title:
A change in the quiescent X-ray spectrum of the neutron star low-mass
  X-ray binary MXB 1659-29

abstract:
  The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into
quiescence in 2001, and we have followed its quiescent X-ray evolution since.
Observations over the first 4 years showed a rapid drop in flux and temperature
of the neutron star atmosphere, interpreted as cooling of the neutron star
crust which had been heated during the 2.5 year outburst. However, observations
taken approximately 1400 and 2400 days into quiescence were consistent with
each other, suggesting the crust had reached thermal equilibrium with the core.
Here we present a new Chandra observation of MXB 1659-29 taken 11 years into
quiescence and 4 years since the last Chandra observation. This new observation
shows an unexpected factor of ~3 drop in count rate and change in spectral
shape since the last observation, which cannot be explained simply by continued
cooling. Two possible scenarios are that either the neutron star temperature
has remained unchanged and there has been an increase in the column density,
or, alternatively the neutron star temperature has dropped precipitously and
the spectrum is now dominated by a power-law component. The first scenario may
be possible given that MXB 1659-29 is a near edge-on system, and an increase in
column density could be due to build-up of material in, and a thickening of, a
truncated accretion disk during quiescence. But, a large change in disk height
may not be plausible if standard accretion disk theory holds during quiescence.
Alternatively, the disk may be precessing, leading to a higher column density
during this latest observation.


title:
OH/IR stars and their superwinds as observed by the Herschel Space
  Observatory

abstract:
  Aim : In order to study the history of mass loss in extreme OH/IR stars, we
observed a number of these objects using CO as a tracer of the density and
temperature structure of their circumstellar envelopes.
  Method : Combining CO observations from the Herschel Space Observatory with
those from the ground, we trace mass loss rates as a function of radius in five
extreme OH/IR stars. Using radiative transfer modelling, we modelled the dusty
envelope as well as the CO emission. The high-rotational transitions of CO
indicate that they originate in a dense superwind region close to the star
while the lower transitions tend to come from a more tenuous outer wind which
is a result of the mass loss since the early AGB phase.
  Result : The models of the circumstellar envelopes around these stars suggest
that they have entered a superwind phase in the past 200 - 500 years. The low
18O/17O (~ 0.1 compared to the solar abundance ratio of ~ 5) and 12C/13C (3-30
cf. the solar value of 89) ratios derived from our study support the idea that
these objects have undergone hot-bottom burning and hence that they are massive
M >= 5 solar-mass AGB stars.


title:
Flux Calibration of Broadband Far Infrared and Submillimetre Photometric
  Instruments: Theory and Application to Herschel-SPIRE

abstract:
  Photometric instruments operating at far infrared to millimetre wavelengths
often have broad spectral passbands (central wavelength/bandwidth ~ 3 or less),
especially those operating in space. A broad passband can result in significant
variation of the beam profile and aperture efficiency across the passband,
effects which thus far have not generally been taken into account in the flux
calibration of such instruments. With absolute calibration uncertainties
associated with the brightness of primary calibration standards now in the
region of 5% or less, variation of the beam properties across the passband can
be a significant contributor to the overall calibration accuracy for extended
emission. We present a calibration framework which takes such variations into
account for both antenna-coupled and absorber-coupled focal plane
architectures. The scheme covers point source and extended source cases, and
also the intermediate case of a semi-extended source profile. We apply the new
method to the Herschel-SPIRE space-borne photometer.


title: T-duality For Orientifolds and Twisted KR-theory

abstract:
  D-brane charges in orientifold string theories are classified by the
KR-theory of Atiyah. However, this is assuming that all O-planes have the same
sign. When there are O-planes of different signs, physics demands a "KR-theory
with a sign choice" which up until now has not been studied by mathematicians
(with the unique exception of Moutuou, who didn't have a specific application
in mind). We give a definition of this theory and compute it for orientifold
theories compactified on a circle and 2-torus. We also explain how and why
additional "twisting" is implemented. We show that our results satisfy all
possible T-duality relationships for orientifold string theories on elliptic
curves, which will be studied further in subsequent work.


title: Natural Light Cloaking for Aquatic and Terrestrial Creatures

abstract:
  A cloak that can hide living creatures from sight is a common feature of
mythology but still remains unrealized as a practical device. To preserve the
phase of wave, the previous cloaking solution proposed by Pendry \emph{et al.}
required transforming electromagnetic space around the hidden object in such a
way that the rays bending around it have to travel much faster than those
passing it by. The difficult phase preservation requirement is the main
obstacle for building a broadband polarization insensitive cloak for large
objects. Here, we suggest a simplifying version of Pendry's cloak by abolishing
the requirement for phase preservation as irrelevant for observation in
incoherent natural light with human eyes that are phase and polarization
insensitive. This allows the cloak design to be made in large scale using
commonly available materials and we successfully report cloaking living
creatures, a cat and a fish, in front of human eyes.


title: The Composition of Wage Differentials between Migrants and Natives

abstract:
  We consider the role of unobservables, such as differences in search
frictions, reservation wages, and productivities for the explanation of wage
differentials between migrants and natives. We disentangle these by estimating
an empirical general equilibrium search model with on-the-job search due to
Bontemps, Robin, and van den Berg (1999) on segments of the labour market
defined by occupation, age, and nationality using a large scale German
administrative dataset.
  The native-migrant wage differential is then decomposed into several parts,
and we focus especially on the component that we label "migrant effect", being
the difference in wage offers between natives and migrants in the same
occupation-age segment in firms of the same productivity. Counterfactual
decompositions of wage differentials allow us to identify and quantify their
drivers, thus explaining within a common framework what is often labelled the
unexplained wage gap.


title: Granular Convection in Microgravity

abstract:
  We investigate the role of gravity on convection in a dense granular shear
flow. Using a microgravity modified Taylor-Couette shear cell under the
conditions of parabolic flight microgravity, we demonstrate experimentally that
secondary, convective-like flows in a sheared granular material are close to
zero in microgravity and enhanced under high-gravity conditions, though the
primary flow fields are unaffected by gravity. We suggest that gravity tunes
the frictional particle-particle and particle-wall interactions, which have
been proposed to drive the secondary flow. In addition, the degree of plastic
deformation increases with increasing gravitational forces, supporting the
notion that friction is the ultimate cause.


title: Inhomogeneity effect in Wainwright-Marshman space-times

abstract:
  Green and Wald have presented a mathematically rigorous framework to study,
within general relativity, the effect of small scale inhomogeneities on the
global structure of space-time. The framework relies on the existence of a
one-parameter family of metrics that approaches the effective background metric
in a certain way. Although it is not necessary to know this family in an exact
form to predict properties of the backreaction effect, it would be instructive
to find explicit examples. In this paper, we provide the first example of such
a family of exact non-vacuum solutions to the Einstein's equations. It belongs
to the Wainwright-Marshman class and satisfies all of the assumptions of the
Green-Wald framework.


title: Higgs Search in $b\bar{b}$ Signatures at ATLAS and CMS

abstract:
  We report on searches for the Standard Model Higgs boson decaying to $b
\bar{b}$ in $pp$ collisions at the ATLAS and CMS experiments. These rely on
signatures where the Higgs boson is produced in association with a vector boson
or in association with a top-quark pair. Results are presented, based on
$5.0~\mathrm{fb}^{-1}$ of $pp$ collision data at $\sqrt{s} = 7$~TeV and up to
$13.0~\mathrm{fb}^{-1}$ of data at $\sqrt{s} = 8$~TeV collected by the LHC
accelerator. These are expressed in terms of 95\% confidence level upper limits
on the production cross section of the Standard Model Higgs boson times the
branching ratio to decay to $b$-quark pair.


title:
Dynamic Regimes for Driven Colloidal Particles on a Periodic Substrate
  at Commensurate and Incommensurate Fillings

abstract:
  We examine colloidal particles driven over a periodic muffin tin substrate
using numerical simulations. In the absence of a driving force this system
exhibits a rich variety of commensurate and incommensurate static phases in
which topological defects can form domain walls, ordered stripes,
superlattices, and disordered patchy regimes as a function of the filling
fraction. When an external drive is applied, these different static phases
generate distinct dynamical responses. At incommensurate fillings the flow
generally occurs in the form of localized pulses or solitons correlated with
the motion of the topological defect structures. We also find dynamic
transitions between different types of moving states that are associated with
changes in the velocity force curves, structural transitions in the topological
defect arrangements, and modifications of the velocity distributions and
particle trajectories. We find that the dynamic transitions between ordered and
disordered flows exhibit hysteresis, while in strongly disordered regimes there
is no hysteresis and the velocity force curves are smooth. When stripe patterns
are present, transport can occur along the stripe direction rather than along
the driving direction. Structural dynamic transitions can also occur within the
pinned regimes when the applied drive causes distortions of the interstitially
pinned particles while the particles trapped at pinning sites remain immobile.


title: A phonon laser utilizing quantum-dot spin states

abstract:
  We propose a nano-scale realization of a phonon laser utilizing
phonon-assisted spin flips in quantum dots to amplify sound. Owing to a long
spin relaxation time, the device can be operated in a strong pumping regime, in
which the population inversion is close to its maximal value allowed under
Fermi statistics. In this regime, the threshold for stimulated emission is
unaffected by spontaneous spin flips. Considering a nanowire with quantum dots
defined along its length, we show that a further improvement arises from
confining the phonons to one dimension, and thus reducing the number of phonon
modes available for spontaneous emission. Our work calls for the development of
nanowire-based, high-finesse phonon resonators.


title:
Generalized Macaulay representations and the flag $f$-vectors of
  generalized colored complexes

abstract:
  A colored complex of type $\mathbf{a} = (a_1, \dots, a_n)$ is a simplicial
complex ${\Delta}$ on a vertex set $V$, together with an ordered partition
$(V_1, \dots, V_n)$ of $V$, such that every face $F$ of ${\Delta}$ satisfies
$|F \cap V_i| \leq a_i$. For each $\mathbf{b} = (b_1, \dots, b_n) \leq
\mathbf{a}$, let $f_{\mathbf{b}}$ be the number of faces $F$ of ${\Delta}$ such
that $|F \cap V_i| = b_i$. The array of integers
$\{f_{\mathbf{b}}\}_{\mathbf{b} \leq \mathbf{a}}$ is called the fine $f$-vector
of ${\Delta}$, and it is a refinement of the $f$-vector of ${\Delta}$. In this
paper, we generalize the notion of Macaulay representations and give a
numerical characterization of the fine $f$-vectors of colored complexes of
arbitrary type, in terms of these generalized Macaulay representations. As part
of the proof, we introduce the property of $\mathbf{a}$-Macaulay
decomposability for simplicial complexes, which implies vertex-decomposability,
and we show that every pure color-shifted balanced complex ${\Delta}$ of type
$\mathbf{a}$ is $\mathbf{a}$-Macaulay decomposable. Combined with previously
known results, we also obtain a numerical characterization of the flag
$f$-vectors of completely balanced Cohen-Macaulay complexes.


title: Perfect orderings on Bratteli diagrams II: general Bratteli diagrams

abstract:
  We continue our study of orderings on Bratteli diagrams started in previous
work, joint with Jan Kwiatkowski, where Bratteli diagrams of finite rank were
considered. We extend the notions of languages, permutations (called
correspondences in this paper), skeletons and associated graphs to the case of
general Bratteli diagrams, and show their relevance to the study of perfect
orderings: those that support Vershik maps; in particular, perfect orderings
with several extremal paths. A perfect ordering comes equipped with a skeleton
and a correspondence, and conversely, given a skeleton and correspondence, we
describe explicitly how to construct perfect orderings, by showing that paths
in the associated directed graphs determine the language of the order. We
describe an explicit algorithmic method to create perfect orderings on Bratteli
diagrams based on the study of certain relations between the entries of the
diagram's incidence matrices and properties of the associated graphs, with the
latter relations characterizing diagrams which support perfect orderings. Also,
we apply the notions of skeletons and associated graphs, to give a new
combinatorial proof of the fact that diagrams supporting perfect orderings with
k maximal paths have a direct sum of k-1 copies of the integers contained in
their infinitesimal subgroup. Under certain conditions, we show that a similar
result holds if the diagram supports countably many maximal paths. Our results
are illustrated by numerous examples.


title: Externally Fed Star Formation: A Numerical Study

abstract:
  We investigate, through a series of numerical calculations, the evolution of
dense cores that are accreting external gas up to and beyond the point of star
formation. Our model clouds are spherical, unmagnetized configurations with
fixed outer boundaries, across which gas enters subsonically. When we start
with any near-equilibrium state, we find that the cloud's internal velocity
also remains subsonic for an extended period, in agreement with observations.
However, the velocity becomes supersonic shortly before the star forms.
Consequently, the accretion rate building up the protostar is much greater than
the benchmark value c_s^3/G, where c_s is the sound speed in the dense core.
This accretion spike would generate a higher luminosity than those seen in even
the most embedded young stars. Moreover, we find that the region of supersonic
infall surrounding the protostar races out to engulf much of the cloud, again
in violation of the observations, which show infall to be spatially confined.
Similar problematic results have been obtained by all other hydrodynamic
simulations to date, regardless of the specific infall geometry or boundary
conditions adopted. Low-mass star formation is evidently a quasi-static
process, in which cloud gas moves inward subsonically until the birth of the
star itself. We speculate that magnetic tension in the cloud's deep interior
helps restrain the infall prior to this event.


title:
Revisiting XENON100's Constraints (and Signals?) For Low-Mass Dark
  Matter

abstract:
  Although observations made with the CoGeNT and CDMS experiments have been
interpreted as possible signals of low-mass (~7-10 GeV) dark matter particles,
constraints from the XENON100 collaboration appear to be incompatible with this
hypothesis, at least at face value. In this paper, we revisit XENON100's
constraint on dark matter in this mass range, and consider how various
uncertainties and assumptions made might alter this conclusion. We also note
that while XENON100's two nuclear recoil candidates each exhibit very low
ratios of ionization-to-scintillation signals, making them difficult to
attribute to known electronic or neutron backgrounds, they are consistent with
originating from dark matter particles in the mass range favored by CoGeNT and
CDMS. We argue that with lower, but not implausible, values for the relative
scintillation efficiency of liquid xenon (L_eff), and the suppression of the
scintillation signal in liquid xenon at XENON100's electric field (S_nr), these
two events could consistently arise from dark matter particles with a mass and
cross section in the range favored by CoGeNT and CDMS. If this interpretation
is correct, we predict that the LUX experiment, with a significantly higher
light yield than XENON100, should observe dark matter induced events at an
observable rate of ~3-24 per month.


title: Sliding on a Nanotube: Interplay of Friction, Deformations and Structure

abstract:
  The frictional properties of individual carbon nanotubes (CNTs) are studied
by sliding an atomic force microscopy tip across and along its principle axis.
This direction-dependent frictional behavior is found to correlate strongly
with the presence of structural defects, surface chemistry, and CNT chirality.
This study shows that it is experimentally possible to tune the
frictional/adhesion properties of a CNT by controlling the CNT structure and
surface chemistry, as well as use friction force to predict its structural and
chemical properties.


title: High energy emission from galactic jets

abstract:
  In this chapter we review some aspects of X-ray binaries, particularly those
presenting steady jets, i.e. microquasars. Because of their proximity and
similarities with active galactic nuclei (AGN), galactic jet sources are unique
laboratories to test astrophysical theories of a universal scope. Due to recent
observational progress made with the new generation of gamma-ray imaging
atmospheric Cherenkov telescopes and in view of the upcoming km3-size neutrino
detectors, we focus especially on the possible high-energy gamma radiation and
neutrino emission. In connection with this, we also comment about astrophysical
jets present in young stellar objects, and we briefly discuss similarities and
differences with extragalactic AGN and gamma-ray bursters.


title: XMM-Newton and Swift observations of XTE J1743-363

abstract:
  XTEJ1743-363 is a poorly known hard X-ray transient, that displays short and
intense flares similar to those observed from Supergiant Fast X-ray Transients.
The probable optical counterpart shows spectral properties similar to those of
an M8 III giant, thus suggesting that XTEJ1743-363 belongs to the class of the
Symbiotic X-ray Binaries. In this paper we report on the first dedicated
monitoring campaign of the source in the soft X-ray range with XMM-Newton and
Swift/XRT. T hese observations confirmed the association of XTEJ1743-363 with
the previously suggested M8 III giant and the classification of the source as a
member of the Symbiotic X-ray binaries. In the soft X-ray domain, XTEJ1743-363
displays a high absorption (~6x10^22 cm^-2 ) and variability on time scales of
hundreds to few thousand seconds, typical of wind accreting systems. A
relatively faint flare (peak X-ray flux 3x10^-11 erg/cm^2/s) lasting ~4 ks is
recorded during the XMM-Newton observation and interpreted in terms of the wind
accretion scenario.


title:
Some supplements to Feferman-Vaught related to the model theory of
  adeles

abstract:
  We give foundational results for the model theory of the ring of finite
adeles over a number field, construed as a restricted product of local fields.
In contrast to Weispfenning we work in the language of ring theory, and various
sortings interpretable therein. In particular we give a systematic treatment of
the product valuation and the valuation monoid. Deeper results are given for
the adelic version of Krasner's hyperfields, relating them to the
Basarab-Kuhlmann formalism.


title: Quantum state cloning using Deutschian closed timelike curves

abstract:
  We show that it is possible to clone quantum states to arbitrary accuracy in
the presence of a Deutschian closed timelike curve (D-CTC), with a fidelity
converging to one in the limit as the dimension of the CTC system becomes
large---thus resolving an open conjecture from [Brun et al., Physical Review
Letters 102, 210402 (2009)]. This result follows from a D-CTC-assisted scheme
for producing perfect clones of a quantum state prepared in a known eigenbasis,
and the fact that one can reconstruct an approximation of a quantum state from
empirical estimates of the probabilities of an informationally-complete
measurement. Our results imply more generally that every continuous, but
otherwise arbitrarily non-linear map from states to states can be implemented
to arbitrary accuracy with D-CTCs. Furthermore, our results show that Deutsch's
model for CTCs is in fact a classical model, in the sense that two arbitrary,
distinct density operators are perfectly distinguishable (in the limit of a
large CTC system); hence, in this model quantum mechanics becomes a classical
theory in which each density operator is a distinct point in a classical phase
space.


title:
Self-consistent tight-binding description of Dirac points moving and
  merging in two dimensional optical lattices

abstract:
  We present an accurate ab initio tight-binding model, capable of describing
the dynamics of Dirac points in tunable honeycomb optical lattices following a
recent experimental realization [L. Tarruell et al., Nature 483, 302 (2012)].
Our scheme is based on first-principle maximally localized Wannier functions
for composite bands. The tunneling coefficients are calculated for different
lattice configurations, and the spectrum properties are well reproduced with
high accuracy. In particular, we show which tight binding description is needed
in order to accurately reproduce the position of Dirac points and the
dispersion law close to their merging, for different laser intensities.


title:
Large time behaviour for a nonlocal diffusion - convection equation
  related with the gas dynamics

abstract:
  In this paper we consider a model that involves nonlocal diffusion and a
classical convective term. Using a scaling argument and a new compactness
argument we obtain the first term in the asymptotic behavior of the solutions.


title: Granular Shear Flow in Varying Gravitational Environments

abstract:
  Despite their very low surface gravities, asteroids exhibit a number of
different geological processes involving granular matter. Understanding the
response of this granular material subject to external forces in microgravity
conditions is vital to the design of a successful asteroid sub-surface sampling
mechanism, and in the interpretation of the fascinating geology on an asteroid.
We have designed and flown a Taylor-Couette shear cell to investigate granular
flow due to rotational shear forces under the conditions of parabolic flight
microgravity. The experiments occur under weak compression. First, we present
the technical details of the experimental design with particular emphasis on
how the equipment has been specifically designed for the parabolic flight
environment. Then, we investigate how a steady state granular flow induced by
rotational shear forces differs in varying gravitational environments. We find
that the effect of constant shearing on the granular material, in a direction
perpendicular to the effective acceleration, does not seem to be strongly
influenced by gravity. This means that shear bands can form in the presence of
a weak gravitational field just as on Earth.


title:
Numerical simulations of granular dynamics II. Particle dynamics in a
  shaken granular material

abstract:
  Surfaces of planets and small bodies of our Solar System are often covered by
a layer of granular material that can range from a fine regolith to a
gravel-like structure of varying depths. Therefore, the dynamics of granular
materials are involved in many events occurring during planetary and small-body
evolution thus contributing to their geological properties.
  We demonstrate that the new adaptation of the parallel N-body hard-sphere
code pkdgrav has the capability to model accurately the key features of the
collective motion of bidisperse granular materials in a dense regime as a
result of shaking. As a stringent test of the numerical code we investigate the
complex collective ordering and motion of granular material by direct
comparison with laboratory experiments. We demonstrate that, as experimentally
observed, the scale of the collective motion increases with increasing
small-particle additive concentration.
  We then extend our investigations to assess how self-gravity and external
gravity affect collective motion. In our reduced-gravity simulations both the
gravitational conditions and the frequency of the vibrations roughly match the
conditions on asteroids subjected to seismic shaking, though real regolith is
likely to be much more heterogeneous and less ordered than in our idealised
simulations. We also show that collective motion can occur in a granular
material under a wide range of inter-particle gravity conditions and in the
absence of an external gravitational field. These investigations demonstrate
the great interest of being able to simulate conditions that are to relevant
planetary science yet unreachable by Earth-based laboratory experiments.


title: Left-invariant evolutions of wavelet transforms on the Similitude Group

abstract:
  Enhancement of multiple-scale elongated structures in noisy image data is
relevant for many biomedical applications but commonly used PDE-based
enhancement techniques often fail at crossings in an image. To get an overview
of how an image is composed of local multiple-scale elongated structures we
construct a multiple scale orientation score, which is a continuous wavelet
transform on the similitude group, SIM(2). Our unitary transform maps the space
of images onto a reproducing kernel space defined on SIM(2), allowing us to
robustly relate Euclidean (and scaling) invariant operators on images to
left-invariant operators on the corresponding continuous wavelet transform.
Rather than often used wavelet (soft-)thresholding techniques, we employ the
group structure in the wavelet domain to arrive at left-invariant evolutions
and flows (diffusion), for contextual crossing preserving enhancement of
multiple scale elongated structures in noisy images. We present experiments
that display benefits of our work compared to recent PDE techniques acting
directly on the images and to our previous work on left-invariant diffusions on
orientation scores defined on Euclidean motion group.


title: The Lichnerowicz equation on compact manifolds with boundary

abstract:
  In this article we initiate a systematic study of the well-posedness theory
of the Einstein constraint equations on compact manifolds with boundary. This
is an important problem in general relativity, and it is particularly important
in numerical relativity, as it arises in models of Cauchy surfaces containing
asymptotically flat ends and/or trapped surfaces. Moreover, a number of
technical obstacles that appear when developing the solution theory for open,
asymptotically Euclidean manifolds have analogues on compact manifolds with
boundary. As a first step, here we restrict ourselves to the Lichnerowicz
equation, also called the Hamiltonian constraint equation, which is the main
source of nonlinearity in the constraint system. The focus is on low regularity
data and on the interaction between different types of boundary conditions,
which has not been carefully analyzed before. In order to develop a
well-posedness theory that mirrors the existing theory for the case of closed
manifolds, we first generalize the Yamabe classification to nonsmooth metrics
on compact manifolds with boundary. We then extend a result on conformal
invariance to manifolds with boundary, and prove a uniqueness theorem. Finally,
by using the method of sub- and super-solutions (order-preserving map
iteration), we establish several existence results for a large class of
problems covering a broad parameter regime, which includes most of the cases
relevant in practice.


title:
Uniformly defining valuation rings in Henselian valued fields with
  finite or pseudo-finite residue fields

abstract:
  We give a definition, in the ring language, of Z_p inside Q_p and of F_p[[t]]
inside F_p((t)), which works uniformly for all $p$ and all finite field
extensions of these fields, and in many other Henselian valued fields as well.
The formula can be taken existential-universal in the ring language, and in
fact existential in a modification of the language of Macintyre. Furthermore,
we show the negative result that in the language of rings there does not exist
a uniform definition by an existential formula and neither by a universal
formula for the valuation rings of all the finite extensions of a given
Henselian valued field. We also show that there is no existential formula of
the ring language defining Z_p inside Q_p uniformly for all p. For any fixed
finite extension of Q_p, we give an existential formula and a universal formula
in the ring language which define the valuation ring.


title:
The maximum number of complete subgraphs in a graph with given maximum
  degree

abstract:
  Extremal problems involving the enumeration of graph substructures have a
long history in graph theory. For example, the number of independent sets in a
$d$-regular graph on $n$ vertices is at most $(2^{d+1}-1)^{n/2d}$ by the
Kahn-Zhao theorem. Relaxing the regularity constraint to a minimum degree
condition, Galvin conjectured that, for $n\geq 2d$, the number of independent
sets in a graph with $\delta(G)\geq d$ is at most that in $K_{d,n-d}$.
  In this paper, we give a lower bound on the number of independent sets in a
$d$-regular graph mirroring the upper bound in the Kahn-Zhao theorem. The main
result of this paper is a proof of a strengthened form of Galvin's conjecture,
covering the case $n\leq 2d$ as well. We find it convenient to address this
problem from the perspective of $\complement{G}$. In other words, we give an
upper bound on the number of complete subgraphs of a graph $G$ on $n$ vertices
with $\Delta(G)\leq r$, valid for all values of $n$ and $r$.


title: An analytic model for redshift-space distortions

abstract:
  Understanding the formation and evolution of large-scale structure is a
central problem in cosmology and enables precise tests of General Relativity on
cosmological scales and constraints on dark energy. An essential ingredient is
an accurate description of the pairwise velocities of biased tracers of the
matter field. In this paper we compute the first and second moments of the
pairwise velocity distribution by extending the Convolution Lagrangian
Perturbation theory (CLPT) formalism of Carlson et al. (2012). Our predictions
outperform standard perturbation theory calculations in many cases when
compared to statistics measured in N-body simulations. We combine the CLPT
predictions of real-space clustering and velocity statistics in the Gaussian
streaming model of Reid & White (2011) to obtain predictions for the monopole
and quadrupole correlation functions accurate to 2 and 4 per cent respectively
down to <25Mpc/h for halos hosting the massive galaxies observed by SDSS-III
BOSS. We also discuss contours of the 2D correlation function and clustering
"wedges". We generalize the scheme to cross-correlation functions.


title:
Two-dimensional spatial coherence of excitons in semicrystalline
  polymeric semiconductors: The effect of molecular weight

abstract:
  The electronic properties of macromolecular semiconductor thin films depend
profoundly on their solid-state microstructure, which in turn is governed,
among other things, by the processing conditions selected and the polymer
chemical nature and molecular weight. Specifically, low-molecular-weight
materials form crystalline domains of cofacially $\pi$-stacked molecules, while
the usually entangled nature of higher molecular-weight polymers leads to
microstructures comprised of molecularly ordered crystallites interconnected by
amorphous regions. Here, we examine the interplay between extended exciton
states delocalized along the polymer backbones and across polymer chains within
the $\pi$-stack, depending on the structural development with molecular weight.
We combine optical spectroscopies, thermal probes, and theoretical modeling,
focusing on neat poly(3-hexylthiophene) (P3HT), one of the most extensively
studied polymer semiconductors, of weight-average molecular weight of
3-450\,kg/mol. The spatial coherence within the chain is significantly reduced
(by nearly 30\%). These observations give valuable structural information; they
suggest that the macromolecules in aggregated regions of high-molecular-weight
P3HT adopt a more planar conformation compared to low-molecular-weight
materials. This results in the observed increase in intrachain exciton
coherence. In contrast, shorter chains seem to lead to torsionally more
disordered architectures. A rigorous, fundamental description of primary
photoexcitations in $\pi$-conjugated polymers is hence developed:
two-dimensional excitons are defined by the chain-length dependent molecular
arrangement and interconnectivity of the conjugated macromolecules, leading to
interplay between intramolecular and intermolecular spatial coherence.


title:
Purification and redistribution of entanglement via single local
  filtering

abstract:
  The effect of filtering operation with respect to purification and
concentration of entanglement in quantum states are discussed in this paper. It
is shown, through examples, that the local action of the filtering operator on
a part of the composite quantum state allows for purification of the remaining
part of the state. The redistribution of entanglement in the subsystems of a
noise affected state is shown to be due to the action of local filtering on the
non-decohering part of the system. The varying effects of the filtering
parameter, on the entanglement transfer between the subsystems, depending on
the choice of the initial quantum state is illustrated.


title: Unidirectional quantum walks: evolution and exit times

abstract:
  In this paper we focus our attention on a particle that follows a
unidirectional quantum walk, an alternative version of the nowadays widespread
discrete-time quantum walk on a line. Here the walker at each time step can
either remain in place or move in a fixed direction, e.g., rightward or upward.
While both formulations are essentially equivalent, the present approach leads
to consider Discrete Fourier Transforms, which eventually results in obtaining
explicit expressions for the wave functions in terms of finite sums, and allows
the use of efficient algorithms based on the Fast Fourier Transform. The wave
functions here obtained govern the probability of finding the particle at any
given location, but determine as well the exit-time probability of the walker
from a fixed interval, which is also analyzed.

categories: quant-ph cond-mat.stat-mech math-ph math.MP


title: Ultra High Energy Neutrinos: Absorption, Thermal Effects and Signatures

abstract:
  We study absorption of ultra high energy neutrinos by the cosmic neutrino
background, with full inclusion of the effect of the thermal distribution of
the background on the resonant annihilation channel. For a hierarchical
neutrino mass spectrum (with at least one neutrino with mass below $\sim
10^{-2}$ eV), thermal effects are important for ultra high energy neutrino
sources at $z \gtrsim 16$. The neutrino transmission probability shows no more
than two separate suppression dips since the two lightest mass eigenstates
contribute as a single species when thermal effects are included. Results are
applied to a number of models of ultra high energy neutrino emission.
Suppression effects are strong for sources that extend beyond $z \sim 10$,
which can be realized for certain top down scenarios, such as superheavy dark
matter decays, cosmic strings and cosmic necklaces. For these, a broad
suppression valley should affect the neutrino spectrum at least in the energy
interval $10^{12} - 10^{13}$ GeV -- which therefore is disfavored for ultra
high energy neutrino searches -- with only a mild dependence on the neutrino
mass spectrum and hierarchy. The observation of absorption effects would
indicate a population of sources beyond $z \sim 10$, and favor top-down
mechanisms; it would also be an interesting probe of the physics of the relic
neutrino background in the unexplored redshift interval $z \sim 10 -100$.


title: A Curious Explanation of Some Cosmological Phenomena

abstract:
  While observational cosmology has shown tremendous growth over the last
decade, deep mysteries continue to haunt our theoretical understanding of the
ingredients of the concordance cosmological model, which are mainly `dark'.
More than 95 percent of the content of the energy-stress tensor has to be in
the form of inflaton, dark matter and dark energy, which do not have any
non-gravitational or laboratory evidence and remain unidentified. Moreover, the
dark energy poses a serious confrontation between fundamental physics and
cosmology. This makes a strong case to discover alternative theories which do
not require the dark sectors of the standard approach to explain the
observations.
  In the present situation, it would be important to gain insight about the
requirements of the `would be' final theory from all possible means. In this
context, the present paper highlights some, hitherto unnoticed, interesting
coincidences which may prove useful to develop insight about the `holy grail'
of gravitation. It appears that the requirement of the speculative dark sectors
by the energy-stress tensor, is indicative of a possible way out of the present
crisis appearing in the standard cosmology, in terms of a theory wherein the
energy-stress tensor does not play a direct role in the dynamics. It is shown
that various cosmological observations can be explained satisfactorily in the
framework of one such theory $-$ the Milne model, without requiring the dark
sectors of the standard approach. Moreover, the model evades the horizon,
flatness and the cosmological constant problems afflicting the standard
cosmology.
  Though Milne's theory is an incomplete, phenomenological theory, and cannot
be the final theory of gravitation, nevertheless, it would be worthwhile to
study these coincidences, which may help us develop insight about the would-be
final theory.


title: Matrix orbit closures

abstract:
  Let $G$ be the group $GL_r(C) \times (C^\times)^n$. We conjecture that the
finely-graded Hilbert series of a $G$ orbit closure in the space of $r$-by-$n$
matrices is wholly determined by the associated matroid. In support of this, we
prove that the coefficients of this Hilbert series corresponding to certain
hook-shaped Schur functions in the $GL_r(C)$ variables are determined by the
matroid, and that the orbit closure has a set-theoretic system of ideal
generators whose combinatorics are also so determined. We also discuss
relations between these Hilbert series for related matrices, including their
stabilizing behaviour as $r$ increases.


title: The Multiplicity of High-Mass Stars

abstract:
  We report about an ongoing photometric and spectroscopic monitoring survey of
about 250 O- and 540 B-type stars in the southern Milky Way with the aim to
determine the fraction of close binary systems as a function of mass and to
determine the physical parameters of the individual components in the multiple
systems. Preliminary results suggest that the multiplicity rate drops from 80%
for the highest masses to 20% for stars of 3 solar masses. Our analysis
indicates that the binary systems often contain close pairs with components of
similar mass. This coincidence cannot originate from a random tidal capture in
a dense cluster but is likely due to a particular formation process for
high-mass stars. The large percentage of multiple systems requires a new
photometric calibration for the absolute magnitudes of O-type stars.


title: Orbital-free Bond Breaking via Machine Learning

abstract:
  Machine learning is used to approximate the kinetic energy of one dimensional
diatomics as a functional of the electron density. The functional can
accurately dissociate a diatomic, and can be systematically improved with
training. Highly accurate self-consistent densities and molecular forces are
found, indicating the possibility for ab-initio molecular dynamics simulations.


title:
Mesoscopic Aharonov-Bohm Interferometers:Decoherence and Thermoelectric
  Transport

abstract:
  Two important features of mesoscopic Aharonov-Bohm (A-B) electronic
interferometers are analyzed: decoherence due to coupling with other degrees of
freedom and the coupled transport of charge and heat. We first review the
principles of decoherence of electronic interference. We then analyze the
thermoelectric transport in a ring threaded by such a flux, with a molecular
bridge on one of its arms. The charge carriers may also interact inelastically
with the molecular vibrations. This nano-system is connected to three termi-
nals; two of them are electric and thermal, held at slightly different chemical
potentials and temperatures, and the third is purely thermal. For example, a
phonon bath thermalizing the molecular vibrations. When this third terminal is
held at a temperature different from those of the electronic reservoirs, both
an electrical and a heat current are, in general, gen- erated between the
latter. Likewise, a voltage and/or temperature difference between the
electronic terminals leads to thermal current between the thermal and
electronic terminals. The transport coefficients governing these conversions
(due to energy exchange between the electrons and the vibrations) and their
dependences on the A-B flux are analyzed. Finally, the decoherence due to these
inelastic events is discussed.


title: Law of refraction for generalised confocal lenslet arrays

abstract:
  We derive the law of generalised refraction for generalised confocal lenslet
arrays, which are arrays of misaligned telescopes. We have implemented this law
of refraction in TIM, a custom open-source ray tracer.


title:
Transmittance and reflectance measurements at terahertz frequencies on a
  superconducting BaFe_{1.84}Co_{0.16}As_2 ultrathin film: an analysis of the
  optical gaps in the Co-doped BaFe_2As_2 pnictide

abstract:
  Here we report an optical investigation in the terahertz region of a 40 nm
ultrathin BaFe$_{1.84}$Co$_{0.16}$As$_2$ superconducting film with
superconducting transition temperature T$_c$ = 17.5 K. A detailed analysis of
the combined reflectance and transmittance measurements showed that the optical
properties of the superconducting system can be described in terms of a
two-band, two-gap model. The zero temperature value of the large gap
$\Delta_B$, which seems to follow a BCS-like behavior, results to be
$\Delta_B$(0) = 17 cm$^{-1}$. For the small gap, for which $\Delta_A$(0) = 8
cm$^{-1}$, the temperature dependence cannot be clearly established. These gap
values and those reported in the literature for the BaFe$_{2-x}$Co$_{x}$As$_2$
system by using infrared spectroscopy, when put together as a function of
T$_c$, show a tendency to cluster along two main curves, providing a unified
perspective of the measured optical gaps. Below a temperature around 20 K, the
gap-sizes as a function of T$_c$ seem to have a BCS-like linear behavior, but
with different slopes. Above this temperature, both gaps show different
supra-linear behaviors.


title:
Krein signatures of transfer operators for half-space topological
  insulators

abstract:
  We propose a complementary point of view on the topological invariants of
two-dimensional tight-binding models restricted to half-spaces. The transfer
operators for such systems are $J$-unitary on a infinite dimensional Krein
space $(\mathcal{K},J)$ and, for energies in the bulk gap, only have discrete
spectrum on the unit circle. These eigenvalues have Krein inertia which can be
used to define topological invariants determining the nature of the surface
modes and allowing to distinguish different topological phases. This is
illustrated by numerical results.


title: Anomalous Edge Transport in the Quantum Anomalous Hall State

abstract:
  We predict by first-principles calculations that thin films of Cr-doped
(Bi,Sb)$_2$Te$_3$ magnetic topological insulator have gapless non-chiral edge
states coexisting with the chiral edge state. Such gapless non-chiral states
are not immune to backscattering, which would explain dissipative transport in
the quantum anomalous Hall (QAH) state observed in this system experimentally.
Here we study the edge transport with both chiral and non-chiral states by
Landaur-B\"{u}ttiker formalism, and find that the longitudinal resistance is
nonzero whereas Hall resistance is quantized to $h/e^2$. In particular, the
longitudinal resistance can be greatly reduced by adding an extra floating
probe even if it is not used, while the Hall resistance remains at the
quantized value. We propose several transport experiments to detect the
dissipative non-chiral edge channels. These results will facilitate the
realization of pure dissipationless transport of QAH states in magnetic
topological insulators.


title:
Sodium Chloride interaction with solvated and crystalline cellulose :
  sodium ion affects the tetramer and fibril in aqueous solution

abstract:
  Inorganic salts are a natural component of biomass which have a significant
effect on the product yields from a variety of biomass conversion processes.
Understanding their effect on biomass at the microscopic level can help
discover their mechanistic role. We present a study of the effect of aqueous
sodium chloride (NaCl) on the largest component of biomass, cellulose, focused
on the thermodynamic and structural effect of a sodium ion on the cellulose
tetramer, and fibril. Replica exchange molecular dynamics simulations of a
cellulose tetramer reveal a number of preferred cellulose-Na contacts and
bridging positions. Large scale MD simulations on a model cellulose fibril find
that Na+ perturbs the hydroxymethyl rotational state population and
consequently disrupts the "native" hydrogen bonding network.


title:
KIC 4544587: an Eccentric, Short Period Binary System with delta Sct
  Pulsations and Tidally Excited Modes

abstract:
  We present Kepler photometry and ground based spectroscopy of KIC 4544587, a
short-period eccentric eclipsing binary system with self-excited pressure and
gravity modes, tidally excited modes, tidally influenced p modes, and rapid
apsidal motion of 182 y per cycle. The primary and secondary components of KIC
4544587 reside within the delta Scuti and gamma Dor instability region of the
Hurtzsprung-Russell diagram, respectively. By applying the binary modelling
software PHOEBE to prewhitened Kepler photometric data and radial velocity data
obtained using the William Herschel Telescope and 4-m Mayall telescope at KPNO,
the fundamental parameters of this important system have been determined,
including the stellar masses, 1.98+/-0.07 MSun and 1.60+/-0.06 MSun, and radii,
1.76+/-0.03 RSun and 1.42+/-0.02 RSun, for the primary and secondary
components, respectively. Frequency analysis of the residual data revealed 31
modes, 14 in the gravity mode region and 17 in the pressure mode region. Of the
14 gravity modes 8 are orbital harmonics: a signature of tidal resonance. While
the measured amplitude of these modes may be partially attributed to residual
signal from binary model subtraction, we demonstrate through consideration of
the folded light curve that these frequencies do in fact correspond to tidally
excited pulsations. Furthermore, we present an echelle diagram of the pressure
mode frequency region (modulo the orbital frequency) and demonstrate that the
tides are also influencing the p modes. A first look at asteroseismology hints
that the secondary component is responsible for the p modes, which is contrary
to our expectation that the hotter star should pulsate in higher radial
overtone, higher frequency p modes.


title: Risk-Constrained Microgrid Reconfiguration Using Group Sparsity

abstract:
  The system reconfiguration task is considered for existing power distribution
systems and microgrids, in the presence of renewable-based generation and load
foresting errors. The system topology is obtained by solving a
chance-constrained optimization problem, where loss-of-load (LOL) constraints
and Ampacity limits of the distribution lines are enforced. Similar to various
distribution system reconfiguration renditions, solving the resultant problem
is computationally prohibitive due to the presence of binary line selection
variables. Further, lack of closed form expressions for the joint probability
distribution of forecasting errors hinders tractability of LOL constraints.
Nevertheless, a convex problem re-formulation is developed here by resorting to
a scenario approximation technique, and by leveraging the underlying
group-sparsity attribute of currents flowing on distribution lines equipped
with tie and sectionalizing switches. The novel convex LOL-constrained
reconfiguration scheme can also afford a distributed solution using the
alternating direction method of multipliers, to address the case where
multi-facilities are managed autonomously from the rest of the system.


title: Methods for Bayesian power spectrum inference with galaxy surveys

abstract:
  We derive and implement a full Bayesian large scale structure inference
method aiming at precision recovery of the cosmological power spectrum from
galaxy redshift surveys. Our approach improves over previous Bayesian methods
by performing a joint inference of the three dimensional density field, the
cosmological power spectrum, luminosity dependent galaxy biases and
corresponding normalizations. We account for all joint and correlated
uncertainties between all inferred quantities. Classes of galaxies with
different biases are treated as separate sub samples. The method therefore also
allows the combined analysis of more than one galaxy survey.
  In particular, it solves the problem of inferring the power spectrum from
galaxy surveys with non-trivial survey geometries by exploring the joint
posterior distribution with efficient implementations of multiple block Markov
chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high
statistical efficiency in low signal to noise regimes by using a deterministic
reversible jump algorithm. We test our method on an artificial mock galaxy
survey, emulating characteristic features of the Sloan Digital Sky Survey data
release 7, such as its survey geometry and luminosity dependent biases. These
tests demonstrate the numerical feasibility of our large scale Bayesian
inference frame work when the parameter space has millions of dimensions.
  The method reveals and correctly treats the anti-correlation between bias
amplitudes and power spectrum, which are not taken into account in current
approaches to power spectrum estimation, a 20 percent effect across large
ranges in k-space. In addition, the method results in constrained realizations
of density fields obtained without assuming the power spectrum or bias
parameters in advance.


title:
Illumination-invariant face recognition from a single image across
  extreme pose using a dual dimension AAM ensemble in the thermal infrared
  spectrum

abstract:
  Over the course of the last decade, infrared (IR) and particularly thermal IR
imaging based face recognition has emerged as a promising complement to
conventional, visible spectrum based approaches which continue to struggle when
applied in practice. While inherently insensitive to visible spectrum
illumination changes, IR data introduces specific challenges of its own, most
notably sensitivity to factors which affect facial heat emission patterns, e.g.
emotional state, ambient temperature, and alcohol intake. In addition, facial
expression and pose changes are more difficult to correct in IR images because
they are less rich in high frequency detail which is an important cue for
fitting any deformable model. In this paper we describe a novel method which
addresses these major challenges. Specifically, when comparing two thermal IR
images of faces, we mutually normalize their poses and facial expressions by
using an active appearance model (AAM) to generate synthetic images of the two
faces with a neutral facial expression and in the same view (the average of the
two input views). This is achieved by piecewise affine warping which follows
AAM fitting. A major contribution of our work is the use of an AAM ensemble in
which each AAM is specialized to a particular range of poses and a particular
region of the thermal IR face space. Combined with the contributions from our
previous work which addressed the problem of reliable AAM fitting in the
thermal IR spectrum, and the development of a person-specific representation
robust to transient changes in the pattern of facial temperature emissions, the
proposed ensemble framework accurately matches faces across the full range of
yaw from frontal to profile, even in the presence of scale variation (e.g. due
to the varying distance of a subject from the camera).


title:
Estimating Saturated Hydraulic Conductivity from Surface
  Ground-Penetrating Radar Monitoring of Infiltration

abstract:
  In this study we used Hydrus-1D to simulate water infiltration from a ring
infiltrometer. We generated water content profiles at each time step of
infiltration, based on a particular value of the saturated hydraulic
conductivity while knowing the other van Genuchten parameters. Water content
profiles were converted to dielectric permittivity profiles using the Complex
Refractive Index Method relation. We then used the GprMax suite of programs to
generate radargrams and to follow the wetting front using arrival time of
electromagnetic waves recorded by a Ground-Penetrating Radar (GPR).
Theoretically, the depth of the inflection point of the water content profile
simulated at any infiltration time step is related to the peak of the reflected
amplitude recorded in the corresponding trace in the radargram. We used this
relationship to invert the saturated hydraulic conductivity for constant and
falling head infiltrations. We present our method on synthetic examples and on
two experiments carried out on sand. We further discuss the possibility of
estimating two other van Genuchten parameters, n and \alpha, in addition to the
saturated hydraulic conductivity.


title: Reciprocal Space and Crystal Planes in Geometric Algebra

abstract:
  This contribution discusses the geometry of $k$D crystal cells given by
$(k+1)$ points in a projective space $\R^{n+1}$. We show how the concepts of
barycentric and fractional (crystallographic) coordinates, reciprocal vectors
and dual representati on are related (and geometrically interpreted) in the
projective geometric algebra $\R_{n+1}$ (see H. Grassmann, edited by F. Engel,
Sie Ausdehnungslehre von 1844 und die Geom. Anal., vol. 1, part 1, Teubner,
Leipzig, 1894.) and in the conformal algebra $\R_{n+1,1}$. The crystallographic
notions of $d$-spacing, phase angle (in structure factors), extinction of Bragg
reflections, and the interfacial angles of crystal planes are obtained in the
same context.


title: Angles between subspaces computed in Clifford Algebra

abstract:
  We first review the definition of the angle between subspaces and how it is
computed using matrix algebra. Then we introduce the Grassmann and Clifford
algebra description of subspaces. The geometric product of two subspaces yields
the full relative angular information in an explicit manner. We explain and
interpret the result of the geometric product of subspaces gaining thus full
practical access to the relative orientation information.


title: Time travel, Clock Puzzles and Their Experimental Tests

abstract:
  Is time travel possible? What is Einstein's theory of relativity
mathematically predicting in that regard? Is time travel related to the
so-called clock 'paradoxes' of relativity and if so how? Is there any accurate
experimental evidence of the phenomena regarding the different flow of time
predicted by General Relativity and is there any possible application of the
temporal phenomena predicted by relativity to our everyday life? Which temporal
phenomena are predicted in the vicinities of a rotating body and of a
mass-energy current, and do we have any experimental test of the occurrence of
these phenomena near a rotating body? In this paper, we address and answer some
of these questions.


title:
Wave function of the Universe, Preferred reference frame effects and
  metric signature transition

abstract:
  Gravitational model of non-minimally coupled Brans Dicke (BD) scalar field
$\phi$ with dynamical unit time-like four vector field is used to study flat
Robertson Walker (RW) cosmology in the presence of variable cosmological
parameter $V(\phi)=\Lambda\phi.$ Aim of the paper is to seek cosmological
models which exhibit metric signature transition. The problem is studied in
both classical and quantum cosmological approach with large values of BD
parameter $\omega>>1$. Scale factor of RW metric is obtained as
$R(t)=6\sqrt{\frac{3}{\Lambda}}\cosh\big(\frac{t}{4}\sqrt{\frac{\Lambda}{3}}\big)$
which describes nonsingular inflationary universe in Lorentzian signature
sector. Euclidean signature sector of our solution describes a re-collapsing
universe and is obtained from analytic continuation of the Lorentzian sector by
exchanging $t\to it$ as
$R(t)=6\sqrt{\frac{3}{\Lambda}}\cos\big(\frac{t}{4}\sqrt{\frac{\Lambda}{3}}\big).$
  Dynamical vector field together with the BD scalar field are treated as fluid
with time dependent barotropic index. They have regular (dark) matter dominance
in the Euclidean (Lorentzian) sector. We solved Wheeler De
  Witt (WD) quantum wave equation of the cosmological system. Assuming a
discrete non-zero ADM mass $M_j=4\sqrt{2}(2j+1)\sqrt{\frac{\Lambda}{3}}$ with
$j=0,1,2,\cdots$, we obtained solutions of the WD equation as simple harmonic
quantum Oscillator eigen functionals described by Hermite polynomials. Absolute
values of these eigen functionals have nonzero values on the hypersurface
$R=6\sqrt{\frac{3}{\Lambda}}$ in which metric field has signature degeneracy.
Our eigen functionals describe nonzero probability of the space time with
Lorentzian (Euclidean) signature for $R>6\sqrt{\frac{3}{\Lambda}}$
($R<6\sqrt{\frac{3}{\Lambda}}$). Maximal probability corresponds to the ground
state $j=0.$


title: Thermal Photons From Magnetized Bare Strange Stars

abstract:
  A plasma made out of strange-quark matter (SQM) and electrons, has a rather
high plasma frequency (>20 MeV). Thus, a compact star made of such material all
the way up to its surface, i.e., a bare strange star, would be unable to
radiate away its thermal emission.
  We use the MIT-bag model and assume that SQM is the ground state of nuclear
matter at high density. We investigate whether the presence of a magnetic field
will allow propagation of radiation at frequencies below the SQM plasma
frequencies. Hence, we study the presence of gyrofrequencies in a SQM plasma
permeated by a strong magnetic field (B > 10^{12} G). We find that small
regions in the frequency spectrum allow radiation propagation due to the
presence of the magnetic fields. It is likely that narrow bands of radiation
would likely be observable from magnetized bare strange stars .


title:
Confronting Models of Dwarf Galaxy Quenching with Observations of the
  Local Group

abstract:
  A number of mechanisms have been proposed to connect star-forming dwarf
irregular galaxies with the formation of non-star-forming dwarf spheroidal
galaxies, but distinguishing between these mechanisms has been difficult. We
use the Via Lactea dark matter only cosmological simulations to test two
well-motivated simple hypotheses---transformation of irregulars into dwarf
spheroidal galaxies by tidal stirring and ram pressure stripping following a
close passage to the host galaxy, and transformation via mergers between
dwarfs---and predict the radial distribution and inferred formation times of
the resulting dwarf spheroidal galaxies. We compare this to the observed
distribution in the Local Group and show that 1) the observed dSph distribution
far from the Galaxy or M31 can be matched by the VL halos that have passed near
the host galaxy at least once, though significant halo-to-halo scatter exists,
2) models that require two or more pericenter passages for dSph-formation
cannot account for the dSphs beyond 500 kpc such as Cetus and Tucana, and 3)
mergers predict a flat radial distribution of dSphs and cannot account for the
high dSph fraction near the Galaxy, but are not ruled out at large distances.
The models also suggest that for dSphs found today beyond 500 kpc, mergers tend
to occur significantly earlier than dwarf--host encounters, thus leading to a
potentially observable difference in stellar populations. We argue that tidal
interactions are sufficient to reproduce the observed distribution of dSphs if
and only if a single pericenter passage is sufficient to form a dSph.


title:
Higgs boson production in association with three jets via gluon fusion
  at the LHC: Gluonic contributions

abstract:
  Higgs production in association with three jets via gluon fusion (GF) is an
important channel for the measurement of the CP-properties of the Higgs
particle at the LHC. In this letter, we go beyond the heavy top effective
theory approximation and include at LO the full mass dependence of the top- and
bottom-quark contributions. We consider the dominant sub-channel gg -> H ggg
which involves the manipulation of massive rank-5 hexagon integrals.
Furthermore, we present results for several differential distributions and show
deviations from the effective theory as large as 100% at high pT for light
Higgs masses.


title:
Probing the Interstellar Medium of z~1 Ultra-luminous Infrared Galaxies
  through Interferometric Observations of CO and Spitzer Mid-infrared
  Spectroscopy

abstract:
  We explore the relationship between gas, dust and star formation in a sample
of 12 ultra-luminous infrared galaxies (ULIRGs) at high redshift compared to a
similar sample of local galaxies. We present new CO observations and/or Spitzer
mid-IR spectroscopy for 6 70 micron selected galaxies at z~1 in order to
quantify the properties of the molecular gas reservoir, the contribution of an
active galactic nuclei (AGN) to the mid-IR luminosity and the star formation
efficiency (SFE=LIR/L'CO). The mid-IR spectra show strong polycyclic aromatic
hydrocarbon (PAH) emission and our spectral decomposition suggests that the AGN
makes a minimal contribution (<25%) to the mid-IR luminosity. The 70 micron
selected ULIRGs which we find to be spectroscopic close pairs, are observed to
have high SFE, similar to local ULIRGs and high redshift submillimeter
galaxies, consistent with enhanced IR luminosity due to an ongoing major
merger. Combined with existing observations of local and high redshift ULIRGs,
we further compare the PAH, IR and CO luminosities. We show that the ratio
LPAH6.2/LIR decreases with increasing IR luminosity for both local and high
redshift galaxies but the trend for high redshift galaxies is shifted to higher
IR luminosities; the average LPAH6.2/LIR ratio at a given LIR is ~3 times
higher at high redshift. When we normalize by the molecular gas, we find this
trend to be uniform for galaxies at all redshifts and that the molecular gas is
correlated with the PAH dust emission.The similar trends seen in the [CII] to
molecular gas ratios in other studies suggests that PAH emission, like [CII],
continues to be a good tracer of photodissociation regions even at high
redshift. Together the CO, PAH and far-IR fine structure lines should be useful
for constraining the interstellar medium conditions in high redshift galaxies.


title: Matter From Geometry Without Resolution

abstract:
  We utilize the deformation theory of algebraic singularities to study charged
matter in compactifications of M-theory, F-theory, and type IIa string theory
on elliptically fibered Calabi-Yau manifolds. In F-theory, this description is
more physical than that of resolution. We describe how two-cycles can be
identified and systematically studied after deformation. For ADE singularities,
we realize non-trivial ADE representations as sublattices of Z^N, where N is
the multiplicity of the codimension one singularity before deformation. We give
a method for the determination of Picard-Lefschetz vanishing cycles in this
context and utilize this method for one-parameter smooth deformations of ADE
singularities. We give a general map from junctions to weights and demonstrate
that Freudenthal's recursion formula applied to junctions correctly reproduces
the structure of high-dimensional ADE representations, including the 126 of
SO(10) and the 43,758 of E_6. We identify the Weyl group action in some
examples, and verify its order in others. We describe the codimension two
localization of matter in F-theory in the case of heterotic duality or simple
normal crossing and demonstrate the branching of adjoint representations.
Finally, we demonstrate geometrically that deformations correctly reproduce the
appearance of non-simply-laced algebras induced by monodromy around codimension
two singularities, showing the reduction of D_4 to G_2 in an example. A
companion mathematical paper will follow.


title: The Differential of All Two-Loop MHV Amplitudes in N=4 Yang-Mills Theory

abstract:
  We present an explicit analytic calculation of the differential of the planar
n-particle, two-loop MHV scattering amplitude in N=4 super Yang-Mills theory.
The result is expressed only in terms of the polylogarithm functions Li_k(-x),
for k=1,2,3, with arguments x belonging to the special class of dual conformal
cross-ratios known as cluster X-coordinates. The surprising fact that these
amplitudes may be expressed in this way provides a striking example of the
manner in which the cluster structure on the kinematic configuration space
underlies the structure of amplitudes in SYM theory.


title:
Spectrum Syntheses of High Resolution Integrated Light Spectra of
  Galactic Globular Clusters

abstract:
  Spectrum syntheses for three elements (Mg, Na, and Eu) in high-resolution
integrated light spectra of the Galactic globular clusters 47 Tuc, M3, M13, NGC
7006, and M15 are presented, along with calibration syntheses of the Solar and
Arcturus spectra. Iron abundances in the target clusters are also derived from
integrated light equivalent width analyses. Line profiles in the spectra of
these five globular clusters are well fit after careful consideration of the
atomic and molecular spectral features, providing levels of precision that are
better than equivalent width analyses of the same integrated light spectra, and
that are comparable to the precision in individual stellar analyses. The
integrated light abundances from the 5528 and 5711 A Mg I lines, the 6154 and
6160 A Na I lines, and the 6645 A Eu II line fall within the observed ranges
from individual stars; however, these integrated light abundances do not always
agree with the average literature abundances. Tests with the second parameter
clusters M3, M13, and NGC 7006 show that assuming an incorrect horizontal
branch morphology is likely to have only a small (< 0.06 dex) effect on these
Mg, Na, and Eu abundances. These tests therefore show that integrated light
spectrum syntheses can be applied to unresolved globular clusters over a wide
range of metallicities and horizontal branch morphologies. Such high precision
in integrated light spectrum syntheses is valuable for interpreting the
chemical abundances of globular cluster systems around other galaxies.


title: Gravity with Auxiliary Fields

abstract:
  Modifications of General Relativity usually include extra dynamical degrees
of freedom, which to date remain undetected. Here we explore the possibility of
modifying Einstein's theory by adding solely nondynamical fields. With the
minimal requirement that the theory satisfies the weak equivalence principle
and admits a covariant Lagrangian formulation, we show that the field equations
generically have to include higher-order derivatives of the matter fields. This
has profound consequences for the viability of these theories. We develop a
parametrization based on a derivative expansion and show that - to next to
leading order - all theories are described by just two parameters. Our approach
can be used to put stringent, theory-independent constraints on such theories,
as we demonstrates using the Newtonian limit as an example.


title:
Measures of Galaxy Environment - III. Difficulties in identifying
  proto-clusters at z ~ 2

abstract:
  Galaxy environment is frequently discussed, but inconsistently defined. It is
especially difficult to measure at high redshift where only photometric
redshifts are available. With a focus on early forming proto-clusters, we use a
semi-analytical model of galaxy formation to show how the environment
measurement around high redshift galaxies is sensitive to both scale and
metric, as well as to cluster viewing angle, evolutionary state, and the
availability of either spectroscopic or photometric data. We use two types of
environment metrics (nearest neighbour and fixed aperture) at a range of scales
on simulated high-z clusters to see how "observed" overdensities compare to
"real" overdensities. We also "observationally" identify z = 2 proto-cluster
candidates in our model and track the growth histories of their parent halos
through time, considering in particular their final state at z = 0. Although
the measured environment of early forming clusters is critically dependent on
all of the above effects (and in particular the viewing angle), we show that
such clusters are very likely (< 90%) to remain overdense at z = 0, although
many will no longer be among the most massive. Object to object comparisons
using different methodologies and different data, however, require much more
caution.


title: Modularity, Quaternion-Kahler spaces and Mirror Symmetry

abstract:
  We provide an explicit twistorial construction of quaternion-Kahler manifolds
obtained by deformation of c-map spaces and carrying an isometric action of the
modular group SL(2,Z). The deformation is not assumed to preserve any
continuous isometry and therefore this construction presents a general
framework for describing NS5-brane instanton effects in string
compactifications with N=2 supersymmetry. In this context the modular invariant
parametrization of twistor lines found in this work yields the complete
non-perturbative mirror map between type IIA and type IIB physical fields.


title: Valid Orderings of Real Hyperplane Arrangements

abstract:
  Given a real finite hyperplane arrangement A and a point p not on any of the
hyperplanes, we define an arrangement vo(A,p), called the *valid order
arrangement*, whose regions correspond to the different orders in which a line
through p can cross the hyperplanes in A. If A is the set of affine spans of
the facets of a convex polytope P and p lies in the interior of P, then the
valid orderings with respect to p are just the line shellings of p where the
shelling line contains p. When p is sufficiently generic, the intersection
lattice of vo(A,p) is the *Dilworth truncation* of the semicone of A. Various
applications and examples are given. For instance, we determine the maximum
number of line shellings of a d-polytope with m facets when the shelling line
contains a fixed point p. If P is the order polytope of a poset, then the sets
of facets visible from a point involve a generalization of chromatic
polynomials related to list colorings.


title:
Strain-Induced Hybrid Improper Ferroelectricity in Simple Perovskites
  from First Principles

abstract:
  We performed first principles calculations for epitaxially strained
orthorhombic CaTiO$_3$. The computational results reveal the existence of a
metastable ferroelectric phase at compressive strain with unexpected in-plane
polarization. Symmetry analysis indicates that two distortion modes at the X
point combine to induce the polarization, leading to characterization as a
hybrid improper ferroelectric. Our work demonstrates a mechanism for improper
ferroelectricity in simple perovskites without the need for symmetry lowering
by layering or cation ordering.


title: Loss-Proportional Subsampling for Subsequent ERM

abstract:
  We propose a sampling scheme suitable for reducing a data set prior to
selecting a hypothesis with minimum empirical risk. The sampling only considers
a subset of the ultimate (unknown) hypothesis set, but can nonetheless
guarantee that the final excess risk will compare favorably with utilizing the
entire original data set. We demonstrate the practical benefits of our approach
on a large dataset which we subsample and subsequently fit with boosted trees.


title: Isoperimetric inequality, $Q$-curvature and $A_p$ weights

abstract:
  A well known question in differential geometry is to control the constant in
isoperimetric inequality by intrinsic curvature conditions. In dimension 2, the
constant can be controlled by the integral of the positive part of the Gaussian
curvature. In this paper, we showed that on simply connected conformal flat
manifolds of higher dimensions, the role of the Gaussian curvature can be
replaced by the Branson $Q$- curvature. We achieve this by exploring the
relationship between $A_p$ weights and integrals of the Q-curvature.


title:
Density of warm ionized gas near the Galactic Center: Low radio
  frequency observations

abstract:
  We have observed the Galactic Center (GC) region at 0.154 and 0.255 GHz with
the GMRT. A total of 62 compact likely extragalactic sources are detected.
Their scattering sizes go down linearly with increasing angular distance from
the GC up to about 1 deg. The apparent scattering sizes of sources are more
than an order of magnitude down than predicted earlier by the NE2001 model of
Galactic electron distribution within 359.5 deg < l < 0.5 deg and -0.5 deg <b
<0.5 deg (Hyperstrong scattering region) of the Galaxy. High free-free optical
depths are observed towards most of the extended nonthermal sources within 0.6
deg from the GC. Significant variation of optical depth indicate the absorbing
medium is patchy at an angular scale of 10' and electron density is ~10 per cc
that matches with the NE2001 model. This model predicts the extragalactic (EG)
sources to be resolved out from 1.4 GHz interferometric surveys. However, 8
likely EG sources out of 10 expected in the region are present in 1.4 GHz
catalog. Ionized interfaces of dense molecular clouds to the ambient medium are
most likely responsible for strong scattering and low radio frequency
absorption. However, dense GC clouds traced by CS $J=1-0$ emission are found to
have a narrow distribution of ~0.2 deg across the Galactic plane. Angular
distribution of most of the EG sources seen through the so called Hyperstrong
scattering region are random in $b$, and typically ~7 out of 10 sources will
not be seen through to the dense molecular clouds, and it explains why most of
them are not scatter broadened at 1.4 GHz.


title:
Differential Proper-Motion Measurements of The Cygnus Egg Nebula: The
  Presence of Equatorial Outflow

abstract:
  We present the results of differential proper-motion analyses of the Egg
Nebula (RAFGL 2688, V1610 Cyg) based on the archived two-epoch optical data
taken with the Hubble Space Telescope. First, we determined that the
polarization characteristics of the Egg Nebula is influenced by the higher
optical depth of the central regions of the nebula (i.e., the "dustsphere" of
about 1000 AU radius), causing the nebula illuminated in two steps -- the
direct starlight is first channeled into bipolar cavities and then scattered
off to the rest of the nebula. We then measured the amount of motion of local
structures and the signature concentric arcs by determining their relative
shifts over the 7.25 yr interval. Based on our analysis, which does not rely on
the single-scattering assumption, we concluded that the lobes have been
excavated by a linear expansion along the bipolar axis for the past 400 yr,
while the concentric arcs have been generated continuously and moving out
radially at about 10 km/s for the past 5,500 yr, and there appears to be a
colatitudinally-increasing trend in the radial expansion velocity field of the
concentric arcs. There exist numerical investigations into the mass-loss
modulation by the central binary system, which predict such a
colatitudinally-increasing expansion velocity field in the spiral-shock trails
of the mass-loss ejecta. Therefore, the Egg Nebula may represent a rare edge-on
case of the binary-modulated circumstellar environs, corroborating the previous
theoretical predictions.


title:
Superstring/Supergravity Mellin Correspondence in Grassmannian
  Formulation

abstract:
  We extend the recently established Mellin correspondence of supergravity and
superstring amplitudes to the case of arbitrary helicity configurations. The
amplitudes are discussed in the framework of Grassmannian varieties. We
generalize Hodges' determinant to a function of two sets of independent
coordinates and show that tree-level supergravity amplitudes can be obtained by
contour integrations of both sets in separate Grassmannians while in
superstring theory, one set of coordinates is identified with string vertex
positions at the disk boundary and Mellin transformed into generalized
hypergeometric functions of Mandelstam invariants.


title: Local linear dependence seen through duality I

abstract:
  A vector space S of linear operators between vector spaces U and V is called
locally linearly dependent (in abbreviated form: LLD) when every vector x of U
is annihilated by a non-zero operator in S. A duality argument bridges the
theory of LLD spaces to the one of vector spaces of non-injective operators.
This new insight yields a unified approach to rediscover basic LLD theorems and
obtain many additional ones thanks to the power of formal matrix computations.
  In this article, we focus on the minimal rank for a non-zero operator in an
LLD space. Among other things, we reprove the Bresar-Semrl theorem, which
states that an n-dimensional LLD operator space always contains a non-zero
operator with rank less than n, and we improve the Meshulam-Semrl theorem that
examines the case when no non-zero operator has rank less than n-1.
  We also tackle the minimal rank problem for a non-zero operator in an
n-dimensional operator space that is not algebraically reflexive. A theorem of
Meshulam and Semrl states that, for all fields with large enough cardinality, a
non-reflexive operator space with dimension n must contain a non-zero operator
with rank at most 2n-2. We show that there are infinitely many integers n for
which this bound is optimal for general infinite fields. Moreover, under mild
cardinality assumptions, we obtain a complete classification of the
non-reflexive n-dimensional operator spaces in which no non-zero operator has
rank less than 2n-2. This classification involves a new algebraic structure
called left-division-bilinearizable (in abbreviated form: LDB) division
algebras, which generalize a situation that is encountered with quaternions and
octonions and whose systematic study occupies a large part of the present
article.


title:
Forster Resonance Energy Transfer and Laser Fluorescent Analysis of
  Defects in DNA Double Helix

abstract:
  Real time laser induced fluorescence spectroscopy usage for microanalysis of
DNA double helix defects is shown. The method is based on Forster resonance
energy transfer (FRET) in intercalator-donor pair (acridine orange as a donor
and ethidium bromide as an acceptor). Transition metal ions such as Cu(II),
Cu(I), Ag(I), silver nanoparticles (AgNPs), photo- and thermo effects were used
to cause double helix defects in DNA.
  FRET radii were experimentally estimated in background electrolyte solution
(0.01 M NaNO3) and proved to be 3.9 +- 0.3 nm and the data are in satisfactory
agreement with the theoretically calculated value Ro = 3.5 +- 0.3 nm.
  Concentration of DNA sites, exposed to Cu(II), Cu(I), Ag(I) ions, AgNPs
impact as well as laser irradiation ({\lambda} = 457 nm) and temperature, which
are applicable for intercalation, were estimated in relative units.
  FRET method allows to estimate the concentration of double helix areas with
high quality stability applicable for intercalation in DNA after it was
subjected to stress effect. It gives the opportunity to compare DNAs of 1)
different origin; 2) with various damage degrees; 3) being in various
functional state.


title: On the many-field f(R) brane

abstract:
  We consider the Randall-Sundrum braneworld theory with a single extra
dimension of infinite extent to investigate generalized $f(R)$ braneworld
models in the presence of several real scalar fields. In particular, we solve
the modified Einstein equations for the case of flat brane, with zero
cosmological constant, and for the case of bent brane, with a nonvanishing
cosmological constant. In both cases we found explicit solutions for the scalar
fields with analytical expressions for the respective warp factors.


title:
The Mg II 2797, 2803 emission in low-metallicity star-forming galaxies
  from the SDSS

abstract:
  We present 65 Sloan Digital Sky Survey (SDSS) spectra of 62 star-forming
galaxies with oxygen abundances 12 + logO/H ~ 7.5-8.4. Redshifts of selected
galaxies are in the range z~0.36-0.70. This allows us to detect the redshifted
MgII 2797,2803 emission lines. Our aim is to use these lines for the magnesium
abundance determination. The MgII emission was detected in ~2/3 of the
galaxies. We find that the MgII 2797 emission-line intensity follows a trend
with the excitation parameter x= O^{2+}/O that is similar to that predicted by
CLOUDY photoionised HII region models, suggesting a nebular origin of MgII
emission. The Mg/O abundance ratio is lower by a factor ~2 than the solar
ratio. This is probably the combined effect of interstellar MgII absorption and
depletion of Mg onto dust. However, the effect of dust depletion in selected
galaxies, if present, is small, by a factor of ~2 lower than that of iron.


title: New Results on Equilibria in Strategic Candidacy

abstract:
  We consider a voting setting where candidates have preferences about the
outcome of the election and are free to join or leave the election. The
corresponding candidacy game, where candidates choose strategically to
participate or not, has been studied %initially by Dutta et al., who showed
that no non-dictatorial voting procedure satisfying unanimity is
candidacy-strategyproof, that is, is such that the joint action where all
candidates enter the election is always a pure strategy Nash equilibrium. Dutta
et al. also showed that for some voting tree procedures, there are candidacy
games with no pure Nash equilibria, and that for the rule that outputs the
sophisticated winner of voting by successive elimination, all games have a pure
Nash equilibrium. No results were known about other voting rules. Here we prove
several such results. For four candidates, the message is, roughly, that most
scoring rules (with the exception of Borda) do not guarantee the existence of a
pure Nash equilibrium but that Condorcet-consistent rules, for an odd number of
voters, do. For five candidates, most rules we study no longer have this
guarantee. Finally, we identify one prominent rule that guarantees the
existence of a pure Nash equilibrium for any number of candidates (and for an
odd number of voters): the Copeland rule. We also show that under mild
assumptions on the voting rule, the existence of strong equilibria cannot be
guaranteed.


title:
Enhancement of a Novel Method for Mutational Disease Prediction using
  Bioinformatics Techniques and Backpropagation Algorithm

abstract:
  The noval method for mutational disease prediction using bioinformatics tools
and datasets for diagnosis the malignant mutations with powerful Artificial
Neural Network (Backpropagation Network) for classifying these malignant
mutations are related to gene(s) (like BRCA1 and BRCA2) cause a disease (breast
cancer). This noval method did not take in consideration just like adopted for
dealing, analyzing and treat the gene sequences for extracting useful
information from the sequence, also exceeded the environment factors which play
important roles in deciding and calculating some of genes features in order to
view its functional parts and relations to diseases. This paper is proposed an
enhancement of a novel method as a first way for diagnosis and prediction the
disease by mutations considering and introducing multi other features show the
alternations, changes in the environment as well as genes, comparing sequences
to gain information about the structure or function of a query sequence, also
proposing optimal and more accurate system for classification and dealing with
specific disorder using backpropagation with mean square rate 0.000000001.
Index Terms (Homology sequence, GC content and AT content, Bioinformatics,
Backpropagation Network, BLAST, DNA Sequence, Protein Sequence)


title:
A Factor Graph Approach to Joint OFDM Channel Estimation and Decoding in
  Impulsive Noise Environments

abstract:
  We propose a novel receiver for orthogonal frequency division multiplexing
(OFDM) transmissions in impulsive noise environments. Impulsive noise arises in
many modern wireless and wireline communication systems, such as Wi-Fi and
powerline communications, due to uncoordinated interference that is much
stronger than thermal noise. We first show that the bit-error-rate optimal
receiver jointly estimates the propagation channel coefficients, the noise
impulses, the finite-alphabet symbols, and the unknown bits. We then propose a
near-optimal yet computationally tractable approach to this joint estimation
problem using loopy belief propagation. In particular, we merge the recently
proposed "generalized approximate message passing" (GAMP) algorithm with the
forward-backward algorithm and soft-input soft-output decoding using a "turbo"
approach. Numerical results indicate that the proposed receiver drastically
outperforms existing receivers under impulsive noise and comes within 1 dB of
the matched-filter bound. Meanwhile, with N tones, the proposed
factor-graph-based receiver has only O(N log N) complexity, and it can be
parallelized.


title: Sisyphus cooling in a continuously loaded trap

abstract:
  We demonstrate continuous Sisyphus cooling combined with a continuous loading
mechanism used to efficiently slow down and accumulate atoms from a guided
beam. While the loading itself is based on a single slowing step, applying a
radio frequency field forces the atoms to repeat this step many times resulting
in a so-called Sisyphus cooling. This extension allows efficient loading and
cooling of atoms from a wide range of initial beam conditions. We study the
interplay of the continuous loading and simultaneous Sisyphus cooling in
different density regimes. In the case of a low density flux we observe a
relative gain in phase-space density of nine orders of magnitude. This makes
the presented scheme an ideal tool for reaching collisional densities enabling
evaporative cooling - in spite of unfavourable initial conditions.


title: Solar system tests of f(R) gravity

abstract:
  In this paper, we revisit the solar system tests of f(R) gravity. When the
Sun sits in a vacuum, the field f' is light, which leads to a metric different
from the observations. We reobtain this result in a simpler way by directly
focusing on the equations of motion for f(R) gravity in the Jordan frame. The
discrepancy between the metric in the f(R) gravity and the observations can be
alleviated by the chameleon mechanism. The implications from the chameleon
mechanism on the functional form f(R) are discussed. Considering the analogy of
the solar system tests to the false vacuum decay problem, the effective
potentials in different cases are also explored. The combination of analytic
and numerical approaches enables us to ascertain whether an f(R) model can pass
the solar system tests or not.


title: Families of nodal curves in P^r with the expected number of moduli

abstract:
  Let V^{r}_{d,g, \delta} be the Hilbert scheme of nodal curves in P^r of
degree d and arithmetic genus g with \delta nodes. Under suitable numerical
assumptions on d and g, for every 0 \le \delta \le g we construct an
irreducible component of V^{r}_{d,g, \delta} having the expected number of
moduli.


title: Unit Grid Intersection Graphs: Recognition and Properties

abstract:
  It has been known since 1991 that the problem of recognizing grid
intersection graphs is NP-complete. Here we use a modified argument of the
above result to show that even if we restrict to the class of unit grid
intersection graphs (UGIGs), the recognition remains hard, as well as for all
graph classes contained inbetween. The result holds even when considering only
graphs with arbitrarily large girth. Furthermore, we ask the question of
representing UGIGs on grids of minimal size. We show that the UGIGs that can be
represented in a square of side length 1+epsilon, for a positive epsilon no
greater than 1, are exactly the orthogonal ray graphs, and that there exist
families of trees that need an arbitrarily large grid.


title:
Carrier multiplication between interacting nanocrystals for fostering
  silicon-based photovoltaics

abstract:
  Being a source of clean and renewable energy, the possibility to convert
solar radiation in electric current with high efficiency is one of the most
important topics of modern scientific research. Currently the exploitation of
interaction between nanocrystals seems to be a promising route to foster the
establishment of third generation photovoltaics. Here we adopt a fully
ab-initio scheme to estimate the role of nanoparticle interplay on the carrier
multiplication dynamics of interacting silicon nanocrystals. Energy and charge
transfer-based carrier multiplication events are studied as a function of
nanocrystal separation showing benefits induced by the wavefunction sharing
regime. We prove the relevance of these recombinative mechanisms for
photovoltaic applications in the case of silicon nanocrystals arranged in dense
arrays, quantifying at an atomistic scale which conditions maximize the
outcome.


title: Decomposition Lemmas

abstract:
  We define two recursive functions obtained by decomposition of a given
interval into four close parts and prove two lemmas which determine features of
these functions.


title: Lowering the Threshold in the DAMA Dark Matter Search

abstract:
  The DAMA experiment searches for Weakly Interacting Massive Particle (WIMP)
dark matter via its expected but rare interactions within the detector, where
the interaction rates will modulate throughout the year due to the orbital
motion of the Earth. Over the course of more than 10 years of operation, DAMA
has indeed detected a strong modulation in the event rate above the detector
threshold of 2 keVee. Under standard assumptions regarding the dark matter halo
and WIMP interactions, this signal is consistent with that expected of WIMPs of
two different approximate masses: ~ 10 GeV and ~ 70 GeV. We examine how a lower
threshold, allowed by recent upgrades to the DAMA detector, may shed light on
this situation. We find that the lower threshold data should rule out one of
the two mass ranges for spin-independent couplings (in the worst case,
disfavoring one of the masses by still more than 2.6$\sigma$) and is likely,
though not certain, to do the same for spin-dependent couplings. Furthermore,
the data may indicate whether the interaction is predominantly spin-independent
or spin-dependent in some cases. Our findings illustrate the importance of a
low threshold in modulation searches.


title:
Quantum Hall Effects with High Spin-Chern Numbers in Buckled Honeycomb
  Structure with Magnetic Order

abstract:
  As a topological insulator, the quantum Hall (QH) effect is indexed by the
Chern and spin-Chern numbers $\mathcal{C}$ and $\mathcal{C}_{\text{spin}}$. We
have only $\mathcal{C}_{\text{spin}}=0$ or $\pm \frac{1}{2}$ in conventional QH
systems. We investigate QH effects in generic monolayer honeycomb systems. We
search for spin-resolved characteristic patterns by exploring Hofstadter's
butterfly diagrams in the lattice theory and fan diagrams in the low-energy
Dirac theory. The Chern and spin-Chern numbers are calculated based on the
bulk-edge correspondence in the lattice theory and on the Kubo formula in the
Dirac theory. It is shown that the spin-Chern number can takes an arbitrary
high value for certain QH systems in coexistence with buckled structure and
magnetic order. This is a new type of topological insulators. Samples may be
provided by silicene with ferromagnetic order and transition-metal oxide with
antiferromagnetic order.


title: A Solution of Simultaneous Recurrences

abstract:
  The paper is devoted to the methods of solving simultaneous recurrences.
Specifically, we discuss transformation of matrix recurrences to regular
recurrences and propose a way of solving special matrix recurrences of order
three by their decomposition to matrix recurrences of order two.


title:
Online Parallel Scheduling of Non-uniform Tasks: Trading Failures for
  Energy

abstract:
  Consider a system in which tasks of different execution times arrive
continuously and have to be executed by a set of processors that are prone to
crashes and restarts. In this paper we model and study the impact of
parallelism and failures on the competitiveness of such an online system. In a
fault-free environment, a simple Longest-in-System scheduling policy, enhanced
by a redundancy-avoidance mechanism, guarantees optimality in a long-term
execution. In the presence of failures though, scheduling becomes a much more
challenging task. In particular, no parallel deterministic algorithm can be
competitive against an offline optimal solution, even with one single processor
and tasks of only two different execution times. We find that when additional
energy is provided to the system in the form of processor speedup, the
situation changes. Specifically, we identify thresholds on the speedup under
which such competitiveness cannot be achieved by any deterministic algorithm,
and above which competitive algorithms exist. Finally, we propose algorithms
that achieve small bounded competitive ratios when the speedup is over the
threshold.


title:
Centaurs and Scattered Disk Objects in the Thermal Infrared: Analysis of
  WISE/NEOWISE Observations

abstract:
  The Wide-field Infrared Survey Explorer (WISE) observed 52 Centaurs and
Scattered Disk Objects in the thermal infrared, including the 15 discoveries
that were new. We present analyses of these observations to estimate sizes and
mean optical albedos. We find mean albedos of 0.08 +/- 0.04 for the entire data
set. Thermal fits yield average beaming parameters of 0.9 +/- 0.2 that are
similar for both SDO and Centaur sub-classes. Biased cumulative size
distributions yield size-frequency distribution power law indices ~ -1.7 +/-
0.3. The data also reveal a relation between albedo and color at the 3-sigma
level. No significant relation between diameter and albedos is found.


title:
Exchange-correlation energy for the 3D homogeneous electron gas at
  arbitrary temperature

abstract:
  We fit finite-temperature path integral Monte Carlo calculations of the
exchange-correlation energy of the 3D finite-temperature homogeneous electron
gas in the warm-dense regime (r_{s} = (3/4\pi n)^{1/3} a_{B}^{-1} < 40 and
\Theta = T/T_{F} > 0.0625). In doing so, we construct a Pad\'{e} approximant
which collapses to Debye-H\"{u}ckel theory in the high-temperature, low-density
limit. Likewise, the zero-temperature limit matches the numerical results of
ground-state quantum Monte Carlo, as well as analytical results in the
high-density limit.


title:
An independent constraint on the secular rate of variation of the
  gravitational constant from pulsating white dwarfs

abstract:
  A secular variation of the gravitational constant modifies the structure and
evolutionary time scales of white dwarfs. Using an state-of-the-art stellar
evolutionary code and an up-to-date pulsational code we compute the effects of
a secularly varying $G$ on the pulsational properties of variable white dwarfs.
Comparing the the theoretical results obtained taking into account the effects
of a running $G$ with the observed periods and measured rates of change of the
periods of two well studied pulsating white dwarfs, G117--B15A and R548, we
place constraints on the rate of variation of Newton's constant. We derive an
upper bound $\dot G/G\sim -1.8\times 10^{-10}$ yr$^{-1}$ using the variable
white dwarf G117--B15A, and $\dot G/G\sim -1.3\times 10^{-10}$ yr$^{-1}$ using
R548. Although these upper limits are currently less restrictive than those
obtained using other techniques, they can be improved in a future measuring the
rate of change of the period of massive white dwarfs.


title: Comments on multibrane solutions in cubic superstring field theory

abstract:
  In a previous paper, we have studied multi-brane solutions in the context of
cubic superstring field theory. The kinetic term of the action was computed for
these multi-brane solutions, and for the evaluation of the energy, the equation
of motion contracted with the solutions itself was simply assumed to be
satisfied. In this paper, we compute the cubic term of the action and discuss
the validity of the previous assumption. Additionally, we evaluate the
Ellwood's gauge invariant observable.