title:
A limit equation criterion for applying the conformal method to
  asymptotically cylindrical initial data sets

abstract:
  We prove that in a certain class of conformal data on an asymptotically
cylindrical manifold, if the conformally decomposed Einstein constraint
equations do not admit a solution, then one can always find a nontrivial
solution to the limit equation first explored by Dahl, Gicquaud, and Humbert in
[DGH11]. We also give an example of a Ricci curvature condition on the manifold
which precludes the existence of a solution to this limit equation, showing
that such a limit criterion can be a useful tool for studying the Einstein
constraint equations on manifolds with asymptotically cylindrical ends.


title: Classification of invariant valuations on the quaternionic plane

abstract:
  We describe the orbit space of the action of the group
$\mathrm{Sp}(2)\mathrm{Sp}(1)$ on the real Grassmann manifolds
$\mathrm{Gr}_k(\mathbb{H}^2)$ in terms of certain quaternionic matrices of
Moore rank not larger than $2$. We then give a complete classification of
valuations on the quaternionic plane $\mathbb{H}^2$ which are invariant under
the action of the group $\mathrm{Sp}(2)\mathrm{Sp}(1)$.


title:
Numerical proof of stability of roll waves in the small-amplitude limit
  for inclined thin film flow

abstract:
  We present a rigorous numerical proof based on interval arithmetic
computations categorizing the linearized and nonlinear stability of periodic
viscous roll waves of the KdV-KS equation modeling weakly unstable flow of a
thin fluid film on an incline in the small-amplitude KdV limit. The argument
proceeds by verification of a stability condition derived by Bar-Nepomnyashchy
and Johnson-Noble-Rodrigues-Zumbrun involving inner products of various
elliptic functions arising through the KdV equation. One key point in the
analysis is a bootstrap argument balancing the extremely poor sup norm bounds
for these functions against the extremely good convergence properties for
analytic interpolation in order to obtain a feasible computation time. Another
is the way of handling analytic interpolation in several variables by a
two-step process carving up the parameter space into manageable pieces for
rigorous evaluation. These and other general aspects of the analysis should
serve as blueprints for more general analyses of spectral stability.


title:
An integrated mid-infrared, far-infrared and terahertz optical Hall
  effect instrument

abstract:
  We report on the development of the first integrated mid-infrared,
far-infrared and terahertz optical Hall effect instrument, covering an ultra
wide spectral range from 3 cm$^{-1}$ to 7000 cm$^{-1}$ (0.1-210 THz or 0.4-870
meV). The instrument comprises four sub-systems, where the
magneto-cryostat-transfer sub-system enables the usage of the magneto-cryostat
sub-system with the mid-infrared ellipsometer sub-system, and the
far-infrared/terahertz ellipsometer sub-system. Both ellipsometer sub-systems
can be used as variable angle-of-incidence spectroscopic ellipsometers in
reflection or transmission mode, and are equipped with multiple light sources
and detectors. The ellipsometer sub-systems are operated in
polarizer-sample-rotating-analyzer configuration granting access to the upper
left $3\times 3$ block of the normalized $4\times 4$ Mueller matrix. The closed
cycle magneto-cryostat sub-system provides sample temperatures between room
temperature and 1.4 K and magnetic fields up to 8 T, enabling the detection of
transverse and longitudinal magnetic field-induced birefringence. We discuss
theoretical background and practical realization of the integrated
mid-infrared, far-infrared and terahertz optical Hall effect instrument, as
well as acquisition of optical Hall effect data and the corresponding model
analysis procedures. Exemplarily, epitaxial graphene grown on 6H-SiC, a
tellurium doped bulk GaAs sample and an AlGaN/GaN high electron mobility
transistor structure are investigated. The selected experimental datasets
display the full spectral, magnetic field and temperature range of the
instrument and demonstrate data analysis strategies. Effects from free charge
carriers in two dimensional confinement and in a volume material, as well as
quantum mechanical effects (inter-Landau-level transitions) are observed and
discussed exemplarily.


title: Local a Priori Estimate on the General Scale Subdomains

abstract:
  The local a priori estimate for the finite element approximation is essential
for underlying the local and parallel technique. It is well known that the
constant coefficients in the inequality is independent of the mesh size. But it
is not so clear whether the constant depends on the scale of the local
subdomains. The aim of this note is to derive a new local a priori estimate on
the general scale domains. We also show that the dependence of the constant
appearing in the local a priori estimate on the scale of the subdomains.


title: Formation and appearance of pulsar-like white dwarfs

abstract:
  Accretion-driven spin-up of a magnetized white dwarf in a close binary system
is discussed. We address a situation in which the magnetic field of the white
dwarf is screening during the accretion phase and re-generating due to the
field diffusion through the accreted material after it. We find this scenario
to be effective for a formation of massive pulsar-like white dwarfs.


title:
Iterative regularization for ensemble data assimilation in reservoir
  models

abstract:
  We propose the application of iterative regularization for the development of
ensemble methods for solving Bayesian inverse problems. In concrete, we
construct (i) a variational iterative regularizing ensemble Levenberg-Marquardt
method (IR-enLM) and (ii) a derivative-free iterative ensemble Kalman smoother
(IR-ES). The aim of these methods is to provide a robust ensemble approximation
of the Bayesian posterior. The proposed methods are based on fundamental ideas
from iterative regularization methods that have been widely used for the
solution of deterministic inverse problems [21]. In this work we are interested
in the application of the proposed ensemble methods for the solution of
Bayesian inverse problems that arise in reservoir modeling applications. The
proposed ensemble methods use key aspects of the regularizing
Levenberg-Marquardt scheme developed by Hanke [16] and that we recently applied
for history matching in [18].
  In the case where the forward operator is linear and the prior is Gaussian,
we show that the proposed IR-enLM and IR-ES coincide with standard randomized
maximum likelihood (RML) and the ensemble smoother (ES) respectively. For the
general nonlinear case, we develop a numerical framework to assess the
performance of the proposed ensemble methods at capturing the posterior. This
framework consists of using a state-of-the art MCMC method for resolving the
Bayesian posterior from synthetic experiments. The resolved posterior via MCMC
then provides a gold standard against to which compare the proposed IR-enLM and
IR-ES. We show that for the careful selection of regularization parameters,
robust approximations of the posterior can be accomplished in terms of mean and
variance. Our numerical experiments showcase the advantage of using iterative
regularization for obtaining more robust and stable approximation of the
posterior than standard unregularized methods.


title: Remarks on geometric properties of SQG sharp fronts and $\alpha$-patches

abstract:
  Guided by numerical simulations, we present the proof of two results
concerning the behaviour of SQG sharp fronts and $\alpha$-patches. We establish
that ellipses are not rotational solutions and we prove that initially convex
interfaces may lose this property in finite time.


title:
Trigonometric Parallaxes of High Mass Star Forming Regions: the
  Structure and Kinematics of the Milky Way

abstract:
  Over 100 trigonometric parallaxes and proper motions for masers associated
with young, high-mass stars have been measured with the BeSSeL Survey, a VLBA
key science project, the EVN, and the Japanese VERA project. These measurements
provide strong evidence for the existence of spiral arms in the Milky Way,
accurately locating many arm segments and yielding spiral pitch angles ranging
from 7 to 20 degrees. The widths of spiral arms increase with distance from the
Galactic center. Fitting axially symmetric models of the Milky Way with the 3-D
position and velocity information and conservative priors for the solar and
average source peculiar motions, we estimate the distance to the Galactic
center, Ro, to be 8.34 +/- 0.16 kpc, a circular rotation speed at the Sun, To,
to be 240 +/- 8 km/s, and a rotation curve that is nearly flat (a slope of -0.2
+/- 0.4 km/s/kpc) between Galactocentric radii of 5 and 16 kpc. Assuming a
"universal" spiral galaxy form for the rotation curve, we estimate the thin
disk scale length to be 2.44 +/- 0.16 kpc. The parameters Ro and To are not
highly correlated and are relatively insensitive to different forms of the
rotation curve. Adopting a theoretically motivated prior that high-mass star
forming regions are in nearly circular Galactic orbits, we estimate a global
solar motion component in the direction of Galactic rotation, Vsun = 14.6 +/-
5.0 km/s. While To and Vsun are significantly correlated, the sum of these
parameters is well constrained, To + Vsun = 255.2 +/- 5.1 km/s, as is the
angular speed of the Sun in its orbit about the Galactic center, (To + Vsun)/Ro
= 30.57 +/- 0.43 km/s/kpc. These parameters improve the accuracy of estimates
of the accelerations of the Sun and the Hulse-Taylor binary pulsar in their
Galactic orbits, significantly reducing the uncertainty in tests of
gravitational radiation predicted by general relativity.


title:
A Multigrid Method Based On Shifted-Inverse Power Technique for
  Eigenvalue Problems

abstract:
  A multigrid method is proposed in this paper to solve eigenvalue problems by
the finite element method based on the shifted-inverse power iteration
technique. With this scheme, solving eigenvalue problem is transformed to a
series of nonsingular solutions of boundary value problems on multilevel
meshes. Since replacing the difficult eigenvalue solving by the easier solution
of boundary value problems, the multigrid way can improve the overall
efficiency of the eigenvalue problem solving. Some numerical experiments are
presented to validate the efficiency of this new method.


title:
Quotients of trees for arithmetic subgroups of PGL2 over a rational
  function field

abstract:
  In this note we compute the fundamental domain of the action on the
corresponding Bruhat-Tits tree of the arithmetic subgroup of PGL2 with respect
to an arbitrary place of the rational function field.


title: Heavy hybrid stars from multi-quark interactions

abstract:
  We explore the possibility of obtaining heavy hybrid stars within the
framework of the two flavor Nambu--Jona-Lasinio model with 8-quark interactions
in the scalar and in the vector channel. The main impact of the 8-quark scalar
channel is to reduce the onset of quark matter, while the 8-quark vector
channel acts to stiff the equation of state at high densities. Within the
parameter space where the 4-quark vector channel is small, and the 8-quark
vector channel sizeable, stable stars with $2 M_\odot$ and above are found to
hold quark matter in their cores.


title: Microcausality in strongly interacting fields

abstract:
  We study the properties of strongly interacting massive quantum fields in
space-time as resulting from a parametric decay of the fields with a large
decay width $\gamma$. The resulting imaginary part of the retarded and advanced
propagators in this case is of Lorentzian form and the theory conserves
microcausality, i.e. the commutator between the fields vanishes for space-like
distances in space-time. However, when considering separately space-like and
time-like components of the spectral function in momentum space we find
microcausality to be violated for each component separately. This implies that
the modeling of effective field theories for strongly interacting systems has
to be considered with great care and restrictions to time-like four momenta in
case of broad spectral functions have to be ruled out. Furthermore, when
employing effective propagators with a width $\gamma({\bf p}^2)$ depending
explicitly on three-momentum ${\bf p}$ the commutator of the fields no longer
vanishes for $r>t$ since the related field theory becomes nonlocal and violates
microcausality.


title:
Continuous Speech Recognition Based on Deterministic Finite Automata
  Machine using Utterance and Pitch Verification

abstract:
  This paper introduces a set of acoustic modeling techniques for utterance
verification (UV) based continuous speech recognition (CSR). Utterance
verification in this work implies the ability to determine when portions of a
hypothesized word string correspond to incorrectly decoded vocabulary words or
out-of-vocabulary words that may appear in an utterance. This capability is
implemented here as a likelihood ratio (LR). There are two UV techniques that
are presented here. The first is voice verification along with the vocabulary
testing, at the same time the parameters for UV models are generated based on
the optimization criterion which is directly related to the LR measure. The
second technique is a pitch recognition based on weighted finite-state
transducers. These transducers provide a common and natural representation for
major components of speech recognition systems, including hidden Markov models
(HMMs), context-dependency models, pronunciation dictionaries, statistical
grammars, and word or phone lattices. The finite state machine processes the
acoustic parameters of UV models. The results of an experimental study
presented in the paper shows that LR based parameter estimation results in a
significant improvement in UV performance for this task. The study also found
that the use of the LR based weighted finite-state transducers along with the
UV, can provide as much as an 11% improvement in UV performance when compared
to existing UV procedures. Finally, it was also found that the performance of
the finite state machine was highly dependent on the use of the LR criterion in
training acoustic models. Several observations are made in the paper concerning
the formation of confidence measures for UV and the interaction of these
techniques with statistical language models.


title: On the representation of de Bruijn graphs

abstract:
  The de Bruijn graph plays an important role in bioinformatics, especially in
the context of de novo assembly. However, the representation of the de Bruijn
graph in memory is a computational bottleneck for many assemblers. Recent
papers proposed a navigational data structure approach in order to improve
memory usage. We prove several theoretical space lower bounds to show the
limitation of these types of approaches. We further design and implement a
general data structure (DBGFM) and demonstrate its use on a human whole-genome
dataset, achieving space usage of 1.5 GB and a 46% improvement over previous
approaches. As part of DBGFM, we develop the notion of frequency-based
minimizers and show how it can be used to enumerate all maximal simple paths of
the de Bruijn graph using only 43 MB of memory. Finally, we demonstrate that
our approach can be integrated into an existing assembler by modifying the
ABySS software to use DBGFM.


title: On a linear interpolation problem for n-dimensional vector polynomials

abstract:
  This work provides a complete characterization of the solutions of a linear
interpolation problem for vector polynomials. The interpolation problem
consists in finding n scalar polynomials such that an equation involving a
linear combination of them is satisfied for each one of the N interpolation
nodes. The results of this work generalize previous results on the so-called
rational interpolation and have applications to direct and inverse spectral
analysis of band matrices.


title:
Silicon Oxide Passivation of Single-Crystalline CVD Diamond Evaluated by
  the Time-of-Flight Technique

abstract:
  The excellent material properties of diamond make it highly desirable for
many extreme electronic applications that are out of reach of conventional
electronic materials. For commercial diamond devices to become a reality, it is
necessary to have an effective surface passivation since the passivation
determines the ability of the device to withstand high surface electric fields.
In this paper we present data from lateral Time-of-Flight studies on
SiO2-passivated intrinsic single-crystalline CVD diamond. The SiO2 films were
deposited using three different techniques. The influence of the passivation on
hole transport was studied, which resulted in the increase of hole mobilities.
The results from the three different passivations are compared.


title: Logarithmic AdS Waves and Zwei-Dreibein Gravity

abstract:
  We show that the parameter space of Zwei-Dreibein Gravity (ZDG) in AdS3
exhibits critical points, where massive graviton modes coincide with pure gauge
modes and new `logarithmic' modes appear, similar to what happens in New
Massive Gravity. The existence of critical points is shown both at the
linearized level, as well as by finding AdS wave solutions of the full
non-linear theory, that behave as logarithmic modes towards the AdS boundary.
In order to find these solutions explicitly, we give a reformulation of ZDG in
terms of a single Dreibein, that involves an infinite number of derivatives. At
the critical points, ZDG can be conjectured to be dual to a logarithmic
conformal field theory with zero central charges, characterized by new
anomalies whose conjectured values are calculated.


title: Observation of entanglement propagation in a quantum many-body system

abstract:
  The key to explaining a wide range of quantum phenomena is understanding how
entanglement propagates around many-body systems. Furthermore, the controlled
distribution of entanglement is of fundamental importance for quantum
communication and computation. In many situations, quasiparticles are the
carriers of information around a quantum system and are expected to distribute
entanglement in a fashion determined by the system interactions. Here we report
on the observation of magnon quasiparticle dynamics in a one-dimensional
many-body quantum system of trapped ions representing an Ising spin model.
Using the ability to tune the effective interaction range, and to prepare and
measure the quantum state at the individual particle level, we observe new
quasiparticle phenomena. For the first time, we reveal the entanglement
distributed by quasiparticles around a many-body system. Second, for long-range
interactions we observe the divergence of quasiparticle velocity and breakdown
of the light-cone picture that is valid for short-range interactions. Our
results will allow experimental studies of a wide range of phenomena, such as
quantum transport, thermalisation, localisation and entanglement growth, and
represent a first step towards a new quantum-optical regime with on-demand
quasiparticles with tunable non-linear interactions.

categories: quant-ph cond-mat.mes-hall cond-mat.quant-gas cond-mat.supr-con physics.atom-ph


title:
Rayleigh-Taylor instability in partially ionized compressible plasmas:
  one fluid approach

abstract:
  We study the modification of the classical criterion for the linear onset and
growth rate of the Rayleigh-Taylor instability (RTI) in a partially ionized
(PI) plasma in the one-fluid description, considering a generalized induction
equation. The governing linear equations and appropriate boundary conditions,
including gravitational terms, are derived and applied to the case of the RTI
in a single interface between two partially ionized plasmas. The boundary
conditions lead to an equation for the frequencies in which some of them have
positive complex parts, marking the appearance of the RTI. We study the
ambipolar term alone first, extending the result to the full induction equation
later. We find that the configuration is always unstable because of the
presence of a neutral species. In the classical stability regime the growth
rate is small, since the collisions prevent the neutral fluid to fully develop
the RTI. For parameters in the classical instability regime the growth rate is
lowered, but for the considered theoretical values of the collision frequencies
and diffusion coefficients for solar prominences the differences with the
compressible MHD case are small. We conclude that PI modifies some aspects of
the linear RTI instability, since it takes into account that neutrals do not
feel the stabilizing effect of the magnetic field. For the set of parameters
representative for solar prominences, our model gives the resulting timescale
comparable with observed lifetimes of RTI plumes.


title:
Which Clustering Do You Want? Inducing Your Ideal Clustering with
  Minimal Feedback

abstract:
  While traditional research on text clustering has largely focused on grouping
documents by topic, it is conceivable that a user may want to cluster documents
along other dimensions, such as the authors mood, gender, age, or sentiment.
Without knowing the users intention, a clustering algorithm will only group
documents along the most prominent dimension, which may not be the one the user
desires. To address the problem of clustering documents along the user-desired
dimension, previous work has focused on learning a similarity metric from data
manually annotated with the users intention or having a human construct a
feature space in an interactive manner during the clustering process. With the
goal of reducing reliance on human knowledge for fine-tuning the similarity
function or selecting the relevant features required by these approaches, we
propose a novel active clustering algorithm, which allows a user to easily
select the dimension along which she wants to cluster the documents by
inspecting only a small number of words. We demonstrate the viability of our
algorithm on a variety of commonly-used sentiment datasets.


title: Learning to Win by Reading Manuals in a Monte-Carlo Framework

abstract:
  Domain knowledge is crucial for effective performance in autonomous control
systems. Typically, human effort is required to encode this knowledge into a
control algorithm. In this paper, we present an approach to language grounding
which automatically interprets text in the context of a complex control
application, such as a game, and uses domain knowledge extracted from the text
to improve control performance. Both text analysis and control strategies are
learned jointly using only a feedback signal inherent to the application. To
effectively leverage textual information, our method automatically extracts the
text segment most relevant to the current game state, and labels it with a
task-centric predicate structure. This labeled text is then used to bias an
action selection policy for the game, guiding it towards promising regions of
the action space. We encode our model for text analysis and game playing in a
multi-layer neural network, representing linguistic decisions via latent
variables in the hidden layers, and game action quality via the output layer.
Operating within the Monte-Carlo Search framework, we estimate model parameters
using feedback from simulated games. We apply our approach to the complex
strategy game Civilization II using the official game manual as the text guide.
Our results show that a linguistically-informed game-playing agent
significantly outperforms its language-unaware counterpart, yielding a 34%
absolute improvement and winning over 65% of games when playing against the
built-in AI of Civilization.


title: The semantic marriage of monads and effects

abstract:
  Wadler and Thiemann unified type-and-effect systems with monadic semantics
via a syntactic correspondence and soundness results with respect to an
operational semantics. They conjecture that a general, "coherent" denotational
semantics can be given to unify effect systems with a monadic-style semantics.
We provide such a semantics based on the novel structure of an indexed monad,
which we introduce. We redefine the semantics of Moggi's computational
lambda-calculus in terms of (strong) indexed monads which gives a one-to-one
correspondence between indices of the denotations and the effect annotations of
traditional effect systems. Dually, this approach yields indexed comonads which
gives a unified semantics and effect system to contextual notions of effect
(called coeffects), which we have previously described.


title:
Shear viscosity of pion gas due to $\rho\pi\pi$ and $\sigma\pi\pi$
  interactions

abstract:
  We have evaluated the shear viscosity of pion gas taking into account its
scattering with the low mass resonances, $\sigma$ and $\rho$ during propagation
in the medium. The thermal width (or collisional rate) of the pions is
calculated from $\pi\sigma$ and $\pi\rho$ loop diagrams using effective
interactions in the real time formulation of finite temperature field theory. A
very small value of shear viscosity by entropy density ratio ($\eta/s$), close
to the KSS bound, is obtained which approximately matches the range of values
of $\eta/s$ used by Niemi et al. \cite{Niemi} in order to fit the RHIC data of
elliptic flow.


title: Irreducibility for log arc schemes

abstract:
  We characterise when the log arc scheme of a fine log scheme $(X, M)$, with
$X$ a variety over a field of characteristic zero, is irreducible. This
generalises the theorem of Kolchin that the (ordinary) arc scheme of $X$ is
irreducible exactly when $X$ is irreducible.


title: Determinising Parity Automata

abstract:
  Parity word automata and their determinisation play an important role in
automata and game theory. We discuss a determinisation procedure for
nondeterministic parity automata through deterministic Rabin to deterministic
parity automata. We prove that the intermediate determinisation to Rabin
automata is optimal. We show that the resulting determinisation to parity
automata is optimal up to a small constant. Moreover, the lower bound refers to
the more liberal Streett acceptance. We thus show that determinisation to
Streett would not lead to better bounds than determinisation to parity. As a
side-result, this optimality extends to the determinisation of B\"uchi
automata.


title: Hydrodynamics associated to the X-ray light curve of A0620-00

abstract:
  From 1975 to 1976, an outburst was detected in the light curve of the X-ray
transient A0620-00 using the Ariel V and SAS-3 experiments. In this letter we
model the outburst with the hydrodynamical model proposed by Mendoza et al.
(2009). The physical model is constructed assumming basic mass and momentum
conservation laws associated to the motion of the shock waves developed inside
the expanding relativistic jet of the source. These internal shock waves are
produced as a result of periodic variations of the inyected mass and velocity
of the flow at the base of the jet. The observations of this X-ray light curve
present two clear bumps. The first one is modelled assuming periodic variations
of the inyected velocity at the base of the jet, while the second one can
either be modelled by a further velocity oscillations, or by a periodic
variation of the mass injection rate at the base of the jet at a latter time.
The fitting of the data fixes different parameters of the model, such as the
mean mass injection rate at the base of the jet and the oscillation frequency
of the flow as measured on the rest frame of the central source.


title:
Lamb shift enhancement and detection in strongly driven superconducting
  circuits

abstract:
  It is shown that strong driving of a quantum system substantially enhances
the Lamb shift induced by broadband reservoirs which are typical for
solid-state devices. By varying drive parameters the impact of environmental
vacuum fluctuations with continuous spectral distribution onto system
observables can be tuned in a distinctive way. This provides experimentally
feasible measurement schemes for the Lamb shift in superconducting circuits
based on Cooper pair boxes, where it can be detected either in shifted dressed
transition frequencies or in pumped charge currents.


title:
Exact solutions of the Klein-Gordon equation in the Kerr-Newman
  background and Hawking radiation

abstract:
  This work considers the influence of the gravitational field produced by a
charged and rotating black hole (Kerr-Newman spacetime) on a charged massive
scalar field. We obtain exact solutions of both angular and radial parts of the
Klein-Gordon equation in this spacetime, which are given in terms of the
confluent Heun functions. From the radial solution, we obtain the exact wave
solutions near the exterior horizon of the black hole, and discuss the Hawking
radiation of charged massive scalar particles.


title: Dirichlet-Laplace priors for optimal shrinkage

abstract:
  Penalized regression methods, such as $L_1$ regularization, are routinely
used in high-dimensional applications, and there is a rich literature on
optimality properties under sparsity assumptions. In the Bayesian paradigm,
sparsity is routinely induced through two-component mixture priors having a
probability mass at zero, but such priors encounter daunting computational
problems in high dimensions. This has motivated an amazing variety of
continuous shrinkage priors, which can be expressed as global-local scale
mixtures of Gaussians, facilitating computation. In sharp contrast to the
frequentist literature, little is known about the properties of such priors and
the convergence and concentration of the corresponding posterior distribution.
In this article, we propose a new class of Dirichlet--Laplace (DL) priors,
which possess optimal posterior concentration and lead to efficient posterior
computation exploiting results from normalized random measure theory. Finite
sample performance of Dirichlet--Laplace priors relative to alternatives is
assessed in simulated and real data examples.


title:
Horizontal gradient of polynomial functions for the standard Engel
  structure on $\mathbb R^4$

abstract:
  We investigate the set $V_f$ of horizontal critical points of a polynomial
function $f$ for the standard Engel structure defined by the 1-forms
$\omega_3=dx_3-x_1dx_2,$ $\omega_4=dx_4-x_3dx_2$, endowed with the
sub-Riemannian metric $g_{SR}=dx_1^2+dx_2^2$. For a generic polynomial, we show
that the intersection of any fiber of $f$ and $V_f$ does not contain a
horizontal curve. Then we prove that each trajectory of the horizontal gradient
of $f$ approaching the set $V_f$ has a limit.


title: Counting derangements and Nash equilibria

abstract:
  The maximal number of totally mixed Nash equilibria in games of several
players equals the number of block derangements, as proved by McKelvey and
McLennan.On the other hand, counting the derangements is a well studied
problem. The numbers are identified as linearization coefficients for Laguerre
polynomials. MacMahon derived a generating function for them as an application
of his master theorem. This article relates the algebraic, combinatorial and
game-theoretic problems that were not connected before. New recurrence
relations, hypergeometric formulas and asymptotics for the derangement counts
are derived. An upper bound for the total number of all Nash equilibria is
given.


title:
Linear MIMO Precoding in Jointly-Correlated Fading Multiple Access
  Channels with Finite Alphabet Signaling

abstract:
  In this paper, we investigate the design of linear precoders for
multiple-input multiple-output (MIMO) multiple access channels (MAC). We assume
that statistical channel state information (CSI) is available at the
transmitters and consider the problem under the practical finite alphabet input
assumption. First, we derive an asymptotic (in the large-system limit) weighted
sum rate (WSR) expression for the MIMO MAC with finite alphabet inputs and
general jointly-correlated fading. Subsequently, we obtain necessary conditions
for linear precoders maximizing the asymptotic WSR and propose an iterative
algorithm for determining the precoders of all users. In the proposed
algorithm, the search space of each user for designing the precoding matrices
is its own modulation set. This significantly reduces the dimension of the
search space for finding the precoding matrices of all users compared to the
conventional precoding design for the MIMO MAC with finite alphabet inputs,
where the search space is the combination of the modulation sets of all users.
As a result, the proposed algorithm decreases the computational complexity for
MIMO MAC precoding design with finite alphabet inputs by several orders of
magnitude. Simulation results for finite alphabet signalling indicate that the
proposed iterative algorithm achieves significant performance gains over
existing precoder designs, including the precoder design based on the Gaussian
input assumption, in terms of both the sum rate and the coded bit error rate.


title: Tunable negative permeability in a quantum plasmonic metamaterial

abstract:
  We consider the integration of quantum emitters into a negative permeability
metamaterial design in order to introduce tunability as well as nonlinear
behavior. The unit cell of our metamaterial is a ring of metamolecules, each
consisting of a metal nanoparticle and a two-level semiconductor quantum dot
(QD). Without the QDs, the ring of the unit cell is known to act as an
artificial optical magnetic resonator. By adding the QDs we show that a Fano
interference profile is introduced into the magnetic field scattered from the
ring. This induced interference is shown to cause an appreciable effect in the
collective magnetic resonance of the unit cell. We find that the interference
provides a means to tune the response of the negative permeability
metamaterial. The exploitation of the QD's inherent nonlinearity is proposed to
modulate the metamaterial's magnetic response with a separate control field.


title: Selfacceleration with Quasidilaton

abstract:
  Quasidilaton massive gravity is an extension of massive General Relativity to
a theory with additional scale invariance and approximate internal Galilean
symmetry. The theory has a novel self-accelerated solution with the metric
indistinguishable (in the decoupling limit) from the de Sitter space, its
curvature set by the graviton mass. The spectra of tensor, vector, and scalar
perturbations on this solution contain neither ghosts, nor gradient
instabilities or superluminal modes, for a range of the parameter space. This
represents an example of a self-accelerated solution with viable perturbations,
attainable within a low energy effective field theory.


title:
Tunable VUV laser based spectrometer for Angle Resolved Photoemission
  Spectroscopy (ARPES)

abstract:
  We have developed an angle-resolved photoemission spectrometer with tunable
VUV laser as a photon source. The photon source is based on the fourth harmonic
generation of a near IR beam from a Ti:sapphire laser pumped by a CW green
laser and tunable between 5.3eV and 7eV. The most important part of the set-up
is a compact, vacuum enclosed fourth harmonic generator based on KBBF crystals,
grown hydrothermally in the US. This source can deliver a photon flux of over
10^14 photons/s. We demonstrate that this energy range is sufficient to measure
the kz dispersion in an iron arsenic high temperature superconductor, which was
previously only possible at synchrotron facilities.


title:
Solutions to a singularly perturbed supercritical elliptic equation on a
  Riemannian manifold concentrating at a submanifold

abstract:
  Given a smooth Riemannian manifold (M,g)we investigate the existence of
positive solutions to a singularly perturbed supercritical elliptic equation
which concentrate at some submanifold of M. We obtain a posive answer for some
manifolds, which include warped products.


title:
Semiclassical states for a static supercritical
  Klein-Gordon-Maxwell-Proca system on a closed Riemannian manifold

abstract:
  We establish the existence of semiclassical states for a nonlinear
Klein-Gordon-Maxwell-Proca system in static form, with Proca mass 1 on a closed
Riemannian manifold.
  Our results include manifolds of arbitrary dimension and allow supercritical
nonlinearities. In particular, we exhibit a large class of 3-dimensional
manifolds on which the system has semiclassical solutions for every exponent
p>2. The solutions we obtain concentrate at closed submanifolds of positive
dimension as the singular perturbation parameter goes to zero


title:
Patterns of Ship-borne Species Spread: A Clustering Approach for Risk
  Assessment and Management of Non-indigenous Species Spread

abstract:
  The spread of non-indigenous species (NIS) through the global shipping
network (GSN) has enormous ecological and economic cost throughout the world.
Previous attempts at quantifying NIS invasions have mostly taken "bottom-up"
approaches that eventually require the use of multiple simplifying assumptions
due to insufficiency and/or uncertainty of available data. By modeling implicit
species exchanges via a graph abstraction that we refer to as the Species Flow
Network (SFN), a different approach that exploits the power of network science
methods in extracting knowledge from largely incomplete data is presented.
Here, coarse-grained species flow dynamics are studied via a graph clustering
approach that decomposes the SFN to clusters of ports and inter-cluster
connections. With this decomposition of ports in place, NIS flow among clusters
can be very efficiently reduced by enforcing NIS management on a few chosen
inter-cluster connections. Furthermore, efficient NIS management strategy for
species exchanges within a cluster (often difficult due higher rate of travel
and pathways) are then derived in conjunction with ecological and environmental
aspects that govern the species establishment. The benefits of the presented
approach include robustness to data uncertainties, implicit incorporation of
"stepping-stone" spread of invasive species, and decoupling of species spread
and establishment risk estimation. Our analysis of a multi-year (1997--2006)
GSN dataset using the presented approach shows the existence of a few large
clusters of ports with higher intra-cluster species flow that are fairly stable
over time. Furthermore, detailed investigations were carried out on vessel
types, ports, and inter-cluster connections. Finally, our observations are
discussed in the context of known NIS invasions and future research directions
are also presented.


title: On change point detection using the fused lasso method

abstract:
  In this paper we analyze the asymptotic properties of l1 penalized maximum
likelihood estimation of signals with piece-wise constant mean values and/or
variances. The focus is on segmentation of a non-stationary time series with
respect to changes in these model parameters. This change point detection and
estimation problem is also referred to as total variation denoising or l1 -mean
filtering and has many important applications in most fields of science and
engineering. We establish the (approximate) sparse consistency properties,
including rate of convergence, of the so-called fused lasso signal approximator
(FLSA). We show that this only holds if the sign of the corresponding
consecutive changes are all different, and that this estimator is otherwise
incapable of correctly detecting the underlying sparsity pattern. The key idea
is to notice that the optimality conditions for this problem can be analyzed
using techniques related to brownian bridge theory.


title: Trivial Meet and Join within the Lattice of Monotone Triangles

abstract:
  The lattice of monotone triangles $(\mathfrak{M}_n,\le)$ ordered by
entry-wise comparisons is studied. Let $\tau_{\min}$ denote the unique minimal
element in this lattice, and $\tau_{\max}$ the unique maximum. The number of
$r$-tuples of monotone triangles $(\tau_1,\ldots,\tau_r)$ with minimal infimum
$\tau_{\min}$ (maximal supremum $\tau_{\max}$, resp.) is shown to
asymptotically approach $r|\mathfrak{M}_n|^{r-1}$ as $n \to \infty$. Thus, with
high probability this event implies that one of the $\tau_i$ is $\tau_{\min}$
($\tau_{\max}$, resp.). Higher-order error terms are also discussed.


title: $f(R)$ gravity: scalar perturbations in the late Universe

abstract:
  In this paper we study scalar perturbations of the metric for nonlinear
$f(R)$ models. We consider the Universe at the late stage of its evolution and
deep inside the cell of uniformity. We investigate the astrophysical approach
in the case of Minkowski spacetime background and two cases in the cosmological
approach, the large scalaron mass approximation and the quasi-static
approximation, getting explicit expressions for scalar perturbations for both
these cases. In the most interesting quasi-static approximation, the scalar
perturbation functions depend on both the nonlinearity function $f(R)$ and the
scale factor $a$. Hence, we can study the dynamical behavior of the
inhomogeneities (e.g., galaxies and dwarf galaxies) including into
consideration their gravitational attraction and the cosmological expansion,
and also taking into account the effects of nonlinearity. Our investigation is
valid for functions $f(R)$ which have stable de Sitter points in future with
respect to the present time, that is typical for the most popular $f(R)$
models.


title:
Blowing-up solutions concentrating along minimal submanifolds for some
  supercritical elliptic problems on Riemannian manifolds

abstract:
  Let $(M,g)$ and $(K,\kappa)$ be two Riemannian manifolds of dimensions $m$
and $k ,$ respectively. Let $\omega\in C^2(N),$ $\omega> 0.$
  The warped product $ M\times _\omega K$ is the $ (m+k)$-dimensional product
manifold $M\times K$ furnished with metric $ g+\omega^2 \kappa.$ We prove that
the supercritical problem $$-\Delta _{g+\omega^2 \kappa}u+h u=u^{ {m+2\over
m-2} \pm\varepsilon},\ u>0,\ \hbox{in}\ (M\times _\omega K,g+\omega^2 \kappa)$$
has a solution which concentrate along a $k$-dimensional minimal submanifold
$\Gamma$ of $M\times _\omega N$ as the real parameter $\varepsilon$ goes to
zero, provided the function $h$ and the sectional curvatures along $\Gamma$
satisfy a suitable condition.


title: Optimal linear Glauber model

abstract:
  Contrary to the actual nonlinear Glauber model (NLGM), the linear Glauber
model (LGM) is exactly solvable, although the detailed balance condition is not
generally satisfied. This motivates us to address the issue of writing the
transition rate ($w_j$) in a best possible linear form such that the mean
squared error in satisfying the detailed balance condition is least. The
advantage of this work is that, by studying the LGM analytically, we will be
able to anticipate how the kinetic properties of an arbitrary Ising system
depend on the temperature and the coupling constants. The analytical
expressions for the optimal values of the parameters involved in the linear
$w_j$ are obtained using a simple Moore-Penrose pseudoinverse matrix. This
approach is quite general, in principle applicable to any system and can
reproduce the exact results for one dimensional Ising system. In the continuum
limit, we get a linear time-dependent Ginzburg-Landau (TDGL) equation from the
Glauber's microscopic model of non-conservative dynamics. We analyze the
critical and dynamic properties of the model, and show that most of the
important results obtained in different studies can be reproduced by our new
mathematical approach. We will also show in this paper that the effect of
magnetic field can easily be studied within our approach; in particular, we
show that the inverse of relaxation time changes quadratically with (weak)
magnetic field and that the fluctuation-dissipation theorem is valid for our
model.


title: On the truncated matrix power moment problem with an open gap

abstract:
  In this paper we study the truncated power moment problem with an odd number
of prescribed moments. A Nevanlinna-type formula is derived for this moment
problem in the case when the moment problem has more than one solution (the
indeterminate case). The coefficients of the corresponding linear fractional
transformation are expressed explicitly in terms of the given moments. In the
determinate case the solution to the moment problem is constructed, as well.
Those solutions of the moment problem, which satisfy the following condition:
$M(\Delta)=0$, where $\Delta$ is a prescribed open subset of $\mathbb{R}$, and
$M$ is the matrix measure generated by a solution of the moment problem, are
described.


title:
On the one-loop effective potential in the higher-derivative
  four-dimensional chiral superfield theory with a nonconventional kinetic term

abstract:
  We explicitly calculate the one-loop effective potential for a
higher-derivative four-dimensional chiral superfield theory with a
nonconventional kinetic term. We consider the cases of minimal and nonminimal
general Lagrangians. In particular, we find that in the minimal case the
divergent part of the one-loop effective potential vanishes by reason of the
chirality.


title: Notes on isotropic geometry of production models

abstract:
  The production function is one of the key concepts of mainstream neoclassical
theories in economics. The study of the shape and properties of the production
possibility frontier is a subject of great interest in economic analysis. In
this respect, Cobb-Douglas and CES production functions with flat graph
hypersurfaces in Euclidean spaces are first studied in [19,20]. Later, more
general studies of production models were given in [4-10, 12, 21]. On the other
hand, from visual-physical experiences, the second and third authors proposed
in [14] to study production models via isotropic geometry. The purpose of this
paper is thus to investigate important production models via isotropic
geometry.


title:
Dramatic Changes in the Electronic Structure Upon Transition to the
  Collapsed Tetragonal Phase in CaFe2As2

abstract:
  We use angle-resolved photoemission spectroscopy (ARPES) and density
functional theory (DFT) calculations to study the electronic structure of
CaFe$_2$As$_2$ in previously unexplored collapsed tetragonal (CT) phase. This
unusual phase of the iron arsenic high temperature superconductors was hard to
measure as it exists only under pressure. By inducing internal strain, via the
post growth, thermal treatment of the single crystals, we were able to
stabilize the CT phase at ambient-pressure. We find significant differences in
the Fermi surface topology and band dispersion data from the more common
orthorhombic-antiferromagnetic or tetragonal-paramagnetic phases, consistent
with electronic structure calculations. The top of the hole bands sinks below
the Fermi level, which destroys the nesting present in parent phases. The
absence of nesting in this phase along with apparent loss of Fe magnetic
moment, are now clearly experimentally correlated with the lack of
superconductivity in this phase.


title: Confronting Outflow-Regulated Cluster Formation Model with Observations

abstract:
  Protostellar outflows have been shown theoretically to be capable of
maintaining supersonic turbulence in cluster-forming clumps and keeping the
star formation rate per free-fall time as low as a few percent. We aim to test
two basic predictions of this outflow-regulated cluster formation model, namely
(1) the clump should be close to virial equilibrium and (2) the turbulence
dissipation rate should be balanced by the outflow momentum injection rate,
using recent outflow surveys toward 8 nearby cluster-forming clumps (B59,
L1551, L1641N, Serpens Main Cloud, Serpens South, $\rho$ Oph, IC 348, and NGC
1333). We find, for almost all sources, that the clumps are close to virial
equilibrium and the outflow momentum injection rate exceeds the turbulence
momentum dissipation rate. In addition, the outflow kinetic energy is
significantly smaller than the clump gravitational energy for intermediate and
massive clumps with $M_{\rm cl} \gtrsim {\rm a \ few} \times 10^2 M_\odot$,
suggesting that the outflow feedback is not enough to disperse the clump as a
whole. The number of observed protostars also indicates that the star formation
rate per free-fall time is as small as a few percent for all clumps. These
observationally-based results strengthen the case for outflow-regulated cluster
formation.


title:
The Generalized Method of Moments for Electromagnetic Boundary Integral
  Equations

abstract:
  The Generalized Method of Moments (GMM) is a partition of unity based
technique for solving electromagnetic and acoustic boundary integral equations.
Past work on the GMM for electromagnetics was confined to geometries modeled by
piecewise flat tessellations and suffered from spurious internal line charges.
In the present article, we redesign the GMM scheme and demonstrate its ability
to model scattering from PEC scatterers composed of mixtures of smooth and
non-smooth geometrical features. Furthermore, we demonstrate that because the
partition of unity provides function and effective geometrical continuity
between patches, the GMM permits mixtures of local geometry descriptions and
approximation function spaces with significantly more freedom than traditional
moment methods.


title:
Perturbations of symmetric elliptic Hamiltonians of degree four in a
  complex domain

abstract:
  The cyclicity of the exterior period annulus of the asymmetrically perturbed
Duffing oscillator is a well known problem extensively studied in the
literature. In the present paper we provide a complete bifurcation diagram for
the number of the zeros of the associated Melnikov function in a suitable
complex domain.


title:
Reply to a Commentary "Asking photons where they have been without
  telling them what to say"

abstract:
  Interesting objections to conclusions of our experiment with nested
interferometers raised by Salih in a recent Commentary are analysed and
refuted.


title:
Three-Dimensional Superconformal Field Theory on Conic Space as Hologram
  of Charged Topological Black Hole

abstract:
  We construct three-dimensional N=2 supersymmetric conformal field theories on
conic spaces. Built upon the fact that the partition function depends solely on
the Reeb vector of the Killing vector, we propose that holographic dual of
these theories are four-dimensional, supersymmetric charged topological black
holes. With the supersymmetry localization technique, we study conserved
supercharges, free energy, and Renyi entropy. At planar large N limit, we
demonstrate perfect agreement between the superconformal field theories and the
supersymmetric charged topological black holes.


title:
On the Laurent coefficients of the Riemann map for the complement of the
  Mandelbrot set

abstract:
  We straighten a result of [5] about arithmetic properties of the Laurent
coefficients of the conformal isomorphism from the complement of the unit disk
onto the complement of the Mandelbrot set. This confirms an empirical
observation by Don Zagier, see [1]


title: State-specific detection of trapped HfF$^+$ by photodissociation

abstract:
  We use (1+1$'$) resonance-enhanced multiphoton photodissociation (REMPD) to
detect the population in individual rovibronic states of trapped HfF$^+$ with a
single-shot absolute efficiency of 18%, which is over 200 times better than
that obtained with fluorescence detection. The first photon excites a specific
rotational level to an intermediate vibronic band at 35,000-36,500 cm$^{-1}$,
and the second photon, at 37,594 cm$^{-1}$ (266 nm), dissociates HfF$^+$ into
Hf$^+$ and F. Mass-resolved time-of-flight ion detection then yields the number
of state-selectively dissociated ions. Using this method, we observe
rotational-state heating of trapped HfF$^+$ ions from collisions with neutral
Ar atoms. Furthermore, we measure the lifetime of the $^3\Delta_1$ $v=0,\, J=1$
state to be 2.1(2) s. This state will be used for a search for a permanent
electric dipole moment of the electron.


title: Real Time Strategy Language

abstract:
  Real Time Strategy (RTS) games provide complex domain to test the latest
artificial intelligence (AI) research. In much of the literature, AI systems
have been limited to playing one game. Although, this specialization has
resulted in stronger AI gaming systems it does not address the key concerns of
AI researcher. AI researchers seek the development of AI agents that can
autonomously interpret learn, and apply new knowledge. To achieve human level
performance, current AI systems rely on game specific knowledge of an expert.
The paper presents the full RTS language in hopes of shifting the current
research focus to the development of general RTS agents. General RTS agents are
AI gaming systems that can play any RTS games, defined in the RTS language.
This prevents game specific knowledge from being hard coded into the system,
thereby facilitating research that addresses the fundamental concerns of
artificial intelligence.


title: A new candidate Wolf-Rayet X-ray binary in NGC 253

abstract:
  We have discovered a persistent, but highly variable X-ray source in the
nearby starburst galaxy NGC 253. The source varies at the level of a factor of
about 5 in count rate on timescales of a few hours. Two long observations of
the source with Chandra and XMM-Newton show suggestive evidence for the source
having a period of about 14-15 hours, but the time sampling in existing data is
insufficient to allow a firm determination that the source is periodic. Given
the amplitude of variation and the location in a nuclear starburst, the source
is likely to be a Wolf-Rayet X-ray binary, with the tentative period being the
orbital period of the system. In light of the fact that we have demonstrated
that careful examination of the variability of moderately bright X-ray sources
in nearby galaxies can turn up candidate Wolf-Rayet X-ray binaries, we discuss
the implications of Wolf-Rayet X-ray binaries for predictions of the
gravitational wave source event rate, and, potentially, interpretations of the
events.


title:
Underluminous Type II Plateau Supernovae: II. Pointing towards moderate
  mass precursors

abstract:
  We present new data for five under-luminous type II-plateau supernovae (SNe
IIP), namely SN 1999gn, SN 2002gd, SN 2003Z, SN 2004eg and SN 2006ov. This new
sample of low-luminosity SNe IIP (LL SNe IIP) is analyzed together with similar
objects studied in the past. All of them show a flat light curve plateau
lasting about 100 days, an under luminous late-time exponential tail, intrinsic
colours that are unusually red, and spectra showing prominent and narrow
P-Cygni lines. A velocity of the ejected material below 10^3 km/s is inferred
from measurements at the end of the plateau. The 56Ni masses ejected in the
explosion are very small (less than 10^-2 solar masses). We investigate the
correlations among 56Ni mass, expansion velocity of the ejecta and absolute
magnitude in the middle of the plateau, confirming the main findings of Hamuy
(2003), according to which events showing brighter plateau and larger expansion
velocities are expected to produce more 56Ni. We propose that these faint
objects represent the low luminosity tail of a continuous distribution in
parameters space of SNe IIP. The physical properties of the progenitors at the
explosion are estimated through the hydrodynamical modeling of the observables
for two representative events of this class, namely SN 2005cs and SN 2008in. We
find that the majority of LL SNe IIP, and quite possibly all, originate in the
core-collapse of intermediate mass stars, in the mass range 10-15 solar masses.


title: Band Tunneling through Double Barrier in Bilayer Graphene

abstract:
  By taking into account the full four band energy spectrum, we calculate the
transmission probability and conductance of electrons across symmetric and
asymmetric double potential barrier with a confined interlayer potential
difference in bilayer graphene. For energies less than the interlayer coupling
\gamma_{1}, E<\gamma_1, we have one channel for transmission which exhibits
resonances, even for incident particles with energies less than the strength of
barriers, E < U_j, depending on the double barrier geometry. In contrast, for
higher energies E > \gamma_{1}, we obtain four possible ways for transmission
resulting from the two propagating modes. We compute the associated
transmission probabilities as well as their contribution to the conductance,
study the effect of the double barrier geometry.

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


title:
Shearing process and an example of a bounded support function in
  $S^0(\mathbb B^2)$

abstract:
  We introduce a process, that we call "shearing", which for any given normal
Loewner chain produces a normal Loewner chain made of shears automorphisms. As
an application, and in stringent contrast to the one-dimensional case, we prove
the existence of a starlike bounded function in the class $S^0$ of the ball
$\mathbb B^2$ (in fact the restriction of a shear automorphism of $\mathbb
C^2$) which is a support point for a linear continuous functional.


title:
Interplay of Coulomb Blockade and Ferroelectricity in Nano-Granular
  Materials

abstract:
  We study electron transport properties of composite ferroelectrics ---
materials consisting of metallic grains embedded in a ferroelectric matrix. In
particular, we calculate the conductivity in a wide range of temperatures and
electric fields, showing pronounced hysteretic behavior. In weak fields,
electron cotunneling is the main transport mechanism. In this case, we show
that the ferroelectric matrix strongly influences the transport properties
through two effects: i) the dependence of the Coulomb gap on the dielectric
permittivity of the ferroelectric matrix, which in turn is controlled by
temperature and external field; and ii) the dependence of the tunneling matrix
elements on the electric polarization of the ferroelectric matrix, which can be
tuned by temperature and applied electric field as well. In the case of strong
electric fields, the Coulomb gap is suppressed and only the second mechanism is
important. Our results are important for i) thermometers for precise
temperature measurements and ii) ferrroelectric memristors.


title: Non-destructive testing of composite plates by holographic vibrometry

abstract:
  We report on a wide-field optical monitoring method for revealing local
delaminations in sandwich-type composite plates at video-rate by holographic
vibrometry. Non-contact measurements of low frequency flexural waves is
performed with time-averaged heterodyne holography. It enables narrowband
imaging of local out-of-plane nanometric vibration amplitudes under sinusoidal
excitation, and reveals delamination defects, which cause local resonances of
flexural waves. The size of the defect can be estimated from the first
resonance frequency of the flexural wave and the mechanical parameters of the
observed layer of the composite plate.


title: On multicurve models for the term structure

abstract:
  In the context of multi-curve modeling we consider a two-curve setup, with
one curve for discounting (OIS swap curve) and one for generating future cash
flows (LIBOR for a give tenor). Within this context we present an approach for
the clean-valuation pricing of FRAs and CAPs (linear and nonlinear derivatives)
with one of the main goals being also that of exhibiting an "adjustment factor"
when passing from the one-curve to the two-curve setting. The model itself
corresponds to short rate modeling where the short rate and a short rate spread
are driven by affine factors; this allows for correlation between short rate
and short rate spread as well as to exploit the convenient affine structure
methodology. We briefly comment also on the calibration of the model
parameters, including the correlation factor.


title: On the cohomology of pseudoeffective line bundles

abstract:
  The goal of this survey is to present various results concerning the
cohomology of pseudoeffective line bundles on compact K{\"a}hler manifolds, and
related properties of their multiplier ideal sheaves. In case the curvature is
strictly positive, the prototype is the well known Nadel vanishing theorem,
which is itself a generalized analytic version of the fundamental
Kawamata-Viehweg vanishing theorem of algebraic geometry. We are interested
here in the case where the curvature is merely semipositive in the sense of
currents, and the base manifold is not necessarily projective. In this
situation, one can still obtain interesting information on cohomology, e.g. a
Hard Lefschetz theorem with pseudoeffective coefficients, in the form of a
surjectivity statement for the Lefschetz map. More recently, Junyan Cao, in his
PhD thesis defended in Grenoble, obtained a general K{\"a}hler vanishing
theorem that depends on the concept of numerical dimension of a given
pseudoeffective line bundle. The proof of these results depends in a crucial
way on a general approximation result for closed (1,1)-currents, based on the
use of Bergman kernels, and the related intersection theory of currents.
Another important ingredient is the recent proof by Guan and Zhou of the strong
openness conjecture. As an application, we discuss a structure theorem for
compact K{\"a}hler threefolds without nontrivial subvarieties, following a
joint work with F.Campana and M.Verbitsky. We hope that these notes will serve
as a useful guide to the more detailed and more technical papers in the
literature; in some cases, we provide here substantially simplified proofs and
unifying viewpoints.


title:
SoaDssPm: A new Service-Oriented Architecture of the decision support
  system for the Project Management

abstract:
  This paper presents an architecture for the Project Management, which is
defined using the concepts behind ServiceOriented and Decision Support System.
The framework described, denominated as SoaDssPm, represents the following: a
coherent solution to the problem of control Project Management the existing gap
between the real execution of Project Management by describing the business
process and relationships required by a SOA solution, and its objectives
representation, in which the decisional aspects determine the final shape of
the system, providing decision support to the identified business processes and
constraints.


title: Multi-variable orthogonal polynomials

abstract:
  We characterize the atomic probability measure on $\mathbb{R}^d$ which having
a finite number of atoms. We further prove that the Jacobi sequences associated
to the multiple Hermite (resp. Laguerre, resp. Jacobi) orthogonal polynomials
are diagonal matrices. Finally, as a consequence of the multiple Jacobi
orthogonal polynomials case, we give the Jacobi sequences of the
  Gegenbauer, Chebyshev and Legendre orthogonal polynomials.


title: High electric field development for the SNS nEDM Experiment

abstract:
  A new experiment to search for the permanent electric dipole moment of the
neutron is being developed for installation at the Spallation Neutron Source at
Oak Ridge National Laboratory. This experiment will be performed in liquid
helium at ? 0:4 K and requires a large electric field (E ~ 75 kV/cm) to be
applied in liquid helium. We have constructed a new HV test apparatus to study
electric breakdown in liquid helium. Initial results demonstrated that it is
possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two
electropolished stainless steel electrodes12 cm in diameter for a wide range of
pressures.


title: Charge transport in holography with momentum dissipation

abstract:
  In this work, we examine how charge is transported in a theory where momentum
is relaxed by spatially dependent, massless scalars. We analyze the possible IR
phases in terms of various scaling exponents and the (ir)relevance of operators
in the IR effective holographic theory with a dilaton. We compute the (finite)
resistivity and encounter broad families of (in)coherent metals and insulators,
characterized by universal scaling behaviour. The optical conductivity at zero
temperature and low frequencies exhibits power tails which can violate scaling
symmetries, due to the running of the dilaton. At low temperatures, our model
captures features of random-field disorder.


title:
Quantum Entanglement in Carbon-Carbon, Carbon-Phosphorus and
  Silicon-Silicon Bonds

abstract:
  The chemical bond is an important local concept to understand chemical
compounds and processes. Unfortunately, like most local concepts, the chemical
bond and the bond order do not correspond to any physical observable and thus
cannot be determined as an expectation value of a quantum chemical operator. We
recently demonstrated [Boguslawski et al., J. Chem. Theory Comput., 2013, 9,
2959--2973] that one- and two-orbital-based entanglement measures can be
applied to interpret electronic wave functions in terms of orbital correlation.
Orbital entanglement emerged to be a powerful tool to provide a qualitative
understanding of bond-forming and bond-breaking processes, and allowed for an
estimation of bond orders of simple diatomic molecules beyond the classical
bonding models. In this article we demonstrate that the orbital entanglement
analysis can be extended to polyatomic molecules to understand chemical
bonding.


title: On the Reduction of Singularly-Perturbed Linear Differential Systems

abstract:
  In this article, we recover singularly-perturbed linear differential systems
from their turning points and reduce the rank of the singularity in the
parameter to its minimal integer value. Our treatment is Moser-based; that is
to say it is based on the reduction criterion introduced for linear singular
differential systems by Moser. Such algorithms have proved their utility in the
symbolic resolution of the systems of linear functional equations, giving rise
to the package ISOLDE, as well as in the perturbed algebraic eigenvalue
problem. Our algorithm, implemented in the computer algebra system Maple, paves
the way for efficient symbolic resolution of singularly-perturbed linear
differential systems as well as further applications of Moser-based reduction
over bivariate (differential) fields.


title: Formal Solutions of a Class of Pfaffian Systems in Two Variables

abstract:
  In this paper, we present an algorithm which computes a fundamental matrix of
formal solutions of completely integrable Pfaffian systems with normal
crossings in two variables, based on (Barkatou, 1997). A first step was set in
(Barkatou-LeRoux, 2006) where the problem of rank reduction was tackled via the
approach of (Levelt, 1991). We give instead a Moser-based approach. And, as a
complementary step, we associate to our problem a system of ordinary linear
singular differential equations from which the formal invariants can be
efficiently derived via the package ISOLDE, implemented in the computer algebra
system Maple.


title:
Characterizing Binary Properties of $5\, M_\odot$ Stars: New Approaches
  Using Cepheids

abstract:
  Cepheids provide approaches to determining binary parameters which are often
complementary to those for main sequence massive and intermediate mass stars.
Specifically, we are using high resolution imaging, radial velocities, and
X-ray studies to determine binary characteristics. Among the results are that
they have both a high frequency of binary systems, and also a high proportion
of triple systems.


title: A class of symmetric association schemes as inclusion of biplanes

abstract:
  Let ${\cal B}$ be a nontrivial biplane of order $k-2$ represented by
symmetric canonical incidence matrix with trace $1+ \binom{k}{2}$. We proved
that ${\cal B}$ includes a partially balanced incomplete design with
association scheme of three classes. Consequently, these structures are
symmetric, having $2k-6$ points. While it is not known whether this class is
finite or infinite, we show that there is a related superclass with infinitely
many representatives.


title:
The chemodynamical evolution of the Milky Way disc -- A new modeling
  approach

abstract:
  Despite the recent advancements in the field of galaxy formation and
evolution, fully self-consistent simulations are still unable to make the
detailed predictions necessary for the planned and ongoing large spectroscopic
and photometry surveys of the Milky Way disc. These difficulties arise from the
very uncertain nature of sub-grid physical energy feedback within models,
affecting both star formation rates and chemical enrichment. To avoid these
problems, we have introduced a new approach which consists of fusing disc
chemical evolution models with compatible numerical simulations. We demonstrate
the power of this method by showing that a range of observational results can
be explained by our new model. We show that due to radial migration from
mergers at high redshift and the central bar at later times, a sizable fraction
of old metal-poor, high-[alpha/Fe] stars can reach the solar vicinity. This
naturally accounts for a number of recent observations related to both the thin
and thick discs, despite the fact that we use thin-disc chemistry only. Within
the framework of our model, the MW thick disc has emerged naturally from (i)
stars born with high velocity dispersions at high redshift, (ii) stars
migrating from the inner disc very early on due to strong merger activity, and
(iii) further radial migration driven by the bar and spirals at later times. A
significant fraction of old stars with thick-disc characteristics could have
been born near the solar radius.


title:
Top-quark forward-backward asymmetry from a color-octet t-channel
  resonance

abstract:
  We consider new physics contributions to the top-quark forward-backward
asymmetry from a neutral $V^0_8$ or charged $V^+_8$ color-octet vector
exchanged in the $t$-channel. We study the phenomenological constraints on
these particles arising from the Tevatron and LHC7 measurements and compare
them with those on their color singlet counterparts $Z^\prime$ and $W^\prime$.
We find that the color octets fare better than the singlets in that they
generate a lower $A_C$, a lower high-invariant mass cross-section at LHC7 and a
lower same sign top-pair cross-section. However, they also generate a lower
$A_{FB}$ than their color-singlet counterparts.


title: Exploiting Spectral Leakage for Spectrogram Frequency Super-resolution

abstract:
  The spectrogram is a classical DSP tool used to view signals in both time and
frequency. Unfortunately, the Heisenberg Uncertainty Principal limits our
ability to use them for detecting and measuring narrowband signal modulation in
wideband environments. On a spectrogram, instantaneous frequency can only be
measured to the nearest bin without additional interpolation. This work
presents a novel technique for extracting higher accuracy frequency estimates.
Whereas most practitioners seek to suppress spectral leakage, we use mismatched
windows to exploit such artifacts in order to produce super-resolved spectral
displays. We present a derivation of our methodology and exhibit several
interesting examples.


title: On the structure of the Nx phase of symmetric dimers

abstract:
  NMR measurements on a selectively deuteriated liquid crystal dimer CB-C9-CB
exhibiting two nematic phases show that the molecules in the lower temperature
nematic phase, Nx, experience a chiral environment and are ordered about a
unique direction. The results are contrasted with previous reports that
proposed a twist-bend spatial variation of the director. A structural model is
proposed wherein the molecules show organization into highly correlated
assemblies of opposite chirality.


title:
Asymptotics of the Tacnode process: a transition between the gap
  probabilities from the Tacnode to the Airy process

abstract:
  We study the gap probabilities of the single-time Tacnode process. Through
steepest descent analysis of a suitable Riemann-Hilbert problem, we show that
under appropriate scaling regimes the gap probability of the Tacnode process
degenerates into a product of two independent gap probabilities of the Airy
processes.


title:
Modules with many non-associates and norm form equations with many
  families of solutions

abstract:
  For every number field $\mathbb{K}$, with $[\mathbb{K}:\mathbb{Q}] \geq 3$,
we show that the number of non-associates of the same norm in a full module in
$\mathbb{K}$ does not depend only on $\mathbb{K}$, but can also depend on the
module itself. As a corollary, the same can be true for the number of families
of solutions of degenerate norm form equations. So the uniform bound obtained
by Schmidt for the number of solutions in the non-degenerate case does not
always hold in the degenerate case. For three-variable norm forms not arising
from full modules, we do obtain a Schmidt-type bound for the number of families
of solutions that, together with the above result, completes this aspect of the
study of three-variable norm forms.


title: Topological Photonic Phase in Chiral Hyperbolic Metamaterials

abstract:
  Recently the possibility of achieving one-way backscatter immune
transportation of light by mimicking the topological order present within
certain solid state systems, such as topological insulators, has received much
attention. Thus far however, demonstrations of non-trivial topology in
photonics have relied on photonic crystals with precisely engineered lattice
structures, periodic on the scale of the operational wavelength and composed of
finely tuned, complex materials. Here we propose a novel effective medium
approach towards achieving topologically protected photonic surface states
robust against disorder on all length scales and for a wide range of material
parameters. Remarkably, the non-trivial topology of our metamaterial design
results from the Berry curvature arising from the transversality of
electromagnetic waves in a homogeneous medium. Our investigation therefore acts
to bridge the gap between the advancing field of topological band theory and
classical optical phenomena such as the Spin Hall effect of light. The
effective medium route to topological phases will pave the way for highly
compact one-way transportation of electromagnetic waves in integrated photonic
circuits.


title: Local Constants for Heisenberg Representations

abstract:
  We can attach a local constant to every finite dimensional continuous complex
representation of a local Galois group of a non-archimedean local field
$F/\mathbb{Q}_p$ by Deligne and Langlands. Tate \cite{JT1} gives an explicit
formula for computing local constants for linear characters of $F^\times$, but
there is no explicit formula of local constant for any arbitrary representation
of a local Galois group. In this article we study Heisenberg representations of
the absolute Galois group $G_F$ of $F$ and give invariant formulas of local
constants for Heisenberg representations of dimension prime to $p$.


title:
Complete solution of the diophantine equation $X^{2}+1=dY^{4}$ and a
  related family of quartic Thue equations

abstract:
  In this paper, we use the method of Thue and Siegel, based on explicit Pade
approximations to algebraic functions, to completely solve a family of quartic
Thue equations. From this result, we can also solve the diophantine equation in
the title. We prove that this equation has at most one solution in positive
integers when $d \geq 3$. Moreover, when such a solution exists, it is of the
form $(u,\sqrt{v})$ where $(u,v)$ is the fundamental solution of
$X^{2}+1=dY^{2}$.


title: Thermodynamic relations for DNA phase transitions

abstract:
  The force induced unzipping transition of a double stranded DNA is considered
from a purely thermodynamic point of view. This analysis provides us with a set
of relations that can be used to test microscopic theories and experiments. The
thermodynamic approach is based on the hypothesis of impenetrability of the
force in the zipped state. The melting and the unzipping transitions are
considered in the same framework and compared with the existing statistical
model results. The analysis is then extended to a possible continuous unzipping
transition.

categories: cond-mat.soft cond-mat.stat-mech physics.bio-ph q-bio.BM


title:
Modeling the stylized facts of wholesale system marginal price (SMP) and
  the impacts of regulatory reforms on the Greek Electricity Market

abstract:
  This work presents the results of an empirical research with the target of
modeling the stylized facts of the daily expost System Marginal Price (SMP) of
the Greek wholesale electricity market, using data from January 2004 to
December of 2011. SMP is considered here as the footprint of an underline
stochastic and nonlinear process that bears all the information reflecting not
only the effects of changes in endogenous or fundamental factors of the market
but also the impacts of a series of regulatory reforms that have continuously
changed the market's microstructure. To capture the dynamics of the conditional
mean and volatility of SMP that generate the stylized facts(mean reversion,
price spikes, fat tails price distribution etc), a number of ARMAX GARCH models
have been estimated using as regressors an extensive set of fundamental factors
in the Greek electricity market as well as dummy variables that mimic the
history of Regulator's interventions. The findings show that changes in the
microstructure of the market caused by the reforms have strongly affected the
dynamic evolution of SMP and that the best found model captures adequately the
stylized facts of the series that other electricity and financial markets
share. The dynamics of the conditional volatility generated by the model can be
extremely useful in the efforts that are under way towards market restructuring
so the Greek market to be more compatible with the requirements of the European
Target Model.


title:
Chern Half Metals: A New Class of Topological Materials to Realize the
  Quantum Anomalous Hall Effect

abstract:
  The search of new topological insulators that demonstrate the quantum
anomalous Hall effect (QAHE) is a cutting-edge research topic in condensed
matter physics and materials science. So far, the QAHE has been observed only
in Cr-doped (Bi,Sb)2Te3 at extremely low temperature. Therefore, it is
important to find new materials with large topological band gap and high
thermal stability for the realization of the QAHE. Based on first-principles
and tight-binding model calculations, we discovered a new class of topological
phase$-$Chern half metal which manifests the QAHE in one spin channel while is
metallic in the other spin channel$-$in Co or Rh deposited graphene. Meanwhile,
these systems have large perpendicular magnetic anisotropy energies of 5.3 and
11.5 meV, necessary for the observation of the QAHE at reasonably high
temperature.


title:
Sharp existence criteria for positive solutions of Hardy-Sobolev type
  systems

abstract:
  This paper examines systems of poly-harmonic equations of the Hardy--Sobolev
type and the closely related weighted systems of integral equations involving
Riesz potentials. Namely, it is shown that the two systems are equivalent under
some appropriate conditions. Then a sharp criterion for the existence and
non-existence of positive solutions is determined for both differential and
integral versions of a Hardy--Sobolev type system with variable coefficients.
In the constant coefficient case, Liouville type theorems for positive radial
solutions are also established using radial decay estimates and Pohozaev type
identities in integral form.


title: Some remarks on Davie's uniqueness theorem

abstract:
  We present a new approach to Davie's theorem on the uniqueness of solutions
to the equation $dX_t = b(t, X_t)\,dt + dW_t$ for almost all Brownian paths. A
generalization of this result and a discussion of some close problems are
given.


title: Contractions with necessarily unbounded matrices

abstract:
  We prove that for each dimension not less than five there exists a
contraction between solvable Lie algebras that can be realized only with
matrices whose Euclidean norms necessarily approach infinity at the limit value
of contraction parameter. Therefore, dimension five is the lowest dimension of
Lie algebras between which contractions of the above kind exist.


title:
Boundedness of non-homogeneous square functions and $L^q$ type testing
  conditions with $q \in (1,2)$

abstract:
  We continue the study of local $Tb$ theorems for square functions defined in
the upper half-space $(\mathbb{R}^{n+1}_+, \mu \times dt/t)$. Here $\mu$ is
allowed to be a non-homogeneous measure in $\mathbb{R}^n$. In this paper we
prove a boundedness result assuming local $L^q$ type testing conditions in the
difficult range $q \in (1,2)$. Our theorem is a non-homogeneous version of a
result of S. Hofmann valid for the Lebesgue measure. It is also an extension of
the recent results of M. Lacey and the first named author where non-homogeneous
local $L^2$ testing conditions have been considered.


title: Singularity content

abstract:
  We show that a cyclic quotient surface singularity S can be decomposed, in a
precise sense, into a number of elementary T-singularities together with a
cyclic quotient surface singularity called the residue of S. A normal surface X
with isolated cyclic quotient singularities {S_i} admits a Q-Gorenstein partial
smoothing to a surface with singularities given by the residues of the S_i. We
define the singularity content of a Fano lattice polygon P: this records the
total number of elementary T-singularities and the residues of the
corresponding toric Fano surface X_P. We express the degree of X_P in terms of
the singularity content of P; give a formula for the Hilbert series of X_P in
terms of singularity content; and show that singularity content is an invariant
of P under mutation.


title:
Correcting a SHAPE-directed RNA structure by a mutate-map-rescue
  approach

abstract:
  The three-dimensional conformations of non-coding RNAs underpin their
biochemical functions but have largely eluded experimental characterization.
Here, we report that integrating a classic mutation/rescue strategy with
high-throughput chemical mapping enables rapid RNA structure inference with
unusually strong validation. We revisit a paradigmatic 16S rRNA domain for
which SHAPE (selective 2`-hydroxyl acylation with primer extension) suggested a
conformational change between apo- and holo-ribosome conformations.
Computational support estimates, data from alternative chemical probes, and
mutate-and-map (M2) experiments expose limitations of prior methodology and
instead give a near-crystallographic secondary structure. Systematic
interrogation of single base pairs via a high-throughput mutation/rescue
approach then permits incisive validation and refinement of the M2-based
secondary structure and further uncovers the functional conformation as an
excited state (25+/-5% population) accessible via a single-nucleotide register
shift. These results correct an erroneous SHAPE inference of a ribosomal
conformational change and suggest a general mutate-map-rescue approach for
dissecting RNA dynamic structure landscapes.


title: HAT-P-49b: A 1.7 M_J Planet Transiting a Bright 1.5 M_S F-Star

abstract:
  We report the discovery of the transiting extrasolar planet HAT-P-49b. The
planet transits the bright (V = 10.3) slightly evolved F-star HD 340099 with a
mass of 1.54M_S and a radius of 1.83 R_S. HAT-P-49b is orbiting one of the 25
brightest stars to host a transiting planet which makes this a favorable
candidate for detailed follow-up. This system is an especially strong target
for Rossiter- McLaughlin follow-up due to the fast rotation of the host star,
16 km/s. The planetary companion has a period of 2.6915 d, mass of 1.73 M_J and
radius of 1.41 R_J. The planetary characteristics are consistent with that of a
classical hot Jupiter but we note that this is the fourth most massive star to
host a transiting planet with both M_p and R_p well determined.


title:
Inelastic scattering puts in question recent claims of Anderson
  localization of light

abstract:
  The interplay between nonlinear effects and Anderson localization in
disordered optical fibres1 has recently attracted great interest, and it is
important in the action of random lasers in which closed multiple scattering
loops have enhanced intensity. As optical nonlinearities in TiO2 can give
valuable information on the nature of light transport in strongly scattering
powders, we studied these effects in an extended experimental and theoretical
investigation (to be published). Now, Scheffold and Wiersma have ...

categories: cond-mat.dis-nn cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.soft physics.optics


title:
Generalised Chern-Simons Theory and ${\rm G}_2$-Instantons over
  Associative Fibrations

abstract:
  Adjusting conventional Chern-Simons theory to ${\rm G}_2$-manifolds, one
describes ${\rm G}_2$-instantons on bundles over a certain class of
$7$-dimensional flat tori which fiber non-trivially over $T^4$, by a pullback
argument. Moreover, if $c_2\neq0$, any (generic) deformation of the ${\rm
G}_2$-structure away from such a fibred structure causes all instantons to
vanish. A brief investigation in the general context of (conformally
compatible) associative fibrations $f:Y^7\to X^4$ relates ${\rm
G}_2$-instantons on pullback bundles $f^*E\to Y$ and self-dual connections on
the bundle $E\to X$ over the base, a fact which may be of independent interest.


title: Coexistence of Superconductivity and Ferromagnetism in P-doped EuFe2As2

abstract:
  The magnetic structure of the Eu2+ moments in the superconducting
EuFe2(As1-xPx)2 sample with x = 0.15 has been determined using element specific
x-ray resonant magnetic scattering. Combining magnetic, thermodynamic and
scattering measurements, we conclude that the long range ferromagnetic order of
the Eu2+ moments aligned primarily along the c axis coexists with the bulk
superconductivity at zero field. At an applied magnetic field >= 0.6 T,
superconductivity still coexists with the ferromagnetic Eu2+ moments which are
polarized along the field direction. We propose a spontaneous vortex state for
the coexistence of superconductivity and ferromagnetism in EuFe2(As0.85P0.15)2.


title:
Computation of Minimal Filtered Free Resolutions over
  $\mathbb{N}$-Filtered Solvable Polynomial Algebras

abstract:
  Let $A=K[a_1,\ldots,a_n]$ be a weighted $\mathbb{N}$-filtered solvable
polynomial algebra with filtration $FA=\{ F_pA\}_{p\in\mathbb{N}}$, where
solvable polynomial algebras are in the sense of (A. Kandri-Rody and V.
Weispfenning, Non-commutative Gr\"obner bases in algebras of solvable type.
{\it J. Symbolic Comput.}, 9(1990), 1--26), and $FA$ is constructed with
respect to a positive-degree function $d(~)$ on $A$. By introducing minimal
F-bases and minimal standard bases respectively for left $A$-modules and their
submodules with respect to good filtrations, minimal filtered free resolutions
for finitely generated $A$-modules are introduced. It is shown that any two
minimal F-bases, respectively any two minimal standard bases have the same
number of elements and the same number of elements of the same filtered degree;
that minimal filtered free resolutions are unique up to strict filtered
isomorphism of chain complexes in the category of filtered $A$-modules; and
that minimal finite filtered free resolutions can be algorithmically computed
by employing Gr\"obner basis theory for modules over $A$ with respect to any
graded left monomial ordering on free left $A$-modules.


title: BDGS: A Scalable Big Data Generator Suite in Big Data Benchmarking

abstract:
  Data generation is a key issue in big data benchmarking that aims to generate
application-specific data sets to meet the 4V requirements of big data.
Specifically, big data generators need to generate scalable data (Volume) of
different types (Variety) under controllable generation rates (Velocity) while
keeping the important characteristics of raw data (Veracity). This gives rise
to various new challenges about how we design generators efficiently and
successfully. To date, most existing techniques can only generate limited types
of data and support specific big data systems such as Hadoop. Hence we develop
a tool, called Big Data Generator Suite (BDGS), to efficiently generate
scalable big data while employing data models derived from real data to
preserve data veracity. The effectiveness of BDGS is demonstrated by developing
six data generators covering three representative data types (structured,
semi-structured and unstructured) and three data sources (text, graph, and
table data).


title: The Zeldovich approximation

abstract:
  This year marks the 100th anniversary of the birth of Yakov Zel'dovich.
Amongst his many legacies is the Zel'dovich approximation for the growth of
large-scale structure, which remains one of the most successful and insightful
analytic models of structure formation. We use the Zel'dovich approximation to
compute the two-point function of the matter and biased tracers, and compare to
the results of N-body simulations and other Lagrangian perturbation theories.
We show that Lagrangian perturbation theories converge well and that the
Zel'dovich approximation provides a good fit to the N-body results except for
the quadrupole moment of the halo correlation function. We extend the
calculation of halo bias to 3rd order and also consider non-local biasing
schemes, none of which remove the discrepancy. We argue that a part of the
discrepancy owes to an incorrect prediction of inter-halo velocity
correlations. We use the Zel'dovich approximation to compute the ingredients of
the Gaussian streaming model and show that this hybrid method provides a good
fit to clustering of halos in redshift space down to scales of tens of Mpc.


title:
First results from the Dragonfly Telephoto Array: the apparent lack of a
  stellar halo in the massive spiral galaxy M101

abstract:
  We use a new telescope concept, the Dragonfly Telephoto Array, to study the
low surface brightness outskirts of the spiral galaxy M101. The radial surface
brightness profile is measured down to mu_g ~ 32 mag/arcsec^2, a depth that
approaches the sensitivity of star count studies in the Local Group. We convert
surface brightness to surface mass density using the radial g-r color profile.
The mass density profile shows no significant upturn at large radius and is
well-approximated by a simple bulge + disk model out to R = 70 kpc,
corresponding to 18 disk scale lengths. Fitting a bulge + disk + halo model we
find that the best-fitting halo mass M_halo ~ 1.7 x 10^8 M_sun. The total
stellar mass of M101 is M_tot,* ~ 5.3 x 10^10 Msun, and we infer that the halo
mass fraction f_halo = M_halo / M_tot,* ~ 0.003. This mass fraction is lower
than that of the Milky Way (f_halo ~ 0.02) and M31 (f_halo ~ 0.04). All three
galaxies fall below the f_halo - M_tot,* relation predicted by recent
cosmological simulations that trace the light of disrupted satellites, with
M101's halo mass a factor of ~10 below the median expectation. However, the
predicted scatter in this relation is large, and more galaxies are needed to
better quantify this possible tension with galaxy formation models. Dragonfly
is well suited for this project: as integrated-light surface brightness is
independent of distance, large numbers of galaxies can be studied in a uniform
way.

categories: astro-ph.GA astro-ph.CO astro-ph.IM astro-ph.SR


title:
Precursors prior to Type IIn supernova explosions are common: precursor
  rates, properties, and correlations

abstract:
  There is a growing number of supernovae (SNe), mainly of Type IIn, which
present an outburst prior to their presumably final explosion. These precursors
may affect the SN display, and are likely related to some poorly charted
phenomena in the final stages of stellar evolution. Here we present a sample of
16 SNe IIn for which we have Palomar Transient Factory (PTF) observations
obtained prior to the SN explosion. By coadding these images taken prior to the
explosion in time bins, we search for precursor events. We find five Type IIn
SNe that likely have at least one possible precursor event, three of which are
reported here for the first time. For each SN we calculate the control time.
Based on this analysis we find that precursor events among SNe IIn are common:
at the one-sided 99% confidence level, more than 50% of SNe IIn have at least
one pre-explosion outburst that is brighter than absolute magnitude -14, taking
place up to 1/3 yr prior to the SN explosion. The average rate of such
precursor events during the year prior to the SN explosion is likely larger
than one per year, and fainter precursors are possibly even more common. We
also find possible correlations between the integrated luminosity of the
precursor, and the SN total radiated energy, peak luminosity, and rise time.
These correlations are expected if the precursors are mass-ejection events, and
the early-time light curve of these SNe is powered by interaction of the SN
shock and ejecta with optically thick circumstellar material.


title: A spectral synthesis code for rapid modelling of supernovae

abstract:
  We present TARDIS - an open-source code for rapid spectral modelling of
supernovae (SNe). Our goal is to develop a tool that is sufficiently fast to
allow exploration of the complex parameter spaces of models for SN ejecta. This
can be used to analyse the growing number of high-quality SN spectra being
obtained by transient surveys. The code uses Monte Carlo methods to obtain a
self-consistent description of the plasma state and to compute a synthetic
spectrum. It has a modular design to facilitate the implementation of a range
of physical approximations that can be compared to asses both accuracy and
computational expediency. This will allow users to choose a level of
sophistication appropriate for their application. Here, we describe the
operation of the code and make comparisons with alternative radiative transfer
codes of differing levels of complexity (SYN++, PYTHON, and ARTIS). We then
explore the consequence of adopting simple prescriptions for the calculation of
atomic excitation, focussing on four species of relevance to Type Ia supernova
spectra - Si II, S II, Mg II, and Ca II. We also investigate the influence of
three methods for treating line interactions on our synthetic spectra and the
need for accurate radiative rate estimates in our scheme.


title:
Eccentric Planets and Stellar Evolution as a Cause of Polluted White
  Dwarfs

abstract:
  A significant fraction of white dwarfs (WDs) are observed to be polluted with
metals despite high surface gravities and short settling times. The current
theoretical model for this pollution is accretion of rocky bodies delivered to
the WD through perturbations by orbiting planets. Using N-body simulations, we
examine the possibility of a single planet as the source of pollution. We
determine the stability of test particles on circular orbits in systems with a
single planet located at 4 au for a range of masses and eccentricities,
comparing the fractions that are ejected and accreted. In particular, we
compare the instabilities that develop before and after the star loses mass to
form a WD, a process which causes orbiting bodies to migrate outward. We
determine that a planet must be eccentric (e > 0.02) to deliver significant (>
0.5 per cent) amounts of material to the host and that the amount increases
with the planetary eccentricity. This result is robust with respect to the
initial eccentricities of the particles for planetary eccentricity above ~0.4
and for randomly-distributed particle long. of pericentre. We also find that
the efficiency of pollution is enhanced as planetary mass is reduced. We
demonstrate that a 0.03 M_Jup planet with substantial eccentricity (e > 0.4)
can account for the observed levels of pollution for initial disc masses of
order 1 M_Earth. Such discs are within the range estimated for initial
planetesimals discs and below that estimated for the solar system. However,
their survival to the WD stage is uncertain as estimates for the collisional
evolution of planetesimal discs suggest they should be ground down below the
required levels on Gyr timescales. Thus, planetary scattering by eccentric,
sub-Jovian planets can explain the observed levels of WD pollution, but only if
current estimates of the collisional erosion of planetesimal discs are in
error.


title: Relativistic Reconnection: an Efficient Source of Non-Thermal Particles

abstract:
  In magnetized astrophysical outflows, the dissipation of field energy into
particle energy via magnetic reconnection is often invoked to explain the
observed non-thermal signatures. By means of two- and three-dimensional
particle-in-cell simulations, we investigate anti-parallel reconnection in
magnetically-dominated electron-positron plasmas. Our simulations extend to
unprecedentedly long temporal and spatial scales, so we can capture the
asymptotic state of the system beyond the initial transients, and without any
artificial limitation by the boundary conditions. At late times, the
reconnection layer is organized into a chain of large magnetic islands
connected by thin X-lines. The plasmoid instability further fragments each
X-line into a series of smaller islands, separated by X-points. At the
X-points, the particles become unmagnetized and they get accelerated along the
reconnection electric field. We provide definitive evidence that the late-time
particle spectrum integrated over the whole reconnection region is a power-law,
whose slope is harder than -2 for magnetizations sigma>10. Efficient particle
acceleration to non-thermal energies is a generic by-product of the long-term
evolution of relativistic reconnection in both two and three dimensions. In
three dimensions, the drift-kink mode corrugates the reconnection layer at
early times, but the long-term evolution is controlled by the plasmoid
instability, that facilitates efficient particle acceleration, in analogy to
the two-dimensional physics. Our findings have important implications for the
generation of hard photon spectra in pulsar winds and relativistic
astrophysical jets.