title:
Unexpected trend of exchange interactions in Fe clusters on Rh(111) and
  Ru(0001)

abstract:
  We use first-principles calculations based on density functional theory to
investigate the magnetic exchange interaction of Fe clusters on Rh(111) and
Ru(0001). We consider dimers, trimers, tetramers, and pentamers of different
shape in fcc and hcp stacking as well as infinite atomic and biatomic chains.
From the dimer calculations we extract the exchange interaction as a function
of adatom distance by mapping total energies to a Heisenberg model. The
nearest-neighbor (NN) exchange constant is about one order of magnitude smaller
than reported for other substrates due to the strong hybridization between the
Fe atoms and the partly filled $4d$-band of the surface. We also find a
transition from a ferromagnetic NN exchange interaction for Fe dimers on
Rh(111) to an antiferromagnetic one on Ru(0001). The distance-dependent
exchange coupling displays a RKKY-like oscillatory behavior which is nearly
inverted for Fe dimers on the Rh(111) surface compared to those on Ru(0001).
Unexpectedly, for Fe clusters beyond dimers, a complex trend of the magnetic
ground state is observed which alternates between ferro- and antiferromagnetic
configurations depending on cluster size and shape. In view of the exchange
constants obtained for dimers, it is surprising that on both surfaces small
compact clusters are ferromagnetic while open structures such as linear trimers
or tetramers become antiferromagnetic. We demonstrate that both vertical and
lateral structural relaxations of the clusters are crucial in order to
understand this unexpected trend of magnetic order and connected to the
competition of direct ferromagnetic exchange among Fe atoms in the cluster and
the hybridization with the substrate.


title:
Suppression of deterministic and stochastic extreme desynchronization
  events using anticipated synchronization

abstract:
  We numerically show that extreme events induced by parameter mismatches or
noise in coupled oscillatory systems can be anticipated and suppressed before
they actually occur. We show this in a main system unidirectionally coupled to
an auxiliary system subject to a negative delayed feedback. Each system
consists of two electronic oscillators coupled in a master-slave configuration.
Extreme events are observed in this coupled system as large and sporadic
desynchronization events. Under certain conditions, the auxiliary system can
predict the dynamics of the main system. We use this to efficiently suppress
the extreme events by applying a direct corrective reset to the main system.


title:
Angular control of optical cavities in a radiation pressure dominated
  regime: the Enhanced LIGO case

abstract:
  We describe the angular sensing and control of the 4 km detectors of the
Laser Interferometer Gravitational-wave Observatory (LIGO). The culmination of
first generation LIGO detectors, Enhanced LIGO operated between 2009 and 2010
with about 40 kW of laser power in the arm cavities. In this regime, radiation
pressure effects are significant and induce instabilities in the angular
opto-mechanical transfer functions. Here we present and motivate the angular
sensing and control (ASC) design in this extreme case and present the results
of its implementation in Enhanced LIGO. Highlights of the ASC performance are:
successful control of opto-mechanical torsional modes, relative mirror motions
of 1x10^{-7} rad rms, and limited impact on in-band strain sensitivity.


title:
Groupe de Brauer non ramifi\'e des espaces homog\`enes \`a stabilisateur
  fini (Unramified Brauer group of homogeneous spaces with finite stabilizer)

abstract:
  We develop different formulas of algebraic and/or arithmetic nature allowing
an explicit calculation, both over a finite field and over a field of
characteristic 0, of the algebraic part of the unramified Brauer group of a
homogeneous space G\G' under a semisiple simply connected linear group G' with
finite stabilizer G. We also give examples of the calculations that can be done
with these formulas.


title: High order methods for irreversible equations

abstract:
  In this work, we show high order splitting methods of integration without
negative steps, allowing us to solve numerically irreversible problems, like
reaction-diffusion equations. The methods consist in a suitable affine
combinations of Lie-Trotter schemes with different steps. We prove convergence
of this methods for a large class of semi-linear problems, that includes
Hamiltonian and reaction-diffusion systems.


title: A tour on Hermitian symmetric manifolds

abstract:
  Hermitian symmetric manifolds are Hermitian manifolds which are homogeneous
and such that every point has a symmetry preserving the Hermitian structure.
The aim of these notes is to present an introduction to this important class of
manifolds, trying to survey the several different perspectives from which
Hermitian symmetric manifolds can be studied.


title: Local gauge conditions for ellipticity in conformal geometry

abstract:
  In this article we introduce local gauge conditions under which many
curvature tensors appearing in conformal geometry, such as the Weyl, Cotton,
Bach, and Fefferman-Graham obstruction tensors, become elliptic operators. The
gauge conditions amount to fixing an $n$-harmonic coordinate system and
normalizing the determinant of the metric. We also give corresponding elliptic
regularity results and characterizations of local conformal flatness in low
regularity settings.


title: Finite system size effects on Drift Wave stability

abstract:
  Unstable electrostatic resistive modes, driven by density gradients, are
identified in a bounded sheared slab. The boundary conditions play a crucial
role and are shown to change the nature of the problem, which is related to so
called "universal" mode. The dispersion relation and the structure of the
eigenmodes of the instability are derived and are shown to depend on a limited
set of dimensionless parameters. The occurrence and possible impact of these
modes on numerical simulations and actual plasmas are discussed.


title: The Radon transform and its dual for limits of symmetric spaces

abstract:
  The Radon transform and its dual are central objects in geometric analysis on
Riemannian symmetric spaces of the noncompact type. In this article we study
algebraic versions of those transforms on inductive limits of symmetric spaces.
In particular, we show that normalized versions exists on some spaces of
regular functions on the limit. We give a formula for the normalized transform
using integral kernels and relate them to limits of double fibration transforms
on spheres.


title:
A study of one-dimensional transport of Bose-Einstein condensates using
  exterior complex scaling

abstract:
  We numerically investigate the one-dimensional transport of Bose-Einstein
condensates in the context of guided atom lasers using a mean-field description
of the condensate in terms of a spatially discretized Gross-Pitaevskii
equation. We specifically consider a waveguide configuration in which spatial
inhomogeneities and nonvanishing atom-atom interactions are restricted to a
spatially localized scattering region of finite extent. We show how the method
of smooth exterior complex scaling can be implemented for this particular
configuration in order to efficiently absorb the outgoing flux within the
waveguide. A numerical comparison with the introduction of a complex absorbing
potential as well as with the analytically exact elimination of the dynamics of
the free non-interacting motion outside the scattering region, giving rise to
transparent boundary conditions, clearly confirms the accuracy and efficiency
of the smooth exterior complex scaling method.


title: Exact large-deviation statistics for a nonequilibrium quantum spin chain

abstract:
  We consider a one-dimensional XX spin chain in a nonequilibrium setting with
a Lindblad-type boundary driving. By calculating large deviation rate function
in the thermodynamic limit, being a generalization of free energy to a
nonequilibrium setting, we obtain a complete distribution of current, including
closed expressions for lower-order cumulants. We also identify two
phase-transition-like behaviors in either the thermodynamic limit, at which the
current probability distribution becomes discontinuous, or, at maximal driving,
when the range of possible current values changes discontinuously. In the
thermodynamic limit the current has a finite upper and lower bound. We also
explicitly confirm nonequilibrium fluctuation relation and show that the
current distribution is the same under mapping of the coupling strength Gamma
-> 1/Gamma.


title:
Signatures of two-level defects in the temperature-dependent damping of
  nanomechanical silicon nitride resonators

abstract:
  The damping rates of high quality factor nanomechanical resonators are well
beyond intrinsic limits. Here, we explore the underlying microscopic loss
mechanisms by investigating the temperature-dependent damping of the
fundamental and third harmonic transverse flexural mode of a doubly clamped
silicon nitride string. It exhibits characteristic maxima reminiscent of
two-level defects typical for amorphous materials. Coupling to those defects
relaxes the momentum selection rules, allowing energy transfer from discrete
long wavelength resonator modes to the high frequency phonon environment.


title: Joint resummation for pion wave function and pion transition form factor

abstract:
  We construct an evolution equation for the pion wave function in the $k_T$
factorization theorem, whose solution sums the mixed logarithm $\ln x\ln k_T$
to all orders, with $x$ ($k_T$) being a parton momentum fraction (transverse
momentum). This joint resummation induces strong suppression of the pion wave
function in the small $x$ and large $b$ regions, $b$ being the impact parameter
conjugate to $k_T$, and improves the applicability of perturbative QCD to hard
exclusive processes. The above effect is similar to those from the conventional
threshold resummation for the double logarithm $\ln^2 x$ and the conventional
$k_T$ resummation for $\ln^2 k_T$. Combining the evolution equation for the
hard kernel, we are able to organize all large logarithms in the $\gamma^{\ast}
\pi^{0} \to \gamma$ scattering, and to establish a scheme-independent $k_T$
factorization formula. It will be shown that the significance of
next-to-leading-order contributions and saturation behaviors of this process at
high energy differ from those under the conventional resummations. It implies
that QCD logarithmic corrections to a process must be handled appropriately,
before its data are used to extract a hadron wave function. Our predictions for
the involved pion transition form factor, derived under the joint resummation
and the input of a non-asymptotic pion wave function with the second Gegenbauer
moment $a_2=0.05$, match reasonably well the CLEO, BaBar, and Belle data.


title: Evaluation of DNF Formulas

abstract:
  Stochastic Boolean Function Evaluation (SBFE) is the problem of determining
the value of a given Boolean function $f$ on an unknown input $x$, when each
bit of $x_i$ of $x$ can only be determined by paying a given associated cost
$c_i$. Further, $x$ is drawn from a given product distribution: for each $x_i$,
$Prob[x_i=1] = p_i$, and the bits are independent. The goal is to minimize the
expected cost of evaluation. Stochastic Boolean Function Evaluation (SBFE) is
the problem of determining the value of a given Boolean function $f$ on an
unknown input $x$, when each bit of $x_i$ of $x$ can only be determined by
paying a given associated cost $c_i$. Further, $x$ is drawn from a given
product distribution: for each $x_i$, $Prob[x_i=1] = p_i$, and the bits are
independent. The goal is to minimize the expected cost of evaluation. In this
paper, we study the complexity of the SBFE problem for classes of DNF formulas.
We consider both exact and approximate versions of the problem for subclasses
of DNF, for arbitrary costs and product distributions, and for unit costs
and/or the uniform distribution.


title: Weak Bases of Boolean Co-Clones

abstract:
  Universal algebra and clone theory have proven to be a useful tool in the
study of constraint satisfaction problems since the complexity, up to logspace
reductions, is determined by the set of polymorphisms of the constraint
language. For classifications where primitive positive definitions are
unsuitable, such as size-preserving reductions, weaker closure operations may
be necessary. In this article we consider strong partial clones which can be
seen as a more fine-grained framework than Post's lattice where each clone
splits into an interval of strong partial clones. We investigate these
intervals and give simple relational descriptions, weak bases, of the largest
elements. The weak bases have a highly regular form and are in many cases
easily relatable to the smallest members in the intervals, which suggests that
the lattice of strong partial clones is considerably simpler than the full
lattice of partial clones.


title:
Search for charginos nearly mass-degenerate with the lightest neutralino
  based on a disappearing-track signature in pp collisions at sqrt(s) = 8 TeV
  with the ATLAS detector

abstract:
  A search is presented for direct chargino production based on a
disappearing-track signature using 20.3 fb-1 of proton-proton collisions at
sqrt(s) = 8 TeV collected with the ATLAS experiment at the LHC. In
anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is
nearly mass-degenerate with the lightest neutralino and its lifetime is long
enough to be detected in the tracking detectors by identifying decays that
result in tracks with no associated hits in the outer region of the tracking
system. Some models with supersymmetry also predict charginos with a
significant lifetime. This analysis attains sensitivity for charginos with a
lifetime between 0.1 ns and 10 ns, and significantly surpasses the reach of the
LEP experiments. No significant excess above the background expectation is
observed for candidate tracks with large transverse momentum, and constraints
on chargino properties are obtained. In the AMSB scenarios, a chargino mass
below 270 GeV is excluded at 95% confidence level.


title: Entanglement thermodynamics for non-conformal D-branes

abstract:
  We study thermodynamics of entanglement entropy for weakly excited states in
certain non-conformal fields theories, whose gravity duals are given by
non-conformal Dp-branes. We observe that the entanglement entropy of a
sufficiently small system in non-conformal backgrounds still obeys a first-law
like relation, just as the AdS counterparts investigated in arXiv: 1212.1164
[hep-th]. The effective temperature is proportional to the inverse of the size
of the subsystem. The proportionality is a dimensionless constant which is only
determined by the shape of the entangling region and independent of any
coupling. This universality is confirmed by working with the ten-dimensional
string frame metric as well as the lower-dimensional effective metric. When the
entangling region is a strip and translational invariance is broken by metric
fluctuations, we derive a first-law like relation where additional components
of the stress energy tensor are involved.


title: Gradient flows driven by a non-smooth repulsive interaction potential

abstract:
  This thesis analyze the Wasserstein gradient flow of a functional defined as
a double convolution of a non-smooth repulsive interaction potential. To be
more precise, the potential under investigation has a -|x| behavior close to
the origin. The already existent machinery of Wasserstein gradient flow is well
posed for lambda-convex potential. In this case this property is lost, but it
is proven that in the one dimensional case existence and uniqueness of the
solution is still achieved.


title: Surface magnetism of cool giant and supergiant stars

abstract:
  The existence of starspots on late-type giant stars in close binary systems,
that exhibit rapid rotation due to tidal locking, has been known for more than
five decades. Photometric monitoring spanning decades has allowed studying the
long-term magnetic activity in these stars revealing complicated activity
cycles. The development of observing and analysis techniques that has occurred
during the past two decades has also enabled us to study the detailed starspot
and magnetic field configurations on these active giants. In the recent years
magnetic fields have also been detected on slowly rotating giants and
supergiant stars. In this paper I review what is known of the surface magnetism
in the cool giant and supergiant stars.


title:
Elliptic and parabolic reguarity for second order divergence operators
  with mixed boundary conditions

abstract:
  We study second order equations and systems on non-Lipschitz domains
including mixed boundary conditions. The key result is interpolation for
suitable function spaces. From this, elliptic and parabolic regularity results
are deduced by means of Sneiberg's isomorphism theorem.


title: Magnetic fields during the formation of supermassive black holes

abstract:
  Observations of quasars at $\rm z> 6$ report the existence of a billion solar
mass black holes. Comprehending their formation in such a short time scale is a
matter of ongoing research. One of the most promising scenarios to assemble
supermassive black holes is a monolithic collapse of protogalactic gas clouds
in atomic cooling halos with $\rm T_{vir} \geq 10^{4} K$. In this article, we
study the amplification and impact of magnetic fields during the formation of
seed black holes in massive primordial halos. We perform high resolution
cosmological magnetohydrodynamics simulations for four distinct halos and
follow their collapse for a few free-fall times until the simulations reach a
peak density of $\rm 7 \times 10^{-10} g/cm^{3}$. Our findings show that
irrespective of the initial seed field, the magnetic field strength reaches a
saturated state in the presence of strong accretion shocks. Under such
conditions, the growth time becomes very short and amplification occurs rapidly
within a small fraction of the free-fall time. We find that the presence of
such strong magnetic fields provides additional support against gravity and
helps in suppressing fragmentation. Massive clumps of a few hundred solar
masses are formed at the end of our simulations and high accretion rates of
$\rm 1 M_{\odot}/yr$ are observed. We expect that in the presence of such
accretion rates, the clumps will grow to form supermassive stars of $\rm \sim
10^{5} M_{\odot}$. Overall, the role of the magnetic fields seems supportive
for the formation of massive black holes.


title:
Klein-Dirac Quadric and Multidimensional Toda Lattice via
  Pseudo-positive Moment Problem

abstract:
  In 1974 J\"urgen Moser has shown that the classical Moment Problem plays a
fundamental role for the theory of completely integrable systems, by proving
that the simplest case of the finite Toda lattice is described exhaustively in
its terms. In particular, the Jacobi matrix defined by the Flaschka variables
corresponds to the Schr\"odinger operator related to the Korteweg-de Vries
operator.
  In the present paper we use a recent breakthrough in the area of the
multidimensional Moment Problem in order to develop a multidimensional
generalization of the finite Toda lattice. Our construction is based on the
notion of pseudo-positive measure and the notion of multidimensional
Markov-Stieltjes transform naturally defined on the Klein-Dirac quadric. An
important consequence of the properties of the Markov-Stieltjes transform is a
new method for summation of multidimensional divergent series on the
Klein-Dirac quadric.

categories: math.AP math-ph math.CV math.MP math.SP quant-ph


title:
Lattice cohomology and Seiberg-Witten invariants of normal surface
  singularities

abstract:
  One of the main questions in the theory of normal surface singularities is to
understand the relations between their geometry and topology. The lattice
cohomology is an important tool in the study of topological properties of a
plumbed 3-manifold M associated with a connected negative definite plumbing
graph G. It connects the topological properties with analytic ones when M is
realized as a singularity link, i.e. when G is a good resolution graph of the
singularity. Its computation is based on the (Riemann-Roch) weights of the
lattice points of \Z^s, where s is the number of vertices of G. The first part
of the thesis reduces the rank of this lattice to the number of `bad' vertices
of the graph. Usually, the geometry/topology of M is encoded exactly by these
`bad' vertices and their number measures how far the plumbing graph stays from
a rational one. In the second part, we identify the following three objects:
the Seiberg-Witten invariant of a plumbed 3-manifold, the periodic constant of
its topological Poincare series, and a coefficient of an equivariant
multivariable Ehrhart polynomial. For this, we construct the corresponding
polytope from the plumbing graph, together with an action of H_1(M,\Z), and we
develop Ehrhart theory for them. The effect of the reduction appears also at
the level of the multivariable topological Poincare series, simplifying the
corresponding polytope and the Ehrhart theory as well. We end the thesis with
detailed calculations and examples.


title:
Deep high spectral resolution spectroscopy and chemical composition of
  ionized nebulae

abstract:
  High spectral resolution spectroscopy has proved to be very useful for the
advancement of chemical abundances studies in photoionized nebulae, such as H
II regions and planetary nebulae (PNe). Classical analyses make use of the
intensity of bright collisionally excited lines (CELs), which have a strong
dependence on the electron temperature and density. By using high resolution
spectrophotometric data, our group has led the determination of chemical
abundances of some heavy element ions, mainly O++, O+ and C++ from faint
recombination lines (RLs), allowing us to deblend them from other nearby
emission lines or sky features. The importance of these lines is that their
emissivity depends weakly on the temperature and density structure of the gas.
The unresolved issue in this field is that recombination lines of heavy element
ions give abundances that are about 2-3 times higher than those derived from
CELs -in H II regions- for the same ion, and can even be a factor of 70 times
higher in some PNe. This uncertainty puts into doubt the validity of face
values of metallicity that we use as representative not only for ionized
nebulae in the Local Universe, but also for star-forming dwarf and spiral
galaxies at different redshifts. Additionally, high-resolution data can allow
us to detect and deblend faint lines of neutron capture element ions in PNe.
This information would introduce further restrictions to evolution models of
AGBs and would help to quantify the chemical enrichment in s-elements produced
by low and intermediate mass stars. The availability of an echelle spectrograph
at the E-ELT will be of paramount interest to: (a) extend the studies of heavy
element recombination lines to low metallicity objects, (b) to extend abundance
determinations of s-elements to planetary nebulae in the extragalactic domain
and to bright Galactic and extragalactic H II regions.


title: What Do Experiments in Optics tell us about Photon Momentum in Media?

abstract:
  In order to get some insight in the intricacies of the Abraham-Minkowski
energy-momentum problem in phenomenological electrodynamics, we briefly analyze
eight different experimental situations in radiation optics. Six of the
experiments are already existing, while the remaining two are suggestions for
future endeavors. Among the first six, we distinguish between three which are
incapable of informing about photon momentum in a medium, and the remaining
three which are able to give us useful information. Our general conclusion is
that the Abraham-Minkowski "problem" is essentially a matter of convenience. In
actual physical situations it is the Minkowski expression which is most natural
alternative to employ. Also, in a canonical context, it is the Minkowski
energy-momentum tensor which is the most convenient alternative to work with,
as this tensor is divergence-free causing the total radiation momentum and
energy to make up a four-vector, although notably a spacelike one.


title:
Aeppli Cohomology Classes Associated with Gauduchon Metrics on Compact
  Complex Manifolds

abstract:
  We propose the study of a Monge-Amp\`ere-type equation in bidegree
$(n-1,\,n-1)$ rather than $(1,\,1)$ on a compact complex manifold $X$ of
dimension $n$ for which we prove uniqueness of the solution subject to
positivity and normalisation restrictions. Existence will hopefully be dealt
with in future work. The aim is to construct a special Gauduchon metric
uniquely associated with any Aeppli cohomology class of bidegree $(n-1,\,n-1)$
lying in the Gauduchon cone of $X$ that we hereby introduce as a subset of the
real Aeppli cohomology group of type $(n-1,\,n-1)$ and whose first properties
we study. Two directions for applications of this new equation are envisaged:
to moduli spaces of Calabi-Yau $\partial\bar\partial$-manifolds and to a
further study of the deformation properties of the Gauduchon cone beyond those
given in this paper.


title: Element spots in HgMn stars

abstract:
  A fraction of late B-type stars, the so-called HgMn stars, exhibit enhanced
absorption lines of certain chemical elements, notably Hg and Mn, combined with
an underabundance of He. For about a decade now the elements with anomalously
high abundances in HgMn stars are known to be distributed inhomogeneously over
the stellar surface. Temporal evolution of these elemental spots have been
reported in a few HgMn stars, first secular evolution of the mercury spots in
alpha And, and recently also a fast evolution of yttrium and strontium spots in
HD 11753. The fast evolution of spots in HD 11753 is combined with a slower
change in the overall abundance of the affected elements. In this paper I
review what is known of elemental spots in HgMn stars and their secular and
fast temporal evolution.


title:
Search for the standard model Higgs boson produced in association with a
  W or a Z boson and decaying to bottom quarks

abstract:
  A search for the standard model Higgs boson (H) decaying to b b-bar when
produced in association with a weak vector boson (V) is reported for the
following channels: W(mu nu)H, W(e nu)H, W(tau nu)H, Z(mu mu)H, Z(e e)H, and
Z(nu nu)H. The search is performed in data samples corresponding to integrated
luminosities of up to 5.1 inverse femtobarns at sqrt(s) = 7 TeV and up to 18.9
inverse femtobarns at sqrt(s) = 8 TeV, recorded by the CMS experiment at the
LHC. An excess of events is observed above the expected background with a local
significance of 2.1 standard deviations for a Higgs boson mass of 125 GeV,
consistent with the expectation from the production of the standard model Higgs
boson. The signal strength corresponding to this excess, relative to that of
the standard model Higgs boson, is 1.0 +/- 0.5.


title: Self-consistent Green's functions formalism with three-body interactions

abstract:
  We extend the self-consistent Green's functions formalism to take into
account three-body interactions. We analyze the perturbative expansion in terms
of Feynman diagrams and define effective one- and two-body interactions, which
allows for a substantial reduction of the number of diagrams. The procedure can
be taken as a generalization of the normal ordering of the Hamiltonian to fully
correlated density matrices. We give examples up to third order in perturbation
theory. To define nonperturbative approximations, we extend the equation of
motion method in the presence of three-body interactions. We propose schemes
that can provide nonperturbative resummation of three-body interactions. We
also discuss two different extensions of the Koltun sum rule to compute the
ground state of a many-body system.


title:
A variational approach to reaction diffusion equations with forced speed
  in dimension 1

abstract:
  We investigate in this paper a scalar reaction diffusion equation with a
nonlinear reaction term depending on x-ct. Here, c is a prescribed parameter
modelling the speed of climate change and we wonder whether a population will
survive or not, that is, we want to determine the large-time behaviour of the
associated solution. This problem has been solved recently when the
nonlinearity is of KPP type. We consider in the present paper general reaction
terms, that are only assumed to be negative at infinity. Using a variational
approach, we construct two thresholds determining the existence and the
non-existence of travelling waves. Numerics support the conjecture that the two
thresholds are equal. We then prove that any solution of the initial-value
problem converges at large times, either to 0 or to a travelling wave. In the
case of bistable nonlinearities, where the steady state 0 is assumed to be
stable, our results lead to constrasting phenomena with respect to the KPP
framework. Lastly, we illustrate our results and discuss several open questions
through numerics.


title:
Parameters of the brightest star formation regions in the two principal
  spiral arms of NGC 628

abstract:
  We study photometric properties, chemical abundances and sizes of star
formation regions in the two principal arms of the galaxy NGC 628 (M74). The
GALEX ultraviolet, optical UBVRI, and H-alpha? surface photometry data are
used, including those obtained with the 1.5-m telescope of the Maidanak
Observatory. The thirty brightest star formation regions in ultraviolet light
located in the spiral arms of NGC 628 are identified and studied. We find that
the star formation regions in one (longer) arm are systematically brighter and
larger than the regions in the other (shorter) arm. However, both luminosity
and size distribution functions have approximately the same slopes for the
samples of star formation regions in both arms. The star formation regions in
the longer arm have a higher star formation rate density than the regions in
the shorter arm. The regions in the shorter arm show higher N/O ratio at a
higher oxygen abundance, but they have lower ultraviolet and H-alpha?
luminosities. These findings can be explained if we assume that star formation
regions in the shorter arm had higher star formation rate in the past, but now
it is lower than for those in the opposite arm. Results of stellar evolutionary
synthesis show that the brightest regions in the longer arm are slightly
younger than the ones in the shorter arm (3.5+-2.2 Myr versus 6.0+-1.1 Myr).
Our results demonstrate that there is a difference in the inner structures and
parameters of the interstellar medium between the spiral arms of NGC 628, one
of which is long and hosts a regular chain of bright star formation complexes
and the other, shorter one does not.


title: The b-functions of semi-invariants of quivers

abstract:
  In this paper we compute b-functions (or Bernstein-Sato polynomials) of
various semi-invariants of quivers. The main tool is an explicit relation for
the b-functions between semi-invariants that correspond to each other under
reflection functors (or castling transforms). This enables us to compute
recursively the b-functions for all Dynkin quivers, and extended Dynkin quivers
with prehomogeneous dimension vectors.


title: Changing the Environment based on Intrinsic Motivation

abstract:
  One of the remarkable feats of intelligent life is that it restructures the
world it lives in for its own benefit. This extended abstract outlines how the
information-theoretic principle of empowerment, as an intrinsic motivation, can
be used to restructure the environment an agent lives in. We present a first
qualitative evaluation of how an agent in a 3d-gridworld builds a
staircase-like structure, which reflects the agent's embodiment.


title:
Counting and correcting thermodynamically infeasible flux cycles in
  genome-scale metabolic networks

abstract:
  Thermodynamics constrains the flow of matter in a reaction network to occur
through routes along which the Gibbs energy decreases, implying that viable
steady-state flux patterns should be void of closed reaction cycles.
Identifying and removing cycles in large reaction networks can unfortunately be
a highly challenging task from a computational viewpoint. We propose here a
method that accomplishes it by combining a relaxation algorithm and a Monte
Carlo procedure to detect loops, with ad hoc rules (discussed in detail) to
eliminate them. As test cases, we tackle (a) the problem of identifying
infeasible cycles in the E. coli metabolic network and (b) the problem of
correcting thermodynamic infeasibilities in the Flux-Balance-Analysis solutions
for 15 human cell-type specific metabolic networks. Results for (a) are
compared with previous analyses of the same issue, while results for (b) are
weighed against alternative methods to retrieve thermodynamically viable flux
patterns based on minimizing specific global quantities. Our method on one hand
outperforms previous techniques and, on the other, corrects loopy solutions to
Flux Balance Analysis. As a byproduct, it also turns out to be able to reveal
possible inconsistencies in model reconstructions.

categories: q-bio.MN cond-mat.dis-nn cond-mat.stat-mech physics.bio-ph q-bio.QM


title: A primal-dual algorithm for BSDEs

abstract:
  We generalize the primal-dual methodology, which is popular in the pricing of
early-exercise options, to a backward dynamic programming equation associated
with time discretization schemes of (reflected) backward stochastic
differential equations (BSDEs). Taking as an input some approximate solution of
the backward dynamic program, which was pre-computed, e.g., by least-squares
Monte Carlo, our methodology allows to construct a confidence interval for the
unknown true solution of the time discretized (reflected) BSDE at time 0. We
numerically demonstrate the practical applicability of our method in two
five-dimensional nonlinear pricing problems where tight price bounds were
previously unavailable.


title: Lowest Density MDS Array Codes for Reliable Smart Meter Networks

abstract:
  In this paper we introduce a lowest density MDS array code which is applied
to a Smart Meter network to introduce reliability. By treating the network as
distributed storage with multiple sources, information can be exchanged between
the nodes in the network allowing each node to store parity symbols relating to
data from other nodes. A lowest density MDS array code is then applied to make
the network robust against outages, ensuring low overhead and data transfers.
We show the minimum amount of overhead required to be able to recover from r
node erasures in an n node network and explicitly design an optimal array code
with lowest density. In contrast to existing codes, this one has no
restrictions on the number of nodes or erasures it can correct. Furthermore we
consider incomplete networks where all nodes are not connected to each other.
This limits the exchange of data for purposes of redundancy and we derive
conditions on the minimum node degree that allow lowest density MDS codes to
exist. We also present an explicit code design for incomplete networks that is
capable of correcting two node failures.


title: On Weyl modules over affine Lie algebras in prime characteristic

abstract:
  We construct a family of homomorphisms between Weyl modules for affine Lie
algebras in characteristic p, which supports our conjecture on the strong
linkage principle in this context. We also exhibit a large class of reducible
Weyl modules beyond level one, for p not necessarily small.


title: Variance Adjusted Actor Critic Algorithms

abstract:
  We present an actor-critic framework for MDPs where the objective is the
variance-adjusted expected return. Our critic uses linear function
approximation, and we extend the concept of compatible features to the
variance-adjusted setting. We present an episodic actor-critic algorithm and
show that it converges almost surely to a locally optimal point of the
objective function.


title: Quantum theory realises all joint measurability graphs

abstract:
  Joint measurability of sharp quantum observables is determined pairwise, and
so can be captured in a graph. We prove the converse: any graph, whose vertices
represent sharp observables, and whose edges represent joint measurability, is
realised by quantum theory. This leads us to show that it is not always
possible to use Neumark dilation to turn unsharp observables into sharp ones
with the same joint measurability relations, highlighting a caveat in the
church of the larger Hilbert space".


title: Nakayama twisted centers and dual bases of Frobenius cellular algebras

abstract:
  For a Frobenius cellular algebra, we prove that if the left (right) dual
basis of a cellular basis is again cellular, then the algebra is symmetric.
Moreover, some ideals of the center are constructed by using the so-called
Nakayama twisted center.


title:
High-energy femtosecond Yb:CaF2 laser for efficient THz pulse generation
  in lithium niobate

abstract:
  We present a study on THz generation in lithium niobate pumped by a powerful
and versatile Yb:CaF2 laser. The unique laser system delivers transform-limited
pulses of variable duration (0.38-0.65 ps) with pulse energy of up to 15 mJ at
a center wavelength of 1030 nm. From theoretical investigations it is expected
that those laser parameters are ideally suited for efficient THz generation.
Here we present experimental results on both the conversion efficiency and the
THz spectral shape for variable pump pulse durations and for different crystal
temperatures down to 25 K. We experimentally verify the optimum pump parameters
for most efficient and broadband THz generation.


title:
Medium modifications of photon-tagged jet fragmentation function in
  high-energy heavy-ion collisions

abstract:
  Based on a multiphase transport model, medium modifications of prompt
photon-tagged jet fragmentation function are investigated by comparing prompt
photon-tagged hadron azimuthal correlation in Au+Au collisions (0-40\%) with
that in p+p collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV. The measured
modification factor, $I_{AA}$, increases with the increasing integration range
of the away side, which reveals a medium-modified jet shape in which the medium
enhancement of soft particles is preferentially located far away from the jet
axis. The $I_{AA}$ largely results from strong interactions between jets and
partonic matter. However, both hadronization of coalescence and hadronic
rescatterings play certain roles to modify the $I_{AA}$. These behaviors
reflect a dynamical evolution of modifications of the prompt photon-tagged jet
fragmentation function in high-energy heavy-ion collisions.


title:
Generalised friezes and a modified Caldero-Chapoton map depending on a
  rigid object

abstract:
  The (usual) Caldero-Chapoton map is a map from the set of objects of a
category to a Laurent polynomial ring over the integers. In the case of a
cluster category, it maps "reachable" indecomposable objects to the
corresponding cluster variables in a cluster algebra. This formalises the idea
that the cluster category is a "categorification" of the cluster algebra.
  The definition of the Caldero-Chapoton map requires the category to be
2-Calabi-Yau, and the map depends on a cluster tilting object in the category.
  We study a modified version of the Caldero-Chapoton map which only requires
the category to have a Serre functor, and only depends on a rigid object in the
category.
  It is well-known that the usual Caldero-Chapoton map gives rise to so-called
friezes, for instance Conway-Coxeter friezes. We show that the modified
Caldero-Chapoton map gives rise to what we call generalised friezes, and that
for cluster categories of Dynkin type A, it recovers the generalised friezes
introduced by combinatorial means by Bessenrodt and us.


title: Dynamics of Snapping Beams and Jumping Poppers

abstract:
  We consider the dynamic snapping instability of elastic beams and shells.
Using the Kirchhoff rod and F\"{o}ppl-von K\'{a}rm\'{a}n plate equations, we
study the stability, deformation modes, and snap-through dynamics of an elastic
arch with clamped boundaries and subject to a concentrated load. For parameters
typical of everyday and technological applications of snapping, we show that
the stretchability of the arch plays a critical role in determining not only
the post-buckling mode of deformation but also the timescale of snapping and
the frequency of the arch's vibrations about its final equilibrium state. We
show that the growth rate of the snap-through instability and its subsequent
ringing frequency can both be interpreted physically as the result of a sound
wave in the material propagating over a distance comparable to the length of
the arch. Finally, we extend our analysis of the ringing frequency of indented
arches to understand the `pop' heard when everted shell structures snap-through
to their stable state. Remarkably, we find that not only are the scaling laws
for the ringing frequencies in these two scenarios identical but also the
respective prefactors are numerically close; this allows us to develop a master
curve for the frequency of ringing in snapping beams and shells.


title: Nonlinear hydrodynamic theory of crystallization

abstract:
  We present an isothermal fluctuating nonlinear hydrodynamic theory of
crystallization in molecular liquids. A dynamic coarse-graining technique is
used to derive the velocity field, a phenomenology, which allows a direct
coupling between the free energy functional of the classical Density Functional
Theory and the Navier-Stokes equation. Contrary to the Ginzburg-Landau type
amplitude theories, the dynamic response to elastic deformations is described
by parameter-free kinetic equations. Employing our approach to the free energy
functional of the Phase-Field Crystal model, we recover the classical spectrum
for the phonons and the steady-state growth fronts. The capillary wave spectrum
of the equilibrium crystal-liquid interface is in a good qualitative agreement
with the molecular dynamics simulations.


title:
Quantum magnetism without lattices in strongly interacting
  one-dimensional spinor gases

abstract:
  We show that strongly interacting multicomponent gases in one dimension
realize an effective spin chain, offering an alternative simple scenario for
the study of one-dimensional quantum magnetism in cold gases in the absence of
an optical lattice. The spin-chain model allows for an intuitive understanding
of recent experiments and for a simple calculation of relevant observables. We
analyze the adiabatic preparation of antiferromagnetic and ferromagnetic ground
states, and show that many-body spin states may be efficiently probed in
tunneling experiments. The spin-chain model is valid for more than two
components, opening the possibility of realizing SU(N) quantum magnetism in
strongly interacting one-dimensional alkaline-earth-metal or ytterbium Fermi
gases.


title:
MOA-2011-BLG-293Lb: First Microlensing Planet possibly in the Habitable
  Zone

abstract:
  We used Keck adaptive optics observations to identify the first planet
discovered by microlensing to lie in or near the habitable zone, i.e., at
projected separation $r_\perp=1.1\pm 0.1\,$AU from its $M_{L}=0.86\pm
0.06\,M_\odot$ host, being the highest microlensing mass definitely identified.
The planet has a mass $m_p = 4.8\pm 0.3\,M_{\rm Jup}$, and could in principle
have habitable moons. This is also the first planet to be identified as being
in the Galactic bulge with good confidence: $D_L=7.72\pm 0.44$ kpc. The
planet/host masses and distance were previously not known, but only estimated
using Bayesian priors based on a Galactic model (Yee et al. 2012). These
estimates had suggested that the planet might be a super-Jupiter orbiting an M
dwarf, a very rare class of planets. We obtained high-resolution $JHK$ images
using Keck adaptive optics to detect the lens and so test this hypothesis. We
clearly detect light from a G dwarf at the position of the event, and exclude
all interpretations other than that this is the lens with high confidence
(95%), using a new astrometric technique. The calibrated magnitude of the
planet host star is $H_{L}=19.16\pm 0.13$. We infer the following probabilities
for the three possible orbital configurations of the gas giant planet: 53% to
be in the habitable zone, 35% to be near the habitable zone, and 12% to be
beyond the snow line, depending on the atmospherical conditions and the
uncertainties on the semimajor axis.


title: Ballistic spin resonance in multisubband quantum wires

abstract:
  Ballistic spin resonance was experimentally observed in a
quasi-one-dimensional wire by Frolov et al. [Nature (London) 458, 868 (2009)].
The spin resonance was generated by a combination of an external static
magnetic field and the oscillating effective spin-orbit magnetic field due to
periodic bouncings of the electrons off the boundaries of a narrow channel. An
increase of the D'yakonov-Perel spin relaxation rate was observed when the
frequency of the spin-orbit field matched that of the Larmor precession
frequency around the external magnetic field. Here we develop a model to
account for the D'yakonov-Perel mechanism in multisubband quantum wires with
both the Rashba and Dresselhaus spin-orbit interactions. Considering elastic
spin-conserving impurity scatterings in the time-evolution operator (Heisenberg
representation), we extract the spin relaxation time by evaluating the
time-dependent average of the spin operators. The magnetic field dependence of
the nonlocal voltage, which is related to the spin relaxation time behavior,
shows a wide plateau, in agreement with the experimental observation. This
plateau arises due to injection in higher subbands and small-angle scattering.
In this quantum mechanical approach, the spin resonance occurs near the
spin-orbit induced energy anticrossings of the quantum wire subbands with
opposite spins. We also predict anomalous dips in the spin relaxation time as a
function of the magnetic field in systems with strong spin-orbit couplings.


title: Universality for polynomial invariants on ribbon graphs with flags

abstract:
  In this paper, we analyze the Bollobas and Riordan polynomial for ribbon
graphs with flags introduced in arXiv:1301.1987 and prove its universality. We
also show that this polynomial can be defined on some equivalence classes of
ribbon graphs involving flag moves and that the new polynomial is still
universal on these classes.


title: Quantum Hall phases of two-component bosons

abstract:
  The recent production of synthetic magnetic fields acting on electroneutral
particles, like atoms or photons, has boosted the interest in the quantum Hall
physics of bosons. Adding pseudospin-1/2 to the bosons greatly enriches the
scenario, as it allows them to form an interacting integer quantum Hall (IQH)
phase with no fermionic counterpart. Here we show that, for a small
two-component Bose gas on a disk, the complete strongly correlated regime,
extending from the integer phase at filling factor $\nu=2$ to the Halperin
phase at filling factor $\nu=2/3$, is well described by composite
fermionization of the bosons. Moreover we study the edge excitations of the IQH
state, which, in agreement with expectations from topological field theory, are
found to consist of forward-moving charge excitations and backward-moving spin
excitations. Finally, we demonstrate how pair-correlation functions allow one
to experimentally distinguish the IQH state from competing states, like
non-Abelian spin singlet (NASS) states.


title:
Coexistence of Superconductor and Spin-Density Wave in (TMTSF)2ClO4:
  Spatial Structure of the Two-phase State

abstract:
  We report comprehensive (magneto)transport studies of the two-phase state in
(TMTSF)2ClO4, where superconducting (SC) phase coexists with spin-density wave
insulator (SDW). By tuning the degree of ClO4 anion ordering in controlled
manner we drive SDW state and study the evolution of the SC spatial texture. We
find that as SDW is suppressed, SC regions initially appear inside the SDW
insulator in a form of filaments extended in the interlayer direction and
further merge into the two-dimensional sheets across the most conducting axis
of the crystal. We demonstrate that almost all our results can be explained
within the soliton phase model, though with several assumptions they can also
be interpreted by the creation of non-uniform deformations. We believe that the
anisotropy is intrinsic to SC/SDW coexistence in quasi one-dimensional
superconductors.


title:
Modulation of CMB polarization with a warm rapidly-rotating half-wave
  plate on the Atacama B-Mode Search (ABS) instrument

abstract:
  We evaluate the modulation of Cosmic Microwave Background (CMB) polarization
using a rapidly-rotating, half-wave plate (HWP) on the Atacama B-Mode Search
(ABS). After demodulating the time-ordered-data (TOD), we find a significant
reduction of atmospheric fluctuations. The demodulated TOD is stable on time
scales of 500-1000 seconds, corresponding to frequencies of 1-2 mHz. This
facilitates recovery of cosmological information at large angular scales, which
are typically available only from balloon-borne or satellite experiments. This
technique also achieves a sensitive measurement of celestial polarization
without differencing the TOD of paired detectors sensitive to two orthogonal
linear polarizations. This is the first demonstration of the ability to remove
atmospheric contamination at these levels from a ground-based platform using a
rapidly-rotating HWP.


title: Thermal counterflow in a periodic channel with solid boundaries

abstract:
  We perform numerical simulations of finite temperature quantum turbulence
produced through thermal counterflow in superfluid $^4$He, using the vortex
filament model. We investigate the effects of solid boundaries along one of the
Cartesian directions, assuming a laminar normal fluid with a Poiseuille
velocity profile, whilst varying the temperature and the normal fluid velocity.
We analyze the distribution of the quantized vortices, reconnection rates and
quantized-vorticity production as a function of the wall-normal direction. We
find that the quantized vortex lines tend to concentrate close to the solid
boundaries with their position depending only on temperature and not on the
counterflow velocity. We offer an explanation of this phenomenon by considering
the balance of two competing effects, namely the rate of turbulent diffusion of
an isotropic tangle near the boundaries and the rate of quantized-vorticity
production at the centre. Moreover, this yields the observed scaling of the
position of the peak vortex line density with the mutual friction parameter.
Finally we provide evidence that upon the transition from laminar to turbulent
normal fluid flow, there is a dramatic increase in the homogeneity of the
tangle, which could be used as an indirect measure of the transition to
turbulence in the normal fluid component for experiments.


title:
Computing the Kullback-Leibler Divergence between two Weibull
  Distributions

abstract:
  We derive a closed form solution for the Kullback-Leibler divergence between
two Weibull distributions. These notes are meant as reference material and
intended to provide a guided tour towards a result that is often mentioned but
seldom made explicit in the literature.


title:
The Multiplexed Imaging Method: High-Resolution Wide Field Imaging Using
  Physically Small Detectors

abstract:
  We present the method of multiplexed imaging designed for astronomical
observations of large sky areas in the IR, visible and UV frequencies. Our
method relies on the sparse nature of astronomical observations. The method
consists of an optical system that directs light from different locations on
the focal plane of a telescope onto the same detector area and an algorithm
that reconstructs the original wide-field image. In this way we can use a
physically small detector to cover a wide field of view. We test our
reconstruction algorithm using public space telescope data. Our tests
demonstrate the reliability and power of the multiplexed imaging method. Using
our method it will be possible to increase the sky area covered with space
telescopes by 1-3 orders of magnitude, depending on the specific scientific
goal and optical parameters. This method can significantly increase the volume
of astronomical surveys, including search programs for exoplanets and
transients using space and ground instruments.


title: Quantum Simulation of the Haldane Phase Using Trapped Ions

abstract:
  A proposal to use trapped ions to simulate spin-one XXZ antiferromagnetic
(AFM) chains as an experimental tool to explore the Haldane phase is presented.
We explain how to reach the Haldane phase adiabatically, demonstrate the
robustness of the ground states to noise in the magnetic field and Rabi
frequencies, and propose a way to detect them using their characterizations: an
excitation gap and exponentially decaying correlations, a nonvanishing nonlocal
string order and a double degenerate entanglement spectrum. Scaling up to
higher dimensions and more frustrated lattices, we obtain richer phase
diagrams, and we can reach spin liquid phase, which can be detected by its
entanglement entropy which obeys the boundary law.


title: The Relation Between Global Migration and Trade Networks

abstract:
  In this paper we develop a methodology to analyze and compare multiple global
networks. We focus our analysis on the relation between human migration and
trade. First, we identify the subset of products for which the presence of a
community of migrants significantly increases trade intensity. To assure
comparability across networks, we apply a hypergeometric filter to identify
links for which migration and trade intensity are both significantly higher
than expected. Next we develop an econometric methodology, inspired by spatial
econometrics, to measure the effect of migration on international trade while
controlling for network interdependencies. Overall, we find that migration
significantly boosts trade across sectors and we are able to identify product
categories for which this effect is particularly strong.


title: Misfire Detection in IC Engine using Kstar Algorithm

abstract:
  Misfire in an IC Engine continues to be a problem leading to reduced fuel
efficiency, increased power loss and emissions containing heavy concentration
of hydrocarbons. Misfiring creates a unique vibration pattern attributed to a
particular cylinder. Useful features can be extracted from these patterns and
can be analyzed to detect misfire. Statistical features from these vibration
signals were extracted. Out of these, useful features were identified using the
J48 decision tree algorithm and selected features were used for classification
using the Kstar algorithm. In this paper performance analysis of Kstar
algorithm is presented.


title: Notes on A-infinity algebra and its endomorphism I

abstract:
  In this notes, we study some basic deformation of A-infinity algebra. It
includes a two-dimensional rescaling deformation and the Maurer-Cartan element
or bounding cochain deformation used in Lagrangian Floer Homology theory. We
show that such deformation always can be derived from some (weakly) strict
endomorphism equivalently.


title: On three-dimensional dilational elastic metamaterials

abstract:
  Dilational materials are stable three-dimensional isotropic auxetics with an
ultimate Poisson's ratio of -1. We design, evaluate, fabricate, and
characterize crystalline metamaterials approaching this ideal. To reveal all
modes, we calculate the phonon band structures. On this basis, using cubic
symmetry, we can unambiguously retrieve all different non-zero elements of the
rank-4 effective metamaterial elasticity tensor, from which all effective
elastic metamaterial properties follow. While the elastic properties and the
phase velocity remain anisotropic, the effective Poisson's ratio indeed becomes
isotropic and approaches -1 in the limit of small internal connections. This
finding is also supported by independent static continuum-mechanics
calculations. In static experiments on macroscopic polymer structures
fabricated by three-dimensional printing, we measure Poisson's ratios as low as
-0.8 in good agreement with theory. Microscopic samples are also presented.


title: Besov regularity of functions with sparse random wavelet coefficients

abstract:
  This paper addresses the problem of regularity properties of functions
represented as an expansion in a wavelet basis with random coefficients in
terms of finiteness of their Besov norm with probability 1. Such
representations are used to specify a prior measure in Bayesian nonparametric
wavelet regression. Investigating regularity of such functions is an important
problem since the support of the posterior measure does not include functions
that are not in the support of the prior measure, and therefore determines the
functions that are possible to estimate using specified Bayesian model. We
consider a more general parametrisation than has been studied previously which
allows to study a priori regularity of functions under a wider class of priors.
We also emphasise the difference between the abstract stochastic expansions
that have been studied in the literature, and the expansions actually arising
in nonparametric regression, and show that the latter cover a wider class of
functions than the former. We also extend these results to stochastic
expansions in an overcomplete wavelet dictionary.


title:
High energy terahertz pulses from organic crystals: DAST and DSTMS
  pumped at Ti:sapphire wavelength

abstract:
  High energy terahertz pulses are produced by optical rectification (OR) in
organic crystals DAST and DSTMS by a Ti:sapphire amplifier system centered at
0.8 microns. The simple scheme provides broadband spectra between 1 and 5 THz,
when pumped by collimated 60 fs near-infrared pump pulse and it is scalable in
energy. Fluence-dependent conversion efficiency and damage threshold are
reported as well as optimized OR at visible wavelength.


title:
Lattice QCD calculation of form factors describing the rare decays $B
  \to K^* \ell^+ \ell^-$ and $B_s \to \phi \ell^+ \ell^-$

abstract:
  The rare decays $B^0 \to K^{*0} \mu^+ \mu^-$ and $B_s \to \phi \mu^+ \mu^-$
are now being observed with enough precision to test Standard Model
predictions. A full understanding of these decays requires accurate
determinations of the corresponding hadronic form factors. Here we present
results of lattice QCD calculations of the $B \to K^*$ and $B_s \to \phi$ form
factors; we also determine the form factors relevant for the tree-level decays
$B_s \to K^* \ell \nu$. We use full-QCD configurations including 2+1 flavors of
sea quarks using an improved staggered action, and we employ lattice
non-relativistic QCD to describe the bottom quark.


title: Security policies for distributed systems

abstract:
  A security policy specifies a security property as the maximal information
flow. A distributed system composed of interacting processes implicitly defines
an intransitive security policy by repudiating direct information flow between
processes that do not exchange messages directly. We show that implicitly
defined security policies in distributed systems are enforced, provided that
processes run in separation, and possible process communication on a technical
platform is restricted to specified message paths of the system. Furthermore,
we propose to further restrict the allowable information flow by adding filter
functions for controlling which messages may be transmitted between processes,
and we prove that locally checking filter functions is sufficient for ensuring
global security policies. Altogether, global intransitive security policies are
established by means of local verification conditions for the (trusted)
processes of the distributed system. Moreover, security policies may be
implemented securely on distributed integration platforms which ensure
partitioning. We illustrate our results with a smart grid case study, where we
use CTL model checking for discharging local verification conditions for each
process under consideration.


title: Spatially Coupled Sparse Codes on Graphs - Theory and Practice

abstract:
  Since the discovery of turbo codes 20 years ago and the subsequent
re-discovery of low-density parity-check codes a few years later, the field of
channel coding has experienced a number of major advances. Up until that time,
code designers were usually happy with performance that came within a few
decibels of the Shannon Limit, primarily due to implementation complexity
constraints, whereas the new coding techniques now allow performance within a
small fraction of a decibel of capacity with modest encoding and decoding
complexity. Due to these significant improvements, coding standards in
applications as varied as wireless mobile transmission, satellite TV, and deep
space communication are being updated to incorporate the new techniques. In
this paper, we review a particularly exciting new class of low-density
parity-check codes, called spatially-coupled codes, which promise excellent
performance over a broad range of channel conditions and decoded error rate
requirements.


title: Transforming High School Physics with Modeling and Computation

abstract:
  The Engage to Excel (PCAST) report, the National Research Council's Framework
for K-12 Science Education, and the Next Generation Science Standards all call
for transforming the physics classroom into an environment that teaches
students real scientific practices. This work describes the early stages of one
such attempt to transform a high school physics classroom. Specifically, a
series of model-building and computational modeling exercises were piloted in a
ninth grade Physics First classroom. Student use of computation was assessed
using a proctored programming assignment, where the students produced and
discussed a computational model of a baseball in motion via a high-level
programming environment (VPython). Student views on computation and its link to
mechanics was assessed with a written essay and a series of think-aloud
interviews. This pilot study shows computation's ability for connecting
scientific practice to the high school science classroom.


title: Hamiltonian dynamics of an exotic action for gravity in three dimensions

abstract:
  The Hamiltonian dynamics and the canonical covariant formalism for an exotic
action in three dimensions are performed. By working with the complete phase
space, we report a complete Hamiltonian description of the theory such as the
extended action, the extended Hamiltonian, the algebra among the constraints,
the Dirac's brackets and the correct gauge transformations. In addition, we
show that in spite of exotic action and tetrad gravity with a cosmological
constant give rise to the same equations of motion, they are not equivalent, in
fact, we show that their corresponding Dirac's brackets are quite different.
Finally, we construct a gauge invariant symplectic form which in turn
represents a complete Hamiltonian description of the covariant phase space.


title: NHEG Mechanics: Laws of Near Horizon Extremal Geometry (Thermo)Dynamics

abstract:
  Near Horizon Extremal Geometries (NHEG) are solutions to gravity theories
with $ SL(2,R) \times U(1)^N $ (for some N) symmetry, are smooth geometries and
have no event horizon, unlike black holes. Following the ideas by R. M. Wald,
we derive laws of NHEG dynamics, the analogs of laws of black hole dynamics for
the NHEG. Despite the absence of horizon in the NHEG, one may associate an
entropy to the NHEG, as a Noether-Wald conserved charge. We work out entropy
and entropy perturbation laws, which are respectively universal relations
between conserved Noether charges corresponding to the NHEG and a system
probing the NHEG. Our entropy law is closely related to Sen's entropy function.
We also discuss whether the laws of NHEG dynamics can be obtained from the laws
of black hole thermodynamics in the extremal limit.


title:
Field-induced nematic-like magnetic transition in an iron pnictide
  superconductor,
  Ca$_{10}$(Pt$_{3}$As$_{8}$)((Fe$_{1-x}$Pt$_{x}$)$_{2}$As$_{2}$)$_{5}$

abstract:
  We report a high magnetic field study up to 55 T of the nearly optimally
doped iron-pnictide superconductor Ca$_{10}$(Pt$_{3}$As$_{8}$)
((Fe$_{1-x}$Pt$_{x}$)$_{2}$As$_{2}$)$_{5}$ (x=0.078(6)) with a Tc 10 K using
magnetic torque, tunnel diode oscillator technique and transport measurements.
We determine the superconducting phase diagram, revealing an anisotropy of the
irreversibility field up to a factor of 10 near Tc and signatures of multiband
superconductivity. Unexpectedly, we find a spin-flop like anomaly in magnetic
torque at 22 T, when the magnetic field is applied perpendicular to the ab
planes, which becomes significantly more pronounced as the temperature is
lowered to 0.33 K. As our superconducting sample lies well outside the
antiferromagnetic region of the phase diagram, the observed field-induced
transition in torque indicates a spin-flop transition not of long-range ordered
moments, but of nematic-like antiferromagnetic fluctuations.


title:
Navier-Stokes hydrodynamics in a granular gas fluidized by a non-uniform
  stochastic field

abstract:
  We show a case of steady flow in a granular gas that, for small shear rates,
is accurately described by Navier-Stokes hydrodynamics, even for high
inelasticity. The (low density) granular gas is composed of identical inelastic
spheres and is fluidized by a temperature field produced by a stochastic volume
force plus thermal walls. We prove that the theoretical Navier-Stokes transport
coefficients exhibit good agreement with numerical solutions of the
corresponding the kinetic equation (direct simulation Monte Carlo method) in
the steady state.


title: Phase Diagram of a Reentrant Gel of Patchy Particles

abstract:
  We study the phase diagram of a binary mixture of patchy particles which has
been designed to form a reversible gel. For this we perform Monte Carlo and
molecular dynamics simulations to investigate the thermodynamics of such a
system and compare our numerical results with predictions based on the
analytical parameter-free Wertheim theory. We explore a wide range of the
temperature-density-composition space that defines the three-dimensional phase
diagram of the system. As a result, we delimit the region of thermodynamic
stability of the fluid. We find that for a large region of the phase diagram
the Wertheim theory is able to give a quantitative description of the system.
For higher densities our simulations show that the system is crystallizing into
a BCC structure. Finally we study the relaxation dynamics of the system by
means of the density and temperature dependences of the diffusion coefficient.
We show that there exists a density range where the system passes reversibly
from a gel to a fluid upon both heating and cooling, encountering neither
demixing nor phase separation.


title: LHCf: physics results on forward particle production at LHC

abstract:
  The LHCf experiment is dedicated to the measurement of very forward particle
production in the high energy hadron-hadron collisions at LHC, with the aim of
improving the cosmic-ray air shower developments models. The detector has taken
data in p-p collisions at $\sqrt s$ = 900 GeV, 2.76 TeV and 7 TeV, and in p/Pb
collisions at $\sqrt s$ = 5 TeV. The results of forward production spectra of
photons, neutral pions and neutrons, compared with the models most widely used
in the High Energy Cosmic Ray physics, are presented in this paper.


title: Geo-neutrinos

abstract:
  We review a new interdisciplinary field between Geology and Physics: the
study of the Earth's geo-neutrino flux. We describe competing models for the
composition of the Earth, present geological insights into the make up of the
continental and oceanic crust, those parts of the Earth that concentrate Th and
U, the heat producing elements, and provide details of the regional settings in
the continents and oceans where operating and planned detectors are sited.
Details are presented for the only two operating detectors that are capable of
measuring the Earth's geo-neutrinos flux: Borexino and KamLAND; results
achieved to date are presented, along with their impacts on geophysical and
geochemical models of the Earth. Finally, future planned experiments are
highlighted.


title:
Standard form of the scattering matrix for time reversal symmetric
  system

abstract:
  In this paper, we present the standard form of the scattering matrix of
mesocopic system with spin-orbital coupling which preserves time reversal
symmetry. We found some analytical structure of the scattering matrix related
to the sub-matrices between arbitrary two channels. In particular, we proved
that in the two-terminal mono-channel scattering problem, the transmission
matrix is proportional to a SU(2) matrix. We obtained these properties through
direct and elementary way and found it in agreement with polar decomposition
known before.


title:
Impact of hadronic and nuclear corrections on global analysis of
  spin-dependent parton distributions

abstract:
  We present the first results of a new global next-to-leading order analysis
of spin-dependent parton distribution functions from the most recent world data
on inclusive polarized deep-inelastic scattering, focusing in particular on the
large-x and low-Q^2 regions. By directly fitting polarization asymmetries we
eliminate biases introduced by using polarized structure function data
extracted under nonuniform assumptions for the unpolarized structure functions.
For analysis of the large-x data we implement nuclear smearing corrections for
deuterium and 3He nuclei, and systematically include target mass and higher
twist corrections to the g_1 and g_2 structure functions at low Q^2. We also
explore the effects of Q^2 and W^2 cuts in the data sets, and the potential
impact of future data on the behavior of the spin-dependent parton
distributions at intermediate and large x.


title:
Low-temperature thermal conductivity of antiferromagnetic S = 1/2 chain
  material CuCl_2$\cdot$2((CH_3)_2SO)

abstract:
  We study the heat transport of S = 1/2 chain compound
CuCl_2$\cdot$2((CH_3)_2SO) along the b axis (vertical to the chain direction)
at very low temperatures. The zero-field thermal conductivity (\kappa) shows a
distinct kink at about 0.9 K, which is related to the long-range
antiferromagnetic (AF) transition. With applying magnetic field along the c
axis, \kappa(H) curves also show distinct changes at the phase boundaries
between the AF and the high-field disordered states. These results indicate a
strong spin-phonon interaction and the magnetic excitations play a role in the
b-axis heat transport as phonon scatterers.


title: Tensorial methods and renormalization in Group Field Theories

abstract:
  In this thesis, we study the structure of Group Field Theories (GFTs) from
the point of view of renormalization theory. Such quantum field theories are
found in approaches to quantum gravity related to Loop Quantum Gravity (LQG) on
the one hand, and to matrix models and tensor models on the other hand. They
model quantum space-time, in the sense that their Feynman amplitudes label
triangulations, which can be understood as transition amplitudes between LQG
spin network states. The question of renormalizability is crucial if one wants
to establish interesting GFTs as well-defined (perturbative) quantum field
theories, and in a second step connect them to known infrared gravitational
physics. Relying on recently developed tensorial tools, this thesis explores
the GFT formalism in two complementary directions. First, new results on the
large cut-off expansion of the colored Boulatov-Ooguri models allow to explore
further a non-perturbative regime in which infinitely many degrees of freedom
contribute. The second set of results provide a new rigorous framework for the
renormalization of so-called Tensorial GFTs (TGFTs) with gauge invariance
condition. In particular, a non-trivial 3d TGFT with gauge group SU(2) is
proven just-renormalizable at the perturbative level, hence opening the way to
applications of the formalism to (3d Euclidean) quantum gravity.


title:
Law of Urination: all mammals empty their bladders over the same
  duration

abstract:
  Many urological studies rely upon animal models such as rats and pigs whose
urination physics and correlation to humans are poorly understood. Here we
elucidate the hydrodynamics of urination across five orders of magnitude in
animal mass. Using high-speed videography and flow rate measurement at Zoo
Atlanta, we discover the "Law of Urination," which states animals empty their
bladders over nearly constant duration of average 21 seconds (standard
deviation 13 seconds). This feat is made possible by larger animals having
longer urethras, thus higher gravitational force and flow speed. Smaller
mammals are challenged during urination due to high viscous and surface tension
forces that limit their urine to single drops. Our findings reveal the urethra
constitutes as a flow enhancing device, enabling the urinary system to be
scaled up without compromising its function. This study may help in the
diagnosis of urinary problems in animals and in inspiring the design of
scalable hydrodynamic systems based on those in nature.


title: Reverse Monte Carlo modeling in confined systems

abstract:
  An extension of the well established Reverse Monte Carlo (RMC) method for
modeling systems under close confinement has been developed. The method
overcomes limitations induced by close confinement in systems such as fluids
adsorbed in microporous materials. As a test of the method, we investigate a
model system of $^{36}$Ar adsorbed into two zeolites with significantly
different pore sizes: Silicalite-I (a pure silica form of ZSM-5 zeolite,
characterized by relatively narrow channels forming a 3D network) at partial
and full loadings and siliceous Faujasite (which exhibits relatively wide
channels and large cavities). The model systems are simulated using Grand
Canonical Monte Carlo and, in each case, its structure factor is used as input
for the proposed method, which shows a rapid convergence and yields an
adsorbate microscopic structure in good agreement with that of the model
system, even to the level of three body correlations, when these are induced by
the confining media. The application to experimental systems is straightforward
incorporating factors such as the experimental resolution and appropriate
q-sampling, along the lines of previous experiences of RMC modeling of powder
diffraction data including Bragg and diffuse scattering.


title:
The X-ray Spectrum and Spectral Energy Distribution of FIRST
  J155633.8+351758: a LoBAL Quasar with a Probable Polar Outflow

abstract:
  We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD
Imaging Spectrometer S-array (ACIS-S) observation of the reddened,
radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We
investigated a number of models of varied sophistication to fit the 531-photon
spectrum. These models ranged from simple power laws to power laws absorbed by
hydrogen gas in differing ionization states and degrees of partial covering.
Preferred fits indicate that the intrinsic X-ray flux is consistent with that
expected for quasars of similarly high luminosity, i.e., an intrinsic,
dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot
tightly constrain the intrinsic X-ray power-law slope, but find indications
that it is flat (photon index Gamma = 1.7 or flatter at a >99% confidence for a
neutral hydrogen absorber model). Absorption is present, with a column density
a few times 10^23 cm^-2, with both partially ionized models and partially
covering neutral hydrogen models providing good fits. We present several lines
of argument that suggest the fraction of X-ray emissions associated with the
radio jet is not large.
  We combine our Chandra data with observations from the literature to
construct the spectral energy distribution of FIRST J1556+3517 from radio to
X-ray energies. We make corrections for Doppler beaming for the pole-on radio
jet, optical dust reddening, and X-ray absorption, in order to recover a
probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an
intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a
Doppler-boosted but intrinsically weak radio jet, and an X-ray absorber not
dissimilar from that of other broad absorption line quasars.


title:
Halo Abundance Matching: accuracy and conditions for numerical
  convergence

abstract:
  Accurate predictions of the abundance and clustering of dark matter haloes
play a key role in testing the standard cosmological model. Here, we
investigate the accuracy of one of the leading methods of connecting the
simulated dark matter haloes with observed galaxies -- the Halo Abundance
Matching (HAM) technique. We show how to choose the optimal values of the mass
and force resolution in large-volume N-body simulations so that they provide
accurate estimates for correlation functions and circular velocities for haloes
and their subhaloes -- crucial ingredients of the HAM method. At the 10%
accuracy, results converge for 50 particles for haloes and 150 particles for
progenitors subhaloes. In order to achieve this level of accuracy a number of
conditions should be satisfied. The force resolution for the smallest resolved
(sub)haloes should be in the range (0.1-0.3)rs, where rs is the scale radius of
(sub)haloes. The number of particles for progenitors of subhaloes should be
150. We also demonstrate that the two-body scattering plays a minor role for
the accuracy of N-body simulations thanks to the relatively small number of
crossing-times of dark matter in haloes, and the limited force resolution of
cosmological simulations.


title: Evaluating parametric holonomic sequences using rectangular splitting

abstract:
  We adapt the rectangular splitting technique of Paterson and Stockmeyer to
the problem of evaluating terms in holonomic sequences that depend on a
parameter. This approach allows computing the $n$-th term in a recurrent
sequence of suitable type using $O(n^{1/2})$ "expensive" operations at the cost
of an increased number of "cheap" operations.
  Rectangular splitting has little overhead and can perform better than either
naive evaluation or asymptotically faster algorithms for ranges of $n$
encountered in applications. As an example, fast numerical evaluation of the
gamma function is investigated. Our work generalizes two previous algorithms of
Smith.


title: Chiral pions in a magnetic background

abstract:
  We investigate the modification of the pion self-energy at finite temperature
due to its interaction with a low-density, isospin-symmetric nuclear medium
embedded in a constant magnetic background. To one loop, for fixed temperature
and density, we find that the pion effective mass increases with the magnetic
field. For the $\pi^{-}$, interestingly, this happens solely due to the trivial
Landau quantization shift $\sim |eB|$, since the real part of the self-energy
is negative in this case. In a scenario in which other charged particle species
are present and undergo an analogous trivial shift, the relevant behavior of
the effective mass might be determined essentially by the real part of the
self-energy. In this case, we find that the pion mass decreases by $\sim 10%$
for a magnetic field $|eB|\sim m_\pi^2$, which favors pion condensation at high
density and low temperatures.


title: Inertial Rise in Short Capillaries

abstract:
  In this fluid dynamics video we show capillary rise experiments with diethyl
ether in short tubes. The height of each short tube is less than the maximum
height the liquid can achieve, and therefore the liquid reaches the top of the
tube while still rising. Over a narrow range of heights, the ether bulges out
from the top of the tube and spreads onto the external wall.


title:
Superconducting fluctuations in organic molecular metals enhanced by
  Mott criticality

abstract:
  Unconventional superconductivity typically occurs in materials in which a
small change of a parameter such as bandwidth or doping leads to
antiferromagnetic or Mott insulating phases. As such competing phases are
approached, the properties of the superconductor often become increasingly
exotic. For example, in organic superconductors and underdoped
high-$T_\mathrm{c}$ cuprate superconductors a fluctuating superconducting state
persists to temperatures significantly above $T_\mathrm{c}$. By studying alloys
of quasi-two-dimensional organic molecular metals in the
$\kappa$-(BEDT-TTF)$_2$X family, we reveal how the Nernst effect, a sensitive
probe of superconducting phase fluctuations, evolves in the regime of extreme
Mott criticality. We find strong evidence that, as the phase diagram is
traversed through superconductivity towards the Mott state, the temperature
scale for superconducting fluctuations increases dramatically, eventually
approaching the temperature at which quasiparticles become identifiable at all.


title: Alternating Minimization for Mixed Linear Regression

abstract:
  Mixed linear regression involves the recovery of two (or more) unknown
vectors from unlabeled linear measurements; that is, where each sample comes
from exactly one of the vectors, but we do not know which one. It is a classic
problem, and the natural and empirically most popular approach to its solution
has been the EM algorithm. As in other settings, this is prone to bad local
minima; however, each iteration is very fast (alternating between guessing
labels, and solving with those labels).
  In this paper we provide a new initialization procedure for EM, based on
finding the leading two eigenvectors of an appropriate matrix. We then show
that with this, a re-sampled version of the EM algorithm provably converges to
the correct vectors, under natural assumptions on the sampling distribution,
and with nearly optimal (unimprovable) sample complexity. This provides not
only the first characterization of EM's performance, but also much lower sample
complexity as compared to both standard (randomly initialized) EM, and other
methods for this problem.


title: On the characterization of the SU(3)-subgroups of type C and D

abstract:
  We investigate the two classes of finite subgroups of SU(3) that are called
type C and D in the book of Miller, Blichfeldt and Dickson. We present two
theorems which fully determine the form of the generators in a suitable basis.
After exploring further properties of these groups, we are able to construct a
complete list of infinite series in which these groups are arranged. For type C
there are infinitely many series whereas for type D there are only two.
Explicit examples of these series are presented which illustrate the general
results.


title: Why does a beer bottle foam up after a sudden impact on its mouth?

abstract:
  A sudden vertical impact on the mouth of a beer bottle generates a
compression wave that propagates through the glass towards the bottom. When
this wave reaches the base of the bottle, it is transmitted to the liquid as an
expansion wave that travels to free surface, where it bounces back as a
compression wave. This train of expansion-compression waves drives the forced
cavitation of existing air pockets, leading to their violent collapse. A cloud
of very small daughter bubbles are generated upon these collapses, that expand
much faster than their mothers due to their smaller size. These rapidly growing
bubble clusters effectively act as buoyancy sources, what leads to the
formation of bubble-laden plumes whose void fraction increases quickly by
several orders of magnitude, eventually turning most of the liquid into foam.


title: PMN: a minimal induced-moment soft pseudo-spin glass perspective

abstract:
  An argument that relaxor ferroelectricity in the isovalent alloy $\mathrm
{Ba(Zr}_{1-x}\mathrm{Ti}_{x})\mathrm{O}_3$ can be understood as an induced
moment soft pseudo-spin glass on the B-ions of the $\mathrm{ABO}_{3}$ matrix is
extended to the experimentally paradigmic but theoretically more complex
heterovalent relaxor $\mathrm {Pb(Mg}_{1/3}\mathrm{Nb}_{2/3}\mathrm{)O}_3$
(PMN). It is argued that interesting behaviour of the onset of non-ergodicity,
frequency-dependent susceptibility peaks and precursor nanodomains can be
understood from analagous considerations of the B-ions, with the displacements
of the Pb ions a largely independent, but distracting, side-feature. This
contrasts with conventional conceptualizations.


title: In-situ growth optimization in focused electron-beam induced deposition

abstract:
  We present the application of an evolutionary genetic algorithm for the
in-situ optimization of nanostructures prepared by focused
electron-beam-induced deposition. It allows us to tune the properties of the
deposits towards highest conductivity by using the time gradient of the
measured in-situ rate of change of conductance as fitness parameter for the
algorithm. The effectiveness of the procedure is presented for the precursor
W(CO)6 as well as for post-treatment of Pt-C deposits obtained by dissociation
of MeCpPt(Me)3. For W(CO)6-based structures an increase of conductivity by one
order of magnitude can be achieved, whereas the effect for MeCpPt(Me)3 is
largely suppressed. The presented technique can be applied to all beam-induced
deposition processes and has great potential for further optimization or tuning
of parameters for nanostrucures prepared by FEBID or related techniques.


title: Improved quantum metrology using quantum error-correction

abstract:
  We consider quantum metrology in noisy environments, where the effect of
noise and decoherence limits the achievable gain in precision by quantum
entanglement. We show that by using tools from quantum error-correction this
limitation can be overcome. This is demonstrated in two scenarios, including a
many-body Hamiltonian with single-qubit dephasing or depolarizing noise, and a
single-body Hamiltonian with transversal noise. In both cases we show that
Heisenberg scaling, and hence a quadratic improvement over the classical case,
can be retained. Moreover, for the case of frequency estimation we find that
the inclusion of error-correction allows, in certain instances, for a finite
optimal interrogation time even in the asymptotic limit.


title: Time variability of viscosity parameter in differentially rotating discs

abstract:
  We propose a mechanism to produce fluctuations in the viscosity parameter
($\alpha$) in differetially rotating discs. We carried out a nonlinear analysis
of a general accretion flow, where any perturbation on the background $\alpha$
was treated as a passive/slave variable in the sense of dynamical system
theory. We demonstrate a complete physical picture of growth, saturation and
final degradation of the perturbation as a result of the nonlinear nature of
coupled system of equations. The strong dependence of this fluctuation on the
radial location in the accretion disc and the base angular momentum
distribution is demonstrated. The growth of fluctuations is shown to have a
time scale comparable to the radial drift time and hence the physical
significance is discussed. The fluctuation is found to be a power law in time
in the growing phase and we briefly discuss its statistical significance.


title:
Two-point correlator of twist-2 light-ray operators in N=4 SYM in BFKL
  approximation

abstract:
  We generalize local operators of the leading twist-2 of N=4 SYM theory to the
case of complex Lorentz spin j using principal series representation of
sl(2,R). We give the direct computation of correlation function of two such
non-local operators in the BFKL regime when j -> 1. The correlator appears to
have the expected conformal coordinate dependence governed by the anomalous
dimension of twist-2 operator in NLO BFKL approximation predicted by Kotikov
and Lipatov.


title:
Dark matter as a Bose--Einstein Condensate: the relativistic
  non-minimally coupled case

abstract:
  Bose--Einstein Condensates have been recently proposed as dark matter
candidates. In order to characterise the phenomenology associated to such
models, we extend previous investigations by studying the most general case of
a relativistic BEC on a curved background including a non-minimal coupling to
curvature. In particular, we discuss the possibility of a two phase
cosmological evolution: a cold dark matter-like phase at the large scales/early
times and a condensed phase inside dark matter halos. During the first phase
dark matter is described by a minimally coupled weakly self-interacting scalar
field, while in the second one dark matter condensates and, we shall argue,
develops as a consequence the non-minimal coupling. Finally, we discuss how
such non-minimal coupling could provide a new mechanism to address cold dark
matter paradigm issues at galactic scales.


title:
Optimizing working memory with heterogeneity of recurrent cortical
  excitation

abstract:
  A neural correlate of parametric working memory is a stimulus specific rise
in neuron firing rate that persists long after the stimulus is removed. Network
models with local excitation and broad inhibition support persistent neural
activity, linking network architecture and parametric working memory. Cortical
neurons receive noisy input fluctuations which causes persistent activity to
diffusively wander about the network, degrading memory over time. We explore
how cortical architecture that supports parametric working memory affects the
diffusion of persistent neural activity. Studying both a spiking network and a
simplified potential well model, we show that spatially heterogeneous
excitatory coupling stabilizes a discrete number of persistent states, reducing
the diffusion of persistent activity over the network. However, heterogeneous
coupling also coarse-grains the stimulus representation space, limiting the
capacity of parametric working memory. The storage errors due to
coarse-graining and diffusion tradeoff so that information transfer between the
initial and recalled stimulus is optimized at a fixed network heterogeneity.
For sufficiently long delay times, the optimal number of attractors is less
than the number of possible stimuli, suggesting that memory networks can
under-represent stimulus space to optimize performance. Our results clearly
demonstrate the effects of network architecture and stochastic fluctuations on
parametric memory storage.


title:
The HST/ACS Coma Cluster Survey - VII. Structure and Assembly of Massive
  Galaxies in the Center of the Coma Cluster

abstract:
  We constrain the assembly history of galaxies in the projected central 0.5
Mpc of the Coma cluster by performing structural decomposition on 69 massive
(M_star >= 10^9 M_sun) galaxies using high-resolution F814W images from the HST
Treasury Survey of Coma. Each galaxy is modeled with up to three Sersic
components having a free Sersic index n. After excluding the two cDs in the
projected central 0.5 Mpc of Coma, 57% of the galactic stellar mass in the
projected central 0.5 Mpc of Coma resides in classical bulges/ellipticals while
43% resides in cold disk-dominated structures. Most of the stellar mass in Coma
may have been assembled through major (and possibly minor) mergers. Hubble
types are assigned based on the decompositions, and we find a strong
morphology-density relation; the ratio of (E+S0):spirals is (91.0%):9.0%. In
agreement with earlier work, the size of outer disks in Coma S0s/spirals is
smaller compared with lower-density environments captured with SDSS (Data
Release 2). Among similar-mass clusters from a hierarchical semi-analytic
model, no single cluster can simultaneously match all the global properties of
the Coma cluster. The model strongly overpredicts the mass of cold gas and
underpredicts the mean fraction of stellar mass locked in hot components over a
wide range of galaxy masses. We suggest that these disagreements with the model
result from missing cluster physics (e.g., ram-pressure stripping), and certain
bulge assembly modes (e.g., mergers of clumps). Overall, our study of Coma
underscores that galaxy evolution is not solely a function of stellar mass, but
also of environment.


title:
A table-top, repetitive pulsed magnet for nonlinear and ultrafast
  spectroscopy in high magnetic fields up to 30 T

abstract:
  We have developed a mini-coil pulsed magnet system with direct optical
access, ideally suited for nonlinear and ultrafast spectroscopy studies of
materials in high magnetic fields up to 30 T. The apparatus consists of a small
coil in a liquid nitrogen cryostat coupled with a helium flow cryostat to
provide sample temperatures down to below 10 K. Direct optical access to the
sample is achieved with the use of easily interchangeable windows separated by
a short distance of ~135 mm on either side of the coupled cryostats with
numerical apertures of 0.20 and 0.03 for measurements employing the Faraday
geometry. As a demonstration, we performed time-resolved and time-integrated
photoluminescence measurements as well as transmission measurements on InGaAs
quantum wells.


title: The superconformal bootstrap for structure constants

abstract:
  We report on non-perturbative bounds for structure constants on N=4 SYM. Such
bounds are obtained by applying the conformal bootstrap recently extended to
superconformal theories. We compare our results with interpolating functions
suitably restricted by the S-duality of the theory. Within numerical errors,
these interpolations support the conjecture that the bounds found in this paper
are saturated at duality invariant values of the coupling. This extends recent
conjectures for the anomalous dimension of leading twist operators.


title:
Hamiltonian analysis for abelian and non-abelian massive theories in
  three dimensions

abstract:
  A pure Dirac's method for abelian and non-abelian massive theories in three
dimensions is performed. Our analysis is developed on the extended phase space
reporting the relevant structure of the theories, namely, the extended action,
the extended Hamiltonian, the full structure of the constraints and the
counting of degrees of freedom. In addition, we compare our results with those
found in the literature.


title: A pure Dirac's method for Husain-Kuchar theory

abstract:
  A pure Dirac's canonical analysis, defined in the full phase space for the
Husain-Kuchar model is discussed in detail. This approach allows us to
determine the extended action, the extended Hamiltonian, the complete
constraint algebra and the gauge transformations for all variables that occur
in the action principle. The complete set of constraints defined on the full
phase space allow us to calculate the Dirac algebra structure of the theory and
a local weighted measure for the path integral quantization method. Finally, we
discuss briefly the necessary mathematical structure to perform the canonical
quantization program within the framework of the loop quantum gravity approach.


title:
Hamiltonian dynamics: four dimensional BF-like theories with a compact
  dimension

abstract:
  A detailed Dirac's canonical analysis for a topological four dimensional
$BF$-like theory with a compact dimension is developed. By performing the
compactification process we find out the relevant symmetries of the theory,
namely, the full structure of the constraints and the extended action. We show
that the extended Hamiltonian is a linear combination of first class
constraints, which means that the general covariance of the theory is not
affected by the compactification process. Furthermore, in order to carry out
the correct counting of physical degrees of freedom, we show that must be taken
into account reducibility conditions among the first class constraints
associated to the excited KK modes. Moreover, we perform the Hamiltonian
analysis of Maxwell theory written as a $BF$-like theory with a compact
dimension, we analyze the constraints of the theory and we calculate the
fundamental Dirac's brackets, finally the results obtained are compared with
those found in the literature.


title:
Stochastic analysis of biochemical reaction networks with absolute
  concentration robustness

abstract:
  It has recently been shown that structural conditions on the reaction
network, rather than a 'fine-tuning' of system parameters, often suffice to
impart 'absolute concentration robustness' on a wide class of biologically
relevant, deterministically modeled mass-action systems [Shinar and Feinberg,
Science, 2010]. We show here that fundamentally different conclusions about the
long-term behavior of such systems are reached if the systems are instead
modeled with stochastic dynamics and a discrete state space. Specifically, we
characterize a large class of models that exhibit convergence to a positive
robust equilibrium in the deterministic setting, whereas trajectories of the
corresponding stochastic models are necessarily absorbed by a set of states
that reside on the boundary of the state space, i.e. the system undergoes an
extinction event. If the time to extinction is large relative to the relevant
time-scales of the system, the process will appear to settle down to a
stationary distribution long before the inevitable extinction will occur. This
quasi-stationary distribution is considered for two systems taken from the
literature, and results consistent with absolute concentration robustness are
recovered by showing that the quasi-stationary distribution of the robust
species approaches a Poisson distribution.


title: Vortex distribution in a confining potential

abstract:
  We study a model of interacting vortices in a type II superconductor. In the
weak coupling limit, we constructed a mean-field theory which allows us to
accurately calculate the vortex density distribution inside a confining
potential. In the strong coupling limit, the correlations between the particles
become important and the mean-field theory fails. Contrary to recent
suggestions, this does not imply failure of the Boltzmann-Gibbs statistical
mechanics, as we clearly demonstrate by comparing the results of Molecular
Dynamics and Monte Carlo simulations.