title:
Categories enriched over a quantaloid: Isbell adjunctions and Kan
  adjunctions

abstract:
  Each distributor between categories enriched over a small quantaloid Q gives
rise to two adjunctions between the categories of contravariant and covariant
presheaves, and hence to two monads. These two adjunctions are respectively
generalizations of Isbell adjunctions and Kan extensions in category theory. It
is proved that these two processes are functorial with infomorphisms playing as
morphisms between distributors; and that the free cocompletion functor of
Q-categories factors through both of these functors.


title: SSM: Inference for time series analysis with State Space Models

abstract:
  The main motivation behind the open source library SSM is to reduce the
technical friction that prevents modellers from sharing their work, quickly
iterating in crisis situations, and making their work directly usable by public
authorities to serve decision-making.


title: Topological quantum phase transition in Kane-Mele-Kondo lattice model

abstract:
  We systematically explore the ground-state phase diagram of the
Kane-Mele-Kondo lattice model on the honeycomb lattice, in particular, we focus
on its magnetic properties which has not been studied in the previous
publication[Feng, Dai, Chung, and Si, Phys. Rev. Lett. \textbf{111}, 016402
(2013)]. Beside the Kondo insulator found in that paper, two kinds of
antiferromagnetic spin-density-wave phases are identified. One is the normal
antiferromagnetic spin-density-wave state and the other is a nontrivial
topological antiferromagnetic spin-density-wave state with a quantized spin
Hall conductance and a helical edge-state. The quantum spin Hall insulator is
found to be absent since it is always unstable to antiferromagnetic
spin-density-wave states at least at the mean-field level in our model.
Furthermore, the transition between the two spin-density-wave phases are
topological quantum phase transition described by the three-dimensional quantum
electrodynamics, in which conduction electrons contribute to the low-energy
Dirac fermions while the spin-wave fluctuation of local spins gives rise to an
effective dynamic U(1) gauge-field. Such nontrivial transition shows radical
critical thermodynamic, transport and single-particle behaviors, which provide
a fingerprint for this transition. Additionally, the transition of
antiferromagnetic spin-density-wave states to the Kondo insulator is found to
be first-order. The introduction of two novel magnetic phases and their
topological quantum phase transition show rich and intrinsic physics involving
in the Kane-Mele-Kondo lattice model.


title: Detection by regular schemes in degree two

abstract:
  Using Lipman's results on resolution of two-dimensional singularities, we
provide a form of resolution of singularities in codimension two for reduced
quasi-excellent schemes. We deduce that operations of degree less than two on
algebraic cycles are characterised by their values on classes of regular
schemes. We provide several applications of this "detection principle", when
the base is an arbitrary regular excellent scheme: integrality of the Chern
character in codimension less than three, existence of weak forms of the second
and third Steenrod squares, Adem relation for the first Steenrod square,
commutativity and Poincar\'e duality for bivariant Chow groups in small
degrees. We also provide an application to the possible values of the Witt
indices of non-degenerate quadratic forms in characteristic two.


title: Probe Branes Thermalization in External Electric and Magnetic Fields

abstract:
  We study thermalization on rotating probe branes in AdS_5 x S^5 background in
the presence of constant external electric and magnetic fields. In the AdS/CFT
framework this corresponds to thermalization in the flavour sector in field
theory. The horizon appears on the worldvolume of the probe brane due to its
rotation in one of the sphere directions. For both electric and magnetic fields
the behaviour of the temperature is independent of the probe brane dimension.
We also study the open string metric and the fluctuations of the probe brane in
such a set-up. We show that the temperatures obtained from open string metric
and observed by the fluctuations are larger than the one calculated from the
induced metric.


title: Local probe of fractional edge states of S=1 Heisenberg spin chains

abstract:
  Spin chains are among the simplest physical systems in which
electron-electron interactions induce novel states of matter. Here we show that
the combination of atomic scale engineering and spectroscopic capabilities of
state of the art scanning tunnel microscopy enables probing the fractionalized
edge states of individual atomic scale S=1 spin chains. These edge states arise
from the topological order of the ground state in the Haldane phase. We also
show that the Haldane gap and the spin-spin correlation length can be measured
with the same technique.


title: Collective behaviour without collective order in wild swarms of midges

abstract:
  Collective behaviour is a widespread phenomenon in biology, cutting through a
huge span of scales, from cell colonies up to bird flocks and fish schools. The
most prominent trait of collective behaviour is the emergence of global order:
individuals synchronize their states, giving the stunning impression that the
group behaves as one. In many biological systems, though, it is unclear whether
global order is present. A paradigmatic case is that of insect swarms, whose
erratic movements seem to suggest that group formation is a mere epiphenomenon
of the independent interaction of each individual with an external landmark. In
these cases, whether or not the group behaves truly collectively is debated.
Here, we experimentally study swarms of midges in the field and measure how
much the change of direction of one midge affects that of other individuals. We
discover that, despite the lack of collective order, swarms display very strong
correlations, totally incompatible with models of noninteracting particles. We
find that correlation increases sharply with the swarm's density, indicating
that the interaction between midges is based on a metric perception mechanism.
By means of numerical simulations we demonstrate that such growing correlation
is typical of a system close to an ordering transition. Our findings suggest
that correlation, rather than order, is the true hallmark of collective
behaviour in biological systems.


title: Handlebody-knot invariants derived from unimodular Hopf algebras

abstract:
  A handlebody-knot is a handlebody embedded in the 3-sphere. We establish a
uniform method to construct invariants for handlebody-links. We introduce the
category $\mathcal{T}$ of handlebody-tangles and present it by generators and
relations. The result tells us that every functor on $\mathcal{T}$ that gives
rise to invariants is derived from what we call a quantum-commutative
quantum-symmetric algebra in the target category. The example of such algebras
of our main concern is finite-dimensional unimodular Hopf algebras. We
investigate how those Hopf algebras give rise to handlebody-knot invariants.


title: Geometrical and physical models of abrasion

abstract:
  We extend the geometrical theory presented in [5] for collisional and
frictional particle abrasion to include an independent physical equation for
the evolution of mass and volume. We introduce volume weight functions as
multipliers of the geometric equations and use these mutipliers to enforce
physical volume evolution in the unified equations. The latter predict, in
accordance with Sternberg's Law, exponential decay for volume evolution. We
describe both the PDE versions, which are generalisations of Bloore's equations
and their heuristic ODE approximations, called the box equations. The latter
are suitable for tracking the collective abrasion of large particle
populations. The mutual abrasion of identical particles, called the self-dual
ows, play a key role in explaining geological scenarios. We give stability
criteria for the self-dual ows in terms of the parameters of the physical
volume evolution models and show that under reasonable assumptions these
criteria can be met by physical systems. We also study a natural
generalisation, the unidirectional Bloore equation, covering the case of
unidirectional abrasion. We have previously shown that his equation admits
travelling front solutions with circular profiles. More generally, in three
dimensions, they are so-called linear or special Weingarten surfaces.

categories: physics.geo-ph cond-mat.soft math-ph math.MP


title:
True reentry of the glassy state in geometrically frustrated
  LiCr(1-x)Mn(x)O(2)

abstract:
  The development of spin glass like state in a geometrically frustrated (GF)
magnet is a matter of great debate. We investigated the effect of magnetic (Mn)
and nonmagnetic (Ga) doping at the Cr site of the layered GF antiferromagnetic
compound LiCrO2. 10% Ga doping at the Cr site does not invoke any metastability
typical of a glassy magnetic state. However, similar amount of Mn doping
certainly drives the system to a spin glass state which is particularly evident
from the relaxation, magnetic memory and heat capacity studies. The onset of
glassy state in 10% Mn doped sample is of reentrant type developing out of
higher temperature antiferromagnetic state. The spin glass state in the
Mn-doped sample shows a true reentry with the complete disappearance of the
antiferromagnetic phase below the spin glass transition. Mn doping at the Cr
site can invoke random ferromagnetic Cr-Mn bonds in the otherwise 120 degree
antiferromagnetic triangular lattice leading to the non-ergodic spin frozen
state. The lack of spin glass state on Ga doping indicates the importance of
random ferromagnetic/antiferromagnetic bonds for the glassy ground state in
LiCrO2. Spin glass state in GF system has been earlier observed even for small
non-magnetic disorder, and our result indicates that the issue is quite
nontrivial and depends strongly on the material system concerned.


title: Relativistic Frequency Synthesis of Light Fields

abstract:
  Waveform shaping and frequency synthesis based on waveform modulation is
ubiquitous in electronics, telecommunication technology, and optics. For
optical waveforms, the carrier frequency is on the order of several hundred
THz, while the modulation frequencies used in conventional devices like
electro- or acousto-optical modulators are orders of magnitude lower. As a
consequence, any new frequencies are typically very close to the fundamental.
The synthesis of new frequencies in the extreme ultraviolet (XUV), e.g. by
using relativistic oscillating mirrors, requires modulation frequencies in the
optical regime or even in the extreme ultraviolet. The latter has not been
proven possible to date. Here we demonstrate that individual strong harmonics
can indeed be generated by reflecting light off a plasma surface that
oscillates at XUV frequencies. The strong harmonics are explained by nonlinear
frequency mixing of near-infrared light and a laser-driven plasma oscillation
in the extreme ultra-violet mediated by a relativistic non-linearity.


title: A generalized back-door criterion

abstract:
  We generalize Pearl's back-door criterion for directed acyclic graphs (DAGs)
to more general types of graphs that describe Markov equivalence classes of
DAGs and/or allow for arbitrarily many hidden variables. We also give easily
checkable necessary and sufficient graphical criteria for the existence of a
set of variables that satisfies our generalized back-door criterion, when
considering a single intervention and a single outcome variable. Moreover, if
such a set exists, we provide an explicit set that fulfills the criterion. We
illustrate the results in several examples. R-code is available in the
R-package pcalg.


title: ASTROSAT: Some Key Science Prospects

abstract:
  ASTROSAT is an astronomy satellite designed for simultaneous multi-wavelength
studies in the Optical/UV and a broad X-ray energy range. With four X-ray
instruments and a pair of UV-Optical telescopes, ASTROSAT will provide
unprecendented opportunity for simultaneous multi-wavelength observations,
which is of immense value in study of highly variable sources, especially X-ray
binaries and Active Galactic Nuclei. The Large Area X-ray Proportional Counters
(LAXPC) of ASTROSAT, which has the largest effective area in the hard X-ray
band compared to all previous X-ray missions, will enable high time resolution
X-ray measurements in the 2-80 keV band with moderate energy resolution. Here
we give a brief summary of the payload characteristics of ASTROSAT and discuss
some of the main science topics that will be addressed with the LAXPC, and with
simultaneous observations with the UVIT telescopes, with particular emphasis on
X-ray binaries and compact objects. The possibility of aiding gravitational
wave experiments is also briefly mentioned.


title: Molecular simulation of nano-dispersed fluid phases

abstract:
  Fluid phase equilibria involving nano-dispersed phases, where at least one of
the coexisting phases is confined to a small volume, are investigated by
molecular dynamics simulation. Complementing previous studies on nanoscopic
droplets, simulation volumes containing a nanoscopic gas bubble surrounded by a
subsaturated liquid phase under tension, i.e. at negative pressure, are
conducted in the canonical ensemble. The boundary conditions are chosen such
that the phase equilibrium at the curved interface is thermodynamically stable.
Two distinct size-dependent effects are found: Curvature induces a
subsaturation of the system, leading to a smaller liquid density. For the gas
in the centre of the bubble, the small diameter has an additional obverse
effect, increasing its density. The curvature dependence of the surface tension
is discussed by evaluating average radial density profiles to obtain the excess
equimolar radius, which is found to be positive, corresponding to a negative
Tolman length.


title:
A sub-parsec resolution simulation of the Milky Way: Global structure of
  the ISM and properties of molecular clouds

abstract:
  We present a self-consistent hydrodynamical simulation of a Milky Way-like
galaxy, at the resolution of 0.05 pc. The model includes star formation and a
new implementation of stellar feedback through photo-ionization, radiative
pressure and supernovae. The simulation resolves the structure of the
interstellar medium at subparsec resolution for a few cloud lifetimes, and at
0.05 pc for about a cloud crossing time. Turbulence cascade and gravitation
from the kpc scales are de facto included in smaller structures like molecular
clouds. We show that the formation of a bar influences the dynamics of the
central ~100 pc by creating resonances. At larger radii, the spiral arms host
the formation of regularly spaced clouds: beads on a string and spurs. These
instabilities pump turbulent energy into the gas, generally in the supersonic
regime. Because of asymmetric drift, the supernovae explode outside of their
gaseous nursery, which diminishes the effect of feedback on the structure of
clouds. The evolution of clouds is thus mostly due to fragmentation and gas
consumption, regulated mainly by supersonic turbulence. The transition from
turbulence supported to self-gravitating gas is detected in the gas density
probability distribution function at ~2000 cm^-3. The power spectrum density
suggests that gravitation governs the hierarchical organisation of structures
from the galactic scale down to a few parsecs.


title:
The Scenario Approach for Stochastic Model Predictive Control with
  Bounds on Closed-Loop Constraint Violations

abstract:
  Many practical applications of control require that constraints on the inputs
and states of the system be respected, while optimizing some performance
criterion. In the presence of model uncertainties or disturbances, for many
control applications it suffices to keep the state constraints at least for a
prescribed share of the time, as e.g. in building climate control or load
mitigation for wind turbines. For such systems, a new control method of
Scenario-Based Model Predictive Control (SCMPC) is presented in this paper. It
optimizes the control inputs over a finite horizon, subject to robust
constraint satisfaction under a finite number of random scenarios of the
uncertainty and/or disturbances. While previous approaches have shown to be
conservative (i.e. to stay far below the specified rate of constraint
violations), the new method is the first to account for the special structure
of the MPC problem in order to significantly reduce the number of scenarios. In
combination with a new framework for interpreting the probabilistic constraints
as average-in-time, rather than pointwise-in-time, the conservatism is
eliminated. The presented method retains the essential advantages of SCMPC,
namely the reduced computational complexity and the handling of arbitrary
probability distributions. It also allows for adopting sample-and-remove
strategies, in order to trade performance against computational complexity.


title: Robotic Arm for Remote Surgery

abstract:
  Recent advances in telecommunications have enabled surgeons to operate
remotely on patients with the use of robotics. The investigation and testing of
remote surgery using a robotic arm is presented. The robotic arm is designed to
have four degrees of freedom that track the surgeon's x, y, z positions and the
rotation angle of the forearm {\theta}. The system comprises two main
subsystems viz. the detecting and actuating systems. The detection system uses
infrared light-emitting diodes, a retroreflective bracelet and two infrared
cameras which as a whole determine the coordinates of the surgeon's forearm.
The actuation system, or robotic arm, is based on a lead screw mechanism which
can obtain a maximum speed of 0.28 m/s with a 1.5 degree/step for the
end-effector. The infrared detection and encoder resolutions are below 0.6
mm/pixel and 0.4 mm respectively, which ensures the robotic arm can operate
precisely. The surgeon is able to monitor the patient with the use of a
graphical user interface on the display computer. The lead screw system is
modelled and compared to experimentation results. The system is controlled
using a simple proportional-integrator (PI) control scheme which is implemented
on a dSpace control unit. The control design results in a rise time of less
than 0.5 s, a steady-state error of less than 1 mm and settling time of less
than 1.4 s. The system accumulates, over an extended period of time, an error
of approximately 4 mm due to inertial effects of the robotic arm. The results
show promising system performance characteristics for a relatively inexpensive
solution to a relatively advanced application.


title: Optimal exponents in weighted estimates without examples

abstract:
  We present a general approach for proving the optimality of the exponents on
weighted estimates. We show that if an operator $T$ satisfies a bound like $$
\|T\|_{L^{p}(w)}\le c\, [w]^{\beta}_{A_p} \qquad w \in A_{p}, $$ then the
optimal lower bound for $\beta$ is closely related to the asymptotic behaviour
of the unweighted $L^p$ norm $\|T\|_{L^p(\mathbb{R}^n)}$ as $p$ goes to 1 and
$+\infty$, which is related to Yano's classical extrapolation theorem. By
combining these results with the known weighted inequalities, we derive the
sharpness of the exponents, without building any specific example, for a wide
class of operators including maximal-type, Calder\'on--Zygmund and fractional
operators. In particular, we obtain a lower bound for the best possible
exponent for Bochner-Riesz multipliers. We also present a new result concerning
a continuum family of maximal operators on the scale of logarithmic Orlicz
functions. Further, our method allows to consider in a unified way maximal
operators defined over very general Muckenhoupt bases.


title:
Single Plasmon Switching with n Quantum Dots System Coupled to
  One-Dimentional Waveguide

abstract:
  Switching of a single plasmon interacting with equally spaced quantum dots
coupled to one-dimensional surface plasmonic waveguide is investigated
theoretically via the real-space approach. We showed that the transmission and
reflection of a single plasmon can be switched on or off by dynamically tuning
and changing the number of the equal transition frequencies of the quantum
dots.


title: Some remarks on quasi-Hermitian operators

abstract:
  A quasi-Hermitian operator is an operator that is similar to its adjoint in
some sense, via a metric operator, i.e., a strictly positive self-adjoint
operator. Whereas those metric operators are in general assumed to be bounded,
we analyze the structure generated by unbounded metric operators in a Hilbert
space. Following our previous work, we introduce several generalizations of the
notion of similarity between operators. Then we explore systematically the
various types of quasi-Hermitian operators, bounded or not. Finally we discuss
their application in the so-called pseudo-Hermitian quantum mechanics.


title:
Robinson-Schensted-Knuth algorithm, jeu de taquin and Kerov-Vershik
  measures on infinite tableaux

abstract:
  We investigate Robinson-Schensted-Knuth algorithm (RSK) and
Sch\"utzenberger's jeu de taquin in the infinite setup. We show that the
recording tableau in RSK defines an isomorphism of the following two dynamical
systems: (i) a sequence of i.i.d. random letters equipped with Bernoulli shift,
and (ii) a random infinite Young tableau (with the distribution given by
Vershik-Kerov measure, corresponding to some Thoma character of the infinite
symmetric group) equipped with jeu de taquin transformation. As a special case
we recover the results on non-colliding random walks and multidimensional
Pitman transform.


title:
On the Optimality of Basis Transformations to Secure Entanglement
  Swapping Based QKD Protocols

abstract:
  In this article, we discuss the optimality of basis transformations as a
security measure for quantum key distribution protocols based on entanglement
swapping. To estimate the security, we focus on the information an adversary
obtains on the raw key bits from a generic version of a collective attack
strategy. In the scenario described in this article, the application of general
basis transformations serving as a counter measure by one or both legitimate
parties is analyzed. In this context, we show that the angles, which describe
these basis transformations can be optimized compared to the application of a
Hadamard operation, which is the standard basis transformation recurrently
found in literature. As a main result, we show that the adversary's information
can be reduced to an amount of approximately 0.20752 when using a single basis
transformation and to an amount of approximately 0.0548 when combining two
different basis transformations. This is less than half the information
compared to other protocols using a Hadamard operation and thus represents an
advantage regarding the security of entanglement swapping based protocols.


title:
On house renovation and coauthoring (with a little excursus on the Holy
  Grail of bibliometrics)

abstract:
  More than a paper, this is just a little divertissement about coauthoring,
the Hirsch h-index, and bibliometric evaluation in general. Without pretending
to yield any general conclusions, what I found rummaging through the physics
literature made me think quite a bit. I hope the same will happen to my
readers, even it they will likely be much less than 25, which is the audience
one of the greatest Italian writers (whom, is left to the reader to single out)
addresses to.


title:
Exciton-Plasmon Coupling Effects on the Nonlinear Optical Susceptibility
  of Hybrid Quantum Dot-Metallic Nanoparticle System

abstract:
  We have studied theoretically the exciton-plasmon coupling effects on the
third-order optical nonlinearity of a coherently coupled hybrid system of a
metal nanoparticle and a semiconductor quantum dot in the presence of a strong
control field with a weak probe field.


title:
Influence of Pulse width and Rabi frequency on the Population dynamics
  of three-level system in two-photon absorption process

abstract:
  We investigate the population dynamics of the three-level system in the
two-photon absorption (TPA) process, mainly focusing the influence of pulse
width and Rabi frequency on the population dynamics of the system. We observe
the dependency of the population with the Rabi frequency and the pulse width.
We also show that the arbitrary superposition state consisted in two states,
upper state and lower state, is possible by controlling the pulse width and
Rabi frequency. The results obtained can be used to the case of more complex
multilevel system and they can be valuable for coherent quantum control in
quantum information processing.


title:
$\mathbb Q$-bases of the N\'eron-Severi groups of certain elliptic
  surfaces

abstract:
  P. Stiller computed the Picard numbers of several families of elliptic
surfaces, the rank of the N\'eron-Severi groups of these surfaces. However he
did not give the generators of these groups. In this paper we give $\mathbb
Q$-bases of these groups explicitly. If these surfaces are rational, then we
also show that they are $\mathbb Z$-bases.


title: Asymptotically flat spacetimes in three-dimensional higher spin gravity

abstract:
  A consistent set of asymptotic conditions for higher spin gravity in three
dimensions is proposed in the case of vanishing cosmological constant. The
asymptotic symmetries are found to be spanned by a higher spin extension of the
BMS3 algebra with an appropriate central extension. It is also shown that our
results can be recovered from the ones recently found for asymptotically AdS3
spacetimes by virtue of a suitable gauge choice that allows to perform the
vanishing cosmological constant limit.


title: The Liouville property for groups acting on rooted trees

abstract:
  We show that on groups generated by bounded activity automata, every
symmetric, finitely supported probability measure has the Liouville property.
More generally we show this for every group of automorphisms of bounded type of
a rooted tree. For automaton groups, we also give a uniform upper bound for the
entropy of convolutions of every symmetric, finitely supported measure.


title: Online Tracking Parameter Adaptation based on Evaluation

abstract:
  Parameter tuning is a common issue for many tracking algorithms. In order to
solve this problem, this paper proposes an online parameter tuning to adapt a
tracking algorithm to various scene contexts. In an offline training phase,
this approach learns how to tune the tracker parameters to cope with different
contexts. In the online control phase, once the tracking quality is evaluated
as not good enough, the proposed approach computes the current context and
tunes the tracking parameters using the learned values. The experimental
results show that the proposed approach improves the performance of the
tracking algorithm and outperforms recent state of the art trackers. This paper
brings two contributions: (1) an online tracking evaluation, and (2) a method
to adapt online tracking parameters to scene contexts.


title: Dispersive analysis for $\eta\to \gamma\gamma^*$

abstract:
  A dispersion integral is derived that connects data on $\eta\to
\pi^+\pi^-\gamma$ to the $\eta\to \gamma\gamma^*$ transition form factor. A
detailed analysis of the uncertainties is provided. We find for the slope of
the $\eta$ transition form factor at the origin $b_\eta = (2.05
{}^{+0.22}_{-0.10})\, {\rm GeV}^{-2}$. Using an additional, plausible
assumption, one finds for the corresponding slope of the $\eta'$ transition
form factor, $b_{\eta'} = (1.58 {}^{+0.15}_{-0.08})\, {\rm GeV}^{-2}$. Both
values are consistent with all recent data, but differ from some previous
theoretical analyses.


title: Fast polynomial evaluation and composition

abstract:
  The library \emph{fast\_polynomial} for Sage compiles multivariate
polynomials for subsequent fast evaluation. Several evaluation schemes are
handled, such as H\"orner, divide and conquer and new ones can be added easily.
Notably, a new scheme is introduced that improves the classical divide and
conquer scheme when the number of terms is not a pure power of two. Natively,
the library handles polynomials over gmp big integers, boost intervals, python
numeric types. And any type that supports addition and multiplication can
extend the library thanks to the template design. Finally, the code is
parallelized for the divide and conquer schemes, and memory allocation is
localized and optimized for the different evaluation schemes. This extended
abstract presents the concepts behind the \emph{fast\_polynomial} library. The
sage package can be downloaded at
\url{http://trac.sagemath.org/sage_trac/ticket/13358}.


title: Confined packings of frictionless spheres and polyhedra

abstract:
  By means of numerical simulations, we study the influence of confinement on
three-dimensional random close packed (RCP) granular materials subject to
gravity. The effects of grain shape (spherical or polyhedral) and
polydispersity on this dependence are investigated. In agreement with a simple
geometrical model, the solid fraction is found to decrease linearly for
increasing confinement no matter the grain shape. This decrease remains valid
for bidisperse sphere packings although the gradient seems to reduce
significantly when the proportion of small particles reaches 40% by volume. The
aforementioned model is extended to capture the effect of the confinement on
the coordination number.


title:
An embedded method-of-lines approach to solving partial differential
  equations on surfaces

abstract:
  We introduce a method-of-lines formulation of the closest point method, a
numerical technique for solving partial differential equations (PDEs) defined
on surfaces. This is an embedding method, which uses an implicit representation
of the surface in a band containing the surface. We define a modified equation
in the band, obtained in a straightforward way from the original evolution PDE,
and show that the solutions of this equation are consistent with those of the
surface equation. The resulting system can then be solved with standard
implicit or explicit time-stepping schemes, and the solutions in the band can
be restricted to the surface. Our derivation generalizes existing formulations
of the closest point method and is amenable to standard convergence analysis.


title: Derived Hochschild functors over commutative adic algebras

abstract:
  Let $\k$ be a commutative ring, and let $(A,\mfrak{a})$ be an adic ring which
is a $\k$-algebra. We study complete and torsion versions of the derived
Hochschild homology and cohomology functors of $A$ over $\k$. To do this, we
first establish weak proregularity of certain ideals in flat base changes of
noetherian rings. Next, we develop a theory of DG-affine formal schemes,
extending the Greenlees-May duality and the MGM equivalence to this setting.
Finally, we define complete and torsion derived Hochschild homology and
cohomology functors in this setting, and show that if $\k$ is noetherian and
$(A,\mfrak{a})$ is essentially of finite type (in the adic sense) over $\k$,
then there are formulas to compute them that stay inside the noetherian
category. In the classical case, where $\k$ is a field, we deduce that
topological Hochschild cohomology and discrete Hochschild cohomology are
isomorphic.


title:
Systematic search for gamma-ray emitting molecular clouds in the
  vicinity of supernova remnants

abstract:
  Observations of very-high-energy (VHE) gamma-ray emission from supernova
remnants (SNR) established them as sources of accelerated particles up to
energies of 100 TeV. The dominant process - leptonic or hadronic - responsible
for the VHE emission is still not proven for most of the SNRs.
  Molecular clouds (MCs) in the vicinity of SNRs provide increased amount of
target material for accelerated particles escaping the SNRs, thus making MCs
potential gamma-ray sources. The predicted gamma-ray flux for MCs offset from
the SNR shock depends on the applied diffusion model for VHE particles and the
SNR and MC properties, which encounter large uncertainties. While the the
average galactic diffusion coefficient is estimated, the spatially resolved
propagation properties of VHE cosmic rays are unknown. gamma-ray emitting MCs
provide a unique possibility to derive new information on the propagation of
VHE particles through the ISM and on the acceleration of hadrons at SNRs.
  We present in this paper a strategy and first results of a systematic search
for TeV gamma-ray emitting MCs in the vicinity of SNRs in the galactic plane
region. Based on a theoretical model and current SNR and MC catalogues the
detectable parameter space (e.g. diffusion coefficient, SNR age) for current
Imaging Atmospheric Cherenkov Telescope systems (IACTs) is obtained. This
allows to identify potential gamma-ray emitting regions.


title:
Variation of the Bergman kernels under deformations of complex
  structures

abstract:
  Inspired by Berndtsson's work on the subharmonicity property of the Bergman
kernel, we give a local variation formula of the full Bergman kernels
associated to deformations of complex manifolds. In compact case, it follows
from the reproducing property of the Bergman kernel and the curvature formula
of the 0-th direct image sheaf. In general, following Schumacher's idea, we use
the Lie derivative to compute the variation. An equivalent criterion for the
triviality of holomorphic motions of planar domains in terms of the Bergman
kernel is given as an application.


title: Growth models on the Bethe lattice

abstract:
  I report on an extensive numerical investigation of various discrete growth
models describing equilibrium and nonequilibrium interfaces on a substrate of a
finite Bethe lattice. An unusual logarithmic scaling behavior is observed for
the nonequilibrium models describing the scaling structure of the infinite
dimensional limit of the models in the Kardar-Parisi-Zhang (KPZ) class. This
gives rise to the classification of different growing processes on the Bethe
lattice in terms of logarithmic scaling exponents which depend on both the
model and the coordination number of the underlying lattice. The equilibrium
growth model also exhibits a logarithmic temporal scaling but with an ordinary
power law scaling behavior with respect to the appropriately defined lattice
size. The results may imply that no finite upper critical dimension exists for
the KPZ equation.


title:
Anisotropic magnetic properties and crystal electric field studies on
  CePd$_2$Ge$_2$ single crystal

abstract:
  The anisotropic magnetic properties of the antiferromagnetic compound
CePd$_2$Ge$_2$, crystallizing in the tetragonal crystal structure have been
investigated in detail on a single crystal grown by Czochralski method. From
the electrical transport, magnetization and heat capacity data, the N\'{e}el
temperature is confirmed to be 5.1 K. Anisotropic behaviour of magnetization
and resistivity is observed along the two principal crystallographic directions
viz., [100] and [001]. The isothermal magnetization measured in the
magnetically ordered state at 2 K exhibits a spin re-orientation at 13.5 T for
field applied along [100] direction, whereas the magnetization was linear along
the [001] direction attaining a value of 0.94 $\mu_{\rm B}$/Ce at 14 T. The
reduced value of the magnetization is attributed to the crystalline electric
field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering
temperature is observed. After subtracting the phononic contribution, the jump
in the heat capacity amounts to 12.5 J/K mol which is the expected value for a
spin ${1}{2}$ system. From the CEF analysis of the magnetization data the
excited crystal field split energy levels were estimated to be at 120 K and 230
K respectively, which quantitatively explain the observed Schottky anomaly in
the heat capacity. A magnetic phase diagram has been constructed based on the
field dependence of magnetic susceptibility and the heat capacity data.


title:
Tuning inter-dot tunnel coupling of an etched graphene double quantum
  dot by adjacent metal gates

abstract:
  Graphene double quantum open the possibility to use charge or spin degrees of
freedom for storing and manipulating quantum information in this new electronic
material. However, impurities and edge disorders in etched graphene
nano-structures hinder the ability to control the inter-dot tunnel coupling,
tc,the most important property of the artificial molecule. Here we report
measurements of tc in an all-metal-gates-tuned graphene DQD. We find that tc
can be controlled continuously about a factor of four by employing a single
gate. Furthermore, tc, can be changed monotonically about another factor of
four as electrons are gate-pumped into the dot one by one. The results suggest
that the strength of tunnel coupling in etched DQDs can be varied in a rather
broad range and in a controllable manner, which improves the outlook to use
graphene as a base material for qubit applications.


title: Expander Chunked Codes

abstract:
  Chunked codes are efficient random linear network coding (RLNC) schemes with
low computational cost, where the input packets are encoded into small chunks
(i.e., subsets of the coded packets). During the network transmission, RLNC is
performed within each chunk. In this paper, we first introduce a simple
transfer matrix model to characterize the transmission of chunks, and derive
some basic properties of the model to facilitate the performance analysis. We
then focus on the design of overlapped chunked codes, a class of chunked codes
whose chunks are non-disjoint subsets of input packets, which are of special
interest since they can be encoded with negligible computational cost and in a
causal fashion. We propose expander chunked (EC) codes, the first class of
overlapped chunked codes that have an analyzable performance,where the
construction of the chunks makes use of regular graphs. Numerical and
simulation results show that in some practical settings, EC codes can achieve
rates within 91 to 97 percent of the optimum and outperform the
state-of-the-art overlapped chunked codes significantly.


title: Variational Integrators in Plasma Physics

abstract:
  Variational integrators are a special kind of geometric discretisation
methods applicable to any system of differential equations that obeys a
Lagrangian formulation. In this thesis, variational integrators are developed
for several important models of plasma physics: guiding centre dynamics
(particle dynamics), the Vlasov-Poisson system (kinetic theory), and ideal
magnetohydrodynamics (plasma fluid theory). Special attention is given to
physical conservation laws like conservation of energy and momentum.
  Most systems in plasma physics do not possess a Lagrangian formulation to
which the variational integrator methodology is directly applicable. Therefore
the theory is extended towards nonvariational differential equations by linking
it to Ibragimov's theory of integrating factors and adjoint equations. It
allows us to find a Lagrangian for all ordinary and partial differential
equations and systems thereof. Consequently, the applicability of variational
integrators is extended to a much larger family of systems than envisaged in
the original theory. This approach allows for the application of Noether's
theorem to analyse the conservation properties of the system, both at the
continuous and the discrete level.
  In numerical examples, the conservation properties of the derived schemes are
analysed. In case of guiding centre dynamics, momentum in the toroidal
direction of a tokamak is preserved exactly. The particle energy exhibits an
error, but the absolute value of this error stays constant during the entire
simulation. Therefore numerical dissipation is absent. In case of the kinetic
theory, the total number of particles, total linear momentum and total energy
are preserved exactly, i.e., up to machine accuracy. In case of
magnetohydrodynamics, the total energy, cross helicity and the divergence of
the magnetic field are preserved up to machine precision.

categories: math.NA math-ph math.MP physics.plasm-ph


title: Erd\H{o}s - Szekeres Theorem for Lines

abstract:
  According to the Erd\H{o}s-Szekeres theorem, for every $n$, a sufficiently
large set of points in general position in the plane contains $n$ in convex
position. In this note we investigate the line version of this result, that is,
we want to find $n$ lines in convex position in a sufficiently large set of
lines that are in general position. We prove almost matching upper and lower
bounds for the minimum size of the set of lines in general position that always
contains $n$ in convex position. This is quite unexpected, since in the case of
points, the best known bounds are very far from each other. We also establish
the dual versions of many variants and generalizations of the Erd\H os-Szekeres
theorem.


title:
New Optimization Approach Using Clustering-Based Parallel Genetic
  Algorithm

abstract:
  In many global Optimization Problems, it is required to evaluate a global
point (min or max) in large space that calculation effort is very high. In this
paper is presented new approach for optimization problem with subdivision
labeling method (SLM) but in this method for higher dimensional has high
calculation effort. Clustering-Based Parallel Genetic Algorithm (CBPGA) in
optimization problems is one of the solutions of this problem. That the initial
population is crossing points and subdividing in each step is according to
mutation. After labeling all of crossing points, selecting is according to
polytope that has complete label. In this method we propose an algorithm, based
on parallelization scheme using master-slave. SLM algorithm is implemented by
CBPGA and compared the experimental results. The numerical examples and
numerical results show that SLMCBPGA is improved speed up and efficiency.


title: Electrochemical polymerization of anilinium hydrochloride

abstract:
  Electropolymerization of anilinium hydrochloride was carried out on platinum
plate electrode in a protic medium by cyclic voltammetry. The effects on the
electrodeposition of the sweep rate, monomer concentration, pH of the medium
and electrode nature are discussed.


title: Tubular configurations: equivariant scanning and splitting

abstract:
  Replacing configurations of points by configurations of tubular
neighbourhoods (or discs) in a manifold, we are able to define a natural
scanning map that is equivariant under the action of the diffeomorphism group
of the manifold. We also construct the so-called power set map of configuration
spaces diffeomorphism equivariantly. Combining these two constructions yields
stable splittings in the sense of Snaith and generalisations thereof that are
equivariant. In particular one deduces stable splittings of homotopy orbit
spaces. As an application the homology injectivity is proved for diffeomorphism
of manifolds that fix an increasing number of points. Throughout we work with
configurations spaces with labels in a fibre bundle.


title:
Non-linear thermoelectric transport: A class of nano-devices for high
  efficiency and large power output

abstract:
  Molecular junctions and similar devices described by an energy dependent
transmission coefficient can have a high linear response thermoelectric figure
of merit. Since such devices are inherently non-linear, the full thermodynamic
efficiency valid for any temperature and chemical potential difference across
the leads is calculated. The general features in the energy dependence of the
tranmission function that lead to high efficiency and also high power output
are determined. It is shown that the device with the highest efficiency does
not necessarily lead to large power output. To illustrate this, we use a model
called the t-stub model representing tunneling through an energy level
connected to another energy level. Within this model both high efficiency and
high power output are achievable. Futhermore, by connecting many nanodevices it
is shown to be possible to scale up the power output without compromising
efficiency in an (exactly solvable) n-channel model even with tunneling between
the devices.


title: The ASTRI Mini-Array Science Case

abstract:
  ASTRI is a Flagship Project financed by the Italian Ministry of Education,
University and Research, and led by INAF, the Italian National Institute of
Astrophysics. Within this framework, INAF is currently developing an end-to-end
prototype of a Small Size Telescope in a dual-mirror configuration (SST-2M) for
the Cherenkov Telescope Array (CTA), scheduled to start data acquisition in
2014. Although the ASTRI SST-2M prototype is mainly a technological
demonstrator, it will perform scientific observations of the Crab Nebula, Mrk
421 and Mrk 501 at E>1 TeV. A remarkable improvement in terms of performance
could come from the operation, in 2016, of a SST-2M mini-array, composed of a
few SST-2M telescopes to be placed at final CTA Southern Site. The SST
mini-array will be able to study in great detail relatively bright sources (a
few x 10E-12 erg/cm2/s at 10 TeV) with angular resolution of a few arcmin and
energy resolution of about 10-15%. Thanks to the stereo approach, it will be
possible to verify the wide field of view (FoV) performance through the
detections of very high-energy showers with core located at a distance up to
500 m, to compare the mini-array performance with the Monte Carlo expectations
by means of deep observations of selected targets, and to perform the first CTA
science at the beginning of the mini-array operations. Prominent sources such
as extreme blazars, nearby well-known BL Lac objects and radio-galaxies,
galactic pulsar wind nebulae, supernovae remnants, micro-quasars, and the
Galactic Center can be observed in a previously unexplored energy range, in
order to investigate the electron acceleration and cooling, relativistic and
non relativistic shocks, the search for cosmic-ray (CR) Pevatrons, the study of
the CR propagation, and the impact of the extragalactic background light on the
spectra of the sources.


title: A scalable, fast and multichannel arbitrary waveform generator

abstract:
  This article reports on development of a multichannel arbitrary waveform
generator (MAWG), which simultaneously generates arbitrary voltage waveforms on
24 independent channels with a dynamic update rate of up to 25 Msps. A
real-time execution of a single waveform and/or sequence of multiple waveforms
in succession, with a user programmable arbitrary sequence order is provided
under the control of a stand-alone sequencer circuit implemented using an FPGA.
The device is operated using an internal clock and can be synced to other
devices by means of the TTL pulses. The device can be used for output voltages
in the range of up to +-9 V with a drift rate below +-10 uV/min and a maximum
deviation less than +-300 uVpp over a period of two hours.


title: Coherent radio emission from the cosmic ray air shower sudden death

abstract:
  We describe the characteristics of a new radio signal, generated by the
secondary electrons and positrons of the shower front when they reach the
ground. The very fast deceleration of these particles induces the coherent
emission of an electric field at frequencies smaller than 20 MHz. We show,
using simulations with the code SELFAS, that this sudden death signal should be
detectable with a simple dedicated antenna and could provide many informations
on the shower, in particular the nature of the primary cosmic ray. We also show
that this signal permits to estimate the atmospheric depth of maximum of
electric field emission X_{max}^{prod}, which occurs max well before the
atmospheric depth corresponding to the maximum number of secondary particles in
the shower (Xmax). Observation of this signal should be considered for the
design of future radio experiments.


title: Solving Traveling Salesman Problem by Marker Method

abstract:
  In this paper we use marker method and propose a new mutation operator that
selects the nearest neighbor among all near neighbors solving Traveling
Salesman Problem.


title: Models, Entropy and Information of Temporal Social Networks

abstract:
  Temporal social networks are characterized by {heterogeneous} duration of
contacts, which can either follow a power-law distribution, such as in
face-to-face interactions, or a Weibull distribution, such as in mobile-phone
communication. Here we model the dynamics of face-to-face interaction and
mobile phone communication by a reinforcement dynamics, which explains the data
observed in these different types of social interactions. We quantify the
information encoded in the dynamics of these networks by the entropy of
temporal networks. Finally, we show evidence that human dynamics is able to
modulate the information present in social network dynamics when it follows
circadian rhythms and when it is interfacing with a new technology such as the
mobile-phone communication technology.


title: The strong mixing and the selfdecomposability properties

abstract:
  It is proved that infinitesimal triangular arrays obtained from normalized
partial sums of strongly mixing (but not necessarily stationary) random
sequences, can produce as lilmits only selfdecomposable distributions.


title:
Evolution of the Relativistic Plasmoid-Chain in the Poynting-Dominated
  Plasma

abstract:
  In this paper, we investigate the evolution of the plasmoid-chain in a
Poynting-dominated plasma. We model the relativistic current sheet with cold
background plasma using the relativistic resistive magnetohydrodynamic
approximation, and solve its temporal evolution numerically. We perform various
calculations using different magnetization parameters of the background plasma
and different Lundquist numbers. Numerical results show that the initially
induced plasmoid triggers a secondary tearing instability, which gradually
fills the current sheet with plasmoids, as has also been observed in the
non-relativistic case. We find the plasmoid-chain greatly enhances the
reconnection rate, which becomes independent of the Lundquist number, when this
exceeds a critical value. In addition, we show the distribution of plasmoid
size becomes a power law. Since magnetic reconnection is expected to play an
important role in various high energy astrophysical phenomena, our results can
be used for explaining the physical mechanism of them.

categories: astro-ph.HE astro-ph.EP astro-ph.SR physics.plasm-ph


title: Profinite iterated monodromy groups arising from quadratic polynomials

abstract:
  We study in detail the profinite group G arising as geometric \'etale
iterated monodromy group of an arbitrary quadratic polynomial over a field of
characteristic different from two. This is a self-similar closed subgroup of
the group of automorphisms of a regular rooted binary tree. (When the base
field is \C it is the closure of the finitely generated iterated monodromy
group for the usual topology which is also often studied.) Among other things
we prove that the conjugacy class and hence the isomorphism class of G depends
only on the combinatorial type of the post-critical orbit of the polynomial.
  We represent a chosen instance of G by explicit recursively defined
generators. The uniqueness up to conjugacy depends on a certain semirigidity
property, which ensures that arbitrary conjugates of these generators under the
automorphism group of the tree always generate a subgroup that is conjugate to
G. We determine the Hausdorff dimension, the maximal abelian factor group, and
the normalizer of G using further explicit generators. The description of the
normalizer is then used to describe the arithmetic \'etale iterated monodromy
group of the quadratic polynomial.
  The methods used are purely group theoretical and do not involve fundamental
groups over \C at all.


title: Sub-Dividing Genetic Method for Optimization Problems

abstract:
  Nowadays, optimization problem have more application in all major but they
have problem in computation. Computation global point in continuous functions
have high calculation and this became clearer in large space .In this paper, we
proposed Sub- Dividing Genetic Method(SGM) that have less computation than
other method for achieving global points . This method userotation mutation and
crossover based sub-division method that sub diving method is used for minimize
search space and rotation mutation with crossover is used for finding global
optimal points. In experimental, SGM algorithm is implemented on De Jong
function. The numerical examples show that SGM is performed more optimal than
other methods such as Grefensstette, Random Value, and PNG.


title: Ultracold neutron depolarization in magnetic bottles

abstract:
  We analyze the depolarization of ultracold neutrons confined in a magnetic
field configuration similar to those used in existing or proposed
magneto-gravitational storage experiments aiming at a precise measurement of
the neutron lifetime. We use an extension of the semi-classical Majorana
approach as well as an approximate quantum mechanical analysis, both pioneered
by Walstrom et al. [Nucl. Instr. Meth. Phys. Res. A 599, 82 (2009)]. In
contrast with this previous work we do not restrict the analysis to purely
vertical modes of neutron motion. The lateral motion is shown to cause the
predominant depolarization loss in a magnetic storage trap. The system studied
also allowed us to estimate the depolarization loss suffered by ultracold
neutrons totally reflected on a non-magnetic mirror immersed in a magnetic
field. This problem is of preeminent importance in polarized neutron decay
studies such as the measurement of the asymmetry parameter A using ultracold
neutrons, and it may limit the efficiency of ultracold neutron polarizers based
on passage through a high magnetic field.


title:
Stabilizing Spin Coherence Through Environmental Entanglement in
  Strongly Dissipative Quantum Systems

abstract:
  The key feature of a quantum spin coupled to a harmonic bath---a model
dissipative quantum system---is competition between oscillator potential energy
and spin tunneling rate. We show that these opposing tendencies cause
environmental entanglement through superpositions of adiabatic and
antiadiabatic oscillator states, which then stabilizes the spin coherence
against strong dissipation. This insight motivates a fast-converging
variational coherent-state expansion for the many-body ground state of the
spin-boson model, which we substantiate via numerical quantum tomography.


title: Role of Magnetic Interaction in Dense Plasma

abstract:
  Quasiparticle excitations and associated phenomena of energy and momentum
transfer rates have been calculated in terms of the drag and the diffusion
coefficients exposing clearly the dominance of the magnetic interaction over
its electric counterpart. The results have been compared with the finite
temperature results highlighting the similarities and dissimilarities in the
two extreme regimes of temperature and density. Non-Fermi-liquid behavior of
various physical quantities like neutrino mean free path and thermal relaxation
time due to the inclusion of magnetic interaction has clearly been revealed.
All the results presented in the current review are pertinent to the degenerate
and ultradegenerate plasma.


title: Understanding the B->K*mu+mu- Anomaly

abstract:
  We present a global analysis of the B->K*(->K pi)mu+mu- decay using the
recent LHCb measurements of the primary observables P_{1,2} and P'_{4,5,6,8}.
Some of them exhibit large deviations with respect to the SM predictions. We
explain the observed pattern of deviations through a large New Physics
contribution to the Wilson coefficient of the semileptonic operator O9. This
contribution has an opposite sign to the SM one, i.e., reduces the size of this
coefficient significantly. A good description of data is achieved by allowing
for New Physics contributions to the Wilson coefficients C7 and C9 only. We
find a 4.5 sigma deviation with respect to the SM prediction, combining the
large-recoil B->K*(->K pi)mu+mu- observables with other radiative processes.
Once low-recoil observables are included the significance gets reduced to 3.9
sigma. We have tested different sources of systematics, none of them modifying
our conclusions significantly. Finally, we propose additional ways of measuring
the primary observables through new foldings.


title:
Using a Dynamic Neural Field Model to Explore a Direct Collicular
  Inhibition Account of Inhibition of Return

abstract:
  When the interval between a transient ash of light (a "cue") and a second
visual response signal (a "target") exceeds at least 200ms, responding is
slowest in the direction indicated by the first signal. This phenomenon is
commonly referred to as inhibition of return (IOR). The dynamic neural field
model (DNF) has proven to have broad explanatory power for IOR, effectively
capturing many empirical results. Previous work has used a short-term
depression (STD) implementation of IOR, but this approach fails to explain many
behavioral phenomena observed in the literature. Here, we explore a variant
model of IOR involving a combination of STD and delayed direct collicular
inhibition. We demonstrate that this hybrid model can better reproduce
established behavioural results. We use the results of this model to propose
several experiments that would yield particularly valuable insight into the
nature of the neurophysiological mechanisms underlying IOR.


title: An Evaluation of Caching Policies for Memento TimeMaps

abstract:
  As defined by the Memento Framework, TimeMaps are ma-chine-readable lists of
time-specific copies -- called "mementos" -- of an archived original resource.
In theory, as an archive acquires additional mementos over time, a TimeMap
should be monotonically increasing. However, there are reasons why the number
of mementos in a TimeMap would decrease, for example: archival redaction of
some or all of the mementos, archival restructuring, and transient errors on
the part of one or more archives. We study TimeMaps for 4,000 original
resources over a three month period, note their change patterns, and develop a
caching algorithm for TimeMaps suitable for a reverse proxy in front of a
Memento aggregator. We show that TimeMap cardinality is constant or
monotonically increasing for 80.2% of all TimeMap downloads observed in the
observation period. The goal of the caching algorithm is to exploit the ideally
monotonically increasing nature of TimeMaps and not cache responses with fewer
mementos than the already cached TimeMap. This new caching algorithm uses
conditional cache replacement and a Time To Live (TTL) value to ensure the user
has access to the most complete TimeMap available. Based on our empirical data,
a TTL of 15 days will minimize the number of mementos missed by users, and
minimize the load on archives contributing to TimeMaps.


title: The Realizability of Curves in a Tropical Plane

abstract:
  Let E be a plane in an algebraic torus over an algebraically closed field.
Given a balanced 1-dimensional fan C in the tropicalization of E, i.e. in the
Bergman fan of the corresponding matroid, we give a complete algorithmic answer
to the question whether or not C can be realized as the tropicalization of an
algebraic curve contained in E. Moreover, in the case of realizability the
algorithm also determines the dimension of the moduli space of all algebraic
curves in E tropicalizing to C, a concrete simple example of such a curve, and
whether C can also be realized by an irreducible algebraic curve in E. In the
first important case when E is a general plane in a 3-dimensional torus we also
use our algorithm to prove some general criteria for C that imply its
realizability resp. non-realizability. They include and generalize the main
known obstructions by Brugalle-Shaw and Bogart-Katz coming from tropical
intersection theory.


title:
A search for an additional neutrino mass eigenstate in 2 to 100 eV
  region from "Troitsk nu-mass" data - detailed analysis

abstract:
  In this paper we present the details of our previously published results for
a search for an additional neutrino mass state in $\beta$-electron spectrum
from the Troitsk nu-mass experiment. Here we present steps of the analysis,
show a set of likelihood functions obtained for each additional heavy mass
value. We demonstrate how systematic errors were estimated. We also compare our
results with those published recently for a similar analysis for Mainz data and
try to explain why there is a factor of 2-3 difference in the sensitivity for
an additional heavy mass.


title:
Asymptotic behaviour of the relativistic Boltzmann equation in the
  Robertson-Walker spacetime

abstract:
  In this paper, we study the relativistic Boltzmann equation in the spatially
flat Robertson-Walker spacetime. For a certain class of scattering kernels,
global existence of classical solutions is proved. We use the standard method
of Illner and Shinbrot for the global existence and apply the splitting
technique of Guo and Strain for the regularity of solutions. The main interest
of this paper is to study the evolution of matter distribution, rather than the
evolution of spacetime. We obtain the asymptotic behaviour of solutions and
will understand how the expansion of the universe affects the evolution of
matter distribution.


title:
Extended calibration range for prompt photon emission in ion beam
  irradiation

abstract:
  Monitoring the dose delivered during proton and carbon ion therapy is still a
matter of research. Among the possible solutions, several exploit the
measurement of the single photon emission from nuclear decays induced by the
irradiation. To fully characterize such emission the detectors need
development, since the energy spectrum spans the range above the MeV that is
not traditionally used in medical applications. On the other hand, a deeper
understanding of the reactions involving gamma production is needed in order to
improve the physic models of Monte Carlo codes, relevant for an accurate
prediction of the prompt-gamma energy spectrum.This paper describes a
calibration technique tailored for the range of energy of interest and
reanalyzes the data of the interaction of a 80MeV/u fully stripped carbon ion
beam with a Poly-methyl methacrylate target. By adopting the FLUKA simulation
with the appropriate calibration and resolution a significant improvement in
the agreement between data and simulation is reported.


title:
Some new trace formulas of tensors with applications in spectral
  hypergraph theory

abstract:
  We give some graph theoretical formulas for the trace $Tr_k(\mathbb {T})$ of
a tensor $\mathbb {T}$ which do not involve the differential operators and
auxiliary matrix. As applications of these trace formulas in the study of the
spectra of uniform hypergraphs, we give a characterization (in terms of the
traces of the adjacency tensors) of the $k$-uniform hypergraphs whose spectra
are $k$-symmetric, thus give an answer to a question raised in [3]. We
generalize the results in [3, Theorem 4.2] and [5, Proposition 3.1] about the
$k$-symmetry of the spectrum of a $k$-uniform hypergraph, and answer a question
in [5] about the relation between the Laplacian and signless Laplacian spectra
of a $k$-uniform hypergraph when $k$ is odd. We also give a simplified proof of
an expression for $Tr_2(\mathbb {T})$ and discuss the expression for
$Tr_3(\mathbb {T})$.


title: A study of parameters affecting visual saliency assessment

abstract:
  Since the early 2000s, computational visual saliency has been a very active
research area. Each year, more and more new models are published in the main
computer vision conferences. Nowadays, one of the big challenges is to find a
way to fairly evaluate all of these models. In this paper, a new framework is
proposed to assess models of visual saliency. This evaluation is divided into
three experiments leading to the proposition of a new evaluation framework.
Each experiment is based on a basic question: 1) there are two ground truths
for saliency evaluation: what are the differences between eye fixations and
manually segmented salient regions?, 2) the properties of the salient regions:
for example, do large, medium and small salient regions present different
difficulties for saliency models? and 3) the metrics used to assess saliency
models: what advantages would there be to mix them with PCA? Statistical
analysis is used here to answer each of these three questions.


title: Cubic Thue inequalities with positive discriminant

abstract:
  We will give an explicit upper bound for the number of solutions to cubic
inequality |F(x, y)| \leq h, where F(x, y) is a cubic binary form with integer
coefficients and positive discriminant D. Our upper bound is independent of h,
provided that h is smaller than D^{1/4}.


title:
Visual saliency estimation by integrating features using multiple kernel
  learning

abstract:
  In the last few decades, significant achievements have been attained in
predicting where humans look at images through different computational models.
However, how to determine contributions of different visual features to overall
saliency still remains an open problem. To overcome this issue, a recent class
of models formulates saliency estimation as a supervised learning problem and
accordingly apply machine learning techniques. In this paper, we also address
this challenging problem and propose to use multiple kernel learning (MKL) to
combine information coming from different feature dimensions and to perform
integration at an intermediate level. Besides, we suggest to use responses of a
recently proposed filterbank of object detectors, known as Object-Bank, as
additional semantic high-level features. Here we show that our MKL-based
framework together with the proposed object-specific features provide
state-of-the-art performance as compared to SVM or AdaBoost-based saliency
models.


title: Universal orderability of Legendrian isotopy classes

abstract:
  It is shown that non-negative Legendrian isotopy defines a partial order on
the universal cover of the Legendrian isotopy class of the fibre of the
spherical cotangent bundle of any manifold. This result is applied to Lorentz
geometry in the spirit of the authors' earlier work on the Legendrian Low
conjecture.


title: Dynamics of wave fluctuations in the homogeneous Yang-Mills condensate

abstract:
  In the present work, the Yang-Mills (YM) quantum-wave excitations of the
classical homogeneous YM condensate have been studied in quasi-classical
approximation. The formalism is initially formulated in the Hamilton gauge and
is based upon canonical quantisation in the Heisenberg representation. This
canonical framework is then extended and related to YM dynamics in arbitrary
gauge and symmetry group containing at least one $SU(2)$ subgroup. Such generic
properties of the interacting YM system as excitation of longitudinal wave
modes and energy balance between the evolving YM condensate and waves have been
established. In order to prove these findings, the canonical quasi-classical YM
system "waves + condensate" in the pure simplest $SU(2)$ gauge theory has been
thoroughly analysed numerically in the linear and next-to-linear approximations
in the limit of small wave amplitudes. The effective gluon mass dynamically
generated by wave self-interactions in the gluon plasma has been derived. A
complete set of equations of motion for the YM "condensate + waves" system
accounting for second- and third-order interactions between the waves has been
obtained. In the next-to-linear approximation in waves we have found that due
to interactions between the YM waves and the YM condensate, the latter looses
its energy leading to the growth of amplitudes of the YM wave modes. A similar
effect has been found in the maximally-supersymmetric ${\cal N}=4$ Yang-Mills
theory as well as in two-condensate $SU(4)$ model. Possible implications of
these findings to Cosmology and gluon plasma physics have been discussed.


title:
Tensor renormalization of quantum many-body systems using projected
  entangled simplex states

abstract:
  We propose a new class of tensor-network states, which we name projected
entangled simplex states (PESS), for studying the ground-state properties of
quantum lattice models. These states extend the pair-correlation basis of
projected entangled pair states (PEPS) to a simplex. PESS are an exact
representation of the simplex solid states and provide an efficient trial wave
function that satisfies the area law of entanglement entropy. We introduce a
simple update method for evaluating the PESS wave function based on
imaginary-time evolution and the higher-order singular-value decomposition of
tensors. By applying this method to the spin-1/2 antiferromagnetic Heisenberg
model on the kagome lattice, we obtain accurate and systematic results for the
ground-state energy, which approach the lowest upper bounds yet estimated for
this quantity.


title: Dimension Reduction via Colour Refinement

abstract:
  Colour refinement is a basic algorithmic routine for graph isomorphism
testing, appearing as a subroutine in almost all practical isomorphism solvers.
It partitions the vertices of a graph into "colour classes" in such a way that
all vertices in the same colour class have the same number of neighbours in
every colour class. Tinhofer (Disc. App. Math., 1991), Ramana, Scheinerman, and
Ullman (Disc. Math., 1994) and Godsil (Lin. Alg. and its App., 1997)
established a tight correspondence between colour refinement and fractional
isomorphisms of graphs, which are solutions to the LP relaxation of a natural
ILP formulation of graph isomorphism.
  We introduce a version of colour refinement for matrices and extend existing
quasilinear algorithms for computing the colour classes. Then we generalise the
correspondence between colour refinement and fractional automorphisms and
develop a theory of fractional automorphisms and isomorphisms of matrices.
  We apply our results to reduce the dimensions of systems of linear equations
and linear programs. Specifically, we show that any given LP L can efficiently
be transformed into a (potentially) smaller LP L' whose number of variables and
constraints is the number of colour classes of the colour refinement algorithm,
applied to a matrix associated with the LP. The transformation is such that we
can easily (by a linear mapping) map both feasible and optimal solutions back
and forth between the two LPs. We demonstrate empirically that colour
refinement can indeed greatly reduce the cost of solving linear programs.


title:
Residual component analysis of hyperspectral images -- Application to
  joint nonlinear unmixing and nonlinearity detection

abstract:
  This paper presents a nonlinear mixing model for joint hyperspectral image
unmixing and nonlinearity detection. The proposed model assumes that the pixel
reflectances are linear combinations of known pure spectral components
corrupted by an additional nonlinear term, affecting the endmembers and
contaminated by an additive Gaussian noise. A Markov random field is considered
for nonlinearity detection based on the spatial structure of the nonlinear
terms. The observed image is segmented into regions where nonlinear terms, if
present, share similar statistical properties. A Bayesian algorithm is proposed
to estimate the parameters involved in the model yielding a joint nonlinear
unmixing and nonlinearity detection algorithm. The performance of the proposed
strategy is first evaluated on synthetic data. Simulations conducted with real
data show the accuracy of the proposed unmixing and nonlinearity detection
strategy for the analysis of hyperspectral images.


title: Breaking entanglement-breaking by classical correlations

abstract:
  The inevitable interaction between quantum systems and environment induces
effects of decoherence which may be so strong as to destroy any initial
entanglement between the systems, a phenomenon known as "entanglement
breaking". Here we show the simplest examples where the combination of two
entanglement-breaking channels into a joint correlated-noise environment
reactivates the distribution of entanglement, with classes of entangled states
which are perfectly transmitted from a middle station (Charlie) to two remote
stations (Alice and Bob). Surprisingly, this reactivation is induced by the
presence of purely-classical correlations in the joint environment, whose state
is separable with zero discord. This paradoxical effect is proven for quantum
systems with Hilbert spaces of any dimension, both finite and infinite.


title: Mulitbeam GPU Transient Pipeline for the Medicina BEST-2 Array

abstract:
  Radio transient discovery using next generation radio telescopes will pose
several digital signal processing and data transfer challenges, requiring
specialized high-performance backends. Several accelerator technologies are
being considered as prototyping platforms, including Graphics Processing Units
(GPUs). In this paper we present a real-time pipeline prototype capable of
processing multiple beams concurrently, performing Radio Frequency Interference
(RFI) rejection through thresholding, correcting for the delay in signal
arrival times across the frequency band using brute-force dedispersion, event
detection and clustering, and finally candidate filtering, with the capability
of persisting data buffers containing interesting signals to disk. This setup
was deployed at the BEST-2 SKA pathfinder in Medicina, Italy, where several
benchmarks and test observations of astrophysical transients were conducted.
These tests show that on the deployed hardware eight 20MHz beams can be
processed simultaneously for $\sim$640 Dispersion Measure (DM) values.
Furthermore, the clustering and candidate filtering algorithms employed prove
to be good candidates for online event detection techniques. The number of
beams which can be processed increases proportionally to the number of servers
deployed and number of GPUs, making it a viable architecture for current and
future radio telescopes.


title: Latest Progress on the QUBIC Instrument

abstract:
  QUBIC is a unique instrument that crosses the barriers between classical
imaging architectures and interferometry taking advantage from both for high
sensitivity and systematics mitigation. The scientific target is the detection
of the primordial gravitational waves imprint on the Cosmic Microwave
Background which are the proof of inflation, holy grail of modern cosmology. In
this paper, we show the latest advances in the development of the architecture
and the sub-systems of the first module of this instrument to be deployed in
Dome Charlie Concordia base - Antarctica in 2015.


title: Is Bottom-Up Attention Useful for Scene Recognition?

abstract:
  The human visual system employs a selective attention mechanism to understand
the visual world in an eficient manner. In this paper, we show how
computational models of this mechanism can be exploited for the computer vision
application of scene recognition. First, we consider saliency weighting and
saliency pruning, and provide a comparison of the performance of different
attention models in these approaches in terms of classification accuracy.
Pruning can achieve a high degree of computational savings without
significantly sacrificing classification accuracy. In saliency weighting,
however, we found that classification performance does not improve. In
addition, we present a new method to incorporate salient and non-salient
regions for improved classification accuracy. We treat the salient and
non-salient regions separately and combine them using Multiple Kernel Learning.
We evaluate our approach using the UIUC sports dataset and find that with a
small training size, our method improves upon the classification accuracy of
the baseline bag of features approach.


title:
Fourier analysis on finite groups and the Lov\'asz theta-number of
  Cayley graphs

abstract:
  We apply Fourier analysis on finite groups to obtain simplified formulations
for the Lov\'asz theta-number of a Cayley graph. We put these formulations to
use by checking a few cases of a conjecture of Ellis, Friedgut, and Pilpel made
in a recent article proving a version of the Erd\H{o}s-Ko-Rado theorem for
$k$-intersecting families of permutations. We also introduce a $q$-analog of
the notion of $k$-intersecting families of permutations, and we verify a few
cases of the corresponding Erd\H{o}s-Ko-Rado assertion by computer.


title: The displaced disks problem via symplectic topology

abstract:
  We prove that a $C^0$--small area preserving homeomorphism of a closed
surface with vanishing mass flow can not displace a topological disk of large
area. This resolves the displaced disks problem posed by F. B\'eguin, S.
Crovisier, and F. Le Roux.


title: The Phase Synchronized State of Oriented Active Fluids

abstract:
  We present a theory for self-driven fluids, such as motorized cytoskeletal
extracts or bacterial suspensions, that takes into account the underlying
periodic duty cycle carried by the active particles of which the system is
composed. We show that the fluid can enter a state in which the constituent
elements synchronize their phases. This spontaneous breaking of
time-translation invariance gives rise to flow instabilities distinct from
those arising in phase-incoherent active matter.


title: The spatial sign covariance matrix with unknown location

abstract:
  The consistency and asymptotic normality of the spatial sign covariance
matrix with unknown location are shown. Simulations illustrate the different
asymptotic behavior when using the mean and the spatial median as location
estimator.


title:
Quantum Gibbs distribution from dynamical thermalization in classical
  nonlinear lattices

abstract:
  We study numerically time evolution in classical lattices with weak or
moderate nonlinearity which leads to interactions between linear modes. Our
results show that in a certain strength range a moderate nonlinearity generates
a dynamical thermalization process which drives the system to the quantum Gibbs
distribution of probabilities, or average oscillation amplitudes. The effective
dynamical temperature of the lattice varies from large positive to large
negative values depending on energy of initially excited modes. This quantum
Gibbs distribution is drastically different from usually expected energy
equipartition over linear modes corresponding to a regime of classical
thermalization. Possible experimental observations of this dynamical
thermalization are discussed for cold atoms in optical lattices, nonlinear
photonic lattices and optical fiber arrays.


title: Vertex-Frequency Analysis on Graphs

abstract:
  One of the key challenges in the area of signal processing on graphs is to
design dictionaries and transform methods to identify and exploit structure in
signals on weighted graphs. To do so, we need to account for the intrinsic
geometric structure of the underlying graph data domain. In this paper, we
generalize one of the most important signal processing tools - windowed Fourier
analysis - to the graph setting. Our approach is to first define generalized
convolution, translation, and modulation operators for signals on graphs, and
explore related properties such as the localization of translated and modulated
graph kernels. We then use these operators to define a windowed graph Fourier
transform, enabling vertex-frequency analysis. When we apply this transform to
a signal with frequency components that vary along a path graph, the resulting
spectrogram matches our intuition from classical discrete-time signal
processing. Yet, our construction is fully generalized and can be applied to
analyze signals on any undirected, connected, weighted graph.


title: The Near Field Refractor

abstract:
  We present an abstract method in the setting of compact metric spaces which
is applied to solve a number of problems in geometric optics. In particular, we
solve the one source near field refraction problem. That is, we construct
surfaces separating two homogenous media with different refractive indices that
refract radiation emanating from the origin into a target domain contained in
an n-1 dimensional hypersurface. The input and output energy are prescribed.
This implies the existence of lenses focusing radiation in a prescribed manner.


title:
Saliency-Guided Perceptual Grouping Using Motion Cues in Region-Based
  Artificial Visual Attention

abstract:
  Region-based artificial attention constitutes a framework for bio-inspired
attentional processes on an intermediate abstraction level for the use in
computer vision and mobile robotics. Segmentation algorithms produce regions of
coherently colored pixels. These serve as proto-objects on which the
attentional processes determine image portions of relevance. A single
region---which not necessarily represents a full object---constitutes the focus
of attention. For many post-attentional tasks, however, such as identifying or
tracking objects, single segments are not sufficient. Here, we present a
saliency-guided approach that groups regions that potentially belong to the
same object based on proximity and similarity of motion. We compare our results
to object selection by thresholding saliency maps and a further
attention-guided strategy.


title:
Alignment of the Angular Momentum Vectors of Planetary Nebulae in the
  Galactic Bulge

abstract:
  We use high-resolution H {\alpha} images of 130 planetary nebulae (PNe) to
investigate whether there is a preferred orientation for PNe within the
Galactic Bulge. The orientations of the full sample have an uniform
distribution. However, at a significance level of 0.01, there is evidence for a
non-uniform distribution for those planetary nebulae with evident bipolar
morphology. If we assume that the bipolar PNe have an unimodal distribution of
the polar axis in Galactic coordinates, the mean Galactic position angle is
consistent with 90{\deg}, i.e. along the Galactic plane, and the significance
level is better than 0.001 (the equivalent of a 3.7{\sigma} significance level
for a Gaussian distribution).
  The shapes of PNe are related to angular momentum of the original star or
stellar system, where the long axis of the nebula measures the angular momentum
vector. In old, low-mass stars, the angular momentum is largely in binary
orbital motion. Consequently, the alignment of bipolar nebulae that we have
found indicates that the orbital planes of the binary systems are oriented
perpendicular to the Galactic plane. We propose that strong magnetic fields
aligned along the Galactic plane acted during the original star formation
process to slow the contraction of the star forming cloud in the direction
perpendicular to the plane. This would have produced a propensity for wider
binaries with higher angular momentum with orbital axes parallel to the
Galactic plane. Our findings provide the first indication of a strong,
organized magnetic field along the Galactic plane that impacted on the angular
momentum vectors of the resulting stellar population.


title: Pseudo-Dirac neutrinos via mirror-world and depletion of UHE neutrinos

abstract:
  We propose a possible particle physics explanation of the non-observation of
muon neutrino events at IceCube coincident with GRB gamma ray at the rates
predicted by the standard Bahcall-Waxman model, in terms of neutrino
oscillations. Our model is based on assuming that (a) all neutrinos are
pseudo-Dirac particles and (b) there exists a mirror world interacting
gravitationally with the observed world. This scenario has three sterile
neutrinos associated with each flavour of ordinary neutrinos. Very tiny mass
splitting between these neutrinos is assumed to arise from lepton number
violating dimension five operators suppressed by the Planck scale. We show that
if a mass splitting of 10^(-15) eV^2 is induced between the four mass
eigenstates of a given species, then its flux will be suppressed at IceCube
energies by a factor of 4 which could be the explanation of the IceCube
observation that the muon neutrino flux is lower than expected. Hierarchies in
mass splitting among different flavours may result in different amount of
suppression of each flavour and based on this, we predict a difference in the
flavour ratios of the observed neutrinos which is significantly different
compared to the standard prediction of nu_e:nu_mu:nu_tau=1:1:1 which could
serve as a test for this model.


title: Understanding Humans' Strategies in Maze Solving

abstract:
  Navigating through a visual maze relies on the strategic use of eye movements
to select and identify the route. When navigating the maze, there are
trade-offs between exploring to the environment and relying on memory. This
study examined strategies used to navigating through novel and familiar mazes
that were viewed from above and traversed by a mouse cursor. Eye and mouse
movements revealed two modes that almost never occurred concurrently:
exploration and guidance. Analyses showed that people learned mazes and were
able to devise and carry out complex, multi-faceted strategies that traded-off
visual exploration against active motor performance. These strategies took into
account available visual information, memory, confidence, the estimated cost in
time for exploration, and idiosyncratic tolerance for error. Understanding the
strategies humans used for maze solving is valuable for applications in
cognitive neuroscience as well as in AI, robotics and human-robot interactions.


title: Silence is Golden: exploiting jamming and radio silence to communicate

abstract:
  Jamming techniques require just moderate resources to be deployed, while
their effectiveness in disrupting communications is unprecedented. In this
paper we introduce several contributions to jamming mitigation. In particular,
we introduce a novel adversary model that has both (unlimited) jamming reactive
capabilities as well as powerful (but limited) proactive jamming capabilities.
Under this powerful but yet realistic adversary model, the communication
bandwidth provided by current anti-jamming solutions drops to zero. We then
present Silence is Golden (SiG): a novel anti jamming protocol that,
introducing a tunable, asymmetric communication channel, is able to mitigate
the adversary capabilities, enabling the parties to communicate. For instance,
with SiG it is possible to deliver a 128 bits long message with a probability
greater than 99% in 4096 time slots in the presence of a jammer that jams all
the on-the-fly communications and the 74% of the silent radio spectrum---while
competing proposals simply fail. The provided solution enjoys a thorough
theoretical analysis and is supported by extensive experimental results,
showing the viability of our proposal.


title: CompOSE - CompStar Online Supernovae Equations of State

abstract:
  This paper is the manual of the CompOSE service, see http://compose.obspm.fr,
an equation of state (EoS) database for use in nuclear physics and in
astrophysical applications, e.g. the simulation of core-collapse supernovae and
compact stars. The main aims of the service are the following: to offer a
robust, easily extendable data format to store and read EoS data tables and
related physical quantities; to make these data available to the public --
respecting the original work by the contributors -- in a standard format
designed for easy access and flexibility; and to provide routines to
interpolate these data in the parameter space of density, temperature and
hadronic charge fraction. The manual contains a detailed description of the
service. It is divided into three parts, containing a general introduction as
well as instructions for potential contributors and for users.


title:
Goldstone modes and bifurcations in phase-separated binary condensates
  at finite temperature

abstract:
  We show that the third Goldstone mode, which emerges in binary condensates at
phase-separation, persists to higher inter-species interaction for density
profiles where one component is surrounded on both sides by the other
component. This is not the case with symmetry-broken density profiles where one
species is to entirely to the left and the other is entirely to the right. We,
then, use Hartree-Fock-Bogoliubov theory with Popov approximation to examine
the mode evolution at $T\neq0$ and demonstrate the existence of mode
bifurcation near the critical temperature. The Kohn mode, however, exhibits
deviation from the natural frequency at finite temperatures after the phase
separation. This is due to the exclusion of the non-condensate atoms in the
dynamics.


title: Dynamical friction in cuspy galaxies

abstract:
  In this paper we treat the problem of the dynamical friction decay of a
massive object moving in an elliptical galaxy with a cuspidal inner
distribution of the mass density. We present results obtained by both
self-consistent, direct summation, N-body simulations, as well as by a new
semi-analytical treatment of dynamical friction valid in such cuspy central
regions of galaxies. A comparison of these results indicates that the proposed
semi-analytical approximation is the only reliable in cuspy galactic central
regions, where the standard Chandrasekhar's local approximation fails, and,
also, gives estimates of decay times that are correct at 1% respect to those
given by N-body simulations. The efficiency of dynamical friction in cuspy
galaxies is found definitively higher than in core galaxies, especially on more
radially elongated satellite orbits. As another relevant result, we find a
proportionality of the dynamical friction decay time to the -0.67 power of the
satellite mass, M, shallower than the standardly adopted 1/M dependence.


title:
\'Etale fundamental groups of Kawamata log terminal spaces, flat
  sheaves, and quotients of Abelian varieties

abstract:
  Given a quasi-projective variety X with only Kawamata log terminal
singularities, we study the obstructions to extending finite \'etale covers
from the smooth locus $X_{\mathrm{reg}}$ of $X$ to $X$ itself. A simplified
version of our main results states that there exists a Galois cover $Y
\rightarrow X$, ramified only over the singularities of $X$, such that the
\'etale fundamental groups of $Y$ and of $Y_{\mathrm{reg}}$ agree. In
particular, every \'etale cover of $Y_{\mathrm{reg}}$ extends to an \'etale
cover of $Y$.
  As first major application, we show that every flat holomorphic bundle
defined on $Y_{\mathrm{reg}}$ extends to a flat bundle that is defined on all
of $Y$. As a consequence, we generalise a classical result of Yau to the
singular case: every variety with at worst terminal singularities and with
vanishing first and second Chern class is a finite quotient of an Abelian
variety. As a further application, we verify a conjecture of Nakayama and Zhang
describing the structure of varieties that admit polarised endomorphisms.


title: Gonality of the modular curve X1(N)

abstract:
  In this paper we compute the gonality over Q of the modular curve X1(N) for
all N <= 40 and give upper bounds for each N <= 250. This allows us to
determine all N for which X1(N) has infinitely points of degree <= 8. We
conjecture that the modular units of Q(X1(N)) are freely generated by
f_2,...,f_{[N/2]+1} where f_k is obtained from the equation for X1(k).


title:
Top-down and Bottom-up Feature Combination for Multi-sensor Attentive
  Robots

abstract:
  The information available to robots in real tasks is widely distributed both
in time and space, requiring the agent to search for relevant data. In humans,
that face the same problem when sounds, images and smells are presented to
their sensors in a daily scene, a natural system is applied: Attention. As
vision plays an important role in our routine, most research regarding
attention has involved this sensorial system and the same has been replicated
to the robotics field. However,most of the robotics tasks nowadays do not rely
only in visual data, that are still costly. To allow the use of attentive
concepts with other robotics sensors that are usually used in tasks such as
navigation, self-localization, searching and mapping, a generic attentional
model has been previously proposed. In this work, feature mapping functions
were designed to build feature maps to this attentive model from data from
range scanner and sonar sensors. Experiments were performed in a high fidelity
simulated robotics environment and results have demonstrated the capability of
the model on dealing with both salient stimuli and goal-driven attention over
multiple features extracted from multiple sensors.


title: Synchronisation and liquid crystalline order in soft active fluids

abstract:
  We introduce a phenomenological theory for a new class of soft active fluids,
with the ability to synchronise. Our theoretical framework describes the
macroscopic behaviour of a collection of interacting anisotropic elements with
cyclic internal dynamics and a periodic phase variable. This system (i) can
spontaneously undergo a transition to a state with macroscopic orientational
order, with the elements aligned: a liquid crystal, (ii) attain another broken
symmetry state characterised by synchronisation of their phase variables or
(iii) a combination of both types of order. We derive the equations describing
a spatially homogeneous system and also study the hydrodynamic fluctuations of
the soft modes in some of the ordered states. We find that synchronisation can
promote the transition to a state with orientational order; and vice-versa.
Finally, we provide an explicit microscopic realisation: a suspension of
micro-swimmers driven by cyclic strokes.


title: Lorentz Breaking and Gravity

abstract:
  Gravitational theories with Lorentz violation must account for a number of
possible features in order to be consistent theoretically and
phenomenologically. A brief summary of these features is given here. They
include evasion of a no-go theorem, connections between spontaneous Lorentz
breaking and diffeomorphism breaking, the appearance of massless
Nambu-Goldstone modes and massive Higgs modes, and the possibility of a Higgs
mechanism in gravity.


title: Some sums over the non-trivial zeros of the Riemann zeta function

abstract:
  We prove some identities, which involve the non-trivial zeros of the Riemann
zeta function. From them we derive some convergent asymptotic expansions
related to the work by Cram\'er, and also new representations for some
arithmetical functions in terms of the non-trivial zeros.


title: Pseudo-reflection groups and essential dimension

abstract:
  We give a simple formula for the essential dimension of a finite
pseudo-reflection group at a prime p and determine the absolute essential
dimension for most irreducible pseudo-reflection groups. We also study the
"poor man's essential dimension" of an arbitrary finite group, an intermediate
notion between the absolute essential dimension and the essential dimension at
a prime p.


title:
Damping Noise-Folding and Enhanced Support Recovery in Compressed
  Sensing

abstract:
  The practice of compressed sensing suffers importantly in terms of the
efficiency/accuracy trade-off when acquiring noisy signals prior to
measurement. It is rather common to find results treating the noise affecting
the measurements, avoiding in this way to face the so-called
$\textit{noise-folding}$ phenomenon, related to the noise in the signal,
eventually amplified by the measurement procedure. In this paper, we present
two new decoding procedures, combining $\ell_1$-minimization followed by either
a regularized selective least $p$-powers or an iterative hard thresholding,
which not only are able to reduce this component of the original noise, but
also have enhanced properties in terms of support identification with respect
to the sole $\ell_1$-minimization or iteratively re-weighted
$\ell_1$-minimization. We prove such features, providing relatively simple and
precise theoretical guarantees. We additionally confirm and support the
theoretical results by extensive numerical simulations, which give a statistics
of the robustness of the new decoding procedures with respect to more classical
$\ell_1$-minimization and iteratively re-weighted $\ell_1$-minimization.


title: Spin liquid phases of alkaline-earth-metal atoms at finite temperature

abstract:
  We study spin liquid phases of spin-5/2 alkaline earth atoms on a honeycomb
lattice at finite temperatures. Our analysis is based on a Gutzwiller
projection variational approach recast to a path-integral formalism. In the
framework of a saddle-point approximation we determine spin liquid phases with
lowest free energy and study their temperature dependence. We identify a
critical temperature, where all the spin liquid phases melt and the system goes
to the paramagnetic phase. We also study the stability of the saddle-point
solutions and show that a time-reversal symmetry breaking state, a so called
chiral spin liquid phase is realized even at finite temperatures. We also
determine the spin structure factor, which, in principle, is an experimentally
measurable quantity and is the basic tool to map the spectrum of elementary
excitations of the system.


title: Uniform Random Planar Graphs with Degree Constraints

abstract:
  Random planar graphs have been the subject of much recent work. Many basic
properties of the standard uniform random planar graph P_{n}, by which we mean
a graph chosen uniformly at random from the set of all planar graphs with
vertex set {1,2,...,n}, are now known, and variations on this standard random
graph are also attracting interest.
  Prominent among the work on P_{n} have been asymptotic results for the
probability that P_{n} will be connected or contain given components/subgraphs.
Such progress has been achieved through a combination of counting arguments and
a generating function approach.
  More recently, attention has turned to P_{n,m}, the graph taken uniformly at
random from the set of all planar graphs on {1,2,...,n} with exactly m(n) edges
(this can be thought of as a uniform random planar graph with a constraint on
the average degree). The case when m(n) = qn for fixed q in (1,3) has been
investigated, and results obtained for the events that P_{n,qn} will be
connected and that P_{n,qn} will contain given subgraphs.
  In Part I of this thesis, we use elementary counting arguments to extend the
current knowledge of P_{n,m}. We investigate the probability that P_{n,m} will
contain given components, the probability that P_{n,m} will contain given
subgraphs, and the probability that P_{n,m} will be connected, all for general
m(n), and show that there is different behaviour depending on which `region'
the ratio m(n)/n falls into. In Part II, we investigate the same three topics
for a uniform random planar graph with constraints on the maximum and minimum
degrees.