title: Interpolation of the magnetic field at the test masses in eLISA

abstract:
  A feasible design for a magnetic diagnostics subsystem for eLISA will be
based on that of its precursor mission, LISA Pathfinder. Previous experience
indicates that magnetic field estimation at the positions of the test masses
has certain complications. This is due to two reasons. The first one is that
magnetometers usually back-act due to their measurement principles (i.e., they
also create their own magnetic fields), while the second is that the sensors
selected for LISA Pathfinder have a large size, which conflicts with space
resolution and with the possibility of having a sufficient number of them to
properly map the magnetic field around the test masses. However,
high-sensitivity and small-size sensors that significantly mitigate the two
aforementioned limitations exist, and have been proposed to overcome these
problems. Thus, these sensors will be likely selected for the magnetic
diagnostics subsystem of eLISA. Here we perform a quantitative analysis of the
new magnetic subsystem, as it is currently conceived, and assess the
feasibility of selecting these sensors in the final configuration of the
magnetic diagnostic subsystem.


title: Gravitational Origin of Dark Matter

abstract:
  Observational evidence for the existence of Dark Matter is limited to its
gravitational effects. The extensive program for dedicated searches has yielded
null results so far, challenging the most popular models. Here we propose that
this is the case because the very existence of cold Dark Matter is a
manifestation of gravity itself. The consistent bimetric theory of gravity, the
only known ghost-free extension of General Relativity involving a massless and
a massive spin-2 field, automatically contains a perfect Dark Matter candidate.
We demonstrate that the massive spin-2 particle can be heavy, stable on
cosmological scales, and that it interacts with matter only through a
gravitational type of coupling. Remarkably, these features persist in the same
region of parameter space where bimetric theory satisfies the current gravity
tests. We show that the observed Dark Matter abundance can be generated via
freeze-in and suggest possible particle physics and gravitational signatures of
our bimetric Dark Matter model.


title:
Single-Particle Dynamics in a Nonlinear Accelerator Lattice: Attaining a
  Large Tune Spread with Octupoles in IOTA

abstract:
  Fermilab is constructing the Integrable Optics Test Accelerator (IOTA) as the
centerpiece of the Accelerator R&D Program towards high-intensity circular
machines. One of the factors limiting the beam intensity in present circular
accelerators is collective instabilities, which can be suppressed by a spread
of betatron frequencies (tunes) through the Landau damping mechanism or by an
external damper, if the instability is slow enough. The spread is usually
created by octupole magnets, which introduce the tune dependence on the
amplitude and, in some cases, by a chromatic spread (tune dependence on
particle's momentum). The introduction of octupoles usually has both the
beneficial (improved Landau damping) and harmful properties, such as a resonant
behavior and a reduction of the dynamic aperture. One of the research goals at
the IOTA ring is to achieve a large betatron tune spread, while retaining a
large dynamic aperture, using conventional octupole magnets in a special but
realistic accelerator configuration. In this paper, we present results of
computer simulations of an electron beam in the IOTA by particle tracking and
the Frequency Map Analysis. The results show that the ring's octupole magnets
can be configured to provide a betatron tune shift of 0.08 (for particles at
large amplitudes) with the dynamical aperture of over 20 beam sigma for a
150-MeV electron beam. The influence of the synchrotron motion, lattice errors,
and magnet imperfections is insignificant for the parameters and levels of
tolerances set by the design of the ring. The described octupole insert could
be beneficial for enhancing Landau damping in high intensity machines.


title: Broadband Observations of High Redshift Blazars

abstract:
  We present a multi-wavelength study of four high redshift blazars, S5 0014+81
($z=3.37$), CGRaBS J0225+1846 ($z=2.69$), BZQ J1430+4205 ($z=4.72$), and 3FGL
J1656.2$-$3303 ($z=2.40$), using the quasi-simultaneous data from {\it Swift},
{\it NuSTAR}, and {\it Fermi}-Large Area Telescope (LAT) and also the archival
{\it XMM-Newton} observations. Other than 3FGL J1656.2$-$3303, none of the
sources were known as $\gamma$-ray emitters and our analysis of $\sim$7.5 years
of LAT data reveals the first time detection of the statistically significant
$\gamma$-ray emission from CGRaBS J0225+1846. We generate the broadband
spectral energy distributions (SED) of all the objects, centering at the epoch
of {\it NuSTAR} observations and reproduce them using a one zone leptonic
emission model. The optical$-$UV emission in all the objects can be explained
by the radiation from the accretion disk, whereas, X-ray to $\gamma$-ray window
of the SEDs are found to be dominated by the inverse Compton scattering off the
broad line region photons. All of them host billion solar mass black holes.
Comparing the accretion disk luminosity and the jet power of these sources with
a large sample of blazars, we find them to occupy high disk luminosity-jet
power regime. We also investigate the X-ray spectral properties of the sources
in detail with a major focus on studying the causes of soft X-ray deficit, a
feature generally seen in high redshift radio-loud quasars. We summarize that
this feature could be explained based on the intrinsic curvature in the jet
emission rather than due to external effects predicted in the earlier studies,
such as host galaxy and/or warm absorption.


title:
Diffusive and subdiffusive spin transport in the ergodic phase of a
  many-body localizable system

abstract:
  We study high temperature spin transport in a disordered Heisenberg chain in
the ergodic regime. By employing a density matrix renormalization group
technique for the study of the stationary states of the boundary-driven
Lindblad equation we are able to study extremely large systems (400 spins). We
find both a diffusive and a subdiffusive phase depending on the strength of the
disorder and on the anisotropy parameter of the Heisenberg chain. Studying
finite-size effects we show numerically and theoretically that a very large
crossover length exists that controls the passage of a clean-system dominated
dynamics to one observed in the thermodynamic limit. Such a large length scale,
being larger than the sizes studied before, explains previous conflicting
results. We also predict spatial profiles of magnetization in steady states of
generic nondiffusive systems.


title: Towards Temporal Graph Databases

abstract:
  In spite of the extensive literature on graph databases (GDBs), temporal GDBs
have not received too much attention so far. Temporal GBDs can capture, for
example, the evolution of social networks across time, a relevant topic in data
analysis nowadays. In this paper we propose a data model and query language
(denoted TEG-QL) for temporal GDBs, based on the notion of attribute graphs.
This allows a straightforward translation to Neo4J, a well-known GBD. We
present extensive examples of the use of TEG-QL, and comment our
implementation.


title: Commutants for enriched algebraic theories and monads

abstract:
  We define and study a notion of $\textit{commutant}$ for
$\mathcal{V}$-enriched $\mathcal{J}$-algebraic theories for a system of arities
$\mathcal{J}$, recovering the usual notion of commutant or centralizer of a
subring as a special case alongside Wraith's notion of commutant for Lawvere
theories as well as a notion of commutant for $\mathcal{V}$-monads on a
symmetric monoidal closed category $\mathcal{V}$. This entails a thorough study
of commutation and Kronecker products of operations in $\mathcal{J}$-theories.
In view of the equivalence between $\mathcal{J}$-theories and $\mathcal{J}$-ary
monads we reconcile this notion of commutation with Kock's notion of
commutation of cospans of monads and, in particular, the notion of commutative
monad. We obtain notions of $\mathcal{J}$-$\textit{ary commutant}$ and
$\textit{absolute commutant}$ for $\mathcal{J}$-ary monads, and we show that
for finitary monads on Set the resulting notions of finitary commutant and
absolute commutant coincide. We examine the relation of the notion of commutant
to both the notion of $\textit{codensity monad}$ and the notion of
$\textit{algebraic structure}$ in the sense of Lawvere.


title:
The impact of rotation on turbulent tidal friction in stellar and
  planetary convective regions

abstract:
  Turbulent friction in convective regions in stars and planets is one of the
key physical mechanisms that drive the dissipation of the kinetic energy of
tidal flows in their interiors and the evolution of their systems. This
friction acts both on the equilibrium/non-wave like tide and on tidal inertial
waves in these layers. It is thus necessary to obtain a robust prescription for
this friction. In the current state-of-the-art, it is modeled by a turbulent
eddy-viscosity coefficient, based on mixing-length theory, applied on
velocities of tides. However, none of the current prescriptions take into
account the action of rotation that can strongly affects turbulent convection.
Therefore, we use theoretical scaling laws for convective velocities and
characteristic lengthscales in rotating stars and planets that have been
recently confirmed by 3-D high-resolution nonlinear Cartesian numerical
simulations to derive a new prescription. A corresponding local model of tidal
waves is used to understand the consequences for the linear tidal dissipation.
Finally, new grids of rotating stellar models and published values of planetary
convective Rossby numbers are used to discuss astrophysical consequences. The
action of rotation on convection deeply modifies the turbulent friction applied
on tides. In the regime of rapid rotation (with a convective Rossby number
below 0.25), the eddy-viscosity may be decreased by several ordres of
magnitude. It may lead to a loss of efficiency of the viscous dissipation of
the equilibrium tide and to a more efficient complex and resonant dissipation
of tidal inertial waves in the bulk of convective regions. Therefore, it is
necessary to have a completely coupled treatment of the tidal/rotational
evolution of star-planet systems and multiple stars with a coherent treatment
of the variations of tidal flows and of their dissipation as a function of
rotation.


title:
A new form of (unexpected) Dirac fermions in the strongly-correlated
  cerium monopnictides

abstract:
  Discovering Dirac fermions with novel properties has become an important
front in condensed matter and materials sciences. Here, we report the
observation of unusual Dirac fermion states in a strongly-correlated electron
setting, which are uniquely distinct from those of graphene and conventional
topological insulators. In strongly-correlated cerium monopnictides, we find
two sets of highly anisotropic Dirac fermions that interpenetrate each other
with negligible hybridization, and show a peculiar four-fold degeneracy where
their Dirac nodes overlap. Despite the lack of protection by crystalline or
time-reversal symmetries, this four-fold degeneracy is robust across magnetic
phase transitions. Comparison of these experimental findings with our
theoretical calculations suggests that the observed surface Dirac fermions
arise from bulk band inversions at an odd number of high-symmetry points, which
is analogous to the band topology which describes a
$\mathbb{Z}_{2}$-topological phase. Our findings open up an unprecedented and
long-sought-for platform for exploring novel Dirac fermion physics in a
strongly-correlated semimetal.


title: Stored energies for electric and magnetic current densities

abstract:
  Electric and magnetic current densities are an essential part of
electromagnetic theory. The goal of the present paper is to define and
investigate stored energies that are valid for structures that can support both
electric and magnetic current densities. Stored energies normalized with the
dissipated power give us the Q factor, or antenna Q, for the structure. Lower
bounds of the Q factor provide information about the available bandwidth for
passive antennas that can be realized in the structure. The definition that we
propose is valid beyond the leading order small antenna limit. Our starting
point is the energy density with subtracted far-field form which we obtain an
explicit and numerically attractive current density representation. This
representation gives us the insight to propose a coordinate independent stored
energy. Furthermore, we find here that lower bounds on antenna Q for structures
with e.g. electric dipole radiation can be formulated as convex optimization
problems. We determine lower bounds on both open and closed surfaces that
support electric and magnetic current densities.
  The here derived representation of stored energies has in its electrical
small limit an associated Q factor that agrees with known small antenna bounds.
These stored energies have similarities to earlier efforts to define stored
energies. However, one of the advantages with this method is the above
mentioned formulation as convex optimization problems, which makes it easy to
predict lower bounds for antennas of arbitrary shapes. The present formulation
also gives us insight into the components that contribute to Chu's lower bound
for spherical shapes. We utilize scalar and vector potentials to obtain a
compact direct derivation of these stored energies. Examples and comparisons
end the paper.


title: On extreme points of the diffusion polytope

abstract:
  We consider a class of diffusion problems defined on simple graphs in which
the populations at any two vertices may be averaged if they are connected by an
edge. The diffusion polytope is the convex hull of the set of population
vectors attainable using finite sequences of these operations. A number of
physical problems have linear programming solutions taking the diffusion
polytope as the feasible region, e.g. the free energy that can be removed from
plasma using waves, so there is a need to describe and enumerate its extreme
points. We review known results for the case of the complete graph $K_n$, and
study a variety of problems for the path graph $P_n$ and the cyclic graph
$C_n$. We describe the different kinds of extreme points that arise, and
identify the diffusion polytope in a number of simple cases. In the case of
increasing initial populations on $P_n$ the diffusion polytope is topologically
an $n$-dimensional hypercube.


title:
Axial compression of a thin elastic cylinder: bounds on the minimum
  energy scaling law

abstract:
  We consider the axial compression of a thin elastic cylinder placed about a
hard cylindrical core. Treating the core as an obstacle, we prove upper and
lower bounds on the minimum energy of the cylinder that depend on its relative
thickness and the magnitude of axial compression. We focus exclusively on the
setting where the radius of the core is greater than or equal to the natural
radius of the cylinder. We consider two cases: the "large mandrel" case, where
the radius of the core exceeds that of the cylinder, and the "neutral mandrel"
case, where the radii of the core and cylinder are the same. In the large
mandrel case, our upper and lower bounds match in their scaling with respect to
thickness, compression, and the magnitude of pre-strain induced by the core. We
construct three types of axisymmetric wrinkling patterns whose energy scales as
the minimum in different parameter regimes, corresponding to the presence of
many wrinkles, few wrinkles, or no wrinkles at all. In the neutral mandrel
case, our upper and lower bounds match in a certain regime in which the
compression is small as compared to the thickness; in this regime, the minimum
energy scales as that of the unbuckled configuration. We achieve these results
for both the von K\'arm\'an-Donnell model and a geometrically nonlinear model
of elasticity.


title:
Universal symmetry energy contribution to the neutron star equation of
  state

abstract:
  We discuss the observation that under neutron star conditions of charge
neutrality and $\beta-$equilibrium the contribution from the symmetry energy to
the equation of state (EoS) follows a universal behaviour. We call this
behaviour the conjecture of a Universal Symmetry Energy Contribution (USEC). We
find that an USEC holds provided the density dependence of the symmetry energy
$E_s(n)$ follows a behaviour that limits the proton fraction $x(n)$ to values
below the threshold for the direct Urca (DU) cooling process. The absence of DU
cooling in typical mass neutron stars appears to be supported by the
phenomenology of neutron star cooling data and allows to constrain the
behaviour of $E_s(n)$ at high densities. Two classes of symmetry energy
functions are investigated more in detail to elucidate the USEC. We derive an
analytic formula for the USEC to the neutron star EoS based on the result for
the symmetry energy extracted from isobaric analog states of nuclei.


title: $W^{\pm}Z$ production at hadron colliders in NNLO QCD

abstract:
  We report on the first computation of the next-to-next-to-leading order
(NNLO) QCD corrections to $W^{\pm}Z$ production in proton collisions. We
consider both the inclusive production of on-shell $W^{\pm}Z$ pairs at LHC
energies and the total $W^{\pm}Z$ rates including off-shell effects of the $W$
and $Z$ bosons. In the off-shell computation, the invariant mass of the lepton
pairs from the $Z$ boson decay is required to be in a given mass window, and
the results are compared with the corresponding measurements obtained by the
ATLAS and CMS collaborations. The NNLO corrections range from 8% at
$\sqrt{s}$=7 TeV to 11% at $\sqrt{s}$=14 TeV and significantly improve the
agreement with the LHC data at $\sqrt{s}$=7 and 8 TeV.


title:
Uniqueness of self-shrinkers to the degree-one curvature flow with a
  tangent cone at infinity

abstract:
  Given a smooth, symmetric, homogeneous of degree one function
$f=f\left(\lambda_{1},\cdots,\,\lambda_{n}\right)$ satisfying $\partial_{i}f>0$
for all $i=1,\cdots,\, n$, and an oriented, properly embedded smooth cone
$\mathcal{C}^n$ in $\mathbb{R}^{n+1}$, we show that under some suitable
conditions on $f$ and the covariant derivatives of the second fundamental form
of $\mathcal{C}$, there is at most one $f$ self-shrinker (i.e. an oriented
hypersurface $\Sigma^n$ in $\mathbb{R}^{n+1}$ for which
$f\left(\kappa_{1},\cdots,\,\kappa_{n}\right)+\frac{1}{2}X\cdot N=0$ holds,
where $X$ is the position vector, $N$ is the unit normal vector, and
$\kappa_{1},\cdots,\,\kappa_{n}$ are principal curvatures of $\Sigma$) that is
asymptotic to the given cone $\mathcal{C}$ at infinity.


title:
CMB Lensing Bispectrum from Nonlinear Growth of the Large Scale
  Structure

abstract:
  We discuss detectability of the nonlinear growth of the large-scale structure
in the cosmic microwave background (CMB) lensing. Lensing signals involved in
CMB anisotropies have been measured from multiple CMB experiments, such as
Atacama Cosmology Telescope (ACT), Planck, POLARBEAR, and South Pole Telescope
(SPT). Reconstructed lensing signals are useful to constrain cosmology via
their angular power spectrum, while detectability and cosmological application
of their bispectrum induced by the nonlinear evolution are not well studied.
Extending the analytic estimate of the galaxy lensing bispectrum presented by
Takada and Jain (2004) to the CMB case, we show that even near term CMB
experiments such as Advanced ACT, Simons Array and SPT3G could detect the CMB
lensing bispectrum induced by the nonlinear growth of the large-scale
structure. In the case of the CMB Stage-IV, we find that the lensing bispectrum
is detectable at $\gtrsim 50\sigma$ statistical significance. This precisely
measured lensing bispectrum has rich cosmological information, and could be
used to constrain cosmology, e.g., the sum of the neutrino masses and the
dark-energy properties.


title:
A primer on Carnot groups: homogenous groups, CC spaces, and regularity
  of their isometries

abstract:
  Carnot groups are distinguished spaces that are rich of structure: they are
those Lie groups equipped with a path distance that is invariant by
left-translations of the group and admit automorphisms that are dilations with
respect to the distance. We present the basic theory of Carnot groups together
with several remarks. We consider them as special cases of graded groups and as
homogeneous metric spaces. We discuss the regularity of isometries in the
general case of Carnot-Caratheodory spaces and of nilpotent metric Lie groups.


title: Non-Koszulness of operads and positivity of Poincar\'e series

abstract:
  We prove that the operad of mock partially associative $n$-ary algebras is
not Koszul, as conjectured by the second and the third author in 2009, and
utilise the Zeilberger's algorithm for hypergeometric summation to demonstrate
that non-Koszulness of that operad cannot be established by hunting for
negative coefficients in the inverse of its Poincar\'e series.


title:
Two-Loop Master Integrals for the mixed EW-QCD virtual corrections to
  Drell-Yan scattering

abstract:
  We present the calculation of the master integrals needed for the two-loop
QCDxEW corrections to $ q + \bar{q} \to l^- + l^+$ and $ q + \bar{q}' \to l^- +
\overline{\nu} \, , $ for massless external particles. We treat W and Z bosons
as degenerate in mass. We identify three types of diagrams, according to the
presence of massive internal lines: the no-mass type, the one-mass type, and
the two-mass type, where all massive propagators, when occurring, contain the
same mass value. We find a basis of 49 master integrals and evaluate them with
the method of the differential equations. The Magnus exponential is employed to
choose a set of master integrals that obeys a canonical system of differential
equations. Boundary conditions are found either by matching the solutions onto
simpler integrals in special kinematic configurations, or by requiring the
regularity of the solution at pseudo-thresholds. The canonical master integrals
are finally given as Taylor series around d=4 space-time dimensions, up to
order four, with coefficients given in terms of iterated integrals,
respectively up to weight four.


title: Quantum Key Distribution Using Multiple Gaussian Focused Beams

abstract:
  The secret key rate attained by a free-space QKD system in the {\em
near-field} propagation regime (relevant for $1$-$10$ km range using $\approx
7$ cm radii transmit and receive apertures and $1.55~\mu$m transmission center
wavelenght) can benefit from the use of multiple spatial modes. A suite of
theoretical research in recent years have suggested the use of
orbital-angular-momentum (OAM) bearing spatial modes of light to obtain this
improvement in rate. We show that most of the aforesaid rate improvement in the
near field afforded by spatial-mode multiplexing can be realized by a
simple-to-build overlapping Gaussian beam array (OGBA) and a pixelated detector
array. With the current state-of-the-art in OAM-mode-sorting efficiencies, the
key-rate performance of our OGBA architecture could come very close to, if not
exceed, that of a system employing OAM modes, but at a fraction of the cost.


abstract:
  While the tracking detectors of the ATLAS and CMS experiments have shown
excellent performance in Run 1 of LHC data taking, and are expected to continue
to do so during LHC operation at design luminosity, both experiments will have
to exchange their tracking systems when the LHC is upgraded to the
high-luminosity LHC (HL-LHC) around the year 2024. The new tracking systems
need to operate in an environment in which both the hit densities and the
radiation damage will be about an order of magnitude higher than today. In
addition, the new trackers need to contribute to the first level trigger in
order to maintain a high data-taking efficiency for the interesting processes.
Novel detector technologies have to be developed to meet these very challenging
goals. The German groups active in the upgrades of the ATLAS and CMS tracking
systems have formed a collaborative "Project on Enabling Technologies for
Silicon Microstrip Tracking Detectors at the HL-LHC" (PETTL), which was
supported by the Helmholtz Alliance "Physics at the Terascale" during the years
2013 and 2014. The aim of the project was to share experience and to work
together on key areas of mutual interest during the R&D phase of these
upgrades. The project concentrated on five areas, namely exchange of
experience, radiation hardness of silicon sensors, low mass system design,
automated precision assembly procedures, and irradiations. This report
summarizes the main achievements.


title: Black Hole Remnants in Hayward Solutions and Noncommutative Effects

abstract:
  In this paper, we explore the final stages of the black hole evaporation for
Hayward solutions. Our results show that the behavior of Hawking's radiation
changes considerably at the small radii regime such that the black hole does
not evaporate completely and a stable remnant is left. We show that stability
conditions hold for the Hayward solutions found in the Einstein gravity coupled
with nonlinear electrodynamics. We analyse the effect that an inspired model of
the noncommutativity of spacetime can have on the thermodynamics of Hayward
spacetimes. This has been done by applying the noncommutative effects to the
non-rotating and rotating Hayward black holes. In this setup, all point
structures get replaced by smeared distributions owing to this inspired
approach. The noncommutative effects result in a colder black hole in the small
radii regime as Hayward's free parameter $g$ increases. As well as the effects
of noncommutativity and the rotation factor, the configuration of the remnant
can be substantially affected by the parameter $g$. However, in the rotating
solution it is not so sensitive to $g$ with respect to the non-rotating case.
As a consequence, Hayward's parameter, the noncommutativity and the rotation
may raise the minimum value of energy for the possible formation of black holes
in TeV-scale collisions. This observation can be used as a potential
explanation for the absence of black holes in the current energy scales
produced at particle colliders. However, it is also found that if extra
dimensions do exist, then the possibility of the black hole production at
energy scales accessible at the LHC for large numbers of extra dimensions will
be larger.


title: Groupoids viewed as inverse semigroups

abstract:
  A simple observation, showing that every groupoid becomes an inverse
semigroup after adding one element. In such inverse semigroups all idempotents
are mutually orthogonal. This fact implies that every C*-algebra of a discrete
groupoid is a C*-algebra of an inverse semigroup.


title: NEC violation in mimetic cosmology revisited

abstract:
  In the context of Einstein gravity, if the null energy condition (NEC) is
satisfied, the energy density in expanding space-times always decreases while
in contracting space-times the energy density grows and the universe eventually
collapses into a singularity. In particular, no non-singular bounce is
possible. It is, though, an open question if this energy condition can be
violated in a controlled way, i.e., without introducing pathologies, such as
unstable negative-energy states or an imaginary speed of sound. In this paper,
we will re-examine the claim that the recently proposed mimetic scenario can
violate the NEC without pathologies. We show that mimetic cosmology is prone to
gradient instabilities even in cases when the NEC is satisfied (except for
trivial examples). Most interestingly, the source of the instability is always
the Einstein-Hilbert term in the action. The matter stress-energy component
does not contribute spatial gradient terms but instead makes the problematic
curvature modes dynamical. We also show that mimetic cosmology can be
understood as a singular limit of known, well-behaved theories involving
higher-derivative kinetic terms and discuss ways of removing the instability.


title:
Semi-implicit anisotropic cosmic ray transport on an unstructured moving
  mesh

abstract:
  In the interstellar medium of galaxies and the intracluster gas of galaxy
clusters, the charged particles making up cosmic rays are moving almost
exclusively along (but not across) magnetic field lines. The resulting
anisotropic transport of cosmic rays in the form of diffusion or streaming not
only affects the gas dynamics but also rearranges the magnetic fields
themselves. The coupled dynamics of magnetic fields and cosmic rays can thus
impact the formation and evolution of galaxies and the thermal evolution of
galaxy clusters in critical ways. Numerically studying these effects requires
solvers for anisotropic diffusion that are accurate, efficient, and robust,
requirements that have proven difficult to satisfy in practice. Here, we
present an anisotropic diffusion solver on an unstructured moving mesh that is
conservative, does not violate the entropy condition, allows for semi-implicit
time integration with individual timesteps, and only requires solving a single
linear system of equations per timestep. We apply our new scheme to a large
number of test problems and show that it works as well or better than previous
implementations. Finally, we demonstrate for a numerically demanding simulation
of the formation of an isolated disk galaxy that our local time-stepping scheme
reproduces the results obtained with global time-stepping at a fraction of the
computational cost.


title:
The Minimal SUSY $B-L$ Model: Simultaneous Wilson Lines and String
  Thresholds

abstract:
  In previous work, we presented a statistical scan over the soft supersymmetry
breaking parameters of the minimal SUSY $B-L$ model. For specificity of
calculation, unification of the gauge parameters was enforced by allowing the
two ${\mathbb Z}_{3}\times {\mathbb Z}_{3}$ Wilson lines to have mass scales
separated by approximately an order of magnitude. This introduced an additional
"left-right" sector below the unification scale. In this paper, for three
important reasons, we modify our previous analysis by demanding that the mass
scales of the two Wilson lines be simultaneous and equal to an "average
unification" mass $\left<M_{U}\right>$. The present analysis is 1) more
"natural" than the previous calculations, which were only valid in a very
specific region of the Calabi-Yau moduli space, 2) the theory is conceptually
simpler in that the left-right sector has been removed and 3) in the present
analysis the lack of gauge unification is due to threshold
effects--particularly heavy string thresholds, which we calculate statistically
in detail. As in our previous work, the theory is renormalization group evolved
from $\left<M_{U}\right>$ to the electroweak scale--being subjected,
sequentially, to the requirement of radiative $B-L$ and electroweak symmetry
breaking, the present experimental lower bounds on the $B-L$ vector boson and
sparticle masses, as well as the lightest neutral Higgs mass of $\sim$125 GeV.
The subspace of soft supersymmetry breaking masses that satisfies all such
constraints is presented and shown to be substantial.


title:
Interpreting the subtle spectral variations of the 11.2 and 12.7 {\mu}m
  polycyclic aromatic hydrocarbon bands

abstract:
  We report new properties of the 11 and 12.7 {\mu}m emission complexes of
polycyclic aromatic hydrocarbons (PAHs) by applying a Gaussian-based
decomposition technique. Using high-resolution \textit{Spitzer} Space Telescope
data, we study in detail the spectral and spatial characteristics of the 11 and
12.7 {\mu}m emission bands in maps of reflection nebulae NGC 7023 and NGC 2023
(North and South) and the star-forming region M17. Profile variations are
observed in both the 11 and 12.7 {\mu}m emission bands. We identify a neutral
contribution to the traditional 11.0 {\mu}m PAH band and a cationic
contribution to the traditional 11.2 {\mu}m band, the latter of which affects
the PAH class of the 11.2 {\mu}m emission in our sample. The peak variations of
the 12.7 {\mu}m complex are explained by the competition between two underlying
blended components. The spatial distributions of these components link them to
cations and neutrals. We conclude that the 12.7 {\mu}m emission originates in
both neutral and cationic PAHs, lending support to the use of the 12.7/11.2
intensity ratio as a charge proxy.


title: Deep imaging of Eridanus II and its lone star cluster

abstract:
  We present deep imaging of the most distant dwarf discovered by the Dark
Energy Survey, Eridanus II (Eri II). Our Magellan/Megacam stellar photometry
reaches $\sim$$3$ mag deeper than previous work, and allows us to confirm the
presence of a stellar cluster whose position is consistent with Eri II's
center. This makes Eri II, at $M_V=-7.1$, the least luminous galaxy known to
host a (possibly central) cluster. The cluster is partially resolved, and at
$M_V=-3.5$ it accounts for $\sim$$4\%$ of Eri II's luminosity. We derive
updated structural parameters for Eri II, which has a half-light radius of
$\sim$$280$ pc and is elongated ($\epsilon$$\sim$$0.48$), at a measured
distance of $D$$\sim$$370$ kpc. The color-magnitude diagram displays a blue,
extended horizontal branch, as well as a less populated red horizontal branch.
A central concentration of stars brighter than the old main sequence turnoff
hints at a possible intermediate-age ($\sim$$3$ Gyr) population; alternatively,
these sources could be blue straggler stars. A deep Green Bank Telescope
observation of Eri II reveals no associated atomic gas.


title: All Majorana Models with Translation Symmetry are Supersymmetric

abstract:
  We establish results similar to Kramers and Lieb-Schultz-Mattis theorems but
involving only translation symmetry and for Majorana modes. In particular, we
show that all states are at least doubly degenerate in any one and two
dimensional array of Majorana modes with translation symmetry, periodic
boundary conditions, and an odd number of modes per unit cell. Moreover, we
show that all such systems have an underlying $\mathcal{N}=2$ supersymmetry and
explicitly construct the generator of the supersymmetry. Furthermore, we
establish that there cannot be a unique gapped ground state in such one
dimensional systems with anti-periodic boundary conditions. These general
results are fundamentally a consequence of the fact that translations for
Majorana modes are represented projectively, which in turn stems from the
anomalous nature of a single Majorana mode. An experimental signature of the
degeneracy arising from supersymmetry is a zero-bias peak in tunneling
conductance.


title: MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models

abstract:
  This is the first of a series of papers presenting the Modules for
Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST)
project, a new comprehensive set of stellar evolutionary tracks and isochrones
computed using MESA, a state-of-the-art open-source 1D stellar evolution
package. In this work, we present models with solar-scaled abundance ratios
covering a wide range of ages ($5 \leq \rm \log(Age)\;[yr] \leq 10.3$), masses
($0.1 \leq M/M_{\odot} \leq 300$), and metallicities ($-2.0 \leq \rm [Z/H] \leq
0.5$). The models are self-consistently and continuously evolved from the
pre-main sequence to the end of hydrogen burning, the white dwarf cooling
sequence, or the end of carbon burning, depending on the initial mass. We also
provide a grid of models evolved from the pre-main sequence to the end of core
helium burning for $-4.0 \leq \rm [Z/H] < -2.0$. We showcase extensive
comparisons with observational constraints as well as with some of the most
widely used existing models in the literature. The evolutionary tracks and
isochrones can be downloaded from the project website at
http://waps.cfa.harvard.edu/MIST/.


title: Resolved atomic lines reveal outflows in two ultraluminous X-ray sources

abstract:
  Ultraluminous X-ray sources are extragalactic, off-nucleus, point sources in
galaxies with an X-ray luminosity above 3x10^39 erg/s, thought to be powered by
accretion onto a compact object. Possible explanations include accretion onto
neutron stars with strong magnetic fields, stellar-mass black holes (< 20
Msolar) at or in excess of the classical Eddington limit or intermediate-mass
black holes (10^3-5 Msolar). The lack of sufficient energy resolution in
previous analyses has hitherto prevented an unambiguous identification of any
emission or absorption lines in the X-ray band, thereby precluding a detailed
analysis of the accretion flow. Here we report the presence of X-ray emission
lines arising from highly ionized iron, oxygen and neon with a cumulative
significance > 5 sigma, and blueshifted (~0.2c) absorption lines (5 sigma) in
the high-resolution X-ray spectrum of the ultraluminous X-ray source NGC 1313
X-1. In a similar source, NGC 5408 X-1, we also detect emission lines at rest
and blueshifted absorption. The blueshifted absorption lines must occur in a
fast outflowing gas, whereas the emission lines originate in slow-moving gas
around the source. We conclude that the compact object is surrounded by
powerful winds with an outflow velocity of about 0.2c as predicted by models of
accreting supermassive black holes and hyper-accreting stellar mass black
holes.


title: Are Some Milky Way Globular Clusters Hosted by Undiscovered Galaxies?

abstract:
  The confirmation of a globular cluster (GC) in the recently discovered
ultrafaint galaxy Eridanus II (Eri II) motivated us to examine the question
posed in the title. After estimating the halo mass of Eri II using a published
stellar mass - halo mass relation, the one GC in this galaxy supports extending
the relationship between the number of GCs hosted by a galaxy and the galaxy's
total mass about two orders of magnitude in stellar mass below the previous
limit. For this empirically determined specific frequency of between 0.06 and
0.39 globular clusters per 10$^9$ $M_\odot$ of total mass, the surviving Milky
Way (MW) subhalos with masses smaller than $10^{10} M_\odot$ could host as many
as 5 to 31 GCs, broadly consistent with the actual population of outer halo MW
GCs, although matching the radial distribution in detail remains a challenge.
Using a subhalo mass function from published high resolution numerical
simulations and a Poissonian model for populating those halos with the
aforementioned empirically constrained frequency, we find that about 90$\%$ of
these GCs lie in lower-mass subhalos than that of Eri II. From what we know
about the stellar mass-halo mass function, the subhalo mass function, and the
mass-normalized GC specific frequency, we conclude that some of the MW's outer
halo GCs are likely to be hosted by undetected subhalos with extremely modest
stellar populations.


title:
How Unequal Fluxes of High Energy Astrophysical Neutrinos and
  Antineutrinos can Fake New Physics

abstract:
  Flavor ratios of very high energy astrophysical neutrinos, which can be
studied at the Earth by a neutrino telescope such as IceCube, can serve to
diagnose their production mechanism at the astrophysical source. The flavor
ratios for neutrinos and antineutrinos can be quite different as we do not know
how they are produced in the astrophysical environment. Due to this uncertainty
the neutrino and antineutrino flavor ratios at the Earth also could be quite
different. Nonetheless, it is generally assumed that flavor ratios for
neutrinos and antineutrinos are the same at the Earth, in fitting the high
energy astrophysical neutrino data. This is a reasonable assumption for the
limited statistics for the data we currently have. However, in the future the
fit must be performed allowing for a possible discrepancy in these two
fractions in order to be able to disentangle different production mechanisms at
the source from new physics in the neutrino sector. To reinforce this issue, in
this work we show that a wrong assumption about the distribution of neutrino
flavor ratios at the Earth may indeed lead to misleading interpretations of
IceCube results.


title:
Left-Right Symmetry and Lepton Number Violation at the Large Hadron
  Electron Collider

abstract:
  We show that the proposed Large Hadron electron Collider (LHeC) will provide
an opportunity to search for left-right symmetry and establish lepton number
violation, complementing current and planned searches based on LHC data and
neutrinoless double beta decay. We consider several plausible configurations
for the LHeC -- including different electron energies and polarizations, as
well as distinct values for the charge misidentification rate. Within
left-right symmetric theories we determine the values of right-handed neutrino
and gauge boson masses that could be tested at the LHeC after one, five and ten
years of operation. Our results indicate that this collider might probe, via
the $\Delta L =2$ signal $e^-p\to e^+jjj$, Majorana neutrino masses up to 1 TeV
and $W_R$ masses up to 6.5 TeV. Interestingly, part of this parameter space is
beyond the expected reach of the LHC and of future neutrinoless double beta
decay experiments.


title:
The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen
  Gas in the Outskirts of Star Forming Galaxies from z~1 to z~3

abstract:
  Current observational evidence suggests that the star formation rate (SFR)
efficiency of neutral atomic hydrogen gas measured in Damped Ly-alpha Systems
(DLAs) at z~3 is more than 10 times lower than predicted by the
Kennicutt-Schmidt (KS) relation. To understand the origin of this deficit, and
to investigate possible evolution with redshift and galaxy properties, we
measure the SFR efficiency of atomic gas at z~1, z~2, and z~3 around
star-forming galaxies. We use new robust photometric redshifts in the Hubble
Ultra Deep Field to create galaxy stacks in these three redshift bins, and
measure the SFR efficiency by combining DLA absorber statistics with the
observed rest-frame UV emission in the galaxies' outskirts. We find that the
SFR efficiency of HI gas at z>1 is ~1-3% of that predicted by the KS relation.
Contrary to simulations and models that predict a reduced SFR efficiency with
decreasing metallicity and thus with increasing redshift, we find no
significant evolution in the SFR efficiency with redshift. Our analysis instead
suggests that the reduced SFR efficiency is driven by the low molecular content
of this atomic-dominated phase, with metallicity playing a secondary effect in
regulating the conversion between atomic and molecular gas. This interpretation
is supported by the similarity between the observed SFR efficiency and that
observed in local atomic-dominated gas, such as in the outskirts of local
spiral galaxies and local dwarf galaxies.


title:
Hydrodynamic theory of thermoelectric transport and negative
  magnetoresistance in Weyl semimetals

abstract:
  We present a theory of thermoelectric transport in weakly disordered Weyl
semimetals where the electron-electron scattering time is faster than the
electron-impurity scattering time. Our hydrodynamic theory consists of
relativistic fluids at each Weyl node, coupled together by perturbatively small
inter-valley scattering, and long-range Coulomb interactions. The conductivity
matrix of our theory is Onsager reciprocal and positive-semidefinite. In
addition to the usual axial anomaly, we account for the effects of a distinct,
axial-gravitational anomaly expected to be present in Weyl semimetals. Negative
thermal magnetoresistance is a sharp, experimentally accessible signature of
this axial-gravitational anomaly, even beyond the hydrodynamic limit.


title:
Determining the large-scale environmental dependence of gas-phase
  metallicity in dwarf galaxies

abstract:
  We study how the cosmic environment affects galaxy evolution in the Universe
by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies
in more dense regions. Ratios of the fluxes of emission lines, particularly
those of the forbidden [O III] and [S II] transitions, provide estimates of a
region's electron temperature and number density. From these two quantities and
the emission line fluxes [O II] 3727, [O III] 4363, and [O III] 4959,5007, we
estimate the abundance of oxygen with the Direct Te method. We estimate the
metallicity of 42 blue, star-forming void dwarf galaxies and 89 blue,
star-forming dwarf galaxies in more dense regions using spectroscopic
observations from the Sloan Digital Sky Survey Data Release 7, as re-processed
in the MPA-JHU value-added catalog. We find very little difference between the
two sets of galaxies, indicating little influence from the large-scale
environment on their chemical evolution. Of particular interest are a number of
extremely metal-poor dwarf galaxies that are less prevalent in voids than in
the denser regions.


title: Caching and Delivery via Interference Elimination

abstract:
  We propose a new caching scheme where linear combinations of the file
segments are cached at the users, for the cases where the number of files is no
greater than the number of users. When a user requests a certain file in the
delivery phase, the other file segments in the cached linear combinations can
be viewed as interferences. The proposed scheme combines rank metric codes and
maximum distance separable codes to facilitate the decoding and elimination of
these interferences, and also to simultaneously deliver useful contents to the
intended users. The performance of the proposed scheme can be explicitly
evaluated, and we show that the tradeoff points achieved by this scheme can
strictly improve known tradeoff inner bounds in the literature; for certain
special cases, the new tradeoff points can be shown to be optimal.


title: The chiral anomaly factory: Creating Weyl fermions with a magnetic field

abstract:
  Weyl fermions can be created in materials with both time reversal and
inversion symmetry by applying a magnetic field, as evidenced by recent
measurements of anomalous negative magnetoresistance. Here, we do a thorough
analysis of the Weyl points in these materials: by enforcing crystal
symmetries, we classify the location and monopole charges of Weyl points
created by fields aligned with high-symmetry axes. The analysis applies
generally to materials with band inversion in the $T_d$, $D_{4h}$ and $D_{6h}$
point groups. For the $T_d$ point group, we find that Weyl nodes persist for
all directions of the magnetic field. Further, we compute the anomalous
magnetoresistance of field-created Weyl fermions in the semiclassical regime.
We find that the magnetoresistance can scale non-quadratically with magnetic
field, in contrast to materials with intrinsic Weyl nodes. Our results are
relevant to future experiments in the semi-classical regime.


title: The exceptional story of massive IIA supergravity

abstract:
  The framework of exceptional field theory is extended by introducing
consistent deformations of its generalised Lie derivative. For the first time,
massive type IIA supergravity is reproduced geometrically as a solution of the
section constraint. This provides a unified description of all ten- and
eleven-dimensional maximal supergravities. The action of the E7 deformed theory
is constructed, and reduces to those of exceptional field theory and gauged
maximal supergravity in respective limits. The relation of this new framework
to other approaches for generating the Romans mass non-geometrically is
discussed.


title: Decomposing Cubic Graphs into Connected Subgraphs of Size Three

abstract:
  Let $S=\{K_{1,3},K_3,P_4\}$ be the set of connected graphs of size 3. We
study the problem of partitioning the edge set of a graph $G$ into graphs taken
from any non-empty $S'\subseteq S$. The problem is known to be NP-complete for
any possible choice of $S'$ in general graphs. In this paper, we assume that
the input graph is cubic, and study the computational complexity of the problem
of partitioning its edge set for any choice of $S'$. We identify all polynomial
and NP-complete problems in that setting, and give graph-theoretic
characterisations of $S'$-decomposable cubic graphs in some cases.


title:
Robo-AO Kepler Planetary Candidate Survey II: Adaptive Optics Imaging of
  969 Kepler Exoplanet Candidate Host Stars

abstract:
  We initiated the Robo-AO Kepler Planetary Candidate Survey in 2012 to observe
each Kepler exoplanet candidate host star with high-angular-resolution
visible-light laser-adaptive-optics imaging. Our goal is to find nearby stars
lying in Kepler's photometric apertures that are responsible for the relatively
high probability of false-positive exoplanet detections and that cause
underestimates of the size of transit radii. Our comprehensive survey will also
shed light on the effects of stellar multiplicity on exoplanet properties and
will identify rare exoplanetary architectures. In this second part of our
ongoing survey, we observed an additional 969 Kepler planet candidate hosts and
we report blended stellar companions up to $\Delta m \approx 6$ that contribute
to Kepler's measured light curves. We found 203 companions within $\sim$4" of
181 of the Kepler stars, of which 141 are new discoveries. We measure the
nearby-star probability for this sample of Kepler planet candidate host stars
to be 10.6% $\pm$ 1.1% at angular separations up to 2.5", significantly higher
than the 7.4% $\pm$ 1.0% probability discovered in our initial sample of 715
stars; we find the probability increases to 17.6% $\pm$ 1.5% out to a
separation of 4.0". The median position of KOIs observed in this survey are
1.1$^{\circ}$ closer to the galactic plane which may account for some of the
nearby-star probability enhancement. We additionally detail 50 Keck adaptive
optics images of Robo-AO observed KOIs in order to confirm 37 companions
detected at a $<5\sigma$ significance level and to obtain additional infrared
photometry on higher-significance detected companions.


title: Dislocation core properties of \beta-tin: A first-principles study

abstract:
  Dislocation core properties of tin (\beta-Sn) were investigated using the
semi-discrete variational Peierls-Nabarro model (SVPN). The SVPN model, which
connects the continuum elasticity treatment of the long-range strain field
around a dislocation with an approximate treatment of the dislocation core, was
employed to calculate various core properties, including the core energetics,
widths, and Peierls stresses for different dislocation structures. The role of
core energetics and properties on dislocation character and subsequent slip
behavior in \beta-Sn was investigated. For instance, this work shows that a
widely spread dislocation core on the {110} plane as compared to dislocations
on the {100} and {101} planes. Physically, the narrowing or widening of the
core will significantly affect the mobility of dislocations as the Peierls
stress is exponentially related to the dislocation core width in \beta-Sn. In
general, the Peierls stress for the screw dislocation was found to be orders of
magnitude higher than the edge dislocation, i.e., the more the edge component
of a mixed dislocation, the greater the dislocation mobility (lower the Peierls
stress). The largest Peierls stress observed was 365 MPa for the dislocation on
the {101} plane. Furthermore, from the density plot, we see a double peak for
the 0deg (screw) and 30deg dislocations which suggests the dissociation of
dislocations along these planes. Thus, for the {101} <-101> slip system, we
observed dislocation dissociation into three partials with metastable states.
Overall, this work provides qualitative insights that aid in understanding the
plastic deformation in \beta-Sn.


title:
Von Neumann Algebras of Sofic Groups with $\beta_{1}^{(2)}=0$ are
  Strongly $1$-Bounded

abstract:
  We show that if $\Gamma$ is an infinite finitely generated finitely presented
sofic group with zero first $L^{2}$ Betti number then the von Neumann algebra
$L(\Gamma)$ is strongly $1$-bounded in the sense of Jung. In particular,
$L(\Gamma)\not\cong L(\Lambda)$ if $\Lambda$ is any group with free entropy
dimension $>1$, for example a free group. The key technical result is a short
proof of an estimate of Jung using non-microstates entropy techniques.


title:
Magnetization Saturation Process in the Magnonic Anti-dot Structures
  Based on (Ga,Mn)As: A Magnetometric Study

abstract:
  Applicability of dilute magnetic semiconductors (DMS) in electronic devices
relies upon the understanding and control of their magnetic anisotropy. This
paper explores one of the ways in engineering magnetic anisotropy in epitaxial
layers of DMS by forming them into magnonic structures. For this purpose the
canonical ferromagnetic DMS, namely (Ga,Mn)As, is employed. The anti-dot
systems based on (Ga,Mn)As layers of various thicknesses are fabricated with
focused ion beam apparatus and studied by means of microscopy as well as
magnetometry. The magnetometric data - collected along two nonequivalent
in-plane crystallographic directions of (Ga,Mn)As: [110] and [1-10] - shows the
effect of structuring on high-field magnetization process, whereas no
significant change of the width of hysteresis loop in anti-dot samples is
observed.


title:
A movie genre prediction based on Multivariate Bernoulli model and genre
  correlations

abstract:
  Movie ratings play an important role both in determining the likelihood of a
potential viewer to watch the movie and in reflecting the current viewer
satisfaction with the movie. They are available in several sources like the
television guide, best-selling reference books, newspaper columns, and
television programs. Furthermore, movie ratings are crucial for recommendation
engines that track the behavior of all users and utilize the information to
suggest items they might like. Movie ratings in most cases, thus, provide
information that might be more important than movie feature-based data. It is
intuitively appealing that information about the viewing preferences in movie
genres is sufficient for predicting a genre of an unlabeled movie. In order to
predict movie genres, we treat ratings as a feature vector, apply the Bernoulli
event model to estimate the likelihood of a movies given genre, and evaluate
the posterior probability of the genre of a given movie using the Bayes rule.
The goal of the proposed technique is to efficiently use the movie ratings for
the task of predicting movie genres. In our approach we attempted to answer the
question: "Given the set of users who watched a movie, is it possible to
predict the genre of a movie based on its ratings?" Our simulation results with
MovieLens 100k data demonstrated the efficiency and accuracy of our proposed
technique, achieving 59% prediction rate for exact prediction and 69% when
including correlated genres.


title: Supersymmetric Theory of Stochastic ABC Model: A Numerical Study

abstract:
  In this paper, we investigate numerically the stochastic ABC model, a toy
model in the theory of astrophysical kinematic dynamos, within the recently
proposed supersymmetric theory of stochastics (STS). STS characterises
stochastic differential equations (SDEs) by the spectrum of the stochastic
evolution operator (SEO) on elements of the exterior algebra or differentials
forms over the system's phase space, X. STS can thereby classify SDEs as
chaotic or non-chaotic by identifying the phenomenon of stochastic chaos with
the spontaneously broken topological supersymmetry that all SDEs possess. We
demonstrate the following three properties of the SEO, deduced previously
analytically and from physical arguments: the SEO spectra for zeroth and top
degree forms never break topological supersymmetry, all SDEs possesses
pseudo-time-reversal symmetry, and each de Rahm cohomology class provides one
supersymmetric eigenstate. Our results also suggests that the SEO spectra for
forms of complementary degrees, i.e., k and dim X -k, may be isospectral.

categories: nlin.CD astro-ph.GA math-ph math.DS math.MP


title: Artistic style transfer for videos

abstract:
  In the past, manually re-drawing an image in a certain artistic style
required a professional artist and a long time. Doing this for a video sequence
single-handed was beyond imagination. Nowadays computers provide new
possibilities. We present an approach that transfers the style from one image
(for example, a painting) to a whole video sequence. We make use of recent
advances in style transfer in still images and propose new initializations and
loss functions applicable to videos. This allows us to generate consistent and
stable stylized video sequences, even in cases with large motion and strong
occlusion. We show that the proposed method clearly outperforms simpler
baselines both qualitatively and quantitatively.


title: Tidal stripping as a test of satellite quenching in redMaPPer clusters

abstract:
  When dark matter halos are accreted by massive host clusters, strong
gravitational tidal forces begin stripping mass from the accreted subhalos.
This stripping eventually removes all mass beyond a subhalo's tidal radius, but
the unbound mass remains in the vicinity of the satellite for at least a
dynamical time t_dyn. The N-body subhalo study of Chamberlain et al. verified
this picture and pointed out a useful observational consequence: measurements
of subhalo correlations beyond the tidal radius are sensitive to the infall
time, t_infall, of the subhalo onto its host. We perform this cross-correlation
measurement using ~ 160,000 red satellite galaxies in SDSS redMaPPer clusters
and find evidence that subhalo correlations do persist well beyond the tidal
radius, suggesting that many of the observed satellites fell into their current
host less than a dynamical time ago, t_infall < t_dyn. Combined with estimated
dynamical times t_dyn ~ 3-5 Gyr and SED fitting results for the time at which
satellites stopped forming stars, t_quench ~ 6 Gyr, we infer that for a
significant fraction of the satellites, star formation quenched before those
satellites entered their current hosts. The result holds for red satellites
over a large range of cluster-centric distances 0.1 - 0.6 Mpc/h. We discuss the
implications of this result for models of galaxy formation.


title: Mysteries of Visual Experience

abstract:
  Science is a crowning glory of the human spirit and its applications remain
our best hope for social progress. But there are limitations to current science
and perhaps to any science. The general mind-body problem is known to be
intractable and currently mysterious. This is one of many deep problems that
are universally agreed to be beyond the current purview of Science, including
quantum phenomena, etc. But all of these famous unsolved problems are either
remote from everyday experience (entanglement, dark matter) or are hard to even
define sharply (phenomenology, consciousness, etc.).
  An updated summary of this work has been published as: Feldman, J. (2022).
Computation, perception, and mind. Behavioral and Brain Sciences, 45, E48.
doi:10.1017/S0140525X21001886 A more readable, open access, version is:
https://escholarship.org/uc/item/6cs78450


title:
Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical
  Evolution Models

abstract:
  Chemical evolution models are powerful tools for interpreting stellar
abundance surveys and understanding galaxy evolution. However, their
predictions depend heavily on the treatment of inflow, outflow, star formation
efficiency (SFE), the stellar initial mass function, the Type Ia supernova
delay time distribution, stellar yields, and stellar population mixing. Using
flexCE, a flexible one-zone chemical evolution code, we investigate the effects
of and trade-offs between parameters. Two critical parameters are SFE and the
outflow mass-loading parameter, which shift the knee in [O/Fe]-[Fe/H] and the
equilibrium abundances that the simulations asymptotically approach,
respectively. One-zone models with simple star formation histories follow
narrow tracks in [O/Fe]-[Fe/H] unlike the observed bimodality (separate
high-alpha and low-alpha sequences) in this plane. A mix of one-zone models
with inflow timescale and outflow mass-loading parameter variations, motivated
by the inside-out galaxy formation scenario with radial mixing, reproduces the
two sequences better than a one-zone model with two infall epochs. We present
[X/Fe]-[Fe/H] tracks for 20 elements assuming three different supernova yield
models and find some significant discrepancies with solar neighborhood
observations, especially for elements with strongly metallicity-dependent
yields. We apply principal component abundance analysis (PCAA) to the
simulations and existing data to reveal the main correlations amongst
abundances and quantify their contributions to variation in abundance space.
For the stellar population mixing scenario, the abundances of alpha-elements
and elements with metallicity-dependent yields dominate the first and second
principal components, respectively, and collectively explain 99% of the
variance in the model. flexCE is a python package available at
https://github.com/bretthandrews/flexCE.


title: A New Target for Cosmic Axion Searches

abstract:
  Future CMB experiments have the potential to probe the density of
relativistic species at the sub-percent level. Sensitivity at this level allows
light thermal relics to be detected up to arbitrarily high decoupling
temperatures. Conversely, the absence of a detection would require extra light
species never to have been in equilibrium with the Standard Model. In this
paper, we exploit this feature to demonstrate the sensitivity of future
cosmological observations to the couplings of axions to all of the Standard
Model degrees of freedom. In many cases, the constraints achievable from
cosmology will surpass existing bounds from laboratory experiments and
astrophysical observations by orders of magnitude.


title:
Ferromagnetism and d+id superconductivity in 1/2 doped correlated
  systems on triangular lattice

abstract:
  We investigate the quantum phase diagram of t-J model on triangular lattice
at 1/2 doping with various lattice sizes by using a combination of density
matrix renormalization group (DMRG), variational Monte Carlo and quantum field
theories. To sharply distinguish different phases, we calculated the symmetry
quantum numbers of the ground state wave functions, and the results are further
confirmed by studying correlation functions. Our results show there is a first
order phase transition from ferromagnetism to d+id superconductivity, with the
transition taking place at $J/t=0.4\pm0.2$.


title:
Black-box optimization on hyper-rectangle using Recursive Modified
  Pattern Search and application to ROC-based Classification Problem

abstract:
  In Statistics, multi-modal and non-smooth likelihood (or, objective function)
maximization problems often arise with known upper and lower bound of the
parameters. A novel derivative-free global optimization technique is developed
to optimize any black-box function on a hyper-rectangular euclidean space. In
literature, pattern search technique has been shown to be a powerful tool for
blackbox optimization. The proposed algorithm follows the principle of pattern
search technique where new updated solution is obtained from the current
solution making movements (within the constrained sample space) along the
coordinates. Before making a jump from the current solution point to a new
solution point, objective function is evaluated in several neighborhood points
around the current solution and the best solution point is chosen based on the
objective function values at those points. Parallel threading can be used to
make the algorithm more scalable. Performance of the proposed method is
evaluated based on optimization of upto 5000 dimensional multi-modal benchmark
functions. The proposed algorithm is shown to perform upto 40 and 368 times
faster compared to Genetic Algorithm (GA) and Simulated Annealing (SA)
respectively. The proposed method is used to estimate the optimal biomarker
combination from Alzheimer data by maximizing the empirical estimates of area
under ROC curve.


title:
Hawking Radiation Spectra for Scalar Fields by a Higher-Dimensional
  Schwarzschild-de-Sitter Black Hole

abstract:
  In this work, we study the propagation of scalar fields in the gravitational
background of a higher-dimensional Schwarzschild-de-Sitter black hole as well
as on the projected-on-the-brane 4-dimensional background. The scalar fields
have also a non-minimal coupling to the corresponding, bulk or brane, scalar
curvature. We perform a comprehensive study by deriving exact numerical results
for the greybody factors, and study their profile in terms of particle and
spacetime properties. We then proceed to derive the Hawking radiation spectra
for a higher-dimensional Schwarzschild-de-Sitter black hole, and we study both
bulk and brane channels. We demonstrate that the non-minimal field coupling,
that creates an effective mass term for the fields, suppresses the energy
emission rates while the cosmological constant assumes a dual role. By
computing the relative energy rates and the total emissivity ratio for bulk and
brane emission, we demonstrate that the combined effect of a large number of
extra dimensions and value of the field coupling gives to the bulk channel the
clear domination in the bulk-brane energy balance.


title:
Stringer: Balancing Latency and Resource Usage in Service Function Chain
  Provisioning

abstract:
  Network Functions Virtualization, or NFV, enables telecommunications
infrastructure providers to replace special-purpose networking equipment with
commodity servers running virtualized network functions (VNFs). A service
provider utilizing NFV technology faces the SFC provisioning problem of
assigning VNF instances to nodes in the physical infrastructure (e.g., a
datacenter), and routing Service Function Chains (sequences of functions
required by customers, a.k.a. SFCs) in the physical network. In doing so, the
provider must balance between various competing goals of performance and
resource usage. We present an approach for SFC provisioning, consisting of
three elements. The first element is a fast, scalable round-robin heuristic.
The second element is a Mixed Integer Programming (MIP) based approach. The
third element is a queueing-theoretic model to estimate the average latency
associated with any SFC provisioning solution. Combined, these elements create
an approach that generates a set of SFC provisioning solutions, reflecting
different tradeoffs between resource usage and performance.


title:
Spectral triples for noncommutative solenoidal spaces from
  self-coverings

abstract:
  Examples of noncommutative self-coverings are described, and spectral triples
on the base space are extended to spectral triples on the inductive family of
coverings, in such a way that the covering projections are locally isometric.
Such triples are shown to converge, in a suitable sense, to a semifinite
spectral triple on the direct limit of the tower of coverings, which we call
noncommutative solenoidal space. Some of the self-coverings described here are
given by the inclusion of the fixed point algebra in a C$^*$-algebra acted upon
by a finite abelian group. In all the examples treated here, the noncommutative
solenoidal spaces have the same metric dimension and volume as on the base
space, but are not quantum compact metric spaces, namely the pseudo-metric
induced by the spectral triple does not produce the weak$^*$ topology on the
state space.


title:
Computer keyboard interaction as an indicator of early Parkinson's
  disease

abstract:
  Parkinson's disease (PD) is a slowly progressing neurodegenerative disease
with early manifestation of motor signs. Objective measurements of motor signs
are of vital importance for diagnosing, monitoring and developing disease
modifying therapies, particularly for the early stages of the disease when
putative neuroprotective treatments could stop neurodegeneration. Current
medical practice has limited tools to routinely monitor PD motor signs with
enough frequency and without undue burden for patients and the healthcare
system. In this paper, we present data indicating that the routine interaction
with computer keyboards can be used to detect motor signs in the early stages
of PD. We explore a solution that measures the key hold times (the time
required to press and release a key) during the normal use of a computer
without any change in hardware and converts it to a PD motor index. This is
achieved by the automatic discovery of patterns in the time series of key hold
times using an ensemble regression algorithm. This new approach discriminated
early PD groups from controls with an AUC = 0.81 (n = 42/43; mean age =
59.0/60.1; women = 43%/60%;PD/controls). The performance was comparable or
better than two other quantitative motor performance tests used clinically:
alternating finger tapping (AUC = 0.75) and single key tapping (AUC = 0.61).


title: Synthesis of Arbitrary Quantum Circuits to Topological Assembly

abstract:
  Given a quantum algorithm, it is highly nontrivial to devise an efficient
sequence of physical gates implementing the algorithm on real hardware and
incorporating topological quantum error correction. In this paper, we present a
first step towards this goal, focusing on generating correct and simple
arrangements of topological structures that correspond to a given quantum
circuit and largely neglecting their efficiency. We detail the many challenges
that will need to be tackled in the pursuit of efficiency. The software source
code can be consulted at https://github.com/alexandrupaler/tqec.


title:
Enabling Micro-level Demand-Side Grid Flexiblity in Resource Constrained
  Environments

abstract:
  The increased penetration of uncertain and variable renewable energy presents
various resource and operational electric grid challenges. Micro-level
(household and small commercial) demand-side grid flexibility could be a
cost-effective strategy to integrate high penetrations of wind and solar
energy, but literature and field deployments exploring the necessary
information and communication technologies (ICTs) are scant. This paper
presents an exploratory framework for enabling information driven grid
flexibility through the Internet of Things (IoT), and a proof-of-concept
wireless sensor gateway (FlexBox) to collect the necessary parameters for
adequately monitoring and actuating the micro-level demand-side. In the summer
of 2015, thirty sensor gateways were deployed in the city of Managua
(Nicaragua) to develop a baseline for a near future small-scale demand response
pilot implementation. FlexBox field data has begun shedding light on
relationships between ambient temperature and load energy consumption, load and
building envelope energy efficiency challenges, latency communication network
challenges, and opportunities to engage existing demand-side user behavioral
patterns. Information driven grid flexibility strategies present great
opportunity to develop new technologies, system architectures, and
implementation approaches that can easily scale across regions, incomes, and
levels of development.


title: Analytic aspects of the bi-free partial R-transform

abstract:
  Since Voiculescu introduced his bi-free probability theory in 2013, the major
development of the theory has been on its combinatorial side; in particular, on
the combinatorics of bi-free cumulants and its application to the bi-free
R-transform. In this article we propose a harmonic analysis approach to the
bi-free R-transform, which is solely based on integral transforms of two
variables. To accommodate the harmonic analysis tools, we confine ourselves in
the simplest situation of bi-freeness with commuting faces. Our method allows
us to treat measures with unbounded support, and we show that the classical
limit theory of infinitely divisible laws, due to Levy and Khintchine, has a
perfect bi-free analogue.


title: Octupole strength in the neutron-rich calcium isotopes

abstract:
  Low-lying excited states of the neutron-rich calcium isotopes $^{48-52}$Ca
have been studied via $\gamma$-ray spectroscopy following inverse-kinematics
proton scattering on a liquid hydrogen target using the GRETINA $\gamma$-ray
tracking array. The energies and strengths of the octupole states in these
isotopes are remarkably constant, indicating that these states are dominated by
proton excitations.


title: Throughput and range characterization of IEEE 802.11ah

abstract:
  The most essential part of Internet of Things (IoT) infrastructure is the
wireless communication system that acts as a bridge for the delivery of data
and control messages. However, the existing wireless technologies lack the
ability to support a huge amount of data exchange from many battery driven
devices spread over a wide area. In order to support the IoT paradigm, the IEEE
802.11 standard committee is in process of introducing a new standard, called
IEEE 802.11ah. This is one of the most promising and appealing standards, which
aims to bridge the gap between traditional mobile networks and the demands of
the IoT. In this paper, we first discuss the main PHY and MAC layer amendments
proposed for IEEE 802.11ah. Furthermore, we investigate the operability of IEEE
802.11ah as a backhaul link to connect devices over a long range. Additionally,
we compare the aforementioned standard with previous notable IEEE 802.11
amendments (i.e. IEEE 802.11n and IEEE 802.11ac) in terms of throughput (with
and without frame aggregation) by utilizing the most robust modulation schemes.
The results show an improved performance of IEEE 802.11ah (in terms of power
received at long range while experiencing different packet error rates) as
compared to previous IEEE 802.11 standards.


title:
On the evolution of the inner disk radius with flux in the neutron star
  low-mass X-ray binary Serpens X-1

abstract:
  We analyze the latest \emph{Suzaku} observation of the bright neutron star
low-mass X-ray binary Serpens X-1 taken in 2013 October and 2014 April. The
observation was taken using the burst mode and only suffered mild pile-up
effects. A broad iron line is clearly detected in the X-ray spectrum. We test
different models and find that the iron line is asymmetric and best interpreted
by relativistic reflection. The relativistically broadened iron line is
generally believed to originate from the innermost regions of the accretion
disk, where strong gravity causes a series of special and general relativistic
effects. The iron line profile indicates an inner radius of $\sim8$ $R_{\rm
G}$, which gives an upper limit on the size of the neutron star. The asymmetric
iron line has been observed in a number of previous observations, which gives
several inner radius measurements at different flux states. We find that the
inner radius of Serpens X-1 does not evolve significantly over the range of
$L/L_{\rm Edd}\sim0.4-0.6$, and the lack of flux dependence of the inner radius
implies that the accretion disk may be truncated outside the innermost stable
circular orbit by the boundary layer rather than the stellar magnetic field.


title: Spectroscopic Confirmation of a Protocluster at z=3.786

abstract:
  We present new observations of the field containing the z=3.786 protocluster,
PC217.96+32.3. We confirm that it is one of the largest and most overdense
high-redshift structures known. Such structures are rare even in the largest
cosmological simulations. We used the Mayall/MOSAIC1.1 imaging camera to image
a 1.2x0.6 deg area (~150x75 comoving Mpc) surrounding the protocluster's core
and discovered 165 candidate Lyman Alpha emitting galaxies (LAEs) and 788
candidate Lyman Break galaxies (LBGs). There are at least 2 overdense regions
traced by the LAEs, the largest of which shows an areal overdensity in its core
(i.e., within a radius of 2.5 comoving Mpc) of 14+/-7 relative to the average
LAE spatial density in the imaged field. Further, the average LAE spatial
density in the imaged field is twice that derived by other field LAE surveys.
Spectroscopy with Keck/DEIMOS yielded redshifts for 164 galaxies (79 LAEs and
85 LBGs); 65 lie at a redshift of 3.785+/-0.010. The velocity dispersion of
galaxies near the core is 350+/-40 km/s, a value robust to selection effects.
The overdensities are likely to collapse into systems with present-day masses
of >10^{15} solar masses and >6x10^{14} solar masses. The low velocity
dispersion may suggest a dynamically young protocluster. We find a weak trend
between narrow-band (Lyman Alpha) luminosity and environmental density: the
Lyman Alpha luminosity is enhanced on average by 1.35X within the protocluster
core. There is no evidence that the Lyman Alpha equivalent width depends on
environment. These suggest that star-formation and/or AGN activity is enhanced
in the higher density regions of the structure. PC217.96+32.3 is a Coma cluster
analog, witnessed in the process of formation.


title: Thermal expansion in nanoresonators

abstract:
  Inspired by some recent experiments and numerical works related to
nanoresonators, we perform classical molecular dynamics simulations to
investigate the thermal expansion and the ability of the device to act as a
strain sensor assisted by thermally-induced vibrations. The proposed model
consists in a chain of atoms interacting anharmonically with both ends clamped
to thermal reservoirs. We analyze the thermal expansion and resonant frequency
shifts as a function of temperature and the applied strain. For the transversal
modes the shift is approximately linear with strain. We also present analytical
results from canonical calculations in the harmonic approximation showing that
thermal expansion is uniform along the device. This prediction also works when
the system operates in a nonlinear oscillation regime at moderate and high
temperatures.


title:
Membrane tension is a key determinant of bud morphology in
  clathrin-mediated endocytosis

abstract:
  In clathrin-mediated endocytosis (CME), clathrin and various adaptor proteins
coat a patch of the plasma membrane, which is reshaped to form a budded
vesicle. Experimental studies have demonstrated that elevated membrane tension
can inhibit bud formation by a clathrin coat. In this study, we investigate the
impact of membrane tension on the mechanics of membrane budding by simulating
clathrin coats that either grow in area or progressively induce greater
curvature. At low membrane tension, progressively increasing the area of a
curvature-generating coat causes the membrane to smoothly evolve from a flat to
budded morphology, whereas the membrane remains essentially flat at high
membrane tensions. Interestingly, at physiologically relevant, intermediate
membrane tensions, the shape evolution of the membrane undergoes a snapthrough
instability in which increasing coat area causes the membrane to "snap" from an
open, U-shaped bud to a closed, $\Omega$-shaped bud. This instability is
accompanied by a large energy barrier, which could cause a developing endocytic
pit to stall if the binding energy of additional coat is insufficient to
overcome this barrier. Similar results were found for a coat of constant area
in which the spontaneous curvature progressively increases. Additionally, a
pulling force on the bud, simulating a force from actin polymerization, is
sufficient to drive a transition from an open to closed bud, overcoming the
energy barrier opposing this transition.


title: Spin-Orbit Semimetals in the Layer Groups

abstract:
  Recent interest in point and line node semimetals has led to the proposal and
discovery of these phenomena in numerous systems. Frequently, though, these
nodal systems are described in terms of individual properties reliant on
specific space group intricacies or band-tuning conditions. Restricting
ourselves to cases with strong spin-orbit interaction, we develop a general
framework which captures existing systems and predicts new examples of nodal
materials. In many previously proposed systems, the three-dimensional nature of
the space group has obscured key generalities. Therefore, we show how within
our framework one can predict and characterize a diverse set of nodal phenomena
even in two-dimensional systems constructed of three-dimensional sites, known
as the "Layer Groups". Expanding on an existing discussion by Watanabe, Po,
Vishwanath, and Zaletel of the relationship between minimal insulating filling,
nonsymmorphic symmetries, and compact flat manifolds, we characterize the
allowed semimetallic structures in the layer groups and draw connections to
related three-dimensional systems.


title:
Secular models and Kozai resonance for planets in coorbital non-coplanar
  motion

abstract:
  In this work, we construct and test an analytical and a semianalytical
secular models for two planets locked in a coorbital non-coplanar motion,
comparing some results with the case of restricted three body problem.
  The analytical average model replicates the numerical N-body integrations,
even for moderate eccentricities ($\lesssim$ 0.3) and inclinations
($\lesssim10^\circ$), except for the regions corresponding to quasi-satellite
and Lidov-Kozai configurations. Furthermore, this model is also useful in the
restricted three body problem, assuming very low mass ratio between the
planets. We also describe a four-degree-of-freedom semianalytical model valid
for any type of coorbital configuration in a wide range of eccentricities and
inclinations.
  {Using a N-body integrator, we have found that the phase space of the General
Three Body Problem is different to the restricted case for inclined systems,
and establish the location of the Lidov-Kozai equilibrium configurations
depending on mass ratio. We study the stability of periodic orbits in the
inclined systems, and find that apart from the robust configurations $L_4$,
$AL_4$, and $QS$ is possible to harbour two Earth-like planets in orbits
previously identified as unstable $U$ and also in Euler $L_3$ configurations,
with bounded chaos.


title: Licensed-Assisted Access to Unlicensed Spectrum in LTE Release 13

abstract:
  Exploiting the unlicensed spectrum is considered by 3GPP as one promising
solution to meet the ever-increasing traffic growth. As a result, one major
enhancement for LTE in Release 13 has been to enable its operation in the
unlicensed spectrum via Licensed-Assisted Access (LAA). In this article, we
provide an overview of the Release 13 LAA technology including motivation, use
cases, LTE enhancements for enabling the unlicensed band operation, and the
coexistence evaluation results contributed by 3GPP participants.


title: Word Ordering Without Syntax

abstract:
  Recent work on word ordering has argued that syntactic structure is
important, or even required, for effectively recovering the order of a
sentence. We find that, in fact, an n-gram language model with a simple
heuristic gives strong results on this task. Furthermore, we show that a long
short-term memory (LSTM) language model is even more effective at recovering
order, with our basic model outperforming a state-of-the-art syntactic model by
11.5 BLEU points. Additional data and larger beams yield further gains, at the
expense of training and search time.


title:
Optimal Transport vs. Fisher-Rao distance between Copulas for Clustering
  Multivariate Time Series

abstract:
  We present a methodology for clustering N objects which are described by
multivariate time series, i.e. several sequences of real-valued random
variables. This clustering methodology leverages copulas which are
distributions encoding the dependence structure between several random
variables. To take fully into account the dependence information while
clustering, we need a distance between copulas. In this work, we compare
renowned distances between distributions: the Fisher-Rao geodesic distance,
related divergences and optimal transport, and discuss their advantages and
disadvantages. Applications of such methodology can be found in the clustering
of financial assets. A tutorial, experiments and implementation for
reproducible research can be found at www.datagrapple.com/Tech.


title:
Statistical Hauser-Feshbach theory with width fluctuation correction
  including direct reaction channels for neutron induced reaction at low
  energies

abstract:
  A model to calculate particle-induced reaction cross sections with
statistical Hauser-Feshbach theory including direct reactions is given. The
energy average of scattering matrix from the coupled-channels optical model is
diagonalized by the transformation proposed by Engelbrecht and
Weidenm\"{u}ller. The ensemble average of $S$-matrix elements in the
diagonalized channel space is approximated by a model of Moldauer [Phys.Rev.C
{\bf 12}, 744 (1975)] using newly parametrized channel degree-of-freedom
$\nu_a$ to better describe the Gaussian Orthogonal Ensemble (GOE) reference
calculations. Moldauer approximation is confirmed by a Monte Carlo study using
randomly generated $S$-matrix, as well as the GOE three-fold integration
formula. The method proposed is applied to the $^{238}$U(n,n') cross section
calculation in the fast energy range, showing an enhancement in the inelastic
scattering cross sections.


title:
Recursive Modified Pattern Search on High-dimensional Simplex : A
  Blackbox Optimization Technique

abstract:
  In this paper, a novel derivative-free pattern search based algorithm for
Black-box optimization is proposed over a simplex constrained parameter space.
At each iteration, starting from the current solution, new possible set of
solutions are found by adding a set of derived step-size vectors to the initial
starting point. While deriving these step-size vectors, precautions and
adjustments are considered so that the set of new possible solution points
still remain within the simplex constrained space. Thus, no extra time is spent
in evaluating the (possibly expensive) objective function at infeasible points
(points outside the unit-simplex space). While minimizing any objective
function of m parameters, within each iteration, the objective function is
evaluated at 2m new possible solution points. So, upto 2m parallel threads can
be incorporated which makes the computation even faster while optimizing
expensive objective functions over high-dimensional parameter space. Once a
local minimum is discovered, in order to find a better solution, a novel
`re-start' strategy is considered to increase the likelihood of finding a
better solution. Unlike existing pattern search based methods, a sparsity
control parameter is introduced which can be used to induce sparsity in the
solution in case the solution is expected to be sparse in prior. A comparative
study of the performances of the proposed algorithm and other existing
algorithms are shown for a few low, moderate and high-dimensional optimization
problems. Upto 338 folds improvement in computation time is achieved using the
proposed algorithm over Genetic algorithm along with better solution. The
proposed algorithm is used to estimate the simultaneous quantiles of North
Atlantic Hurricane velocities during 1981-2006 by maximizing a non-closed form
likelihood function with (possibly) multiple maximums.


title: Molecular spectra in collective Dicke states

abstract:
  We study a model describing competition of interactions between $N$ two-level
systems (TLSs) against decoherence. We apply it to analyze dye molecules in an
optical microcavity, where molecular vibrations provide a local source for
decoherence. Most interesting is the case when decoherence strongly affects
each individual TLS, e.g. via broadening of emission lines as well as
vibrational satellites, however its influence is strongly suppressed for large
$N$ due to the interactions between TLSs. In this interaction dominated regime
we find unique signatures in the emission spectrum, including strong
$\mathcal{O}(\sqrt{N})$ level shifts, as well as $1/N$ suppression of both the
decoherence width and of the vibrational satellites.


title: Ostrogradsky in Theories with Multiple Fields

abstract:
  We review how the (absence of) Ostrogradsky instability manifests itself in
theories with multiple fields. It has recently been appreciated that when
multiple fields are present, the existence of higher derivatives may not
automatically imply the existence of ghosts. We discuss the connection with
gravitational theories like massive gravity and beyond Horndeski which manifest
higher derivatives in some formulations and yet are free of Ostrogradsky ghost.
We also examine an interesting new class of Extended Scalar-Tensor Theories of
gravity which has been recently proposed. We show that for a subclass of these
theories, the tensor modes are either not dynamical or are infinitely strongly
coupled. Among the remaining theories for which the tensor modes are
well-defined one counts one new model that is not field-redefinable to
Horndeski via a conformal and disformal transformation but that does require
the vacuum to break Lorentz invariance. We discuss the implications for the
effective field theory of dark energy and the stability of the theory.


title: On quotients of generalized Euclidean group rings

abstract:
  Let $R = Z[C]$ be the integral group ring of a finite cyclic group $C$.
Dennis and al. proved that $R$ is a generalized Euclidean ring in the sense of
P. M. Cohn, i.e., $SL_n(R)$ is generated by the elementary matrices for all
$n$. We prove that every proper quotient of $R$ is also a generalized Euclidean
ring.


title:
Hilbert Exclusion: Improved Metric Search through Finite Isometric
  Embeddings

abstract:
  Most research into similarity search in metric spaces relies upon the
triangle inequality property. This property allows the space to be arranged
according to relative distances to avoid searching some subspaces. We show that
many common metric spaces, notably including those using Euclidean and
Jensen-Shannon distances, also have a stronger property, sometimes called the
four-point property: in essence, these spaces allow an isometric embedding of
any four points in three-dimensional Euclidean space, as well as any three
points in two-dimensional Euclidean space. In fact, we show that any space
which is isometrically embeddable in Hilbert space has the stronger property.
This property gives stronger geometric guarantees, and one in particular, which
we name the Hilbert Exclusion property, allows any indexing mechanism which
uses hyperplane partitioning to perform better. One outcome of this observation
is that a number of state-of-the-art indexing mechanisms over high dimensional
spaces can be easily extended to give a significant increase in performance;
furthermore, the improvement given is greater in higher dimensions. This
therefore leads to a significant improvement in the cost of metric search in
these spaces.


title: Convex Polytopes for the Central Degeneration of the Affine Grassmannian

abstract:
  We study the algebraic geometry and combinatorics of the central degeneration
(the degeneration that shows up in local models of Shimura varieties and
Gaitsgory's central sheaves) in type A. More specifically, we elucidate the
central degeneration of semi-infinite orbits and explain its relations with
Levi restriction. Also, we discuss the central degeneration of
Mirkovi$\acute{\text{c}}$-Vilonen cycles in the affine Grassmannian, and the
corresponding transformations of Mirkovi$\acute{\text{c}}$-Vilonen polytopes.
In addition, we shed some light on the geometry of Iwahori MV cycles in the
affine Grassmannian and generalized MV cycles in the affine flag variety, which
are closely related to Demazure modules and affine Deligne-Lusztig varieties
respectively.


title:
On the representation and embedding of knowledge bases beyond binary
  relations

abstract:
  The models developed to date for knowledge base embedding are all based on
the assumption that the relations contained in knowledge bases are binary. For
the training and testing of these embedding models, multi-fold (or n-ary)
relational data are converted to triples (e.g., in FB15K dataset) and
interpreted as instances of binary relations. This paper presents a canonical
representation of knowledge bases containing multi-fold relations. We show that
the existing embedding models on the popular FB15K datasets correspond to a
sub-optimal modelling framework, resulting in a loss of structural information.
We advocate a novel modelling framework, which models multi-fold relations
directly using this canonical representation. Using this framework, the
existing TransH model is generalized to a new model, m-TransH. We demonstrate
experimentally that m-TransH outperforms TransH by a large margin, thereby
establishing a new state of the art.


title:
Higher order corrected trapezoidal rules in Lebesgue and Alexiewicz
  spaces

abstract:
  If $f\!:\![a,b]\to\R$ such that $f^{(n)}$ is integrable then integration by
parts gives the formula \begin{align*} &\intab f(x)\,dx =
&\frac{(-1)^n}{n!}\sum_{k=0}^{n-1}(-1)^{n-k-1}\left[
\phi_n^{(n-k-1)}(a)f^{(k)}(a)- \phi_n^{(n-k-1)}(b)f^{(k)}(b)\right] +E_n(f),
\end{align*} where $\phi_n$ is a monic polynomial of degree $n$ and the error
is given by $E_n(f)=\frac{(-1)^n}{n!}\int_a^b f^{(n)}(x)\phi_n(x)\,dx$. This
then gives a quadrature formula for $\int_a^bf(x)\,dx$. The polynomial $\phi_n$
is chosen to optimize the error estimate under the assumption that $f^{(n)}\in
L^p([a,b])$ for some $1\leq p\leq\infty$ or if $f^{(n)}$ is integrable in the
distributional or Henstock--Kurzweil sense. Sharp error estimates are obtained.
It is shown that this formula is exact for all such $\phi_n$ if $f$ is a
polynomial of degree at most $n-1$. If $\phi_n$ is a Legendre polynomial then
the formula is exact for $f$ a polynomial of degree at most $2n-1$.


title: Spectro-timing study of GX 339-4 in a hard intermediate state

abstract:
  We present an analysis of NuSTAR observations of a hard intermediate state of
the transient black hole GX 339-4 taken in January 2015. As the source softened
significantly over the course of the 1.3 d-long observation we split the data
into 21 sub-sets and find that the spectrum of all of them can be well
described by a power-law continuum with an additional relativistically blurred
reflection component. The photon index increases from ~1.69 to ~1.77 over the
course of the observation. The accretion disk is truncated at around 9
gravitational radii in all spectra. We also perform timing analysis on the same
21 individual data sets, and find a strong type-C quasi-periodic oscillation
(QPO), which increase in frequency from ~0.68 to ~1.05 Hz with time. The
frequency change is well correlated with the softening of the spectrum. We
discuss possible scenarios for the production of the QPO and calculate
predicted inner radii in the relativistic precession model as well as the
global disk mode oscillations model. We find discrepancies with respect to the
observed values in both models unless we allow for a black hole mass of ~100
M_sun , which is highly unlikely. We discuss possible systematic uncertainties,
in particular with the measurement of the inner accretion disk radius in the
relativistic reflection model. We conclude that the combination of observed QPO
frequencies and inner accretion disk radii, as obtained from spectral fitting,
is difficult to reconcile with current models.


title:
Observation of second-harmonic generation in silicon nitride waveguides
  through bulk nonlinearities

abstract:
  We present experimental results on the observation of a bulk second-order
nonlinear susceptibility derived from both free-space and integrated
measurements in silicon nitride. Phase-matching is achieved through dispersion
engineering of the waveguide cross-section, independently revealing multiple
components of the nonlinear susceptibility, namely X(2)yyy and X(2)xxy.
Additionally, we show how the generated second-harmonic signal may be actively
tuned through the application of bias voltages across silicon nitride. The
nonlinear material properties measured here are anticipated to allow for the
practical realization of new nanophotonic devices in CMOS-compatible silicon
nitride waveguides, adding to their viability for telecommunication, data
communication, and optical signal processing applications.


title:
A dynamic subgrid-scale modeling framework for large eddy simulation
  using approximate deconvolution

abstract:
  We put forth a dynamic modeling framework for sub-grid parametrization of
large eddy simulation of turbulent flows based upon the use of the approximate
deconvolution procedure to compute the Smagorinsky constant self-adaptively
from the resolved flow quantities. Our numerical assessments for solving the
Burgers turbulence problem shows that the proposed approach could be used as a
viable tool to address the turbulence closure problem due to its flexibility.


title:
Hermitian Clifford Analysis and Its Connections with Representation
  Theory

abstract:
  This work reconsiders the holomorphic and anti-holomorphic Dirac operators of
Hermitian Clifford analysis to determine whether or not they are the natural
generalization of the orthogonal Dirac operator to spaces with complex
structure. We argue the generalized gradient construction of Stein and Weiss
based on representation theory of Lie groups is the natural way to construct
such a Dirac-type operator because applied to a Riemannian spin manifold it
provides the Atiyah-Singer Dirac operator. This method, however, does not apply
to these Hermitian Dirac operators because the representations of the unitary
group used are not irreducible, causing problems in considering invariance
under a group larger than U(n). This motivates either the development of
Clifford analysis over a complex vector space with respect to a Hermitian inner
product or the development of Dirac-type operators on Cauchy-Riemann
structures.