title: The Maximum Entropy Relaxation Path

abstract:
  The relaxed maximum entropy problem is concerned with finding a probability
distribution on a finite set that minimizes the relative entropy to a given
prior distribution, while satisfying relaxed max-norm constraints with respect
to a third observed multinomial distribution. We study the entire relaxation
path for this problem in detail. We show existence and a geometric description
of the relaxation path. Specifically, we show that the maximum entropy
relaxation path admits a planar geometric description as an increasing,
piecewise linear function in the inverse relaxation parameter. We derive fast
algorithms for tracking the path. In various realistic settings, our algorithms
require $O(n\log(n))$ operations for probability distributions on $n$ points,
making it possible to handle large problems. Once the path has been recovered,
we show that given a validation set, the family of admissible models is reduced
from an infinite family to a small, discrete set. We demonstrate the merits of
our approach in experiments with synthetic data and discuss its potential for
the estimation of compact n-gram language models.


title:
Phase coherence and spectral functions in the two-dimensional excitonic
  systems

abstract:
  The nonlocal correlation mechanism between excitonic pairs is considered for
a two dimensional exciton system. On the base of the unitary decomposition of
the usual electron operator, we include the electron phase degrees of freedom
into the problem of interacting excitons. Applying the path integral formalism,
we treat the excitonic insulator state (EI) and the Bose-Einstein condensation
(BEC) of preformed excitonic pairs as two independent problems. For the BEC of
excitons the phase field variables play a crucial role. We derive the
expression of the local EI order parameter by integrating out the phase
variables. Then, considering the zero temperature limit, we obtain the
excitonic BEC transition probability function, by integrating out the fermions.
We calculate the normal excitonic Green functions for the conduction and
valence band electrons and we derive the excitonic spectral functions, both
analytically and numerically. Different values of the Coulomb interaction
parameter are considered.


title:
Linear Response Theory for the Density Matrix Renormalization Group:
  Efficient Algorithms for Strongly Correlated Excited States

abstract:
  Linear response theory for the density matrix renormalization group
(DMRG-LRT) was first presented in terms of the DMRG renormalization projectors
[Dorando et al., J. Chem. Phys. 130, 184111 (2009)]. Later, with an
understanding of the manifold structure of the matrix product state (MPS)
ansatz, which lies at the basis of the DMRG algorithm, a way was found to
construct the linear response space for general choices of the MPS gauge in
terms of the tangent space vectors [Haegeman et al., Phys. Rev. Lett. 107,
070601 (2011)]. These two developments led to the formulation of the
Tamm-Dancoff and random phase approximations (TDA and RPA) for MPS. This work
describes how these LRTs may be efficiently implemented through minor
modifications of the DMRG sweep algorithm, at a computational cost which scales
the same as the ground-state DMRG algorithm. In fact, the mixed canonical MPS
form implicit to the DMRG sweep is essential for efficient implementation of
the RPA, due to the structure of the second-order tangent space. We present ab
initio DMRG-TDA results for excited states of polyenes, the water molecule, and
a [2Fe-2S] iron-sulfur cluster.


title: A Pathwise Fractional one Compartment Intra-Veinous Bolus Model

abstract:
  Extending deterministic compartments pharmacokinetic models as diffusions
seems not realistic on biological side because paths of these stochastic
processes are not smooth enough. In order to extend one compartment
intra-veinous bolus models, this paper suggests to modelize the concentration
process $C$ by a class of stochastic differential equations driven by a
fractional Brownian motion of Hurst parameter belonging to $]1/2,1[$.
  The first part of the paper provides probabilistic and statistical results on
the concentration process $C$ : the distribution of $C$, a control of the
uniform distance between $C$ and the solution of the associated ordinary
differential equation, an ergodic theorem for the concentration process and its
application to the estimation of the elimination constant, and consistent
estimators of the driving signal's Hurst parameter and of the volatility
constant.
  The second part of the paper provides applications of these theoretical
results on simulated concentration datas : a qualitative procedure for choosing
parameters on small sets of observations, and simulations of the estimators of
the elimination constant and of the driving signal's Hurst parameter. The
relationship between the estimations quality and the size/length of the sample
is discussed.


title: Two-sided boundary functionals for Kou process

abstract:
  In this paper the moment generating function of two-sided boundary
functionals for double exponential jump diffusion processes are treated.


title:
On the Formation of SMC X-1: the Effect of Mass and Orbital Angular
  Momentum Loss

abstract:
  SMC X-1 is a high-mass X-ray binary with an orbital period of 3.9 days. The
mass of the neutron star is as low as $\sim 1 M_{\sun}$, suggesting that it was
likely to be formed through an electron-capture supernova rather an iron-core
collapse supernova. From the present system configurations, we argue that the
orbital period at the supernova was $\lesssim 10$ days. Since the mass transfer
process between the neutron star's progenitor and the companion star before the
supernova should have increased the orbital period to tens of days, a mechanism
with efficient orbit angular momentum loss and relatively small mass loss is
required to account for its current orbital period. We have calculated the
evolution of the progenitor binary systems from zero-age main-sequence to the
pre-supernova stage with different initial parameters and various mass and
angular momentum loss mechanisms. Our results show that the outflow from the
outer Langrangian point or a circumbinary disk formed during the mass transfer
phase may be qualified for this purpose. We point out that these mechanisms may
be popular in binary evolution and significantly affect the formation of
compact star binaries.


title:
Magnetic domain and magnetic resistance phase transition in strongly
  correlated electronic material of perovskites junction

abstract:
  The junction magnetoresistivity and domain phase transition were studied
between ZnO and La0.4Gd0.1Sr0.5CoO3 thin films grown on LaAlO3 (100) substrates
epitaxially by pulse laser deposit. The ferromagnetic transformation into
phase-separated (two phase) state was displayed below Tc~127 and has observed
that the lattice change discontinuously in the doped cobalt perovskites
La0.4Gd0.1Sr0.5CoO3. The Ginzburg-Landau phase field is introduced to deduce
antiferroelectric domain structure in LGSCO thin film. On the basis of the
domain structures, the phase boundary of thin film is strongly dependent on the
combination of electric-mechanical coupling. The phase transformation into
phase separated state occurs below Tc~127-128K, and have displayed that the
lattice constants change discontinuously at the transformation. The positive MR
of ZnO/LGSCO heterojunction exhibited the MIT behavior at 0.2 T is 4.86%, at
0.5 T is 6.05% for approximately 140K.


title:
Population Density as an Equalizing (or Misbalancing) Mechanism for
  Species Coexistence

abstract:
  Despite the general acknowledgment of the role of niche and fitness
differences in community dynamics, species abundance has been coined as a
relevant feature not just regarding niche perspectives, but also according to
neutral perspectives. Here we explore a minimum probabilistic stochastic model
to evaluate the role of populations relative initial and total abundances on
species chances to outcompete each other and their persistence in time (i.e.,
unstable coexistence). The present results show that taking into account the
stochasticity in demographic properties and conservation of individuals in
closed communities (zero-sum assumption), population initial abundance can
strongly influence species chances to outcompete each other, and also influence
the period of coexistence of these species in a particular time interval.
Systems carrying capacity can have an important role in species coexistence by
exacerbating fitness inequalities and affecting the size of the period of
coexistence. This study also shows that populations initial abundances can act
as an equalizing mechanism, reducing fitness inequalities, which can favor
species coexistence and even make less fitted species to be more likely to
outcompete better fitted species, and thus to dominate ecological communities
in the absence of niche mechanisms.


title:
Global existence for diffusion-electromigration systems in space
  dimension three and higher

abstract:
  We prove existence of global weak solutions for the Nernst-Planck-Poisson
problem which describes the evolution of concentrations of charged species
$X_1, ..., X_P$ subject to Fickian diffusion and chemical reactions in the
presence of an electrical field, including in particular the Boltzmann
statistics case. In contrast to the existing literature, existence is proved in
any dimension. Moreover, we do not need the assumption $P = 2$ nor the
assumption of equal diffusivities for all $P$ components. Our approach relies
on the intrinsic energy structure and on an adequate nonlinear and curiously
more regular approximate problem. The delicate passing to the limit is done in
adequate functional spaces which lead to only weak solutions.


title:
A photometric comprehensive study of circumnuclear star forming rings:
  the sample

abstract:
  We present photometry in U, B, V, R and I continuum bands and in H$\alpha$
and H$\beta$ emission lines for a sample of 336 circumnuclear star forming
regions (CNSFR) located in early type spiral galaxies with different levels of
activity in their nuclei. They are nearby galaxies, with distances less than
100 Mpc, 60\% of which are considered as interacting objects.
  This survey of 20 nuclear rings aims to provide insight into their star
formation properties as age, stellar population and star formation rate.
Extinction corrected H$\alpha$ luminosities range from $1.3\times 10^{38}$ to
$4\times 10^{41} erg s^{-1}$, with most of the regions showing values between
39.5 $\leq log L(H\alpha) \leq$ 40, which implies masses for the ionizing
clusters higher than $2\times 10^{5} M_\odot $.
  H$\alpha$ and H$\beta$ images have allowed us to obtain an accurate measure
of extinction. We have found an average value of A$_V$ = 1.85 magnitudes. (U-B)
colour follows a two maximum distribution around (U-B)$ \simeq$ -0.7, and -0.3;
(R-I) also presents a bimodal behaviour, with maximum values of 0.6 and 0.9.
Reddest (U-B) and (R-I) regions appear in non-interacting galaxies. Reddest
(R-I) regions lie in strongly barred galaxies.
  For a significant number of HII regions the observed colours and equivalent
widths are not well reproduced by single burst evolutionary theoretical models.


title:
Universality of transverse-momentum resummation and hard factors at the
  NNLO

abstract:
  We consider QCD radiative corrections to the production of colourless
high-mass systems in hadron collisions. The logarithmically-enhanced
contributions at small transverse momentum are treated to all perturbative
orders by a universal resummation formula that depends on a single
process-dependent hard factor. We show that the hard factor is directly related
to the all-order virtual amplitude of the corresponding partonic process. The
direct relation is universal (process independent), and it is expressed by an
all-order factorization formula that we explicitly evaluate up to the
next-to-next-to-leading order (NNLO) in QCD perturbation theory. Once the NNLO
scattering amplitude is available, the corresponding hard factor is directly
determined: it controls NNLO contributions in resummed calculations at full
next-to-next-to-leading logarithmic accuracy, and it can be used in
applications of the q_T subtraction formalism to perform fully-exclusive
perturbative calculations up to NNLO. The universality structure of the hard
factor and its explicit NNLO form are also extended to the related formalism of
threshold resummation.


title:
Evidence for interacting two-level systems from the 1/f noise of a
  superconducting resonator

abstract:
  Here we find the increase in 1/f noise of superconducting resonators at low
temperatures to be completely incompatible with the standard tunneling model
(STM) of Two Level Systems (TLS), which has been used to describe low-frequency
noise for over three decades. We revise the STM to include a significant TLS -
TLS interaction. The new model is able to explain the temperature and power
dependence of noise in our measurements, as well as recent studies of
individual TLS lifetimes using superconducting qubits. The measurements were
made possible by implementing an ultra-stable frequency-tracking technique used
in atomic clocks and by producing a superconducting resonator insensitive to
temperature fluctuations. The latter required an epitaxially grown Nb film with
a Pt capping layer to minimize detrimental oxides at all interfaces.


title:
Charge-mass ratio bound and optimization in the Parikh-Wilczek tunneling
  model of Hawking radiation

abstract:
  In this letter, we study the mutual information hidden in the Parikh-Wilczek
tunneling model of Hawking radiation for Reissner-Norstrom black holes. We
argue that the condition of nonnegativity of mutual information suggests
bound(s) for charge-mass ratio of emitted particles. We further view the
radiation as an optimization process and discuss its effect on time evolution
of a charged black hole.


title:
Planck intermediate results. XVI. Profile likelihoods for cosmological
  parameters

abstract:
  We explore the 2013 Planck likelihood function with a high-precision
multi-dimensional minimizer (Minuit). This allows a refinement of the
Lambda-cdm best-fit solution with respect to previously-released results, and
the construction of frequentist confidence intervals using profile likelihoods.
The agreement with the cosmological results from the Bayesian framework is
excellent, demonstrating the robustness of the Planck results to the
statistical methodology. We investigate the inclusion of neutrino masses, where
more significant differences may appear due to the non-Gaussian nature of the
posterior mass distribution. By applying the Feldman--Cousins prescription, we
again obtain results very similar to those of the Bayesian methodology.
However, the profile-likelihood analysis of the CMB combination
(Planck+WP+highL) reveals a minimum well within the unphysical negative-mass
region. We show that inclusion of the Planck CMB-lensing information
regularizes this issue, and provide a robust frequentist upper limit $M_\nu <
0.26 eV$ ($95%$ confidence) from the CMB+lensing+BAO data combination.


title: Antinucleon-nucleon interaction in chiral effective field theory

abstract:
  Results of an exploratory study of the antinucleon-nucleon interaction within
chiral effective field theory are reported. The antinucleon-nucleon potential
is derived up to next-to-next-to-leading order, based on a modified Weinberg
power counting, in close analogy to pertinent studies of the nucleon-nucleon
interaction. The low-energy constants associated with the arising contact
interactions are fixed by a fit to phase shifts and inelasticities provided by
a recently published phase-shift analysis of antiproton-proton scattering data.
The overall quality of the achieved description of the antinucleon-nucleon
amplitudes is comparable to the one found in case of the nucleon-nucleon
interaction at the same order. For most S-waves and several P-waves good
agreement with the antinucleon-nucleon phase shifts and inelasticities is
obtained up to laboratory energies of around 200 MeV.


title: Primitive forms via polyvector fields

abstract:
  We develop a complex differential geometric approach to the theory of higher
residues and primitive forms from the viewpoint of Kodaira-Spencer gauge
theory, unifying the semi-infinite period maps for Calabi-Yau models and
Landau-Ginzburg models. We give an explicit perturbative construction of
primitive forms with respect to opposite filtrations and primitive elements.
This leads to a concrete algorithm to compute the Taylor expansions of
primitive forms as well as the description of their moduli space for all
weighted homogenous cases. As an example, we present unknown perturbative
expressions for the primitive form of E_12 singularity and illustrate its
application to Landau-Ginzburg mirror symmetry with FJRW-theory.


title:
Functorial relationships between quantum cohomology of complete and
  partial flag varieties, (II)

abstract:
  We show a canonical injective morphism from the quantum cohomology ring
QH(G/P) to the associated graded algebra of QH(G/B), which is with respect to a
nice filtration on QH(G/B) introduced by Leung and the author. This tells us
the vanishing of a lot of genus zero, three-pointed Gromov-Witten invariants of
flag varieties G/P.


title: Chow groups of ind-schemes and extensions of Saito's filtration

abstract:
  Let $K$ be a field of characteristic zero and let $Sm/K$ be the category of
smooth and separated schemes over $K$. For an ind-scheme $\mathcal X$ (and more
generally for any presheaf of sets on $Sm/K$), we define its Chow groups
$\{CH^p(\mathcal X)\}_{p\in \mathbb Z}$. We also introduce Chow groups
$\{\mathcal{CH}^p(\mathcal G)\}_{p\in \mathbb Z}$ for a presheaf with transfers
$\mathcal G$ on $Sm/K$. Then, we show that we have natural isomorphisms of Chow
groups $$ CH^p(\mathcal X)\cong \mathcal{CH}^p(Cor(\mathcal
X))\qquad\forall\textrm{ }p \in \mathbb Z$$ where $Cor(\mathcal X)$ is the
presheaf with transfers that associates to any $Y\in Sm/K$ the collection of
finite correspondences from $Y$ to $\mathcal X$. Additionally, when $K=\mathbb
C$, we show that Saito's filtration on the Chow groups of a smooth projective
scheme can be extended to the Chow groups $CH^p(\mathcal X)$ and more
generally, to the Chow groups of an arbitrary presheaf of sets on $Sm/\mathbb
C$. Similarly, there exists an extension of Saito's filtration to the Chow
groups of a presheaf with transfers on $Sm/\mathbb C$. Finally, when the
ind-scheme $\mathcal X$ is ind-proper, we show that the isomorphism
$CH^p(\mathcal X)\cong \mathcal{CH}^p(Cor(\mathcal X))$ is actually a filtered
isomorphism.


title: Photoluminescence of high-density exciton-polariton condensates

abstract:
  We examine the photoluminescence of highly-excited exciton-polariton
condensates in semiconductor microcavities. Under strong pumping,
exciton-polariton condensates have been observed to undergo a lasing transition
where strong coupling between the excitons and photons is lost. We discuss an
alternative high-density scenario, where the strong coupling is maintained. We
find that the photoluminescence smoothly transitions between the lower
polariton energy to the cavity photon energy. An intuitive understanding of the
change in spectral characteristics is given, as well as differences to the
photoluminescence characteristics of the lasing case.


title:
Implications of LHC search results on the W boson mass prediction in the
  MSSM

abstract:
  We present the currently most precise W boson mass (M_W) prediction in the
Minimal Supersymmetric Standard Model (MSSM) and discuss how it is affected by
recent results from the LHC. The evaluation includes the full one-loop result
and all known higher order corrections of SM and SUSY type. We show the MSSM
prediction in the M_W-m_t plane, taking into account constraints from Higgs and
SUSY searches. We point out that even if stops and sbottoms are heavy,
relatively large SUSY contributions to M_W are possible if either charginos,
neutralinos or sleptons are light. In particular we analyze the effect on the
M_W prediction of the Higgs signal at about 125.6 GeV, which within the MSSM
can in principle be interpreted as the light or the heavy CP-even Higgs boson.
For both interpretations the predicted MSSM region for M_W is in good agreement
with the experimental measurement. We furthermore discuss the impact of
possible future LHC results in the stop sector on the M_W prediction,
considering both the cases of improved limits and of the detection of a scalar
top quark.


title: Crystal lattice rules disordered states

abstract:
  Based on classical statistical thermodynamics, we develop a theoretical
approach that provides new insight into how macroscopic and microscopic
physical properties are bridged via crystal lattice for condensed mat- ters. We
find that in order to determine macroscopic physical properties and their
temperature dependence in equilibrium disordered state, information about a few
specially selected microscopic states, established from geometrical
characteristics of the crystal lattice, is sufficient. These special states are
found to be independent of constitument elements as well as of temperature,
which is in contrast to the standard conception in statistical thermodyanamics
where a set of microscopic states mainly contributing to determining
macroscopic physical properties depend on temperature and constituent elements.
Validity and applicability of the theoretical ap- proach is confirmed through
prediction of macroscopic physical properties in practical alloys, compared
with prediction by full thermodynamic simulation. The present findings provide
efficient and systematic prediction of macroscopic physical properties for
equilibrium disordered states based on those for special microscopic states
without any information of interactions for given system.


title:
Counting rational points on del Pezzo surfaces with a conic bundle
  structure

abstract:
  For any number field k, upper bounds are established for the number of
k-rational points of bounded height on non-singular del Pezzo surfaces defined
over k, which are equipped with suitable conic bundle structures over k.


title: Quantum Circuits and Spin(3n) Groups

abstract:
  All quantum gates with one and two qubits may be described by elements of
$Spin$ groups due to isomorphisms $Spin(3) \simeq SU(2)$ and $Spin(6) \simeq
SU(4)$. However, the group of $n$-qubit gates $SU(2^n)$ for $n > 2$ has bigger
dimension than $Spin(3n)$. A quantum circuit with one- and two-qubit gates may
be used for construction of arbitrary unitary transformation $SU(2^n)$.
Analogously, the `$Spin(3n)$ circuits' are introduced in this work as products
of elements associated with one- and two-qubit gates with respect to the
above-mentioned isomorphisms.
  The matrix tensor product implementation of the $Spin(3n)$ group together
with relevant models by usual quantum circuits with $2n$ qubits are
investigated in such a framework. A certain resemblance with well-known sets of
non-universal quantum gates e.g., matchgates, noninteracting-fermion quantum
circuits) related with $Spin(2n)$ may be found in presented approach. Finally,
a possibility of the classical simulation of such circuits in polynomial time
is discussed.


title: 3D Cache Hierarchy Optimization

abstract:
  3D integration has the potential to improve the scalability and performance
of Chip Multiprocessors (CMP). A closed form analytical solution for optimizing
3D CMP cache hierarchy is developed. It allows optimal partitioning of the
cache hierarchy levels into 3D silicon layers and optimal allocation of area
among cache hierarchy levels under constrained area and power budgets. The
optimization framework is extended by incorporating the impact of multithreaded
data sharing on the private cache miss rate. An analytical model for cache
access time as a function of cache size and a number of 3D partitions is
proposed and verified using CACTI simulation.


title: Dynamics of two-dimensional complex plasmas in a magnetic field

abstract:
  We consider a two-dimensional complex plasma layer containing charged dust
particles in a perpendicular magnetic field. Computer simulations of both
one-component and binary systems are used to explore the equilibrium particle
dynamics in the fluid state. The mobility is found to scale with the inverse of
the magnetic field strength (Bohm diffusion) for strong fields. For bidisperse
mixtures, the magnetic field dependence of the long-time mobility depends on
the particle species providing an external control of their mobility ratio. For
large magnetic fields, even a two-dimensional model porous matrix can be
realized composed by the almost immobilized high-charge particles which act as
obstacles for the mobile low-charge particles.


title: Neutrino and axion bounds from the globular cluster M5 (NGC 5904)

abstract:
  The red-giant branch (RGB) in globular clusters is extended to larger
brightness if the degenerate helium core loses too much energy in "dark
channels." Based on a large set of archival observations, we provide
high-precision photometry for the Galactic globular cluster M5 (NGC 5904),
allowing for a detailed comparison between the observed tip of the RGB with
predictions based on contemporary stellar evolution theory. In particular, we
derive 95% confidence limits of $g_{ae}<4.3\times10^{-13}$ on the
axion-electron coupling and $\mu_\nu<4.5\times10^{-12}\,\mu_{\rm B}$ (Bohr
magneton $\mu_{\rm B}=e/2m_e$) on a neutrino dipole moment, based on a detailed
analysis of statistical and systematic uncertainties. The cluster distance is
the single largest source of uncertainty and can be improved in the future.


title: Rotation properties of isotropic dilation matrices

abstract:
  In the paper, we consider bivariate isotropic dilation matrices that are
similar (up to constant factors) to rotation matrices; and we show that, in
this case, the two-scale relation can be considered also as the relation
between not only dilated but also rotated scaling functions. We present
sufficient conditions on a dilation matrix to be similar to a rotation matrix,
where the similarity transformation matrix is symmetric positive definite. Also
we present a simple test that the dilation matrix performs the rotation by an
incommensurable to $\pi$ angle. We show that if a dilation matrix is similar to
a rotation matrix, then an ellipse defined by the similarity transformation
matrix is invariant (up to a homogeneous dilation) under the transformation by
the dilation matrix.


title: Maximally discordant separable two qubit $X$ states

abstract:
  In a recent article S. Gharibian
[\href{http://dx.doi.org/10.1103/PhysRevA.86.042106}{Phys. Rev. A {\bf 86},
042106 (2012)}] has conjectured that no two qubit separable state of rank
greater than two could be maximally non classical (defined to be those which
have normalized geometric discord $1/4$) and asked for an analytic proof. In
this work we prove analytically that among the subclass of $X$ states, there is
a unique (up to local unitary equivalence) maximal separable state of rank two.
Partial progress has been made towards the general problem and some necessary
conditions have been derived.


title: Generalized Dirac and Klein-Gordon equations for spinor wavefunctions

abstract:
  A novel method is developed to derive the original Dirac equation and
demonstrate that it is the only Poincare invariant dynamical equation for
4-component spinor wavefunctions. New Poincare invariant generalized Dirac and
Klein-Gordon equations are also derived. In the non-relativistic limit the
generalized Dirac equation gives the generalized Levy-Leblond equation and the
generalized Pauli-Schrodinger equation. The main difference between the
original and generalized Dirac equations is that the former and latter are
obtained with zero and nonzero phase functions, respectively. Otherwise, both
equations describe free elementary particles with spin 1/2, which have all
other physical properties the same except their masses. The fact that the
generalized Dirac equation describes elementary particles with larger masses is
used to suggest that non-zero phase functions may account for the existence of
three families of elementary particles in the Standard Model. This suggestion
significantly differs from those previously made to account for the three
families of particle physics.


title: The Wave Trace Invariants of the Spectrum of the $G$-Invariant Laplacian

abstract:
  Given a compact boundaryless Riemannian manifold $Y$ on which a compact Lie
group $G$ acts, there is always a metric on $Y$ such that the action is by
isometries. Assuming $Y$ is equipped with such a metric, recall that the
$G$-invariant Laplacian is the restriction of the ordinary Laplacian to the
space of functions which are constant along the orbits of $G$. In this paper,
the author analyzes the wave trace of the $G$-invariant Laplacian and shows
that the singularities of this wave trace occur at the lengths of certain
geodesic arcs--those that are orthogonal to the orbits and whose endpoints are
related by the action of $G$. This defines a notion of the length spectrum for
the group action. Further, using the deep connection between foliated manifolds
and isometric group actions on manifolds, the asymptotics of these
singularities are calculated for an arbitrary non-zero number in the length
spectrum.


title:
Recent progress on phase-space turbulence and dynamical response in
  collisionless plasmas

abstract:
  In the presence of wave dissipation, phase-space structures emerge in
nonlinear Vlasov dynamics. Their dynamics can lead to a nonlinear continuous
shifting of the wave frequency (chirping). This report summarizes my personal
contribution to these topics in the fiscal year 2012. The effects of collisions
on chirping characteristics were investigated, with a one-dimensional
beam-plasma kinetic model. The long-time nonlinear evolution was systematically
categorized as damped, steady-state, periodic, chaotic and chirping. The
chirping regime was sub-categorized as periodic, chaotic, bursty, and
intermittent. Existing analytic theory was extended to account for Krook-like
collisions. Relaxation oscillations, associated with chirping bursts, were
investigated in the presence of dynamical friction and velocity-diffusion. The
period increases with decreasing drag, and weakly increases with decreasing
diffusion. A new theory gives a simple relation between the growth of
phase-space structures and that of the wave energy. When dissipation is modeled
by a linear term in the field equation, simple expressions of a single hole
growth rate and of the initial perturbation threshold are in agreement with
numerical simulations.


title:
Global Solution of the Electromagnetic Field-Particle System of
  Equations

abstract:
  In this paper we discuss global existence of the solution of the Maxwell and
Newton system of equations, describing the interaction of a rigid charge
distribution with the electromagnetic field it generates. A unique solution is
proved to exist (for regular charge distributions) on suitable homogeneous and
non-homogeneous Sobolev spaces, for the electromagnetic field, and on
coordinate and velocity space for the charge; provided initial data belong to
the subspace that satisfies the divergence part of Maxwell's equations.


title: On Lagrangian submersions

abstract:
  In this paper, we study Riemannian, anti-invariant Riemannian and Lagrangian
submersions. We prove that the horizontal distribution of a Lagrangian
submersion from a Kaehlerian manifold is integrable. We also give some
applications of this result. Moreover, we investigate the effect of the
submersion to the geometry of its total manifold and its fibers.


title: Seven characterizations of non-meager P-filters

abstract:
  We give several topological/combinatorial conditions that, for a filter on
$\omega$, are equivalent to being a non-meager $\mathsf{P}$-filter. In
particular, we show that a filter is countable dense homogeneous if and only if
it is a non-meager $\mathsf{P}$-filter. Here, we identify a filter with a
subspace of $2^\omega$ through characteristic functions. Along the way, we
generalize to non-meager $\mathsf{P}$-filters a result of Miller about
$\mathsf{P}$-points, and we employ and give a new proof of results of
Marciszewski. We also employ a theorem of Hern\'andez-Guti\'errez and
Hru\v{s}\'ak, and answer two questions that they posed. Our result also
resolves several issues raised by Medini and Milovich, and proves false one
"theorem" of theirs. Furthermore, we show that the statement "Every non-meager
filter contains a non-meager $\mathsf{P}$-subfilter" is independent of
$\mathsf{ZFC}$ (more precisely, it is a consequence of
$\mathfrak{u}<\mathfrak{g}$ and its negation is a consequence of $\Diamond$).
It follows from results of Hru\v{s}\'ak and van Mill that, under
$\mathfrak{u}<\mathfrak{g}$, a filter has less than $\mathfrak{c}$ types of
countable dense subsets if and only if it is a non-meager $\mathsf{P}$-filter.
In particular, under $\mathfrak{u}<\mathfrak{g}$, there exists an ultrafilter
with $\mathfrak{c}$ types of countable dense subsets. We also show that such an
ultrafilter exists under $\mathsf{MA(countable)}$.


title: Pair Production in Rotating Electric Fields

abstract:
  We explore Schwinger pair production in rotating time-dependent electric
fields using the real-time DHW formalism. We determine the time evolution of
the Wigner function as well as asymptotic particle distributions neglecting
back-reactions on the electric field. Whereas qualitative features can be
understood in terms of effective Keldysh parameters, the field rotation leaves
characteristic imprints in the momentum distribution that can be interpreted in
terms of interference and multiphoton effects. These phenomena may seed
characteristic features of QED cascades created in the antinodes of a
high-intensity standing wave laser field.


title: New Constructions of Sonar Sequences

abstract:
  A set A is a Sidon set in an additive group G if every element of G can be
written at most one way as sum of two elements of A. A particular case of
two-dimensional Sidon sets are the sonar sequences, which are two-dimensional
synchronization patterns. The main known constructions of sonar sequences are
reminiscent of Costas arrays constructions (Welch and Golomb). Other
constructions are Quadratic and Shift. In this work we present new
constructions of sonar sequences, independent of the named above, using
one-dimensional Sidon sets.


title:
Investigating the Sharpe-Singleton scenario on the lattice by direct
  eigenvalue computation

abstract:
  We investigate the phase structure of lattice QCD with dynamical Wilson
fermions. Wilson chiral perturbation theory predicts that the Aoki phase and
the Sharpe-Singleton scenario manifest themselves in very distinct behavior of
the Wilson Dirac eigenvalue spectrum. To test this prediction we perform a
direct calculation of the eigenvalues of the non-Hermitian Wilson Dirac
operator in dynamical lattice simulations. Moreover, we demonstrate an
unexpected quark mass dependence on the shape of the eigenvalue distribution in
the positive quark mass side.


title: N=1 supersymmetric Yang-Mills theory on the lattice

abstract:
  Numerical simulations of supersymmetric theories on the lattice are intricate
and challenging with respect to their theoretical foundations and algorithmic
realisation. Nevertheless, the simulations of a four-dimensional supersymmetric
gauge theory have made considerable improvements over the recent years. In this
contribution we summarise the results of our collaboration concerning the mass
spectrum of this theory. The investigation of systematic errors allows now a
more precise estimate concerning the expected formation of supersymmetric
multiplets of the lightest particles. These multiplets contain flavour singlet
mesons, glueballs, and an additional fermionic state.


title:
A Simple Proof of the Fourier Inversion Theorem Using Nonstandard
  Analysis

abstract:
  We give a simple proof of the Fourier Inversion Theorem, using the methods of
nonstandard analysis.


title: Levy Processes and Quasi-Shuffle Algebras

abstract:
  We investigate the algebra of repeated integrals of semimartingales. We prove
that a minimal family of semimartingales generates a quasi-shuffle algebra. In
essence, to fulfill the minimality criterion, first, the family must be a
minimal generator of the algebra of repeated integrals generated by its
elements and by quadratic covariation processes recursively constructed from
the elements of the family. Second, recursively constructed quadratic
covariation processes may lie in the linear span of previously constructed ones
and of the family, but may not lie in the linear span of repeated integrals of
these. We prove that a finite family of independent Levy processes that have
finite moments generates a minimal family. Key to the proof are the Teugels
martingales and a strong orthogonalization of them. We conclude that a finite
family of independent Levy processes form a quasi-shuffle algebra. We discuss
important potential applications to constructing efficient numerical methods
for the strong approximation of stochastic differential equations driven by
Levy processes.


title:
Size-Dependent Luminescence Properties of Chromatographically-Separated
  Graphene Quantum Dots

abstract:
  We studied the photoluminescence (PL) properties of graphene quantum dots
(GQDs) separated by size-exclusion high performance liquid chromatography. The
size separation of GQDs was confirmed by transmission electron microcopy
images. PL excitation maps of chromatographically-separated GQDs show four
distinct emission peaks at 330, 440, 520, and 600 nm, respectively. The
dominant luminescence features of the separated GQDs show discrete change
depending on the overall size of GQDs, indicating that PL variation occurs
because of differences in density, shape, and size of sp2 fragments available
in the GQDs. On the basis of the experimental results of PL peak wavelength and
pH dependence, the emission is attributed to quasi-molecular PL from the
fragments composed of a few aromatic rings with oxygen containing functional
groups.


title: Entanglement entropy of spherical domains in anti-de Sitter space

abstract:
  It was proposed by Ryu and Takayanagi that the entanglement entropy in
conformal field theory (CFT) is related through the AdS/CFT correspondence to
the area of a minimal surface in the bulk. We apply this holographic
geometrical method of calculating the entanglement entropy to study the vacuum
case of a CFT which is holographically dual to empty anti-de Sitter (AdS)
spacetime. We present all possible minimal surfaces spanned on one or two
spherical boundaries at AdS infinity. We give exact analytical expressions for
the regularized areas of these surfaces and identify finite renormalized
quantities. In the case of two disjoint boundaries the existence of two
different phases of the entanglement entropy is confirmed. A trivial phase
corresponds to two disconnected minimal surfaces, while the other one
corresponds to a tube connecting the spherical boundaries. A transition between
these phases is reminiscent of the finite temperature deconfinement transition
in the CFT on the boundary. The exact analytical results are thus consistent
with previous numerical and approximate computations. We also briefly discuss
the character of a spacetime extension of the minimal surface spanned on two
uniformly accelerated boundaries.


title: X-rays from the redshift 7.1 quasar ULAS J1120+0641

abstract:
  We present X-ray imaging and spectroscopy of the redshift z=7.084 radio-quiet
quasar ULAS J112001.48+064124.3 obtained with Chandra and XMM-Newton. The
quasar is detected as a point source with both observatories. The Chandra
observation provides a precise position, confirming the association of the
X-ray source and the quasar, while a sufficient number of photons is detected
in the XMM-Newton observation to yield a meaningful X-ray spectrum. In the
XMM-Newton observation the quasar has a 2-10 keV luminosity of 4.7+-0.9 times
10^44 erg/s and a spectral slope alpha = 1.6+0.4/-0.3 (where f_nu is
proportional to nu^-alpha). The quasar appears to have dimmed in the 15 months
between the two observations, with a 2-10 keV luminosity of $1.8+1.0/-0.7 times
10^45 erg/s during the Chandra observation. We derive optical to X-ray spectral
slopes alpha_OX of 1.76+-0.07 and 1.54+0.09/-0.08 at the times of the
XMM-Newton and Chandra observations respectively, consistent with the range of
alpha_OX found in other quasars of comparable ultraviolet luminosity. The very
soft X-ray spectrum suggests that the quasar is accreting above the Eddington
rate, L/L_Edd = 5+15/-4, compared to L/L_Edd = 1.2+0.6/-0.5 derived from the
rest-frame ultraviolet. Super-Eddington accretion would help to reduce the
discrepancy between the age of the quasar implied by the small size of the
ionized near zone in which it sits (<10^7 years), and the characteristic
e-folding time (2.5 times 10^7 years if L/L_Edd=2). Such super-Eddington
accretion would also alleviate the challenging constraints on the seed black
hole mass provided that the quasar has been rapidly accreting throughout its
history. The remnant of an individual population III star is a plausible
progenitor if an average L/L_Edd>1.46 has been maintained over the quasar's
lifetime.


title: Estimate dependence in medium dimensions, using ranks and sub-sampling

abstract:
  It is well known that non-parametric methods suffer from the "curse of
dimensionality". We propose here a new estimation method for a multivariate
distribution, using sub-sampling and ranks, which seems not to suffer from this
"curse". We prove that in case of independence, the uncertainty of the
estimated distribution increases almost linearly w.r.t. the dimension, for
dimensions around 6. Otherwise, a simulation study shows that if we use this
estimation to build an independence test, the number of observations needed to
obtain a given power increases linearly with the dimension. Finally, we give
examples of a regression using this estimation: with 3000 observations, in
dimension 5, with a markedly complicated dependence, the estimated distribution
is graphically very similar to the real one.


title:
Performance of an LPD prototype detector at MHz frame rates under
  Synchrotron and FEL radiation

abstract:
  A MHz frame rate X-ray area detector (LPD - Large Pixel Detector) is under
development by the Rutherford Appleton Laboratory for the European XFEL. The
detector will have 1 million pixels and allows analogue storage of 512 images
taken at 4.5 MHz in the detector front end. The LPD detector has 500 mm thick
silicon sensor tiles that are bump bonded to a readout ASIC. The ASICs
preamplifier provides relatively low noise at high speed which results in a
high dynamic range of 10^5 photons over an energy range of 5-20 keV. Small
scale prototypes of 32x256 pixels (LPD 2-Tile detector) and 256x256 pixels (LPD
supermodule detector) are now available for X-ray tests. The performance of
prototypes of the detector is reported for first tests under synchrotron
radiation (PETRA III at DESY) and Free-Electron-Laser radiation (LCLS at SLAC).
The initial performance of the detector in terms of signal range and noise,
radiation hardness and spatial and temporal response are reported. The main
result is that the 4.5 MHz sampling detection chain is reliably working,
including the analogue on-chip memory concept. The detector is at least
radiation hard up to 5 MGy at 12 keV. In addition the multiple gain concept has
been demonstrated over a dynamic range to 10^4 at 12 keV with a readout noise
equivalent to <1 photon rms in its most sensitive mode.


title: Irrational anomalies in one-dimensional Anderson localization

abstract:
  We revisit the problem of one-dimensional Anderson localization, by providing
perturbative expression for Lyapunov exponent of Anderson model with
next-nearest-neighbor (nnn) hopping. By comparison with exact numerical
results, we discuss the range of validity of the naive perturbation theory. The
stability of band center anomaly is examined against the introduction of nnn
hopping. New anomalies of Kappus-Wegner type emerge at nonuniversal values of
wavelength when hopping to second neighbor is allowed. It is shown that
covariances in the first order of perturbation theory, develop singularities at
these resonant energies which enable us to locate them.


title: Probing locally the onset of slippage at a model multi-contact interface

abstract:
  We report on the multi-contact frictional dynamics of model elastomer
surfaces rubbed against bare glass slides. The surfaces consist of layers
patterned with thousands spherical caps (radius of curvature 100 $\mu$m)
distributed both spatially and in height, regularly or randomly. Use of
spherical asperities yields circular micro-contacts whose radius is a direct
measure of the contact pressure distribution. In addition, optical tracking of
individual contacts provides the in-plane deformations of the tangentially
loaded interface, yielding the shear force distribution. We then investigate
the stick-slip frictional dynamics of a regular hexagonal array. For all stick
phases including the initial one, slip precursors are evidenced. They are found
to propagate quasi-statically, normally to the iso- pressure contours. A simple
quasi-static model relying on the existence of interfacial stress gradients is
derived and predicts qualitatively the position of slip precursors.


title:
Observations of Sy2 galaxy NGC 3281 by XMM-Newton and INTEGRAL
  satellites

abstract:
  We present here the results of our analysis of X-ray properties of Seyfert 2
galaxy NGC 3281, based on the observational data obtained by XMM-Newton and
INTEGRAL within the energy ranges 0.2-12 keV and 20-150 keV, respectively. The
XMM-Newton spectrum of this object is presented for the first time. We show
that fitting the X-ray spectrum of this galaxy with models based on the
reflection from the disc with infinite column density yields non-physical
results. More appropriate fit takes into account both transmitted and reflected
emission, passed through a gas-dusty torus-like structure. Keeping this in
mind, to model the inhomogeneous clumpy torus, we used the MYTorus model.
Hence, we propose that the torus of NGC 3281 is not continuous structure, but
it consists of separate clouds, which is in a good agreement with the results
of near-IR observations. Using this assumption, we found that the torus
inclination angle and the hydrogen column density are 66.98^{+2.63}_{-1.34}
degrees and 2.08^{+0.35}_{-0.18}x10^{24} cm^{-2}, respectively. Also, the
emission of the hot diffuse gas with temperature ~590 eV and warm absorption
were detected.


title:
Well-Posedness and asymptotic behavior of solutions for the
  Blackstock-Crighton-Westervelt equation

abstract:
  We consider a nonlinear fourth order in space partial differential equation
arising in the context of the modeling of nonlinear acoustic wave propagation
in thermally relaxing viscous fluids. We use the theory of operator semigroups
in order to investigate the linearization of the underlying model and see that
the underlying semigroup is analytic. This leads to exponential decay results
for the linear homogeneous equation. Moreover, we prove local in time
well-posedness of the model under the assumption that initial data are
sufficiently small by employing a fixed point argument. Global in time
well-posedness is obtained by performing energy estimates and using the
classical barrier method, again for sufficiently small initial data.
Additionally, we provide results concerning exponential decay of solutions of
the nonlinear equation.


title:
Emission line diagnostics to constrain high temperature populations in
  early-type galaxies

abstract:
  Once thought to be devoid of warm and cold interstellar matter, elliptical
galaxies are now commonly observed to host extended regions of neutral and
ionized gas. Outside of the innermost nuclear regions of these galaxies, the
favoured candidate ionizing source remains some component of the stellar
population, with mounting evidence suggesting post-asymptotic-giant-branch
stars (pAGBs). In a recent paper, we demonstrated that observations of
recombination lines of He II (or upper limits thereof) may provide a strong
constraint on the presence of any other, higher temperature ionizing sources,
in particular nuclear-burning white dwarfs in the context of the single
degenerate (SD) scenario for type Ia supernovae. The sensitivity of the HeII
test is greatest for WD effective temperatures ~ 2 x 10^5 K. Here we extend our
analysis to include predictions for all of the "classical" strong optical
lines, as well as UV, optical, and infra-red lines of neutral Oxygen, Nitrogen,
and singly-ionized Carbon. This allows us to extend the temperature range over
which we can meaningfully constrain the collective luminosity of
nuclear-burning WDs to 10^5 K <~ T <~ 10^6 K. We then demonstrate how
observations of nearby early-type and post-starburst galaxies can place strong
limits on the origin of type Ia supernovae.


title:
Biometric Signature Processing & Recognition Using Radial Basis Function
  Network

abstract:
  Automatic recognition of signature is a challenging problem which has
received much attention during recent years due to its many applications in
different fields. Signature has been used for long time for verification and
authentication purpose. Earlier methods were manual but nowadays they are
getting digitized. This paper provides an efficient method to signature
recognition using Radial Basis Function Network. The network is trained with
sample images in database. Feature extraction is performed before using them
for training. For testing purpose, an image is made to undergo
rotation-translation-scaling correction and then given to network. The network
successfully identifies the original image and gives correct output for stored
database images also. The method provides recognition rate of approximately 80%
for 200 samples.


title: Computing the smallest eigenpairs of the graph Laplacian

abstract:
  The graph Laplacian, a typical representation of a network, is an important
matrix that can tell us much about the network structure. In particular its
eigenpairs (eigenvalues and eigenvectors) incubate precious topological
information about the network at hand, including connectivity, partitioning,
node distance and centrality. Real networks might be very large in number of
nodes (actors); luckily, most real networks are sparse, meaning that the number
of edges (binary connections among actors) are few with respect to the maximum
number of possible edges. In this paper we experimentally compare three
state-of-the-art algorithms for computation of a few among the smallest
eigenpairs of large and sparse matrices: the Implicitly Restarted Lanczos
Method, which is the current implementation in the most popular scientific
computing environments (Matlab \R), the Jacobi-Davidson method, and the
Deflation Accelerated Conjugate Gradient method. We implemented the algorithms
in a uniform programming setting and tested them over diverse real-world
networks including biological, technological, information, and social networks.
It turns out that the Jacobi-Davidson method displays the best performance in
terms of number of matrix-vector products and CPU time.


title:
Transition electromagnetic form factor in the Minkowski space
  Bethe-Salpeter approach

abstract:
  Using the solutions of the Bethe-Salpeter equation in Minkowski space for
bound and scattering states found in previous works, we calculate the
transition electromagnetic form factor describing the electro-disintegration of
a bound system.


title: The Naked-eye Optical Transient OT 120926

abstract:
  A previously unknown optical transient (OT 120926) has been observed in the
constellation Bootes. The transient flared to magnitude 4.7, which is
comparable to the visual magnitudes of the nearby stars $\pi$ Boo and
$\omicron$ Boo. Database searches do not yield an unambiguous identification of
a quiescent counterpart of this transient but do identify several candidates.
However, none of the candidate stellar counterparts have shown any credible
evidence of previous variability in the All-Sky Automated Survey or the
Catalina Real-time Transient Survey. A flare on the nearby high proper motion,
probable M dwarf star LP 440-48 could have produced OT 120926, but the
amplitude of the flare would be an unprecedented 11.3 magnitudes. The current
record amplitude for such flares on M dwarfs is 9.5 magnitudes.


title:
A Survey on the State of the Practice in Distributed Software
  Development: Criteria for Task Allocation

abstract:
  The allocation of tasks can be seen as a success-critical management activity
in distributed development projects. However, such task allocation is still one
of the major challenges in global software development due to an insufficient
understanding of the criteria that influence task allocation decisions. This
article presents a qualitative study aimed at identifying and understanding
such criteria that are used in practice. Based on interviews with managers from
selected software development organizations, criteria currently applied in
industry are identified. One important result is, for instance, that the
sourcing strategy and the type of software to be developed have a significant
effect on the applied criteria. The article presents the goals, design, and
results of the study as well as an overview of related and future work.


title:
The Analysis to Quasi-Local Energy and Hamiltonian Constraint based on
  Variation

abstract:
  In this paper, by arising condition in variation, from equal time to
non-equal time, I reconsider how geometrodynamics equations allow to be derived
from variational principle in general relativity and then find the variation of
extrinsic curvature dependent only locally on its induced metric and unit
normal. I thus try to attribute the quasi-local energy to the integrability of
submanifold. At last I discuss the dynamical degrees of freedom on Hamiltonian
constraint by analyzing non-equal time variation which also represents a global
transformation.


title:
Image Steganography using Karhunen-Loeve Transform and Least Bit
  Substitution

abstract:
  As communication channels are increasing in number, reliability of faithful
communication is reducing. Hacking and tempering of data are two major issues
for which security should be provided by channel. This raises the importance of
steganography. In this paper, a novel method to encode the message information
inside a carrier image has been described. It uses Karhunen-Lo\`eve Transform
for compression of data and Least Bit Substitution for data encryption.
Compression removes redundancy and thus also provides encoding to a level. It
is taken further by means of Least Bit Substitution. The algorithm used for
this purpose uses pixel matrix which serves as a best tool to work on. Three
different sets of images were used with three different numbers of bits to be
substituted by message information. The experimental results show that
algorithm is time efficient and provides high data capacity. Further, it can
decrypt the original data effectively. Parameters such as carrier error and
message error were calculated for each set and were compared for performance
analysis.


title: A closed form expression for the causal set d'Alembertian

abstract:
  Recently a definition for a Lorentz invariant operator approximating the
d'Alembertian in d-dimensional causal set space-times has been proposed. This
operator contains several dimension-dependent constants which have been
determined for d=2,...,7. In this note we derive closed form expressions for
these constants, which are valid in all dimensions. Using these we prove that
the causal set action in any dimension can be defined through this discrete
d'Alembertian, with a dimension independent prefactor.


title: Anomalies in conductance and localization length of disordered ladders

abstract:
  We discuss the conditions under which an anomaly occurs in conductance and
localization length of Anderson model on a lattice. Using the ladder
hamiltonian and analytical calculation of average conductance we find the set
of resonance conditions which complements the $\pi$-coupling rule for
anomalies. We identify those anomalies that might vanish due to the symmetry of
the lattice or the distribution of the disorder. In terms of the dispersion
relation it is known from strictly one-dimensional model that the lowest order
(i.e., the most strong) anomalies satisfy the equation $E(k)=E(3k)$. We show
that the anomalies of the generalized model studied here are also the solutions
of the same equation with modified dispersion relation.


title: Projections of random covering sets

abstract:
  We show that, almost surely, the Hausdorff dimension $s_0$ of a random
covering set is preserved under all orthogonal projections to linear subspaces
with dimension $k>s_0$. The result holds for random covering sets with a
generating sequence of ball-like sets, and is obtained by investigating
orthogonal projections of a class of random Cantor sets.


title: Scalable Recommendation with Poisson Factorization

abstract:
  We develop a Bayesian Poisson matrix factorization model for forming
recommendations from sparse user behavior data. These data are large user/item
matrices where each user has provided feedback on only a small subset of items,
either explicitly (e.g., through star ratings) or implicitly (e.g., through
views or purchases). In contrast to traditional matrix factorization
approaches, Poisson factorization implicitly models each user's limited
attention to consume items. Moreover, because of the mathematical form of the
Poisson likelihood, the model needs only to explicitly consider the observed
entries in the matrix, leading to both scalable computation and good predictive
performance. We develop a variational inference algorithm for approximate
posterior inference that scales up to massive data sets. This is an efficient
algorithm that iterates over the observed entries and adjusts an approximate
posterior over the user/item representations. We apply our method to large
real-world user data containing users rating movies, users listening to songs,
and users reading scientific papers. In all these settings, Bayesian Poisson
factorization outperforms state-of-the-art matrix factorization methods.


title: Products of Bessel functions and associated polynomials

abstract:
  The symbolic method is used to get explicit formulae for the products or
powers of Bessel functions and for the relevant integrals.


title: The Terzan 5 puzzle: discovery of a third, metal-poor component

abstract:
  We report on the discovery of 3 metal-poor giant stars in Terzan 5, a complex
stellar system in the the Galactic bulge, known to have two populations at
[Fe/H]=-0.25 and +0.3. For these 3 stars we present new echelle spectra
obtained with NIRSPEC at Keck II, which confirm their radial velocity
membership and provide average [Fe/H]=-0.79 dex iron abundance and
[alpha/Fe]=+0.36 dex enhancement. This new population extends the metallicity
range of Terzan~5 0.5 dex more metal poor, and it has properties consistent
with having formed from a gas polluted by core collapse supernovae.


title: The probabilistic approach to limited packings in graphs

abstract:
  We consider (closed neighbourhood) packings and their generalization in
graphs. A vertex set X in a graph G is a k-limited packing if for any vertex
$v\in V(G)$, $\left|N[v] \cap X\right| \le k$, where N[v] is the closed
neighbourhood of v. The k-limited packing number $L_k(G)$ of a graph G is the
largest size of a k-limited packing in G. Limited packing problems can be
considered as secure facility location problems in networks.
  In this paper, we develop a new probabilistic approach to limited packings in
graphs, resulting in lower bounds for the k-limited packing number and a
randomized algorithm to find k-limited packings satisfying the bounds. In
particular, we prove that for any graph G of order n with maximum vertex degree
$\Delta$, $$L_k(G) \ge {kn \over (k+1)\sqrt[k]{\pmatrix{\Delta \cr k} (\Delta
+1)}}.$$ The problem of finding a maximum size k-limited packing is known to be
NP-complete even in split or bipartite graphs.


title: Game theory in models of pedestrian room evacuation

abstract:
  We analyze the pedestrian evacuation of a rectangular room with a single door
considering a Lattice Gas scheme with the addition of behavioral aspects of the
pedestrians. The movement of the individuals is based on random and rational
choices and is affected by conflicts between two or more agents that want to
advance to the same position. Such conflicts are solved according to certain
rules closely related to the concept of strategies in Game Theory, cooperation
and defection. We consider game rules analogous to those from the Prisoner's
Dilemma and Stag Hunt games, with payoffs associated to the probabilities of
the individuals to advance to the selected site. We find that, even when
defecting is the rational choice for any agent, under certain conditions,
cooperators can take advantage from mutual cooperation and leave the room more
rapidly than defectors.


title: Meromorphy of the rank one unit root L-function revisited

abstract:
  We demonstrate that Wan's alternate description of Dwork's unit root
L-function in the rank one case may be modified to give a proof of meromorphy
that is classical, eliminating the need to study sequences of uniform
meromorphic functions.


title: Using gaps in N-body tidal streams to probe missing satellites

abstract:
  We use N-body simulations to model the tidal disruption of a star cluster in
a Milky-Way-sized dark matter halo, which results in a narrow stream comparable
to (but slightly wider than) Pal-5 or GD-1. The mean Galactic dark matter halo
is modeled by a spherical Navarro-Frenk-White (NFW) potential with subhalos
predicted by the LCDM cosmological model. The distribution and mass function of
the subhalos follow the results from the Aquarius simulation. We use a matched
filter approach to look for "gaps" in tidal streams at 12 length scales from
0.1 kpc to 5 kpc, which appear as characteristic dips in the linear densities
along the streams. We find that, in addition to the subhalos' perturbations,
the epicyclic overdensities (EOs) due to the coherent epicyclic motions of
particles in a stream also produce gap-like signals near the progenitor. We
measure the gap spectra - the gap formation rates as functions of gap length -
due to both subhalo perturbations and EOs, which have not been accounted for
together by previous studies. Finally, we project the simulated streams onto
the sky to investigate issues when interpreting gap spectra in observations. In
particular, we find that gap spectra from low signal-to-noise observations can
be biased by the orbital phase of the stream. This indicates that the study of
stream gaps will benefit greatly from high-quality data from future missions.


title: Helium Ion Microscopy

abstract:
  Helium Ion Microcopy (HIM) based on Gas Field Ion Sources (GFIS) represents a
new ultra high resolution microscopy and nano-fabrication technique. It is an
enabling technology that not only provides imagery of conducting as well as
uncoated insulating nano-structures but also allows to create these features.
The latter can be achieved using resists or material removal due to sputtering.
The close to free-form sculpting of structures over several length scales has
been made possible by the extension of the method to other gases such as Neon.
A brief introduction of the underlying physics as well as a broad review of the
applicability of the method is presented in this review.


title:
Approximate Bayesian Probabilistic-Data-Association-Aided Iterative
  Detection for MIMO Systems Using Arbitrary M-ary Modulation

abstract:
  In this paper, the issue of designing an iterative-detection-and-decoding
(IDD)-aided receiver, relying on the low-complexity probabilistic data
association (PDA) method, is addressed for turbo-coded
multiple-input-multiple-output (MIMO) systems using general M-ary modulations.
We demonstrate that the classic candidate-search-aided bit-based extrinsic
log-likelihood ratio (LLR) calculation method is not applicable to the family
of PDA-based detectors. Additionally, we reveal that, in contrast to the
interpretation in the existing literature, the output symbol probabilities of
existing PDA algorithms are not the true a posteriori probabilities (APPs) but,
rather, the normalized symbol likelihoods. Therefore, the classic relationship,
where the extrinsic LLRs are given by subtracting the a priori LLRs from the a
posteriori LLRs, does not hold for the existing PDA-based detectors. Motivated
by these revelations, we conceive a new approximate Bayesian-theorem-based
logarithmic-domain PDA (AB-Log-PDA) method and unveil the technique of
calculating bit-based extrinsic LLRs for the AB-Log-PDA, which facilitates the
employment of the AB-Log-PDA in a simplified IDD receiver structure.
Additionally, we demonstrate that we may dispense with inner iterations within
the AB-Log-PDA in the context of IDD receivers. Our complexity analysis and
numerical results recorded for Nakagami-m fading channels demonstrate that the
proposed AB-Log-PDA-based IDD scheme is capable of achieving a performance
comparable with that of the optimal maximum a posteriori (MAP)-detector-based
IDD receiver, while imposing significantly lower computational complexity in
the scenarios considered.


title: Suzaku study of gas properties along filaments of A2744

abstract:
  Context: We present the results of Suzaku observations of a massive galaxy
cluster A2744, which is an active merger at $z=0.308$. Aims: By using long
X-ray observations of A2744, we aim to understand the growth of the cluster and
the gas heating process through mass accretion along the surrounding filaments.
Methods: We analyzed data from two-pointed Suzaku observations of A2744 to
derive the temperature distribution out to the virial radius in three different
directions. We also performed a deprojection analysis to study radial profiles
of gas temperature, density, and entropy and compared the X-ray results with
multi-wavelength data to investigate correlations with the surface density of
galaxies and with radio relics. Results: The gas temperature was measured out
to the virial radius $r_{200}$ in the north-east region and to about
$1.5r_{200}$ in the north-west and south regions. The radial profile of the gas
temperature is rather flat and the temperature is very high (even near
$r_{200}$); it is comparable to the mean temperature of this cluster ($kT=9$
keV). These characteristics have not been reported in any other cluster. We
find a hint of temperature jump in the northeast region whose location
coincides with a large radio relic, indicating that the cluster experienced gas
heating because of merger or mass accretion onto the main cluster. The
temperature distribution is anisotropic and shows no clear positive correlation
with the galaxy density, which suggests an inhomogeneous mass structure and a
complex merger history in A2744.


title: KaHIP v3.00 -- Karlsruhe High Quality Partitioning -- User Guide

abstract:
  This paper severs as a user guide to the graph partitioning framework KaHIP
(Karlsruhe High Quality Partitioning). We give a rough overview of the
techniques used within the framework and describe the user interface as well as
the file formats used. Moreover, we provide a short description of the current
library functions provided within the framework. Since version 3.00 we support
multilevel partitioning, memetic algorithms, distributed and shared-memory
parallel algorithms, node separator and ordering algorithms, edge partitioning
algorithms as well as ILP solvers.


title:
Portfolio Choice with Stochastic Investment Opportunities: a User's
  Guide

abstract:
  This survey reviews portfolio choice in settings where investment
opportunities are stochastic due to, e.g., stochastic volatility or return
predictability. It is explained how to heuristically compute candidate optimal
portfolios using tools from stochastic control, and how to rigorously verify
their optimality by means of convex duality. Special emphasis is placed on
long-horizon asymptotics, that lead to particularly tractable results.


title: Mode spectrum and temporal soliton formation in optical microresonators

abstract:
  The formation of temporal dissipative solitons in optical microresonators
enables compact, high repetition rate sources of ultra-short pulses as well as
low noise, broadband optical frequency combs with smooth spectral envelopes.
Here we study the influence of the resonator mode spectrum on temporal soliton
formation. Using frequency comb assisted diode laser spectroscopy, the measured
mode structure of crystalline MgF2 resonators are correlated with temporal
soliton formation. While an overal general anomalous dispersion is required, it
is found that higher order dispersion can be tolerated as long as it does not
dominate the resonator's mode structure. Mode coupling induced avoided
crossings in the resonator mode spectrum are found to prevent soliton
formation, when affecting resonator modes close to the pump laser. The
experimental observations are in excellent agreement with numerical simulations
based on the nonlinear coupled mode equations, which reveal the rich interplay
of mode crossings and soliton formation.


title: Shockwave Compression and Joule-Thomson Expansion

abstract:
  Structurally-stable atomistic one-dimensional shockwaves have long been
simulated by injecting fresh cool particles and extracting old hot particles at
opposite ends of a simulation box. The resulting shock profiles demonstrate
tensor temperature, with the longitudinal temperature exceeding the transverse,
and Maxwell's delayed response, with stress lagging strainrate and heat flux
lagging temperature gradient. Here this same geometry, supplemented by a
short-ranged external "plug" field, is used to simulate steady Joule-Kelvin
throttling flow of hot dense fluid through a porous plug, producing a dilute
and cooler product fluid.


title: Nucleon structure from stochastic estimators

abstract:
  Using stochastic estimators for connected meson and baryon three-point
functions has successfully been tried in the past years. Compared to the
standard sequential source method we trade the freedom to compute the
current-to-sink propagator independently of the hadron sink for additional
stochastic noise in our observables. In the case of the nucleon we can use this
freedom to compute many different sink-momentum/polarization combinations,
which grants access to more virtualities. We will present preliminary results
on the scalar, electro-magnetic and axial form factors of the nucleon in
$N_f=2+1$ lattice QCD and contrast the performance of the stochastic method to
the sequential source method. We find the stochastic method to be competitive
in terms of errors at fixed cost.


title: Regular spaces of small extent are omega-resolvable

abstract:
  We improve some results of Pavlov and of Filatova, respectively, concerning a
problem of Malychin by showing that every regular space X that satisfies
Delta(X)>ext(X) is omega-resolvable. Here Delta(X), the dispersion character of
X, is the smallest size of a non-empty open set in X and ext(X), the extent of
X, is the supremum of the sizes of all closed-and-discrete subsets of X. In
particular, regular Lindel\"of spaces of uncountable dispersion character are
omega-resolvable.
  We also prove that any regular Lindel\"of space X with |X|=\Delta(X)=omega_1
is even omega_1-resolvable. The question if regular Lindel\"of spaces of
uncountable dispersion character are maximally resolvable remains wide open.


title:
Frame functions in finite-dimensional Quantum Mechanics and its
  Hamiltonian formulation on complex projective spaces

abstract:
  This work concerns some issues about the interplay of standard and geometric
(Hamiltonian) approaches to finite-dimensional quantum mechanics, formulated in
the projective space. Our analysis relies upon the notion and the properties of
so-called frame functions, introduced by A.M. Gleason to prove his celebrated
theorem. In particular, the problem of associating quantum state with positive
Liouville densities is tackled from an axiomatic point of view, proving a
theorem classifying all possible correspondences. A similar result is
established for classical observables representing quantum ones. These
correspondences turn out to be encoded in a one-parameter class and, in both
cases, the classical objects representing quantum ones result to be frame
functions. The requirements of $U(n)$ covariance and (convex) linearity play a
central r\^ole in the proof of those theorems. A new characterization of
classical observables describing quantum observables is presented, together
with a geometric description of the $C^*$-algebra structure of the set of
quantum observables in terms of classical ones.


title: Kan injectivity in order-enriched categories

abstract:
  Continuous lattices were characterised by Martin Escardo as precisely the
objects that are Kan-injective w.r.t. a certain class of morphisms. We study
Kan-injectivity in general categories enriched in posets. For every class H of
morphisms we study the subcategory of all objects Kan-injective w.r.t. H and
all morphisms preserving Kan-extensions. For categories such as Top_0 and Pos
we prove that whenever H is a set of morphisms, the above subcategory is
monadic, and the monad it creates is a Kock-Zoeberlein monad. However, this
does not generalise to proper classes: we present a class of continuous
mappings in Top_0 for which Kan-injectivity does not yield a monadic category.


title:
On Coinductive Equivalences for Higher-Order Probabilistic Functional
  Programs (Long Version)

abstract:
  We study bisimulation and context equivalence in a probabilistic
$\lambda$-calculus. The contributions of this paper are threefold. Firstly we
show a technique for proving congruence of probabilistic applicative
bisimilarity. While the technique follows Howe's method, some of the
technicalities are quite different, relying on non-trivial "disentangling"
properties for sets of real numbers. Secondly we show that, while bisimilarity
is in general strictly finer than context equivalence, coincidence between the
two relations is attained on pure $\lambda$-terms. The resulting equality is
that induced by Levy-Longo trees, generally accepted as the finest extensional
equivalence on pure $\lambda$-terms under a lazy regime. Finally, we derive a
coinductive characterisation of context equivalence on the whole probabilistic
language, via an extension in which terms akin to distributions may appear in
redex position. Another motivation for the extension is that its operational
semantics allows us to experiment with a different congruence technique, namely
that of logical bisimilarity.


title: On Probability Estimation via Relative Frequencies and Discount

abstract:
  Probability estimation is an elementary building block of every statistical
data compression algorithm. In practice probability estimation is often based
on relative letter frequencies which get scaled down, when their sum is too
large. Such algorithms are attractive in terms of memory requirements, running
time and practical performance. However, there still is a lack of theoretical
understanding. In this work we formulate a typical probability estimation
algorithm based on relative frequencies and frequency discount, Algorithm RFD.
Our main contribution is its theoretical analysis. We show that the code length
it requires above an arbitrary piecewise stationary model with bounded and
unbounded letter probabilities is small. This theoretically confirms the
recency effect of periodic frequency discount, which has often been observed
empirically.


title: Neutrino and Charged Lepton Flavour Today

abstract:
  Flavour physics is a priceless window on physics beyond the Standard Model.
In particular, flavour violation in the lepton sector looks very promising, as
high precision measurements are prospected in future experiments investigating
on $\mu\rightarrow e$ conversion in atomic nuclei: the predictions for this
observable are analysed in the context of the type I Seesaw mechanism.
Furthermore, new ideas to explain the Flavour Puzzle recently appeared, mainly
based on a possible dynamical origin of the Yukawa couplings and on flavour
symmetries. The focus of this proceeding will be set on the Minimal Flavour
Violation ansatz and on the role of the neutrino Majorana character: when an
$O(2)_{N}$ flavour symmetry acts on the right-handed neutrino sector, the
minimum of the scalar potential allows for large mixing angles -in contrast to
the simplest quark case- and predicts a maximal Majorana phase. This leads to a
strong correlation between neutrino mass hierarchy and mixing pattern.


title: Tagging and Linking Lecture Audio Recordings: Goals and Practice

abstract:
  Making and distributing audio recordings of lectures is cheap and technically
straightforward, and these recordings represent an underexploited teaching
resource. We explore the reasons why such recordings are not more used; we
believe the barriers inhibiting such use should be easily overcome. Students
can listen to a lecture they missed, or re-listen to a lecture at revision
time, but their interaction is limited by the affordances of the replaying
technology. Listening to lecture audio is generally solitary, linear, and
disjoint from other available media.
  In this paper, we describe a tool we are developing at the University of
Glasgow, which enriches students' interactions with lecture audio. We describe
our experiments with this tool in session 2012--13. Fewer students used the
tool than we expected would naturally do so, and we discuss some possible
explanations for this.


title: Internal water and microsecond dynamics in myoglobin

abstract:
  Myoglobin (Mb) binds diatomic ligands, like O$_2$, CO, and NO, in a cavity
that is only transiently accessible. Crystallography and molecular simulations
show that the ligands can migrate through an extensive network of transiently
connected cavities, but disagree on the locations and occupancy of internal
hydration sites. Here, we use water $^2$H and $^{17}$O magnetic relaxation
dispersion (MRD) to characterize the internal water molecules in Mb under
physiological conditions. We find that equine carbonmonoxy Mb contains 4.5
$\pm$ 1.0 ordered internal water molecules with a mean survival time of 5.6
$\pm$ 0.5 $\mu$s at 25 $^\circ$C. The likely location of these water molecules
are the four polar hydration sites, including one of the xenon-binding
cavities, that are fully occupied in all high-resolution crystal structures of
equine Mb. The finding that water escapes from these sites, located 17 -- 31
{\AA} apart in the protein, on the same $\mu$s time scale suggests a global
exchange mechanism. We propose that this mechanism involves transient
penetration of the protein by H-bonded water chains. Such a mechanism could
play a functional role by eliminating trapped ligands. In addition, the MRD
results indicate that two or three of the 11 histidine residues of equine Mb
undergo intramolecular hydrogen exchange on a $\mu$s time scale.


title: Periodic Orbit Theory Revisited in the Anisotropic Kepler Problem

abstract:
  The Gutzwiller's trace formula for the anisotropic Kepler problem is Fourier
transformed with a convenient variable $u=1/\sqrt{-2E}$ which takes care of the
scaling property of the AKP action $S(E)$. Proper symmetrization procedure
(Gutzwiller's prescription) is taken by the introduction of half-orbits that
close under symmetry transformations so that the two dimensional semi-classical
formulas match correctly the quantum subsectors $m^\pi=0^+$ and $m^\pi=0^-$.
Response functions constructed from half orbits in the POT side are explicitly
given. In particular the response function $g_X$ from $X$-symmetric half orbit
has an amplitude where the root of the monodromy determinant is inverse
hyperbolic.
  The resultant {\it weighted densities of periodic orbits $D^{m=0}_e(\phi)$
and $D^{m=0}_o(\phi)$} from both quantum subsectors show peaks at the actions
of the periodic orbits with correct peak heights corresponding to the Lyapunov
exponents of them. The formulation takes care of the cut off of the energy
levels, and the agreement between the $D(\phi)$s of QM and POT sides is
observed independent for the choice of the cut off. The systematics appeared in
the densities of the periodic orbits is explained in terms of features of
periodic orbits.
  It is shown that from quantum energy levels one can extract the information
of AKP periodic orbits, even the Lyapunov exponents-- the success of inverse
quantum chaology in AKP.


title:
Acoustic scaling of anisotropic flow in shape-engineered events:
  implications for extraction of the specific shear viscosity of the quark
  gluon plasma

abstract:
  It is shown that the acoustic scaling patterns of anisotropic flow for
different event shapes at a fixed collision centrality (shape-engineered
events), provide robust constraints for the event-by-event fluctuations in the
initial-state density distribution from ultrarelativistic heavy ion collisions.
The empirical scaling parameters also provide a dual-path method for extracting
the specific shear viscosity $(\eta/s)_\mathrm{QGP}$ of the quark-gluon plasma
(QGP) produced in these collisions. A calibration of these scaling parameters
via detailed viscous hydrodynamical model calculations, gives
$(\eta/s)_\mathrm{QGP}$ estimates for the plasma produced in collisions of
Au+Au ($\sqrt{s_{NN}}= 0.2$ TeV) and Pb+Pb ($\sqrt{s_{NN}}= 2.76$ TeV). The
estimates are insensitive to the initial-state geometry models considered.


title: Managing Requirement Elicitation Issues Using Step-Wise Refinement Model

abstract:
  In this paper, a Step-wise Refinement model is proposed to elicit
requirements in a more effective manner.


title: Supercharacters of unipotent groups defined by involutions

abstract:
  We construct supercharacter theories of finite unipotent groups in the
orthogonal, symplectic and unitary types. Our method utilizes group actions in
a manner analogous to that of Diaconis and Isaacs in their construction of
supercharacters of algebra groups. The resulting supercharacter theories agree
with those of Andr\'e and Neto in the case of the unipotent orthogonal and
symplectic matrices and generalize to a large collection of subgroups. In the
unitary group case, we describe the supercharacters and superclasses in terms
of labeled set partitions and calculate the supercharacter table.


title:
Stochastic blockmodel approximation of a graphon: Theory and consistent
  estimation

abstract:
  Non-parametric approaches for analyzing network data based on exchangeable
graph models (ExGM) have recently gained interest. The key object that defines
an ExGM is often referred to as a graphon. This non-parametric perspective on
network modeling poses challenging questions on how to make inference on the
graphon underlying observed network data. In this paper, we propose a
computationally efficient procedure to estimate a graphon from a set of
observed networks generated from it. This procedure is based on a stochastic
blockmodel approximation (SBA) of the graphon. We show that, by approximating
the graphon with a stochastic block model, the graphon can be consistently
estimated, that is, the estimation error vanishes as the size of the graph
approaches infinity.

categories: stat.ME cs.LG cs.SI physics.data-an stat.ML


title:
An error estimate for viscous approximate solutions to degenerate
  anisotropic convection-diffusion equations

abstract:
  We consider a viscous approximation for a nonlinear degenerate
convection-diffusion equations in two space dimensions, and prove an $L^1$
error estimate. Precisely, we show that the $L^1_{\mathrm{loc}}$ difference
between the approximate solution and the unique entropy solution converges at a
rate $\mathcal{O}(\eps^{1/2})$, where $\eps$ is the viscous parameter.


title: The Unexpected 2012 Draconid Meteor Storm

abstract:
  An unexpected intense outburst of the Draconid meteor shower was detected by
the Canadian Meteor Orbit Radar (CMOR) on October 8, 2012. The peak flux
occurred at ~16:40 UT on October 8 with a maximum of 2.4 +/- 0.3 hr-1 km-2
(appropriate to meteoroid mass larger than 10-7 kg), equivalent to a ZHRmax =
9000 +/- 1000 using 5-minute intervals, using a mass distribution index of s =
1.88 +/- 0.01 as determined from the amplitude distribution of underdense
Draconid echoes. This makes the out- burst among the strongest Draconid returns
since 1946 and the highest flux shower since the 1966 Leonid meteor storm,
assuming a constant power-law distribution holds from radar to visual meteoroid
sizes. The weighted mean geocentric radiant in the time interval of 15-19h UT,
Oct 8, 2012 was {\alpha}g = 262.4 +/- 0.1 deg, {\delta}g = 55.7 +/- 0.1 deg
(epoch J2000.0). Visual observers also reported increased activity around the
peak time, but with a much lower rate (ZHR 200), suggesting that the
magnitude-cumulative num- ber relationship is not a simple power-law. Ablation
modeling of the observed meteors as a population does not yield a unique
solution for the grain size and distribution of Draconid meteoroids, but is
consistent with a typical Draconid meteoroid of mtotal between 10-6 to 10-4 kg
being composed of 10 - 100 grains. Dynamical simulations indicate that the
outburst was caused by dust particles released during the 1966 per- ihelion
passage of the parent comet, 21P/Giacobini-Zinner, although there are dis-
crepancies between the modelled and observed timing of the encounter,
presumably caused by approaches of the comet to Jupiter during 1966-1972. Based
on the results of our dynamical simulation, we predict possible increased
activity of the Draconid meteor shower in 2018, 2019, 2021 and 2025.


title:
Mathematical models for sleep-wake dynamics: comparison of the
  two-process model and a mutual inhibition neuronal model

abstract:
  Sleep is essential for the maintenance of the brain and the body, yet many
features of sleep are poorly understood and mathematical models are an
important tool for probing proposed biological mechanisms. The most well-known
mathematical model of sleep regulation, the two-process model, models the
sleep-wake cycle by two oscillators: a circadian oscillator and a homeostatic
oscillator. An alternative, more recent, model considers the mutual inhibition
of sleep promoting neurons and the ascending arousal system regulated by
homeostatic and circadian processes. Here we show there are fundamental
similarities between these two models. The implications are illustrated with
two important sleep-wake phenomena. Firstly, we show that in the two-process
model, transitions between different numbers of daily sleep episodes occur at
grazing bifurcations.This provides the theoretical underpinning for numerical
results showing that the sleep patterns of many mammals can be explained by the
mutual inhibition model. Secondly, we show that when sleep deprivation disrupts
the sleep-wake cycle, ostensibly different measures of sleepiness in the two
models are closely related. The demonstration of the mathematical similarities
of the two models is valuable because not only does it allow some features of
the two-process model to be interpreted physiologically but it also means that
knowledge gained from study of the two-process model can be used to inform
understanding of the mutual inhibition model. This is important because the
mutual inhibition model and its extensions are increasingly being used as a
tool to understand a diverse range of sleep-wake phenomena such as the design
of optimal shift-patterns, yet the values it uses for parameters associated
with the circadian and homeostatic processes are very different from those that
have been experimentally measured in the context of the two-process model.


title: Towards an optical potential for rare-earths through coupled channels

abstract:
  The coupled-channel theory is a natural way of treating nonelastic channels,
in particular those arising from collective excitations, defined by nuclear
deformations. Proper treatment of such excitations is often essential to the
accurate description of reaction experimental data. Previous works have applied
different models to specific nuclei with the purpose of determining
angular-integrated cross sections. In this work, we present an extensive study
of the effects of collective couplings and nuclear deformations on integrated
cross sections as well as on angular distributions in a consistent manner for
neutron-induced reactions on nuclei in the rare-earth region. This specific
subset of the nuclide chart was chosen precisely because of a clear static
deformation pattern. We analyze the convergence of the coupled-channel
calculations regarding the number of states being explicitly coupled. Inspired
by the work done by Dietrich \emph{et al.}, a model for deforming the spherical
Koning-Delaroche optical potential as function of quadrupole and hexadecupole
deformations is also proposed. We demonstrate that the obtained results of
calculations for total, elastic and inelastic cross sections, as well as
elastic and inelastic angular distributions correspond to a remarkably good
agreement with experimental data for scattering energies above around a few
MeV.


title: On the Grothendieck ring of varieties

abstract:
  Let $\operatorname{K}_0(\operatorname{Var}_k)$ denote the Grothendieck ring
of $k$-varieties over an algebraically closed field $k$. Larsen and Lunts asked
if two $k$-varieties having the same class in $\operatorname{K}_0
(\operatorname{Var}_k)$ are piecewise isomorphic. Gromov asked if a birational
self-map of a $k$-variety can be extended to a piecewise automorphism. We show
that these two questions are equivalent over any algebraically closed field. If
these two questions admit a positive answer, then we prove that its underlying
abelian group is a free abelian group. Furthermore, if $\mathfrak B$ denotes
the multiplicative monoid of birational equivalence classes of irreducible
$k$-varieties then we also prove that the associated graded ring of the
Grothendieck ring is the monoid ring $\mathbb Z[\mathfrak B]$.


title: Pattern formation in a diffusion-ODE model with hysteresis

abstract:
  Coupling diffusion process of signaling molecules with nonlinear interactions
of intracellular processes and cellular growth/transformation leads to a system
of reaction-diffusion equations coupled with ordinary differential equations
(diffusion-ODE models), which differ from the usual reaction-diffusion systems.
One of the mechanisms of pattern formation in such systems is based on the
existence of multiple steady states and hysteresis in the ODE subsystem.
Diffusion tries to average different states and is the cause of spatio-temporal
patterns. In this paper we provide a systematic description of stationary
solutions of such systems, having the form of transition or boundary layers.
The solutions are discontinuous in the case of non-diffusing variables whose
quasi-stationary dynamics exhibit hysteresis. The considered model is motivated
by biological applications and elucidates a possible mechanism of formation of
patterns with sharp transitions.


title: Asymptotic quantization of exponential random graphs

abstract:
  We describe the asymptotic properties of the edge-triangle exponential random
graph model as the natural parameters diverge along straight lines. We show
that as we continuously vary the slopes of these lines, a typical graph drawn
from this model exhibits quantized behavior, jumping from one complete
multipartite graph to another, and the jumps happen precisely at the normal
lines of a polyhedral set with infinitely many facets. As a result, we provide
a complete description of all asymptotic extremal behaviors of the model.


title:
General model for simulation of the measurement-device independent
  quantum key distribution

abstract:
  We present a general model on the simulation of the measurement-device
independent quantum key distribution (MDI-QKD). It can be used to predict
experimental observations of a MDI-QKD with linear channel loss, simulating
corresponding values for the gains, the error rates in different basis, and
also the final key rates. Our model can be applicable to the MDI-QKDs with
whatever convex source states or using whatever coding schemes. Therefore, it
is useful in characterizing and evaluating the performance of any MDI-QKD
protocols, making it a valuable tool in studying the quantum key distributions.


title: 3D manipulation with scanning near field optical nanotweezers

abstract:
  Recent advances in Nanotechnologies have prompted the need for tools to
accurately and non-invasively manipulate individual nano-objects. Among
possible strategies, optical forces have been foreseen to provide researchers
with nano-optical tweezers capable to trap a specimen and move it in 3D. In
practice though, the combination of weak optical forces involved and
photothermal issues have thus far prevented their experimental realization.
Here, we demonstrate first 3D optical manipulation of single 50 nm dielectric
objects with near field nano-tweezers. The nano-optical trap is built by
engineering a bowtie plasmonic aperture at the extremity of a tapered
metal-coated optical fiber. Both the trapping operation and monitoring are
performed through the optical fiber making these nano-tweezers totally
autonomous and free of bulky optical elements. The achieved trapping
performances allow for the trapped specimen to be moved over tens of
micrometers during several minutes with very low in-trap intensities. This
novel non-invasive approach is foreseen to open new horizons in nanosciences by
offering an unprecedented level of control of nano-sized objects including
heat-sensitive bio-specimens.


title:
Architectural improvements and 28 nm FPGA implementation of the APEnet+
  3D Torus network for hybrid HPC systems

abstract:
  Modern Graphics Processing Units (GPUs) are now considered accelerators for
general purpose computation. A tight interaction between the GPU and the
interconnection network is the strategy to express the full potential on
capability computing of a multi-GPU system on large HPC clusters; that is the
reason why an efficient and scalable interconnect is a key technology to
finally deliver GPUs for scientific HPC. In this paper we show the latest
architectural and performance improvement of the APEnet+ network fabric, a
FPGA-based PCIe board with 6 fully bidirectional off-board links with 34 Gbps
of raw bandwidth per direction, and X8 Gen2 bandwidth towards the host PC. The
board implements a Remote Direct Memory Access (RDMA) protocol that leverages
upon peer-to-peer (P2P) capabilities of Fermi- and Kepler-class NVIDIA GPUs to
obtain real zero-copy, low-latency GPU-to-GPU transfers. Finally, we report on
the development activities for 2013 focusing on the adoption of the latest
generation 28 nm FPGAs and the preliminary tests performed on this new
platform.


title:
Growth of whisker-like and bulk single crystals of PrFeAs(O,F) under
  high pressure

abstract:
  Superconducting whisker like and bulk single crystals of PrFeAs(O,F) were
grown at 3 GPa and 1500 C from NaAs flux using the cubic anvil high pressure
and high temperature technique. The ribbon shaped whisker like crystals were
400-1300 micrometers in length, 40-70 micrometers in width, and 5-10
micrometers in thickness with the long sharp edge in the ab plane and the c
axis perpendicular to the face. The grown bulk crystals were found to have
irregular plate like shapes with linear sizes up to 1 mm and 120 micrometers in
thickness. The both type of single crystalline objects are crystallized in the
same tetragonal structure and showed a single phase behavior in the temperature
dependence of magnetization with a superconducting transition temperature of
about 31 K. The presence of temperature gradient and reactive flux seems to
play an important role for the growth of single crystalline whiskers and bulk
single crystals of PrFeAs(O,F). These observations demonstrate that the
morphological properties of the crystals are depending not only on the symmetry
of the crystal structure of the desired material, but also of the growth
medium.


title: Exploration in Free Word Association Networks: Models and Experiment

abstract:
  Free association is a task that requires a subject to express the first word
to come to their mind when presented with a certain cue. It is a task which can
be used to expose the basic mechanisms by which humans connect memories. In
this work we have made use of a publicly available database of free
associations to model the exploration of the averaged network of associations
using a statistical and the \emph{ACT-R} model. We performed, in addition, an
online experiment asking participants to navigate the averaged network using
their individual preferences for word associations. We have investigated the
statistics of word repetitions in this guided association task. We find that
the considered models mimic some of the statistical properties, viz the
probability of word repetitions, the distance between repetitions and the
distribution of association chain lengths, of the experiment, with the
\emph{ACT-R} model showing a particularly good fit to the experimental data for
the more intricate properties as, for instance, the ratio of repetitions per
length of association chains.


title: Reflections on the direct detection of particle dark matter

abstract:
  The LUX experimental group has just announced the most stringent upper limits
so far obtained on the cross section of WIMP-nucleon elastic scattering [1].
This result is a factor of two to five below the previous best upper limit [2]
and effectively rules out earlier suggestions of low mass WIMP detection
signals. The experimental expertise exhibited by this group is extremely
impressive, but the fact of continued negative results raises the more basic
question of whether or not this is the right approach to solving the dark
matter problem. Here I comment upon this question, using as a basis the final
chapter of my book on dark matter [3], somewhat revised and extended. I muse on
dark matter and its alternative, modified Newtonian dynamics, or MOND.