title: Superluminality, Black Holes and Effective Field Theory

abstract:
  Under the assumption that a UV theory does not display superluminal behavior,
we ask what constraints on superluminality are satisfied in the effective field
theory (EFT). We study two examples of effective theories: quantum
electrodynamics (QED) coupled to gravity after the electron is integrated out,
and the flat-space galileon. The first is realized in nature, the second is
more speculative, but they both exhibit apparent superluminality around
non-trivial backgrounds. In the QED case, we attempt, and fail, to find
backgrounds for which the superluminal signal advance can be made larger than
the putative resolving power of the EFT. In contrast, in the galileon case it
is easy to find such backgrounds, indicating that if the UV completion of the
galileon is (sub)luminal, quantum corrections must become important at distance
scales of order the Vainshtein radius of the background configuration, much
larger than the naive EFT strong coupling distance scale. Such corrections
would be reminiscent of the non-perturbative Schwarzschild scale quantum
effects that are expected to resolve the black hole information problem.
Finally, a byproduct of our analysis is a calculation of how perturbative
quantum effects alter charged Reissner-Nordstrom black holes.


title: QSL Squasher: A Fast Quasi-Separatrix Layer Map Calculator

abstract:
  Quasi-Separatrix Layers (QSLs) are a useful proxy for the locations where
current sheets can develop in the solar corona, and give valuable information
about the connectivity in complicated magnetic field configurations. However,
calculating QSL maps even for 2-dimensional slices through 3-dimensional models
of coronal magnetic fields is a non-trivial task as it usually involves tracing
out millions of magnetic field lines with immense precision. Thus, extending
QSL calculations to three dimensions has rarely been done until now. In order
to address this challenge, we present QSL Squasher -- a public, open-source
code, which is optimized for calculating QSL maps in both two and three
dimensions on GPUs. The code achieves large processing speeds for three
reasons, each of which results in an order-of-magnitude speed-up. 1) The code
is parallelized using OpenCL. 2) The precision requirements for the QSL
calculation are drastically reduced by using perturbation theory. 3) A new
boundary detection criterion between quasi-connectivity domains is used, which
quickly identifies possible QSL locations which need to be finely sampled by
the code. That boundary detection criterion relies on finding the locations of
abrupt field-line length changes, which we do by introducing a new Field-line
Length Edge (FLEDGE) map. We find FLEDGE maps useful on their own as a
quick-and-dirty substitute for QSL maps. QSL Squasher allows constructing
high-resolution 3D FLEDGE maps in a matter of minutes, which is two orders of
magnitude faster than calculating the corresponding 3D QSL maps. We include a
sample of calculations done using QSL Squasher to demonstrate its capabilities
as a QSL calculator, as well as to compare QSL and FLEDGE maps.


title:
Equation of state effects and one-arm spiral instability in hypermassive
  neutron stars formed in eccentric neutron star mergers

abstract:
  We continue our investigations of the development and importance of the
one-arm spiral instability in long-lived hypermassive neutron stars (HMNSs)
formed in dynamical capture binary neutron star mergers. Employing hydrodynamic
simulations in full general relativity, we find that the one-arm instability is
generic in that it can develop in HMNSs within a few tens of milliseconds after
merger for all equations of state in our survey. We find that mergers with
stiffer equations of state tend to produce HMNSs with stronger $m=2$ azimuthal
mode density deformations, and weaker $m=1$ components, relative to softer
equations of state. We also find that for equations of state that can give rise
to double-core HMNSs, large $m=1$ density modes can already be present due to
asymmetries in the two cores. This results in the generation of $l=2$, $m=1$
gravitational wave modes even before the dominance of a one-arm mode that
ultimately arises following merger of the two cores. Our results further
suggest that stiffer equations of state give rise to HMNSs generating lower
$m=1$ gravitational wave frequencies. Thus, if gravitational waves from the
one-arm instability are detected, they could in principle constrain the neutron
star equation of state. We estimate that, depending on the equation of state,
the one-arm mode could potentially be detectable by second generation
gravitational wave detectors at $\sim 10$ Mpc and by third generation ones at
$\sim 100$ Mpc. Finally, we provide estimates of the properties of dynamical
ejecta, as well as the accompanying kilonovae signatures.


title:
Zodiacal Exoplanets in Time (ZEIT) IV: seven transiting planets in the
  Praesepe cluster

abstract:
  Open clusters and young stellar associations are attractive sites to search
for planets and to test theories of planet formation, migration, and evolution.
We present our search for, and characterization of, transiting planets in the
~800 Myr old Praesepe (Beehive, M44) Cluster from K2 light curves. We identify
seven planet candidates, six of which we statistically validate to be real
planets, the last of which requires more data. For each host star we obtain
high-resolution NIR spectra to measure its projected rotational broadening and
radial velocity, the latter of which we use to confirm cluster membership. We
combine low-resolution spectra with the known cluster distance and metallicity
to provide precise temperatures, masses, radii, and luminosities for the host
stars. Combining our measurements of rotational broadening, rotation periods,
and our derived stellar radii, we show that all planetary orbits are consistent
with alignment to their host star's rotation. We fit the K2 light curves,
including priors on stellar density to put constraints on the planetary
eccentricities, all of which are consistent with zero. The difference between
the number of planets found in Praesepe and Hyades (8 planets) and a similar
dataset for Pleiades (0 planets, ~125 Myr) suggests a trend with age, but may
be due to incompleteness of current search pipelines for younger,
faster-rotating stars. We see increasing evidence that some planets continue to
lose atmosphere past 800 Myr, as now two planets at this age have radii
significantly larger than their older counterparts from Kepler.


title:
No evidence for Population III stars or a Direct Collapse Black Hole in
  the z = 6.6 Lyman-$\alpha$ emitter 'CR7'

abstract:
  The z = 6.6 Lyman-$\alpha$ emitter 'CR7' has been claimed to have a
Population III-like stellar population, or alternatively, be a candidate Direct
Collapse Black Hole (DCBH). In this paper we investigate the evidence for these
exotic scenarios using recently available, deeper, optical, near-infrared and
mid-infrared imaging. We find strong Spitzer/IRAC detections for the main
component of CR7 at 3.6 and 4.5 microns, and show that it has a blue colour
([3.6] - [4.5] $= -1.2\pm 0.3$). This colour cannot be reproduced by current
Pop. III or pristine DCBH models. Instead, the results suggest that the [3.6]
band is contaminated by the [OIII]4959,5007 emission line with an implied
rest-frame equivalent width of EW_0 (H$\beta$ + [OIII]) $\gtrsim 2000$\AA.
Furthermore, we find that new near-infrared data from the UltraVISTA survey
supports a weaker He II 1640 emission line than previously measured, with EW_0
$= 40 \pm 30$\AA. For the fainter components of CR7 visible in Hubble Space
Telescope imaging, we find no evidence that they are particularly red as
previously claimed, and show that the derived masses and ages are considerably
uncertain. In light of the likely detection of strong [OIII] emission in CR7 we
discuss other more standard interpretations of the system that are consistent
with the data. We find that a low-mass, narrow-line AGN can reproduce the
observed features of CR7, including the lack of radio and X-ray detections.
Alternatively, a young, low-metallicity (~1/200 solar) starburst, modelled
including binary stellar pathways, can reproduce the inferred strength of the
He II line and simultaneously the strength of the observed [OIII] emission, but
only if the gas shows super-solar $\alpha$-element abundances (O/Fe ~ 5 O/Fe
solar).


title: Gaia Parallax Zero Point From RR Lyrae Stars

abstract:
  Like Hipparcos, Gaia is designed to give absolute parallaxes, independent of
any astrophysical reference system. And indeed, Gaia's internal zero-point
error for parallaxes is likely to be smaller than any individual parallax
error. Nevertheless, due in part to mechanical issues of unknown origin, there
are many astrophysical questions for which the parallax zero-point error
$\sigma(\pi_0)$ will be the fundamentally limiting constraint. These include
the distance to the Large Magellanic Cloud and the Galactic Center. We show
that by using the photometric parallax estimates for RR Lyrae stars (RRL)
within 8kpc, via the ultra-precise infrared period-luminosity relation, one can
independently determine a hyper-precise value for $\pi_{0}$. Despite their
paucity relative to bright quasars, we show that RRL are competitive due to
their order-of-magnitude improved parallax precision for each individual object
relative to bright quasars. We show that this method is mathematically robust
and well-approximated by analytic formulae over a wide range of relevant
distances.


title: Minkowski flux vacua of type II supergravities

abstract:
  We study flux compactifications of 10d type II supergravities to 4d Minkowski
space-time, supported by parallel orientifold Op-planes with 3 $\leq$ p $\leq$
8. With some restrictions, the 4d Ricci scalar can be written as a negative sum
of squares involving BPS-like conditions. Setting all squares to zero provides
automatically a solution to 10d equations of motion. This way, we characterize
a broad class, if not the complete set, of Minkowski flux vacua. We also
conjecture an extension to include non-geometric fluxes. None of our results
rely on supersymmetry.


title:
Constrained simulations and excursion sets: understanding the risks and
  benefits of `genetically modified' haloes

abstract:
  Constrained realisations of Gaussian random fields are used in cosmology to
design special initial conditions for numerical simulations. We review this
approach and its application to density peaks providing several worked-out
examples. We then critically discuss the recent proposal to use constrained
realisations to modify the linear density field within and around the
Lagrangian patches that form dark-matter haloes. The ambitious concept is to
forge `genetically modified' haloes with some desired properties after the
non-linear evolution. We demonstrate that the original implementation of this
method is not exact but approximate because it tacitly assumes that protohaloes
sample a set of random points with a fixed mean overdensity. We show that
carrying out a full genetic modification is a formidable and daunting task
requiring a mathematical understanding of what determines the biased locations
of protohaloes in the linear density field. We discuss approximate solutions
based on educated guesses regarding the nature of protohaloes. We illustrate
how the excursion-set method can be adapted to predict the non-linear evolution
of the modified patches and thus fine tune the constraints that are necessary
to obtain preselected halo properties. This technique allows us to explore the
freedom around the original algorithm for genetic modification. We find that
the quantity which is most sensitive to changes is the halo mass-accretion rate
at the mass scale on which the constraints are set. Finally we discuss
constraints based on the protohalo angular momenta.


title: Photometry and spectroscopy of SN 2015bh in the galaxy NGC 2770

abstract:
  We present medium-resolution spectroscopy and multicolor photometry for the
optical transient PSN J09093496+3307204 (SN 2015bh) in the galaxy NGC 2770,
which has transferred into the supernova phase. The observations were carried
out between February 2015 to May 2016. Both at the phase of the SN impostor
(2015a) and at the supernova phase (2015b), besides Balmer emissions, the
strong Fe II emissions are seen in the spectrum; so, these spectra resemble
those of Williams Fe II type classical novae. The star is located near the edge
of a dark nebula and notably absorbed (Av = 1.14 +/-0.15 mag). Taking into
account this absorption, we determined maximum absolute magnitudes of Mv =
-15.0 +/-0.3 mag at the 2015a phase and of Mv = -18.14 +/-0.30 mag at the 2015b
phase. The light curve at the 2015b phase is similar to those of SN IIL. The
supernova progenitor is a luminous blue variable (LBV) star with the powerful
H{\alpha} emission. We considered several hypotheses of supernovae explosions
following optical transients related with LBV. The hypothesis of core collapse
of an evolved massive star interrupting the process of its merging with massive
companion in a binary system (a failed luminous red nova) was chosen as the
preferable one for this event.


title: 4D Scattering Amplitudes and Asymptotic Symmetries from 2D CFT

abstract:
  We reformulate the scattering amplitudes of 4D flat space gauge theory and
gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT
structure exhibits an OPE constructed from 4D collinear singularities, as well
as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic
symmetries of 4D flat space. We derive these results by recasting 4D dynamics
in terms of a convenient foliation of flat space into 3D Euclidean AdS and
Lorentzian dS geometries. Tree-level scattering amplitudes take the form of
Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to
CFT correlators via the (A)dS/CFT dictionary. The Ward identities for the 2D
conserved currents are dual to 4D soft theorems, while the bulk-boundary
propagators of massless (A)dS modes are superpositions of the leading and
subleading Weinberg soft factors of gauge theory and gravity. In general, the
massless (A)dS modes are 3D Chern-Simons gauge fields describing the soft,
single helicity sectors of 4D gauge theory and gravity. Consistent with the
topological nature of Chern-Simons theory, Aharonov-Bohm effects record the
"tracks" of hard particles in the soft radiation, leading to a simple
characterization of gauge and gravitational memories. Soft particle exchanges
between hard processes define the Kac-Moody level and Virasoro central charge,
which are thereby related to the 4D gauge coupling and gravitational strength
in units of an infrared cutoff. Finally, we discuss a toy model for black hole
horizons via a restriction to the Rindler region.


title:
A Fixed-point Scheme for the Numerical Construction of
  Magnetohydrostatic Atmospheres in Three Dimensions

abstract:
  Magnetohydrostatic models of the solar atmosphere are often based on
idealized analytic solutions because the underlying equations are too difficult
to solve in full generality. Numerical approaches, too, are often limited in
scope and have tended to focus on the two-dimensional problem. In this article
we develop a numerical method for solving the nonlinear magnetohydrostatic
equations in three dimensions. Our method is a fixed-point iteration scheme
that extends the method of Grad and Rubin (Proc. 2nd Int. Conf. on Peaceful
Uses of Atomic Energy 31, 190, 1958) to include a finite gravity force. We
apply the method to a test case to demonstrate the method in general and our
implementation in code in particular.


title:
Role of gravity waves in vertical coupling during sudden stratospheric
  warmings

abstract:
  Gravity waves are primarily generated in the lower atmosphere, and can reach
thermospheric heights in the course of their propagation. This paper reviews
the recent progress in understanding the role of gravity waves in vertical
coupling during sudden stratospheric warmings. Modeling of gravity wave effects
is briefly reviewed, and the recent developments in the field are presented.
Then, the impact of these waves on the general circulation of the upper
atmosphere is outlined. Finally, the role of gravity waves in vertical coupling
between the lower and the upper atmosphere is discussed in the context of
sudden stratospheric warmings.


title: Complexity of quantum impurity problems

abstract:
  We give a quasi-polynomial time classical algorithm for estimating the ground
state energy and for computing low energy states of quantum impurity models.
Such models describe a bath of free fermions coupled to a small interacting
subsystem called an impurity. The full system consists of $n$ fermionic modes
and has a Hamiltonian $H=H_0+H_{imp}$, where $H_0$ is quadratic in
creation-annihilation operators and $H_{imp}$ is an arbitrary Hamiltonian
acting on a subset of $O(1)$ modes. We show that the ground energy of $H$ can
be approximated with an additive error $2^{-b}$ in time $n^3 \exp{[O(b^3)]}$.
Our algorithm also finds a low energy state that achieves this approximation.
The low energy state is represented as a superposition of $\exp{[O(b^3)]}$
fermionic Gaussian states. To arrive at this result we prove several theorems
concerning exact ground states of impurity models. In particular, we show that
eigenvalues of the ground state covariance matrix decay exponentially with the
exponent depending very mildly on the spectral gap of $H_0$. A key ingredient
of our proof is Zolotarev's rational approximation to the $\sqrt{x}$ function.
We anticipate that our algorithms may be used in hybrid quantum-classical
simulations of strongly correlated materials based on dynamical mean field
theory. We implemented a simplified practical version of our algorithm and
benchmarked it using the single impurity Anderson model.

categories: quant-ph cond-mat.str-el math-ph math.MP


title: A robust covariance testing approach for high-throughput data

abstract:
  The problem of testing changes in covariance has received increasing
attention in recent years, especially in the context of high-dimensional
testing. A number of approaches have been proposed, all limited to the
two-sample problem and involving varying statistics and assumptions on the
number of features $p$ vs. the sample size $n$. There are no general approaches
to test association of covariances with a continuous outcome. We propose a
uniform framework for testing association of covariances with an experimental
variable, whether discrete or continuous. The approach is not limited by the
data dimensions. Our test procedure (i) does not rely on parametric
assumptions, (ii) works well for a range of $p$ and $n$ (e.g., does not require
$n > p$), (iii) provides correct type I error control, and (iv) includes four
different statistics, to ensure power and flexibility under various settings,
including a new "connectivity" statistic that is sensitive to changes in
overall covariance magnitude. We demonstrate that, for the two-sample special
case, the proposed statistics are permutationally equivalent or similar to
existing proposed statistics. We demonstrate the power and utility of our
approaches via simulation and analysis of real data. The approach is
implemented in an $R$ package.


title: Space Development and Space Science Together, an Historic Opportunity

abstract:
  The national space programs have an historic opportunity to help solve the
global-scale economic and environmental problems of Earth while becoming more
effective at science through the use of space resources. Space programs will be
more cost-effective when they work to establish a supply chain in space, mining
and manufacturing then replicating the assets of the supply chain so it grows
to larger capacity. This has become achievable because of advances in robotics
and artificial intelligence. It is roughly estimated that developing a lunar
outpost that relies upon and also develops the supply chain will cost about 1/3
or less of the existing annual budgets of the national space programs. It will
require a sustained commitment of several decades to complete, during which
time science and exploration become increasingly effective. At the end, this
space industry will capable of addressing global-scale challenges including
limited resources, clean energy, economic development, and preservation of the
environment. Other potential solutions, including nuclear fusion and
terrestrial renewable energy sources, do not address the root problem of our
limited globe and there are real questions whether they will be inadequate or
too late. While industry in space likewise cannot provide perfect assurance, it
is uniquely able to solve the root problem, and it gives us an important chance
that we should grasp. What makes this such an historic opportunity is that the
space-based solution is obtainable as a side-benefit of doing space science and
exploration within their existing budgets. Thinking pragmatically, it may take
some time for policymakers to agree that setting up a complete supply chain is
an achievable goal, so this paper describes a strategy of incremental progress.

categories: astro-ph.IM astro-ph.EP physics.pop-ph physics.soc-ph


title: Harder-Narasimhan theory for linear codes

abstract:
  In this text we develop some aspects of Harder-Narasimhan theory, slopes,
semistability and canonical filtration, in the setting of combinatorial
lattices. Of noticeable importance is the Harder-Narasimhan structure
associated to a Galois connection between two lattices. It applies, in
particular, to matroids.
  We then specialize this to linear codes. This could be done from at least
three different approaches: using the sphere-packing analogy, or the geometric
view, or the Galois connection construction just introduced. A remarkable fact
is that these all lead to the same notion of semistability and canonical
filtration. Relations to previous propositions towards a classification of
codes, and to Wei's generalized Hamming weight hierarchy, are also discussed.
  Last, we study the important question of the preservation of semistability
(or more generally the behaviour of slopes) under duality, and under tensor
product. The former essentially follows from Wei's duality theorem for higher
weights---and its matroid version---which we revisit in an appendix, developing
analogues of the Riemann-Roch, Serre duality, Clifford, and gap and gonality
sequence theorems for codes. Likewise the latter is closely related to the
bound on higher weights of a tensor product, conjectured by Wei and Yang, and
proved by Schaathun in the geometric language, which we reformulate directly in
terms of codes. From this material we then derive semistability of tensor
product.


title: Bypassing damaged nervous tissue

abstract:
  We show the principal ability of bypassing damaged demyelinated portions of
nervous tissue, thereby restoring its normal function for the passage of action
potentials. We carry out a theoretical analysis on the basis of the
synchronization mechanism of action potential propagation along a bundle of
neurons, proposed recently in [1]. And we discuss the feasibility of implement
a bypass to restore damaged nervous tissue and creating an artificial neuron
network.


title:
Fully Automated Treatment Planning for Head and Neck Radiotherapy using
  a Voxel-Based Dose Prediction and Dose Mimicking Method

abstract:
  Recent works in automated radiotherapy treatment planning have used machine
learning based on historical treatment plans to infer the spatial dose
distribution for a novel patient directly from the planning image. We present
an atlas-based approach which learns a dose prediction model for each patient
(atlas) in a training database, and then learns to match novel patients to the
most relevant atlases. The method creates a spatial dose objective, which
specifies the desired dose-per-voxel, and therefore replaces any requirement
for specifying dose-volume objectives for conveying the goals of treatment
planning. A probabilistic dose distribution is inferred from the most relevant
atlases, and is scalarized using a conditional random field to determine the
most likely spatial distribution of dose to yield a specific dose prior
(histogram) for relevant regions of interest. Voxel-based dose mimicking then
converts the predicted dose distribution to a deliverable treatment plan dose
distribution. In this study, we investigated automated planning for right-sided
oropharaynx head and neck patients treated with IMRT and VMAT. We compare four
versions of our dose prediction pipeline using a database of 54 training and 12
independent testing patients. Our preliminary results are promising; automated
planning achieved a higher number of dose evaluation criteria in 7 patients and
an equal number in 4 patients compared with clinical. Overall, the relative
number of criteria achieved was higher for automated planning versus clinical
(17 vs 8) and automated planning demonstrated increased sparing for organs at
risk (52 vs 44) and better target coverage/uniformity (41 vs 31).


title: A Conic Section Approach to the Relativistic Reflection Law

abstract:
  We consider the reflection of light, from a stationary source, off of a
uniformly moving flat mirror, and derive the relativistic reflection law using
well-known properties of conic sections. The effective surface of reflection
(ESR) is defined as the loci of intersection of all beams, emanating from the
source at a given time, with the moving mirror. Fermat principle of least time
is then applied to ESR and it is shown that, assuming the independence of speed
of light, the result is identical with the relativistic reflection law. For a
uniformly moving mirror ESR is a conic and the reflection law becomes a case of
bi-angular equation of the conic, with the incident and reflected beams
coinciding with the focal rays of the conic. A short calculus-based proof for
accelerating mirrors is also given.


title:
Influence of coupling on thermal forces and dynamic friction in plasmas
  with multiple ion species

abstract:
  The recently proposed effective potential theory [Phys. Rev. Lett. 110,
235001 (2013)] is used to investigate the influence of coupling on
inter-ion-species diffusion and momentum exchange in multi-component plasmas.
Thermo-diffusion and the thermal force are found to diminish rapidly as strong
coupling onsets. For the same coupling parameters, the dynamic friction
coefficient is found to tend to unity. These results provide an impetus for
addressing the role of coupling on diffusive processes in inertial confinement
fusion experiments.


title:
Extended self-similarity in moment-generating-functions in wall-bounded
  turbulence at high Reynolds number

abstract:
  In wall-bounded turbulence, the moment generating functions (MGFs) of the
streamwise velocity fluctuations $\left<\exp(qu_z^+)\right>$ develop power-law
scaling as a function of the wall normal distance $z/\delta$. Here $u$ is the
streamwise velocity fluctuation, $+$ indicates normalization in wall units
(averaged friction velocity), $z$ is the distance from the wall, $q$ is an
independent variable and $\delta$ is the boundary layer thickness. Previous
work has shown that this power-law scaling exists in the log-region {\small
$3Re_\tau^{0.5}\lesssim z^+$, $z\lesssim 0.15\delta$}, where $Re_\tau$ is the
friction velocity-based Reynolds numbers. Here we present empirical evidence
that this self-similar scaling can be extended, including bulk and
viscosity-affected regions $30<z^+$, $z<\delta$, provided the data are
interpreted with the Extended-Self-Similarity (ESS), i.e. self-scaling of the
MGFs as a function of one reference value, $q_o$. ESS also improves the scaling
properties, leading to more precise measurements of the scaling exponents. The
analysis is based on hot-wire measurements from boundary layers at $Re_\tau$
ranging from $2700$ to $13000$ from the Melbourne
High-Reynolds-Number-Turbulent-Boundary-Layer-Wind-Tunnel. Furthermore, we
investigate the scalings of the filtered, large-scale velocity fluctuations
$u^L_z$ and of the remaining small-scale component, $u^S_z=u_z-u^L_z$. The
scaling of $u^L_z$ falls within the conventionally defined log region and
depends on a scale that is proportional to {\small $l^+\sim Re_\tau^{1/2}$};
the scaling of $u^{S}_z$ extends over a much wider range from $z^+\approx 30$
to $z\approx 0.5\delta$. Last, we present a theoretical construction of two
multiplicative processes for $u^L_z$ and $u^S_z$ that reproduce the empirical
findings concerning the scalings properties as functions of $z^+$ and in the
ESS sense.


title: Which subsets of an infinite random graph look random?

abstract:
  Given a countable graph, we say a set $A$ of its vertices is \emph{universal}
if it contains every countable graph as an induced subgraph, and $A$ is
\emph{weakly universal} if it contains every finite graph as an induced
subgraph. We show that, for almost every graph on $\mathbb N$, $(1)$ every set
of positive upper density is universal, and $(2)$ every set with divergent
reciprocal sums is weakly universal. We show that the second result is sharp
(i.e., a random graph on $\mathbb N$ will almost surely contain non-universal
sets with divergent reciprocal sums) and, more generally, that neither of these
two results holds for a large class of partition regular families.


title:
Qualitative Analysis and Numerical Simulation of Equations of the
  Standard Cosmological Model

abstract:
  On the basis of qualitative theory of differential equations it is shown that
dynamic system based on the system of Einstein - Klein - Gordon equations with
regard to Friedman Universe has a stable center corresponding to zero values of
scalar potential and its derivative at infinity. Thus, the cosmological model
based on single massive classical scalar field in infinite future would give a
flat Universe. The carried out numerical simulation of the dynamic system
corresponding to the system of Einstein - Klein - Gordon equations showed that
at great times of the evolution the invariant cosmological acceleration has a
microscopic oscillating character ($T\sim 2\pi mt$), while macroscopic value of
the cosmological acceleration varies from $+1$ at inflation stage after which
if decreases fast to $-1/2$ (non-relativistic stage), and then slowly tends to
$-1$ (ultrarelativistic stage).


title:
Revisiting the equivalence of light-front and covariant QED in the
  light-cone gauge

abstract:
  We discuss the equivalence between light-front time-ordered-perturbation
theory and covariant quantum field theory in light-front quantization, in the
case of quantum electrodynamics at one-loop level. In particular, we review the
one-loop calculation of the vertex correction, fermion self-energy and vacuum
polarization. We apply the procedure of integration by residue over the
light-front energy in the loop to show how the perturbative expansion in
covariant terms can be reduced to a sum of propagating and instantaneous
diagrams of light-front time-ordered perturbation theory. The detailed proof of
equivalence between the two formulations of the theory resolves the
controversial question on which form should be used for the gauge-field
propagator in the light-cone gauge in the covariant approach.


title:
Novel quantum phenomena induced by strong magnetic fields in heavy-ion
  collisions

abstract:
  The relativistic heavy-ion collisions create both hot quark-gluon matter and
strong magnetic fields, and provide an arena to study the interplay between
quantum chromodynamics and quantum electrodynamics. In recent years, it has
been shown that such an interplay can generate a number of interesting quantum
phenomena in hadronic and quark-gluon matter. In this short review, we first
discuss some properties of the magnetic fields in heavy-ion collisions and then
give an overview of the magnetic field-induced novel quantum effects. In
particular, we focus on the magnetic effect on the heavy flavor mesons, the
heavy-quark transports, and the phenomena closely related to chiral anomaly.


title: Spectrally similar incommensurable 3-manifolds

abstract:
  Reid has asked whether hyperbolic manifolds with the same geodesic length
spectrum must be commensurable. Building toward a negative answer to this
question, we construct examples of hyperbolic 3-manifolds that share an
arbitrarily large portion of the length spectrum but are not commensurable.
More precisely, for all sufficiently large n, we construct a pair of
incommensurable hyperbolic 3-manifolds $N_n$ and $N_n^\mu$ whose volume is
approximately n and whose length spectra agree up to length n.
  Both $N_n$ and $N_n^\mu$ are built by gluing two standard submanifolds along
a complicated pseudo-Anosov map, ensuring that these manifolds have a very
thick collar about an essential surface. The two gluing maps differ by a
hyper-elliptic involution along this surface. Our proof also involves a new
commensurability criterion based on pairs of pants.


title:
Transversly Polarized Proton-Proton Collisions and the Collins
  Fragmentation Function

abstract:
  The Sivers Function is briefly reviewed and the Collins Fragmentation
Function to produce a hadron from a polarized quark is defined. We estimate
$\pi^{+},\pi^{-}$ +X production, where X represents particles which are not
detected, via proton collisions with a polarized proton target using the
Collins Fragmentation Function derived using the gluon distribution functions
for polarized p-p collisions at E=$\sqrt{s}$=200 GeV.


title: Predicting Signed Edges with $O(n^{1+o(1)} \log{n})$ Queries

abstract:
  Social networks and interactions in social media involve both positive and
negative relationships. Signed graphs capture both types of relationships:
positive edges correspond to pairs of "friends", and negative edges to pairs of
"foes". The {\em edge sign prediction problem}, which aims to predict whether
an interaction between a pair of nodes will be positive or negative, is an
important graph mining task for which many heuristics have recently been
proposed \cite{leskovec2010predicting,leskovec2010signed}.
  Motivated by social balance theory, we model the edge sign prediction problem
as a noisy correlation clustering problem with two clusters. We are allowed to
query each pair of nodes whether they belong to the same cluster or not, but
the answer to the query is corrupted with some probability $0<q<\frac{1}{2}$.
Let $c=\frac{1}{2}-q$ be the gap. We provide an algorithm that recovers the
clustering with high probability in the presence of noise for any constant gap
$c$ with $O(n^{1+\tfrac{1}{\log\log{n}}}\log{n})$ queries. Our algorithm uses
simple breadth first search as its main algorithmic primitive. Finally, we
provide a novel generalization to $k \geq 3$ clusters and prove that our
techniques can recover the clustering if the gap is constant in this
generalized setting.


title:
Existence and Blowup Results for Asymptotically Euclidean Initial Data
  Sets Generated by the Conformal Method

abstract:
  For each set of (freely chosen) seed data, the conformal method reduces the
Einstein constraint equations to a system of elliptic equations, the conformal
constraint equations. We prove an admissibility criterion, based on a
(conformal) prescribed scalar curvature problem, which provides a necessary
condition on the seed data for the conformal constraint equations to (possibly)
admit a solution. We then consider sets of asymptotically Euclidean (AE) seed
data for which solutions of the conformal constraint equations exist, and
examine the blowup properties of these solutions as the seed data sets approach
sets for which no solutions exist. We also prove that there are AE seed data
sets which include a Yamabe nonpositive metric and lead to solutions of the
conformal constraints. These data sets allow the mean curvature function to
have zeroes.


title: Improved Inference for the Signal Significance

abstract:
  We study the properties of several likelihood-based statistics commonly used
in testing for the presence of a known signal under a mixture model with known
background, but unknown signal fraction. Under the null hypothesis of no
signal, all statistics follow a standard normal distribution in large samples,
but substantial deviations can occur at low sample sizes. Approximations for
respective $p$-values are derived to various orders of accuracy using the
methodology of Edgeworth expansions. Adherence to normality is studied, and the
magnitude of deviations is quantified according to resulting inflation or
deflation. We find that approximations to third-order accuracy are generally
sufficient to guarantee $p$-values with nominal false positive error rates in
the five sigma range ($p$-value $= 2.87 \times 10^{-7}$) for the classic Wald,
score, and likelihood ratio (LR) statistics at relatively low samples. Not only
does LR have better adherence to normality, but it also consistently
outperforms all other statistics in terms of false negative error rates. The
reasons for this are shown to be connected with high-order cumulant behavior
gleaned from fourth order Edgeworth expansions. Finally, a conservative
procedure is suggested for making finite sample adjustments while accounting
for the look elsewhere effect with the theory of random fields (a.k.a. the
Gross-Vitells method).


title:
Matrix models from localization of five-dimensional supersymmetric
  noncommutative U(1) gauge theory

abstract:
  We study localization of five-dimensional supersymmetric $U(1)$ gauge theory
on $\mathbb{S}^3 \times \mathbb{R}_{\theta}^{2}$ where
$\mathbb{R}_{\theta}^{2}$ is a noncommutative (NC) plane. The theory can be
isomorphically mapped to three-dimensional supersymmetric $U(N \to \infty)$
gauge theory on $\mathbb{S}^3$ using the matrix representation on a separable
Hilbert space on which NC fields linearly act. Therefore the NC space
$\mathbb{R}_{\theta}^{2}$ allows for a flexible path to derive matrix models
via localization from a higher-dimensional supersymmetric NC $U(1)$ gauge
theory. The result shows a rich duality between NC $U(1)$ gauge theories and
large $N$ matrix models in various dimensions.


title: A heuristic extending the Squarified treemapping algorithm

abstract:
  A heuristic extending the Squarified Treemap technique for the representation
of hierarchical information as treemaps is presented. The original technique
gives high quality treemap views, since items are laid out with rectangles that
approximate squares, allowing easy comparison and selection operations. New key
steps, with a low computational impact, have been introduced to yield treemaps
with even better aspect ratios and higher homogeneity among items.


title: Algorithms for Visualizing Phylogenetic Networks

abstract:
  We study the problem of visualizing phylogenetic networks, which are
extensions of the Tree of Life in biology. We use a space filling visualization
method, called DAGmaps, in order to obtain clear visualizations using limited
space. In this paper, we restrict our attention to galled trees and galled
networks and present linear time algorithms for visualizing them as DAGmaps.


title:
Renormalization of the Unitary Evolution Equation for Coined Quantum
  Walks

abstract:
  We consider discrete-time evolution equations in which the stochastic
operator of a classical random walk is replaced by a unitary operator. Such a
problem has gained much attention as a framework for coined quantum walks that
are essential for attaining the Grover limit for quantum search algorithms in
physically realizable, low-dimensional geometries. In particular, we analyze
the exact real-space renormalization group (RG) procedure recently introduced
to study the scaling of quantum walks on fractal networks. While this
procedure, when implemented numerically, was able to provide some deep insights
into the relation between classical and quantum walks, its analytic basis has
remained obscure. Our discussion here is laying the groundwork for a rigorous
implementation of the RG for this important class of transport and algorithmic
problems, although some instances remain unresolved. Specifically, we find that
the RG fixed-point analysis of the classical walk, which typically focuses on
the dominant Jacobian eigenvalue $\lambda_{1}$, with walk dimension
$d_{w}^{RW}=\log_{2}\lambda_{1}$, needs to be extended to include the
subdominant eigenvalue $\lambda_{2}$, such that the dimension of the quantum
walk obtains $d_{w}^{QW}=\log_{2}\sqrt{\lambda_{1}\lambda_{2}}$. With that
extension, we obtain analytically previously conjectured results for
$d_{w}^{QW}$ of Grover walks on all but one of the fractal networks that have
been considered.


title:
Bound states for rapidly oscillatory Schr\"odinger operators in
  dimension 2

abstract:
  We study the eigenvalues of Schr\"odinger operators on $\mathbb{R}^2$ with
rapidly oscillatory potential $V(x) = W(x,x/\varepsilon)$, where $W(x,y) \in
C^\infty_0(\mathbb{R}^2 \times \mathbb{T}^2)$ satisfies $\int_{\mathbb{T}^2}
W(x,y) dy =0$. We show that for $\varepsilon$ small enough, such operators have
a unique negative eigenvalue, that is exponentially close to $0$.


title: Electric Current Induced Ultrafast Demagnetization

abstract:
  We report the magnetic response of Co/Pt multilayers to picosecond electrical
heating. Using photoconductive Auston switches, we generate electrical pulses
with 5.5 picosecond duration and hundreds of pico-Joules to pass through Co/Pt
multilayers. The electrical pulse heats the electrons in the Co/Pt multilayers
and causes an ultrafast reduction in the magnetic moment. A comparison between
optical and electrically induced demagnetization of the Co/Pt multilayers
reveals significantly different dynamics for optical vs. electrical heating. We
attribute the disparate dynamics to the dependence of the electron-phonon
interaction on the average energy and total number of initially excited
electrons.


title: A MIP Backend for the IDP System

abstract:
  The IDP knowledge base system currently uses MiniSAT(ID) as its backend
Constraint Programming (CP) solver. A few similar systems have used a Mixed
Integer Programming (MIP) solver as backend. However, so far little is known
about when the MIP solver is preferable. This paper explores this question. It
describes the use of CPLEX as a backend for IDP and reports on experiments
comparing both backends.


title:
Three Photon Absorption in Optical Parametric Oscillators Based on
  OP-GaAs

abstract:
  We report on the first singly-resonant (SR), synchronously pumped optical
parametric oscillator (OPO) based on orientation-patterned gallium arsenide
(OP-GaAs). Together with a doubly resonant (DR) degenerate OPO based on the
same OP-GaAs material, the output spectra cover 3 to 6 ${\mu}$m within ~3 dB of
relative power. The DR-OPO has the highest output power reported to date from a
femtosecond, synchronously pumped OPO based on OP-GaAs. We discovered strong
three photon absorption with a coefficient of 0.35 ${\pm}$ 0.06
cm${^3}$/GW${^2}$ for our OP-GaAs sample, which limits the output power of
these OPOs as mid-IR light sources. We present a detailed study of the three
photon loss on the performance of both the SR and DR-OPOs, and compare them to
those without this loss mechanism.


title: Shaping single photons and biphotons by inherent losses

abstract:
  Inherent loss is always to be avoided in generating single photons or
biphotons, but interestingly it provides opportunities for manipulating the
photon wave packet. In this paper we show how inherent loss in parametric
down-conversion can be employed to tailor the wave packets of single photons
and biphotons. As an example, we propose a scheme to realize a single photon in
a single cycle using inherent loss. Our work has potential applications in
quantum communication, quantum computation, and quantum interface.


title:
Correlation-based model of artificially induced plasticity in motor
  cortex by a bidirectional brain-computer interface

abstract:
  Experiments show that spike-triggered stimulation performed with
Bidirectional Brain-Computer-Interfaces (BBCI) can artificially strengthen
connections between separate neural sites in motor cortex (MC). What are the
neuronal mechanisms responsible for these changes and how does targeted
stimulation by a BBCI shape population-level synaptic connectivity? The present
work describes a recurrent neural network model with probabilistic spiking
mechanisms and plastic synapses capable of capturing both neural and synaptic
activity statistics relevant to BBCI conditioning protocols. When spikes from a
neuron recorded at one MC site trigger stimuli at a second target site after a
fixed delay, the connections between sites are strengthened for spike-stimulus
delays consistent with experimentally derived spike time dependent plasticity
(STDP) rules. However, the relationship between STDP mechanisms at the level of
networks, and their modification with neural implants remains poorly
understood. Using our model, we successfully reproduces key experimental
results and use analytical derivations, along with novel experimental data. We
then derive optimal operational regimes for BBCIs, and formulate predictions
concerning the efficacy of spike-triggered stimulation in different regimes of
cortical activity.


title: On DP-coloring of graphs and multigraphs

abstract:
  While solving a question on list coloring of planar graphs, Dvo\v{r}\'{a}k
and Postle introduced the new notion of DP-coloring (they called it
correspondence coloring). A DP-coloring of a graph $G$ reduces the problem of
finding a coloring of $G$ from a given list $L$ to the problem of finding a
"large" independent set in an auxiliary graph $H(G,L)$ with vertex set
$\{(v,c)\,: \, v\in V(G) \text{ and } {c\in L(v)} \}$. It is similar to the old
reduction by Plesnevi\v{c} and Vizing of the $k$-coloring problem to the
problem of finding an independent set of size $|V(G)|$ in the Cartesian product
$G\square K_k$. Some properties of the DP-chromatic number $\chi_{DP}(G)$
resemble the properties of the list chromatic number $\chi_{\ell}(G)$ but some
differ quite a lot. It is always the case that $\chi_{DP}(G)\geq
\chi_{\ell}(G)$. The goal of this note is to introduce DP-colorings for
multigraphs and to prove for them an analog of the result of Borodin and
Erd\H{o}s, Rubin, and Taylor characterizing the multigraphs that do not admit
DP-colorings from some DP-degree-lists. This characterization yields an analog
of Gallai's Theorem on the minimum number of edges in $n$-vertex graphs
critical with respect to DP-coloring.


title: Gamma-ray Bursts and the Early Star-formation History

abstract:
  We review the uncertainties in high-z star-formation rate (SFR) measures and
the constraints that one obtains from high-z gamma-ray burst (GRB) rates on
them. We show that at the present time, the GRB rates per unit star-formation
at z>3 are higher than at lower redshift. We also compare metallicity
predictions made using a hierarchical model of cosmic chemical evolution based
on two recently proposed SFRs, one based on the observed galaxy luminosity
function at high redshift and one based on the GRB rate and find that within
the considerable scatter in metal abundance measures, they both are consistent
with the data. Analyzing the ensemble of different measurements together, we
conclude that despite metallicity biases, GRBs may be a less biased probe of
star-formation at z>3 than at z<2. There is likely to be a common origin to the
high GRB rate per unit star-formation and the high observed Lyman-continuum
production rate in high redshift galaxies and that this may be due to a
relative overabundance of stars with mass $>$25Msun which are likely GRB
progenitors. We also find that to reconcile these measurements with the Thomson
scattering cross section of cosmic microwave background (CMB) photons measured
by Planck, the escape fraction of Lyman-continuum photons from galaxies must be
low, about 15 percent or less and that the clumping factor of the IGM is likely
to be small, about 3. Finally, we demonstrate that GRBs are unique probes of
metallicity evolution in low-mass galaxy samples and that GRB hosts likely lost
a significant fraction of metals to the intergalactic medium (IGM) due to
feedback processes such as stellar winds and supernovae.


title: On the DPG method for Signorini problems

abstract:
  We derive and analyze discontinuous Petrov-Galerkin methods with optimal test
functions for Signorini-type problems as a prototype of a variational
inequality of the first kind. We present different symmetric and non-symmetric
formulations where optimal test functions are only used for the PDE part of the
problem, not the boundary conditions. For the symmetric case and lowest order
approximations, we provide a simple a posteriori error estimate. In a second
part, we apply our technique to the singularly perturbed case of reaction
dominated diffusion. Numerical results show the performance of our method and,
in particular, its robustness in the singularly perturbed case.


title: Free-Space Nonlinear Beam Combining Towards Filamentation

abstract:
  Multi-filamentation opens new degrees of freedom for manipulating
electromagnetic waves in air. However, without control, multiple filament
interactions, including attraction, repulsion or fusion often result in
formation of complex disordered filament distributions. Moreover, high power
beams conventionally used in multi-filament formation experiments often cause
significant surface damage. The growing number of applications for laser
filaments requires fine control of their formation and propagation. We
demonstrate, experimentally and theoretically, that the attraction and fusion
of ultrashort beams with initial powers below the critical value enable the
eventual formation of a filament downstream. Filament formation is delayed to a
predetermined distance in space, avoiding optical damage to external beam
optics while still enabling robust filaments with controllable properties as if
formed from a single high power beam. This paradigm introduces new
opportunities for filament engineering eliminating the need to use high peak
power lasers sources.


title: Brazilian Congress structural balance analysis

abstract:
  In this work, we study the behavior of Brazilian politicians and political
parties with the help of clustering algorithms for signed social networks. For
this purpose, we extract and analyze a collection of signed networks
representing voting sessions of the lower house of Brazilian National Congress.
We process all available voting data for the period between 2011 and 2016, by
considering voting similarities between members of the Congress to define
weighted signed links. The solutions obtained by solving Correlation Clustering
(CC) problems are the basis for investigating deputies voting networks as well
as questions about loyalty, leadership, coalitions, political crisis, and
social phenomena such as mediation and polarization.


title:
Ultrafast Broadband Photodetectors based on Three-dimensional Dirac
  Semimetal Cd3As2

abstract:
  The efforts to pursue photo detection with extreme performance in terms of
ultrafast response time, broad detection wavelength range, and high sensitivity
have never been exhausted as driven by its wide range of optoelectronic and
photonic applications such as optical communications, interconnects, imaging
and remote sensing1. 2D Dirac semimetal graphene has shown excellent potential
toward high performance photodetector with high operation speed, broadband
response and efficient carrier multiplications benefiting from its linear
dispersion band structure with high carrier mobility and zero bandgap2-4. As
the three dimensional analogues of graphene, Dirac semimetal Cd3As2 processes
all advantages of graphene as a photosensitive material but potentially has
stronger interaction with light as bulk material and thus enhanced
responsivity5,6, which promises great potential in improving the performance of
photodetector in various aspects . In this work, we report the realization of
an ultrafast broadband photodetector based on Cd3As2. The prototype
metal-Cd3As2-metal photodetector exhibits a responsivity of 5.9 mA/W with
response time of about 6.9 ps without any special device optimization.
Broadband responses from 0.8 eV to 2.34 eV are measured with potential
detection range extendable to far infrared and terahertz. Systematical studies
indicate that the photo-thermoelectric effect plays important roles in
photocurrent generation, similar to that in graphene. Our results suggest this
emerging class of exotic quantum materials can be harnessed for photo detection
with high sensitivity and high speed (~145 GHz) in challenging
middle/far-infrared and THz range.


title:
A probabilistic Harnack inequality and strict positivity of stochastic
  partial differential equations

abstract:
  Under general conditions we show an a priori probabilistic Harnack inequality
for the non-negative solution of a stochastic partial differential equation of
the following form d_tu = div (A\nabla u) + f (t, x, u;w) + g_i(t, x,
u;w)\dot{w}^i_t. We will also show that the solution of the above equation will
be almost surely strictly positive if the initial condition is non-negative and
not identically vanishing.


title: Stochastic Bouncy Particle Sampler

abstract:
  We introduce a novel stochastic version of the non-reversible, rejection-free
Bouncy Particle Sampler (BPS), a Markov process whose sample trajectories are
piecewise linear. The algorithm is based on simulating first arrival times in a
doubly stochastic Poisson process using the thinning method, and allows
efficient sampling of Bayesian posteriors in big datasets. We prove that in the
BPS no bias is introduced by noisy evaluations of the log-likelihood gradient.
On the other hand, we argue that efficiency considerations favor a small,
controllable bias in the construction of the thinning proposals, in exchange
for faster mixing. We introduce a simple regression-based proposal intensity
for the thinning method that controls this trade-off. We illustrate the
algorithm in several examples in which it outperforms both unbiased, but slowly
mixing stochastic versions of BPS, as well as biased stochastic gradient-based
samplers.


title: Rotation Numbers of Elements in Thompson's Group ${\bf T}$

abstract:
  We give a simple combinatorial proof that the rotation number for each
element in Thompson's group ${\bf T}$ is rational.


title: Periodicity and ergodicity in the trihexagonal tiling

abstract:
  We consider the dynamics of light rays in the trihexagonal tiling where
triangles and hexagons are transparent and have equal but opposite indices of
refraction. We find that almost every ray of light is dense in a region of a
particular form: the regions have infinite area and consist of the plane with a
periodic family of triangles removed. We also completely describe initial
conditions for periodic and drift-periodic light rays.


abstract:
  In this paper, we develop symplectic Hodge theory on transversely symplectic
foliations. In particular, we establish the symplectic $d\delta$-lemma for any
such foliations with the (transverse) $s$-Lefschetz property. As transversely
symplectic foliations include many geometric structures, such as contact
manifolds, co-symplectic manifolds, symplectic orbifolds, and symplectic
quasi-folds as special examples, our work provides a unifying treatment of
symplectic Hodge theory in these geometries.
  As an application, we show that on compact $K$-contact manifolds, the
$s$-Lefschetz property implies a general result on the vanishing of cup
products, and that the cup length of a $2n+1$ dimensional compact $K$-contact
manifold with the (transverse) $s$-Lefschetz property is at most $2n-s$. For
any even integer $s\geq 2$, we also apply our main result to produce examples
of $K$-contact manifolds that are $s$-Lefschetz but not $(s+1)$-Lefschetz.


title:
Equivariant formality of transversely symplectic foliations and
  Frobenius manifolds

abstract:
  Consider the Hamiltonian action of a compact connected Lie group on a
transversely symplectic foliation which satisfies the transverse hard Lefschetz
property. We establish an equivariant formality theorem and an equivariant
symplectic $d\delta$-lemma in this setting. As an application, we show that if
the foliation is also Riemannian, then there exists a natural formal Frobenius
manifold structure on the equivariant basic cohomology of the foliation.


title:
An Error Covariance Splitting Technique for Multi-User MIMO Interference
  Environment

abstract:
  This paper investigates an error covariance matrix splitting technique for
multiuser multiple input and multiple output (MIMO) interference downlink
channel. Most of the related work has thus far considered the traditional error
covariance matrix which has not been well-shaped for maximizing the system
capacity. Thus, we split and propose a new iterative error covariance matrix to
mitigate the system error and maximize the system capacity in this paper.
Numerical results illustrate that our proposed method is strictly better than
the traditional method.


title: Study of a fifth order PDE using symmetries

abstract:
  We study a family of PDEs, which was derived as an approximation of an
extended Lotka-Volterra system, from the point of view of symmetries. Also, by
performing the self adjoint classification on that family we offer special
cases possessing non trivial conservation laws. Using both classifications we
justify the particular cases studied in the literature, and we give additional
cases that may be of importance.


title:
Towards End-to-End Reinforcement Learning of Dialogue Agents for
  Information Access

abstract:
  This paper proposes KB-InfoBot -- a multi-turn dialogue agent which helps
users search Knowledge Bases (KBs) without composing complicated queries. Such
goal-oriented dialogue agents typically need to interact with an external
database to access real-world knowledge. Previous systems achieved this by
issuing a symbolic query to the KB to retrieve entries based on their
attributes. However, such symbolic operations break the differentiability of
the system and prevent end-to-end training of neural dialogue agents. In this
paper, we address this limitation by replacing symbolic queries with an induced
"soft" posterior distribution over the KB that indicates which entities the
user is interested in. Integrating the soft retrieval process with a
reinforcement learner leads to higher task success rate and reward in both
simulations and against real users. We also present a fully neural end-to-end
agent, trained entirely from user feedback, and discuss its application towards
personalized dialogue agents. The source code is available at
https://github.com/MiuLab/KB-InfoBot.


title:
Euler characteristics for spaces of string links and the modular
  envelope of $L_\infty$

abstract:
  We make calculations in graph homology which further understanding of the
topology of spaces of string links, in particular calculating the Euler
characteristics of finite-dimensional summands in their homology and homotopy.
In doing so, we also determine the supercharacter of the symmetric group action
on the positive arity components of the modular envelope of $L_\infty$.


title:
A Scalable Algorithm for Structure Identification of Complex Gene
  Regulatory Network from Temporal Expression Data

abstract:
  Motivation: Gene regulatory interactions are of fundamental importance to
various biological functions and processes. However, only a few previous
computational studies have claimed success in revealing genome-wide regulatory
landscapes from temporal gene expression data, especially for complex
eukaryotes like human. Moreover, recent work suggests that these methods still
suffer from the curse of dimensionality if network size increases to 100 or
higher.
  Result: We present a novel scalable algorithm for identifying genome-wide
regulatory network structures. The highlight of our method is that its superior
performance does not degenerate even for a network size on the order of $10^4$,
and is thus readily applicable to large-scale complex networks. Such a
breakthrough is achieved by considering both prior biological knowledge and
multiple topological properties (i.e., sparsity and hub gene structure) of
complex networks in the regularized formulation. We also illustrate the
application of our algorithm in practice using the time-course expression data
from an influenza infection study in respiratory epithelial cells.
  Availability and Implementation: The algorithm described in this article is
implemented in MATLAB$^\circledR$. The source code is freely available from
https://github.com/Hongyu-Miao/DMI.git.
  Contact: jliu@cs.rochester.edu; hongyu.miao@uth.tmc.edu
  Supplementary information: Supplementary data are available online.


title:
ESO 243-49 HLX-1: scaling of X-ray spectral properties and black hole
  mass determination

abstract:
  We report the results of Swift/XRT observations (2008-2015) of a
hyper-luminous X-ray source, ESO 243-49 HLX-1. We found a strong observational
evidence that ESO 243-49 HLX-1 underwent spectral transitions from the low/hard
state to the high/soft state during these observations. The spectra of ESO
243-49 HLX-1 are well fitted by the so-{called} bulk motion Comptonization
model for all spectral states. We have established the photon index Gamma
saturation level, Gamma_{sat}$=3.0+/-0.1, in the correlation of Gamma versus
mass accretion rate dot M. This Gamma-dot M correlation allows us to estimate
the black hole (BH) mass in ESO 243-49 HLX-1 to be M_{BH}~ 7x 10^4 solar
masses, assuming the distance to ESO 243-49 of 95 Mpc. For the BH mass estimate
we used the scaling method, taking Galactic BHs XTE~J1550-564, H~1743-322 and
4U~1630-472, and an extragalactic BH source, M101 ULX-1 as reference sources.
The Gamma-dot M correlation revealed in ESO 243-49 HLX-1 is similar to those in
a number of Galactic and extragalactic BHs and it clearly shows the correlation
along with the strong Gamma saturation at ~ 3. This is a reliable observational
evidence of a BH in ESO 243-49 HLX-1. We also found that the seed (disk) photon
temperatures are quite low, of order of 50-140 eV which are consistent with a
high BH mass in ESO 243-49 HLX-1.


title:
On the method of strained parameters for a KdV type of equation with
  exact dispersion property

abstract:
  This paper provides an alternative methodology for analysis of three-wave
interactions under the exact dispersion relation associated with gravity waves
in fluid of intermediate depth. A Korteweg-de Vries type of equation with exact
dispersion property is adopted as the governing equation for unidirectional
wave packet evolution. Following the idea from Zakharov's seminal paper
(Zakharov, V. E. (1968) Stability of periodic waves of finite amplitude on the
surface of a deep fluid. \textit{Journal of Applied Mechanics and Technical
Physics}, {\bf 9}, 190--194), the equation is transformed from the
spatial--temporal domain to the wavenumber--temporal domain. The solution of
the transformed equation is sought using the perturbation theory, for which the
ansatz is expressed in the form of a regular expansion in the increasing order
of a small parameter. After implementing the na\"{i}ve perturbation method, due
to nonlinear mode generation and particular combinations of wavenumbers, the
third-order solution contains spurious secular growth terms which appear as a
consequence of resonant interaction and nonlinear mode generation. These
spurious secular growth terms can be prevented by implementing the method of
strained parameters for which nonlinear dispersion relation terms are produced
for particular combination of wavenumbers.


title: Optimal maps in essentially non-branching spaces

abstract:
  In this note we prove that in a metric measure space $(X, d, m)$ verifying
the measure contraction property with parameters $K \in \mathbb{R}$ and $1< N<
\infty$, any optimal transference plan between two marginal measures is induced
by an optimal map, provided the first marginal is absolutely continuous with
respect to $m$ and the space itself is essentially non-branching. In particular
this shows that there exists a unique transport plan and it is induced by a
map.


title:
Linear stability analysis and direct numerical simulation of two layer
  channel flow

abstract:
  We study the stability of two-fluid flow through a plane channel at Reynolds
numbers of a hundred to a thousand in the linear and nonlinear regimes. The two
fluids have the same density but different viscosities. The fluids, when
miscible, are separated from each other by a mixed layer of small but finite
thickness, across which viscosity changes from that of one fluid to that of the
other. When immiscible, the interface is sharp. Our study spans a range of
Schmidt numbers, viscosity ratios and location and thickness of the mixed
layer. A region of instability distinct from that of the Tollmien-Schlichting
mode is obtained at moderate Reynolds numbers. We show that the overlap of the
layer of viscosity-stratification with the critical layer of the dominant
disturbance provides a mechanism for this instability. At very low values of
diffusivity, the miscible flow behaves exactly like the immiscible in terms of
stability characteristics. High levels of miscibility make the flow more
stable. At intermediate levels of diffusivity however, in both linear and
non-linear regimes, miscible flow can be more unstable than the corresponding
immiscible flow without surface tension.


title: Commutators, Little BMO and Weak Factorization

abstract:
  In this paper, we provide a direct and constructive proof of weak
factorization of $h^1(\mathbb{R})$ (the predual of little BMO space
bmo$(\mathbb{R}\times\mathbb{R})$ studied by Cotlar-Sadosky and
Ferguson-Sadosky), i.e., for every $f\in h^1(\mathbb{R}\times\mathbb{R})$ there
exist sequences $\{\alpha_j^k\}\in\ell^1$ and functions $g_j^k,h^k_j\in
L^2(\mathbb{R}^2)$ such that \begin{align*}
f=\sum_{k=1}^\infty\sum_{j=1}^\infty\alpha^k_j\Big(\, h^k_j H_1H_2 g^k_j -
g^k_j H_1H_2 h^k_j\Big) \end{align*} in the sense of $h^1(\mathbb{R})$, where
$H_1$ and $H_2$ are the Hilbert transforms on the first and second variable,
respectively. Moreover, the norm $\|f\|_{h^1(\mathbb{R}\times\mathbb{R})}$ is
given in terms of $\|g^k_j\|_{L^2(\mathbb{R}^2)}$ and
$\|h^k_j\|_{L^2(\mathbb{R}^2)}$. By duality, this directly implies a lower
bound on the norm of the commutator $[b,H_1H_2]$ in terms of $\|b\|_{{\rm
bmo}(\mathbb{R}\times\mathbb{R})}$.
  Our method bypasses the use of analyticity and the Fourier transform, and
hence can be extended to the higher dimension case in an arbitrary
$n$-parameter setting for the Riesz transforms.


title:
Magnon-phonon coupling and two-magnon continuum in two-dimensional
  triangular antiferromagnet CuCrO2

abstract:
  CuCrO2 is a manifestation of a two-dimensional triangular antiferromagnet
which exhibits an incommensurate noncollinear magnetic structure similar to a
classical 120 degree ordering. Using the inelastic neutron scattering
technique, direct evidence of a magnon-phonon coupling in CuCrO2 is revealed
via the mixed magnon-phonon character of the excitation mode at 12.5 meV as
well as a minimum at the zone boundary. A simple model Hamiltonian that
incorporates an exchange striction type magnon-phonon coupling reproduces the
observed features accurately. Also, continuum excitations originating from the
interaction between quasiparticles are observed with strong intensity at the
zone boundary. These features of the magnetic excitations are key to an
understanding of the emergent excitations in noncollinear antiferromagnetic
compounds.


title:
Shubnikov-de Haas quantum oscilations reveal a reconstructed Fermi
  surface near optimal doping in a thin film of the cuprate superconductor
  Pr$_{1.86}$Ce$_{0.14}$CuO$_{4\pm\delta}$

abstract:
  We study magnetotransport properties of the electron-doped superconductor
Pr$_{2-x}$Ce$_x$CuO$_{4\pm\delta}$ with $x$ = 0.14 in magnetic fields up to
92~T, and observe Shubnikov de-Haas magnetic quantum oscillations. The
oscillations display a single frequency $F$=255$\pm$10~T, indicating a small
Fermi pocket that is $\sim$~1\% of the two-dimensional Brillouin zone and
consistent with a Fermi surface reconstructed from the large hole-like cylinder
predicted for these layered materials. Despite the low nominal doping, all
electronic properties including the effective mass and Hall effect are
consistent with overdoped compounds. Our study demonstrates that the
exceptional chemical control afforded by high quality thin films will enable
Fermi surface studies deep into the overdoped cuprate phase diagram.


title:
Why the entropy of spacetime is independent of species of particles --
  the species problem

abstract:
  The Hawking radiation emits all species of particles, but the
Bekenstein-Hawking entropy is independent of the number of the species of
particles. This is the so-called species problem --- a puzzling problem for a
long time. In this paper, we suggest a solution to this problem. A result of
the scheme is that the black hole atmosphere has a mass equaling 3/8 mass of a
classical Schwarzschild black hole, which agrees with 't Hooft's brick wall
model.


title:
Challenges in Modeling Complexity of Neglected Tropical Diseases:
  Assessment of Visceral Leishmaniasis Dynamics in Resource Limited Settings

abstract:
  Neglected tropical diseases (NTD), particularly vector-borne diseases (VBD),
account for a large proportion of the global disease burden, and their control
faces several challenges including diminishing human and financial resources
for those distressed from such diseases. Visceral Leishmaniasis (VL), the
second-largest parasitic killer in the world (after malaria) affects poor
populations in endemic countries and causes considerable cost to the affected
individuals and their society. Mathematical models can serve as a critical tool
for understanding the driving mechanisms of a NTD such as VL. The WHO promotes
integrated control programs for VL but this policy is not well supported by
systematic quantitative and dynamic evidence and so potential benefits of the
policy are limited. Moreover, mathematical models can be readily developed and
used to understand the functioning of the VL system cheaply and systematically.
The focus of this research is three-fold: (i) to identify non-traditional but
critical mechanisms for ongoing VL transmission in resource limited regions,
(ii) to review mathematical models used for other infectious diseases that have
the potential to capture identified factors of VL, and (iii) to suggest novel
quantitative models for understanding VL dynamics and for evaluating control
programs in such frameworks for achieveing VL elimination goals.


title:
Nuclear mean field and double-folding model of the nucleus-nucleus
  optical potential

abstract:
  Realistic density dependent CDM3Yn versions of the M3Y interaction have been
used in an extended Hartree-Fock (HF) calculation of nuclear matter (NM), with
the nucleon single-particle potential determined from the total NM energy based
on the Hugenholtz-van Hove theorem that gives rise naturally to a rearrangement
term (RT). Using the RT of the single-nucleon potential obtained exactly at
different NM densities, the density- and energy dependence of the CDM3Yn
interactions was modified to account properly for both the RT and observed
energy dependence of the nucleon optical potential. Based on a local density
approximation, the double-folding model of the nucleus-nucleus optical
potential has been extended to take into account consistently the rearrangement
effect and energy dependence of the nuclear mean-field potential, using the
modified CDM3Yn interactions. The extended double-folding model was applied to
study the elastic $^{12}$C+$^{12}$C and $^{16}$O+$^{12}$C scattering at the
refractive energies, where the Airy structure of the nuclear rainbow has been
well established. The RT was found to affect significantly the real
nucleus-nucleus optical potential at small internuclear distances, giving the
potential strength close to that implied by the realistic optical model
description of the Airy oscillation.


title: Scalable Betweenness Centrality Maximization via Sampling

abstract:
  Betweenness centrality is a fundamental centrality measure in social network
analysis. Given a large-scale network, how can we find the most central nodes?
This question is of key importance to numerous important applications that rely
on betweenness centrality, including community detection and understanding
graph vulnerability. Despite the large amount of work on designing scalable
approximation algorithms for betweenness centrality, estimating it on
large-scale networks remains a computational challenge.
  In this paper, we study the Betweenness Centrality Maximization problem:
given a graph $G=(V,E)$ and a positive integer $k$, find a set $S^* \subseteq
V$ that maximizes betweenness centrality subject to the cardinality constraint
$|S^*| \leq k$. We present an efficient randomized algorithm that provides a
$(1-1/e-\epsilon)$-approximation with high probability, where $\epsilon>0$. Our
results improve the current state-of-the-art result by
Yoshida~\cite{yoshida2014almost}. Furthermore, we provide theoretical evidence
for the validity of a crucial assumption in the literature of betweenness
centrality estimation, namely that in real-world networks $O(|V|^2)$ shortest
paths pass through the top-$k$ central nodes, where $k$ is a constant. On the
experimental side, we perform an extensive experimental analysis of our method
on real-world networks, demonstrate its accuracy and scalability, and study
different properties of central nodes. Finally, we provide three graph mining
applications of our method.


title: Reprowd: Crowdsourced Data Processing Made Reproducible

abstract:
  Crowdsourcing is a multidisciplinary research area including disciplines like
artificial intelligence, human-computer interaction, database, and social
science. To facilitate cooperation across disciplines, reproducibility is a
crucial factor, but unfortunately, it has not gotten enough attention in the
HCOMP community. In this paper, we present Reprowd, a system aiming to make it
easy to reproduce crowdsourced data processing research. We have open sourced
Reprowd at http://sfu-db.github.io/reprowd/.


title: 2014-2015 Multiple Outbursts of 15P/Finlay

abstract:
  Multiple outbursts of a Jupiter-family comet, 15P/Finlay, occurred from late
2014 to early 2015. We conducted an observation of the comet after the first
outburst and subsequently witnessed another outburst on 2015 January 15.6-15.7.
The gas, consisting mostly of C2 and CN, and dust particles expanded at speeds
of 1,110 +/- 180 m/s and 570 +/- 40 m/s at a heliocentric distance of 1.0 AU.
We estimated the maximum ratio of solar radiation pressure with respect to the
solar gravity beta_max = 1.6 +/- 0.2, which is consistent with porous dust
particles composed of silicates and organics. We found that 10^8-10^9 kg of
dust particles (assumed to be 0.3 micron - 1 mm) were ejected through each
outburst. Although the total mass is three orders of magnitude smaller than
that of the 17P/Holmes event observed in 2007, the kinetic energy per unit mass
(104 J/kg) is equivalent to the estimated values of 17P/Holmes and 332P/2010 V1
(Ikeya-Murakami), suggesting that the outbursts were caused by a similar
physical mechanism. From a survey of cometary outbursts on the basis of
voluntary reports, we conjecture that 15P/Finlay-class outbursts occur >1.5
times annually and inject dust particles from Jupiter-family comets and
Encke-type comets into interplanetary space at a rate of ~10 kg/s or more.


title:
Multiscale simulation of polymer melt spinning by using the dumbbell
  model

abstract:
  We investigated the spinning process of a polymeric material by using a
multiscale simulation method which connects the macroscopic and microscopic
states through the stress and strain-rate tensor fields, by using Lagrangian
particles (filled with polymer chains) along the spinning line. We introduce a
large number of Lagrangian fluid particles into the fluid, each containing
Np-Hookean-dumbbells to mimic the polymer chains (Np=$10^4$), which is
equivalent to the upper convected Maxwell fluid in the limit that
Np$\rightarrow \infty$. Depending on the Reynolds number Re, we studied the
dynamical behaviors of fibers for the (a) Re =0 and (b) finite Re cases, for
different draw ratios Dr, ranging from 10 to 30, and two typical Deborah
numbers De=$10^{-3}$ and De=$10^{-2}$. In the limit Re$\rightarrow$ 0 (a), as
the Deborah number De increases, the elastic effect makes the system stable. At
finite Re (b), we found that inertial effects play an important role in
determining the dynamical behavior of the spinning process, and for
Dr=$10^{-2}$ the system is quite stable, at least up to a draw ratio of Dr=30.
We also found that the fiber velocity and cross section area are determined
solely by the draw ratio. By comparing the velocity and cross section area
profiles with the end-point distribution for the dumbbell connective vectors,
for dumbbells located in Lagrangian particles along typical places along the
spinning line, we show that our multiscale simulation method successfully
bridges the microscopic state of the system with its simultaneous macroscopic
flow behavior. It is also confirmed that the present schemes gives good
agreements with the results obtained by the Maxwell constitutive equation.


title:
Dynamics in chemotaxis models of parabolic-elliptic type on bounded
  domain with time and space dependent logistic sources

abstract:
  This paper considers the dynamics of the following chemotaxis system $$
\begin{cases} u_t=\Delta u-\chi\nabla (u\cdot \nabla
v)+u\left(a_0(t,x)-a_1(t,x)u-a_2(t,x)\int_{\Omega}u\right),\quad x\in \Omega\cr
0=\Delta v+ u-v,\quad x\in \Omega \quad \cr \frac{\partial u}{\partial
n}=\frac{\partial v}{\partial n}=0,\quad x\in\partial\Omega, \end{cases} $$
where $\Omega \subset \mathbb{R}^n(n\geq 1)$ is a bounded domain with smooth
boundary $\partial\Omega$ and $a_i(t,x)$ ($i=0,1,2$) are locally H\"older
continuous in $t\in\mathbb{R}$ uniformly with respect to $x\in\bar{\Omega}$ and
continuous in $x\in\bar{\Omega}$. We first prove the local existence and
uniqueness of classical solutions $(u(x,t;t_0,u_0),v(x,t;t_0,u_0))$ with
$u(x,t_0;t_0,u_0)=u_0(x)$ for various initial functions $u_0(x)$. Next, under
some conditions on the coefficients $a_1(t,x)$, $a_2(t,x)$, $\chi$ and $n$, we
prove the global existence and boundedness of classical solutions
$(u(x,t;t_0,u_0),v(x,t;t_0,u_0))$ with given nonnegative initial function
$u(x,t_0;t_0,u_0)=u_0(x)$. Then, under the same conditions for the global
existence, we show that the system has an entire positive classical solution
$(u^*(x,t),v^*(x,t))$. Moreover, if $a_i(t,x)$ $(i=0,1,2)$ are periodic in $t$
with period $T$ or are independent of $t$, then the system has a time periodic
positive solution $(u^*(x,t),v^*(x,t))$ with periodic $T$ or a steady state
positive solution $(u^*(x),v^*(x))$. If $a_i(t,x)$ $(i=0,1,2)$ are independent
of $x$ , then the system has a spatially homogeneous entire positive solution
$(u^*(t),v^*(t))$. Finally, under some further assumptions, we prove that the
system has a unique entire positive solution $(u^*(x,t),v^*(x,t))$ which is
globally stable . Moreover, if $a_i(t,x)$ $(i=0,1,2)$ are periodic or almost
periodic in $t$, then $(u^*(x,t),v^*(x,t))$ is also periodic or almost periodic
in $t$.


title:
Creation of a tight PSF array for scanning structured illumination via
  phase retrieval

abstract:
  In this work, we propose a structured illumination (SI) method based on a
two-photon excitation (TPE) scanning laser beam. Advantages of TPE methods
include optical sectioning, low photo-toxicity, and robustness in the face of
sample induced scattering. We designed a novel multi-spot point spread function
(PSF) for a fast, two-photon scanning SIM microscope. Our multi-spot PSF is
generated with a phase retrieval algorithm. We show how to obtain the phase
distribution and then simulate the effect of this distribution on a spatial
light modulator (SLM), which produces the multi-spot PSF in the object plane of
the microscope. We produce simulations that show the viability of this method.
The results are simulated and a multi-spot PSF scanning SIM microscope is
proposed.


title:
Turbulent-diffusion Mediated CO Depletion in Weakly Turbulent
  Protoplanetary disks

abstract:
  Volatiles, especially CO, are important gas tracers of protoplanetary disks
(PPDs). Freeze-out and sublimation processes determine their division between
gas and solid phases, which affects both which disk regions can be traced by
which volatiles, and the formation and composition of planets. Recently,
multiple lines of evidence suggest that CO is substantially depleted from the
gas in the outer regions of PPDs. In this letter, we show that the gas dynamics
in the outer PPDs facilitates volatile depletion through a mechanism which we
term "runaway freeze-out". Using a simple 1D model that incorporates dust
settling, turbulent diffusion of dust and volatiles, as well as volatile
freeze-out/sublimation processes, we show that as long as turbulence in the
cold midplane is sufficiently weak to allow majority of the small grains to
settle, CO in the warm surface layer can be turbulently mixed into the midplane
region and depleted by freeze-out. The level of depletion sensitively depends
on the level of disk turbulence. Based on recent disk simulations that suggest
a layered turbulence profile with very weak midplane turbulence and strong
turbulence at disk surface, CO and other volatiles can be efficiently depleted
by a factor of a few over Myr timescales.


title:
Discussion on Lorentz Invariance Violation of Non-commutative Field
  Theory and Neutrino Oscillation

abstract:
  Depending on deformed canonical anti-commutation relations, massless neutrino
oscillation based on Lorentz invariance violation in non-commutative field
theory is discussed. It is found that the previous studies about massless
neutrino oscillation within deformed canonical anti-commutation relations
should satisfy the condition of new Moyal product and new non standard
commutation relations. Furthermore, comparing the Lorentz Invariant Violation
parameters $\mathit{A}$ in the previous studies with new Moyal product and new
non standard commutation relations, we find that the orders of magnitude of
non-commutative parameters (Lorentz invariant Violation parameters
$\mathit{A}$) is not self-consistent. This inconsistency means that the
previous studies of Lorentz invariance violation in non-commutative field
theory may not naturally explain massless neutrino oscillation. In other words,
it should be impossible to explain neutrino oscillation by Lorentz invariance
violation in non-commutative field theory. This conclusion is supported by the
latest atmospheric neutrinos experimental results from the Super-Kamiokande
Collaboration, which show that no evidence of Lorentz invariance violation on
atmospheric neutrinos was observed.


title:
Zero, Normal and Super-radiant Modes for Scalar and Spinor Fields in
  Kerr-anti de Sitter Spacetime

abstract:
  Zero and normal modes for scalar and spinor fields in Kerr-anti de Sitter
spacetime are studied as bound state problem with Dirichlet and Neumann
boundary conditions. Zero mode is defined as the momentum near the horizon to
be zero: $p_{\rm H}=\omega-\Omega_{\rm H}m=0$, and is shown not to exist as
physical state for both scalar and spinor fields. Physical normal modes satisfy
the spectrum condition $p_{\rm H}>0$ as a result of non-existence of zero mode
and the analyticity with respect to rotation parameter $a$ of Kerr-anti de
Sitter black hole. Comments on the super-radiant modes and the thermodynamics
of black hole are given in relation to the spectrum condition for normal modes.
Preliminary numerical analysis on normal modes is presented.


title: Lexical-Morphological Modeling for Legal Text Analysis

abstract:
  In the context of the Competition on Legal Information Extraction/Entailment
(COLIEE), we propose a method comprising the necessary steps for finding
relevant documents to a legal question and deciding on textual entailment
evidence to provide a correct answer. The proposed method is based on the
combination of several lexical and morphological characteristics, to build a
language model and a set of features for Machine Learning algorithms. We
provide a detailed study on the proposed method performance and failure cases,
indicating that it is competitive with state-of-the-art approaches on Legal
Information Retrieval and Question Answering, while not needing extensive
training data nor depending on expert produced knowledge. The proposed method
achieved significant results in the competition, indicating a substantial level
of adequacy for the tasks addressed.


title:
Dependence of in-situ Bose condensate size on frequency of RF-field used
  for evaporative cooling

abstract:
  We report the results of in-situ characterization of $ ^{87}$Rb atom cloud in
a quadrupole Ioffe configuration (QUIC) magnetic trap after radio frequency
(RF) evaporative cooling of the trapped atom cloud. The in-situ absorption
images of the atom cloud have shown clear bimodal optical density (OD) profiles
which indicate the Bose-Einstein condensation (BEC) phase transition in the
trapped gas. Also, we report the measured variation in the sizes of the
condensate and thermal clouds with the final frequency in the frequency scan of
the RF-field applied for evaporative cooling. The results are consistent with
the theoretical understanding and predictions reported earlier.


title: Holographic Description of 2D Conformal Block in Semi-classical Limit

abstract:
  In this paper, we study the holographic descriptions of the conformal block
of heavy operators in two-dimensional large c conformal field theory. We
consider the case that the operators are pairwise inserted such that the
distance between the operators in a pair is much smaller than the others. In
this case, each pair of heavy operators creates a conical defect in the bulk.
We propose that the conformal block is dual to the on-shell action of three
dimensional geometry with conical defects in the semi-classical limit. We show
that the variation of the on-shell action with respect to the conical angle is
equal to the length of the corresponding conical defect. We derive this
differential relation on the conformal block in the field theory by introducing
two extra light operators as both the probe and the perturbation. Our study
also suggests that the area law of the holographic Renyi entropy must holds for
a large class of states generated by a finite number of heavy operators
insertion.


title:
Strong gravitational lensing by a Konoplya-Zhidenko rotating non-Kerr
  compact object

abstract:
  Konoplya and Zhidenko have proposed recently a rotating non-Kerr black hole
metric beyond General Relativity and make an estimate for the possible
deviations from the Kerr solution with the data of GW 150914. We here study the
strong gravitational lensing in such a rotating non-Kerr spacetime with an
extra deformation parameter. We find that the condition of existence of
horizons is not inconsistent with that of the marginally circular photon orbit.
Moreover, the deflection angle of the light ray near the weakly naked
singularity covered by the marginally circular orbit diverges logarithmically
in the strong-field limit. In the case of the completely naked singularity, the
deflection angle near the singularity tends to a certain finite value, whose
sign depends on the rotation parameter and the deformation parameter. These
properties of strong gravitational lensing are different from those in the
Johannsen-Psaltis rotating non-Kerr spacetime and in the Janis-Newman-Winicour
spacetime. Modeling the supermassive central object of the Milk Way Galaxy as a
Konoplya-Zhidenko rotating non-Kerr compact object, we estimated the numerical
values of observables for the strong gravitational lensing including the time
delay between two relativistic images.


title: Wire Recycling for Quantum Circuit Optimization

abstract:
  Quantum information processing is expressed using quantum bits (qubits) and
quantum gates which are arranged in the terms of quantum circuits. Here, each
qubit is associated to a quantum circuit wire which is used to conduct the
desired operations. Most of the existing quantum circuits allocate a single
quantum circuit wire for each qubit and, hence, introduce a significant
overhead. In fact, qubits are usually not needed during the entire computation
but only between their initialization and measurement. Before and after that,
corresponding wires may be used by other qubits. In this work, we propose a
solution which exploits this fact in order to optimize the design of quantum
circuits with respect to the required wires. To this end, we introduce a
representation of the lifetimes of all qubits which is used to analyze the
respective need for wires. Based on this analysis, a method is proposed which
"recycles" the available wires and, by this, reduces the size of the resulting
circuit. Experimental evaluations based on established reversible and
fault-tolerant quantum circuits confirm that the proposed solution reduces the
amount of wires by more than 90% compared to unoptimized quantum circuits.


title: Randomized Prediction Games for Adversarial Machine Learning

abstract:
  In spam and malware detection, attackers exploit randomization to obfuscate
malicious data and increase their chances of evading detection at test time;
e.g., malware code is typically obfuscated using random strings or byte
sequences to hide known exploits. Interestingly, randomization has also been
proposed to improve security of learning algorithms against evasion attacks, as
it results in hiding information about the classifier to the attacker. Recent
work has proposed game-theoretical formulations to learn secure classifiers, by
simulating different evasion attacks and modifying the classification function
accordingly. However, both the classification function and the simulated data
manipulations have been modeled in a deterministic manner, without accounting
for any form of randomization. In this work, we overcome this limitation by
proposing a randomized prediction game, namely, a non-cooperative
game-theoretic formulation in which the classifier and the attacker make
randomized strategy selections according to some probability distribution
defined over the respective strategy set. We show that our approach allows one
to improve the trade-off between attack detection and false alarms with respect
to state-of-the-art secure classifiers, even against attacks that are different
from those hypothesized during design, on application examples including
handwritten digit recognition, spam and malware detection.


title: Notes on linearly H-closed spaces and od-selection principles

abstract:
  A space is called linearly H-closed iff any chain cover possesses a dense
member. This property lies strictly between feeble compactness and
H-closedness. While regular H-closed spaces are compact, there are linearly
H-closed spaces which are even collectionwise normal and Fr\'echet-Urysohn. We
give examples in other classes, and ask whether there is a first countable
normal linearly H-closed non-compact space in ZFC. We show that PFA implies a
negative answer if the space is moreover either locally separable or locally
compact and locally ccc. Ostaszewski space (built with $\diamondsuit$) is an
example which is even perfectly normal. We also investigate Menger-like
properties for the class of od-covers, that is, covers whose members are open
and dense.


title: Waves on accelerating dodecahedral universes

abstract:
  We investigate the wave propagation on a compact 3-manifold of constant
positive curvature with a non trivial topology, the Poincar\'e dodecahedral
space, when the scale factor is exponentially increasing. We prove the
existence of a limit state as t tends to infinity and we get its analytic
expression. The deep sky is described by this asymptotic profile thanks to the
Sachs-Wolfe formula. We transform the Cauchy problem into a mixed problem posed
on a fundamental domain determined by the quaternionic calculus. We perform an
accurate scheme of computation: we employ a variational method using a space of
second order finite elements that is invariant under the action of the binary
icosahedral group.


title:
Quasi-Optimal Error Estimates for the Incompressible Navier-Stokes
  Problem Discretized by Finite Element Methods and Pressure-Correction
  Projection with Velocity Stabilization

abstract:
  We consider error estimates for the fully discretized instationary
Navier-Stokes problem. For the spatial approximation we use conforming inf-sup
stable finite element methods in conjunction with grad-div and local projection
stabilization acting on the streamline derivative. For the temporal
discretization a pressure-correction projection algorithm based on BDF2 is
used. We can show quasi-optimal rates of convergence with respect to time and
spatial discretization for all considered error measures. Some of the error
estimates are quasi-robust with respect to the Reynolds number.


title: Approximating Vizing's independence number conjecture

abstract:
  In 1965, Vizing conjectured that the independence ratio of edge-chromatic
critical graphs is at most $\frac{1}{2}$. We prove that for every $\epsilon >
0$ this conjecture is equivalent to its restriction on a specific set of
edge-chromatic critical graphs with independence ratio smaller than
$\frac{1}{2} + \epsilon$.


title: The ARCHES project

abstract:
  ARCHES (Astronomical Resource Cross-matching for High Energy Studies) is a
FP7-Space funded project whose aim is to provide the international astronomical
community with well-characterised multi-wavelength data in the form of spectral
energy distributions (SEDs) for large samples of objects extracted from the
3XMM DR5 X-ray catalogue of serendipitous sources. The project has developed
new tools implementing fully probabilistic simultaneous cross-correlation of
several catalogues for unresolved sources and a multi-wavelength finder for
clusters of galaxies for extended sources. These enhanced resources have been
tested in the framework of several science cases.


title: Greedy MAXCUT Algorithms and their Information Content

abstract:
  MAXCUT defines a classical NP-hard problem for graph partitioning and it
serves as a typical case of the symmetric non-monotone Unconstrained Submodular
Maximization (USM) problem. Applications of MAXCUT are abundant in machine
learning, computer vision and statistical physics. Greedy algorithms to
approximately solve MAXCUT rely on greedy vertex labelling or on an edge
contraction strategy. These algorithms have been studied by measuring their
approximation ratios in the worst case setting but very little is known to
characterize their robustness to noise contaminations of the input data in the
average case. Adapting the framework of Approximation Set Coding, we present a
method to exactly measure the cardinality of the algorithmic approximation sets
of five greedy MAXCUT algorithms. Their information contents are explored for
graph instances generated by two different noise models: the edge reversal
model and Gaussian edge weights model. The results provide insights into the
robustness of different greedy heuristics and techniques for MAXCUT, which can
be used for algorithm design of general USM problems.


title:
Theory of gravity admitting arbitrary choice of the energy density
  reference level

abstract:
  Five-vectors theory of gravity is proposed, which admits an arbitrary choice
of the energy density reference level. This theory is formulated as the
constraint theory, where the Lagrange multipliers turn out to be restricted to
some class of vector fields unlike the General Relativity (GR), where they are
arbitrary. The possible cosmological implication of the model proposed is that
the residual vacuum fluctuations dominate during the whole evolution of the
universe. That resembles the universe having a nearly linear dependence of
scale factor on cosmic time.


title: The Cesaro operator in growth Banach spaces of analytic functions

abstract:
  The Cesaro operator $\mathsf{C}$, when acting in the classical growth Banach
spaces $A^{-\gamma}$ and $A_0^{-\gamma}$, for $\gamma > 0 $, of analytic
functions on $\mathbb{D}$, is investigated. Based on a detailed knowledge of
their spectra (due to A. Aleman and A.-M. Persson) we are able to determine the
norms of these operators precisely. It is then possible to characterize the
mean ergodic and related properties of $\mathsf{C}$ acting in these spaces. In
addition, we determine the largest Banach space of analytic functions on
$\mathbb{D}$ which $\mathsf{C}$ maps into $A^{-\gamma}$ (resp. into
$A_0^{-\gamma}$); this optimal domain space always contains $A^{-\gamma}$
(resp. $A_0^{-\gamma}$) as a proper subspace.


title:
Performance of Adaptive Link Selection with Buffer-Aided Relays in
  Underlay Cognitive Networks

abstract:
  In this paper, we investigate the performance of a three-node dual-hop
cognitive radio network (CRN) with a half-duplex (HD) decode-and-forward (DF)
buffer-aided relay. We derive expressions for the average rate and symbol error
rate (SER) performance of an adaptive link selection based channel-aware
buffer-aided relay (CABR) scheme that imposes peak-power and peak-interference
constraints on the secondary nodes, and compare them with those of conventional
non-buffer-aided relay (CNBR) and conventional buffer-aided relay (CBR) schemes
for a delay-tolerant system. For finite-delay systems, we analyze the
performance of a modified threshold-based scheme for fixed-rate transmission,
and demonstrate that use of a last-in-first-out buffer is advantageous in some
situations. We bring out the trade-offs between delay, throughput and SER.
Computer simulation results are presented to demonstrate accuracy of the
derived expressions.