title:
Stationary Large Amplitude Dynamics of the Finite Chain of Harmonically
  Coupled Pendulums

abstract:
  We present an analytical description of the large-amplitude stationary
oscillations of the finite discrete system of harmonically-coupled pendulums
without any restrictions to their amplitudes (excluding a vicinity of $\pi$).
Although this model has numerous applications in different fields of physics it
was studied earlier in the infinite limit only. The developed approach allows
to find the dispersion relations for arbitrary amplitudes of the nonlinear
normal modes. We underline that the long-wavelength approximation, which is
described by well- known sine-Gordon equation leads to inadequate zone
structure for the amplitude order of $\pi/2$ even if the chain is long enough.
The extremely complex zone structure at the large amplitudes corresponds to lot
of resonances between nonlinear normal modes even with strongly different wave
numbers. Due to complexity of the dispersion relations the more short
wavelength modes can possess the smaller frequencies. The numerical simulation
of the dynamics of the finite-length chain is in a good agreement with obtained
analytical predictions.


title: Slow motion for the 1D Swift-Hohenberg equation

abstract:
  The goal of this paper is to study the behavior of certain solutions to the
Swift-Hohenberg equation on a one-dimensional torus $\mathbb{T}$. Combining
results from $\Gamma$-convergence and ODE theory, it is shown that solutions
corresponding to initial data that is $L^1$-close to a jump function $v$,
remain close to $v$ for large time. This can be achieved by regarding the
equation as the $L^2$-gradient flow of a second order energy functional, and
obtaining asymptotic lower bounds on this energy in terms of the number of
jumps of $v$.


title: Taylor line swimming in microchannels and cubic lattices of obstacles

abstract:
  Microorganisms naturally move in microstructured fluids. Using the simulation
method of multi-particle collision dynamics, we study an undulatory Taylor line
swimming in a two-dimensional microchannel and in a cubic lattice of obstacles,
which represent simple forms of a microstructured environment. In the
microchannel the Taylor line swims at an acute angle along a channel wall with
a clearly enhanced swimming speed due to hydrodynamic interactions with the
bounding wall. While in a dilute obstacle lattice swimming speed is also
enhanced, a dense obstacle lattice gives rise to geometric swimming. This new
type of swimming is characterized by a drastically increased swimming speed.
Since the Taylor line has to fit into the free space of the obstacle lattice,
the swimming speed is close to the phase velocity of the bending wave traveling
along the Taylor line. While adjusting its swimming motion within the lattice,
the Taylor line chooses a specific swimming direction, which we classify by a
lattice vector. When plotting the swimming velocity versus the magnitude of the
lattice vector, all our data collapse on a single master curve. Finally, we
also report more complex trajectories within the obstacle lattice.


title: Weak factorization of Hardy spaces in the Bessel setting

abstract:
  We provide the weak factorization of the Hardy spaces $H^{p}(\mathbb{R}_+,
dm_{\lambda})$ in the Bessel setting, for $p\in \left(\frac{2\lambda +
1}{2\lambda + 2}, 1\right]$. As a corollary we obtain a characterization of the
boundedness of the commutator $[b, R_{\Delta_{\lambda}}]$ from
$L^{q}(\mathbb{R}_+, dm_{\lambda})$ to $L^{r}(\mathbb{R}_+, dm_{\lambda})$ when
$b\in \textrm{Lip}_{\alpha}(\mathbb{R}_+, dm_{\lambda})$ provided that $\alpha
= \frac{1}{q} - \frac{1}{r}$. The results are a slight generalization and
modification of the work of Duong, Li, Yang, and the second named author, which
in turn are based on modifications and adaptations of work by Uchiyama.


title: Twists of non-hyperelliptic curves of genus 3

abstract:
  In this paper we explicitly compute equations for the twists of all the
smooth plane quartic curves defined over a number field k. Since the plane
quartic curves are non-hyperelliptic curves of genus 3 we can apply the method
developed by the author in a previous article. The starting point is a
classification due to Henn of the plane quartic curves with non-trivial
automorphism group up to C-isomorphism.


title:
Observation of Large Topologically Trivial Fermi-Arcs in the Candidate
  Type-II Weyl Semimetal WTe2

abstract:
  We report angle-resolved photoemission experiments resolving the distinct
electronic structure of the inequivalent top and bottom (001) surfaces of WTe2.
On both surfaces, we identify a surface state that forms a large Fermi-arc
emerging out of the bulk electron pocket. Using surface electronic structure
calculations, we show that these Fermi arcs are topologically trivial and that
their existence is independent of the presence of type-II Weyl points in the
bulk band structure. This implies that the observation of surface Fermi arcs
alone does not allow the identification of WTe2 as a topological Weyl
semimetal. We further use the identification of the two different surfaces to
clarify the number of Fermi surface sheets in WTe2.


title: Multiple Comparative Metagenomics using Multiset k-mer Counting

abstract:
  Background. Large scale metagenomic projects aim to extract biodiversity
knowledge between different environmental conditions. Current methods for
comparing microbial communities face important limitations. Those based on
taxonomical or functional assignation rely on a small subset of the sequences
that can be associated to known organisms. On the other hand, de novo methods,
that compare the whole sets of sequences, either do not scale up on ambitious
metagenomic projects or do not provide precise and exhaustive results.
  Methods. These limitations motivated the development of a new de novo
metagenomic comparative method, called Simka. This method computes a large
collection of standard ecological distances by replacing species counts by
k-mer counts. Simka scales-up today's metagenomic projects thanks to a new
parallel k-mer counting strategy on multiple datasets.
  Results. Experiments on public Human Microbiome Project datasets demonstrate
that Simka captures the essential underlying biological structure. Simka was
able to compute in a few hours both qualitative and quantitative ecological
distances on hundreds of metagenomic samples (690 samples, 32 billions of
reads). We also demonstrate that analyzing metagenomes at the k-mer level is
highly correlated with extremely precise de novo comparison techniques which
rely on all-versus-all sequences alignment strategy or which are based on
taxonomic profiling.


title: Small gaps in the spectrum of the rectangular billiard

abstract:
  We study the size of the minimal gap between the first N eigenvalues of the
Laplacian on a rectangular billiard having irrational squared aspect ratio
$\alpha$, in comparison to the corresponding quantity for a Poissonian
sequence. If $\alpha$ is a quadratic irrationality of certain type, such as the
square root of a rational number, we show that the minimal gap is roughly of
size 1/N, which is essentially consistent with Poisson statistics. We also give
related results for a set of $\alpha$'s of full measure. However, on a fine
scale we show that Poisson statistics is violated for all $\alpha$. The proofs
use a variety of ideas of an arithmetical nature, involving Diophantine
approximation, the theory of continued fractions, and results in analytic
number theory.


title:
Optimal feedback control of two-qubit entanglement in dissipative
  environments

abstract:
  We study the correction of errors intervening in two-qubit dissipating into
their own environments. This is done by resorting to local feedback actions
with the aim of preserving as much as possible the initial amount of
entanglement. Optimal control is found by first gaining insights from the
subsystem purity and then by numerical analysis on the concurrence. This is
tantamount to a double optimization, on the actuation and on the measurement
processes. Repeated feedback action is also investigated, thus paving the way
for a continuous time formulation and solution of the problem.


title:
Search for methane isotope fractionation due to Rayleigh distillation on
  Titan

abstract:
  We search for meridional variation in the abundance of CH$_3$D relative to
CH$_4$ on Titan using near-IR spectra obtained with NIRSPAO at Keck, which have
a photon-limited signal-to-noise ratio of $\sim$50. Our observations can rule
out a larger than 10% variation in the column of CH$_3$D below 50 km. The
preferential condensation of the heavy isotopologues will fractionate methane
by reducing CH$_3$D in the remaining vapor, and therefore these observations
place limits on the amount of condensation that occurs in the troposphere.
While previous estimates of CH$_3$D fractionation on Titan have estimated an
upper limit of -6 per mil, assuming a solid condensate, we consider more recent
laboratory data for the equilibrium fractionation over liquid methane, and use
a Rayleigh distillation model to calculate fractionation in an ascending parcel
of air that is following a moist adiabat. We find that deep, precipitating
convection can enhance the fractionation of the remaining methane vapor by -10
to -40 per mil, depending on the final temperature of the rising parcel. By
relating fractionation of our reference parcel model to the pressure level
where the moist adiabat achieves the required temperature, we argue that the
measured methane fractionation constrains the outflow level for a deep
convective event. Observations with a factor of at least 4 to 6 times larger
signal-to-noise are required to detect this amount of fractionation, depending
on the altitude range over which the outflow from deep convection occurs.


title: How deep is knowledge tracing?

abstract:
  In theoretical cognitive science, there is a tension between highly
structured models whose parameters have a direct psychological interpretation
and highly complex, general-purpose models whose parameters and representations
are difficult to interpret. The former typically provide more insight into
cognition but the latter often perform better. This tension has recently
surfaced in the realm of educational data mining, where a deep learning
approach to predicting students' performance as they work through a series of
exercises---termed deep knowledge tracing or DKT---has demonstrated a stunning
performance advantage over the mainstay of the field, Bayesian knowledge
tracing or BKT. In this article, we attempt to understand the basis for DKT's
advantage by considering the sources of statistical regularity in the data that
DKT can leverage but which BKT cannot. We hypothesize four forms of regularity
that BKT fails to exploit: recency effects, the contextualized trial sequence,
inter-skill similarity, and individual variation in ability. We demonstrate
that when BKT is extended to allow it more flexibility in modeling statistical
regularities---using extensions previously proposed in the literature---BKT
achieves a level of performance indistinguishable from that of DKT. We argue
that while DKT is a powerful, useful, general-purpose framework for modeling
student learning, its gains do not come from the discovery of novel
representations---the fundamental advantage of deep learning. To answer the
question posed in our title, knowledge tracing may be a domain that does not
require `depth'; shallow models like BKT can perform just as well and offer us
greater interpretability and explanatory power.


title:
On the phenomenon of mixed dynamics in Pikovsky-Topaj system of coupled
  rotators

abstract:
  A one-parameter family of time-reversible systems on $\mathbb{T}^3$ is
considered. It is shown that the dynamics is not conservative, namely the
attractor and repeller intersect but not coincide. We explain this as the
manifestation of the so-called mixed dynamics phenomenon which corresponds to a
persistent intersection of the closure of stable periodic orbits and the
closure of the completely unstable periodic orbits. We search for the stable
and unstable periodic orbits indirectly, by finding non-conservative saddle
periodic orbits and heteroclinic connections between them. In this way, we are
able to claim the existence of mixed dynamics for a large range of parameter
values. We investigate local and global bifurcations that can be used for the
detection of mixed dynamics.


title: Gradient estimates of Dirichlet heat kernels for unimodal Levy processes

abstract:
  Under some mild assumptions on the Levy measure and the symbol we obtain
gradient estimates of Dirichlet heat kernels for pure-jump isotropic unimodal
Levy processes in $R^d$.


title: Regular formal moduli spaces and arithmetic transfer conjectures

abstract:
  We define various formal moduli spaces of p-divisible groups which are
regular, and morphisms between them. We formulate arithmetic transfer
conjectures, which are variants of the arithmetic fundamental lemma conjecture
of the third author in the presence of ramification. These conjectures include
the AT conjecture of our previous joint paper. We prove these conjectures in
low-dimensional cases.


title:
Displaced vertex searches for sterile neutrinos at future lepton
  colliders

abstract:
  We investigate the sensitivity of future lepton colliders to displaced
vertices from the decays of long-lived heavy (almost sterile) neutrinos with
electroweak scale masses and detectable time of flight. As future lepton
colliders we consider the FCC-ee, the CEPC, and the ILC, searching at the
Z-pole and at the center-of-mass energies of 240, 350 and 500 GeV. For a
realistic discussion of the detector response to the displaced vertex signal
and the Standard Model background we consider the ILC's Silicon Detector (SiD)
as benchmark for the future lepton collider detectors. We find that displaced
vertices constitute a powerful search channel for sterile neutrinos, sensitive
to squared active-sterile mixing angles as small as $10^{-11}$.


title: Form factor ratio from unpolarized elastic electron proton scattering

abstract:
  A reanalysis of unpolarized electron-proton elastic scattering data is done
in terms of the electric to magnetic form factor squared ratio. This observable
is in principle more robust against experimental correlations and global
normalizations. The present analysis shows indeed that it is a useful quantity
that contains reliable and coherent information. The comparison with the ratio
extracted from the measurement of the longitudinal to transverse polarization
of the recoil proton in polarized electron-proton scattering shows that the
results are compatible within the experimental errors. Limits are set on the
kinematics where the physical information on the form factors can be safely
extracted. The results presented in this work bring a decisive piece of
information to the controversy on the deviation of the proton form factors from
the dipole dependence.


title:
A Jacobian module for disentanglements and applications to Mond's
  conjecture

abstract:
  Given a germ of holomorphic map $f$ from $\mathbb C^n$ to $\mathbb C^{n+1}$,
we define a module $M(f)$ whose dimension over $\mathbb C$ is an upper bound
for the $\mathscr A$-codimension of $f$, with equality if $f$ is weighted
homogeneous. We also define a relative version $M_y(F)$ of the module, for
unfoldings $F$ of $f$. The main result is that if $(n,n+1)$ are nice
dimensions, then the dimension of $M(f)$ over $\mathbb C$ is an upper bound of
the image Milnor number of $f$, with equality if and only if the relative
module $M_y(F)$ is Cohen-Macaulay for some stable unfolding $F$. In particular,
if $M_y(F)$ is Cohen-Macaulay, then we have Mond's conjecture for $f$.
Furthermore, if $f$ is quasi-homogeneous, then Mond's conjecture for $f$ is
equivalent to the fact that $M_y(F)$ is Cohen-Macaulay. Finally, we observe
that to prove Mond's conjecture, it suffices to prove it in a suitable family
of examples.


title:
Phase transitions in two tunnel-coupled HgTe quantum wells. Bilayer
  graphene analogy and beyond

abstract:
  HgTe quantum wells possess remarkable physical properties as for instance the
quantum spin Hall state and the 'single-valley' analog of graphene, depending
on their layer thicknesses and barrier composition. However, double HgTe
quantum wells yet contain more fascinating and still unrevealed features. Here
we report on the study of the quantum phase transitions in tunnel-coupled HgTe
layers separated by CdTe barrier. We demonstrate that this system has a 3/2
pseudo spin degree of freedom, which features a number of particular properties
associated with the spin-dependent coupling between HgTe layers. We discover a
specific metal phase arising in a wide range of HgTe and CdTe layer
thicknesses, in which a gapless bulk and a pair of helical edge states coexist.
This phase holds some properties of bilayer graphene such as an unconventional
quantum Hall effect and an electrically-tunable band gap. In this 'bilayer
graphene' phase, electric field opens the band gap and drives the system into
the quantum spin Hall state. Furthermore, we discover a new type of quantum
phase transition arising from a mutual inversion between second electron- and
hole-like subbands. This work paves the way towards novel materials based on
multi-layered topological insulators.


title:
QCD fixed points: Banks-Zaks scenario or dynamical gluon mass
  generation?

abstract:
  Fixed points in QCD can appear when the number of quark flavors ($N_f$) is
increased above a certain critical value as proposed by Banks and Zaks (BZ).
There is also the possibility that QCD possess an effective charge indicating
an infrared frozen coupling constant. In particular, an infrared frozen
coupling associated to dynamical gluon mass generation (DGM) does lead to a
fixed point even for a small number of quarks. We compare the BZ and DGM
mechanisms, their $\beta$ functions and fixed points, and within the
approximations of this work, which rely basically on extrapolations of the
dynamical gluon masses at large $N_f$, we verify that near the so called QCD
conformal window both cases exhibit fixed points at similar coupling constant
values ($g^*$). We argue that the states of minimum vacuum energy, as a
function of the coupling constant up to $g^*$ and for several $N_f$ values, are
related to the dynamical gluon mass generation mechanism.


title: Maximum Principle for Quasi-linear Reflected Backward SPDEs

abstract:
  This paper establishes a maximum principle for quasi-linear reflected
backward stochastic partial differential equations (RBSPDEs for short). We
prove the existence and uniqueness of the weak solution to RBSPDEs allowing for
non-zero Dirichlet boundary conditions and, using a stochastic version of De
Giorgi's iteration, establish the maximum principle for RBSPDEs on a general
domain. The maximum principle for RBSPDEs on a bounded domain and the maximum
principle for backward stochastic partial differential equations (BSPDEs for
short) on a general domain can be obtained as byproducts. Finally, the local
behavior of the weak solutions is considered.


title:
CNN Image Retrieval Learns from BoW: Unsupervised Fine-Tuning with Hard
  Examples

abstract:
  Convolutional Neural Networks (CNNs) achieve state-of-the-art performance in
many computer vision tasks. However, this achievement is preceded by extreme
manual annotation in order to perform either training from scratch or
fine-tuning for the target task. In this work, we propose to fine-tune CNN for
image retrieval from a large collection of unordered images in a fully
automated manner. We employ state-of-the-art retrieval and
Structure-from-Motion (SfM) methods to obtain 3D models, which are used to
guide the selection of the training data for CNN fine-tuning. We show that both
hard positive and hard negative examples enhance the final performance in
particular object retrieval with compact codes.


title: Topological Mirror Insulators in One Dimension

abstract:
  We demonstrate the existence of topological insulators in one dimension
protected by mirror and time-reversal symmetries. They are characterized by a
nontrivial $\mathbb{Z}_2$ topological invariant defined in terms of the
"partial" polarizations, which we show to be quantized in presence of a 1D
mirror point. The topological invariant determines the generic presence or
absence of integer boundary charges at the mirror-symmetric boundaries of the
system. We check our findings against spin-orbit coupled Aubry-Andr\'e-Harper
models that can be realized, e.g. in cold-atomic Fermi gases loaded in
one-dimensional optical lattices or in density- and Rashba spin-orbit-modulated
semiconductor nanowires. In this setup, in-gap end-mode Kramers doublets
appearing in the topologically non-trivial state effectively constitute a
double-quantum-dot with spin-orbit coupling.


title:
Electronic Structure, Optical and Dielectric Spectroscopy Study of
  TbMnO3

abstract:
  Spectral ellipsometry studies of the optical functions, first observation of
photoluminescence and low frequency dielectric permittivity investigations were
performed in ferroelectric - multiferroic TbMnO3 single crystals. The main
attention was paid to electronic band structure, nature of the main optical
transitions and unusual behavior of the dielectric permittivity in the region
of the sharp narrow temperature maximum, associated with ferroelectric phase
transition. It was found that magnitude of the permittivity maximum decreases
strongly with frequency, whereas position of maximum is frequency independent.
Observed features of polarization response can be described satisfactorily in
the frame of on the basis of the Landau-Khalatnikov theory for critical
relaxation polarization


title: Spin-Superfluidity and Spin-Current Mediated Non-Local Transport

abstract:
  Some strategies for reducing energy consumption in information processing
devices involve the use of spin rather than charge to carry information. This
idea is especially attractive when the spin current is a collective one carried
by the condensate of a magnetically ordered state, rather than a quasiparticle
current carried by electrons or magnons. In this Chapter we explain how
easy-plane magnets can be viewed as Bose-Einstein condensates of magnons,
defined in terms of quanta of the spin-component perpendicular to the easy
plane, and how they can carry dissipationless spin-currents that induce
non-local interactions between electrically isolated conducting channels. We
comment specifically on important differences between superconductivity in
normal/superconducting/normal circuits and spin-superfluidity in
normal/magnetic/normal circuits.


title:
Local and global holomorphic extensions of time-varying real analytic
  vector fields

abstract:
  In this paper, we consider time-varying real analytic vector fields as curves
on the space of real analytic vector fields. Using a suitable topology on the
space of real analytic vector fields, we study and characterize different
properties of time-varying real analytic vector fields. We study holomorphic
extensions of time-varying real analytic vector fields and show that under
suitable integrability conditions, a time-varying real analytic vector field on
a manifold can be extended to a time-varying holomorphic vector field on a
neighbourhood of that manifold. Moreover, we develop an operator setting, where
the nonlinear differential equation governing the flow of a time-varying real
analytic vector field can be considered as a linear differential equation on an
infinite dimensional locally convex vector space. Using the holomorphic
extension results, we show that the integrability of the time-varying vector
field ensures the convergence of the sequence of Picard iterations for this
linear differential equation. This gives us a series representation for the
flow of an integrable time-varying real analytic vector field. We also define
the exponential map between integrable time-varying real analytic vector fields
and their flows. Using the holomorphic extensions of time-varying real analytic
vector fields, we show that the exponential map is sequentially continuous.


title: Sterile neutrino dark matter and core-collapse supernovae

abstract:
  We have explored the impact of sterile neutrino dark matter on core-collapse
supernova explosions. We have included oscillations between electron neutrinos
or mixed $\mu,\tau$ neutrinos and right-handed sterile neutrinos into a
supernova model. We have chosen sterile neutrino masses and mixing angles that
are consistent with sterile neutrino dark matter candidates as indicated by
recent x-ray flux measurements. Using these simulations, we have explored the
impact of sterile neutrinos on the core bounce and shock reheating. We find
that, for ranges of sterile neutrino mass and mixing angle consistent with most
dark matter constraints, the shock energy can be significantly enhanced and
even a model that does not explode can be made to explode. In addition, we have
found that the presence of a sterile neutrino may lead to detectable changes in
the observed neutrino luminosities.


title: On small-time local controllability

abstract:
  In this paper, we study small-time local controllability of real analytic
control-affine systems under small perturbations of their vector fields.
Consider a real analytic control system $\mathcal{X}$ which is small-time
locally controllable and whose reachable sets shrink with the polynomial rate
of order $N$ with respect to time. We will prove a general theorem which states
that any real analytic control-affine system whose vector fields are
perturbations of the vector fields of $\mathcal{X}$ with polynomials of order
higher than $N$ is again small-time locally controllable. In particular, we
show that this result connects two long-standing open conjectures about
small-time local controllability of systems.


title: A Parallax-based Distance Estimator for Spiral Arm Sources

abstract:
  The spiral arms of the Milky Way are being accurately located for the first
time via trigonometric parallaxes of massive star forming regions with the
BeSSeL Survey, using the Very Long Baseline Array and the European VLBI
Network, and with the Japanese VERA project. Here we describe a computer
program that leverages these results to significantly improve the accuracy and
reliability of distance estimates to other sources that are known to follow
spiral structure. Using a Bayesian approach, sources are assigned to arms based
on their (l,b,v) coordinates with respect to arm signatures seen in CO and HI
surveys. A source's kinematic distance, displacement from the plane, and
proximity to individual parallax sources are also considered in generating a
full distance probability density function. Using this program to estimate
distances to large numbers of star forming regions, we generate a realistic
visualization of the Milky Way's spiral structure as seen from the northern
hemisphere.


title: Interface-induced Polarization in SrTiO$_3$-LaCrO$_3$ Superlattices

abstract:
  Epitaxial interfaces and superlattices comprised of polar and non-polar
perovskite oxides have generated considerable interest because they possess a
range of desirable properties for functional devices. In this work, emergent
polarization in superlattices of SrTiO$_3$ (STO) and LaCrO$_3$ (LCO) is
demonstrated. By controlling the interfaces between polar LCO and non-polar
STO, polarization is induced throughout the STO layers of the superlattice.
Using x-ray absorption near-edge spectroscopy and aberration-corrected scanning
transmission electron microscopy displacements of the Ti cations off-center
within TiO6 octahedra along the superlattice growth direction are measured.
This distortion gives rise to built-in potential gradients within the STO and
LCO layers, as measured by in situ x-ray photoelectron spectroscopy. Density
functional theory models explain the mechanisms underlying this behavior,
revealing the existence of both an intrinsic polar distortion and a built-in
electric field, which are due to alternately positively and negatively charged
interfaces in the superlattice. This study paves the way for controllable
polarization for carrier separation in multilayer materials and highlights the
crucial role that interface structure plays in governing such behavior.


title:
Incentivizing Sharing in Realtime D2D Streaming Networks: A Mean Field
  Game Perspective

abstract:
  We consider the problem of streaming live content to a cluster of co-located
wireless devices that have both an expensive unicast base-station-to-device
(B2D) interface, as well as an inexpensive broadcast device-to-device (D2D)
interface, which can be used simultaneously. Our setting is a streaming system
that uses a block-by-block random linear coding approach to achieve a target
percentage of on-time deliveries with minimal B2D usage. Our goal is to design
an incentive framework that would promote such cooperation across devices,
while ensuring good quality of service. Based on ideas drawn from truth-telling
auctions, we design a mechanism that achieves this goal via appropriate
transfers (monetary payments or rebates) in a setting with a large number of
devices, and with peer arrivals and departures. Here, we show that a Mean Field
Game can be used to accurately approximate our system. Furthermore, the
complexity of calculating the best responses under this regime is low. We
implement the proposed system on an Android testbed, and illustrate its
efficient performance using real world experiments.


title:
Schroedinger operators on exterior domains with Robin boundary
  conditions: heat kernel estimates

abstract:
  We study Schroedinger operators with Robin boundary conditions on exterior
domains in $\R^d$. We prove sharp point-wise estimates for the associated
semi-groups which show, in particular, how the boundary conditions affect the
time decay of the heat kernel in dimensions one and two. Applications to
spectral estimates are discussed as well.


title:
Locally topologically generic diffeomorphisms with Lyapunov unstable
  Milnor attractors

abstract:
  We prove that for every smooth compact manifold $M$ and any $r \ge 1$,
whenever there is an open domain in $\mathrm{Diff}^r(M)$ exhibiting a
persistent homoclinic tangency related to a basic set with a sectionally
dissipative periodic saddle, topologically generic diffeomorphisms in this
domain have Lyapunov unstable Milnor attractors. This implies, in particular,
that the instability of Milnor attractors is locally topologically generic in
$C^1$ if $\mathrm{dim}\,M \ge 3$ and in $C^2$ if $\mathrm{dim}\,M = 2$.
Moreover, it follows from the results of C. Bonatti, L. J. D\'iaz and E. R.
Pujals that, for a $C^1$ topologically generic diffeomorphism of a closed
manifold, either any homoclinic class admits some dominated splitting, or this
diffeomorphism has an unstable Milnor attractor, or the inverse diffeomorphism
has an unstable Milnor attractor. The same results hold for statistical and
minimal attractors.


title: Energetics of Cs in Sigma3 grain boundary of 3C-SiC

abstract:
  Energetics of Cs defects at Sigma3 grain boundaries of 3C-SiC has been
studied using density functional theory to understand the role of the grain
boundaries in Cs diffusion and its eventual release from the tristructural
isotropic fuel particles (TRISO). Cs is shown to be much more stable at the
Sigma3 grain boundary than in bulk of SiC with a significant decrease (7-17eV)
in the formation energies at the grain boundaries than in bulk. It is found to
have even lower formation energies than those of Ag at the Sigma3 grain
boundaries, while this trend was opposite in the bulk SiC as demonstrate
previously from similar density functional theory calculations. Based on these
results, a possible route to control Cs release from SiC layer via
grain-boundary-engineering is suggested.


title:
Ultrafast energy and momentum resolved dynamics of magnetic correlations
  in photo-doped Mott insulator Sr$_2$IrO$_4$

abstract:
  Measuring how the magnetic correlations throughout the Brillouin zone evolve
in a Mott insulator as charges are introduced dramatically improved our
understanding of the pseudogap, non-Fermi liquids and high $T_C$
superconductivity. Recently, photoexcitation has been used to induce similarly
exotic states transiently. However, understanding how these states emerge has
been limited because of a lack of available probes of magnetic correlations in
the time domain, which hinders further investigation of how light can be used
to control the properties of solids. Here we implement magnetic resonant
inelastic X-ray scattering at a free electron laser, and directly determine the
magnetization dynamics after photo-doping the Mott insulator Sr$_2$IrO$_4$. We
find that the non-equilibrium state 2~ps after the excitation has strongly
suppressed long-range magnetic order, but hosts photo-carriers that induce
strong, non-thermal magnetic correlations. The magnetism recovers its
two-dimensional (2D) in-plane N\'eel correlations on a timescale of a few ps,
while the three-dimensional (3D) long-range magnetic order restores over a far
longer, fluence-dependent timescale of a few hundred ps. The dramatic
difference in these two timescales, implies that characterizing the
dimensionality of magnetic correlations will be vital in our efforts to
understand ultrafast magnetic dynamics.


title: On the ground state energy of the delta-function Fermi gas

abstract:
  The weak coupling asymptotics to order $\gamma$ of the ground state energy of
the delta-function Fermi gas, derived heuristically in the literature, is here
made rigorous. Further asymptotics are in principle computable. The analysis
applies to the Gaudin integral equation a method previously used by one of the
authors for the asymptotics of large Toeplitz matrices.


title: An introduction to varieties in weighted projective space

abstract:
  Weighted projective space arises when we consider the usual geometric
definition for projective space and allow for non-trivial weights. On its own,
this extra freedom gives rise to more than enough interesting phenomena, but it
is the fact that weighted projective space arises naturally in the context of
classical algebraic geometry that can be surprising. Using the Riemann-Roch
theorem to calculate l(E,nD) where E is a non-singular cubic curve inside
projective 2-space and D=p is a point in E we obtain a non-negatively graded
ring R(E) by taking the direct sum of the L(E,nD) for n greater than or equal
to 0. This gives rise to an embedding of E inside the weighted projective space
P(1,2,3).
  To understand a space it is always a good idea to look at the things inside
it. The main content of this paper is the introduction and explanation of many
basic concepts of weighted projective space and its varieties. There are
already many brilliant texts on the topic but none of them are aimed at an
audience with only an undergraduate's knowledge of mathematics. This paper
hopes to partially fill this gap whilst maintaining a good balance between
'interesting' and 'simple'.
  The main result of this paper is a reasonably simple degree-genus formula for
non-singular 'sufficiently general' plane curves, proved using not much more
than the Riemann-Hurwitz formula.


title:
On the Secrecy Capacity Region of the 2-user Z Interference Channel with
  Unidirectional Transmitter Cooperation

abstract:
  In this work, the role of unidirectional limited rate transmitter cooperation
is studied in the case of the 2-user Z interference channel (Z-IC) with secrecy
constraints at the receivers, on achieving two conflicting goals
simultaneously: mitigating interference and ensuring secrecy. First, the
problem is studied under the linear deterministic model. The achievable schemes
for the deterministic model use a fusion of cooperative precoding and
transmission of a jamming signal. The optimality of the proposed scheme is
established for the deterministic model for all possible parameter settings
using the outer bounds derived by the authors in a previous work. Using the
insights obtained from the deterministic model, a lower bound on the secrecy
capacity region of the 2-user Gaussian Z-IC are obtained. The achievable scheme
in this case uses stochastic encoding in addition to cooperative precoding and
transmission of a jamming signal. The secure sum generalized degrees of freedom
(GDOF) is characterized and shown to be optimal for the weak/moderate
interference regime. It is also shown that the secure sum capacity lies within
2 bits/s/Hz of the outer bound for the weak/moderate interference regime for
all values of the capacity of the cooperative link. Interestingly, in case of
the deterministic model, it is found that there is no penalty on the capacity
region of the Z-IC due to the secrecy constraints at the receivers in the
weak/moderate interference regimes. Similarly, it is found that there is no
loss in the secure sum GDOF for the Gaussian case due to the secrecy constraint
at the receiver, in the weak/moderate interference regimes. The results
highlight the importance of cooperation in facilitating secure communication
over the Z-IC.


title: On the last digits of consecutive primes

abstract:
  Recently Oliver and Soundararajan made conjectures based on computational
enumerations about the frequency of occurrence of pairs of last digits for
consecutive primes. By studying Eratosthenes sieve, we have identified discrete
dynamic systems that exactly model the populations of gaps across stages of
Eratosthenes sieve. Our models provide some insight into the observed biases in
the occurrences of last digits in consecutive primes, and the models suggest
that the biases will ultimately be reversed for large enough primes.
  The exact model for populations of gaps across stages of Eratosthenes sieve
provides a constructive complement to the probabilistic models rooted in the
work of Hardy and Littlewood, and it provides time constants that describe the
evolution of the populations of larger gaps.


title: Predicting the evolution of complex networks via local information

abstract:
  Almost all real-world networks are subject to constant evolution, and plenty
of evolving networks have been investigated to uncover the underlying
mechanisms for a deeper understanding of the organization and development of
them. Compared with the rapid expansion of the empirical studies about
evolution mechanisms exploration, the future links prediction methods
corresponding to the evolution mechanisms are deficient. Real-world information
always contain hints of what would happen next, which is also the case in the
observed evolving networks. In this paper, we firstly propose a
structured-dependent index to strengthen the robustness of link prediction
methods. Then we treat the observed links and their timestamps in evolving
networks as known information. We envision evolving networks as dynamic systems
and model the evolutionary dynamics of nodes similarity. Based on the iterative
updating of nodes' network position, the potential trend of evolving networks
is uncovered, which improves the accuracy of future links prediction.
Experiments on various real-world networks show that the proposed index
performs better than baseline methods and the spatial-temporal position drift
model performs well in real-world evolving networks.


title: Mixed Heavy-Light Matching in the Universal One-Loop Effective Action

abstract:
  Recently, a general result for evaluating the path integral at one loop was
obtained in the form of the Universal One-Loop Effective Action. It may be used
to derive effective field theory operators of dimensions up to six, by
evaluating the traces of matrices in this expression, with the mass-dependence
encapsulated in the universal coefficients. Here we show that it can account
for loops of mixed heavy-light particles in the matching procedure. Our
prescription for computing these mixed contributions to the Wilson coefficients
is conceptually simple. Moreover it has the advantage of maintaining the
universal structure of the effective action, which we illustrate using the
example of integrating out a heavy electroweak triplet scalar coupling to a
light Higgs doublet. Finally we also identify new structures that were
previously neglected in the universal results.


title:
A Wide-Field Camera and Fully Remote Operations at the Wyoming Infrared
  Observatory

abstract:
  Upgrades at the 2.3 meter Wyoming Infrared Observatory telescope have
provided the capability for fully-remote operations by a single operator from
the University of Wyoming campus. A line-of-sight 300 Megabit/s 11 GHz radio
link provides high-speed internet for data transfer and remote operations that
include several real-time video feeds. Uninterruptable power is ensured by a 10
kVA battery supply for critical systems and a 55 kW autostart diesel generator
capable of running the entire observatory for up to a week. Construction of a
new four-element prime-focus corrector with fused-silica elements allows
imaging over a 40' field-of-view with a new 4096x4096 UV-sensitive prime-focus
camera and filter wheel. A new telescope control system facilitates the remote
operations model and provides 20'' rms pointing over the usable sky. Taken
together, these improvements pave the way for a new generation of sky surveys
supporting space-based missions and flexible-cadence observations advancing
emerging astrophysical priorities such as planet detection, quasar variability,
and long-term time-domain campaigns.


title:
L1599B: Cloud Envelope and C+ Emission in a Region of Moderately
  Enhanced Radiation Field

abstract:
  We study the effects of an asymmetric radiation field on the properties of a
molecular cloud envelope. We employ observations of carbon monoxide (12CO and
13CO), atomic carbon, ionized carbon, and atomic hydrogen to analyze the
chemical and physical properties of the core and envelope of L1599B, a
molecular cloud forming a portion of the ring at approximately 27 pc from the
star Lambda Ori. The O III star provides an asymmetric radiation field that
produces a moderate enhancement of the external radiation field. Observations
of the [CII] fine structure line with the GREAT instrument on SOFIA indicate a
significant enhanced emission on the side of the cloud facing the star, while
the [Ci], 12CO and 13CO J = 1-0 and 2-1, and 12CO J = 3-2 data from the PMO and
APEX telescopes suggest a relatively typical cloud interior. The atomic, ionic,
and molecular line centroid velocities track each other very closely, and
indicate that the cloud may be undergoing differential radial motion. The HI
data from the Arecibo GALFA survey and the SOFIA/GREAT [CII] data do not
suggest any systematic motion of the halo gas, relative to the dense central
portion of the cloud traced by 12CO and 13CO.


title: Off-shell Dark Matter: A Cosmological relic of Quantum Gravity

abstract:
  We study a novel proposal for the origin of cosmological cold dark matter
(CDM) which is rooted in the quantum nature of spacetime. In this model,
off-shell modes of quantum fields can exist in asymptotic states as a result of
spacetime nonlocality (expected in generic theories of quantum gravity), and
play the role of CDM, which we dub off-shell dark matter (OfDM). However, their
rate of production is suppressed by the scale of non-locality (e.g. Planck
length). As a result, we show that OfDM is only produced in the first moments
of big bang, and then effectively decouples (except through its gravitational
interactions). We examine the observational predictions of this model: In the
context of cosmic inflation, we show that this proposal relates the reheating
temperature to the inflaton mass, which narrows down the uncertainty in the
number of e-foldings of specific inflationary scenarios. We also demonstrate
that OfDM is indeed cold, and discuss potentially observable signatures on
small scale matter power spectrum.


title:
Performance analysis of Markovian queue with impatience and vacation
  times

abstract:
  We consider an $M/M/1$ queueing system with impatient customers with multiple
and single vacations. It is assumed that customers are impatient whenever the
state of the server. We derive the probability generating functions of the
number of customers in the system and we obtain some performance measures.


title: Efficient Summing over Sliding Windows

abstract:
  This paper considers the problem of maintaining statistic aggregates over the
last W elements of a data stream. First, the problem of counting the number of
1's in the last W bits of a binary stream is considered. A lower bound of
{\Omega}(1/{\epsilon} + log W) memory bits for W{\epsilon}-additive
approximations is derived. This is followed by an algorithm whose memory
consumption is O(1/{\epsilon} + log W) bits, indicating that the algorithm is
optimal and that the bound is tight. Next, the more general problem of
maintaining a sum of the last W integers, each in the range of {0,1,...,R}, is
addressed. The paper shows that approximating the sum within an additive error
of RW{\epsilon} can also be done using {\Theta}(1/{\epsilon} + log W) bits for
{\epsilon}={\Omega}(1/W). For {\epsilon}=o(1/W), we present a succinct
algorithm which uses B(1 + o(1)) bits, where B={\Theta}(Wlog(1/W{\epsilon})) is
the derived lower bound. We show that all lower bounds generalize to randomized
algorithms as well. All algorithms process new elements and answer queries in
O(1) worst-case time.


title: Emergence and oscillation of cosmic space by joining M1-branes

abstract:
  Recently, it has been proposed by Padmanabhan that the difference between the
number of degrees of freedom on the boundary surface and the number of degrees
of freedom in a bulk region leads to the expansion of the universe. Now, a
natural question arises, how this model could explain the oscillation of
universe between contraction and expansion branches? We try to address this
issue in the framework of BIonic system. In this model, $M0$-branes join to
each other and give rise to a pair of $M1$-anti-$M1$-branes. The fields which
live on these branes play the roles of massive gravitons that cause the
emergence of a wormhole between them and formation of a BIon system. This
wormhole dissolves into M1-branes and causes a divergence between the number of
degrees of freedom on the boundary surface of $M1$ and the bulk leading to an
expansion of $M1$-branes. When $M1$-branes become close to each other, the
square energy of their system becomes negative and some tachyonic states
emerge. To removes these states, $M1$-branes compact, the sign of compacted
gravity changes, causing the arising of anti-gravity: in this case, branes get
away from each other. By articulating $M1$-BIons, an M3-brane and an
anti-$M3$-brane are created and connected by three wormholes forming an
$M3$-BIon. This new system behaves like the initial system and by closing
branes to each other, they compact and, by getting away from each other, they
open. Our universe is located on one of these M3-branes and, by compacting
$M3$-brane, it contracts and, by opening it, it expands.


title:
Scattering amplitudes for the rationally extended P T symmetric complex
  potentials

abstract:
  In this paper, we consider the rational extensions of two different P T
symmetric complex potentials namely the asymptotically vanishing Scarf II and
asymptotically non-vanishing Rosen-Morse II [ RM-II] potentials and obtain
bound state eigenfunc- tions in terms of newly found exceptional Xm Jacobi
polynomials and also some new type of orthogonal polynomials respectively. By
considering the asymptotic behaviour of the exceptional polynomials, we obtain
the reflection and transmission amplitudes for them and discuss the various
novel properties of the corresponding amplitudes.


title:
A critical assessment of models of pair-interactions and screening used
  in analyzing recent warm-dense matter (WDM) experiments

abstract:
  Ultra-fast laser experiments yield increasingly reliable data on warm-dense
matter (WDM), but rely on entrenched simplistic theoretical models. We
re-analyze two topical experiments, avoiding (i) {\it ad hoc} core-repulsion
models, (ii) "Yukawa screening" models and (iii) electron-ion equilibrium
assumptions. An accurate, rapid density-functional neutral-pseudoatom model
coupled to a hyper-netted-chain (HNC) equation with a bridge term is used to
compute structure factors, X-Ray scattering, compressibility, phonons and
resistivity. Electronic-structure codes are used to confirm the calculations.
The Yukawa and core-repulsion models are shown to be misleading.


title:
High temporal variability in the occurrence of consumer-resource
  interactions in ecological networks

abstract:
  Ecological networks are theoretical abstractions that represent ecological
communities. These networks are usually defined as static entities, in which
the occurrence of a particular interaction between species is considered fixed
despite the intrinsic dynamics of ecological systems. However, empirical
analysis of the temporal variation of trophic interactions is constrained by
the lack of data with high spatial, temporal, and taxonomic resolution. Here,
we evaluate the spatiotemporal variability of multiple consumer-resource
interactions of large marine networks. The tropic interactions of all of the
analyzed networks had low temporal persistence, which was well described by a
common exponential decay in the rank-frequency relationship of
consumer-resource interactions. This common pattern of low temporal persistence
was evident despite the dissimilarities of environmental conditions among
sites. Between-site rank correlations of frequency of occurrence of
interactions ranged from 0.59 to 0.73. After removing the interactions with
<50% frequency, the between-site correlations decreased to values between 0.60
and 0.28, indicating that low-frequency interactions accounted for the apparent
similarities between sites. Our results showed that the communities studied
were characterized by few persistent interactions and a large number of
transient trophic interactions. We suggest that consumer-resource temporal
asynchrony in addition to varying local environmental conditions and
opportunistic foraging could be among the mechanisms generating the observed
rank-frequency relationship of trophic interactions. Therefore, our results
question the analysis of ecological communities as static and persistent
natural entities and stress the need for strengthening the analysis of temporal
variability in ecological networks and long-term studies.


title: Binary neutron star mergers: a jet engine for short gamma-ray bursts

abstract:
  We perform magnetohydrodynamic simulations in full general relativity (GRMHD)
of quasi-circular, equal-mass, binary neutron stars that undergo merger. The
initial stars are irrotational, $n=1$ polytropes and are magnetized. We explore
two types of magnetic-field geometries: one where each star is endowed with a
dipole magnetic field extending from the interior into the exterior, as in a
pulsar, and the other where the dipole field is initially confined to the
interior. In both cases the adopted magnetic fields are initially dynamically
unimportant. The merger outcome is a hypermassive neutron star that undergoes
delayed collapse to a black hole (spin parameter $a/M_{\rm BH} \sim 0.74$)
immersed in a magnetized accretion disk. About $4000M \sim 60(M_{\rm
NS}/1.625M_\odot)$ ms following merger, the region above the black hole poles
becomes strongly magnetized, and a collimated, mildly relativistic outflow ---
an incipient jet --- is launched. The lifetime of the accretion disk, which
likely equals the lifetime of the jet, is $\Delta t \sim 0.1 (M_{\rm
NS}/1.625M_\odot)$ s. In contrast to black hole--neutron star mergers, we find
that incipient jets are launched even when the initial magnetic field is
confined to the interior of the stars.


title:
The Nature of H$\beta+$[O{\sc iii}] and [O{\sc ii}] emitters to $z \sim
  5$ with HiZELS: stellar mass functions and the evolution of EWs

abstract:
  We investigate the properties of $\sim7000$ narrow-band selected galaxies
with strong H$\beta+$[OIII] and [OII] nebular emission lines from the High-$z$
Emission Line Survey (HiZELS) between $z \sim 0.8 - 5.0$. Our sample covers a
wide range in stellar mass ($M\sim10^{7.5 - 12.0}$ M$_\odot$), rest-frame
equivalent widths (EW$_\mathrm{rest}\sim 10 - 10^5$ \AA), and line luminosities
($L\sim10^{40.5 - 43.2}$ erg s$^{-1}$). We measure the H$\beta+$[OIII] and
[OII]-selected stellar mass functions out to $z \sim 3.5$ and find that both
$M_\star$ and $\phi_\star$ increases with cosmic time, which may be due to the
[OIII] selection including an increasing fraction of AGN at lower redshifts.
The [OII]-selected stellar mass functions show a constant
$M_\star\sim10^{11.6}$ M$_\odot$ and a strong, increasing evolution with cosmic
time in $\phi_\star$ in line with H$\alpha$ studies. We also investigate the
EW$_\mathrm{rest}$ evolution as a function of redshift with a fixed mass range
(10$^{9.5 - 10.0}$ M$_\odot$) and find an increasing trend best represented by
$(1+z)^{3.81\pm0.14}$ and $(1+z)^{2.72\pm0.19}$ up to $z\sim 2$ and $\sim 3$
for H$\beta$+[OIII] and [OII] emitters, respectively. This is the first time
that the EW evolution has been directly measured for H$\beta+$[OIII] and [OII]
emitters up to these redshifts. There is evidence for a slower evolution for $z
> 2$ in the H$\beta+$[OIII] EW and a decreasing trend for $z > 3$ in the [OII]
EW evolution, which would imply low [OII] EW at the highest redshifts and
higher [OIII]/[OII] line ratios. This suggests that the ionization parameter at
higher redshift may be significantly higher than the local Universe. Our
results set the stage for future near-IR space-based spectroscopic surveys to
test our extrapolated predictions and also produce $z > 5$ measurements to
constrain the high-$z$ end of the EW$_\mathrm{rest}$ and [OIII]/[OII]
evolution.


title:
The Darkest Hour Before Dawn: Contributions to Cosmic Reionization from
  Dark Matter Annihilation and Decay

abstract:
  Dark matter annihilation or decay could have a significant impact on the
ionisation and thermal history of the universe. In this paper, we study the
potential contribution of dark matter annihilation (s-wave- or
p-wave-dominated) or decay to cosmic reionisation, via the production of
electrons, positrons and photons. We map out the possible perturbations to the
ionisation and thermal histories of the universe due to dark matter processes,
over a broad range of velocity-averaged annihilation cross-sections/decay
lifetimes and dark matter masses. We have employed recent numerical studies of
the efficiency with which annihilation/decay products induce heating and
ionization in the intergalactic medium, and in this work extended them down to
a redshift of $1+z = 4$ for two different reionisation scenarios. We also
improve on earlier studies by using the results of detailed structure formation
models of dark matter haloes and subhaloes that are consistent with up-to-date
$N$-body simulations, with estimates on the uncertainties that originate from
the smallest scales. We find that for dark matter models that are consistent
with experimental constraints, a contribution of more than 10% to the
ionisation fraction at reionisation is disallowed for all annihilation
scenarios. Such a contribution is possible only for decays into
electron/positron pairs, for light dark matter with mass $m_\chi \lesssim $ 100
MeV, and a decay lifetime $\tau_\chi \sim 10^{24} - 10^{25}$ s.


title: Chilly Dark Sectors and Asymmetric Reheating

abstract:
  In a broad class of theories, the relic abundance of dark matter is
determined by interactions internal to a thermalized dark sector, with no
direct involvement of the Standard Model (SM). We point out that these theories
raise an immediate cosmological question: how was the dark sector initially
populated in the early universe? Motivated in part by the difficulty of
accommodating large amounts of entropy carried in dark radiation with cosmic
microwave background measurements of the effective number of relativistic
species at recombination, $N_{\mathrm{eff}}$, we aim to establish which
admissible cosmological histories can populate a thermal dark sector that never
reaches thermal equilibrium with the SM. The minimal cosmological origin for
such a dark sector is asymmetric reheating, when the same mechanism that
populates the SM in the early universe also populates the dark sector at a
lower temperature. Here we demonstrate that the resulting inevitable
inflaton-mediated scattering between the dark sector and the SM can wash out a
would-be temperature asymmetry, and establish the regions of parameter space
where temperature asymmetries can be generated in minimal reheating scenarios.
Thus obtaining a temperature asymmetry of a given size either restricts
possible inflaton masses and couplings or necessitates a non-minimal cosmology
for one or both sectors. As a side benefit, we develop techniques for
evaluating collision terms in the relativistic Boltzmann equation when the full
dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be
retained, and present several new results on relativistic thermal averages in
an appendix.


title: Bandwidth manipulation of quantum light by an electro-optic time lens

abstract:
  The ability to manipulate the spectral-temporal waveform of optical pulses
has enabled a wide range of applications from ultrafast spectroscopy to
high-speed communications. Extending these concepts to quantum light has the
potential to enable breakthroughs in optical quantum science and technology.
However, filtering and amplifying often employed in classical pulse shaping
techniques are incompatible with non-classical light. Controlling the pulsed
mode structure of quantum light requires efficient means to achieve
deterministic, unitary manipulation that preserves fragile quantum coherences.
Here we demonstrate an electro-optic method for modifying the spectrum of
non-classical light by employing a time lens. In particular we show
highly-efficient wavelength-preserving six-fold compression of single-photon
spectral intensity bandwidth, enabling over a two-fold increase of
single-photon flux into a spectrally narrowband absorber. These results pave
the way towards spectral-temporal photonic quantum information processing and
facilitate interfacing of different physical platforms where quantum
information can be stored or manipulated.


title: Timing the evolution of quiescent and star-forming local galaxies

abstract:
  Constraining the star formation histories (SFHs) of individual galaxies is
crucial to understanding the mechanisms that regulate their evolution. Here, we
combine multi-wavelength (ultraviolet, optical, and infrared) measurements of a
very large sample of galaxies (~230,000) at z<0.16, with physically motivated
models of galaxy spectral energy distributions to extract constraints on galaxy
physical parameters (such as stellar mass and star formation rate) as well as
individual SFHs. In particular, we set constraints on the timescales in which
galaxies form a certain percentage of their total stellar mass (namely, 10, 50
and 90%). The large statistics allows us to average such measurements over
different populations of galaxies (quiescent and star-forming) and in narrow
ranges of stellar mass. As in the downsizing scenario, we confirm that low-mass
galaxies have more extended SFHs than high-mass galaxies. We also find that at
the same observed stellar mass, galaxies that are now quiescent evolve more
rapidly than galaxies that are currently still forming stars. This suggests
that stellar mass is not the only driver of galaxy evolution, but plays along
with other factors such as merger events and other environmental effects.


title: Electromagnetic perturbations in new brane world scenarios

abstract:
  In this work we consider electromagnetic dynamics in Randall-Sundrum branes.
It is derived a family of four-dimensional spacetimes compatible with
Randall-Sundrum brane worlds, focusing on asymptotic flat backgrounds. Maximal
extensions of the solutions are constructed and their causal structures are
discussed. These spacetimes include singular, non-singular and extreme black
holes. Maxwell's electromagnetic field is introduced and its evolution is
studied in an extensive numerical survey. Electromagnetic quasinormal mode
spectra are derived and analyzed with time-dependent and high-order WKB
methods. Our results indicate that the black holes in the brane are
electromagnetically stable.


title:
NuSTAR reveals the extreme properties of the super-Eddington accreting
  SMBH in PG 1247+267

abstract:
  PG1247+267 is one of the most luminous known quasars at $z\sim2$ and is a
strongly super-Eddington accreting SMBH candidate. We obtained NuSTAR data of
this intriguing source in December 2014 with the aim of studying its
high-energy emission, leveraging the broad band covered by the new NuSTAR and
the archival XMM-Newton data. Several measurements are in agreement with the
super-Eddington scenario for PG1247+267: the soft power law
($\Gamma=2.3\pm0.1$); the weak ionized Fe emission line and a hint of the
presence of outflowing ionized gas surrounding the SMBH. The presence of an
extreme reflection component is instead at odds with the high accretion rate
proposed for this quasar. This can be explained with three different scenarios;
all of them are in good agreement with the existing data, but imply very
different conclusions: i) a variable primary power law observed in a low state,
superimposed on a reflection component echoing a past, higher flux state; ii) a
power law continuum obscured by an ionized, Compton thick, partial covering
absorber; and iii) a relativistic disk reflector in a lamp-post geometry, with
low coronal height and high BH spin. The first model is able to explain the
high reflection component in terms of variability. The second does not require
any reflection to reproduce the hard emission, while a rather low high-energy
cutoff of $\sim100$ keV is detected for the first time in such a high redshift
source. The third model require a face-on geometry, which may affect the SMBH
mass and Eddington ratio measurements. Deeper X-ray broad-band data are
required in order to distinguish between these possibilities.


title:
Low vibration high numerical aperture automated variable temperature
  Raman microscope

abstract:
  Raman micro-spectroscopy is well suited for studying a variety of properties
and has been applied to wide- ranging areas. Combined with tuneable
temperature, Raman spectra can offer even more insights into the properties of
materials. However, previous designs of variable temperature Raman microscopes
have made it extremely challenging to measure samples with low signal levels
due to thermal and positional instability as well as low collection
efficiencies. Thus, contemporary Raman microscope has found limited
applicability to probing the subtle physics involved in phase transitions and
hysteresis. This paper describes a new design of a closed-cycle, Raman
microscope with full polarization rotation. High collection efficiency, thermal
and mechanical stability are ensured by both deliberate optical, cryogenic, and
mechanical design. Measurements on two samples, Bi2Se3 and V2O3, which are
known as challenging due to low thermal conductivities, low signal levels
and/or hysteretic effects, are measured with previously undemonstrated
temperature resolution.


title:
Geometrical mutual information at the tricritical point of the
  two-dimensional Blume-Capel model

abstract:
  The spin-1 classical Blume-Capel model on a square lattice is known to
exhibit a finite-temperature phase transition described by the tricritical
Ising CFT in 1+1 space-time dimensions. This phase transition can be accessed
with classical Monte Carlo simulations, which, via a replica-trick calculation,
can be used to study the shape-dependence of the classical R\'enyi entropies
for a torus divided into two cylinders. From the second R\'enyi entropy, we
calculate the Geometrical Mutual Information (GMI) introduced by St\'ephan et.
al. [Phys. Rev. Lett. 112, 127204 (2014)] and use it to extract a numerical
estimate for the value of the central charge near the tricritical point. By
comparing to the known CFT result, $c=7/10$, we demonstrate how this type of
GMI calculation can be used to estimate the position of the tricritical point
in the phase diagram.

categories: cond-mat.stat-mech cond-mat.str-el hep-th quant-ph


title:
Comparative testing of dark matter models with 15 HSB and 15 LSB
  galaxies

abstract:
  We assemble a database of 15 HSB and 15 LSB galaxies, for which surface
brightness density and spectroscopic rotation curve data are both available and
representative for various morphologies. We use this dataset to test the
Navarro-Frenk-White, the Einasto, and the pseudo-isothermal sphere dark matter
(DM) models. We investigate the compatibility of the pure baryonic model and
baryonic plus one of the three DM models with observations on the assembled
galaxy database. When a DM component improves the fit with the spectroscopic
rotational curve, we rank the models according to the goodness of fit to the
datasets. We constructed the spatial luminosity density of the baryonic
component based on the surface brightness profile of the galaxies. We estimated
the mass-to-light (M/L) ratio of the stellar component through a previously
proposed color-mass-to-light ratio relation (CMLR). We assumed an axissymetric
baryonic mass model with variable axis ratios together with one of the three DM
models to provide the theoretical rotational velocity curves, and we compared
them with the dataset. In a second attempt, we addressed the question whether
the dark component could be replaced by a pure baryonic model with fitted M/L
ratios. We employed the Akaike information criterion (AIC) to establish the
performance of the best-fit models. For 7 galaxies, neither model fits the
dataset within the 1{\sigma} confidence level. For the other 23 cases, one of
the models with DM explains the rotation curve data best. According to the AIC,
the PSE emerges as most favored in 14 cases, followed by the NFW (6 cases) and
the Einasto (3 cases) DM models. We find that the pure baryonic model with
fitted M/L ratios falls within the 1{\sigma} confidence level for 10 HSB and 2
LSB galaxies, at the price of growing the M/Ls on average by a factor of two,
but the fits are inferior compared to the best-fitting DM model.


title: Critical points of the anyon-Hubbard model

abstract:
  Anyons are particles with fractional statistics that exhibit a nontrivial
change in the wavefunction under an exchange of particles. Anyons can be
considered to be a general category of particles that interpolate between
fermions and bosons. We determined the position of the critical points of the
one-dimensional anyon-Hubbard model, which was mapped to a modified
Bose-Hubbard model where the tunneling depends on the local density and the
interchange angle. We studied the latter model by using the density matrix
renormalization group method and observed that gapped (Mott insulator) and
gapless (superfluid) phases characterized the phase diagram, regardless of the
value of the statistical angle. The phase diagram for higher densities was
calculated and showed that the Mott lobes increase (decrease) as a function of
the statistical angle (global density). The position of the critical point
separating the gapped and gapless phases was found using quantum information
tools, namely the block von Neumann entropy. We also studied the evolution of
the critical point with the global density and the statistical angle and showed
that the anyon-Hubbard model with a statistical angle $\theta =\pi/4$ is in the
same universality class as the Bose-Hubbard model with two body interactions.


title: Finding Mutated Subnetworks Associated with Survival in Cancer

abstract:
  Next-generation sequencing technologies allow the measurement of somatic
mutations in a large number of patients from the same cancer type. One of the
main goals in analyzing these mutations is the identification of mutations
associated with clinical parameters, such as survival time. This goal is
hindered by the genetic heterogeneity of mutations in cancer, due to the fact
that genes and mutations act in the context of pathways. To identify mutations
associated with survival time it is therefore crucial to study mutations in the
context of interaction networks.
  In this work we study the problem of identifying subnetworks of a large
gene-gene interaction network that have mutations associated with survival. We
formally define the associated computational problem by using a score for
subnetworks based on the test statistic of the log-rank test, a widely used
statistical test for comparing the survival of two populations. We show that
the computational problem is NP-hard and we propose a novel algorithm, called
Network of Mutations Associated with Survival (NoMAS), to solve it. NoMAS is
based on the color-coding technique, that has been previously used in other
applications to find the highest scoring subnetwork with high probability when
the subnetwork score is additive. In our case the score is not additive;
nonetheless, we prove that under a reasonable model for mutations in cancer
NoMAS does identify the optimal solution with high probability. We test NoMAS
on simulated and cancer data, comparing it to approaches based on single gene
tests and to various greedy approaches. We show that our method does indeed
find the optimal solution and performs better than the other approaches.
Moreover, on two cancer datasets our method identifies subnetworks with
significant association to survival when none of the genes has significant
association with survival when considered in isolation.


title:
Outer Bounds on the Secrecy Capacity Region of the 2-user Z Interference
  Channel With Unidirectional Transmitter Cooperation

abstract:
  This paper derives outer bounds on the secrecy capacity region of the 2-user
Z interference channel (Z-IC) with rate-limited unidirectional cooperation
between the transmitters. First, the model is studied under the linear
deterministic setting. The derivation of the outer bounds on the secrecy
capacity region involves careful selection of the side information to be
provided to the receivers and using the secrecy constraints at the receivers in
a judicious manner. To this end, a novel partitioning of the encoded messages
and outputs is proposed for the deterministic model based on the strength of
interference and signal. The obtained outer bounds are shown to be tight using
the achievable scheme derived by the authors in a previous work. Using the
insight obtained from the deterministic model, outer bounds on the secrecy
capacity region of the 2-user Gaussian Z-IC are obtained. The equivalence
between the outer bounds for both the models is also established. It is also
shown that secrecy constraint at the receiver does not hurt the capacity region
of the 2-user Z-IC for the deterministic model in the weak/moderate
interference regime. On the other hand, the outer bounds developed for the
Gaussian case shows that secrecy constraint at the receiver can reduce the
capacity region for the weak/moderate interference regime. The study of the
relative performance of these bounds reveals insight into the fundamental
limits of the 2-user Z-IC with limited rate transmitter cooperation.


title: Image segmentation of cross-country scenes captured in IR spectrum

abstract:
  Computer vision has become a major source of information for autonomous
navigation of robots of various types, self-driving cars, military robots and
mars/lunar rovers are some examples. Nevertheless, the majority of methods
focus on analysing images captured in visible spectrum. In this manuscript we
elaborate on the problem of segmenting cross-country scenes captured in IR
spectrum. For this purpose we proposed employing salient features. Salient
features are robust to variations in scale, brightness and view angle. We
suggest the Speeded-Up Robust Features as a basis for our salient features for
a number of reasons discussed in the paper. We also provide a comparison of two
SURF implementations. The SURF features are extracted from images of different
terrain types. For every feature we estimate a terrain class membership
function. The membership values are obtained by means of either the multi-layer
perceptron or nearest neighbours. The features' class membership values and
their spatial positions are then applied to estimate class membership values
for all pixels in the image. To decrease the effect of segmentation blinking
that is caused by rapid switching between different terrain types and to speed
up segmentation, we are tracking camera position and predict features'
positions. The comparison of the multi-layer perception and the nearest
neighbour classifiers is presented in the paper. The error rate of the terrain
segmentation using the nearest neighbours obtained on the testing set is
16.6+-9.17%.


title: Implications of extreme flatness in a general f(R) theory

abstract:
  We discuss a modified gravity theory defined by $f(R) = \sum_{n}^{l} \alpha_n
M^{2(1-n)} R^n$. We consider both finite and infinite number of terms in the
series while requiring that the Einstein frame potential of the theory has a
flat area around any of its stationary points. We show that the requirement of
maximally flat stationary point leads to the existence of the saddle point
(local maximum) for even (odd) $l$. In both cases for $l\to\infty$ one obtains
the Starobinsky model with small, exponentially suppressed corrections. Besides
the GR minimum the Einstein frame potential has an anti de Sitter vacuum.
However we argue that the GR vacuum is absolutely stable and AdS cannot be
reached neither via classical evolution nor via quantum tunnelling. Our results
show that a Starobinsky-like model is the only possible realisation of $f(R)$
theory with an extremely flat area in the Einstein frame potential.


title: The spectrum on $p$-forms of a lens space

abstract:
  We give an explicit description of the spectrum of the Hodge--Laplace
operator on $p$-forms of an arbitrary lens space for any $p$. We write the two
generating functions encoding the $p$-spectrum as rational functions. As a
consequence, we prove a geometric characterization of lens spaces that are
$p$-isospectral for every $p$ in an interval of the form $[0,p_0]$.


title: Radio Emission Physics in the Crab Pulsar

abstract:
  We review our high-time-resolution radio observations of the Crab pulsar and
compare our data to a variety of models for the emission physics. The Main
Pulse and the Low-Frequency Interpulse come from regions somewhere in the
high-altitude emission zones (caustics) that also produce pulsed X-ray and
gamma-ray emission. Although no emission model can fully explain these two
components, the most likely models suggest they arise from a combination of
beam-driven instabilities, coherent charge bunching and strong electromagnetic
turbulence. Because the radio power fluctuates on a wide range of timescales,
we know the emission zones are patchy and dynamic. It is tempting to invoke
unsteady pair creation in high-altitude gaps as source of the variability, but
current pair cascade models cannot explain the densities required by any of the
likely models. It is harder to account for the mysterious High-Frequency
Interpulse. We understand neither its origin within the magnetosphere nor the
striking emission bands in its dynamic spectrum. The most promising models are
based on analogies with solar zebra bands, but they require unusual plasma
structures which are not part of our standard picture of the magnetosphere. We
argue that radio observations can reveal much about the upper magnetosphere,
but work is required before the models can address all of the data.


title: Gruff Ultrafilters

abstract:
  We investigate the question of whether $\mathbb Q$ carries an ultrafilter
generated by perfect sets (such ultrafilters were called gruff ultrafilters by
van Douwen). We prove that one can (consistently) obtain an affirmative answer
to this question in three different ways: by assuming a certain parametrized
diamond principle, from the cardinal invariant equality $\mathfrak d=\mathfrak
c$, and in the Random real model.
  [Edit: replace "the Randor real model" with "the model obtained by adding
$\omega_1$ Cohen reals to a model of $\mathsf{CH}$, and subsequently forcing
with the Random algebra"; this is clarified in the corrigendum attached at the
end of the paper.]


title: Space-Efficient Latent Contracts

abstract:
  Standard higher-order contract monitoring breaks tail recursion and leads to
space leaks that can change a program's asymptotic complexity; space-efficiency
restores tail recursion and bounds the amount of space used by contracts.
Space-efficient contract monitoring for contracts enforcing simple type
disciplines (a/k/a gradual typing) is well studied. Prior work establishes a
space-efficient semantics for manifest contracts without dependency (Greenberg
2015); we adapt that work to a latent calculus with dependency. We guarantee
space efficiency when no dependency is used; we cannot generally guarantee
space efficiency when dependency is used, but instead offer a framework for
making such programs space efficient on a case-by-case basis.


title: Performance Limits for Noisy Multi-Measurement Vector Problems

abstract:
  Compressed sensing (CS) demonstrates that sparse signals can be estimated
from under-determined linear systems. Distributed CS (DCS) further reduces the
number of measurements by considering joint sparsity within signal ensembles.
DCS with jointly sparse signals has applications in multi-sensor acoustic
sensing, magnetic resonance imaging with multiple coils, remote sensing, and
array signal processing. Multi-measurement vector (MMV) problems consider the
estimation of jointly sparse signals under the DCS framework. Two related MMV
settings are studied. In the first setting, each signal vector is measured by a
different independent and identically distributed (i.i.d.) measurement matrix,
while in the second setting, all signal vectors are measured by the same i.i.d.
matrix. Replica analysis is performed for these two MMV settings, and the
minimum mean squared error (MMSE), which turns out to be identical for both
settings, is obtained as a function of the noise variance and number of
measurements. To showcase the application of MMV models, the MMSE's of complex
CS problems with both real and complex measurement matrices are also analyzed.
Multiple performance regions for MMV are identified where the MMSE behaves
differently as a function of the noise variance and the number of measurements.
  Belief propagation (BP) is a CS signal estimation framework that often
achieves the MMSE asymptotically. A phase transition for BP is identified. This
phase transition, verified by numerical results, separates the regions where BP
achieves the MMSE and where it is suboptimal. Numerical results also illustrate
that more signal vectors in the jointly sparse signal ensemble lead to a better
phase transition.


title:
Boundary controllability of a nonlinear coupled system of two
  Korteweg-de Vries equations with critical size restrictions on the spatial
  domain

abstract:
  This article is dedicated to improve the controllability results obtained by
Cerpa et al. in Commun. Contemp. Math 13 (2011) and by Micu et al. in Commun.
Contemp. Math 11 (5) (2009) for a nonlinear coupled system of two Korteweg-de
Vries (KdV) equations posed on a bounded interval. Initially, in Micu et al.,
the authors proved that the nonlinear system is exactly controllable by using
four boundary controls without any restriction on the length L of the interval.
Later on, in Cerpa et al., two boundary controls were considered to prove that
the same system is exactly controllable for small values of the length L and
large time of control T. Here, we use the ideas contained in Capistrano-Filho
et al. (arXiv 1508.07525) to prove that, with another configuration of four
controls, it is possible to prove the existence of the so-called critical
length phenomenon for the nonlinear system, i. e., whether the system is
controllable depends on the length of the spatial domain. In addition, when we
consider only one control input, the boundary controllability still holds for
suitable values of the length L and time of control T. In both cases, the
control spaces are sharp due a technical lemma which reveals a hidden
regularity for the solution of the adjoint system.


title: One-class classifiers based on entropic spanning graphs

abstract:
  One-class classifiers offer valuable tools to assess the presence of outliers
in data. In this paper, we propose a design methodology for one-class
classifiers based on entropic spanning graphs. Our approach takes into account
the possibility to process also non-numeric data by means of an embedding
procedure. The spanning graph is learned on the embedded input data and the
outcoming partition of vertices defines the classifier. The final partition is
derived by exploiting a criterion based on mutual information minimization.
Here, we compute the mutual information by using a convenient formulation
provided in terms of the $\alpha$-Jensen difference. Once training is
completed, in order to associate a confidence level with the classifier
decision, a graph-based fuzzy model is constructed. The fuzzification process
is based only on topological information of the vertices of the entropic
spanning graph. As such, the proposed one-class classifier is suitable also for
data characterized by complex geometric structures. We provide experiments on
well-known benchmarks containing both feature vectors and labeled graphs. In
addition, we apply the method to the protein solubility recognition problem by
considering several representations for the input samples. Experimental results
demonstrate the effectiveness and versatility of the proposed method with
respect to other state-of-the-art approaches.


title:
Transformation of bound states of relativistic hydrogen-l ike atom into
  two-component form

abstract:
  A single-step Eriksen transformation of~$1S_{1/2}$,~$2P_{1/2}$ and~$2P_{3/2}$
states of the relativistic hydrogen-like atom is performed exactly by
expressing each transformed function (TF) as a linear combination of
eigenstates of the Dirac Hamiltonian. The transformed functions, which are
four-component spinors with vanishing two lower components, are calculated
numerically and have the same symmetries as the initial states. For all nuclear
charges~$Z \in [1\ldots 92]$ a contribution of the initial state to TFs exceeds
86\% of the total probability density. Next large contribution to TFs comes
from continuum states with negative energies close to~$-m_0c^2-E_b$,
where~$E_b$ is the binding energy of initial state. Contribution of other
states to TFs is less than~$0.1\%$ of the total probability density. Other
components of TFs are nearly zero which confirms both validity of the Eriksen
transformation and accuracy of the numerical calculations. The TFs
of~$1S_{1/2}$ and~$2P_{1/2}$ states are close to~$1s$ and~$2p$ states of the
nonrelativistic hydrogen-like atom, respectively, but the TF of~$2P_{3/2}$
state differs qualitatively from the~$2p$ state. Functions calculated with use
of a linearized Eriksen transformation, being equivalent to the second order
Foldy-Wouthuysen transformation, are compared with corresponding functions
obtained by Eriksen transformation. A very good agreement between both results
is obtained.


title: Local growth of icosahedral quasicrystalline tilings

abstract:
  Icosahedral quasicrystals (IQCs) with extremely high degrees of translational
order have been produced in the laboratory and found in naturally occurring
minerals, yet questions remain about how IQCs form. In particular, the
fundamental question of how locally determined additions to a growing cluster
can lead to the intricate long-range correlations in IQCs remains open. In
answer to this question, we have developed an algorithm that is capable of
producing a perfectly ordered IQC, yet relies exclusively on local rules for
sequential, face-to-face addition of tiles to a cluster. When the algorithm is
seeded with a special type of cluster containing a defect, we find that growth
is forced to infinity with high probability and that the resultant IQC has a
vanishing density of defects. The geometric features underlying this algorithm
can inform analyses of experimental systems and numerical models that generate
highly ordered quasicrystals.


title: Refinement Types for TypeScript

abstract:
  We present Refined TypeScript (RSC), a lightweight refinement type system for
TypeScript, that enables static verification of higher-order, imperative
programs. We develop a formal core of RSC that delineates the interaction
between refinement types and mutability. Next, we extend the core to account
for the imperative and dynamic features of TypeScript. Finally, we evaluate RSC
on a set of real world benchmarks, including parts of the Octane benchmarks,
D3, Transducers, and the TypeScript compiler.


title: Unitarity Constraints on non-minimal Universal Extra Dimensional Model

abstract:
  We examine the unitarity constraints in gauge and scalar sectors of
non-minimal Universal Extra Dimensional model. We show that some of the
tree-level two-body scattering amplitudes in gauge and scalar sectors do not
respect partial wave unitarity. Unitarity analysis of this model leads to an
upper bound on corresponding boundary-localized (BLT) parameter which depends
on the maximum number of Kaluza-Klein (KK) mode considered in the analysis.
This upper bound of the relevant BLT parameter decreases with the increasing
KK-modes. The results are, in effect, independent of the inverse of
compactifiaction radius. The upper bound on BLT parameter also results in a
lower bound on gauge and scalar KK-masses.


title: Hammer events, neutrino energies, and nucleon-nucleon correlations

abstract:
  Neutrino oscillation measurements depend on a difference between the rate of
neutrino-nucleus interactions at different neutrino energies or different
distances from the source. Knowledge of the neutrino energy spectrum and
neutrino-detector interactions are crucial for these experiments. Short range
nucleon-nucleon correlations in nuclei (SRC) affect properties of nuclei. The
ArgoNeut liquid Argon Time Projection Chamber (lArTPC) observed neutrino-argon
scattering events with two protons back-to-back in the final state ("hammer"
events) which they associated with SRC pairs. The MicroBoone lArTPC will
measure far more of these events.
  We simulate hammer events using two simple models. We use the well-known
electron-nucleon cross section to calculate e-argon interactions where the e-
scatters from a proton, ejecting a pi+, and the pi+ is then absorbed on a
moving deuteron-like $np$ pair. We also use a model where the electron excites
a nucleon to a Delta, which then deexcites by interacting with a second
nucleon.
  The pion production model results in two protons very similar to those of the
hammer events. These distributions are insensitive to the momentum of the $np$
pair that absorbed the $\pi$. The incident neutrino energy can be reconstructed
from just the outgoing lepton. The Delta process results in two protons that
are less similar to the observed events.
  ArgoNeut hammer events can be described by a simple pion production and
reabsorption model. These hammer events in MicroBooNE can be used to determine
the incident neutrino energy but not to learn about SRC. We suggest that this
reaction channel could be used for neutrino oscillation experiments to
complement other channels with higher statistics but different systematic
uncertainties.


title: On the Hessian of Shape Matching Energy

abstract:
  In this technical report we derive the analytic form of the Hessian matrix
for shape matching energy. Shape matching is a useful technique for meshless
deformation, which can be easily combined with multiple techniques in real-time
dynamics. Nevertheless, it has been rarely applied in scenarios where implicit
integrators are required, and hence strong viscous damping effect, though
popular in simulation systems nowadays, is forbidden for shape matching. The
reason lies in the difficulty to derive the Hessian matrix of the shape
matching energy. Computing the Hessian matrix correctly, and stably, is the key
to more broadly application of shape matching in implicitly-integrated systems.


title: On the motion of a viscous liquid filling space

abstract:
  A translation to English of the 1934 paper of Leray, Sur le mouvement d'un
liquide visqueux emplissant l'espace.


title: Machine Learning for Visual Navigation of Unmanned Ground Vehicles

abstract:
  The use of visual information for the navigation of unmanned ground vehicles
in a cross-country environment recently received great attention. However,
until now, the use of textural information has been somewhat less effective
than color or laser range information. This manuscript reviews the recent
achievements in cross-country scene segmentation and addresses their
shortcomings. It then describes a problem related to classification of high
dimensional texture features. Finally, it compares three machine learning
algorithms aimed at resolving this problem. The experimental results for each
machine learning algorithm with the discussion of comparisons are given at the
end of the manuscript.


title:
The Salesman's Improved Paths: 3/2+1/34 Integrality Gap and
  Approximation Ratio

abstract:
  We give a new, strongly polynomial-time algorithm and improved analysis for
the metric $s-t$ path TSP. It finds a tour of cost less than 1.53 times the
optimum of the subtour elimination LP, while known examples show that 1.5 is a
lower bound for the integrality gap.
  A key new idea is the deletion of some edges of Christofides' trees, which is
then accompanied by novel arguments of the analysis: edge-deletion disconnects
the trees, which are then partly reconnected by `parity correction'. We show
that the arising `connectivity correction' can be achieved for a minor extra
cost.
  On the one hand this algorithm and analysis extend previous tools such as the
best-of-many Christofides algorithm. On the other hand, powerful new tools are
solicited, such as a flow problem for analyzing the reconnection cost, and the
construction of a set of more and more restrictive spanning trees, each of
which can still be found by the greedy algorithm. We show that these trees can
replace the convex combination of spanning trees in the best-of-may
Christofides algorithm.
  These new methods lead to improving the integrality ratio and approximation
guarantee below 1.53, as it is already sketched in the preliminary shortened
version of this article that appeared in FOCS 2016. The algorithm and analysis
have been significantly simplified in the current article, and details of
proofs and explanations have been added.


title:
Automated deconvolution of structured mixtures from bulk tumor genomic
  data

abstract:
  Motivation: As cancer researchers have come to appreciate the importance of
intratumor heterogeneity, much attention has focused on the challenges of
accurately profiling heterogeneity in individual patients. Experimental
technologies for directly profiling genomes of single cells are rapidly
improving, but they are still impractical for large-scale sampling. Bulk
genomic assays remain the standard for population-scale studies, but conflate
the influences of mixtures of genetically distinct tumor, stromal, and
infiltrating immune cells. Many computational approaches have been developed to
deconvolute these mixed samples and reconstruct the genomics of genetically
homogeneous clonal subpopulations. All such methods, however, are limited to
reconstructing only coarse approximations to a few major subpopulations. In
prior work, we showed that one can improve deconvolution of genomic data by
leveraging substructure in cellular mixtures through a strategy called
simplicial complex inference. This strategy, however, is also limited by the
difficulty of inferring mixture structure from sparse, noisy assays. Results:
We improve on past work by introducing enhancements to automate learning of
substructured genomic mixtures, with specific emphasis on genome-wide copy
number variation (CNV) data. We introduce methods for dimensionality estimation
to better decompose mixture model substructure; fuzzy clustering to better
identify substructure in sparse, noisy data; and automated model inference
methods for other key model parameters. We show that these improvements lead to
more accurate inference of cell populations and mixture proportions in
simulated scenarios. We further demonstrate their effectiveness in identifying
mixture substructure in real tumor CNV data. Availability: Source code is
available at http://www.cs.cmu.edu/~russells/software/WSCUnmix.zip


title:
Application of Multifractal Analysis to Segmentation of Water Bodies in
  Optical and Synthetic Aperture Radar Satellite Images

abstract:
  A method for segmenting water bodies in optical and synthetic aperture radar
(SAR) satellite images is proposed. It makes use of the textural features of
the different regions in the image for segmentation. The method consists in a
multiscale analysis of the images, which allows us to study the images
regularity both, locally and globally. As results of the analysis, coarse
multifractal spectra of studied images and a group of images that associates
each position (pixel) with its corresponding value of local regularity (or
singularity) spectrum are obtained. Thresholds are then applied to the
multifractal spectra of the images for the classification. These thresholds are
selected after studying the characteristics of the spectra under the assumption
that water bodies have larger local regularity than other soil types.
Classifications obtained by the multifractal method are compared quantitatively
with those obtained by neural networks trained to classify the pixels of the
images in covered against uncovered by water. In optical images, the
classifications are also compared with those derived using the so-called
Normalized Differential Water Index (NDWI).


title: IPr* recurrence and nilsystems

abstract:
  We prove that nilsystems possess the IPr*-recurrence property and, moreover,
are characterized by this property.


title: General scaling relations for locomotion in granular media

abstract:
  We derive a general dimensionless form for granular locomotion, which is
validated in experiments and Discrete Element Method (DEM) simulations. The
form instructs how to scale size, mass, and driving parameters in order to
relate dynamic behaviors of different locomotors in the same granular media.
The scaling can be derived by assuming intrusion forces arise from Resistive
Force Theory (RFT) or equivalently by assuming the granular material behaves as
a continuum obeying a frictional yield criterion. The scalings are
experimentally confirmed using pairs of wheels of various shapes and sizes
under many driving conditions in a common sand bed. We discuss why the two
models provide such a robust set of scaling laws even though they neglect a
number of the complexities of granular rheology. Motivated by potential
extra-planetary applications, the dimensionless form also implies a way to
predict wheel performance in one ambient gravity based on tests in a different
ambient gravity. We confirm this using DEM simulations, which show that scaling
relations are satisfied over an array of driving modes even when gravity
differs between scaled tests.


title: SL_2-Tilings Do Not Exist in Higher Dimensions (mostly)

abstract:
  We define a family of generalizations of $\operatorname{SL}_2$-tilings to
higher dimensions called $\boldsymbol{\epsilon}$-$\operatorname{SL}_2$-tilings.
We show that, in each dimension 3 or greater,
$\boldsymbol{\epsilon}$-$\operatorname{SL}_2$-tilings exist only for certain
choices of $\boldsymbol{\epsilon}$. In the case that they exist, we show that
they are essentially unique and have a concrete description in terms of odd
Fibonacci numbers.


title: Challenges in Bayesian Adaptive Data Analysis

abstract:
  Traditional statistical analysis requires that the analysis process and data
are independent. By contrast, the new field of adaptive data analysis hopes to
understand and provide algorithms and accuracy guarantees for research as it is
commonly performed in practice, as an iterative process of interacting
repeatedly with the same data set, such as repeated tests against a holdout
set. Previous work has defined a model with a rather strong lower bound on
sample complexity in terms of the number of queries, $n\sim\sqrt q$, arguing
that adaptive data analysis is much harder than static data analysis, where
$n\sim\log q$ is possible. Instead, we argue that those strong lower bounds
point to a limitation of the previous model in that it must consider wildly
asymmetric scenarios which do not hold in typical applications.
  To better understand other difficulties of adaptivity, we propose a new
Bayesian version of the problem that mandates symmetry. Since the other lower
bound techniques are ruled out, we can more effectively see difficulties that
might otherwise be overshadowed. As a first contribution to this model, we
produce a new problem using error-correcting codes on which a large family of
methods, including all previously proposed algorithms, require roughly
$n\sim\sqrt[4]q$. These early results illustrate new difficulties in adaptive
data analysis regarding slightly correlated queries on problems with
concentrated uncertainty.