title:
Quantification of uncertainty from high-dimensional scattered data via
  polynomial approximation

abstract:
  This paper discusses a methodology for determining a functional
representation of a random process from a collection of scattered pointwise
samples. The present work specifically focuses onto random quantities lying in
a high dimensional stochastic space in the context of limited amount of
information. The proposed approach involves a procedure for the selection of an
approximation basis and the evaluation of the associated coefficients. The
selection of the approximation basis relies on the a priori choice of the
High-Dimensional Model Representation format combined with a modified Least
Angle Regression technique. The resulting basis then provides the structure for
the actual approximation basis, possibly using different functions, more
parsimonious and nonlinear in its coefficients. To evaluate the coefficients,
both an alternate least squares and an alternate weighted total least squares
methods are employed. Examples are provided for the approximation of a random
variable in a high-dimensional space as well as the estimation of a random
field. Stochastic dimensions up to 100 are considered, with an amount of
information as low as about 3 samples per dimension, and robustness of the
approximation is demonstrated w.r.t. noise in the dataset. The computational
cost of the solution method is shown to scale only linearly with the
cardinality of the a priori basis and exhibits a (N_q)^s, 2 <= s <= 3,
dependence with the number N_q of samples in the dataset. The provided
numerical experiments illustrate the ability of the present approach to derive
an accurate approximation from scarce scattered data even in the presence of
noise.


title:
Ill-posedness of the incompressible Navier-Stokes equations in
  $\dot{F}^{-1,q}_{\infty}({R}^3)$

abstract:
  In this paper, authors show the ill-posedness of 3D incompressible
Navier-Stokes equations in the critical Triebel-Lizorkin spaces $
\dot{F}^{-1,q}_{\infty} (\mathbb{R}^3) $ for any $ q>2 $ in the sense that
arbitrarily small initial data of $ \dot{F}^{-1,q}_{\infty}(\mathbb{R}^3) $ can
lead the corresponding solution to become arbitrarily large after an
arbitrarily short time. In view of the well-posedness of 3D-incompressible
Navier-Stokes equations in $ BMO^{-1} $ (i.e. the Triebel-Lizorkin space $
\dot{F}^{-1,2}_{\infty}(\mathbb{R}^3) $) by Koch and Tataru, our work completes
a dichotomy of well-posedness and ill-posedness in the Triebel-Lizorkin space
framework depending on $ q=2 $ or $ q>2 $.


title: On Maximum Differential Coloring of Planar Graphs

abstract:
  We study the \emph{maximum differential coloring problem}, where the vertices
of an $n$-vertex graph must be labeled with distinct numbers ranging from $1$
to $n$, so that the minimum absolute difference between two labels of any two
adjacent vertices is maximized. As the problem is \NPH for general
graphs~\cite{leung1984}, we consider planar graphs and subclasses thereof. We
initially prove that the maximum differential coloring problem remains \NPH,
even for planar graphs. Then, we present tight bounds for regular caterpillars
and spider graphs. Using these new bounds, we prove that the Miller-Pritikin
labeling scheme~\cite{miller89} for forests is optimal for regular caterpillars
and for spider graphs. Finally, we describe close-to-optimal differential
coloring algorithms for general caterpillars and biconnected triangle-free
outer-planar graphs.


title: Two signs of a Schwinger term in a commutator of fermionic currents

abstract:
  We consider central extensions of two dimensional abelian current algebra and
Virasoro algebra and see that the sign of the Schwinger term changes if we
arrange the Fourier modes of the fermion in the commutator in the order
opposite to the normal. We argue that this is permissible in the case of
fermions, but not in the case of bosons.


title:
Deterministic macroscopic quantum superpositions of motion via quadratic
  optomechanical coupling

abstract:
  We propose a scheme to prepare macroscopic quantum superpositions of motion
in optomachanical nano- or micromechanical oscillators quadratically coupled to
an intracavity field. The nonlinear optomechanical coupling leads to an
effective degenerate three-wave mixing interaction between the mechanical and
cavity modes. The quantum superpositions result from the combined effects of
the interaction and cavity dissipation. We show analytically and confirm
numerically that various deterministic quantum superpositions can be achieved,
depending on initial mechanical state. The effect of mechanical damping is also
studied in detail via the negativity of the Wigner function. The present scheme
can be realized in various optomechanical systems with current technology.


title: Continuous-time Infinite Dynamic Topic Models

abstract:
  Topic models are probabilistic models for discovering topical themes in
collections of documents. In real world applications, these models provide us
with the means of organizing what would otherwise be unstructured collections.
They can help us cluster a huge collection into different topics or find a
subset of the collection that resembles the topical theme found in an article
at hand.
  The first wave of topic models developed were able to discover the prevailing
topics in a big collection of documents spanning a period of time. It was later
realized that these time-invariant models were not capable of modeling 1) the
time varying number of topics they discover and 2) the time changing structure
of these topics. Few models were developed to address this two deficiencies.
The online-hierarchical Dirichlet process models the documents with a time
varying number of topics. It varies the structure of the topics over time as
well. However, it relies on document order, not timestamps to evolve the model
over time. The continuous-time dynamic topic model evolves topic structure in
continuous-time. However, it uses a fixed number of topics over time.
  In this dissertation, I present a model, the continuous-time infinite dynamic
topic model, that combines the advantages of these two models 1) the
online-hierarchical Dirichlet process, and 2) the continuous-time dynamic topic
model. More specifically, the model I present is a probabilistic topic model
that does the following: 1) it changes the number of topics over continuous
time, and 2) it changes the topic structure over continuous-time.
  I compared the model I developed with the two other models with different
setting values. The results obtained were favorable to my model and showed the
need for having a model that has a continuous-time varying number of topics and
topic structure.


title: Performance Limits for Field Effect Transistors as Terahertz Detectors

abstract:
  We present estimates of the performance limits of terahertz detectors based
on the field effect transistors (FET) in the regime of broadband detection. The
maximal responsivity is predicted for short-channel FETs in the subthreshold
regime. We also calculate the conversion efficiency Q of the device defined as
the ratio of the power dissipated by radiation-induced dc current to the THz
dissipated power. We show that Q has an absolute maximum as a function of two
variables: the power and the frequency of the incoming radiation. The maximal
value of Q is on the order of 10%


title: Adaptive Control in Swarm Robotics

abstract:
  Swarm robotic systems are mainly inspired by swarms of socials insects and
the collective emergent behavior that arises from their cooperation at the
lower lever. Despite the limited sensory ability, computational power, and
communication means of each swarm member, the swarm as a group manages to
achieve difficult tasks such as searching for food in terrains with obstacles
that individual robots cannot achieve in isolation of the other group members.
Moreover, such tasks are usually achieved without having information sharing
capabilities at the swarm level or having a centralized decision making system.
In this report, I survey the state of the field of applying adaptive control
method to increase swarm robotic systems robustness to the failure of
individual robots, and increase its efficiency in performing its task. A few
techniques for the division of labor problem are briefly presented while one of
them is given in more detail. A discussion of the advantages and disadvantages
of this system is given and suggestions of potential improvements that can be
made to the system are presented.


title:
Spin mixing conductance at a well-controlled platinum/yttrium iron
  garnet interface

abstract:
  A platinum (Pt)/yttrium iron garnet (YIG) bilayer system with a
well-controlled interface has been developed; spin mixing conductance at the
Pt/YIG interface has been studied. Crystal perfection at the interface is
experimentally demonstrated to contribute to large spin mixing conductance. The
spin mixing conductance is obtained to be $1.3\times10^{18} \rm{m^{-2}}$ at the
well-controlled Pt/YIG interface, which is close to a theoretical prediction.


title: On Concept of Mechanical System

abstract:
  The paper gives a screw axiomatics of rational mechanics, namely:
  1. introduces the main measures of mechanics: the mass measure, the scalar
and (vector) screw measures of motion, the (vector) screw measure of impressed
action, the increment velocity of the vector measure of motion, the (vector)
screw measure of constraint action;
  2. postulates the (stronger) local integral form of conservation law for the
vector measuare of motion (fundamental principle of dynamics), and
  3. defines the central concept of rational mechanics {mechanical system being
realized in the form of all classical mechanical systems (mass-points, rigid
bodies, continua, point-bodies, etc.).
  The presentation is based on new notions of vector calculus -- homogeneous
and inhomogeneous vector and tensor slider-functions and screw measures.


title:
Secondary implementation of interactive engagement teaching techniques:
  Choices and challenges in a Gulf Arab context

abstract:
  We report on a "Collaborative Workshop Physics" instructional strategy to
deliver the first IE calculus-based physics course at Khalifa University, UAE.
To these authors' knowledge, this is the first such course on the Arabian
Peninsula using PER-based instruction. A brief history of general university
and STEM teaching in the UAE is given. We present this secondary implementation
(SI) as a case study of a novel context and use it to determine if PER-based
instruction can be successfully implemented far from the cultural context of
the primary developer and, if so, how might such SIs differ from SIs within the
US. With these questions in view, a pre-reform baseline of MPEX, FCI, course
exam and English language proficiency data are used to design a hybrid
implementation of Cooperative Group Problem Solving. We find that for students
with high English proficiency, normalized gain on FCI improves from <g> =
0.16+/-0.10 pre- to <g> = 0.47+/-0.08 post-reform, indicating successful SI. We
also find that <g> is strongly modulated by language proficiency and discuss
likely causes. Regardless of language skill, problem-solving skill is also
improved and course DFW rates drop from 50% to 24%. In particular, we find
evidence in post-reform student interviews that prior classroom experiences,
and not broader cultural expectations about education, are the more significant
cause of expectations at odds with the classroom norms of well-functioning
PER-based instruction. This result is evidence that PER-based innovations can
be implemented across great changes in cultural context, provided that the
method is thoughtfully adapted in anticipation of context and culture-specific
student expectations. This case study should be valuable for future reforms at
other institutions, both in the Gulf Region and developing world, facing
similar challenges involving SI of PER-based instruction outside the US.


title: The Relativity Concept Inventory: development, analysis and results

abstract:
  We report on a concept inventory for special relativity: the development
process, data analysis methods, and results from an introductory relativity
class. The Relativity Concept Inventory tests understanding of kinematic
relativistic concepts. An unusual feature is confidence testing for each
question. This can provide additional information; for example high confidence
correlated with incorrect answers suggests a misconception. A novel aspect of
our data analysis is the use of Monte Carlo simulations to determine the
significance of correlations. This approach is particularly useful for small
sample sizes, such as ours. Our results include a gender bias that was not
present in other assessment, similar to that reported for the Force Concept
Inventory.


title: Hattori-Stallings trace and character

abstract:
  It is shown that Hattori-Stallings trace induces a homomorphism of abelian
groups, called Hattori-Stallings character, from the $K_1$-group of
endomorphisms of the perfect derived category of an algebra to its zero-th
Hochschild homology, which provides a new proof of Igusa-Liu-Paquette Theorem,
i.e., the strong no loop conjecture for finite-dimensional elementary algebras,
on the level of complexes. Moreover, the Hattori-Stallings traces of projective
bimodules and one-sided projective bimodules are studied, which provides
another proof of Igusa-Liu-Paquette Theorem on the level of modules.


title: Using Artificial Intelligence Models in System Identification

abstract:
  Artificial Intelligence (AI) techniques are known for its ability in tackling
problems found to be unyielding to traditional mathematical methods. A recent
addition to these techniques are the Computational Intelligence (CI) techniques
which, in most cases, are nature or biologically inspired techniques. Different
CI techniques found their way to many control engineering applications,
including system identification, and the results obtained by many researchers
were encouraging. However, most control engineers and researchers used the
basic CI models as is or slightly modified them to match their needs.
Henceforth, the merits of one model over the other was not clear, and full
potential of these models was not exploited.
  In this research, Genetic Algorithm (GA) and Particle Swarm Optimization
(PSO) methods, which are different CI techniques, are modified to best suit the
multimodal problem of system identification. In the first case of GA, an
extension to the basic algorithm, which is inspired from nature as well, was
deployed by introducing redundant genetic material. This extension, which come
in handy in living organisms, did not result in significant performance
improvement to the basic algorithm. In the second case, the Clubs-based PSO
(C-PSO) dynamic neighborhood structure was introduced to replace the basic
static structure used in canonical PSO algorithms. This modification of the
neighborhood structure resulted in significant performance of the algorithm
regarding convergence speed, and equipped it with a tool to handle multimodal
problems.
  To understand the suitability of different GA and PSO techniques in the
problem of system identification, they were used in an induction motor's
parameter identification problem. The results enforced previous conclusions and
showed the superiority of PSO in general over the GA in such a multimodal
problem.


title:
Astrometric mock observations for determining the local dark matter
  density

abstract:
  To determine the local dark matter density (LDMD) of the solar system is a
classical problem in astronomy. Recently, a novel method of determining the
LDMD from stellar distribution and vertical velocity dispersion profiles
perpendicular to the Galactic plane was devised. This method has the advantage
of abolishing conventional approximations and using only a few assumptions. Our
aims are to carefully scrutinize this method and to examine influences by
uncertainties of astrometric observations. We discuss how the determinations of
the LDMD vary with observational precisions on parallax, proper motion, and
line-of-sight velocity measurements. To examine the influences by the
observational imprecision, we created mock observation data for stars that are
dynamical tracers based on an analytical galaxy model and applied parametrized
observational errors to the mock data. We evaluated the accuracy of determining
the LDMD by applying the method to the mock data. In addition, we estimated a
sample size and observational precision required to determine the LDMD with
accuracy. We find that the method is capable of determining the LDMD with
accuracy if the sample size and observational precisions are satisfactory. The
random errors of parallaxes and proper motions can cause systematic
overestimation of the LDMD. We estimate the required precisions of the parallax
measurements to be approximately 0.1-0.3 milliarcseconds at 1 kpc away from the
Sun; the proper motion precisions do not seem to be as important as the
parallaxes. From these results, we expect that using the Hipparcos catalog
would overestimate the LDMD because of the imprecise parallax measurements if
this method is applied; however, we emphasize the capability of the method. We
expect that Gaia will provide data precise enough to determine the LDMD.


title:
The influence of boundary conditions on the contact problem in a 3D
  Navier-Stokes Flow

abstract:
  We consider the free fall of a sphere above a wall in a viscous
incompressible fluid. We investigate the influence of boundary conditions on
the finite-time occurrence of contact between the sphere and the wall. We prove
that slip boundary conditions enable to circumvent the "no-collision" paradox
associated with no-slip boundary conditions. We also examine the case of mixed
boundary conditions.


title: Community Detection in Random Networks

abstract:
  We formalize the problem of detecting a community in a network into testing
whether in a given (random) graph there is a subgraph that is unusually dense.
We observe an undirected and unweighted graph on N nodes. Under the null
hypothesis, the graph is a realization of an Erd\"os-R\'enyi graph with
probability p0. Under the (composite) alternative, there is a subgraph of n
nodes where the probability of connection is p1 > p0. We derive a detection
lower bound for detecting such a subgraph in terms of N, n, p0, p1 and exhibit
a test that achieves that lower bound. We do this both when p0 is known and
unknown. We also consider the problem of testing in polynomial-time. As an
aside, we consider the problem of detecting a clique, which is intimately
related to the planted clique problem. Our focus in this paper is in the
quasi-normal regime where n p0 is either bounded away from zero, or tends to
zero slowly.


title: Properties Of The Classical Action Of Quantum Gravity

abstract:
  The classical action of quantum gravity, determined by renormalization,
contains infinitely many independent couplings and can be expressed in
different perturbatively equivalent ways. We organize it in a convenient form,
which is based on invariants constructed with the Weyl tensor. We show that the
FLRW metrics are exact solutions of the field equations in arbitrary
dimensions, and so are all locally conformally flat solutions of the Einstein
equations. Moreover, expanding the metric tensor around locally conformally
flat backgrounds the quadratic part of the action is free of higher
derivatives. Black-hole solutions of Schwarzschild and Kerr type are modified
in a non-trivial way. We work out the first corrections to their metrics and
study their properties.


title: Representations of the Yokonuma-Temperley-Lieb algebra

abstract:
  We determine the representations of the Yokonuma-Temperley-Lieb algebra,
which is defined as a quotient of the Yokonuma-Hecke algebra by generalising
the construction of the classical Temperley-Lieb algebra.


title:
Periodic correlation structures in bacterial and archaeal complete
  genomes

abstract:
  The periodic transference of nucleotide strings in bacterial and archaeal
complete genomes is investigated by using the metric representation and the
recurrence plot method. The generated periodic correlation structures exhibit
four kinds of fundamental transferring characteristics: a single increasing
period, several increasing periods, an increasing quasi-period and almost
noincreasing period. The mechanism of the periodic transference is further
analyzed by determining all long periodic nucleotide strings in the bacterial
and archaeal complete genomes and is explained as follows: both the repetition
of basic periodic nucleotide strings and the transference of non-periodic
nucleotide strings would form the periodic correlation structures with
approximately the same increasing periods.


title:
Effects of Marangoni numbers on thermocapillary drop migration: constant
  for quasi-steady state?

abstract:
  The overall {\it steady}-state energy balance with two phases in a flow
domain requires that the change in energy of the domain is equal to the
difference between the total energy entering the domain and that leaving the
domain. From the condition, the integral thermal flux across the surface is
studied for a {\it steady} thermocapillary drop migration in a flow field with
uniform temperature gradient at small and large Marangoni (Reynolds) numbers.
The drop is assumed to have only a slight axisymmetric deformation from a
sphere. It is identified that a conservative/nonconservative integral thermal
flux across the surface in the {\it steady} thermocapillary drop migration at
small/large Marangoni (Reynolds) numbers. The conservative flux confirms the
assumption of {\it quasi-steady} state in the thermocapillary drop migration at
small Marangoni (Reynolds) numbers. The nonconservative flux may well result
from the invalid assumption of {\it quasi-steady} state, which indicates that
the thermocapillary drop migration at large Marangoni (Reynolds) numbers cannot
reach {\it steady} state and is thus a {\it unsteady} process.


title: Polar coordinate lattice Boltzmann modeling of compressible flows

abstract:
  We present a polar coordinate lattice Boltzmann kinetic model for
compressible flows. A method to recover the continuum distribution function
from the discrete distribution function is indicated. Within the model, a
hybrid scheme being similar to, but different from, the operator splitting is
proposed. The temporal evolution is calculated analytically, and the convection
term is solved via a modifiedWarming-Beam (MWB) scheme.Within theMWB scheme a
suitable switch function is introduced. The current model works not only for
subsonic flows but also for supersonic flows. It is validated and verified via
the following well-known benchmark tests: (i) the rotational flow, (ii) the
stable shock tube problem, (iii) the Richtmyer-Meshkov (RM) instability, and
(iv) the Kelvin-Helmholtz instability. As an original application, we studied
the nonequilibrium characteristics of the system around three kinds of
interfaces, the shock wave, the rarefaction wave, and the material interface,
for two specific cases. In one of the two cases, the material interface is
initially perturbed, and consequently the RMinstability occurs. It is found
that themacroscopic effects due to deviating from thermodynamic equilibrium
around thematerial interface differ significantly from those around the
mechanical interfaces. The initial perturbation at the material interface
enhances the coupling of molecular motions in different degrees of freedom. The
amplitude of deviation from thermodynamic equilibrium around the shock wave is
much higher than those around the rarefaction wave and material interface. By
comparing each component of the high-order moments and its value in
equilibrium, we can draw qualitatively the main behavior of the actual
distribution function.


title: Taylor approximations of operator functions

abstract:
  This survey on approximations of perturbed operator functions addresses
recent advances and some of the successful methods.


title:
Transformation of Zernike coefficients: A Fourier based method for
  scaled, translated and rotated wavefront apertures

abstract:
  This paper studies the effects on Zernike coefficients of aperture scaling,
translation and rotation, when a given aberrated wavefront is described on the
Zernike polynomial basis. It proposes a new analytical method for computing the
matrix that enables the building of the transformed Zernike coefficients from
the original ones. The technique is based on the properties of Zernike
polynomials Fourier Transform and, in the case of a full aperture without
central obstruction, the coefficients of the matrix are given in terms of
integrals of Bessel functions. The integral formulas are exact and do not
depend on any specific ordering of the polynomials.


title:
Spin-polarized Shapiro steps and spin-precession-assisted multiple
  Andreev reflection

abstract:
  We investigate the charge and spin transport of a voltage-biased
superconducting point contact coupled to a nanomagnet. The magnetization of the
nanomagnet is assumed to precess with the Larmor frequency, $\omega_L$, due to
ferromagnetic resonance. The interplay between the ac Josephson current and the
magnetization dynamics leads to spin-polarized Shapiro steps at voltages
$|V|=\hbar \omega_L/2en$ for $n=1,2,...$ and the subharmonic steps with $n>1$
are a consequence of multiple Andreev reflection (MAR). Moreover, the
spin-precession-assisted MAR generates quasiparticle scattering amplitudes
that, due to interference, lead to current-voltage characteristics of the dc
charge and spin currents with subharmonic gap structures displaying an even-odd
effect.


title: Theory of giant magnetoresistance at misfit interfaces

abstract:
  We study theoretically the resistance at the interface between the two planar
systems with different lattice constants a and b. The resistance and the effect
of the magnetic field depends sensitively on the ratio a/b. The size of the
enlarged unit cell $\lambda = n_Aa = n_Bb$ ($n_A$, $n_B$: integers) is the
crucial quantity, and the magnetic flux penetrating this enlarged unit cell
determines the oscillation of the resistance. Therefore, the magnetoresistance
is very much enhanced at (nearly) incommensurate relation between a and b.


title:
Reconstructing multisets over commutative groupoids and affine functions
  over nonassociative semirings

abstract:
  A reconstruction problem is formulated for multisets over commutative
groupoids. The cards of a multiset are obtained by replacing a pair of its
elements by their sum. Necessary and sufficient conditions for the
reconstructibility of multisets are determined. These results find an
application in a different kind of reconstruction problem for functions of
several arguments and identification minors: classes of linear or affine
functions over nonassociative semirings are shown to be weakly reconstructible.
Moreover, affine functions of sufficiently large arity over finite fields are
reconstructible.


title:
The Breton-Manko equatorially antisymmetric binary configuration
  revisited

abstract:
  The Breton-Manko solution for two identical counter-rotating Kerr-Newman
charged masses is rewritten in the physical parametrization involving Komar
quantities. The new form of the solution turns out to be very convenient for
verifying that the black-hole sector of the Bret\'on-Manko binary configuration
saturates a recent geometric inequality for interacting black holes with struts
discovered by Gabach Clement.


title: Syllogisms in Rudimentary Linear Logic, Diagrammatically

abstract:
  We present a reading of the traditional syllogistics in a fragment of the
propositional intuitionistic multiplicative linear logic and prove that with
respect to a diagrammatic logical calculus that we introduced in a previous
paper, a syllogism is provable in such a fragment if and only if it is
diagrammatically provable. We extend this result to syllogistics with
complemented terms \`a la De Morgan, with respect to a suitable extension of
the diagrammatic reasoning system for the traditional case and a corresponding
reading of such De Morgan style syllogistics in the previously referred to
fragment of linear logic.


title: Muon-induced background in the EDELWEISS dark matter search

abstract:
  A dedicated analysis of the muon-induced background in the EDELWEISS dark
matter search has been performed on a data set acquired in 2009 and 2010. The
total muon flux underground in the Laboratoire Souterrain de Modane (LSM) was
measured to be $\Phi_{\mu}=(5.4\pm 0.2 ^{+0.5}_{-0.9})$\,muons/m$^2$/d. The
modular design of the muon-veto system allows the reconstruction of the muon
trajectory and hence the determination of the angular dependent muon flux in
LSM. The results are in good agreement with both MC simulations and earlier
measurements. Synchronization of the muon-veto system with the phonon and
ionization signals of the Ge detector array allowed identification of
muon-induced events. Rates for all muon-induced events $\Gamma^{\mu}=(0.172 \pm
0.012)\, \rm{evts}/(\rm{kg \cdot d})$ and of WIMP-like events $\Gamma^{\mu-n} =
0.008^{+0.005}_{-0.004}\, \rm{evts}/(\rm{kg \cdot d})$ were extracted. After
vetoing, the remaining rate of accepted muon-induced neutrons in the
EDELWEISS-II dark matter search was determined to be $\Gamma^{\mu-n}_{\rm
irred} < 6\cdot 10^{-4} \, \rm{evts}/(\rm{kg \cdot d})$ at 90%\,C.L. Based on
these results, the muon-induced background expectation for an anticipated
exposure of 3000\,\kgd\ for EDELWEISS-3 is $N^{\mu-n}_{3000 kg\cdot d} < 0.6$
events.


title: The seven year Swift-XRT point source catalog (1SWXRT)

abstract:
  Swift is a multi-wavelength observatory specifically designed for gamma-ray
burst (GRB) astronomy that is operational since 2004. Swift is also a very
flexible multi-purpose facility that supports a wide range of scientific fields
such as active galactic nuclei, supernovae, cataclysmic variables, Galactic
transients, active stars and comets. The Swift X-ray Telescope (XRT) has
collected more than 150 Ms of observations in its first seven years of
operations. We present the list of all the X-ray point sources detected in XRT
imaging data taken in photon counting mode during the first seven years of
Swift operations. All these point-like sources, excluding the Gamma-Ray Bursts
(GRB), will be stored in a catalog publicly available (1SWXRT). We consider all
XRT observations with exposure time > 500 s taken in the period 2005-2011. Data
were reduced and analyzed with standard techniques and a list of detected
sources for each observation was produced. A careful visual inspection was
performed to remove extended, spurious and piled-up sources. Positions, count
rates, fluxes and the corresponding uncertainties were computed. We have
analyzed more than 35,000 XRT fields, with exposures ranging between 500 s and
100 ks, for a total exposure time of 140 Ms. The catalog includes ~ 89,000
entries, of which almost 85,000 are not affected by pile-up and are not GRBs.
Since many XRT fields were observed several times, we have a total of ~36,000
distinct celestial sources. We computed count rates in three energy bands:
0.3-10 keV (Full, or F), 0.3-3 keV (Soft, or S) and 2-10 keV (Hard, or H). Each
entry has a detection in at least one of these bands. In particular, we detect
~ 80,000, ~ 70,000 and ~ 25,500$ in the F, S and H band, respectively. Count
rates were converted into fluxes in the 0.5-10, 0.5-2 and 2-10 keV bands. Some
possible scientific uses of the catalog are also highlighted.


title: Coronal Mass Ejections Associated with Slow Long Duration Flares

abstract:
  It is well known that there is temporal relationship between coronal mass
ejections (CMEs) and associated flares. The duration of the acceleration phase
is related to the duration of the rise phase of a flare. We investigate CMEs
associated with slow long duration events (LDEs), i.e. flares with the long
rising phase. We determined the relationships between flares and CMEs and
analyzed the CME kinematics in detail. The parameters of the flares (GOES flux,
duration of the rising phase) show strong correlations with the CME parameters
(velocity, acceleration during main acceleration phase and duration of the CME
acceleration phase). These correlations confirm the strong relation between
slow LDEs and CMEs. We also analyzed the relation between the parameters of the
CMEs, i.e. a velocity, an acceleration during the main acceleration phase, a
duration of the acceleration phase, and a height of a CME at the end of the
acceleration phase. The CMEs associated with the slow LDEs are characterized by
high velocity during the propagation phase, with the median equal 1423 km/s. In
half of the analyzed cases, the main acceleration was low (a<300 m/s^2), which
suggests that the high velocity is caused by the prolongated acceleration phase
(the median for the duration of the acceleration phase is equal 90 minutes).
The CMEs were accelerated up to several solar radii (with the median 7 Rsun),
which is much higher than in typical impulsive CMEs. Therefore, slow LDEs may
potentially precede extremely strong geomagnetic storms. The analysis of slow
LDEs and associated CMEs may give important information for developing more
accurate space weather forecasts, especially for extreme events.


title: Damping of Quantum Vibrations Revealed in Deep Sub-barrier Fusion

abstract:
  We demonstrate that when two colliding nuclei approach each other, their
quantum vibrations are damped near the touching point. We show that this
damping is responsible for the fusion hindrance phenomena measured in the deep
sub-barrier fusion reactions. To show those, we for the first time apply the
random-phase-approximation (RPA) method to the two-body $^{16}$O + $^{16}$O and
$^{40}$Ca + $^{40}$Ca systems. We calculate the octupole transition strengths
for the two nuclei adiabatically approaching each other. The calculated
transition strength drastically decreases near the touching point, strongly
suggesting the vanishing of the quantum couplings between the relative motion
and the vibrational intrinsic degrees of freedom of each nucleus. Based on this
picture, we also calculate the fusion cross section for the $^{40}$Ca +
$^{40}$Ca system using the coupled-channel method with the damping factor
simulating the vanishing of the couplings. The calculated results reproduce
well the experimental data, indicating that the smooth transition from the
sudden to adiabatic processes indeed occurs in the deep sub-barrier fusion
reactions.


title: Projections of orbital measures, Gelfand-Tsetlin polytopes, and splines

abstract:
  The unitary group U(N) acts by conjugations on the space H(N) of NxN
Hermitian matrices, and every orbit of this action carries a unique invariant
probability measure called an orbital measure. Consider the projection of the
space H(N) onto the real line assigning to an Hermitian matrix its (1,1)-entry.
Under this projection, the density of the pushforward of a generic orbital
measure is a spline function with N knots. This fact was pointed out by Andrei
Okounkov in 1996, and the goal of the paper is to propose a multidimensional
generalization. Namely, it turns out that if instead of the (1,1)-entry we cut
out the upper left matrix corner of arbitrary size KxK, where K=2,...,N-1, then
the pushforward of a generic orbital measure is still computable: its density
is given by a KxK determinant composed from one-dimensional splines. The result
can also be reformulated in terms of projections of the Gelfand-Tsetlin
polytopes.


title:
Spontaneous fission half-lives of heavy and superheavy nuclei within a
  generalized liquid drop model

abstract:
  We systematically calculate the spontaneous fission half-lives for heavy and
superheavy nuclei between U and Fl isotopes. The spontaneous fission process is
studied within the semi-empirical WKB approximation. The potential barrier is
obtained using a generalized liquid drop model, taking into account the nuclear
proximity, the mass asymmetry, the phenomenological pairing correction, and the
microscopic shell correction. Macroscopic inertial-mass function has been
employed for the calculation of the fission half-life. The results reproduce
rather well the experimental data. Relatively long half-lives are predicted for
many unknown nuclei, sufficient to detect them if synthesized in a laboratory.


title: Asymptotics of Discrete Chebyshev Polynomials

abstract:
  The discrete Chebyshev polynomials $t_n(x,N)$ are orthogonal with respect to
a distribution, which is a step function with jumps one unit at the points
$x=0,1,\cdots, N-1$, $N$ being a fixed positive integer. By using a double
integral representation, we have recently obtained asymptotic expansions for
$t_{n}(aN,N+1)$ in the double scaling limit, namely, $N\rightarrow\infty$ and
$n/N\rightarrow b$, where $b\in (0,1)$ and $a\in(-\infty,\infty)$; see [Studies
in Appl. Math. \textbf{128} (2012), 337-384]. In the present paper, we continue
to investigate the behaviour of these polynomials when the parameter $b$
approaches the endpoints of the interval $(0,1)$. While the case $b\rightarrow
1$ is relatively simple (since it is very much like the case when $b$ is
fixed), the case $b\rightarrow 0$ is quite complicated. The discussion of the
latter case is divided into several subcases, depending on the quantities $n$,
$x$ and $xN/n^2$, and different special functions have been used as
approximants, including Airy, Bessel and Kummer functions.


title: Symmetries of trivial systems of ODEs of mixed order

abstract:
  We compute symmetry algebras of a system of two equations y^(k)=z^(l)=0,
where 2<=k<l. It appears that there are many ways to convert such system of
ODEs to an exterior differential system. They lead to different series of
finite-dimensional symmetry algebras. For example, for (k,l)=(2,3) we get two
non-isomorphic symmetry algebras of the same dimension. We explore how these
symmetry algebras are related to both Sternberg prolongation of G-structures
and Tanaka prolongation of graded nilpotent Lie algebras.
  Surprisingly, the case (k,l)=(2,3) provides an example of a linear subalgebra
g in gl(5,R) such that the Sternberg prolongations of g and g^t are both of the
same dimension, but are non-isomorphic.
  We also discuss the non-linear case and the link with flag structures on
smooth manifolds.


title: Open End Correction for Flanged Circular Tube from the Diffusion Process

abstract:
  In the physics lessons on waves and resonance phenomena in high school and
college, we usually consider sound waves in a tube with open or closed ends
\cite{ResnikHalliday}. However, it is well known that we need a tube with open
end correction $\Delta L$. The correction for a flanged circular tube was first
given by Rayleigh \cite{Rayleigh} and experimentally checked by several authors
\cite{exp}. In this paper, we show the different methods of obtaining the end
correction for a circular tube by a diffusion process.


title: A literature survey of low-rank tensor approximation techniques

abstract:
  During the last years, low-rank tensor approximation has been established as
a new tool in scientific computing to address large-scale linear and
multilinear algebra problems, which would be intractable by classical
techniques. This survey attempts to give a literature overview of current
developments in this area, with an emphasis on function-related tensors.


title:
A young protoplanet candidate embedded in the circumstellar disk of
  HD100546

abstract:
  We present high-contrast observations of the circumstellar environment of the
Herbig Ae/Be star HD100546. The final 3.8 micron image reveals an emission
source at a projected separation of 0.48"+-0.04" (corresponding to ~47+-4 AU at
a position angle of 8.9+-0.9 degree. The emission appears slightly extended
with a point source component with an apparent magnitude of 13.2+-0.4 mag. The
position of the source coincides with a local deficit in polarization fraction
in near-infrared polarimetric imaging data, which probes the surface of the
well-studied circumstellar disk of HD100546. This suggests a possible physical
link between the emission source and the disk. Assuming a disk inclination of
~47 degree the de-projected separation of the object is ~68 AU. Assessing the
likelihood of various scenarios we favor an interpretation of the available
high-contrast data with a planet in the process of forming. Follow-up
observations in the coming years can easily distinguish between the different
possible scenarios empirically. If confirmed, HD100546 "b" would be a unique
laboratory to study the formation process of a new planetary system, with one
giant planet currently forming in the disk and a second planet possibly
orbiting in the disk gap at smaller separations.


title: Half Metallic Bilayer Graphene

abstract:
  Charge neutral bilayer graphene has a gapped ground state as transport
experiments demonstrate. One of the plausible such ground states is layered
antiferromagnetic spin density wave (LAF) state, where the spins in top and
bottom layers have same magnitude with opposite directions. We propose that
lightly charged bilayer graphene in an electric field perpendicular to the
graphene plane may be a half metal as a consequence of the inversion and
particle-hole symmetry broken in the LAF state. We show this explicitly by
using a mean field theory on a 2-layer Hubbard model for the bilayer graphene.


title:
Excitation of highly charged hydrogen-like ions by the impact of
  equivelocity electrons and protons: a comparative study

abstract:
  We consider excitation of highly charged hydrogen-like ions by the impact of
equivelocity electrons and protons. The kinetic energy of the protons is more
than three orders of magnitude larger than that of the equivelocity electrons.
It is shown, however, that despite this fact, the electrons can be much more
effective in inducing excitation at collision velocities (slightly) above the
threshold for electron impact excitation. The basic reason for this is the
strong distortion of the motion of the electron by the attractive field of the
nucleus of the highly charged ion.


title:
Wormholes and Time-Machines in Nonminimally Coupled Matter-Curvature
  Theories of Gravity

abstract:
  In this work we show the existence of traversable wormhole and time-machine
solutions in a modified theory of gravity where matter and curvature are
nonminimally coupled. Those solutions present a nontrivial redshift function
and exist even in the presence of ordinary matter which satisfies the dominant
energy condition.


title: Growing multiplex networks

abstract:
  We propose a modeling framework for growing multiplexes where a node can
belong to different networks. We define new measures for multiplexes and we
identify a number of relevant ingredients for modeling their evolution such as
the coupling between the different layers and the arrival time distribution of
nodes. The topology of the multiplex changes significantly in the different
cases under consideration, with effects of the arrival time of nodes on the
degree distribution, average shortest paths and interdependence.


title: The Complexity of Simultaneous Geometric Graph Embedding

abstract:
  Given a collection of planar graphs $G_1,\dots,G_k$ on the same set $V$ of
$n$ vertices, the simultaneous geometric embedding (with mapping) problem, or
simply $k$-SGE, is to find a set $P$ of $n$ points in the plane and a bijection
$\phi: V \to P$ such that the induced straight-line drawings of $G_1,\dots,G_k$
under $\phi$ are all plane.
  This problem is polynomial-time equivalent to weak rectilinear realizability
of abstract topological graphs, which Kyn\v{c}l (doi:10.1007/s00454-010-9320-x)
proved to be complete for $\exists\mathbb{R}$, the existential theory of the
reals. Hence the problem $k$-SGE is polynomial-time equivalent to several other
problems in computational geometry, such as recognizing intersection graphs of
line segments or finding the rectilinear crossing number of a graph.
  We give an elementary reduction from the pseudoline stretchability problem to
$k$-SGE, with the property that both numbers $k$ and $n$ are linear in the
number of pseudolines. This implies not only the $\exists\mathbb{R}$-hardness
result, but also a $2^{2^{\Omega (n)}}$ lower bound on the minimum size of a
grid on which any such simultaneous embedding can be drawn. This bound is
tight. Hence there exists such collections of graphs that can be simultaneously
embedded, but every simultaneous drawing requires an exponential number of bits
per coordinates. The best value that can be extracted from Kyn\v{c}l's proof is
only $2^{2^{\Omega (\sqrt{n})}}$.


title: Explicit construction of a dynamic Bessel bridge of dimension 3

abstract:
  Given a deterministically time-changed Brownian motion $Z$ starting from 1,
whose time-change $V(t)$ satisfies $V(t) > t$ for all $t > 0$, we perform an
explicit construction of a process $X$ which is Brownian motion in its own
filtration and that hits zero for the first time at $V(\tau)$, where $\tau :=
\inf\{t>0: Z_t =0\}$. We also provide the semimartingale decomposition of $X$
under the filtration jointly generated by $X$ and $Z$. Our construction relies
on a combination of enlargement of filtration and filtering techniques. The
resulting process $X$ may be viewed as the analogue of a 3-dimensional Bessel
bridge starting from 1 at time 0 and ending at 0 at the random time $V(\tau)$.
We call this {\em a dynamic
  Bessel bridge} since $V(\tau)$ is not known in advance.
  Our study is motivated by insider trading models with default risk, where the
insider observes the firm's value continuously on time.


title: Stellar parallax in the Neo-Tychonian planetary system

abstract:
  The recent paper published in European Journal of Physics [1] aimed to
demonstrate the kinematical and dynamical equivalence of heliocentric and
geocentric systems. The work is performed in the Neo-Tychonian system, with key
assumption that orbits of distant masses around the Earth are synchronized with
the Sun's orbit. Motion of Sun and Mars have been analysed, and the conclusion
was reached that the very fact of the accelerated motion of the Universe as a
whole produces the so-called "pseudo-potential" that not only explains the
origin of the pseudo-forces, but also the very motion of the celestial bodies
as seen from the static Earth. After the paper was published, the question was
raised if that same potential can explain the motion of the distant stars that
are not affected by the Sun's gravity (unlike Mars), and if it can be used to
reproduce the observation of the stellar parallax. The answer is found to be
positive.


title:
Order estimates of the best $n$-term orthogonal trigonometric
  approximations of the classes ${\cal F}_{q}^{\psi}$ of periodic functions in
  the integral metrics

abstract:
  We obtain order estimates in the spaces $L_p$ of the best $n$-term
trigonometric orthogonal approximations of the classes ${\cal F}_{q}^{\psi}$ of
periodic functions, whose Fourier coefficients decrease faster then any power
function. We also obtain order estimates of the quantities of approximations by
$n$-term Greedy approximants of such classes in the spaces $L_p$.


title: Presence Factor-Oriented Blog Summarization

abstract:
  The research that has been carried out on blogs focused on blog posts only,
ignoring the title of the blog page. Also, in summarization only a set of
representative sentences are extracted. Some analysis has been done and it has
been found that the blog post contains the content that is likely to be related
to the topic of the blog post. Thus, proposed system of summarization makes use
of title contained in a blog page. The approach makes use of the Presence
factor that indicates the presence of each term of the title in each sentence
of the blog post. This is a key feature because it considers those sentences as
more relevant for summarization that contain each of the term present in the
title. The system has been implemented and evaluated experimentally. The system
has shown promising results.


title: The distance to NGC1316 (Fornax A): yet another curious case

abstract:
  The distance of NGC1316, the brightest galaxy in Fornax, is an interesting
test for the cosmological distance scale. First, because Fornax is the 2nd
largest cluster of galaxies at <~25 Mpc after Virgo and, in contrast to Virgo,
has a small line-of-sight depth; and second, because NGC1316 is the galaxy with
the largest number of detected SNeIa, giving the opportunity to test the
consistency of SNeIa distances internally and against other indicators.
  We measure SBF mags in NGC1316 from ground and space-based imaging data,
providing a homogeneous set of measurements over a wide wavelength interval.
The SBF, coupled with empirical and theoretical calibrations, are used to
estimate the distance to the galaxy. We present the first B-band SBF
measurements of NGC1316 and use them together with the optical and near-IR SBF
data to analyze the properties of field stars.
  Our distance modulus m-M=31.59 +-0.05(stat) +-0.14(sys), when placed in a
consistent Cepheid distance scale, agrees with the results from other
indicators. However, our result is ~17% larger than the most recent estimate
based on SNeIa. Possible explanations for this disagreement are the
uncertainties on internal extinction, or calibration issues. Concerning the
stellar population analysis, we confirm earlier results from other indicators:
the field stars in NGC1316 are dominated by a solar metallicity, intermediate
age component. A substantial mismatch exists between B-band SBF models and
data, a behavior that can be accounted for by an enhanced percentage of hot
horizontal branch stars.
  Our study of the SBF distance to NGC1316, and the comparison with distances
from other indicators, raises some concern about the homogeneity between the
calibrations of different indicators. If not properly placed in the same
reference scale, significant differences can occur, with dramatic impact on the
cosmological distance ladder.


title: Orbital Evolution of 4179 Toutatis

abstract:
  Asteroid 1934 CT;1989 AC, well known as 4179 Toutatis, is an Apollo and
Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with
Jupiter and a 1:4 resonance with the Earth, and frequent close approaches to
the Earth. It is listed as a potential hazardous object (PHA). The aim of this
study is to investigate the possibility of 4179 Toutatis to be ejected from the
Solar System. This paper presents an orbital evolution of 4179 Toutatis in time
interval of ~300 kyr. Investigation of its orbital evolution is conducted by
using the Mercury subroutine package, where the gravitational perturbations of
eight major planets in the Solar System are considered. Over very short time
scales (~300 kyr) relative to the Solar System life time (~10 Gyr), the
asteroid 4179 Toutatis gave an example of chaotic motion that can cause
asteroid to move outward and may be followed by escaping from the Solar System.


title:
Search for 2\beta\ decays of 96Ru and 104Ru by ultra-low background HPGe
  gamma spectrometry at LNGS: final results

abstract:
  An experiment to search for double beta decay processes in 96Ru and 104Ru,
which are accompanied by gamma rays, has been realized in the underground Gran
Sasso National Laboratories of the I.N.F.N. (Italy). Ruthenium samples with
masses of about (0.5-0.7) kg were measured with the help of ultra-low
background high purity Ge gamma ray spectrometry. After 2162 h of data taking
the samples were deeply purified to reduce the internal contamination of 40K.
The last part of the data has been accumulated over 5479 h. New improved half
life limits on 2\beta+/\epsilon \beta+/2\epsilon\ processes in 96Ru have been
established on the level of 10^{20} yr, in particular for decays to the ground
state of 96Mo: T1/2(2\nu 2\beta+) > 1.4 10^{20} yr, T1/2(2\nu \epsilon\beta+) >
8.0 10^{19} yr and T1/2(0\nu 2K) > 1.0 10^{21} yr (all limits are at 90% C.L.).
The resonant neutrinoless double electron captures to the 2700.2 keV and 2712.7
keV excited states of 96Mo are restricted as: T1/2(0\nu KL) > 2.0 10^{20} yr
and T1/2(0\nu 2L) > 3.6 10^{20} yr, respectively. Various two neutrino and
neutrinoless 2\beta\ half lives of 96Ru have been estimated in the framework of
the QRPA approach. In addition, the T1/2 limit for 0\nu 2\beta- transitions of
104Ru to the first excited state of 104Pd has been set as > 6.5 10^{20} yr.


title: Fields and Laplacians on Quantum Geometries

abstract:
  In fundamentally discrete approaches to quantum gravity such as loop quantum
gravity, spin-foam models, group field theories or Regge calculus observables
are functions on discrete geometries. We present a bra-ket formalism of
function spaces and discrete calculus on abstract simplicial complexes equipped
with geometry and apply it to the mentioned theories of quantum gravity. In
particular we focus on the quantum geometric Laplacian and discuss as an
example the expectation value of the heat kernel trace from which the spectral
dimension follows.


title:
Logarithmic correlators or responses in non-relativistic analogues of
  conformal invariance

abstract:
  Recent developments on emergence of logarithmic terms in correlators or
response functions of models which exhibit dynamical symmetries analogous to
conformal invariance in not necessarily relativistic systems are reviewed. The
main examples of these are logarithmic Schr\"odinger-invariance and logarithmic
conformal Galilean invariance. Some applications of these ideas to statistical
physics are described.

categories: hep-th cond-mat.stat-mech math-ph math.MP


title: Unimodular Cosmological Space-times

abstract:
  Some cosmological solutions of the unimodular theory of gravity are studied.
These solutions can always be mapped to solutions of Einstein's general
relativity in an appropiate frame. Constant scalar potentials however do not
gravitate. Some physical consequences are pointed out.


title: Quantum Harmonic Black Holes

abstract:
  Inspired by the recent conjecture that black holes are condensates of
gravitons, we investigate a simple model for the black hole degrees of freedom
that is consistent both from the point of view of Quantum mechanics and of
General Relativity. Since the two perspectives should "converge" into a unified
picture for small, Planck size, objects, we expect our construction is a useful
step for understanding the physics of microscopic, quantum black holes. In
particular, we show that a harmonically trapped condensate gives rise to two
horizons, whereas the extremal case (corresponding to a remnant with vanishing
Hawking temperature) naturally falls out of its spectrum.


title: Simulating a dual beam combiner at SUSI for narrow-angle astrometry

abstract:
  The Sydney University Stellar Interferometer (SUSI) has two beam combiners,
i.e. the Precision Astronomical Visible Observations (PAVO) and the
Microarcsecond University of Sydney Companion Astrometry (MUSCA). The primary
beam combiner, PAVO, can be operated independently and is typically used to
measure properties of binary stars of less than 50 milliarc- sec (mas)
separation and the angular diameters of single stars. On the other hand, MUSCA
was recently installed and must be used in tandem with the for- mer. It is
dedicated for microarcsecond precision narrow-angle astrometry of close binary
stars. The performance evaluation and development of the data reduction
pipeline for the new setup was assisted by an in-house computer simulation tool
developed for this and related purposes. This paper describes the framework of
the simulation tool, simulations carried out to evaluate the performance of
each beam combiner and the expected astrometric precision of the dual beam
combiner setup, both at SUSI and possible future sites.


title: Scaling Laws for Planetary Dynamos

abstract:
  We propose new scaling laws for the properties of planetary dynamos. In
particular, the Rossby number, the magnetic Reynolds number, the ratio of
magnetic to kinetic energy, the Ohmic dissipation timescale and the
characteristic aspect ratio of the columnar convection cells are all predicted
to be power-law functions of two observable quantities: the magnetic dipole
moment and the planetary rotation rate. The resulting scaling laws constitute a
somewhat modified version of the scalings proposed in Christensen & Aubert
(2006) and Christensen (2010). The main difference is that, in view of the
small value of the Rossby number in planetary cores, we insist that the
nonlinear inertial term, (u.grad)u, is negligible. This changes the exponents
in the power-laws which relate the various properties of the fluid dynamo to
the planetary dipole moment and rotation rate. Our scaling laws are consistent
with the available numerical evidence.


title:
The union-closed sets conjecture almost holds for almost all random
  bipartite graphs

abstract:
  Frankl's union-closed sets conjecture states that in every finite
union-closed set of sets, there is an element that is contained in at least
half of the member-sets (provided there are at least two members). The
conjecture has an equivalent formulation in terms of graphs: In every bipartite
graph with least one edge, both colour classes contain a vertex belonging to at
most half of the maximal stable sets.
  We prove that, for every fixed edge-probability, almost every random
bipartite graph almost satisfies Frankl's conjecture.


title: Holonomy Operator and Quantization Ambiguities on Spinor Space

abstract:
  We construct the holonomy-flux operator algebra in the recently developed
spinor formulation of loop gravity. We show that, when restricting to
SU(2)-gauge invariant operators, the familiar grasping and Wilson loop
operators are written as composite operators built from the gauge-invariant
`generalized ladder operators' recently introduced in the U(N) approach to
intertwiners and spin networks. We comment on quantization ambiguities that
appear in the definition of the holonomy operator and use these ambiguities as
a toy model to test a class of quantization ambiguities which is present in the
standard regularization and definition of the Hamiltonian constraint operator
in loop quantum gravity.


title:
Electrostatics controls the formation of amyloid-like superstructures in
  protein aggregation

abstract:
  The possibility for proteins to aggregate in different superstructures, i.e.
large-scale polymorphism, has been widely observed, but an understanding of the
physico-chemical mechanisms behind it is still out of reach. Here we present a
theoretical model for the description of a generic aggregate formed from an
ensemble of charged proteins. The model predicts the formation of multi-fractal
structures with the geometry of the growth determined by the electrostatic
interactions between single proteins. The model predictions are successfully
verified in comparison with experimental curves for aggregate growth. The model
is general and is able to predict aggregate morphologies occurring both in vivo
and in vitro. Our findings provide for the first time a unifying and general
framework where the physical interactions between single proteins, the
aggregate morphology and the growth kinetics are connected into a single model
in excellent agreement with the experimental data.


title:
Multi-time Lagrangian 1-forms for families of B\"acklund
  transformations. Toda-type systems

abstract:
  General Lagrangian theory of discrete one-dimensional integrable systems is
illustrated by a detailed study of B\"acklund transformations for Toda-type
systems. Commutativity of B\"acklund transformations is shown to be equivalent
to consistency of the system of discrete multi-time Euler-Lagrange equations.
The precise meaning of the commutativity in the periodic case, when all maps
are double-valued, is established. It is shown that gluing of different
branches is governed by the so called superposition formulas. The closure
relation for the multi-time Lagrangian 1-form on solutions of the variational
equations is proved for all Toda-type systems. Superposition formulas are
instrumental for this proof. The closure relation was previously shown to be
equivalent to the spectrality property of B\"acklund transformations, i.e., to
the fact that the derivative of the Lagrangian with respect to the spectral
parameter is a common integral of motion of the family of B\"acklund
transformations. We relate this integral of motion to the monodromy matrix of
the zero curvature representation which is derived directly from equations of
motion in an algorithmic way. This serves as a further evidence in favor of the
idea that B\"acklund transformations serve as zero curvature representations
for themselves.


title: Adaptive Modulation (QPSK, QAM)

abstract:
  In this paper, introduced below are the concepts of digital modulation used
in many communication systems today. Techniques described include quadrature
phase shift keying (QPSK) and quadrature amplitude modulation (QAM) and how
these techniques can be used to increase the capacity and speed of a wireless
network. These modulation techniques are the basis of communications for
systems like cable modems, DSL modems, CDMA, 3G, Wi-Fi* (IEEE 802.11) and
WiMAX* (IEEE 802.16).


title:
Dispersive perturbations of Burgers and hyperbolic equations I : local
  theory

abstract:
  The aim of this paper is to show how a weakly dispersive perturbation of the
inviscid Burgers equation improve (enlarge) the space of resolution of the
local Cauchy problem. More generally we will review several problems arising
from weak dispersive perturbations of nonlinear hyperbolic equations or
systems.


title:
Survival distribution of the stretching and tilting of vortical
  structures in isotropic turbulence. Anisotropic filtering analysis

abstract:
  Using a Navier-Stokes isotropic turbulent field numerically simulated
(Biferale et al., Phys. Fluids (2005)), we show that the probability of having
a stretching-tilting larger than twice the local enstrophy is negligible. By
using an anisotropic filter in the Fourier space we analyze these survival
statistics when the large, the small inertial or the small inertial and
dissipation scales are filtered out. The probability that the ratio (|{\omega}
\dot U|/|{\omega}|^2) is higher than a given threshold is higher in the
unfiltered isotropic field than in the fields where the large scales were
filtered out and is lower than in the fields were the small inertial and
dissipative scales are filtered out. This is due to the suppression of compact
structures in the removed ranges. The partial removal of the background of
filaments and sheets does not have a first order effect on these statistics.
These results are discussed in the light of a hypothesized relation between
vortical filaments, sheets and blobs. The study can be viewed as a test for
this idea and tries to highlight its limits. A qualitative relation in physical
space and in Fourier space can be supposed to exist for blobs only. That is for
the near isotropic structures which are sufficiently described by a single
spatial scale and do not suffer from the disambiguation problem as filaments
and sheets do. Information is also given on the filtering effect on the angles
between the strain rate tensor eigenvectors and the vorticity: eigenvector 2
reduces its alignment, while eigenvector 3 reduces its misalignment. All
filters increase the gap between the most extensional eigenvalue and the
intermediate one and the gap between this last and the contractile eigenvalue.
When the large scales are missing, eigenvalue modulus 1 and 3 become nearly
equal, similar to the modulus of the related components of the enstrophy
production.


title:
Environmental Effects on the Star Formation Activity at z~0.9 in the
  COSMOS Field

abstract:
  We investigated the fraction of [OII] emitters in galaxies at z~0.9 as a
function of the local galaxy density in the Hubble Space Telescope (HST) COSMOS
2 square degree field. [OII] emitters are selected by the narrow-band excess
technique with the NB711-band imaging data taken with Suprime-Cam on the Subaru
telescope. We carefully selected 614 photo-z selected galaxies with M_U3500 <
-19.31 at z=0.901-0.920, which includes 195 [OII] emitters, to directly compare
results with our previous study at z~1.2. We found that the fraction is almost
constant at 0.3 Mpc^-2 < Sigma_10th < 10 Mpc^-2. We also checked the fraction
of galaxies with blue rest-frame colors of NUV-R < 2 in our photo-z selected
sample, and found that the fraction of blue galaxies does not significantly
depend on the local density. On the other hand, the semi-analytic model of
galaxy formation predicted that the fraction of star-forming galaxies at z~0.9
decreases with increasing the projected galaxy density even if the effects of
the projection and the photo-z error in our analysis were taken into account.
The fraction of [OII] emitters decreases from ~60% at z~1.2 to ~30% at z~0.9
independent of the galaxy environment. The decrease of the [OII] emitter
fraction could be explained mainly by the rapid decrease of the star formation
activity in the universe from z~1.2 to z~0.9.


title:
Uncertainty Quantification in Complex Simulation Models Using Ensemble
  Copula Coupling

abstract:
  Critical decisions frequently rely on high-dimensional output from complex
computer simulation models that show intricate cross-variable, spatial and
temporal dependence structures, with weather and climate predictions being key
examples. There is a strongly increasing recognition of the need for
uncertainty quantification in such settings, for which we propose and review a
general multi-stage procedure called ensemble copula coupling (ECC), proceeding
as follows: 1. Generate a raw ensemble, consisting of multiple runs of the
computer model that differ in the inputs or model parameters in suitable ways.
2. Apply statistical postprocessing techniques, such as Bayesian model
averaging or nonhomogeneous regression, to correct for systematic errors in the
raw ensemble, to obtain calibrated and sharp predictive distributions for each
univariate output variable individually. 3. Draw a sample from each
postprocessed predictive distribution. 4. Rearrange the sampled values in the
rank order structure of the raw ensemble to obtain the ECC postprocessed
ensemble. The use of ensembles and statistical postprocessing have become
routine in weather forecasting over the past decade. We show that seemingly
unrelated, recent advances can be interpreted, fused and consolidated within
the framework of ECC, the common thread being the adoption of the empirical
copula of the raw ensemble. Depending on the use of Quantiles, Random draws or
Transformations at the sampling stage, we distinguish the ECC-Q, ECC-R and
ECC-T variants, respectively. We also describe relations to the Schaake shuffle
and extant copula-based techniques. In a case study, the ECC approach is
applied to predictions of temperature, pressure, precipitation and wind over
Germany, based on the 50-member European Centre for Medium-Range Weather
Forecasts (ECMWF) ensemble.


title: Apparent horizons in Clifton-Mota-Barrow inhomogeneous universe

abstract:
  We analyze the apparent horizon dynamics in the inhomogeneous
Clifton-Mota-Barrow solution of Brans-Dicke theory. This solution models a
central matter configuration embedded in a cosmological background. In certain
regions of the parameter space we find solutions exhibiting dynamical creation
or merging of two horizons.


title: Electronic and Magnetic Reconstructions in Manganite Superlattices

abstract:
  We investigate the electronic reconstruction at the interface between
ferromagnetic metallic (FM) and antiferromagnetic insulating (AFI) manganites
in superlattices using a two-orbital double-exchange model including
superexchange interactions, Jahn-Teller lattice distortions, and long range
Coulomb interactions. The magnetic and the transport properties critically
depend on the thickness of the AFI layers. We focus on superlattices where the
constituent parent manganites have the same electron density n = 0.6. The
induced ferromagnetic moment in the AFI layers decreases monotonically with
increasing layer width, and the electron-density profile and the magnetic
structure in the center of the AFI layer gradually return to the bulk limit.
The width of the AFI layers and the charge-transfer profile at the interfaces
control the magnitude of the magnetoresistance and the metal-insulator
transition of the FM/AFI superlattices.


title: A Late-Time View of the Progenitors of Five Type IIP Supernovae

abstract:
  The acquisition of late-time imaging is an important step in the analysis of
pre-explosion observations of the progenitors of supernovae. We present
late-time HST ACS WFC observations of the sites of five Type IIP SNe: 1999ev,
2003gd, 2004A, 2005cs and 2006my. Observations were conducted using the F435W,
F555W and F814W filters. We confirm the progenitor identifications for SNe
2003gd, 2004A and 2005cs, through their disappearance. We find that a source
previously excluded as being the progenitor of SN 2006my has now disappeared.
The late-time observations of the site of SN 1999ev cast significant doubt over
the nature of the source previously identified as the progenitor in
pre-explosion WFPC2 images. The use of image subtraction techniques yields
improved precision over photometry conducted on just the pre-explosion images
alone. In particular, we note the increased depth of detection limits derived
on pre-explosion frames in conjunction with late-time images. We use SED
fitting techniques to explore the effect of different reddening components
towards the progenitors. For SNe 2003gd and 2005cs, the pre-explosion
observations are sufficiently constraining that only limited amounts of dust
(either interstellar or circumstellar) are permitted. Assuming only a Galactic
reddening law, we determine the initial masses for the progenitors of SNe
2003gd, 2004A, 2005cs and 2006my of 8.4+/-2.0, 12.0+/-2.1, 9.5(+3.4,-2.2) and
9.8+/-1.7Msun, respectively.


title:
Agent-based simulation of pedestrian behaviour in closed spaces: a
  museum case study

abstract:
  In order to analyse the behaviour of pedestrians at the very fine scale,
while moving along the streets, in open spaces or inside a building, simulation
modelling becomes an essential tool. In these spatial environments, in the
presence of unusual demand flows, simulation requires the ability to model the
local dynamics of individual decision making and behaviour, which is strongly
affected by the geometry, randomness, social preferences, local and collective
behaviour of other individuals. The dynamics of people visiting and evacuating
a museum offers an excellent case study along this line. In this paper we
realize an agent-based simulation of the Castello Ursino museum in Catania
(Italy), evaluating its carrying capacity in terms of both satisfaction of the
visitors in regime of normal fruition and their safety under alarm conditions.


title: Topological regulation of activation barriers on fractal substrates

abstract:
  We study phase-ordering dynamics of a ferromagnetic system with a scalar
order-parameter on fractal graphs. We propose a scaling approach, inspired by
renormalization group ideas, where a crossover between distinct dynamical
behaviors is induced by the presence of a length $\lambda $ associated to the
topological properties of the graph. The transition between the early and the
asymptotic stage is observed when the typical size $L(t)$ of the growing
ordered domains reaches the crossover length $\lambda $. We consider two
classes of inhomogeneous substrates, with different activated processes, where
the effects of the free energy barriers can be analytically controlled during
the evolution. On finitely ramified graphs the free energy barriers encountered
by domains walls grow logarithmically with $L(t)$ while they increase as a
power-law on all the other structures. This produces different asymptotic
growth laws (power-laws vs logarithmic) and different dependence of the
crossover length $\lambda $ on the model parameters. Our theoretical picture
agrees very well with extensive numerical simulations.


title: High-z cosmography at a glance

abstract:
  Cosmography is the tool that makes possible to untie the interpretation of
cosmological observations from the definition of any dynamical prior. We review
the constraints on the cosmographic parameter obtained using the most thorough
data set ensemble available. We focus on some specific topics about the
statistically based selection of the most stringent fitting expansion.


title: Basic properties of ultrafunctions

abstract:
  Ultrafunctions are a particular class of functions defined on a
non-Archimedean field. They provide generalized solutions to functional
equations which do not have any solutions among the real functions or the
distributions. In this paper we analyze sistematically some basic properties of
the spaces of ultrafunctions.


title:
The GREGOR Fabry-P\'erot Interferometer and its companion the Blue
  Imaging Solar Spectrometer

abstract:
  The GREGOR Fabry-P\'erot Interferometer (GFPI) is one of three first-light
instruments of the German 1.5-meter GREGOR solar telescope at the Observatorio
del Teide, Tenerife, Spain. The GFPI allows fast narrow-band imaging and
post-factum image restoration. The retrieved physical parameters will be a
fundamental building block for understanding the dynamic Sun and its magnetic
field at spatial scales down to about 50 km on the solar surface. The GFPI is a
tunable dual-etalon system in a collimated mounting. It is designed for
spectrometric and spectropolarimetric observations between 530-860 nm and
580-660 nm, respectively, and possesses a theoretical spectral resolution R of
about 250,000. Large-format, high-cadence CCD detectors with sophisticated
computer hard- and software enable the scanning of spectral lines in time-spans
equivalent to the evolution time of solar features. The field-of-view (FOV) of
50" x 38" covers a significant fraction of the typical area of active regions
in the spectroscopic mode. In case of Stokes-vector spectropolarimetry, the FOV
reduces to 25" x 38". We present the main characteristics of the GFPI including
advanced and automated calibration and observing procedures. We discuss
improvements in the optical design of the instrument and show first
observational results. Finally, we lay out first concrete ideas for the
integration of a second FPI, the Blue Imaging Solar Spectrometer (BLISS), which
will explore the blue spectral region below 530 nm.


title:
A large sample of calibration stars for Gaia: log g from Kepler and
  CoRoT

abstract:
  Asteroseismic data can be used to determine surface gravities with precisions
of < 0.05 dex by using the global seismic quantities Deltanu and nu_max along
with Teff and [Fe/H]. Surface gravity is also one of the four stellar
properties to be derived by automatic analyses for 1 billion stars from Gaia
data (workpackage GSP_Phot). We explore seismic data from MS F, G, K stars
(solar-like stars) observed by Kepler as a potential calibration source for
methods that Gaia will use for object characterisation (log g). We calculate
log g for bright nearby stars for which radii and masses are known, and using
their global seismic quantities in a grid-based method, we determine an
asteroseismic log g to within 0.01 dex of the direct calculation, thus
validating the accuracy of our method. We find that errors in Teff and mainly
[Fe/H] can cause systematic errors of 0.02 dex. We then apply our method to a
list of 40 stars to deliver precise values of surface gravity, i.e. sigma <
0.02 dex, and we find agreement with recent literature values. Finally, we
explore the precision we expect in a sample of 400+ Kepler stars which have
their global seismic quantities measured. We find a mean uncertainty
(precision) on the order of <0.02 dex in log g over the full explored range 3.8
< log g < 4.6, with the mean value varying only with stellar magnitude (0.01 -
0.02 dex). We study sources of systematic errors in log g and find possible
biases on the order of 0.04 dex, independent of log g and magnitude, which
accounts for errors in the Teff and [Fe/H] measurements, as well as from using
a different grid-based method. We conclude that Kepler stars provide a wealth
of reliable information that can help to calibrate methods that Gaia will use,
in particular, for source characterisation with GSP_Phot where excellent
precision (small uncertainties) and accuracy in log g is obtained from seismic
data.


title:
Noise-induced canard and mixed-mode oscillations in large stochastic
  networks with multiple timescales

abstract:
  We investigate the dynamics of large stochastic networks with different
timescales and nonlinear mean-field interactions. After deriving the limit
equations for a general class of network models, we apply our results to the
celebrated Wilson-Cowan system with two populations with or without slow
adaptation, paradigmatic example of nonlinear mean-field network. This system
has the property that the dynamics of the mean of the solution exactly
satisfies an ODE. This reduction allows to show that in the mean-field limit
and in multiple populations with multiple timescales, noise induces canard
explosions and Mixed-Mode Oscillations on the mean of the solution. This sheds
new light on the qualitative effects of noise and sensitivity to precise noise
values in large stochastic networks. We further investigate finite-sized
networks and show that systematic differences with the mean-field limits arise
in bistable regimes (where random switches between different attractors occur)
or in mixed-mode oscillations, were the finite-size effects induce early jumps
due to the sensitivity of the attractor.


title:
First-principles calculations of spin and angle-resolved resonant
  photoemission spectra of Cr(110) surfaces at the 2$p$ - 3$d$ resonance

abstract:
  A first principles approach for spin and angle resolved resonant
photoemission is developed within multiple scattering theory and applied to a
Cr(110) surface at the 2$p$-3$d$ resonance. The resonant photocurrent from this
non ferromagnetic system is found to be strongly spin polarized by circularly
polarized light, in agreement with experiments on antiferromagnetic and
magnetically disordered systems. By comparing the antiferromagnetic and
Pauli-paramagnetic phases of Cr, we explicitly show that the spin polarization
of the photocurrent is independent of the existence of local magnetic moments,
solving a long-standing debate on the origin of such polarization. New spin
polarization effects are predicted for the paramagnetic phase even with
unpolarized light, opening new directions for full mapping of spin interactions
in macroscopically non magnetic or nanostructured systems.


title: Orbifold Line Topology and the Cosmic Microwave Background

abstract:
  We extend our study of a universe with a non-classical stringy topology, and
consider an orbifold line topology,
$\mathbb{R}\times\mathbb{R}^2/\mathbb{Z}_p$. This topology has a fixed line and
identifies each point in space with $p-1$ other points. An observable imprint
of an orbifold line on the CMB is the appearance of up to $(p-1)/2$ pairs of
matching circles. Searching the WMAP data for matching circles, we can rule out
an orbifold line topology with $p$ up to 10, except for $p=8$. While the
significance of the peak at $p=8$ varies between data releases of WMAP, it does
not appear in Planck data, enabling us to rule out $p=8$ as well.


title: Seiberg-Witten Instability of Various Topological Black Holes

abstract:
  We review the Seiberg-Witten instability of topological black holes in
Anti-de Sitter space due to nucleation of brane-anti-brane pairs. We start with
black holes in general relativity, and then proceed to discuss the peculiar
property of topological black holes in Ho\v{r}ava-Lifshitz gravity -- they have
instabilities that occur at only finite range of distance away from the
horizon. This behavior is not unique to black holes in Ho\v{r}ava-Lifshitz
theory, as it is also found in the relatively simple systems of charged black
hole with dilaton hair that arise in low energy limit of string theory.


title:
Highly symmetric 2-plane fields on 5-manifolds and 5-dimensional
  Heisenberg group holonomy

abstract:
  Nurowski showed that any generic 2-plane field $D$ on a 5-manifold $M$
determines a natural conformal structure $c_D$ on $M$; these conformal
structures are exactly those (on oriented $M$) whose normal conformal holonomy
is contained in the (split, real) simple Lie group $G_2$. Graham and Willse
showed that for real-analytic $D$ the same holds for the holonomy of the
real-analytic Fefferman-Graham ambient metric of $c_D$, and that both holonomy
groups are equal to $G_2$ for almost all $D$. We investigate here independently
interesting plane fields for which the associated holonomy groups are a proper
subset of $G_2$.
  Cartan solved the local equivalence problem for $2$-plane fields $D$ and
constructed the fundamental curvature tensor $A$ for these objects. He
furthermore claimed to describe locally all $D$ whose infinitesimal symmetry
algebra has rank at least $6$ and gave a local quasi-normal form, depending on
a single function of one variable, for those that furthermore satisfy a natural
degeneracy condition on $A$, but Doubrov and Govorov recently rediscovered a
counterexample to Cartan's claim. We show that for all $D$ given by Cartan's
alleged quasi-normal form, the conformal structures $c_D$ induced via
Nurowski's construction are almost Einstein, that we can write their ambient
metrics explicitly, and that the holonomy groups associated to $c_D$ are always
the $5$-dimensional Heisenberg group, which here acts indecomposably but not
irreducibly. (Not all of these properties hold, however, for Doubrov and
Govorov's counterexample.) We also show that the similar results hold for the
related class of $2$-plane fields defined on suitable jet spaces by ordinary
differential equations $z'(x) = F(y''(x))$ satisfying a simple genericity
condition.


title:
Mean Field and Mean Ensemble Frequencies of a System of Coupled
  Oscillators

abstract:
  We investigate interacting phase oscillators whose mean field is at a
different frequency from the mean or mode of their natural frequencies. The
associated asymmetries lead to a macroscopic travelling wave. We show that the
mean ensemble frequency of such systems differs from their entrainment
frequency. In some scenarios these frequencies take values that,
counter-intuitively, lie beyond the limits of the natural frequencies. The
results indicate that a clear distinction should be drawn between the two
variables describing the macroscopic dynamics of cooperative systems. This has
important implications for real systems where a non-trivial distribution of
parameters is common.


title: Correlations in emitters coupled to plasmonic waveguides

abstract:
  We report on quantum, classical, and total correlations in a set of distant
quantum emitters coupled via their interaction with the plasmon modes of a
one-dimensional waveguide driven by an external laser field. The coupling of
the emitters with the plasmonic modes and its influence on the collective decay
rate suggest that entanglement does not play a significant role in the qubit
dynamics. Rather, discord is the quantity that matters and should be harnessed
as a resource.


title:
Stochastic processes with distributed delays: chemical Langevin equation
  and linear-noise approximation

abstract:
  We develop a systematic approach to the linear-noise approximation for
stochastic reaction systems with distributed delays. Unlike most existing work
our formalism does not rely on a master equation, instead it is based upon a
dynamical generating functional describing the probability measure over all
possible paths of the dynamics. We derive general expressions for the chemical
Langevin equation for a broad class of non-Markovian systems with distributed
delay. Exemplars of a model of gene regulation with delayed auto-inhibition and
a model of epidemic spread with delayed recovery provide evidence of the
applicability of our results.


title:
Proper motions of young stars in Chamaeleon. I. A Virtual Observatory
  study of spectroscopically confirmed members

abstract:
  (abridged) We want to provide further evidence of the origin of the proposed
stellar members of Chamaeleon and to identify interlopers from the foreground
\epsilon Cha and \eta Cha associations. To this aim, we compile lists of
spectroscopically confirmed members of Chamaeleon I and II, \epsilon Cha and
\eta Cha, and of background objects in the same line of sight. Using Virtual
Observatory tools, we cross-match these lists with the UCAC3 catalogue to get
the proper motions of the objects. In the vector point diagram, we identify the
different moving groups, and use this information to study the membership of
proposed candidate members of the associations from the literature. For those
objects with available radial velocities, we compute their Galactic space
velocities. We look for correlations between the known properties of the
objects and their proper motions. The members of the dark clouds exhibit
clearly different proper motions from those of the foreground associations and
of the background stars. The data suggest that Chamaeleon II could have
different dynamical properties from Chamaeleon I. Although the two foreground
clusters \epsilon and \eta Chamaeleontis constitute two different proper motion
groups, they have similar spatial motions, which are different from the spatial
motion of Chamaeleon I. On the other hand, the space motions of the Chamaeleon
II stars look more similar to those of the foreground clusters than to the
Chamaeleon I stars, but the numbers are low. Hence, with the available data it
is unclear to what extent the stellar populations in both clouds are physically
connected to each other. We find no correlations between the proper motions and
the properties of the objects in either of the clouds.


title: Order effects in dynamic semantics

abstract:
  In their target article, \citet{WangBusemeyer13} [A quantum question order
model supported by empirical tests of an a priori and precise prediction.
\emph{Topics in Cognitive Science}] discuss question order effects in terms of
incompatible projectors on a Hilbert space. In a similar vein, Blutner recently
presented an orthoalgebraic query language essentially relying on dynamic
update semantics. Here, I shall comment on some interesting analogies between
the different variants of dynamic semantics and generalized quantum theory to
illustrate other kinds of order effects in human cognition, such as belief
revision, the resolution of anaphors, and default reasoning that result from
the crucial non-commutativity of mental operations upon the belief state of a
cognitive agent.


title: Spin-flip phonon-mediated charge relaxation in double quantum dots

abstract:
  We theoretically study the $(1,1)$ triplet to $(0,2)$ singlet relaxation rate
in a lateral gate-defined double quantum dot tuned to the regime of Pauli spin
blockade. We present a detailed derivation of the effective phonon density of
states for this specific charge transition, keeping track of the contribution
from piezoelectric as well as deformation potential electron-phonon coupling.
We further investigate two different spin-mixing mechanisms which can couple
the triplet and singlet states: a magnetic field gradient over the double dot
(relevant at low external magnetic field) and spin-orbit interaction (relevant
at high field), and we also indicate how the two processes could interfere at
intermediate magnetic field. Finally, we show how to combine all results and
evaluate the relaxation rate for realistic system parameters.


title: Wave Effect in Gravitational Lensing by the Ellis Wormhole

abstract:
  We propose the use of modulated spectra of astronomical sources due to
gravitational lensing to probe Ellis wormholes. The modulation factor due to
gravitational lensing by the Ellis wormhole is calculated. Within the
geometrical optics approximation, the normal point mass lens and the Ellis
wormhole are indistinguishable unless we know the source's unlensed luminosity.
This degeneracy is resolved with the significant wave effect in the low
frequency domain if we take the deviation from the geometrical optics into
account. We can roughly estimate the upper bound for the number density of
Ellis wormholes as $n\lesssim 10^{-9}\{AU}^{-3}$ with throat radius $a\sim1\cm$
from the existing femto-lensing analysis for compact objects.


title:
Physisorption of DNA nucleobases on h-BN and graphene: vdW-corrected DFT
  calculations

abstract:
  We present a comparative study of DNA nucleobases [guanine (G), adenine (A),
thymine (T), and cytosine (C)] adsorbed on hexagonal boron nitride
(\textit{h}-BN) sheet and graphene, using local, semilocal, and van der Waals
(vdW) energy-corrected density-functional theory (DFT) calculations.
Intriguingly, despite the very different electronic properties of BN sheet and
graphene, we find rather similar binding energies for the various nucleobase
molecules when adsorbed on the two types of sheets. The calculated binding
energies of the four nucleobases using the local, semilocal, and DFT+vdW
schemes are in the range of 0.54 ${\sim}$ 0.75 eV, 0.06 ${\sim}$ 0.15 eV, and
0.93 ${\sim}$ 1.18 eV, respectively. In particular, the DFT+vdW scheme predicts
not only a binding energy predominantly determined by vdW interactions between
the base molecules and their substrates decreasing in the order of
G$>$A$>$T$>$C, but also a very weak hybridization between the molecular levels
of the nucleobases and the ${\pi}$-states of the BN sheet or graphene. This
physisorption of G, A, T, and C on the BN sheet (graphene) induces a small
interfacial dipole, giving rise to an energy shift in the work function by 0.11
(0.22), 0.09 (0.15), $-$0.05 (0.01), and 0.06 (0.13) eV, respectively.


title:
Should {\Delta}{\Sigma} Modulators Used in AC Motor Drives be Adapted to
  the Mechanical Load of the Motor?

abstract:
  We consider the use of {\Delta}{\Sigma} modulators in ac motor drives,
focusing on the many additional degrees of freedom that this option offers over
Pulse Width Modulation (PWM). Following some recent results, we show that it is
possible to fully adapt the {\Delta}{\Sigma} modulator Noise Transfer Function
(NTF) to the rest of the drive chain and that the approach can be pushed even
to a fine adaptation of the NTF to the specific motor loading condition. We
investigate whether and to what extent the adaptation should be pursued. Using
a representative test case and extensive simulation, we conclude that a mild
adaptation can be beneficial, leading to Signal to Noise Ratio (SNR)
improvements in the order a few dB, while the advantage pushing the adaptation
to the load tracking is likely to be minimal.


title:
Evidence for a second component in the high-energy core emission from
  Centaurus A?

abstract:
  We report on an analysis of \fermi data from four year of observations of the
nearby radio galaxy Centaurus A (Cen A). The increased photon statistics
results in a detection of high-energy ($>\:100$ MeV) $\gamma$-rays up to 50 GeV
from the core of Cen A, with a detection significance of about 44$\sigma$. The
average gamma-ray spectrum of the core reveals evidence for a possible
deviation from a simple power-law. A likelihood analysis with a broken
power-law model shows that the photon index becomes harder above $E_b \simeq 4$
GeV, changing from $\Gamma_1=2.74\pm0.03$ below to $\Gamma_2=2.09\pm0.20$
above. This hardening could be caused by the contribution of an additional
high-energy component beyond the common synchrotron-self Compton jet emission.
A variability analysis of the light curve with 15-, 30-, and 60-day bins does
not provide evidence for variability for any of the components. Indications for
a possible variability of the observed flux are found on 45-day time scale, but
the statistics do not allow us to make a definite conclusion in this regards.
We compare our results with the spectrum reported by H.E.S.S. in the TeV energy
range and discuss possible origins for the hardening observed.


title:
Dynamical localization of chaotic eigenstates in the mixed-type systems:
  spectral statistics in a billiard system after separation of regular and
  chaotic eigenstates

abstract:
  We study the quantum mechanics of a billiard (Robnik 1983) in the regime of
mixed-type classical phase space (the shape parameter \lambda=0.15) at very
high-lying eigenstates, starting at about 1.000.000th eigenstate and including
the consecutive 587654 eigenstates. By calculating the normalized Poincar\'e
Husimi functions of the eigenstates and comparing them with the classical phase
space structure, we introduce the overlap criterion which enables us to
separate with great accuracy and reliability the regular and chaotic
eigenstates, and the corresponding energies. The chaotic eigenstates appear all
to be dynamically localized, meaning that they do not occupy unformly the
entire available chaotic classical phase space component, but are localized on
a proper subset. We find with unprecedented precision and statistical
significance that the level spacing distribution of the regular levels obeys
the Poisson statistics, and the chaotic ones obey the Brody statistics, as
anticipated in a recent paper by Batisti\'c and Robnik (2010), where the entire
spectrum was found to obey the BRB statistics. There are no effects of
dynamical tunneling in this regime, due to the high energies, as they decay
exponentially with the inverse effective Planck constant which is proportional
to the square root of the energy.


title:
Estimating the Maximum Expected Value: An Analysis of (Nested) Cross
  Validation and the Maximum Sample Average

abstract:
  We investigate the accuracy of the two most common estimators for the maximum
expected value of a general set of random variables: a generalization of the
maximum sample average, and cross validation. No unbiased estimator exists and
we show that it is non-trivial to select a good estimator without knowledge
about the distributions of the random variables. We investigate and bound the
bias and variance of the aforementioned estimators and prove consistency. The
variance of cross validation can be significantly reduced, but not without
risking a large bias. The bias and variance of different variants of cross
validation are shown to be very problem-dependent, and a wrong choice can lead
to very inaccurate estimates.


title: Quantum turbulence in atomic Bose-Einstein condensates

abstract:
  Weakly interacting, dilute atomic Bose-Einstein condensates (BECs) have
proved to be an attractive context for the study of nonlinear dynamics and
quantum effects at the macroscopic scale. Recently, atomic BECs have been used
to investigate quantum turbulence both experimentally and theoretically,
stimulated largely by the high degree of control which is available within
these quantum gases. In this article we motivate the use of atomic BECs for the
study of turbulence, discuss the characteristic regimes of turbulence which are
accessible, and briefly review some selected investigations of quantum
turbulence and recent results. We focus on three stages of turbulence - the
generation of turbulence, its steady state and its decay - and highlight some
fundamental questions regarding our understanding in each of these regimes.


title:
Quantum field theory in de Sitter and quasi-de Sitter spacetimes:
  Revisited

abstract:
  It is possible to associate temperatures with the non-extremal horizons of a
large class of spherically symmetric spacetimes using periodicity in the
Euclidean sector and this procedure works for the de Sitter spacetime as well.
But, unlike e.g., the black hole spacetimes, the de Sitter spacetime also
allows a description in Friedmann coordinates. This raises the question of
whether the thermality of the de Sitter horizon can be obtained, working
entirely in the Friedmann coordinates, without reference to the static
coordinates or using the symmetries of de Sitter spacetime. We discuss several
aspects of this issue for de Sitter and approximately de Sitter spacetimes, in
the Friedmann coordinates (with a time-dependent background and the associated
ambiguities in defining the vacuum states). The different choices for the
vacuum states, behaviour of the mode functions and the detector response are
studied in both (1+1) and (1+3) dimensions. We compare and contrast the
differences brought about by the different choices. In the last part of the
paper, we also describe a general procedure for studying quantum field theory
in spacetimes which are approximately de Sitter and, as an example, derive the
corrections to thermal spectrum due to the presence of pressure-free matter.


title: Superconducting Phases in Potassium-Intercalated Iron Selenides

abstract:
  The ubiquitous coexistence of majority insulating 245 phases and minority
superconducting (SC) phases in AxFe2-ySe2 (A = K, Cs, Rb, Tl/Rb, Tl/K) formed
by high-temperature routes makes pure SC phases highly desirable for studying
the intrinsic properties of this SC family. Here we report that there are at
least two pure SC phases, KxFe2Se2(NH3)y (x ~ 0.3 and 0.6), determined mainly
by potassium concentration in the K-intercalated iron selenides formed via the
liquid ammonia route. K0.3Fe2Se2(NH3)0.47 corresponds to the 44 K phase with
lattice constant c = 15.56(1) angstroms and K0.6Fe2Se2(NH3)0.37 to the 30 K
phase with c = 14.84(1) angstroms. With higher potassium doping, the 44 K phase
can be converted into the 30 K phase. NH3 has little, if any, effect on
superconductivity. Thus, the conclusions should apply to both K0.3Fe2Se2 and
K0.6Fe2Se2 SC phases. K0.3Fe2Se2(NH3)0.47 and K0.6Fe2Se2(NH3)0.37 stand out
among known superconductors as their structures are stable only at particular
potassium doping levels, and hence the variation of Tc with doping is not
dome-like.