title:
Further studies on holographic insulator/superconductor phase
  transitions from Sturm-Liouville eigenvalue problems

abstract:
  We take advantage of the Sturm-Liouville eigenvalue problem to analytically
study the holographic insulator/superconductor phase transition in the probe
limit. The interesting point is that this analytical method can not only
estimate the most stable mode of the phase transition, but also the second
stable mode. We find that this analytical method perfectly matches with other
numerical methods, such as the shooting method. Besides, we argue that only
Dirichlet boundary condition of the trial function is enough under certain
circumstances, which will lead to a more precise estimation. This relaxation
for the boundary condition of the trial function is first observed in this
paper as far as we know.


title: The (n,1)-Reduced DKP Hierarchy, the String Equation and W Constraints

abstract:
  The total descendent potential of a simple singularity satisfies the
Kac-Wakimoto principal hierarchy. Bakalov and Milanov showed recently that it
is also a highest weight vector for the corresponding W-algebra. This was used
by Liu, Yang and Zhang to prove its uniqueness. We construct this principal
hierarchy of type D in a different way, viz. as a reduction of some DKP
hierarchy. This gives a Lax type and a Grassmannian formulation of this
hierarchy. We show in particular that the string equation induces a large part
of the W constraints of Bakalov and Milanov. These constraints are not only
given on the tau function, but also in terms of the Lax and Orlov-Schulman
operators.


title: Discontinuity points of a function with a closed and connected graph

abstract:
  The main result of this paper states that for a function $f:\R^2\to Y$ with a
closed, connected and locally connected graph, where $Y$ is a locally compact,
second-countable metrisable space, the graph over discontinuity points remains
locally connected.


title:
The Lambda CDM-model in quantum field theory on curved spacetime and
  Dark Radiation

abstract:
  In the standard model of cosmology, the universe is described by a
Robertson-Walker spacetime, while its matter/energy content is modeled by a
perfect fluid with three components corresponding to matter/dust, radiation and
a cosmological constant. On the other hand, in particle physics matter and
radiation are described in terms of quantum field theory on Minkowski
spacetime. We unify these seemingly different theoretical frameworks by
analysing the standard model of cosmology from first principles within quantum
field theory on curved spacetime: assuming that the universe is homogeneous and
isotropic on large scales, we specify a class of quantum states whose
expectation value of the energy density is qualitatively and quantitatively of
the standard perfect fluid form up to potential corrections. Qualitatively,
these corrections depend on new parameters not present in the standard Lambda
CDM-model and can account for e.g. the phenomenon of Dark Radiation
(N_eff>3.046), having a characteristic signature which clearly deviates from
other potential Dark Radiation sources such as e.g. sterile neutrinos.
Quantitatively, we find that our more fundamental model can be perfectly
matched to observational data, such that we arrive at a natural and fundamental
extension of the Lambda CDM-model.


title:
Localised distributions and criteria for correctness in complex Langevin
  dynamics

abstract:
  Complex Langevin dynamics can solve the sign problem appearing in numerical
simulations of theories with a complex action. In order to justify the
procedure, it is important to understand the properties of the real and
positive distribution, which is effectively sampled during the stochastic
process. In the context of a simple model, we study this distribution by
solving the Fokker-Planck equation as well as by brute force and relate the
results to the recently derived criteria for correctness. We demonstrate
analytically that it is possible that the distribution has support in a strip
in the complexified configuration space only, in which case correct results are
expected.


title: Some Remarks on the Logic of Quantum Gravity

abstract:
  We discuss some conceptual issues that any approach to quantum gravity has to
confront. In particular, it is argued that one has to find a theory that can be
interpreted in a realist manner, because theories with an instrumentalist
interpretation are problematic for several well-known reasons. Since the
Hilbert space formalism almost inevitably forces an instrumentalist
interpretation on us, we suggest that a theory of quantum gravity should not be
based on the Hilbert space formalism. We briefly sketch the topos approach,
which makes use of the internal logic of a topos associated with a quantum
system and comes with a natural (neo-)realist interpretation. Finally, we make
some remarks on the relation between system logic and metalogic.


title: Modeling Warfare in Social Animals: A "Chemical" Approach

abstract:
  The aim of our study is to describe the dynamics of ant battles, with
reference to laboratory experiments, by means of a chemical stochastic model.
We focus on ants behavior as an interesting topic in order to predict the
ecological evolution of invasive species and their spreading. In our work we
want to describe the interactions between two groups of different ant species
with different war strategies. Our model considers the single ant individuals
and fighting groups in a way similar to atoms and molecules, respectively,
considering that ant fighting groups remain stable for a relative long time.
Starting from a system of differential non-linear equations (DE), derived from
the chemical reactions, we obtain a mean field description of the system. The
DE approach is valid when the number of individuals of each species is large in
the considered unit, while we consider battles of at most 10 vs. 10
individuals, due to the difficulties in following the individual behavior in a
large assembly. Therefore, we also adapt a Gillespie algorithm to reproduce the
fluctuations around the mean field. The DE scheme is exploited to characterize
the stochastic model. The set of parameters of chemical equations, obtained
using a minimization algorithm, are used by the Gillespie algorithm to generate
the stochastic trajectories. We then fit the stochastic paths with the DE, in
order to analyze the variability of the parameters and their variance. Finally,
we estimate the goodness of the applied methodology and we confirm that the
stochastic approach must be considered for a correct description of the ant
fighting dynamics. With respect to other war models, our chemical one considers
all phases of the battle and not only casualties. Thus, we can count on more
experimental data, but we also have more parameters to fit. In any case, our
model allows a much more detailed description of the fights.


title: THz beam steering by optical coherent control

abstract:
  We demonstrate optical coherent control of the emission direction of THz
radiation. Femtosecond laser pulses are used to excite different types of
ultrafast photocurrents along different directions in a bulk GaAs sample. The
overall emission pattern can be modified by changing the phase of the optical
excitation. With this method, THz beam steering of about 8 degrees is realized.
A simple dipole-based model allows us to relate the size of the steering effect
to the amplitude ratio between the different photocurrent contributions and to
diffraction effects resulting from the excitation spot size.


title:
Global Existence and Decay of Solutions to the Fokker-Planck-Boltzmann
  Equation

abstract:
  The Cauchy problem to the Fokker-Planck-Boltzmann equation under Grad's
angular cut-off assumption is investigated. When the initial data is a small
perturbation of an equilibrium state, global existence and optimal temporal
decay estimates of classical solutions are established. Our analysis is based
on the coercivity of the Fokker-Planck operator and an elementary weighted
energy method.


title: An exponential integrator for a highly oscillatory Vlasov equation

abstract:
  In the framework of a Particle-In-Cell scheme for some 1D Vlasov-Poisson
system depending on a small parameter, we propose a time-stepping method which
is numerically uniformly accurate when the parameter goes to zero. Based on an
exponential time differencing approach, the scheme is able to use large time
steps with respect to the typical size of the fast oscillations of the
solution.


title: Limits of limit sets II: Geometrically Infinite Groups

abstract:
  We show that for a strongly convergent sequence of purely loxodromic finitely
generated Kleinian groups with incompressible ends, Cannon-Thurston maps,
viewed as maps from a fixed base limit set to the Riemann sphere, converge
uniformly. For algebraically convergent sequences we show that there exist
examples where even pointwise convergence of Cannon-Thurston maps fails.


title: Conditioned random walks from Kac-Moody root systems

abstract:
  Random paths are time continuous interpolations of random walks. By using
Littelmann path model, we associate to each irreducible highest weight module
of a Kac Moody algebra g a random path W. Under suitable hypotheses, we make
explicit the probability of the event E: W never exits the Weyl chamber of g.
We then give the law of the random walk defined by W conditioned by the event E
and proves this law can be recovered by applying to W the generalized Pitmann
transform introduced by Biane, Bougerol and O'Connell. This generalizes the
main results of [10] and [16] to Kac Moody root systems and arbitrary highest
weight modules. Moreover, we use here a completely new approach by exploiting
the symmetry of our construction under the action of the Weyl group of g rather
than renewal theory and Doob's theorem on Martin kernels.


title: Improving production process performance thanks to neuronal analysis

abstract:
  Product quality level is become a key factor for companies' competitiveness.
A lot of time and money are required to ensure and guaranty it. Besides,
motivated by the need of traceability, collecting production data is now
commonplace in most companies. Our paper aims to show that we can ensure the
required quality thanks to an "on-line quality approch" and proposes a neural
network based process to determine the optimal setting for production machines.
We will illustrate this with the Acta-Mobilier case, which is a high quality
lacquerer company.


title:
Segmentation et Interpr\'etation de Nuages de Points pour la
  Mod\'elisation d'Environnements Urbains

abstract:
  Dans cet article, nous pr\'esentons une m\'ethode pour la d\'etection et la
classification d'artefacts au niveau du sol, comme phase de filtrage
pr\'ealable \`a la mod\'elisation d'environnements urbains. La m\'ethode de
d\'etection est r\'ealis\'ee sur l'image profondeur, une projection de nuage de
points sur un plan image o\`u la valeur du pixel correspond \`a la distance du
point au plan. En faisant l'hypoth\`ese que les artefacts sont situ\'es au sol,
ils sont d\'etect\'es par une transformation de chapeau haut de forme par
remplissage de trous sur l'image de profondeur. Les composantes connexes ainsi
obtenues, sont ensuite caract\'eris\'ees et une analyse des variables est
utilis\'ee pour la s\'election des caract\'eristiques les plus discriminantes.
Les composantes connexes sont donc classifi\'ees en quatre cat\'egories
(lampadaires, pi\'etons, voitures et "Reste") \`a l'aide d'un algorithme
d'apprentissage supervis\'e. La m\'ethode a \'et\'e test\'ee sur des nuages de
points de la ville de Paris, en montrant de bons r\'esultats de d\'etection et
de classification dans l'ensemble de donn\'ees.---In this article, we present a
method for detection and classification of artifacts at the street level, in
order to filter cloud point, facilitating the urban modeling process. Our
approach exploits 3D information by using range image, a projection of 3D
points onto an image plane where the pixel intensity is a function of the
measured distance between 3D points and the plane. By assuming that the
artifacts are on the ground, they are detected using a Top-Hat of the hole
filling algorithm of range images. Then, several features are extracted from
the detected connected components and a stepwise forward variable/model
selection by using the Wilk's Lambda criterion is performed. Afterward, CCs are
classified in four categories (lampposts, pedestrians, cars and others) by
using a supervised machine learning method. The proposed method was tested on
cloud points of Paris, and have shown satisfactory results on the whole
dataset.


title: The QCD sign problem as a total derivative

abstract:
  We consider the distribution of the complex phase of the fermion determinant
in QCD at nonzero chemical potential and examine the physical conditions under
which the distribution takes a Gaussian form. We then calculate the baryon
number as a function of the complex phase of the fermion determinant and show
1) that the exponential cancellations produced by the sign problem take the
form of total derivatives 2) that the full baryon number is orthogonal to this
noise. These insights allow us to define a self-consistency requirement for
measurements of the baryon number in lattice simulations.


title:
Investigation of the quaternary Fe2-xCoxMnSi alloys by structural,
  magnetic, resistivity and spin polarization measurements

abstract:
  Effects of the Co substitution have been observed on the structural, magnetic
and magneto-transport properties of Fe2-xCoxMnSi alloy. Curie temperature (TC)
and saturation magnetization (MS) of these alloys increased linearly with the
Co substitution. Competitive magnetic interaction between ferromagnetic (FM)
and anti-ferromagnetic (AFM) phases exists in Fe2-xCoxMnSi for x less than 0.2,
AFM phase is completely disappears for x greater than or equal to 0.2. The
value of Rhodes-Wohlfarth ratio pc/ps is greater than one for these alloys
which is the characteristics of iterant magnetism present in the system.
M\"ossbauer spectroscopic measurements have been done to investigate the atomic
disorder and local magnetic moment for some x values. Resistivity measurements
also confirm the stability of ferromagnetism with the concentration of Co and
also show a sign of half metallicity. Resistivity shows semiconducting
behaviour for x = 0.4 which is interesting in view of spin gapless
semiconductors.


title: Embeddings between partially commutative groups: two counterexamples

abstract:
  In this note we give two examples of partially commutative subgroups of
partially commutative groups. Our examples are counterexamples to the Extension
Graph Conjecture and to the Weakly Chordal Conjecture of Kim and Koberda,
\cite{KK}. On the other hand we extend the class of partially commutative
groups for which it is known that the Extension Graph Conjecture holds, to
include those with commutation graph containing no induced $C_4$ or $P_3$. In
the process, some new embeddings of surface groups into partially commutative
groups emerge.


title:
Shortest cycle covers and cycle double covers with large 2-regular
  subgraphs

abstract:
  In this paper we show that many snarks have shortest cycle covers of length
$\frac{4}{3}m+c$ for a constant $c$, where $m$ is the number of edges in the
graph, in agreement with the conjecture that all snarks have shortest cycle
covers of length $\frac{4}{3}m+o(m)$.
  In particular we prove that graphs with perfect matching index at most 4 have
cycle covers of length $\frac{4}{3}m$ and satisfy the $(1,2)$-covering
conjecture of Zhang, and that graphs with large circumference have cycle covers
of length close to $\frac{4}{3}m$. We also prove some results for graphs with
low oddness and discuss the connection with Jaeger's Petersen colouring
conjecture.


title:
Low-energy E1 strength in select nuclei: Possible constraints on the
  neutron skins and the symmetry energy

abstract:
  Correlations between low-lying electric dipole (E1) strength and neutron skin
thickness are systematically investigated with the fully self-consistent
random-phase approximation using the Skyrme energy functionals. The presence of
strong correlation among these quantities is currently under dispute. We find
that the strong correlation is present in properly selected nuclei, namely in
spherical neutron-rich nuclei in the region where the neutron Fermi levels are
located at orbits with low orbital angular momenta. The significant correlation
between the fraction of the energy-weighted sum value and the slope of the
symmetry energy is also observed. The deformation in the ground state seems to
weaken the correlation.


title: The Surface Tension of Magnetized Quark Matter

abstract:
  The surface tension of quark matter plays a crucial role for the possibility
of quark matter nucleation during the formation of compact stellar objects and
also for the existence of a mixed phase within hybrid stars. However, despite
its importance, this quantity does not have a well established numerical value.
Some early estimates have predicted that, at zero temperature, the value falls
within the wide range $\gamma_0\approx10-300{\rm\ MeV/fm^2}$ but, very
recently, different model applications have reduced these numerical values to
fall within the range $\gamma_0\approx5-30{\rm\ MeV/fm^2}$ which would favor
the phase conversion process as well as the appearance of a mixed phase in
hybrid stars. In magnetars one should also account for the presence of very
high magnetic fields which may reach up to about $ eB\approx 3-30\, m_\pi^2$
($B \approx 10^{19}-10^{20} \,G$) at the core of the star so that it may also
be important to analyze how the presence of a magnetic field affects the
surface tension. With this aim we consider magnetized two flavor quark matter,
described by the Nambu--Jona-Lasinio model. We show that although the surface
tension oscillates around its B=0 value, when $0 < eB \lesssim 10 \, m_\pi^2$,
it only reaches values which are still relatively small. For $eB \approx 5\,
m_\pi^2$ the B=0 surface tension value drops by about 30% while for $eB \gtrsim
10\, m_\pi^2$ it quickly raises with the field intensity so that the phase
conversion and the presence of a mixed phase should be suppressed if extremely
high fields are present. We also investigate how thermal effects influence the
surface tension for magnetized quark matter.


title: The straight line complexity of small factorials and primorials

abstract:
  In this paper we determine the straight-line complexity of $n!$ for $n\leq
22$ and give bounds for the complexities up to $n=46$. In the same way we
determine the straight-line complexity of the product of the first primes up to
$p=31$ and gives bounds for $p\leq 43$.
  Our results are based on an exhaustive computer search of the short length
straight-line programs.


title:
Marginal inferential models: prior-free probabilistic inference on
  interest parameters

abstract:
  The inferential models (IM) framework provides prior-free,
frequency-calibrated, posterior probabilistic inference. The key is the use of
random sets to predict unobservable auxiliary variables connected to the
observable data and unknown parameters. When nuisance parameters are present, a
marginalization step can reduce the dimension of the auxiliary variable which,
in turn, leads to more efficient inference. For regular problems, exact
marginalization can be achieved, and we give conditions for marginal IM
validity. We show that our approach provides exact and efficient marginal
inference in several challenging problems, including a many-normal-means
problem. In non-regular problems, we propose a generalized marginalization
technique and prove its validity. Details are given for two benchmark examples,
namely, the Behrens--Fisher and gamma mean problems.


title:
Multi-user Scheduling Schemes for Simultaneous Wireless Information and
  Power Transfer

abstract:
  In this paper, we study the downlink multi-user scheduling problem for a
time-slotted system with simultaneous wireless information and power transfer.
In particular, in each time slot, a single user is scheduled to receive
information, while the remaining users opportunistically harvest the ambient
radio frequency (RF) energy. We devise novel scheduling schemes in which the
tradeoff between the users' ergodic capacities and their average amount of
harvested energy can be controlled. To this end, we modify two fair scheduling
schemes used in information-only transfer systems. First, proportionally fair
maximum normalized signal-to-noise ratio (N-SNR) scheduling is modified by
scheduling the user having the jth ascendingly ordered (rather than the
maximum) N-SNR. We refer to this scheme as order-based N-SNR scheduling.
Second, conventional equal-throughput (ET) fair scheduling is modified by
scheduling the user having the minimum moving average throughput among the set
of users whose N-SNR orders fall into a certain set of allowed orders Sa
(rather than the set of all users). We refer to this scheme as order-based ET
scheduling. The feasibility conditions required for the users to achieve ET
with this scheme are also derived. We show that the smaller the selection order
j for the order-based N-SNR scheme, and the lower the orders in Sa for the
order-based ET scheme, the higher the average amount of energy harvested by the
users at the expense of a reduction in their ergodic capacities. We analyze the
performance of the considered scheduling schemes for independent and
non-identically distributed (i.n.d.) Ricean fading channels, and provide
closed-form results for the special case of i.n.d. Rayleigh fading.


title:
Gibbs-Tolman approach to the curved interface effects in asymmetric
  nuclei

abstract:
  We redefine the surface tension coefficient and the symmetry energy for an
asymmetric nuclear Fermi-liquid drop with a finite diffuse layer. Considering
two-component charged Fermi-liquid drop and following Gibbs-Tolman concept, we
introduce the equimolar radius $R_{e}$ of sharp surface droplet at which the
surface tension is applied and the radius of tension surface $R_{s}$ (Laplace
radius) which provides the minimum of the surface tension coefficient $\sigma$.
We have shown that the nuclear Tolman length $\xi$ is negative and the modulus
of $\xi$ growth quadratically with asymmetry parameter $X=(N-Z)/(N+Z)$.


title:
Measurement-device-independent quantum key distribution with quantum
  memories

abstract:
  We generalize measurement-device-independent quantum key distribution [ H.-K.
Lo, M. Curty, and B. Qi, Phys. Rev. Lett. 108, 130503 (2012) ] to the scenario
where the Bell-state measurement station contains also heralded quantum
memories. We find analytical formulas, in terms of device imperfections, for
all quantities entering in the secret key rates, i.e., the quantum bit error
rate and the repeater rate. We assume either single-photon sources or weak
coherent pulse sources plus decoy states. We show that it is possible to
significantly outperform the original proposal, even in presence of decoherence
of the quantum memory. Our protocol may represent the first natural step for
implementing a two-segment quantum repeater.


title: Production of the X(3872) in charmonia radiative decays

abstract:
  We discuss the possibilities of producing the X(3872), which is assumed to be
a D \bar D^* bound state, in radiative decays of charmonia. We argue that the
ideal energy regions to observe the X(3872) associated with a photon in e^+e^-
annihilations are around the Y(4260) mass and around 4.45 GeV, due to the
presence of the S-wave D \bar D_1(2420) and D^* \bar D_1(2420) threshold,
respectively. Especially, if the Y(4260) is dominantly a D \bar D_1 molecule
and the X(3872) a D \bar D^* molecule, the radiative transition strength will
be quite large.


title: Bundle-theoretic methods for higher-order variational calculus

abstract:
  We present a geometric interpretation of the integration-by-parts formula on
an arbitrary vector bundle. As an application we give a new geometric
formulation of higher-order variational calculus.


title: On the essential hyperbolicity of sectional-Anosov flows

abstract:
  We prove that every sectional-Anosov flow of a compact 3-manifold $M$
exhibits a finite collection of hyperbolic attractors and singularities whose
basins form a dense subset of $M$. Applications to the dynamics of
sectional-Anosov flows on compact 3-manifolds include a characterization of
essential hyperbolicity, sensitivity to the initial conditions (improving
\cite{ams}) and a relationship between the topology of the ambient manifold and
the denseness of the basin of the singularities.


title:
Random weighted projections, random quadratic forms and random
  eigenvectors

abstract:
  We present a concentration result concerning random weighted projections in
high dimensional spaces. As applications, we prove
  (1) New concentration inequalities for random quadratic forms;
  (2) The infinity norm of most unit eigenvectors of a random $\pm 1$ matrix is
of order $O( \sqrt { \log n/n})$;
  (3) An estimate on the threshold for the local semi-circle law which is tight
up to a $\sqrt {\log n}$ factor.


title: Direct Imaging Search for Extrasolar Planets in the Pleiades

abstract:
  We carried out an imaging survey for extrasolar planets around stars in the
Pleiades (125 Myr, 135 pc) in the $H$ and $K_{S}$ bands using HiCIAO combined
with the adaptive optics, AO188, on the Subaru telescope. We found 13 companion
candidates fainter than 14.5 mag in the $H$ band around 9 stars. Five of these
13 were confirmed to be background stars by measurement of their proper motion.
One was not found in the second epoch observation, and thus was not a
background or companion object. One had multi-epoch image, but the precision of
its proper motion was not sufficient to conclude whether it was background
object. Four other candidates are waiting for second epoch observations to
determine their proper motion. Finally, the remaining 2 were confirmed to be 60
$M_{J}$ brown dwarf companions orbiting around HD 23514 (G0) and HII 1348 (K5)
respectively, as had been reported in previous studies. In our observations,
the average detection limit for a point source was 20.3 mag in the $H$ band
beyond 1''.5 from the central star. On the basis of this detection limit, we
calculated the detection efficiency to be 90% for a planet with 6 to 12 Jovian
masses and a semi-major axis of 50--1000 AU. For this we extrapolated the
distribution of planet mass and semi-major axis derived from RV observations
and adopted the planet evolution model of Baraffe et al. (2003). As there was
no detection of a planet, we estimated the frequency of such planets to be less
than 17.9% ($2\sigma$) around one star of the Pleiades cluster.


title: Modelling Giant Radio Halos

abstract:
  We review models for giant radio halos in clusters of galaxies, with a focus
on numerical and theoretical work. After summarising the most important
observations of these objects, we present an introduction to the theoretical
aspects of hadronic models. We compare these models with observations using
simulations and find severe problems for hadronic models. We give a short
introduction to reacceleration models and show results from the first
simulation of CRe reaccel- eration in cluster mergers. We find that in-line
with previous theoretical work, reacceleration models are able to elegantly
explain main observables of giant radio halos.


title:
The Extended GMRT Radio Halo Survey I: New upper limits on radio halos
  and mini-halos

abstract:
  A fraction of galaxy clusters host diffuse radio sources called radio halos,
radio relics and mini-halos. We present the sample and first results from the
Extended GMRT Radio Halo Survey (EGRHS)- an extension of the GMRT Radio Halo
Survey (GRHS, Venturi et al. 2007, 2008). It is a systematic radio survey of
galaxy clusters selected from the REFLEX and eBCS X-ray catalogs . Analysis of
GMRT data at 610/ 235/ 325 MHz on 12 galaxy clusters are presented. We report
the detection of a newly discovered mini-halo in the cluster RXJ1532.9+3021 at
610 MHz. A small scale relic (~200 kpc) is suspected in the cluster Z348. We do
not detect cluster-scale diffuse emission in 11 clusters. Robust upper limits
on the detection of radio halo of size of 1 Mpc are determined. We also present
upper limits on the detections of mini-halos in a sub-sample of cool-core
clusters. The upper limits for radio halos and mini-halos are plotted in the
radio power- X-ray luminosity plane and the correlations are discussed. Diffuse
extended emission, not related to the target clusters, but detected as
by-products in the sensitive images of two of the cluster fields (A689 and
RXJ0439.0+0715) are reported. Based on the information about the presence of
radio halos (or upper limits), available on 48 clusters out of the total sample
of 67 clusters (EGRHS+GRHS), we find that ~23% of the clusters host radio
halos. The radio halo fraction rises to ~31%, when only the clusters with X-ray
luminosities >8x10^44 erg/s are considered. Mini-halos are found in ~50 % of
cool-core clusters. A qualitative examination of the X-ray images of the
clusters with no diffuse radio emission indicates that a majority of these
clusters do not show extreme dynamical disturbances and supports the idea that
mergers play an important role in the generation of radio halos/relics.


title:
A geometric uncertainty principle with an application to Pleijel's
  estimate

abstract:
  Consider partitions of an open, bounded domain in $\mathbb{R}^n$. Then an
average element of the partition has either its Fraenkel asymmetry or its
deviation from the smallest element in the partition bounded away from 0 by a
universal constant. As an application, we give an (unspecified) improvement of
Pleijel's estimate on the number of nodal domains of a Laplacian eigenfunction
similar to recent work of Bourgain and improve a bound coming from spectral
partition problems.


title:
The Logarithmic Singularities of the Green Functions of the Conformal
  Powers of the Laplacian

abstract:
  Green functions play an important role in conformal geometry. In this paper,
we explain how to compute explicitly the logarithmic singularities of the Green
functions of the conformal powers of the Laplacian. These operators include the
Yamabe and Paneitz operators, as well as the conformal fractional powers of the
Laplacian arising from scattering theory for Poincar\'e-Einstein metrics. The
results are formulated in terms of Weyl conformal invariants arising from the
ambient metric of Fefferman-Graham. As applications we obtain "Green function"
characterizations of locally conformally flat manifolds and a spectral
theoretic characterization of the conformal class of the round sphere.


title:
A lower bound on the two-arms exponent for critical percolation on the
  lattice

abstract:
  We consider the standard site percolation model on the $d$-dimensional
lattice. A direct consequence of the proof of the uniqueness of the infinite
cluster of Aizenman, Kesten and Newman [Comm. Math. Phys. 111 (1987) 505-531]
is that the two-arms exponent is larger than or equal to $1/2$. We improve
slightly this lower bound in any dimension $d\geq2$. Next, starting only with
the hypothesis that $\theta(p)>0$, without using the slab technology, we derive
a quantitative estimate establishing long-range order in a finite box.


title:
Beam Energy Dependence of Higher Moments of Net-proton Multiplicity
  Distributions in Heavy-ion Collisions at RHIC

abstract:
  We present various order moments (Variance ($\sigma^2$), Skewness($S$),
Kurtosis($\kappa$)) of net-proton multiplicity distributions in Au+Au
collisions from the first phase of RHIC beam energy scan ({\sNN}=7.7$-$200
GeV). The measurements are carried out by the STAR detector at mid-rapidity
($|y|<0.5$) and within transverse momentum range $0.4<p_{T}<0.8$ {\gevc}. The
product of moments ({\SD} and \KV) are predicted to be sensitive to the
correlation length and connected to ratios of baryon number susceptibility. We
observe deviations below Poisson expectations in the most central collisions
for all of the energies. These results are compared with a transport model to
understand the effects not related to critical physics. We also discuss the
error estimation methods and the techniques to suppress centrality resolution
effect in the moment analysis.


title:
Exchange Interactions in Paramagnetic Amorphous and Disordered
  Crystalline CrN-based Systems

abstract:
  We present a first principles supercell methodology for the calculation of
exchange interactions of magnetic materials with arbitrary degrees of
structural and chemical disorder in their high temperature paramagnetic state.
It is based on a projection of the total magnetic energy of the system onto
local pair clusters, allowing the interactions to vary independently as a
response to their local environments. We demonstrate our method by deriving the
distance dependent exchange interactions in vibrating crystalline CrN, a
Ti$_{0.5}$Cr$_{0.5}$N solid solution as well as in amorphous CrN. Our method
reveals strong local environment effects in all three systems. In the amorphous
case we use the full set of exchange interactions in a search for the
non-collinear magnetic ground state.


title: Guaranteed Classification via Regularized Similarity Learning

abstract:
  Learning an appropriate (dis)similarity function from the available data is a
central problem in machine learning, since the success of many machine learning
algorithms critically depends on the choice of a similarity function to compare
examples. Despite many approaches for similarity metric learning have been
proposed, there is little theoretical study on the links between similarity
met- ric learning and the classification performance of the result classifier.
In this paper, we propose a regularized similarity learning formulation
associated with general matrix-norms, and establish their generalization
bounds. We show that the generalization error of the resulting linear separator
can be bounded by the derived generalization bound of similarity learning. This
shows that a good gen- eralization of the learnt similarity function guarantees
a good classification of the resulting linear classifier. Our results extend
and improve those obtained by Bellet at al. [3]. Due to the techniques
dependent on the notion of uniform stability [6], the bound obtained there
holds true only for the Frobenius matrix- norm regularization. Our techniques
using the Rademacher complexity [5] and its related Khinchin-type inequality
enable us to establish bounds for regularized similarity learning formulations
associated with general matrix-norms including sparse L 1 -norm and mixed
(2,1)-norm.


title:
Computer Architecture with Associative Processor Replacing Last Level
  Cache and SIMD Accelerator

abstract:
  This study presents a novel computer architecture where a last level cache
and a SIMD accelerator are replaced by an Associative Processor. Associative
Processor combines data storage and data processing and provides parallel
computational capabilities and data memory at the same time. An analytic
performance model of the new computer architecture is introduced. Comparative
analysis supported by simulation shows that this novel architecture may
outperform a conventional architecture comprising a SIMD coprocessor and a
shared last level cache while consuming less power.


title: Some applications of first-passage ideas to finance

abstract:
  Many problems in finance are related to first passage times. Among all of
them, we chose three on which we contributed personally. Our first example
relates Kolmogorov-Smirnov like goodness-of-fit tests, modified in such a way
that tail events and core events contribute equally to the test (in the
standard Kolmogorov-Smirnov, the tails contribute very little to the measure of
goodness-of-fit). We show that this problem can be mapped onto that of a random
walk inside moving walls. The second example is the optimal time to sell an
asset (modelled as a random walk with drift) such that the sell time is as
close as possible to the time at which the asset reaches its maximum value. The
last example concerns optimal trading in the presence of transaction costs. In
this case, the optimal strategy is to wait until the predictor reaches (plus or
minus) a threshold value before buying or selling. The value of this threshold
is found by mapping the problem onto that of a random walk between two walls.


title: Kirkman Equiangular Tight Frames and Codes

abstract:
  An equiangular tight frame (ETF) is a set of unit vectors in a Euclidean
space whose coherence is as small as possible, equaling the Welch bound. Also
known as Welch-bound-equality sequences, such frames arise in various
applications, such as waveform design and compressed sensing. At the moment,
there are only two known flexible methods for constructing ETFs: harmonic ETFs
are formed by carefully extracting rows from a discrete Fourier transform;
Steiner ETFs arise from a tensor-like combination of a combinatorial design and
a regular simplex. These two classes seem very different: the vectors in
harmonic ETFs have constant amplitude, whereas Steiner ETFs are extremely
sparse. We show that they are actually intimately connected: a large class of
Steiner ETFs can be unitarily transformed into constant-amplitude frames,
dubbed Kirkman ETFs. Moreover, we show that an important class of harmonic ETFs
is a subset of an important class of Kirkman ETFs. This connection informs the
discussion of both types of frames: some Steiner ETFs can be transformed into
constant-amplitude waveforms making them more useful in waveform design; some
harmonic ETFs have low spark, making them less desirable for compressed
sensing. We conclude by showing that real-valued constant-amplitude ETFs are
equivalent to binary codes that achieve the Grey-Rankin bound, and then
construct such codes using Kirkman ETFs.


title: Speed limit of FePt spin dynamics on femtosecond timescales

abstract:
  Magnetization manipulation is becoming an indispensable tool for both basic
and applied research. Theory predicts two types of ultrafast demagnetization
dynamics classified as type I and type II. In type II materials, a second
slower process takes place after the initial fast drop of magnetization. In
this letter we investigate this behavior for FePt recording materials with
perpendicular anisotropy. The magnetization dynamics have been simulated using
a thermal micromagnetic model based on the Landau-Lifshitz-Bloch equation. We
identify a transition to type II behavior and relate it to the electron
temperatures reached by the laser heating. This slowing down is a fundamental
limit to reconding speeds in heat assisted reversal.


title: Multimaterial Front Tracking

abstract:
  We present the first triangle mesh-based technique for tracking the evolution
of general three-dimensional multimaterial interfaces undergoing complex
topology changes induced by deformations and collisions. Our core
representation is a non-manifold triangle surface mesh with material labels
assigned to each half-face to distinguish volumetric regions. We advect the
vertices of the mesh in a Lagrangian manner, and employ a complete set of
collision-safe mesh improvement and topological operations that track and
update material labels. In particular, we develop a unified, collision-safe
strategy for handling complex topological operations acting on evolving triple-
and higher-valence junctions, and a flexible method to merge colliding
multimaterial meshes. We demonstrate our approach with a number of challenging
geometric flows, including passive advection, normal flow, and mean curvature
flow.


title:
Can the Differential Emission Measure constrain the timescale of energy
  deposition

abstract:
  In this paper, the ability of the Hinode/EIS instrument to detect radiative
signatures of coronal heating is investigated. Recent observational studies of
AR cores suggest that both the low and high frequency heating mechanisms are
consistent with observations. Distinguishing between these possibilities is
important for identifying the physical mechanism(s) of the heating. The
Differential Emission Measure (DEM) tool is one diagnostic that allows to make
this distinction, through the amplitude of the DEM slope coolward of the
coronal peak. It is therefore crucial to understand the uncertainties
associated with these measurements. Using proper estimations of the
uncertainties involved in the problem of DEM inversion, we derive confidence
levels on the observed DEM slope. Results show that the uncertainty in the
slope reconstruction strongly depends on the number of lines constraining the
slope. Typical uncertainty is estimated to be about $\pm 1.0$, in the more
favorable cases.


title:
The comfortable driving model revisited: Traffic phases and phase
  transitions

abstract:
  We study the spatiotemporal patterns resulting from different boundary
conditions for a microscopic traffic model and contrast it with empirical
results. By evaluating the time series of local measurements, the local traffic
states are assigned to the different traffic phases of Kerner's three-phase
traffic theory. For this classification we use the rule-based FOTO-method,
which provides `hard' rules for this assignment. Using this approach, our
analysis shows that the model is indeed able to reproduce three qualitatively
different traffic phases: free flow (F), synchronized traffic (S), and wide
moving jams (J). In addition, we investigate the likelihood of transitions
between the three traffic phases. We show that a transition from free flow (F)
to a wide moving jam (J) often involves an intermediate transition; first from
free flow F to synchronized flow S and then from synchronized flow to a wide
moving jam. This is supported by the fact that the so called F->S transition
(from free flow to synchronized traffic) is much more likely than a direct F->J
transition.
  The model under consideration has a functional relation between traffic flow
and traffic density. The fundamental hypothesis of the three-phase traffic
theory, however, postulates that the steady states of synchronized flow occupy
a two-dimensional region in the flow-density plane. Due to the obvious
discrepancy between the model investigated here and the postulate of the
three-phase traffic theory, the good agreement that we found could not be
expected. For a more detailed analysis, we also studied the vehicle dynamics at
a microscopic level and provide a comparison of real detector data with
simulated data of the identical highway segment.


title:
A Peculiar Microwave Quasi-periodic Pulsation with Zigzag Pattern in a
  CME-related Flare on 2005-01-15

abstract:
  A peculiar microwave quasi-periodic pulsation with zigzag pattern (Z-QPP) is
observed first by the Chinese Solar Broadband Spectrometer in Huairou
(SBRS/Huairou) at 1.10-1.34 GHz in a solar flare on 2005-01-15. The Z-QPP
occurred just in the early rising phase of the flare with weakly right-handed
circular polarization. Its period is only several decades millisecond.
Particularly, before and after the pulsation, there are many spectral fine
structures, such as zebra patterns, fibers, and millisecond spikes. The
microwave Z-QPP can provide some kinematic information of the source region in
the early rising phase of the flare, and the source width changes from about
1000 km to 3300 km, even if we have no imaging observations. The abundant
spectral fine structures possibly reflect the dynamic features of non-thermal
particles.


title: Signs of Susy

abstract:
  This doctoral thesis addresses aspects of Supersymmetry (Susy) phenomenology.
In addition to previously published work, it contains introductions to the
following topics: from classical mechanics to quantum field theory for the more
casual reader, electroweak naturalness, the Higgs as a pseudo-Nambu-Goldstone
boson, the MSSM and NMSSM, simple and less simple models of gauge-mediated Susy
breaking (GMSB), collider searches for Susy and other new theories, transverse
mass observables with missing energy, and Brazil-band plots. The previously
published work is as follows.
  The optimally natural Higgs-stop sector in the MSSM in light of the 2012
discovery of a Higgs boson is derived, namely that of almost maximal mixing,
with the scalar top partners almost as light as can be. The discovery is also
interpreted numerically in the NMSSM, with greater emphasis placed on the
visibility of the Higgs boson at the observed mass, i.e. on signal strengths. I
investigate the role played by the mediation scale of GMSB: this is found to be
as a control of the extent to which Yukawa couplings de-tune flavour-blind
relations set by gauge couplings. Finally, issues relating to the discovery or
exclusion of Susy at colliders are discussed. Bounds are derived for the masses
of new particles from LHC searches for excesses of jets and missing energy
without leptons, and compared to constraints arising from Higgs boson searches,
for models of GMSB and the Constrained Minimal Supersymmetric Standard Model. I
present a novel search strategy for new physics signatures with two neutral,
stable particles, when such particles are produced by boosted decays. (Susy
motivations include models with light gravitinos, pseudo-goldstinos, singlinos
or new photinos.) The method is shown to produce sharp mass peaks that enhance
the visibility of the signal, with mass reconstruction to 5% from O(100)
events.


title: Near Earth Asteroids:The Celestial Chariots

abstract:
  In this paper we put forward a proposal to use Near Earth Objects as
radiation shield for deep space exploration. In principle these objects can
provide also a spacious habitat for the astronauts and their supplies on their
journeys. We undertake also a detailed assessment of this proposal for a
mission from Earth to Mars.


title: Uncapacitated Flow-based Extended Formulations

abstract:
  An extended formulation of a polytope is a linear description of this
polytope using extra variables besides the variables in which the polytope is
defined. The interest of extended formulations is due to the fact that many
interesting polytopes have extended formulations with a lot fewer inequalities
than any linear description in the original space. This motivates the
development of methods for, on the one hand, constructing extended formulations
and, on the other hand, proving lower bounds on the sizes of extended
formulations.
  Network flows are a central paradigm in discrete optimization, and are widely
used to design extended formulations. We prove exponential lower bounds on the
sizes of uncapacitated flow-based extended formulations of several polytopes,
such as the (bipartite and non-bipartite) perfect matching polytope and TSP
polytope. We also give new examples of flow-based extended formulations, e.g.,
for 0/1-polytopes defined from regular languages. Finally, we state a few open
problems.


title: The hybrid spectral test

abstract:
  The starting point of this paper is the interplay between the construction
principle of a sequence and the characters of the compact abelian group that
underlies the construction. In case of the Halton sequence in base $\mathbf
b=(b_1, \ldots, b_s)$ in the $s$-dimensional unit cube $[0,1)^s$, which is an
important type of a digital sequence, this kind of duality principle leads to
the so-called $\mathbf b$-adic function system and provides the basis for the
$\mathbf b$-adic method, which we present in connection with hybrid sequences.
This method employs structural properties of the compact group of $\mathbf
b$-adic integers as well as $\mathbf b$-adic arithmetic to derive tools for the
analysis of the uniform distribution of sequences in $[0,1)^s$.
  We first clarify the point which function systems are needed to analyze
digital sequences. Then, we present the hybrid spectral test in terms of
trigonometric-, Walsh-, and $\mathbf b$-adic functions. Various notions of
diaphony as well as many figures of merit for rank-1 quadrature rules in
Quasi-Monte Carlo integration and for certain linear types of pseudo-random
number generators are included in this measure of uniform distribution.
Further, discrepancy may be approximated arbitrarily close by suitable versions
of the spectral test.


title: The Paraconsistent Logic of Quantum Superpositions

abstract:
  Physical superpositions exist both in classical and in quantum physics.
However, what is exactly meant by 'superposition' in each case is extremely
different. In this paper we discuss some of the multiple interpretations which
exist in the literature regarding superpositions in quantum mechanics. We argue
that all these interpretations have something in common: they all attempt to
avoid 'contradiction'. We argue in this paper, in favor of the importance of
developing a new interpretation of superpositions which takes into account
contradiction, as a key element of the formal structure of the theory, "right
from the start". In order to show the feasibility of our interpretational
project we present an outline of a paraconsistent approach to quantum
superpositions which attempts to account for the contradictory properties
present in general within quantum superpositions. This approach must not be
understood as a closed formal and conceptual scheme but rather as a first step
towards a different type of understanding regarding quantum superpositions.


title:
Spontaneous breaking of the BRST symmetry in presence of the Gribov
  horizon: renormalizability

abstract:
  An all orders algebraic proof of the multiplicative renormalizability of the
novel formulation of the Gribov-Zwanziger action proposed in Phys. Rev. D 86,
045005 (2012) [arXiv:1205.3934], and allowing for an exact but spontaneously
broken BRST symmetry, is provided.


title: Words with unbounded periodicity complexity

abstract:
  If an infinite non-periodic word is uniformly recurrent or is of bounded
repetition, then the limit of its periodicity complexity is infinity. Moreover,
there are uniformly recurrent words with the periodicity complexity arbitrarily
high at infinitely many positions.


title:
From antiferromagnetic order to magnetic textures in the two dimensional
  Fermi Hubbard model with synthetic spin orbit interaction

abstract:
  We study the interacting Fermi-Hubbard model in two spatial dimensions with
synthetic gauge coupling of the spin orbit Rashba type, at half-filling. Using
real space mean field theory, we numerically determine the phase as a function
of the interaction strength for different values of the gauge field parameters.
For a fixed value of the gauge field, we observe that when the strength of the
repulsive interaction is increased, the system enters into an antiferromagnetic
phase, then undergoes a first order phase transition to an non collinear
magnetic phase. Depending on the gauge field parameter, this phase further
evolves to the one predicted from the effective Heisenberg model obtained in
the limit of large interaction strength. We explain the presence of the
antiferromagnetic phase at small interaction from the computation of the
spin-spin susceptibility which displays a divergence at low temperatures for
the antiferromagnetic ordering. We discuss, how the divergence is related to
the nature of the underlying Fermi surfaces. Finally, the fact that the first
order phase transitions for different gauge field parameters occur at unrelated
critical interaction strengths arises from a Hofstadter-like situation, i.e.
for different magnetic phases, the mean-field Hamiltonians have different
translational symmetries.


title:
Alternative method for the quantitative determination of Rashba- and
  Dresselhaus spin-orbit interaction using the magnetization

abstract:
  The quantum oscillatory magnetization M of a two-dimensional electron system
in a magnetic field B is found to provide quantitative information on both the
Rashba- and Dresselhaus spin-orbit interaction (SOI). This is shown by first
numerically solving the model Hamiltonian including the linear Rashba- and
Dresselhaus SOI and the Zeeman term in an in particular doubly tilted magnetic
field and second evaluating the intrinsically anisotropic magnetization for
different directions of the in-plane magnetic field component. The amplitude of
specific magnetic quantum oscillations in M(B) is found to be a direct measure
of the SOI strength at fields B where SOI-induced Landau level anticrossings
occur. The anisotropic M allows one to quantify the magnitude of both
contributions as well as their relative sign. We use realistic sample
parameters and show that recently reported experimental techniques provide a
sensitivity which allows for the detection of the predicted phenomena.


title: The International Linear Collider

abstract:
  The International Linear Collider (ILC) is a proposed electron-positron
collider for the centre-of-mass energy range of 200 to 500 GeV and with upgrade
options towards 1 TeV. The ILC would be the ideal tool to explore with high
precision the properties of the new Higgs-like particle that has recently been
discovered at the LHC with a mass of around 125 GeV. The ILC accelerator design
is based on the mature superconducting technology that has been developed in
the TESLA collaboration and that is currently being used for the European XFEL.
The exploitation of the huge physics potential of the ILC is a challenge for
the design of the ILC detectors.


title:
Behavior in a Shared Resource Game with Cooperative, Greedy, and
  Vigilante Players

abstract:
  We study a problem of trust in a distributed system in which a common
resource is shared by multiple parties. In such naturally information-limited
settings, parties abide by a behavioral protocol that leads to fair sharing of
the resource. However, greedy players may defect from a cooperative protocol
and achieve a greater than fair share of resources, often without significant
adverse consequences to themselves. In this paper, we study the role of a few
vigilante players who also defect from a cooperative resource-sharing protocol
but only in response to perceived greedy behavior. For a simple model of
engagement, we demonstrate surprisingly complex dynamics among greedy and
vigilante players. We show that the best response function for the
greedy-player under our formulation has a jump discontinuity, which leads to
conditions under which there is no Nash equilibrium. To study this property, we
formulate an exact representation for the greedy player best response function
in the case when there is one greedy player, one vigilante player and $N-2$
cooperative players. We use this formulation to show conditions under which a
Nash equilibrium exists. We also illustrate that in the case when there is no
Nash equilibrium, then the discrete dynamic system generated from fictitious
play will not converge, but will oscillate indefinitely as a result of the jump
discontinuity. The case of multiple vigilante and greedy players is studied
numerically. Finally, we explore the relationship between fictitious play and
the better response dynamics (gradient descent) and illustrate that this
dynamical system can have a fixed point even when the discrete dynamical system
arising from fictitious play does not.


title:
Modified 2D Proca theory: off-shell nilpotent symmetries and their
  mathematical as well as physical implications

abstract:
  We derive the off-shell nilpotent Becchi-Rouet-Stora-Tyutin (BRST),
anti-BRST, (anti-)co-BRST, a bosonic and the ghost-scale symmetry
transformations for a couple of equivalent Lagrangian densities of the two (1 +
1)-dimensional (2D) Stueckelberg-modified version of Proca theory which also
incorporates a pseudo-scalar field. We also discuss algebraically suitable
discrete symmetry transformations of the theory. Finally, we demonstrate the
relevance of the above continuous and discrete symmetries in the context of
differential geometry and establish that our present massive 2D theory is a
tractable field theoretic model for the Hodge theory. One of the key novel
observations of our present investigation is the appearance of Curci-Ferrari
(CF) type restrictions even in the case of our present massive 2D Abelian
1-form gauge theory. We also point out the mathematical as well as physical
implications of the above pseudo-scalar field in our present theory.


title: Diffusion-limited aggregation on the hyperbolic plane

abstract:
  We consider an analogous version of the diffusion-limited aggregation model
defined on the hyperbolic plane. We prove that almost surely the aggregate
viewed at time infinity will have a positive density.


title: Performance of the ALICE VZERO system

abstract:
  ALICE is an LHC experiment devoted to the study of strongly interacting
matter in proton-proton, proton--nucleus and nucleus-nucleus collisions at
ultra-relativistic energies. The ALICE VZERO system, made of two scintillator
arrays at asymmetric positions, one on each side of the interaction point,
plays a central role in ALICE. In addition to its core function as a trigger,
the VZERO system is used to monitor LHC beam conditions, to reject beam-induced
backgrounds and to measure basic physics quantities such as luminosity,
particle multiplicity, centrality and event plane direction in nucleus-nucleus
collisions. After describing the VZERO system, this publication presents its
performance over more than four years of operation at the LHC.


title:
Wavelet decomposition techniques and Hardy inequalities for function
  spaces on cellular domains

abstract:
  A rather tricky question is the construction of wavelet bases on domains for
suitable function spaces (Sobolev, Besov, Triebel-Lizorkin type). In his
monograph from 2008, Triebel presented an approach how to construct wavelet
(Riesz) bases in function spaces of Besov and Triebel-Lizorkin type on cellular
domains, in particular on the cube. However, he had to exclude essential
exceptional values of the smoothness parameter $s$, for instance the theorems
do not cover the Sobolev space W_2^1(Q) on the n-dimensional cube Q for n at
least 2.
  Triebel also gave an idea how to deal with those exceptional values for the
Triebel-Lizorkin function space scale on the cube Q: He suggested to introduce
modified function spaces for the critical values, the so-called reinforced
spaces. In this paper we start examining these reinforced spaces and transfer
the crucial decomposition theorems necessary for establishing a wavelet basis
from the non-critical values to analogous results for the critical cases now
decomposing the reinforced function spaces of Triebel-Lizorkin type.


title:
Chromospheric mass motions and intrinsic sunspot rotations for NOAA
  Active Regions 10484, 10486, and 10488 using ISOON data

abstract:
  This work utilizes Improved Solar Observing Optical Network (ISOON: Neidig et
al. 2003) continuum (630.2 nm) and H{\alpha} (656.2 nm) data to: 1) detect and
measure intrinsic sunspot rotations occurring in the photosphere and
chromosphere, 2) identify and measure chromospheric filament mass motions, and
3) assess any large-scale photospheric and chromospheric mass couplings.
Significant results from October 27-29, 2003, using the techniques of Brown et
al. (2003), indicate significant counter-rotation between the two large
sunspots in NOAA AR 10486 on October 29, as well as discrete filament mass
motions in NOAA AR 10484 on October 27 that appears associated with at least
one C-class solar flare.


title:
Crowds, Bluetooth, and Rock-n-Roll. Understanding Music Festival
  Participant Behavior

abstract:
  In this paper we present a study of sensing and analyzing an offline social
network of participants at a large-scale music festival (8 days, 130,000+
participants). We place 33 fixed-location Bluetooth scanners in strategic spots
around the festival area to discover Bluetooth-enabled mobile phones carried by
the participants, and thus collect spatio-temporal traces of their mobility and
interactions. We subsequently analyze the data on two levels. On the micro
level, we run a community detection algorithm to reveal a variety of groups the
festival participants form. On the macro level, we employ an Infinite
Relational Model (IRM) in order to recover the structure of the social network
related to participants' music preferences. The obtained structure in the form
of clusters of concerts and participants is then interpreted using
meta-information about music genres, band origins, stages, and dates of
performances. We show that most of the concerts clusters can be described by
one or more of the meta-features, effectively revealing preferences of
participants (e.g. a cluster of US bands) and discuss the significance of the
findings and the potential and limitations of the used method. Finally, we
discuss the possibility of employing the described method and techniques for
creating user-oriented applications and extending the sensing capabilities
during large-scale events by introducing user involvement.


title: Opinion dynamics and wisdom under out-group discrimination

abstract:
  We study a DeGroot-like opinion dynamics model in which agents may oppose
other agents. As an underlying motivation, in our setup, agents want to adjust
their opinions to match those of the agents of their 'in-group' and, in
addition, they want to adjust their opinions to match the 'inverse' of those of
the agents of their 'out-group'. Our paradigm can account for persistent
disagreement in connected societies as well as bi- and multi-polarization.
Outcomes depend upon network structure and the choice of deviation function
modeling the mode of opposition between agents. For a particular choice of
deviation function, which we call soft opposition, we derive necessary and
sufficient conditions for long-run polarization. We also consider social
influence (who are the opinion leaders in the network?) as well as the question
of wisdom in our naive learning paradigm, finding that wisdom is difficult to
attain when there exist sufficiently strong negative relations between agents.


title:
Electrical control of phonon mediated spin relaxation rate in
  semiconductor quantum dots: the Rashba vs the Dresselhaus spin-orbit
  couplings

abstract:
  In symmetric quantum dots (QDs), it is well known that the spin-hot spot
(i.e., the cusp-like structure due to the presence of degeneracy near the level
or anticrossing point) is present for the pure Rashba case but is absent for
the pure Dresselhaus case [Phys. Rev. Lett. 95, 076805 (2005)]. Since the
Dresselhaus spin-orbit coupling dominates over the Rashba spin-orbit coupling
in GaAs and GaSb QDs, it is important to find the exact location of the
spin-hot spot or the cusp-like structure even for the pure Dresselhaus case. In
this paper, for the first time, we present analytical and numerical results
that show that the spin-hot spot can also be seen for the pure Dresselhaus
spin-orbit coupling case by inducing large anisotropy through external gates.
At or nearby the spin-hot spot, the spin transition rate enhances and the
decoherence time reduces by several orders of magnitude compared to the case
with no spin-hot spot. Thus one should avoid such locations when designing QD
spin based transistors for the possible implementation in quantum logic gates,
solid state quantum computing and quantum information processing. It is also
possible to extract the exact experimental data (Phys. Rev. Lett. 100, 046803
(2008)) for the phonon mediated spin-flip rates from our developed theoretical
model.


title:
Galactic winds - How to launch galactic outflows in typical Lyman-break
  galaxies

abstract:
  We perform hydrodynamical simulations of a young galactic disc embedded in a
hot gaseous halo using parameters typical for Lyman break galaxies (LBGs). We
take into account the (static) gravitational potentials due to a dark matter
halo, a stellar bulge and a disc of stars and gas. Star formation is treated by
a local Kennicutt-Schmidt law. We simplify the structure of the interstellar
medium by restricting the computational domain to a 25th of the full azimuthal
angle, effectively assuming large-scale axisymmetry and neglecting any effects
of spiral structure, and focus on the large-scale ISM drivers, the
superbubbles. Supernovae are triggered randomly and have preset event sizes of
several tens to hundreds. We further investigate different halo gas pressures
and energy injection methods. Many of our simulated galaxies, but not all,
develop bipolar outflows. We characterise the strength of the outflow by mass
and energy outflow rates, and investigate the effect of changes to the details
of the model. We find that supernovae are more effective if comprised into
larger superbubbles. The weight and the pressure of the halo gas is able to
quench galactic outflows. The wind emerges from a series of superbubbles in
regions where a critical star formation density is exceeded. The superbubbles
expand into the gaseous halo at slightly supersonic speed, producing radiative
shock waves with similar characteristics as the absorptions systems observed
around LBGs.


title: Superradiance without event horizons in General Relativity

abstract:
  Superradiant scattering processes are studied in general relativistic systems
which, unlike rotating and/or charged black holes, do not exhibit an event
horizon. Inspired by Zel'dovich's seminal works on the amplification of waves
by a rotating cylinder, we analyse, in the context of General Relativity, the
possibility of superradiance for electromagnetic waves reflecting off a
rotating star and for charged scalar perturbations impinging on a charged
sphere. The role of energy dissipation in these systems is analysed and
compared with the role of the event horizon in black hole superradiance.


title:
Soft-boundary graphene nanoribbon formed by a graphene sheet above a
  perturbed ground plane: conductivity profile and SPP modal current
  distribution

abstract:
  An infinite sheet of graphene lying above a perturbed ground plane is
studied. The perturbation is a two dimensional ridge, and a bias voltage is
applied between the graphene and the ground plane, resulting in a graphene
nanoribbonlike structure with a soft-boundary (SB) The spatial distribution of
the graphene conductivity forming the soft-boundary is studied as a function of
the ridge parameters and the bias voltage. The current distribution of the
fundamental TM surface plasmon polariton (SPP) is considered. The effect of the
ridge parameters and shape of the soft boundary on the current distributions
are investigated, and the conditions are studied under which the mode remains
confined to the vicinity of the ridge region.


title:
First-principles calculations of the structural, elastic and electronic
  properties of MNxC1-x (M=Ti, Zr, Hf; 0<x<1) carbonitrides at ambient and
  elevated hydrostatic pressure

abstract:
  The structural, electronic, and elastic properties of three mixed transition
metal carbonitrides TiNxC1-x, ZrNxC1-x, and HfNxC1-x (0<x<1) with the rock-salt
structure were calculated at ambient and elevated up to 50 GPa hydrostatic
pressures in the framework of the density functional theory methods. The
lattice constants, densities, and bulk moduli of the considered compounds were
shown to behave as linear functions of the nitrogen concentration x. The
obtained linear dependencies of all these parameters allow for getting their
estimates at any value of x in the range from 0 to 1. Gradual enhancement of
the ionicity of the chemical bonds with gradual replacement of carbon by
nitrogen was demonstrated by calculating the bond orders and electron density
difference distributions.


title: Charmonium Potentials at Finite Temperature

abstract:
  The charmonium states at non-zero temperature are studied on anisotropic
lattices with 2 dynamical quark flavours. Non-local operators are used to
determine the Nambu-Bethe-Salpeter (NBS) wavefunctions via both conventional
fitting methods and the Maximum Entropy Method. The interquark potential is
determined from the solution of the Schrodinger equation, given the NBS
wavefunction as input following the HAL QCD method. We observe a temperature
dependent potential which becomes steeper as the temperature decreases.


title: Idempotent generated algebras and Boolean powers of commutative rings

abstract:
  A Boolean power S of a commutative ring R has the structure of a commutative
R-algebra, and with respect to this structure, each element of S can be written
uniquely as an R-linear combination of orthogonal idempotents so that the sum
of the idempotents is 1 and their coefficients are distinct. In order to
formalize this decomposition property, we introduce the concept of a Specker
R-algebra, and we prove that the Boolean powers of R are up to isomorphism
precisely the Specker R-algebras. We also show that these algebras are
characterized in terms of a functorial construction having roots in the work of
Bergman and Rota. When R is indecomposable, we prove that S is a Specker
R-algebra iff S is a projective R-module, thus strengthening a theorem of
Bergman, and when R is a domain, we show that S is a Specker R-algebra iff S is
a torsion-free R-module. For an indecomposable R, we prove that the category of
Specker R-algebras is equivalent to the category of Boolean algebras, and hence
is dually equivalent to the category of Stone spaces. In addition, when R is a
domain, we show that the category of Baer Specker R-algebras is equivalent to
the category of complete Boolean algebras, and hence is dually equivalent to
the category of extremally disconnected compact Hausdorff spaces. For a totally
ordered R, we prove that there is a unique partial order on a Specker R-algebra
S for which it is an f-algebra over R, and show that S is equivalent to the
R-algebra of piecewise constant continuous functions from a Stone space X to R
equipped with the interval topology.


title: On quantum Renyi entropies: a new generalization and some properties

abstract:
  The Renyi entropies constitute a family of information measures that
generalizes the well-known Shannon entropy, inheriting many of its properties.
They appear in the form of unconditional and conditional entropies, relative
entropies or mutual information, and have found many applications in
information theory and beyond. Various generalizations of Renyi entropies to
the quantum setting have been proposed, most notably Petz's quasi-entropies and
Renner's conditional min-, max- and collision entropy. Here, we argue that
previous quantum extensions are incompatible and thus unsatisfactory.
  We propose a new quantum generalization of the family of Renyi entropies that
contains the von Neumann entropy, min-entropy, collision entropy and the
max-entropy as special cases, thus encompassing most quantum entropies in use
today. We show several natural properties for this definition, including
data-processing inequalities, a duality relation, and an entropic uncertainty
relation.


title:
Surface plasmon polaritons on soft-boundary graphene nanoribbons and
  their application as voltage controlled plasmonic switches and frequency
  demultiplexers

abstract:
  A graphene sheet gated with a ridged ground plane, creating a soft-boundary
(SB) graphene nanoribbon, is considered. By adjusting the ridge parameters and
bias voltage a channel can be created on the graphene which can guide TM
surface plasmon polaritons (SPP). Two types of modes are found; fundemental and
higher-order modes with no apparent cutoff frequency and with energy
distributed over the created channel, and edge modes with energy concen-trated
at the soft-boundary edge. Dispersion curves, electric near-field patterns, and
current distributions of these modes are determined. Since the location where
energy is concentrated in the edge modes can be easily controlled
electronically by the bias voltage and frequency, the edge-mode phenomena is
used to propose a novel voltage controlled plasmonic switch and a plasmonic
frequency demultiplexer.


title:
Parameter estimation using NOON states over a relativistic quantum
  channel

abstract:
  We study the effect of the acceleration of the observer on a parameter
estimation protocol using NOON states. An inertial observer, Alice, prepares a
NOON state in Unruh modes of the quantum field, and sends it to an accelerated
observer, Rob. We calculate the quantum Fisher information of the state
received by Rob. We find the counter-intuitive result that the single rail
encoding outperforms the dual rail. The NOON states have an optimal $N$ for the
maximum information extractable by Rob, given his acceleration. This optimal
$N$ decreases with increasing acceleration.


title:
Universal current fluctuations in the symmetric exclusion process and
  other diffusive systems

abstract:
  We show, using the macroscopic fluctuation theory of Bertini, De Sole,
Gabrielli, Jona-Lasinio, and Landim, that the statistics of the current of the
symmetric simple exclusion process (SSEP) connected to two reservoirs are the
same on an arbitrary large finite domain in dimension $d$ as in the one
dimensional case. Numerical results on squares support this claim while results
on cubes exhibit some discrepancy. We argue that the results of the macroscopic
fluctuation theory should be recovered by increasing the size of the contacts.
The generalization to other diffusive systems is straightforward.


title: Extremal part of the PBW-filtration and E-polynomials

abstract:
  Given a reduced irreducible root system, the corresponding nil-DAHA is used
to calculate the extremal coefficients of nonsymmetric Macdonald polynomials,
also called E-polynomails, in the limit t=infinity and for antidominant
weights, which is an important ingredient of the new theory of nonsymmetric
q-Whittaker function. These coefficients are pure q-powers and their degrees
are expected to coincide in the untwisted setting with the extremal degrees of
the so-called PBW-filtration in the corresponding finite-dimensional
irreducible representations of the simple Lie algebra for any root systems.
This is a particular case of a general conjecture in terms of the level-one
Demazure modules. We prove this coincidence for all Lie algebras of classical
type and for G_2, and also establish the relations of our extremal degrees to
minimal q-degrees of the extremal terms of the Kostant q-partition function;
they coincide with the latter only for some root systems.


title:
Modelling Carbon Radio Recombination Line observation towards the
  Ultra-Compact HII region W48A

abstract:
  We model Carbon Recombination Line (CRL) emission from the Photo Dissociation
Region (PDR) surrounding the Ultra-Compact (UC) HII region W48A. Our modelling
shows that the inner regions ($A_V \sim 1$) of the CII layer in the PDR
contribute significantly to the CRL emission. The dependence of line ratios of
CRL emission with the density of the PDR and the far ultra-violet (FUV)
radiation incident on the region is explored over a large range of these
parameters that are typical for the environments of UCHII regions. We find that
by observing a suitable set of CRLs it is possible to constrain the density of
the PDR. If the neutral density in the PDR is high ($\gtrsim 10^7$ \cmthree)
CRL emission is bright at high frequencies ($\gtrsim 20$ GHz), and absorption
lines from such regions can be detected at low frequencies ($\lesssim 10$ GHz).
Modelling CRL observations towards W48A shows that the UCHII region is embedded
in a molecular cloud of density of about $4 \times$ 10$^7$ \cmthree.


title:
Leaving no stone unturned in the hunt for SUSY naturalness: A Snowmass
  whitepaper

abstract:
  Imposing electroweak scale naturalness constraints (low \Delta_{EW}) on SUSY
models leads to mass spectra characterized by light higgsinos ~100-300 GeV,
highly mixed top-squarks and gluinos at the 1-5 TeV scale and allows for m_h
~125 GeV. First and second generation squarks can easily live at the 5-20 TeV
scale, thus providing at least a partial solution to the SUSY flavor/CP
problems. For such models at the LHC, gluino pair production is followed by
cascade decays to t- and b-quark rich final states along with multileptons. The
reach of LHC14 with 300 fb^{-1} is computed to be around m_{\tg} 1.8 TeV.
However, the small magnitude of the \mu-parameter-- a necessary condition for
naturalness-- leads to a unique hadronically quite same-sign diboson (W^\pm
W^\pm) signature from wino pair production. In low \Delta_{EW} models with
unified gaugino masses, this signature yields a somewhat higher reach up to
m_{\tg} 2.1 TeV. The smallness of |\mu| implies that the ILC should be a
higgsino factory in addition to a Higgs factory, and a complete search for SUSY
naturalness seems possible for \sqrt{s} 600 GeV. Since a thermal
under-abundance of higgsino-like WIMP dark matter (DM) is expected, there is
ample room for an axion DM contribution. A thorough search for higgsino-like
WIMPs can be made by next generation WIMP detectors, such as those with
ton-scale noble liquid targets.


title: Sharp Transition between Coalescence and Noncoalescence of Sessile Drops

abstract:
  Unexpectedly, under certain conditions, sessile drops from different but
completely miscible liquids do not always coalesce instantaneously upon
contact: the drop bodies remain separated in a temporary state of
noncoalescence, connected through a thin liquid bridge. Here we investigate the
transition between the states of instantaneous coalescence and temporary
noncoalescence. Experiments reveal that it is barely influenced by viscosities
and absolute surface tensions. The main system control parameters for the
transition are the arithmetic means of the three-phase angles,
$\overline{\Theta}_a$ and the surface tension differences $\Delta\gamma$
between both liquids. These relevant parameters can be combined into a single
system parameter, a speciffic Marangoni number $\widetilde{M} = 3\Delta\gamma /
(2\overline{\gamma}\overline{\Theta}_a^2)$. This $\widetilde{M}$ universally
characterizes the coalescence respectively transition behavior as a function of
both, the physicochemical liquid properties and the shape of the liquid body in
the contact region. The transition occurs at a certain threshold value
$\widetilde{M}_t$ and is sharp within the experimental resolution. The
experimentally observed threshold value of $\widetilde{M}_t \approx 2$ agrees
quantitatively with values obtained by simulations assuming authentic real
space data. The simulations indicate that the absolute value of
$\widetilde{M}_t$ very weakly depends on the molecular diffusivity.


title:
Reconstruction of the refractive index from experimental backscattering
  data using a globally convergent inverse method

abstract:
  The problem to be studied in this work is within the context of coefficient
identification problems for the wave equation. More precisely, we consider the
problem of reconstruction of the refractive index (or equivalently, the
dielectric constant) of an inhomogeneous medium using one backscattering
boundary measurement. The goal of this paper is to analyze the performance of a
globally convergent algorithm of Beilina and Klibanov on experimental data
acquired in the Microwave Laboratory at University of North Carolina at
Charlotte. The main challenge working with experimental data is the the huge
misfit between these data and computationally simulated data. We present data
pre-processing steps to make the former somehow look similar to the latter.
Results of both non-blind and blind targets are shown indicating good
reconstructions even for high contrasts between the targets and the background
medium.


title: Non-locality breaking qubit channels

abstract:
  Entanglement breaking channels play a significant role in quantum information
theory. In this work we investigate qubit channels through their property of
`non-locality breaking', defined in a natural way but within the purview of
CHSH nonlocality. This also provides a different perspective on the
relationship between entanglement and nonlocality through the dual picture of
quantum channels instead of through states. For a channel to be entanglement
breaking it is sufficient to `break' the entanglement of maximally entangled
states. We provide examples to show that for CHSH nonlocality breaking such a
property does not hold in general, though for certain channels and for a
restricted class of states for all channels this holds.We also consider
channels whose output remains local under SLOCC and call them `strongly
non-locality breaking'.
  We provide a closed form necessary-sufficient condition for any two-qubit
state to show hidden CHSH nonlocality, which is likely to be useful for other
purposes as well. This in turn allows us to characterize all strongly
non-locality breaking qubit channels. It turns out that unital qubit channels
breaking nonlocality of maximally entangled states are strongly non-locality
breaking while extremal qubit channels cannot be so unless they are
entanglement breaking.


title:
Temperature- and Magnetic-Field-Tuning of Magnetic Phases in
  Multiferroic NdFe3(BO3)4

abstract:
  We report the low-temperature coexistence in NdFe3(BO3)4 of an incommensurate
magnetic phase with a strained commensurate magnetic phase that is primarily at
the surface of the crystal. Increasing the temperature or magnetic field
decreases the incommensurability and stabilizes the commensurate magnetic phase
above Tic ~14 K or Hic = 0.9 T. A comparison to published studies indicates the
onset of longitudinal magnetostriction and electric polarization at the
magnetic-field-induced transition, which may arise due to a basal plane
spin-flop and canting of the moments along the field direction.


title:
Diffraction anomalies in hybrid structures based on chalcogenide-coated
  opal photonic crystals

abstract:
  The results of spectroscopic studies of the diffraction anomalies (the
so-called resonant Wood anomalies) in spatially-periodic hybrid structures
based on halcogenide (GST225)-coated opal films of various thickness are
presented. A theoretical analysis of spectral-angular dependencies of the Wood
anomalies has been made by means of a phenomenological approach using the
concept of the effective refractive index of waveguiding surface layer.


title:
Hidden beauty molecules within the local hidden gauge approach and heavy
  quark spin symmetry

abstract:
  Using a coupled channel unitary approach, combining the heavy quark spin
symmetry and the dynamics of the local hidden gauge, we investigate the
meson-meson interaction with hidden beauty and obtain several new states. Both
I=0 and I=1 states are analyzed and it is shown that in the I=1 sector, the
interactions are too weak to create any bound states within our framework. In
total, we predict with confidence the existence of 6 bound states, and weakly
bound 6 more possible states. The existence of these weakly bound states depend
on the influence of the coupled channel effects.


title:
Quarkonium and glueball admixtures of the scalar-isoscalar resonances
  f0(1370), f0(1500) and f0(1710)

abstract:
  Using the U(3)R x U(3)L extended Linear Sigma Model with the ordinary
(pseudo)scalar and (axial)vector mesons as well as a scalar glueball, we study
the vacuum phenomenology of the scalar-isoscalar resonances f0(1370), f0(1500)
and f0(1710). We present here a solution, based only on the masses and not yet
on decays, in which the resonances f0(1370) and f0(1500) are predominantly
nonstrange and strange qbar-q states respectively, and the resonance f0(1710)
is predominantly a scalar glueball.


title: Determination of the far-infrared dust opacity in a prestellar core

abstract:
  (abridged) We correlated near-infrared stellar H-Ks colour excesses of
background stars from NTT/SOFI with the far-IR optical depth map, tauFIR,
derived from Herschel 160, 250, 350, and 500 um data. The Herschel maps were
also used to construct a model for the cloud to examine the effect of
temperature gradients on the estimated optical depths and dust absorption
cross-sections. A linear correlation is seen between the colour H-Ks and tauFIR
up to high extinctions (AV ~ 25). The correlation translates to the average
extinction ratio A250um/AJ = 0.0014 +/- 0.0002, assuming a standard
near-infrared extinction law and a dust emissivity index beta=2. Using an
empirical NH/AJ ratio we obtain an average absorption cross-section per H
nucleus of sigmaH(250um) = (1.8 +/- 0.3) * 10^(-25) cm^2 / H-atom,
corresponding to a cross-section per unit mass of gas kappaG(250 um) = 0.08 +/-
0.01 cm^2 / g. The cloud model however suggests that owing to the bias caused
by temperature changes along the line-of-sight these values underestimate the
true cross-sections by up to 40% near the centre of the core. Assuming that the
model describes the effect of the temperature variation on tauFIR correctly, we
find that the relationship between H-Ks and tauFIR agrees with the recently
determined relationship between sigmaH and NH in Orion A. The derived far-IR
cross-section agrees with previous determinations in molecular clouds with
moderate column densities, and is not particularly large compared with some
other cold cores. We suggest that this is connected to the core not beng very
dense (the central density is likely to be ~10^5 cm^-3) and judging from
previous molecular line data, it appears to be at an early stage of chemical
evolution.


title:
A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself To Be A
  Very Long Period, Highly Eccentric Spectroscopic Stellar Binary

abstract:
  We report the discovery of a highly eccentric, double-lined spectroscopic
binary star system (TYC 3010-1494-1), comprising two solar-type stars that we
had initially identified as a single star with a brown dwarf companion. At the
moderate resolving power of the MARVELS spectrograph and the spectrographs used
for subsequent radial-velocity (RV) measurements (R ~ <30,000), this particular
stellar binary mimics a single-lined binary with an RV signal that would be
induced by a brown dwarf companion (Msin(i)~50 M_Jup) to a solar-type primary.
At least three properties of this system allow it to masquerade as a single
star with a very low-mass companion: its large eccentricity (e~0.8), its
relatively long period (P~238 days), and the approximately perpendicular
orientation of the semi-major axis with respect to the line of sight (omega~189
degrees). As a result of these properties, for ~95% of the orbit the two sets
of stellar spectral lines are completely blended, and the RV measurements based
on centroiding on the apparently single-lined spectrum is very well fit by an
orbit solution indicative of a brown dwarf companion on a more circular orbit
(e~0.3). Only during the ~5% of the orbit near periastron passage does the
true, double-lined nature and large RV amplitude of ~15 km/s reveal itself. The
discovery of this binary system is an important lesson for RV surveys searching
for substellar companions; at a given resolution and observing cadence, a
survey will be susceptible to these kinds of astrophysical false positives for
a range of orbital parameters. Finally, for surveys like MARVELS that lack the
resolution for a useful line bisector analysis, it is imperative to monitor the
peak of the cross-correlation function for suspicious changes in width or
shape, so that such false positives can be flagged during the candidate vetting
process.


title: Reversible Diffusion by Thermal Fluctuations

abstract:
  A model for diffusion in liquids that couples the dynamics of tracer
particles to a fluctuating Stokes equation for the fluid is investigated in the
limit of large Schmidt number. In this limit, the concentration of tracers is
shown to satisfy a closed-form stochastic advection-diffusion equation that is
used to investigate the collective diffusion of hydrodynamically-correlated
tracers through a combination of Eulerian and Lagrangian numerical methods.
This analysis indicates that transport in liquids is quite distinct from the
traditional Fickian picture of diffusion. While the ensemble-averaged
concentration follows Fick's law with a diffusion coefficient that obeys the
Stokes-Einstein relation, each instance of the diffusive mixing process
exhibits long-ranged giant fluctuations around its average behavior. We
construct a class of mesoscopic models for diffusion in liquids at different
observation scales in which the renormalized diffusion coefficient depends on
this scale. This indicates that the Fickian diffusion coefficient in liquids is
not a material constant, but rather, changes with the scale at which
experimental measurements are performed.


title:
A Minimally-Resolved Immersed Boundary Model for Reaction-Diffusion
  Problems

abstract:
  We develop an immersed-boundary approach to modeling reaction-diffusion
processes in dispersions of reactive spherical particles, from the
diffusion-limited to the reaction-limited setting. We represent each reactive
particle with a minimally-resolved 'blob' using many fewer degrees of freedom
per particle than standard discretization approaches. More complicated or more
highly resolved particle shapes can be built out of a collection of reactive
blobs. We demonstrate numerically that the blob model can provide an accurate
representation at low to moderate packing densities of the reactive particles,
at a cost not much larger than solving a Poisson equation in the same domain.
Unlike multipole expansion methods, our method does not require
analytically-computed Green's functions, but rather, computes regularized
discrete Green's functions on the fly by using a standard grid-based
discretization of the Poisson equation. This allows for great flexibility in
implementing different boundary conditions, coupling to fluid flow or thermal
transport, and the inclusion of other effects such as temporal evolution and
even nonlinearities. We develop multigrid-based preconditioners for solving the
linear systems that arise when using implicit temporal discretizations or
studying steady states. In the diffusion-limited case the resulting linear
system is a saddle-point problem, the efficient solution of which remains a
challenge for suspensions of many particles. We validate our method by
comparing to published results on reaction-diffusion in ordered and disordered
suspensions of reactive spheres.


title:
Modeling and Control of Rare Segments in BitTorrent with Epidemic
  Dynamics

abstract:
  Despite its existing incentives for leecher cooperation, BitTorrent file
sharing fundamentally relies on the presence of seeder peers. Seeder peers
essentially operate outside the BitTorrent incentives, with two caveats: slow
downlinks lead to increased numbers of "temporary" seeders (who left their
console, but will terminate their seeder role when they return), and the
copyright liability boon that file segmentation offers for permanent seeders.
Using a simple epidemic model for a two-segment BitTorrent swarm, we focus on
the BitTorrent rule to disseminate the (locally) rarest segments first. With
our model, we show that the rarest-segment first rule minimizes transition time
to seeder (complete file acquisition) and equalizes the segment populations in
steady-state. We discuss how alternative dissemination rules may {\em
beneficially increase} file acquisition times causing leechers to remain in the
system longer (particularly as temporary seeders). The result is that leechers
are further enticed to cooperate. This eliminates the threat of extinction of
rare segments which is prevented by the needed presence of permanent seeders.
Our model allows us to study the corresponding trade-offs between performance
improvement, load on permanent seeders, and content availability, which we
leave for future work. Finally, interpreting the two-segment model as one
involving a rare segment and a "lumped" segment representing the rest, we study
a model that jointly considers control of rare segments and different uplinks
causing "choking," where high-uplink peers will not engage in certain
transactions with low-uplink peers.


title: Learning Using Privileged Information: SVM+ and Weighted SVM

abstract:
  Prior knowledge can be used to improve predictive performance of learning
algorithms or reduce the amount of data required for training. The same goal is
pursued within the learning using privileged information paradigm which was
recently introduced by Vapnik et al. and is aimed at utilizing additional
information available only at training time -- a framework implemented by SVM+.
We relate the privileged information to importance weighting and show that the
prior knowledge expressible with privileged features can also be encoded by
weights associated with every training example. We show that a weighted SVM can
always replicate an SVM+ solution, while the converse is not true and we
construct a counterexample highlighting the limitations of SVM+. Finally, we
touch on the problem of choosing weights for weighted SVMs when privileged
features are not available.


title: Learning to encode motion using spatio-temporal synchrony

abstract:
  We consider the task of learning to extract motion from videos. To this end,
we show that the detection of spatial transformations can be viewed as the
detection of synchrony between the image sequence and a sequence of features
undergoing the motion we wish to detect. We show that learning about synchrony
is possible using very fast, local learning rules, by introducing
multiplicative "gating" interactions between hidden units across frames. This
makes it possible to achieve competitive performance in a wide variety of
motion estimation tasks, using a small fraction of the time required to learn
features, and to outperform hand-crafted spatio-temporal features by a large
margin. We also show how learning about synchrony can be viewed as performing
greedy parameter estimation in the well-known motion energy model.


title:
Robustness of first-order phase transitions in one-dimensional
  long-range contact processes

abstract:
  It has been proposed (Phys. Rev. E {\bf 71}, 026121 (2005)) that unlike the
short range contact process, a long-range counterpart may lead to the existence
a discontinuous phase transition in one dimension. Aiming at exploring such
link, here we investigate thoroughly a family of long-range contact processes.
They are introduced through the transition rate $1+a\ell^{-\sigma}$, where
$\ell$ is the length of inactive islands surrounding particles. In the former
approach we reconsider the original model (called $\sigma-$contact process), by
considering distinct mechanisms of weakening the long-range interaction toward
the short-range limit. Second, we study the effect of different rules,
including creation and annihilation by clusters of particles and distinct
versions with infinitely many absorbing states. Our results show that all
examples presenting a single absorbing state, a discontinuous transition is
possible for small $\sigma$. On the other hand, the presence of infinite
absorbing states leads to distinct scenario depending on the interactions at
the frontier of inactive sites.


title: f(R,T) Cosmological Models in Phase Space

abstract:
  We investigate cosmological solutions of f(R,T) modified theories of gravity
for perfect fluid in spatially FLRW metric through phase space analysis, where
R is Ricci scalar and T denotes the trace of energy-momentum tensor of matter
content. We explore and analyze three general theories with Lagrangians of
minimal $g(R)+h(T)$, pure non--minimal g(R)h(T) and non-minimal $g(R)(1+h(T))$
couplings through dynamical systems approach. We introduce a few variables and
dimensionless parameters to simplify the equations in more concise forms. The
conservation of energy-momentum tensor leads to a constraint equation that, in
the minimal gravity, confines functionality of h(T) to a particular form,
hence, relates the dynamical variables. In this case, acceptable cosmological
solutions that contain a long enough matter dominated era followed by a
late-time accelerated expansion are found. To support theoretical results, we
also obtain numerical solutions for a few functions of g(R), and results of the
corresponding models confirm the predictions. We classify solutions into six
classes which demonstrate more acceptable solutions and there is more freedom
to have the matter dominated era than in the f(R) gravity. In particular, there
is a new fixed point which can represent late-time acceleration. We draw
different diagrams of the matter densities (consistent with the present
values), the related scale factors and effective equation of state. The
corresponding diagrams of parameters illustrate that there is a saddle
acceleration era which is a middle era before final stable acceleration de
Sitter era for some models. All presented diagrams determine radiation, matter
and late-time acceleration eras very well.

categories: gr-qc astro-ph.CO hep-th math-ph math.MP physics.space-ph


title: On the evolution of cluster scaling relations

abstract:
  Understanding the evolution of scaling relations between the observable
properties of clusters and their total mass is key to realizing their potential
as cosmological probes. In this study, we investigate whether the evolution of
cluster scaling relations is affected by the spurious evolution of mass caused
by the evolving reference density with respect to which halo masses are defined
(pseudo-evolution). We use the relation between mass, M, and velocity
dispersion, sigma, as a test case, and show that the deviation from the M-sigma
relation of cluster-sized halos caused by pseudo-evolution is smaller than 10%
for a wide range of mass definitions. The reason for this small impact is a
tight relation between the velocity dispersion and mass profiles, sigma(<r) =
const * (GM(<r) / r)^1/2, which holds across a wide range of radii. We show
that such a relation is generically expected for a variety of density profiles,
as long as halos are in approximate Jeans equilibrium. Thus, as the outer
"virial" radius used to define the halo mass, R, increases due to
pseudo-evolution, halos approximately preserve their M-sigma relation. This
result highlights the fact that tight scaling relations are the result of tight
equilibrium relations between radial profiles of physical quantities. We find
exceptions at very small and very large radii, where the profiles deviate from
the relations they exhibit at intermediate radii. We discuss the implications
of these results for other cluster scaling relations, and argue that
pseudo-evolution should have a small effect on most scaling relations, except
for those that involve the stellar masses of galaxies. In particular, we show
that the relation between stellar-mass fraction and total mass is affected by
pseudo-evolution and is largely shaped by it for halo masses of less than 10^14
solar masses.