional methods in this category inherently suffer three
limitations: 1) they commonly adopt a two-stage scheme where similarity matrix
is first constructed, followed by a subsequent hash function learning; 2) these
methods are commonly developed on the assumption that data samples with
multiple representations are noise-free,which is not practical in real-life
applications; 3) they often incur cumbersome training model caused by the
neighborhood graph construction using all $N$ points in the database ($O(N)$).
In this paper, we motivate the problem of jointly and efficiently training the
robust hash functions over data objects with multi-feature representations
which may be noise corrupted. To achieve both the robustness and training
efficiency, we propose an approach to effectively and efficiently learning
low-rank kernelized \footnote{We use kernelized similarity rather than kernel,
as it is not a squared symmetric matrix for data-landmark affinity matrix.}
hash functions shared across views. Specifically, we utilize landmark graphs to
construct tractable similarity matrices in multi-views to automatically
discover neighborhood structure in the data. To learn robust hash functions, a
latent low-rank kernel function is used to construct hash functions in order to
accommodate linearly inseparable data. In particular, a latent kernelized
similarity matrix is recovered by rank minimization on multiple kernel-based
similarity matrices. Extensive experiments on real-world multi-view datasets
validate the efficacy of our method in the presence of error corruptions.


title: Dust Attenuation in Clumpy, Star-Forming Galaxies at 0.07 < z < 0.14

abstract:
  Dust attenuation in galaxies has been extensively studied nearby, however,
there are still many unknowns regarding attenuation in distant galaxies. We
contribute to this effort using observations of star-forming galaxies in the
redshift range z = 0.05-0.15 from the DYNAMO survey. Highly star-forming DYNAMO
galaxies share many similar attributes to clumpy, star-forming galaxies at high
redshift. Considering integrated Sloan Digital Sky Survey observations, trends
between attenuation and other galaxy properties for DYNAMO galaxies are well
matched to star-forming galaxies at high redshift. Integrated gas attenuations
of DYNAMO galaxies are 0.2-2.0 mags in the V-band, and the ratio of stellar
E(B-V) and gas E(B-V) is 0.78-0.08 (compared to 0.44 at low redshift). Four
highly star-forming DYNAMO galaxies were observed at H-alpha using the Hubble
Space Telescope and at Pa-alpha using integral field spectroscopy at Keck. The
latter achieve similar resolution (~0.8-1 kpc) to our HST imaging using
adaptive optics, providing resolved observations of gas attenuations of these
galaxies on sub-kpc scales. We find < 1.0 mag of variation in attenuation (at
H-alpha) from clump to clump, with no evidence of highly attenuated star
formation. Attenuations are in the range 0.3-2.2 mags in the V band, consistent
with attenuations of low redshift star-forming galaxies. The small spatial
variation on attenuation suggests that a majority of the star-formation
activity in these four galaxies occurs in relatively unobscured regions and,
thus, star-formation is well characterised by our H-alpha observations.


title: A covariant Hamiltonian tetrad approach to numerical relativity

abstract:
  A Hamiltonian approach to the equations of general relativity is proposed
using the powerful mathematical language of multivector-valued differential
forms. In the approach, the gravitational coordinates are the 12 spatial
components of the line interval (the vierbein) including their antisymmetric
parts, and their 12 conjugate momenta. A feature of the proposed formalism is
that it allows Lorentz gauge freedoms to be imposed on the Lorentz connections
rather than on the vierbein, which may facilitate numerical integration in some
challenging problems. The 40 Hamilton's equations comprise 12 + 12 = 24
equations of motion, 10 constraint equations (first class constraints, which
must be arranged on the initial hypersurface of constant time, but which are
guaranteed thereafter by conservation laws), and 6 identities (second class
constraints). The 6 identities define a trace-free spatial tensor that is the
gravitational analog of the magnetic field of electromagnetism. If the
gravitational magnetic field is promoted to an independent field satisfying its
own equation of motion, then the system becomes the WEBB system, which is known
to be strongly hyperbolic. Some other approaches, including ADM, BSSN, WEBB,
and Loop Quantum Gravity, are translated into the language of
multivector-valued forms, bringing out their underlying mathematical structure.


title: Hawking radiation inside a Schwarzschild black hole

abstract:
  The boundary of any observer's spacetime is the boundary that divides what
the observer can see from what they cannot see. The boundary of an observer's
spacetime in the presence of a black hole is not the true (future event)
horizon of the black hole, but rather the illusory horizon, the dimming,
redshifting surface of the star that collapsed to the black hole long ago. The
illusory horizon is the source of Hawking radiation seen by observers both
outside and inside the true horizon. The perceived acceleration (gravity) on
the illusory horizon sets the characteristic frequency scale of Hawking
radiation, even if that acceleration varies dynamically, as it must do from the
perspective of an infalling observer. The acceleration seen by a non-rotating
free-faller both on the illusory horizon below and in the sky above is
calculated for a Schwarzschild black hole. Remarkably, as an infaller
approaches the singularity, the acceleration becomes isotropic, and diverging
as a power law. The isotropic, power-law character of the Hawking radiation,
coupled with conservation of energy-momentum, the trace anomaly, and the
familiar behavior of Hawking radiation far from the black hole, leads to a
complete description of the quantum energy-momentum inside a Schwarzschild
black hole. The quantum energy-momentum near the singularity diverges as
$r^{-6}$, and consists of relativistic Hawking radiation and negative energy
vacuum in the ratio $3 : -2$. The classical back reaction of the quantum
energy-momentum on the geometry, calculated using the Einstein equations,
serves merely to exacerbate the singularity. All the results are consistent
with traditional calculations of the quantum energy-momentum in 1+1 spacetime
dimensions.


title: The Present and Future of Searching for Dark Matter with LUX and LZ

abstract:
  The LUX collaboration new results advance the search for dark matter
candidate particles in the 4 GeV/c^2 and higher mass range, with a maximal
spin-independent 90% C.L. limit of 2 x 10^-46 cm^2 at 50 GeV/c^2 for its 332
live-day run, following after 6 x 10^-46 cm^2 cross-section for 33 GeV/c^2 mass
from the re-analysis of its initial 95 live-day WIMP search data from December
2015. LUX has performed multiple advanced in situ neutron and beta/gamma
calibrations of light and charge yields down to 1.1 and 0.7 keV, respectively,
in nuclear recoil energy and 1.3 and 0.2 keV in units of electron recoil
energy, thereby bypassing the past practice of extrapolating yields from ex
situ calibrations or simulation models alone. For this conference proceedings,
consequences of the new calibrations for the limit on the interaction
cross-sections for low-mass WIMPs will be highlighted. Previous claims of a
WIMP signal, from other detectors, are now even more strongly disfavored,
assuming isospin invariance and the standard WIMP halo model. Both
spin-independent and spin-dependent limits will be discussed, including the
recent completion of LUX's 332-live-day blind run. Lastly, we highlight the
conceptual design and future plan for its 10-ton-scale, next-generation
successor LZ, which plans on achieving < 3 x 10^-48 cm^2 sensitivity for a WIMP
of mass 40 GeV/c^2.


title: Thompson's conjecture for alternating group

abstract:
  Let $G$ be a finite group, and let $N(G)$ be the set of sizes of its
conjugacy classes. We show that if a finite group $G$ has trivial center and
$N(G)$ equals to $N(Alt_n)$ or $N(Sym_n)$ for $n\geq 23$, then $G$ has a
composition factor isomorphic to an alternating group $Alt_k$ such that $k\leq
n$ and the half-interval $(k, n]$ contains no primes. As a corollary, we prove
the Thompson's conjecture for simple alternating groups.


title:
Automatic Node Selection for Deep Neural Networks using Group Lasso
  Regularization

abstract:
  We examine the effect of the Group Lasso (gLasso) regularizer in selecting
the salient nodes of Deep Neural Network (DNN) hidden layers by applying a
DNN-HMM hybrid speech recognizer to TED Talks speech data. We test two types of
gLasso regularization, one for outgoing weight vectors and another for incoming
weight vectors, as well as two sizes of DNNs: 2048 hidden layer nodes and 4096
nodes. Furthermore, we compare gLasso and L2 regularizers. Our experiment
results demonstrate that our DNN training, in which the gLasso regularizer was
embedded, successfully selected the hidden layer nodes that are necessary and
sufficient for achieving high classification power.


title:
On Concentration of least energy solutions for magnetic critical
  Choquard equations

abstract:
  In the present paper, we consider the following magnetic nonlinear Choquard
equation $$ \left\{
  \begin{array}{ll}
  & (-i \nabla+A(x))^2u + \mu g(x)u = \lambda u + (|x|^{-\alpha} *
|u|^{2^*_\alpha})|u|^{2^*_\alpha-2}u ,\; u>0 \;\text{in} \; \mathbb{ R}^n ,
  & u \in H^1(\mathbb{R}^n, \mathbb{ C})
  \end{array} \right\}.$$ where $n \geq 4$, $2^*_\alpha=
\frac{2n-\alpha}{n-2}$, $\lambda>0$, $\mu \in \mathbb{ R}$ is a parameter,
$\alpha \in (0,n)$, $A(x): \mathbb{R}^n \rightarrow \mathbb{ R}^n$ is a
magnetic vector potential and $g(x)$ is a real valued potential function on
$\mathbb{R}^n$. Using variational methods, we establish the existence of least
energy solution under some suitable conditions. Moreover, the concentration
behavior of solutions is also studied as $\mu \rightarrow +\infty$.


title: Conformal nets are factorization algebras

abstract:
  We prove that conformal nets of finite index are an instance of the notion of
a factorization algebra. This result is an ingredient in our proof that, for
$G=SU(n)$, the Drinfel'd center of the category of positive energy
representations of the based loop group is equivalent to the category of
positive energy representations of the free loop group.


title:
An Improved Integrality Gap for the Calinescu-Karloff-Rabani Relaxation
  for Multiway Cut

abstract:
  We construct an improved integrality gap instance for the
Calinescu-Karloff-Rabani LP relaxation of the Multiway Cut problem. In
particular, for $k \geqslant 3$ terminals, our instance has an integrality
ratio of $6 / (5 + \frac{1}{k - 1}) - \varepsilon$, for every constant
$\varepsilon > 0$. For every $k \geqslant 4$, our result improves upon a
long-standing lower bound of $8 / (7 + \frac{1}{k - 1})$ by Freund and Karloff
(2000). Due to Manokaran et al.'s result (2008), our integrality gap also
implies Unique Games hardness of approximating Multiway Cut of the same ratio.


title:
Convolutional Neural Networks Applied to Neutrino Events in a Liquid
  Argon Time Projection Chamber

abstract:
  We present several studies of convolutional neural networks applied to data
coming from the MicroBooNE detector, a liquid argon time projection chamber
(LArTPC). The algorithms studied include the classification of single particle
images, the localization of single particle and neutrino interactions in an
image, and the detection of a simulated neutrino event overlaid with cosmic ray
backgrounds taken from real detector data. These studies demonstrate the
potential of convolutional neural networks for particle identification or event
detection on simulated neutrino interactions. We also address technical issues
that arise when applying this technique to data from a large LArTPC at or near
ground level.


title:
A solid state emitter embedded in a microcavity under intense
  excitation: a variational master equation approach

abstract:
  In this work, dissipative effects from a phonon bath on the resonance
fluorescence of a solid state two level system embedded in a high quality
semiconductor microcavity and driven by an intense laser, are investigated.
  Within the density operator formalism, we derive a variational master
equation valid for broader ranges of temperatures, pumping rates, and
radiation-matter couplings, than previous studies. From the obtained master
equation, fluorescence spectra for various thermal and exciting conditions are
numerically calculated, and compared to those computed from weak coupling and
polaronic master equations, respectively. Our results evidence the break down
of those rougher approaches under increased temperature and strong pumping.


title: Viscosity Solutions to Path-Dependent HJB Equation and Applications

abstract:
  In this article, the notion of viscosity solution is introduced for the
path-dependent Hamilton-Jacobi-Bellman (PHJB) equations associated with the
optimal control problems for path-dependent stochastic differential equations.
We identify the value functional of the optimal control problems as unique
viscosity solution to the associated PHJB equations. Applications to backward
stochastic Hamilton-Jacobi-Bellman equations are also given.


title: PUMA: The Positional Update and Matching Algorithm

abstract:
  We present new software to cross-match low-frequency radio catalogues: the
Positional Update and Matching Algorithm (PUMA). PUMA combines a positional
Bayesian probabilistic approach with spectral matching criteria, allowing for
confusing sources in the matching process. We go on to create a radio sky model
using PUMA based on the Murchison Widefield Array Commissioning Survey, and are
able to automatically cross-match 98.5% of sources. Using the characteristics
of this sky model, we create simple simulated mock catalogues on which to test
PUMA, and find that PUMA can reliably find the correct spectral indices of
sources, along with being able to recover ionospheric offsets. Finally, we use
this sky model to calibrate and remove foreground sources from simulated
interferometric data, generated using OSKAR (the Oxford University visibility
generator). We demonstrate that there is a substantial improvement in
foreground source removal when using higher frequency and higher resolution
source positions, even when correcting positions by an average of 0.3 given a
synthesized beam-width of 2.3.


title:
Probing autoionizing states of molecular oxygen with XUV transient
  absorption: Electronic symmetry dependent lineshapes and laser induced
  modification

abstract:
  The dynamics of autoionizing Rydberg states of oxygen are studied using
attosecond transient absorption technique, where extreme ultraviolet (XUV)
initiates molecular polarization and near infrared (NIR) pulse perturbs its
evolution. Transient absorption spectra show positive optical density (OD)
change in the case of $ns\sigma_g$ and $nd\pi_g$ autoionizing states of oxygen
and negative OD change for $nd\sigma_g$ states. Multiconfiguration
time-dependent Hartree-Fock (MCTDHF) calculation are used to simulate the
transient absorption spectra and their results agree with experimental
observations. The time evolution of superexcited states is probed in
electronically and vibrationally resolved fashion and we observe the dependence
of decay lifetimes on effective quantum number of the Rydberg series. We model
the effect of near-infrared (NIR) perturbation on molecular polarization and
find that the laser induced phase shift model agrees with the experimental and
MCTDHF results, while the laser induced attenuation model does not. We relate
the electron state symmetry dependent sign of the OD change to the Fano
parameters of the static absorption lineshapes.

categories: physics.atom-ph physics.chem-ph physics.optics quant-ph


title: Two-Photon-Exchange Effects and $\Delta(1232)$ Deformation

abstract:
  The two-photon-exchange (TPE) contribution in $ep\rightarrow ep\pi ^0$ with
$W=M_{\Delta}$ and small $Q^2$ is calculated and its corrections to the ratios
of electromagnetic transition form factors $R_{EM} =
E_{1+}^{(3/2)}/M_{1+}^{(3/2)} $ and $R_{SM} = S_{1+}^{(3/2)}/M_{1+}^{(3/2)}$,
are analysed. A simple hadronic model is used to estimate the TPE amplitude.
Two phenomenological models, MAID2007 and SAID, are used to approximate the
full $ep\rightarrow ep\pi ^0$ cross sections which contain both the TPE and the
one-photon-exchange (OPE) contributions. The genuine the OPE amplitude is then
extracted from an integral equation by iteration. We find that the TPE
contribution is not sensitive to whether MAID or SAID is used as input in the
region with $Q^2<2$ GeV$^2$.
  It gives small correction to $R_{EM}$ while for $R_{SM}$, the correction is
about -10\% at small $\epsilon$ and about $1\%$ at large $\epsilon$ for
$Q^2\approx2.5$ GeV$^2$. The large correction from TPE at small $\epsilon$ must
be included in the analysis to get a reliable extraction of $R_{SM}$.


title: Duplication Distance to the Root for Binary Sequences

abstract:
  We study the tandem duplication distance between binary sequences and their
roots. In other words, the quantity of interest is the number of tandem
duplication operations of the form $\seq x = \seq a \seq b \seq c \to \seq y =
\seq a \seq b \seq b \seq c$, where $\seq x$ and $\seq y$ are sequences and
$\seq a$, $\seq b$, and $\seq c$ are their substrings, needed to generate a
binary sequence of length $n$ starting from a square-free sequence from the set
$\{0,1,01,10,010,101\}$. This problem is a restricted case of finding the
duplication/deduplication distance between two sequences, defined as the
minimum number of duplication and deduplication operations required to
transform one sequence to the other. We consider both exact and approximate
tandem duplications. For exact duplication, denoting the maximum distance to
the root of a sequence of length $n$ by $f(n)$, we prove that $f(n)=\Theta(n)$.
For the case of approximate duplication, where a $\beta$-fraction of symbols
may be duplicated incorrectly, we show that the maximum distance has a sharp
transition from linear in $n$ to logarithmic at $\beta=1/2$. We also study the
duplication distance to the root for sequences with a given root and for
special classes of sequences, namely, the de Bruijn sequences, the Thue-Morse
sequence, and the Fibbonaci words. The problem is motivated by genomic tandem
duplication mutations and the smallest number of tandem duplication events
required to generate a given biological sequence.


title:
Alfvenic Ion Temperature Gradient Activities in a Weak Magnetic Shear
  Plasma

abstract:
  We report the first experimental evidence of Alfvenic ion temperature
gradient (AITG) modes in HL-2A Ohmic plasmas. A group of oscillations with
$f=15-40$ kHz and $n=3-6$ is detected by various diagnostics in high-density
Ohmic regimes. They appear in the plasmas with peaked density profiles and weak
magnetic shear, which indicates that corresponding instabilities are excited by
pressure gradients. The time trace of the fluctuation spectrogram can be either
a frequency staircase, with different modes excited at different times or
multiple modes may simultaneously coexist. Theoretical analyses by the extended
generalized fishbone-like dispersion relation (GFLDR-E) reveal that mode
frequencies scale with ion diamagnetic drift frequency and $\eta_i$, and they
lie in KBM-AITG-BAE frequency ranges. AITG modes are most unstable when the
magnetic shear is small in low pressure gradient regions. Numerical solutions
of the AITG/KBM equation also illuminate why AITG modes can be unstable for
weak shear and low pressure gradients. It is worth emphasizing that these
instabilities may be linked to the internal transport barrier (ITB) and H-mode
pedestal physics for weak magnetic shear.


title: Fog Computing: A Taxonomy, Survey and Future Directions

abstract:
  In recent years, the number of Internet of Things (IoT) devices/sensors has
increased to a great extent. To support the computational demand of real-time
latency-sensitive applications of largely geo-distributed IoT devices/sensors,
a new computing paradigm named "Fog computing" has been introduced. Generally,
Fog computing resides closer to the IoT devices/sensors and extends the
Cloud-based computing, storage and networking facilities. In this chapter, we
comprehensively analyse the challenges in Fogs acting as an intermediate layer
between IoT devices/ sensors and Cloud datacentres and review the current
developments in this field. We present a taxonomy of Fog computing according to
the identified challenges and its key features.We also map the existing works
to the taxonomy in order to identify current research gaps in the area of Fog
computing. Moreover, based on the observations, we propose future directions
for research.


title: Prompt atmospheric neutrino flux from the various QCD models

abstract:
  We evaluate the prompt atmospheric neutrino flux using the different QCD
models for heavy quark production including the $b$ quark contribution. We
include the nuclear correction and find it reduces the fluxes by $10 \% - 50\%$
according to the models. Our heavy quark results are compared with experimental
data from RHIC, LHC and LHCb.


title: A Study of Central Galaxy Rotation with Stellar Mass and Environment

abstract:
  We present a pilot analysis of the influence of galaxy stellar mass and
cluster environment on the probability of slow rotation in 22 central galaxies
at mean redshift $z=0.07$. This includes new integral-field observations of 5
central galaxies selected from the Sloan Digital Sky Survey, observed with the
SPIRAL integral-field spectrograph on the Anglo-Australian Telescope. The
composite sample presented here spans a wide range of stellar masses,
$10.9<$log(M$_{*}/$M$_{\odot})<12.0$, and are embedded in halos ranging from
groups to clusters, $12.9<$log(M$_{200}/$M$_{\odot})<15.6$. We find a mean
probability of slow rotation in our sample of P(SR)$=54\pm7$percent. Our
results show an increasing probability of slow rotation in central galaxies
with increasing stellar mass. However, when we examine the dependence of slow
rotation on host cluster halo mass we do not see a significant relationship. We
also explore the influence of cluster dominance on slow rotation in central
galaxies. Clusters with low dominance are associated with dynamically younger
systems. We find that cluster dominance has no significant effect on the
probability of slow rotation in central galaxies. These results conflict with a
paradigm in which halo mass alone predetermines central galaxy properties.


title:
Distributed Nonsmooth Optimization with Coupled Inequality Constraints
  via Modified Lagrangian Function

abstract:
  This technical note considers a distributed convex optimization problem with
nonsmooth cost functions and coupled nonlinear inequality constraints. To solve
the problem, we first propose a modified Lagrangian function containing local
multipliers and a nonsmooth penalty function. Then we construct a distributed
continuous-time algorithm by virtue of a projected primal-dual subgradient
dynamics. Based on the nonsmooth analysis and Lyapunov function, we obtain the
existence of the solution to the nonsmooth algorithm and its convergence.


title: Efficient simulation of sparse Markovian quantum dynamics

abstract:
  Quantum algorithms for simulating Hamiltonian dynamics have been extensively
developed, but there has been much less work on quantum algorithms for
simulating the dynamics of open quantum systems. We give the first efficient
quantum algorithms for simulating Markovian quantum dynamics generated by
Lindbladians that are not necessarily local. We introduce two approaches to
simulating sparse Lindbladians. First, we show how to simulate Lindbladians
that act within small invariant subspaces using a quantum algorithm to
implement sparse Stinespring isometries. Second, we develop a method for
simulating sparse Lindblad operators by concatenating a sequence of short-time
evolutions. We also show limitations on Lindbladian simulation by proving a
no-fast-forwarding theorem for simulating sparse Lindbladians in black-box
models.


title: Laser controlled charge-transfer reaction at low temperatures

abstract:
  We study the low-temperature charge transfer reaction between a neutral atom
and an ion under the influence of near-resonant laser light. By setting up a
multi-channel model with field-dressed states we demonstrate that the reaction
rate coefficient can be enhanced by several orders of magnitude with laser
intensities of $10^6$ W/cm$^2$ or larger. In addition, depending on laser
frequency one can induce a significant enhancement or suppression of the
charge-exchange rate coefficient. For our intensities multi-photon processes
are not important.


title: Stochastic Gradient Descent in Continuous Time

abstract:
  Stochastic gradient descent in continuous time (SGDCT) provides a
computationally efficient method for the statistical learning of
continuous-time models, which are widely used in science, engineering, and
finance. The SGDCT algorithm follows a (noisy) descent direction along a
continuous stream of data. SGDCT performs an online parameter update in
continuous time, with the parameter updates $\theta_t$ satisfying a stochastic
differential equation. We prove that $\lim_{t \rightarrow \infty} \nabla \bar
g(\theta_t) = 0$ where $\bar g$ is a natural objective function for the
estimation of the continuous-time dynamics. The convergence proof leverages
ergodicity by using an appropriate Poisson equation to help describe the
evolution of the parameters for large times. SGDCT can also be used to solve
continuous-time optimization problems, such as American options. For certain
continuous-time problems, SGDCT has some promising advantages compared to a
traditional stochastic gradient descent algorithm. As an example application,
SGDCT is combined with a deep neural network to price high-dimensional American
options (up to 100 dimensions).


title: Zero-Shot Visual Question Answering

abstract:
  Part of the appeal of Visual Question Answering (VQA) is its promise to
answer new questions about previously unseen images. Most current methods
demand training questions that illustrate every possible concept, and will
therefore never achieve this capability, since the volume of required training
data would be prohibitive. Answering general questions about images requires
methods capable of Zero-Shot VQA, that is, methods able to answer questions
beyond the scope of the training questions. We propose a new evaluation
protocol for VQA methods which measures their ability to perform Zero-Shot VQA,
and in doing so highlights significant practical deficiencies of current
approaches, some of which are masked by the biases in current datasets. We
propose and evaluate several strategies for achieving Zero-Shot VQA, including
methods based on pretrained word embeddings, object classifiers with semantic
embeddings, and test-time retrieval of example images. Our extensive
experiments are intended to serve as baselines for Zero-Shot VQA, and they also
achieve state-of-the-art performance in the standard VQA evaluation setting.


title:
Burst intensification by singularity emitting radiation in multi-stream
  flows

abstract:
  In various media the elementary components can emit traveling waves such as
electromagnetic, gravitational or acoustic types. If these elementary emitters
are synchronized, the resulting emission is coherent. Moreover, the faster the
emitters approach an observer, the more intense and directional their apparent
emission is, with associated frequency increase. Multi-stream flows
ubiquitously occur in media (such as with shock waves and jets in astrophysical
and laboratory plasmas) and produce fast moving density singularities, where
high concentration and synchronism can bring constructive interference.
However, a singularity emitting such characteristic coherent radiation has not
been demonstrated yet. We show this general phenomenon in laser-driven
relativistic plasma, which is an ideal medium for realizing these effects in
the laboratory under controllable conditions. Our experiments and simulations
reveal bright coherent soft x-ray radiation from nanoscale electron density
singularities in multi-stream plasma. They constitute a new compact x-ray
source of ultrashort duration, demanded in numerous applications. In general,
singularities can be bright sources of other types of traveling waves. Thus our
findings open new opportunities in different fields of science. For example,
gravitational wave generation, as proposed in ultrahigh-energy accelerators,
can be significantly enhanced by intentionally induced density singularities in
the particle bunches. Further, we anticipate that multi-stream flows in cosmic
media can produce intense bursts of coherent electromagnetic and/or
gravitational waves, especially at longer wavelengths which facilitate
constructive interference. We can then expect to observe more directional short
wavelength bursts from cosmic emitters approaching at relativistic speeds.
Thus, we present a new framework for interpreting a broad range of experimental
results.


title:
Multiple Access Technologies for cellular M2M Communications: An
  Overview

abstract:
  This paper reviews the multiple access techniques for machine-to-machine
(M2M) communications in future wireless cellular networks. M2M communications
aims at providing te communication infrastructure for the emerging Internet of
Things (IoT), which will revolutionize the way we interact with our surrounding
physical environment. We provide an overview of the multiple access strategies
and explain their limitations when used for M2M communications. We show the
throughput efficiency of different multiple access techniques when used in
coordinated and uncoordinated scenarios. Non-orthogonal multiple access is also
shown to support a larger number of devices compared to orthogonal multiple
access techniques, especially in uncoordinated scenarios. We also detail the
issues and challenges of different multiple access techniques to be used for
M2M applications in cellular networks.


title: Parallel multiple selection by regular sampling

abstract:
  In this paper we present a deterministic parallel algorithm solving the
multiple selection problem in congested clique model. In this problem for given
set of elements S and a set of ranks $K = \{k_1 , k_2 , ..., k_r \}$ we are
asking for the $k_i$-th smallest element of $S$ for $1 \leq i \leq r$. The
presented algorithm is deterministic, time optimal , and needs $O(\log^*_{r+1}
(n))$ communication rounds, where $n$ is the size of the input set, and $r$ is
the size of the rank set. This algorithm may be of theoretical interest, as for
$r = 1$ (classic selection problem) it gives an improvement in the asymptotic
synchronization cost over previous $O(\log \log p)$ communication rounds
solution, where $p$ is size of clique.


title: $e$PCA: High Dimensional Exponential Family PCA

abstract:
  Many applications, such as photon-limited imaging and genomics, involve large
datasets with noisy entries from exponential family distributions. It is of
interest to estimate the covariance structure and principal components of the
noiseless distribution. Principal Component Analysis (PCA), the standard method
for this setting, can be inefficient when the noise is non-Gaussian.
  We develop $e$PCA (exponential family PCA), a new methodology for PCA on
exponential family distributions. $e$PCA can be used for dimensionality
reduction and denoising of large data matrices. $e$PCA involves the
eigendecomposition of a new covariance matrix estimator, constructed in a
simple and deterministic way using moment calculations, shrinkage, and random
matrix theory.
  We provide several theoretical justifications for our estimator, including
the finite-sample convergence rate, and the Marchenko-Pastur law in high
dimensions. $e$PCA compares favorably to PCA and various PCA alternatives for
exponential families, in simulations as well as in XFEL and SNP data analysis.
An open-source implementation is available.


title: Local Conjugacy of Irreducible Hyperbolic Toral Automorphisms

abstract:
  This paper is dedicated to the conjugacy problem in $GL(n,\Z)$ and its
connection with algebraic number theory. This connection may be summed up in
the Latimer-MacDuffee-Taussky Theorem, which, in a very broad sense, identifies
the conjugacy relation in $GL(n,\Z)$ with the relation of arithmetic
equivalence between certain ideals of algebraic numbers. The main purpouse is
to clarify the link between a weaker relation between ideals, weak equivalence,
and local conjugacy in $GL(n,\Z)$, i.e., the conjugacy of $GL(n,\Z)$ matrices
in the groups $GL(n,\Z_{p})$ of invertible matrices over the $p$-adic integers.


title:
DelugeNets: Deep Networks with Efficient and Flexible Cross-layer
  Information Inflows

abstract:
  Deluge Networks (DelugeNets) are deep neural networks which efficiently
facilitate massive cross-layer information inflows from preceding layers to
succeeding layers. The connections between layers in DelugeNets are established
through cross-layer depthwise convolutional layers with learnable filters,
acting as a flexible yet efficient selection mechanism. DelugeNets can
propagate information across many layers with greater flexibility and utilize
network parameters more effectively compared to ResNets, whilst being more
efficient than DenseNets. Remarkably, a DelugeNet model with just model
complexity of 4.31 GigaFLOPs and 20.2M network parameters, achieve
classification errors of 3.76% and 19.02% on CIFAR-10 and CIFAR-100 dataset
respectively. Moreover, DelugeNet-122 performs competitively to ResNet-200 on
ImageNet dataset, despite costing merely half of the computations needed by the
latter.


title:
Tunable Photonic Radiofrequency Filter with An Ultra-high Out-Of-Band
  Rejection

abstract:
  As radiofrequency filtering plays a vital role in electromagnetic devices and
systems, recently photonic techniques have been intensively studied to
implement radiofrequency filters to harness wide frequency coverage, large
instantaneous bandwidth, low frequency-dependent loss, flexible tunability and
strong immunity to electromagnetic interference. However, one crucial challenge
facing the photonic radiofrequency filter (PRF) is the less impressive
out-of-band rejection. Here, to the best of our knowledge, we demonstrate a
tunable PRF with a record out-of-band rejection of 80 dB, which is 3 dB higher
than the maximum value (~77 dB) reported so far, when incorporating highly
selective polarization control and large narrow-band amplification enabled by
stimulated Brillouin scattering effect. In particular, this record rejection is
arduous to be achieved for a narrow passband (e.g., a few megahertz) and a high
finesse in a PRF. Moreover, the proposed PRF is an active one capable of
providing negligible insertion loss and even signal gain. Tunable central
frequency ranging from 2.1 to 6.1 GHz is also demonstrated. The proposed PRF
will provide an ultra-high noise or clutter suppression for harsh
electromagnetic scenarios, particularly when room-temperature implementation
and remote distribution are needed.


title:
Studying neutral hydrogen structures during the epoch of reionization
  using fractal dimensions

abstract:
  Fractal dimensions can be used to characterize the clustering and
lacunarities in density distributions. We use generalized fractal dimensions to
study the neutral hydrogen distribution (HI) during the epoch of reionization.
Using a semi-numeric model of ionized bubbles to generate the HI field, we
calculate the fractal dimensions for length scales $\sim 10 h^{-1}$ cMpc. We
find that the HI field displays significant multifractal behaviour and is not
consistent with homogeneity at these scales when the mass averaged neutral
fraction $\bar{x}_{\rm HI}^M \gtrsim 0.5$. This multifractal nature is driven
entirely by the shapes and distribution of the ionized regions. The sensitivity
of the fractal dimension to the neutral fraction implies that it can be used
for constraining reionization history. We find that the fractal dimension is
relatively less sensitive to the value of the minimum mass of ionizing haloes
when it is in the range $\sim 10^9 - 10^{10} h^{-1} M_{\odot}$. Interestingly,
the fractal dimension is very different when the reionization proceeds
inside-out compared to when it is outside-in. Thus the multifractal nature of
HI density field at high redshifts can be used to study the nature of
reionization.


title: A Homology Theory For A Special Family Of Semi-groups

abstract:
  In this paper, we construct a new homology theory for semi-groups satisfying
the self distributivity axiom or the idempotency axiom. Next, we consider the
geometric realization corresponding to the homology theory. We continue with
the comparison of this homology theory with one term and two term (rack)
homology theories of self-distributive algebraic structures. Finally, we
propose connections between the homology theory and knot theory via
Temperley-Lieb algebras.


title: Throughput of TCP over Cognitive Radio Channels

abstract:
  In this paper, we study the performance of a TCP connection over cognitive
radio networks. In these networks, the network may not always be available for
transmission. Also, the packets can be lost due to wireless channel
impairments. We evaluate the throughput and packet retransmission timeout
probability of a secondary TCP connection over an ON/OFF channel. We first
assume that the ON and OFF time durations are exponential and later extend it
to more general distributions. We then consider multiple TCP connections over
the ON/OFF channel. We validate our theoretical models and the approximations
made therein via ns2 simulations.


title:
A Prudent-Precedence Concurrency Control Protocol for High Data
  Contention Database Enviornments

abstract:
  In this paper, we propose a concurrency control protocol, called the
Prudent-Precedence Concurrency Control (PPCC) protocol, for high data
contention database environments. PPCC is prudently more aggressive in
permitting more serializable schedules than two-phase locking. It maintains a
restricted precedence among conflicting transactions and commits the
transactions according to the serialization order established in the
executions. A detailed simulation model has been constructed and extensive
experiments have been conducted to evaluate the performance of the proposed
approach. The results demonstrate that the proposed algorithm outperforms the
two-phase locking and optimistic concurrency control in all ranges of system
workload.


title: Probabilistic Rank and Matrix Rigidity

abstract:
  We consider a notion of probabilistic rank and probabilistic sign-rank of a
matrix, which measures the extent to which a matrix can be probabilistically
represented by low-rank matrices. We demonstrate several connections with
matrix rigidity, communication complexity, and circuit lower bounds, including:
  The Walsh-Hadamard Transform is Not Very Rigid. We give surprising upper
bounds on the rigidity of a family of matrices whose rigidity has been
extensively studied, and was conjectured to be highly rigid. For the $2^n
\times 2^n$ Walsh-Hadamard transform $H_n$ (a.k.a. Sylvester matrices, or the
communication matrix of Inner Product mod 2), we show how to modify only
$2^{\epsilon n}$ entries in each row and make the rank drop below
$2^{n(1-\Omega(\epsilon^2/\log(1/\epsilon)))}$, for all $\epsilon > 0$, over
any field. That is, it is not possible to prove arithmetic circuit lower bounds
on Hadamard matrices, via L. Valiant's matrix rigidity approach. We also show
non-trivial rigidity upper bounds for $H_n$ with smaller target rank.
  Matrix Rigidity and Threshold Circuit Lower Bounds. We give new consequences
of rigid matrices for Boolean circuit complexity. We show that explicit $n
\times n$ Boolean matrices which maintain rank at least $2^{(\log
n)^{1-\delta}}$ after $n^2/2^{(\log n)^{\delta/2}}$ modified entries would
yield a function lacking sub-quadratic-size $AC^0$ circuits with two layers of
arbitrary linear threshold gates. We also prove that explicit 0/1 matrices over
$\mathbb{R}$ which are modestly more rigid than the best known rigidity lower
bounds for sign-rank would imply strong lower bounds for the infamously
difficult class $THR\circ THR$.


title: Boosting Variational Inference

abstract:
  Variational inference (VI) provides fast approximations of a Bayesian
posterior in part because it formulates posterior approximation as an
optimization problem: to find the closest distribution to the exact posterior
over some family of distributions. For practical reasons, the family of
distributions in VI is usually constrained so that it does not include the
exact posterior, even as a limit point. Thus, no matter how long VI is run, the
resulting approximation will not approach the exact posterior. We propose to
instead consider a more flexible approximating family consisting of all
possible finite mixtures of a parametric base distribution (e.g., Gaussian).
For efficient inference, we borrow ideas from gradient boosting to develop an
algorithm we call boosting variational inference (BVI). BVI iteratively
improves the current approximation by mixing it with a new component from the
base distribution family and thereby yields progressively more accurate
posterior approximations as more computing time is spent. Unlike a number of
common VI variants including mean-field VI, BVI is able to capture
multimodality, general posterior covariance, and nonstandard posterior shapes.


title:
MHz Gravitational Wave Constraints with Decameter Michelson
  Interferometers

abstract:
  A new detector, the Fermilab Holometer, consists of separate yet identical
39-meter Michelson interferometers. Strain sensitivity achieved is better than
$10^{-21} /{\sqrt{\rm{Hz}}}$ between 1 to 13 MHz from a 130-hr dataset. This
measurement exceeds the sensitivity and frequency range made from previous high
frequency gravitational wave experiments by many orders of magnitude.
Constraints are placed on a stochastic background at 382 Hz resolution. The
3$\sigma$ upper limit on $\Omega_{\rm{GW}}$, the gravitational wave energy
density normalized to the closure density, ranges from $5.6 \times 10^{12}$ at
1 MHz to $8.4 \times 10^{15}$ at 13 MHz. Another result from the same dataset
is a search for nearby primordial black hole binaries (PBHB). There are no
detectable monochromatic PBHBs in the mass range $0.83$ - $3.5 \times 10^{21}$g
between the earth and the moon. Projections for a chirp search with the same
dataset increases the mass range to $0.59 - 2.5 \times 10^{25}$g and distances
out to Jupiter. This result presents a new method for placing limits on a
poorly constrained mass range of primordial black holes. Additionally, solar
system searches for PBHBs place limits on their contribution to the total dark
matter fraction.


title:
A Fast and Provable Method for Estimating Clique Counts Using Tur\'an's
  Theorem

abstract:
  Clique counts reveal important properties about the structure of massive
graphs, especially social networks. The simple setting of just 3-cliques
(triangles) has received much attention from the research community. For larger
cliques (even, say 6-cliques) the problem quickly becomes intractable because
of combinatorial explosion. Most methods used for triangle counting do not
scale for large cliques, and existing algorithms require massive parallelism to
be feasible.
  We present a new randomized algorithm that provably approximates the number
of k-cliques, for any constant k. The key insight is the use of (strengthenings
of) the classic Tur\'an's theorem: this claims that if the edge density of a
graph is sufficiently high, the k-clique density must be non-trivial. We define
a combinatorial structure called a Tur\'an shadow, the construction of which
leads to fast algorithms for clique counting.
  We design a practical heuristic, called TUR\'AN-SHADOW, based on this
theoretical algorithm, and test it on a large class of test graphs. In all
cases,TUR\'AN-SHADOW has less than 2% error, in a fraction of the time used by
well-tuned exact algorithms. We do detailed comparisons with a range of other
sampling algorithms, and find that TUR\'AN-SHADOW is generally much faster and
more accurate. For example, TUR\'AN-SHADOW estimates all cliques numbers up to
size 10 in social network with over a hundred million edges. This is done in
less than three hours on a single commodity machine.


title:
On the extreme values of the Riemann zeta function on random intervals
  of the critical line

abstract:
  In the present paper, we show that under the Riemann hypothesis, and for
fixed $h, \epsilon > 0$, the supremum of the real and the imaginary parts of
$\log \zeta (1/2 + it)$ for $t \in [UT -h, UT + h]$ are in the interval
$[(1-\epsilon) \log \log T, (1+ \epsilon) \log \log T]$ with probability
tending to $1$ when $T$ goes to infinity, if $U$ is uniformly distributed in
$[0,1]$. This proves a weak version of a conjecture by Fyodorov, Hiary and
Keating, which has recently been intensively studied in the setting of random
matrices. We also unconditionally show that the supremum of $\Re \log \zeta(1/2
+ it)$ is at most $\log \log T + g(T)$ with probability tending to $1$, $g$
being any function tending to infinity at infinity.


title:
Central charge from adiabatic transport of cusp singularities in the
  quantum Hall effect

abstract:
  We study quantum Hall (QH) states on a punctured Riemann sphere. We compute
the Berry curvature under adiabatic motion in the moduli space in the large N
limit. The Berry curvature is shown to be finite in the large N limit and
controlled by the conformal dimension of the cusp singularity, a local property
of the mean density. Utilizing exact sum rules obtained from a Ward identity,
we show that for the Laughlin wave function, the dimension of a cusp
singularity is given by the central charge, a robust geometric response
coefficient in the QHE. Thus, adiabatic transport of curvature singularities
can be used to determine the central charge of QH states. We also consider the
effects of threaded fluxes and spin-deformed wave functions. Finally, we give a
closed expression for all moments of the mean density in the integer QH state
on a punctured disk.


title: A Note on Quantum-Secure PRPs

abstract:
  We show how to construct pseudorandom permutations (PRPs) that remain secure
even if the adversary can query the permutation on a quantum superposition of
inputs. Such PRPs are called \emph{quantum-secure}. Our construction combines a
quantum-secure pseudorandom \emph{function} together with constructions of
\emph{classical} format preserving encryption. By combining known results, we
obtain the first quantum-secure PRP in this model whose security relies only on
the existence of one-way functions. Previously, to the best of the author's
knowledge, quantum security of PRPs had to be assumed, and there were no prior
security reductions to simpler primitives, let alone one-way functions.


title: 3FGL J1924.8-1034 : A Spatially-Extended Stable Unidentified GeV Source?

abstract:
  Milky Way-like galaxies are predicted to host a very large number of dark
matter subhalos. Some massive and nearby subhalos could generate detectable
gamma-rays, appearing as unidentified, spatially-extended and stable gamma-ray
sources. We search for such sources in the third Fermi Large Area Telescope
source List (3FGL) and report the identification of a new candidate, 3FGL
J1924.8-1034. With the Fermi-LAT Pass 8 data, we find that 3FGL J1924.8-1034 is
spatially-extended at a high confidence level of $5.4\sigma$, with a best-fit
extension radius of $\sim0.15^{\circ}$. No significant variability has been
found and its gamma-ray spectrum is well fitted by the dark matter annihilation
into $b\bar{b}$ with a mass of $\sim 43$ GeV. All these facts make 3FGL
J1924.8-1034 a possible dark matter subhalo candidate. However, due to the
limited angular resolution, the possibility of that the spatial extension of
3FGL J1924.8-1034 is caused by the contamination from the other un-resolved
point source can not be ruled out.


title: Are Quasiparticles and Phonons Identical in Bose--Einstein Condensates?

abstract:
  We study an interacting spinless Bose-Einstein condensate to clarify
theoretically whether the spectra of its quasiparticles (one-particle
excitations) and collective modes (two-particle excitations) are identical, as
concluded by Gavoret and Nozi\`eres [Ann. Phys. 28, 349 (1964)]. We derive
analytic expressions for their first and second moments so as to extend the
Bijl-Feynman formula for the peak of the collective-mode spectrum to its width
(inverse lifetime) and also to the one-particle channel. The obtained formulas
indicate that the width of the collective-mode spectrum manifestly vanishes in
the long-wavelength limit, whereas that of the quasiparticle spectrum
apparently remains finite. We also evaluate the peaks and widths of the two
spectra numerically for a model interaction potential in terms of the Jastrow
wave function optimized by a variational method. It is thereby found that the
width of the quasiparticle spectrum increases towards a constant as the
wavenumber decreases. This marked difference in the spectral widths implies
that the two spectra are distinct. In particular, the lifetime of the
quasiparticles remains finite even in the long-wavelength limit.

categories: cond-mat.quant-gas cond-mat.stat-mech cond-mat.str-el cond-mat.supr-con


title:
Refined global Gross-Prasad conjecture on special Bessel periods and
  Boecherer's conjecture

abstract:
  In this paper we pursue the refined global Gross-Prasad conjecture for Bessel
periods formulated by Yifeng Liu in the case of special Bessel periods for
$\mathrm{SO}\left(2n+1\right)\times\mathrm{SO}\left(2\right)$. Recall that a
Bessel period for $\mathrm{SO}\left(2n+1\right)\times\mathrm{SO}\left(2\right)$
is called special when the representation of $\mathrm{SO}\left(2\right)$ is
trivial. Let $\pi$ be an irreducible cuspidal tempered automorphic
representation of a special orthogonal group of an odd dimensional quadratic
space over a totally real number field $F$ whose local component $\pi_v$ at any
archimedean place $v$ of $F$ is a discrete series representation. Let $E$ be a
quadratic extension of $F$ and suppose that the special Bessel period
corresponding to $E$ does not vanish identically on $\pi$. Then we prove the
Ichino-Ikeda type explicit formula conjectured by Liu for the central value
$L\left(1/2,\pi\right)L\left(1/2,\pi\times\chi_E\right)$, where $\chi_E$
denotes the quadratic character corresponding to $E$. Our result yields a proof
of Boecherer's conecture on holomorphic Siegel cusp forms of degree two which
are Hecke eigenforms.


title:
Hund's metallicity and orbital-selective Mott localization of CrO$_{2}$
  in the paramagnetic state

abstract:
  We present electronic structure calculations of a CrO$_{2}$ compound in the
paramagnetic state within the computational scheme of density-functional theory
combined with dynamical mean-field theory. We find that CrO$_{2}$ in the
paramagnetic state is a strongly-correlated Hund's metal with mixed-valent Cr
ions. At high temperatures, CrO$_{2}$ shows an orbital-selective Mott phase, in
which the Cr $d_{xy}$ orbital is Mott-localized while the other Cr $t_{2g}$ $d$
orbitals remain itinerant. When the temperature is lowered, the
orbital-selective Mott state is found to evolve into a Kondo-like heavy-fermion
state with a small pseudo gap at the Fermi level if the system remains in the
paramagnetic state.


title: An Analytical Model for S-ALOHA Performance Evaluation in M2M Networks

abstract:
  The S-ALOHA (i.e. slotted-ALOHA) protocol is recently regaining interest in
Lower Power Wide Area Networks (LPWAN) handling M2M traffic. Despite intensive
studies since the birth of S-ALOHA, the special features of M2M traffic and
requirements highlight the importance of analytical models taking into account
performance-affecting factors and giving a thorough performance evaluation.
Fulfilling this necessity is the main focus of this paper: we jointly consider
the impact of capture effect, diversity of transmit power levels with imperfect
power control. We propose a low-complexity but still accurate analytical model
capable of evaluating S-ALOHA in terms of packet loss rate, throughput,
energy-efficiency and average number of transmissions. The proposed model is
able to facilitate dimensioning and design of S-ALOHA based LPWAN. The
comparison between simulation and analytical results confirms the accuracy of
our proposed model. The design guides about S-ALOHA based LPWAN deduced from
our model are: the imperfect power control can be positive with capture effect
and and appropriate transmit power diversity strategy. The transmit power
diversity strategy should be determined by jointly considering network charges
level, power control precision and capture ratio to achieve optimal performance
of S-ALOHA.


title: Discovering the Unexpected in Astronomical Survey Data

abstract:
  Most major discoveries in astronomy are unplanned, and result from surveying
the Universe in a new way, rather than by testing a hypothesis or conducting an
investigation with planned outcomes. For example, of the 10 greatest
discoveries made by the Hubble Space Telescope, only one was listed in its key
science goals. So a telescope that merely achieves its stated science goals is
not achieving its potential scientific productivity. Several next-generation
astronomical survey telescopes are currently being designed and constructed
that will significantly expand the volume of observational parameter space, and
should in principle discover unexpected new phenomena and new types of object.
However, the complexity of the telescopes and the large data volumes mean that
these discoveries are unlikely to be found by chance. Therefore, it is
necessary to plan explicitly for these unexpected discoveries in the design and
construction of the telescope. Two types of discovery are recognised:
unexpected objects, and unexpected phenomena. This paper argues that
next-generation astronomical surveys require an explicit process for detecting
the unexpected, and proposes an implementation of this process. This
implementation addresses both types of discovery, and relies heavily on
machine-learning techniques, and also on theory-based simulations that
encapsulate our current understanding of the Universe to compare with the data.


title: Random matrix approach to estimation of high-dimensional factor models

abstract:
  In dealing with high-dimensional data sets, factor models are often useful
for dimension reduction. The estimation of factor models has been actively
studied in various fields. In the first part of this paper, we present a new
approach to estimate high-dimensional factor models, using the empirical
spectral density of residuals. The spectrum of covariance matrices from
financial data typically exhibits two characteristic aspects: a few spikes and
bulk. The former represent factors that mainly drive the features and the
latter arises from idiosyncratic noise. Motivated by these two aspects, we
consider a minimum distance between two spectrums; one from a covariance
structure model and the other from real residuals of financial data that are
obtained by subtracting principal components. Our method simultaneously
provides estimators of the number of factors and information about correlation
structures in residuals. Using free random variable techniques, the proposed
algorithm can be implemented and controlled effectively. Monte Carlo
simulations confirm that our method is robust to noise or the presence of weak
factors. Furthermore, the application to financial time-series shows that our
estimators capture essential aspects of market dynamics.


title:
On the central role of the scale invariant Poisson processes on
  (0,infty)

abstract:
  The scale invariant Poisson processes on (0,infty) play a central but mildly
disguised role in number theory, combinatorics, and genetics. They give the
continuous limits which underly and unify diverse discrete structures,
including the prime factorization of a uniformly chosen integer, the
factorization of polynomials over finite fields, the decomposition into cycles
of random permutations, the decomposition into components of random mappings,
and the Ewens sampling formula. They deserve attention as one of the
fundamental and central objects of probability theory.


title: Weyl Bogoliubov excitations in Bose-Hubbard extension of Weyl semimetal

abstract:
  In this paper, a Bose-Hubbard extension of a Weyl semimetal is proposed that
can be realized for ultracold atoms using laser assisted tunneling and Feshbach
resonance technique in three dimensional optical lattices. The global phase
diagram is obtained consisting of a superfluid phase and various Mott insulator
phases by using Landau theory. The Bogoliubov excitation modes for the weakly
interacting case have nontrivial properties (Weyl nodes, bosonic surface arc,
etc.) analogs of those in Weyl semimetals of electronic systems, which are
smoothly carried over to that of Bloch bands for the noninteracting case. The
properties of the insulating phases for the strongly interacting case are
explored by calculating both the quasiparticle and quasihole dispersion
relation, which shows two quasiparticle spectra touch at Weyl nodes.


title:
Intrinsic parallel rotation drive by electromagnetic ion temperature
  gradient turbulence

abstract:
  The quasilinear intrinsic parallel flow drive including parallel residual
stress, kinetic stress, cross Maxwell stress and parallel turbulent
acceleration by electromagnetic ion temperature gradient (ITG) turbulence is
calculated analytically using electromagnetic gyrokinetic theory. Both the
kinetic stress and cross Maxwell stress also enter the mean parallel flow
velocity equation via their divergence, as for the usual residual stress. The
turbulent acceleration driven by ion pressure gradient along the total magnetic
field (including equilibrium magnetic field and fluctuating radial magnetic
field) cannot be written as a divergence of stress, and so should be treated as
a local source/sink. All these terms can provide intrinsic parallel rotation
drive. Electromagnetic effects reduce the non-resonant electrostatic stress
force and even reverse it, but enhance the resonant stress force. Both the
non-resonant and resonant turbulent acceleration terms are also enhanced by
electromagnetic effects. The possible implications of our results for
experimental observations are discussed.


title:
Deformation behaviour of body centered cubic iron nanopillars containing
  coherent twin boundaries

abstract:
  Molecular dynamics simulations were performed to understand the role of twin
boundaries on deformation behaviour of body-centred cubic (BCC) iron (Fe)
nanopillars. The twin boundaries varying from one to five providing twin
boundary spacing in the range 8.5 - 2.8 nm were introduced perpendicular to the
loading direction. The simulation results indicated that the twin boundaries in
BCC Fe play a contrasting role during deformation under tensile and compressive
loadings. During tensile deformation, a large reduction in yield stress was
observed in twinned nanopillars compared to perfect nanopillar. However, the
yield stress exhibited only marginal variation with respect to twin boundary
spacing. On the contrary, a decrease in yield stress with increase in twin
boundary spacing was obtained during compressive deformation. This contrasting
behaviour originates from difference in operating mechanisms during yielding
and subsequent plastic deformation. It has been observed that the deformation
under tensile loading was dominated mainly by twin growth mechanism, due to
which the twin boundaries offers a negligible resistance to slip of twinning
partials. This is reflected in the negligible variation of yield stress as a
function of twin boundary spacing. On the other hand, the deformation was
dominated by nucleation and slip of full dislocations under compressive
loading. The twin boundaries offer a strong repulsive force on full
dislocations resulting in the yield stress dependence on twin boundary spacing.
Further, it has been observed that the curved twin boundary can acts as a
source for full dislocation. The occurrence of twin-twin interaction during
tensile deformation and dislocation-twin interaction during compressive
deformation were presented and discussed.


title:
Multigrid Methods for A Mixed Finite Element Method of The
  Darcy-Forchheimer Model

abstract:
  An efficient nonlinear multigrid method for a mixed finite element method of
the Darcy-Forchheimer model is constructed in this paper. A Peaceman-Rachford
type iteration is used as a smoother to decouple the nonlinearity from the
divergence constraint. The nonlinear equation can be solved element-wise with a
closed formulae. The linear saddle point system for the constraint is reduced
into a symmetric positive definite system of Poisson type. Furthermore an
empirical choice of the parameter used in the splitting is proposed and the
resulting multigrid method is robust to the so-called Forchheimer number which
controls the strength of the nonlinearity. By comparing the number of
iterations and CPU time of different solvers in several numerical experiments,
our multigrid method is shown to convergent with a rate independent of the mesh
size and the Forchheimer number and with a nearly linear computational cost.


title: Hexagonalization of Correlation Functions

abstract:
  We propose a nonperturbative framework to study general correlation functions
of single-trace operators in $\mathcal{N}=4$ supersymmetric Yang-Mills theory
at large $N$. The basic strategy is to decompose them into fundamental building
blocks called the hexagon form factors, which were introduced earlier to study
structure constants using integrability. The decomposition is akin to a
triangulation of a Riemann surface, and we thus call it hexagonalization. We
propose a set of rules to glue the hexagons together based on symmetry, which
naturally incorporate the dependence on the conformal and the R-symmetry cross
ratios. Our method is conceptually different from the conventional operator
product expansion and automatically takes into account multi-trace operators
exchanged in OPE channels. To illustrate the idea in simple set-ups, we compute
four-point functions of BPS operators of arbitrary lengths and correlation
functions of one Konishi operator and three short BPS operators, all at one
loop. In all cases, the results are in perfect agreement with the perturbative
data. We also suggest that our method can be a useful tool to study conformal
integrals, and show it explicitly for the case of ladder integrals.


title: Low-temperature heat transport of spin-gapped quantum magnets

abstract:
  This article reviews low-temperature heat transport studies of spin-gapped
quantum magnets in the last few decades. Quantum magnets with small spins and
low dimensionality exhibit a variety of novel phenomena. Among them, some
systems are char-acteristic of having quantum-mechanism spin gap in their
magnetic excitation spectra, including spin-Peierls systems, S = 1 Haldane
chains, S = 1/2 spin ladders, and spin dimmers. In some particular spin-gapped
systems, the XY-type antiferromagnetic state induced by magnetic field that
closes the spin gap can be described as a magnon Bose-Einstein condensation
(BEC). Heat transport is effective in probing the magnetic excitations and
magnetic phase transitions, and has been extensively studied for the
spin-gapped systems. A large and ballistic spin thermal conductivity was
observed in the two-leg Heisenberg S = 1/2 ladder compounds. The characteristic
of magnetic thermal transport of the Haldane chain systems is quite
controversial on both the theoretical and experimental results. For the
spin-Peierls system, the spin excitations can also act as heat carriers. In
spin-dimer compounds, the magnetic excitations mainly play a role of scattering
phonons. The magnetic excitations in the magnon BEC systems displayed dual
roles, carrying heat or scattering phonons, in different materials.


title:
Bus Stops Location and Bus Route Planning Using Mean Shift Clustering
  and Ant Colony in West Jakarta

abstract:
  Traffic Jam has been a daily problem for people in Jakarta which is one of
the busiest city in Indonesia up until now. Even though the official government
has tried to reduce the impact of traffic issues by developing a new public
transportation which takes up a lot of resources and time, it failed to
diminish the problem. The actual concern to this problem actually lies in how
people move between places in Jakarta where they always using their own vehicle
like cars, and motorcycles that fill most of the street in Jakarta. Among much
other public transportations that roams the street of Jakarta, Buses is
believed to be an efficient transportation that can move many people at once.
However, the location of the bus stop is now have moved to the middle of the
main road, and it is too far for the nearby residence to access to it. This
paper proposes an optimal location of optimal bus stops in West Jakarta that is
experimentally proven to have a maximal distance of 350 m. The optimal location
is estimated by means of mean shift clustering method while the optimal routes
are calculated using Ant Colony algorithm. The bus stops locations rate of
error is 0.07% with overall route area of 32 km. Based on our experiments, we
believe our proposed bus stop plan can be an interesting alternative to reduce
traffic congestion in West Jakarta.


title:
Radio-interferometric monitoring of FRB 131104: A coincident AGN flare,
  but no evidence for a cosmic fireball

abstract:
  The localization of fast radio bursts (FRBs) has been hindered by the poor
angular resolution of the detection observations and inconclusive
identification of transient or variable counterparts. Recently a $\gamma$-ray
pulse of $380$ s duration has been associated with the fast radio burst FRB
131104. We report on radio-continuum imaging observations of the original
localization region of the FRB, beginning three days after the event and
comprising 25 epochs over 2.5 yr. Besides probabilistic arguments that suggest
that the association between the $\gamma$-ray transient and the FRB is not
compelling, we provide upper limits on a putative radio afterglow of this
transient that are at odds with standard models for its progenitor. We further
report the discovery of an unusual variable radio source spatially and
temporally coincident with FRB 131104, but not spatially coincident with the
$\gamma$-ray event. The radio variable flares by a factor of $3$ above its long
term average within $10$ d of the FRB at 7.5 GHz, with a factor-of-$2$ increase
at $5.5$ GHz. Within our observations, the variable has persisted with only
modest modulation and never approached the flux density observed in the days
after the FRB. We identify an optical counterpart to the variable. Optical and
infrared photometry, and deep optical spectroscopy, suggest that the object is
a narrow-line radio AGN.


title:
Higher genus Kashiwara-Vergne problems and the Goldman-Turaev Lie
  bialgebra

abstract:
  We define a family ${\rm KV}^{(g,n)}$ of Kashiwara-Vergne problems associated
with compact connected oriented 2-manifolds of genus $g$ with $n+1$ boundary
components. The problem ${\rm KV}^{(0,3)}$ is the classical Kashiwara-Vergne
problem from Lie theory. We show the existence of solutions of ${\rm
KV}^{(g,n)}$ for arbitrary $g$ and $n$. The key point is the solution of ${\rm
KV}^{(1,1)}$ based on the results by B. Enriquez on elliptic associators. Our
construction is motivated by applications to the formality problem for the
Goldman-Turaev Lie bialgebra $\mathfrak{g}^{(g, n+1)}$. In more detail, we show
that every solution of ${\rm KV}^{(g,n)}$ induces a Lie bialgebra isomorphism
between $\mathfrak{g}^{(g, n+1)}$ and its associated graded ${\rm gr} \,
\mathfrak{g}^{(g, n+1)}$. For $g=0$, a similar result was obtained by G.
Massuyeau using the Kontsevich integral.
  This paper is a summary of our results. Details and proofs will appear
elsewhere.


title: Black hole evaporation in conformal gravity

abstract:
  We study the formation and the evaporation of a spherically symmetric black
hole in conformal gravity. From the collapse of a spherically symmetric thin
shell of radiation, we find a singularity-free non-rotating black hole. This
black hole has the same Hawking temperature as a Schwarzschild black hole with
the same mass, and it completely evaporates either in a finite or in an
infinite time, depending on the ensemble. We consider the analysis both in the
canonical and in the micro-canonical statistical ensembles. Last, we discuss
the corresponding Penrose diagram of this physical process.

categories: gr-qc astro-ph.HE hep-th math-ph math.MP


title:
The Thermal Proximity Effect: A New Probe of He II Reionization History
  and the Quasar Lifetime

abstract:
  Despite decades of effort, the timing and duration of He II reionization, as
well as its morphology and the properties of the quasars believed to drive it,
are still not well constrained. In this paper we present a new method to study
both He II reionization and quasars via the thermal proximity effect -- the
photoelectric heating of the intergalactic medium around quasars when their
hard radiation doubly ionizes helium. We post-process a SPH simulation with 1D
radiative calculations, and study how the thermal proximity effect depends on
the amount of singly ionized helium, $x_{\rm HeII,0}$, which prevailed in the
IGM before the quasar turned on, and the characteristic lifetime $t_{\rm Q}$
for which quasars shine. We find that the amplitude of the temperature boost in
the quasar environment depends on $x_{\rm HeII,0}$, with a characteristic value
of $\Delta T \simeq 10^4\,{\rm K}$ for an initially singly ionized IGM ($x_{\rm
HeII,0} = 1.0$), whereas the size of the thermal proximity zone is sensitive to
quasar lifetime $t_{\rm Q}$, with typical sizes of ~100 cMpc for luminous
quasars shining for $t_{\rm Q}=10^8$ yr. This temperature boost is manifest as
a change in the thermal broadening of H I absorption lines near the quasar. We
introduce a new method based on measuring the Ly$\alpha$ forest power spectrum
as a function of distance from the quasar, and conduct Bayesian MCMC analysis
to demonstrate that the thermal proximity effect should be easily detectable.
For a mock dataset of 50 quasars at z~4, we predict that one can measure
$x_{\rm HeII,0}$ to a precision $\approx 0.04$, and $t_{\rm Q}$ to a precision
of $\approx 0.1$ dex. By applying our formalism to existing high-resolution
Ly$\alpha$ forest spectra of quasars at $3.1 \lesssim z \lesssim 5.0$, one
should be able to detect the thermal proximity effect, and reconstruct the full
reionization history of He II.


title:
Effect of symmetry on the electronic DOS, charge fluctuations and
  electron-phonon coupling in carbon chains

abstract:
  A theoretical model is provided to address the parameters influencing the
electronic properties of kink-structured carbon chain at 0K. It is studied by
the principle of DFT and solving the numerical 1D time-independent
Schr\"odinger equation of electron and phonon simultaneously. Two different
lengths of branches A and B, are occupied alternatively to generate the
asymmetric carbon chain. The ratio of the asymmetric branch length,RAB=A/B,
plays an important role in the electronic density of states DOS around Fermi
level Ef . The highest DOS(Ef) occurs if the RAB equals to 2 and while the
Fermi level coincides with the Von-Hove singularity at RAB=3. The location of
the singularity point relative to the Ef is controllable via branch length
interestingly. By comparison with the symmetric case, tuning the branch length
asymmetrically shows a stronger impact to shift the Ef to the singularity
point. The numerical solution of the 1D time independent Schrodinger equation
of phonon indicates that the kink reinforces the charge fluctuations but the
fluctuations are minimized when the RAB goes up. Based on the simulation
results, the electron phonon coupling of the carbon nanowire decreases with
chain length. In comparison to the symmetric structure, the electron phonon
coupling of the asymmetric carbon chain is higher. The maximum electron phonon
coupling of the asymmetric carbon chain takes place at RAB=2 . However, the
weakening of the electron phonon coupling is observed owing to ultrahigh
concentration of kinks. The reduction of the electron phonon coupling of the
carbon chain is occurred under pressure.


title:
Exact convergence order of the $L_r$-quantization error for Markov-type
  measures

abstract:
  Let $E$ be a graph-directed set associated with a di-graph $G$. Let $\mu$ be
a Markov-type measure on $E$. Assuming a separation condition for $E$, we
determine the exact convergence order of the $L_r$-quantization error for
$\mu$. This result provides us with accurate information on the asymptotics of
the quantization error, especially when the quantization coefficient is
infinite.