title: The B1 shock in the L1157 outflow as seen at high spatial resolution

abstract:
  We present high spatial resolution (750 AU at 250 pc) maps of the B1 shock in
the blue lobe of the L1157 outflow in four lines: CS (3-2), CH3OH (3_K-2_K),
HC3N (16-15) and p-H2CO (2_02-3_01). The combined analysis of the morphology
and spectral profiles has shown that the highest velocity gas is confined in a
few compact (~ 5 arcsec) bullets while the lowest velocity gas traces the wall
of the gas cavity excavated by the shock expansion. A large velocity gradient
model applied to the CS (3-2) and (2-1) lines provides an upper limit of 10^6
cm^-3 to the averaged gas density in B1 and a range of 5x10^3< n(H2)< 5x10^5
cm^-3 for the density of the high velocity bullets. The origin of the bullets
is still uncertain: they could be the result of local instabilities produced by
the interaction of the jet with the ambient medium or could be clump already
present in the ambient medium that are excited and accelerated by the expanding
outflow. The column densities of the observed species can be reproduced
qualitatively by the presence in B1 of a C-type shock and only models where the
gas reaches temperatures of at least 4000 K can reproduce the observed HC3N
column density.


title: Carries, group theory, and additive combinatorics

abstract:
  Given a group G and a normal subgroup H we study the problem of choosing
coset representatives with few carries.


title: Algorithms for perfectly contractile graphs

abstract:
  We consider the class ${\cal A}$ of graphs that contain no odd hole, no
antihole of length at least 5, and no "prism" (a graph consisting of two
disjoint triangles with three disjoint paths between them) and the class ${\cal
A}'$ of graphs that contain no odd hole, no antihole of length at least 5 and
no odd prism (prism whose three paths are odd). These two classes were
introduced by Everett and Reed and are relevant to the study of perfect graphs.
We give polynomial-time recognition algorithms for these two classes. We proved
previously that every graph $G\in{\cal A}$ is "perfectly contractile", as
conjectured by Everett and Reed [see the chapter "Even pairs" in the book {\it
Perfect Graphs}, J.L. Ram\'{\i}rez-Alfons\'{\i}n and B.A. Reed, eds., Wiley
Interscience, 2001]. The analogous conjecture concerning graphs in ${\cal A}'$
is still open.


title:
A Non-Interactive Quantum Bit Commitment Scheme that Exploits the
  Computational Hardness of Quantum State Distinction

abstract:
  We propose an efficient quantum protocol performing quantum bit commitment,
which is a simple cryptographic primitive involved with two parties, called a
committer and a verifier. Our protocol is non-interactive, uses no supplemental
shared information, and achieves computational concealing and statistical
binding under a natural complexity-theoretical assumption. An earlier protocol
in the literature relies on the existence of an efficient quantum one-way
function. Our protocol, on the contrary, exploits a seemingly weaker assumption
on computational difficulty of distinguishing two specific ensembles of reduced
quantum states. This assumption is guaranteed by, for example, computational
hardness of solving the graph automorphism problem efficiently on a quantum
computer.


title: Resurgent Deformation Quantisation

abstract:
  We construct a version of the complex Heisenberg algebra based on the idea of
endless analytic continuation. In particular, we exhibit an integral formula
for the product of resurgent operators with algebraic singularities. This
algebra would be large enough to capture quantum effects that escape ordinary
formal deformation quantisation.

categories: math-ph math.AG math.MP math.QA quant-ph


title: A class of perfectly contractile graphs

abstract:
  We consider the class ${\cal A}$ of graphs that contain no odd hole, no
antihole, and no "prism" (a graph consisting of two disjoint triangles with
three disjoint paths between them). We prove that every graph $G\in{\cal A}$
different from a clique has an "even pair" (two vertices that are not joined by
a chordless path of odd length), as conjectured by Everett and Reed [see the
chapter "Even pairs" in the book {\it Perfect Graphs}, J.L.
Ram\'{\i}rez-Alfons\'{\i}n and B.A. Reed, eds., Wiley Interscience, 2001]. Our
proof is a polynomial-time algorithm that produces an even pair with the
additional property that the contraction of this pair yields a graph in ${\cal
A}$. This entails a polynomial-time algorithm, based on successively
contracting even pairs, to color optimally every graph in ${\cal A}$. This
generalizes several results concerning some classical families of perfect
graphs.


title:
Novel T-Violation observable open to any pair of decay channels at meson
  factories

abstract:
  Quantum Entanglement between the two neutral mesons produced in meson
factories has allowed the first indisputable direct observation of Time
Reversal Violation in the time evolution of the neutral meson between the two
decays. The exceptional meson transitions are directly connected to
semileptonic and CP-eigenstate decay channels. The possibility of extending the
observable asymmetries to more decay channels confronts the problem of the
"orthogonality condition", which can be stated with this tongue-twister: Given
a decay channel $f$, Which is the decay channel $f'$ such that the meson state
not decaying to $f'$ is orthogonal to the meson state not decaying to $f$? In
this paper we propose an alternative $T$-Violation Asymmetry at meson factories
which allows its opening to any pair of decay channels. Instead of searching
which is the pair of decay channels associated to the $T$-reverse meson
transition, we build an asymmetry which tags the initial states of both the
Reference and the $T$-reverse meson transitions. This observable filters the
appropriate final states by means of two measurable survival probabilities. We
discuss the methodology to be followed in the analysis of the new observable
and the results expected in specific examples.


title: The nuclear energy density functional formalism

abstract:
  The present document focuses on the theoretical foundations of the nuclear
energy density functional (EDF) method. As such, it does not aim at reviewing
the status of the field, at covering all possible ramifications of the approach
or at presenting recent achievements and applications. The objective is to
provide a modern account of the nuclear EDF formalism that is at variance with
traditional presentations that rely, at one point or another, on a {\it
Hamiltonian-based} picture. The latter is not general enough to encompass what
the nuclear EDF method represents as of today. Specifically, the traditional
Hamiltonian-based picture does not allow one to grasp the difficulties
associated with the fact that currently available parametrizations of the
energy kernel $E[g',g]$ at play in the method do not derive from a genuine
Hamilton operator, would the latter be effective. The method is formulated from
the outset through the most general multi-reference, i.e. beyond mean-field,
implementation such that the single-reference, i.e. "mean-field", derives as a
particular case. As such, a key point of the presentation provided here is to
demonstrate that the multi-reference EDF method can indeed be formulated in a
{\it mathematically} meaningful fashion even if $E[g',g]$ does {\it not} derive
from a genuine Hamilton operator. In particular, the restoration of symmetries
can be entirely formulated without making {\it any} reference to a projected
state, i.e. within a genuine EDF framework. However, and as is illustrated in
the present document, a mathematically meaningful formulation does not
guarantee that the formalism is sound from a {\it physical} standpoint. The
price at which the latter can be enforced as well in the future is eventually
alluded to.

categories: nucl-th cond-mat.str-el nucl-ex quant-ph


title: Undecidability in number theory

abstract:
  These lecture notes cover classical undecidability results in number theory,
Hilbert's 10th problem and recent developments around it, also for rings other
than the integers. It also contains a sketch of the authors result that the
integers are universally definable in the rationals.


title:
A Verifiable and Correct-by-Construction Controller for Robot Functional
  Levels

abstract:
  Autonomous robots are complex systems that require the interaction and
cooperation between numerous heterogeneous software components. In recent
times, robots are being increasingly used for complex and safety-critical
tasks, such as exploring Mars and assisting/replacing humans. Consequently,
robots are becoming critical systems that must meet safety properties, in
particular, logical, temporal and real-time constraints. To this end, we
present an evolution of the LAAS architecture for autonomous systems, in
particular its GenoM tool. This evolution relies on the BIP component-based
design framework, which has been successfully used in other domains such as
embedded systems. We show how we integrate BIP into our existing methodology
for developing the lowest (functional) level of robots. Particularly, we
discuss the componentization of the functional level, the synthesis of an
execution controller for it, and how we verify whether the resulting functional
level conforms to properties such as deadlock-freedom. We also show through
experimentation that the verification is feasible and usable for complex, real
world robotic systems, and that the BIP-based functional levels resulting from
our new methodology are, despite an overhead during execution, still practical
on real world robotic platforms. Our approach has been fully implemented in the
LAAS architecture, and the implementation has been used in several experiments
on a real robot.


title: The asymptotic formula in Waring's problem: higher order expansions

abstract:
  When k > 1 and s is sufficiently large in terms of k, we derive an explicit
multi-term asymptotic expansion for the number of representations of a large
natural number as the sum of s positive integral k-th powers.


title: Towards Zeptosecond-Scale Pulses from X-Ray Free-Electron Lasers

abstract:
  The short wavelength and high peak power of the present generation of
free-electron lasers (FELs) opens the possibility of ultra-short pulses even
surpassing the present (tens to hundreds of attoseconds) capabilities of other
light sources - but only if x-ray FELs can be made to generate pulses
consisting of just a few optical cycles. For hard x-ray operation (~0.1nm),
this corresponds to durations of approximately a single attosecond, and below
into the zeptosecond scale. This talk will describe a novel method to generate
trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL
facilities by using a relatively short 'afterburner'. Such pulses would enhance
research opportunity in atomic dynamics and push capability towards the
investigation of electronic-nuclear and nuclear dynamics. The corresponding
multi-colour spectral output, with a bandwidth envelope increased by up to two
orders of magnitudes over SASE, also has potential applications.


title:
One Atomic Beam as a Detector of Classical Harmonic Vibrations with
  Micro Amplitudes and Low Frequencies

abstract:
  We propose a simplest detector of harmonic vibrations with micro amplitudes
and low frequencies, i.e. the detector consisting of one atomic beam. Here the
atomic beam is induced by a plane harmonic wave and has a classical collective
harmonic vibrations, which vibrant directions are perpendicular to the wave
vectors of atomic beam. Compared with the detector consisting of atomic
Mach-Zehnder interferometer, the new detector has two advantages: (1) it is
suitable for the detection of the harmonic vibrations induced either by a
longitudinal plane harmonic wave or by a transverse plane harmonic wave; (2)
the quantum noise fluctuation of the atomic beam is exactly zero.


title:
A combined IRAM and Herschel/HIFI study of cyano(di)acetylene in Orion
  KL: tentative detection of DC3N

abstract:
  We present a study of cyanoacetylene (HC3N) and cyanodiacetylene (HC5N) in
Orion KL, through observations from two line surveys performed with the IRAM
30m telescope and the HIFI instrument on board the Herschel telescope. The
frequency ranges covered are 80-280 GHz and 480-1906 GHz. We model the observed
lines of HC3N, HC5N, their isotopologues (including DC3N), and vibrational
modes, using a non-LTE radiative transfer code. To investigate the chemical
origin of HC3N and DC3N in Orion KL, we use a time-dependent chemical model. We
detect 40 lines of the ground state of HC3N and 68 lines of its 13C
isotopologues. We also detect 297 lines of six vibrational modes of this
molecule (nu_7, 2nu_7, 3nu_7, nu_6, nu_5, and nu_6+nu_7) and 35 rotational
lines of the ground state of HC5N. We report the first tentative detection of
DC3N in a giant molecular cloud with a DC3N/HC3N abundance ratio of 0.015. We
provide column densities and isotopic and molecular abundances. We also perform
a 2x2" map around Orion IRc2 and we present maps of HC3N lines and maps of
lines of the HC3N vibrational modes nu_6 and nu_7. In addition, a comparison of
our results for HC3N with those in other clouds allows us to derive
correlations between the column density, the FWHM, the mass, and the luminosity
of the clouds. The high column densities of HC3N obtained in the hot core, make
this molecule an excellent tracer of hot and dense gas. In addition, the large
frequency range covered reveals the need to consider a temperature and density
gradient in the hot core in order to obtain better line fits. The high D/H
ratio (comparable to that obtained in cold clouds) that we derive suggests a
deuterium enrichment. Our chemical models indicate that the possible deuterated
HC3N present in Orion KL is formed during the gas-phase. This fact provides new
hints concerning the processes leading to deuteration.


title: p-Buchsbaum rank 2 bundles on the projective space

abstract:
  It has been proved by various authors that a normalized, 1-Buchsbaum rank 2
vector bundle on P3 is a nullcorrelation bundle, while a normalized,
2-Buchsbaum rank 2 vector bundle on P3 is an instanton bundle of charge 2. We
find that the same is not true for 3-Buchsbaum rank 2 vector bundles on P3, and
propose a conjecture regarding the classification of such objects.


title:
Distributed Sensing and Transmission of Sporadic Random Samples in a
  Multiple-Access Channel

abstract:
  This work considers distributed sensing and transmission of sporadic random
samples. Lower bounds are derived for the reconstruction error of a single
normally or uniformly-distributed finite-dimensional vector imperfectly
measured by a network of sensors and transmitted with finite energy to a common
receiver via an additive white Gaussian noise asynchronous multiple-access
channel. Transmission makes use of a perfect causal feedback link to the
encoder connected to each sensor. A retransmission protocol inspired by the
classical scheme in [1] applied to the transmission of single and bi-variate
analog samples analyzed in [2] and [3] is extended to the more general network
scenario, for which asymptotic upper-bounds on the reconstruction error are
provided. Both the upper and lower-bounds show that collaboration can be
achieved through energy accumulation under certain circumstances. In order to
investigate the practical performance of the proposed retransmission protocol
we provide a numerical evaluation of the upper-bounds in the non-asymptotic
energy regime using low-order quantization in the sensors. The latter includes
a minor modification of the protocol to improve reconstruction fidelity.
Numerical results show that an increase in the size of the network brings
benefit in terms of performance, but that the gain in terms of energy
efficiency diminishes quickly at finite energies due to a non-coherent
combining loss.


title: Odd pairs of cliques

abstract:
  A graph is Berge if it has no induced odd cycle on at least 5 vertices and no
complement of induced odd cycle on at least 5 vertices. A graph is perfect if
the chromatic number equals the maximum clique number for every induced
subgraph. Chudnovsky, Robertson, Seymour and Thomas proved that every Berge
graph either falls into some classical family of perfect graphs, or has a
structural fault that cannot occur in a minimal imperfect graph. A corollary of
this is the strong perfect graph theorem conjectured by Berge: every Berge
graph is perfect. An even pair of vertices in a graph is a pair of vertices
such that every induced path between them has even length. Meyniel proved that
a minimal imperfect graph cannot contain an even pair. So even pairs may be
considered as a structural fault. Chudnovsky et al. do not use them, and it is
known that some classes of Berge graph have no even pairs.
  The aim of this work is to investigate an "even-pair-like" notion that could
be a structural fault present in every Berge graph. An odd pair of cliques is a
pair of cliques $\{K_1, K_2\}$ such that every induced path from $K_1$ to $K_2$
with no interior vertex in $K_1 \cup K_2$ has odd length. We conjecture that
for every Berge graph $G$ on at least two vertices, either one of $G, \bar{G}$
has an even pair, or one of $G, \bar{G}$ has an odd pair of cliques. We
conjecture that a minimal imperfect graph has no odd pair of maximal cliques.
We prove these conjectures in some special cases. We show that adding all edges
between any 2 vertices of the cliques of an odd pair of cliques is an operation
that preserves perfectness.


title: Faithful tropicalization of the Grassmannian of planes

abstract:
  We show that the tropical projective Grassmannian of planes is homeomorphic
to a closed subset of the analytic Grassmannian in Berkovich's sense by
constructing a continuous section to the tropicalization map. Our main tool is
an explicit description of the algebraic coordinate rings of the toric strata
of the Grassmannian. We determine the fibers of the tropicalization map and
compute the initial degenerations of all the toric strata. As a consequence, we
prove that the tropical multiplicities of all points in the tropical projective
Grassmannian are equal to one. Finally, we determine a piecewise linear
structure on the image of our section that corresponds to the polyhedral
structure on the tropical projective Grassmannian.


title:
N-body simulations of globular clusters in tidal fields: Effects of
  intermediate-mass black holes

abstract:
  Intermediate-mass black holes (IMBHs) may provide the missing link to
understanding the growth of supermassive black holes in the early Universe.
Some formation scenarios predict that IMBHs could have formed by runaway
collisions in globular clusters (GCs). Understanding the influence of an IMBH
in the center of a GC on its environment might provide indirect detection
methods. Our goal is to test the effects of different initial compositions of
GCs on their evolution in a tidal field. We pin down the crucial observables
that indicate the presence of an IMBH at the center of the cluster. In addition
to central IMBHs, we also consider the effects of different stellar-mass black
hole retention and stellar binary fractions. We performed a set of 22 N-body
simulations and varied particle numbers, IMBH masses, stellar-mass black-hole
retention fractions, and stellar binary fractions. These models are all run in
an external tidal field to study the effect of black holes on the cluster mass
loss, mass function, and life times. Finally, we compared our results with
observational data. We found that a central massive black hole increases the
escape rate of high-mass stars from a star cluster, implying that the relative
depletion of the mass function at the low-mass end proceeds less rapidly.
Furthermore, we found a similar behavior for a cluster hosting a high number of
stellar-mass black holes instead of one massive central IMBH. The presence of
an IMBH also weakly affects the fraction of the cluster mass that is
constituted by stellar remnants, as does the presence of primordial binaries.
We compared our simulations with observational data from the literature and
found good agreement between our models and observed mass functions and
structural parameters of GCs. We exploited this agreement to identify GCs that
could potentially host IMBHs.


title: Quiver algebras as Fukaya categories

abstract:
  We embed triangulated categories defined by quivers with potential arising
from ideal triangulations of marked bordered surfaces into Fukaya categories of
quasi-projective 3-folds associated to meromorphic quadratic differentials.
Together with previous results, this yields non-trivial computations of spaces
of stability conditions on Fukaya categories of symplectic 6-manifolds.


title:
Creation of ensembles of nitrogen-vacancy centers in diamond by neutron
  and electron irradiation

abstract:
  We created dense ensembles of negatively charged nitrogen-vacancy (NV-)
centers in diamond by neutron and electron irradiation for applications in
hybrid quantum systems and magnetometry. We characterize fluorescence
intensity, optical and coherence properties of the resulting defects by
confocal microscopy, UV/Vis and FTIR spectroscopy, optically detected magnetic
resonance and small angle X-ray scattering. We find the highest densities of
NV- at neutron fluences on the order of 10^17 cm^-2 and electron doses of 10^18
cm^-2, with spin resonance linewidths of 6 MHz. Lower electron energies
increase the ratio of centers in the desired negative charge state to those in
the neutral one. Annealing at 900 {\deg}C during the irradiation reduces the
spin resonance linewidth. Electron irradiation furthermore results in
substantially higher optical transparency compared to neutron irradiation.


title:
On a novel distance indicator for Gamma-Ray Bursts associated with
  Supernovae

abstract:
  It has been proposed that the temporal coincidence of a gamma-ray burst (GRB)
and a type Ib/c supernova (SN) can be explained with the concept of induced
gravitational collapse (IGC), induced by the matter ejected from an SN Ib/c
accreting onto a neutron star (NS). We found a standard luminosity light curve
behavior in the late-time X-ray emission of this subclass of GRBs. We interpret
this as the result of a common physical mechanism in this particular phase of
the X-ray emission, possibly related to the creation of the NS from the SN
process. Moreover, this scaling law could be a fundamental tool for estimating
the redshift of GRBs that belong to this subclass of events.


title: An alternative to the breeder's and Lande's equations

abstract:
  The breeder's equation is a cornerstone of quantitative genetics and is
widely used in evolutionary modeling. The equation which reads R=h^{2}S relates
response to selection R (the mean phenotype of the progeny) to the selection
differential S (mean phenotype of selected parents) through a simple
proportionality relation. The validity of this relation however relies strongly
on the normal (Gaussian) distribution of parent's genotype which is an
unobservable quantity and cannot be ascertained. In contrast, we show here that
if the fitness (or selection) function is Gaussian, an alternative, exact
linear equation in the form of R'=j^{2}S' can be derived, regardless of the
parental genotype distribution. Here R' and S' stand for the mean phenotypic
lag behind the mean of the fitness function in the offspring and selected
populations. To demonstrate this relation, we derive the exact functional
relation between the mean phenotype in the selected and the offspring
population and deduce all cases that lead to a linear relation between these
quantities. These computations, which are confirmed by individual based
numerical simulations, generalize naturally to the multivariate Lande's
equation \Delta\mathbf{\bar{z}}=GP^{-1}\mathbf{S} .


title: The Harmony Platform

abstract:
  According to Wikipedia, The Mining Software Repositories (MSR) field analyzes
the rich data available in software repositories, such as version control
repositories, mailing list archives, bug tracking systems, issue tracking
systems, etc. to uncover interesting and actionable information about software
systems, projects and software engineering. The MSR field has received a great
deal of attention and has now its own research conference :
http://www.msrconf.org/. However performing MSR studies is still a technical
challenge. Indeed, data sources (such as version control system or bug tracking
systems) are highly heterogeneous. Moreover performing a study on a lot of data
sources is very expensive in terms of execution time. Surprisingly, there are
not so many tools able to help researchers in their MSR quests. This is why we
created the Harmony platform, as a mean to assist researchers in performing MSR
studies.


title: The spinor representation formula in 3 and 4 dimensions

abstract:
  In the literature, two approaches to the Weierstrass representation formula
using spinors are known, one explicit, going back to Kusner & Schmitt, and
generalized by Konopelchenko and Taimanov, and one abstract due to Friedrich,
Bayard, Lawn and Roth. In this article, we show that both points of view are
indeed equivalent, for surfaces in R^3, Nil_3 and R^4. The correspondence
between the equations of both approaches is explicitly given and as a
consequence we derive alternate (and simpler) proofs of these previous
theorems.


title: Capacity of Non-Malleable Codes

abstract:
  Non-malleable codes, introduced by Dziembowski, Pietrzak and Wichs (ICS
2010), encode messages $s$ in a manner so that tampering the codeword causes
the decoder to either output $s$ or a message that is independent of $s$. While
this is an impossible goal to achieve against unrestricted tampering functions,
rather surprisingly non-malleable coding becomes possible against every fixed
family $F$ of tampering functions that is not too large (for instance, when
$|F| \le \exp(2^{\alpha n})$ for some $\alpha \in [0, 1)$ where $n$ is the
number of bits in a codeword).
  In this work, we study the "capacity of non-malleable coding", and establish
optimal bounds on the achievable rate as a function of the family size,
answering an open problem from Dziembowski et al. (ICS 2010). Specifically,
  1. We prove that for every family $F$ with $|F| \le \exp(2^{\alpha n})$,
there exist non-malleable codes against $F$ with rate arbitrarily close to
$1-\alpha$ (this is achieved w.h.p. by a randomized construction).
  2. We show the existence of families of size $\exp(n^{O(1)} 2^{\alpha n})$
against which there is no non-malleable code of rate $1-\alpha$ (in fact this
is the case w.h.p for a random family of this size).
  3. We also show that $1-\alpha$ is the best achievable rate for the family of
functions which are only allowed to tamper the first $\alpha n$ bits of the
codeword, which is of special interest.
  As a corollary, this implies that the capacity of non-malleable coding in the
split-state model (where the tampering function acts independently but
arbitrarily on the two halves of the codeword) equals 1/2.
  We also give an efficient Monte Carlo construction of codes of rate close to
1 with polynomial time encoding and decoding that is non-malleable against any
fixed $c > 0$ and family $F$ of size $\exp(n^c)$, in particular tampering
functions with, say, cubic size circuits.


title: Clustering and the hyperbolic geometry of complex networks

abstract:
  Clustering is a fundamental property of complex networks and it is the
mathematical expression of a ubiquitous phenomenon that arises in various types
of self-organized networks such as biological networks, computer networks or
social networks. In this paper, we consider what is called the global
clustering coefficient of random graphs on the hyperbolic plane. This model of
random graphs was proposed recently by Krioukov et al. as a mathematical model
of complex networks, under the fundamental assumption that hyperbolic geometry
underlies the structure of these networks. We give a rigorous analysis of
clustering and characterize the global clustering coefficient in terms of the
parameters of the model. We show how the global clustering coefficient can be
tuned by these parameters and we give an explicit formula for this function.


title: The Expected Codimension of a Matroid Variety

abstract:
  Matroid varieties are the closures in the Grassmannian of sets of points
defined by specifying which Pl\"ucker coordinates vanish and which don't. In
general these varieties are very ill-behaved, but in many cases one can
estimate their codimension by keeping careful track of the conditions imposed
by the vanishing of each Pl\"ucker coordinates on the columns of the matrix
representing a point of the Grassmannian. This paper presents a way to make
this procedure precise, producing a number for each matroid variety called its
expected codimension that can be computed combinatorially solely from the list
of Pl\"ucker coordinates that are prescribed to vanish. We prove that for a
special, well-studied class of matroid varieties called positroid varieties,
the expected codimension coincides with the actual codimension.


title:
A Non-Markovian Liquidation Problem and Backward SPDEs with Singular
  Terminal Conditions

abstract:
  We establish existence, uniqueness and regularity of solution results for a
class of backward stochastic partial differential equations with singular
terminal condition. The equation describes the value function of non-Markovian
stochastic optimal control problem in which the terminal state of the
controlled process is pre-specified. The analysis of such control problems is
motivated by models of optimal portfolio liquidation.


title: Extensions of Fast-Lipschitz Optimization

abstract:
  The need of fast distributed solvers for optimization problems in networked
systems has motivated the recent development of the Fast-Lipschitz optimization
framework. In such an optimization, problems satisfying certain qualifying
conditions, such as monotonicity of the objective function and contractivity of
the constraints, have a unique optimal solution obtained via fast distributed
algorithms that compute the fixed point of the constraints. This paper extends
the set of problems for which the Fast-Lipschitz framework applies. Existing
assumptions on the problem form are relaxed and new and generalized qualifying
conditions are established by novel results based on Lagrangian duality. It is
shown for which cases of more constraints than decision variables, and less
constraints than decision variables Fast-Lipschitz optimization applies. New
results are obtained by imposing non strict monotonicity of the objective
functions. The extended Fast-Lipschitz framework is illustrated by a number of
examples, including a non-linear optimal control problem.


title: Existence of rational points as a homotopy limit problem

abstract:
  We show that the existence of rational points on smooth varieties over a
field can be detected using homotopy fixed points of etale topological types
under the Galois action. As our main example we show that the surjectivity
statement in Grothendieck's Section Conjecture would follow from the
surjectivity of the map from fixed points to continuous homotopy fixed points
on the level of connected components. Along the way we define a new model for
the continuous etale homotopy fixed point space of a smooth variety over a
field under the Galois action.


title: Transport coefficients for driven granular mixtures at low-density

abstract:
  The transport coefficients of a granular binary mixture driven by a
stochastic bath with friction are determined from the inelastic Boltzmann
kinetic equation. A normal solution is obtained via the Chapman-Enskog method
for states near homogeneous steady states. The mass, momentum, and heat fluxes
are determined to first order in the spatial gradients of the hydrodynamic
fields, and the associated transport coefficients are identified. They are
given in terms of the solutions of a set of coupled linear integral equations.
As in the monocomponent case, since the collisional cooling cannot be
compensated locally for by the heat produced by the external driving, the
reference distributions (zeroth-order approximations) $f_i^{(0)}$ ($i=1,2$) for
each species depend on time through their dependence on the pressure and the
temperature. Explicit forms for the diffusion transport coefficients and the
shear viscosity coefficient are obtained by assuming the steady state
conditions and by considering the leading terms in a Sonine polynomial
expansion. A comparison with previous results obtained for granular Brownian
motion and by using a (local) stochastic thermostat is also carried out. The
present work extends previous theoretical results derived for monocomponent
dense gases [V. Garz\'o, M. G. Chamorro, and F. Vega Reyes, Phys. Rev. E
\textbf{87}, 032201 (2013)] to granular mixtures at low density.


title:
Superluminal propagation and broadband omnidirectional antireflection in
  optical reflectionless potentials

abstract:
  Reflectionless potentials (RPs) represent a class of potentials that offer
total transmission in the context of one dimensional scattering. Optical
realization of RPs in stratified medium can exhibit broadband omnidirectional
antireflection property. In addition to the antireflection property, RPs are
also expected to demonstrate negative delay. We designed refractive index
profiles conforming to RPs and realize them in stratified media consisting of
Al2O3 and TiO2 heterolayers. In these structures we observed < 1% reflection
over the broad wavelength range of 350 nm to 2500 nm for angles of incidence 0
- 50 degrees. The observed reflection and transmission response of RPs are
polarization independent. A negative delay of about 31 fsec with discernible
pulse narrowing was observed in passage through two RPs. These RPs can be
interesting for optical instrumentation as broadband, omni-directional
antireflection coatings as well as in pulse control and transmission
applications like delay lines.


title: Minimal genera of open 4-manifolds

abstract:
  We study exotic smoothings of open 4-manifolds using the minimal genus
function and its analog for end homology. While traditional techniques in open
4-manifold smoothing theory give no control of minimal genera, we make progress
by using the adjunction inequality for Stein surfaces. Smoothings can be
constructed with much more control of these genus functions than the compact
setting seems to allow. As an application, we expand the range of 4-manifolds
known to have exotic smoothings (up to diffeomorphism). For example, every
2-handlebody interior (possibly infinite or nonorientable) has an exotic
smoothing, and "most" have infinitely, or sometimes uncountably many,
distinguished by the genus function and admitting Stein structures when
orientable. Manifolds with 3-homology are also accessible. We investigate
topological submanifolds of smooth 4-manifolds. Every domain of holomorphy
(Stein open subset) in the complex plane $C^2$ is topologically isotopic to
uncountably many other diffeomorphism types of domains of holomorphy with the
same genus functions, or with varying but controlled genus functions.


title:
A characterization of {\mu}-equicontinuity for topological dynamical
  systems

abstract:
  Two different notions of {\mu}-equicontinuity that apply to topological
dynamical systems and probability measures were studied by Gilman (1987) and
Huang-Lu-Ye (2011). One was used to classify measure preserving topological
dynamical systems and the other for cellular automata. We show that if the
probability space satisfies Lebesgue's density theorem and Vitali's covering
theorem (for example a Cantor set or a subset of R^{d}) then both properties
are equivalent. To do this we characterize when a function is Lusin measurable.


title:
The induced PBW filtration, Frobenius splitting of double flag
  varieties, and Wahl's conjecture

abstract:
  Let G be a semisimple algebraic group over an algebraically closed field of
positive characteristic p. Generalizing the construction of the PBW filtration
on Weyl modules for G we construct a G-stable filtration on tensor products of
Weyl modules which we call the induced PBW filtration. We use this filtration
to give some purely representation-theoretic conditions which are equivalent to
the existence of a Frobenius splitting of the double flag variety $G/B \times
G/B$ that maximally compatibly splits the diagonal. In particular, this gives a
sufficient condition for Wahl's conjecture to hold for G and we use this
criterion to prove that Wahl's conjecture holds in type G2 for p at least 11.


title: Semi-stable vector bundles on fibred varieties

abstract:
  Let $\pi:Y\to X$ be a surjective morphism between two irreducible, smooth
complex projective varieties with ${\rm dim}Y>{\rm dim}X >0$. We consider
polarizations of the form $L_c=L+c\cdot\pi^*A$ on $Y$, with $c>0$, where $L,A$
are ample line bundles on $Y,X$ respectively.
  For $c$ sufficiently large, we show that the restriction of a torsion free
sheaf $\mathcal{F}$ on $Y$ to the generic fibre $\Phi$ of $\pi$ is semi-stable
as soon as $\mathcal{F}$ is $L_c$-semi-stable; conversely, if
$\mathcal{F}\otimes\mathcal{O}_\Phi$ is $L$-stable on $\Phi$, then
$\mathcal{F}$ is $L_c$-stable. We obtain explicit lower bounds for $c$
satisfying these properties.
  Using this result, we discuss the construction of semi-stable vector bundles
on Hirzebruch surfaces and on $\mathbb{P}^2$-bundles over $\mathbb{P}^1$, and
establish the irreducibility and the rationality of the corresponding moduli
spaces.


title:
Origin of long-lived oscillations in 2D-spectra of a Quantum Vibronic
  Model: Electronic vs Vibrational coherence

abstract:
  We demonstrate that the coupling of excitonic and vibrational motion in
biological complexes can provide mechanisms to explain the long-lived
oscillations that have been obtained in non linear spectroscopic signals of
different photosynthetic pigment protein complexes and we discuss the
contributions of excitonic versus purely vibrational components to these
oscillatory features. Considering a dimer model coupled to a structured
spectral density we exemplify the fundamental aspects of the electron-phonon
dynamics, and by analyzing separately the different contributions to the non
linear signal, we show that for realistic parameter regimes purely electronic
coherence is of the same order as purely vibrational coherence in the
electronic ground state. Moreover, we demonstrate how the latter relies upon
the excitonic interaction to manifest. These results link recently proposed
microscopic, non-equilibrium mechanisms to support long lived coherence at
ambient temperatures with actual experimental observations of oscillatory
behaviour using 2D photon echo techniques to corroborate the fundamental
importance of the interplay of electronic and vibrational degrees of freedom in
the dynamics of light harvesting aggregates.

categories: physics.chem-ph physics.bio-ph q-bio.BM quant-ph


title:
Decoy state method for measurement device independent quantum key
  distribution with different intensities in only one basis

abstract:
  We show that the three-intensity protocol for measurement device independent
quantum key distribution (MDI QKD) can be done with different light intensities
in {\em only one} basis. Given the fact that the exact values yields of
single-photon pairs in the $X$ and $Z$ bases must be the same, if we have lower
bound of the value in one basis, we can also use this as the lower bound in
another basis. Since in the existing set-up for MDI-QKD, the yield of sources
in different bases are normally different, therefore our method can improve the
key rate drastically if we choose to only use the lower bound of yield of
single-photon pairs in the advantageous basis. Moreover, since our proposal
here uses fewer intensities of light, the probability of intensity mismatch
will be smaller than the existing protocols do. This will further improve the
advantage of our method. The advantage of using Z basis or X basis of our
method is studied and significant improvement of key rates are numerically
demonstrated.


title: Near-field optical random mapping (NORM) microscopy

abstract:
  In recent years several methods to overcome diffraction limit in the far
field microscopy have been demonstrated. Still the problem of superresolution
is reliably solved only for fluorescent microscopy, giving a resolution of up
to 20-30nm. Obtaining the optical resolution lower than 100nm without
fluorescent dyes requires using rather slow and complicated technique of
scanning near filed optical microscope (SNOM). We propose and demonstrate a
method of optical near field acquisition by far-field microscope through
observation of nanoparticles Brownian motion in immersion liquid. The
resolution of the method is restricted only by the size of nanoparticles that
can be registered (detected) by a given far field microscope. From this point
of view this resolution can achieve up to 10-20nm. Up to now we achieved a
resolution of about 140nm observing 120nm particles through an objective with
N.A.=0.4. The resolution is thus improved by factor of five for a given
microscope objective.


title: Running Couplings in Quantum Theory of Gravity Coupled with Gauge Fields

abstract:
  In this paper we study the coupled system of non-abelian gauge fields with
higher-derivative gravity. Charge renormalization is investigated in this
coupled system. It is found that the leading term in the gauge coupling beta
function comes due to interaction of gauge fields with gravitons. This is shown
to be a universal quantity in the sense that it doesn't depend on the gauge
coupling and the gauge group, but may depend on the other couplings of the
action (gravitational and matter). The coupled system is studied at one-loop.
It is found that the leading term of gauge beta function is zero at one-loop in
four dimensions. The effect of gauge fields on the running of gravitational
couplings is investigated. The coupled system of gauge field with
higher-derivative gravity is shown to satisfy unitarity when quantum
corrections are taken in to account. Moreover, it is found that Newton constant
goes to zero at short distances. In this renormalizable and unitary theory of
gauge field coupled with higher-derivative gravity, the leading term of the
gauge beta function, found to be universal for all gauge groups, is further
studied in more detail by isolating it in the context of abelian gauge theories
coupled with gravity in four dimensions. Using self-duality of abelian gauge
theories in four dimensions, this term of the gauge beta function is shown to
be zero to all loops. This is found to be independent of the gravity action,
regularization scheme and gauge fixing condition. An explicit one-loop
computation for arbitrary gravity action further demonstrates the vanishing of
this term in the gauge beta function in four dimensions, independent of the
regularization scheme and gauge fixing condition. Consequences of this are
discussed.


title:
Smooth solutions to portfolio liquidation problems under price-sensitive
  market impact

abstract:
  We consider the stochastic control problem of a financial trader that needs
to unwind a large asset portfolio within a short period of time. The trader can
simultaneously submit active orders to a primary market and passive orders to a
dark pool. Our framework is flexible enough to allow for price-dependent impact
functions describing the trading costs in the primary market and
price-dependent adverse selection costs associated with dark pool trading. We
prove that the value function can be characterized in terms of the unique
smooth solution to a PDE with singular terminal value, establish its explicit
asymptotic behavior at the terminal time, and give the optimal trading strategy
in feedback form.


title: Non-Gaussian Spatial Correlations Dramatically Weaken Localization

abstract:
  We perform variational studies of the interaction-localization problem to
describe the interaction-induced renormalizations of the effective (screened)
random potential seen by quasiparticles. Here we present results of careful
finite-size scaling studies for the conductance of disordered Hubbard chains at
half-filling and zero temperature. While our results indicate that
quasiparticle wave functions remain exponentially localized even in the
presence of moderate to strong repulsive interactions, we show that
interactions produce a strong decrease of the characteristic conductance scale
g* signaling the crossover to strong localization. This effect, which cannot be
captured by a simple renormalization of the disorder strength, instead reflects
a peculiar non-Gaussian form of the spatial correlations of the screened
disordered potential, a hitherto neglected mechanism to dramatically reduce the
impact of Anderson localization (interference) effects.


title: Existence of regular solutions to the full Liquid Crystal System

abstract:
  We study the general Ericksen-Leslie system with non-constant density, which
describes the flow of nematic liquid crystal. In particular the model
investigated here is associated with Parodi's relation. We prove that: in two
dimension, the solutions are globally regular with general data; in three
dimension, the solutions are globally regular with small initial data, or for
short time with large data. Moreover, a weak-strong type of uniqueness result
is obtained.


title: Motion of slightly compressible fluids in a bounded domain. II

abstract:
  We study the problem of inviscid slightly compressible fluids in a bounded
domain. We find a unique solution to the initial-boundary value problem and
show that it is near the analogous solution for an incompressible fluid
provided the initial conditions for the two problems are close. In particular,
the divergence of the initial velocity of the compressible flow at time zero is
assumed to be small. Furthermore we find that solutions to the compressible
motion problem in Lagrangian coordinates depend differentiably on their initial
data, an unexpected result for this type of non-linear equations.


title: Informational Approach to Identical Particles in Quantum Theory

abstract:
  A remarkable feature of quantum theory is that particles with identical
intrinsic properties must be treated as indistinguishable if the theory is to
give valid predictions. In the quantum formalism, indistinguishability is
expressed via the symmetrization postulate, which restricts a system of
identical particles to the set of symmetric states (`bosons') or the set of
antisymmetric states (`fermions'). However, the physical basis and range of
validity of the symmetrization postulate has not been established. A well-known
topological derivation of the postulate implies that its validity depends on
the dimensionality of the space in which the particles move. However, this
derivation relies on the labeling of indistinguishable particles, a notion that
cannot be justified on an informational basis. Here we show that the
symmetrization postulate can be derived by strictly adhering to the
informational requirement that particles which cannot be experimentally
distinguished from one another are not labeled. Our key novel postulate is the
operational indistinguishability postulate, which posits that the amplitude of
a process involving several indistinguishable particles is determined by the
amplitudes of all possible transitions of these particles when treated as
distinguishable. The symmetrization postulate follows by requiring consistency
with the rest of the quantum formalism. The derivation implies that the
symmetrization postulate admits no natural variants. In particular, the
possibility that identical particles generically exhibit anyonic behavior in
two dimensions is excluded.


title: On the Interval [n,2n]: Primes, Composites and Perfect Powers

abstract:
  In this paper we show that for every positive integer $n$ there exists a
prime number in the interval $[n,9(n+3)/8]$. Based on this result, we prove
that if $a$ is an integer greater than 1, then for every integer $n>14.4a$
there are at least four prime numbers $p$, $q$, $r$, and $s$ such that
$n<ap<3n/2<aq<2n$ and $n<r<3n/2<s<2n$. Moreover, we also prove that if $m$ is a
positive integer, then for every positive integer
$n>14.4/(|\sqrt[m]{1.5}|-1)^m$ there exist a positive integer $a$ and a prime
number $s$ such that $n<a^m<3n/2<s<2n$, as well as the fact that for every
positive integer $n>14.4/(|\sqrt[m]{2}|-|\sqrt[m]{1.5}|)^m$ there exist a prime
number $r$ and a positive integer $a$ such that $n<r<3n/2<a^m<2n$.


title:
Single-bunch transverse emittance growth due to collimator wakefield
  effects

abstract:
  In this paper we revisit the calculation of the emittance dilution of charged
particle bunches due to collimator wakefield effects in the paraxial
approximation. We also compare analytical results with numerical simulations
considering the example of a collimator structure installed in the Accelerator
Test Facility 2 (ATF2) at KEK


title: Rotational spectroscopy with an optical centrifuge

abstract:
  We demonstrate a new spectroscopic method for studying electronic transitions
in molecules with extremely broad range of angular momentum. We employ an
optical centrifuge to create narrow rotational wave packets in the ground
electronic state of $^{16}$O$_2$. Using the technique of resonance-enhanced
multi-photon ionization, we record the spectrum of multiple ro-vibrational
transitions between $X^3\Sigma_{g}^{-}$ and $C^3\Pi_{g}$ electronic manifolds
of oxygen. Direct control of rotational excitation, extending to rotational
quantum numbers as high as $N\gtrsim 120$, enables us to interpret the complex
structure of rotational spectra of $C^3\Pi_{g}$ beyond thermally accessible
levels.


title:
Law of Log Determinant of Sample Covariance Matrix and Optimal
  Estimation of Differential Entropy for High-Dimensional Gaussian
  Distributions

abstract:
  Differential entropy and log determinant of the covariance matrix of a
multivariate Gaussian distribution have many applications in coding,
communications, signal processing and statistical inference. In this paper we
consider in the high dimensional setting optimal estimation of the differential
entropy and the log-determinant of the covariance matrix. We first establish a
central limit theorem for the log determinant of the sample covariance matrix
in the high dimensional setting where the dimension $p(n)$ can grow with the
sample size $n$. An estimator of the differential entropy and the log
determinant is then considered. Optimal rate of convergence is obtained. It is
shown that in the case $p(n)/n \rightarrow 0$ the estimator is asymptotically
sharp minimax. The ultra-high dimensional setting where $p(n) > n$ is also
discussed.


title: Ore and Goldie theorems for skew PBW extensions

abstract:
  Many rings and algebras arising in quantum mechanics can be interpreted as
skew PBW (Poincar\'e-Birkhoff-Witt) extensions. Indeed, Weyl algebras,
enveloping algebras of finite-dimensional Lie algebras (and its quantization),
Artamonov quantum polynomials, diffusion algebras, Manin algebra of quantum
matrices, among many others, are examples of skew PBW extensions. In this paper
we extend the classical Ore and Goldie theorems, known for skew polynomial
rings, to this wide class of non-commutative rings. As application, we prove
the quantum version of the Gelfand-Kirillov conjecture for the skew quantum
polynomials.


title:
Affine pavings of regular nilpotent Hessenberg varieties and
  intersection theory of the Peterson variety

abstract:
  This paper describes a paving by affines for regular nilpotent Hessenberg
varieties in all Lie types, namely a kind of cell decomposition that can be
used to compute homology despite its weak closure conditions. Precup recently
proved a stronger result; we include ours because we use different methods. We
then use this paving to prove that the homology of the Peterson variety injects
into the homology of the full flag variety. The proof uses intersection theory
and expands the class of the Peterson variety in the homology of the flag
variety in terms of the basis of Schubert classes. We explicitly identify some
of the coefficients of Schubert classes in this expansion, which is a problem
of independent interest in Schubert calculus.


title:
Stationarity against integration in the autoregressive process with
  polynomial trend

abstract:
  We tackle the stationarity issue of an autoregressive path with a polynomial
trend, and we generalize some aspects of the LMC test, the testing procedure of
Leybourne and McCabe. First, we show that it is possible to get the asymptotic
distribution of the test statistic under the null hypothesis of
trend-stationarity as well as under the alternative of nonstationarity, for any
polynomial trend of order $r$. Then, we explain the reason why the LMC test,
and by extension the KPSS test, does not reject the null hypothesis of
trend-stationarity, mistakenly, when the random walk is generated by a unit
root located at $-1$. We also observe it on simulated data and we correct the
procedure. Finally, we describe some useful stochastic processes that appear in
our limiting distributions.


title:
Counting Tropically Degenerate Valuations and p-adic Approaches to the
  Hardness of the Permanent

abstract:
  The Shub-Smale Tau Conjecture is a hitherto unproven statement (on integer
roots of polynomials) whose truth implies both a variant of $P\neq NP$ (for the
BSS model over C) and the hardness of the permanent. We give alternative
conjectures, some potentially easier to prove, whose truth still implies the
hardness of the permanent. Along the way, we discuss new upper bounds on the
number of $p$-adic valuations of roots of certain sparse polynomial systems,
culminating in a connection between quantitative p-adic geometry and complexity
theory.


title:
Magnetism- and impurity-assisted chain creation in Ir and Pt break
  junctions

abstract:
  Applying the generalization of the model for chain formation in
break-junctions [JPCM 24, 135501 (2012)], we study the effect of light
impurities on the energetics and elongation properties of Pt and Ir chains. Our
model enables us with a tool ideal for detailed analysis of impurity assisted
chain formation, where zigzag bonds play an important role. In particular we
focus on H (s-like) and O (p-like) impurities and assume, for simplicity, that
the presence of impurity atoms in experiments results in ..M-X-M-X-... (M:
metal, X: impurity) chain structure in between the metallic leads. Feeding our
model with material-specific parameters from systematic full-potential
first-principles calculations, we find that the presence of such impurities
strongly affects the binding properties of the chains. We find that while both
types of impurities enhance the probability of chains to be elongated, the
s-like impurities lower the chain's stability. We also analyze the effect of
magnetism and spin-orbit interaction on the growth properties of the chains.


title: A Holographic Model of Two-Band Superconductor

abstract:
  We construct a holographic two-band superconductor model with interband
Josephson coupling. We investigate the effects the Josephson coupling has on
the superconducting condensates and the critical temperature for their
formation numerically, as well as analytically where possible. We calculate the
AC conductivity and find it qualitatively similar to the single band
superconductor. We investigate the nodal structure of our holographic two-band
superconductor from the low temperature behavior of the thermal conductivity
and find it nodeless.


title: Relative Comparison Kernel Learning with Auxiliary Kernels

abstract:
  In this work we consider the problem of learning a positive semidefinite
kernel matrix from relative comparisons of the form: "object A is more similar
to object B than it is to C", where comparisons are given by humans. Existing
solutions to this problem assume many comparisons are provided to learn a high
quality kernel. However, this can be considered unrealistic for many real-world
tasks since relative assessments require human input, which is often costly or
difficult to obtain. Because of this, only a limited number of these
comparisons may be provided. In this work, we explore methods for aiding the
process of learning a kernel with the help of auxiliary kernels built from more
easily extractable information regarding the relationships among objects. We
propose a new kernel learning approach in which the target kernel is defined as
a conic combination of auxiliary kernels and a kernel whose elements are
learned directly. We formulate a convex optimization to solve for this target
kernel that adds only minor overhead to methods that use no auxiliary
information. Empirical results show that in the presence of few training
relative comparisons, our method can learn kernels that generalize to more
out-of-sample comparisons than methods that do not utilize auxiliary
information, as well as similar methods that learn metrics over objects.


title: Monodromy of Inhomogeneous Picard-Fuchs Equations

abstract:
  We study low-degree curves on one-parameter Calabi-Yau hypersurfaces, and
their contribution to the space-time superpotential in a superstring
compactification with D-branes. We identify all lines that are invariant under
at least one permutation of the homogeneous variables, and calculate the
inhomogeneous Picard-Fuchs equation. The irrational large volume expansions
satisfy the recently discovered algebraic integrality. The bulk of our work is
a careful study of the topological integrality of monodromy under navigation
around the complex structure moduli space. This is a powerful method to recover
the single undetermined integration constant that is itself also of arithmetic
significance. The examples feature a variety of residue fields, both abelian
and non-abelian extensions of the rationals, thereby providing a glimpse of the
arithmetic D-brane landscape.


title:
Contagion among Central and Eastern European stock markets during the
  financial crisis

abstract:
  This paper contributes to the literature on international stock market
comovements and contagion. The novelty of our approach lies in application of
wavelet tools to high-frequency financial market data, which allows us to
understand the relationship between stock markets in a time-frequency domain.
While major part of economic time series analysis is done in time or frequency
domain separately, wavelet analysis combines these two fundamental approaches.
Wavelet techniques uncover interesting dynamics of correlations between the
Central and Eastern European (CEE) stock markets and the German DAX at various
investment horizons. The results indicate that connection of the CEE markets to
the leading market of the region is significantly lower at higher frequencies
in comparison to the lower frequencies. Contrary to previous literature, we
document significantly lower contagion between the CEE markets and the German
DAX after the large 2008 stock market crash.


title: Commensurators of solvable S-arithmetic groups

abstract:
  We show that the abstract commensurator of an S-arithmetic subgroup of a
solvable algebraic group over Q is isomorphic to the Q-points of an algebraic
group, and compare this with examples of nonlinear abstract commensurators of
S-arithmetic groups in positive characteristic. In particular, we include a
description of the abstract commensurator of the lamplighter group.


title: Anthropic Bounds on Lambda from the No-Boundary Quantum State

abstract:
  We show that anthropic selection emerges inevitably in the general framework
for prediction in quantum cosmology. There the predictions of anthropic
reasoning depend on the prior implied by the universe's quantum state. To
illustrate this we compute the probabilities specified by the no-boundary wave
function for our observations at the present time of the values of Lambda and Q
in an inflationary landscape model in which both quantities vary. Within the
anthropic range of values the no-boundary state yields an approximately flat
distribution on Lambda and strongly favors small values of Q. This restores
Weinberg's successful prediction of Lambda.


title: Scaling Limits of Coalescent Processes Near Time Zero

abstract:
  In this paper we obtain scaling limits of $\Lambda$-coalescents near time
zero under a regularly varying assumption. In particular this covers the case
of Kingman's coalescent and beta coalescents. The limiting processes are
coalescents with infinite mass, obtained geometrically as tangent cones of
Evans metric space associated with the coalescent. In the case of Kingman's
coalescent we are able to obtain a simple construction of the limiting space
using a two-sided Brownian motion.


title: Stellar Oscillations in Modified Gravity

abstract:
  Starting from the equations of modified gravity hydrodynamics, we derive the
equ tions of motion governing linear, adiabatic, radial perturbations of stars
in scalar-tensor theories. There are two new features: first, the eigenvalue
equation for the period of stellar oscillations is modified such that the
eigenfrequencies are always larger than predicted by General Relativity.
Second, the General Relativity condition for stellar instability is altered so
that the adiabatic index can fall below 4/3 before unstable modes appear. Stars
are more stable in modified gravity theories. Specialising to the case of
chameleon-like theories, we investigate these effects numerically using both
polytropic Lane-Emden stars and models coming from modified gravity stellar
structure simulations. The change in the oscillation period can be as large as
50% and the critical adiabatic index for instability falls by a composition
dependent amount of order 10^(-1). By solving the new equation for Cepheid
models, it is found that the change in the inferred distance using the
period-luminosity relation can be up to three times larger than if one had only
considered the modified equilibrium structure. We discuss the implications of
these results for recent and up-coming astrophysical tests and estimate that
previous methods can produce new constraints such that the modifications are
screened in regions of Newtonian potential of order 10^(-8).


title: Mukai's program for curves on a K3 surface

abstract:
  Let C be a general element in the locus of curves in M_g lying on some K3
surface, where g is congruent to 3 mod 4 and greater than or equal to 15.
Following Mukai's ideas, we show how to reconstruct the K3 surface as a
Fourier-Mukai transform of a Brill-Noether locus of rank two vector bundles on
C.


title: Infrared Saturation and Phases of Gauge Theories with BRST Symmetry

abstract:
  We investigate the infrared limit of the quantum equation of motion of the
gauge boson propagator in various gauges and models with a BRST symmetry. We
find that the saturation of this equation at low momenta distinguishes between
the Coulomb, Higgs and confining phase of the gauge theory. The Coulomb phase
is characterized by a massless gauge boson. Physical states contribute to the
saturation of the transverse equation of motion of the gauge boson at low
momenta in the Higgs phase, while the saturation is entirely due to unphysical
degrees of freedom in the confining phase. This corollary to the Kugo-Ojima
confinement criterion in linear covariant gauges also is sufficient for
confinement in general covariant gauges with BRST- and anti-BRST symmetry,
maximal Abelian gauges with an equivariant BRST symmetry, non-covariant Coulomb
gauge and in the Gribov-Zwanziger theory.


title: Nuclear dimension and sums of commutators

abstract:
  The problem of expressing a selfadjoint element that is zero on every bounded
trace as a finite sum (or a limit of sums) of commutators is investigated in
the setting of C*-algebras of finite nuclear dimension. Upper bounds -- in
terms of the nuclear dimension of the C*-algebra -- are given for the number of
commutators needed in these sums. An example is given of a simple, nuclear
C*-algebra (of infinite nuclear dimension) with a unique tracial state and with
elements that vanish on all bounded traces and yet are "badly" approximated by
finite sums of commutators. Finally, the same problem is investigated on
(possibly non-nuclear) simple unital C*-algebras assuming suitable regularity
properties in their Cuntz semigroups.


title: Families of mutually isospectral Riemannian orbifolds

abstract:
  In this paper we consider three arithmetic families of isospectral
non-isometric Riemannian orbifolds and in each case derive an upper bound for
the size of the family which is polynomial as a function of the volume of the
orbifolds. The first family that we consider are those constructed by Vigneras'
method. The second and third families are those whose covering groups are the
minimal covolume arithmetic subgroups and maximal arithmetic subgroups of
PGL_2(R)^a x PGL_2(C)^b.


title:
Precise Higgs-background predictions: merging NLO QCD and squared
  quark-loop corrections to four-lepton + 0,1 jet production

abstract:
  We present precise predictions for four-lepton plus jets production at the
LHC obtained within the fully automated Sherpa+OpenLoops framework. Off-shell
intermediate vector bosons and related interferences are consistently included
using the complex-mass scheme. Four-lepton plus 0- and 1-jet final states are
described at NLO accuracy, and the precision of the simulation is further
increased by squared quark-loop NNLO contributions in the gg -> 4l, gg -> 4l+g,
gq -> 4l+q, and qq -> 4l+g channels. These NLO and NNLO contributions are
matched to the Sherpa parton shower, and the 0- and 1-jet final states are
consistently merged using the MEPS@NLO technique. Thanks to Sudakov
resummation, the parton shower provides improved predictions and uncertainty
estimates for exclusive observables. This is important when jet vetoes or jet
bins are used to separate four-lepton final states arising from Higgs decays,
diboson production, and top-pair production. Detailed predictions are presented
for the ATLAS and CMS H->WW analyses at 8 TeV in the 0- and 1-jet bins.
Assessing renormalisation-, factorisation- and resummation-scale uncertainties,
which reflect also unknown subleading Sudakov logarithms in jet bins, we find
that residual perturbative uncertainties are as small as a few percent.


title:
Topological defects of N\'eel order and Kondo singlet formation for
  Kondo-Heisenberg model on a honeycomb lattice

abstract:
  Heavy fermion systems represent a prototypical setting to study magnetic
quantum phase transitions. A particular focus has been on the physics of Kondo
destruction, which captures quantum criticality beyond the Landau framework of
order-parameter fluctuations. In this context, we study the spin one-half
Kondo-Heisenberg model on a honeycomb lattice at half filling. The problem is
approached from the Kondo destroyed, antiferromagnetically ordered insulating
phase. We describe the local moments in terms of a coarse grained quantum
non-linear sigma model, and show that the skyrmion defects of the
antiferromagnetic order parameter host a number of competing order parameters.
In addition to the spin Peierls, charge and current density wave order
parameters, we identify for the first time Kondo singlets as the competing
orders of the antiferromagnetism. We show that the antiferromagnetism and
various competing singlet orders can be related to each other via generalized
chiral transformations of the underlying fermions. We also show that the
conduction electrons acquire a Berry phase through their coupling to the
hedgehog configurations of the N\'eel order, which cancels the Berry phase of
the local moments. Our results demonstrate the competition between the
Kondo-singlet formation and spin-Peierls order when the antiferromagnetic order
is suppressed, thereby shedding new light on the global phase diagram of heavy
fermion systems at zero temperature.


title:
Hawking non-thermal and Purely thermal radiations of Kerr-de Sitter
  black hole by Hamilton-Jacobi method

abstract:
  Incorporating Parikh and Wilczek's opinion to the Kerr de-Sitter (KdS) black
hole Hawking non-thermal and purely thermal radiations have been investigated
using Hamilton-Jacobi method. We have taken the background spacetime of KdS
black hole as dynamical, involving the self-gravitation effect of the emitted
particles, energy and angular momentum has been taken as conserved and show
that the tunneling rate is related to the change of Bekenstein-Hawking entropy
and the derived emission spectrum deviates from the pure thermal spectrum. The
explored results gives a correction to the Hawking radiation of KdS black hole.


title:
A Search for L/T Transition Dwarfs With Pan-STARRS1 and WISE: Discovery
  of Seven Nearby Objects Including Two Candidate Spectroscopic Variables

abstract:
  We present initial results from a wide-field (30,000 deg^2) search for L/T
transition brown dwarfs within 25 pc using the Pan-STARRS1 and WISE surveys.
Previous large-area searches have been incomplete for L/T transition dwarfs,
because these objects are faint in optical bands and have near-infrared colors
that are difficult to distinguish from background stars. To overcome these
obstacles, we have cross-matched the Pan-STARRS1 (optical) and WISE (mid-IR)
catalogs to produce a unique multi-wavelength database for finding ultracool
dwarfs. As part of our initial discoveries, we have identified seven brown
dwarfs in the L/T transition within 9-15 pc of the Sun. The L9.5 dwarf PSO
J140.2308+45.6487 and the T1.5 dwarf PSO J307.6784+07.8263 (both independently
discovered by Mace et al. 2013) show possible spectroscopic variability at the
Y- and J-bands. Two more objects in our sample show evidence of photometric
J-band variability, and two others are candidate unresolved binaries based on
their spectra. We expect our full search to yield a well-defined,
volume-limited sample of L/T transition dwarfs that will include many new
targets for study of this complex regime. PSO J307.6784+07.8263 in particular
may be an excellent candidate for in-depth study of variability, given its
brightness (J = 14.2 mag) and proximity (11 pc).


title: A new method to measure galaxy bias

abstract:
  We present a new approach for modelling galaxy/halo bias that utilizes the
full non-linear information contained in the moments of the matter density
field, which we derive using a set of numerical simulations. Although our
method is general, we perform a case study based on the local Eulerian bias
scheme truncated to second-order. Using 200 N-body simulations covering a total
comoving volume of 675 (Gpc/h)^3, we measure several 2- and 3-point statistics
of the halo distribution to unprecedented accuracy. We use the bias model to
fit the halo-halo power spectrum, the halo-matter cross spectrum and the
corresponding three bispectra for wavenumbers in the range 0.04 < k < 0.12 h
Mpc^-1. We find the constraints on the bias parameters obtained using the full
non-linear information differ significantly from those derived using standard
perturbation theory at leading order. Hence, neglecting the full non-linear
information leads to biased results for this particular scale range. We also
test the validity of the second-order Eulerian local biasing scheme by
comparing the parameter constraints derived from different statistics. Analysis
of the halo-matter cross-correlation coefficients defined for the 2- and
3-point statistics reveals further inconsistencies contained in the
second-order Eulerian bias scheme, suggesting it is too simple a model to
describe halo bias with high accuracy.


title:
Comparing molecular gas across cosmic time-scales: the Milky Way as both
  a typical spiral galaxy and a high-redshift galaxy analogue

abstract:
  Detailed observations of the nearest star-forming regions in the Milky Way
(MW) provide the ultimate benchmark for studying star formation. The extent to
which the results of these Galaxy-based studies can be extrapolated to
extragalactic systems depends on the overlap of the environmental conditions
probed. In this paper, we compare the properties of clouds and star-forming
regions in the MW with those in nearby galaxies and in the high-redshift
Universe. We find that in terms of their baryonic composition, kinematics, and
densities, the clouds in the solar neighbourhood are similar to those in nearby
galaxies. The clouds and regions in the Central Molecular Zone (CMZ, i.e. the
inner 250 pc) of the MW are indistinguishable from high-redshift clouds and
galaxies. The presently low star formation rate in the CMZ therefore implies
that either (1) its gas represents the initial conditions for high-redshift
starbursts or (2) some yet unidentified process consistently suppresses star
formation over >100 Myr time-scales. We conclude that the MW contains large
reservoirs of gas with properties directly comparable to most of the known
range of star formation environments and is therefore an excellent template for
studying star formation across cosmological time-scales.


title:
A fundamental metallicity relation for galaxies at z = 0.84 - 1.47 from
  HiZELS

abstract:
  We obtained Subaru FMOS observations of Halpha emitting galaxies selected
from the HiZELS narrow-band survey, to investigate the relationship between
stellar mass, metallicity and star-formation rate at z = 0.84 - 1.47, for
comparison with the Fundamental Metallicity Relation seen at low redshift. Our
findings demonstrate, for the first time with a homogeneously selected sample,
that a relationship exists for typical star-forming galaxies at z = 1 - 1.5 and
that it is surprisingly similar to that seen locally. Therefore, star-forming
galaxies at z = 1 - 1.5 are no less metal abundant than galaxies of similar
mass and star formation rate (SFR) at z = 0.1, contrary to claims from some
earlier studies. We conclude that the bulk of the metal enrichment for this
star-forming galaxy population takes place in the 4 Gyr before z = 1.5. We fit
a new mass-metallicity-SFR plane to our data which is consistent with other
high redshift studies. However, there is some evidence that the
mass-metallicity component of this high redshift plane is flattened, at all
SFR, compared with z = 0.1, suggesting that processes such as star-formation
driven winds, thought to remove enriched gas from low mass halos, are yet to
have as large an impact at this early epoch. The negative slope of the
SFR-metallicity relation from this new plane is consistent with the picture
that the elevation in the SFR of typical galaxies at z > 1 is fuelled by the
inflow of metal-poor gas and not major merging.


title: Strain-induced time-reversal odd superconductivity in graphene

abstract:
  Time-reversal symmetry breaking superconductors are exotic phases of matter
with fascinating properties, which are, however, encountered rather sparsely.
Here we identify the possibility of realizing such a superconducting ground
state that exhibits an $f+is$ pairing symmetry in strained graphene. Although
the underlying attractive interactions need to be sufficiently strong and
comparable in pristine graphene to support such pairing state, we argue that
strain can be conducive for its formation even for weak interactions. We show
that quantum-critical behavior near the transition is controlled by a
multicritical point, characterized by various critical exponents computed here
in the framework of an $\epsilon$-expansion near four spacetime dimensions.
Furthermore, a vortex in this mixed superconducting state hosts a pair of
Majorana fermions supporting a quartet of insulating and superconducting
orders, among which topologically nontrivial quantum spin Hall insulator. These
findings suggest that strained graphene could provide a platform for the
realization of exotic superconducting states of Dirac fermions.

categories: cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con hep-th


title: Characterising thermal sweeping: a rapid disc dispersal mechanism

abstract:
  (Abridged) We consider the properties of protoplanetary discs that are
undergoing inside-out clearing by photoevaporation. In particular, we aim to
characterise the conditions under which a protoplanetary disc may undergo
`thermal sweeping', a rapid (< 1e4 years) disc destruction mechanism proposed
to occur when a clearing disc reaches sufficiently low surface density at its
inner edge and where the disc is unstable to runaway penetration by the X-rays.
We use a large suite of 1D radiation-hydrodynamic simulations to probe the
observable parameter space, which is unfeasible in higher dimensions. These
models allow us to determine the surface density at which thermal sweeping will
take over the disc's evolution and to evaluate this critical surface density as
a function of X-ray luminosity, stellar mass and inner hole radius. We find
that this critical surface density scales linearly with X-ray luminosity,
increases with inner hole radius and decreases with stellar mass and we develop
an analytic model that reproduces these results.
  This surface density criterion is then used to determine the evolutionary
state of protoplanetary discs at the point that they become unstable to
destruction by thermal sweeping. We find that transition discs created by
photoevaporation will undergo thermal sweeping when their inner holes reach
20-40 AU, implying that transition discs with large holes and no accretion
(which were previously a predicted outcome of the later stages of all flavours
of photoevaporation model) will not form.
  We emphasise that the surface density criteria that we have developed apply
to all situations where the disc develops an inner hole that is optically thin
to X-rays. It thus applies not only to the case of holes originally created by
photoevaporation but also to holes formed, for example, by the tidal influence
of planets.


title:
Classification of X-ray Sources in the XMM-Newton Serendipitous Source
  Catalog: Objects of Special Interest

abstract:
  We analyze 18 sources that were found to show interesting properties of
periodicity, very soft spectra and/or large long-term variability in X-rays in
our project of classification of sources from the 2XMMi-DR3 catalog but were
poorly studied in the literature, in order to investigate their nature. Two
hard sources show X-ray periodicities of ~1.62 hr (2XMM J165334.4-414423) and
~2.1 hr (2XMM J133135.2-315541) and are probably magnetic cataclysmic
variables. The source 2XMM J123103.2+110648 is an active galactic nucleus (AGN)
candidate showing very soft X-ray spectra (kT~0.1 keV) and exhibiting an
intermittent ~3.8 hr quasi-periodic oscillation. There are six other very soft
sources (with kT<0.2 keV), which might be in other galaxies with luminosities
between ~10^{38}-10^{42} erg/s. They probably represent a diverse group that
might include objects such as ultrasoft AGNs and cool thermal disk emission
from accreting intermediate-mass black holes. Six highly variable sources with
harder spectra are probably in nearby galaxies with luminosities above 10^{37}
erg/s and thus are great candidates for extragalactic X-ray binaries. One of
them (2XMMi J004211.2+410429, in M 31) is probably a new-born persistent
source, having been X-ray bright and hard in 0.3--10 keV for at least four
years since it was discovered to enter an outburst in 2007. Three highly
variable hard sources appear at low galactic latitudes and have maximum
luminosities below ~10^{34} erg/s if they are in our Galaxy, thus great
candidates for cataclysmic variables or very faint X-ray transients harboring a
black hole or neutron star. Our interpretations of these sources can be tested
with future long-term X-ray monitoring and multi-wavelength observations.


title: Twining Genera of (0,4) Supersymmetric Sigma Models on K3

abstract:
  Conformal field theories with (0,4) worldsheet supersymmetry and K3 target
can be used to compactify the E8xE8 heterotic string to six dimensions in a
supersymmetric manner. The data specifying such a model includes an appropriate
configuration of 24 gauge instantons in the E8xE8 gauge group to satisfy the
constraints of anomaly cancellation. In this note, we compute twining genera -
elliptic genera with appropriate insertions of discrete symmetry generators in
the trace - for (0,4) theories with various instanton embeddings. We do this by
constructing linear sigma models which flow to the desired conformal field
theories, and using the techniques of localization. We present several examples
of such twining genera which are consistent with a moonshine relating these
(0,4) models to the finite simple sporadic group M24.


title:
PAOLO: a Polarimeter Add-On for the LRS Optics at a Nasmyth focus of the
  TNG

abstract:
  We describe a new polarimetric facility available at the Istituto Nazionale
di AstroFisica / Telescopio Nazionale Galileo at La Palma, Canary islands. This
facility, PAOLO (Polarimetric Add-On for the LRS Optics), is located at a
Nasmyth focus of an alt-az telescope and requires a specific modeling in order
to remove the time- and pointing position-dependent instrumental polarization.
We also describe the opto-mechanical structure of the instrument and its
calibration and present early examples of applications.


title: Supersymmetric non-Abelian multiwaves in D=3 AdS superspace

abstract:
  We present a covariant, supersymmetric and kappa-symmetric action for
non-Abelian multiwave system (nAmW) in D=3 AdS superspace. Its flat superspace
limit provides a simplest counterpart of the recently proposed action for 11
dimensional system of N nearly coincident M-waves (multiple M0-branes), which
is presently known for the case of flat target superspace only.


title:
[NeIII]/[OII] as an Ionization Parameter Diagnostic in Star-Forming
  Galaxies

abstract:
  We present our parameterizations of the log([NeIII]3869/[OII]3727) (Ne3O2)
and log([OIII]5007/[OII]3727) ratios as comparable and effective diagnostics of
ionization parameter in star-forming galaxies. Our calibrations are based on
the most recent generations of the Starburst99/Mappings III photoionization
models, which extend up to the extremely high values of ionization parameter
found in high-redshift galaxies. While similar calibrations have been presented
previously for O3O2, this is the first such calibration of Ne3O2. We illustrate
the tight correlation between these two ratios for star-forming galaxies and
discuss the underlying physics that dictates their very similar evolution.
Based on this work, we propose the Ne3O2 ratio as a new and useful diagnostic
of ionization parameter for star-forming galaxies. Given the Ne3O2 ratio's
relative insensitivity to reddening, this ratio is particularly valuable for
use with galaxies that have uncertain amounts of extinction. The short
wavelengths of the Ne3O2 ratio can also be applied out to very high redshifts,
extending studies of galaxies' ionization parameters out to z ~ 1.6 with
optical spectroscopy and z ~ 5.2 with ground-based near-infrared spectra.


title: String order in dipole-blockaded quantum liquids

abstract:
  We study the quantum melting of quasi-one-dimensional lattice models in which
the dominant energy scale is given by a repulsive dipolar interaction. By
constructing an effective low-energy theory, we show that the melting of
crystalline phases can occur into two distinct liquid phases, having the same
algebraic decay of density-density correlations, but showing a different
non-local correlation function expressing string order. We present possible
experimental realizations using ultracold atoms and molecules, introducing an
implementation based on resonantly driven Rydberg atoms that offers additional
benefits compared to a weak admixture of the Rydberg state.


title:
Classification and Description of Bosonic Symmetry Protected Topological
  Phases with semiclassical Nonlinear Sigma models

abstract:
  In this paper we systematically classify and describe bosonic symmetry
protected topological (SPT) phases in all physical spatial dimensions using
semiclassical nonlinear Sigma model (NLSM) field theories. All the SPT phases
on a $d-$dimensional lattice discussed in this paper can be described by the
same NLSM, which is an O(d+2) NLSM in $(d+1)-$dimensional space-time, with a
topological $\Theta-$term. The field in the NLSM is a semiclassical Landau
order parameter with a unit length constraint. The classification of SPT phases
discussed in this paper based on their NLSMs is consistent with the more
mathematical classification based on group cohomology. Besides the
classification, the formalism used in this paper also allows us to explicitly
discuss the physics at the boundary of the SPT phases, and it reveals the
relation between SPT phases with different symmetries. For example, it gives
many of these SPT states a natural "decorated defect" construction.


title:
Topological Properties of Time Reversal Symmetric Kitaev Chain and
  Applications to Organic Superconductors

abstract:
  We show that the pair of Majorana modes at each end of a 1D spin triplet
superconductor with total Cooper pair spin S_x=0 (i.e., Delta_{up,up} =
-Delta_{down,down} = p*Delta_0; two uncoupled time reversed copies of the
Kitaev p-wave chain) are topologically robust to perturbations such as mixing
by the S_z=0 component of the order parameter
(Delta_{up,down}=Delta_{down,up}), transverse hopping (in quasi-1D systems),
non-magnetic disorder, and also, most importantly, to time reversal breaking
perturbations such as applied Zeeman fields/magnetic impurities and the mixing
by the S_y=0 component of the triplet order parameter
(Delta_{up,up}=Delta_{down,down}). We show that the robustness to time reversal
breaking results from a hidden chiral symmetry which places the system in the
BDI topological class with an integer Z invariant. Our work has important
implications for the quasi-1D organic superconductors (TMTSF)_2X (X=PF_6,
CIO_4) (Bechgaard salts) which have been proposed as triplet superconductors
with equal spin pairing (Delta_{up,up},Delta_{down,down} \neq 0,
Delta_{up,down}=0) in applied magnetic fields.


title:
Generalized isospin, generalized mass groups, and generalized
  Gell-Mann--Okubo formalism

abstract:
  The current concepts of isospin and baryon mass groups are only well-adapted
to deal with baryon multiplets involving both the u and d quarks, and some
other quark k. In this paper, we generalize isospin and mass groups to
accommodate baryon multiplets involving quarks of any flavor, and the
Gell-Mann--Okubo (GMO) formalism is generalized accordingly. Generalized
isospin proves to be a simple and valuable framework when working in non-udk
baryon multiplets, and provides new quantum numbers that allows us to
distinguish $\Lambda$-like baryons from $\Sigma$-like baryons in the non-udk
multiplets. The generalized GMO formalism allows us to quantify the quality of
flavor symmetries seen in baryon multiplets, and also allows us to predict the
masses of all observable $J^P = \frac{1}{2}^+$ and $\frac{3}{2}^+$ baryons with
an estimated accuracy on the order of 50 MeV in the worst cases, on mass scales
that span anywhere from 1000 MeV to 15000 MeV.


title:
Textured electronic states of the triangular lattice Hubbard model and
  Na$_x$CoO$_2$

abstract:
  We show that geometric frustration and strong correlation in the triangular
lattice Hubbard model lead a rich and novel phase structure of
$\sqrt{3}\times\sqrt{3}$ spin-charge textured electronic states over a wide
region of electron doping $0\le x \le 0.40$. In addition to the 120$^\circ$
N\'eel ordered insulator at half-filling, we found a novel spin-charge ordered
insulator at $x=1/3$ with collinear antiferromagnetic (AF) order on the
underlying unfrustrated honeycomb lattice. Separating the two insulating phases
is a Lifshitz transition between a noncollinear AF ordered metal and one with
coexisting charge order. We obtain the phase diagram and the evolution of the
Fermi surface (FS). Remarkably, the correlated ground states near $x=1/3$
emerges as doping the "1/3 AF insulator" by excess carriers, leading to
electron and hole FS pockets with important implications for the cobaltate
superconducting state.


title: Mainly axion cold dark matter from natural supersymmetry

abstract:
  By eschewing finetuning from the electroweak and QCD sectors of supersymmetry
(natural supersymmetry or SUSY), and by invoking the Kim-Nilles solution to the
SUSY mu problem, one is lead to models wherein the dark matter is comprised of
a mixture of axions and higgsino-like WIMPs. Over a large range of Peccei-Quinn
breaking scale f_a~ 10^9-10^{12} GeV, one then expects about 90-95% axion dark
matter. In such a scenario, both axion and WIMP direct detection may be
expected.


title:
Constraining Stellar Feedback: Shock-ionized Gas in Nearby Starburst
  Galaxies

abstract:
  (abridged) We investigate the properties of feedback-driven shocks in 8
nearby starburst galaxies using narrow-band imaging data from the Hubble Space
Telescope (HST). We identify the shock--ionized component via the line
diagnostic diagram \oiii/\hb vs. \sii (or \nii)/\ha, applied to resolved
regions 3--15 pc in size. We divide our sample into three sub-samples:
sub-solar (Holmberg II, NGC 1569, NGC 4214, NGC 4449, and NGC 5253), solar (He
2-10, NGC 3077) and super-solar (NGC 5236) for consistent shock measurements.
For the sub-solar sub-sample, we derive three scaling relations: (1) $L_{shock}
\propto {SFR}^{~0.62}$, (2) $L_{shock} \propto {\Sigma_{SFR,HL}}^{~0.92}$, and
(3) $L_{shock}/L_{tot} \propto {(L_H/L_{\odot,H})}^{-0.65}$, where $L_{shock}$
is the \ha luminosity from shock--ionized gas, ${\Sigma_{SFR,HL}}$ the SFR per
unit half-light area, $L_{tot}$ the total \ha luminosity, and $L_H/L_{\odot,H}$
the absolute H-band luminosity from 2MASS normalized to solar luminosity. The
other two sub--samples do not have enough number statistics, but appear to
follow the first scaling relation. The energy recovered indicates that the
shocks from stellar feedback in our sample galaxies are fully radiative. If the
scaling relations are applicable in general to stellar feedback, our results
are similar to those by Hopkins et al. (2012) for galactic super winds. This
similarity should, however, be taken with caution at this point, as the
underlying physics that enables the transition from radiative shocks to gas
outflows in galaxies is still poorly understood.


title:
Investigating Information Security Risks of Mobile Device Use within
  Organizations

abstract:
  Mobile devices, such as phones, tablets and laptops, expose businesses and
governments to a multitude of information security risks. While Information
Systems research has focused on the security and privacy aspects from the
end-user perspective regarding mobile devices, very little research has been
conducted within corporate environments. In this work, thirty-two mobile
devices were returned by employees in a global Fortune 500 company. In the
empirical analysis, a number of significant security risks were uncovered which
may have led to leakage of valuable intellectual property or exposed the
organization to future legal conflicts. The research contribution is an initial
empirical report highlighting examples of corporate policy breaches by users
along with providing a foundation for future research on the security risks of
the pervasive presence of mobile devices in corporate environments.


title:
Botnet economics and devising defence schemes from attackers own reward
  processes

abstract:
  This paper focuses on botnet economics and design of defensive strategies. It
takes the view that by combining scarce information on the attackers business
models, with rational economic analysis of these business processes, one can
identify design rules for economic defense mechanisms which the target can
implement, often in a cheap way in addition to technical means. A short survey
of game theory in the security area, is followed by a real case of an Internet
casino. This leads to develop a model, applicable to this case and others,
which is presented first qualitatively then quantitatively. This allows
carrying out different analyses based on different equilibrium or termination
principles; the ones studied are reward break-even analysis, and Max-Min
analysis from game theory, for the target and the attackers. On that basis, a
number of specific economic and information led defense strategies are
identified which can be further studied using the model and specific
adaptations to other data or cases.


title:
Formation and detection of a chiral orbital Bose liquid in an optical
  lattice

abstract:
  Recent experiments on $p$-orbital atomic bosons have suggested the emergence
of a spectacular ultracold superfluid with staggered orbital currents in
optical lattices. This raises fundamental questions like the effects of
collective thermal fluctuations, and how to directly observe such chiral order.
Here, we show via Monte Carlo simulations that thermal fluctuations destroy
this superfluid in an unexpected two-step process, unveiling an intermediate
normal phase with spontaneously broken time-reversal symmetry, dubbed "chiral
Bose liquid". For integer fillings ($n\geq 2$) in the chiral Mott regime,
thermal fluctuations are captured by an effective orbital Ising model, and
Onsager's powerful exact solution is adopted to determine the transition from
this intermediate liquid to the para-orbital normal phase at high temperature.
A suitable lattice quench is designed to convert the staggered angular
momentum, previously thought by experts difficult to directly probe, into
coherent orbital oscillations, providing a smoking-gun signature of chiral
order.


title: Cluster-based reduced-order modelling of a mixing layer

abstract:
  We propose a novel cluster-based reduced-order modelling (CROM) strategy of
unsteady flows. CROM combines the cluster analysis pioneered in Gunzburger's
group (Burkardt et al. 2006) and and transition matrix models introduced in
fluid dynamics in Eckhardt's group (Schneider et al. 2007). CROM constitutes a
potential alternative to POD models and generalises the Ulam-Galerkin method
classically used in dynamical systems to determine a finite-rank approximation
of the Perron-Frobenius operator. The proposed strategy processes a
time-resolved sequence of flow snapshots in two steps. First, the snapshot data
are clustered into a small number of representative states, called centroids,
in the state space. These centroids partition the state space in complementary
non-overlapping regions (centroidal Voronoi cells). Departing from the standard
algorithm, the probabilities of the clusters are determined, and the states are
sorted by analysis of the transition matrix. Secondly, the transitions between
the states are dynamically modelled using a Markov process. Physical mechanisms
are then distilled by a refined analysis of the Markov process, e.g. using
finite-time Lyapunov exponent and entropic methods. This CROM framework is
applied to the Lorenz attractor (as illustrative example), to velocity fields
of the spatially evolving incompressible mixing layer and the three-dimensional
turbulent wake of a bluff body. For these examples, CROM is shown to identify
non-trivial quasi-attractors and transition processes in an unsupervised
manner. CROM has numerous potential applications for the systematic
identification of physical mechanisms of complex dynamics, for comparison of
flow evolution models, for the identification of precursors to desirable and
undesirable events, and for flow control applications exploiting nonlinear
actuation dynamics.


title:
Stringent Constraints On The Dark Matter Annihilation Cross Section From
  Subhalo Searches With The Fermi Gamma-Ray Space Telescope

abstract:
  The dark matter halo of the Milky Way is predicted to contain a very large
number of smaller subhalos. As a result of the dark matter annihilations taking
place within such objects, the most nearby and massive subhalos could appear as
point-like or spatially extended gamma-ray sources, without observable
counterparts at other wavelengths. In this paper, we use the results of the
Aquarius simulation to predict the distribution of nearby subhalos, and compare
this to the characteristics of the unidentified gamma-ray sources observed by
the Fermi Gamma-Ray Space Telescope. Focusing on the brightest high latitude
sources, we use this comparison to derive limits on the dark matter
annihilation cross section. For dark matter particles lighter than ~200 GeV,
the resulting limits are the strongest obtained to date, being modestly more
stringent than those derived from observations of dwarf galaxies or the
Galactic Center. We also derive independent limits based on the lack of
unidentified gamma-ray sources with discernible spatial extension, but these
limits are a factor of ~2-10 weaker than those based on point-like subhalos.
Lastly, we note that four of the ten brightest high-latitude sources exhibit a
similar spectral shape, consistent with 30-60 GeV dark matter particles
annihilating to b quarks with an annihilation cross section on the order of
sigma v ~ (5-10) x 10^-27 cm^3/s, or 8-10 GeV dark matter particles
annihilating to taus with sigma v ~ (2.0-2.5) x 10^-27 cm^3/s.

categories: hep-ph astro-ph.CO astro-ph.GA astro-ph.HE