title:
A Comparison of Two- and Three-dimensional Neutrino-hydrodynamics
  simulations of Core-collapse Supernovae

abstract:
  We present numerical results on two- (2D) and three-dimensional (3D)
hydrodynamic core-collapse simulations of an 11.2$M_\odot$ star. By changing
numerical resolutions and seed perturbations systematically, we study how the
postbounce dynamics is different in 2D and 3D. The calculations were performed
with an energy-dependent treatment of the neutrino transport based on the
isotropic diffusion source approximation scheme, which we have updated to
achieve a very high computational efficiency. All the computed models in this
work including nine 3D models and fifteen 2D models exhibit the revival of the
stalled bounce shock, leading to the possibility of explosion. All of them are
driven by the neutrino-heating mechanism, which is fostered by neutrino-driven
convection and the standing-accretion-shock instability (SASI). Reflecting the
stochastic nature of multi-dimensional (multi-D) neutrino-driven explosions,
the blast morphology changes from models to models. However, we find that the
final fate of the multi-D models whether an explosion is obtained or not, is
little affected by the explosion stochasticity. In agreement with some previous
studies, higher numerical resolutions lead to slower onset of the shock revival
in both 3D and 2D. Based on the self-consistent supernova models leading to the
possibility of explosions, our results systematically show that the revived
shock expands more energetically in 2D than in 3D.


title: The Riemann Hypothesis for Symmetrised Combinations of Zeta Functions

abstract:
  This paper studies combinations of the Riemann zeta function, based on one
defined by P.R. Taylor, which was shown by him to have all its zeros on the
critical line. With a rescaled complex argument, this is denoted here by ${\cal
T}_-(s)$, and is considered together with a counterpart function ${\cal
T}_+(s)$, symmetric rather than antisymmetric about the critical line. We prove
that ${\cal T}_+(s)$ has all its zeros on the critical line, and that the zeros
of both functions are all of first order. We establish a link between the zeros
of ${\cal T}_-(s)$ and of ${\cal T}_+(s)$ with those of the zeros of the
Riemann zeta function $\zeta(2 s-1)$, which enables us to prove that, if the
Riemann hypothesis holds, then the distribution function of the zeros of $\zeta
(2 s-1)$ agrees with those for ${\cal T}_-(s)$ and of ${\cal T}_+(s)$ in all
terms which do not remain finite as $t\rightarrow \infty$.


title: Polygonal Bicycle Paths and the Darboux Transformation

abstract:
  A Bicycle $(n,k)$-gon is an equilateral $n$-gon whose $k$ diagonals are of
equal length. In this paper we consider periodic bicycle $(n,k)$-paths, which
are a natural variation in which the polygon is replaced with a periodic
polygonal path.


title:
X6.9-class Flare Induced Vertical Kink Oscillations in a Large-Scale
  Plasma Curtain as Observed by SDO/AIA

abstract:
  We present rare observational evidence of vertical kink oscillations in a
laminar and diffused large-scale plasma curtain as observed by the Atmospheric
Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The X6.9
class flare in the Active Region 11263 on 09 August 2011, induces a global
large-scale disturbance that propagates in a narrow lane above the plasma
curtain and creates a low density region that appears as a dimming in the
observational image data. This large-scale propagating disturbance acts as a
non-periodic driver that interacts asymmetrically and obliquely with the top of
the plasma curtain, and triggers the observed oscillations. In the deeper
layers of the curtain, we find evidence of vertical kink oscillations with two
periods (795 s and 530 s). On the magnetic surface of the curtain where the
density is inhomogeneous due to the coronal dimming, non-decaying vertical
oscillations are also observed (period $\approx$ 763-896 s). We infer that the
global large-scale disturbance triggers vertical kink oscillations in the
deeper layers as well as on the surface of the large-scale plasma curtain. The
properties of the excited waves strongly depend on the local plasma and
magnetic field conditions.


title:
Introduction to Khovanov Homologies. III. A new and simple
  tensor-algebra construction of Khovanov-Rozansky invariants

abstract:
  We continue to develop the tensor-algebra approach to knot polynomials with
the goal to present the story in elementary and comprehensible form. The
previously reviewed description of Khovanov cohomologies for the gauge group of
rank N-1=1 was based on the cut-and-join calculus of the planar cycles, which
are involved rather artificially. We substitute them by alternative and natural
set of cycles, not obligatory planar. Then the whole construction is
straightforwardly lifted from SL(2) to SL(N) and reproduces Khovanov-Rozansky
(KR) polynomials, simultaneously for all values of N. No matrix factorization
and related tedious calculations are needed in such approach, which can
therefore become not only conceptually, but also practically useful.

categories: hep-th math-ph math.AG math.CO math.GT math.MP


title:
Multi-Wavelength Studies of Spectacular Ram Pressure Stripping of a
  Galaxy: Discovery of an X-ray Absorption Feature

abstract:
  We report the detection of an X-ray absorption feature near the galaxy M86 in
the Virgo cluster. The absorber has a column density of 2-3 E20 /cm^2, and its
position coincides with the peak of an intracluster HI cloud which was removed
from the galaxy NGC 4388 presumably by ram pressure. These results indicate
that the HI cloud is located in front of M86 along the line-of-sight, and
suggest that the stripping was primarily created by an interaction between NGC
4388 and the hot plasmas of the Virgo cluster, not the M86 halo. By calculating
an X-ray temperature map, we further detected an X-ray counterpart of the HI
cloud up to about 3' south of M86. It has a temperature of 0.89 keV and a mass
of ~4.5 E8 solar mass, exceeding the estimated HI gas mass. The high
hot-to-cold gas ratio in the cloud indicates a significant evaporation of the
HI gas, probably by thermal conduction from the hotter cluster plasma with a
sub-Spitzer rate.


title:
Experimental Demonstration of non-Markovian Dynamics via a Temporal
  Bell-like Inequality

abstract:
  We assess non-Markovianity of a quantum open-system dynamics through the
violation of temporal bell-like inequalities in a controllable Nuclear Magnetic
Resonance system. We investigate experimentally the connections between the
violation of the addressed temporal Bell-like inequality and the
non-divisibility of the effective evolution of our system, which we fully
characterize in a broad range of experimentally controllable regimes. Finally,
we investigate the link between our approach and Leggett-Garg-like inequalities
based on time-translational two-time correlation functions. These results open
up interesting perspectives for the effective, non-tomographic characterization
of dynamical evolution by combining tools of different nature.


title:
Interpretation of a Short-Term Anomaly in the Gravitational Microlensing
  Event MOA-2012-BLG-486

abstract:
  A planetary microlensing signal is generally characterized by a short-term
perturbation to the standard single lensing light curve. A subset of
binary-source events can produce perturbations that mimic planetary signals,
thereby introducing an ambiguity between the planetary and binary-source
interpretations. In this paper, we present analysis of the microlensing event
MOA-2012-BLG-486, for which the light curve exhibits a short-lived
perturbation. Routine modeling not considering data taken in different
passbands yields a best-fit planetary model that is slightly preferred over the
best-fit binary-source model. However, when allowed for a change in the color
during the perturbation, we find that the binary-source model yields a
significantly better fit and thus the degeneracy is clearly resolved. This
event not only signifies the importance of considering various interpretations
of short-term anomalies, but also demonstrates the importance of multi-band
data for checking the possibility of false-positive planetary signals.


title:
Creating Magnetic Fields in excess of 1000 T by Misoriented Stacking in
  a Graphene Bilayer

abstract:
  It is well established that some kinds of lattice deformations in graphene
monolayer, which change electron hopping in sublattice and affect in-plane
motion of electrons, may induce out-of-plane pseudo-magnetic fields as large as
100 T. Here, we demonstrate that stacking misorientation in graphene bilayers
mimics the effect of huge in-plane pseudo-magnetic fields greater than 1000 T
on the interlayer hopping of electrons. As well as addressing the similarity
between the effect of in-plane pseudo-magnetic fields and twisting on the
electronic band structure of Bernal graphene bilayer, we point out that
in-plane magnetic fields (or twisting) could modify the low-energy pseudospin
texture of the graphene bilayer (the pseudospin winding number is reduced from
2 to 1), thereby changing the chiralities of quasiparticles from that of spin 1
to spin 1/2. Our results illustrate the possibility of controllably
manipulating electronic properties of Bernal graphene bilayer by introducing
the in-plane magnetic field or twisting.


title: On orbifold embeddings

abstract:
  For an orbifold, there is a notion of an orbifold embedding, which is more
general than the one of sub-orbifolds. We develop several properties of
orbifold embeddings. In the case of translation groupoids, we show that such a
notion is equivalent to a strong equivariant immersion.


title: Tensor Perturbations from Brane-World Inflation with Curvature Effects

abstract:
  The brane-world scenario provides an intriguing possibility to explore the
phenomenological cosmology implied by string/M theory. In this paper, we
consider a modified Randall-Sundrum single brane model with two natural
generalizations: a Gauss-Bonnet term in the five-dimensional bulk action as
well as an induced gravity term in the four-dimensional brane action, which are
the leading-order corrections to the Randall-Sundrum model. We study the
influence of these combined effects on the evolution of the primordial
gravitational waves generated during an extreme slow-roll inflation on the
brane. The background, for the early inflationary era, is then modeled through
a de Sitter brane embedded within an anti-de Sitter bulk. In this framework, we
show that both effects tend to suppress the Randall-Sundrum enhancement of the
amplitude of the tensor perturbations at relatively high energies. Moreover,
the Gauss-Bonnet effect, relative to standard general relativity, will abruptly
enhance the tensor-to-scalar ratio and break the standard consistency relation
at high energies, which cannot be evaded by invoking the induced gravity
effect, even though the induced gravity strength would mildly counterbalance
these significant changes at high energies. We note that the brane-world model
with or without the induced gravity effect fulfills the consistency relation.
Finally, we discuss some implications of the observational constraints.


title: On the construction of non-2-colorable uniform hypergraphs

abstract:
  The problem of 2-coloring uniform hypergraphs has been extensively studied
over the last few decades. An n-uniform hypergraph is not 2-colorable if its
vertices can't be colored with two colors, Red and Blue, such that every
hyperedge contains Red as well as Blue vertices. The least possible number of
hyperedges in an n-uniform hypergraph which is not 2-colorable is denoted by
m(n). In this paper, we consider the problem of finding an upper bound on m(n)
for small values of n. We provide constructions which improve the existing
results for some such values of n. We obtain the first improvement in the case
of n=8.


title: Optimal tests in AR(m) time series model

abstract:
  A method for an evaluation of the error between an unknown parameter and its
estimator is developed. Its application enables us to preserve the asymptotic
power of a constructed test. Testing problems in AR(1) and ARCH models are
studied with a derivation of the asymptotic power function. Also the results
are extended to AR(m) time series model.


title: Generically stable regular types

abstract:
  We study non-orthogonality of symmetric, regular types and show that it
preserves generic stability and is an equivalence relation on the set of all
generically stable, regular types. We will also prove that some of the nice
properties from the stable context hold in general. In the case of strongly
regular types we will relate non-orthogonality to the global Rudin-Keisler
order.


title:
Ergodicity of the 2D Navier-Stokes Equations with Degenerate
  Multiplicative Noise

abstract:
  Consider the two-dimensional, incompressible Navier-Stokes equations on the
torus We prove that the semigroup P_t generated by the solutions to stochastic
Navier-stokes equations is asymptotically strong Feller. Moreover, we also
prove that semigroup P_t is exponentially ergodic in some sense


title:
Gauss-Bonnet Braneworld Cosmology with Modified Induced Gravity on the
  Brane

abstract:
  We analyze the background cosmology for an extension of the DGP gravity with
Gauss-Bonnet term in the bulk and $f(R)$ gravity on the brane. We investigate
implications of this setup on the late-time cosmic history. Within a dynamical
system approach, we study cosmological dynamics of this setup focusing on the
role played by curvature effects. Finally we constraint the parameters of the
model by confrontation with recent observational data.


title:
Improved Family of Estimators of Population Mean in Simple Random
  Sampling

abstract:
  In this paper, a procedure is given for estimating the population mean in
simple random sampling without replacement in the presence of auxiliary
information. The mean squared error expressions of the proposed estimators have
been derived under large sample approximation. We have compared the
performances of the proposed estimators with several existing estimators. Both
theoretical and empirical findings are encouraging and support the soundness of
the proposed procedure for mean estimation.


title:
Cosmological dynamics of a non-minimally coupled bulk scalar field in
  DGP setup

abstract:
  We consider cosmological dynamics of a canonical bulk scalar field, which is
coupled non-minimally to 5-dimensional Ricci scalar in a DGP setup. We show
that presence of this non-minimally coupled bulk scalar field affects the jump
conditions of the original DGP model significantly. Within a superpotential
approach, we perform some numerical analysis of the model parameter space and
consider bulk-brane energy exchange in this setup. Also we show that the
normal, ghost-free branch of the DGP solutions in this case has the potential
to realize a self-consistent phantom-like behavior and therefore explains late
time acceleration of the universe in a consistent way.


title:
On Improvement in Estimating Population Parameter(s) Using Auxiliary
  Information

abstract:
  The purpose of writing this book is to suggest some improved estimators using
auxiliary information in sampling schemes like simple random sampling and
systematic sampling.
  This volume is a collection of five papers. The following problems have been
discussed in the book:
  In chapter one an estimator in systematic sampling using auxiliary
information is studied in the presence of non-response. In second chapter some
improved estimators are suggested using auxiliary information. In third chapter
some improved ratio-type estimators are suggested and their properties are
studied under second order of approximation.
  In chapter four and five some estimators are proposed for estimating unknown
population parameter(s) and their properties are studied.
  This book will be helpful for the researchers and students who are working in
the field of finite population estimation.


title:
Study of Magnetic Helicity Injection in the Active Regions NOAA 9236
  Producing Multiple Flare-associated CME Events

abstract:
  To better understand a preferred magnetic field configuration and its
evolution during Coronal Mass Ejection events, we investigated the spatial and
temporal evolution of photospheric magnetic fields in the active region NOAA
9236 that produced eight flare-associated CMEs during the time period of 2000
November 23-26. The time variations of the total magnetic helicity injection
rate and the total unsigned magnetic flux are determined and examined not only
in the entire active region but also in some local regions such as the main
sunspots and the CME-associated flaring regions using SOHO/MDI magnetogram
data. As a result, we found that: (1) in the sunspots, a large amount of
postive (right-handed) magnetic helicity was injected during most of the
examined time period, (2) in the flare region, there was a continuous injection
of negative (left-handed) magnetic helicity during the entire period,
accompanied by a large increase of the unsigned magnetic flux, and (3) the
flaring regions were mainly composed of emerging bipoles of magnetic fragments
in which magnetic field lines have substantially favorable conditions for
making reconnection with large-scale, overlying, and oppositely directed
magnetic field lines connecting the main sunspots. These observational findings
can also be well explained by some MHD numerical simulations for CME initiation
(e.g., reconnection-favored emerging flux models). We therefore conclude that
reconnection-favored magnetic fields in the flaring emerging flux regions play
a crucial role in producing the multiple flare-associated CMEs in NOAA 9236.


title:
Some Aspects of Supersymmetric Field Theories with Minimal Length and
  Maximal Momentum

abstract:
  We consider a real scalar field and a Majorana fermion field to construct a
supersymmetric quantum theory of free fermion fields based on the deformed
Heisenberg algebra $[x,p]=i\hbar\big(1-\beta p+2\beta^{2}p^{2}\big)$, where
$\beta $ is a deformation parameter. We present a deformed supersymmetric
algebra in the presence of minimal length and maximal momentum.


title: Malliavin Matrix of Degenerate SDE and Gradient Estimate

abstract:
  In this paper, we prove that the inverse of Malliavin matrix is p integrable
for a kind of degenerate stochastic differential equation under some
conditions, which like to Hormander condition, but don't need all the
coefficients of the SDE are smooth. Furthermore, we obtain a uniform estimation
for Malliavin matrix, a gradient estimate, and prove that the semigroup
generated by the SDE is strong Feller. Also some examples are given.


title:
Reflection and refraction of (magneto-)acoustic waves at the magnetic
  canopy: further evidences from multi-height seismic data

abstract:
  We recently presented evidences (Rajaguru et al. 2012) that seismic halos
around expanding magnetic structures in the lower solar atmosphere are related
to the acoustic to magnetoacoustic wave conversions, using multi-height data
from Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly
(AIA) (1700 and 1600 \AA channels) onboard Solar Dynamics Observatory (SDO).
Using the same data, we here present and discuss further evidences through
analyses of maps of phase-shifts between observables from different heights and
their correspondence with oscillation power. The phase shift maps provide more
direct signatures of reflection and refraction of (magneto-)acoustic wave
modes.


title: Microtubule catastrophe from protofilament dynamics

abstract:
  The disappearance of the guanosine triphosphate (GTP)-tubulin cap is widely
believed to be the forerunner event for the growth-shrinkage transition
(`catastrophe') in microtubule filaments in eukaryotic cells. We study a
discrete version of a stochastic model of the GTP cap dynamics, originally
proposed by Flyvbjerg, Holy and Leibler (Flyvbjerg, Holy and Leibler, Phys.
Rev. Lett. 73, 2372, 1994). Our model includes both spontaneous and vectorial
hydrolysis, as well as dissociation of a non-hydrolyzed dimer from the filament
after incorporation. In the first part of the paper, we apply this model to a
single protofilament of a microtubule. A catastrophe transition is defined for
each protofilament, similar to the earlier one-dimensional models, the
frequency of occurrence of which is then calculated under various conditions,
but without explicit assumption of steady state conditions. Using a
perturbative approach, we show that the leading asymptotic behavior of the
protofilament catastrophe in the limit of large growth velocities is remarkably
similar across different models. In the second part of the paper, we extend our
analysis to the entire filament by making a conjecture that a minimum number of
such transitions are required to occur for the onset of microtubule
catastrophe. The frequency of microtubule catastrophe is then determined using
numerical simulations, and compared with analytical/semi-analytical estimates
made under steady state/quasi-steady state assumptions respectively for the
protofilament dynamics. A few relevant experimental results are analyzed in
detail, and compared with predictions from the model. Our results indicate that
loss of GTP cap in 2-3 protofilaments is necessary to trigger catastrophe in a
microtubule.


title:
Search for eta-mesic helium via deuteron-deuteron reactions with the
  WASA-at-COSY facility

abstract:
  The eta-mesic nuclei in which the eta meson is bound with nucleus via strong
interaction was postulated already in 1986, however till now no experiment
confirmed empirically its existence. The discovery of this new kind of an
exotic nuclear matter would be very important for better understanding of the
eta meson structure and its interaction with nucleons. The search for eta-mesic
helium is carried out with high statistic and high acceptance with the
WASA-at-COSY detection setup in the Forschungszentrum Julich. The search is
conducted via the measurement of the excitation function for the chosen decay
channels of the 4He-eta system. Untill now two reactions dd->(4He-eta)bs->3He p
pi- and dd->(4He-eta)bs->3He n pi0 have been measured with the beam momentum
ramped around the eta production threshold. This report includes the
description of experimental method and status of the analysis.


title:
Level repulsion in hybrid photonic-plasmonic microresonators for
  enhanced biodetection

abstract:
  We theoretically analyse photonic-plasmonic coupling between a high Q
whispering gallery mode (WGM) resonator and a core-shell nanoparticle. Blue and
red shifts of WGM resonances are shown to arise from crossing of the photonic
and plasmonic modes. Level repulsion in the hybrid system is further seen to
enable sensitivity enhancements in WGM sensors: maximal when the two resonators
are detuned by half the plasmon linewidth. Approximate bounds are given to
quantify possible enhancements. Criteria for reactive vs. resistive coupling
are also established.


title: Numerical analysis of detection-mechanism models of SNSPD

abstract:
  The microscopic mechanism of photon detection in superconducting nanowire
single-photon detectors is still under debate. We present a simple, but
powerful theoretical model that allows us to identify essential differences
between competing detection mechanisms. The model is based on quasi-particle
multiplication and diffusion after the absorption of a photon. We then use the
calculated spatial and temporal evolution of this quasi-particle cloud to
determine detection criteria of three distinct detection mechanisms, based on
the formation of a normal conducting spot, the reduction of the effective
depairing critical current below the bias current and a vortex-crossing
scenario, respectively. All our calculations as well as a comparison to
experimental data strongly support the vortex-crossing detection mechanism by
which vortices and antivortices enter the superconducting strip from the edges
and subsequently traverse it thereby triggering the detectable normal
conducting domain. These results may therefore help to reveal the microscopic
mechanism responsible for the detection of photons in superconducting
nanowires.


title: The divisor function and divisor problem

abstract:
  The purpose of this text is twofold. First we discuss some divisor problems
involving Paul Erd\H os (1913-1996), whose centenary of birth is this year. In
the second part some recent results on divisor problems are discussed, and
their connection with the powers moments of $|\zeta(\frac{1}{2}+it)|$ is
pointed out. This is an extended version of the lecture given at the conference
ERDOS100 in Budapest, July 1-5, 2013.


title:
On the asymptotic behaviour of a dynamic version of the Neyman
  contagious point process

abstract:
  We consider a dynamic version of the Neyman contagious point process that can
be used for modelling the spacial dynamics of biological populations, including
species invasion scenarios. Starting with an arbitrary finite initial
configuration of points in ${\bf R}^d$ with nonnegative weights, at each time
step a point is chosen at random from the process according to the distribution
with probabilities proportional to the points' weights. Then a finite random
number of new points is added to the process, each displaced from the location
of the chosen "mother" point by a random vector and assigned a random weight.
Under broad conditions on the sequences of the numbers of newly added points,
their weights and displacement vectors (which include a random environments
setup), we derive the asymptotic behaviour of the locations of the points added
to the process at time step $n$ and also that of the scaled mean measure of the
point process after time step $n\to\infty$.


title: Multiple Higgs-Portal and Gauge-Kinetic Mixings

abstract:
  We develop a phenomenological formalism for mixing effects between the
Standard Model and hidden-sector fields, motivated by dark matter in the
Universe as well as string theories. The scheme includes multiple Higgs-portal
interactions in the scalar sector as well as multiple gauge-kinetic mixings in
the abelian gauge sector. While some of the mixing effects can be cast in
closed form, other elements can be controlled analytically only by means of
perturbative expansions in the ratio of standard scales over large hidden
scales. Higgs and vector-boson masses and mixings are illustrated numerically
for characteristic processes.


title:
Diversity of photonic differentiators based on flexible demodulation of
  phase signals

abstract:
  We theoretically prove a multifunctional photonic differentiation (DIFF)
scheme based on phase demodulation using two cascaded linear filters. The
photonic DIFF has a diversity of output forms, such as 1st order intensity
DIFF, 1st order field DIFF and its inversion, 2nd order field DIFF, dependent
on the relative shift between the optical carrier and the filter's resonant
notches. As a proof, we also experimentally demonstrate the DIFF diversity
using a phase modulator and two delay interferometers (DIs). The calculated
average deviation is less than 7% for all DIFF waveforms. Our schemes show the
advantages of flexible DIFF functions and forms, which may have different
optical applications. For example, high order field differentiators can be used
to generate complex temporal waveforms. And intensity differentiators are
useful for ultra-wideband pulse generation.


title:
Real-time dynamic spectrum management for multi-user multi-carrier
  communication systems

abstract:
  Dynamic spectrum management is recognized as a key technique to tackle
interference in multi-user multi-carrier communication systems and networks.
However existing dynamic spectrum management algorithms may not be suitable
when the available computation time and compute power are limited, i.e., when a
very fast responsiveness is required. In this paper, we present a new paradigm,
theory and algorithm for real-time dynamic spectrum management (RT-DSM) under
tight real-time constraints. Specifically, a RT-DSM algorithm can be stopped at
any point in time while guaranteeing a feasible and improved solution. This is
enabled by the introduction of a novel difference-of-variables (DoV)
transformation and problem reformulation, for which a primal coordinate ascent
approach is proposed with exact line search via a logarithmicly scaled grid
search. The concrete proposed algorithm is referred to as iterative power
difference balancing (IPDB). Simulations for different realistic wireline and
wireless interference limited systems demonstrate its good performance, low
complexity and wide applicability under different configurations.


title:
On the importance of using exact pairing in the study of pygmy dipole
  resonance

abstract:
  The strength functions of giant dipole resonance (GDR) in oxygen $^{18 -
24}$O, calcium $^{50 - 60}$Ca, and tin $^{120 - 130}$Sn isotopes are calculated
within the phonon damping model under three approximations: without superfluid
pairing, including BCS pairing, and exact pairing gaps. The analysis of the
numerical results shows that exact pairing decreases the two-neutron separation
energy in light nuclei, but increases it in heavy nuclei as compared to that
obtained within the BCS theory. In neutron-rich medium and heavy nuclei, exact
pairing significantly enhances the strength located at the low-energy tail of
the GDR, which is usually associated with the pygmy dipole resonance. The line
shape of the GDR changes significantly with increasing the neutron number
within an isotopic chain if the model parameter is kept fixed at the value
determined for the stable isotope.


title: Quantum interactive proofs and the complexity of separability testing

abstract:
  We identify a formal connection between physical problems related to the
detection of separable (unentangled) quantum states and complexity classes in
theoretical computer science. In particular, we show that to nearly every
quantum interactive proof complexity class (including BQP, QMA, QMA(2), and
QSZK), there corresponds a natural separability testing problem that is
complete for that class. Of particular interest is the fact that the problem of
determining whether an isometry can be made to produce a separable state is
either QMA-complete or QMA(2)-complete, depending upon whether the distance
between quantum states is measured by the one-way LOCC norm or the trace norm.
We obtain strong hardness results by proving that for each n-qubit maximally
entangled state there exists a fixed one-way LOCC measurement that
distinguishes it from any separable state with error probability that decays
exponentially in n.


title: Conformal symmetry and accelerating cosmology in teleparallel gravity

abstract:
  We discuss conformal issues of pure and extended teleparallel gravity. In
particular, we present formulations of conformal transformation in teleparallel
gravity. Furthermore, we propose conformal scalar and gauge field theories in
teleparallel gravity and study conformal torsion gravity. We explicitly
demonstrate that a power-law acceleration (including the $\Lambda$CDM universe)
as well as the de Sitter expansion of the universe can be realized in extended
teleparallel gravity with a conformal scalar field, and that pure teleparallel
gravity with a conformal scalar field can lead to the $\Lambda$CDM model. It is
also shown that there can exist the de Sitter solution in conformal torsion
gravity.


title: Scale-dependent CMB asymmetry from primordial configuration

abstract:
  We demonstrate that a topological defect can explain the hemispherical power
asymmetry of the CMB. The first point is that a defect configuration, which
already exists prior to inflation, can source asymmetry of the CMB. The second
point is that modulation mechanisms, such as the curvaton and other modulation
mechanisms, can explain scale-dependence of the asymmetry. Using a simple
analysis of the $\delta N$ formalism, we show models in which scale-dependent
hemispherical power asymmetry is explained by primordial configuration of a
defect.


title:
Wigner crystals for a planar, equimolar binary mixture of classical,
  charged particles

abstract:
  We have investigated the ground state configurations of an equimolar, binary
mixture of classical charged particles (with nominal charges $Q_1$ and $Q_2$)
that condensate on a neutralizing plane. Using efficient Ewald summation
techniques for the calculation of the ground state energies, we have identified
the energetically most favourable ordered particle arrangements with the help
of a highly reliable optimization tool based on ideas of evolutionary
algorithms. Over a large range of charge ratios, $q = Q_2 / Q_1$, we identify
six non-trivial ground states, some of which show a remarkable and unexpected
structural complexity. For $0.59 \lesssim q < 1$ the system undergoes a phase
separation where the two charge species populate in a hexagonal arrangement
spatially separated areas.


title: Non-isothermal filaments in equilibrium

abstract:
  The physical properties of the so-called Ostriker isothermal filament
(Ostriker 1964) have been classically used as benchmark to interpret the
stability of the filaments observed in nearby clouds. However, recent continuum
studies have shown that the internal structure of the filaments depart from the
isothermality, typically exhibiting radially increasing temperature gradients.
The presence of internal temperature gradients within filaments suggests that
the equilibrium configuration of these objects should be therefore revisited.
The main goal of this work is to theoretically explore how the equilibrium
structure of a filament changes in a non-isothermal configuration. We solve the
hydrostatic equilibrium equation assuming temperature gradients similar to
those derived from observations. We obtain a new set of equilibrium solutions
for non-isothermal filaments with both linear and asymptotically constant
temperature gradients. Our results show that, for sufficiently large internal
temperature gradients, a non-isothermal filament could present significantly
larger masses per unit length and shallower density profiles than the
isothermal filament without collapsing by its own gravity. We conclude that
filaments can reach an equilibrium configuration under non-isothermal
conditions. Detailed studies of both the internal mass distribution and
temperature gradients within filaments are then needed in order to judge the
physical state of filaments.


title: Channel Upgradation for Non-Binary Input Alphabets and MACs

abstract:
  Consider a single-user or multiple-access channel with a large output
alphabet. A method to approximate the channel by an upgraded version having a
smaller output alphabet is presented and analyzed. The original channel is not
necessarily symmetric and does not necessarily have a binary input alphabet.
Also, the input distribution is not necessarily uniform. The approximation
method is instrumental when constructing capacity achieving polar codes for an
asymmetric channel with a non-binary input alphabet. Other settings in which
the method is instrumental are the wiretap setting as well as the lossy source
coding setting.


title: Magnetic ghosts and monopoles

abstract:
  While the physics of equilibrium systems composed of many particles is well
known, the interplay between small-scale physics and global properties is still
a mystery for athermal systems. Non-trivial patterns and metastable states are
often reached in those systems. We explored the various arrangements adopted by
magnetic beads along chains and rings. Here, we show that it is possible to
create mechanically stable defects in dipole arrangements keeping the memory of
dipole frustration. Such defects, nicknamed "ghost junctions", seem to act as
macroscopic magnetic monopoles, in a way reminiscent of spin ice systems.


title: Unifying the Dynkin and Lebesgue-Stieltjes formulae

abstract:
  We establish a local martingale $M$ associate with $f(X,Y)$ under some
restrictions on $f$, where $Y$ is a process of bounded variation (on compact
intervals) and either $X$ is a jump diffusion (a special case being a L\'evy
process) or $X$ is some general (c\'adl\'ag metric space valued) Markov
process. In the latter case $f$ is restricted to the form
$f(x,y)=\sum_{k=1}^K\xi_k(x)\eta_k(y)$. This local martingale unifies both
Dynkin's formula for Markov processes and the Lebesgue-Stieltjes integration
(change of variable) formula for (right continuous) functions of bounded
variation. For the jump diffusion case, when further relatively easily
verifiable conditions are assumed then this local martingale becomes an $L^2$
martingale. Convergence of the product of this Martingale with some
deterministic function (of time) to zero both in $L^2$ and a.s. is also
considered and sufficient conditions for functions for which this happens are
identified.


title:
Boundedness of Maximal Calder\'on-Zygmund Operators on Non-homogeneous
  Metric Measure Spaces

abstract:
  Let $(\cx,\,d,\,\mu)$ be a metric measure space and satisfy the so-called
upper doubling condition and the geometrically doubling condition. In this
paper, the authors show that for the maximal Calder\'on-Zygmund operator
associated with a singular integral whose kernel satisfies the standard size
condition and the H\"ormander condition, its $L^p(\mu)$ boundedness with
$p\in(1,\infty)$ is equivalent to its boundedness from $L^1(\mu)$ into
$L^{1,\infty}(\mu)$. Moreover, applying this, together with a new Cotlar type
inequality, the authors show that if the Calder\'on-Zygmund operator $T$ is
bounded on $L^2(\mu)$, then the corresponding maximal Calder\'on-Zygmund is
bounded on $L^p(\mu)$ for all $p\in(1,\infty)$, and bounded from $L^1(\mu)$
into $L^{1,\infty}(\mu)$. These results essentially improve the existing
results.


title: Four open questions in massive star evolution

abstract:
  We discuss four questions dealing with massive star evolution. The first one
is about the origin of slowly rotating, non-evolved, nitrogen rich stars. We
propose that these stars may originate from initially fast rotating stars whose
surface has been braked down. The second question is about the evolutionary
status of alpha-Cygni variables. According to their pulsation properties, these
stars should be post red supergiant stars. However, some stars at least present
surface abundances indicating that they should be pre red supergiant stars. How
to reconcile these two contradictory requirements? The third one concerns the
various supernova types which are the end point of the evolution of stars with
initial masses between 18 and 30 Msun, i.e. the most massive stars which go
through a red supergiant phase during their lifetime. Do they produce types
IIP, IIL, IIn, IIb or Ib supernovae or do they end without producing any SN
event? Finally, we shall discuss reasons why so few progenitors of type Ibc
supernovae have yet been detected?


title: Neighborly inscribed polytopes and Delaunay triangulations

abstract:
  We construct a large family of neighborly polytopes that can be realized with
all the vertices on the boundary of any smooth strictly convex body. In
particular, we show that there are superexponentially many combinatorially
distinct neighborly polytopes that admit realizations inscribed on the sphere.
These are the first examples of inscribable neighborly polytopes that are not
cyclic polytopes, and provide the current best lower bound for the number of
combinatorial types of inscribable polytopes (which coincides with the current
best lower bound for the number of combinatorial types of polytopes). Via
stereographic projections, this translates into a superexponential lower bound
for the number of combinatorial types of (neighborly) Delaunay triangulations.


title: Integration by Parts Formula and Applications for SDEs with L\'evy Noise

abstract:
  By using the Malliavin calculus and finite-jump approximations, the
Driver-type integration by parts formula is established for the semigroup
associated to stochastic differential equations with noises containing a
subordinate Brownian motion. As applications, the shift-Harnack inequality and
heat kernel estimates are derived. The main results are illustrated by SDEs
driven by $\aa$-stable like processes.


title: Local dynamics of a randomly pinned crack front: A numerical study

abstract:
  We investigate numerically the dynamics of crack propagation along a weak
plane using a model consisting of fibers connecting a soft and a hard clamp.
This bottom-up model has previously been shown to contain the competition of
two crack propagation mechanisms: coalescence of damage with the front on small
scales and pinned elastic line motion on large scales. We investigate the
dynamical scaling properties of the model, both on small and large scale. The
model results compare favorable with experimental results.


title: Transparent Dirac potentials in one dimension: the time-dependent case

abstract:
  We generalize the original derivation of transparent, static Schroedinger
potentials by Kay and Moses, to obtain a large class of time-dependent
transparent Dirac potentials in one spatial dimension. They contain all known
transparent potentials as special cases and play a key role in the
semi-classical solution of 1+1 dimensional, fermionic quantum field theories of
Gross-Neveu and Nambu-Jona-Lasinio type.


title:
Neutrinoless Double Beta Decay in the Presence of Light Sterile
  Neutrinos

abstract:
  We investigate the predictions for neutrinoless double beta ($(\beta
\beta)_{0 \nu}$-) decay effective Majorana mass $\left| \langle \, m \, \rangle
\right|$ in the 3+1 and 3+2 schemes with one and two additional sterile
neutrinos with masses at the eV scale. The two schemes are suggested by the
neutrino oscillation interpretation of the reactor neutrino and Gallium
"anomalies" and of the data of the LSND and MiniBooNE experiments. We analyse
in detail the possibility of a complete or partial cancellation between the
different terms in $\left| \langle \, m \, \rangle \right|$, leading to a
strong suppression of $\left| \langle \, m \, \rangle \right|$. We determine
the regions of the relevant parameter spaces where such a suppression can
occure. This allows us to derive the conditions under which the effective
Majorana mass satisfies $\left| \langle \, m \, \rangle \right| > 0.01$ eV,
which is the range planned to be exploited by the next generation of $(\beta
\beta)_{0 \nu}$-experiments.


title: Suzaku Observation of the Symbiotic X-Ray Binary IGR J16194-2810

abstract:
  We observed IGR J16194-2810 in the low/hard state with the Suzaku X-ray
satellite in 2009. The source is a Symbiotic X-ray Binary (SyXB) classified as
a category of a Low-Mass X-ray Binary (LMXB), since the system is composed of
an M-type giant and probably a neutron star (NS). We detected the 0.8-50 keV
signal with the XIS and HXD-PIN. The 2-10 keV luminosity was L ~ 7 x 10^34 erg
s^-1 corresponding to ~10^-3 L_Edd, where L_Edd is the Eddington Luminosity of
a 1.4 M_o NS and a source distance of 3.7 kpc is assumed. The luminosity is
similar to those of past observations. The spectral analysis showed that there
are two emission components below and above ~2 keV. The hard emission component
is represented by a Comptonized black-body emission model with the seed-photon
temperature ~1.0 keV and the emission radius ~700 m. The seed photon is
considered to come from a small fraction of the NS surface. The soft component
is reproduced by either a raw black-body (~0.4 keV, ~1.7 km) or a Comptonized
emission (~0.1 keV, ~75 km). We think the origin is the emission from other
part of the NS surface or the accreting stream. The physical parameters of the
hard emission component of IGR J16194-2810 are compared with those of an SyXB
(4U 1700+24) and LMXBs (Aql X-1 and 4U 0614+091). This comparison reveals that
these SyXBs in the low/hard state have a smaller radiation region (< 1 km) on
the NS surface with a higher seed-photon temperature (~1 keV) than the compared
LMXBs.


title:
The effect of UV/Soft X-ray excess emission on the warm absorber
  properties of Active Galactic Nuclei -- A case study of IRAS 13349+2438

abstract:
  The UV to X-ray continuum of active galactic nuclei (AGN) is important for
maintaining the ionisation and thermal balance of the warm absorbers (WAs).
However, the spectra in the sensitive energy range $\sim \,13.6 -300 \ev$ are
unobservable due to Galactic extinction. Moreover, many AGN show soft X-ray
excess emission of varying strength in the $0.1-2\kev$ band whose origin is
still highly debated. This soft-excess connects to the UV bump in the
unobserved region of $13.6 -300 \ev$. Here we investigate the effect of the
assumed physical model for the soft-excess on the flux of the unobserved part
of the spectrum and its effect on the WA properties. We perform a case study
using the \xmm{} observations of the bright Seyfert 1 galaxy IRAS 13349+2438
with WA features. The two different physical models for the soft excess:
blurred Compton reflection from an ionised disk, and, optically thick thermal
Comptonisation of the disk photons, predict different fluxes in the unobserved
energy range. However the current X-ray data quality does not allow us to
distinguish between them using derived WA parameters. This, in turn, implies
that it is difficult to determine the origin of the soft-excess emission using
the warm absorber features.


title:
Beyond mean-field behavior of large Bose-Einstein condensates in
  double-well potentials

abstract:
  For the dynamics of Bose-Einstein condensates (BECs), differences between
mean-field (Gross-Pitaevskii) physics and $N$-particle quantum physics often
disappear if the BEC becomes larger and larger. In particular, the timescale
for which both dynamics agree should thus become larger if the particle number
increases. For BECs in a double-well potential, we find both examples for which
this is the case and examples for which differences remain even for huge BECs
on experimentally realistic short timescales. By using a combination of
numerical and analytical methods, we show that the differences remain visible
on the level of expectation values even beyond the largest possible numbers
realized experimentally for BECs with ultracold atoms.


title:
AFTER@LHC: a precision machine to study the interface between particle
  and nuclear physics

abstract:
  We outline the opportunities to study with high precision the interface
between nuclear and particle physics, which are offered by a next generation
and multi-purpose fixed-target experiment exploiting the proton and ion LHC
beams extracted by a bent crystal.


title:
Multi-Objective Particle Swarm Optimization for Facility Location
  Problem in Wireless Mesh Networks

abstract:
  Wireless mesh networks have seen a real progress due of their implementation
at a low cost. They present one of Next Generation Networks technologies and
can serve as home, companies and universities networks. In this paper, we
propose and discuss a new multi-objective model for nodes deployment
optimization in Multi-Radio Multi-Channel Wireless Mesh Networks. We exploit
the trade-off between network cost and the overall network performance. This
optimization problem is solved simultaneously by using a meta-heuristic method
that returns a non-dominated set of near optimal solutions. A comparative study
was driven to evaluate the efficiency of the proposed model.


title:
Improved generalized gradient approximation for positron states in
  solids

abstract:
  Several first-principles calculations of positron-annihilation
characteristics in solids have added gradient corrections to the local-density
approximation within the theory by Arponen and Pajanne [Ann. Phys. (N.Y.) 121,
343 (1979)] since this theory systematically overestimates the annihilation
rates. As a further remedy we propose to use gradient corrections for other
local density approximation schemes based on perturbed hypernetted-chain and on
Quantum Monte Carlo results. Our calculations for various metals and
semiconductors show that the proposed schemes generally improve the positron
lifetimes when they are confronted with experiment. We also compare the
resulting positron affinities in solids with data from slow-positron
measurements.


title:
Spectrum optimization in multi-user multi-carrier systems with iterative
  convex and nonconvex approximation methods

abstract:
  Several practical multi-user multi-carrier communication systems are
characterized by a multi-carrier interference channel system model where the
interference is treated as noise. For these systems, spectrum optimization is a
promising means to mitigate interference. This however corresponds to a
challenging nonconvex optimization problem. Existing iterative convex
approximation (ICA) methods consist in solving a series of improving convex
approximations and are typically implemented in a per-user iterative approach.
However they do not take this typical iterative implementation into account in
their design. This paper proposes a novel class of iterative approximation
methods that focuses explicitly on the per-user iterative implementation, which
allows to relax the problem significantly, dropping joint convexity and even
convexity requirements for the approximations. A systematic design framework is
proposed to construct instances of this novel class, where several new
iterative approximation methods are developed with improved per-user convex and
nonconvex approximations that are both tighter and simpler to solve (in
closed-form). As a result, these novel methods display a much faster
convergence speed and require a significantly lower computational cost.
Furthermore, a majority of the proposed methods can tackle the issue of getting
stuck in bad locally optimal solutions, and hence improve solution quality
compared to existing ICA methods.


title:
Deep multi-telescope photometry of NGC 5466. I. Blue Stragglers and
  binary systems

abstract:
  We present a detailed investigation of the radial distribution of blue
straggler star and binary populations in the Galactic globular cluster NGC
5466, over the entire extension of the system. We used a combination of data
acquired with the ACS on board the Hubble Space Telescope, the LBC-blue mounted
on the Large Binocular Telescope, and MEGACAM on the Canadian-France-Hawaii
Telescope. Blue straggler stars show a bimodal distribution with a mild central
peak and a quite internal minimum. This feature is interpreted in terms of a
relatively young dynamical age in the framework of the "dynamical clock"
concept proposed by Ferraro et al. (2012). The estimated fraction of binaries
is 6-7% in the central region (r<90") and slightly lower (5.5%) in the
outskirts, at r>200". Quite interestingly, the comparison with the results of
Milone et al. (2012) suggests that also binary systems may display a bimodal
radial distribution, with the position of the minimum consistent with that of
blue straggler stars. If confirmed, this feature would give additional support
to the scenario where the radial distribution of objects more massive than the
average cluster stars is primarily shaped by the effect of dynamical friction.
Moreover, this would also be consistent with the idea that the unperturbed
evolution of primordial binaries could be the dominant BSS formation process in
low-density environments.


title: Clean-Slate Design of Next-Generation Optical Access

abstract:
  We report the current status of our research on the clean-slate design of
next-generation optical access (NGOA). We have been studying candidate
architectures with a major focus on their elasticity to user demands, energy
efficiency, and support of better Quality of Experience (QoE). One of the major
challenges in this study is to establish a comparative analysis framework where
we can assess the performances of candidate architectures in an objective and
quantifiable way. In this paper we describe our efforts to meet this challenge:
(1) the development of a new comparison framework based on integrated QoE and
statistical hypothesis testing and (2) the implementation of a virtual test bed
capturing important aspects from physical layer to application layer to
end-user behaviour governing traffic generation. The comparison framework and
the virtual test bed will provide researchers a sound basis and useful tools
for comparative analysis in the clean-slate design of NGOA.


title: Roton excitations in a trapped dipolar Bose-Einstein condensate

abstract:
  We consider the quasi-particle excitations of a trapped dipolar Bose-Einstein
condensate. By mapping these excitations onto radial and angular momentum we
show that the roton modes are clearly revealed as discrete fingers in parameter
space, whereas the other modes form a smooth surface. We examine the properties
of the roton modes and characterize how they change with the dipole interaction
strength. We demonstrate how the application of a perturbing potential can be
used to engineer angular rotons, i.e. allowing us to controllably select modes
of non-zero angular momentum to become the lowest energy rotons.


title:
Quantum Mechanics and CPT tests with neutral kaons at the KLOE
  experiment

abstract:
  Neutral kaons produced in the correlated pairs at the DAFNE phi-factory offer
unique possibilities to perform fundamental tests of CPT invariance, as well as
of the basic principles of quantum mechanics. The analysis of the data
collected by the KLOE experiment allows to improve results on several
parameters describing CPT violation and decoherence and to measure the
regeneration cross section on the beam pipe materials.


title:
The computation of averages from equilibrium and nonequilibrium Langevin
  molecular dynamics

abstract:
  We consider numerical methods for thermodynamic sampling, i.e. computing
sequences of points distributed according to the Gibbs-Boltzmann distribution,
using Langevin dynamics and overdamped Langevin dynamics (Brownian dynamics). A
wide variety of numerical methods for Langevin dynamics may be constructed
based on splitting the stochastic differential equations into various component
parts, each of which may be propagated exactly in the sense of distributions.
Each such method may be viewed as generating samples according to an associated
invariant measure that differs from the exact canonical invariant measure by a
stepsize-dependent perturbation. We provide error estimates a la Talay-Tubaro
on the invariant distribution for small stepsize, and compare the sampling bias
obtained for various choices of splitting method. We further investigate the
overdamped limit and apply the methods in the context of driven systems where
the goal is sampling with respect to a nonequilibrium steady state. Our
analyses are illustrated by numerical experiments.


title:
Direct method for measuring of purity, superfidelity, and subfidelity of
  photonic two-qubit mixed states

abstract:
  The Uhlmann-Jozsa fidelity (or, equivalently, the Bures distance) is a basic
concept of quantum communication and quantum information, which however is very
difficult to measure efficiently without recourse to quantum tomography. Here
we propose a direct experimental method to estimate the fidelity between two
unknown two-qubit mixed states via the measurement of the upper and lower
bounds of the fidelity, which are referred to as the superfidelity and
subfidelity, respectively. Our method enables a direct measurement of the
first- and second-order overlaps between two arbitrary two-qubit states. In
particular, the method can be applied to measure the purity (or linear entropy)
of a single two-qubit mixed state in a direct experiment. We also propose and
critically compare several experimental strategies for measuring the sub- and
superfidelities of polarization states of photons in various linear-optical
setups.


title: Suppression of Excited-State Contributions to Stellar Reaction Rates

abstract:
  It has been shown in previous work [Phys. Rev. Lett. 101, 191101 (2008);
Phys. Rev. C 80, 035801 (2009)] that a suppression of the stellar enhancement
factor (SEF) occurs in some endothermic reactions at and far from stability.
This effect is re-evaluated using the ground-state contributions to the stellar
reaction rates, which were shown to be better suited to judge the importance of
excited state contributions than the previously applied SEFs. An update of the
tables shown in Phys. Rev. C 80, 035801 (2009) is given. The new evalution
finds 2350 cases (out of a full set of 57513 reactions) for which the
ground-state contribution is larger in the reaction direction with negative
reaction Q-value than in the exothermic direction, thus providing exceptions to
the commonly applied Q-value rule. The results confirm the Coulomb suppression
effect but lead to a larger number of exceptions than previously found. This is
due to the fact that often a large variation in the g.s. contribution does not
lead to a sizeable change in the SEF. On the other hand, several previously
identified cases do not appear anymore because it is found that their g.s.
contribution is smaller than inferred from the SEF.


title: Voltage Controlled Switching Phenomenon in Disordered Superconductors

abstract:
  Superconductor-to-Insulator transition (SIT) is a phenomenon occurring for
highly disordered superconductors and is suitable for a superconducting switch
development. SIT has been demonstrated to be induced by different external
parameters such as temperature, magnetic field, electric field, etc. However,
electric field induced SIT (ESIT), which has been experimentally demonstrated
for some specific materials, holds the promise of any practical device
development. Here, we demonstrate, from theoretical considerations, the
occurrence of ESIT. We also propose a general switching device architecture
using ESIT and study some of its universal behavior, such as the effect of
sample size, disorder strength and temperature on the switching action. This
work provides a general framework for development of such a device.


title: Bernstein inequalities with nondoubling weights

abstract:
  We answer Totik's question on weighted Bernstein's inequalities showing that
$$ \|T_n'\|_{L_p(\omega)} \le C(p,\omega)\, {n}\,\|T_n\|_{L_p(\omega)},\qquad
0<p\le \infty, $$ holds for all trigonometric polynomials $T_n$ and certain
nondoubling weights $\omega$. Moreover, we find necessary conditions on
$\omega$ for Bernstein's inequality to hold. We also prove weighted
Bernstein-Markov, Remez, and Nikolskii inequalities for trigonometric and
algebraic polynomials.


title: Carbon Nanotubes Production Using Arc Ignition Under Magnetic Field

abstract:
  We demonstrate that AC arc discharge under de-ionized water which has been
recently used for carbon nanotubes (CNT) production can be modified to increase
the quantity and quality of carbon nanotubes by applying a magnetic field. The
carbon soot thus obtained was analyzed using SEM, TEM and Raman spectroscopy.
The Raman scattering measurements showed interesting results. Radial breathing
modes (RBM) were observed in the Raman data in the range 150 - 700 cm-1. The
presence of RBM is good enough indication of the presence of the carbon
nanotubes in the soot collected by us. The RBM data was analyzed further which
indicated a superposition of two closely lying modes. It showed the
distribution of tube diameter which depended on the application of magnetic
field.


title:
Design of a non-linear power system stabiliser using the concept of the
  feedback linearisation based on the back-stepping technique

abstract:
  This study proposes a feedback linearisation based on the back-stepping
method with simple implementation and unique design process to design a
non-linear controller with a goal of improving both steady-state and transient
stability. The proposed method is designed based on a standard third-order
model of synchronous generator. A comparison based on simulation is then
performed between the proposed method and two conventional control schemes
(i.e. conventional power system stabiliser and direct feedback linearisation).
The simulation results demonstrate that fast response, robustness, damping,
steady-state and transient stability as well as voltage regulation are all
achieved satisfactorily.


title:
Upper limits on bolometric luminosities of three type Ia supernova
  progenitors - New results in the ongoing Chandra archival search for type Ia
  supernova progenitors

abstract:
  We present analysis of Chandra archival, pre-explosion data of the positions
of three nearby (< 25 Mpc) type Ia supernovae, SN2011iv, SN2012cu & SN2012fr.
No sources corresponding to the progenitors were found in any of the
observations. Combining all sources with well defined backgrounds does not
reveal any evidence for X-ray emission from the progenitors either. We
calculated upper limits on the bolometric luminosities of the progenitors,
under the assumption that they were black bodies with effective temperatures
between 30 and 150 eV, corresponding to 'canonical' supersoft X-ray sources.
The upper limits of SN2012fr straddles the Eddington luminosity of canonical
supersoft sources, but fainter canonical supersoft sources cannot be ruled out
by this study. We also compare our upper limits with known compact binary
supersoft X-ray sources. This study is a continuation of the campaign to
directly detect or constrain the X-ray characteristics of pre-explosion
observations of nearby type Ia supernova progenitors; with the results reported
in Nielsen, Voss & Nelemans (see reference in Introduction), the number of
nearby type Ia supernovae for which pre-explosion images are available in the
Chandra archive is now 13 and counting.


title:
Global survey of star clusters in the Milky Way II. The catalogue of
  basic parameters

abstract:
  Although they are the main constituents of the Galactic disk population, for
half of the open clusters in the Milky Way reported in the literature nothing
is known except the raw position and an approximate size. The main goal of this
study is to determine a full set of uniform spatial, structural, kinematic, and
astrophysical parameters for as many known open clusters as possible. On the
basis of stellar data from PPMXL and 2MASS, we used a dedicated data-processing
pipeline to determine kinematic and photometric membership probabilities for
stars in a cluster region. For an input list of 3784 targets from the
literature, we confirm that 3006 are real objects, the vast majority of them
are open clusters, but associations and globular clusters are also present. For
each confirmed object we determined the exact position of the cluster centre,
the apparent size, proper motion, distance, colour excess, and age. For about
1500 clusters, these basic astrophysical parameters have been determined for
the first time. For the bulk of the clusters we also derived the tidal radius.
We estimated additionally average radial velocities for more than 30% of the
confirmed clusters. The present sample (called MWSC) reaches both the central
parts of the Milky Way and its outer regions. It is almost complete up to 1.8
kpc from the Sun and also covers neighbouring spiral arms. However, for a small
subset of the oldest open clusters ($\log t \gtrsim 9$) we found some evidence
of incompleteness within about 1 kpc from the Sun.


title:
Nonlocal transport and heating in superconductors under dual-bias
  conditions

abstract:
  We report on an experimental and theoretical study of nonlocal transport in
superconductor hybrid structures, where two normal-metal leads are attached to
a central superconducting wire. As a function of voltage bias applied to both
normal-metal electrodes, we find surprisingly large nonlocal conductance
signals, almost of the same magnitude as the local conductance. We demonstrate
that these signals are the result of strong heating of the superconducting
wire, and that under symmetric bias conditions, heating mimics the effect of
Cooper pair splitting.


title: Aromatic Butcher Series

abstract:
  We show that without other further assumption than affine equivariance and
locality, a numerical integrator has an expansion in a generalized form of
Butcher series (B-series) which we call aromatic B-series. We obtain an
explicit description of aromatic B-series in terms of elementary differentials
associated to aromatic trees, which are directed graphs generalizing trees. We
also define a new class of integrators, the class of aromatic Runge-Kutta
methods, that extends the class of Runge-Kutta methods, and have aromatic
B-series expansion but are not B-series methods. Finally, those results are
partially extended to the case of more general affine group equivariance.


title: The puzzling radio source in the cool core cluster A 2626

abstract:
  We report on new VLA radio observations performed at 1.4 GHz and 4.8 GHz with
unprecedented sensitivity and angular resolution (~1 arcsec) of the cool core
cluster A 2626, which is known to possess a radio mini-halo at its center. The
most unusual features of A 2626 are two elongated radio features detected in
previous observations to the north and south, having morphologies not common to
the typical jet-lobe structures in cool cores. In our new sensitive images the
two elongated features appears clearly as bright radio arcs, and we discover
the presence of a new arc to the west. These radio arcs are not detected at 4.8
GHz, implying a steep (alpha >1) spectrum, and their origin is puzzling. After
subtracting the flux density contributed by these discrete features from the
total flux measured at low resolution, we estimate a residual 18.0 +/- 1.8 mJy
flux density of diffuse radio emission at 1.4 GHz. We therefore confirm the
detection of diffuse radio emission, which appears distinct from the discrete
radio arcs embedded in it. Although its radio power is lower (1.4x10^23 W/Hz)
than previously known, the diffuse emission may still be classified as a radio
mini-halo.


title: A Computational Model of Liver Iron Metabolism

abstract:
  Iron is essential for all known life due to its redox properties, however
these same properties can also lead to its toxicity in overload through the
production of reactive oxygen species. Robust systemic and cellular control are
required to maintain safe levels of iron and the liver seems to be where this
regulation is mainly located. Iron misregulation is implicated in many diseases
and as our understanding of iron metabolism improves the list of iron-related
disorders grows. Recent developments have resulted in greater knowledge of the
fate of iron in the body and have led to a detailed map of its metabolism,
however a quantitative understanding at the systems level of how its components
interact to produce tight regulation remains elusive.
  A mechanistic computational model of human liver iron metabolism, which
includes the core regulatory components, was constructed based on known
mechanisms of regulation and on their kinetic properties, obtained from several
publications. The model was then quantitatively validated by comparing its
results with previously published physiological data, and it is able to
reproduce multiple experimental findings. A time course simulation following an
oral dose of iron was compared to a clinical time course study and the
simulation was found to recreate the dynamics and time scale of the systems
response to iron challenge. A disease simulation of haemochromatosis was
created by altering a single reaction parameter that mimics a human
haemochromatosis gene (HFE) mutation. The simulation provides a quantitative
understanding of the liver iron overload that arises in this disease.
  This model supports and supplements understanding of the role of the liver as
an iron sensor and provides a framework for further modelling, including
simulations to identify valuable drug targets and design of experiments to
improve further our knowledge of this system.


title:
Statistical mechanics of Roskilde liquids: Configurational adiabats,
  specific heat contours and density dependence of the scaling exponent

abstract:
  We derive exact results for the rate of change of thermodynamic quantities,
in particular the configurational specific heat at constant volume, $C_V$,
along configurational adiabats (curves of constant excess entropy
$S_{\textrm{ex}}$). Such curves are designated isomorphs for so-called Roskilde
liquids, in view of the invariance of various structural and dynamical
quantities along them. Their slope in a double logarithmic representation of
the density-temperature phase diagram, $\gamma$ can be interpreted as one third
of an effective inverse power-law potential exponent. We show that in liquids
where $\gamma$ increases (decreases) with density, the contours of $C_V$ have
smaller (larger) slope than configurational adiabats. We clarify also the
connection between $\gamma$ and the pair potential. A fluctuation formula for
the slope of the $C_V$-contours is derived. The theoretical results are
supported with data from computer simulations of two systems, the Lennard-Jones
fluid and the Girifalco fluid. The sign of $d\gamma/d\rho$ is thus a third key
parameter in characterizing Roskilde liquids, after $\gamma$ and the
virial-potential energy correlation coefficient $R$. To go beyond isomorph
theory we compare invariance of a dynamical quantity, the self-diffusion
coefficient along adiabats and $C_V$-contours, finding it more invariant along
adiabats.


title:
Monopoles without magnetic charges: Finite energy monopole-antimonopole
  configurations in CP1 model and restricted QCD

abstract:
  We propose a new type of regular monopole-like field configuration in quantum
chromodynamics (QCD) and CP^1 model. The monopole configuration can be treated
as a monopole-antimonopole pair without localized magnetic charges. An exact
numeric solution for a simple monopole-antimonopole solution has been obtained
in CP^1 model with an appropriate potential term. We suppose that similar
monopole solutions may exist in effective theories of QCD and in the
electroweak standard model.


title: Nuclear beta decay with Lorentz violation

abstract:
  We consider the possibility of Lorentz-invariance violation in weak-decay
processes. We present a general approach that entails modifying the W-boson
propagator by adding a Lorentz-violating tensor to it. We describe the effects
of Lorentz violation on nuclear beta decay in this scenario. In particular we
show the expression for a first-forbidden transition with a spin change of two.
Using data from an old experiment on the rotational invariance of yttrium-90,
we derive several bounds on the Lorentz-violating parameters of the order of
10^(-6)-10^(-8).


title:
On Computer-Intensive Simulation and Estimation Methods for Rare Event
  Analysis in Epidemic Models

abstract:
  This article focuses, in the context of epidemic models, on rare events that
may possibly correspond to crisis situations from the perspective of Public
Health. In general, no close analytic form for their occurrence probabilities
is available and crude Monte-Carlo procedures fail. We show how recent
intensive computer simulation techniques, such as interacting branching
particle methods, can be used for estimation purposes, as well as for
generating model paths that correspond to realizations of such events.
Applications of these simulation-based methods to several epidemic models are
also considered and discussed thoroughly.


title:
Phase Behavior of Active Swimmers in Depletants: Molecular Dynamics and
  Integral Equation Theory

abstract:
  We study the structure and phase behavior of a binary mixture where one of
the components is self-propelling in nature. The inter-particle interactions in
the system were taken from the Asakura-Oosawa model, for colloid-polymer
mixtures, for which the phase diagram is known. In the current model version
the colloid particles were made active using the Vicsek model for
self-propelling particles. The resultant active system was studied by molecular
dynamics methods and integral equation theory. Both methods produce results
consistent with each other and demonstrate that the Vicsek model based activity
facilitates phase separation, thus broadening the coexistence region.


title: Rank 2 fusion rings are complete intersections

abstract:
  We give a non-constructive proof that fusion rings attached to a simple
complex Lie algebra of rank 2 are complete intersections.


title: Local stresses in the Janssen granular column

abstract:
  We study experimentally the distribution of local stresses in a granular
material confined inside a vertical cylinder. We use an image correlation
technique to measure the displacement field of the container induced by the
forces exerted by the grains on the inner wall. We describe an optimization
procedure based on the linear theory of elastic shells to deduce the
distribution of these forces from the measured displacement field. They
correspond to the stress field of the granular material close to the
container's inner wall. We first confirm the validity of Janssen's description
for various experiments, including the influence of the bead diameter and the
effect of an additional mass on top of the granular column. We then apply this
method to determine the stress field during the gravity-driven discharge of a
silo through an aperture.


title:
On the effective superpotential in the generic higher-derivative
  three-dimensional scalar superfield theory

abstract:
  We formulate a generic three-dimensional higher-derivative superfield theory
for self-interacting scalar superfield action. We consider the cases of real
and complex scalar superfields. For these theories, we explicitly calculate the
one-loop effective potential.


title:
Backhaul-Aware Interference Management in the Uplink of Wireless Small
  Cell Networks

abstract:
  The design of distributed mechanisms for interference management is one of
the key challenges in emerging wireless small cell networks whose backhaul is
capacity limited and heterogeneous (wired, wireless and a mix thereof). In this
paper, a novel, backhaul-aware approach to interference management in wireless
small cell networks is proposed. The proposed approach enables macrocell user
equipments (MUEs) to optimize their uplink performance, by exploiting the
presence of neighboring small cell base stations. The problem is formulated as
a noncooperative game among the MUEs that seek to optimize their delay-rate
tradeoff, given the conditions of both the radio access network and the --
possibly heterogeneous -- backhaul. To solve this game, a novel, distributed
learning algorithm is proposed using which the MUEs autonomously choose their
optimal uplink transmission strategies, given a limited amount of available
information. The convergence of the proposed algorithm is shown and its
properties are studied. Simulation results show that, under various types of
backhauls, the proposed approach yields significant performance gains, in terms
of both average throughput and delay for the MUEs, when compared to existing
benchmark algorithms.


title: Semiparametric stochastic volatility modelling using penalized splines

abstract:
  Stochastic volatility (SV) models mimic many of the stylized facts attributed
to time series of asset returns, while maintaining conceptual simplicity. The
commonly made assumption of conditionally normally distributed or
Student-t-distributed returns, given the volatility, has however been
questioned. In this manuscript, we introduce a novel maximum penalized
likelihood approach for estimating the conditional distribution in an SV model
in a nonparametric way, thus avoiding any potentially critical assumptions on
the shape. The considered framework exploits the strengths both of the powerful
hidden Markov model machinery and of penalized B-splines, and constitutes a
powerful and flexible alternative to recently developed Bayesian approaches to
semiparametric SV modelling. We demonstrate the feasibility of the approach in
a simulation study before outlining its potential in applications to three
series of returns on stocks and one series of stock index returns.


title:
Nonstandard Hausdorff dimension in $\mathbb{R}^n$ and an application to
  the Kakeya conjecture in $\mathbb{R}^3$

abstract:
  Through the use of a nonstandard version of Frostman's lemma, the notion of
Hausdorff dimension is formulated in nonstandard euclidean space of arbitrary
dimension. This allows for a nonstandard proof of the Kakeya conjecture in two
dimensions, which can then be extended to the three-dimensional case.


title:
Global cosmological dynamics for the scalar field representation of the
  modified Chaplygin gas

abstract:
  In this paper we investigate the global dynamics for the minimally coupled
scalar field representation of the modified Chaplygin gas in the context of
flat FLRW cosmology. The tool for doing this is a new set of bounded variables
that lead to a regular dynamical system. It is shown that the exact modified
Chaplygin gas perfect fluid solution appears as a straight line in the
associated phase plane. It is also shown that no other solutions stay close to
this solution during their entire temporal evolution, but that there exists an
open subset of solutions that stay arbitrarily close during an intermediate
time interval, and into the future in the case the scalar field potential
exhibits a global minimum.


title:
Coherent manipulation of spin qubits based on polyoxometalates: the case
  of the single ion magnet [GdW$_{30}$P$_5$O$_{110}$]$^{12-}$

abstract:
  Polyoxometalate single ion magnet [GdW$_{30}$P$_5$O$_{110}$]$^{12-}$ has been
studied by generalized Rabi oscillation experiments. It was possible to
increase the number of coherent rotations tenfold through matching the Rabi
frequency with the frequency of the proton. Achieving high coherence with
polyoxometalate chemistry, we show their excellent potential not only for the
storage of quantum information but even for the realization of quantum
algorithms.


title: Hierarchy of Fermion Masses in the 5D Standing Wave Braneworld

abstract:
  The localization problem for massive fermions in the 5D standing wave
braneworld is considered. The fermion generations on the brane are explained by
the existence of three nodes of standing waves in the bulk, where the left and
right modes of the 5D fermion are localized and Dirac-type couplings mixes
them. We show that in this model the structure of peaks of the left and right
fermion wavefunctions in extra dimension leads to the observed mass spectrum of
the up and down quark families.


title:
An Investigation of the Incidences of Repetitive Strain Injury among
  computer Users in Nigeria

abstract:
  Computer has been incorporated into day to day activities of almost every
field of human endeavour, offices to different shops. Therefore many people are
now working with computer for longer hours of time. There is no doubt that this
incorporation of computer has helped users a lot but it also brings problems to
the users. One of the problems is Repetitive Strain Injury (RSI). Five hundred
and thirty one (531) questionnaires were personally administered to different
categories of people that use computer in various works of life, ranging from
banking sector, civil service, educational sector, health sector to private
sector. The distribution cut across different professions. A statistical
analysis was conducted on the data obtained using frequency distribution,
Pearson Correlation and Linear Regression. The result obtained showed that
94.3% of the respondents suffered pain from one or more parts of the body.
86.8% of the respondents suffered from eyestrain, 63.9% suffered from low back
pain, 67.4% with wrist pain, 64.7% finger pain while the least suffered pain
was foot pain which only 19% responded positively to it. There are significant
relationships between duration of computer usage, type of chair used, type and
size of monitor used and the incidence of RSI. RSI modeled was formulated
through linear regression which showed that a unit change in computer will
result in corresponding 1.76 unit increases in RSI and a unit change in
ergonomic deficiency will also result in corresponding 0.66 increases in RSI.
The existence of RSI was established and it was discovered that the more time
spent on the computer system, the more the proximity of having strain or pain
in one or more part(s) of the body.


title: A Probabilistic Model for LCF

abstract:
  Fatigue life of components or test specimens often exhibit a significant
scatter. Furthermore, size effects have a non-negligible influence on fatigue
life of parts with different geometries. We present a new probabilistic model
for low-cycle fatigue (LCF) in the context of polycrystalline metal. The model
takes size effects and inhomogeneous strain fields into account by means of the
Poisson point process (PPP). This approach is based on the assumption of
independently occurring LCF cracks and the Coffin-Manson-Basquin (CMB)
equation. Within the probabilistic model, we give a new and more physical
interpretation of the CMB parameters which are in the original approach no
material parameters in a strict sense, as they depend on the specimen geometry.
Calibration and validation of the proposed model is performed using results of
strain controlled LCF tests of specimens with different surface areas. The test
specimens are made of the nickel base superalloy RENE 80.


title:
Affordable Virtual Reality System Architecture for Representation of
  Implicit Object Properties

abstract:
  A flexible, scalable and affordable virtual reality software system
architecture is proposed. This solution can be easily implemented on different
hardware configurations: on a single computer or on a computer cluster. The
architecture is aimed to be integrated in the workflow for solving engineering
tasks and oriented towards presenting implicit object properties through
multiple sensorial channels (visual, audio and haptic). Implicit properties
represent hidden object features (i.e. magnetization, radiation, humidity,
toxicity, etc.) which cannot be perceived by the observer through his or her
senses but require specialized equipment in order to expand the sensory ability
of the observer. Our approach extends the underlying general scene graph
structure incorporating additional effects nodes for implicit properties
representation.


title:
On the structure of numerical sparse semigroups and applications to
  Weierstrass points

abstract:
  In this work, we are concerned with the structure of sparse semigroups and
some applications of them to Weierstrass points. We manage to describe,
classify and find an upper bound for the genus of sparse semigroups. We also
study the realization of some sparse semigroups as Weierstrass semigroups. The
smoothness property of monomial curves associated to (hyper)ordinary semigroups
presented by Pinkham and Rim-Vitulli, and the results on double covering of
curves by Torres are crucial in this.


title:
Coupling driven exclusion and diffusion processes on parallel lanes:
  boundary induced phase transitions and boundary layers

abstract:
  We study a driven many particle system comprising of two identical lanes of
finite lengths. On one lane, particles hop diffusively with a bias in a
specific direction. On the other lane, particles hop in a specific direction
obeying mutual exclusion rule. In addition, the two lanes are connected with
each other through exchange of particles with certain rules. The system, at its
two ends, is in contact with particle reservoirs which maintain specific
particle densities at the two ends. In this paper, we study boundary-induced
phase transitions exhibited by this system and predict the phase diagram using
the technique of fixed point based boundary layer analysis. An interesting
manifestation of the interplay of two density variables associated with two
lanes is found in the shock phase in which the particle density profile across
the lane with unidirectional hopping shows a jump discontinuity (shock) from a
low- to a high-density region. The density profile on the diffusion-lane never
exhibits a shock. However, the shock in the other lane gives rise to a
discontinuity in the slope of the diffusion-lane density profile. We show how
an approximate solution for the slope can be obtained in the boundary layer
analysis framework.


title:
A Domain Decomposition Approach to Implementing Fault Slip in
  Finite-Element Models of Quasi-static and Dynamic Crustal Deformation

abstract:
  We employ a domain decomposition approach with Lagrange multipliers to
implement fault slip in a finite-element code, PyLith, for use in both
quasi-static and dynamic crustal deformation applications. This integrated
approach to solving both quasi-static and dynamic simulations leverages common
finite-element data structures and implementations of various boundary
conditions, discretization schemes, and bulk and fault rheologies. We have
developed a custom preconditioner for the Lagrange multiplier portion of the
system of equations that provides excellent scalability with problem size
compared to conventional additive Schwarz methods. We demonstrate application
of this approach using benchmarks for both quasi-static viscoelastic
deformation and dynamic spontaneous rupture propagation that verify the
numerical implementation in PyLith.


title:
Post-processing of Engineering Analysis Results for Visualization in VR
  Systems

abstract:
  The applicability of Virtual Reality for evaluating engineering analysis
results is beginning to receive increased appreciation in the last years. The
problem many engineers are still facing is how to import their model together
with the analysis results in a virtual reality environment for exploration and
results validation. In this paper we propose an algorithm for transforming
model data and results from finite element analysis (FEA) solving application
to a format easily interpretable by a virtual reality application. The
algorithm includes also steps for reducing the face-count of the resulting mesh
by eliminating faces from the inner part of the model in the cases when only
the surfaces of the model is analyzed. We also describe a possibility for
simultaneously assessing multiple analysis results relying on multimodal
results presentation by stimulating different senses of the operator.


title: Primitivity of prime countable-dimensional regular algebras

abstract:
  Let $k$ be a field and let $R$ be a countable dimensional prime von Neumann
regular $k$-algebra. We show that $R$ is primitive, answering a special case of
a question of Kaplansky.


title:
Ramsey-type results on singletons, co-singletons and monotone sequences
  in large collections of sets

abstract:
  We say that a 0-1 matrix $N$ of size $a\times b$ can be found in a collection
of sets $\mathcal{H}$ if we can find sets $H_{1}, H_{2}, \dots, H_{a}$ in
$\mathcal{H}$ and elements $e_1, e_2, \dots, e_b$ in $\cup_{H \in \mathcal{H}}
H$ such that $N$ is the incidence matrix of the sets $H_{1}, H_{2}, \dots,
H_{a}$ over the elements $e_1, e_2, \dots, e_b$. We prove the following
Ramsey-type result: for every $n\in \N$, there exists a number S(n) such that
in any collection of at least S(n) sets, one can find either the incidence
matrix of a collection of $n$ singletons, or its complementary matrix, or the
incidence matrix of a collection of $n$ sets completely ordered by inclusion.
We give several results of the same extremal set theoretical flavour. For some
of these, we give the exact value of the number of sets required.


title: Modelling group dynamic animal movement

abstract:
  Group dynamic movement is a fundamental aspect of many species' movements.
The need to adequately model individuals' interactions with other group members
has been recognised, particularly in order to differentiate the role of social
forces in individual movement from environmental factors. However, to date,
practical statistical methods which can include group dynamics in animal
movement models have been lacking. We consider a flexible modelling framework
that distinguishes a group-level model, describing the movement of the group's
centre, and an individual-level model, such that each individual makes its
movement decisions relative to the group centroid. The basic idea is framed
within the flexible class of hidden Markov models, extending previous work on
modelling animal movement by means of multi-state random walks. While in
simulation experiments parameter estimators exhibit some bias in non-ideal
scenarios, we show that generally the estimation of models of this type is both
feasible and ecologically informative. We illustrate the approach using real
movement data from 11 reindeer (Rangifer tarandus). Results indicate a
directional bias towards a group centroid for reindeer in an encamped state.
Though the attraction to the group centroid is relatively weak, our model
successfully captures group-influenced movement dynamics. Specifically, as
compared to a regular mixture of correlated random walks, the group dynamic
model more accurately predicts the non-diffusive behaviour of a cohesive mobile
group.


title:
A candidate supermassive binary black hole system in the brightest
  cluster galaxy of RBS 797

abstract:
  The radio source at the center of the cool core galaxy cluster RBS 797
(z=0.35) is known to exhibit a misalignment of its radio jets and lobes
observed at different VLA-scale, with the innermost kpc-scale jets being almost
orthogonal to the radio emission which extends for tens of kpc filling the
X-ray cavities. Gitti et al. suggested that this peculiar radio morphology may
indicate a recurrent activity of the central radio source, where the jet
orientation is changing between the different outbursts due to the effects of
supermassive binary black holes (SMBBHs). We aim at unveiling the nuclear radio
properties of the brightest cluster galaxy (BCG) in RBS 797 and at
investigating the presence of a SMBBH system in its center. We have performed
new high-resolution observations at 5 GHz with the European VLBI Network (EVN),
reaching an angular resolution of 9x5 mas^2 and a sensitivity of 36
microJy/beam. We report the EVN detection of two compact components in the BCG
of RBS 797, with a projected separation of ~77 pc. We can envisage two possible
scenarios: the two components are two different nuclei in a close binary
system, or they are the core and a knot of its jet. Both interpretations are
consistent with the presence of SMBBHs. Our re-analysis of VLA archival data
seems to favor the first scenario, as we detect two pairs of radio jets
misaligned by ~90 degrees on the same kpc scale emanating from the central
radio core. If the two outbursts are almost contemporaneous, this is clear
evidence of the presence of two active SMBHs, whose radio nuclei are unresolved
at VLA resolution. The nature of the double source detected by our EVN
observations in the BCG of RBS 797 can be established only by future sensitive,
multi-frequency VLBI observations. If confirmed, RBS 797 would be the first
SMBBH system observed at medium-high redshift at VLBI resolution. (abridged)


title: Calculating Time Lags From Unevenly-Sampled Light Curves

abstract:
  Timing techniques offer powerful tools to study dynamical astrophysical
phenomena. In the X-ray band, they offer the potential of probing accretion
physics down to the event horizon. Recent work has used frequency and
energy-dependent time lags as a tool for studying relativistic reverberation
around the black holes in several Seyfert galaxies. This was achieved thanks to
the evenly-sampled light curves obtained using XMM-Newton. Continuous-sampled
data is however not always available and standard Fourier techniques are not
applicable. Here, building on the work of Miller et al. (2010), we discuss and
use a maximum likelihood method to obtain frequency-dependent lags that takes
into account light curve gaps. Instead of calculating the lag directly, the
method estimates the most likely lag values at a particular frequency given two
observed light curves. We use Monte Carlo simulations to assess the method's
applicability, and use it to obtain lag-energy spectra from Suzaku data for two
objects, NGC 4151 and MCG-5-23-16, that had previously shown signatures of iron
K reverberation. The lags obtained are consistent with those calculated using
standard methods using XMM-Newton data.


title: Locally Nilpotent Groups and Hyperfinite Equivalence Relations

abstract:
  A long standing open problem in the theory of hyperfinite equivalence
relations asks if the orbit equivalence relation generated by a Borel action of
a countable amenable group is hyperfinite. In this paper we show that this
question has a positive answer when the acting group is locally nilpotent. This
extends previous results obtained by Gao-Jackson for abelian groups and by
Jackson-Kechris-Louveau for finitely generated nilpotent-by-finite groups. Our
proof is based on a mixture of coarse geometric properties of locally nilpotent
groups together with an adaptation of the Gao-Jackson machinery.


title:
Approximations of a complex Brownian motion with processes constructed
  from a process with independent increments

abstract:
  In this paper, we show an approximation in law of the complex Brownian motion
by processes constructed from a stochastic process with independent increments.
We give sufficient conditions for the characteristic function of the process
with independent increments that ensure the existence of the approximation. We
apply these results to L\'evy processes. Finally we extend this results to the
$m$-dimensional complex Brownian motion.


title:
Baumslag-Solitar groups, relative profinite completions and measure
  equivalence rigidity

abstract:
  We introduce an algebraic invariant for aperiodic inclusions of probability
measure preserving equivalence relations. We use this invariant to prove that
every stable orbit equivalence between free pmp actions of direct products of
non-amenable Baumslag-Solitar groups whose canonical subgroup acts
aperiodically forces the number of factors of the products to be the same and
the factors to be isomorphic after permutation. This generalises some of the
results obtained by Kida and moreover provides new measure equivalence rigidity
phenomena for Baumslag-Solitar groups. We also obtain a complete classification
of direct products of relative profinite completions of Baumslag-Solitar
groups, continuing recent work of Elder and Willis.


title: A presentation for the mapping class group of a nonorientable surface

abstract:
  Let $N_{g,n}$ denote the nonorientable surface of genus $g$ with $n$ boundary
components and $M(N_{g,n})$ its mapping class group. We obtain an explicit
finite presentation of $M(N_{g,n})$ for $n=0,1$ and all $g$ such that $g+n>3$.


title: Size of the Gribov region in curved spacetime

abstract:
  Recent work in the literature has argued that the joint effect of spacetime
curvature and the Gribov ambiguity may introduce further modifications to the
Green functions in the infrared. This paper focuses on a simple criterion for
studying the effect of spacetime curvature on the size of the Gribov region,
improving the accuracy of the previous analysis. It is shown that, depending on
the sign of the scalar and Riemann curvature, the Gribov horizon moves inward
or, instead, outward with respect to the case of flat spacetime. This is made
clear by two novel inequalities here derived for the first time.


title: Thue's 1914 paper: a translation

abstract:
  This paper includes notes to accompany a reading of Thue's 1914 paper
"Probleme uber Veranderungen von Zeichenreihen nach gegebenen Reglen", along
with a translation of that paper. Thue's 1914 paper is mainly famous for
proving an early example of an undecidable problem, cited prominently by Post.
However, Post's paper principally makes use of the definition of Thue systems,
described on the first two pages of Thue's paper, and does not depend on the
more specific results in the remainder of Thue's paper. A closer study of the
remaining parts of that paper highlight a number of important themes in the
history of computing: the transition from algebra to formal language theory,
the analysis of the "computational power" (in a pre-1936 sense) of rules, and
the development of algorithms to generate rule-sets.


title:
Evidence for topological band inversion of the phase change material
  Ge2Sb2Te5

abstract:
  We present an angle-resolved photoemission study of a ternary phase change
material, namely Ge2Sb2Te5, epitaxially grown on Si(111) in the metastable
cubic phase. The observed upper bulk valence band shows a minimum at Gamma-bar
being 0.3 eV below the Fermi level E_F and a circular Fermi contour around
Gamma-bar with a dispersing diameter of 0.27-0.36 Anstroms^-1. This is in
agreement with density functional theory calculations of the Petrov stacking
sequence in the cubic phase which exhibits a topological surface state. The
topologically trivial cubic KH stacking shows a valence band maximum at Gamma
in line with all previous calculations of the hexagonal stable phase exhibiting
the valence band maximum at Gamma for a trivial Z_2 topological invariant nu_0
and away from Gamma for non-trivial nu_0. Scanning tunneling spectroscopy
exhibits a band gap of 0.4 eV around E_F.


title:
Triangular Bose-Hubbard trimer as a minimal model for a superfluid
  circuit

abstract:
  The triangular Bose-Hubbard trimer is topologically the minimal model for a
BEC superfluid circuit. As a dynamical system of two coupled freedoms it has
mixed phase-space with chaotic dynamics. We employ a semiclassical perspective
to study triangular trimer physics beyond the conventional picture of the
superfluid-to-insulator transition. From the analysis of the Peierls-Nabarro
energy landscape, we deduce the various regimes in the $(\Omega,u)$
parameter-space, where $u$ is the interaction, and $\Omega$ is the superfluid
rotation-velocity. We thus characterize the superfluid-stability and chaoticity
of the many-body eigenstates throughout the Hilbert space.


title: What are symmetries of nonlinear PDEs and what are they themselves?

abstract:
  The general theory of (nonlinear) partial differential equations originated
by S. Lie had a significant development in the past 30-40 years. Now this
theory has solid foundations, a proper language, proper techniques and
problems, and a wide area of applications to physics, mechanics, to say nothing
about traditional mathematics. However, the results of this development are not
yet sufficiently known to a wide public. An informal introduction in a
historical perspective to this subject presented in this paper aims to give to
the reader an idea about this new area of mathematics and, possibly, to attract
new researchers to this, in our opinion, very promising area of modern
mathematics.