title: The Chow ring of the moduli space of curves of genus 6

abstract:
  We determine the Chow ring (with Q-coefficients) of M_6 by showing that all
Chow classes are tautological. In particular, all algebraic cohomology is
tautological, and the natural map from Chow to cohomology is injective. To
demonstrate the utility of these methods, we also give quick derivations of the
Chow groups of moduli spaces of curves of lower genus. The genus 6 case relies
on the particularly beautiful Brill-Noether theory in this case, and in
particular on a rank 5 vector bundle "relativizing" a baby case of a celebrated
construction of Mukai, which we interpret as a subbundle of the rank 6 vector
bundle of quadrics cutting out the canonical curve.


title:
On the macroscopic quantization in mesoscopic rings and single-electron
  devices

abstract:
  In this letter the phenomenon of macroscopic quantization is investigated
using the particle on the ring interacting with the dissipative environment as
an example. It is shown that the phenomenon of macroscopic quantization has the
clear physical origin in that case. It follows from the angular momentum
conservation combined with momentum quantization for bare particle on the ring
. The existence an observable which can take only integer values in the zero
temperature limit is rigorously proved. With the aid of the mapping between
particle on the ring and Ambegaokar-Eckern-Schon model, which can be used to
describe single-electron devices, it is demonstrated that this observable is
analogous to the "effective charge" introduced by Burmistrov and Pruisken for
the single-electron box problem. Different consequences of the revealed physics
are discussed, as well as a generalization of the obtained results to the case
of more complicated systems.


title:
Does generalization performance of $l^q$ regularization learning depend
  on $q$? A negative example

abstract:
  $l^q$-regularization has been demonstrated to be an attractive technique in
machine learning and statistical modeling. It attempts to improve the
generalization (prediction) capability of a machine (model) through
appropriately shrinking its coefficients. The shape of a $l^q$ estimator
differs in varying choices of the regularization order $q$. In particular,
$l^1$ leads to the LASSO estimate, while $l^{2}$ corresponds to the smooth
ridge regression. This makes the order $q$ a potential tuning parameter in
applications. To facilitate the use of $l^{q}$-regularization, we intend to
seek for a modeling strategy where an elaborative selection on $q$ is
avoidable. In this spirit, we place our investigation within a general
framework of $l^{q}$-regularized kernel learning under a sample dependent
hypothesis space (SDHS). For a designated class of kernel functions, we show
that all $l^{q}$ estimators for $0< q < \infty$ attain similar generalization
error bounds. These estimated bounds are almost optimal in the sense that up to
a logarithmic factor, the upper and lower bounds are asymptotically identical.
This finding tentatively reveals that, in some modeling contexts, the choice of
$q$ might not have a strong impact in terms of the generalization capability.
From this perspective, $q$ can be arbitrarily specified, or specified merely by
other no generalization criteria like smoothness, computational complexity,
sparsity, etc..


title: Symmetry-Protected Topological Entanglement

abstract:
  We propose an order parameter for the Symmetry-Protected Topological (SPT)
phases which are protected by Abelian on-site symmetries. This order parameter,
called the "SPT-entanglement", is defined as the entanglement between A and B,
two distant regions of the system, given that the total charge (associated with
the symmetry) in a third region C is measured and known, where C is a connected
region surrounded by A, B and the boundaries of the system. In the case of
1-dimensional systems we prove that in the limit where A and B are large and
far from each other compared to the correlation length, the SPT-entanglement
remains constant throughout a SPT phase, and furthermore, it is zero for the
trivial phase while it is nonzero for all the non-trivial phases. Moreover, we
show that the SPT-entanglement is invariant under the low-depth quantum
circuits which respect the symmetry, and hence it remains constant throughout a
SPT phase in the higher dimensions as well. Also, we show that there is an
intriguing connection between SPT-entanglement and the Fourier transform of the
string order parameters, which are the traditional tool for detecting SPT
phases. This leads to a new algorithm for extracting the relevant information
about the SPT phase of the system from the string order parameters. Finally, we
discuss implications of our results in the context of measurement-based quantum
computation.

categories: quant-ph cond-mat.str-el math-ph math.MP


title:
Survival and extinction results for a patch model with sexual
  reproduction

abstract:
  This article is concerned with a version of the contact process with sexual
reproduction on a graph with two levels of interactions modeling
metapopulations. The population is spatially distributed into patches and
offspring are produced in each patch at a rate proportional to the number of
pairs of individuals in the patch (sexual reproduction) rather than simply the
number of individuals as in the basic contact process. Offspring produced at a
given patch either stay in their parents' patch or are sent to a nearby patch
with some fixed probabilities. Specifically, we prove lower and upper bounds
for the probability of long-term survival for the process starting with a
single fully occupied patch. Our main finding is that, with probability close
to one and for a certain set of parameters, the metapopulation survives in the
presence of nearest neighbor interactions while it dies out in the presence of
long range interactions, suggesting that the best strategy for the population
to expand in space is to use intermediate dispersal ranges. This result is due
to the presence of a so-called strong Allee effect induced by the birth
mechanism and does not hold for the basic contact process.


title:
Measuring the matter energy density and Hubble parameter from Large
  Scale Structure

abstract:
  We investigate the method to measure both the present value of the matter
energy density contrast and the Hubble parameter directly from the measurement
of the linear growth rate which is obtained from the large scale structure of
the Universe. From this method, one can obtain the value of the nuisance
cosmological parameter $\Omo$ (the present value of the matter energy density
contrast) within 3% error if the growth rate measurement can be reached $z >
3.5$. One can also investigate the evolution of the Hubble parameter without
any prior on the value of $H_0$ (the current value of the Hubble parameter).
Especially, estimating the Hubble parameter are insensitive to the errors on
the measurement of the normalized growth rate $f \sigma_8$. However, this
method requires the high $z$ ($z > 3.5$) measurement of the growth rate in
order to get the less than 5% errors on the measurements of $H(z)$ at $z \leq
1.2$ with the redshift bin $\Delta z = 0.2$. Thus, this will be suitable for
the next generation large scale structure galaxy surveys like WFMOS and LSST.


title: Energy of solenoidal vector fields on spherical domains

abstract:
  We present a boundary version of a theorem about solenoidal unit vector
fields with minimum energy on a spherical domain of an odd dimensional
Euclidean sphere.


title: Rate-dependent morphology of Li2O2 growth in Li-O2 batteries

abstract:
  Compact solid discharge products enable energy storage devices with high
gravimetric and volumetric energy densities, but solid deposits on active
surfaces can disturb charge transport and induce mechanical stress. In this
Letter we develop a nanoscale continuum model for the growth of Li2O2 crystals
in lithium-oxygen batteries with organic electrolytes, based on a theory of
electrochemical non-equilibrium thermodynamics originally applied to Li-ion
batteries. As in the case of lithium insertion in phase-separating LiFePO4
nanoparticles, the theory predicts a transition from complex to uniform
morphologies of Li2O2 with increasing current. Discrete particle growth at low
discharge rates becomes suppressed at high rates, resulting in a film of
electronically insulating Li2O2 that limits cell performance. We predict that
the transition between these surface growth modes occurs at current densities
close to the exchange current density of the cathode reaction, consistent with
experimental observations.


title: Priority-aware Gray-box Placement of Virtual Machines in Cloud Platforms

abstract:
  Virtual machine (VM) placement is very important for cloud platforms. While
techniques, such as live virtual machine migration, are very useful to balance
the load in the data centers, they are expensive operations. In this position
paper, we propose to minimize the chance of the load hot spots in the data
center by applying the workload patterns of the VMs in the virtual machine
placement algorithms - place VMs that require a lot of same type of resource
across different physical servers. In this way, the resource competition of VMs
on the same physical server is significantly mitigated. Meanwhile, we also
consider the priorities of applications and VMs in our virtual machine
placement algorithms.


title: Representations of the Drazin inverse involving idempotents in a ring

abstract:
  We present some formulae for the Drazin inverse of difference and product of
idempotents in a ring. A number of results of bounded linear operators in
Banach spaces are extended to the ring case.


title: Triple Massey products and Galois theory

abstract:
  We show that any triple Massey product with respect to prime 2 contains 0
whenever it is defined over any field. This extends the theorem of M. J.
Hopkins and K. G. Wickelgren, from global fields to any fields. This is the
first time when the vanishing of any $n$-Massey product for some prime $p$ has
been established for all fields. This leads to a strong restriction on the
shape of relations in the maximal pro-2-quotients of absolute Galois groups,
which was out of reach until now. We also develop an extension of Serre's
transgression method to detect triple commutators in relations of
pro-$p$-groups, where we do not require that all cup products vanish. We prove
that all $n$-Massey products, $n\geq 3$, vanish for general Demushkin groups.
We formulate and provide evidence for two conjectures related to the structure
of absolute Galois groups of fields. In each case when these conjectures can be
verified, they have some interesting concrete Galois theoretic consequences.
They are also related to the Bloch-Kato conjecture.


title: Dimension-Raising Maps in a Large Scale

abstract:
  Hurewicz's dimension-raising theorem states that for every n-to-1 map f : X
\to Y, dim Y =< dim X + n holds. In this paper we introduce a new notion of
finite-to-one like map in a large scale setting. Using this notion we formulate
a dimension-raising type theorem for the asymptotic dimension and the
asymptotic Assouad-Nagata dimension. It is also well-known as Hurewicz's
finite-to-one mapping theorem that dim X =< n if and only if there exists an (n
+ 1)-to-1 map from a 0-dimensional space onto X. We formulate a finite-to-one
mapping type theorem for the asymptotic dimension and the asymptotic
Assouad-Nagata dimension.


title:
On the $k$-error linear complexity of binary sequences derived from
  polynomial quotients

abstract:
  We investigate the $k$-error linear complexity of $p^2$-periodic binary
sequences defined from the polynomial quotients (including the well-studied
Fermat quotients), which is defined by $$ q_{p,w}(u)\equiv \frac{u^w-u^{wp}}{p}
\bmod p ~ \mathrm{with} 0 \le q_{p,w}(u) \le p-1, ~u\ge 0, $$ where $p$ is an
odd prime and $1\le w<p$. Indeed, first for all integers $k$, we determine
exact values of the $k$-error linear complexity over the finite field $\F_2$
for these binary sequences under the assumption of f2 being a primitive root
modulo $p^2$, and then we determine their $k$-error linear complexity over the
finite field $\F_p$ for either $0\le k<p$ when $w=1$ or $0\le k<p-1$ when $2\le
w<p$. Theoretical results obtained indicate that such sequences possess `good'
error linear complexity.


title: Minimum d-dimensional arrangement with fixed points

abstract:
  In the Minimum $d$-Dimensional Arrangement Problem (d-dimAP) we are given a
graph with edge weights, and the goal is to find a 1-1 map of the vertices into
$\mathbb{Z}^d$ (for some fixed dimension $d\geq 1$) minimizing the total
weighted stretch of the edges. This problem arises in VLSI placement and chip
design.
  Motivated by these applications, we consider a generalization of d-dimAP,
where the positions of some of the vertices (pins) is fixed and specified as
part of the input. We are asked to extend this partial map to a map of all the
vertices, again minimizing the weighted stretch of edges. This generalization,
which we refer to as d-dimAP+, arises naturally in these application domains
(since it can capture blocked-off parts of the board, or the requirement of
power-carrying pins to be in certain locations, etc.). Perhaps surprisingly,
very little is known about this problem from an approximation viewpoint.
  For dimension $d=2$, we obtain an $O(k^{1/2} \cdot \log n)$-approximation
algorithm, based on a strengthening of the spreading-metric LP for 2-dimAP. The
integrality gap for this LP is shown to be $\Omega(k^{1/4})$. We also show that
it is NP-hard to approximate 2-dimAP+ within a factor better than
$\Omega(k^{1/4-\eps})$. We also consider a (conceptually harder, but
practically even more interesting) variant of 2-dimAP+, where the target space
is the grid $\mathbb{Z}_{\sqrt{n}} \times \mathbb{Z}_{\sqrt{n}}$, instead of
the entire integer lattice $\mathbb{Z}^2$. For this problem, we obtain a $O(k
\cdot \log^2{n})$-approximation using the same LP relaxation. We complement
this upper bound by showing an integrality gap of $\Omega(k^{1/2})$, and an
$\Omega(k^{1/2-\eps})$-inapproximability result.
  Our results naturally extend to the case of arbitrary fixed target dimension
$d\geq 1$.


title: Applied Similarity Problems Using Frechet Distance

abstract:
  In the first part of this thesis, we consider an instance of Frechet distance
problem in which the speed of traversal along each segment of the curves is
restricted to be within a specfied range. This setting is more realistic than
the classical Frechet distance setting, specially in GIS applications. We also
study this problem in the setting where the polygonal curves are inside a
simple polygon.
  In the second part of this thesis, we present a data structure, called the
free-space map, that enables us to solve several variants of the Frechet
distance problem efficiently. Our data structure encapsulates all the
information available in the free-space diagram, yet it is capable of answering
more general type of queries efficiently. Given that the free-space map has the
same size and construction time as the standard free-space diagram, it can be
viewed as a powerful alternative to it. As part of the results in Part II of
the thesis, we exploit the free-space map to improve the long-standing bound
for computing the partial Frechet distance and obtain improved algorithms for
computing the Frechet distance between two closed curves, and the so-called
minimum/maximum walk problem. We also improve the map matching algorithm for
the case when the map is a directed acyclic graph.
  As the last part of this thesis, given a point set S and a polygonal curve P
in R^d, we study the problem of finding a polygonal curve Q through S, which
has a minimum Frechet distance to P. Furthermore, if the problem requires that
curve Q visits every point in S, we show it is NP-complete.


title:
Existence and regularity of mean curvature flow with transport term in
  higher dimensions

abstract:
  Given an initial $C^1$ hypersurface and a time-dependent vector field in a
Sobolev space, we prove a time-global existence of a family of hypersurfaces
which start from the given hypersurface and which move by the velocity equal to
the mean curvature plus the given vector field. We show that the hypersurfaces
are $C^1$ for a short time and, even after some singularities occur, almost
everywhere $C^1$ away from higher multiplicity region.


title: Jacobi-Trudi determinants and characters of minimal affinizations

abstract:
  In their study of characters of minimal affinizations of representations of
orthogonal and symplectic Lie algebras, Chari and Greenstein conjectured that
certain Jacobi-Trudi determinants satisfy an alternating sum formula. In this
note, we prove their conjecture and slightly more. The proof relies on some
symmetries of the ring of symmetric functions discovered by Koike and Terada.
Using results of Hernandez, Mukhin-Young, and Naoi, this implies that the
characters of minimal affinizations in types B, C, and D are given by a
Jacobi-Trudi determinant.


title: Squeezing in Bose-Einstein condensates with large numbers of atoms

abstract:
  We examine the feasibility of creating and measuring large relative number
squeezing in multicomponent trapped Bose-Einstein condensates. In the absence
of multimode effects, this squeezing can be arbitrarily large for arbitrarily
large condensates, but a range of processes limit the measurable squeezing in
realistic trap configurations. We examine these processes, and suggest methods
to mitigate them. We conclude that high levels of squeezing with large numbers
of atoms is feasible, but can realistically only be achieved in particular trap
geometries. We also introduce a method of maximising the measurable squeezing
by using a $\pi$-pulse during the process to improve spatial mode-matching.


title:
Kelvin modes as Nambu-Goldstone modes along superfluid vortices and
  relativistic strings: finite volume size effects

abstract:
  We study Kelvin modes and translational zero modes excited along a quantized
vortex and relativistic global string in superfluids and a relativistic field
theory, respectively, by constructing the low-energy effective theory of these
modes. We find that they become exact gapless Nambu-Goldstone modes only in a
system with infinite volume limit. On the other hand, in a system with the
finite volume, we find an imaginary massive gap causing the tachyonic
instability above some critical wavelength in the relativistic theory. We also
find in the non-relativistic theory that Kelvin modes with wavelengths longer
than some critical value propagate in the direction opposite to those with
shorter length, contrary to conventional understanding. The number of
Nambu-Goldstone modes also saturate the equality of the Nielsen-Chadha
inequality for both relativistic and non-relativistic theories.


title:
Non-equilibrium steady state and induced currents of a
  mesoscopically-glassy system: interplay of resistor-network theory and Sinai
  physics

abstract:
  We introduce an explicit solution for the non-equilibrium steady state (NESS)
of a ring that is coupled to a thermal bath, and is driven by an external hot
source with log-wide distribution of couplings. Having time scales that stretch
over several decades is similar to glassy systems. Consequently there is a wide
range of driving intensities where the NESS is like that of a random walker in
a biased Brownian landscape. We investigate the resulting statistics of the
induced current $I$. For a single ring we discuss how $sign(I)$ fluctuates as
the intensity of the driving is increased, while for an ensemble of rings we
highlight the fingerprints of Sinai physics on the $abs(I)$ distribution.


title:
Experimental verification of the surface termination in the topological
  insulator TlBiSe$_{2}$ using core-level photoelectron spectroscopy and
  scanning tunneling microscopy

abstract:
  The surface termination of the promising topological insulator TlBiSe$_{2}$
has been studied by surface and bulk sensitive probes. Our scanning tunneling
microscopy has unmasked for the first time the unusual surface morphology of
TlBiSe$_{2}$ obtained by cleaving, where islands are formed by residual atoms
on the cleaved plane. The chemical condition of these islands was identified
using core-level spectroscopy. We observed thallium core-level spectra that are
strongly deformed by a surface component in sharp contrast to the other
elements. We propose a simple explanation for this behavior by assuming that
the sample cleaving breaks the bonding between thallium and selenium atoms,
leaving the thallium layer partially covering the selenium layer. These
findings will assist the interpretation of future experimental and theoretical
studies on this surface.


title:
Geometrical considerations in the Control and manipulation of conductive
  heat flux

abstract:
  We indicate the fundamental rationale underlying the control of temperature
and the manipulation of thermal flux, with reference to a multilayered
composite material. We show that when the orientation of the layers in the
composite is physically rotated with respect to a constant temperature
gradient, there would then be a corresponding introduction of off-diagonal
components in the thermal conductivity tensor and thermal anisotropy is
induced. The consequent bending of the heat flux lines is found to depend on
both the (i) composite rotation angle, as well as the (ii) ratio of the thermal
conductivities of the constituent materials.


title:
Inversion Symmetry of Gravitational Coupling in Cubic String Field
  Theory

abstract:
  It was found that the canonical energy of multi-brane solutions in CSFT
constructed by the KBc algebra has a symmetry under the exchange of K=0 and
K=\infty (inversion symmetry). On the other hand, the gauge invariant
observable (GIO), which is regarded as the energy defined by the gravitational
coupling of open string, cannot count the energy from K=\infty and therefore is
not equal to the canonical energy. To resolve this discrepancy, we examine the
recent argument of Baba and Ishibashi which directly relates the two energies.
We find that the gravitational coupling which is equivalent to the canonical
energy consists of the GIO and another new term, and the whole has the
inversion symmetry.


title:
Microlensed image centroid motions by an exotic lens object with
  negative convergence or negative mass

abstract:
  Gravitational lens models with negative convergence inspired by modified
gravity theories, exotic matter and energy have been recently examined, in such
a way that a static and spherically symmetric modified spacetime metric depends
on the inverse distance to the $n$-th power ($n=1$ for Schwarzschild metric,
$n=2$ for Ellis wormhole, and $n \neq 1$ for an extended spherical distribution
of matter such as an isothermal sphere) in the weak-field approximation
[Kitamura, Nakajima and Asada, PRD 87, 027501 (2013), Izumi et al. PRD 88
024049 (2013)]. Some of the models act as if a convex lens, whereas the others
are repulsive on light rays like a concave lens. The present paper considers
microlensed image centroid motions by the exotic lens models. Numerical
calculations show that, for large $n$ cases in the convex-type models, the
centroid shift from the source position might move on a multiply-connected
curve like a bow tie, while it is known to move on an ellipse for $n=1$ case
and to move on an oval curve for $n=2$. The distinctive feature of the
microlensed image centroid may be used for searching (or constraining)
localized exotic matter or energy with astrometric observations. It is shown
also that the centroid shift trajectory for concave-type repulsive models might
be elongated vertically to the source motion direction like a prolate spheroid,
whereas that for convex-type models such as the Schwarzschild one is
tangentially elongated like an oblate spheroid.


title:
Supporting 64-bit global indices in Epetra and other Trilinos packages
  -- Techniques used and lessons learned

abstract:
  The Trilinos Project is an effort to facilitate the design, development,
integration and ongoing support of mathematical software libraries within an
object-oriented framework. It is intended for large-scale, complex multiphysics
engineering and scientific applications. Epetra is one of its basic packages.
It provides serial and parallel linear algebra capabilities. Before Trilinos
version 11.0, released in 2012, Epetra used the C++ int data-type for storing
global and local indices for degrees of freedom (DOFs). Since int is typically
32-bit, this limited the largest problem size to be smaller than approximately
two billion DOFs. This was true even if a distributed memory machine could
handle larger problems. We have added optional support for C++ long long
data-type, which is at least 64-bit wide, for global indices. To save memory,
maintain the speed of memory-bound operations, and reduce further changes to
the code, the local indices are still 32-bit. We document the changes required
to achieve this feature and how the new functionality can be used. We also
report on the lessons learned in modifying a mature and popular package from
various perspectives -- design goals, backward compatibility, engineering
decisions, C++ language features, effects on existing users and other packages,
and build integration.


title: Observational Viability and Stability of Nonlocal Cosmology

abstract:
  We show that a class of nonlocal gravity models, proposed to explain current
cosmic acceleration without dark energy, passes two major tests: First, they
can be defined so as not to alter the, observationally correct, general
relativity predictions for gravitationally bound systems. Second, they are
stable, ghost-free, with no additional excitations beyond those of general
relativity. In this they differ from their, ghostful, localized versions. The
systems' initial value constraints are the same as in general relativity, and
our nonlocal modifications never convert the original gravitons into ghosts.


title:
Low-energy electron holographic imaging of gold nanorods supported by
  ultraclean graphene

abstract:
  An ideal support for electron microscopy shall be as thin as possible and
interact as little as possible with the primary electrons. Since graphene is
atomically thin and made up of carbon atoms arranged in a honeycomb lattice,
the potential to use graphene as substrate in electron microscopy is enormous.
Until now graphene has hardly ever been used for this purpose because the
cleanliness of freestanding graphene before or after deposition of the objects
of interest was insufficient. We demonstrate here by means of low-energy
electron holographic imaging that freestanding graphene prepared with the
Platinum-metal catalysis method remains ultraclean even after re-exposure to
ambient conditions and deposition of gold-nanorods from the liquid phase. In
the holographic reconstruction of the gold particles the organic shell
surrounding the objects is imaged while it is not detectable in SEM images of
the very same sample, demonstrating the tremendous potential of low-energy
electron holography for the imaging of graphene-supported single biomolecules.

categories: cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.other physics.atm-clus


title: 1/2-BPS Domain wall from N=10 three dimensional gauged supergravity

abstract:
  We explicitly construct $N=10$ Chern-Simons gaged supergravity in three
dimensions with non-semisimple gauge group $SO(5)\ltimes \mathbf{T}^{10}$. The
gauge group is embedded in $E_{6(-14)}$ which is the isometry group of the
32-dimensional scalar manifold $E_{6(-14)}/SO(10)\times U(1)$. The resulting
theory is on-shell equivalent to $SO(5)$ Yang-Mills gauged supergravity coming
from dimensional reduction on $S^1$ of $SO(5)$ $N=5$ gauged supergravity in
four dimensions. We discuss the spectrum of the corresponding reduction. The
$SO(5)\ltimes \mathbf{T}^{10}$ gauged supergravity, describing the reduced
theory, admits a $\frac{1}{2}$-BPS domain wall vacuum solution whose explicit
form is also given. This provides an example of a domain wall in non-maximal
gauged supergravity.


title: Non-monochromatic non-rainbow colourings of $\sigma$-hypergraphs

abstract:
  One of the most interesting new developments in hypergraph colourings in
these last few years has been Voloshin's notion of colourings of mixed
hypergraphs. In this paper we shall study a specific instance of Voloshin's
idea: a non-monochromatic non-rainbow (NMNR) colouring of a hypergraph is a
colouring of its vertices such that every edge has at least two vertices
coloured with different colours (non-monochromatic) and no edge has all of its
vertices coloured with distinct colours (non-rainbow). Perhaps the most
intriguing phenomenon of such colourings is that a hypergraph can have gaps in
its NMNR chromatic spectrum, that is, for some $k_1 < k_2 < k_3$, the
hypergraph is NMNR colourable with $k_1$ and with $k_3$ colours but not with
$k_2$ colours.
  Several beautiful examples have been constructed of NMNR colourings of
hypergraphs exhibiting phenomena not seen in classical colourings. Many of
these examples are either \emph{ad hoc} or else are based on designs. The
latter are difficult to construct and they generally give uniform
$r$-hypergraphs only for low values of $r$, generally $r=3$. In this paper we
shall study the NMNR colourings of a type of $r$-uniform hypergraph which we
call $\sigma$-hypergraphs. The attractive feature of these $\sigma$-hypergraphs
is that they are easy to define, even for large $r$, and that, by suitable
modifications of their parameters, they can give families of hypergraphs which
are guaranteed to have NMNR spectra with gaps or NMNR spectra without gaps.
These $\sigma$-hypergraphs also team up very well with the notion of
colour-bounded hypergraphs recently introduced by Bujt{\'a}s and Tuza to give
further control on the appearance of gaps and perhaps explain better the
existence of gaps in the colouring of mixed hypergraphs.


title:
The Pre-merger Impact Velocity of the Binary Cluster A1750 from X-ray,
  Lensing and Hydrodynamical Simulations

abstract:
  Since the discovery of the "bullet cluster" several similar cases have been
uncovered suggesting relative velocities well beyond the tail of high speed
collisions predicted by the concordance LCDM model. However, quantifying such
post-merger events with hydrodynamical models requires a wide coverage of
possible initial conditions. Here we show that it is simpler to interpret
pre-merger cases, such as A1750, where the gas between the colliding clusters
is modestly affected, so that the initial conditions are clear. We analyze
publicly available Chandra data confirming a significant increase in the
projected X-ray temperature between the two cluster centers in A1750 consistent
with our expectations for a merging cluster. We model this system with a
self-consistent hydrodynamical simulation of dark matter and gas using the
FLASH code. Our simulations reproduce well the X-ray data, and the measured
redshift difference between the two clusters in the phase before the first core
passage viewed at an intermediate projection angle. The deprojected initial
relative velocity derived using our model is 1460 km/sec which is considerably
higher than the predicted mean impact velocity for simulated massive haloes
derived by recent LCDM cosmological simulations, but it is within the allowed
range. Our simulations demonstrate that such systems can be identified using a
multi-wavelength approach and numerical simulations, for which the statistical
distribution of relative impact velocities may provide a definitive examination
of a broad range of dark matter scenarios.


title:
Variable Stars in Large Magellanic Cloud Globular Clusters III:
  Reticulum

abstract:
  This is the third in a series of papers studying the variable stars in old
globular clusters in the Large Magellanic Cloud. The primary goal of this
series is to look at how the characteristics and behavior of RR Lyrae stars in
Oosterhoff-intermediate systems compare to those of their counterparts in
Oosterhoff-I/II systems. In this paper we present the results of our new
time-series BVI photometric study of the globular cluster Reticulum. We found a
total of 32 variables stars (22 RRab, 4 RRc, and 6 RRd stars) in our field of
view. We present photometric parameters and light curves for these stars. We
also present physical properties, derived from Fourier analysis of light
curves, for some of the RR Lyrae stars. We discuss the Oosterhoff
classification of Reticulum and use our results to re-derive the distance
modulus and age of the cluster.


title:
A novel scheme for the wave function renormalization of the composite
  operators

abstract:
  We propose a novel renormalization scheme for the hadronic operators. The
renormalization factor of the operator in this scheme is normalized by the
correlation function at tree level in coordinate space. If we focus on the
pseudo scalar operator, then its renormalization factor is related to the mass
renormalization factor of the fermion through the partially conserved
axial-vector current (PCAC) relation. Using the renormalization factor for the
pseudo scalar operator in our scheme, we obtain the mass anomalous dimension of
the SU(3) gauge theory coupled to N_f=12 massless fundamental fermions, which
has an infrared fixed point (IRFP). The mass anomalous dimension at the IRFP is
estimated as gamma_m^*= 0.044_{-0.024}^{+0.025} (stat.)_{-0.032}^{+0.057}
(syst.).


title: Corruption Drives the Emergence of Civil Society

abstract:
  Peer punishment of free-riders (defectors) is a key mechanism for promoting
cooperation in society. However, it is highly unstable since some cooperators
may contribute to a common project but refuse to punish defectors. Centralized
sanctioning institutions (for example, tax-funded police and criminal courts)
can solve this problem by punishing both defectors and cooperators who refuse
to punish. These institutions have been shown to emerge naturally through
social learning and then displace all other forms of punishment, including peer
punishment. However, this result provokes a number of questions. If centralized
sanctioning is so successful, then why do many highly authoritarian states
suffer from low levels of cooperation? Why do states with high levels of public
good provision tend to rely more on citizen-driven peer punishment? And what
happens if centralized institutions can be circumvented by individual acts of
bribery? Here, we consider how corruption influences the evolution of
cooperation and punishment. Our model shows that the effectiveness of
centralized punishment in promoting cooperation breaks down when some actors in
the model are allowed to bribe centralized authorities. Counterintuitively,
increasing the sanctioning power of the central institution makes things even
worse, since this prevents peer punishers from playing a role in maintaining
cooperation. As a result, a weaker centralized authority is actually more
effective because it allows peer punishment to restore cooperation in the
presence of corruption. Our results provide an evolutionary rationale for why
public goods provision rarely flourishes in polities that rely only on strong
centralized institutions. Instead, cooperation requires both decentralized and
centralized enforcement. These results help to explain why citizen
participation is a fundamental necessity for policing the commons.


title: Efficient simulation of the random-cluster model

abstract:
  The simulation of spin models close to critical points of continuous phase
transitions is heavily impeded by the occurrence of critical slowing down. A
number of cluster algorithms, usually based on the Fortuin-Kasteleyn
representation of the Potts model, and suitable generalizations for
continuous-spin models have been used to increase simulation efficiency. The
first algorithm making use of this representation, suggested by Sweeny in 1983,
has not found widespread adoption due to problems in its implementation.
However, it has been recently shown that it is indeed more efficient in
reducing critical slowing down than the more well-known algorithm due to
Swendsen and Wang. Here, we present an efficient implementation of Sweeny's
approach for the random-cluster model using recent algorithmic advances in
dynamic connectivity algorithms.


title: Modular anomaly equation, heat kernel and S-duality in N=2 theories

abstract:
  We investigate epsilon-deformed N=2 superconformal gauge theories in four
dimensions, focusing on the N=2* and Nf=4 SU(2) cases. We show how the modular
anomaly equation obeyed by the deformed prepotential can be efficiently used to
derive its non-perturbative expression starting from the perturbative one. We
also show that the modular anomaly equation implies that S-duality is
implemented by means of an exact Fourier transform even for arbitrary values of
the deformation parameters, and then we argue that it is possible,
perturbatively in the deformation, to choose appropriate variables such that it
reduces to a Legendre transform.


title: Towards Securing APIs in Cloud Computing

abstract:
  Every organisation today wants to adopt cloud computing paradigm and leverage
its various advantages. Today everyone is aware of its characteristics which
have made it so popular and how it can help the organisations focus on their
core activities leaving all IT services development and maintenance to the
cloud service providers. Application Programming Interfaces (APIs) act as the
interface between the CSPs and the consumers. This paper proposes an improved
access control mechanism for securing the Cloud APIs.


title: Anomalous and Quantum Hall Effects in Lossy Photonic Lattices

abstract:
  We theoretically discuss analogues of the anomalous and the integer quantum
Hall effect in driven-dissipative two-dimensional photonic lattices in the
presence of a synthetic gauge field. Photons are coherently injected by a
spatially localized pump, and the transverse shift of the in-plane light
distribution under the effect of an additional uniform force is considered.
Depending on pumping parameters, the transverse shift turns out to be
proportional either to the global Chern number (integer quantum Hall effect) or
to the local Berry curvature (anomalous Hall effect). This suggests a viable
route to experimentally measure these quantities in photonic lattices.


title:
Effects of anisotropy of turbulent convection in mean-field solar dynamo
  models

abstract:
  We study how anisotropy of turbulent convection affects diffusion of
large-scale magnetic fields and the dynamo process on the Sun. The effect of
anisotropy is calculated in a mean-field magneto-hydrodynamics framework using
the minimal $\tau$-approximation. We examine two types of mean-field dynamo
models: the well-known benchmark flux-transport model, and a distributed-dynamo
model with the subsurface rotational shear layer. For both models we
investigate effects of the double-cell meridional circulation, recently
suggested by helioseismology. We introduce a parameter of anisotropy as a ratio
of the radial and horizontal intensity of turbulent mixing, to characterize the
anisotropy effects. It is found that the anisotropy of turbulent convection
affects the distribution of magnetic fields inside the convection zone. The
concentration of the magnetic flux near the bottom and top boundaries of the
convection zone is greater when the anisotropy is stronger. It is shown that
the critical dynamo number and the dynamo period approach to constant values
for the large anisotropy parameter. The anisotropy reduces the overlap of the
toroidal fields of subsequent cycles in the time-latitude ``butterfly' diagram.
If we assume that sunspots are formed in the vicinity of the subsurface shear
layer, then the distributed dynamo model with anisotropic diffusivity satisfies
the observational constraints from heloseismology results and is consistent
with the value of effective turbulent diffusion, estimated from the dynamics of
surface magnetic fields.


title:
Three dimensional stationary cyclic symmetric Einstein-Maxwell
  solutions; energy, mass, momentum, and algebraic tensors characteristics

abstract:
  The main purpose of this contribution is to determine physical and
geometrical characterizations of whole classes of stationary cyclic symmetric
gravitational fields coupled to Maxwell electromagnetic fields within the
$(2+1)$-dimensional gravity. The physical characterization is based on the
determination of the local and global energy-momentum-mass quantities using the
Brown-York approach. As far as to the algebraic-geometrical characterization is
concerned, the eigenvalue problem for the electromagnetic field,
energy-momentum and Cotton tensors is solved and their types are established.
  The families of Einstein-Maxwell solutions to be considered are: all uniform
electromagnetic solutions possessing electromagnetic fields with vanishing
covariant derivatives (stationary uniform and spinning Clement classes), all
fields having constant electromagnetic field and energy-momentum tensors'
invariants (Kamata-Koikawa solutions), the whole classes of hybrid
electromagnetic Ayon-Cataldo-Garcia solutions, a new family of stationary
electromagnetic solutions, the electrostatic and magnetostatic solutions with
Peldan limit, the Clement spinning charged metric, the
Martinez-Teitelboim-Zanelli black hole solution, and Dias-Lemos electromagnetic
solution.


title:
Effective theory approach to new physics in $b \to u$ and $b \to c$
  leptonic and semileptonic decays

abstract:
  Recent measurements of exclusive $B^{-} \to \tau^{-}\,\nu$ and $B^0 \to
\pi^{+}\,l^{-}\,\bar{\nu}_l$ decays via the $b \to u\,l\,\nu$ transition
process differ from the standard model expectation and, if they persist in
future $B$ experiments, will be a definite hint of the physics beyond the
standard model. Similar hints of new physics have been observed in $b \to c$
semileptonic transition processes as well. BABAR measures the ratio of
branching fractions of $B \to (D,\,D^{\ast})\,\tau\,\nu$ to the corresponding
$B \to (D,\,D^{\ast})\,l\nu$, where $l$ represents either an electron or a
muon, and finds $3.4\sigma$ discrepancy with the standard model expectation. In
this context, we consider a most general effective Lagrangian for the $b \to
u\,l\,\nu$ and $b \to c\,l\,\nu$ transition processes in the presence of new
physics and perform a combined analysis of all the $b \to u$ and $b \to c$
semi-(leptonic) data to explore various new physics operators and their
couplings. We consider various new physics scenarios and give predictions for
the $B_c \to \tau\nu$ and $B \to \pi\tau\nu$ decay branching fractions. We also
study the effect of these new physics parameters on the ratio of the branching
ratios of $B \to \pi\tau\nu$ to the corresponding $B \to \pi\,l\,\nu$ decays.


title:
Estimating the mass of the hidden charm $1^+(1^{+})$ tetraquark state
  via QCD sum rules

abstract:
  By using QCD sum rules, the mass of the hidden charm tetraquark
$[cu][\bar{c}\bar{d}]$ state with $I^{G} (J^{P}) = 1^+ (1^{+})$ (HCTV) is
estimated, which presumably will turn out to be the newly observed
charmonium-like resonance $Z_c^+(3900)$. In the calculation, contributions up
to dimension eight in the operator product expansion(OPE) are taken into
account. We find $m_{1^+}^c = (3912^{+306}_{-153}) \, \text{MeV}$, which is
consistent, within the errors, with the experimental observation of
$Z_c^+(3900)$. Extending to the b-quark sector, $m_{1^+}^b =
(10561^{+395}_{-163}) \,\text{MeV}$ is obtained. The calculational result
strongly supports the tetraquark picture for the "exotic" states of
$Z_c^+(3900)$ and $Z_b^+(10610)$.


title:
Three dimensional stationary cyclic symmetric Einstein-Maxwell
  solutions; black holes

abstract:
  From a general metric for stationary cyclic symmetric gravitational fields
coupled to Maxwell electromagnetic fields within the $(2+1)$-dimensional
gravity the uniqueness of wide families of exact solutions is established,
among them, all uniform electromagnetic solutions possessing electromagnetic
fields with vanishing covariant derivatives, all fields having constant
electromagnetic invariants $F_{\mu\nu}\,F^{\mu\nu}$ and
$T_{\mu\nu}\,T^{\mu\nu}$, the whole classes of hybrid electromagnetic
solutions, and also wide classes of stationary solutions are derived for a
third order nonlinear key equations. Certain of these families can be thought
of as black hole solutions. For the most general set of Einstein-Maxwell
equations, reducible to three non-linear equations for the three unknown
functions, two new classes of solutions-having anti-de Sitter spinning metric
limit-are derived. The relationship of various families with those reported by
different authors' solutions has been established. Among the classes of
solutions with cosmological constant a relevant place occupy: the electrostatic
and magnetostatic Peldan solutions, the stationary uniform and spinning Clement
classes, the constant electromagnetic invariant branches with the particular
Kamata-Koikawa solution, the hybrid cyclic symmetric stationary black hole
fields, and the non-less important solutions generated via $SL(2,R)$
transformations where the Clement spinning charged solution, the
Martinez-Teitelboim-Zanelli black hole solution, and Dias-Lemos metric merit
mention.


title: Characterization of four-qubit states via Bell inequalities

abstract:
  A set of Bell inequalities classifying the quantum entanglement of four-qubit
states is presented. These inequalities involve only two measurement settings
per observer and can characterize fully separable, bi-separable and
tri-separable quantum states. In addition, a quadratic inequality of the Bell
operators for four-qubit systems is derived.


title: A Note on Resistance of NPT to Mixture of Separable States

abstract:
  We study the stability of NPT property of an arbitrary pure entangled state
under the mixture of arbitrary pure separable states. For bipartite pure states
with Schmidt number $n$ $(n>1)$ which is NPT, we show that this state is still
NPT when it is mixed with no more than $\frac{n(n-1)}{2}-1$ arbitrary pure
separable states. This result is generalized to multipartite case.


title:
A Reputation Based Framework to Avoid Free-riding in Unstructured
  Peer-to-Peer network

abstract:
  Free riding is a major problem in peer-to-peer networks. Reputation
management systems are generally proposed to overcome this problem. In this
paper we have discussed a possible way of resource allocation on the basis of
reputation management system i.e. probabilistic allocation based on reputation.
This seems to be a better way for allocation of resources because in this case
nodes that do not have very good reputation about each other, may also serve
each other at least some amount of resource with finite probability. This
avoids disconnect between them. Algorithms are presented for optimizing the
shared capacity, reputation based probabilistic allocation that is optimal for
a node, and formation of interest groups on the basis of similarity between
interests of nodes.


title: Local unitary invariants for multipartite states

abstract:
  We study the invariants of arbitrary dimensional multipartite quantum states
under local unitary transformations. For multipartite pure states, we give a
set of invariants in terms of singular values of coefficient matrices. For
multipartite mixed states, we propose a set of invariants in terms of the trace
of coefficient matrices. For full ranked mixed states with nondegenerate
eigenvalues, this set of invariants is also the necessary and sufficient
conditions for the local unitary equivalence of such two states.


title: One-way Unlocalizable Information Deficit

abstract:
  We introduce one-way unlocalizable information deficit with respect to the
one-way information deficit, similar to the definition of one-way unlocalizable
quantum discord with respect to one-way quantum discord. The properties of the
one-way unlocalizable information deficit and the relations among one-way
unlocalizable information deficit, one-way unlocalizable quantum discord,
one-way quantum discord, one-way information deficit and other quantum
correlations are investigated. Analytical formulas of the one-way unlocalizable
quantum discord are given to detailed examples.


title: Eccentricity is not the only source of elliptic flow fluctuations

abstract:
  Sources of event-by-event elliptic flow fluctuations in relativistic
heavy-ion collisions are investigated in a multiphase transport model. Besides
the well-known initial eccentricity fluctuations, several other sources of
dynamical fluctuations are identified. One is fluctuations in initial parton
configurations at a given eccentricity. Second is quantum fluctuations in
parton interactions during system evolution. Third is fluctuations caused by
hadronization and final-state hadronic scatterings. The magnitudes of these
fluctuations are investigated relative to eccentricity fluctuations and average
flow magnitude. The fluctuations from the latter two sources are found to be
negative. The results may have important implications to the interpretation of
elliptic flow data.


title: Expansion of conjugacy classes in PSL(2,q)

abstract:
  For any conjugacy class C in G=PSL(2,q) we compute C^2 and discuss whether C
contains a triple of elements whose product is 1 which generate G. Moreover, we
determine which elements in G can be written as a product of two conjugate
elements that generate G.


title: On Complexities of Minus Domination

abstract:
  A function f: V \rightarrow \{-1,0,1\} is a minus-domination function of a
graph G=(V,E) if the values over the vertices in each closed neighborhood sum
to a positive number. The weight of f is the sum of f(x) over all vertices x
\in V. The minus-domination number \gamma^{-}(G) is the minimum weight over all
minus-domination functions. The size of a minus domination is the number of
vertices that are assigned 1. In this paper we show that the minus-domination
problem is fixed-parameter tractable for d-degenerate graphs when parameterized
by the size of the minus-dominating set and by d. The minus-domination problem
is polynomial for graphs of bounded rankwidth and for strongly chordal graphs.
It is NP-complete for splitgraphs. Unless P=NP there is no fixed-parameter
algorithm for minus-domination. 79,1 5%


title:
Comparison of electron-ion energy transfer in dense plasmas obtained
  from numerical simulations and quantum kinetic theory

abstract:
  We evaluate various analytical models for the electron-ion energy transfer
and compare the results to data from molecular dynamics (MD) simulations. The
models tested includes energy transfer via strong binary collisions,
Landau-Spitzer rates with different choices for the cut-off parameters in the
Coulomb logarithm, rates based on Fermi's golden rule (FGR) and theories taking
coupled collective modes (CM) into account. In search of a model easy to apply,
we first analyze different approximations of the FGR energy transfer rate. Then
we investigate several numerical studies using MD simulations and try to
uncover CM effects in the data obtained. Most MD data published so far show no
distinct CM effects and, thus, can be interpreted within a FGR or binary
collision approach. We show that this finding is related to the parameter
regime, in particular the initial temperature difference, considered in these
investigations.


title: Architecture of Network and Client-Server model

abstract:
  With the development of Internet technology, the Web is becoming more and
more important in our lives so that it has even become an essential element.
The application of the Web has never been limited to computers; it has been
opened to all kinds of intelligent digital devices like mobile ones. In this
paper, we discuss the main and substantial difference between UDP and TCP, and
how to implement Client-Server model. We also discuss the efficiency of
multi-thread server and its relationship with internet.


title: Basin of attraction of triangular maps with applications

abstract:
  We consider some planar triangular maps. These maps preserve certain
fibration of the plane. We assume that there exists an invariant attracting
fiber and we study the limit dynamics of those points in the basin of
attraction of this invariant fiber, assuming that either it contains a global
attractor, or it is filled by fixed or 2-periodic points. Finally, we apply our
results to a variety of examples, from particular cases of triangular systems
to some planar quasi-homogeneous maps, and some multiplicative and additive
difference equations, as well.


title:
Electronic structure and magnetic properties of Mn, Co, and
  Ni-substitution of Fe in Fe4N

abstract:
  The magnetic properties of Mn, Co and Ni substituted Fe4N are calculated from
first principles theory. It is found that the generalized gradient
approximation reproduces with good accuracy the magnetic moment and equilibrium
volume for the parent Fe4N structure, with the atomic moment largest for the Fe
atom furthest away from the N atom (Fe I site), approaching a value of 3
muB/atom, whereas the Fe atom closer to the N atom (Fe II site) has a moment
closer to that of bcc Fe. Substitution of Fe for Mn, Co or Ni, shows an
intricate behavior in which the Mn substitution clearly favors the Fe II site,
Ni favors substitution on the Fe I site and Co shows no strong preference for
either lattice site. Ni and Co substitution results in a ferromagnetic coupling
to the Fe atoms, whereas Mn couples antiferromagnetically on the Fe II site and
ferromagnetically on the Fe I site. For all types of doping, the total magnetic
moment is enhanced compared with Fe4N only in the energetically very
unfavorable case of Mn doping at the Fe I site.


title:
Impact of nucleon matrix element uncertainties on the interpretation of
  direct and indirect dark matter search results

abstract:
  We study in detail the impact of the current uncertainty in nucleon matrix
elements on the sensitivity of direct and indirect experimental techniques for
dark matter detection. We perform two scans in the framework of the cMSSM: one
using recent values of the pion-sigma term obtained from Lattice QCD, and the
other using values derived from experimental measurements. The two choices
correspond to extreme values quoted in the literature and reflect the current
tension between different ways of obtaining information about the structure of
the nucleon. All other inputs in the scans, astrophysical and from particle
physics, are kept unchanged. We use two experiments, XENON100 and IceCube, as
benchmark cases to illustrate our case. We find that the interpretation of dark
matter search results from direct detection experiments is more sensitive to
the choice of the central values of the hadronic inputs than the results of
indirect search experiments. The allowed regions of cMSSM parameter space after
including XENON100 constrains strongly differ depending on the assumptions on
the hadronic matrix elements used. On the other hand, the constraining
potential of IceCube is almost independent of the choice of these values.


title:
Search for time-independent neutrino emission from astrophysical sources
  with 3 years of IceCube data

abstract:
  We present the results of a search for neutrino point sources using the
IceCube data collected between April 2008 and May 2011 with three partially
completed configurations of the detector: the 40-, 59- and 79-string
configurations. The live-time of this data set are 1,040 days. An unbinned
maximum likelihood ratio test was used to search for an excess of neutrinos
above the atmospheric background at any given direction in the sky. By adding
two more years of data with improved event selection and reconstruction
techniques, the sensitivity was improved by a factor 3.5 or more with respect
to the previously published results obtained with the 40-string configuration
of IceCube. We performed an all-sky survey and a dedicated search using a
catalog of \textit{a priori} selected objects observed by other telescopes. In
both searches, the data are compatible with the background-only hypothesis. In
the absence of evidence for a signal, we set upper limits on the flux of muon
neutrinos. For an E$^{-2}$ neutrino spectrum, the observed limits are between
0.9 and $23.2\times 10^{-12}$ TeV$^{-1}$ cm$^{-2}$s$^{-1}$. We also report
upper limits for neutrino emission from groups of sources which were selected
according to theoretical models or observational parameters and analysed with a
stacking approach.


title: Asteroseismology of DAV white dwarf stars and G29-38

abstract:
  Asteroseismology is a powerful tool to detect the inner structure of stars.
It is also widely used to study white dwarfs. In this paper, we discuss the
asteroseismology work of DAV stars. The detailed period to period fitting
method is fully discussed, including the reliability to detect the inner
structure of DAV stars. If we assume that all observed modes of some DAV star
are the $l$ = 1 ones, the errors of model fitting will be always great. If we
assume that the observed modes are composed of $l$ = 1 and 2 modes, the errors
of model fitting will be small. However, there will be modes identified as $l$
= 2 without quintuplets observed. G29-38 has been observed spectroscopically
and photometrically for many years. Thompson et al. (2008) made $l$
identifications for the star through limb darkening effect. With eleven known
$l$ modes, we also do the asteroseismology work for G29-38, which reduces the
blind $l$ fittings and is a fair choice. Unfortunately, our two best-fitting
models are not in line with the previous atmospheric results. Based on factors
of only a few modes observed, stability and identification of eigenmodes,
identification of spherical degrees, construction of physical and realistic
models and so on, detecting the inner structure of DAV stars by
asteroseismology needs further development.


title:
Near-forward Raman scattering by bulk and surface phonon-polaritons in
  the model percolation-type ZnBeSe alloy

abstract:
  We study the bulk and surface phonon-polaritons of the Zn0.67Be0.33Se
zincblende alloy by near-forward Raman scattering. The short (Be-Se) bond
exhibits a distinct percolation doublet in the conventional backscattering
Raman spectra, corresponding to a three-mode behavior in total
[1(Zn-Se),2(Be-Se)] for Zn0.67Be0.33Se. This offers an opportunity to achieve a
refined understanding of the phonon-polariton modes of a zincblende alloy
beyond the current two-mode approximation, corresponding to a
[1(Zn-Se),1(Be-Se)] description in the present case. The discussion is
supported by contour modeling of the Raman signals of the multi-mode bulk and
surface phonon-polaritons within the formalism of the linear dielectric
response.


title:
Lagrangian acceleration of passive tracers in statistically-steady
  rotating turbulence

abstract:
  The statistical properties of the Lagrangian acceleration vector of passive
tracers in statistically-steady rotating turbulence is studied by Particle
Tracking Velocimetry. Direct effects of the background rotation are the
suppression of high-acceleration events parallel to the (vertical) rotation
axis, the enhancement of high-acceleration events for the horizontal
acceleration, and the strong amplification of the auto-correlation of the
acceleration component perpendicular to both the rotation vector \Omega\ and
local velocity vector u. The auto-correlation of the acceleration component in
the plane set up by \Omega\ and u is only mildly enhanced.


title: Mutual information matrices are not always positive semi-definite

abstract:
  For discrete random variables X_1,..., X_n we construct an n by n matrix. In
the (i,j) entry we put the mutual information I(X_i;X_j) between X_i and X_j.
In particular, in the (i,i) entry we put the entropy H(X_i)=I(X_i;X_i) of X_i.
This matrix, called the mutual information matrix of (X_1,...,X_n), has been
conjectured to be positive semi-definite. In this note, we give counterexamples
to the conjecture, and show that the conjecture holds for up to three random
variables.


title:
Fluctuations in the zero set of the hyperbolic Gaussian analytic
  function

abstract:
  The zero set of the hyperbolic Gaussian analytic function is a random point
process in the unit disc whose distribution is invariant under automorphisms of
the disc. We study the variance of the number of points in a disc of increasing
radius. Somewhat surprisingly, we find a change of behaviour at a certain value
of the `intensity' of the process, which appears to be novel.


title: Tuning the Conductance of Monatomic Carbon Chain

abstract:
  Ab initio calculations show that the conductance of short monatomic carbon
chain can be dramatically modified by adhering a single H, N, or O atom to the
chain. For example, the conductance of the pristine chain gets about two orders
of magnitude smaller if an H atom is adhered to the chain. By a statistical
model, the structure of the carbon chain with the single atom adhered is found
to be quite stable at room temperature, indicating that the method can be used
to tune the conductance of monatomic carbon chain.


title: On the non-Markovian Enskog Equation for Granular Gases

abstract:
  We develop a rigorous formalism for the description of the kinetic evolution
of many-particle systems with the dissipative interaction. The relationships of
the evolution of a hard sphere system with inelastic collisions described
within the framework of marginal observables governed by the dual BBGKY
hierarchy and the evolution of states described by the Cauchy problem of the
Enskog kinetic equation for granular gases are established. Moreover, we
consider the Boltzmann--Grad asymptotic behavior of the constructed
non-Markovian Enskog kinetic equation for granular gases in a one-dimensional
space.


title:
Large deviations for solutions to stochastic recurrence equations under
  Kesten's condition

abstract:
  In this paper we prove large deviations results for partial sums constructed
from the solution to a stochastic recurrence equation. We assume Kesten's
condition [Acta Math. 131 (1973) 207-248] under which the solution of the
stochastic recurrence equation has a marginal distribution with power law
tails, while the noise sequence of the equations can have light tails. The
results of the paper are analogs to those obtained by A. V. Nagaev [Theory
Probab. Appl. 14 (1969) 51-64; 193-208] and S. V. Nagaev [Ann. Probab. 7 (1979)
745-789] in the case of partial sums of i.i.d. random variables. In the latter
case, the large deviation probabilities of the partial sums are essentially
determined by the largest step size of the partial sum. For the solution to a
stochastic recurrence equation, the magnitude of the large deviation
probabilities is again given by the tail of the maximum summand, but the exact
asymptotic tail behavior is also influenced by clusters of extreme values, due
to dependencies in the sequence. We apply the large deviation results to study
the asymptotic behavior of the ruin probabilities in the model.


title: Highest-weight vectors for the adjoint action of GL_n on polynomials, II

abstract:
  Let G=GL_n be the general linear group over an algebraically closed field k
and let g=gl_n be its Lie algebra. Let U be the subgroup of G which consists of
the upper unitriangular matrices. Let k[g] be the algebra of polynomial
functions on g and let k[g]^G be the algebra of invariants under the
conjugation action of G. For all weights chi in Z^n with chi_2<=0 or
chi_{n-1}>=0 we give explicit bases for the k[g]^G-module k[g]^U_chi of highest
weight vectors of weight chi. This extends earlier results to a much bigger
class of weights. To express our semi-invariants in terms of matrix powers we
prove certain Cayley-Hamilton type identities.


title:
Expurgated Random-Coding Ensembles: Exponents, Refinements and
  Connections

abstract:
  This paper studies expurgated random-coding bounds and exponents for channel
coding with a given (possibly suboptimal) decoding rule. Variations of
Gallager's analysis are presented, yielding several asymptotic and
non-asymptotic bounds on the error probability for an arbitrary codeword
distribution. A simple non-asymptotic bound is shown to attain an exponent of
Csisz\'ar and K\"orner under constant-composition coding. Using Lagrange
duality, this exponent is expressed in several forms, one of which is shown to
permit a direct derivation via cost-constrained coding which extends to
infinite and continuous alphabets. The method of type class enumeration is
studied, and it is shown that this approach can yield improved exponents and
better tightness guarantees for some codeword distributions. A generalization
of this approach is shown to provide a multi-letter exponent which extends
immediately to channels with memory. Finally, a refined analysis expurgated
i.i.d. random coding is shown to yield a O\big(\frac{1}{\sqrt{n}}\big)
prefactor, thus improving on the standard O(1) prefactor. Moreover, the implied
constant is explicitly characterized.


title: Bell inequality and nonlocality in a two-dimensional mixed spin systems

abstract:
  In this paper, we use Bell inequality and nonlocality to study the bipartite
correlation in an exactly soluble two-dimensional mixed spin system. Bell
inequality turns out to be a valuable detector for phase transitions in this
model. It can detect not only the quantum phase transition, but also the
thermal phase transitions, of the system. The property of bipartite correlation
in the system is also analyzed. In the quantum anti-ferromagnetic phase, the
Bell inequality is violated thus nonlocality is present. It is interesting that
the nonlocality is enhanced by thermal fluctuation, and similar results have
not been observed in anti-ferromagnetic phase. In the ferromagnetic phase, the
quantum correlation turns out to be very novel, which cannot be captured by
entanglement or nonlocality.


title: Oscillating Entropy

abstract:
  The log-periodic equation for the entropy $S = - (k/a) \sum_{i=1}^{N} p_{i}
\sin(a \ln p_{i})$, based on the forgotten Sharma-Taneja entropy measure, is
studied for the first time with $N$ the total number of system states and
$p_{i}$ the associated probabilities. It is argued that an oscillatory regime
for $S$ could in principle be understood in terms of a linear time-dependent
behavior for the associated probabilities in analogy with a spring system of
frequency $w$ gaining momentum from the surroundings. The physical meaning for
the production of entropy given by the parameter $a$ relates the angle $\omega
t$. We discuss its properties, and make a connection with the non-extensive
Tsallis, R\'{e}nyi, Boltzmann-Gibbs and Shannon entropies as special limiting
cases for systems with constant mass. Our non-trivial form of entropy displays
peculiar concavity and addition properties. Log-periodicity in $S$, concavity
lost, and non-additivity are manifested by increasing the value of the
coefficient $a$, which sets the variations with respect to the behavior of the
monotonic Gibbs entropy function. We have considered systems with linearly
increasing mass and have explained how "oscillating entropy" in such systems
may appear.


title: Phase Model with Feedback Control for Power Grids

abstract:
  A phase model with feedback control is studied as a dynamical model of power
grids. As an example, we study a model network corresponding to the power grid
in the Kyushu region. The standard frequency is maintained by the mutual
synchronization and the feedback control. Electric failures are induced by an
overload. We propose a local feedback method in which the strength of feedback
control is proportional to the magnitude of generators. We find that the
electric failures do not occur until the utilization ratio is close to 1 under
this feedback control. We also find that the temporal response for the
time-varying input power is suppressed under this feedback control. We explain
the mechanisms using the corresponding global feedback method.


title:
Completeness of first and second order ODE flows and of Euler-Lagrange
  equations

abstract:
  Two results on the completeness of maximal solutions to first and second
order ordinary differential equations (or inclusions) over complete Riemannian
manifolds, with possibly time-dependent metrics, are obtained. Applications to
Lagrangian mechanics and gravitational waves are given.


title: Variational approximations for stationary states of Ising-like models

abstract:
  We introduce a new variational approach to the stationary state of kinetic
Ising-like models. The approach is based on the cluster expansion of the
entropy term appearing in a functional which is minimized by the system
history. We rederive a known mean-field theory and propose a new method, here
called diamond approximation, which turns out to be more accurate and faster
than other methods of comparable computational complexity.


title: GARCH-extended models: theoretical properties and applications

abstract:
  This paper is concerned with some properties of the generalized GARCH models,
obtained by extending GARCH models with exogenous variables, the so-called
GARCH extended (GARCHX) models. For these, we establish sufficient conditions
for some properties such as stationarity, existence of moments, ergodicity,
geometric ergodicity, consistence and asymptotic normality of likelihood
estimators of the model parameters. For some of these properties we show that
the conditions that we propose are also necessary. We further provide examples
and applications to illustrate and highlight the importance of our findings.


title: Shock Waves in Falling Coupled Harmonic Oscillators

abstract:
  Shock waves propagate in falling coupled harmonic oscillators. The bottom end
of coupled harmonic oscillators does not fall downwards until a shock wave
reaches the bottom end. The exact solution can be expressed by the Fourier
series expansion, and an approximate solution can be expressed by the integral
of the Airy function. The width of the shock wave increases slowly in
accordance with a power law.


title:
Nonequilibrium dynamics of an exactly solvable Ising-like model and
  protein translocation

abstract:
  Using an Ising-like model of protein mechanical unfolding, we introduce a
diffusive dynamics on its exactly known free energy profile, reducing the
nonequilibrium dynamics of the model to a biased random walk. As an
illustration, the model is then applied to the protein translocation
phenomenon, taking inspiration from a recent experiment on the green
fluorescent protein pulled by a molecular motor. The average translocation time
is evaluated exactly, and the analysis of single trajectories shows that
translocation proceeds through an intermediate state, similar to that observed
in the experiment.


title:
Gaussian lower bounds on the Dirichlet heat kernel and non-existence of
  local solutions for semilinear heat equations of Osgood type

abstract:
  We give a simple proof of a lower bound for the Dirichlet heat kernel in
terms of the Gaussian heat kernel. Using this we establish a non-existence
result for semilinear heat equations with zero Dirichlet boundary conditions
and initial data in $L^q(\Omega)$ when the source term $f$ is non-decreasing
and $\limsup_{s\to\infty}s^{-\gamma}f(s)=\infty$ for some $\gamma>q(1+2/n)$.
This allows us to construct a locally Lipschitz $f$ satisfying the Osgood
condition $\int_{1}^{\infty}1/f(s)\ \,\d s =\infty$, which ensures global
existence for bounded initial data, such that for every $q$ with $1\le
q<\infty$ there is an initial condition $u_0\in L^q(\Om)$ for which the
corresponding semilinear problem has no local-in-time solution.


title:
Rapidity and momentum transfer distributions of coherent $J/\psi$
  photoproduction in ultraperipheral pPb collisions at the LHC

abstract:
  Based on accurate calculations of the flux of equivalent photons of the
proton and heavy nuclei and the pQCD framework for the gluon distribution in
the proton and nuclei, we analyze the rapidity and momentum transfer
distributions of coherent $J/\psi$ photoproduction in ultraperipheral proton-Pb
collisions at the LHC. We demonstrate that unlike the case of proton-proton
UPCs marred by certain theoretical uncertainties and experimental limitations,
after a cut excluding the region of small momentum transfers, ultraperipheral
proton-Pb collisions offer a clean way to study the gluon distribution in the
proton down to $x \approx 10^{-5}$. Our analysis of the momentum transfer
distributions shows that an interplay of $J/\psi$ production by low-energy
photons on the nucleus and by high-energy photons on the proton in proton-Pb
UPCs can result in some excess of events at small $p_t$ in a definite region of
the rapidity y.


title:
Spectroscopic evidence for giant orbital moment and magnetic anisotropy
  induced by local distortions in alpha-CoV2O6

abstract:
  We present a combined experimental and theoretical study on the local
magnetism of the Co ions in the spin-chain compound CoV2O6, which crystallizes
in two different allotropic phases, alpha- and gamma-CoV2O6. Using x-ray
magnetic circular dichroism, we have found a very large and a moderate orbital
contribution to the magnetism in alpha- and gamma-CoV2O6, respectively.
Full-multiplet calculations indicate that the differences in the magnetic
behavior of alpha- and gamma-CoV2O6 phases originate from different local
distortions of the CoO6 octahedra. In particular, the strong compression of the
CoO6 octahedra in alpha-CoV2O6 lead to a strong mixture of t2g and eg orbitals
which, via the local atomic Coulomb and exchange interactions, results in an
exceptionally large orbital moment.


title: Dynamics of exciton-polaritons in a Josephson double dimer

abstract:
  We study the dynamics of exciton-polaritons in a double-well configuration.
The system consists of two weakly coupled Bose-Josephson junctions, each
corresponding to a different circular polarization of the polaritons, forming a
{\it Josephson double dimer}. We show that the Josephson oscillation between
the wells is strongly coupled to the polarization rotation and that
consequently Josephson excitation is periodically exchanged between the two
polarizations. Linearized analysis agrees well with numerical simulations using
typical experimental parameters.


title: A General Formula for the Generation Time

abstract:
  We show that the generation time -- a notion usually described in a
biological context -- can be defined in a general way as a return time in a
conveniently constructed finite Markov chain. The simple formula we obtain
agrees with previous results derived for structured populations projected in
discrete time, and allows to define the generation time of any process
described by a weighted directed graph whose matrix is primitive.


title: A short proof of a famous combinatorial identity

abstract:
  We explain how the identity
$$\sum_{i+j=n}\binom{2i}{i}\binom{2j}{j}\;=\;\displaystyle4^n$$ is an easy
consequence of the inclusion-exclusion principle.


title:
Conformally related metrics and Lagrangians and their physical
  interpretation in cosmology

abstract:
  Conformally related metrics and Lagrangians are considered in the context of
scalar-tensor gravity cosmology. After the discussion of the problem, we pose a
lemma in which we show that the field equations of two conformally related
Lagrangians are also conformally related if and only if the corresponding
Hamiltonian vanishes. Then we prove that to every non-minimally coupled scalar
field, we may associate a unique minimally coupled scalar field in a
conformally related space with an appropriate potential. The latter result
implies that the field equations of a non-minimally coupled scalar field are
the same at the conformal level with the field equations of the minimally
coupled scalar field. This fact is relevant in order to select physical
variables among conformally equivalent systems. Finally, we find that the above
propositions can be extended to a general Riemannian space of n-dimensions.


title: Where Do Thin Tails Come From?

abstract:
  The literature of heavy tails (typically) starts with a random walk and finds
mechanisms that lead to fat tails under aggregation. We follow the inverse
route and show how starting with fat tails we get to thin-tails when deriving
the probability distribution of the response to a random variable. We introduce
a general dose-response curve and argue that the left and right-boundedness or
saturation of the response in natural things leads to thin-tails, even when the
"underlying" random variable at the source of the exposure is fat-tailed.


title:
Lattice Study on quantum-mechanical dynamics of two-color QCD with six
  light flavors

abstract:
  We investigate the chiral properties of SU(2) gauge theory with six flavors,
i.e. six light Dirac fermions in the fundamental representations by lattice
simulation, and point out that the spontaneous breakdown of chiral symmetry
does not occur in this system. The quark mass dependence of the mesonic
spectrum provides an evidence for such a possibility. The decay constant tends
to be increased by the finite size effect, which is opposite to the behavior
predicted by chiral perturbation theory and indicates that the long distance
dynamics in the six-flavor theory could be different from the theory with
chiral symmetry breaking. The subtracted chiral condensate, whose utility is
demonstrated by the simulation of two-flavor theory, is shown to vanish in the
chiral limit within the precision of available data.


title:
Representations of fundamental groups of 3-manifolds into PGL(3,C):
  Exact computations in low complexity

abstract:
  In this paper we are interested in computing representations of the
fundamental group of a 3-manifold into PSL(3;C) (in particular in PSL(2;C);
PSL(3;R) and PU(2; 1)). The representations are obtained by gluing decorated
tetrahedra of flags. We list complete computations (giving 0-dimensional or
1-dimensional solution sets) for the first complete hyperbolic non-compact
manifolds with finite volume which are obtained gluing less than three
tetrahedra with a description of the computer methods used to find them.


title: Synchronous motion in a devil's stick -- variation on a theme by Kapitza

abstract:
  The counter-intuitive rotational motion of the propeller of a devil's stick
when the agitator is rubbed against the pylon has long intrigued performers,
audiences and scientists. The apparently unrelated phenomenon of
self-stabilization of a Kapitza pendulum at the inverted position, once again
an amazing lecture demonstration, has on the other hand been subjected to years
of investigation and research. Here we show that the two systems are in fact
identical, and obtain a previously unreported, friction-stabilized
synchronously rotating state in the Kapitza pendulum, which in fact explains
the rotational motion of the Devil's stick.


title: Phenomenology of the exclusive rare semileptonic decay B -> K pi l^+ l^-

abstract:
  I review the phenomenology of exclusive Bbar -> Kbar pi l^+ l^- decays, with
focus on the intermediate resonant Kbar^*(892) mode. The status of angular
observables at both ends of the dilepton mass spectrum is revisited.
Constraints on the b -> s Wilson coefficients C_7,C_9,C_10 based on 2011 data
from the B factories, CDF and LHCb are presented.


title: X-ray observations of powerful AGN outflows - implications for feedback

abstract:
  Highly ionised winds with velocities ~ 0.1-0.2c were first detected in X-ray
spectra of non-BAL AGN a decade ago. Subsequent observations and archival
searches have shown such winds to be a common feature of luminous AGN,
increasing the belief that powerful ionised winds have a wider importance in
galaxy feedback models. Paradoxically, for the best-quantified high velocity
outflow (the luminous Seyfert PG1211+143) the wind appears too powerful to be
compatible with the observed stellar bulge and black hole masses, suggesting
the energy coupling of wind to bulge gas must be inefficient. A recent
XMM-Newton observation of the narrow line Seyfert NGC 4051 offers an
explanation of this apparent paradox, finding evidence for the fast ionised
wind to lose most of its kinetic energy after shocking against the ISM.
Importantly, the wind momentum is maintained through such a shock, supporting
the view that a momentum-driven flow provides the critical link between black
hole and stellar bulge masses implied by the observed M-sigma relationship.


title:
Iterative Estimation of Solutions to Noisy Nonlinear Operator Equations
  in Nonparametric Instrumental Regression

abstract:
  This paper discusses the solution of nonlinear integral equations with noisy
integral kernels as they appear in nonparametric instrumental regression. We
propose a regularized Newton-type iteration and establish convergence and
convergence rate results. A particular emphasis is on instrumental regression
models where the usual conditional mean assumption is replaced by a stronger
independence assumption. We demonstrate for the case of a binary instrument
that our approach allows the correct estimation of regression functions which
are not identifiable with the standard model. This is illustrated in computed
examples with simulated data.


title: A unified approach to the performance analysis of caching systems

abstract:
  We propose a unified methodology to analyse the performance of caches (both
isolated and interconnected), by extending and generalizing a decoupling
technique originally known as Che's approximation, which provides very accurate
results at low computational cost. We consider several caching policies, taking
into account the effects of temporal locality. In the case of interconnected
caches, our approach allows us to do better than the Poisson approximation
commonly adopted in prior work. Our results, validated against simulations and
trace-driven experiments, provide interesting insights into the performance of
caching systems.


title:
Pattern Formation in Liquid-Vapor Systems under Periodic Potential and
  Shear

abstract:
  In this paper the phase behavior and pattern formation in a sheared non-ideal
fluid under a periodic potential is studied. An isothermal two-dimensional
formulation of a lattice Boltzmann scheme for a liquid-vapor system with the
van der Waals equation of state is presented and validated. Shear is applied by
moving walls and the periodic potential will vary along the flow direction. A
region of the parameter space, where in absence of flow a striped phase with
oscillating density is stable, will be considered. At low shear rates the
periodic patterns are preserved and slightly distorted by the flow. At high
shear rates the striped phase looses its stability and a new phase with
interface waves between the liquid and vapor regions will appear. Velocity
field patterns will be also shown.


title: Texture of ZnO thin films deposited through microwave irradiation

abstract:
  We report the crystallographic texture of ZnO thin films comprising nanorods
grown by a microwave irradiation assisted method. Different substrates were
used, namely Si, Ge, metal coated Si, PMMA coated Si and ITO coated glass, to
examine the respective development of crystallographic texture. The films were
characterized by Xray diffraction and scanning electron microscopy, while the
texture analysis was done by Xray pole figure analysis using the Schultz
reflection method. The ZnO film deposited on Si and Ge showed a mixed texture.
On all the other substrates, c axis oriented ZnO films were obtained.


title: Drawing dynamical and parameter planes of iterative families and methods

abstract:
  In this paper the complex dynamical analysis of the parametric fourth-order
Kim's iterative family is made on quadratic polynomials, showing the Matlab
codes generated to draw the fractal images necessary to complete the study. The
parameter spaces associated to the free critical points have been analyzed,
showing the stable (and unstable) regions where the selection of the parameter
will provide us excellent schemes (or dreadful ones).


title: Automorphicity and Mean-Periodicity

abstract:
  If C is a smooth projective curve over a number field k, then, under fair
hypotheses, its L-function admits meromorphic continuation and satisfies the
anticipated functional equation if and only if a related function is
X-mean-periodic for some appropriate functional space X. Building on the work
of Masatoshi Suzuki for modular elliptic curves, we will explore the dual
relationship of this result to the widely believed conjecture that such
L-functions should be automorphic. More precisely, we will directly show the
orthogonality of the matrix coefficients of GL_{2g}-automorphic representations
to certain vector spaces which are constructed from the Mellin transforms of
specified products of arithmetic zeta functions corresponding to a model of the
curve and the base number field. To compare automorphicity and
mean-periodicity, we use a technique emulating the Rankin-Selberg method, in
which the function mean-periodic function plays the role of an Eisenstein
series, exploiting the spectral interpretation of the zeros of automorphic
$L$-functions.


title:
"We Think That We Think Clearly, But That's Only Because We Don't Think
  Clearly": Mathematics, Mind, and the Human World

abstract:
  This paper is concerned with a dialogue between Rabindranath Tagore and
Albert Einstein, where Tagore argued that our knowledge is essentially human,
while Einstein maintained that some kinds of knowledge are more objective.
Arguments by Davis and Hersh concerning the nature of mathematics support the
idea of mathematical truth being a human construct. It may further be argued
that the scientific theories we arrive at are very much a result of the
particular mathematical and experimental tools that we use. There may however
be a deeper kind of knowledge that science has yet to understand.


title: Extremal edge polytopes

abstract:
  The "edge polytope" of a finite graph G is the convex hull of the columns of
its vertex-edge incidence matrix. We study extremal problems for this class of
polytopes. For k =2, 3, 5 we determine the maximum number of vertices of
k-neighborly edge polytopes up to a sublinear term. We also construct a family
of edge polytopes with exponentially-many facets.


title:
Formation and collision of traveling bands in interacting deformable
  self-propelled particles

abstract:
  We study collective dynamics of interacting deformable self-propelled
particles whose migration velocity increases when the local density of
particles is increased. Numerical simulations in two dimensions reveal that
traveling bands similar to those found previously in the Vicsek-type model is
easily formed by this local density dependence of the migration velocity. We
show that a pair of stripe bands which are traveling to the opposite directions
is not destructed by a head-on collision but survives again after collision.


title: Fundamental monogamy relation between contextuality and nonlocality

abstract:
  We show that the no-disturbance principle imposes a tradeoff between locally
contextual correlations violating the Klyachko-Can-Binicioglu-Shumovski
inequality and spatially separated correlations violating the
Clauser-Horne-Shimony-Holt inequality. The violation of one inequality forbids
the violation of the other. We also obtain the corresponding monogamy relation
imposed by quantum theory for a qutrit-qubit system. Our results show the
existence of fundamental monogamy relations between contextuality and
nonlocality that suggest that entanglement might be a particular form of a more
fundamental resource.


title: Study of Encryption and Decryption of Wave File in Image Formats

abstract:
  This paper describes a novel method of encrypting wave files in popular image
formats like JPEG, TIF and PNG along with retrieving them from these image
files. MATLAB software is used to perform matrix manipulation to encrypt and
decrypt sound files into and from image files. This method is not only a
stenographic means but also a data compression technique.


title:
WZ Sge-type dwarf novae with multiple rebrightenings: MASTER OT
  J211258.65+242145.4 and MASTER OT J203749.39+552210.3

abstract:
  We report on photometric observations of WZ Sge-type dwarf novae, MASTER OT
J211258.65+242145.4 and MASTER OT J203749.39+552210.3 which underwent outbursts
in 2012. Early superhumps were recorded in both systems. During superoutburst
plateau, ordinary superhumps with a period of 0.060291(4) d (MASTER J211258)
and of 0.061307(9) d (MASTER J203749) in average were observed. MASTER J211258
and MASTER J203749 exhibited eight and more than four post-superoutburst
rebrightenings, respectively. In the final part of the superoutburst, an
increase in the superhump periods was seen in both systems. We have made a
survey of WZ Sge-type dwarf novae with multiple rebrightenings, and confirmed
that the superhump periods of WZ Sge-type dwarf novae with multiple
rebrightenings were longer than those of WZ Sge-type dwarf novae without a
rebrightening. Although WZ Sge-type dwarf novae with multiple rebrightenings
have been thought to be the good candidates for period bouncers based on their
low mass ratio (q) from inferred from the period of fully grown (stage B)
superhumps, our new method using the period of growing superhumps (stage A
superhumps), however, implies higher q than those expected from stage B
superhumps. These q values appear to be consistent with the duration of the
stage A superoutbursts, which likely reflects the growth time of the 3:1
resonance. We present a working hypothesis that the small fractional superhump
excesses for stage B superhumps in these systems may be explained as a result
that a higher gas pressure effect works in these systems than in ordinary SU
UMa-type dwarf novae. This result leads to a new picture that WZ Sge-type dwarf
novae with multiple rebrightenings and SU UMa-type dwarf novae without a
rebrightening (they are not period bouncers) are located in the same place on
the evolutionary track.


title:
A large-area single photon sensor employing wavelength-shifting and
  light-guiding technology

abstract:
  Large-scale underground water-Cherenkov neutrino observatories rely on single
photon sensors whose sensitive area for Cherenkov photons one wants to
maximise. Low dark noise rates and dense module spacing will thereby allow to
substantially decrease the energy threshold in future projects. We describe a
feasibility study of a novel type of single photon sensor that employs organic
wavelength-shifting material (WLS) to capture Cherenkov photons and guide them
to a PMT readout. Different WLS materials have been tested in lab measurements
as candidates for use in such a sensor and photon capture efficiencies as high
as 50 % have been achieved. Based on these findings we estimate that the
effective photosensitive area of a prototype built with existing technology can
easily exceed that of modules currently used e. g. in IceCube. Additionally,
the dark noise rate of such a module can be exceptionally low in the order of
10 Hz. This is of special importance when targeting low-energy neutrinos that
yield only few photons that need to be distinguished from noise hits.


title: Neutron Star Matter

abstract:
  In this presentation I discuss two aspects of the neutron-matter equation of
state. One relates to the symmetry energy of nuclear matter and empirical
constraints on its slope parameter at saturation density. The second deals with
spatially inhomogeneous chiral phases of deconfined quark matter in the inner
core of a neutron star.


title:
Numerical Study of Drop Motion on a Surface with Wettability Gradient
  and Contact Angle Hysteresis

abstract:
  In this work, the motion of a 2-D drop on a surface with given wettability
gradient is studied numerically by a hybrid lattice-Boltzmann finite-difference
method using the multiple-relaxation-time collision model. We incorporate the
geometric wetting boundary condition that allows accurate implementation of a
contact angle hysteresis model. The method is first validated through three
benchmark tests, including the layered Poiseuille flow with a viscosity
contrast, the motion of a liquid column in a channel with specified wettability
gradient and the force balance for a static drop attached to a surface with
hysteresis subject to a body force. Then, simulations of a drop on a wall with
given wettability gradient are performed under different conditions. The
effects of the Reynolds number, the viscosity ratio, the wettability gradient,
as well as the contact angle hysteresis on the drop motion are investigated in
detail. It is found that the capillary number of the drop in steady state is
significantly affected by the viscosity ratio, the magnitudes of the
wettability gradient and the contact angle hysteresis, whereas it only shows
very weak dependence on the Reynolds number.


title:
Aggregation and Control of Populations of Thermostatically Controlled
  Loads by Formal Abstractions

abstract:
  This work discusses a two-step procedure, based on formal abstractions, to
generate a finite-space stochastic dynamical model as an aggregation of the
continuous temperature dynamics of a homogeneous population of Thermostatically
Controlled Loads (TCL). The temperature of a single TCL is described by a
stochastic difference equation and the TCL status (ON, OFF) by a deterministic
switching mechanism. The procedure is formal as it allows the exact
quantification of the error introduced by the abstraction -- as such it builds
and improves on a known, earlier approximation technique in the literature.
Further, the contribution discusses the extension to the case of a
heterogeneous population of TCL by means of two approaches resulting in the
notion of approximate abstractions. It moreover investigates the problem of
global (population-level) regulation and load balancing for the case of TCL
that are dependent on a control input. The procedure is tested on a case study
and benchmarked against the mentioned alternative approach in the literature.


title: An algorithm for producing F-pure ideals

abstract:
  This paper describes a method for computing all F-pure ideals for a given
Cartier map of a polynomial ring over a finite field.


title: Van der Waals heterostructures

abstract:
  Research on graphene and other two-dimensional atomic crystals is intense and
likely to remain one of the hottest topics in condensed matter physics and
materials science for many years. Looking beyond this field, isolated atomic
planes can also be reassembled into designer heterostructures made layer by
layer in a precisely chosen sequence. The first - already remarkably complex -
such heterostructures (referred to as 'van der Waals') have recently been
fabricated and investigated revealing unusual properties and new phenomena.
Here we review this emerging research area and attempt to identify future
directions. With steady improvement in fabrication techniques, van der Waals
heterostructures promise a new gold rush, rather than a graphene aftershock.


title: Weyl asymptotics for Hanoi attractors

abstract:
  The asymptotic behaviour of the eigenvalue counting function of Laplacians on
Hanoi attractors is determined. To this end, Dirichlet and resistance forms are
constructed. Due to the non self-similarity of these sets, the classical
construction of the Laplacian for p.c.f. self-similar fractals has to be
modified by combining discrete and quantum graphs methods.


title: Non-symmetric magnetohydrostatic equilibria: a multigrid approach

abstract:
  Aims. Linear magnetohydrostatic (MHS) models of solar magnetic fields balance
plasma pressure gradients, gravity and Lorentz forces where the current density
is composed of a linear force-free component and a cross-field component that
depends on gravitational stratification. In this paper, we investigate an
efficient numerical procedure for calculating such equilibria.
  Methods. The MHS equations are reduced to two scalar elliptic equations - one
on the lower boundary and the other within the interior of the computational
domain. The normal component of the magnetic field is prescribed on the lower
boundary and a multigrid method is applied on both this boundary and within the
domain to find the poloidal scalar potential. Once solved to a desired
accuracy, the magnetic field, plasma pressure and density are found using a
finite difference method.
  Results. We investigate the effects of the cross-field currents on the linear
MHS equilibria. Force-free and non-force-free examples are given to demonstrate
the numerical scheme and an analysis of speed-up due to parallelization on a
graphics processing unit (GPU) is presented. It is shown that speed-ups of x30
are readily achievable.


title: Graph homomorphisms between trees

abstract:
  In this paper we study several problems concerning the number of
homomorphisms of trees. We give an algorithm for the number of homomorphisms
from a tree to any graph by the Transfer-matrix method. By using this algorithm
and some transformations on trees, we study various extremal problems about the
number of homomorphisms of trees. These applications include a far reaching
generalization of Bollob\'as and Tyomkyn's result concerning the number of
walks in trees.
  Some other highlights of the paper are the following. Denote by $\hom(H,G)$
the number of homomorphisms from a graph $H$ to a graph $G$. For any tree $T_m$
on $m$ vertices we give a general lower bound for $\hom(T_m,G)$ by certain
entropies of Markov chains defined on the graph $G$. As a particular case, we
show that for any graph $G$,
$$\exp(H_{\lambda}(G))\lambda^{m-1}\leq\hom(T_m,G),$$ where $\lambda$ is the
largest eigenvalue of the adjacency matrix of $G$ and $H_{\lambda}(G)$ is a
certain constant depending only on $G$ which we call the spectral entropy of
$G$. In the particular case when $G$ is the path $P_n$ on $n$ vertices, we
prove that $$\hom(P_m,P_n)\leq \hom(T_m,P_n)\leq \hom(S_m,P_n),$$ where $T_m$
is any tree on $m$ vertices, and $P_m$ and $S_m$ denote the path and star on
$m$ vertices, respectively. We also show that if $T_m$ is any fixed tree and
$$\hom(T_m,P_n)>\hom(T_m,T_n),$$ for some tree $T_n$ on $n$ vertices, then
$T_n$ must be the tree obtained from a path $P_{n-1}$ by attaching a pendant
vertex to the second vertex of $P_{n-1}$.
  All the results together enable us to show that $$
|\End(P_m)|\leq|\End(T_m)|\leq|\End(S_m)|, $$ where $\End(T_m)$ is the set of
all endomorphisms of $T_m$ (homomorphisms from $T_m$ to itself).