title: Disordered dimer state in electron-doped Sr$_{3}$Ir$_{2}$O$_{7}$

abstract:
  Spin excitations are explored in the electron-doped spin-orbit Mott insulator
(Sr$_{1-x}$La$_{x}$)$_3$Ir$_2$O$_7$. As this bilayer square lattice system is
doped into the metallic regime, long-range antiferromagnetism vanishes, yet a
spectrum of gapped spin excitation remains. Excitation lifetimes are strongly
damped with increasing carrier concentration, and the energy integrated
spectral weight becomes nearly momentum independent as static spin order is
suppressed. Local magnetic moments, absent in the parent system, grow in
metallic samples and approach values consistent with one $J=\frac{1}{2}$
impurity per electron doped. Our combined data suggest that the magnetic
spectra of metallic (Sr$_{1-x}$La$_{x}$)$_3$Ir$_2$O$_7$ are best described by
excitations out of a disordered dimer state.


title:
A collision model for grain-resolving simulations of flows over dense,
  mobile, polydisperse granular sediment beds

abstract:
  We present a collision model for phase-resolved Direct Numerical Simulations
of sediment transport that couple the fluid and particles by the Immersed
Boundary Method. Typically, a contact model for these types of simulations
comprises a lubrication force for particles in close proximity to another solid
object, a normal contact force to prevent particles from overlapping, and a
tangential contact force to account for friction. Our model extends the work of
previous authors to improve upon the time integration scheme to obtain
consistent results for particle-wall collisions. Furthermore, we account for
polydisperse spherical particles and introduce new criteria to account for
enduring contact, which occurs in many sediment transport situations. This is
done without using arbitrary values for physically-defined parameters and by
maintaining the full momentum balance of a particle in enduring contact. We
validate our model against several test cases for binary particle-wall
collisions as well as the collective motion of a sediment bed sheared by a
viscous flow, yielding satisfactory agreement with experimental data by various
authors.


title:
A Laplace-type representation of the generalized spherical functions
  associated to the root systems of type A

abstract:
  In this paper, we extend the iterative expression for the generalized
spherical functions associated to the root systems of type $A$ previously
obtained beyond regular elements. We also provide the corresponding expression
in the flat case. From there, we derive a Laplace-type representation for the
generalized spherical functions associated to the root systems of type $A$ in
the Dunkl setting as well as in the trigonometric Dunkl setting. This
representation leads us to describe precisely the support of the generalized
Abel transform. Thanks to a recent result of Rejeb, this allows us to give the
support for the Dunkl intertwining operator.


title: Berry Phase Physics in Free and Interacting Fermionic Systems

abstract:
  Berry phase plays an important role in many non-trivial phenomena over a
broad range of many-body systems. In this thesis we focus on the Berry phase
due to the change of the particles' momenta, and study its effects in free and
interacting fermionic systems. We start with reviewing the semi-classical
kinetic theory with Berry phase for a non-interacting ensemble of fermions -- a
Berry Fermi gas -- which might be far-from-equilibrium. We particularly review
the famous Berry phase contribution to the anomalous Hall current. We then
provide a concrete and general path integral derivation for the semi-classical
theory. Then we turn to the specific example of Weyl fermion, which exhibits
the profound quantum phenomenon of chiral anomaly; we review how this quantum
effect, and its closely related chiral magnetic effect and chiral vortical
effect, arise from Berry phase in the semi-classical kinetic theory. We also
discuss how Lorentz symmetry in the kinetic theory of Weyl fermion, seemly
violated by the Berry phase term, is realized non-trivially; we provide a
physical interpretation for this non-trivial realization, and discuss its
mathematical foundation in Wigner translation. Next, we turn towards
interacting fermionic systems. We consider Fermi liquid near equilibrium, and
propose the Berry Fermi liquid theory -- the extension to Landau Fermi liquid
theory incorporating Berry phase (and other) effects. In our proposed Berry
Fermi liquid theory, we can show the Berry phase is a Fermi surface property,
qualitatively unmodified by interactions. But there also arise new effects from
interactions, most notably the emergent electric dipole moment which
contributes to the anomalous Hall current in addition to the usual Berry phase
contribution. We prove our proposed Berry Fermi liquid theory from quantum
field theory to all orders in Feynman diagram expansion under very general
assumptions.


title:
Interactive Exploration of the Employment Situation Report: From Fixed
  Tables to Dynamic Discovery

abstract:
  The monthly Bureau of Labor Statistics Employment Situation Report is widely
anticipated by economists, journalists, and politicians as it is used to
forecast the economic condition of the United States. The report has broad
impact on public and corporate economic confidence; however, the online access
to this data employs outdated techniques, using a PDF format containing solely
text and fixed tabular information. Creating an interactive interface for
dynamic discovery on the BLS website could elicit more dialogue between the
public and government spheres, drawing more traffic to government websites and
triggering greater civic engagement. Our work suggests that the implementation
of interactive visual analysis techniques to enable dynamic discovery leads to
rapid interpretation of data as well as provides the means to explore the data
for further insights. This paper presents two inspirational prototypes: a
dashboard of interactive visualizations and an interactive time series
explorer, allowing for temporal and spatial analyses and enabling users to
combine data sets to create their own customized visualization.


title: Target space supergeometry of $\eta$ and $\lambda$-deformed strings

abstract:
  We study the integrable $\eta$ and $\lambda$-deformations of supercoset
string sigma models, the basic example being the deformation of the $AdS_5
\times S^5$ superstring. We prove that the kappa symmetry variations for these
models are of the standard Green-Schwarz form, and we determine the target
space supergeometry by computing the superspace torsion. We check that the
$\lambda$-deformation gives rise to a standard (generically type II*)
supergravity background; for the $\eta$-model the requirement that the target
space is a supergravity solution translates into a simple condition on the
R-matrix which enters the definition of the deformation. We further construct
all such non-abelian R-matrices of rank four which solve the homogeneous
classical Yang-Baxter equation for the algebra so(2,4). We argue that the
corresponding backgrounds are equivalent to sequences of non-commuting
TsT-transformations, and verify this explicitly for some of the examples.


title: Radio emission in Mercury magnetosphere

abstract:
  Context: Active stars possess magnetized wind that has a direct impact on
planets that can lead to radio emission. Mercury is a good test case to study
the effect of the solar wind and interplanetary magnetic field on radio
emission driven in the planet magnetosphere. Such studies could be used as
proxies to characterize the magnetic field topology and intensity of
exoplanets. Aims: The aim of this study is to quantify the radio emission in
the Hermean magnetosphere. Methods: We use the MHD code PLUTO in spherical
coordinates with an axisymmetric multipolar expansion for the Hermean magnetic
field, to analyze the effect of the interplanetary magnetic field (IMF)
orientation and intensity, as well as the hydrodynamic parameters of the solar
wind (velocity, density and temperature), on the net power dissipated on the
Hermean day and night side. We apply the formalism derived by Zarka [2001,
2007] to infer the radio emission level from the net dissipated power. We
perform a set of simulations with different hydrodynamic parameters of the
solar wind, IMF orientations and intensities, that allow us to calculate the
dissipated power distribution and infer the existence of radio emission hot
spots on the planet day side, and to calculate the integrated radio emission of
the Hermean magnetosphere. Results: The obtained radio emission distribution of
dissipated power is determined by the IMF orientation (associated with the
reconnection regions in the magnetosphere), although the radio emission
strength is dependent on the IMF intensity and solar wind hydro parameters. The
calculated total radio emission level is in agreement with the one estimated in
[Zarka, 2001], between $5 \times 10^{5}$ and $2 \times 10^{6}$ W.


title:
Determining the action dimension of an Artin group by using its complex
  of abelian subgroups

abstract:
  Suppose that $(W,S)$ is a Coxeter system with associated Artin group $A$ and
with a simplicial complex $L$ as its nerve. We define the notion of a "standard
abelian subgroup" in $A$. The poset of such subgroups in $A$ is parameterized
by the poset of simplices in a certain subdivision $L_\oslash$ of $L$. This
complex of standard abelian subgroups is used to generalize an earlier result
from the case of right-angled Artin groups to case of general Artin groups, by
calculating, in many instances, the smallest dimension of a manifold model for
$BA$. (This is the "action dimension" of $A$ denoted actdim $A$.) If $H_d(L;
\mathbb Z/2)\neq 0$, where $d=\dim L$, then actdim $A \ge 2d+2$. Moreover, when
the $K(\pi,1)$-Conjecture holds for $A$, the inequality is an equality.


title:
Effect of the interplanetary magnetic field orientation and intensity in
  the mass and energy deposition on the Hermean surface

abstract:
  The aim of the present study is to simulate the interaction between the solar
wind and the Hermean magnetosphere. We use the MHD code PLUTO in spherical
coordinates with an axisymmetric multipolar expansion of the Hermean magnetic
field, to perform a set of simulations with different interplanetary magnetic
field orientations and intensities. We fix the hydrodynamic parameters of the
solar wind to study the distortions driven by the interplanetary magnetic field
in the topology of the Hermean magnetosphere, leading to variations of the mass
and energy deposition distributions, the integrated mass deposition, the oval
aperture, the area covered by open magnetic field lines and the regions of
efficient particle sputtering on the planet surface. The simulations show a
correlation between the reconnection regions and the local maxima of plasma
inflow and energy deposition on the planet surface.


title: Inapproximability Results for Approximate Nash Equilibria

abstract:
  We study the problem of finding approximate Nash equilibria that satisfy
certain conditions, such as providing good social welfare. In particular, we
study the problem $\epsilon$-NE $\delta$-SW: find an $\epsilon$-approximate
Nash equilibrium ($\epsilon$-NE) that is within $\delta$ of the best social
welfare achievable by an $\epsilon$-NE. Our main result is that, if the
exponential-time hypothesis (ETH) is true, then solving $\left(\frac{1}{8} -
\mathrm{O}(\delta)\right)$-NE $\mathrm{O}(\delta)$-SW for an $n\times n$
bimatrix game requires $n^{\mathrm{\widetilde \Omega}(\log n)}$ time. Building
on this result, we show similar conditional running time lower bounds on a
number of decision problems for approximate Nash equilibria that do not involve
social welfare, including maximizing or minimizing a certain player's payoff,
or finding approximate equilibria contained in a given pair of supports. We
show quasi-polynomial lower bounds for these problems assuming that ETH holds,
where these lower bounds apply to $\epsilon$-Nash equilibria for all $\epsilon
< \frac{1}{8}$. The hardness of these other decision problems has so far only
been studied in the context of exact equilibria.


title: The Einstein-Lambda flow on product manifolds

abstract:
  We consider the vacuum Einstein flow with a positive cosmological constant on
spatial manifolds of product form. In spatial dimension at least four we show
the existence of continuous families of recollapsing models whenever at least
one of the factors or admits a Riemannian Einstein metric with positive
Einstein constant. We moreover show that these families belong to larger
continuous families with models that have two complete time directions, i.e. do
not recollapse. Complementarily, we show that whenever no factor has positive
curvature, then any model in the product class expands in one time direction
and collapses in the other. In particular, positive curvature of one factor is
a necessary criterion for recollapse within this class. Finally, we relate our
results to the instability of the Nariai solution in three spatial dimensions
and point out why a similar construction of recollapsing models in that
dimension fails. The present results imply that there exist different classes
of initial data which exhibit fundamentally different types of long-time
behavior under the Einstein flow whenever the spatial dimension is strictly
larger than three. Moreover, this behavior is related to the spatial topology
through the existence of Riemannian Einstein metrics of positive curvature.


title: Nanoscale Structure and Elasticity of Pillared DNA Nanotubes

abstract:
  We present an atomistic model of pillared DNA nanotubes (DNTs) and their
elastic properties which will facilitate further studies of these nanotubes in
several important nanotechnological and biological applications. In particular,
we introduce a computational design to create an atomistic model of a 6-helix
DNT (6HB) along with its two variants, 6HB flanked symmetrically by two double
helical DNA pillars (6HB+2) and 6HB flanked symmetrically by three double
helical DNA pillars (6HB+3). Analysis of 200 ns all-atom simulation
trajectories in the presence of explicit water and ions shows that these
structures are stable and well behaved in all three geometries. Hydrogen
bonding is well maintained for all variants of 6HB DNTs. We calculate the
persistence length of these nanotubes from their equilibrium bend angle
distributions. The values of persistence length are ~10 {\mu}m, which is 2
orders of magnitude larger than that of dsDNA. We also find a gradual increase
of persistence length with an increasing number of pillars, in quantitative
agreement with previous experimental findings. To have a quantitative
understanding of the stretch modulus of these tubes we carried out
nonequilibrium Steered Molecular Dynamics (SMD). The linear part of the force
extension plot gives stretch modulus in the range of 6500 pN for 6HB without
pillars which increases to 11,000 pN for tubes with three pillars. The values
of the stretch modulus calculated from contour length distributions obtained
from equilibrium MD simulations are similar to those obtained from
nonequilibrium SMD simulations. The addition of pillars makes these DNTs very
rigid.


title: Powheg-Pythia matching scheme effects in NLO simulation of dijet events

abstract:
  One of the most important developments in Monte Carlo simulation of collider
events for the LHC has been the arrival of schemes and codes for matching of
parton showers to matrix elements calculated at next-to-leading order in the
QCD coupling. The POWHEG scheme, and particularly its implementation in the
POWHEG-BOX code, has attracted most attention due to ease of use and effective
portability between parton shower algorithms.
  But formal accuracy to NLO does not guarantee predictivity, and the
beyond-fixed-order corrections associated with the shower may be large.
Further, there are open questions over which is the "best" variant of the
POWHEG matching procedure to use, and how to evaluate systematic uncertainties
due to the degrees of freedom in the scheme.
  In this paper we empirically explore the scheme variations allowed in Pythia8
matching to POWHEG-BOX dijet events, demonstrating the effects of both discrete
and continuous freedoms in emission vetoing details for both tuning to data and
for estimation of systematic uncertainties from the matching and parton shower
aspects of the POWHEG-BOX+Pythia8 generator combination.


title:
The comptonization parameter from simulations of single-frequency,
  single-dish, dual-beam, cm-wave observations of galaxy clusters and
  mitigating CMB confusion using the Planck sky survey

abstract:
  Systematic effects in dual-beam, differential, radio observations of extended
objects are discussed in the context of the One Centimeter Receiver Array
(OCRA). We use simulated samples of Sunyaev-Zel'dovich (SZ) galaxy clusters at
low ($z<0.4$) and intermediate ($0.4<z<1.0$) redshifts to study the
implications of operating at a single frequency (30 GHz) on the accuracy of
extracting SZ flux densities and of reconstructing comptonization parameters
with OCRA. We analyze dependences on cluster mass, redshift, observation
strategy, and telescope pointing accuracy. Using $Planck$ data to make primary
cosmic microwave background (CMB) templates, we test the feasibility of
mitigating CMB confusion effects in observations of SZ profiles at angular
scales larger than the separation of the receiver beams.


title: Finite generation of cohomology of finite groups

abstract:
  We give a proof of the finite generation of the cohomology ring of a finite
p-group over F_p by reduction to the case of elementary abelian groups, based
on Serre's Theorem on products of Bocksteins.


title:
Optimal Hashing-based Time-Space Trade-offs for Approximate Near
  Neighbors

abstract:
  [See the paper for the full abstract.]
  We show tight upper and lower bounds for time-space trade-offs for the
$c$-Approximate Near Neighbor Search problem. For the $d$-dimensional Euclidean
space and $n$-point datasets, we develop a data structure with space $n^{1 +
\rho_u + o(1)} + O(dn)$ and query time $n^{\rho_q + o(1)} + d n^{o(1)}$ for
every $\rho_u, \rho_q \geq 0$ such that: \begin{equation} c^2 \sqrt{\rho_q} +
(c^2 - 1) \sqrt{\rho_u} = \sqrt{2c^2 - 1}. \end{equation}
  This is the first data structure that achieves sublinear query time and
near-linear space for every approximation factor $c > 1$, improving upon
[Kapralov, PODS 2015]. The data structure is a culmination of a long line of
work on the problem for all space regimes; it builds on Spherical
Locality-Sensitive Filtering [Becker, Ducas, Gama, Laarhoven, SODA 2016] and
data-dependent hashing [Andoni, Indyk, Nguyen, Razenshteyn, SODA 2014] [Andoni,
Razenshteyn, STOC 2015].
  Our matching lower bounds are of two types: conditional and unconditional.
First, we prove tightness of the whole above trade-off in a restricted model of
computation, which captures all known hashing-based approaches. We then show
unconditional cell-probe lower bounds for one and two probes that match the
above trade-off for $\rho_q = 0$, improving upon the best known lower bounds
from [Panigrahy, Talwar, Wieder, FOCS 2010]. In particular, this is the first
space lower bound (for any static data structure) for two probes which is not
polynomially smaller than the one-probe bound. To show the result for two
probes, we establish and exploit a connection to locally-decodable codes.


title:
Nonlinear quantitative photoacoustic tomography with two-photon
  absorption

abstract:
  Two-photon photoacoustic tomography (TP-PAT) is a non-invasive optical
molecular imaging modality that aims at inferring two-photon absorption
property of heterogeneous media from photoacoustic measurements. In this work,
we analyze an inverse problem in quantitative TP-PAT where we intend to
reconstruct optical coefficients in a semilinear elliptic PDE, the mathematical
model for the propagation of near infra-red photons in tissue-like optical
media with two-photon absorption, from the internal absorbed energy data. We
derive uniqueness and stability results on the reconstructions of single and
multiple optical coefficients, and present some numerical reconstruction
results based on synthetic data to complement the theoretical analysis.

categories: math.AP math-ph math.MP math.NA physics.comp-ph


title: Chiral magnetic excitations in FeGe films

abstract:
  Although chiral magnetic materials have emerged as a potential ingredient in
future spintronic memory devices, there are few comprehensive studies of
magnetic properties in scalably-grown thin films. We present growth, systematic
physical and magnetic characterization, and microwave absorption spectroscopy
of B20 FeGe thin films. We also perform micromagnetic simulations and
analytical theory to understand the dynamical magnetic behavior of this
material. We find magnetic resonance features in both the helical and
field-polarized magnetic states that are well explained by micromagnetic
simulations and analytical calculations. In particular, we show the resonant
enhancement of spin waves along the FeGe film thickness that has a wave vector
matching the helical vector. Using our analytic model, we also describe the
resonance frequency of a helical magnetic state, which depends solely on its
untwisting field. Our results pave the way for understanding and manipulating
high frequency spin waves in thin-film chiral-magnet FeGe near room
temperature.


title:
Patterns of Selection of Human Movements I: Movement Utility, Metabolic
  Energy, and Normal Walking Gaits

abstract:
  The biomechanics of the human body allow humans a range of possible ways of
executing movements to attain specific goals. Nevertheless, humans exhibit
significant patterns in how they execute movements. We propose that the
observed patterns of human movement arise because subjects select those ways to
execute movements that are, in a rigorous sense, optimal. In this project, we
show how this proposition can guide the development of computational models of
movement selection and thereby account for human movement patterns. We proceed
by first developing a movement utility formalism that operationalizes the
concept of a best or optimal way of executing a movement using a utility
function so that the problem of movement selection becomes the problem of
finding the movement that maximizes the utility function. Since the movement
utility formalism includes a contribution of the metabolic energy of the
movement (maximum utility movements try to minimize metabolic energy), we also
develop a metabolic energy formalism that we can use to construct estimators of
the metabolic energies of particular movements. We then show how we can
construct an estimator for the metabolic energies of normal walking gaits and
we use that estimator to construct a movement utility model of the selection of
normal walking gaits and show that the relationship between avg. walking speed
and avg. step length predicted by this model agrees with observation. We
conclude by proposing a physical mechanism that a subject might use to estimate
the metabolic energy of a movement in practice.


title:
Forward-backward SDEs with jumps and classical solutions to nonlocal
  quasilinear parabolic PDEs

abstract:
  We obtain an existence and uniqueness theorem for fully coupled
forward-backward SDEs (FBSDEs) with jumps via the classical solution to the
associated quasilinear parabolic partial integro-differential equation (PIDE),
and provide the explicit form of the FBSDE solution. Moreover, we embed the
associated PIDE into a suitable class of non-local quasilinear parabolic PDEs
which allows us to extend the methodology of Ladyzhenskaya et al (1968) to
non-local PDEs of this class. Namely, we obtain the existence and uniqueness of
a classical solution to both the Cauchy problem and the initial-boundary value
problem for non-local quasilinear parabolic second-order PDEs.


title: Warm Starting Bayesian Optimization

abstract:
  We develop a framework for warm-starting Bayesian optimization, that reduces
the solution time required to solve an optimization problem that is one in a
sequence of related problems. This is useful when optimizing the output of a
stochastic simulator that fails to provide derivative information, for which
Bayesian optimization methods are well-suited. Solving sequences of related
optimization problems arises when making several business decisions using one
optimization model and input data collected over different time periods or
markets. While many gradient-based methods can be warm started by initiating
optimization at the solution to the previous problem, this warm start approach
does not apply to Bayesian optimization methods, which carry a full metamodel
of the objective function from iteration to iteration. Our approach builds a
joint statistical model of the entire collection of related objective
functions, and uses a value of information calculation to recommend points to
evaluate.


title: Characterizing Many-Body Localization by Out-of-Time-Ordered Correlation

abstract:
  The out-of-time-ordered (OTO) correlation is a key quantity for quantifying
quantum chaoticity and has been recently used in the investigation of quantum
holography. Here we use it to study and characterize many-body localization
(MBL). We find that a long-time logarithmic variation of the OTO correlation
occurs in the MBL phase but is absent in the Anderson localized and ergodic
phases. We extract a localization length in the MBL phase, which depends
logarithmically on interaction and diverges at a critical interaction.
Furthermore, the infinite-time `thermal' fluctuation of the OTO correlation is
zero (finite) in the ergodic (MBL) phase and thus can be considered as an order
parameter for the ergodic-MBL transition, through which the transition can be
identified and characterized. Specifically, the critical point and the related
critical exponents can be calculated.


title:
The statistical trade-off between word order and word structure -
  large-scale evidence for the principle of least effort

abstract:
  Languages employ different strategies to transmit structural and grammatical
information. While, for example, grammatical dependency relationships in
sentences are mainly conveyed by the ordering of the words for languages like
Mandarin Chinese, or Vietnamese, the word ordering is much less restricted for
languages such as Inupiatun or Quechua, as those languages (also) use the
internal structure of words (e.g. inflectional morphology) to mark grammatical
relationships in a sentence. Based on a quantitative analysis of more than
1,500 unique translations of different books of the Bible in more than 1,100
different languages that are spoken as a native language by approximately 6
billion people (more than 80% of the world population), we present large-scale
evidence for a statistical trade-off between the amount of information conveyed
by the ordering of words and the amount of information conveyed by internal
word structure: languages that rely more strongly on word order information
tend to rely less on word structure information and vice versa. In addition, we
find that - despite differences in the way information is expressed - there is
also evidence for a trade-off between different books of the biblical canon
that recurs with little variation across languages: the more informative the
word order of the book, the less informative its word structure and vice versa.
We argue that this might suggest that, on the one hand, languages encode
information in very different (but efficient) ways. On the other hand,
content-related and stylistic features are statistically encoded in very
similar ways.


title:
Measurement of the low-energy quenching factor in germanium using an
  $^{88}$Y/Be photoneutron source

abstract:
  We employ an $^{88}$Y/Be photoneutron source to derive the quenching factor
for neutron-induced nuclear recoils in germanium, probing recoil energies from
a few hundred eV$_{nr}$ to 8.5keV$_{nr}$. A comprehensive Monte Carlo
simulation of our setup is compared to experimental data employing a Lindhard
model with a free electronic energy loss $k$ and an adiabatic correction for
sub-keV$_{nr}$ nuclear recoils. The best fit $k=0.179\pm 0.001$ obtained using
a Monte Carlo Markov Chain (MCMC) ensemble sampler is in good agreement with
previous measurements, confirming the adequacy of the Lindhard model to
describe the stopping of few-keV ions in germanium crystals at a temperature of
$\sim$77 K. This value of $k$ corresponds to a quenching factor of 13.7 % to
25.3 % for nuclear recoil energies between 0.3 keV$_{nr}$ and 8.5 keV$_{nr}$,
respectively.

categories: physics.ins-det astro-ph.CO astro-ph.IM hep-ex hep-ph nucl-ex


title: Fast Backprojection Techniques for High Resolution Tomography

abstract:
  Fast image reconstruction techniques are becoming important with the
increasing number of scientific cases in high resolution micro and nano
tomography. The processing of the large scale three-dimensional data demands
new mathematical tools for the tomographic reconstruction task because of the
big computational complexity of most current algorithms as the sizes of
tomographic data grow with the development of more powerful acquisition
hardware and more refined scientific needs. In the present paper we propose a
new fast back-projection operator for the processing of tomographic data and
compare it against other fast reconstruction techniques.


title: Liouville-type theorems for twisted and warped products manifolds

abstract:
  In the present paper we prove Liouville-type theorems: non-existence theorems
for complete twisted and warped products of Riemannian manifolds which
generalize and complement similar results for compact manifolds.


title:
Particle Physics Models for the 17 MeV Anomaly in Beryllium Nuclear
  Decays

abstract:
  The 6.8$\sigma$ anomaly in excited 8Be nuclear decays via internal pair
creation is fit well by a new particle interpretation. In a previous analysis,
we showed that a 17 MeV protophobic gauge boson provides a particle physics
explanation of the anomaly consistent with all existing constraints. Here we
begin with a review of the physics of internal pair creation in 8Be decays and
the characteristics of the observed anomaly. To develop its particle
interpretation, we provide an effective operator analysis for excited 8Be
decays to particles with a variety of spins and parities and show that these
considerations exclude simple models with scalar particles. We discuss the
required couplings for a gauge boson to give the observed signal, highlighting
the significant dependence on the precise mass of the boson and isospin mixing
and breaking effects. We present anomaly-free extensions of the Standard Model
that contain protophobic gauge bosons with the desired couplings to explain the
8Be anomaly. In the first model, the new force carrier is a U(1)B gauge boson
that kinetically mixes with the photon; in the second model, it is a U(1)(B-L)
gauge boson with a similar kinetic mixing. In both cases, the models predict
relatively large charged lepton couplings ~ 0.001 that can resolve the
discrepancy in the muon anomalous magnetic moment and are amenable to many
experimental probes. The models also contain vectorlike leptons at the weak
scale that may be accessible to near future LHC searches.


title: Prompt planetesimal formation beyond the snow line

abstract:
  We develop a simple model to predict the radial distribution of planetesimal
formation. The model is based on the observed growth of dust to mm-sized
particles, which drift radially, pile-up, and form planetesimals where the
stopping time and dust-to-gas ratio intersect the allowed region for streaming
instability-induced gravitational collapse. Using an approximate analytic
treatment, we first show that drifting particles define a track in
metallicity--stopping time space whose only substantial dependence is on the
disk's angular momentum transport efficiency. Prompt planetesimal formation is
feasible for high particle accretion rates (relative to the gas, $\dot{M}_p /
\dot{M} > 3 \times 10^{-2}$ for $\alpha = 10^{-2}$), that could only be
sustained for a limited period of time. If it is possible, it would lead to the
deposition of a broad and massive belt of planetesimals with a sharp outer
edge. Including turbulent diffusion and vapor condensation processes
numerically, we find that a modest enhancement of solids near the snow line
occurs for cm-sized particles, but that this is largely immaterial for
planetesimal formation. We note that radial drift couples planetesimal
formation across radii in the disk, and suggest that considerations of
planetesimal formation favor a model in which the initial deposition of
material for giant planet cores occurs well beyond the snow line.


title: Testing General Relativity with Accretion-Flow Imaging of Sgr A*

abstract:
  The Event Horizon Telescope is a global very-long baseline interferometer
capable of probing potential deviations from the Kerr metric, which is believed
to provide the unique description of astrophysical black holes. Here we report
an updated constraint on the quadrupolar deviation of Sagittarius A* within the
context of a radiatively inefficient accretion flow model in a quasi-Kerr
background. We also simulate near-future constraints obtainable by the
forthcoming eight-station array and show that in this model already a one-day
observation can measure the spin magnitude to within $0.005$, the inclination
to within $0.09^\circ$, the position angle to within $0.04^\circ$, and the
quadrupolar deviation to within $0.005$ at $3\sigma$ confidence. Thus, we are
entering an era of high-precision strong gravity measurements.


title:
Stochastic competitive exclusion leads to a cascade of species
  extinctions

abstract:
  Community ecology has traditionally relied on the competitive exclusion
principle, a piece of common wisdom in conceptual frameworks developed to
describe species assemblages. Key concepts in community ecology, such as
limiting similarity and niche partitioning, are based on competitive exclusion.
However, this classical paradigm in ecology relies on implications derived from
simple, deterministic models. Here we show how the predictions of a symmetric,
deterministic model about the way extinctions proceed can be utterly different
from the results derived from the same model when ecological drift (demographic
stochasticity) is explicitly considered. Using analytical approximations to the
steady-state conditional probabilities for assemblages with two and three
species, we demonstrate that stochastic competitive exclusion leads to a
cascade of extinctions, whereas the symmetric, deterministic model predicts a
multiple collapse of species. To test the robustness of our results, we have
studied the effect of environmental stochasticity and relaxed the species
symmetry assumption. Our conclusions highlight the crucial role of
stochasticity when deriving reliable theoretical predictions for species
community assembly.


title:
Prototyping the graphical user interface for the operator of the
  Cherenkov Telescope Array

abstract:
  The Cherenkov Telescope Array (CTA) is a planned gamma-ray observatory. CTA
will incorporate about 100 imaging atmospheric Cherenkov telescopes (IACTs) at
a Southern site, and about 20 in the North. Previous IACT experiments have used
up to five telescopes. Subsequently, the design of a graphical user interface
(GUI) for the operator of CTA involves new challenges. We present a GUI
prototype, the concept for which is being developed in collaboration with
experts from the field of Human-Computer Interaction. The prototype is based on
Web technology; it incorporates a Python web server, Web Sockets and graphics
generated with the d3.js Javascript library.


title: Principles of thermal design with nematic liquid crystals

abstract:
  Highly engineered materials are arousing great interest because of their
ability to manipulate heat, as described by coordinate transformation approach.
Based on the recently developed analog gravity models, this paper presents how
a simple device based on nematic liquid crystal can achieve in principle either
thermal concentration or expulsion. These outcomings are shown to stem from
topological properties of a disclination-like structure, induced in the nematic
by anchoring conditions.


title:
Very Low-Mass Stellar and Substellar Companions to Solar-like Stars From
  MARVELS VI: A Giant Planet and a Brown Dwarf Candidate in a Close Binary
  System HD 87646

abstract:
  We report the detections of a giant planet (MARVELS-7b) and a brown dwarf
candidate (MARVELS-7c) around the primary star in the close binary system, HD
87646. It is the first close binary system with more than one substellar
circum-primary companion discovered to the best of our knowledge. The detection
of this giant planet was accomplished using the first multi-object Doppler
instrument (KeckET) at the Sloan Digital Sky Survey (SDSS) telescope.
Subsequent radial velocity observations using ET at Kitt Peak National
Observatory, HRS at HET, the "Classic" spectrograph at the Automatic
Spectroscopic Telescope at Fairborn Observatory, and MARVELS from SDSS-III
confirmed this giant planet discovery and revealed the existence of a
long-period brown dwarf in this binary. HD 87646 is a close binary with a
separation of $\sim22$ AU between the two stars, estimated using the Hipparcos
catalogue and our newly acquired AO image from PALAO on the 200-inch Hale
Telescope at Palomar. The primary star in the binary, HD 87646A, has Teff =
5770$\pm$80K, log(g)=4.1$\pm$0.1 and [Fe/H] = $-0.17\pm0.08$. The derived
minimum masses of the two substellar companions of HD 87646A are
12.4$\pm$0.7M$_{\rm Jup}$ and 57.0$\pm3.7$M$_{\rm Jup}$. The periods are
13.481$\pm$0.001 days and 674$\pm$4 days and the measured eccentricities are
0.05$\pm$0.02 and 0.50$\pm$0.02 respectively. Our dynamical simulations show
the system is stable if the binary orbit has a large semi-major axis and a low
eccentricity, which can be verified with future astrometry observations.


title:
Ab initio and phenomenological studies of the static response of neutron
  matter

abstract:
  We investigate the problem of periodically modulated strongly interacting
neutron matter. We carry out ab initio non-perturbative auxiliary-field
diffusion Monte Carlo calculations using an external sinusoidal potential in
addition to phenomenological two- and three-nucleon interactions. Several
choices for the wave function ansatz are explored and special care is taken to
extrapolate finite-sized results to the thermodynamic limit. We perform
calculations at various densities as well as at different strengths and
periodicities of the one-body potential. Our microscopic results are then used
to constrain the isovector term from energy-density functional theories of
nuclei at many different densities, while making sure to separate isovector
contributions from bulk properties. Lastly, we use our results to extract the
static density-density linear response function of neutron matter at different
densities. Our findings provide insights into inhomogeneous neutron matter and
are related to the physics of neutron star crusts and neutron-rich nuclei.

categories: nucl-th astro-ph.HE cond-mat.quant-gas cond-mat.str-el


title: Approach of complexity in nature: Entropic nonuniqueness

abstract:
  Boltzmann introduced in the 1870's a logarithmic measure for the connection
between the thermodynamical entropy and the probabilities of the microscopic
configurations of the system. His entropic functional for classical systems was
extended by Gibbs to the entire phase space of a many-body system, and by von
Neumann in order to cover quantum systems as well. Finally, it was used by
Shannon within the theory of information. The simplest expression of this
functional corresponds to a discrete set of $W$ microscopic possibilities, and
is given by $S_{BG}= -k\sum_{i=1}^W p_i \ln p_i$ ($k$ is a positive universal
constant; {\it BG} stands for {\it Boltzmann-Gibbs}). This relation enables the
construction of BG statistical mechanics. The BG theory has provided
uncountable important applications. Its application in physical systems is
legitimate whenever the hypothesis of {\it ergodicity} is satisfied. However,
{\it what can we do when ergodicity and similar simple hypotheses are
violated?}, which indeed happens in very many natural, artificial and social
complex systems. It was advanced in 1988 the possibility of generalizing BG
statistical mechanics through a family of nonadditive entropies, namely
$S_q=k\frac{1-\sum_{i=1}^W p_i^q}{q-1}$, which recovers the additive $S_{BG}$
entropy in the $q \to1$ limit. The index $q$ is to be determined from
mechanical first principles. Along three decades, this idea intensively evolved
world-wide (see Bibliography in \url{http://tsallis.cat.cbpf.br/biblio.htm}),
and led to a plethora of predictions, verifications, and applications in
physical systems and elsewhere. As expected whenever a {\it paradigm shift} is
explored, some controversy naturally emerged as well in the community. The
present status of the general picture is here described, starting from its
dynamical and thermodynamical foundations, and ending with its most recent
physical applications.


title:
On the existence of recurrent structures & statistical bias in the
  Collatz path sequences

abstract:
  This paper enumerate some numerical findings concerning the repetitive
patterns arising in the so-called Collatz path sequences. This is followed by a
closed form finite state machine (FSM) model of these recurrences using a set
of linear congruence equations resulting in a different terminating condition
for the Collatz problem. The completeness of the problem in these finite number
of recurrent forms (here, six recurrent forms), such that the elements of the
Collatz path sequence switches in-between till one of them reaches a number of
the form 2m is shown. Further, by using heuristic analysis on the frequency
distribution of these recurrence forms, the manifestation of statistical bias
and constructive analytical formulation and convergence for some of these
recurrent forms is exhibited. Unlike many other approaches described in
literature, the present contribution illustrates the existence of a recurrence
quantification of the Collatz conjecture. Also if the presented analysis can be
made rigorous to solve the set of linear congruence equations for the Collatz
FSM model, the exact true nature of Collatz problem can be inferred.


title: A remark on the Kottwitz homomorphism

abstract:
  We prove that for any split almost-simple connected reductive group G over a
p-adic field F, the Kottwitz homomorphism exhibits a homomorphic section. We
then extend this result to certain additional split connected reductive groups.


title:
Experimental verification of a quantumness criterion for single systems
  based on a Bell-like inequality

abstract:
  In this letter, we propose and experimentally test a quantumness criterion
for single systems. The criterion is based on the violation of an already
reported classical inequality. This inequality is expressed in terms of joint
probabilities that we identify as realizations of preparation-and-measurement
schemes. Our analysis points out that superposition is the key notion to grasp
the quantum nature of physical systems. We verify our criterion in an
all-optical experimental setup with heralded single photons generated via
spontaneous parametric down conversion and use exclusively projective
preparations and projective measurements.


title:
A Comparative Analysis of Thermal Flow Sensing in Biomedical
  Applications

abstract:
  Flow sensors have diverse applications in the field of biomedical engineering
and also in industries. Micromachining of flow sensors has accomplished a new
goal when it comes to miniaturization. Due to the scaling in dimensions, power
consumption, mass cost, sensitivity and integration with other modules such as
wireless telemetry has improvised to a great extent. Thermal flow sensors find
wide applications in biomedical such as in hydrocephalus shunts and drug
delivery systems. Infrared thermal sensing is used for preclinical diagnosis of
breast cancer, for identifying various neurological disorders and for
monitoring various muscular movements. In this paper, various modes of thermal
flow sensing and transduction methods with respect to different biomedical
applications are discussed. Thermal flow sensing is given prime focus because
of the simplicity in the design. Finally, a comparison of flow sensing
technologies is also presented.


title: Controllability of multiplex, multi-timescale networks

abstract:
  The paradigm of layered networks is used to describe many real-world systems
-- from biological networks, to social organizations and transportation
systems. Recently there has been much progress in understanding the general
properties of multilayer networks, our understanding of how to control such
systems remains limited. One aspect that makes this endeavor challenging is
that each layer can operate at a different timescale, thus we cannot directly
apply standard ideas from structural control theory of individual networks.
Here we address the problem of controlling multilayer and multi-timescale
networks focusing on two-layer multiplex networks with one-to-one interlayer
coupling. We investigate the case when the control signal is applied to the
nodes of one layer. We develop a theory based on disjoint path covers to
determine the minimum number of inputs ($N_\T i$) necessary for full control.
We show that if both layers operate on the same timescale then the network
structure of both layers equally affect controllability. In the presence of
timescale separation, controllability is enhanced if the controller interacts
with the faster layer: $N_\T i$ decreases as the timescale difference increases
up to a critical timescale difference, above which $N_\T i$ remains constant
and is completely determined by the faster layer. In contrast, control becomes
increasingly difficult if the controller interacts with the layer operating on
the slower timescale and increasing timescale separation leads to increased
$N_\T i$, again up to a critical value, above which $N_\T i$ still depends on
the structure of both layers. By identifying the underlying mechanisms that
connect timescale difference and controllability for a simplified model, we
provide insight into disentangling how our ability to control real interacting
complex systems is affected by a variety of sources of complexity.


title: Simple visit behavior unifies complex Zika outbreaks

abstract:
  We analyze the paper of Nathan D. Grubaugh et al. (Nature 546, 401-405, 2017)
and find that it does not offer a convincing quantitative explanation for what
generated the temporal distribution of human Zika virus (ZIKV) cases shown in
their paper (Fig. 1d). We criticize this aspect because it is this
understanding of how human cases develop from day-today and week-to-week within
an area such as these Ground Zeros, that policymakers need in order to mitigate
future outbreaks. We present results that strongly suggest that the missing
piece is everyday human visit-revisit behavior. These results reproduce the
human outbreak data in the key areas of Miami in 2016 very well, and give
policymakers specific predictions for how changes in human flow through these
areas will affect, and hence can be used to mitigate, future ZIka outbreaks in
Miami and beyond.


title:
Parametric study of the solar wind interaction with the Hermean
  magnetosphere for a weak interplanetary magnetic field

abstract:
  The aim of this study is to simulate the interaction of the solar wind with
the Hermean magnetosphere when the interplanetary magnetic field is weak,
performing a parametric study for all the range of hydrodynamic values of the
solar wind predicted on Mercury for the ENLIL + GONG WSA + Cone SWRC model:
density from $12$ to $180$ cm$^{-3}$, velocity from $200$ to $500$ km/s and
temperatures from $2 \cdot 10^4$ to $18 \cdot 10^4$ K, and compare the results
with a real MESSENGER orbit as reference case. We use the code PLUTO in
spherical coordinates and an asymmetric multipolar expansion for the Hermean
magnetic field. The study shows for all simulations a stand off distance larger
than the Mercury radius and the presence of close magnetic field lines on the
day side of the planet, so the dynamic pressure of the solar wind is not high
enough to push the magnetopause on the planet surface if the interplanetary
magnetic field is weak. The simulations with large dynamic pressure lead to a
large compression of the Hermean magnetic field modifying its topology in the
inner magnetosphere as well as the plasma flows from the magnetosheath towards
the planet surface.


title:
Recent developments in 2d $\mathcal{N} = (2,2)$ supersymmetric gauge
  theories

abstract:
  We review recent developments in two-dimensional $\mathcal{N}=(2,2)$
supersymmetric gauge theories focusing on the implementation and applications
of localization techniques.


title:
Aristotle vs. Ringelmann: On Superlinear Production in Open Source
  Software

abstract:
  Organizations exist because they provide additional production gains, in
comparison to horizontal ways of allocating resources, such as markets, and the
open source movement is deemed to be a new kind of peer-production organization
somehow in between hierarchically organized firms and markets. However, to
strive as a new kind of organization, open source must provide production
gains, which in turn should be measurable. The open source movement is
particularly interesting to study for this reason. Here, we confront and
discuss two contrasting views, which were reported in the literature recently.
On the one hand, Sornette et al. uncovered a superlinear production mechanism,
which quantifies Aristotle adage: `the whole is more than the sum of its
parts'. On the other hand, Scholtes et al. found opposite results, and referred
to Maximilien Ringelmann, a French agricultural engineer (1861-1931), who
discovered the tendency for individual members of a group to become
increasingly less productive as the size of their group increases. Since
Ringelmann, the topic of collective intelligence has interested numbers of
researchers in social sciences and social psychology, as well as practitioners
in management aiming at improving the performance of their team. In most
research and practice case studies, the Ringelmann effect has been found to
hold, while, in contrast, the superlinear effect found by Sornette et al.is
novel and may challenge common wisdom. Here, we compare these two theories,
weigh their strengths and weaknesses, and discuss how they have been tested
with empirical data. We find that they may not contradict each other as much as
was claimed by Scholtes et al.


title: Clockwork Convnets for Video Semantic Segmentation

abstract:
  Recent years have seen tremendous progress in still-image segmentation;
however the na\"ive application of these state-of-the-art algorithms to every
video frame requires considerable computation and ignores the temporal
continuity inherent in video. We propose a video recognition framework that
relies on two key observations: 1) while pixels may change rapidly from frame
to frame, the semantic content of a scene evolves more slowly, and 2) execution
can be viewed as an aspect of architecture, yielding purpose-fit computation
schedules for networks. We define a novel family of "clockwork" convnets driven
by fixed or adaptive clock signals that schedule the processing of different
layers at different update rates according to their semantic stability. We
design a pipeline schedule to reduce latency for real-time recognition and a
fixed-rate schedule to reduce overall computation. Finally, we extend clockwork
scheduling to adaptive video processing by incorporating data-driven clocks
that can be tuned on unlabeled video. The accuracy and efficiency of clockwork
convnets are evaluated on the Youtube-Objects, NYUD, and Cityscapes video
datasets.


title:
An approach of IR-Based short-range correspondence systems for swarm
  robot balanced requisitions and communications

abstract:
  This paper exhibits a short-run correspondence method appropriate for swarm
versatile robots application. Infrared is utilized for transmitting and
accepting information and obstruction location. The infrared correspondence
code based swarm signaling is utilized for an independent versatile robot
communication system in this research. A code based signaling system is
developed for transmitting information between different entities of robot. The
reflected infrared sign is additionally utilized for separation estimation for
obstruction evasion. Investigation of robot demonstrates the possibility of
utilizing infrared signs to get a solid nearby correspondence between swarm
portable robots. This paper exhibits a basic decentralized control for swarm of
self-collecting robots. Every robot in the code based swarm signaling is
completely self-governing and controlled utilizing a conduct based methodology
with just infrared-based nearby detecting and correspondences. The viability of
the methodology has been checked with simulation, for a set of swarm robots.


title: Constrained Submodular Maximization: Beyond 1/e

abstract:
  In this work, we present a new algorithm for maximizing a non-monotone
submodular function subject to a general constraint. Our algorithm finds an
approximate fractional solution for maximizing the multilinear extension of the
function over a down-closed polytope. The approximation guarantee is 0.372 and
it is the first improvement over the 1/e approximation achieved by the unified
Continuous Greedy algorithm [Feldman et al., FOCS 2011].


title:
Electrophoresis of Janus Particles: a Molecular Dynamics simulation
  study

abstract:
  In this work, we use Molecular Dynamics and Lattice-Boltzmann simulations to
study the properties of charged Janus particles in an electric field. We show
that for relatively small net charge and thick electrostatic diffuse layer
mobilities of Janus particles and uniformly charged colloids of the same net
charge are identical. However, for higher charges and thinner diffuse layers
Janus particles always show lower electrophoretic mobility. We also demonstrate
that Janus particles align with the electric field and the angular deviation
from the field's direction are related to their dipole moment. We show that the
latter is affected by the thickness of the electrostatic diffuse layer and
strongly correlates with the electrophoretic mobility.


title:
Quantum back action evading measurement of motion in a negative mass
  reference frame

abstract:
  Quantum mechanics dictates that a continuous measurement of the position of
an object imposes a random back action perturbation on its momentum. This
randomness translates with time into position uncertainty, thus leading to the
well known uncertainty on the measurement of motion. Here we demonstrate that
the quantum back action on a macroscopic mechanical oscillator measured in the
reference frame of an atomic spin oscillator can be evaded. The collective
quantum measurement on this novel hybrid system of two distant and disparate
oscillators is performed with light. The mechanical oscillator is a drum mode
of a millimeter size dielectric membrane and the spin oscillator is an atomic
ensemble in a magnetic field. The spin oriented along the field corresponds to
an energetically inverted spin population and realizes an effective negative
mass oscillator, while the opposite orientation corresponds to a positive mass
oscillator. The quantum back action is evaded in the negative mass setting and
is enhanced in the positive mass case. The hybrid quantum system presented here
paves the road to entanglement generation and distant quantum communication
between mechanical and spin systems and to sensing of force, motion and gravity
beyond the standard quantum limit.

categories: quant-ph cond-mat.mes-hall physics.atom-ph physics.optics


title:
Thermal radiation of Er doped dielectric crystals: Probing the range of
  applicability of the Kirchhoff law

abstract:
  The Kirchhoff law of thermal radiation, relating emissivity {\epsilon} and
absorptance {\alpha}, has been originally formulated for opaque bodies in
thermodynamic equilibrium with the environment. However, in many systems of
practical importance, both assumptions are often not satisfied. In this work,
we revisit the century-old law and examine the limits of its applicability in
an example of Er:YAG and Er:YLF dielectric crystals, potential radiation
converters for thermophotovoltaic applications. In our experiments, the (80
at.%) Er:YAG crystal was opaque between 1.45 {\mu}m and 1.64 {\mu}m. In this
spectral range, its absorptance {\alpha}({\lambda}) is spectrally flat and
differentiates from unity only by a small amount of reflection. The shape of
the emissivity spectrum {\epsilon}({\lambda}) closely matches that of
absorptance {\alpha}({\lambda}), suggesting that the Kirchhoff law can
adequately describe thermal radiation of opaque bodies, even if the requirement
of thermodynamic equilibrium is not satisfied. The(20 at.%) Er:YLF crystal had
smaller size, lower concentration of Er ions, and it was not opaque.
Nevertheless, its spectrum of emissivity {\epsilon}({\lambda}) had almost the
same shape (between 1.45 {\mu}m and 1.62 {\mu}m) as the spectrum of absorptance
{\alpha}({\lambda}) derived from the transmission measurements. This
observation is in line with our prediction that the spectra of emissivity and
absorptance should have identical shapes in optically thin slabs. We, thus,
show that the Kirchhoff law of thermal radiation can be extended (with caution)
even to not-opaque bodies away from the thermodynamic equilibrium.


title:
Anisotropic and strong negative magneto-resistance in the
  three-dimensional topological insulator Bi2Se3

abstract:
  We report on high-field angle-dependent magneto-transport measurements on
epitaxial thin films of Bi2Se3, a three-dimensional topological insulator. At
low temperature, we observe quantum oscillations that demonstrate the
simultaneous presence of bulk and surface carriers. The magneto- resistance of
Bi2Se3 is found to be highly anisotropic. In the presence of a parallel
electric and magnetic field, we observe a strong negative longitudinal
magneto-resistance that has been consid- ered as a smoking-gun for the presence
of chiral fermions in a certain class of semi-metals due to the so-called axial
anomaly. Its observation in a three-dimensional topological insulator implies
that the axial anomaly may be in fact a far more generic phenomenon than
originally thought.


title:
Benchmarking confound regression strategies for the control of motion
  artifact in studies of functional connectivity

abstract:
  Since initial reports regarding the impact of motion artifact on measures of
functional connectivity, there has been a proliferation of confound regression
methods to limit its impact. However, recent techniques have not been
systematically evaluated using consistent outcome measures. Here, we provide a
systematic evaluation of 12 commonly used confound regression methods in 193
young adults. Specifically, we compare methods according to three benchmarks,
including the residual relationship between motion and connectivity,
distance-dependent effects of motion on connectivity, and additional degrees of
freedom lost in confound regression. Our results delineate two clear trade-offs
among methods. First, methods that include global signal regression minimize
the relationship between connectivity and motion, but unmask distance-dependent
artifact. In contrast, censoring methods mitigate both motion artifact and
distance-dependence, but use additional degrees of freedom. Taken together,
these results emphasize the heterogeneous efficacy of proposed methods, and
suggest that different confound regression strategies may be appropriate in the
context of specific scientific goals.


title: Automatic detection of moving objects in video surveillance

abstract:
  This work is in the field of video surveillance including motion detection.
The video surveillance is one of essential techniques for automatic video
analysis to extract crucial information or relevant scenes in video
surveillance systems. The aim of our work is to propose solutions for the
automatic detection of moving objects in real time with a surveillance camera.
The detected objects are objects that have some geometric shape (circle,
ellipse, square, and rectangle).


title: On the forced flow around a flapping foil

abstract:
  The two dimensional incompressible viscous flow past a flapping foil immersed
in a uniform stream is studied numerically. Numerical simulations were
performed using a Lattice-Boltzmann model for moderate Reynolds numbers. The
computation of the hydrodynamic force on the foil is related to the the wake
structure. In particular, when the foil's centre of mass is fixed in space,
numerical results suggest a relation between drag coefficient behaviour and the
flapping frequency which determines the transition from the von K\'arm\'an
(vKm) to the inverted von K\'arm\'an wake. Beyond the inverted vKm transition
the foil was released. Upstream swimming was observed at high enough flapping
frequencies. Computed hydrodynamic forces suggest the propulsion mechanism for
the swimming foil.


title:
Modular Segregation of Structural Brain Networks Supports the
  Development of Executive Function in Youth

abstract:
  The human brain is organized into large-scale functional modules that have
been shown to evolve in childhood and adolescence. However, it remains unknown
whether structural brain networks are similarly refined during development,
potentially allowing for improvements in executive function. In a sample of 882
participants (ages 8-22) who underwent diffusion imaging as part of the
Philadelphia Neurodevelopmental Cohort, we demonstrate that structural network
modules become more segregated with age, with weaker connections between
modules and stronger connections within modules. Evolving modular topology
facilitated network integration, driven by age-related strengthening of hub
edges that were present both within and between modules. Critically, both
modular segregation and network integration were associated with enhanced
executive performance, and mediated the improvement of executive functioning
with age. Together, results delineate a process of structural network
maturation that supports executive function in youth.


title:
Generalized nonreciprocity in an optomechanical circuit via synthetic
  magnetism and reservoir engineering

abstract:
  Synthetic magnetism has been used to control charge neutral excitations for
applications ranging from classical beam steering to quantum simulation. In
optomechanics, radiation-pressure-induced parametric coupling between optical
(photon) and mechanical (phonon) excitations may be used to break time-reversal
symmetry, providing the prerequisite for synthetic magnetism. Here we design
and fabricate a silicon optomechanical circuit with both optical and mechanical
connectivity between two optomechanical cavities. Driving the two cavities with
phase-correlated laser light results in a synthetic magnetic flux, which in
combination with dissipative coupling to the mechanical bath, leads to
nonreciprocal transport of photons with 35dB of isolation. Additionally,
optical pumping with blue-detuned light manifests as a particle non-conserving
interaction between photons and phonons, resulting in directional optical
amplification of 12dB in the isolator through direction. These results indicate
the feasibility of utilizing optomechanical circuits to create a more general
class of nonreciprocal optical devices, and further, to enable novel
topological phases for both light and sound on a microchip.


title: A Steeper than Linear Disk Mass-Stellar Mass Scaling Relation

abstract:
  The disk mass is among the most important input parameter for every planet
formation model to determine the number and masses of the planets that can
form. We present an ALMA 887micron survey of the disk population around objects
from 2 to 0.03Msun in the nearby 2Myr-old Chamaeleon I star-forming region. We
detect thermal dust emission from 66 out of 93 disks, spatially resolve 34 of
them, and identify two disks with large dust cavities of about 45AU in radius.
Assuming isothermal and optically thin emission, we convert the 887micron flux
densities into dust disk masses, hereafter Mdust. We find that the Mdust-Mstar
relation is steeper than linear with power law indices 1.3-1.9, where the range
reflects two extremes of the possible relation between the average dust
temperature and stellar luminosity. By re-analyzing all millimeter data
available for nearby regions in a self-consistent way, we show that the 1-3
Myr-old regions of Taurus, Lupus, and Chamaeleon I share the same Mdust-Mstar
relation, while the 10Myr-old Upper Sco association has a steeper relation.
Theoretical models of grain growth, drift, and fragmentation reproduce this
trend and suggest that disks are in the fragmentation-limited regime. In this
regime millimeter grains will be located closer in around lower-mass stars, a
prediction that can be tested with deeper and higher spatial resolution ALMA
observations.


title:
Optimal steering of a linear stochastic system to a final probability
  distribution, Part III

abstract:
  The subject of this work has its roots in the so called Schroedginer Bridge
Problem (SBP) which asks for the most likely distribution of Brownian particles
in their passage between observed empirical marginal distributions at two
distinct points in time. Renewed interest in this problem was sparked by a
reformulation in the language of stochastic control. In earlier works,
presented as Part I and Part II, we explored a generalization of the original
SBP that amounts to optimal steering of linear stochastic dynamical systems
between state-distributions, at two points in time, under full state feedback.
In these works the cost was quadratic in the control input. The purpose of the
present work is to detail the technical steps in extending the framework to the
case where a quadratic cost in the state is also present. In the zero-noise
limit, we obtain the solution of a (deterministic) mass transport problem with
general quadratic cost.


title: Buckled Graphene for Efficient Energy Harvest, Storage, and Conversion

abstract:
  Buckling is one of the most common phenomena in atomic-thick layered
structures like graphene. While the buckling phenomenon usually causes disaster
for most nano-devices, we illustrate one positive application of the buckled
graphene for energy harvest, storage, and conversion. More specifically, we
perform molecular dynamical simulations to show that the buckled graphene can
be used to collect the wasted mechanical energy and store the energy in the
form of internal knotting potential. Through strain engineering, the knotting
potential can be converted into useful kinetic (thermal) energy that is highly
concentrated at the free edges of the buckled graphene. The present study
demonstrates potential applications of the buckled graphene for converting the
dispersed wasted mechanical energy into the concentrated useful kinetic
(thermal) energy.


title:
From Manual Android Tests to Automated and Platform Independent Test
  Scripts

abstract:
  Because Mobile apps are extremely popular and often mission critical
nowadays, companies invest a great deal of resources in testing the apps they
provide to their customers. Testing is particularly important for Android apps,
which must run on a multitude of devices and operating system versions.
Unfortunately, as we confirmed in many interviews with quality assurance
professionals, app testing is today a very human intensive, and therefore
tedious and error prone, activity. To address this problem, and better support
testing of Android apps, we propose a new technique that allows testers to
easily create platform independent test scripts for an app and automatically
run the generated test scripts on multiple devices and operating system
versions. The technique does so without modifying the app under test or the
runtime system, by (1) intercepting the interactions of the tester with the app
and (2) providing the tester with an intuitive way to specify expected results
that it then encode as test oracles. We implemented our technique in a tool
named Barista and used the tool to evaluate the practical usefulness and
applicability of our approach. Our results show that Barista can faithfully
encode user defined test cases as test scripts with built-in oracles, generates
test scripts that can run on multiple platforms, and can outperform a
state-of-the-art tool with similar functionality. Barista and our experimental
infrastructure are publicly available.


title: Orbital and spin order in oxide two-dimensional electron gases

abstract:
  We describe a variational theory of multi-band two-dimensional electron gases
that captures the interplay between electrostatic confining potentials,
orbital-dependent interlayer electronic hopping and electron-electron
interactions, and apply it to the d-band two-dimensional electron gases that
form near perovskite oxide surfaces and heterojunctions. These multi-band
two-dimensional electron gases are prone to the formation of
Coulomb-interaction-driven orbitally-ordered nematic ground-states. We find
that as the electron density is lowered and interaction effects strengthen,
spontaneous orbital order occurs first, followed by spin order. We compare our
results with known properties of single-component two-dimensional electron gas
systems and comment on closely related physics in semiconductor quantum wells
and van der Waals heterostructures.


title: A Positive Operator-Valued Measure for an Iterated Function System

abstract:
  Given an iterated function system (IFS) on a complete and separable metric
space $Y$, there exists a unique compact subset $X \subseteq Y$ satisfying a
fixed point relation with respect to the IFS. This subset is called the
attractor set, or fractal set, associated to the IFS. The attractor set
supports a specific Borel probability measure, called the Hutchinson measure,
which itself satisfies a fixed point relation. P. Jorgensen generalized the
Hutchinson measure to a projection-valued measure, under the assumption that
the IFS does not have essential overlap. In previous work, we developed an
alternative approach to proving the existence of this projection-valued
measure. The situation when the IFS exhibits essential overlap has been studied
by Jorgensen and colleagues in. We build off their work to generalize the
Hutchinson measure to a positive-operator valued measure for an arbitrary IFS,
that may exhibit essential overlap. This work hinges on using a generalized
Kantorovich metric to define a distance between positive operator-valued
measures. It is noteworthy to mention that this generalized metric, which we
use in our previous work as well, was also introduced by R.F. Werner to study
the position and momentum observables, which are central objects of study in
the area of quantum theory. We conclude with a discussion of Naimark's dilation
theorem with respect to this positive operator-valued measure, and at the
beginning of the paper, we prove a metric space completion result regarding the
classical Kantorovich metric.


title: The Orbit and Mass of the Third Planet in the Kepler-56 System

abstract:
  While the vast majority of multiple-planet systems have their orbital angular
momentum axes aligned with the spin axis of their host star, Kepler-56 is an
exception: its two transiting planets are coplanar yet misaligned by at least
40 degrees with respect to their host star. Additional follow-up observations
of Kepler-56 suggest the presence of a massive, non-transiting companion that
may help explain this misalignment. We model the transit data along with
Keck/HIRES and HARPS-N radial velocity data to update the masses of the two
transiting planets and infer the physical properties of the third,
non-transiting planet. We employ a Markov Chain Monte Carlo sampler to
calculate the best-fitting orbital parameters and their uncertainties for each
planet. We find the outer planet has a period of 1002 $\pm$ 5 days and minimum
mass of 5.61 $\pm$ 0.38 Jupiter masses. We also place a 95% upper limit of 0.80
m/s/yr on long-term trends caused by additional, more distant companions.


title: Time Coupled Diffusion Maps

abstract:
  We consider a collection of $n$ points in $\mathbb{R}^d$ measured at $m$
times, which are encoded in an $n \times d \times m$ data tensor. Our objective
is to define a single embedding of the $n$ points into Euclidean space which
summarizes the geometry as described by the data tensor. In the case of a fixed
data set, diffusion maps (and related graph Laplacian methods) define such an
embedding via the eigenfunctions of a diffusion operator constructed on the
data. Given a sequence of $m$ measurements of $n$ points, we construct a
corresponding sequence of diffusion operators and study their product. Via this
product, we introduce the notion of time coupled diffusion distance and time
coupled diffusion maps which have natural geometric and probabilistic
interpretations. To frame our method in the context of manifold learning, we
model evolving data as samples from an underlying manifold with a time
dependent metric, and we describe a connection of our method to the heat
equation over a manifold with time dependent metric.


title:
Search for substellar-mass companions and asymmetries in their parent
  discs

abstract:
  Transitional discs are a class of circumstellar discs around young stars with
extensive clearing of dusty material within their inner regions on 10s of au
scales. One of the primary candidates for this kind of clearing is the
formation of planet(s) within the disc that then accrete or clear their
immediate area as they migrate through the disc.
  Our sample included eight transitional discs. Using the Keck/NIRC2 instrument
we utilised the Sparse Aperture Masking (SAM) interferometry technique to
search for asymmetries indicative of ongoing planet formation. We searched for
close-in companions using both model fitting and interferometric image
reconstruction techniques. Using simulated data, we derived diagnostics that
helped us to distinguish between point sources and extended asymmetric disc
emission. In addition, we investigated the degeneracy between the contrast and
separation that appear for marginally resolved companions.
  We found FP Tau to contain a previously unseen disc wall, and DM Tau, LkHa
330, and TW Hya to contain an asymmetric signal indicative of point source-like
emission.
  We placed upper limits on the contrast of a companion in RXJ1842.9-3532 and
V2246 Oph. We ruled the asymmetry signal in RXJ1615.3-3255 and V2062 Oph to be
false positives.
  In the cases where our data indicated a potential companion we computed
estimates for the value of $M_c \dot M_c$ and found values in the range of
$10^{-5} - 10^{-3} M^2_J yr^{-1}$.
  We found significant asymmetries in four targets. Of these, three were
consistent with companions. We resolved a previously unseen gap in the disc of
FP Tau extending inwards from approximately 10 au.


title: Distributed-memory large deformation diffeomorphic 3D image registration

abstract:
  We present a parallel distributed-memory algorithm for large deformation
diffeomorphic registration of volumetric images that produces large isochoric
deformations (locally volume preserving). Image registration is a key
technology in medical image analysis. Our algorithm uses a partial differential
equation constrained optimal control formulation. Finding the optimal
deformation map requires the solution of a highly nonlinear problem that
involves pseudo-differential operators, biharmonic operators, and pure
advection operators both forward and back- ward in time. A key issue is the
time to solution, which poses the demand for efficient optimization methods as
well as an effective utilization of high performance computing resources. To
address this problem we use a preconditioned, inexact, Gauss-Newton- Krylov
solver. Our algorithm integrates several components: a spectral discretization
in space, a semi-Lagrangian formulation in time, analytic adjoints, different
regularization functionals (including volume-preserving ones), a spectral
preconditioner, a highly optimized distributed Fast Fourier Transform, and a
cubic interpolation scheme for the semi-Lagrangian time-stepping. We
demonstrate the scalability of our algorithm on images with resolution of up to
$1024^3$ on the "Maverick" and "Stampede" systems at the Texas Advanced
Computing Center (TACC). The critical problem in the medical imaging
application domain is strong scaling, that is, solving registration problems of
a moderate size of $256^3$---a typical resolution for medical images. We are
able to solve the registration problem for images of this size in less than
five seconds on 64 x86 nodes of TACC's "Maverick" system.


title:
Searches for Anisotropic Lorentz-Invariance Violation in the Photon
  Sector

abstract:
  Lorentz invariance, the fundamental symmetry of Einstein's theory of Special
Relativity, has been established and tested by many classical and modern
experiments. However, many theories that unify the Standard Model of particle
physics and General Relativity predict a violation of Lorentz invariance at the
Planck scale. While this energy range cannot be reached by current experiments,
minute deviations from Lorentz symmetry may be present at lower energies.
Astrophysical experiments are very suitable to search for these deviations,
since their effects accumulate as photons travel across large distances. In
this paper, we describe astrophysical methods that we used to constrain the
photon dispersion and vacuum birefringence.


title: Forbidden Berge Hypergraphs

abstract:
  A \emph{simple} matrix is a (0,1)-matrix with no repeated columns. For a
(0,1)-matrix $F$, we say that a (0,1)-matrix $A$ has $F$ as a \emph{Berge
hypergraph} if there is a submatrix $B$ of $A$ and some row and column
permutation of $F$, say $G$, with $G\le B$. Letting $||A||$ denote the number
of columns in $A$, we define the extremal function $Bh(m,{ F})=\max\{||A||\,:\,
A \hbox{ is }m\hbox{-rowed simple matrix with no Berge hypergraph }F\}$. We
determine the asymptotics of $Bh(m,F)$ for all $3$- and $4$-rowed $F$ and most
$5$-rowed $F$. For certain $F$, this becomes the problem of determining the
maximum number of copies of $K_r$ in a $m$-vertex graph that has no $K_{s,t}$
subgraph, a problem studied by Alon and Shinkleman.


title: Mixing of the exclusion process with small bias

abstract:
  We analyze the mixing behavior of the biased exclusion process on a path of
length $n$ as the bias $\beta_n$ tends to $0$ as $n \to \infty$. We show that
the sequence of chains has a pre-cutoff, and interpolates between the unbiased
exclusion and the process with constant bias. As the bias increases, the mixing
time undergoes two phase transitions: one when $\beta_n$ is of order $1/n$, and
the other when $\beta_n$ is order $\log n/n$.


title: Dimensional Bounds on Vircator Emission

abstract:
  Vircators (Virtual Cathode Oscillators) are sources of short-pulsed, high
power, microwave (GHz) radiation. An essentially dimensional argument relates
their radiated power, pulse energy and oscillation frequency to their driving
voltage and fundamental physical constants. For a diode of width and gap 10 cm
and for voltages of a few hundred keV the peak radiated power cannot exceed
${\cal O} (\text{30 GW})$ and the broad-band single cycle radiated energy
cannot exceed ${\cal O}(\text{3 J})$. If electrons can be accelerated to
relativistic energies higher powers and radiated energies may be possible.


title:
Euler's partition theorem for all moduli and new companions to
  Rogers-Ramanujan-Andrews-Gordon identities

abstract:
  We generalise Euler's partition theorem involving odd parts and different
parts for all moduli and provide new companions to Rogers-Ramanujan-
Andrews-Gordon identities related to this theorem.


title:
A General Framework for Pairs Trading with a Control-Theoretic Point of
  View

abstract:
  Pairs trading is a market-neutral strategy that exploits historical
correlation between stocks to achieve statistical arbitrage. Existing
pairs-trading algorithms in the literature require rather restrictive
assumptions on the underlying stochastic stock-price processes and the
so-called spread function. In contrast to existing literature, we consider an
algorithm for pairs trading which requires less restrictive assumptions than
heretofore considered. Since our point of view is control-theoretic in nature,
the analysis and results are straightforward to follow by a non-expert in
finance. To this end, we describe a general pairs-trading algorithm which
allows the user to define a rather arbitrary spread function which is used in a
feedback context to modify the investment levels dynamically over time. When
this function, in combination with the price process, satisfies a certain
mean-reversion condition, we deem the stocks to be a tradeable pair. For such a
case, we prove that our control-inspired trading algorithm results in positive
expected growth in account value. Finally, we describe tests of our algorithm
on historical trading data by fitting stock price pairs to a popular spread
function used in literature. Simulation results from these tests demonstrate
robust growth while avoiding huge drawdowns.


title:
Phase transition from egalitarian to hierarchical societies driven by
  competition between cognitive and social constraints

abstract:
  Empirical evidence suggests that social structure may have changed from
hierarchical to egalitarian and back along the evolutionary line of humans. We
model a society subject to competing cognitive and social navigation
constraints. The theory predicts that the degree of hierarchy decreases with
encephalization and increases with group size. Hence hominin groups may have
been driven from a phase with hierarchical order to a phase with egalitarian
structures by the encephalization during the last two million years, and back
to hierarchical due to fast demographical changes during the Neolithic. The
dynamics in the perceived social network shows evidence in the egalitarian
phase of the observed phenomenon of Reverse Dominance. The theory also predicts
for modern hunter-gatherers in mild climates a trend towards an intermediate
hierarchy degree and a phase transition for harder ecological conditions. In
harsher climates societies would tend to bemore egalitarian if organized in
small groups but more hierarchical if in large groups. The theoretical model
permits organizing the available data in the cross-cultural record
(Ethnographic Atlas, N=248 cultures) where the symmetry breaking transition can
be clearly seen.


title:
Downlink Performance of Pilot-Reused HetNet with Large-Scale Antenna
  Arrays

abstract:
  Considering a heterogeneous network (HetNet) where both macro base station
(BS) and small cell (SC) nodes are equipped with massive antennas, this paper
studies the performance for multiple-input multiple-output (MIMO) downlinks
when the macro and small cells share the same spectrum and hence interfere with
each other. Suppose that the large-scale antenna arrays at both macro BS and SC
nodes employ maximum-ratio transmission (MRT) or zero-forcing transmission
(ZFT) precoding, and transmit data streams to the served users simultaneously.
A new pilot reuse pattern among SCs is proposed for channel estimation. Taking
into account imperfect channel state information (CSI), capacity lower bounds
for MRT and ZFT are derived, respectively, in closed-form expressions involving
only statistical CSI. Then asymptotic analyses for massive arrays are presented
under specific power scaling laws. Subsequently, two user scheduling
algorithms, greedy scheduling algorithm and asymptotical scheduling algorithm
(ASA), are proposed based on derived capacity lower bounds and asymptotic
analyses, respectively. ASA is demonstrated to be a near optimal in the
asymptotic regime and has low complexity. Finally, the derived closed-form
expressions are verified to be accurate predictors of the system performance by
Monte-Carlo simulations. Numerical results demonstrate the effectiveness of
asymptotic analysis and proposed user scheduling schemes.


title: Faster Training of Very Deep Networks Via p-Norm Gates

abstract:
  A major contributing factor to the recent advances in deep neural networks is
structural units that let sensory information and gradients to propagate
easily. Gating is one such structure that acts as a flow control. Gates are
employed in many recent state-of-the-art recurrent models such as LSTM and GRU,
and feedforward models such as Residual Nets and Highway Networks. This enables
learning in very deep networks with hundred layers and helps achieve
record-breaking results in vision (e.g., ImageNet with Residual Nets) and NLP
(e.g., machine translation with GRU). However, there is limited work in
analysing the role of gating in the learning process. In this paper, we propose
a flexible $p$-norm gating scheme, which allows user-controllable flow and as a
consequence, improve the learning speed. This scheme subsumes other existing
gating schemes, including those in GRU, Highway Networks and Residual Nets as
special cases. Experiments on large sequence and vector datasets demonstrate
that the proposed gating scheme helps improve the learning speed significantly
without extra overhead.


title: MSE-based Precoding for MIMO Downlinks in Heterogeneous Networks

abstract:
  Considering a heterogeneous network (HetNet) system consisting of a macro
tier overlaid with a second tier of small cells (SCs), this paper studies the
mean square error (MSE) based precoding design to be employed by the macro base
station and the SC nodes for multiple-input multiple-output (MIMO) downlinks.
First, a new sum-MSE of all users based minimization problem is proposed aiming
to design a set of macro cell (MC) and SC transmit precoding matrices or
vectors. To solve it, two different algorithms are presented. One is via a
relaxed-constraints based alternating optimization (RAO) realized by efficient
alternating optimization and relaxing non-convex constraints to convex ones.
The other is via an unconstrained alternating optimization with normalization
(UAON) implemented by introducing the constraints into the iterations with the
normalization operation. Second, a separate MSE minimization based precoding is
proposed by considering the signal and interference terms corresponding to the
macro tier and the SCs separately. Simulation results show that the sum-MSE
based RAO algorithm provides the best MSE performance among the proposed
schemes under a number of system configurations. When the number of antennas at
the macro-BS is sufficiently large, the MSE of the separate MSE-based precoding
is found to approach that of RAO and surpass that of UAON. Together, this paper
provides a suite of three new precoding techniques that is expected to meet the
need in a broad range of HetNet environments with adequate balance between
performance and complexity.


title:
Probing the MSSM explanation of the muon g-2 anomaly in dark matter
  experiments and at a 100 TeV $pp$ collider

abstract:
  We explore the ability of current and future dark matter and collider
experiments in probing anomalous magnetic moment of the muon, $(g-2)_\mu$,
within the Minimal Supersymmetric Standard Model (MSSM). We find that the
latest PandaX-II/LUX-2016 data gives a strong constraint on parameter space
that accommodates the $(g-2)_{\mu}$ within $2\sigma$ range, which will be
further excluded by the upcoming XENON-1T (2017) experiment. We also find that
a 100 TeV $pp$ collider can cover most of our surviving samples that satisfy DM
relic density within $3\sigma$ range through $Z$ or $h$ resonant effect by
searching for trilepton events from $\tilde{\chi}^0_2\tilde{\chi}^+_1$
associated production. While the samples that are beyond future sensitivity of
trilepton search at a 100 TeV $pp$ collider and the DM direct detections are
either higgsino/wino-like LSPs or bino-like LSPs co-annihilating with sleptons.
Such compressed regions may be covered by the monojet(-like) searches at a 100
TeV $pp$ collider.


title:
Tetrahedral shape and surface density wave of $^{16}$O caused by
  $\alpha$-cluster correlations

abstract:
  $\alpha$-cluster correlations in the $0^+_1$ and $3^-_1$ states of $^{12}$C
and $^{16}$O are studied using the method of antisymmetrized molecular
dynamics, with which nuclear structures are described from nucleon degrees of
freedom without assuming existence of clusters. The intrinsic states of
$^{12}$C and $^{16}$O have triangle and tetrahedral shapes, respectively,
because of the $\alpha$-cluster correlations. These shapes can be understood as
spontaneous symmetry breaking of rotational invariance, and the resultant
surface density oscillation is associated with density wave (DW) caused by the
instability of Fermi surface with respect to particle-hole correlations with
the wave number $\lambda=3$. $^{16}$O($0^+_1$) and $^{16}$O($3^-_1$) are
regarded as a set of parity partners constructed from the rigid tetrahedral
intrinsic state, whereas $^{12}$C($0^+_1$) and $^{12}$C($3^-_1$) are not good
parity partners as they have triangle intrinsic states of different sizes with
significant shape fluctuation because of softness of the $3\alpha$ structure.
$E3$ transition strengths from the $3^-_1$ to $0^+_1$ states in $^{12}$C and
$^{16}$O are also discussed.


title: Chi-squared Amplification: Identifying Hidden Hubs

abstract:
  We consider the following general hidden hubs model: an $n \times n$ random
matrix $A$ with a subset $S$ of $k$ special rows (hubs): entries in rows
outside $S$ are generated from the probability distribution $p_0 \sim
N(0,\sigma_0^2)$; for each row in $S$, some $k$ of its entries are generated
from $p_1 \sim N(0,\sigma_1^2)$, $\sigma_1>\sigma_0$, and the rest of the
entries from $p_0$. The problem is to identify the high-degree hubs
efficiently. This model includes and significantly generalizes the planted
Gaussian Submatrix Model, where the special entries are all in a $k \times k$
submatrix. There are two well-known barriers: if $k\geq c\sqrt{n\ln n}$, just
the row sums are sufficient to find $S$ in the general model. For the submatrix
problem, this can be improved by a $\sqrt{\ln n}$ factor to $k \ge c\sqrt{n}$
by spectral methods or combinatorial methods. In the variant with $p_0=\pm 1$
(with probability $1/2$ each) and $p_1\equiv 1$, neither barrier has been
broken.
  We give a polynomial-time algorithm to identify all the hidden hubs with high
probability for $k \ge n^{0.5-\delta}$ for some $\delta >0$, when
$\sigma_1^2>2\sigma_0^2$. The algorithm extends to the setting where planted
entries might have different variances each at least as large as $\sigma_1^2$.
We also show a nearly matching lower bound: for $\sigma_1^2 \le 2\sigma_0^2$,
there is no polynomial-time Statistical Query algorithm for distinguishing
between a matrix whose entries are all from $N(0,\sigma_0^2)$ and a matrix with
$k=n^{0.5-\delta}$ hidden hubs for any $\delta >0$. The lower bound as well as
the algorithm are related to whether the chi-squared distance of the two
distributions diverges. At the critical value $\sigma_1^2=2\sigma_0^2$, we show
that the general hidden hubs problem can be solved for $k\geq c\sqrt n(\ln
n)^{1/4}$, improving on the naive row sum-based method.


title:
Deep Motif Dashboard: Visualizing and Understanding Genomic Sequences
  Using Deep Neural Networks

abstract:
  Deep neural network (DNN) models have recently obtained state-of-the-art
prediction accuracy for the transcription factor binding (TFBS) site
classification task. However, it remains unclear how these approaches identify
meaningful DNA sequence signals and give insights as to why TFs bind to certain
locations. In this paper, we propose a toolkit called the Deep Motif Dashboard
(DeMo Dashboard) which provides a suite of visualization strategies to extract
motifs, or sequence patterns from deep neural network models for TFBS
classification. We demonstrate how to visualize and understand three important
DNN models: convolutional, recurrent, and convolutional-recurrent networks. Our
first visualization method is finding a test sequence's saliency map which uses
first-order derivatives to describe the importance of each nucleotide in making
the final prediction. Second, considering recurrent models make predictions in
a temporal manner (from one end of a TFBS sequence to the other), we introduce
temporal output scores, indicating the prediction score of a model over time
for a sequential input. Lastly, a class-specific visualization strategy finds
the optimal input sequence for a given TFBS positive class via stochastic
gradient optimization. Our experimental results indicate that a
convolutional-recurrent architecture performs the best among the three
architectures. The visualization techniques indicate that CNN-RNN makes
predictions by modeling both motifs as well as dependencies among them.


title:
Hybrid optical-thermal antennas for enhanced light focusing and local
  temperature control

abstract:
  Metal nanoantennas supporting localized surface plasmon resonances have
become an indispensable tool in bio(chemical) sensing and nanoscale imaging
applications. The high plasmon-enhanced electric field intensity in the visible
or near-IR range that enables the above applications may also cause local
heating of nanoantennas. We present a design of hybrid optical-thermal antennas
that simultaneously enable intensity enhancement at the operating wavelength in
the visible and nanoscale local temperature control. We demonstrate a
possibility to reduce the hybrid antenna operating temperature via enhanced
infrared thermal emission. We predict via rigorous numerical modeling that
hybrid optical-thermal antennas that support high-quality-factor
photonic-plasmonic modes enable up to two orders of magnitude enhancement of
localized electric fields and of the optical power absorbed in the nanoscale
metal volume. At the same time, the hybrid antenna temperature can be lowered
by several hundred degrees with respect to its all-metal counterpart under
continuous irradiance of 104-105 W/m2. The temperature reduction effect is
attributed to the enhanced radiative cooling, which is mediated by the
thermally-excited localized surface phonon polariton modes. We further show
that temperature reduction under even higher irradiances can be achieved by a
combination of enhanced radiative and convective cooling in hybrid antennas.
Finally, we demonstrate how hybrid optical-thermal antennas can be used to
achieve strong localized heating of nanoparticles while keeping the rest of the
optical chip at low temperature.

categories: physics.optics cond-mat.mes-hall cond-mat.mtrl-sci physics.chem-ph


title: Bernstein-Sato Polynomials on Normal Toric Varieties

abstract:
  We generalize the Bernstein-Sato polynomials of Budur, Mustata and Saito to
ideals in normal semigroup rings. In the case of monomial ideals, we also
relate the roots of the Bernstein-Sato polynomial to the jumping coefficients
of the corresponding multiplier ideals. In order to prove the latter result, we
obtain a new combinatorial description for the multiplier ideals of a monomial
ideal in a normal semigroup ring.


title: Learning with Value-Ramp

abstract:
  We study a learning principle based on the intuition of forming ramps. The
agent tries to follow an increasing sequence of values until the agent meets a
peak of reward. The resulting Value-Ramp algorithm is natural, easy to
configure, and has a robust implementation with natural numbers.


title: Real algebraic knots and links of small degree

abstract:
  The paper gives topological as well as rigid isotopy classification of smooth
irreducible algebraic curves in the real projective 3-space for the case when
the degree of the curve is at most six and its genus is at most one.


title: Transactive Energy Auction with Hidden User Information in Microgrid

abstract:
  This research proposes a novel auction mechanism for transactive energy
exchange between buyers and sellers, modeled as agents in a microgrid. The
mechanism is implemented by a separate microgrid controller (MC) agent, and
requires big data flow with the other agents through an iterative bidding
process. Although private user information remains hidden to the MC, a
theoretical analysis shows that under the assumption of convexity of the agents
utilities, the proposed auction is still able to maximize the social welfare
(SW), i.e. the aggregate utilities of the agents. In addition, it is shown that
the mechanism exhibits the key desirable features of individual rationality and
weak budget balance, guaranteeing that neither the payoff to any agent nor the
net monetary revenue after termination, is negative. The proposed approach also
incorporates a mechanism to redistribute the sellers shares in a fair manner.
As an example, a maximum entropy based fair redistribution scheme is addressed.
The theoretical analysis reported here is accompanied by extensive set of
simulations that illustrate the various aspects of the proposed mechanism.


title: MiniZinc with Strings

abstract:
  Strings are extensively used in modern programming languages and constraints
over strings of unknown length occur in a wide range of real-world applications
such as software analysis and verification, testing, model checking, and web
security. Nevertheless, practically no CP solver natively supports string
constraints. We introduce string variables and a suitable set of string
constraints as builtin features of the MiniZinc modelling language.
Furthermore, we define an interpreter for converting a MiniZinc model with
strings into a FlatZinc instance relying on only integer variables. This
provides a user-friendly interface for modelling combinatorial problems with
strings, and enables both string and non-string solvers to actually solve such
problems.