title:
First observational application of a connectivity--based helicity flux
  density

abstract:
  Measuring the magnetic helicity distribution in the solar corona can help in
understanding the trigger of solar eruptive events because magnetic helicity is
believed to play a key role in solar activity due to its conservation property.
A new method for computing the photospheric distribution of the helicity flux
was recently developed. This method takes into account the magnetic field
connectivity whereas previous methods were based on photospheric signatures
only. This novel method maps the true injection of magnetic helicity in active
regions. We applied this method for the first time to an observed active
region, NOAA 11158, which was the source of intense flaring activity. We used
high-resolution vector magnetograms from the SDO/HMI instrument to compute the
photospheric flux transport velocities and to perform a nonlinear force-free
magnetic field extrapolation. We determined and compared the magnetic helicity
flux distribution using a purely photospheric as well as a connectivity-based
method. While the new connectivity-based method confirms the mixed pattern of
the helicity flux in NOAA 11158, it also reveals a different, and more correct,
distribution of the helicity injection. This distribution can be important for
explaining the likelihood of an eruption from the active region. The
connectivity-based approach is a robust method for computing the magnetic
helicity flux, which can be used to study the link between magnetic helicity
and eruptivity of observed active regions.


title: Measuring Distance between Reeb Graphs

abstract:
  One of the prevailing ideas in geometric and topological data analysis is to
provide descriptors that encode useful information about hidden objects from
observed data. The Reeb graph is one such descriptor for a given scalar
function. The Reeb graph provides a simple yet meaningful abstraction of the
input domain, and can also be computed efficiently.
  Given the popularity of the Reeb graph in applications, it is important to
understand its stability and robustness with respect to changes in the input
function, as well as to be able to compare the Reeb graphs resulting from
different functions.
  In this paper, we propose a metric for Reeb graphs, called the functional
distortion distance. Under this distance measure, the Reeb graph is stable
against small changes of input functions. At the same time, it remains
discriminative at differentiating input functions. In particular, the main
result is that the functional distortion distance between two Reeb graphs is
bounded from below by (and thus more discriminative than) the bottleneck
distance between both the ordinary and extended persistence diagrams for
appropriate dimensions.
  As an application of our results, we analyze a natural simplification scheme
for Reeb graphs, and show that persistent features in Reeb graph remains
persistent under simplification. Understanding the stability of important
features of the Reeb graph under simplification is an interesting problem on
its own right, and critical to the practical usage of Reeb graphs.


title: Analytic normal forms for convergent saddle-node vector fields

abstract:
  We give unique analytic "normal forms" for germs of a holomorphic vector
field of the complex plane in the neighborhood of an isolated singularity of
saddle-node type having a convergent formal separatrix. We specifically address
the problem of computing the normal form explicitly.


title: Projections of self-similar sets with no separation condition

abstract:
  We investigate how the Hausdorff dimension and measure of a self-similar set
$K\subseteq\mathbb{R}^{d}$ behave under linear images. This depends on the
nature of the group $\mathcal{T}$ generated by the orthogonal parts of the
defining maps of $K$. We show that if $\mathcal{T}$ is finite then every linear
image of $K$ is a graph directed attractor and there exists at least one
projection of $K$ such that the dimension drops under the image of the
projection. In general, with no restrictions on $\mathcal{T}$ we establish that
$\mathcal{H}^{t}(L\circ O(K))=\mathcal{H}^{t}(L(K))$ for every element $O$ of
the closure of $\mathcal{T}$, where $L$ is a linear map and $t=\dim_{H}K$. We
also prove that for disjoint subsets $A$ and \textbf{$B$} of $K$ we have that
$\mathcal{H}^{t}(L(A)\cap L(B))=0$. Hochman and Shmerkin showed that if
$\mathcal{T}$ is dense in $SO(d,\mathbb{R})$ and the strong separation
condition is satisfied then $\dim_{H}(g(K))=\min\{\dim_{H}K,l\} $ where $g$ is
a continuously differentiable map of rank $l$. We deduce the same result
without any separation condition and we generalize a result of
Ero$\breve{\mathrm{g}}$lu by obtaining that $\mathcal{H}^{t}(g(K))=0$.


title:
Direct and inverse scattering at fixed energy for massless charged Dirac
  fields by Kerr-Newman-de Sitter black holes

abstract:
  In this paper, we study the direct and inverse scattering theory at fixed
energy for massless charged Dirac fields evolving in the exterior region of a
Kerr-Newman-de Sitter black hole. In the first part, we establish the existence
and asymptotic completeness of time-dependent wave operators associated to our
Dirac fields. This leads to the definition of the time-dependent scattering
operator that encodes the far-field behavior (with respect to a stationary
observer) in the asymptotic regions of the black hole: the event and
cosmological horizons. We also use the miraculous property (quoting
Chandrasekhar) - that the Dirac equation can be separated into radial and
angular ordinary differential equations - to make the link between the
time-dependent scattering operator and its stationary counterpart. This leads
to a nice expression of the scattering matrix at fixed energy in terms of
stationary solutions of the system of separated equations. In a second part, we
use this expression of the scattering matrix to study the uniqueness property
in the associated inverse scattering problem at fixed energy. Using essentially
the particular form of the angular equation (that can be solved explicitely by
Frobenius method) and the Complex Angular Momentum technique on the radial
equation, we are finally able to determine uniquely the metric of the black
hole from the knowledge of the scattering matrix at a fixed energy.


title: Hawking radiation in a two-component Bose-Einstein condensate

abstract:
  We consider a simple realization of an event horizon in the flow of a
one-dimensional two-component Bose-Einstein condensate. Such a condensate has
two types of quasiparticles; In the system we study, one corresponds to density
fluctuations and the other to polarization fluctuations. We treat the case
where a horizon occurs only for one type of quasiparticles (the polarization
ones). We study the one- and two-body signal associated to the analog of
spontaneous Hawking radiation and demonstrate by explicit computation that it
consists only in the emission of polarization waves. We discuss the
experimental consequences of the present results in the domain of atomic
Bose-Einstein condensates and also for the physics of exciton-polaritons in
semiconductor microcavities.


title:
Generating Robust Optical Entanglement in Weak Coupling Optomechanical
  Systems

abstract:
  A pulsed scheme for generating robust optical entanglement via the coupling
of two optical modes to a mechanical oscillator is proposed. This scheme is
inspired by the S{\o}rensen-M{\o}lmer approach for entangling trapped ions in a
thermal environment and is based on the use of optical driving pulses that are
slightly detuned from the respective sideband resonance. We show that for
certain pulse durations, the optomechanical interaction can return the
mechanical oscillator to its initial state. The corresponding entanglement
generation is robust against thermal mechanical noise in the weak as well as
the strong coupling regimes. Significant optical entanglement can be generated
in the weak coupling regime, even in the presence of a large thermal phonon
occupation.


title:
Analytic, Reidemeister and homological torsion for congruence
  three--manifolds

abstract:
  Starting from the results in math.DG:1212.3161 we prove that for a given
Bianchi group, certain natural coefficent modules and a lot of sequences of
congruence subgroups of the size of the torsion subgroup of the first homology
grows exponentially with the index (we give an explicit rate). We also prove
limit multiplicity results for the irreducible components of the space of
cuspidal forms.


title:
HST FUV imaging of DG Tau: Fluorescent molecular hydrogen emission from
  the wide angle outflow

abstract:
  One of the best-studied jets from all young stellar objects is the jet of DG
Tau, which we imaged in the FUV with HST for the first time. These high spatial
resolution images were obtained with long-pass filters and allow us to
construct images tracing mainly molecular hydrogen and C IV emission. We find
that the H2 emission appears as a limb-brightened cone with additional emission
close to the jet axis. The length of the rims is about 0.3 arcsec or 42 AU
(proj.) before their brightness strongly drops, and the opening angle is about
90 deg. Comparing our FUV data with near-IR data we find that the fluorescent
H2 emission likely traces the outer, cooler part of the disk wind while an
origin of the H2 emission in the surface layers (atmosphere) of the (flared)
disk is unlikely. Furthermore, the spatial shape of the H2 emission shows
little variation over six years which suggests that the outer part of the disk
wind is rather stable and probably not associated with the formation of
individual knots. The C IV image shows that the emission is concentrated
towards the jet axis. We find no indications for additional C IV emission at
larger distances, which strengthens the association with the X-ray emission
observed to originate within the DG Tau jet.


title: Rotating effects on the Dirac oscillator in the cosmic string spacetime

abstract:
  In this contribution, we study the Dirac oscillator under the influence of
noninertial effects of a rotating frame in the cosmic string spacetime. We show
that both noninertial effects and the topology of the cosmic string spacetime
restrict the physical region of the spacetime where the quantum particle can be
placed, and discuss two different cases of bound states solutions of the Dirac
equation by analysing the behaviour of the Dirac oscillator frequency.


title:
Distorted spin-dependent spectral function of an A=3 nucleus and
  semi-inclusive deep inelastic scattering processes

abstract:
  The distorted spin-dependent spectral function of a nucleon inside an A=3
nucleus is introduced as a novel tool for investigating the polarized electron
scattering off polarized $^3$He in semi-inclusive DIS regime (SiDIS), going
beyond the standard plane wave impulse approximation. This distribution
function is applied to the study of the spectator SiDIS, $\vec{^3{\rm He}}(\vec
e, e' ~{^2}{\rm H})X$, in order to properly take into account the final state
interaction between the hadronizing quark and the detected deuteron, with the
final goal of a more reliable extraction of the polarized parton-distribution
$g_1(x)$ inside a bound proton. Our analysis allows to single out two
well-defined kinematical regions where the experimental asymmetries could yield
very interesting information: the region where the final state effects can be
minimized, and therefore the direct access to the parton distributions in the
proton is feasible, and the one where the final state interaction dominates,
and the spectator SiDIS reactions can elucidate the mechanism of the quark
hadronization itself. The perspectives of extending our approach i) to the
mirror nucleus, $^3$H, for achieving a less model-dependent flavor
decomposition, and ii) to the asymmetries measured in the standard SiDIS
reactions, $\vec e + \vec{^3 {\rm He}} \to e' + h+X$ with $h$ a detected fast
hadron, with the aim of extracting the neutron transversity, are discussed.


title:
Continuous-Time Public Good Contribution under Uncertainty: A Stochastic
  Control Approach

abstract:
  In this paper we study continuous-time stochastic control problems with both
monotone and classical controls motivated by the so-called public good
contribution problem. That is the problem of n economic agents aiming to
maximize their expected utility allocating initial wealth over a given time
period between private consumption and irreversible contributions to increase
the level of some public good. We investigate the corresponding social planner
problem and the case of strategic interaction between the agents, i.e. the
public good contribution game. We show existence and uniqueness of the social
planner's optimal policy, we characterize it by necessary and sufficient
stochastic Kuhn-Tucker conditions and we provide its expression in terms of the
unique optional solution of a stochastic backward equation. Similar stochastic
first order conditions prove to be very useful for studying any Nash equilibria
of the public good contribution game. In the symmetric case they allow us to
prove (qualitative) uniqueness of the Nash equilibrium, which we again
construct as the unique optional solution of a stochastic backward equation. We
finally also provide a detailed analysis of the so-called free rider effect.


title: Numerical computations in cobordism categories

abstract:
  The sequence 2,5,15,51,187,... with the form $(2^n+1)(2^{n-1}+1)/3$ has two
interpretations in terms of the density of a language with four letters and the
cardinality of the quotient of $\ZZ_2^n\times \ZZ_2^n$ under the action of the
special linear group $\op{SL}(2,\ZZ)$. The last interpretation follows the rank
of the fundamental group of the $\ZZ_2^n$-cobordism category in dimension 1+1.
This article presents how to pass from one side to another between these two
approaches.


title:
Thermodynamics of (2+1)-flavor strongly interacting matter at nonzero
  isospin

abstract:
  We investigate the phase structure of strongly interacting matter at
non-vanishing isospin before the onset of pion condensation in the framework of
the unquenched Polyakov-Quark-Meson model with 2+1 quark flavors. We show
results for the order parameters and all relevant thermodynamic quantities. In
particular, we obtain a moderate change of the pressure with isospin at
vanishing baryon chemical potential, whereas the chiral condensate decreases
more appreciably. We compare the effective model to recent lattice data for the
decrease of the pseudo-critical temperature with the isospin chemical
potential. We also demonstrate the major role played by the value of the pion
mass in the curvature of the transition line, and the need for lattice results
with a physical pion mass. Limitations of the model at nonzero chemical
potential are also discussed.


title: Competitive Equilibrium Relaxations in General Auctions

abstract:
  The goal of an auction is to determine commodity prices such that all
participants are perfectly happy. Such a solution is called a competitive
equilibrium and does not exist in general. For this reason we are interested in
solutions which are similar to a competitive equilibrium. The article
introduces two relaxations of a competitive equilibrium for general auctions.
Both relaxations determine one price per commodity by solving a difficult
non-convex optimization problem. The first model is a mathematical program with
equilibrium constraints (MPEC), which ensures that each participant is either
perfectly happy or his bid is rejected. An exact algorithm and a heuristic are
provided for this model. The second model is a relaxation of the first one and
only ensures that no participant incurs a loss. In an optimal solution to the
second model, no participant can be made better off without making another one
worse off.


title: On the dimension of max-min convex sets

abstract:
  We introduce a notion of dimension of max-min convex sets, following the
approach of tropical convexity. We introduce a max-min analogue of the tropical
rank of a matrix and show that it is equal to the dimension of the associated
polytope. We describe the relation between this rank and the notion of strong
regularity in max-min algebra, which is traditionally defined in terms of
unique solvability of linear systems and trapezoidal property.


title: Three-body recombination at finite energy within an optical model

abstract:
  We investigate three-boson recombination of equal mass systems as function of
(negative) scattering length, mass, finite energy, and finite temperature. An
optical model with an imaginary potential at short distance reproduces
experimental recombination data and allows us to provide a simple
parametrization of the recombination rate as function of scattering length and
energy. Using the two-body van der Waals length as unit we find that the
imaginary potential range and also the potential depth agree to within thirty
percent for Lithium and Cesium atoms. As opposed to recent studies suggesting
universality of the threshold for bound state formation, our results suggest
that the recombination process itself could have universal features.


title: Flow-Based Algorithms for Local Graph Clustering

abstract:
  Given a subset S of vertices of an undirected graph G, the cut-improvement
problem asks us to find a subset S that is similar to A but has smaller
conductance. A very elegant algorithm for this problem has been given by
Andersen and Lang [AL08] and requires solving a small number of
single-commodity maximum flow computations over the whole graph G. In this
paper, we introduce LocalImprove, the first cut-improvement algorithm that is
local, i.e. that runs in time dependent on the size of the input set A rather
than on the size of the entire graph. Moreover, LocalImprove achieves this
local behaviour while essentially matching the same theoretical guarantee as
the global algorithm of Andersen and Lang.
  The main application of LocalImprove is to the design of better
local-graph-partitioning algorithms. All previously known local algorithms for
graph partitioning are random-walk based and can only guarantee an output
conductance of O(\sqrt{OPT}) when the target set has conductance OPT \in [0,1].
Very recently, Zhu, Lattanzi and Mirrokni [ZLM13] improved this to O(OPT /
\sqrt{CONN}) where the internal connectivity parameter CONN \in [0,1] is
defined as the reciprocal of the mixing time of the random walk over the graph
induced by the target set. In this work, we show how to use LocalImprove to
obtain a constant approximation O(OPT) as long as CONN/OPT = Omega(1). This
yields the first flow-based algorithm. Moreover, its performance strictly
outperforms the ones based on random walks and surprisingly matches that of the
best known global algorithm, which is SDP-based, in this parameter regime
[MMV12].
  Finally, our results show that spectral methods are not the only viable
approach to the construction of local graph partitioning algorithm and open
door to the study of algorithms with even better approximation and locality
guarantees.


title: Mechanical equilibrium of two-component gas mixtures

abstract:
  Evaporation of liquid into a vapor-gas mixture is interesting and important
process as for fundamental research and for different applications. In general,
the rate at which a liquid evaporates is dependent on the transport of mass and
energy occurring within both the liquid and vapor phases. This study is carried
out on the base of continuum conservation equations for two-component medium.
At the beginning the stability conditions for mechanical equilibrium are
deduced. This paper is devoted to this theme.


title:
Ionization of hydrogen by neutrino magnetic moment, relativistic muon,
  and WIMP

abstract:
  We studied the ionization of hydrogen by scattering of neutrino magnetic
moment, relativistic muon, and weakly-interacting massive particle with a
QED-like interaction. Analytic results were obtained and compared with several
approximation schemes often used in atomic physics. As current searches for
neutrino magnetic moment and dark matter have lowered the detector threshold
down to the sub-keV regime, we tried to deduce from this simple case study the
influence of atomic structure on the the cross sections and the applicabilities
of various approximations. The general features being found will be useful for
cases where practical detector atoms are considered.


title: Equivariant Topological Quantum Field Theory in Dimension 2

abstract:
  For $G$ a finite group, we prove in dimension 2 that there is a monoidal
equivalence between the category of $G$-equivariant topological quantum field
theories and the category of $G$-Frobenius algebras, this was proved by G.
Moore and G. Segal. This work consists to give, in more detail, a proof of this
result.


title:
Multiple Detectors for a Short-Baseline Neutrino Oscillation Search Near
  Reactors

abstract:
  Reactor antineutrino experiments have the ability to search for neutrino
oscillations independent of reactor flux predictions using a relative
measurement of the neutrino flux and spectrum across a range of baselines. The
range of accessible oscillation parameters are determined by the baselines of
the detector arrangement. We examine the sensitivity of short-baseline
experiments with more than one detector and discuss the optimization of a
second, far detector. The extended reach in baselines of a 2-detector
experiment will improve sensitivity to short-baseline neutrino oscillations
while also increasing the ability to distinguish between 3+1 mixing and other
non-standard models.


title: Autocatalytic Sets and Biological Specificity

abstract:
  A universal feature of the biochemistry of any living system is that all the
molecules and catalysts that are required for reactions of the system can be
built up from an available food source by repeated application of reactions
from within that system. RAF (reflexively autocatalytic and food-generated)
theory provides a formal way to study such processes. Beginning with Kauffman's
notion of "collectively autocatalytic sets", this theory has been further
developed over the last decade with the discovery of efficient algorithms and
new mathematical analysis. In this paper, we study how the behaviour of a
simple binary polymer model can be extended to models where the pattern of
catalysis more precisely reflects the ligation and cleavage reactions involved.
We find that certain properties of these models are similar to, and can be
accurately predicted from, the simple binary polymer model; however, other
properties lead to slightly different estimates. We also establish a number of
new results concerning the structure of RAFs in these systems.


title: Electronic transport of folded graphene nanoribbons

abstract:
  We investigate the electronic transport properties of a folded graphene
nanoribbon with monolayer nanoribbon contacts. We consider two possible
foldings: either the nanoribbon can be folded onto itself in the shape of a
hairpin with the nanoribbon leads at a $0^\circ$ angle, or the monolayer
contacts have different directions, forming a $60^\circ$ angle. The system is
described by a single $\pi$-band nearest-neighbor tight-binding Hamiltonian
taking into account curvature effects. We have found that for the case of a
nanoribbon folded over itself the conductance oscillates from almost zero and a
finite value depending on the coupling between contacts, whereas in the
$60^\circ$ angle folding the conductance is only slightly perturbed, allowing
for the connection of graphene nanoelectronic components in a variety of
geometries.


title:
On decoupling inequalities and percolation of excursion sets of the
  Gaussian free field

abstract:
  We prove decoupling inequalities for the Gaussian free field on
$\mathbb{Z}^d$, $d\geq 3$. As an application, we obtain exponential decay (with
logarithmic correction for $d=3$) of the connectivity function of excursion
sets for large values of the threshold.


title: Dynamic Data Structure for Tree-Depth Decomposition

abstract:
  We present a dynamic data structure for representing a graph $G$ with
tree-depth at most $D$. Tree-depth is an important graph parameter which arose
in the study of sparse graph classes.
  The structure allows addition and removal of edges and vertices such that the
resulting graph still has tree-depth at most $D$, in time bounds depending only
on $D$. A tree-depth decomposition of the graph is maintained explicitly.
  This makes the data structure useful for dynamization of static algorithms
for graphs with bounded tree-depth. As an example application, we give a
dynamic data structure for MSO-property testing, with time bounds for removal
depending only on $D$ and constant-time testing of the property, while the time
for the initialization and insertion also depends on the size of the formula
expressing the property.


title: Theory of Quantum Friction

abstract:
  Here, we develop a comprehensive quantum theory for the phenomenon of quantum
friction. Based on a theory of macroscopic quantum electrodynamics for unstable
systems, we calculate the quantum expectation of the friction force, and link
the friction effect to the emergence of system instabilities related to the
Cherenkov effect. These instabilities may occur due to the hybridization of
particular guided modes supported by the individual moving bodies, and
selection rules for the interacting modes are derived. It is proven that the
quantum friction effect can take place even when the interacting bodies are
lossless and made of nondispersive dielectrics.


title: Propagation at the vertex of a sector

abstract:
  We discuss holomorphic extension across a boundary point in terms of sector
property. The point is of infinite type and the sector is accordingly "cusped"
at the vertex.


title:
Cobalt-related impurity centers in diamond: electronic properties and
  hyperfine parameters

abstract:
  Cobalt-related impurity centers in diamond have been studied using first
principles calculations. We computed the symmetry, formation and transition
energies, and hyperfine parameters of cobalt impurities in isolated
configurations and in complexes involving vacancies and nitrogen atoms. We
found that the Co impurity in a divacant site is energetically favorable and
segregates nitrogen atoms in its neighborhood. Our results were discussed in
the context of the recently observed Co-related electrically active centers in
synthetic diamond.


title: Tractable Combinations of Global Constraints

abstract:
  We study the complexity of constraint satisfaction problems involving global
constraints, i.e., special-purpose constraints provided by a solver and
represented implicitly by a parametrised algorithm. Such constraints are widely
used; indeed, they are one of the key reasons for the success of constraint
programming in solving real-world problems.
  Previous work has focused on the development of efficient propagators for
individual constraints. In this paper, we identify a new tractable class of
constraint problems involving global constraints of unbounded arity. To do so,
we combine structural restrictions with the observation that some important
types of global constraint do not distinguish between large classes of
equivalent solutions.


title:
Merger states and final states of black hole coalescences: a
  numerical-relativity-assisted effective-one-body approach

abstract:
  We study to what extent the effective-one-body description of the dynamical
state of a nonspinning, coalescing binary black hole (considered either at
merger, or after ringdown) agrees with numerical relativity results. This
comparison uses estimates of the integrated losses of energy and angular
momentum during ringdown, inferred from recent numerical-relativity data. We
find that the values, predicted by the effective-one-body formalism, of the
energy and angular momentum of the system agree at the per mil level with their
numerical-relativity counterparts, both at merger and in the final state. This
gives a new confirmation of the ability of effective-one-body theory to
accurately describe the dynamics of binary black holes even in the
strong-gravitational-field regime. Our work also provides predictions (and
analytical fits) for the final mass and the final spin of coalescing black
holes for all mass ratios


title:
Modelling workplace contact networks: the effects of organizational
  structure, architecture, and reporting errors on epidemic predictions

abstract:
  Face-to-face social contacts are potentially important transmission routes
for acute respiratory infections, and understanding the contact network can
improve our ability to predict, contain, and control epidemics. Although
workplaces are important settings for infectious disease transmission, few
studies have collected workplace contact data and estimated workplace contact
networks. We use contact diaries, architectural distance measures, and
institutional structures to estimate social contact networks within a Swiss
research institute. Some contact reports were inconsistent, indicating
reporting errors. We adjust for this with a latent variable model, jointly
estimating the true (unobserved) network of contacts and duration-specific
reporting probabilities. We find that contact probability decreases with
distance, and research group membership, role, and shared projects are strongly
predictive of contact patterns. Estimated reporting probabilities were low only
for 0-5 minute contacts. Adjusting for reporting error changed the estimate of
the duration distribution, but did not change the estimates of covariate
effects and had little effect on epidemic predictions. Our epidemic simulation
study indicates that inclusion of network structure based on architectural and
organizational structure data can improve the accuracy of epidemic forecasting
models.


title:
The spin-$\frac{1}{2}$ XXZ chain system Cs$_2$CoCl$_4$ in a transverse
  magnetic field

abstract:
  Comparing high-resolution specific heat and thermal expansion measurements to
exact finite-size diagonalization, we demonstrate that Cs$_2$CoCl$_4$ for a
magnetic field along the crystallographic b axis realizes the
spin-$\frac{1}{2}$ XXZ chain in a transverse field. Exploiting both thermal as
well as virtual excitations of higher crystal field states, we find that the
spin chain is in the XY-limit with an anisotropy $J_z/J_\perp \approx 0.12$
substantially smaller than previously believed. A spin-flop Ising quantum phase
transition occurs at a critical field of $\mu_0 H_b^{\rm cr} \approx 2$ T
before around 3.5 T the description in terms of an effective spin-$\frac{1}{2}$
chain becomes inapplicable.


title:
Existence of nonparametric solutions for a capillary problem in warped
  products

abstract:
  We prove that there exist solutions for a non-parametric capillary problem in
a wide class of Riemannian manifolds endowed with a Killing vector field. In
other terms, we prove the existence of Killing graphs with prescribed mean
curvature and prescribed contact angle along its boundary. These results may be
useful for modelling stationary hypersurfaces under the influence of a
non-homogeneous gravitational field defined over an arbitrary Riemannian
manifold.


title: Laser Probing of Neutron-Rich Nuclei in Light Atoms

abstract:
  The neutron-rich 6He and 8He isotopes exhibit an exotic nuclear structure
that consists of a tightly bound 4He-like core with additional neutrons
orbiting at a relatively large distance, forming a halo. Recent experimental
efforts have succeeded in laser trapping and cooling these short-lived, rare
helium atoms, and have measured the atomic isotope shifts along the 4He-6He-8He
chain by performing laser spectroscopy on individual trapped atoms. Meanwhile,
the few-electron atomic structure theory, including relativistic and QED
corrections, has reached a comparable degree of accuracy in the calculation of
the isotope shifts. In parallel efforts, also by measuring atomic isotope
shifts, the nuclear charge radii of lithium and beryllium isotopes have been
studied. The techniques employed were resonance ionization spectroscopy on
neutral, thermal lithium atoms and collinear laser spectroscopy on beryllium
ions. Combining advances in both atomic theory and laser spectroscopy, the
charge radii of these light halo nuclei have now been determined for the first
time independent of nuclear structure models. The results are compared with the
values predicted by a number of nuclear structure calculations, and are used to
guide our understanding of the nuclear forces in the extremely neutron-rich
environment.


title: Doubly Charmed Tetraquarks in B_c and Xi_bc Decays

abstract:
  The phenomenology of the so-called X, Y and Z hadronic resonances is hard to
reconcile with standard charmonium or bottomonium interpretations. It has been
suggested that some of these new hadrons can possibly be described as tightly
bound tetraquark states and/or as loosely bound two-meson molecules. In the
present paper we focus on the hypothetical existence of flavored, doubly
charmed, tetraquarks. Such states might also carry double electric charge, and
in this case, if discovered, they could univocally be interpreted in terms of
compact tetraquarks. Flavored tetraquarks are also amenable to lattice studies
as their interpolating operators do not overlap with ordinary meson ones. We
show that doubly charmed tetraquarks could significantly be produced at LHC
from B_c or Xi_bc heavy baryons.


title: Hard X-ray and ultraviolet emission during the 2011 June 7 solar flare

abstract:
  The relationship between X-ray and UV emission during flares, particularly in
the context of quasi-periodic pulsations, remains unclear. To address this, we
study the impulsive X-ray and UV emission during the eruptive flare of 2011
June 7 utilising X-ray imaging from RHESSI and UV 1700A imaging from SDO/AIA.
This event is associated with quasi-periodic pulsations in X-ray and possibly
UV emission, as well as substantial parallel and perpendicular motion of the
hard X-ray footpoints.
  The motion of the footpoints parallel to the flare ribbons is unusual; it is
shown to reverse direction on at least two occasions. However, there is no
associated short-timescale motion of the UV bright regions. Additionally, we
find that the locations of the brightest X-ray and UV regions are different,
particularly during the early portion of the flare impulsive phase, despite
their integrated emission being strongly correlated in time. Correlation
analysis of measured flare properties, such as the footpoint separation, flare
shear, photospheric magnetic field and coronal reconnection rate, reveals that
- in the impulsive phase - the 25 - 50 keV hard X-ray flux is only weakly
correlated with these properties, in contrast to previous studies.
  We characterise this event in terms of long-term behaviour, where the X-ray
nonthermal, thermal, and UV emission sources appear temporally and spatially
consistent, and short-term behaviour, where the emission sources are
inconsistent and quasi-periodic pulsations are a dominant feature requiring
explanation. We suggest that the short timescale behaviour of hard X-ray
footpoints, and the nature of the observed quasi-periodic pulsations, is
determined by fundamental, as-yet unobserved properties of the reconnection
region and particle acceleration sites. This presents a challenge for current
three-dimensional flare reconnection models.


title: A comment on "Boson stars in AdS"

abstract:
  We comment on asymptotically AdS "large-$\sigma$" initial data, studied in
Phys. Rev. D87, 123006 (2013) [arXiv:1304.4166], that are immune to turbulent
instability.


title: Aspects of elliptic hypergeometric functions

abstract:
  General elliptic hypergeometric functions are defined by elliptic
hypergeometric integrals. They comprise the elliptic beta integral, elliptic
analogues of the Euler-Gauss hypergeometric function and Selberg integral, as
well as elliptic extensions of many other plain hypergeometric and
$q$-hypergeometric constructions. In particular, the Bailey chain technique,
used for proving Rogers-Ramanujan type identities, has been generalized to
integrals. At the elliptic level it yields a solution of the Yang-Baxter
equation as an integral operator with an elliptic hypergeometric kernel. We
give a brief survey of the developments in this field.


title: Wigner function and the successive measurement of position and momentum

abstract:
  Wigner function is a quasi-distribution that provides a representation of the
state of a quantum mechanical system in the phase space of position and
momentum. In this paper we find a relation between Wigner function and
appropriate measurements involving the system position and momentum which
generalize the von Neumann model of measurement. We introduce two probes
coupled successively in time to projectors associated with the system position
and momentum. We show that one can relate Wigner function to Kirkwood joint
quasi-distribution of position and momentum, the latter, in turn, being a
particular case of successive measurements. We first consider the case of a
quantum mechanical system described in a continuous Hilbert space, and then
turn to the case of a discrete, finite-dimensional Hilbert space.


title: Randomly charged polymers in porous environment

abstract:
  We study the conformational properties of charged polymers in a solvent in
the presence of structural obstacles correlated according to a power law $\sim
x^{-a}$. We work within the continuous representation of a model of linear
chain considered as a random sequence of charges $q_i=\pm q_0$. Such a model
captures the properties of polyampholytes -- heteropolymers comprising both
positively and negatively charged monomers. We apply the direct polymer
renormalization scheme and analyze the scaling behavior of charged polymers up
to the first order of an $\epsilon=6-d$, $\delta=4-a$-expansion.


title: Secondary fans and Tropical Severi varieties

abstract:
  This article studies the relationship between tropical Severi varieties and
secondary fans. In the case when tropical Severi varieties are hypersurfaces
this relationship is very well known; specifically, in this case, a tropical
Severi variety of codimension 1 is a subfan of the corresponding secondary fan.
It was expected for some time that this continues to hold more generally, but
Katz found a counterexample in codimension 2, showing that this relationship is
more subtle. The two main results in this paper are as follows. The first
theorem finds a simple condition under which a tropical Severi variety cannot
be a subfan of the corresponding secondary fan. The second theorem provides a
partial converse, namely, we find conditions under which a cone of the
secondary fan is fully contained in the tropical Severi variety. As a first
application of these results, we also find a combinatorial formula for the
tropical intersection multiplicities for secondary fans.


title: Composite Inflation confronts BICEP2 and PLANCK

abstract:
  We examine observational constraints on single-field inflation in which the
inflaton is a composite field stemming from a four-dimensional strongly
interacting field theory. We confront the predictions with the Planck and very
recent BICEP2 data. In the large non-minimal coupling regions, we discover for
MCI model that the predictions lie well inside the joint $68\%$ CL for the
Planck data, but is in tension with the recent BICEP2 observations. In the case
of the GI model, the predictions satisfy the Planck results. However, this
model can produce a large tensor-to-scalar ratio consistent with the recent
BICEP2 observations if the number of e-foldings is slightly smaller than the
range commonly used. For a super Yang-Mills paradigm, we discover that the
predictions satisfy the Planck data, and surprisingly a large tensor-to-scalar
ratio consistent with the BICEP2 results can also be produced for an acceptable
range of the number of e-foldings and of the confining scale. In the small
non-minimal coupling regions, all of the models can satisfy the BICEP2 results.
However, the predictions of GI and SgbI models cannot satisfy the observational
bound on the amplitude of the curvature perturbation launched by Planck, and
the techni-inflaton self-coupling in the MCI model is constrained to be
extremely small.


title: Freezing and melting of vortex ice

abstract:
  We report on the realization of artificial ice using superconducting vortices
in geometrically frustrated pinning arrays. This vortex ice shows two unique
properties among artificial ice systems. The first comes from the possibility
to switch the array geometric frustration on/off through temperature
variations, which allows "freezing" and "melting" the vortex ice. The second is
that the depinning and dynamics of the frozen vortex ice are insensitive to
annealing, which implies that the ordered ground state is spontaneously
approached. The major role of thermal fluctuations and the strong vortex-vortex
interactions are at the origin of this unusual behavior.


title: Holographic geometries for condensed matter applications

abstract:
  Holographic modeling of strongly correlated many-body systems motivates the
study of novel spacetime geometries where the scaling behavior of quantum
critical systems is encoded into spacetime symmetries. Einstein-Dilaton-Maxwell
theory has planar black brane solutions that exhibit Lifshitz scaling and in
some cases hyperscaling violation. Entanglement entropy and Wilson loops in the
dual field theory are studied by inserting simple geometric probes involving
minimal surfaces into the black brane geometry. Coupling to background matter
fields leads to interesting low-energy behavior in holographic models, such as
U(1) symmetry breaking and emergent Lifshitz scaling.


title: Cooling of atomic ensembles in optical cavities: Semiclassical limit

abstract:
  The semiclassical dynamics of atoms are theoretically studied, when the atoms
are confined inside a standing-wave high-finesse resonator. The atoms are
cooled by scattering processes in which the photons of a transverse laser are
coherently scattered into the cavity mode. We derive a Fokker-Planck equation
for the atomic center-of-mass variables which allows us to determine the
equations of motion in the semiclassical limit for any value of the intensity
of the laser field. We extract its prediction for the dynamics when the
resonator is essentially in the vacuum state and the atoms are cooled by
scattering photons into the cavity mode, which then decays. Its predictions for
the stationary atomic distribution are compared with the ones of the
Fokker-Planck equation in [P. Domokos, P. Horak, and H. Ritsch, J. Phys. B 34,
187 (2001)], which has been derived under different assumptions. We find full
agreement in the considered parameter regime.


title: Spin- and valley-dependent magneto-optical properties of MoS2

abstract:
  We investigate the behavior of low-energy electrons in two-dimensional
molybdenum disulfide when submitted to an external magnetic field. Highly
degenerate Landau levels form in the material, between which light-induced
excitations are possible. The dependence of excitations on light polarization
and energy is explicitly determined, and it is shown that it is possible to
induce valley and spin polarization, i.e. to excite electrons of selected
valley and spin. Whereas the effective low-energy model in terms of massive
Dirac fermions yields dipole-type selection rules, higher-order band
corrections allow for the observation of additional transitions. Furthermore,
inter-Landau-level transitions involving the n=0 levels provide a reliable
method for an experimental measurement of the gap and the spin-orbit gap of
molybdenum disulfide.


title: Persistent spin currents in an elastic Landau system

abstract:
  We consider a neutral particle with permanent magnetic dipole moment in an
elastic medium with the presence of a uniform distribution of screw
dislocations interacting with a radial electric field. We show that the uniform
distribution of dislocations plays the role of an effective uniform magnetic
field, and obtain a spectrum of energy which depends on the Aharonov-Casher
geometric phase [Y. Aharonov and A. Casher, Phys. Rev. Lett. 53, 319 (1984)].
Moreover, from the dependence of energy levels on the Aharonov-Casher geometric
phase, we calculate the persistent spin currents in this elastic Landau system.

categories: quant-ph cond-mat.mes-hall math-ph math.MP


title:
Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like
  Star GJ 504

abstract:
  Several exoplanets have recently been imaged at wide separations of >10 AU
from their parent stars. These span a limited range of ages (<50 Myr) and
atmospheric properties, with temperatures of 800--1800 K and very red colors (J
- H > 0.5 mag), implying thick cloud covers. Furthermore, substantial model
uncertainties exist at these young ages due to the unknown initial conditions
at formation, which can lead to an order of magnitude of uncertainty in the
modeled planet mass. Here, we report the direct imaging discovery of a Jovian
exoplanet around the Sun-like star GJ 504, detected as part of the SEEDS
survey. The system is older than all other known directly-imaged planets; as a
result, its estimated mass remains in the planetary regime independent of
uncertainties related to choices of initial conditions in the exoplanet
modeling. Using the most common exoplanet cooling model, and given the system
age of 160 [+350, -60] Myr, GJ 504 b has an estimated mass of 4 [+4.5, -1.0]
Jupiter masses, among the lowest of directly imaged planets. Its projected
separation of 43.5 AU exceeds the typical outer boundary of ~30 AU predicted
for the core accretion mechanism. GJ 504 b is also significantly cooler (510
[+30, -20] K) and has a bluer color (J-H = -0.23 mag) than previously imaged
exoplanets, suggesting a largely cloud-free atmosphere accessible to
spectroscopic characterization. Thus, it has the potential of providing novel
insights into the origins of giant planets, as well as their atmospheric
properties.


title: Total variation cutoff in a tree

abstract:
  We construct a family of trees on which a lazy simple random walk exhibits
total variation cutoff. The main idea behind the construction is that hitting
times of large sets should be concentrated around their means. For this
sequence of trees we compute the mixing time, the relaxation time and the
cutoff window.


title:
On the interaction of the Dirac oscillator with the Aharonov-Casher
  system in topological defect backgrounds

abstract:
  In this paper, we study the influence of the Aharonov-Casher effect [Y.
Aharonov and A. Casher, Phys. Rev. Lett. 53, 319 (1984).] on the Dirac
oscillator in three different scenarios of general relativity: the Minkowski
spacetime, the cosmic string spacetime and the cosmic dislocation spacetime. In
this way, we solve the Dirac equation and obtain the energy levels for bound
states and the Dirac spinors for positive-energy solutions. We show that the
relativistic energy levels depend on the Aharonov-Casher geometric phase. We
also discuss the influence of curvature and torsion on the relativistic energy
levels and the Dirac spinors due to the topology of the cosmic string and
cosmic dislocation spacetimes.


title:
Achieving the Uniform Rate Region of General Multiple Access Channels by
  Polar Coding

abstract:
  We consider the problem of polar coding for transmission over $m$-user
multiple access channels. In the proposed scheme, all users encode their
messages using a polar encoder, while a multi-user successive cancellation
decoder is deployed at the receiver. The encoding is done separately across the
users and is independent of the target achievable rate. For the code
construction, the positions of information bits and frozen bits for each of the
users are decided jointly. This is done by treating the polar transformations
across all the $m$ users as a single polar transformation with a certain
\emph{polarization base}. We characterize the resolution of achievable rates on
the dominant face of the uniform rate region in terms of the number of users
$m$ and the length of the polarization base $L$. In particular, we prove that
for any target rate on the dominant face, there exists an achievable rate, also
on the dominant face, within the distance at most $\frac{(m-1)\sqrt{m}}{L}$
from the target rate. We then prove that the proposed MAC polar coding scheme
achieves the whole uniform rate region with fine enough resolution by changing
the decoding order in the multi-user successive cancellation decoder, as $L$
and the code block length $N$ grow large. The encoding and decoding
complexities are $O(N \log N)$ and the asymptotic block error probability of
$O(2^{-N^{0.5 - \epsilon}})$ is guaranteed. Examples of achievable rates for
the $3$-user multiple access channel are provided.


title:
The stability of tidally deformed neutron stars to three- and four-mode
  coupling

abstract:
  It has recently been suggested that the tidal deformation of a neutron star
excites daughter p- and g-modes to large amplitudes via a quasi-static
instability. This would remove energy from the tidal bulge, resulting in
dissipation and possibly affecting the phase evolution of inspiralling binary
neutron stars and hence the extraction of binary parameters from gravitational
wave observations. This instability appears to arise because of a large
three-mode interaction among the tidal mode and high-order p- and g-modes of
similar radial wavenumber. We show that additional four-mode interactions enter
into the analysis at the same order as the three-mode terms previously
considered. We compute these four-mode couplings by finding a volume-preserving
coordinate transformation that relates the energy of a tidally deformed star to
that of a radially perturbed spherical star. Using this method, we relate the
four-mode coupling to three-mode couplings and show that there is a near-exact
cancellation between the destabilizing effect of the three-mode interactions
and the stabilizing effect of the four-mode interaction. We then show that the
equilibrium tide is stable against the quasi-static decay into daughter p- and
g-modes to leading order. The leading deviation from the quasi-static
approximation due to orbital motion of the binary is considered; while it may
slightly spoil the near-cancellation, any resulting instability timescale is at
least of order the gravitational-wave inspiral time. We conclude that the
p-/g-mode coupling does not lead to a quasi-static instability, and does not
impact the phase evolution of gravitational waves from binary neutron stars.


title: Observational studies of stellar rotation

abstract:
  This course reviews the rotational properties of non-degenerate stars as
observed from the protostellar stage to the end of the main sequence. It
includes an introduction to the various observational techniques used to
measure stellar rotation. Angular momentum evolution models developed over the
mass range from the substellar domain to high-mass stars are briefly discussed


title: Quantum corrections to holographic entanglement entropy

abstract:
  We consider entanglement entropy in quantum field theories with a gravity
dual. In the gravity description, the leading order contribution comes from the
area of a minimal surface, as proposed by Ryu-Takayanagi. Here we describe the
one loop correction to this formula. The minimal surface divides the bulk into
two regions. The bulk loop correction is essentially given by the bulk
entanglement entropy between these two bulk regions. We perform some simple
checks of this proposal.


title: Coexistence in preferential attachment networks

abstract:
  We introduce a new model of competition on growing networks. This extends the
preferential attachment model, with the key property that node choices evolve
simultaneously with the network. When a new node joins the network, it chooses
neighbours by preferential attachment, and selects its type based on the number
of initial neighbours of each type. The model is analysed in detail, and in
particular, we determine the possible proportions of the various types in the
limit of large networks. An important qualitative feature we find is that, in
contrast to many current theoretical models, often several competitors will
coexist. This matches empirical observations in many real-world networks.


title:
A Mass-Dependent Yield Origin of Neutron-Capture Element Abundance
  Distributions in Ultra-Faint Dwarfs

abstract:
  One way to constrain the nature of the high-redshift progenitors of the Milky
Way is to look at the low-metallicity stellar populations of the different
Galactic components today. For example, high-resolution spectroscopy of very
metal poor (VMP) stars demonstrates remarkable agreement between the
distribution of [Ti/Fe] in the stellar populations of the Milky Way halo (MW)
and ultra-faint dwarf (UFD) galaxies. In contrast, for the neutron capture (nc)
abundance ratio distributions [(Sr,Ba)/Fe], the peak of the small UFD sample (6
stars) exhibits a signicant under-abundance relative to the VMP stars in the
larger MW halo sample (~ 300 stars). We present a simple scenario that can
simultaneously explain these similarities and differences by assuming: (i) that
the MW VMP stars were predominately enriched by a prior generation of stars
which possessed a higher total mass than the prior generation of stars that
enriched the UFD VMP stars; and (ii) a much stronger mass-dependent yield (MDY)
for nc-elements than for the (known) MDY for Ti. Simple statistical tests
demonstrate that conditions (i) and (ii) are consistent with the observed
abundance distributions, albeit without strong constraints on model parameters.
A comparison of the broad constraints for these nc-MDY with those derived in
the literature seems to rule out Ba production from low-mass SNs and affirms
models that primarily generate yields from high-mass SN. Our scenario can be
confirmed by a relatively modest (factor of ~ 3-4) increase in the number of
high-resolution spectra of VMP stars in UFDs.


title:
Hierarchical interpolative factorization for elliptic operators:
  differential equations

abstract:
  This paper introduces the hierarchical interpolative factorization for
elliptic partial differential equations (HIF-DE) in two (2D) and three
dimensions (3D). This factorization takes the form of an approximate
generalized LU/LDL decomposition that facilitates the efficient inversion of
the discretized operator. HIF-DE is based on the multifrontal method but uses
skeletonization on the separator fronts to sparsify the dense frontal matrices
and thus reduce the cost. We conjecture that this strategy yields linear
complexity in 2D and quasilinear complexity in 3D. Estimated linear complexity
in 3D can be achieved by skeletonizing the compressed fronts themselves, which
amounts geometrically to a recursive dimensional reduction scheme. Numerical
experiments support our claims and further demonstrate the performance of our
algorithm as a fast direct solver and preconditioner. MATLAB codes are freely
available.


title:
Equilibrium Star Formation In A Constant Q Disk: Model Optimisation and
  Initial Tests

abstract:
  We develop a model for the distribution of the ISM and star formation in
galaxies based on recent studies that indicate that galactic disks stabilise to
a constant stability parameter, which we combine with prescriptions of how the
phases of the ISM are determined and for the Star Formation Law (SFL). The
model predicts the gas surface mass density and star formation intensity of a
galaxy given its rotation curve, stellar surface mass density and the gas
velocity dispersion. This model is tested on radial profiles of neutral and
molecular ISM surface mass density and star formation intensity of 12 galaxies
selected from the THINGS sample. Our tests focus on intermediate radii.
Nevertheless, the model produces reasonable agreement with ISM mass and star
formation rate integrated over the central region in all but one case. To
optimise the model, we evaluate four recipes for the stability parameter, three
recipes for apportioning the ISM into molecular and neutral components, and
eight versions of the SFL. We find no clear-cut best prescription for the
two-fluid (gas and stars) stability parameter Q_2f and therefore for
simplicity, we use the Wang&Silk(1994) approximation (Q_WS). We found that an
empirical scaling between the molecular to neutral ISM ratio (R_mol) and the
stellar surface mass density proposed by Leroy et al. (2008) works marginally
better than the other two prescriptions for this ratio in predicting the ISM
profiles, and noticeably better in predicting star formation intensity from the
ISM profiles produced by our model with the SFLs we tested. Thus in the context
of our modeled ISM profiles, the linear molecular SFL and the two-component SFL
(Krumholz et al. 2009) work better than the other prescriptions we tested. We
incorporate these relations into our `Constant Q disk' (CQ-disk) model.


title: Making systems of Super Earths by inward migration of planetary embryos

abstract:
  Using N-body simulations with planet-disk interactions, we present a
mechanism capable of forming compact systems of hot super Earths such as Kepler
11. Recent studies show that outward migration is common in the inner parts of
radiative disks. However we show that two processes naturally tip the balance
in favor of inward migration. First the corotation torque is too weak to
generate outward migration for planetary embryos less massive than $4\mearth$.
Second, system of multiple embryos generate sustained non-zero eccentricities
that damp the corotation torque and again favor inward migration. Migration and
accretion of planetary embryos in realistic disks naturally produce super
Earths in resonant chains near the disk inner edge. Their compact configuration
is similar to the observed systems.


title:
Unveiling the nature of INTEGRAL objects through optical spectroscopy.
  X. A new multi-year, multi-observatory campaign

abstract:
  Within the framework of our program (running since 2004) of identification of
hard X-ray INTEGRAL sources through optical spectroscopy, we present the
results concerning the nature of 33 high-energy objects. The data were acquired
with the use of six telescopes of different sizes and from one on-line archive.
The results indicate that the majority of these objects (23 out of 33) are
active galactic nuclei (AGNs), whereas 10 are sources in the local Universe
with eight of which in the Galaxy and two in the Small Magellanic Cloud (SMC).
Among the identified AGNs, 13 are of Type 1 (i.e., with broad emission lines),
eight are of Type 2 (with narrow emissions only), and two are X-ray bright,
optically normal galaxies with no apparent nuclear activity in the optical. Six
of these AGNs lie at high redshift (z > 0.5). Concerning local objects, we
found that five of them are Galactic cataclysmic variables, three are high-mass
X-ray binaries (two of which lying in the SMC), one is a low-mass X-ray binary,
and one is classified as a flare star that is likely of RS CVn type. The main
optical properties and inferred physical characteristics of these sources are
presented and discussed.


title:
Probing Our Heliospheric History I: High-Resolution Observations of Na I
  and Ca II Along the Solar Historical Trajectory

abstract:
  Over the course of its motion through the Galaxy, our solar system has
encountered many interstellar environments of varying characteristics.
Interstellar medium (ISM) density variations spanning seven orders of magnitude
are commonly seen throughout the general Galactic environment, and a
sufficiently dense cloud within this range has the potential to dramatically
alter the structure of the heliosphere. We present observations of the ISM
environments the Sun has most recently encountered based on high-resolution
optical spectra toward nearby stars in the direction of the historical solar
trajectory. The data were obtained with the highest-resolution spectrographs
available, including the Tull Spectrograph on the Harlan J. Smith Telescope at
McDonald Observatory and the Ultra-High-Resolution Facility on the
Anglo-Australian Telescope at the Anglo-Australian Observatory. Observations
were made of interstellar Na I and Ca II doublet absorption toward 43 bright
stars within about 500 pc. No absorption is seen out to a distance of 120 pc
(consistent with the outer boundary of the Local Bubble), but a complex
collection of absorbers is seen in stars beyond 120 pc. While common absorbers
are consistently seen in most sight lines, significant spatial variation is
also detected, even between closely spaced sight lines. This pervasive evidence
of small-scale structure not only speaks to the complexity of the morphology or
physical properties of the gas in the ISM, but also emphasizes that dramatic
structural changes to the heliosphere are common and it is important to
understand the implications of such changes, such as the modulation in the
cosmic ray flux, on planets.


title:
Spoon-Feeding Giant Stars to Supermassive Black Holes: Episodic Mass
  Transfer from Evolving Stars and Their Contribution to the Quiescent Activity
  of Galactic Nuclei

abstract:
  Stars may be tidally disrupted if, in a single orbit, they are scattered too
close to a supermassive black hole (SMBH). Tidal disruption events are thought
to power luminous but short-lived accretion episodes that can light up
otherwise quiescent SMBHs in transient flares. Here we explore a more gradual
process of tidal stripping where stars approach the tidal disruption radius by
stellar evolution while in an eccentric orbit. After the onset of mass
transfer, these stars episodically transfer mass to the SMBH every pericenter
passage giving rise to low-level flares that repeat on the orbital timescale.
Giant stars, in particular, will exhibit a runaway response to mass loss and
"spoon-feed" material to the black hole for tens to hundreds of orbital
periods. In contrast to full tidal disruption events, the duty cycle of this
feeding mode is of order unity for black holes with mass greater than
approximately 10 million solar masses. This mode of quasi-steady SMBH feeding
is competitive with indirect SMBH feeding through stellar winds, and spoon-fed
giant stars may play a significant role in determining the quiescent luminosity
of local SMBHs.


title:
The Power of Neutrino Mass Sum Rules for Neutrinoless Double Beta Decay
  Experiments

abstract:
  Neutrino mass sum rules relate the three neutrino masses within generic
classes of flavour models, leading to restrictions on the effective mass
parameter measured in experiments on neutrinoless double beta decay as a
function of the lightest neutrino mass. We perform a comprehensive study of the
implications of such neutrino mass sum rules, which provide a link between
model building, phenomenology, and experiments. After a careful explanation of
how to derive predictions from sum rules, we discuss a large number of examples
both numerically, using all three global fits available for the neutrino
oscillation data, and analytically wherever possible. In some cases, our
results disagree with some of those in the literature for reasons that we
explain. Finally we discuss the experimental prospects for many current and
near-future experiments, with a particular focus on the uncertainties induced
by the unknown nuclear physics involved. We find that, in many cases, the power
of the neutrino mass sum rules is so strong as to allow certain classes of
models to be tested by the next generation of neutrinoless double beta decay
experiments. Our study can serve as both a guideline and a theoretical
motivation for future experimental studies.


title: SU(5) Tops with Multiple U(1)s in F-theory

abstract:
  We study F-theory compactifications with up to two Abelian gauge group
factors that are based on elliptically fibered Calabi-Yau 4-folds describable
as generic hypersurfaces. Special emphasis is put on elliptic fibrations based
on generic Bl^2 P^2[3]-fibrations. These exhibit a Mordell-Weil group of rank
two corresponding to two extra rational sections which give rise to two Abelian
gauge group factors. We show that an alternative description of the same
geometry as a complete intersection makes the existence of a holomorphic
zero-section manifest, on the basis of which we compute the U(1) generators and
a class of gauge fluxes. We analyse the fibre degenerations responsible for the
appearance of localised charged matter states, whose charges, interactions and
chiral index we compute geometrically. We implement an additional SU(5) gauge
group by constructing the four inequivalent toric tops giving rise to SU(5) x
U(1) x U(1) gauge symmetry and analyse the matter content. We demonstrate that
notorious non-flat points can be avoided in well-defined Calabi-Yau 4-folds.
These methods are applied to the remaining possible hypersurface fibrations
with one generic Abelian gauge factor. We analyse the local limit of our SU(5)
x U(1) x U(1) models and show that one of our models is not embeddable into E8
due to recombination of matter curves that cannot be described as a Higgsing of
E8. We argue that such recombination forms a general mechanism that opens up
new model building possibilities in F-theory.


title:
SPT-CLJ2040-4451: An SZ-Selected Galaxy Cluster at z = 1.478 With
  Significant Ongoing Star Formation

abstract:
  SPT-CLJ2040-4451 -- spectroscopically confirmed at z = 1.478 -- is the
highest redshift galaxy cluster yet discovered via the Sunyaev-Zel'dovich
effect. SPT-CLJ2040-4451 was a candidate galaxy cluster identified in the first
720 deg^2 of the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey, and
confirmed in follow-up imaging and spectroscopy. From multi-object spectroscopy
with Magellan-I/Baade+IMACS we measure spectroscopic redshifts for 15 cluster
member galaxies, all of which have strong [O II] 3727 emission.
SPT-CLJ2040-4451 has an SZ-measured mass of M_500,SZ = 3.2 +/- 0.8 X 10^14
M_Sun/h_70, corresponding to M_200,SZ = 5.8 +/- 1.4 X 10^14 M_Sun/h_70. The
velocity dispersion measured entirely from blue star forming members is sigma_v
= 1500 +/- 520 km/s. The prevalence of star forming cluster members (galaxies
with > 1.5 M_Sun/yr) implies that this massive, high-redshift cluster is
experiencing a phase of active star formation, and supports recent results
showing a marked increase in star formation occurring in galaxy clusters at z
>1.4. We also compute the probability of finding a cluster as rare as this in
the SPT-SZ survey to be >99%, indicating that its discovery is not in tension
with the concordance Lambda-CDM cosmological model.


title: (Lack of) Cosmological evidence for dark radiation after Planck

abstract:
  We use Bayesian model comparison to determine whether extensions to
Standard-Model neutrino physics -- primarily additional effective numbers of
neutrinos and/or massive neutrinos -- are merited by the latest cosmological
data. Given the significant advances in cosmic microwave background (CMB)
observations represented by the Planck data, we examine whether Planck
temperature and CMB lensing data, in combination with lower redshift data, have
strengthened (or weakened) the previous findings. We conclude that the
state-of-the-art cosmological data do not show evidence for deviations from the
standard cosmological model (which has three massless neutrino families). This
does not mean that the model is necessarily correct -- in fact we know it is
incomplete as neutrinos are not massless -- but it does imply that deviations
from the standard model (e.g., non-zero neutrino mass) are too small compared
to the current experimental uncertainties to be inferred from cosmological data
alone.


title:
VGS31b: a highly inclined ring along a filament in a void. Implication
  for the cold accretion

abstract:
  VGS31b is a highly-inclined ring galaxy found along a filament in a void
(Kreckel et al. 2012). Detailed photometry, by using u, g, r, i, z SDSS images,
has shown that the overall morphology of VGS31b is very tricky, due to (i) the
presence of a highly inclined (72 deg) ring-like structure, which reaches the
galaxy center tracing a "spiral-like" pattern, (ii) a one sided tail towards
North-East and (iii) a bar in the central regions (Beygu et al. 2013). Such
structure is reasonably the result of a "second event" in the evolution history
of this galaxy, which could be a gravitational interaction with a companion
galaxy or with the environment.
  The main aim of the present work is to address the most reliable formation
scenario for this object, by comparing the observed properties, i.e. structure,
baryonic mass, kinematics and chemical abundances, with the theoretical
predictions. In particular, we have used archival spectroscopic data, to derive
the metallicity in the ring: we found a very low, sub-solar average value of Z
= 0.3 Zsun, comparable with other polar ring/disk galaxies, but lower than
those measured for ordinary spirals of similar luminosity. The study of the
chemical abundances in polar ring/disk galaxies and related objects has
received an increasing attention in recent years, since it has revealed to be a
key-parameter to disentangle among the formation scenarios suggested for this
class of objects: major merging, tidal accretion or cold accretion. In the
present work we check the cold accretion of gas through a "cosmic filament" as
a possible scenario for the formation of the ring-like structure in VGS31b.


title: Redshift Space Distortion Reconstruction

abstract:
  Redshift space distortions of the matter density power spectrum carry
information on the growth rate of cosmic structure but require accurate
modeling of nonlinear and velocity effects on the density field. We test and
advance the reconstruction function of Kwan, Lewis, Linder (2012) in several
ways. First, we compare to the distribution function perturbative approach of
Seljak & McDonald (2012), deriving the mapping between them and showing how the
KLL form can extend the validity of the latter. Second, using cosmological
simulations rather than perturbation theory we calibrate the free functions
within the KLL reconstruction form and fit their behavior in redshift and
wavenumber. An efficient, new analysis pipeline rapidly calculates from
simulation outputs the redshift space power spectrum. The end result is a
robust analytic reconstruction function mapping the linear, real space matter
power spectrum to the nonlinear, anisotropic redshift space power spectrum to
an accuracy of ~2-5% in the range k=0.1-0.5 h/Mpc for z=0-2. As a by-product we
derive RealEasy, an analytic mapping to the nonlinear, real space matter power
spectrum (i.e. an analog to Halofit) to ~1% accuracy over the same range. We
also investigate an approach converse to KLL and find it to be complementary
and capable of achieving an accuracy of ~2-4% over the range k=0.3-1 h/Mpc for
z=0-2.


title:
Bandwidth smearing in infrared long-baseline interferometry. Application
  to stellar companion search in fringe-scanning mode

abstract:
  In long-baseline interferometry, bandwidth smearing of an extended source
occurs at finite bandwidth when its different components produce interference
packets that only partially overlap. In this case, traditional model fitting or
image reconstruction using standard formulas and tools lead to biased results.
  We propose and implement a method to overcome this effect by calculating
analytically a corrective term for the conventional interferometric
observables: the visibility amplitude and closure phase. For that purpose, we
model the interferogram taking into account the finite bandwidth and the
instrumental differential phase. We obtain generic expressions for the
visibility and closure phase in the case of temporally-modulated
interferograms, either processed using Fourier analysis or with the ABCD
method. The expressions can be used to fit arbitrary models to the data. We
then apply our results to the search and characterisation of stellar companions
with PIONIER at the Very Large Telescope Interferometer, assessing the bias on
observables and model-fitted parameters of a binary star. Finally, we consider
the role of the atmosphere, with an analytic model to identify the main
contributions to bias and also a numerical simulation of the turbulence.
  In addition to the analytic expressions, the main results of our study are:
the chromatic dispersion in the beam transport in the instrument has a strong
impact on the closure phase and introduces additional biases even at
separations where smearing is not expected to play an important role; the
atmospheric turbulence introduces additional biases when smearing is present,
but the impact is important only at very low spectral resolution; the bias on
the observables strongly depends on the recombination scheme and data
processing; the goodness of fits is improved by modelling a Gaussian bandpass
as long as the smearing is moderate.


title:
Cake Cutting Algorithms for Piecewise Constant and Piecewise Uniform
  Valuations

abstract:
  Cake cutting is one of the most fundamental settings in fair division and
mechanism design without money. In this paper, we consider different levels of
three fundamental goals in cake cutting: fairness, Pareto optimality, and
strategyproofness. In particular, we present robust versions of envy-freeness
and proportionality that are not only stronger than their standard
counter-parts but also have less information requirements. We then focus on
cake cutting with piecewise constant valuations and present three desirable
algorithms: CCEA (Controlled Cake Eating Algorithm), MEA (Market Equilibrium
Algorithm) and CSD (Constrained Serial Dictatorship). CCEA is polynomial-time,
robust envy-free, and non-wasteful. It relies on parametric network flows and
recent generalizations of the probabilistic serial algorithm. For the subdomain
of piecewise uniform valuations, we show that it is also group-strategyproof.
Then, we show that there exists an algorithm (MEA) that is polynomial-time,
envy-free, proportional, and Pareto optimal. MEA is based on computing a
market-based equilibrium via a convex program and relies on the results of
Reijnierse and Potters [24] and Devanur et al. [15]. Moreover, we show that MEA
and CCEA are equivalent to mechanism 1 of Chen et. al. [12] for piecewise
uniform valuations. We then present an algorithm CSD and a way to implement it
via randomization that satisfies strategyproofness in expectation, robust
proportionality, and unanimity for piecewise constant valuations. For the case
of two agents, it is robust envy-free, robust proportional, strategyproof, and
polynomial-time. Many of our results extend to more general settings in cake
cutting that allow for variable claims and initial endowments. We also show a
few impossibility results to complement our algorithms.


title: Topological Phases in the Zeroth Landau Level of Bilayer Graphene

abstract:
  We analyze the phase diagram of the zeroth Landau level of bilayer graphene,
taking into account the realistic effects of screening of the Coulomb
interaction and the strong mixing between two degenerate sublevels. We identify
robust quantum Hall states at filling factors \nu=-1, -4/3, -5/3, -8/5, -1/2,
and discuss the nature of their ground states, collective excitations, and
relation to the more familiar states in GaAs using a tractable model. In
particular, we present evidence that the \nu=-1/2 state, which was recently
reported experimentally, is non-Abelian, and described by either the Moore-Read
Pfaffian wave function or its particle-hole conjugate, while ruling out other
candidates such as the 331 state.


title:
Absence of damping of low energy excitations in a quasi-2D dipolar Bose
  gas

abstract:
  We develop a theory of damping of low energy, collective excitations in a
quasi-2D, homogenous, dipolar Bose gas at zero temperature, via processes
whereby an excitation decays into two excitations with lower energy. We find
that owing to the nature of the low energy spectrum of a quasi-2D dipolar gas,
such processes cannot occur unless the momentum of the incoming quasi-particle
exceeds a critical value k_{crit}. We find that as the dipolar interaction
strength is increased, this critical value shifts to larger momenta. Our
predictions can be directly verified in current experiments on dipolar Bose
condensates using Bragg spectroscopy, and provide valuable insight into the
quantum many-body physics of dipolar gases.


title: Reproduction and ferromagnetism

abstract:
  I present a stochastic population model that combines cooperative
interactions of the type often used in physics with the process of reproduction
and death familiar to biology, and I refer to reasons why such interlocking may
be of interest to both fields.


title:
An Observation of a Circular Motion using Ordinary Appliances: Train
  Toy, Digital Camera, and Android based Smartphone

abstract:
  Using a digital camera (Sony DSC-S75) in its video mode and a smartphone
(Samsung GT-N700) equipped with an acceleration sensor, observation of a
uniform circular motion of a toy train (Thomas & Friends, Player World, CCF No.
2277-13) is conducted. From the first observation average centripetal
acceleration about 0.154 m/s2 is obtained, while the second gives 0.350 m/s2 of
average centripetal acceleration by assuming ideal condition, where measured
accelerations in z direction is not interpreted.


title:
Collective Effects in Linear Spectroscopy of Dipole-Coupled Molecular
  Arrays

abstract:
  We present a consistent analysis of linear spectroscopy for arrays of nearest
neighbor dipole-coupled two-level molecules that reveals distinct signatures of
weak and strong coupling regimes separated for infinite size arrays by a
quantum critical point. In the weak coupling regime, the ground state of the
molecular array is disordered, but in the strong coupling regime it has
(anti)ferroelectric ordering. We show that multiple molecular excitations
(odd/even in weak/strong coupling regime) can be accessed directly from the
ground state. We analyze the scaling of absorption and emission with system
size and find that the oscillator strengths show enhanced superradiant behavior
in both ordered and disordered phases. As the coupling increases, the single
excitation oscillator strength rapidly exceeds the well known Heitler-London
value. In the strong coupling regime we show the existence of a unique spectral
transition with excitation energy that can be tuned by varying the system size
and that asymptotically approaches zero for large systems. The oscillator
strength for this transition scales quadratically with system size, showing an
anomalous one-photon superradiance. For systems of infinite size, we find a
novel, singular spectroscopic signature of the quantum phase transition between
disordered and ordered ground states. We outline how arrays of ultra cold
dipolar molecules trapped in an optical lattice can be used to access the
strong coupling regime and observe the anomalous superradiant effects
associated with this regime.


title:
Features of adsorbed radioactive chemical elements and their isotopes
  distribution in iodine air filters AU-1500 at nuclear power plants

abstract:
  The main aim of research is to investigate the physical features of spatial
distribution of the adsorbed radioactive chemical elements and their isotopes
in the granular filtering medium in the iodine air filters of the type of
AU1500 in the forced exhaust ventilation systems at the nuclear power plant.
The gamma activation analysis method is applied to accurately characterize the
distribution of the adsorbed radioactive chemical elements and their isotopes
in the granular filtering medium in the AU1500 iodine air filter after its long
term operation at the nuclear power plant. The typical spectrum of the detected
chemical elements and their isotopes in the AU1500 iodine air filter, which was
exposed to the bremsstrahlung gamma quantum irradiation, produced by the
accelerating electrons in the tantalum target, are obtained. The spatial
distributions of the detected chemical element 127I and some other chemical
elements and their isotopes in the layer of absorber, which was made of the
cylindrical coal granules of the type of SKT3, in the AU1500 iodine air filter
are also researched. The possible influences by the standing acoustic wave of
air pressure in the iodine air filter on the spatial distribution of the
chemical elements and their isotopes in the iodine air filter are discussed.
The comprehensive analysis of obtained research results on the distribution of
the adsorbed chemical elements and their isotopes in the absorber of iodine air
filter is performed.


title: Measuring the Optimality of Hadoop Optimization

abstract:
  In recent years, much research has focused on how to optimize Hadoop jobs.
Their approaches are diverse, ranging from improving HDFS and Hadoop job
scheduler to optimizing parameters in Hadoop configurations. Despite their
success in improving the performance of Hadoop jobs, however, very little is
known about the limit of their optimization performance. That is, how optimal
is a given Hadoop optimization? When a Hadoop optimization method X improves
the performance of a job by Y %, how do we know if this improvement is as good
as it can be? To answer this question, in this paper, we first examine the
ideal best case, the lower bound, of running time for Hadoop jobs and develop a
measure to accurately estimate how optimal a given Hadoop optimization is with
respect to the lower bound. Then, we demonstrate how one may exploit the
proposed measure to improve the optimization of Hadoop jobs.


title: Quantum phase transition from the topological viewpoint

abstract:
  This study targets quantum phases which are characterized by topological
properties and no associated with the symmetry breaking. We concern ourselves
primarily with the transitions among these quantum phases. This type of quantum
phase transition was investigated by $G$-cobordism in unified framework. This
framework provides a useful method to investigate a new quantum phase.


title:
Clifford algebra and the projective model of homogeneous metric spaces:
  Foundations

abstract:
  This paper is to serve as a key to the projective (homogeneous) model
developed by Charles Gunn (arXiv:1101.4542 [math.MG]). The goal is to explain
the underlying concepts in a simple language and give plenty of examples. It is
targeted to physicists and engineers and the emphasis is on explanation rather
than rigorous proof. The projective model is based on projective geometry and
Clifford algebra. It supplements and enhances vector and matrix algebras. It
also subsumes complex numbers and quaternions. Projective geometry augmented
with Clifford algebra provides a unified algebraic framework for describing
points, lines, planes, etc, and their transformations, such as rotations,
reflections, projections, and translations. The model is relevant not only to
Euclidean space but to a variety of homogeneous metric spaces.


title:
Fourier series of atomic radial distribution functions: A molecular
  fingerprint for machine learning models of quantum chemical properties

abstract:
  We introduce a fingerprint representation of molecules based on a Fourier
series of atomic radial distribution functions. This fingerprint is unique
(except for chirality), continuous, and differentiable with respect to atomic
coordinates and nuclear charges. It is invariant with respect to translation,
rotation, and nuclear permutation, and requires no pre-conceived knowledge
about chemical bonding, topology, or electronic orbitals. As such it meets many
important criteria for a good molecular representation, suggesting its
usefulness for machine learning models of molecular properties trained across
chemical compound space. To assess the performance of this new descriptor we
have trained machine learning models of molecular enthalpies of atomization for
training sets with up to 10k organic molecules, drawn at random from a
published set of 134k organic molecules. We validate the descriptor on all
remaining molecules of the 134k set. For a training set of 5k molecules the
fingerprint descriptor achieves a mean absolute error of 8.0 kcal/mol,
respectively. This is slightly worse than the performance attained using the
Coulomb matrix, another popular alternative, reaching 6.2 kcal/mol for the same
training and test sets.


title:
Neutrinos and dark energy constraints from future galaxy surveys and CMB
  lensing information

abstract:
  We explore the possibility of obtaining better constraints from future
astronomical data by means of the Fisher information matrix formalism. In
particular, we consider how cosmic microwave background (CMB) lensing
information can improve our parameter error estimation. We consider a massive
neutrino scenario and a time-evolving dark energy equation of state in the
$\Lambda$CDM framework. We use Planck satellite experimental specifications
together with the future galaxy survey Euclid in our forecast. We found
improvements in almost all studied parameters considering Planck alone when CMB
lensing information is used. In this case, the improvement with respect to the
constraints found without using CMB lensing is of 93% around the fiducial value
for the neutrino parameter. The improvement on one of the dark energy parameter
reaches 4.4%. When Euclid information is included in the analysis, the
improvements on the neutrino parameter constraint is of approximately 128%
around its fiducial value. The addition of Euclid information provides smaller
errors on the dark energy parameters as well. For Euclid alone, the FoM is a
factor of $\sim$ 29 higher than that from Planck alone even considering CMB
lensing. Finally, the consideration of a nearly perfect CMB experiment showed
that CMB lensing cannot be neglected specially in more precise future CMB
experiments since it provided in our case a 6 times better FoM in respect to
the unlensed CMB analysis .


title: TMD theory, factorization and evolution

abstract:
  The concepts and methods of factorization using transverse-momentum-dependent
(TMD) parton densities and/or fragmentation functions are summarized.


title:
Apparent strength conceals instability in a model for the collapse of
  historical states

abstract:
  An explanation for the political processes leading to the sudden collapse of
empires and states would be useful for understanding both historical and
contemporary political events. We seek a general description of state collapse
spanning eras and cultures, from small kingdoms to continental empires, drawing
on a suitably diverse range of historical sources. Our aim is to provide an
accessible verbal hypothesis that bridges the gap between mathematical and
social methodology. We use game-theory to determine whether factions within a
state will accept the political status quo, or wish to better their
circumstances through costly rebellion. In lieu of precise data we verify our
model using sensitivity analysis. We find that a small amount of
dissatisfaction is typically harmless, but can trigger sudden collapse when
there is a sufficient buildup of political inequality. Contrary to intuition, a
state is predicted to be least stable when its leadership is at the height of
its political power and thus most able to exert its influence through external
warfare, lavish expense or autocratic decree.


title:
Imprints of Dark Energy on Cosmic Structure Formation: III. Sparsity of
  Dark Matter Halo Profiles

abstract:
  We study the imprint of Dark Energy on the density profile of Dark Matter
halos using a set of high-resolution large volume cosmological N-body
simulations from the Dark Energy Universe Simulation Series (DEUSS). We first
focus on the analysis of the goodness-of-fit of the Navarro-Frenk-White (NFW)
profile which we find to vary with halo mass and redshift. We also find that
the fraction of halos ill-fitted by NFW varies with cosmology, thus indicating
that the mass assembly of halos with perturbed density profiles carries a
characteristic signature of Dark Energy. To access this information
independently of any parametric profile, we introduce a new observable
quantity: the halo sparsity $s_\Delta$. This is defined as the mass ratio
$M_{200}/M_\Delta$, i.e. the ratio of mass inside a sphere of radius $r_{200}$
to that contained within a radius $r_\Delta$, enclosing 200 and $\Delta$ times
the mean matter density respectively. We find the average sparsity to be nearly
independent of the total halo mass, while its value can be inferred to better
than a few percent from the ratio of the integrated halo mass functions at
overdensities $\Delta$ and 200 respectively. This provides a consistency
relation that can validate observational measurements of the halo sparsity.
Most importantly, the sparsity significantly varies with the underlying Dark
Energy model, thus providing an alternative cosmological probe.


title:
Two-Way Relaying under the Presence of Relay Transceiver Hardware
  Impairments

abstract:
  Hardware impairments in physical transceivers are known to have a deleterious
effect on communication systems; however, very few contributions have
investigated their impact on relaying. This paper quantifies the impact of
transceiver impairments in a two-way amplify-and-forward configuration. More
specifically, the effective signal-to-noise-and-distortion ratios at both
transmitter nodes are obtained. These are used to deduce exact and asymptotic
closed-form expressions for the outage probabilities (OPs), as well as
tractable formulations for the symbol error rates (SERs). It is explicitly
shown that non-zero lower bounds on the OP and SER exist in the high-power
regime---this stands in contrast to the special case of ideal hardware, where
the OP and SER go asymptotically to zero.


title: Non-Solvable Graph of a Finite Group and Solvabilizers

abstract:
  Let $G$ be a finite group. For $x \in G$, we define the solvabilizer of $x$
in $G$, denoted $sol_G(x)$, to be the set $\{g \in G \mid \langle g,x \rangle$
is solvable$\}$. A group $G$ is an S-group if $sol_G(x)$ is a subgroup of $G$
for every $x \in G$. In this paper we prove that $G$ is solvable
$\Leftrightarrow$ $G$ is an S-group. Secondly, we define the non-solvable graph
of $G$ (denoted ${\mathcal S}_{G}$). Its vertices are $G$ and there is an edge
between $x,y \in G$ whenever $\langle x,y \rangle$ is not solvable. If $S(G)$
is the solvable radical of $G$ and $G$ is not solvable, we look at the induced
graph over $G \setminus S(G)$, denoted $\hat{{\mathcal S}_{G}}$. We prove that
if $G$ is not solvable, then $\hat{{\mathcal S}_{G}}$ is irregular. In
addition, we prove some properties of solvabilizers and non-solvable graphs.


title: Array Antenna Limitations

abstract:
  This letter defines a physical bound based array figure of merit that
provides a tool to compare the performance of both single and multi-band array
antennas with respect to return-loss, thickness of the array over the
ground-plane, and scan-range. The result is based on a sum-rule result of
Rozanov-type for linear polarization. For single-band antennas it extends an
existing limit for a given fixed scan-angle to include the whole scan-range of
the array, as well as the unit-cell structure in the bound. The letter ends
with an investigation of the array figure of merit for some wideband and/or
wide-scan antennas with linear polarization. We find arrays with a figure of
merit >0.6 that empirically defines high-performance antennas with respect to
this measure.


title: Gap Cycling for SWIFT

abstract:
  Purpose: SWIFT (SWeep Imaging with Fourier Transformation) is a non-
Cartesian MRI method with unique features and capabilities. In SWIFT,
radiofrequency (RF) excitation and reception are performed nearly
simultaneously, by rapidly switching between transmit and receive during a
frequency-swept RF pulse. Because both the transmitted pulse and data
acquisition are simultaneously amplitude-modulated in SWIFT (in contrast to
continuous RF excitation and uninterrupted data acquisition in more familiar
MRI sequences), crosstalk between different frequency bands occurs in the data.
This crosstalk leads to a "bulls-eye" artifact in SWIFT images. We present a
method to cancel this inter-band crosstalk by cycling the pulse and receive gap
positions relative to the un-gapped pulse shape. We call this strategy "gap
cycling."
  Methods: We carry out theoretical analysis, simulation and experiments to
characterize the signal chain, resulting artifacts, and their elimination for
SWIFT.
  Results: Theoretical analysis reveals the mechanism for gap-cycling's
effectiveness in canceling inter-band crosstalk. We show phantom and in-vivo
results demonstrating bulls-eye artifact free images.
  Conclusion: Gap cycling is an effective method to remove bulls-eye artifact
resulting from inter-band crosstalk in SWIFT data.


title:
Clean measurements of the nucleon axial-vector and free-neutron magnetic
  form factors

abstract:
  We discuss the feasibility of a weak charged current experiment using a low
energy electron beam. A first goal is to measure the Q^2 dependence of the
axial-vector form factor g_a(Q^2). It can be measured model-independently and
as robustly as for electromagnetic form factors from typical electron
scattering experiments, in contrast to the methods used so far to measure
g_a(Q^2). If g_a(Q^2) follows a dipole form, the axial mass can be extracted
with a better accuracy than the world data altogether. The most important
detection equipment would be a segmented neutron detector with good momentum
and angular resolution that is symmetric about the beam direction, and covers a
moderate angular range. A high intensity beam (100 uA) is necessary. Beam
polarization is highly desirable as it provides a clean measurement of the
backgrounds. Beam energies between 70 and 110 MeV are ideal. This range would
provide a Q^2 mapping of g_a between 0.01


title:
Magnetic field generation in a jet-sheath plasma via the kinetic
  Kelvin-Helmholtz instability

abstract:
  We have investigated generation of magnetic fields associated with velocity
shear between an unmagnetized relativistic jet and an unmagnetized sheath
plasma. We have examined the strong magnetic fields generated by kinetic shear
(Kelvin-Helmholtz) instabilities. Compared to the previous studies using
counter-streaming performed by Alves et al. (2012), the structure of KKHI of
our jet-sheath configuration is slightly different even for the global
evolution of the strong transverse magnetic field. In our simulations the major
components of growing modes are the electric field $E_{\rm z}$ and the magnetic
field $B_{\rm y}$. After the $B_{\rm y}$ component is excited, an induced
electric field $E_{\rm x}$ becomes significant. However, other field components
remain small. We find that the structure and growth rate of KKHI with mass
ratios $m_{\rm i}/m_{\rm e} = 1836$ and $m_{\rm i}/m_{\rm e} = 20$ are similar.
In our simulations saturation in the nonlinear stage is not as clear as in
counter-streaming cases. The growth rate for a mildly-relativistic jet case
($\gamma_{\rm j} = 1.5$) is larger than for a relativistic jet case
($\gamma_{\rm j} = 15$).


title:
Next-Generation Liquid-Scintillator-Based Detectors: Quantums Dots and
  Picosecond Timing

abstract:
  Liquid-scintillator-based detectors are a robust technology that scales well
to large volumes. For this reason, they are attractive for experiments
searching for neutrinoless double-beta decay. A combination of improved
photo-detection technology and novel liquid scintillators may allow for the
extraction of particle direction in addition to the total energy of the
particle. Such an advance would find applications beyond searches for
neutrinoless double-beta decay.


title: Chemical sensing by nonequilibrium cooperative receptors

abstract:
  Cooperativity arising from local interactions in equilibrium receptor systems
provides gain, but does not increase sensory performance, as measured by the
signal-to-noise ratio (SNR) due to a fundamental tradeoff between gain and
intrinsic noise. Here we allow sensing to be a nonequilibrium process and show
that energy dissipation cannot circumvent the fundamental tradeoff, so that SNR
is still optimal for independent receptors. For systems requiring high gain,
nonequilibrium 2D-coupled receptors maximize SNR, revealing a new design
principle for biological sensors.


title:
Dosimetric and Deformation Effects of Image-Guided Interventions during
  Stereotactic Body Radiation Therapy of the Prostate using an Endorectal
  Balloon

abstract:
  During Stereotactic Body Radiotherapy (SBRT) for the treatment of prostate
cancer, an inflatable endorectal balloon (ERB) may be used to reduce motion of
the target and reduce the dose to the posterior rectal wall. This work assessed
the dosimetric impact of manual interventions on ERB position in patients
receiving prostate SBRT and investigated the impact of ERB interventions on
prostate shape. Daily kilovoltage (kV) cone-beam computed tomography (CBCT)
imaging was performed to localize the PTV, and an automated fusion with the
planning images yielded displacements required for PTV re-localization. When
the ERB volume and/or position were judged to yield inaccurate repositioning,
manual adjustment (ERB re-inflation and/or repositioning) was performed. Based
on all 59 CBCT image sets acquired, a deformable registration algorithm was
used to determine the dose received by, displacement of, and deformation of the
prostate, bladder, and anterior rectal wall. This dose tracking methodology was
applied to images taken before and after manual adjustment of the ERB
(intervention), and the delivered dose was compared to that which would have
been delivered in the absence of intervention. Interventions occurred in 24 out
of 35 (69%) of the treated fractions. The direct effect of these interventions
was an increase in the prostate radiation dose that included 95% of the PTV
(D95) and an increase in prostate coverage. Additionally, ERB interventions
reduced prostate deformation in the anterior-posterior (AP) direction, reduced
errors in the sagittal rotation of the prostate, and increased the similarity
in shape of the prostate to the radiotherapy plan. Image-guided interventions
in ERB volume and/or position during prostate SBRT were necessary to ensure the
delivery of the dose distribution as planned.