title:
Chemical evolution during the process of proto-star formation by
  considering a two dimensional hydrodynamic model

abstract:
  Chemical composition of a molecular cloud is highly sensitive to the physical
properties of the cloud. In order to obtain the chemical composition around a
star forming region, we carry out a two dimensional hydrodynamical simulation
of the collapsing phase of a proto-star. A total variation diminishing scheme
(TVD) is used to solve the set of equations governing hydrodynamics. This
hydrodynamic code is capable of mimicking evolution of the physical properties
during the formation of a proto-star. We couple our reasonably large gas-grain
chemical network to study the chemical evolution during the collapsing phase of
a proto-star. To have a realistic estimate of the abundances of bio-molecules
in the interstellar medium, we include the recently calculated rate
coefficients for the formation of several interstellar bio-molecules into our
gas phase network. Chemical evolution is studied in detail by keeping grain at
the constant temperature throughout the simulation as well as by using the
temperature variation obtained from the hydrodynamical model. By considering a
large gas-grain network with the sophisticated hydrodynamic model more
realistic abundances are predicted. We find that the chemical composition are
highly sensitive to the dynamic behavior of the collapsing cloud, specifically
on the density and temperature distribution.


title: Hawking Radiation from Small Black Holes at Strong Coupling and Large N

abstract:
  In a previous work an approximate static metric was found of a test black
string that stretches from the boundary to the horizon of the planar
Schwarzschild-AdS_5 geometry. This is the gravity dual of the Unruh state for
\mathcal{N}=4, SU(N) super Yang-Mills theory on a 4-dimensional Schwarzschild
background, at large N and large 'tHooft coupling. We compute the holographic
stress tensor of the gravitational solution and it turns out to possess many
essential features of the Unruh state for weakly-coupled Hawking radiation,
such as the appearance of a negative energy density near the black hole horizon
and a positive energy density at infinity. It also confirms recent results that
at leading order in N, the expectation value of the stress tensor in the Unruh
state is finite on both the future and past horizons, and that at this order
there are no flux terms as is expected in the black droplet phase.


title: Equilibrium size distribution function of clusters in finite system

abstract:
  The equilibrium size distribution function of clusters (nanoparticles) in the
system of finite number of molecules (atoms) in finite closed volume with
constant total energy (isolated system) is found using methods of statistical
thermodynamics. The distribution function is found from kinetic equation of
nucleation using one-drop approximation for both isothermal and isolated
systems. The results obtained are compared with computer simulation data of
finite two-dimensional system.


title:
Near infrared and gamma-ray monitoring of TANAMI gamma-ray bright
  sources

abstract:
  Spectral energy distribution and its variability are basic tools for
understanding the physical processes operating in active galactic nuclei (AGN).
In this paper we report the results of a one-year near infra red (NIR) and
optical monitoring of a sample of 22 AGN known to be gamma-ray emitters, aimed
at discovering correlations between optical and gamma-ray emission. We observed
our objects with the Rapid Eye Mount (REM) telescope in J, H, K, and R bands
nearly twice every month during their visibility window and derived light
curves and spectral indexes. We also analyzed the gamma-ray data from the Fermi
gamma-ray Space Telescope, making weekly averages. Six sources were never
detected during our monitoring, proving to be fainter than their historical Two
micron all sky survey (2MASS) level. All of the sixteen detected sources showed
marked flux density variability, while the spectral indexes remained unchanged
within our sensitivity limits. Steeper sources showed, on average, a larger
variability. From the NIR light curves we also computed a variability speed
index for each detected source. Only one source (PKS 0208-512) underwent an NIR
flare during our monitoring. Half of the sources showed a regular flux density
trend on a one-year time scale, but do not show any other peculiar
characteristic. The broadband spectral index alpha_ro appears to be a good
proxy of the NIR spectral index only for BL Lac objects. No clear correlation
between NIR and gamma-ray data is evident in our data, save for PKS 0537-441,
PKS 0521-360, PKS 2155-304, and PKS 1424-418. The gamma-ray/NIR flux ratio
showed a large spread, QSO being generally gamma-louder than BL Lac, with a
marked correlation with the estimated peak frequency nu_peak of the synchrotron
emission.


title:
A Novel Reconfigurable Architecture of a DSP Processor for Efficient
  Mapping of DSP Functions using Field Programmable DSP Arrays

abstract:
  Development of modern integrated circuit technologies makes it feasible to
develop cheaper, faster and smaller special purpose signal processing function
circuits. Digital Signal processing functions are generally implemented either
on ASICs with inflexibility, or on FPGAs with bottlenecks of relatively smaller
utilization factor or lower speed compared to ASIC. Field Programmable DSP
Array (FPDA) is the proposed DSP dedicated device, redolent to FPGA, but with
basic fixed common modules (CMs) (like adders, subtractors, multipliers,
scaling units, shifters) instead of CLBs. This paper introduces the development
of reconfigurable system architecture with a focus on FPDA that integrates
different DSP functions like DFT, FFT, DCT, FIR, IIR, and DWT etc. The
switching between DSP functions is occurred by reconfiguring the
interconnection between CMs. Validation of the proposed architecture has been
achieved on Virtex5 FPGA. The architecture provides sufficient amount of
flexibility, parallelism and scalability.


title: Harmony search algorithm for the container storage problem

abstract:
  Recently a new metaheuristic called harmony search was developed. It mimics
the behaviors of musicians improvising to find the better state harmony. In
this paper, this algorithm is described and applied to solve the container
storage problem in the harbor. The objective of this problem is to determine a
valid containers arrangement, which meets customers delivery deadlines, reduces
the number of container rehandlings and minimizes the ship idle time. In this
paper, an adaptation of the harmony search algorithm to the container storage
problem is detailed and some experimental results are presented and discussed.
The proposed approach was compared to a genetic algorithm previously applied to
the same problem and recorded a good results.


title: Cosmography of the Local Universe

abstract:
  The large scale structure of the universe is a complex web of clusters,
filaments, and voids. Its properties are informed by galaxy redshift surveys
and measurements of peculiar velocities. Wiener Filter reconstructions recover
three-dimensional velocity and total density fields. The richness of the
elements of our neighborhood are revealed with sophisticated visualization
tools. A key component of this paper is an accompanying movie that can be
viewed and downloaded at : http://irfu.cea.fr/cosmography or
http://vimeo.com/pomarede/cosmography .The ability to translate and zoom helps
the viewer follow structures in three dimensions and grasp the relationships
between features on different scales while retaining a sense of orientation.
The ability to dissolve between scenes provides a technique for comparing
different information, for example, the observed distribution of galaxies,
smoothed representations of the distribution accounting for selection effects,
observed peculiar velocities, smoothed and modeled representations of those
velocities, and inferred underlying density fields. The agreement between the
large scale structure seen in redshift surveys and that inferred from
reconstructions based on the radial peculiar velocities of galaxies strongly
supports the standard model of cosmology where structure forms from
gravitational instabilities and galaxies form at the bottom of potential wells.


title: LHCb Semileptonic Asymmetry

abstract:
  A recent LHCb measurement of the CP violating flavour specific asymmetry in
$B_s^0$ decays, \asls, is presented. This measurement is based on a data sample
corresponding to an integrated luminosity of 1 fb$^{-1}$ of $pp$ collisions at
$\sqrt{s}$ $=$ 7 TeV, collected during the 2011 run of the LHC. The result is
$\asls = (-0.24 \pm 0.54_{\rm stat} \pm 0.33_{\rm syst})\times 10^{-2}$, which
is the most precise measurement of this quantity to date and agrees with the
Standard Model prediction.}


title: On a conjecture for the signless Laplacian eigenvalues

abstract:
  Let $G$ be a simple graph with $n$ vertices and $e(G)$ edges, and $q_1(G)\geq
q_2(G)\geq\cdots\geq q_n(G)\geq0$ be the signless Laplacian eigenvalues of $G.$
Let $S_k^+(G)=\sum_{i=1}^{k}q_i(G),$ where $k=1, 2, \ldots, n.$ F. Ashraf et
al. conjectured that $S_k^+(G)\leq e(G)+\binom{k+1}{2}$ for $k=1, 2, \ldots,
n.$ In this paper, we give various upper bounds for $S_k^+(G),$ and prove that
this conjecture is true for the following cases: connected graph with
sufficiently large $k,$ unicyclic graphs and bicyclic graphs for all $k,$ and
tricyclic graphs when $k\neq 3.$


title:
Analysis of Mismatched Estimation Errors Using Gradients of Partition
  Functions

abstract:
  We consider the problem of signal estimation (denoising) from a
statistical-mechanical perspective, in continuation to a recent work on the
analysis of mean-square error (MSE) estimation using a direct relationship
between optimum estimation and certain partition functions. The paper consists
of essentially two parts. In the first part, using the aforementioned
relationship, we derive single-letter expressions of the mismatched MSE of a
codeword (from a randomly selected code), corrupted by a Gaussian vector
channel. In the second part, we provide several examples to demonstrate phase
transitions in the behavior of the MSE. These examples enable us to understand
more deeply and to gather intuition regarding the roles of the real and the
mismatched probability measures in creating these phase transitions.


title: Universal Induction with Varying Sets of Combinators

abstract:
  Universal induction is a crucial issue in AGI. Its practical applicability
can be achieved by the choice of the reference machine or representation of
algorithms agreed with the environment. This machine should be updatable for
solving subsequent tasks more efficiently. We study this problem on an example
of combinatory logic as the very simple Turing-complete reference machine,
which enables modifying program representations by introducing different sets
of primitive combinators. Genetic programming system is used to search for
combinator expressions, which are easily decomposed into sub-expressions being
recombined in crossover. Our experiments show that low-complexity induction or
prediction tasks can be solved by the developed system (much more efficiently
than using brute force); useful combinators can be revealed and included into
the representation simplifying more difficult tasks. However, optimal sets of
combinators depend on the specific task, so the reference machine should be
adaptively chosen in coordination with the search engine.


title:
Generation and Confirmation of a (100x100)-dimensional entangled Quantum
  System

abstract:
  Entangled quantum systems have properties that have fundamentally overthrown
the classical worldview. Increasing the complexity of entangled states by
expanding their dimensionality allows the implementation of novel fundamental
tests of nature, and moreover also enables genuinely new protocols for quantum
information processing. Here we present the creation of a (100x100)-dimensional
entangled quantum system, using spatial modes of photons. For its verification
we develop a novel nonlinear criterion which infers entanglement dimensionality
of a global state by using only information about its subspace correlations.
This allows very practical experimental implementation as well as highly
efficient extraction of entanglement dimensionality information. Applications
in quantum cryptography and other protocols are very promising.


title:
A new class of exact solutions of the Klein-Gordon equation of a charged
  particle interacting with an electromagnetic plane wave in a medium

abstract:
  Exact solutions are presented of the Klein-Gordon equation of a charged
particle moving in a classical monochromatic electromagnetic plane wave in a
medium of index of refraction n < 1. The solutions are expressed in terms of
Ince polynomials, which form a doubly infinite set labeled by two integer
quantum numbers. These integer numbers represent quantized spectra of the
momentum components of the charged particle along the polarization vector and
along the propagation direction of the applied electromagnetic plane wave
field. Since this field may represent a laser radiation of arbitrary high
intensity propagating in an underdense plasma, the solutions obtained may have
relevance, for instance, in describing possible quantum features of laser
acceleration of electrons.


title:
Hyperfine-induced effects on the linear polarization of the K$\alpha_1$
  emission from helium-like ions

abstract:
  The linear polarization of the characteristic photon emission from
few-electron ions is studied for its sensitivity with regard to the nuclear
spin and magnetic moment of the ions. Special attention is paid, in particular,
to the K$\alpha_1$ ($1s 2p_{3/2} ^{1,3}P_{1,2} \to 1s^2 ^1S_0$) decay of
selected helium-like ions following the radiative electron capture into
initially hydrogen-like species. Based on the density matrix theory, a unified
description is developed that includes both, the many-electron and hyperfine
interactions as well as the multipole-mixing effects arising from the expansion
of the radiation field. It is shown that the polarization of the K$\alpha_1$
line can be significantly affected by the mutipole mixing between the leading
$M2$ and hyperfine-induced $E1$ components of $1s2p ^3P_2, F_i \to 1s^2 ^1S_0,
F_f$ transitions. This $E1$-$M2$ mixing strongly depends on the nuclear
properties of the considered isotopes and can be addressed experimentally at
existing heavy-ion storage rings.


title: Supercritical problems in domains with thin toroidal holes

abstract:
  In this paper we study the Lane-Emden-Fowler equation $$(P)_\epsilon\
\{\Delta u+|u|^{q-2}u=0 \ \hbox{in}\ \mathcal D_\epsilon, u=0 \ \hbox{on}\
\partial\mathcal D_\epsilon.$$ Here $\mathcal D_\epsilon = \mathcal D \setminus
\{x \in \mathcal D \ : \ \mathrm{dist}(x,\Gamma_\ell)\le \epsilon\}$, $\mathcal
D$ is a smooth bounded domain in $\mathbb{R}^N$, $\Gamma_\ell$ is an
$\ell-$dimensional closed manifold such that $\Gamma_\ell \subset \mathcal D$
with $1\le \ell \le N-3$ and $q={2(N-\ell)\over N-\ell-2}$. We prove that,
under some symmetry assumptions, the number of sign changing solutions to
$(P)_\epsilon$ increases as $\epsilon$ goes to zero.


title: Are your data really Pareto distributed?

abstract:
  Pareto distributions, and power laws in general, have demonstrated to be very
useful models to describe very different phenomena, from physics to finance. In
recent years, the econophysical literature has proposed a large amount of
papers and models justifying the presence of power laws in economic data. Most
of the times, this Paretianity is inferred from the observation of some plots,
such as the Zipf plot and the mean excess plot. If the Zipf plot looks almost
linear, then everything is ok and the parameters of the Pareto distribution are
estimated. Often with OLS. Unfortunately, as we show in this paper, these
heuristic graphical tools are not reliable. To be more exact, we show that only
a combination of plots can give some degree of confidence about the real
presence of Paretianity in the data. We start by reviewing some of the most
important plots, discussing their points of strength and weakness, and then we
propose some additional tools that can be used to refine the analysis.


title:
Differential Operators on the Weighted Densities on the Supercircle
  $S^{1|n}$

abstract:
  Over the $(1,n)$-dimensional real supercircle, we consider the
$\mathcal{K}(n)$-modules of linear differential operators,
$\frak{D}^n_{\lambda,\mu}$, acting on the superspaces of weighted densities,
where $\mathcal{K}(n)$ is the Lie superalgebra of contact vector fields. We
give, in contrast to the classical setting, a classification of these modules
for $n=1$. We also prove that $\frak{D}^{n}_{\lambda,\mu}$ and
$\frak{D}_{\rho,\nu}^{n}$ are isomorphic for $\rho=\frac{2-n}{2}-\mu$ and
$\nu=\frac{2-n}{2}-\lambda$. This work is the simplest superization of a result
by Gargoubi and Ovsienko [Modules of Differential Operators on the Real Line,
Functional Analysis and Its Applications, Vol. 35, No. 1, pp. 13--18, 2001.]


title:
Muonium annihilation into $\nu_e\bar{\nu}_{\mu}$ and
  $\nu_e\bar{\nu}_{\mu}\gamma$

abstract:
  We calculate in detail the annihilation of Muonium into two-neutrino final
state and two-neutrino and a photon state.


title: Dominant Frequency Extraction

abstract:
  Time series are collected and studied extensively for the knowledge about the
data source characteristics such as the trend or the spectral landscape. Some
peaks in the spectral landscape correspond to dominant frequencies. The
approach here is empirical: all time series are discrete and finite. Contents:
Introduction. 1 Examples of periodic phenomena. 2 Algorithms and libraries. 3
Time series analysis. 4 Dominant frequency in ladar data. Conclusion.
References.


title: Symetries of modules of differential operators on $S^{1|1}$

abstract:
  Let $\frak F_{\l}$ be the space of tensor densities of degree $\lambda$ on
the supercircle $S^{1|1}$. We consider the space $\mathfrak{D}_{\lambda,\mu}^k$
of k-th order linear differential operators from $\frak F_{\l}$ to $\frak
F_{\mu}$ as $\mathfrak{osp}(1|2)$-module and we determine the space
$\mathfrak{I}_{\lambda,\mu}^k$ of linear maps on $\mathfrak{D}_{\lambda,\mu}^k$
commuting with the $\mathfrak{osp}(1|2)$-action.


title:
Analytical homoclinic solution of a two dimensional nonlinear system of
  differential equations

abstract:
  Analytical solution of the homoclinic orbit of a two dimensional system of
differential equations that describes the hamiltonian part of the slow flow of
a three degree of freedom dissipative system of linear coupled oscillators with
an essentially nonlinear attachment.


title:
Collision Energy Evolution of Elliptic and Triangular Flow in a Hybrid
  Model

abstract:
  While the existence of a strongly interacting state of matter, known as
'quark-gluon plasma' (QGP), has been established in heavy ion collision
experiments in the past decade, the task remains to map out the transition from
the hadronic matter to the QGP. This is done by measuring the dependence of key
observables (such as particle suppression and elliptic flow) on the collision
energy of the heavy ions. This procedure, known as 'beam energy scan', has been
most recently performed at the Relativistic Heavy Ion Collider (RHIC).
Utilizing a Boltzmann+hydrodynamics hybrid model, we study the collision energy
dependence of initial state eccentricities and the final state elliptic and
triangular flow. This approach is well suited to investigate the relative
importance of hydrodynamics and hadron transport at different collision
energies.


title:
Weak and strong composition conditions for the Abel differential
  equation

abstract:
  We establish an equivalence between two forms of the composition condition
for the Abel differential equation with trigonometric coefficients.


title: The strong $P$-cleanness over rings

abstract:
  An element of a ring $R$ is strongly $P$-clean provided that it can be
written as the sum of an idempotent and a strongly nilpotent element that
commute. A ring $R$ is strongly $P$-clean in case each of its elements is
strongly $P$-clean. We investigate, in this article, the necessary and
sufficient conditions under which a ring $R$ is strongly $P$-clean. Many
characterizations of such rings are obtained. The criteria on strong
$P$-cleanness of $2\times 2$ matrices over commutative local rings are also
determined.


title:
Physical design of FEL injector based on performance-enhanced EC-ITC RF
  gun

abstract:
  To meet requirements of high performance THz-FEL (Free Electron Laser), a
compact scheme of FEL injector was proposed. Thermionic cathode was chosen to
emit electrons instead of photo-cathode with complex structure and high cost.
The effective bunch charge was improved to ~200pC by adopting enhanced EC-ITC
(External Cathode Independently Tunable Cells) RF gun to extract micro-bunches,
and back bombardment effects were almost eliminated as well. Constant gradient
accelerator structures were designed to improve energy to ~14MeV, while
focusing system was applied for emittance suppressing and bunch state
maintenance. Physical design and beam dynamics of key components for FEL
injector were analyzed. Furthermore, start-to-end simulations with multi-pulses
were performed by using homemade MATLAB and Parmela. The results show that
continual high brightness electron bunches with low energy spread and emittance
could be obtained stably.


title: Evasiveness of Graph Properties and Topological Fixed-Point Theorems

abstract:
  Many graph properties (e.g., connectedness, containing a complete subgraph)
are known to be difficult to check. In a decision-tree model, the cost of an
algorithm is measured by the number of edges in the graph that it queries. R.
Karp conjectured in the early 1970s that all monotone graph properties are
evasive -- that is, any algorithm which computes a monotone graph property must
check all edges in the worst case. This conjecture is unproven, but a lot of
progress has been made. Starting with the work of Kahn, Saks, and Sturtevant in
1984, topological methods have been applied to prove partial results on the
Karp conjecture. This text is a tutorial on these topological methods. I give a
fully self-contained account of the central proofs from the paper of Kahn,
Saks, and Sturtevant, with no prior knowledge of topology assumed. I also
briefly survey some of the more recent results on evasiveness.


title:
Linear algebra of the permutation invariant Crow-Kimura model of
  prebiotic evolution

abstract:
  A particular case of the famous quasispecies model - the Crow-Kimura model
with a permutation invariant fitness landscape - is investigated. Using the
fact that the mutation matrix in the case of a permutation invariant fitness
landscape has a special tridiagonal form, a change of the basis is suggested
such that in the new coordinates a number of analytical results can be
obtained. In particular, using the eigenvectors of the mutation matrix as the
new basis, we show that the quasispecies distribution approaches a binomial one
and give simple estimates for the speed of convergence. Another consequence of
the suggested approach is a parametric solution to the system of equations
determining the quasispecies. Using this parametric solution we show that our
approach leads to exact asymptotic results in some cases, which are not covered
by the existing methods. In particular, we are able to present not only the
limit behavior of the leading eigenvalue (mean population fitness), but also
the exact formulas for the limit quasispecies eigenvector for special cases.
For instance, this eigenvector has a geometric distribution in the case of the
classical single peaked fitness landscape. On the biological side, we propose a
mathematical definition, based on the closeness of the quasispecies to the
binomial distribution, which can be used as an operational definition of the
notorious error threshold. Using this definition, we suggest two approximate
formulas to estimate the critical mutation rate after which the quasispecies
delocalization occurs.


title:
Deciphering the global organization of clustering in real complex
  networks

abstract:
  We uncover the global organization of clustering in real complex networks. As
it happens with other fundamental properties of networks such as the degree
distribution, we find that real networks are neither completely random nor
ordered with respect to clustering, although they tend to be closer to
maximally random architectures. We reach this conclusion by comparing the
global structure of clustering in real networks with that in maximally random
and in maximally ordered clustered graphs. The former are produced with an
exponential random graph model that maintains correlations among adjacent edges
at the minimum needed to conform with the expected clustering spectrum; the
later with a random model that arranges triangles in cliques inducing highly
ordered structures. To compare the global organization of clustering in real
and model networks, we compute $m$-core landscapes, where the $m$-core is
defined, akin to the $k$-core, as the maximal subgraph with edges participating
at least in $m$ triangles. This property defines a set of nested subgraphs
that, contrarily to $k$-cores, is able to distinguish between hierarchical and
modular architectures. To visualize the $m$-core decomposition we developed the
LaNet-vi 3.0 tool.


title:
Trust, but verify: benefits and pitfalls of least-squares refitting in
  high dimensions

abstract:
  Least-squares refitting is widely used in high dimensional regression to
reduce the prediction bias of l1-penalized estimators (e.g., Lasso and
Square-Root Lasso). We present theoretical and numerical results that provide
new insights into the benefits and pitfalls of least-squares refitting. In
particular, we consider both prediction and estimation, and we pay close
attention to the effects of correlations in the design matrices of linear
regression models, since these correlations - although often neglected - are
crucial in the context of linear regression, especially in high dimensional
contexts. First, we demonstrate that the benefit of least-squares refitting
strongly depends on the setting and task under consideration: least-squares
refitting can be beneficial even for settings with highly correlated design
matrices but is not advisable for all settings, and least-squares refitting can
be beneficial for estimation but performs better for prediction. Finally, we
introduce a criterion that indicates whether least-squares refitting is
advisable for a specific setting and task under consideration, and we conduct a
thorough simulation study involving the Lasso to show the usefulness of this
criterion.


title: On the Predictability of Future Impact in Science

abstract:
  Correctly assessing a scientist's past research impact and potential for
future impact is key in recruitment decisions and other evaluation processes.
While a candidate's future impact is the main concern for these decisions, most
measures only quantify the impact of previous work. Recently, it has been
argued that linear regression models are capable of predicting a scientist's
future impact. By applying that future impact model to 762 careers drawn from
three disciplines: physics, biology, and mathematics, we identify a number of
subtle, but critical, flaws in current models. Specifically, cumulative
non-decreasing measures like the h-index contain intrinsic autocorrelation,
resulting in significant overestimation of their "predictive power". Moreover,
the predictive power of these models depend heavily upon scientists' career
age, producing least accurate estimates for young researchers. Our results
place in doubt the suitability of such models, and indicate further
investigation is required before they can be used in recruiting decisions.


title: Symplectic theory of completely integrable Hamiltonian systems

abstract:
  This paper explains the recent developments on the symplectic theory of
Hamiltonian completely integrable systems on symplectic 4-manifolds, compact or
not. One fundamental ingredient of these developments has been the
understanding of singular affine structures. These developments make use of
results obtained by many authors in the second half of the twentieth century,
notably Arnold, Duistermaat and Eliasson, of which we also give a concise
survey. As a motivation, we present a collection of remarkable results proven
in the early and mid 1980s in the theory of Hamiltonian Lie group actions by
Atiyah, Guillemin-Sternberg and Delzant among others, and which inspired many
people, including the authors, to work on more general Hamiltonian systems. The
paper concludes discussing a spectral conjecture for quantum integrable
systems.


title: Harmonic oscillators in a Snyder geometry

abstract:
  We find that, in presence of the Snyder geometry, the quantization of d
isotropic harmonic oscillators can be solved exactly.


title: Algebraic method for the harmonic oscillator with a minimal length

abstract:
  We show that the algebraic method solving the ordinary harmonic oscillator
can be adapted to the non-commutative case.


title: Thermodynamics and Spectroscopy of charged Dilaton black holes

abstract:
  The Bohr-Sommerfeld quantization rule is useful to study the area spectrum of
black holes by employing adiabatic invariants. This method is extended to
charged dilaton black holes in 2+1 dimensions. We put the background space-time
into the Kruskal-like coordinate to find the period with respect to Euclidian
time. Also assuming that the adiabatic invariant obeys Bohr-Sommerfeld
quantization rule, detailed study of area and entropy spectrum has been done.
It is dependent on the charge and is equally spaced as well.
  We also investigate the thermodynamics of the charged dilaton black hole.


title:
A new variational method with SPBC and many stable choreographic
  solutions of the Newtonian 4-body problem

abstract:
  After the existence proof of the first remarkably stable simple choreographic
motion-- the figure eight of the planar three-body problem by Chenciner and
Montgomery in 2000, a great number of simple choreographic solutions have been
discovered numerically but very few of them have rigorous existence proofs and
none of them are stable. Most important to astronomy are stable periodic
solutions which might actually be seen in some stellar system. A question for
simple choreographic solutions on $n$-body problems naturally arises: Are there
any other stable simple choreographic solutions except the figure eight?
  In this paper, we prove the existence of infinitely many simple choreographic
solutions in the classical Newtonian 4-body problem by developing a new
variational method with structural prescribed boundary conditions (SPBC).
Surprisingly, a family of choreographic orbits of this type are all linearly
stable. Among the many stable simple choreographic orbits, the most
extraordinary one is the stable star pentagon choreographic solution. The star
pentagon is assembled out of four pieces of curves which are obtained by
minimizing the Lagrangian action functional over the SPBC.
  We also prove the existence of infinitely many double choreographic periodic
solutions, infinitely many non-choreographic periodic solutions and uncountably
many quasi-periodic solutions. Each type of periodic solutions have many stable
solutions and possibly infinitely many stable solutions.


title: Completeness of compact Lorentzian manifolds with Abelian holonomy

abstract:
  We address the problem of finding conditions under which a compact Lorentzian
manifold is geodesically complete, a property, which always holds for compact
Riemannian manifolds. It is known that a compact Lorentzian manifold is
geodesically complete if it is homogeneous, or has constant curvature, or
admits a time-like conformal vector field. We consider certain Lorentzian
manifolds with Abelian holonomy, which are locally modelled by the so called
pp-waves, and which, in general, do not satisfy any of the above conditions.
%the condition that their curvature sends vectors that are orthogonal to the
vector field to a multiple of the vector field. We show that compact pp-waves
are universally covered by a vector space, determine the metric on the
universal cover, and prove that they are geodesically complete. Using this, we
show that every Ricci-flat compact pp-wave is a plane wave.


title: EPOS LHC : test of collective hadronization with LHC data

abstract:
  EPOS is a Monte-Carlo event generator for minimum bias hadronic interactions,
used for both heavy ion interactions and cosmic ray air shower simulations.
Since the last public release in 2009, the LHC experiments have provided a
number of very interesting data sets comprising minimum bias p-p, p-Pb and
Pb-Pb interactions. We describe the changes required to the model to reproduce
in detail the new data available from LHC and the consequences in the
interpretation of these data. In particular we discuss the effect of the
collective hadronization in p-p scattering. A different parametrization of flow
has been introduced in the case of a small volume with high density of
thermalized matter (core) reached in p-p compared to large volume produced in
heavy ion collisions. Both parametrizations depend only on the geometry and the
amount of secondary particles entering in the core and not on the beam mass or
energy. The transition between the two flow regimes can be tested with p-Pb
data. EPOS LHC is able to reproduce all minimum bias


title:
Concentrating Bound States for Kirchhoff type problems in ${\R^3}$
  involving critical Sobolev exponents

abstract:
  We study the concentration and multiplicity of weak solutions to the
Kirchhoff type equation with critical Sobolev growth \[\left\{\begin{gathered}
  - \Bigl({\varepsilon ^2}a + \varepsilon b\int_{{\R^3}} {{{\left| {\nabla u}
\right|}^2}} \Bigr)\Delta u + V(z)u
  = f(u) + {u^5}{\text{in}}{\R^3}, \hfill u \in {H^1}({\R^3}),{\text{}}u >
0{\text{in}}{\R^3}, \hfill \\ \end{gathered} \right.\] where $\varepsilon $ is
a small positive parameter and $a,b > 0$ are constants, $f \in {C^1}({\R^
+},\R)$ is subcritical, $V:{\R^3} \to \R$ is a locally H\"{o}lder continuous
function.
  We first prove that for ${\varepsilon_0} > 0$ sufficiently small, the above
problem has a weak solution ${u_\varepsilon}$ with exponential decay at
infinity. Moreover, ${u_\varepsilon}$ concentrates around a local minimum point
of $V$ in $\Lambda $ as $\varepsilon \to 0$. With minimax theorems and
Ljusternik-Schnirelmann theory, we also obtain multiple solutions by employing
the topology construct of the set where the potential $V\left(z \right)$
attains its minimum.


title:
Degenerate semigroups and stochastic flows of mappings in foliated
  manifolds

abstract:
  Let $(M, \mathcal{F})$ be a compact Riemannian foliated manifold. We consider
a family of compatible Feller semigroups in $C(M^n)$ associated to laws of the
$n$-point motion. Under some assumptions (Le Jan and Raimond, \cite{Le
Jan-Raimond}) there exists a stochastic flow of measurable mappings in $M$. We
study the degeneracy of these semigroups such that the flow of mappings is
foliated, i.e. each trajectory lays in a single leaf of the foliation a.s,
hence creating a geometrical obstruction for coalescence of trajectories in
different leaves. As an application, an averaging principle is proved for a
first order perturbation transversal to the leaves. Estimates for the rate of
convergence are calculated.


title: First steps in symplectic and spectral theory of integrable systems

abstract:
  The paper intends to lay out the first steps towards constructing a unified
framework to understand the symplectic and spectral theory of finite
dimensional integrable Hamiltonian systems. While it is difficult to know what
the best approach to such a large classification task would be, it is possible
to single out some promising directions and preliminary problems. This paper
discusses them and hints at a possible path, still loosely defined, to arrive
at a classification. It mainly relies on recent progress concerning integrable
systems with only non-hyperbolic and non-degenerate singularities.
  This work originated in an attempt to develop a theory aimed at answering
some questions in quantum spectroscopy. Even though quantum integrable systems
date back to the early days of quantum mechanics, such as the work of Bohr,
Sommerfeld and Einstein, the theory did not blossom at the time. The
development of semiclassical analysis with microlocal techniques in the last
forty years now permits a constant interplay between spectral theory and
symplectic geometry. A main goal of this paper is to emphasize the symplectic
issues that are relevant to quantum mechanical integrable systems, and to
propose a strategy to solve them.


title: Understanding ACT-R - an Outsider's Perspective

abstract:
  The ACT-R theory of cognition developed by John Anderson and colleagues
endeavors to explain how humans recall chunks of information and how they solve
problems. ACT-R also serves as a theoretical basis for "cognitive tutors",
i.e., automatic tutoring systems that help students learn mathematics, computer
programming, and other subjects. The official ACT-R definition is distributed
across a large body of literature spanning many articles and monographs, and
hence it is difficult for an "outsider" to learn the most important aspects of
the theory. This paper aims to provide a tutorial to the core components of the
ACT-R theory.


title:
The fundamental group of a toroidal compactification of a Hermitian
  locally symmetric space

abstract:
  The present work obtains the fundamental group of a toroidal compactification
X' of a non-compact quotient X of a Hermitian symmetric space D of non-compact
type by a lattice L in the isometry group G of D. As a consequence it derives
the equality of the ranks of the first homology groups of X' and X with
integral coefficients. The paper provides also a sufficient condition on a
torsion free non-uniform lattice L, under which the fundamental group of X' is
residually finite. Articles of Hummel-Schroeder, Hummel and Di Cerbo imply that
the toroidal compactifications X' of generic non-compact torsion free quotients
X of the complex balls satisfy this sufficient condition.


title: Consistent Histories as Valuations

abstract:
  Sorkin's coevent interpretation shifts the focus of quantum logic from the
structure of a propositional lattice to the nature of truth valuations thereon.
We apply this shift in emphasis to a simple formulation of the consistent
histories approach, expressing it in terms of truth valuations which are
brought together in a logical framework. We see that these consistent histories
valuations are related to Sorkin's multiplicative coevents, and that they can
be naturally described by an adaptation of Isham's early topos-theoretic
approach.


title: Towards Detection of Bottlenecks in Modular Systems

abstract:
  The paper describes some basic approaches to detection of bottlenecks in
composite (modular) systems. The following basic system bottlenecks detection
problems are examined: (1) traditional quality management approaches (Pareto
chart based method, multicriteria analysis as selection of Pareto-efficient
points, and/or multicriteria ranking), (2) selection of critical system
elements (critical components/modules, critical component interconnection), (3)
selection of interconnected system components as composite system faults (via
clique-based fusion), (4) critical elements (e.g., nodes) in networks, and (5)
predictive detection of system bottlenecks (detection of system components
based on forecasting of their parameters). Here, heuristic solving schemes are
used. Numerical examples illustrate the approaches.


title: Shape of optimal active flagella

abstract:
  Many eukaryotic cells use the active waving motion of flexible flagella to
self-propel in viscous fluids. However, the criteria governing the selection of
particular flagellar waveforms among all possible shapes has proved elusive so
far. To address this question, we derive computationally the optimal shape of
an internally-forced periodic planar flagellum deforming as a travelling wave.
The optimum is here defined as the shape leading to a given swimming speed with
minimum energetic cost. To calculate the energetic cost though, we consider the
irreversible internal power expanded by the molecular motors forcing the
flagellum, only a portion of which ending up dissipated in the fluid. This
optimisation approach allows us to derive a family of shapes depending on a
single dimensionless number quantifying the relative importance of elastic to
viscous effects: the Sperm number. The computed optimal shapes are found to
agree with the waveforms observed on spermatozoon of marine organisms, thus
suggesting that these eukaryotic flagella might have evolved to be mechanically
optimal.


title:
Spontaneous emission can locally create quantum discord out of classical
  correlations

abstract:
  We consider local time evolution given by spontaneous emission in the system
of independent two-level atoms. It is shown that all classically correlated
initial states are driven into the states with transient non-zero quantum
discord. Thus local creation of genuine quantum correlations can be observed in
a simple physical system of non-interacting atoms which are not completely
isolated from the environment.


title: Obituary of Graham Everest

abstract: Obituary of Graham Everest (1957-2010)


title:
A multi-fidelity stochastic collocation method using locally improved
  reduced-order models

abstract:
  Over the last few years there have been dramatic advances in our
understanding of mathematical and computational models of complex systems in
the presence of uncertainty. This has led to a growth in the area of
uncertainty quantification as well as the need to develop efficient, scalable,
stable and convergent computational methods for solving differential equations
with random inputs. Stochastic Galerkin methods based on polynomial chaos
expansions have shown superiority to other non-sampling and many sampling
techniques. However, for complicated governing equations numerical
implementations of stochastic Galerkin methods can become non-trivial. On the
other hand, Monte Carlo and other traditional sampling methods, are
straightforward to implement. However, they do not offer as fast convergence
rates as stochastic Galerkin. Other numerical approaches are the stochastic
collocation (SC) methods, which inherit both, the ease of implementation of
Monte Carlo and the robustness of stochastic Galerkin to a great deal. However,
stochastic collocation and its powerful extensions, e.g. sparse grid stochastic
collocation, can simply fail to handle more levels of complication. The
seemingly innocent Burgers equation driven by Brownian motion is such an
example. In this work we propose a novel enhancement to stochastic collocation
methods using locally improved deterministic model reduction techniques that
can handle this pathological example and hopefully other more complicated
equations like Stochastic Navier-Stokes. Local improvements to reduced-order
models are achieved using sensitivity analysis of the proper orthogonal
decomposition. Our numerical results show that the proposed technique is not
only reliable and robust but also very efficient.


title: Twisted Bhargava Cubes

abstract:
  Let G be a reductive group and P=MN a maximal parabolic subgroup. The group M
acts, by conjugation, on N/[N,N]. It is well known that, over an algebraically
closed field, the group M acts transitively on a Zariski open set. However,
over a general field, the structure of orbits may be quite non-trivial. A
description may involve unexpected invariants. A notable example is when G is a
split, simply connected group of type D_4, and P is the maximal parabolic
corresponding to the branching point of the Dynkin diagram. The space N/[N,N]
is also known as the Bhargava cube, and it was the starting point of his
investigations of prehomogeneous spaces. We consider a version of this problem
for the triality D_4.


title: Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3

abstract:
  Galaxies are thought to be fed by the continuous accretion of intergalactic
gas, but direct observational evidence has been elusive. The accreted gas is
expected to orbit about the galaxy's halo, delivering not just fuel for
star-formation but also angular momentum to the galaxy, leading to distinct
kinematic signatures. Here we report observations showing these distinct
signatures near a typical distant star-forming galaxy where the gas is detected
using a background quasar passing 26 kpc from the host. Our observations
indicate that gas accretion plays a major role in galaxy growth since the
estimated accretion rate is comparable to the star-formation rate.


title:
Stability Criteria for SIS Epidemiological Models under Switching
  Policies

abstract:
  We study the spread of disease in an SIS model. The model considered is a
time-varying, switched model, in which the parameters of the SIS model are
subject to abrupt change. We show that the joint spectral radius can be used as
a threshold parameter for this model in the spirit of the basic reproduction
number for time-invariant models. We also present conditions for persistence
and the existence of periodic orbits for the switched model and results for a
stochastic switched model.


title: Congruences for 9-regular partitions modulo 3

abstract:
  It is proved that the number of 9-regular partitions of n is divisible by 3
when n is congruent to 3 mod 4, and by 6 when n is congruent to 13 mod 16. An
infinite family of congruences mod 3 holds in other progressions modulo powers
of 4 and 5. A collection of conjectures includes two congruences modulo higher
powers of 2 and a large family of "congruences with exceptions" for these and
other regular partitions mod 3.


title: On operator-valued monotone independence

abstract:
  We investigate operator-valued monotone independence, a noncommutative
version of independence for conditional expectation. First we introduce
operator-valued monotone cumulants to clarify the whole theory and show the
moment-cumulant formula. As an application, one can obtain an easy proof of
Central Limit Theorem for operator-valued case. Moreover, we prove a
generalization of Muraki's formula for the sum of independent random variables
and a relation between generating functions of moments and cumulants.


title: LCK metrics on Oeljeklaus-Toma manifolds versus Kronecker's theorem

abstract:
  A locally conformally K\"ahler (LCK) manifold is a manifold which is covered
by a K\"ahler manifold, with the deck transform group acting by homotheties. We
show that the search for LCK metrics on Oeljeklaus-Toma manifolds leads to a
(yet another) variation on Kronecker's theorem on units. In turn, this implies
that on Oeljeklaus-Toma manifold associated to number fields with $2t$ complex
embeddings and $s$ real embeddings with $s<t$ there is no LCK metric.


title: Image Inpainting by Kriging Interpolation Technique

abstract:
  Image inpainting is the art of predicting damaged regions of an image. The
manual way of image inpainting is a time consuming. Therefore, there must be an
automatic digital method for image inpainting that recovers the image from the
damaged regions. In this paper, a novel statistical image inpainting algorithm
based on Kriging interpolation technique was proposed. Kriging technique
automatically fills the damaged region in an image using the information
available from its surrounding regions in such away that it uses the spatial
correlation structure of points inside the k-by-k block. Kriging has the
ability to face the challenge of keeping the structure and texture information
as the size of damaged region heighten. Experimental results showed that,
Kriging has a high PSNR value when recovering a variety of test images from
scratches and text as damaged regions.


title: Nested colourings of graphs

abstract:
  A proper vertex colouring of a graph is \emph{nested} if the vertices of each
of its colour classes can be ordered by inclusion of their open neighbourhoods.
Through a relation to partially ordered sets, we show that the nested chromatic
number can be computed in polynomial time.
  Clearly, the nested chromatic number is an upper bound for the chromatic
number of a graph. We develop multiple distinct bounds on the nested chromatic
number using common properties of graphs. We also determine the behaviour of
the nested chromatic number under several graph operations, including the
direct, Cartesian, strong, and lexicographic product. Moreover, we classify
precisely the possible nested chromatic numbers of graphs on a fixed number of
vertices with a fixed chromatic number.


title:
Inverse proximity effect and influence of disorder on triplet
  supercurrents in strongly spin-polarized ferromagnets

abstract:
  We discuss the Josephson effect in strongly spin-polarized ferromagnets where
triplet correlations are induced by means of spin-active interface scattering,
extending our earlier work [Phys. Rev. Lett. 102, 227005 (2009)] by including
impurity scattering in the ferromagnetic bulk and the inverse proximity effect
in a fully self-consistent way. Our quasiclassical approach accounts for the
differences of Fermi momenta and Fermi velocities between the two spin bands of
the ferromagnet, and thereby overcomes an important short-coming of previous
work within the framework of Usadel theory. We show that non-magnetic disorder
in conjunction with spin-dependent Fermi velocities may induce a reversal of
the spin-current as a function of temperature.


title: Feasible homopolar dynamo with sliding liquid-metal contacts

abstract:
  We present a feasible homopolar dynamo design consisting of a flat, multi-arm
spiral coil, which is placed above a fast-spinning metal ring and connected to
the latter by sliding liquid-metal electrical contacts. Using a simple,
analytically solvable axisymmetric model, we determine the optimal design of
such a setup. For small contact resistance, the lowest magnetic Reynolds
number, Rm~34.6, at which the dynamo can work, is attained at the optimal ratio
of the outer and inner radii of the rings Ri/Ro~0.36 and the spiral pitch angle
54.7 degrees. In a setup of two copper rings with the thickness of 3 cm, Ri=10
cm and Ro=30 cm, self-excitation of the magnetic field is expected at a
critical rotation frequency around 10 Hz.


title: Factorization of quasi-variational relations systems

abstract:
  Variational relation problems allow a general approach for variational
inequalities, equilibrium problems, optimization problems, variational
inclusions. In this paper we consider a system of quasi-variational relations
and determine some conditions in which the solvability of the independent
problems imply the existence of a solution for the system. We particularize
then the result for a system of variational inequalities and for a constrained
Nash equilibrium problem.


title: Feshbach Resonance in a Tight-Binding Model

abstract:
  The physics of Feshbach resonance is analyzed using an analytic expression
for the $s$-wave scattering phase-shift and the scattering length $a$ which we
derive within a two-channel tight-binding model. Employing a unified treatment
of bound states and resonances in terms of the Jost function, it is shown that
for strong inter-channel coupling, Feshbach resonance can occur even when the
closed channel does not have a bound state. This may extend the range of
ultra-cold atomic systems that can be manipulated by Feshbach resonance. The
dependence of the sign of $a$ on the coupling strength in the unitary limit is
elucidated. As a by-product, analytic expressions are derived for the
background scattering length, the external magnetic field at which resonance
occurs, and the energy shift $\varepsilon-\varepsilon_B$, where $\varepsilon$
is the scattering energy and $\varepsilon_B$ is the bound state energy in the
closed channel (when there is one).


title:
A construction of integrated vertex operator in the pure spinor
  sigma-model in AdS5xS5

abstract:
  Vertex operators in string theory come in two varieties: integrated and
unintegrated. Understanding both types is important for the calculation of the
string theory amplitudes. The relation between them is a descent procedure
typically involving the b-ghost. In the pure spinor formalism vertex operators
can be identified as cohomology classes of an infinite-dimensional Lie
superalgebra formed by covariant derivatives. We show that in this language the
construction of the integrated vertex from an unintegrated vertex is very
straightforward, and amounts to the evaluation of the cocycle on the
generalized Lax currents.


title:
Estimation of unsteady aerodynamics in the wake of a freely flying
  European starling

abstract:
  Wing flapping is one of the most widespread propulsion methods found in
nature; however, the current understanding of the aerodynamics in bird wakes is
incomplete. The role of the unsteady motion in the flow and its contribution to
the aerodynamics is still an open question. In the current study, the wake of a
freely flying European starling has been investigated using long-duration
high-speed Particle Image Velocimetry (PIV) in the near wake. Kinematic
analysis of the wings and body of the bird has been performed using additional
high-speed cameras that recorded the bird movement simultaneously with the PIV
measurements. The wake evolution of four complete wingbeats has been
characterized through reconstruction of the time resolved data, and the
aerodynamics in the wake have been analyzed in terms of the streamwise forces
acting on the bird. The profile drag from classical aerodynamics was found to
be positive during most of the wingbeat cycle, yet kinematic images show that
the bird does not decelerate. It is shown that unsteady aerodynamics are
necessary to satisfy the drag/thrust balance by approximating the unsteady drag
term. These findings may shed light on the flight efficiency of birds by
providing a partial answer to how they minimize drag during flapping flight.


title:
Enhancing the Critical Current of a Superconducting Film in a Wide Range
  of Magnetic Fields with a Conformal Array of Nanoscale Holes

abstract:
  The maximum current (critical current) a type-II superconductor can transmit
without energy loss is limited by the motion of the quantized magnetic flux
penetrating into a superconductor. Introducing nanoscale holes into a
superconducting film has been long pursued as a promising way to increase the
critical current. So far the critical current enhancement was found to be
mostly limited to low magnetic fields. Here we experimentally investigate the
critical currents of superconducting films with a conformal array of nanoscale
holes that have non-uniform density while preserving the local ordering. We
find that the conformal array of nanoscle holes provides a more significant
critical current enhancement at high magnetic fields. The better performance
can be attributed to its arching effect that not only gives rise to the
gradient in hole-density for pinning vortices with a wide range of densities
but also prevent vortex channeling occurring in samples with a regular lattice
of holes.


title:
Deconfinement of quark content in neutron stars due to cosmic external
  agents

abstract:
  We summarize in this contribution to the the proceedings of "Compact Stars in
the QCD Phase Diagram III (CSQCD III)", December 12-15, 2012, Guaruja, SP,
Brazil the possibility of an scenario involving the existence of cosmic
external agents able to deposit energy in neutron stars by (co-) or
self-annihilation. This, in turn, may drive a internal phase transition in
neutron stars in a sort of Trojan mechanism disrupting the original
configuration. This event would have macroscopic consequences, by changing the
EoS of the object and by the emission of a multimessenger signal, that in the
photon range could be detected with gamma rays of $\sim10-100$ keV.


title: Nonstationary analogue black holes

abstract:
  We study the existence of analogue nonstationary spherically symmetric black
holes. The prime example is the acoustic model (cf. [V], [U]). We consider also
a more general class of metrics that could be useful in other physical models
of analogue black and white holes.
  We give examples of the appearance of black holes and of disappearance of
white holes. We also discuss the relation between the apparent and the event
horizons for the case of analogue black holes. In the end we study the inverse
problem of determination of black or white holes by boundary measurements for
the spherically symmetric nonstationary metrics.


title:
Simulation of Molecular Signaling in Blood Vessels: Software Design and
  Application to Atherogenesis

abstract:
  This paper presents a software platform, named BiNS2, able to simulate
diffusion-based molecular communications with drift inside blood vessels. The
contribution of the paper is twofold. First a detailed description of the
simulator is given, under the software engineering point of view, by
highlighting the innovations and optimizations introduced. Their introduction
into the previous version of the BiNS simulator was needed to provide to
functions for simulating molecular signaling and communication potentials
inside bounded spaces. The second contribution consists of the analysis,
carried out by using BiNS2, of a specific communication process happening
inside blood vessels, the atherogenesis, which is the initial phase of the
formation of atherosclerotic plaques, due to the abnormal signaling between
platelets and endothelium. From a communication point of view, platelets act as
mobile transmitters, endothelial cells are fixed receivers, sticky to the
vessel walls, and the transmitted signal is made of bursts of molecules emitted
by platelets. The simulator allows evaluating the channel latency and the
footprint on the vessel wall of the transmitted signal as a function of the
transmitter distance from the vessels wall, the signal strength, and the
receiver sensitivity.


title: Particle energization through time-periodic helical magnetic fields

abstract:
  We solve for the motion of charged particles in a helical time-periodic ABC
(Arnold-Beltrami-Childress) magnetic field. The magnetic field lines of a
stationary ABC field with coefficients $A=B=C=1$ are chaotic, and we show that
the motion of a charged particle in such a field is also chaotic at late times
with positive Lyapunov exponent. We further show that in time-periodic ABC
fields, the kinetic energy of a charged particle can increase indefinitely with
time. At late times the mean kinetic energy grows as a power law in time with
an exponent that approaches unity. For an initial distribution of particles,
whose kinetic energy is uniformly distributed within some interval, the PDF of
kinetic energy is, at late times, close to a Gaussian but with steeper tails.


title: An Analysis of the Connections Between Layers of Deep Neural Networks

abstract:
  We present an analysis of different techniques for selecting the connection
be- tween layers of deep neural networks. Traditional deep neural networks use
ran- dom connection tables between layers to keep the number of connections
small and tune to different image features. This kind of connection performs
adequately in supervised deep networks because their values are refined during
the training. On the other hand, in unsupervised learning, one cannot rely on
back-propagation techniques to learn the connections between layers. In this
work, we tested four different techniques for connecting the first layer of the
network to the second layer on the CIFAR and SVHN datasets and showed that the
accuracy can be im- proved up to 3% depending on the technique used. We also
showed that learning the connections based on the co-occurrences of the
features does not confer an advantage over a random connection table in small
networks. This work is helpful to improve the efficiency of connections between
the layers of unsupervised deep neural networks.


title: Lower Bounds for RAMs and Quantifier Elimination

abstract:
  We are considering RAMs $N_{n}$, with wordlength $n=2^{d}$, whose arithmetic
instructions are the arithmetic operations multiplication and addition modulo
$2^{n}$, the unary function $ \min\lbrace 2^{x}, 2^{n}-1\rbrace$, the binary
functions $\lfloor x/y\rfloor $ (with $\lfloor x/0 \rfloor =0$), $\max(x,y)$,
$\min(x,y)$, and the boolean vector operations $\wedge,\vee,\neg$ defined on
$0,1$ sequences of length $n$. It also has the other RAM instructions. The size
of the memory is restricted only by the address space, that is, it is $2^{n}$
words. The RAMs has a finite instruction set, each instruction is encoded by a
fixed natural number independently of $n$. Therefore a program $P$ can run on
each machine $N_{n}$, if $n=2^{d}$ is sufficiently large. We show that there
exists an $\epsilon>0$ and a program $P$, such that it satisfies the following
two conditions.
  (i) For all sufficiently large $n=2^{d}$, if $P$ running on $N_{n}$ gets an
input consisting of two words $a$ and $b$, then, in constant time, it gives a
$0,1$ output $P_{n}(a,b)$.
  (ii) Suppose that $Q$ is a program such that for each sufficiently large
$n=2^{d}$, if $Q$, running on $N_{n}$, gets a word $a$ of length $n$ as an
input, then it decides whether there exists a word $b$ of length $n$ such that
$P_{n}(a,b)=0$. Then, for infinitely many positive integers $d$, there exists a
word $a$ of length $n=2^{d}$, such that the running time of $Q$ on $N_{n}$ at
input $a$ is at least $\epsilon (\log d)^{\frac{1}{2}} (\log \log d)^{-1}$.


title:
Josephson supercurrent through the topological surface states of
  strained bulk HgTe

abstract:
  Strained bulk HgTe is a three-dimensional topological insulator, whose
surface electrons have a high mobility (30,000 cm^2/Vs), while its bulk is
effectively free of mobile charge carriers. These properties enable a study of
transport through its unconventional surface states without being hindered by a
parallel bulk conductance. Here, we show transport experiments on HgTe-based
Josephson junctions to investigate the appearance of the predicted Majorana
states at the interface between a topological insulator and a superconductor.
Interestingly, we observe a dissipationless supercurrent flow through the
topological surface states of HgTe. The current-voltage characteristics are
hysteretic at temperatures below 1 K with critical supercurrents of several
microamperes. Moreover, we observe a magnetic field induced Fraunhofer pattern
of the critical supercurrent, indicating a dominant 2\pi-periodic Josephson
effect in the unconventional surface states. Our results show that strained
bulk HgTe is a promising material system to get a better understanding of the
Josephson effect in topological surface states, and to search for the
manifestation of zero-energy Majorana states in transport experiments.


title: Dynamic Ad Allocation: Bandits with Budgets

abstract:
  We consider an application of multi-armed bandits to internet advertising
(specifically, to dynamic ad allocation in the pay-per-click model, with
uncertainty on the click probabilities). We focus on an important practical
issue that advertisers are constrained in how much money they can spend on
their ad campaigns. This issue has not been considered in the prior work on
bandit-based approaches for ad allocation, to the best of our knowledge.
  We define a simple, stylized model where an algorithm picks one ad to display
in each round, and each ad has a \emph{budget}: the maximal amount of money
that can be spent on this ad. This model admits a natural variant of UCB1, a
well-known algorithm for multi-armed bandits with stochastic rewards. We derive
strong provable guarantees for this algorithm.


title: A skew true INAR(1) process with application

abstract:
  Integer-valued time series models have been a recurrent theme considered in
many papers in the last three decades, but only a few of them have dealt with
models on $\mathbb Z$ (that is, including both negative and positive integers).
Our aim in this paper is to introduce a first-order integer-valued
autoregressive process on $\mathbb Z$ with skew discrete Laplace marginals
(Kozubowski and Inusah, 2006). For this, we define a new operator that acts on
two independent latent processes, similarly as made by Freeland (2010). We
derive some joint and conditional basic properties of the proposed process such
as characteristic function, moments, higher-order moments and jumps. Estimators
for the parameters of our model are proposed and their asymptotic normality are
established. We run a Monte Carlo simulation to evaluate the finite-sample
performance of these estimators. In order to illustrate the potentiality of our
process, we apply it to a real data set about population increase rates.


title:
Bounded size bias coupling: a Gamma function bound, and universal
  Dickman-function behavior

abstract:
  Under the assumption that the distribution of a nonnegative random variable
$X$ admits a bounded coupling with its size biased version, we prove simple and
strong concentration bounds. In particular the upper tail probability is shown
to decay at least as fast as the reciprocal of a Gamma function, guaranteeing a
moment generating function that converges everywhere. The class of infinitely
divisible distributions with finite mean, whose L\'evy measure is supported on
an interval contained in $[0,c]$ for some $c < \infty$, forms a special case in
which this upper bound is logarithmically sharp. In particular the asymptotic
estimate for the Dickman function, that $\rho(u) \approx u^{-u}$ for large $u$,
is shown to be universal for this class.
  A special case of our bounds arises when $X$ is a sum of independent random
variables, each admitting a 1-bounded size bias coupling. In this case, our
bounds are comparable to Chernoff--Hoeffding bounds; however, ours are broader
in scope, sharper for the upper tail, and equal for the lower tail.
  We discuss \emph{bounded} and \emph{monotone} couplings, give a sandwich
principle, and show how this gives an easy conceptual proof that any finite
positive mean sum of independent Bernoulli random variables admits a 1-bounded
coupling with the same conditioned to be nonzero.


title: Virality Prediction and Community Structure in Social Networks

abstract:
  How does network structure affect diffusion? Recent studies suggest that the
answer depends on the type of contagion. Complex contagions, unlike infectious
diseases (simple contagions), are affected by social reinforcement and
homophily. Hence, the spread within highly clustered communities is enhanced,
while diffusion across communities is hampered. A common hypothesis is that
memes and behaviors are complex contagions. We show that, while most memes
indeed behave like complex contagions, a few viral memes spread across many
communities, like diseases. We demonstrate that the future popularity of a meme
can be predicted by quantifying its early spreading pattern in terms of
community concentration. The more communities a meme permeates, the more viral
it is. We present a practical method to translate data about community
structure into predictive knowledge about what information will spread widely.
This connection may lead to significant advances in computational social
science, social media analytics, and marketing applications.

categories: cs.SI cs.CY physics.data-an physics.soc-ph


title: The Ghost in the Quantum Turing Machine

abstract:
  In honor of Alan Turing's hundredth birthday, I unwisely set out some
thoughts about one of Turing's obsessions throughout his life, the question of
physics and free will. I focus relatively narrowly on a notion that I call
"Knightian freedom": a certain kind of in-principle physical unpredictability
that goes beyond probabilistic unpredictability. Other, more metaphysical
aspects of free will I regard as possibly outside the scope of science. I
examine a viewpoint, suggested independently by Carl Hoefer, Cristi Stoica, and
even Turing himself, that tries to find scope for "freedom" in the universe's
boundary conditions rather than in the dynamical laws. Taking this viewpoint
seriously leads to many interesting conceptual problems. I investigate how far
one can go toward solving those problems, and along the way, encounter (among
other things) the No-Cloning Theorem, the measurement problem, decoherence,
chaos, the arrow of time, the holographic principle, Newcomb's paradox,
Boltzmann brains, algorithmic information theory, and the Common Prior
Assumption. I also compare the viewpoint explored here to the more radical
speculations of Roger Penrose. The result of all this is an unusual perspective
on time, quantum mechanics, and causation, of which I myself remain skeptical,
but which has several appealing features. Among other things, it suggests
interesting empirical questions in neuroscience, physics, and cosmology; and
takes a millennia-old philosophical debate into some underexplored territory.


title: Phase Retrieval using Alternating Minimization

abstract:
  Phase retrieval problems involve solving linear equations, but with missing
sign (or phase, for complex numbers) information. More than four decades after
it was first proposed, the seminal error reduction algorithm of (Gerchberg and
Saxton 1972) and (Fienup 1982) is still the popular choice for solving many
variants of this problem. The algorithm is based on alternating minimization;
i.e. it alternates between estimating the missing phase information, and the
candidate solution. Despite its wide usage in practice, no global convergence
guarantees for this algorithm are known. In this paper, we show that a
(resampling) variant of this approach converges geometrically to the solution
of one such problem -- finding a vector $\mathbf{x}$ from
$\mathbf{y},\mathbf{A}$, where $\mathbf{y} =
\left|\mathbf{A}^{\top}\mathbf{x}\right|$ and $|\mathbf{z}|$ denotes a vector
of element-wise magnitudes of $\mathbf{z}$ -- under the assumption that
$\mathbf{A}$ is Gaussian.
  Empirically, we demonstrate that alternating minimization performs similar to
recently proposed convex techniques for this problem (which are based on
"lifting" to a convex matrix problem) in sample complexity and robustness to
noise. However, it is much more efficient and can scale to large problems.
Analytically, for a resampling version of alternating minimization, we show
geometric convergence to the solution, and sample complexity that is off by log
factors from obvious lower bounds. We also establish close to optimal scaling
for the case when the unknown vector is sparse. Our work represents the first
theoretical guarantee for alternating minimization (albeit with resampling) for
any variant of phase retrieval problems in the non-convex setting.


title:
Strain enhancement of high-k dielectric response in (La/Sc)2 O3 and
  LaScO3 : an ab-initio study

abstract:
  We use density functional theory within the generalized gradient
approximation to characterize the dielectric response of rare earth oxides:
(La,Sc)2 O3 bixbyite, and LaScO3 perovskite. We focus on the role of strain on
the phonon contribution of the dielectric constant and find that, contrary to
the classical expectation based on the Clausius-Mossotti relation, tensile
volumetric strain and volume-conserving bi- axial strain on the order of +/-1%
can lead to an increase in dielectric constant of up to 20%. The insight into
the atomic mechanisms responsible for these effects and the quantitative
results in this paper can contribute to the development and understanding of
high-{\kappa} materials.


title: Cellular-Based Statistical Model for Mobile Dispersion

abstract:
  While analyzing mobile systems we often approximate the actual coverage
surface and assume an ideal cell shape. In a multi-cellular network, because of
its tessellating nature, a hexagon is more preferred than a circular geometry.
Despite this reality, perhaps due to the inherent simplicity, only a model for
circular based random spreading is available. However, if used, this results an
unfair terminal distribution for non-circular contours. Therefore, in this
paper we specifically derived an unbiased node density model for a hexagon. We
then extended the principle and established stochastic ways to handle sectored
cells. Next, based on these mathematical findings, we created a generic
modeling tool that can support a complex network with varying position,
capacity, size, user density, and sectoring capability. Last, simulation was
used to verify the theoretical analysis.


title: A Characterization of Mumford Curves with Good Reduction

abstract:
  Mumford defines a certain type of Shimura curves of Hodge type,
parameterizing polarized complex abelian fourfolds. In this paper, we study the
good reduction of such a curve in positive characteristic and give a
characterization in the generically ordinary case.


title:
Waveguide integrated low noise NbTiN nanowire single-photon detectors
  with milli-Hz dark count rate

abstract:
  Superconducting nanowire single-photon detectors are an ideal match for
integrated quantum photonic circuits due to their high detection efficiency for
telecom wavelength photons. Quantum optical technology also requires
single-photon detection with low dark count rate and high timing accuracy. Here
we present very low noise superconducting nanowire single-photon detectors
based on NbTiN thin films patterned directly on top of Si3N4 waveguides. We
systematically investigate a large variety of detector designs and characterize
their detection noise performance. Milli-Hz dark count rates are demonstrated
over the entire operating range of the nanowire detectors which also feature
low timing jitter. The ultra-low dark count rate, in combination with the high
detection efficiency inherent to our traveling wave detector geometry, gives
rise to a measured noise equivalent power at the 10^(-20) W/Hz^(1/2) level.


title:
CRUC: Cold-start Recommendations Using Collaborative Filtering in
  Internet of Things

abstract:
  The Internet of Things (IoT) aims at interconnecting everyday objects
(including both things and users) and then using this connection information to
provide customized user services. However, IoT does not work in its initial
stages without adequate acquisition of user preferences. This is caused by
cold-start problem that is a situation where only few users are interconnected.
To this end, we propose CRUC scheme - Cold-start Recommendations Using
Collaborative Filtering in IoT, involving formulation, filtering and prediction
steps. Extensive experiments over real cases and simulation have been performed
to evaluate the performance of CRUC scheme. Experimental results show that CRUC
efficiently solves the cold-start problem in IoT.


title: Photonic crystal nanofiber using an external grating

abstract:
  We implement a photonic crystal nanofiber device by reversibly combining an
optical nanofiber and a nanofabricated grating. Using the finite-difference
time-domain method, we design the system for minimal optical loss while
tailoring the resonant wavelength and bandwidth of the device. Experimentally
we demonstrate that the combined system shows a strong photonic stop-band in
good agreement with numerical predictions. The resulting device may be used to
realize strong light-matter coupling near to the nanofiber surface.


title:
Correction and strengthening of "How large are the level sets of the
  Takagi function?"

abstract:
  The purpose of this note is to correct an error in an earlier paper by the
author about the level sets of the Takagi function [Monatsh. Math. 167 (2012),
311-331 and arXiv:1102.1616], and to prove a stronger form of one of the main
results of that paper about the propensity of level sets containing uncountably
many local level sets.


title:
Discovery of twin kHz quasi periodic oscillations in the low mass X-ray
  binary XTE J1701-407

abstract:
  We report the discovery of kHz quasi periodic oscillations (QPOs) in three
Rossi X-ray Timing Explorer observations of the low mass X-ray binary (LMXB)
XTE J1701-407. In one of the observations we detect a kHz QPO with a
characteristic frequency of 1153 +/- 5 Hz, while in the other two observations
we detect twin QPOs at characteristic frequencies of 740 +/- 5 Hz, 1112 +/- 17
Hz and 740 +/- 11 Hz, 1098 +/- 5 Hz. All detections happen when XTE J1701-407
was in its high intensity soft state, and their single trial significance are
in the 3.1-7.5 sigma range. The frequency difference in the centroid
frequencies of the twin kHz QPOs (385 +/- 13 Hz) is one of the largest seen
till date. The 3-30 keV fractional rms amplitude of the upper kHz QPO varies
between ~18 % and ~30 %. XTE J1701-407, with a persistent luminosity close to 1
% of the Eddington limit, is among the small group of low luminosity kHz QPO
sources and has the highest rms for the upper kHz QPO detected in any source.
The X-ray spectral and variability characteristics of this source indicate its
atoll source nature.


title: BTZ Black Hole Entropy from a Chern-Simons Matrix Model

abstract:
  We examine a Chern-Simons matrix model which we propose as a toy model for
studying the quantum nature of black holes in 2+1 gravity. Its dynamics is
described by two $N\times N$ matrices, representing the two spatial
coordinates. The model possesses an internal SU(N) gauge symmetry, as well as
an external rotation symmetry. The latter corresponds to the rotational
isometry of the BTZ solution, and does not decouple from SU(N) gauge
transformations. The system contains an invariant which is quadratic in the
spatial coordinates. We obtain its spectrum and degeneracy, and find that the
degeneracy grows exponentially in the large $N$ limit. The usual BTZ black hole
entropy formula is recovered upon identifying the quadratic invariant with the
square of the black hole horizon radius. The quantum system behaves
collectively as an integer (half-integer) spin particle for even (odd) $N$
under $2\pi$-rotations.


title:
Scintillation Efficiency for Low-Energy Nuclear Recoils in Liquid-Xenon
  Dark Matter Detectors

abstract:
  We perform a theoretical study of the scintillation efficiency in the
low-energy region crucial for liquid-xenon dark-matter detectors. We develop a
computer program to simulate the cascading process of the recoiling xenon
nucleus in liquid xenon and calculate the nuclear quenching effect due to
atomic collisions. We use the electronic stopping power extrapolated from the
experimental data to the low-energy region, and take into account the effects
of electrons escaping from the electron-ion pair recombination using the
generalized Thomas-Imel model fitted to scintillation data. Our result agrees
well with the experiments from neutron scattering and vanishes rapidly as the
recoiling energy drops below 3 keV.

categories: physics.ins-det astro-ph.IM hep-ex nucl-ex


title: Hierarchy of Graphene Wrinkles Induced by Thermal Strain Engineering

abstract:
  Graphene is only one atom thick and becomes the ultimate thin film to explore
membrane physics and mechanics. Here we study hierarchy of graphene wrinkles
induced by thermal strain engineering and demonstrate that the wrinkling
hierarchy can be accounted for by the wrinklon theory. We derive an equation
{\lambda} = (ky)0.5 explaining evolution of wrinkling wavelength {\lambda} with
the distance to the edge y observed in our experiment by considering both
bending energy and stretching energy of the graphene flakes. The prefactor k in
the equation is determined to be about 55 nm, which is independent of the size
of the graphene flakes. Our experimental result indicates that the classical
membrane behavior of graphene persists down to about 100 nm of the wrinkling
wavelength.


title:
Dynamical quantum correlations of Ising models on an arbitrary lattice
  and their resilience to decoherence

abstract:
  Ising models, and the physical systems described by them, play a central role
in generating entangled states for use in quantum metrology and quantum
information. In particular, ultracold atomic gases, trapped ion systems, and
Rydberg atoms realize long-ranged Ising models, which even in the absence of a
transverse field can give rise to highly non-classical dynamics and long-range
quantum correlations. In the first part of this paper, we present a detailed
theoretical framework for studying the dynamics of such systems driven (at time
t=0) into arbitrary unentangled non-equilibrium states, thus greatly extending
and unifying the work of Ref. [1]. Specifically, we derive exact expressions
for closed-time-path ordered correlation functions, and use these to study
experimentally relevant observables, e.g. Bloch vector and spin-squeezing
dynamics. In the second part, these correlation functions are then used to
derive closed-form expressions for the dynamics of arbitrary spin-spin
correlation functions in the presence of both T_1 (spontaneous spin
relaxation/excitation) and T_2 (dephasing) type decoherence processes. Even
though the decoherence is local, our solution reveals that the competition
between Ising dynamics and T_1 decoherence gives rise to an emergent non-local
dephasing effect, thereby drastically amplifying the degradation of quantum
correlations. In addition to identifying the mechanism of this deleterious
effect, our solution points toward a scheme to eliminate it via
measurement-based coherent feedback.


title:
Perceptions and Truth: A Mechanism Design Approach to Crowd-Sourcing
  Reputation

abstract:
  We consider a distributed multi-user system where individual entities possess
observations or perceptions of one another, while the truth is only known to
themselves, and they might have an interest in withholding or distorting the
truth. We ask the question whether it is possible for the system as a whole to
arrive at the correct perceptions or assessment of all users, referred to as
their reputation, by encouraging or incentivizing the users to participate in a
collective effort without violating private information and self-interest. Two
specific applications, online shopping and network reputation, are provided to
motivate our study and interpret the results. In this paper we investigate this
problem using a mechanism design theoretic approach. We introduce a number of
utility models representing users' strategic behavior, each consisting of one
or both of a truth element and an image element, reflecting the user's desire
to obtain an accurate view of the other and an inflated image of itself. For
each model, we either design a mechanism that achieves the optimal performance
(solution to the corresponding centralized problem), or present individually
rational sub-optimal solutions. In the latter case, we demonstrate that even
when the centralized solution is not achievable, by using a simple
punish-reward mechanism, not only a user has the incentive to participate and
provide information, but also that this information can improve the system
performance.


title: New simple groups with a BN-pair

abstract:
  We show that there are simple groups with a spherical BN-pair of rank 2 which
are non-Moufang and hence not of algebraic origin.


title: Modulation Algorithms for Manipulating Nuclear Spin States

abstract:
  We exploit the impact of exact frequency modulation on transition time of
steering nuclear spin states from theoretical point of view. 1-stage and
2-stage Frequency-Amplitude-Phase modulation (FAPM) algorithms are proposed in
contrast with 1-stage and 3-stage Amplitude-Phase modulation (APM) algorithms.
The sufficient conditions are further present for transiting nuclear spin
states within the specified time by these four modulation algorithms. It is
demonstrated that transition time performance can be significantly improved if
exact frequency modulation is available. It is exemplified that the transition
time scale with frequency modulation is about 1/4 of that without frequency
modulation. It is also revealed in this research that the hybrid scheme of
1-stage FAPM and APM algorithms is better than all the four modulation
algorithms. A simplified hybrid modulation algorithm is also proposed to reduce
computational burden.


title:
Stochastic Optimization Theory of Backward Stochastic Differential
  Equations Driven by G-Brownian Motion

abstract:
  In this paper, we consider the stochastic optimal control problems under
G-expectation. Based on the theory of backward stochastic differential
equations driven by G-Brownian motion, which was introduced in [10.11], we can
investigate the more general stochastic optimal control problems under
G-expectation than that were constructed in [28]. Then we obtain a generalized
dynamic programming principle and the value function is proved to be a
viscosity solution of a fully nonlinear second-order partial differential
equation.


title:
Signature of multi-channel interference in high-order harmonic
  generation from N2 driven by intense mid-infrared pulses

abstract:
  We investigate the multi-electron dynamics in high-order harmonic generation
(HHG) from N2 molecules. Clear spectral minima are observed in the cutoff
region at all three mid-infrared wavelengths (i.e., 1300, 1400 and 1500 nm)
chosen in our experiment. It is found that the positions of the spectral minima
do not depend on the alignment angles of molecules. In addition, the spectral
minima shift almost linearly with the increasing laser intensity at all three
wavelengths, which provides a strong evidence on the dynamic multi-channel
interference origin of these minima. The advantages of observation of dynamic
multi-channel interference based on HHG driven by long wavelength lasers are
discussed.


title:
Using a bag of Words for Automatic Medical Image Annotation with a
  Latent Semantic

abstract:
  We present in this paper a new approach for the automatic annotation of
medical images, using the approach of "bag-of-words" to represent the visual
content of the medical image combined with text descriptors based approach
tf.idf and reduced by latent semantic to extract the co-occurrence between
terms and visual terms. A medical report is composed of a text describing a
medical image. First, we are interested to index the text and extract all
relevant terms using a thesaurus containing MeSH medical concepts. In a second
phase, the medical image is indexed while recovering areas of interest which
are invariant to change in scale, light and tilt. To annotate a new medical
image, we use the approach of "bagof-words" to recover the feature vector.
Indeed, we use the vector space model to retrieve similar medical image from
the database training. The calculation of the relevance value of an image to
the query image is based on the cosine function. We conclude with an experiment
carried out on five types of radiological imaging to evaluate the performance
of our system of medical annotation. The results showed that our approach works
better with more images from the radiology of the skull.


title: Optimal beam combiner design for nulling interferometers

abstract:
  A scheme to optimally design a beam combiner is discussed for any
pre-determined fixed geometry nulling interferometer aimed at detection and
characterization of exoplanets with multiple telescopes or a single telescope
(aperture masking). We show that considerably higher order nulls can be
achieved with 1-D interferometer geometries than possible with 2-D geometries
with the same number of apertures. Any 1-D interferometer with N apertures can
achieve a 2(N-1)-order null, while the order of the deepest null for a random
2-D aperture geometry interferometer is the order of the N-th term in the
Taylor expansion of e^{i(x^2+y^2)} around x=0, y=0 (2nd order null for N=2,3;
4th order null for N=4,5,6). We also show that an optimal beam combiner for
nulling interferometry relies only 0 or Pi phase shifts. Examples of nulling
interferometer designs are shown to illustrate these findings.


title: Physical limits on cellular directional mechanosensing

abstract:
  Many eukaryotic cells are able to perform directional mechanosensing by
directly measuring minute spatial differences in the mechanical stress on their
membranes. Here, we explore the limits of a single mechanosensitive channel
activation using a two-state double-well model for the gating mechanism. We
then focus on the physical limits of directional mechanosensing by a single
cell having multiple mechanosensors and subjected to a shear flow inducing a
nonuniform membrane tension. Our results demonstrate that the accuracy in
sensing the mechanostimulus direction not only increases with cell size and
exposure to a signal, but also grows for cells with a near-critical membrane
prestress. Finally, the existence of a nonlinear threshold effect,
fundamentally limiting the cell's ability to effectively perform directional
mechanosensing at a low signal-to-noise ratio, is uncovered.


title:
Asymmetric Absorption Profiles of Ly\alpha\ and Ly\beta\ in Damped Lyman
  Alpha Systems

abstract:
  Damped Ly\alpha\ systems (DLAs) observed in the quasar spectra are
characterized by a high neutral hydrogen column density $N_{HI}>2\times
10^{20}{\rm\ cm^{-2}}$. The absorption wing profiles are often fitted using the
Voigt function due to the fact that the scattering cross section near resonant
line center is approximately described by the Lorentzian function. Since a
hydrogen atom has infinitely many $p$ states that participate in the electric
dipole interaction, the cross section starts to deviate from the Lorentzian in
an asymmetric way in the line wing regions. We investigate this asymmetry in
the absorption line profiles around Ly\alpha\ and Ly\beta\ as a function of the
neutral hydrogen column density $N_{HI}$. In terms of
$\Delta\lambda\equiv\lambda-\lambda_\alpha$ we expand the Kramers-Heisenberg
formula around Ly\alpha\ to find $\sigma(\lambda)\simeq (0.5
f_{12})^2\sigma_{T}(\Delta\lambda/\lambda_\alpha)^{-2}[1+3.792
(\Delta\lambda/\lambda_\alpha)]$, where $f_{12}$ and $\sigma_T$ are the
oscillator strength of Ly$\alpha$ and the Thomson scattering cross section,
respectively. In terms of $\Delta\lambda_2\equiv\lambda-\lambda_\beta$ in the
vicinity of Ly\beta, the total scattering cross section, given as the sum of
cross sections for Rayleigh and Raman scattering, is shown to be
$\sigma(\lambda)\simeq \sigma_T(0.5f_{13})^2(1+R_0)
(\Delta\lambda_2/\lambda_\beta)^{-2}[1-24.68(\Delta\lambda_2/\lambda_\beta)]$
with $f_{13}$ and the factor $R_0=0.1342$ being the oscillator strength for
Ly\beta\ and the ratio of Raman cross section to Rayleigh cross section,
respectively. A redward asymmetry develops around Ly\alpha\ whereas a blue
asymmetry is obtained for Ly\beta. The absorption center shifts are found to be
almost proportional to the neutral hydrogen column density.


title: The inapproximability for the (0,1)-additive number

abstract:
  An
  {\it additive labeling} of a graph $G$ is a function $ \ell :V(G)
\rightarrow\mathbb{N}$, such that for every two adjacent vertices $ v $ and $
u$ of $ G $, $ \sum_{w \sim v}\ell(w)\neq \sum_{w \sim u}\ell(w) $ ($ x \sim y
$ means that $ x $ is joined to $y$). The {\it additive number} of $ G $,
denoted by $\eta(G)$, is the minimum number $k $ such that $ G $ has a additive
labeling $ \ell :V(G) \rightarrow \mathbb{N}_k$. The {\it additive
choosability} of a graph $G$, denoted by $\eta_{\ell}(G) $, is the smallest
number $k$ such that $G$ has an additive labeling for any assignment of lists
of size $k$ to the vertices of $G$, such that the label of each vertex belongs
to its own list.
  Seamone (2012) \cite{a80} conjectured that for every graph $G$, $\eta(G)=
\eta_{\ell}(G)$. We give a negative answer to this conjecture and we show that
for every $k$ there is a graph $G$ such that $ \eta_{\ell}(G)- \eta(G) \geq k$.
  A {\it $(0,1)$-additive labeling} of a graph $G$ is a function $ \ell :V(G)
\rightarrow\{0,1\}$, such that for every two adjacent vertices $ v $ and $ u$
of $ G $, $ \sum_{w \sim v}\ell(w)\neq \sum_{w \sim u}\ell(w) $.
  A graph may lack any $(0,1)$-additive labeling. We show that it is $
\mathbf{NP} $-complete to decide whether a $(0,1)$-additive labeling exists for
some families of graphs such as perfect graphs and planar triangle-free graphs.
For a graph $G$ with some $(0,1)$-additive labelings, the $(0,1)$-additive
number of $G$ is defined as $ \sigma_{1} (G) = \min_{\ell \in \Gamma}\sum_{v\in
V(G)}\ell(v) $ where $\Gamma$ is the set of $(0,1)$-additive labelings of $G$.
We prove that given a planar graph that admits a $(0,1)$-additive labeling, for
all $ \varepsilon >0 $, approximating the $(0,1)$-additive number within $
n^{1-\varepsilon} $ is $ \mathbf{NP} $-hard.


title: Cell-Level Modeling of IEEE 802.11 WLANs

abstract:
  We develop a scalable \textit{cell-level} analytical model for multi-cell
infrastructure IEEE 802.11 WLANs under a so-called Pairwise Binary Dependence
(PBD) condition. The PBD condition is a geometric property under which the
relative locations of the nodes inside a cell do not matter and the network is
free of \textit{hidden nodes}. For the cases of saturated nodes and
TCP-controlled long-file downloads, we provide accurate predictions of cell
throughputs. Similar to Bonald et al (Sigmetrics, 2008), we model a multi-cell
WLAN under short-file downloads as "a network of processor-sharing queues with
state-dependent service rates." Whereas the state-dependent service rates
proposed by Bonald et al are based only on the \textit{number} of contending
neighbors, we employ state-dependent service rates that incorporate the the
impact of the overall \textit{topology} of the network. We propose an
\textit{effective service rate approximation} technique and obtain good
approximations for the \textit{mean flow transfer delay} in each cell. For
TCP-controlled downloads where the APs transmit a large fraction of time, we
show that the throughputs predicted under the PBD condition are very good
approximations in two important scenarios where hidden nodes are indeed present
and the PBD condition does not strictly hold.


title: Immigration-extinction dynamics of stochastic populations

abstract:
  How high should be the rate of immigration into a stochastic population in
order to significantly reduce the probability of observing the population
extinct? Is there any relation between the population size distributions with
and without immigration? Under what conditions can one justify the simple patch
occupancy models which ignore the population distribution and its dynamics in a
patch, and treat a patch simply as either occupied or empty? We address these
questions by exactly solving a simple stochastic model obtained by adding a
steady immigration to a variant of the Verhulst model: a prototypical model of
an isolated stochastic population.


title:
Efficient calculation of local dose distribution for response modelling
  in proton and ion beams

abstract:
  We present an algorithm for fast and accurate computation of the local dose
distribution in MeV beams of protons, carbon ions or other heavy-charged
particles. It uses compound Poisson-process modelling of track interaction and
succesive convolutions for fast computation. It can handle mixed particle
fields over a wide range of fluences. Since the local dose distribution is the
essential part of several approaches to model detector efficiency or cellular
response it has potential use in ion-beam dosimetry and radiotherapy.


title: RNADE: The real-valued neural autoregressive density-estimator

abstract:
  We introduce RNADE, a new model for joint density estimation of real-valued
vectors. Our model calculates the density of a datapoint as the product of
one-dimensional conditionals modeled using mixture density networks with shared
parameters. RNADE learns a distributed representation of the data, while having
a tractable expression for the calculation of densities. A tractable likelihood
allows direct comparison with other methods and training by standard
gradient-based optimizers. We compare the performance of RNADE on several
datasets of heterogeneous and perceptual data, finding it outperforms mixture
models in all but one case.


title: Proximal Markov chain Monte Carlo algorithms

abstract:
  This paper presents a new Metropolis-adjusted Langevin algorithm (MALA) that
uses convex analysis to simulate efficiently from high-dimensional densities
that are log-concave, a class of probability distributions that is widely used
in modern high-dimensional statistics and data analysis. The method is based on
a new first-order approximation for Langevin diffusions that exploits
log-concavity to construct Markov chains with favourable convergence
properties. This approximation is closely related to Moreau-Yoshida
regularisations for convex functions and uses proximity mappings instead of
gradient mappings to approximate the continuous-time process. The proposed
method complements existing MALA methods in two ways. First, the method is
shown to have very robust stability properties and to converge geometrically
for many target densities for which other MALA are not geometric, or only if
the step size is sufficiently small. Second, the method can be applied to
high-dimensional target densities that are not continuously differentiable, a
class of distributions that is increasingly used in image processing and
machine learning and that is beyond the scope of existing MALA and HMC
algorithms. To use this method it is necessary to compute or to approximate
efficiently the proximity mappings of the logarithm of the target density. For
several popular models, including many Bayesian models used in modern signal
and image processing and machine learning, this can be achieved with convex
optimisation algorithms and with approximations based on proximal splitting
techniques, which can be implemented in parallel. The proposed method is
demonstrated on two challenging high-dimensional and non-differentiable models
related to image resolution enhancement and low-rank matrix estimation that are
not well addressed by existing MCMC methodology.