title: A Convex Optimization Approach to pMRI Reconstruction

abstract:
  In parallel magnetic resonance imaging (pMRI) reconstruction without using
estimation of coil sensitivity functions, one group of algorithms reconstruct
sensitivity encoded images of the coils first followed by the magnitude only
image reconstruction, e.g. GRAPPA, and another group of algorithms jointly
compute the image and sensitivity functions by regularized optimization which
is a non-convex problem with local only solutions. For the magnitude only image
reconstruction, this paper derives a reconstruction formulation, which is
linear in the magnitude image, and an associated convex hull in the solution
space of the formulated equation containing the magnitude of the image. As a
result, the magnitude only image reconstruction for pMRI is formulated into a
two-step convex optimization problem, which has a globally optimal solution. An
algorithm based on split-bregman and nuclear norm regularized optimizations is
proposed to implement the two-step convex optimization and its applications to
phantom and in-vivo MRI data sets result in superior reconstruction performance
compared with other algorithms.


title: Potentialities of Nonsmooth Optimization

abstract:
  In this paper, we show that higher-order optimality conditions can be obtain
for arbitrary nonsmooth function. We introduce a new higher-order directional
derivative and higher-order subdifferential of Hadamard type of a given proper
extended real function. This derivative is consistent with the classical
higher-order Fr\'echet directional derivative in the sense that both
derivatives of the same order coincide if the last one exists. We obtain
necessary and sufficient conditions of order $n$ ($n$ is a positive integer)
for a local minimum and isolated local minimum of order $n$ in terms of these
derivatives and subdifferentials. We do not require any restrictions on the
function in our results. A special class $\mathcal F_n$ of functions is defined
and optimality conditions for isolated local minimum of order $n$ for a
function $f\in\mathcal F_n$ are derived. The derivative of order $n$ does not
appear in these characterizations. We prove necessary and sufficient criteria
such that every stationary point of order $n$ is a global minimizer. We compare
our results with some previous ones.


title: Data Search by a Laser Ising Machine with Gradual Pumping or Coupling

abstract:
  We study two operational schemes for a coherent Ising machine based on an
injection-locked laser network. These schemes gradually increase the pumping
rate or the mutual coupling among the slave lasers. We numerically simulate the
two schemes against a data search problem implemented with the Ising model in
cubic graphs without frustration. We show the machine can achieve a better
success probability and effective computational time to find a target/ground
state with these gradual schemes than those with the abrupt introduction of the
mutual injection which has been studied previously. The computational time
simulated with typical parameters is almost constant up to the problem size M =
200 and turns into a nearly linear scale holding up to M = 1000.


title: The matching polytope has exponential extension complexity

abstract:
  A popular method in combinatorial optimization is to express polytopes P,
which may potentially have exponentially many facets, as solutions of linear
programs that use few extra variables to reduce the number of constraints down
to a polynomial. After two decades of standstill, recent years have brought
amazing progress in showing lower bounds for the so called extension
complexity, which for a polytope P denotes the smallest number of inequalities
necessary to describe a higher dimensional polytope Q that can be linearly
projected on P.
  However, the central question in this field remained wide open: can the
perfect matching polytope be written as an LP with polynomially many
constraints?
  We answer this question negatively. In fact, the extension complexity of the
perfect matching polytope in a complete n-node graph is 2^Omega(n). By a known
reduction this also improves the lower bound on the extension complexity for
the TSP polytope from 2^Omega(n^1/2) to 2^Omega(n).


title: Mixing angle of $K_1$ axial vector mesons

abstract:
  Analyses of various experimental measurements all indicate that the mixing
angle $\theta_{K_1}$ of $K_1(1270)$ and $K_1(1400)$ is in the vicinity of
$33^\circ$ or $57^\circ$. However, whether $\theta_{K_1}$ is greater or less
than $45^\circ$ is still quite controversial. For example, there were two very
recent studies of the strong decays of $K_1$ mesons. One group claimed that
$\theta_{K_1}\approx 60^\circ$, while the other group obtained
$\theta_{K_1}=(33.6\pm4.3)^\circ$. Since the determination of the mixing angles
$\alpha_{^3\!P_1}$ and $\alpha_{^1\!P_1}$ with the former (latter) being the
mixing angle of $f_1(1285)$ ($h_1(1170)$) and $f_1(1420)$ ($h_1(1380)$) in the
flavor basis through mass relations depend on $\theta_{K_1}$, we show that
$\theta_{K_1}\approx 57^\circ$ is ruled out as it leads to a too large
deviation from ideal mixing in the $^1\!P_1$ sector, inconsistent with the
lattice calculation of $\alpha_{^1\!P_1}$ and the observation of strong decays
of $h_1(1170)$ and $h_1(1380)$. We find that for $\theta_{K_1}\approx
(28-30)^\circ$, the corresponding $\alpha_{^3\!P_1}$ and $\alpha_{^1\!P_1}$
agree well with all lattice and phenomenological analyses. This again
reinforces the statement that $\theta_{K_1}\sim 33^\circ$ is much more favored
than $57^\circ$.


title: Factorization of S^3/Z_n partition function

abstract:
  We investigate S^3/Z_n partition function of 3d N = 2 supersymmetric field
theories. In a gauge theory the partition function is the sum of the
contributions of sectors specified by holonomies, and we should carefully
choose the relative signs among the contributions. We argue that the
factorization to holomorphic blocks is a useful criterion to determine the
signs and propose a formula for them. We show that the orbifold partition
function of a general non-gauge theory is correctly factorized provided that we
take appropriate relative signs. We also present a few examples of gauge
theories. We point out that the sign factor for the orbifold partition function
is closely related to a similar sign factor in the lens space index and the 3d
index.


title: Exponential of a Matrix, a Nonlinear Problem and Quantum Gates

abstract:
  We describe solutions of the matrix equation $\exp(z(A-I_n))=A$, where $z \in
{\mathbb C}$. Applications in quantum computing are given. Both normal and
nonnormal matrices are studied. For normal matrices, the Lambert W-function
plays a central role.


title:
Nuclear-spin-dependent parity nonconservation in s-d_5/2 and s-d_3/2
  transitions

abstract:
  We perform calculations of s-d_5/2 nuclear-spin-dependent parity
nonconservation amplitudes for Rb, Cs, Ba+, Yb+, Fr, Ra+ and Ac++. These
systems prove to be good candidates for the use in atomic experiments to
extract the so-called anapole moment, a P-odd T-even nuclear moment important
for the study of parity violating nuclear forces. We also extend our previous
works by calculating the missed spin-dependent amplitudes for the s-d_3/2
transitions in the above systems.


abstract:
  The classical Riemann-Hilbert correspondence establishes an equivalence
between the triangulated category of regular holonomic D-modules and that of
constructible sheaves. In this paper, we prove a Riemann-Hilbert correspondence
for holonomic D-modules which are not necessarily regular. The construction of
our target category is based on the theory of ind-sheaves by Kashiwara-Schapira
and influenced by Tamarkin's work. Among the main ingredients of our proof is
the description of the structure of flat meromorphic connections due to
Mochizuki and Kedlaya.


title:
Reply to Comment on `Ratchet universality in the presence of thermal
  noise'

abstract:
  The Comment by Quintero et al (arXiv:1309.1065[nlin.PS])does not dispute the
central result of our paper [Phys. Rev. E {87}, 062114 (2013)] which is a
theory explaining the interplay between thermal noise and symmetry breaking in
the ratchet transport of a Brownian particle moving on a periodic substrate
subjected to a temporal biharmonic excitation $\gamma\left[ \eta\sin\left(
\omega t\right) +\alpha\left( 1-\eta\right) \sin\left( 2\omega t+\varphi\right)
\right] $. In the Comment, the authors claim, on the sole basis of their
numerical simulations for the particular case $\alpha=2$, that "there is no
such universal force waveform and that the evidence obtained by the authors
otherwise is due to their particular choice of parameters." Here we demonstrate
by means of theoretical arguments and additional numerical simulations that all
the conclusions of our original article are preserved.


title: Exact Solutions in Structured Low-Rank Approximation

abstract:
  Structured low-rank approximation is the problem of minimizing a weighted
Frobenius distance to a given matrix among all matrices of fixed rank in a
linear space of matrices. We study exact solutions to this problem by way of
computational algebraic geometry. A particular focus lies on Hankel matrices,
Sylvester matrices and generic linear spaces.


title: Entanglement-assisted electron microscopy based on a flux qubit

abstract:
  A notorious problem in high-resolution biological electron microscopy is
radiation damage to the specimen caused by probe electrons. Hence, acquisition
of data with minimal number of electrons is of critical importance. Quantum
approaches may represent the only way to improve the resolution in this
context, but all proposed schemes to date demand delicate control of the
electron beam in highly unconventional electron optics. Here we propose a
scheme that involves a flux qubit based on a radio-frequency superconducting
quantum interference device (rf-SQUID), inserted in essentially a conventional
transmission electron microscope. The scheme significantly improves the
prospect of realizing a quantum-enhanced electron microscope for
radiation-sensitive specimens.


title: An Empirical Evaluation of Sequence-Tagging Trainers

abstract:
  The task of assigning label sequences to a set of observed sequences is
common in computational linguistics. Several models for sequence labeling have
been proposed over the last few years. Here, we focus on discriminative models
for sequence labeling. Many batch and online (updating model parameters after
visiting each example) learning algorithms have been proposed in the
literature. On large datasets, online algorithms are preferred as batch
learning methods are slow. These online algorithms were designed to solve
either a primal or a dual problem. However, there has been no systematic
comparison of these algorithms in terms of their speed, generalization
performance (accuracy/likelihood) and their ability to achieve steady state
generalization performance fast. With this aim, we compare different algorithms
and make recommendations, useful for a practitioner. We conclude that the
selection of an algorithm for sequence labeling depends on the evaluation
criterion used and its implementation simplicity.


title: Creation of entangled universes avoids the big bang singularity

abstract:
  The creation of universes in entangled pairs may avoid the initial
singularity and it would have observable consequences in a large macroscopic
universe like ours, at least in principle. In this paper we describe the
creation of an entangled pair of universes from a double instanton, which
avoids the initial singularity, in the case of a homogeneous and isotropic
universe with a conformally coupled massless scalar field. The thermodynamical
properties of inter-universal entanglement might have observable consequences
on the properties of our single universe provided that the thermodynamics of
entanglement is eventually related to the classical formulation of
thermodynamics.


title:
Hidden Sector Dark Matter with Global $U(1)_X$-symmetry and Fermi-LAT
  130 GeV $\gamma$-ray Excess

abstract:
  We suggest a dark matter scenario which could contribute the possible anomaly
observed by Fermi-LAT $\gamma$-ray space telescope. It is based on the model
recently proposed by Weinberg. In our scenario the gamma-ray line signal comes
from the fermionic dark matter ($M_{\rm DM}=214 $ GeV) annihilating into two
light scalars with mass around 500 MeV which in turn decay into two neutral
pions. Finally the pions can decay into two 130 GeV photons. The strong
constraint from the direct detection leaves only the channel of the dark matter
annihilation into two light scalars for both the relic density and the
Fermi-LAT gamma-ray line signal. The resulting gamma-ray spectrum is rather
broad and does not fit to the data perfectly, but the data also show there may
be fluctuation in the spectrum. There is no associated $Z$-boson or Higgs boson
production contrary to most other works where the signal comes from the loops
of charged particles. The annihilation into the other SM particles are highly
suppressed due to the small mixing from the direct detection. Future
experiments with more data will give more clues on the possible scenarios.


title:
Dynamics of BEC mixtures loaded into the optical lattice in the presence
  of linear inter-component coupling

abstract:
  We consider dynamics of a two-component Bose-Einstein condensate where the
components correspond to different hyperfine states of the same sort of atoms.
External microwave radiation leads to resonant transitions between the states.
The condensate is loaded into the optical lattice. We invoke the tight-binding
approximation and examine the interplay of spatial and internal dynamics of the
mixture. It is shown that internal dynamics qualitatively depends on the
intra-component interaction strength and the phase configuration of the initial
state. We focus attention on two intriguing phenomena occurring for certain
parameter values. The first phenomenon is the spontaneous synchronization of
Rabi oscillations running inside neighbouring lattice sites. Another one is the
demixing of the condensate with formation of immiscible solitons when
nonlinearity becomes sufficiently strong. Demixing is preceded by the transient
regime with highly irregular behavior of the mixture.

categories: cond-mat.quant-gas nlin.CD nlin.PS quant-ph


title: Prominence Mass Supply and the Cavity

abstract:
  A prevalent but untested paradigm is often used to describe the
prominence-cavity system: the cavity is under-dense because it is evacuated by
supplying mass to the condensed prominence. The thermal non-equilibrium (TNE)
model of prominence formation offers a theoretical framework to predict the
thermodynamic evolution of the prominence and the surrounding corona. We
examine the evidence for a prominence-cavity connection by comparing the TNE
model with diagnostics of dynamic extreme ultraviolet emission (EUV)
surrounding the prominence, specifically prominence horns. Horns are correlated
extensions of prominence plasma and coronal plasma which appear to connect the
prominence and cavity. The TNE model predicts that large-scale brightenings
will occur in the SDO/AIA 171\AA\ bandpass near the prominence that are
associated with the cooling phase of condensation formation. In our
simulations, variations in the magnitude of footpoint heating lead to
variations in the duration, spatial scale, and temporal offset between emission
enhancements in the other EUV bandpasses. While these predictions match well a
subset of the horn observations, the range of variations in the observed
structures is not captured by the model. We discuss the implications of our
one-dimensional loop simulations for the three-dimensional time-averaged
equilibrium in the prominence and the cavity. Evidence suggests that horns are
likely caused by condensing prominence plasma, but the larger question of
whether this process produces a density-depleted cavity requires a more tightly
constrained model of heating and better knowledge of the associated magnetic
structure.


title:
Spin relaxation in inhomogeneous quantum dot arrays studied by electron
  spin resonance

abstract:
  Electron states in a inhomogeneous Ge/Si quantum dot array with groups of
closely spaced quantum dots were studied by conventional continuous wave ($cw$)
ESR and spin-echo methods. We find that the existence of quantum dot groups
allows to increase the spin relaxation time in the system. Created structures
allow us to change an effective localization radius of electrons by external
magnetic field. With the localization radius close to the size of a quantum dot
group, we obtain fourfold increasing spin relaxation time $T_1$, as compared to
conventional homogeneous quantum dot arrays. This effect is attributed to
averaging of local magnetic fields related to nuclear spins $^{29}$Si and
stabilization of $S_z$-polarization during electron back-and-forth motion
within a quantum dot group.


title: The Formation of a Cavity in a 3D Flux Rope

abstract:
  There are currently no three dimensional numerical models which describe the
magnetic and energetic formation of prominences self-consistently.
Consequently, there has not been significant progress made in understanding the
connection between the dense prominence plasma and the coronal cavity. We have
taken an ad-hoc approach to understanding the energetic implications of the
magnetic models of prominence structure. We extract one dimensional magnetic
field lines from a 3D MHD model of a flux rope and solve for hydrostatic
balance along these field lines incorporating field-aligned thermal conduction,
uniform heating, and radiative losses. The 1D hydrostatic solutions for density
and temperature are then mapped back into three dimensional space, which allows
us to consider the projection of multiple structures. We find that the 3D flux
rope is composed of several distinct field line types. A majority of the flux
rope interior field lines are twisted but not dipped. These field lines are
density-reduced relative to unsheared arcade field lines. We suggest the cavity
may form along these short interior field lines which are surrounded by a
sheath of dipped field lines. This geometric arrangement would create a cavity
on top of a prominence, but the two structures would not share field lines or
plasma


title: On approximation schemes and compactness

abstract:
  We present an overview of some results about characterization of compactness
in which the concept of approximation scheme has had a role. In particular, we
present several results that were proved by the second author, jointly with
Luther, a decade ago, when these authors were working on a very general theory
of approximation spaces. We then introduce and show the basic properties of a
new concept of compactness, which was studied by the first author in the
eighties, by using a generalized concept of approximation scheme and its
associated Kolmogorov numbers, which generalizes the classical concept of
compactness.


title:
Spectrum of the Laplacian in narrow tubular neighbourhoods of
  hypersurfaces with combined Dirichlet and Neumann boundary conditions

abstract:
  We consider the Laplacian in a domain squeezed between two parallel
hypersurfaces in Euclidean spaces of any dimension, subject to Dirichlet
boundary conditions on one of the hypersurfaces and Neumann boundary conditions
on the other. We derive two-term asymptotics for eigenvalues in the limit when
the distance between the hypersurfaces tends to zero. The asymptotics are
uniform and local in the sense that the coefficients depend only on the
extremal points where the ratio of the area of the Neumann boundary to the
Dirichlet one is locally the biggest.


title: Signal transmission in a Y-shaped one-way chain

abstract:
  It has been found that noise plays a key role to improve signal transmission
in a one-way chain of bistable systems [Zhang et al., Phys. Rev. E 58, 2952
(1998)]. We here show that the signal transmission can be sharply improved
without the aid of noise, if the one-way chain with a single source node is
changed with two source nodes becoming a Y-shaped one-way chain. We further
reveal that the enhanced signal transmission in the Y-shaped one-way chain is
regulated by coupling strength, and that it is robust to noise perturbation and
input signal irregularity. We finally analyze the mechanism of the enhanced
signal transmission by the Y-shaped structure.


title: The parallel TASEP, fixed particle number and weighted Motzkin paths

abstract:
  In this paper the totally asymmetric exclusion process (TASEP) with parallel
update on an open lattice of size $L$ is considered in the maximum-current
region. A formal expression for the generating function for the weight of
configurations with $N$ particles is given. Further an interpretation in terms
of $(u,l,d)$-colored weighted Motzkin paths is presented. Using previous
results (Woelki and Schreckenberg 2009 {\it J. Stat. Mech} P05014, Woelki 2010
{\it Cellular Automata}, pp 637-645) the generating function is compared with
the one for a possible 2nd-class particle dynamics for the parallel TASEP. It
is shown that both become physically equivalent in the thermodynamic limit.


title: The BinaMIcS project: binarity and magnetism

abstract:
  We present the BinaMIcS project, its goals and the first BinaMIcS
spectropolarimetric observations obtained with Narval at TBL and ESPaDOnS at
CFHT: dedicated time-series for targeted hot and cool close double-line
spectroscopic (SB2) binaries and a survey of hot close SB2 binaries. The very
first results are also presented. In particular, our first survey observations
seem to show a lack of magnetic fields in hot close binaries compared to single
stars.


title: The Graviton Propagator with a Non-Conserved External Generating Source

abstract:
  A novel general expression is obtained for the graviton propagator from
Lagrangian field theory by taking into account the necessary fact that in the
functional differential approach of quantum field theory, in order to generate
non-linearities in gravitation and interactions with matter, the external
source $T_{\mu\nu}$, coupled to the gravitational field, should \textit{a
priori} not be conserved $\partial^\mu T_{\mu\nu}\neq 0$, so variations with
respect to its ten components may be varied \textit{independently}. The
resulting propagator is the one which arises in the functional approach and
does \textit{not} coincide with the corresponding time-ordered product of two
fields and it includes so-called Schwinger terms. The quantization is carried
out in a gauge corresponding to physical states with two polarization states to
ensure positivity in quantum applications.


title: Scalar Flat K\"ahler Metrics on Affine Bundles over $\mathbb{CP}^1$

abstract:
  We show that the total space of any affine $\mathbb{C}$-bundle over
$\mathbb{CP}^1$ with negative degree admits an ALE scalar-flat K\"ahler metric.
Here the degree of an affine bundle means the negative of the self-intersection
number of the section at infinity in a natural compactification of the bundle,
and so for line bundles it agrees with the usual notion of the degree.


title:
Gravitons, induced geometry and expectation value formalism at finite
  temperature

abstract:
  After establishing the positivity constraint and spin content of the theory
for gravitons interacting with a necessarily, and \textit{a priori},
\textit{non}-conserved external energy-momentum tensor, the expectation value
formalism of the theory is developed at \textit{finite} temperature in the
functional \textit{differential} treatment of quantum field theory. The
necessity of having, \textit{a priori}, a non-conserved external
energy-momentum tensor is an obvious technical requirement so that its
respective ten components may be varied \textit{independently} in order to
generate expectation values and non-linearities in the theory. The covariance
of the \textit{induced} Riemann curvature tensor, in the initial vacuum, is
established even for the quantization in a gauge corresponding only to two
physical states of the gravitons as established above. As an application, the
\textit{induced} correction to the metric and the underlying geometry is
investigated due to a closed string arising from the Nambu action as a solution
of a circularly oscillating string as, perhaps, the simplest generalization of
a limiting point-like object. Finally it is discussed on why the geometry of
spacetime may, in general, depend on temperature due to radiative corrections
and its physical significance is emphasized.


title:
Electron transport across a metal/MoS$_2$ interface: dependence on
  contact area and binding distance

abstract:
  We investigate the nature of electron transport through monolayer molybdenum
dichalcogenides (MoX$_2$, X=S, Se) suspended between Au and Ti metallic
contacts. The monolayer is placed ontop of the close-packed surfaces of the
metal electrodes and we focus on the role of the metal-MoX$_2$ binding distance
and the contact area. Based on \emph{ab initio} transport calculations we
identify two different scattering mechanisms which depend differently on the
metal-MoX$_2$ binding distance: (i) An interface resistance between the metal
and the supported part of MoX$_2$ which decreases with decreasing binding
distance and increasing contact area. (ii) An edge resistance across the 1D
interface between metal-supported and free-standing MoX$_2$ which increases
with decreasing binding distance and is independent on contact area. The origin
of the edge resistance is a metal-induced potential shift within the MoX$_2$
layer. The optimal metal thus depends on the junction geometry. In the case of
MoS$_2$, we find that for short contacts, L$<$6 nm, Ti electrodes (with short
binding distance) gives the lowest resistance, while for longer contacts, Au
(large binding distance) is a better electrode metal.


title: Two-particle correlations in pp and Pb-Pb collisions with ALICE

abstract:
  The measurement of azimuthal correlations between two particles is a powerful
tool to investigate the properties of strongly-interacting nuclear matter
created in ultra-relativistic heavy-ion collisions. We present measurements of
di-hadron correlations in azimuth angle and pseudorapidity in Pb-Pb collisions
at $\sqrt{s_{\rm NN}} = 2.76 \tev$ and photon-hadron correlations in pp
collisions at $\sqrt{s} = 7 \tev$ with the ALICE detector, respectively. In
di-hadron correlations, the near-side jet shape in the short-range correlation
region is quantitatively analyzed at $\ptt < 8 \gmom$, and the modification of
jet-particle yield, $I_{\rm AA}$ and $I_{\rm CP}$, is measured at $8 < \ptt <
15 \gmom$. In photon-hadron correlations, isolated leading photon and
associated hadrons in its opposite azimuthal direction correlations are used to
estimate the jet fragmentation function via the imbalance parameter, $x_{\rm E}
\equiv -\frac{\vec{p}_{\rm T}^{\gamma}\cdot\vec{p}_{\rm T}^{\rm
h^{\pm}}}{|\vec{p}_{\rm T}^{\gamma}|^{2}}$.


title: Mass anomalous dimension from large N twisted volume reduction

abstract:
  In this work we consider the SU(N) gauge theory with two Dirac fermions in
the adjoint representation, in the limit of large N. Taking advantage of large
N twisted volume reduction we do this on a single site lattice, but we should
still get infinite-volume physics in the large N limit. We describe our
progress in extracting the mass anomalous dimension from the eigenvalue
distribution of the adjoint Dirac operator, using data for N up to 289.


title: NLO mass effects in b anti-b b anti-b production at the LHC

abstract:
  The calculation of NLO QCD corrections to the production cross section of two
bottom pairs at the LHC is briefly summarized. We describe the pp -> b anti-b b
anti-b+X process both in the 4-flavor and 5-flavor scheme and investigate the
effect of the finite bottom quark mass. The results for the total cross section
and a few differential distributions are presented. They have been obtained
with the Nagy-Soper subtraction formalism for real radiation at NLO. A
comparison with results based on the traditional Catani-Seymour subtraction is
also included.


title: Nonlinear quantum dynamics in a PT-symmetric double well

abstract:
  We investigate the mean-field dynamics of a Bose-Einstein condensate (BEC)
described by the Gross-Pitaevskii equation (GPE) in a double-well potential
with particle gain and loss, rendering the system PT-symmetric. The stationary
solutions of the system show a change from elliptically stable behavior to
hyperbolically unstable behavior caused by the appearance of PT-broken
solutions of the GPE and influenced by the nonlinear interaction. The dynamical
behavior is visualized using the Bloch sphere formalism. However, the dynamics
is not restricted to the surface of the sphere due to the nonlinear and
non-Hermitian nature of the system.


title: Tracking individual nanodiamonds in Drosophila melanogaster embryos

abstract:
  Tracking the dynamics of fluorescent nanoparticles during embryonic
development allows insights into the physical state of the embryo and,
potentially, molecular processes governing developmental mechanisms. In this
work, we investigate the motion of individual fluorescent nanodiamonds
micro-injected into Drosophila melanogaster embryos prior to cellularisation.
Fluorescence correlation spectroscopy and wide-field imaging techniques are
applied to individual fluorescent nanodiamonds in blastoderm cells during stage
5 of development to a depth of ~40 \mu m. The majority of nanodiamonds in the
blastoderm cells during cellularisation exhibit free diffusion with an average
diffusion coefficient of (6 $\pm$ 3) x 10$^{-3}$ \mu m$^2$/s, (mean $\pm$ SD).
Driven motion in the blastoderm cells was also observed with an average
velocity of 0.13 $\pm$ 0.10 \mu m/s (mean $\pm$ SD) \mu m/s and an average
applied force of 0.07 $\pm$ 0.05 pN (mean $\pm$ SD). Nanodiamonds in the
periplasm between the nuclei and yolk were also found to undergo free diffusion
with a significantly larger diffusion coefficient of (63 $\pm$ 35) x10$^{-3}$
\mu m$^2$/s (mean $\pm$ SD). Driven motion in this region exhibited similar
average velocities and applied forces compared to the blastoderm cells
indicating the transport dynamics in the two cytoplasmic regions are analogous.


title: Color Magnetism in Non-Abelian Vortex Matter

abstract:
  We propose color magnetism as a generalization of the ordinary Heisenberg
(anti-)ferro magnets on a triangular lattice. Vortex matter consisting of an
Abrikosov lattice of non-Abelian vortices with color magnetic fluxes shows a
color ferro or anti-ferro magnetism, depending on the interaction among the
vortex sites. A prime example is a non-Abelian vortex lattice in rotating dense
quark matter, showing a color ferromagnetism. We show that the low-energy
effective theory for the vortex lattice system in the color ferromagnetic phase
is described by a 3+1 dimensional $CP^{N-1}$ nonlinear sigma model with
spatially anisotropic couplings. We identify gapless excitations independent
from Tkachenko modes as color magnons, that is, Nambu-Goldstone modes
propagating in the vortex lattice with an anisotropic linear dispersion
relation $\omega_p^2 = c_{xy}^2(p_x^2+p_y^2) + c_z^2 p_z^2$. We calculate the
transition temperature between the ordered and disordered phases, and apply it
to dense quark matter. We also identify the order parameter spaces for color
anti-ferromagnets.


title: Look-Ahead Removal for Top-Down Tree Transducers

abstract:
  Top-down tree transducers are a convenient formalism for describing tree
transformations. They can be equipped with regular look-ahead, which allows
them to inspect a subtree before processing it. In certain cases, such a
look-ahead can be avoided and the transformation can be realized by a
transducer without look-ahead. Removing the look-ahead from a transducer, if
possible, is technically highly challenging. For a restricted class of
transducers with look-ahead, namely those that are total, deterministic,
ultralinear, and bounded erasing, we present an algorithm that, for a given
transducer from that class, (1) decides whether it is equivalent to a total
deterministic transducer without look-ahead, and (2) constructs such a
transducer if the answer is positive. For the whole class of total
deterministic transducers with look-ahead we present a similar algorithm, which
assumes that a so-called difference bound is known for the given transducer.
The designer of a transducer can usually also determine a difference bound for
it.


title:
Meson loop singularity, exotic states' productions and decays near
  threshold

abstract:
  We investigate in detail the "triangle singularity" regions of meson loops
where the corresponding intermediate mesons are nearly-on-shell and have
relatively small momenta, and the two heavy mesons strongly interact with each
other in an $S$ wave. This $S$-wave interaction will make such kind of meson
loops always enhanced and can explain experimental observations of threshold
enhancements. We show that the production of the $Y(4260)$ and the recently
observed $Z_c(3900)$ can be related to each other by this mechanism which will
allow for a possible understanding of the nature of these threshold
enhancements.


title: Floquet Theory of Electron Waiting Times in Quantum-Coherent Conductors

abstract:
  We present a Floquet scattering theory of electron waiting time distributions
in periodically driven quantum conductors. We employ a second-quantized
formulation that allows us to relate the waiting time distribution to the
Floquet scattering matrix of the system. As an application we evaluate the
electron waiting times for a quantum point contact, modulating either the
applied voltage (external driving) or the transmission probability (internal
driving) periodically in time. Lorentzian-shaped voltage pulses are of
particular interest as they lead to the emission of clean single-particle
excitations as recently demonstrated experimentally. The distributions of
waiting times provide us with a detailed characterization of the dynamical
properties of the quantum-coherent conductor in addition to what can be
obtained from the shot noise or the full counting statistics.


title:
Topological energy bounds for the Skyrme and Faddeev models with massive
  pions

abstract:
  A topological lower bound on the Skyrme energy which depends explicity on the
pion mass is derived. This bound coincides with the previously best known bound
when the pion mass vanishes, and improves on it whenever the pion mass is
non-zero. The new bound can in particular circumstances be saturated. New
energy bounds are also derived for the Skyrme model on a compact manifold, for
the Faddeev-Skyrme model with a potential term, and for the
Aratyn-Ferreira-Zimerman and Nicole models.


title:
Sailfish: a flexible multi-GPU implementation of the lattice Boltzmann
  method

abstract:
  We present Sailfish, an open source fluid simulation package implementing the
lattice Boltzmann method (LBM) on modern Graphics Processing Units (GPUs) using
CUDA/OpenCL. We take a novel approach to GPU code implementation and use
run-time code generation techniques and a high level programming language
(Python) to achieve state of the art performance, while allowing easy
experimentation with different LBM models and tuning for various types of
hardware. We discuss the general design principles of the code, scaling to
multiple GPUs in a distributed environment, as well as the GPU implementation
and optimization of many different LBM models, both single component (BGK, MRT,
ELBM) and multicomponent (Shan-Chen, free energy). The paper also presents
results of performance benchmarks spanning the last three NVIDIA GPU
generations (Tesla, Fermi, Kepler), which we hope will be useful for
researchers working with this type of hardware and similar codes.


title: Semistable Higgs bundles of small ranks are strongly Higgs semistable

abstract:
  We give a proof of the conjecture that a semistable Higgs bundle is strongly
Higgs semistable in the case of small ranks, based upon the fact that there
exists a gr-semistable Griffiths-transverse filtration on a $\nabla$-invariant
semistable vector bundle. The latter is a generalization of a result of Carlos
Simpson.


title: Simple identification of fake Lax pairs

abstract:
  Two simple ways to identify and explain fake Lax pairs are provided. The two
methods are complementary, one involves finding a gauge transformation which
can be used to remove the associated nonlinear system's dependent variable(s)
from a fake Lax pair. The second method shows that excess degrees of freedom
exist in fake Lax pairs. We provide several examples to illustrate both tests.
The tests proposed here can be applied to all types of Lax pairs, including
scalar or matrix linear problems associated with ordinary or partial difference
and/or differential systems.


title:
Magnetic Moments of Negative Parity Baryons from Effective Hamiltonian
  Approach to QCD

abstract:
  Magnetic moments of $S_{11}(1535)$ and $S_{11}(1650)$ baryons are studied in
the framework of the relativistic three-quark Hamiltonian derived in the Field
Correlation Method. The baryon magnetic moments are expressed via the average
current quark energies which are defined by the fundamental QCD parameters: the
string tension $\sigma$, the quark masses, and the strong coupling constant
$\alpha_s$. For the $J^P=1/2^+$ baryon octet the approach was shown to give a
good first approximation to the experimental moments. Resulting magnetic
moments for the $J^P=1/2^-$ nucleons are compared both to model calculations
and to those from lattice QCD.


title:
A Notable Relation between $N$-Qubit and $2^{N-1}$-Qubit Pauli Groups
  via Binary ${\rm LGr}(N,2N)$

abstract:
  Employing the fact that the geometry of the $N$-qubit ($N \geq 2$) Pauli
group is embodied in the structure of the symplectic polar space
$\mathcal{W}(2N-1,2)$ and using properties of the Lagrangian Grassmannian ${\rm
LGr}(N,2N)$ defined over the smallest Galois field, it is demonstrated that
there exists a bijection between the set of maximum sets of mutually commuting
elements of the $N$-qubit Pauli group and a certain subset of elements of the
$2^{N-1}$-qubit Pauli group. In order to reveal finer traits of this
correspondence, the cases $N=3$ (also addressed recently by L\'evay, Planat and
Saniga [J. High Energy Phys. 2013 (2013), no. 9, 037, 35 pages,
arXiv:1305.5689]) and $N=4$ are discussed in detail. As an apt application of
our findings, we use the stratification of the ambient projective space ${\rm
PG}(2^N-1,2)$ of the $2^{N-1}$-qubit Pauli group in terms of $G$-orbits, where
$G \equiv {\rm SL}(2,2)\times {\rm SL}(2,2)\times\cdots\times {\rm
SL}(2,2)\rtimes S_N$, to decompose $\underline{\pi}({\rm LGr}(N,2N))$ into
non-equivalent orbits. This leads to a partition of ${\rm LGr}(N,2N)$ into
distinguished classes that can be labeled by elements of the above-mentioned
Pauli groups.


title:
Application of a Hough search for continuous gravitational waves on data
  from the 5th LIGO science run

abstract:
  We report on an all-sky search for periodic gravitational waves in the
frequency range $\mathrm{50-1000 Hz}$ with the first derivative of frequency in
the range $-8.9 \times 10^{-10}$ Hz/s to zero in two years of data collected
during LIGO's fifth science run. Our results employ a Hough transform
technique, introducing a $\chi^2$ test and analysis of coincidences between the
signal levels in years 1 and 2 of observations that offers a significant
improvement in the product of strain sensitivity with compute cycles per data
sample compared to previously published searches. Since our search yields no
surviving candidates, we present results taking the form of frequency
dependent, 95$%$ confidence upper limits on the strain amplitude $h_0$. The
most stringent upper limit from year 1 is $1.0\times 10^{-24}$ in the
$\mathrm{158.00-158.25 Hz}$ band. In year 2, the most stringent upper limit is
$\mathrm{8.9\times10^{-25}}$ in the $\mathrm{146.50-146.75 Hz}$ band. This
improved detection pipeline, which is computationally efficient by at least two
orders of magnitude better than our flagship Einstein$@$Home search, will be
important for "quick-look" searches in the Advanced LIGO and Virgo detector
era.


title: Ferromagnetic two-dimensional crystals: Single layers of K2CuF4

abstract:
  The successful isolation of graphene ten years ago has evoked a rapidly
growing scientific interest in the nature of two-dimensional (2D) crystals. A
number of different 2D crystals has been produced since then, with properties
ranging from superconductivity to insulating behavior. Here, we predict the
possibility for realizing ferromagnetic 2D crystals by exfoliating atomically
thin films of K2CuF4. From a first-principles theoretical analysis, we find
that single layers of K2CuF4 form exactly 2D Kosterlitz-Thouless systems. The
2D crystal can form a free-standing membrane, and exhibits an experimentally
accessible transition temperature and robust magnetic moments of 1 Bohr
magneton per formula unit. 2D K2CuF4 unites ferromagnetic and insulating
properties and is a demonstration of principles for nanoelectronics such as
novel 2D-based heterostructures.


title: Be star outbursts: transport of angular momentum by waves

abstract:
  The Be phenomenon, that is the ejection of matter from Be stars into a
circumstellar disk, has been a long lasting mystery. In the last few years, the
CoRoT (Convection, Rotation and planetary Transits) satellite brought clear
evidence that Be outbursts are directly correlated with pulsations. We found
that it may be the transport of angular momentum by waves or pulsation modes
that brings the already rapid stellar rotation to its critical value at the
surface, and allows the star to eject material. The recent discovery of
stochastically excited gravito-inertial modes by CoRoT in a hot Be star
strengthens this scenario. We present the CoRoT observations and modeling of
several Be stars and describe the new picture of the Be phenomenon which arose
from these results.


title: PLOS/Mozilla Scientific Code Review Pilot: Summary of Findings

abstract:
  PLOS and Mozilla conducted a month-long pilot study in which professional
developers performed code reviews on software associated with papers published
in PLOS Computational Biology. While the developers felt the reviews were
limited by (a) lack of familiarity with the domain and (b) lack of two-way
contact with authors, the scientists appreciated the reviews, and both sides
were enthusiastic about repeating the experiment.


title:
Model of the Electronic Structure of Electron-Doped Iron-Based
  Superconductors: Evidence for Enhanced Spin Fluctuations by Diagonal Electron
  Hopping

abstract:
  We present a theoretical understanding of the superconducting phase diagram
of the electron-doped iron pnictides. We show that, besides the Fermi surface
nesting, a peculiar motion of electrons, where the next nearest neighbor
(diagonal) hoppings between iron sites dominate over the nearest neighbor ones,
plays an important role in the enhancement of the spin fluctuation and thus
superconductivity. In the highest $T_c$ materials, the crossover between the
Fermi surface nesting and this "prioritized diagonal motion" regime occurs
smoothly with doping, while in relatively low $T_c$ materials, the two regimes
are separated and therefore results in a double dome $T_c$ phase diagram.


title:
Stability of plane wave solutions in complex Ginzburg-Landau equation
  with delayed feedback

abstract:
  We perform bifurcation analysis of plane wave solutions in one-dimensional
cubic-quintic Ginzburg-Landau equation with delayed feedback. Our study reveals
how multistability and snaking behavior of plane waves emerge as time delay is
introduced. For intermediate values of the delay, bifurcation diagrams are
obtained by a combination of analytical and numerical methods. For large
delays, using an asymptotic approach we classify plane wave solutions into
strongly unstable, weakly unstable, and stable. The results of analytical
bifurcation analysis are in agreement with those obtained by direct numerical
integration of the model equation.


title: Exact representation of truncated variation of Brownian motion

abstract:
  In the recent papers [Lochowski:2011fk, Lochowski:2013yq, Lochowski:2013lr]
the truncated variation has been introduced, characterized and studied in
various stochastic settings. In this note we uncover an intimate link to the
Skorokhod problem. Further, we exploit it to give an explicit representation of
the truncated variation of a Brownian motion. More precisely, we prove that the
inverse of this process is, up to a minor time shift, a L\'evy subordinator
with the exponent \sqrt{2q}\tanh(c\sqrt{q/2}) . This also gives a
representation of a solution of the two-sided Skorokhod problem for a Brownian
motion.


title: The effect of $SU(4)$ group factor in the thick center vortex potentials

abstract:
  The group factor for the higher representations of the $SU(4)$ gauge group is
investigated. For the zero N-ality representations, the minimum values of the
real part of the group factor which appear at large distances, are located at
the points where $50%$ of the maximum vortex flux is in the Wilson loop. This
amount is equal to $60%$ for the representations which belong to N-ality=$1$
class except the fundamental representation. The value of the real part of the
group factor at the minimum points is equal to the value of center of the group
factor at intermediate distances. The appearance of these points is due to the
difference between the asymptotic and intermediate string tensions. The group
factor passes the phase factor to create the larger intermediate string tension
than the asymptotic one.


title:
Orbital and physical properties of planets and their hosts: new insights
  on planet formation and evolution

abstract:
  We explore the relations between physical and orbital properties of planets
and properties of their host stars to identify the main observable signatures
of the formation and evolution processes of planetary systems. We use a large
sample of FGK dwarf planet hosts with stellar parameters derived in a
homogeneous way from the SWEET-Cat database to study the relation between
stellar metallicity and position of planets in the period-mass diagram. In the
second part we use all the RV-detected planets orbiting FGK stars to explore
the role of planet-disk and planet-planet interaction on the evolution of
orbital properties of planets with masses above 1MJup. We show that planets
orbiting metal-poor stars have longer periods than those in metal-rich systems.
This trend is valid for masses at least from 10MEarth to 4MJup. Earth-like
planets orbiting metal-rich stars always show shorter periods (fewer than 20
days) than those orbiting metal-poor stars. We also found statistically
significant evidence that very high mass giants have on average more eccentric
orbits than giant planets with lower mass.Finally, we show that the
eccentricity of planets with masses higher than 4MJup tends to be lower for
planets with shorter periods. Our results suggest that the planets in the P-MP
diagram are evolving differently because of a mechanism that operates over a
wide range of planetary masses. This mechanism is stronger or weaker depending
on the metallicity of the respective system. One possibility is that planets in
metal-poor disks form farther out from their central star and/or they form
later and do not have time to migrate as far as the planets in metal-rich
systems. The trends and dependencies obtained for very high mass planetary
systems suggest that planet-disk interaction is a very important and
orbit-shaping mechanism for planets in the high-mass domain. Shortened.


title: Spectra of sub-Dirac operators on certain nilmanifolds

abstract:
  We study sub-Dirac operators that are associated with left-invariant
bracket-generating sub-Riemannian structures on compact quotients of nilpotent
semi-direct products $G=\mathbb{R}^n\rtimes_A\mathbb{R}$. We will prove that
these operators admit an $L^2$-basis of eigenfunctions. Explicit examples show
that the spectrum of these operators can be non-discrete and that eigenvalues
may have infinite multiplicity.


title: Unfolding of the Spectrum for Chaotic and Mixed Systems

abstract:
  Random Matrix Theory (RMT) is capable of making predictions for the spectral
fluctuations of a physical system only after removing the influence of the
level density by unfolding the spectra. When the level density is known,
unfolding is done by using the integrated level density to transform the
eigenvalues into dimensionless variables with unit mean spacing. When it is not
known, as in most practical cases, one usually approximates the level staircase
function by a polynomial. We here study the effect of unfolding procedure on
the spectral fluctuation of two systems for which the level density is known
asymptotically. The first is a time-reversal-invariant chaotic system, which is
modeled in RMT by a Gaussian Orthogonal Ensemble (GOE). The second is the case
of chaotic systems in which m quantum numbers remain almost undistorted in the
early stage of the stochastic transition. The Hamiltonian of a system may be
represented by a block diagonal matrix with m blocks of the same size, in which
each block is a GOE. Unfolding is done once by using the asymptotic level
densities for the eigenvalues of the m blocks and once by representing the
integrated level density in terms of polynomials of different orders. We find
that the spacing distribution of the eigenvalues shows a little sensitivity to
the unfolding method. On the other hand, the variance of level number
{\Sigma}2(L)is sensitive to the choice of the unfolding function. Unfolding
that utilizes low order polynomials enhances {\Sigma}2(L) relative to the
theoretical value, while the use of high order polynomial reduces it. The
optimal value of the order of the unfolding polynomial depends on the dimension
of the corresponding ensemble.


title:
Monte-Carlo simulation of graphene in terms of occupation numbers for
  the excitonic order parameter at hexagonal lattice

abstract:
  We present the results of the Monte-Carlo simulation of graphene-like
statistical model in terms of occupation numbers. We study the problem of the
phase transition in graphene to an insulating phase. Only antiferromagnetic
order parameter was studied at the moment by means of Hybrid Monte-Carlo
process on the hexagonal lattice because of the sign problem for excitonic
order parameter in fermionic determinant. Therefore we have studied the
possibility of the phase transition to an excitonic phase by means of
simplified Monte-Carlo process on the hexagonal lattice. We show that this
phase, which corresponds to a charge polarization of graphene sublattices, can
appear at some values of Coulomb electron-electron potentials. In this work we
study the dependence of the phase transition characteristics on the strength of
on-site electron-electron interaction. We show that excitonic phase transition
is also impossible in suspended graphene.


title:
Average and recommended half-life values for two neutrino double beta
  decay: upgrade-2013

abstract:
  All existing positive results on two neutrino double beta decay in different
nuclei were analyzed. Using the procedure recommended by the Particle Data
Group, weighted average values for half-lives of $^{48}$Ca, $^{76}$Ge,
$^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{100}$Mo - $^{100}$Ru ($0^+_1$),
$^{116}$Cd, $^{130}$Te, $^{136}$Xe, $^{150}$Nd, $^{150}$Nd - $^{150}$Sm
($0^+_1$) and $^{238}$U were obtained. Existing geochemical data were analyzed
and recommended values for half-lives of $^{128}$Te and $^{130}$Ba are
proposed. I recommend the use of these results as the most currently reliable
values for half-lives.


title:
Clustering Categorical Time Series into Unknown Number of Clusters: A
  Perfect Simulation based Approach

abstract:
  Pamminger and Fruwirth-Schnatter (2010) considered a Bayesian approach to
model-based clustering of categorical time series assuming a fixed number of
clusters. But the popular methods for selecting the number of clusters, for
example, the Bayes Information Criterion (BIC), turned out to have severe
problems in the categorical time series context.
  In this paper, we circumvent the difficulties of choosing the number of
clusters by adopting the Bayesian semiparametric mixture model approach
introduced by Bhattacharya (2008), who assume that the number of clusters is a
random quantity, but is bounded above by a (possibly large) number of clusters.
We adopt the perfect simulation approach of Mukhopadhyay and Bhattacharya
(2012) for posterior simulation for completely solving the problems of
convergence of the underlying Markov chain Monte Carlo (MCMC) approach.
Importantly, within our main perfect simulation algorithm, there arose the
necessity to simulate perfectly from the joint distribution of a set of
continuous random variables with log-concave full conditional densities. We
propose and develop a novel and efficient perfect simulation methodology for
joint distributions with log-concave full conditionals. This perfect sampling
methodology is of independent interest as well since in a very large and
important class of Bayesian applications the full conditionals turn out to be
log-concave.
  We will consider application of our model and methodology to the Austrian
wage mobility data, also analysed by Pamminger and Fruwirth-Schnatter (2010),
and adopting the methods developed in Mukhopadhyay et al. (2011), Mukhopadhyay
et al. (2012), will obtain the posterior modes of clusterings and also the
desired highest posterior distribution credible regions of the posterior
distribution of clusterings.


title:
Application of CellDesigner to the Selection of Anticancer Drug Targets:
  Test Case using P53

abstract:
  Cancer is a disease involving many genes, consequently it has been difficult
to design anticancer drugs that are efficacious over a broad range of cancers.
The robustness of cellular responses to gene knockout and the need to reduce
undesirable side effects also contribute to the problem of effective
anti-cancer drug design. To promote the successful selection of drug targets,
each potential target should be subjected to a systems biology scrutiny to
locate effective and specific targets while minimizing undesirable side
effects. The gene p53 is considered a good candidate for such a target because
it has been implicated in 50% of all cancers and is considered to encode a hub
protein that is highly connected to other proteins. Using P53 as a test case,
this paper explores the capacity of the systems biology tool, CellDesigner, to
aid in the selection of anticancer drug targets and to serve as a teaching
resource for human resource development.


title: On singularities in B-orbit closures of 2-nilpotent matrices

abstract:
  This paper deals with singularities of closures of $2$-nilpotent Borel
conjugacy classes in either a $\text{GL}_n$-conjugacy class or in the nilpotent
cone of $\text{GL}_n$. In the latter case we construct a resolution of
singularities, in the former we show that singularities are rational by
applying a result of M. Brion. We reason why this generalizes the result of N.
Perrin and E. Smirnov on the rationality of singularities of Springer fiber
components in the two-column case. In the case of Borel orbit closures being
contained in orbital varieties, we give an alternative version of L. Fresse's
recent singularity criterion.


title:
An Analytical Study on Fractional Fokker-Planck Equation by Homotopy
  Analysis Transform Method

abstract:
  In this article we introduce an analytical method, namely Homotopy Analysis
Transform Method (HATM) which is a combination of Homotopy Analysis Method
(HAM) and Laplace Decomposition Method (LDM).This scheme is simple to apply
linear and nonlinear fractional differential equations and having less
computational work in comparison of other exiting methods.The most useful
advantage of this method is to solve the fractional nonlinear differential
equation without using Adomian polynomials and He polynomials for the
computation of nonlinear terms.The proposed method has no linearization and
restrictive assumptions throughout the process.Presently homotopy analysis
transform method is used to solve time fractional Fokker-Planck equation and
similar equations.The series solution obtained by HATM converges very fast.A
good agreement between the obtained solution and some well-known results has
been demonstrated


title:
Micro-CernVM: Slashing the Cost of Building and Deploying Virtual
  Machines

abstract:
  The traditional virtual machine building and and deployment process is
centered around the virtual machine hard disk image. The packages comprising
the VM operating system are carefully selected, hard disk images are built for
a variety of different hypervisors, and images have to be distributed and
decompressed in order to instantiate a virtual machine. Within the HEP
community, the CernVM File System has been established in order to decouple the
distribution from the experiment software from the building and distribution of
the VM hard disk images.
  We show how to get rid of such pre-built hard disk images altogether. Due to
the high requirements on POSIX compliance imposed by HEP application software,
CernVM-FS can also be used to host and boot a Linux operating system. This
allows the use of a tiny bootable CD image that comprises only a Linux kernel
while the rest of the operating system is provided on demand by CernVM-FS. This
approach speeds up the initial instantiation time and reduces virtual machine
image sizes by an order of magnitude. Furthermore, security updates can be
distributed instantaneously through CernVM-FS. By leveraging the fact that
CernVM-FS is a versioning file system, a historic analysis environment can be
easily re-spawned by selecting the corresponding CernVM-FS file system
snapshot.


title: On permanents of Sylvester Hadamard matrices

abstract:
  It is well-known that the evaluation of the permanent of an arbitrary
$(-1,1)$-matrix is a formidable problem. Ryser's formula is one of the fastest
known general algorithms for computing permanents. In this paper, Ryser's
formula has been rewritten for the special case of Sylvester Hadamard matrices
by using their cocyclic construction. The rewritten formula presents an
important reduction in the number of sets of $r$ distinct rows of the matrix to
be considered. However, the algorithm needs a preprocessing part which remains
time-consuming in general.


title: Disorder-Driven Spin-Reorientation in Multiferroic $h-YMn_{1-x}Fe_xO_3$

abstract:
  Magnetic structure evolution of multiferroic hexagonal $YMn_{1-x}Fe_{x}O_{3}$
(${x} = 0, 0.05,$ and $0.1$) has been studied by carrying out detailed
temperature-dependent neutron diffraction at zero- and 5T-fields. Thermodynamic
data confirm antiferromagnetic ordering at $T_{N}$ in all the compositions. Our
sub-$T_{N}$ neutron diffraction results assign the magnetic structure of pure
$YMnO_3$ to $\Gamma_{1}$ irreducible representation. Over the
perturbative-doping range, the magnetic configuration changes via
$\Gamma_{1}+\Gamma_{2}$ for $YMn_{0.95}Fe_{0.05}O_{3}$ on to $\Gamma_{2}$ for
$YMn_{0.9}Fe_{0.1}O_{3}$, as the maiden compositional analogue of
spin-reorientation; its occurrence in temperature-domain already reported for
several manganites. Moreover, while the large thermal isostructural changes
observed above ${T}_{N}$ are subdued in the ordered state, small alterations by
the applied 5T-field are relatively uniform across, confirming strong
magneto-elastic nature of the system. Decrease of the ordered magnetic moment
($\mu_{ord}$) and planar magnetic frustration noted with Fe-doping is enhanced
by the applied field, apparently through canting.


title:
High optical efficiency and photon noise limited sensitivity of
  microwave kinetic inductance detectors using phase readout

abstract:
  We demonstrate photon noise limited performance in both phase and amplitude
readout in microwave kinetic inductance detectors (MKIDs) consisting of NbTiN
and Al, down to 100 fW of optical power. We simulate the far field beam pattern
of the lens-antenna system used to couple radiation into the MKID and derive an
aperture efficiency of 75%. This is close to the theoretical maximum of 80% for
a single-moded detector. The beam patterns are verified by a detailed analysis
of the optical coupling within our measurement setup.


title:
The $\mathcal{N}=1$ Chiral Multiplet on $T^2\times S^2$ and
  Supersymmetric Localization

abstract:
  We compute the supersymmetric partition function of an $\mathcal{N}=1$ chiral
multiplet coupled to an external Abelian gauge field on complex manifolds with
$T^2 \times S^2$ topology. The result is locally holomorphic in the complex
structure moduli of $T^2\times S^2$. This computation illustrates in a simple
example some recently obtained constraints on the parameter dependence of
supersymmetric partition functions.
  We also devise a simple method to compute the chiral multiplet partition
function on any four-manifold $\mathcal{M}_4$ preserving two supercharges of
opposite chiralities, via supersymmetric localization. In the case of
$\mathcal{M}_4=S^3\times S^1$, we provide a path integral derivation of the
previously known result, the elliptic gamma function, which emphasizes its
dependence on the $S^3 \times S^1$ complex structure moduli.


title:
A Nitsche-based cut finite element method for a fluid--structure
  interaction problem

abstract:
  We present a new composite mesh finite element method for fluid--structure
interaction problems. The method is based on surrounding the structure by a
boundary-fitted fluid mesh which is embedded into a fixed background fluid
mesh. The embedding allows for an arbitrary overlap of the fluid meshes. The
coupling between the embedded and background fluid meshes is enforced using a
stabilized Nitsche formulation which allows us to establish stability and
optimal order \emph{a priori} error estimates,
see~\cite{MassingLarsonLoggEtAl2013}. We consider here a steady state
fluid--structure interaction problem where a hyperelastic structure interacts
with a viscous fluid modeled by the Stokes equations. We evaluate an iterative
solution procedure based on splitting and present three-dimensional numerical
examples.


title: Magnetic helicity and energy spectra of a solar active region

abstract:
  We compute for the first time magnetic helicity and energy spectra of the
solar active region NOAA 11158 during 11-15 February 2011 at 20^o southern
heliographic latitude using observational photospheric vector magnetograms. We
adopt the isotropic representation of the Fourier-transformed two-point
correlation tensor of the magnetic field. The sign of magnetic helicity turns
out to be predominantly positive at all wavenumbers. This sign is consistent
with what is theoretically expected for the southern hemisphere. The magnetic
helicity normalized to its theoretical maximum value, here referred to as
relative helicity, is around 4% and strongest at intermediate wavenumbers of k
~ 0.4 Mm^{-1}, corresponding to a scale of 2pi/k ~ 16 Mm. The same sign and a
similar value are also found for the relative current helicity evaluated in
real space based on the vertical components of magnetic field and current
density. The modulus of the magnetic helicity spectrum shows a k^{-11/3} power
law at large wavenumbers, which implies a k^{-5/3} spectrum for the modulus of
the current helicity. A k^{-5/3} spectrum is also obtained for the magnetic
energy. The energy spectra evaluated separately from the horizontal and
vertical fields agree for wavenumbers below 3 Mm^{-1}, corresponding to scales
above 2 Mm. This gives some justification to our assumption of isotropy and
places limits resulting from possible instrumental artefacts at small scales.


title:
Joint recovery algorithms using difference of innovations for
  distributed compressed sensing

abstract:
  Distributed compressed sensing is concerned with representing an ensemble of
jointly sparse signals using as few linear measurements as possible. Two novel
joint reconstruction algorithms for distributed compressed sensing are
presented in this paper. These algorithms are based on the idea of using one of
the signals as side information; this allows to exploit joint sparsity in a
more effective way with respect to existing schemes. They provide gains in
reconstruction quality, especially when the nodes acquire few measurements, so
that the system is able to operate with fewer measurements than is required by
other existing schemes. We show that the algorithms achieve better performance
with respect to the state-of-the-art.


title: Basic functions and unramified local L-factors for split groups

abstract:
  According to a program of Braverman, Kazhdan and Ng\^o Bao Ch\^au, for a
large class of split unramified reductive groups $G$ and representations $\rho$
of the dual group $\hat{G}$, the unramified local $L$-factor $L(s,\pi,\rho)$
can be expressed as the trace of $\pi(f_{\rho,s})$ for a suitable function
$f_{\rho,s}$ with non-compact support whenever $\mathrm{Re}(s) \gg 0$. Such
functions can be plugged into the trace formula to study certain sums of
automorphic $L$-functions. It also fits into the conjectural framework of
Schwartz spaces for reductive monoids due to Sakellaridis, who coined the term
basic functions; this is supposed to lead to a generalized
Tamagawa-Godement-Jacquet theory for $(G,\rho)$. In this article, we derive
some basic properties for the basic functions $f_{\rho,s}$ and interpret them
via invariant theory. In particular, their coefficients are interpreted as
certain generalized Kostka-Foulkes polynomials defined by Panyushev. These
coefficients can be encoded into a rational generating function.


title:
The first steps of adaptation of Escherichia coli to the gut are
  dominated by soft sweeps

abstract:
  The accumulation of adaptive mutations is essential for survival in novel
environments. However, in clonal populations with a high mutational supply, the
power of natural selection is expected to be limited. This is due to clonal
interference - the competition of clones carrying different beneficial
mutations - which leads to the loss of many small effect mutations and fixation
of large effect ones. If interference is abundant, then mechanisms for
horizontal transfer of genes, which allow the immediate combination of
beneficial alleles in a single background, are expected to evolve. However, the
relevance of interference in natural complex environments, such as the gut, is
poorly known. To address this issue, we studied the invasion of beneficial
mutations responsible for Escherichia coli's adaptation to the mouse gut and
demonstrate the pervasiveness of clonal interference. The observed dynamics of
change in frequency of beneficial mutations are consistent with soft sweeps,
where a similar adaptive mutation arises repeatedly on different haplotypes
without reaching fixation. The genetic basis of the adaptive mutations revealed
a striking parallelism in independently evolving populations. This was mainly
characterized by the insertion of transposable elements in both coding and
regulatory regions of a few genes. Interestingly in most populations, we
observed a complete phenotypic sweep without loss of genetic variation. The
intense clonal interference during adaptation to the gut environment, here
demonstrated, may be important for our understanding of the levels of strain
diversity of E. coli inhabiting the human gut microbiota and of its
recombination rate.


title: Equivariant spectral asymptotics for h-pseudodifferential operators

abstract:
  We prove equivariant spectral asymptotics for $ h$-pseudodifferential
operators for compact orthogonal group actions generalizing results of
El-Houakmi and Helffer (1991) and Cassanas (2006). Using recent results for
certain oscillatory integrals with singular critical sets (Ramacher 2010) we
can deduce a weak equivariant Weyl law. Furthermore, we can prove a complete
asymptotic expansion for the Gutzwiller trace formula without any additional
condition on the group action by a suitable generalization of the dynamical
assumptions on the Hamilton flow.


title: SPM Bulletin 36

abstract:
  In addition to a number of new developments in the field, this issue
announces the completion of the special issue of Topology and its Applications,
dedicated to the proceedings of the Fourth Workshop on Coverings, Selections
and Games in Topology, on the occasion of Ljubi\v{s}a D.R. Ko\v{c}inac's 65th
birthday.


title:
Interplay of fractional quantum Hall states and localization in quantum
  point contacts

abstract:
  We investigate integer and fractional quantum Hall states in quantum point
contacts (QPCs) of different geometries, defined in AlGaAs/GaAs
heterostructures employing different doping and screening techniques. We find
that, even in the highest mobility samples, interference and localization
strongly influence the transport properties. We propose microscopic models for
these effects, based on single- and many-electron physics. For integer quantum
Hall states, transport is modulated due to the self-consistent formation of
compressible regions of enhanced or reduced density in the incompressible
region of the constriction. In the fractional quantum Hall regime, we observe
the localization of fractionally charged quasi-particles in the constriction
and an interplay of single- and many-electron physics. At low electron
densities and in comparatively weak magnetic fields, single-electron
interference dominates transport. Utilizing optimized growth and gating
techniques, the $\nu$=5/2 state can be observed in a QPC, conserving the bulk
properties in an unprecedented quality. Our results might improve the
understanding of the influence of localization on the transmission properties
of QPCs, which is necessary for the interpretation of interference experiments
employing QPCs, especially at $\nu$=5/2.


title: Derivations and Alberti representations

abstract:
  We relate generalized Lebesgue decompositions of measures in terms of curve
fragments (Alberti representations) and Weaver derivations. This correspondence
leads to a geometric characterization of the local norm on the Weaver cotangent
bundle of a metric measure space $(X,\mu)$: the local norm of a form $df$ sees
how fast $f$ grows on curve fragments seen by $\mu$. This implies a new
characterization of differentiability spaces in terms of the
$\mu$-a.e.~equality of the local norm of $df$ and the local Lipschitz constant
of $f$. As a consequence, the Lip-lip inequality of Keith must be an equality.
We also provide dimensional bounds for the module of derivations in terms of
the Assouad dimension of $X$.


title:
Singlet and triplet bound state spectra in the four-electron Be-like
  atomic systems

abstract:
  A large number of bound singlet and triplet states in the four-electron
Be-atom and Be-like ions B$^+$, C$^{2+}$, F$^{5+}$ and Mg$^{8+}$ are determined
to milli-Hartree numerical accuracy ($1\cdot 10^{-3}$ a.u.). These states
include the bound singlet and triplet $S$-, $P$-, $D$-, $F$-, $G$-, $H$-, $I$-
and $K$-states. Based on computational results we analyze the singlet and
triplet series of the Be atom bound state spectrum and some four-electron ions:
B$^+$, C$^{2+}$, F$^{5+}$ and Mg$^{8+}$ (Be-like ions). The analogous study of
the Be atom triplet states was the topic of our earlier study (A.M. Frolov and
M.B. Ruiz, CPL 595-596, 197 (2014)). The computational data allowed us to draw
the spectral diagram of the bound state spectrum of the Be-atom and other
four-electron ions mentioned above. The Be-atom spectrum contains the two
optical series of bound states: singlets and triplets.


title: On the comparison between MASS and G-SCIDAR techniques

abstract:
  The Multi Aperture Scintillation Sensor (MASS) and the
Generalized-Scintillation Detection and Ranging (Generalized SCIDAR) are two
instruments conceived to measure the optical turbulence (OT) vertical
distribution on the whole troposphere and low stratosphere (~ 20 km) widely
used in the astronomical context. In this paper we perform a detailed
analysis/comparison of measurements provided by the two instruments and taken
during the extended site testing campaign carried out on 2007 at Cerro Paranal
and promoted by the European Southern Observatory (ESO). The main and final
goal of the study is to provide a detailed estimation of the measurements
reliability i.e dispersion of turbulence measurements done by the two
instruments at different heights above the ground. This information is directly
related to our ability in estimating the absolute value of the turbulence
stratification. To better analyse the uncertainties between the MASS and the GS
we took advantage of the availability of measurements taken during the same
campaign by a third independent instrument (DIMM - Differential Imaging Motion
Monitor) measuring the integrated turbulence extended on the whole 20 km. Such
a cross-check comparison permitted us to define the reliability of the
instruments and their measurements, their limits and the contexts in which
their use can present some risk.


title:
StreaMon: a data-plane programming abstraction for Software-defined
  Stream Monitoring

abstract:
  The fast evolving nature of modern cyber threats and network monitoring needs
calls for new, "software-defined", approaches to simplify and quicken
programming and deployment of online (stream-based) traffic analysis functions.
StreaMon is a carefully designed data-plane abstraction devised to scalably
decouple the "programming logic" of a traffic analysis application (tracked
states, features, anomaly conditions, etc.) from elementary primitives
(counting and metering, matching, events generation, etc), efficiently
pre-implemented in the probes, and used as common instruction set for
supporting the desired logic. Multi-stage multi-step real-time tracking and
detection algorithms are supported via the ability to deploy custom states,
relevant state transitions, and associated monitoring actions and triggering
conditions. Such a separation entails platform-independent, portable, online
traffic analysis tasks written in a high level language, without requiring
developers to access the monitoring device internals and program their custom
monitoring logic via low level compiled languages (e.g., C, assembly, VHDL). We
validate our design by developing a prototype and a set of simple (but
functionally demanding) use-case applications and by testing them over real
traffic traces.


title: Symmetry of solutions for some Bernoulli initial-value problems

abstract:
  In this paper, we show that under certain conditions on the coefficients and
initial values, solutions of two different Bernoulli initial-value problems are
symmetric to each other either with respect to the t-axis, or the y-axis, or
the origin. This knowledge of symmetry is very useful since solving one
Bernoulli problem solves automatically the other. To the best of our knowledge,
this interesting property has not been described in any other papers.


title: Flexible Parallel Algorithms for Big Data Optimization

abstract:
  We propose a decomposition framework for the parallel optimization of the sum
of a differentiable function and a (block) separable nonsmooth, convex one. The
latter term is typically used to enforce structure in the solution as, for
example, in Lasso problems. Our framework is very flexible and includes both
fully parallel Jacobi schemes and Gauss-Seidel (Southwell-type) ones, as well
as virtually all possibilities in between (e.g., gradient- or Newton-type
methods) with only a subset of variables updated at each iteration. Our
theoretical convergence results improve on existing ones, and numerical results
show that the new method compares favorably to existing algorithms.


title:
Asymptotic behavior of unregularized and ridge-regularized
  high-dimensional robust regression estimators : rigorous results

abstract:
  We study the behavior of high-dimensional robust regression estimators in the
asymptotic regime where $p/n$ tends to a finite non-zero limit. More
specifically, we study ridge-regularized estimators, i.e
$\widehat{\beta}=\text{argmin}_{\beta \in \mathbb{R}^p} \frac{1}{n}\sum_{i=1}^n
\rho(\varepsilon_i-X_i' \beta)+\frac{\tau}{2}\lVert\beta\rVert^2$. In a
recently published paper, we had developed with collaborators probabilistic
heuristics to understand the asymptotic behavior of $\widehat{\beta}$. We give
here a rigorous proof, properly justifying all the arguments we had given in
that paper. Our proof is based on the probabilistic heuristics we had
developed, and hence ideas from random matrix theory, measure concentration and
convex analysis. While most the work is done for $\tau>0$, we show that under
some extra assumptions on $\rho$, it is possible to recover the case $\tau=0$
as a limiting case. We require that the $X_i$'s be i.i.d with independent
entries, but our proof handles the case where these entries are not Gaussian. A
2-week old paper of Donoho and Montanari [arXiv:1310.7320] studied a similar
problem by a different method and with a different point of view. At this
point, their interesting approach requires Gaussianity of the design matrix.


title:
Optical cavities and waveguides in hyperuniform disordered photonic
  solids

abstract:
  Using finite difference time domain and band structure computer simulations,
we show that it is possible to construct optical cavities and waveguide
architectures in hyperuniform disordered photonic solids that are unattainable
in photonic crystals. The cavity modes can be classified according to the
symmetry (monopole, dipole, quadrupole,etc.) of the confined electromagnetic
wave pattern. Owing to the isotropy of the band gaps characteristic of
hyperuniform disordered solids, high-quality waveguides with freeform
geometries (e.g., arbitrary bending angles) can be constructed that have no
analogue in periodic or quasiperiodic solids. These capabilities have
implications for many photonic applications.


title:
Analysis of an attempt at detection of neutrons produced in a plasma
  discharge electrolytic cell

abstract:
  R. Faccini et al. \cite{Faccini:2013} have attempted a replication of an
earlier experiment by D. Cirillo et al. \cite{Cirillo:2012} in which neutrons
[as well as nuclear transmutations] were observed in a modified Mizuno cell. No
neutron production is observed in the recent experiment \cite{Faccini:2013} and
no evidence for microwave radiation or nuclear transmutations are reported. A
careful analysis shows major technical differences in the two experiments and
we explore the underlying reasons for the lack of any nuclear activity in the
newer experiment.


title: Recovery of Sparse Matrices via Matrix Sketching

abstract:
  In this paper, we consider the problem of recovering an unknown sparse matrix
X from the matrix sketch Y = AX B^T. The dimension of Y is less than that of X,
and A and B are known matrices. This problem can be solved using standard
compressive sensing (CS) theory after converting it to vector form using the
Kronecker operation. In this case, the measurement matrix assumes a Kronecker
product structure. However, as the matrix dimension increases the associated
computational complexity makes its use prohibitive. We extend two algorithms,
fast iterative shrinkage threshold algorithm (FISTA) and orthogonal matching
pursuit (OMP) to solve this problem in matrix form without employing the
Kronecker product. While both FISTA and OMP with matrix inputs are shown to be
equivalent in performance to their vector counterparts with the Kronecker
product, solving them in matrix form is shown to be computationally more
efficient. We show that the computational gain achieved by FISTA with matrix
inputs over its vector form is more significant compared to that achieved by
OMP.


title:
Time-dependent amplitude analysis of semileptonically-tagged D0 -> KS0
  pi+ pi- decays at LHCb

abstract:
  The hadronic decay D0 -> KS0 pi+ pi- provides access to the measurement of
the mixing parameters of the neutral D-meson system and allows to test for CP
violation. A measurement of the mixing parameters x_D and y_D as well as of the
parameters |q/p| and phi=arg(q,p), which govern indirect CP violation, will be
performed based on a time-dependent amplitude-model analysis of the full LHCb
dataset of 2011 and 2012 corresponding to an integrated luminosity of 3/fb.


title: Amenability of Hecke pairs and a question of Eymard

abstract:
  In this short paper we show that if $(G,H)$ is an amenable Hecke pair and
$\Gamma$ is a subgroup of $G$ containing $H$, then the Hecke pair $(\Gamma, H)$
is amenable too. This answers positively a question of Pierre Eymard, asked in
1972, when it is restricted to Hecke pairs


title: Holographic duality and the resistivity of strange metals

abstract:
  We present a strange metal, described by a holographic duality, which
reproduces the famous linear resistivity of the normal state of the copper
oxides, in addition to the linear specific heat. This holographic metal reveals
a simple and general mechanism for producing such a resistivity, which requires
only quenched disorder and a strongly interacting, locally quantum critical
state. The key is the minimal viscosity of the latter: unlike in a
Fermi-liquid, the viscosity is very small and therefore is important for the
electrical transport. This mechanism produces a resistivity proportional to the
electronic entropy.


title: MAGNA: Maximizing Accuracy in Global Network Alignment

abstract:
  Biological network alignment aims to identify similar regions between
networks of different species. Existing methods compute node "similarities" to
rapidly identify from possible alignments the "high-scoring" alignments with
respect to the overall node similarity. However, the accuracy of the alignments
is then evaluated with some other measure that is different than the node
similarity used to construct the alignments. Typically, one measures the amount
of conserved edges. Thus, the existing methods align similar nodes between
networks hoping to conserve many edges (after the alignment is constructed!).
  Instead, we introduce MAGNA to directly "optimize" edge conservation while
the alignment is constructed. MAGNA uses a genetic algorithm and our novel
function for crossover of two "parent" alignments into a superior "child"
alignment to simulate a "population" of alignments that "evolves" over time;
the "fittest" alignments survive and proceed to the next "generation", until
the alignment accuracy cannot be optimized further. While we optimize our new
and superior measure of the amount of conserved edges, MAGNA can optimize any
alignment accuracy measure. In systematic evaluations against existing
state-of-the-art methods (IsoRank, MI-GRAAL, and GHOST), MAGNA improves
alignment accuracy of all methods.


title: Stability of cosmological deflagration fronts

abstract:
  In a cosmological first-order phase transition, bubbles of the stable phase
nucleate and expand in the supercooled metastable phase. In many cases, the
growth of bubbles reaches a stationary state, with bubble walls propagating as
detonations or deflagrations. However, these hydrodynamical solutions may be
unstable under corrugation of the interface. Such instability may drastically
alter some of the cosmological consequences of the phase transition. Here, we
study the hydrodynamical stability of deflagration fronts. We improve upon
previous studies by making a more careful and detailed analysis. In particular,
we take into account the fact that the equation of motion for the phase
interface depends separately on the temperature and fluid velocity on each side
of the wall. Fluid variables on each side of the wall are similar for weakly
first-order phase transitions, but differ significantly for stronger phase
transitions. As a consequence, we find that, for large enough supercooling, any
subsonic wall velocity becomes unstable. Moreover, as the velocity approaches
the speed of sound, perturbations become unstable on all wavelengths. For
smaller supercooling and small wall velocities, our results agree with those of
previous works. Essentially, perturbations on large wavelengths are unstable,
unless the wall velocity is higher than a critical value. We also find a
previously unobserved range of marginally unstable wavelengths. We analyze the
dynamical relevance of the instabilities, and we estimate the characteristic
time and length scales associated to their growth. We discuss the implications
for the electroweak phase transition and its cosmological consequences.


title: The position-momentum symmetry principle

abstract:
  It is shown that the Fourier transformation that relates position and
momentum representations of quantum mechanics can be understood as a
consequence of a symmetry principle that establishes the equivalence of being
and becoming in the description of reality. There are however other
transformation compatible with the same principle that could lead to different
formalisms of quantum mechanics.


title:
Scalar fields with barotropic equation of state: quintessence versus
  phantom

abstract:
  We constrain the parameters of dynamical dark energy in the form of a
classical scalar field with barotropic equation of state jointly with other
cosmological parameters using various combined datasets including the CMB power
spectra from WMAP7, the baryon acoustic oscillations in the space distribution
of galaxies from SDSS DR7 and WiggleZ, the light curves of SN Ia from 3
different compilations: SDSS (SALT2 and MLCS2k2 light curve fittings), SNLS3
and Union2.1. The considered class of models involves both quintessential and
phantom subclasses. The analysis has shown that the phantom models are
generally preferred by the observational data. We discuss the effect of
allowing for non-zero masses of active neutrinos, non-zero curvature or
non-zero contribution from the tensor mode of perturbations on the precision of
dark energy parameters estimation. We also perform a forecast for the Planck
mock data.


title:
Families with infants: a general approach to solve hard partition
  problems

abstract:
  We introduce a general approach for solving partition problems where the goal
is to represent a given set as a union (either disjoint or not) of subsets
satisfying certain properties. Many NP-hard problems can be naturally stated as
such partition problems. We show that if one can find a large enough system of
so-called families with infants for a given problem, then this problem can be
solved faster than by a straightforward algorithm. We use this approach to
improve known bounds for several NP-hard problems as well as to simplify the
proofs of several known results.
  For the chromatic number problem we present an algorithm with
$O^*((2-\varepsilon(d))^n)$ time and exponential space for graphs of average
degree $d$. This improves the algorithm by Bj\"{o}rklund et al. [Theory Comput.
Syst. 2010] that works for graphs of bounded maximum (as opposed to average)
degree and closes an open problem stated by Cygan and Pilipczuk [ICALP 2013].
  For the traveling salesman problem we give an algorithm working in
$O^*((2-\varepsilon(d))^n)$ time and polynomial space for graphs of average
degree $d$. The previously known results of this kind is a polyspace algorithm
by Bj\"{o}rklund et al. [ICALP 2008] for graphs of bounded maximum degree and
an exponential space algorithm for bounded average degree by Cygan and
Pilipczuk [ICALP 2013].
  For counting perfect matching in graphs of average degree~$d$ we present an
algorithm with running time $O^*((2-\varepsilon(d))^{n/2})$ and polynomial
space. Recent algorithms of this kind due to Cygan, Pilipczuk [ICALP 2013] and
Izumi, Wadayama [FOCS 2012] (for bipartite graphs only) use exponential space.


title: An hourglass model for the flare of HST-1 in M87

abstract:
  To explain the multi-wavelength light curves (from radio to X-ray) of HST-1
in the M87 jet, we propose an hourglass model that is a modified two-zone
system of Tavecchio & Ghisellini (hereafter TG08): a slow hourglass-shaped or
Laval nozzle-shaped layer connected by two revolving exponential surfaces
surrounding a fast spine, through which plasma blobs flow. Based on the
conservation of magnetic flux, the magnetic field changes along the axis of the
hourglass. We adopt the result of TG08---the high-energy emission from GeV to
TeV can be produced through inverse Compton by the two-zone system, and the
photons from radio to X-ray are mainly radiated by the fast inner zone system.
Here, we only discuss the light curves of the fast inner blob from radio to
X-ray. When a compressible blob travels down the axis of the first bulb in the
hourglass, because of magnetic flux conservation, its cross section experiences
an adiabatic compression process, which results in particle acceleration and
the brightening of HST-1. When the blob moves into the second bulb of the
hourglass, because of magnetic flux conservation, the dimming of the knot
occurs along with an adiabatic expansion of its cross section. A similar broken
exponential function could fit the TeV peaks in M87, which may imply a
correlation between the TeV flares of M87 and the light curves from radio to
X-ray in HST-1. The Very Large Array (VLA) 22 GHz radio light curve of HST-1
verifies our prediction based on the model fit to the main peak of the VLA 15
GHz radio light curve.


title: First submillimeter observation of CO in the stratosphere of Uranus

abstract:
  Context. Carbon monoxide (CO) has been detected in all Giant Planets and its
origin is both internal and external in Jupiter and Neptune. Despite its first
detection in Uranus a decade ago, the magnitude of its internal and external
sources remains unconstrained.
  Aims. We targeted CO lines in Uranus in the submillimeter range to constrain
its origin.
  Methods. We recorded disk-averaged spectra of Uranus with a very high
spectral resolution at the frequencies of CO rotational lines in the
submillimeter range in 2011-2012. We used empirical and diffusion models of the
atmosphere of Uranus to constrain the origin of CO. We also used a
thermochemical model of its troposphere to derive an upper limit on the O/H
ratio in the deep atmosphere of Uranus.
  Results. We have detected the CO(8-7) rotational line for the first time,
with Herschel-HIFI. Both empirical and diffusion model results show that CO has
an external origin. An empirical profile in which CO is constant above the
100mbar level with a mole fraction of 7.1-9.0E-9 (depending on the adopted
stratospheric thermal structure) reproduces the data. Sporadic and steady
source models cannot be differentiated with our data. Taking Teanby & Irwin's
internal source model upper limit of a mole fraction of 2.1E-9 [Teanby & Irwin
2013. ApJ, 775, L49], the deep O/H ratio of Uranus is lower than 500 times
solar according to our thermochemical computations.
  Conclusions. Our work shows that the average mole fraction of CO decreases
from the stratosphere to the troposphere and thus strongly advocates for an
external source of CO in Uranus. Photochemical modeling of oxygen species in
the atmosphere of Uranus and more sensitive observations are needed to reveal
the nature of the external source.


title: Crystalline Confinement

abstract:
  We show that exotic phases arise in generalized lattice gauge theories known
as quantum link models in which classical gauge fields are replaced by quantum
operators. While these quantum models with discrete variables have a
finite-dimensional Hilbert space per link, the continuous gauge symmetry is
still exact. An efficient cluster algorithm is used to study these exotic
phases. The $(2+1)$-d system is confining at zero temperature with a
spontaneously broken translation symmetry. A crystalline phase exhibits
confinement via multi-stranded strings between charge-anti-charge pairs. A
phase transition between two distinct confined phases is weakly first order and
has an emergent spontaneously broken approximate $SO(2)$ global symmetry. The
low-energy physics is described by a $(2+1)$-d $\mathbb{R}P(1)$ effective field
theory, perturbed by a dangerously irrelevant $SO(2)$ breaking operator, which
prevents the interpretation of the emergent pseudo-Goldstone boson as a dual
photon. This model is an ideal candidate to be implemented in quantum
simulators to study phenomena that are not accessible using Monte Carlo
simulations such as the real-time evolution of the confining string and the
real-time dynamics of the pseudo-Goldstone boson.


title: Vision-Guided Robot Hearing

abstract:
  Natural human-robot interaction in complex and unpredictable environments is
one of the main research lines in robotics. In typical real-world scenarios,
humans are at some distance from the robot and the acquired signals are
strongly impaired by noise, reverberations and other interfering sources. In
this context, the detection and localisation of speakers plays a key role since
it is the pillar on which several tasks (e.g.: speech recognition and speaker
tracking) rely. We address the problem of how to detect and localize people
that are both seen and heard by a humanoid robot. We introduce a hybrid
deterministic/probabilistic model. Indeed, the deterministic component allows
us to map the visual information into the auditory space. By means of the
probabilistic component, the visual features guide the grouping of the auditory
features in order to form AV objects. The proposed model and the associated
algorithm are implemented in real-time (17 FPS) using a stereoscopic camera
pair and two microphones embedded into the head of the humanoid robot NAO. We
performed experiments on (i) synthetic data, (ii) a publicly available data set
and (iii) data acquired using the robot. The results we obtained validate the
approach and encourage us to further investigate how vision can help robot
hearing.


title:
Multi-mode Alfv\'enic Fast Particle Transport and Losses: Numerical vs.
  Experimental Observation

abstract:
  In many discharges at ASDEX Upgrade fast particle losses can be observed due
to Alfv\'enic gap modes, Reversed Shear Alfv\'en Eigenmodes or core-localized
Beta Alfv\'en Eigenmodes. For the first time, simulations of experimental
conditions in the ASDEX Upgrade fusion device are performed for different
plasma equilibria (particularly for different, also non-monotonic q profiles).
The numerical tool is the extended version of the HAGIS code [Pinches'98,
Br\"udgam PhD Thesis, 2010], which also computes the particle motion in the
vacuum region between vessel wall in addition to the internal plasma volume.
For this work, a consistent fast particle distribution function was implemented
to represent the strongly anisotropic fast particle population as generated by
ICRH minority heating. Furthermore, HAGIS was extended to use more realistic
eigenfunctions, calculated by the gyrokinetic eigenvalue solver LIGKA
[Lauber'07]. The main aim of these simulations is to allow fast ion loss
measurements to be interpreted with a theoretical basis. Fast particle losses
are modeled and directly compared with experimental measurements
[Garc\'ia-Mu\~noz'10]. The phase space distribution and the mode-correlation
signature of the fast particle losses allows them to be characterized as
prompt, resonant or diffusive (non-resonant). The experimental findings are
reproduced numerically. It is found that a large number of diffuse losses occur
in the lower energy range (at around 1/3 of the birth energy) particularly in
multiple mode scenarios (with different mode frequencies), due to a phase space
overlap of resonances leading to a so-called domino [Berk'95] transport
process. In inverted q profile equilibria, the combination of radially extended
global modes and large particle orbits leads to losses with energies down to
1/10th of the birth energy.


title: On Scaling Functionality in Urban Form

abstract:
  Assuming that the ultimate purpose of the city is to provide support to human
interaction and that opportunities to that social interaction are unevenly
distributed across the urban fabric, this paper reports some attempts to
describe such a distribution, as well as to infer the role of urban form in it.
In order to do that, it is proposed, firstly, a method to describe urban form
from its smallest components up to the different urban fabric patches, to the
entire spatial system, and second, a model to represent social interaction as a
process associated to the urban morphology. Both the spatial description and
the analytical model are discussed through the examination of some results,
obtained through simulation.


title:
Turbulence decay towards the linearly-stable regime of Taylor-Couette
  flow

abstract:
  Taylor-Couette (TC) flow is used to probe the hydrodynamical stability of
astrophysical accretion disks. Experimental data on the subcritical stability
of TC are in conflict about the existence of turbulence (cf. Ji et al. Nature,
444, 343-346 (2006) and Paoletti et al., A$\&$A, 547, A64 (2012)), with
discrepancies attributed to end-plate effects. In this paper we numerically
simulate TC flow with axially periodic boundary conditions to explore the
existence of sub-critical transitions to turbulence when no end-plates are
present. We start the simulations with a fully turbulent state in the unstable
regime and enter the linearly stable regime by suddenly starting a
(stabilizing) outer cylinder rotation. The shear Reynolds number of the
turbulent initial state is up to $Re_s \sim10^5$ and the radius ratio is
$\eta=0.714$. The stabilization causes the system to behave as a damped
oscillator and correspondingly the turbulence decays. The evolution of the
torque and turbulent kinetic energy is analysed and the periodicity and damping
of the oscillations are quantified and explained as a function of shear
Reynolds number. Though the initially turbulent flow state decays,
surprisingly, the system is found to absorb energy during this decay.


title:
Formal Killing fields for minimal Lagrangian surfaces in complex space
  forms

abstract:
  The differential system for minimal Lagrangian surfaces in a
$2_{\mathbb{C}}$-dimensional, non-flat, complex space form is an elliptic
system defined on the bundle of oriented Lagrangian planes. This is a
6-symmetric space associated with the Lie group SL(3,$\mathbb{C}$), and the
minimal Lagrangian surfaces arise as the primitive maps. Utilizing this
property, we derive the differential algebraic inductive formulas for a pair of
loop algebra $\mathfrak{sl}(3,\mathbb{C})[[\lambda]]$-valued canonical formal
Killing fields. As a result, we give a complete classification of the (infinite
sequence of) Jacobi fields for the minimal Lagrangian system. We also obtain an
infinite sequence of higher-order conservation laws from the components of the
formal Killing fields.