title: Compressive Multiplexing of Correlated Signals

abstract:
  We present a general architecture for the acquisition of ensembles of
correlated signals. The signals are multiplexed onto a single line by mixing
each one against a different code and then adding them together, and the
resulting signal is sampled at a high rate. We show that if the $M$ signals,
each bandlimited to $W/2$ Hz, can be approximated by a superposition of $R < M$
underlying signals, then the ensemble can be recovered by sampling at a rate
within a logarithmic factor of $RW$ (as compared to the Nyquist rate of $MW$).
This sampling theorem shows that the correlation structure of the signal
ensemble can be exploited in the acquisition process even though it is unknown
a priori.
  The reconstruction of the ensemble is recast as a low-rank matrix recovery
problem from linear measurements. The architectures we are considering impose a
certain type of structure on the linear operators. Although our results depend
on the mixing forms being random, this imposed structure results in a very
different type of random projection than those analyzed in the low-rank
recovery literature to date.


title: Functions of perturbed $n$-tuples of commuting self-adjoint operators

abstract:
  Let $(A_1,\cdots,A_n)$ and $(B_1,\cdots,B_n)$ be $n$-tuples of commuting
self-adjoint operators on Hilbert space. For functions $f$ on $\R^n$ satisfying
certain conditions, we obtain sharp estimates of the operator norms (or norms
in operator ideals) of $f(A_1,\cdots,A_n)-f(B_1,\cdots,B_n)$ in terms of the
corresponding norms of $A_j-B_j$, $1\le j\le n$.
  We obtain analogs of earlier results on estimates for functions of perturbed
self-adjoint and normal operators. It turns out that for $n\ge3$, the methods
that were used for self-adjoint and normal operators do not work. We propose a
new method that works for arbitrary $n$.
  We also get sharp estimates for quasicommutators
$f(A_1,\cdots,A_n)R-Rf(B_1,\cdots,B_n)$ in terms of norms of $A_jR-RB_j$, $1\le
j\le n$, for a bounded linear operator $R$.


title:
Collisional processes of on-shell and off-shell heavy quarks in vacuum
  and in the Quark-Gluon-Plasma

abstract:
  We study the heavy quark scattering on partons of the quark gluon plasma
(QGP) being especially interested in the collisional (elastic) scattering
processes of heavy quarks on quarks and gluons. We calculate the different
cross sections for perturbative partons (massless on-shell particles in the
vacuum) and for dynamical quasi-particles (off-shell particles in the QGP
medium as described by the dynamical quasi-particles model "DQPM") using the
leading order Born diagrams. Our results show clearly the effect of a finite
parton mass and width on the perturbative elastic $(q(g) Q \rightarrow q (g)
Q)$ cross sections which depend on temperature $T$, energy density $\epsilon$,
the invariant energy $\sqrt{s}$ and the scattering angle $\theta$. Our detailed
comparisons demonstrate that the finite width of the quasi-particles in the
DQPM - which encodes the multiple partonic scattering - has little influence on
the cross section for $q Q \rightarrow q Q$ as well as $g Q \rightarrow g Q$
scattering except close to thresholds. Thus when studying the dynamics of
energetic heavy quarks in a QGP medium the spectral width of the
degrees-of-freedom may be discarded. We have, furthermore, compared the cross
sections from the DQPM with corresponding results from hard-thermal-loop (HTL)
approaches. The HTL inspired models - essentially fixing the regulators by
elementary vacuum cross sections and decay amplitudes instead of properties of
the QGP at finite temperature - provide quite different results especially
w.r.t. the temperature dependence of the $qQ$ and $gQ$ cross sections (in all
settings). Accordingly, the transport properties of heavy quarks will be very
different as a function of temperature when compared to DQPM results.


title:
Sub-Nyquist Sampling for Power Spectrum Sensing in Cognitive Radios: A
  Unified Approach

abstract:
  In light of the ever-increasing demand for new spectral bands and the
underutilization of those already allocated, the concept of Cognitive Radio
(CR) has emerged. Opportunistic users could exploit temporarily vacant bands
after detecting the absence of activity of their owners. One of the crucial
tasks in the CR cycle is therefore spectrum sensing and detection which has to
be precise and efficient. Yet, CRs typically deal with wideband signals whose
Nyquist rates are very high. In this paper, we propose to reconstruct the power
spectrum of such signals from sub-Nyquist samples, rather than the signal
itself as done in previous work, in order to perform detection. We consider
both sparse and non sparse signals as well as blind and non blind detection in
the sparse case. For each one of those scenarii, we derive the minimal sampling
rate allowing perfect reconstruction of the signal's power spectrum in a
noise-free environment and provide power spectrum recovery techniques that
achieve those rates. The analysis is performed for two different signal models
considered in the literature, which we refer to as the analog and digital
models, and shows that both lead to similar results. Simulations demonstrate
power spectrum recovery at the minimal rate in noise-free settings and show the
impact of several parameters on the detector performance, including
signal-to-noise ratio (SNR), sensing time and sampling rate.


title: Abelian automorphism groups of cubic fourfolds

abstract:
  We list all finite abelian groups which act effectively on smooth cubic
fourfolds.


title:
Dense molecular cocoons in the massive protocluster W3 IRS5: a test case
  for models of massive star formation

abstract:
  [Context] Two competing models describe the formation of massive stars in
objects like the Orion Trapezium. In the turbulent core accretion model, the
resulting stellar masses are directly related to the mass distribution of the
cloud condensations. In the competitive accretion model, the gravitational
potential of the protocluster captures gas from the surrounding cloud for which
the individual cluster members compete. [Aims] With high resolution
submillimeter observations of the structure, kinematics, and chemistry of the
proto-Trapezium cluster W3 IRS5, we aim to determine which mode of star
formation dominates. [Methods] We present 354 GHz Submillimeter Array
observations at resolutions of 1"-3" (1800-5400 AU) of W3 IRS5. ......
[Results] The observations show five emission peaks (SMM1-5). SMM1 and SMM2
contain massive embedded stars (~20 Msun); SMM3-5 are starless or contain
low-mass stars (<8 Msun). The inferred densities are high, >= 10^7 cm^-3, but
the core masses are small, 0.2-0.6 Msun. The detected molecular emission
reveals four different chemical zones. ...... [Conclusions] The proto-Trapezium
cluster W3 IRS5 is an ideal test case to discriminate between models of massive
star formation. Either the massive stars accrete locally from their local
cores; in this case the small core masses imply that W3 IRS5 is at the very end
stages (1000 yr) of infall and accretion, or the stars are accreting from the
global collapse of a massive, cluster forming core. We find that the observed
masses, densities and line widths observed toward W3 IRS 5 and the surrounding
cluster forming core are consistent with the competitive accretion of gas at
rates of Macc~10^-4 Msun yr^-1 by the massive young forming stars. ......


title:
Computation of ruin probabilities for general discrete-time Markov
  models

abstract:
  We study the ruin problem over a risk process described by a discrete-time
Markov model. In contrast to previous studies that focused on the asymptotic
behaviour of ruin probabilities for large values of the initial capital, we
provide a new technique to compute the quantity of interest for any initial
value, and with any given precision. Rather than focusing on a particular model
for risk processes, we give a general characterization of the ruin probability
by providing corresponding recursions and fixpoint equations. Since such
equations for the ruin probability are ill-posed in the sense that they do not
allow for unique solutions, we approximate the ruin probability by a
two-barrier ruin probability, for which fixpoint equations are well-posed. We
also show how good the introduced approximation is by providing an explicit
bound on the error and by characterizing the cases when the error converges to
zero. The presented technique and results are supported by two computational
examples over models known in the literature, one of which is extremely
heavy-tailed.


title: Mather-Yau Theorem in Positive Characteristic

abstract:
  The well-known Mather-Yau theorem says that the isomorphism type of the local
ring of an isolated complex hypersurface singularity is determined by its
Tjurina algebra. It is also well known that this result is wrong as stated for
power series f in K[[x]] over fields K of positive characteristic. In this note
we show that, however, also in positive characteristic the isomorphism type of
an isolated hypersurface singularity f is determined by an Artinian algebra,
namely by a "higher Tjurina algebra" for sufficiently high index, for which we
give an effective bound. We prove also a similar version for the "higher Milnor
algebra" considered as K[[f]]-algebra.


title: Locating Bound Structure in an Accelerating Universe

abstract:
  Given the overwhelming evidence that the universe is currently undergoing an
accelerated expansion, the question of what are the largest gravitationally
bound structures remains. A couple of groups, Busha et al. 2003 (B03) and
Dunner et al. 2006 (D06), have attempted to analytically define these limits,
arriving at substantially different estimates due to differences in their
assumptions about the velocities at the present epoch. In an effort to locate
the largest bound structures in the universe, we selected the Aquarius (ASC),
Microscopium (MSC), Corona Borealis (CBSC), and Shapley (SSC) superclusters for
study, due to their high number density of rich Abell clusters. Simple N-body
simulations, which assumed negligible intercluster mass, were used to assess
the likelihood of these structures being gravitationally bound, and the
predictions of the models of B03 and D06 were compared with those results. We
find that ASC, and MSC contain pairs of clusters which are gravitationally
bound, A2541/A2546 and A3695/A3696 respectively, with no other structures
having a significant chance of being bound. For SSC, we find a group of five
clusters, A3554, A3556, A3558, A3560, and A3562 that are bound, with an
additional pair, A1736/A3559, having a slight chance of being bound. We find
that CBSC has no extended bound structure, contrary to the findings of Small et
al. 1998, who claim that the entire supercluster is bound. In regards to the
analytical models, we find that B03 will identify structure that is definitely
bound, but tends to underestimate the true extent of the structure, while D06
will identify all structure that is bound while overestimating its extent.
Combined, the two models can provide lower and upper limits to the extent of
bound structures so long as there are no other significant structures nearby or
no significant dark matter exterior to the clusters.


title:
Shimura curves within the locus of hyperelliptic Jacobians in genus
  three

abstract:
  We construct an infinite number of Shimura curves contained in the locus of
hyperelliptic Jacobians of genus 3. In the opposite direction, we show that in
genus 3 the only possible non-complete (in the moduli space of abelian
threefolds) Kuga curves contained in the hyperelliptic locus have the same
degeneration data as that of the examples we construct.
  The locus of genus 3 hyperelliptic Jacobians is a divisor within the moduli
space of principally polarized abelian threefolds, and our result demonstrates
the techniques we develop more generally for dealing with Shimura curves
contained within a divisor in the moduli space of abelian varieties.


title:
Planck Scale Induced Speed of Sound in a Trapped Bose-Einstein
  Condensate

abstract:
  In the present work, we analyze the corrections caused by an anomalous
dispersion relation, suggested in several quantum gravity models, upon the
speed of sound in a weakly interacting Bose--Einstein Condensate, trapped in a
potential of the form $V(r)\sim r^{2}$. We show that the corresponding ground
state energy and consequently, the associated speed of sound, present
corrections respect to the usual case, which may be used to explore the
sensitivity to Planck--scale effects on these relevant properties associated
with the condensate. Indeed, we stress that this type of macroscopic bodies may
be more sensitive, under certain conditions, to Planck--scale manifestations
than its constituents. In addition, we prove that the inclusion of a trapping
potential, together with many--body contributions, improves the sensitivity to
Planck--scale signals, compared to the homogeneous system.


title:
The beaming pattern of External Compton Emission from relativistic
  outflows

abstract:
  The beaming pattern of radiation emitted by a relativistically moving source
like jets in microquasars, AGN and GRBs, is a key issue for understanding of
acceleration and radiation processes in these objects. In this paper we
introduce a formalism based on a solution of the photon transfer equation to
study the beaming patterns for emission produced by electrons accelerated in
the jet and upscattering photons of low-energy radiation fields of external
origin (the so-called External Compton scenario). The formalism allows us to
treat non-stationary, non-homogeneous and anisotropic distributions of
electrons, but assuming homogeneous/isotropic and non-variable target photon
fields. We demonstrate the non-negligible impact of the anisotropy in the
electron distribution on angular and spectral characteristics of the EC
radiation.


title: Locally Testable Codes and Cayley Graphs

abstract:
  We give two new characterizations of ($\F_2$-linear) locally testable
error-correcting codes in terms of Cayley graphs over $\F_2^h$:
  \begin{enumerate} \item A locally testable code is equivalent to a Cayley
graph over $\F_2^h$ whose set of generators is significantly larger than $h$
and has no short linear dependencies, but yields a shortest-path metric that
embeds into $\ell_1$ with constant distortion. This extends and gives a
converse to a result of Khot and Naor (2006), which showed that codes with
large dual distance imply Cayley graphs that have no low-distortion embeddings
into $\ell_1$.
  \item A locally testable code is equivalent to a Cayley graph over $\F_2^h$
that has significantly more than $h$ eigenvalues near 1, which have no short
linear dependencies among them and which "explain" all of the large
eigenvalues. This extends and gives a converse to a recent construction of
Barak et al. (2012), which showed that locally testable codes imply Cayley
graphs that are small-set expanders but have many large eigenvalues.
\end{enumerate}


title: Transitive Courant Algebroids, String Structures and T-duality

abstract:
  In this paper, we use reduction by extended actions to give a construction of
transitive Courant algebroids from string classes. We prove that T-duality
commutes with the reductions and thereby determine global conditions for the
existence of T-duals in heterotic string theory. In particular we find that
T-duality exchanges string structures and gives an isomorphism of transitive
Courant algebroids. Consequently we derive the T-duality transformation for
generalised metrics and show that the heterotic Einstein equations are
preserved. The presence of string structures significantly extends the domain
of applicability of T-duality and this is illustrated by several classes of
examples.


title: Log Adjunction: effectiveness and positivity

abstract:
  This is a first instalment of much larger work about relations between
birational geometry and moduli of triples. The extraction of work is mainly
related to Theorem 6. It is a weak version of Kawamata's Conjecture 1 and an
important technical step toward semiampleness of moduli part of adjunction. To
prove Theorem 6, we use relative analogues of b-representations. The proof here
is rather complete except for b-mobile property used in Corollary 1.


title:
A Kinetic Study of Amyloid Formation: Fibril Growth and Length
  Distributions

abstract:
  We propose a kinetic model for the self-aggregation by amyloid proteins. By
extending several well-known models for protein aggregation, the time evolution
of aggregate concentrations containing $r$ proteins, denoted $c_r(t)$, can be
written in terms of generalized Smoluchowski kinetics. With this approach we
take into account all possible aggregation and fragmentation reactions
involving clusters of any size. Correspondingly, an aggregate of size x+y could
be formed by or break-up into two smaller constituent aggregates of sizes x and
y. The rates of each aggregation or fragmentation reaction, called kernels, are
specified in terms of the aggregate size, and we solve $c_r(t)$ for large
cluster sizes using numerical techniques. We show that by using Smoluchowski
kinetics many pathways to fibrillation are possible and quantities, such as the
aggregate length distribution at an arbitrary time, can be calculated. We show
that the predicted results of the model are in agreement with the experimental
observations.


title:
Effect of covalency and interactions on the trigonal splitting in
  NaxCoO2

abstract:
  We calculate the effective trigonal crystal field Delta which splits the t2g
levels of effective models for NaxCoO2 as the local symmetry around a Co ion is
reduced from Oh to D3d. To this end we solve numerically a CoO6 cluster
containing a Co ion with all 3d states and their interactions included, and its
six nearest-neighbor O atoms, with the geometry of the system, in which the
CoO6 octahedron is compressed along a C3 axis. We obtain Delta near 130 meV,
with the sign that agrees with previous quantum chemistry calculations, but
disagrees with first-principles results in the local density approximation
(LDA). We find that Delta is very sensitive to a Coulomb parameter which
controls the Hund coupling and charge distribution among the d orbitals. The
origin of the discrepancy with LDA results is discussed.


title:
Evolving cellular automata for diversity generation and pattern
  recognition: deterministic versus random strategy

abstract:
  Microbiological systems evolve to fulfill their tasks with maximal
efficiency. The immune system is a remarkable example, where self-non self
distinction is accomplished by means of molecular interaction between self
proteins and antigens, triggering affinity-dependent systemic actions.
Specificity of this binding and the infinitude of potential antigenic patterns
call for novel mechanisms to generate antibody diversity. Inspired by this
problem, we develop a genetic algorithm where agents evolve their strings in
the presence of random antigenic strings and reproduce with affinity-dependent
rates. We ask what is the best strategy to generate diversity if agents can
rearrange their strings a finite number of times. We find that endowing each
agent with an inheritable cellular automaton rule for performing rearrangements
makes the system more efficient in pattern-matching than if transformations are
totally random. In the former implementation, the population evolves to a
stationary state where agents with different automata rules coexist.


title: Seven mutually touching infinite cylinders

abstract:
  We solve a problem of Littlewood: there exist seven infinite circular
cylinders of unit radius which mutually touch each other. In fact, we exhibit
two such sets of cylinders. Our approach is algebraic and uses symbolic and
numerical computational techniques. We consider a system of polynomial
equations describing the position of the axes of the cylinders in the 3
dimensional space. To have the same number of equations (namely 20) as the
number of variables, the angle of the first two cylinders is fixed to 90
degrees, and a small family of direction vectors is left out of consideration.
Homotopy continuation method has been applied to solve the system. The number
of paths is about 121 billion, it is hopeless to follow them all. However,
after checking 80 million paths, two solutions are found. Their validity, i.e.,
the existence of exact real solutions close to the approximate solutions at
hand, was verified with the alphaCertified method as well as by the interval
Krawczyk method.


title: Satisfiability Games for Branching-Time Logics

abstract:
  The satisfiability problem for branching-time temporal logics like CTL*, CTL
and CTL+ has important applications in program specification and verification.
Their computational complexities are known: CTL* and CTL+ are complete for
doubly exponential time, CTL is complete for single exponential time. Some
decision procedures for these logics are known; they use tree automata,
tableaux or axiom systems. In this paper we present a uniform game-theoretic
framework for the satisfiability problem of these branching-time temporal
logics. We define satisfiability games for the full branching-time temporal
logic CTL* using a high-level definition of winning condition that captures the
essence of well-foundedness of least fixpoint unfoldings. These winning
conditions form formal languages of \omega-words. We analyse which kinds of
deterministic {\omega}-automata are needed in which case in order to recognise
these languages. We then obtain a reduction to the problem of solving parity or
B\"uchi games. The worst-case complexity of the obtained algorithms matches the
known lower bounds for these logics. This approach provides a uniform, yet
complexity-theoretically optimal treatment of satisfiability for branching-time
temporal logics. It separates the use of temporal logic machinery from the use
of automata thus preserving a syntactical relationship between the input
formula and the object that represents satisfiability, i.e. a winning strategy
in a parity or B\"uchi game. The games presented here work on a Fischer-Ladner
closure of the input formula only. Last but not least, the games presented here
come with an attempt at providing tool support for the satisfiability problem
of complex branching-time logics like CTL* and CTL+.


title: ABM news and benchmarks

abstract:
  We report on progress in the determination of the unpolarised nucleon PDFs
within the ABM global fit framework. The data used in the ABM analysis are
updated including the charm-production and the high-Q2 neutral-current samples
obtained at the HERA collider, as well as the LHC data on the differential
Drell-Yan cross-sections. An updated set of the PDFs with improved experimental
and theoretical accuracy at small x is presented. We find minimal impact of the
t-quark production cross section measured at the Tevatron and the LHC on the
gluon distribution and the value of the strong coupling constant \alpha_s
determined from the ABM fit in the case of the t-quark running-mass definition.
In particular, the value of \alpha_s(M_Z)=0.1133(8) is obtained from the
variant of the ABM12 fit with the Tevatron and CMS t-quark production
cross-section data included and the MSbar value of m_t(m_t)=162 GeV.


title: One-point connectifications

abstract:
  A space Y is called an extension of a space X if Y contains X as a dense
subspace. An extension Y of X is called a one-point extension if Y-X is a
singleton. Compact extensions are called compactifications and connected
extensions are called connectifications.
  It is well known that every locally compact non-compact space has a one-point
compactification (known as the Alexandroff compactification) obtained by adding
a point at infinity. A locally connected disconnected space, however, may fail
to have a one-point connectification. It is indeed a long standing question of
Alexandroff to characterize spaces which have a one-point connectification.
Here we prove that in the class of completely regular spaces, a locally
connected space has a one-point connectification if and only if it contains no
compact component.


title: Is Somebody Watching Your Facebook Newsfeed?

abstract:
  With the popularity of Social Networking Services (SNS), more and more
sensitive information are stored online and associated with SNS accounts. The
obvious value of SNS accounts motivates the usage stealing problem --
unauthorized, stealthy use of SNS accounts on the devices owned/used by account
owners without any technology hacks. For example, anxious parents may use their
kids' SNS accounts to inspect the kids' social status; husbands/wives may use
their spouses' SNS accounts to spot possible affairs. Usage stealing could
happen anywhere in any form, and seriously invades the privacy of account
owners. However, there is no any currently known defense against such usage
stealing. To an SNS operator (e.g., Facebook Inc.), usage stealing is hard to
detect using traditional methods because such attackers come from the same IP
addresses/devices, use the same credentials, and share the same accounts as the
owners do.
  In this paper, we propose a novel continuous authentication approach that
analyzes user browsing behavior to detect SNS usage stealing incidents. We use
Facebook as a case study and show that it is possible to detect such incidents
by analyzing SNS browsing behavior. Our experiment results show that our
proposal can achieve higher than 80% detection accuracy within 2 minutes, and
higher than 90% detection accuracy after 7 minutes of observation time.


title: Degree Correlation in Scale-Free Graphs

abstract:
  We obtain closed form expressions for the expected conditional degree
distribution and the joint degree distribution of the linear preferential
attachment model for network growth in the steady state. We consider the
multiple-destination preferential attachment growth model, where incoming nodes
at each timestep attach to $\beta$ existing nodes, selected by
degree-proportional probabilities. By the conditional degree distribution
$p(\ell| k)$, we mean the degree distribution of nodes that are connected to a
node of degree $k$. By the joint degree distribution $p(k,\ell)$, we mean the
proportion of links that connect nodes of degrees $k$ and $\ell$. In addition
to this growth model, we consider the shifted-linear preferential growth model
and solve for the same quantities, as well as a closed form expression for its
steady-state degree distribution.

categories: cond-mat.stat-mech cs.SI physics.data-an physics.soc-ph


title: Forbidden Directed Minors and Kelly-width

abstract:
  Partial 1-trees are undirected graphs of treewidth at most one. Similarly,
partial 1-DAGs are directed graphs of KellyWidth at most two. It is well-known
that an undirected graph is a partial 1-tree if and only if it has no K_3
minor. In this paper, we generalize this characterization to partial 1-DAGs. We
show that partial 1-DAGs are characterized by three forbidden directed minors,
K_3, N_4 and M_5.


title: Sobolev spaces and averaging I

abstract:
  An apparently new concept of maximal mean difference quotient is defined for
functions in the Lebesgue space $L_{loc}(R^n)$. Our definitions are meaningful
for vector valued functions on general measure metric spaces as well and seem
to lead to the most natural class of metric Sobolev spaces. The discussion of
higher order Sobolev spaces and higher order mean difference quotients on
regular subsets of Euclidean spaces is also possible in the context of the
generalized Taylor-Whitney jets. This paper is a direct sequel to the papers:
  B. Bojarski, Taylor expansions and Sobolev spaces, Bull. Georgian Natl. Acad.
Sci. (N.S.) 5 (2011), no. 2, 5-10.
  B. Bojarski, Sobolev spaces and Lagrange interpolation, Proc. A. Razmadze
Math. Inst. 158 (2012), 1-12.


title: Approaches to Measuring Entanglement in Chemical Magnetometers

abstract:
  Chemical magnetometers are radical pair systems such as solutions of pyrene
and N,N-dimethylaniline (Py-DMA) that show magnetic field effects in their spin
dynamics and their fluorescence. We investigate the existence and decay of
quantum entanglement in free geminate Py-DMA radical pairs and discuss how
entanglement can be assessed in these systems. We provide an entanglement
witness and propose possible observables for experimentally estimating
entanglement in radical pair systems with isotropic hyperfine couplings. As an
application, we analyze how the field dependence of the entanglement lifetime
in Py-DMA could in principle be used for magnetometry and illustrate the
propagation of measurement errors in this approach.


title: Independence ratio and random eigenvectors in transitive graphs

abstract:
  A theorem of Hoffman gives an upper bound on the independence ratio of
regular graphs in terms of the minimum $\lambda_{\min}$ of the spectrum of the
adjacency matrix. To complement this result we use random eigenvectors to gain
lower bounds in the vertex-transitive case. For example, we prove that the
independence ratio of a $3$-regular transitive graph is at least
\[q=\frac{1}{2}-\frac{3}{4\pi}\arccos\biggl(\frac{1-\lambda
_{\min}}{4}\biggr).\] The same bound holds for infinite transitive graphs: we
construct factor of i.i.d. independent sets for which the probability that any
given vertex is in the set is at least $q-o(1)$. We also show that the set of
the distributions of factor of i.i.d. processes is not closed w.r.t. the weak
topology provided that the spectrum of the graph is uncountable.


title: BEEBS: Open Benchmarks for Energy Measurements on Embedded Platforms

abstract:
  This paper presents and justifies an open benchmark suite named BEEBS,
targeted at evaluating the energy consumption of embedded processors.
  We explore the possible sources of energy consumption, then select individual
benchmarks from contemporary suites to cover these areas. Version one of BEEBS
is presented here and contains 10 benchmarks that cover a wide range of typical
embedded applications. The benchmark suite is portable across diverse
architectures and is freely available.
  The benchmark suite is extensively evaluated, and the properties of its
constituent programs are analysed. Using real hardware platforms we show case
examples which illustrate the difference in power dissipation between three
processor architectures and their related ISAs. We observe significant
differences in the average instruction dissipation between the architectures of
4.4x, specifically 170uW/MHz (ARM Cortex-M0), 65uW/MHz (Adapteva Epiphany) and
88uW/MHz (XMOS XS1-L1).


title: On the nature of CP Pup

abstract:
  We present new X-ray and optical spectra of the old nova CP Pup (nova Pup
1942) obtained with Chandra and the CTIO 4m telescope. The X-ray spectrum
reveals a multi-temperature optically thin plasma reaching a maximum
temperature of 36$^{+19}_{-16}$ keV absorbed by local complex neutral material.
The time resolved optical spectroscopy confirms the presence of the $\sim$1.47
hr period, with cycle-to-cycle amplitude changes, as well as of an additional
long term modulation which is suggestive either of a longer period or of
non-Keplerian velocities in the emission line regions. These new observational
facts add further support to CP Pup as a magnetic cataclysmic variable (mCV).
We compare the mCV and the non-mCV scenarios and while we cannot conclude
whether CP Pup is a long period system, all observational evidences point at an
intermediate polar (IP) type CV.


title:
Frequency noise cancellation in optomechanical systems for ponderomotive
  squeezing

abstract:
  Ponderomotive squeezing of the output light of an optical cavity has been
recently observed in the MHz range in two different cavity optomechanical
devices. Quadrature squeezing becomes particularly useful at lower spectral
frequencies, for example in gravitational wave interferometers, despite being
more sensitive to excess phase and frequency noise. Here we show a
phase/frequency noise cancellation mechanism due to destructive interference
which can facilitate the production of ponderomotive squeezing in the kHz range
and we demonstrate it experimentally in an optomechanical system formed by a
Fabry-P\'{e}rot cavity with a micro-mechanical mirror.


title: Policy Specification in Role based Access Control on Clouds

abstract:
  Cloud Computing is a set of IT Services that are provided to a customer over
a network and these services are delivered by third party provider who owns the
infrastructure and reduce the burden at user's end. Nowadays researchers
devoted their work access control method to enhance the security on Cloud. RBAC
is attractive access model because the number of roles is significantly less
hence users can be easily classified according to their roles. The Role-based
Access Control (RBAC) model provides efficient way to manage access to
information while reducing the cost of security administration and complexity
in large networked applications. This paper specify various policies in RBAC on
clouds such as migration policy which helps the user to migrate the database
schema and roles easily to the Cloud using XML with more security. Restriction
policy provide the security enhancement in Role Based Access Model by
restricting the number of transaction per user and if the number of
transactions will increase the admin will come to know through its monitoring
system that unauthorized access has been made and it would be easier to take
action against such happening. This paper proposes backup and restoration
policy in Role Based Access Model in which if the main cloud is crashed or not
working properly then the backup and restoration facility will be available to
avoid the lost of important data. In this case chances of loss of data are very
less so enhance more security on Cloud Computing.


title:
Scalar perturbations in a Friedmann-like metric with non-null Weyl
  tensor

abstract:
  In a previous work the authors have solved the Einstein equations of General
Relativity for a class of metrics with constant spatial curvature, where it was
found a non vanishing Weyl tensor in the presence of a primordial magnetic
field with an anisotropic pressure component. Here, we perform the perturbative
analysis of this model in order to study the gravitational stability under
linear scalar perturbations. For this purpose, we take the Quasi-Maxwellian
formalism of General Relativity as our framework, which offers a naturally
covariant and gauge-invariant approach to deal with perturbations that are
directly linked to observational quantities.


title:
Measuring edge importance: a quantitative analysis of the stochastic
  shielding approximation for random processes on graphs

abstract:
  Mathematical models of cellular physiological mechanisms often involve random
walks on graphs representing transitions within networks of functional states.
Schmandt and Gal\'{a}n recently introduced a novel stochastic shielding
approximation as a fast, accurate method for generating approximate sample
paths from a finite state Markov process in which only a subset of states are
observable. For example, in ion channel models, such as the Hodgkin-Huxley or
other conductance based neural models, a nerve cell has a population of ion
channels whose states comprise the nodes of a graph, only some of which allow a
transmembrane current to pass. The stochastic shielding approximation consists
of neglecting fluctuations in the dynamics associated with edges in the graph
not directly affecting the observable states. We consider the problem of
finding the optimal complexity reducing mapping from a stochastic process on a
graph to an approximate process on a smaller sample space, as determined by the
choice of a particular linear measurement functional on the graph. The
partitioning of ion channel states into conducting versus nonconducting states
provides a case in point. In addition to establishing that Schmandt and
Gal\'{a}n's approximation is in fact optimal in a specific sense, we use recent
results from random matrix theory to provide heuristic error estimates for the
accuracy of the stochastic shielding approximation for an ensemble of random
graphs. Moreover, we provide a novel quantitative measure of the contribution
of individual transitions within the reaction graph to the accuracy of the
approximate process.


title: Poincare linearizers in higher dimensions

abstract:
  It is well-known that a holomorphic function near a repelling fixed point may
be conjugated to a linear function. The function which conjugates is called a
Poincar\'e linearizer and may be extended to a transcendental entire function
in the plane. In this paper, we study the dynamics of a higher dimensional
generalization of Poincar\'e linearizers. These arise by conjugating a
uniformly quasiregular mapping in $\R^m$ near a repelling fixed point to the
mapping $x\mapsto 2x$. In particular, we show that the fast escaping set of
such a linearizer has a spider's web structure.


title: Large grains can grow in circumstellar discs

abstract:
  We perform coagulation & fragmentation simulations to understand grain growth
in T Tauri & brown dwarf discs. We present a physically-motivated approach
using a probability distribution function for the collision velocities and
separating the deterministic & stochastic velocities. We find growth to larger
sizes compared to other models. Furthermore, if brown dwarf discs are
scaled-down versions of T Tauri discs (in terms of stellar & disc mass, and
disc radius), growth at the same location with respect to the outer edge occurs
to similar sizes in both discs.


title: On a remarkable formula of Jerison and Lee in CR geometry

abstract:
  We discuss a remarkable formula discovered by Jerison and Lee to classify
constant scalar curvature pseudohermitian structures on the sphere. We show
that the formula is valid in the wider context of Einstein pseudohermitian
manifolds. As an application we prove a uniqueness result that generalizes the
theorem of Jerison and Lee.


title: Remapping dark matter halo catalogues between cosmological simulations

abstract:
  We present and test a method for modifying the catalogue of dark matter
haloes produced from a given cosmological simulation, so that it resembles the
result of a simulation with an entirely different set of parameters. This
extends the method of Angulo & White (2010), which rescales the full particle
distribution from a simulation. Working directly with the halo catalogue offers
an advantage in speed, and also allows modifications of the internal structure
of the haloes to account for nonlinear differences between cosmologies. Our
method can be used directly on a halo catalogue in a self contained manner
without any additional information about the overall density field: although
the large-scale displacement field is required by the method, this can be
inferred from the halo catalogue alone. We show proof of concept of our method
by rescaling a matter-only simulation with no baryon acoustic oscillation (BAO)
features to a more standard LCDM model containing a cosmological constant and a
BAO signal. In conjunction with the halo occupation approach, this method
provides a basis for the rapid generation of mock galaxy samples spanning a
wide range of cosmological parameters.


title:
Transition form factors of $\pi^0$, $\eta$ and $\eta'$ mesons: What can
  be learned from anomaly sum rule?

abstract:
  We have studied the applications of the anomaly sum rule to the transition
form factors of light pseudoscalar mesons: $\pi^0$, $\eta$ and $\eta'$. This
nonperturbative QCD approach can be used even if the QCD factorization is
broken. The possibility of small non-OPE corrections to the spectral density in
view of the recent BaBar and Belle data is explored. The accuracy of the
applied method and the role of the quark mass contributions are discussed.


title: The geometry of arithmetic noncommutative projective lines

abstract:
  Let k be a perfect field and let K/k be a finite extension of fields. An
arithmetic noncommutative projective line is a noncommutative space equal to
the projectivization of the noncommutative symmetric algebra of a k-central two
-sided vector space of rank two over K. We study the geometry of these spaces.
More precisely, we prove they are integral, we classify vector bundles over
them, we classify them up to isomorphism, and we classify isomorphisms between
them. Using the classification of isomorphisms, we compute the automorphism
group of an arithmetic noncommutative projective line.


title: Baryon masses at nonzero isospin/kaon density

abstract:
  We present a lattice QCD calculation of the ground-state energy shifts of
various baryons in a medium of pions or kaons at a single value of the quark
mass corresponding to a pion mass of m_\pi~390 MeV and a kaon mass of m_K~540
MeV, and in a spatial volume V (4fm)^3. All systems are created using a
canonical formalism in which quark propagators are contracted into correlation
functions of fixed isospin/kaon density. We study four different systems,
\Sigma^+(\pi^+)^n, \Xi^0(\pi^+)^n, p(K^+)^n, and n(K^+)^n, for up to n=11
mesons. From the ground-state energy shifts we extract two- and three-body
scattering parameters, as well as linear combinations of low-energy constants
appearing in tree-level chiral perturbation theory.


title: A criterion for asymptotic completeness in local relativistic QFT

abstract:
  We formulate a generalized concept of asymptotic completeness and show that
it holds in any Haag-Kastler quantum field theory with an upper and lower mass
gap. It remains valid in the presence of pairs of oppositely charged particles
in the vacuum sector, which invalidate the conventional property of asymptotic
completeness. Our result can be restated as a criterion characterizing a class
of theories with complete particle interpretation in the conventional sense.
This criterion is formulated in terms of certain asymptotic observables
(Araki-Haag detectors) whose existence, as strong limits of their approximating
sequences, is our main technical result. It is proven with the help of a novel
propagation estimate, which is also relevant to scattering theory of quantum
mechanical dispersive systems.


title: On the geometric Ramsey numbers of trees

abstract:
  In this paper, we obtain upper bounds for the geometric Ramsey numbers of
trees. We prove that $R_c(T_n,H_m)=(n-1)(m-1)+1$ if $T_n$ is a caterpillar and
$H_m$ is a Hamiltonian outerplanar graph on $m$ vertices. Moreover, if $T_n$
has at most two non-leaf vertices, then $R_g(T_n,H_m)=(n-1)(m-1)+1$. We also
prove that $R_c(T_n,H_m)=O(n^2m)$ and $R_g(T_n,H_m)=O(n^3m^2)$ if $T_n$ is an
arbitrary tree on $n$ vertices and $H_m$ is an outerplanar triangulation with
pathwidth 2. %Further, we prove a uniform polynomial upper bound for the
geometric Ramsey numbers of caterpillars and we also give an upper bound for
$R_g(T_n)$ where $T_n$ is an arbitrary tree.


title: Excursions Above the Minimum for Diffusions

abstract:
  We demonstrate the existence of a "L\'evy system" for the excursions of a
one-dimensional diffusion process above its past-minimum process. As
applications we provide a direct proof of D. Williams' decomposition (in both a
global and a local form) and of a theorem of W. Vervaat.


title: Contraction of online response to major events

abstract:
  Quantifying regularities in behavioral dynamics is of crucial interest for
understanding collective social events such as panics or political revolutions.
With the widespread use of digital communication media it has become possible
to study massive data streams of user-created content in which individuals
express their sentiments, often towards a specific topic. Here we investigate
messages from various online media created in response to major, collectively
followed events such as sport tournaments, presidential elections or a large
snow storm. We relate content length and message rate, and find a systematic
correlation during events which can be described by a power law relation - the
higher the excitation the shorter the messages. We show that on the one hand
this effect can be observed in the behavior of most regular users, and on the
other hand is accentuated by the engagement of additional user demographics who
only post during phases of high collective activity. Further, we identify the
distributions of content lengths as lognormals in line with statistical
linguistics, and suggest a phenomenological law for the systematic dependence
of the message rate to the lognormal mean parameter. Our measurements have
practical implications for the design of micro-blogging and messaging services.
In the case of the existing service Twitter, we show that the imposed limit of
140 characters per message currently leads to a substantial fraction of
possibly dissatisfying to compose tweets that need to be truncated by their
users.


title: Characterisation of the Galactic thick disk

abstract:
  Thick disks appear to be common in external large spiral galaxies and our own
Milky Way also hosts one. The existence of a thick disk is possibly directly
linked to the formation history of the host galaxy and if its properties is
known it can constrain models of galaxy formation and help us to better
understand galaxy formation and evolution. This brief review attempts to
highlight some of the characteristics of the Galactic thick disk and how it
relates to other stellar populations such as the thin disk and the Galactic
bulge. Focus has been put on results from high-resolution spectroscopic data
obtained during the last 10 to 15 years.


title: Dynamics of H II regions around exiled O stars

abstract:
  At least 25 per cent of massive stars are ejected from their parent cluster,
becoming runaways or exiles, travelling with often-supersonic space velocities
through the interstellar medium (ISM). Their overpressurised H II regions
impart kinetic energy and momentum to the ISM, compress and/or evaporate dense
clouds, and can constrain properties of both the star and the ISM. Here we
present one-, two-, and (the first) three-dimensional simulations of the H II
region around a massive star moving supersonically through a uniform,
magnetised ISM, with properties appropriate for the nearby O star Zeta Oph. The
H II region leaves an expanding overdense shell behind the star and, inside
this, an underdense wake that should be filled with hot gas from the shocked
stellar wind. The gas column density in the shell is strongly influenced by the
ISM magnetic field strength and orientation. H-alpha emission maps show the H
II region remains roughly circular, although the star is displaced somewhat
from the centre of emission. For our model parameters, the kinetic energy
feedback from the H II region is comparable to the mechanical luminosity of the
stellar wind, and the momentum feedback rate is >100X larger than that from the
wind and about 10X larger than the total momentum input rate available from
radiation pressure. Compared to the star's eventual supernova explosion, the
kinetic energy feedback from the H II region over the star's main sequence
lifetime is >100X less, but the momentum feedback is up to 4X larger. H II
region dynamics are found to have only a small effect on the ISM conditions
that a bow shock close to the star would encounter.


title: Perturbation Biology: inferring signaling networks in cellular systems

abstract:
  We present a new experimental-computational technology of inferring network
models that predict the response of cells to perturbations and that may be
useful in the design of combinatorial therapy against cancer. The experiments
are systematic series of perturbations of cancer cell lines by targeted drugs,
singly or in combination. The response to perturbation is measured in terms of
levels of proteins and phospho-proteins and of cellular phenotype such as
viability. Computational network models are derived de novo, i.e., without
prior knowledge of signaling pathways, and are based on simple non-linear
differential equations. The prohibitively large solution space of all possible
network models is explored efficiently using a probabilistic algorithm, belief
propagation, which is three orders of magnitude more efficient than Monte Carlo
methods. Explicit executable models are derived for a set of perturbation
experiments in Skmel-133 melanoma cell lines, which are resistant to the
therapeutically important inhibition of Raf kinase. The resulting network
models reproduce and extend known pathway biology. They can be applied to
discover new molecular interactions and to predict the effect of novel drug
perturbations, one of which is verified experimentally. The technology is
suitable for application to larger systems in diverse areas of molecular
biology.


title: Differential calculus with integers

abstract:
  Ordinary differential equations have an arithmetic analogue in which
functions are replaced by numbers and the derivation operator is replaced by a
Fermat quotient operator. In this survey we explain the main motivations,
constructions, results, applications, and open problems of the theory.


title: Properties and origin of the old, metal rich, star cluster, NGC 6791

abstract:
  In this contribution I summarize the unique properties of the old, metal
rich, star cluster NGC 6791, with particular emphasis on its population of
extreme blue horizontal branch stars. I then conclude providing my personal
view on the origin of this fascinating star cluster.


title:
Exact solution of the 1D Hubbard model with NN and NNN interactions in
  the narrow-band limit

abstract:
  We present the exact solution, obtained by means of the Transfer Matrix (TM)
method, of the 1D Hubbard model with nearest-neighbor (NN) and
next-nearest-neighbor (NNN) Coulomb interactions in the atomic limit (t=0). The
competition among the interactions ($U$, $V_1$, and $V_2$) generates a plethora
of T=0 phases in the whole range of fillings. $U$, $V_1$, and $V_2$ are the
intensities of the local, NN and NNN interactions, respectively. We report the
T=0 phase diagram, in which the phases are classified according to the behavior
of the principal correlation functions, and reconstruct a representative
electronic configuration for each phase. In order to do that, we make an
analytic limit $T\to 0$ in the transfer matrix, which allows us to obtain
analytic expressions for the ground state energies even for extended transfer
matrices. Such an extension of the standard TM technique can be easily applied
to a wide class of 1D models with the interaction range beyond NN distance,
allowing for a complete determination of the T=0 phase diagrams.


title: Calculating two-strand jellyfish relations

abstract:
  We construct subfactors where one of the principal graphs is a spoke graph
using an algorithm which computes two-strand jellyfish relations. One of the
subfactors we construct is a 3^{Z/4} subfactor known to Izumi, which has not
previously appeared in the literature. To do so, we provide a systematic
treatment of the space of second annular consequences, which is analogous to
Jones' treatment of the space of first annular consequences in his quadratic
tangles article.
  This article is the natural followup to two recent articles on spoke
subfactor planar algebras and the jellyfish algorithm. Work of Bigelow-Penneys
explains the connection between spoke subfactor planar algebras and the
jellyfish algorithm, and work of Morrison-Penneys automates the construction of
subfactors where both principal graphs are spoke graphs using one-strand
jellyfish.


title:
Multi-Wavelength Observations of the Spatio-Temporal Evolution of Solar
  Flares with AIA/SDO: II. Hydrodynamic Scaling Laws and Thermal Energies

abstract:
  In this study we measure physical parameters of the same set of 155 M and
X-class solar flares observed with AIA/SDO as analyzed in Paper I, by
performing a {\sl differential emission measure (DEM)} analysis to determine
the flare peak emission measure $EM_p$, peak temperature $T_p$, electron
density $n_p$, and thermal energy $E_{th}$, in addition to the spatial scales
$L$, areas $A$, and volumes $V$ measured in Paper I. The parameter ranges for M
and X-class flares are: $\log(EM_p)=47.0-50.5$, $T_p=5.0-17.8$ MK, $n_p=4
\times 10^9-9 \times 10^{11}$ cm$^{-3}$, and thermal energies of $E_{th}=1.6
\times 10^{28}-1.1 \times 10^{32}$ erg. We find that these parameters obey the
Rosner-Tucker-Vaiana (RTV) scaling law $T_p^2 \propto n_p L$ and $H \propto
T^{7/2} L^{-2}$ during the peak time $t_p$ of the flare density $n_p$, when
energy balance between the heating rate $H$ and the conductive and radiative
loss rates is achieved for a short instant, and thus enables the applicability
of the RTV scaling law. The application of the RTV scaling law predicts
powerlaw distributions for all physical parameters, which we demonstrate with
numerical Monte-Carlo simulations as well as with analytical calculations. A
consequence of the RTV law is also that we can retrieve the size distribution
of heating rates, for which we find $N(H) \propto H^{-1.8}$, which is
consistent with the magnetic flux distribution $N(\Phi) \propto \Phi^{-1.85}$
observed by Parnell et al.(2009) and the heating flux scaling law $F_H \propto
H L \propto B/L$ of Schrijver et al.(2004). The fractal-diffusive
self-organized criticality model in conjunction with the RTV scaling law
reproduces the observed powerlaw distributions and their slopes for all
geometrical and physical parameters and can be used to predict the size
distributions for other flare datasets, instruments, and detection algorithms.


title: Fundamental Parameters of Exoplanets and Their Host Stars

abstract:
  For much of human history we have wondered how our solar system formed, and
whether there are any other planets like ours around other stars. Only in the
last 20 years have we had direct evidence for the existence of exoplanets, with
the number of known exoplanets dramatically increasing in recent years,
especially with the success of the Kepler mission. Observations of these
systems are becoming increasingly more precise and numerous, thus allowing for
detailed studies of their masses, radii, densities, temperatures, and
atmospheric compositions. However, one cannot accurately study exoplanets
without examining their host stars in equal detail, and understanding what
assumptions must be made to calculate planetary parameters from the directly
derived observational parameters.
  In this thesis, I present observations and models of the primary transits and
secondary eclipses of transiting exoplanets from both the ground and Kepler in
order to better study their physical characteristics and search for additional
exoplanets. I then identify, observe, and model new eclipsing binaries to
better understand the stellar mass-radius relationship and stellar
limb-darkening, compare these observations to the predictions of stellar
models, and attempt to define to what extent these fundamental stellar
characteristics can impact derived planetary parameters. I also present novel
techniques for the direct determination of exoplanet masses and stellar
inclinations via multi-wavelength astrometry, the ground-based photometric
observation of stars at sub-millimagnitude precision, the reduction of Kepler
photometry from pixel-level data, the extraction of radial velocities from
spectroscopic observations, and the automatic identification, period analysis,
and modeling of eclipsing binaries and transiting planets in large datasets.


title: Manopt, a Matlab toolbox for optimization on manifolds

abstract:
  Optimization on manifolds is a rapidly developing branch of nonlinear
optimization. Its focus is on problems where the smooth geometry of the search
space can be leveraged to design efficient numerical algorithms. In particular,
optimization on manifolds is well-suited to deal with rank and orthogonality
constraints. Such structured constraints appear pervasively in machine learning
applications, including low-rank matrix completion, sensor network
localization, camera network registration, independent component analysis,
metric learning, dimensionality reduction and so on. The Manopt toolbox,
available at www.manopt.org, is a user-friendly, documented piece of software
dedicated to simplify experimenting with state of the art Riemannian
optimization algorithms. We aim particularly at reaching practitioners outside
our field.


title:
Storing Cycles in Hopfield-type Networks with Pseudoinverse Learning
  Rule - Retrievability and Bifurcation Analysis

abstract:
  In this paper, we study retrievability of admissible cycles and the dynamics
of the networks constructed from admissible cycles with the pseudoinverse
learning rule. Retrievability of admissible cycles in networks with $C_0>0$ and
$\lambda$ sufficiently large are discussed. Based on the linear stability
analysis we derive a complete description of all possible local bifurcations of
the trivial solution for the networks constructed from admissible cycles. We
illustrate numerically that, depending on the structural features, the
admissible cycles are respectively stored and retrieved as attracting limit
cycles, unstable periodic solutions and delay-induced long-lasting transient
oscillations, and the transition from fixed points to the attracting limit
cycle bifurcating from the trivial solution takes place through multiple
saddle-nodes on limit cycle bifurcations.


title: Throughput of Cognitive Radio Systems with Finite Blocklength Codes

abstract:
  In this paper, throughput achieved in cognitive radio channels with finite
blocklength codes under buffer limitations is studied. Cognitive users first
determine the activity of the primary users' through channel sensing and then
initiate data transmission at a power level that depends on the channel sensing
decisions. It is assumed that finite blocklength codes are employed in the data
transmission phase. Hence, errors can occur in reception and retransmissions
can be required. Primary users' activities are modeled as a two-state Markov
chain and an eight-state Markov chain is constructed in order to model the
cognitive radio channel. Channel state information (CSI) is assumed to be
perfectly known by either the secondary receiver only or both the secondary
transmitter and receiver. In the absence of CSI at the transmitter, fixed-rate
transmission is performed whereas under perfect CSI knowledge, for a given
target error probability, the transmitter varies the rate according to the
channel conditions. Under these assumptions, throughput in the presence of
buffer constraints is determined by characterizing the maximum constant arrival
rates that can be supported by the cognitive radio channel while satisfying
certain limits on buffer violation probabilities. Tradeoffs between throughput,
buffer constraints, coding blocklength, and sensing duration for both
fixed-rate and variable-rate transmissions are analyzed numerically. The
relations between average error probability, sensing threshold and sensing
duration are studied in the case of variable-rate transmissions.


title: Deuterated molecules in Orion KL from Herschel/HIFI

abstract:
  We present a comprehensive study of the deuterated molecules detected in the
fullband HIFI survey of the Orion KL region. Ammonia, formaldehyde, and
methanol and their singly deuterated isotopologues are each detected through
numerous transitions in this survey with a wide range in optical depths and
excitation conditions. In conjunction with a recent study of the abundance of
HDO and H$_2$O in Orion KL, this study yields the best constraints on deuterium
fractionation in an interstellar molecular cloud to date. As previous studies
have found, both the Hot Core and Compact Ridge regions within Orion KL contain
significant abundances of deuterated molecules, suggesting an origin in cold
grain mantles. In the Hot Core, we find that ammonia is roughly a factor of 2
more fractionated than water. In the Compact Ridge, meanwhile, we find similar
deuterium fractionation in water, formaldehyde, and methanol, with D/H ratios
of (2---8) $\times$ $10^{-3}$. The [CH$_2$DOH]/[CH$_3$OD] ratio in the Compact
Ridge is found to be $1.2 \pm 0.3$. The Hot Core generally has lower deuterium
fractionation than the Compact Ridge, suggesting a slightly warmer origin, or a
greater contribution from warm gas phase chemistry.


title:
High Energy Scattering in Perturbative Quantum Gravity at Next to
  Leading Power

abstract:
  We consider the relativistic scattering of unequal-mass scalar particles
through graviton exchange in the small-angle high-energy regime. We show the
self-consistency of expansion around the eikonal limit and compute the
scattering amplitude up to the next-to-leading power correction of the light
particle energy, including gravitational effects of the same order. The first
power correction is suppressed by a single power of the ratio of momentum
transfer to the energy of the light particle in the rest frame of the heavy
particle, independent of the heavy particle mass. We find that only
gravitational corrections contribute to the exponentiated phase in impact
parameter space in four dimensions. For large enough heavy-particle mass, the
saddle point for the impact parameter is modified compared to the leading order
by a multiple of the Schwarzschild radius determined by the mass of the heavy
particle, independent of the energy of the light particle.


title: Double Bragg diffraction: A tool for atom optics

abstract:
  The use of retro-reflection in light-pulse atom interferometry under
microgravity conditions naturally leads to a double-diffraction scheme. The two
pairs of counterpropagating beams induce simultaneously transitions with
opposite momentum transfer that, when acting on atoms initially at rest, give
rise to symmetric interferometer configurations where the total momentum
transfer is automatically doubled and where a number of noise sources and
systematic effects cancel out. Here we extend earlier implementations for Raman
transitions to the case of Bragg diffraction. In contrast with the
single-diffraction case, the existence of additional off-resonant transitions
between resonantly connected states precludes the use of the adiabatic
elimination technique. Nevertheless, we have been able to obtain analytic
results even beyond the deep Bragg regime by employing the so-called "method of
averaging," which can be applied to more general situations of this kind. Our
results have been validated by comparison to numerical solutions of the basic
equations describing the double-diffraction process.


title: Reconstructing a phylogenetic level-1 network from quartets

abstract:
  We describe a method that will reconstruct an unrooted binary phylogenetic
level-1 network on n taxa from the set of all quartets containing a certain
fixed taxon, in O(n^3) time. We also present a more general method which can
handle more diverse quartet data, but which takes O(n^6) time. Both methods
proceed by solving a certain system of linear equations over GF(2).
  For a general dense quartet set (containing at least one quartet on every
four taxa) our O(n^6) algorithm constructs a phylogenetic level-1 network
consistent with the quartet set if such a network exists and returns an (O(n^2)
sized) certificate of inconsistency otherwise. This answers a question raised
by Gambette, Berry and Paul regarding the complexity of reconstructing a
level-1 network from a dense quartet set.


title:
Approximating the Little Grothendieck Problem over the Orthogonal and
  Unitary Groups

abstract:
  The little Grothendieck problem consists of maximizing
$\sum_{ij}C_{ij}x_ix_j$ over binary variables $x_i\in\{\pm1\}$, where C is a
positive semidefinite matrix. In this paper we focus on a natural
generalization of this problem, the little Grothendieck problem over the
orthogonal group. Given C a dn x dn positive semidefinite matrix, the objective
is to maximize $\sum_{ij}Tr (C_{ij}^TO_iO_j^T)$ restricting $O_i$ to take
values in the group of orthogonal matrices, where $C_{ij}$ denotes the (ij)-th
d x d block of C. We propose an approximation algorithm, which we refer to as
Orthogonal-Cut, to solve this problem and show a constant approximation ratio.
Our method is based on semidefinite programming. For a given $d\geq 1$, we show
a constant approximation ratio of $\alpha_{R}(d)^2$, where $\alpha_{R}(d)$ is
the expected average singular value of a d x d matrix with random Gaussian
$N(0,1/d)$ i.i.d. entries. For d=1 we recover the known $\alpha_{R}(1)^2=2/\pi$
approximation guarantee for the classical little Grothendieck problem. Our
algorithm and analysis naturally extends to the complex valued case also
providing a constant approximation ratio for the analogous problem over the
Unitary Group.
  Orthogonal-Cut also serves as an approximation algorithm for several
applications, including the Procrustes problem where it improves over the best
previously known approximation ratio of~$\frac1{2\sqrt{2}}$. The little
Grothendieck problem falls under the class of problems approximated by a recent
algorithm proposed in the context of the non-commutative Grothendieck
inequality. Nonetheless, our approach is simpler and it provides a more
efficient algorithm with better approximation ratios and matching integrality
gaps.
  Finally, we also provide an improved approximation algorithm for the more
general little Grothendieck problem over the orthogonal (or unitary) group with
rank constraints.


title: Introduction to eXtended Finite Element (XFEM) Method

abstract:
  In the present study the software CrackComput, based on the Xfem and Xcrack
libraries has been used for three problems- to experiment on the convergence
properties of the method applied to elasto-statics crack problems, comparison
of stress intensity factors to simplified analytical results and study of the
Brazilian fracture test. All the problems are treated in two dimensions under
plane strain assumption and the material is supposed elastic and isotropic. For
the first example, comparison for different parameter-enrichment type and
radius, degree of polynomial has been performed. Second example convergence of
SIF with the L/h ratio has been performed and compared with the analytical
solution. Third example is the study of snapback phenomenon.


title: Demonstrating an element of measurement-based quantum error correction

abstract:
  In measurement-based quantum computing an algorithm is performed by
measurements on highly-entangled resource states. To date, several
implementations were demonstrated, all of them assuming perfect noise-free
environments. Here we consider measurement-based information processing in the
presence of noise and demonstrate quantum error detection. We implement the
protocol using a four-qubit photonic cluster state, where we first encode a
general qubit non-locally such that phase errors can be detected. We then read
out the error syndrome and analyze the output states after decoding. Our
demonstration shows a building block for measurement-based quantum computing
which is crucial for realistic scenarios.


title: Consistent Probabilities in Perfect Fluid Quantum Universes

abstract:
  Recently it has been claimed that the Wheeler-DeWitt quantization of gravity
is unable to avoid cosmological singularities. However, in order to make this
assertion, one must specify the underlying interpretation of quantum mechanics
which has been adopted. For instance, several nonsingular models were obtained
in Wheeler-DeWitt quantum cosmology in the framework of the de Broglie-Bohm
quantum theory. Conversely, there are specific situations where the singularity
cannot be avoided in the framework of the Consistent Histories approach to
quantum mechanics. In these specific situations, the matter content is
described by a scalar field, and the Wheeler-DeWitt equation looks-like a
Klein-Gordon equation. The aim of this work is to study the Wheeler-DeWitt
quantization of cosmological models where the matter content is described by an
hydrodynamical perfect fluid, where the Wheeler-DeWitt equation reduces to a
genuine Schr\"odinger equation. In this case, it is shown that the conclusions
of the Consistent Histories and the de Broglie-Bohm approaches coincide in the
quantum cosmological models where the curvature of the spatial sections is not
positive definite, namely, that the cosmological singularities are eliminated.
In the case of positive spatial curvature, the family of histories is no longer
consistent, and no conclusion can be given in this framework.


title: Two-layer Locally Repairable Codes for Distributed Storage Systems

abstract:
  In this paper, we propose locally repairable codes (LRCs) with optimal
minimum distance for distributed storage systems (DSS). A two-layer encoding
structure is employed to ensure data reconstruction and the designated repair
locality. The data is first encoded in the first layer by any existing maximum
distance separable (MDS) codes, and then the encoded symbols are divided into
non-overlapping groups and encoded by an MDS array code in the second layer.
The encoding in the second layer provides enough redundancy for local repair,
while the overall code performs recovery of the data based on redundancy from
both layers. Our codes can be constructed over a finite field with size growing
linearly with the total number of nodes in the DSS, and facilitate efficient
degraded reads.


title: General Solutions to Static Plane Symmetric Einstein's Equations

abstract:
  A general formula for the metric as an explicit function of the generic
energy-momentum tensor is given which satisfies static plane symmetric
Einstein's equations with cosmological constant.In order to illustrate it, the
solutions for the vacuum with cosmological constant, the perfect fluid with a
linear equation of state and the electrically charged plane are derived and
compared with known results. The general solution with a linear relation among
the energy-momentum tensor components is also obtained.


title: Extreme Loading of Aircraft Fan Blade

abstract:
  The response of an aircraft fan blade manufactured by composites under the
action of static and impact load has been studied in this report. The modeling
and analysis of the geometry has been done using CASTEM 2007 version. For the
quasi static analysis, the pressure has been incrementally applied until it
satisfies the failure criteria. The deformed configuration, strain, Von-Mises
stress, and the deflection of the blade have been studied. The response of the
system e.g. deformation time history due to the impact of the projectile has
been studied where the Newmark method for the dynamic problem has been
implemented.


title: Intraoral Pressure in Ethnic Wind Instruments

abstract:
  High intraoral pressure generated when playing some wind instruments has been
linked to a variety of health issues. Prior research has focused on Western
classical instruments, but no work has been published on ethnic wind
instruments. This study measured intraoral pressure when playing six classes of
ethnic wind instruments (N = 149): Native American flutes (n = 71) and smaller
samples of ethnic duct flutes, reed instruments, reedpipes, overtone whistles,
and overtone flutes. Results are presented in the context of a survey of prior
studies, providing a composite view of the intraoral pressure requirements of a
broad range of wind instruments. Mean intraoral pressure was 8.37 mBar across
all ethnic wind instruments and 5.21 +/- 2.16 mBar for Native American flutes.
The range of pressure in Native American flutes closely matches pressure
reported in other studies for normal speech, and the maximum intraoral
pressure, 20.55 mBar, is below the highest subglottal pressure reported in
other studies during singing. Results show that ethnic wind instruments, with
the exception of ethnic reed instruments, have generally lower intraoral
pressure requirements than Western classical wind instruments. This implies a
lower risk of the health issues related to high intraoral pressure.


title:
Numerical Solution of Advection-Diffusion Equation Using Preconditionar
  as Incomplete LU Decomposition and the BiCGSTAB Aceleration Method

abstract:
  In the present study, an advection-diffusion problem has been considered for
the numerical solution. The continuum equation is discretized using both upwind
and centered scheme. The linear system is solved using the ILU preconditioned
BiCGSTAB method. Both Dirichlet and Neumann boundary condition has been
considered. The obtained results have been compared for different cases.


title:
Nonanalyticities in a Strongly Correlated Fermi Liquid: Corrections to
  Scaling at the Fermi-Liquid Fixed Point

abstract:
  We use scaling and renormalization-group techniques to analyze the leading
nonanalyticities in a Fermi liquid. We show that a physically motivated scaling
hypothesis reproduce the results known from perturbation theory for the density
of states, the density-of-states fluctuations, the specific heat, the spin
susceptibility, and the nematic magnetic susceptibility. We also discuss the
absence of nonanalytic terms in the density susceptibility. We then use a
recent effective field theory for clean electron systems to derive the scaling
hypothesis by means of renormalization-group techniques. This shows that the
exponents (although not the prefactors) of the nonanalyticities that were
previously derived by means of perturbative techniques are indeed exact, and
can be understood as the leading corrections to scaling at the stable
Fermi-liquid fixed point.


title:
Curves in R^n with finite total first curvature arising from the
  solutions of an ODE

abstract:
  We use the solution set of a real ordinary differential equation which has
order n which is at least 2 to construct a smooth curve C in R^n. We describe
when C is a proper embedding of infinite length with finite total first
curvature.


title: COAST: A Convex Optimization Approach to Stress-Based Embedding

abstract:
  Visualizing graphs using virtual physical models is probably the most heavily
used technique for drawing graphs in practice. There are many algorithms that
are efficient and produce high-quality layouts. If one requires that the layout
also respect a given set of non-uniform edge lengths, however, force-based
approaches become problematic while energy-based layouts become intractable. In
this paper, we propose a reformulation of the stress function into a two-part
convex objective function to which we can apply semi-definite programming
(SDP). We avoid the high computational cost associated with SDP by a novel,
compact re-parameterization of the objective function using the eigenvectors of
the graph Laplacian. This sparse representation makes our approach scalable. We
provide experimental results to show that this method scales well and produces
reasonable layouts while dealing with the edge length constraints.


title: Electromagnetic Reactions and Few-Nucleon Dynamics

abstract:
  We present an update on recent theoretical studies of electromagnetic
reactions obtained by using the Lorentz integral transform method. The 4He
nucleus will be the main focus of this report: results for the
photo-disintegration and the electro-disintegration processes will be shown, as
well as a recent calculation of polarizability effects in muonic atoms. We also
discuss the exciting possibility to investigate inelastic reactions for
medium-mass nuclei in coupled-cluster theory, highlighted by the recent
application to the 16O photo-nuclear cross section.


title:
Critical Casimir force in the presence of random local adsorption
  preference

abstract:
  We study the critical Casimir force for a film geometry in the Ising
universality class. We employ a homogeneous adsorption preference on one of the
confining surfaces, while the opposing surface exhibits quenched random
disorder, leading to a random local adsorption preference. Disorder is
characterized by a parameter p, which measures, on average, the portion of the
surface that prefers one component, so that p=0, 1 correspond to homogeneous
adsorption preference. By means of Monte Carlo simulations of an improved
Hamiltonian and finite-size scaling analysis, we determine the critical Casimir
force. We show that by tuning the disorder parameter p, the system exhibits a
crossover between an attractive and a repulsive force. At p=1/2, disorder
allows to effectively realize Dirichlet boundary conditions, which are
generically not accessible in classical fluids. Our results are relevant for
the experimental realizations of the critical Casimir force in binary liquid
mixtures.


title:
Exploring Io's atmospheric composition with APEX: first measurement of
  34SO2 and tentative detection of KCl

abstract:
  The composition of Io's tenuous atmosphere is poorly constrained. Only the
major species SO2 and a handful of minor species have been positively
identified, but a variety of other molecular species should be present, based
on thermochemical equilibrium models of volcanic gas chemistry and the
composition of Io's environment. This paper focuses on the spectral search for
expected yet undetected molecular species (KCl, SiO, S2O) and isotopes (34SO2).
We analyze a disk-averaged spectrum of a potentially line-rich spectral window
around 345 GHz, obtained in 2010 at the APEX-12m antenna (Atacama Pathfinder
EXperiment). Using different models assuming either extended atmospheric
distributions or a purely volcanically-sustained atmosphere, we tentatively
measure the KCl relative abundance with respect to SO2 and derive a range of
4x10^{-4}-8x10^{-3}. We do not detect SiO or S2O and present new upper limits
on their abundances. We also present the first measurement of the 34S/32S
isotopic ratio in gas phase on Io, which appears to be twice as high as the
Earth and ISM reference values. Strong lines of SO2 and SO are also analyzed to
check for longitudinal variations of column density and relative abundance. Our
models show that, based on their predicted relative abundance with respect to
SO2 in volcanic plumes, both the tentative KCl detection and SiO upper limit
are compatible with a purely volcanic origin for these species.


title: Schwarzschild-de Sitter Metric and Inertial Beltrami Coordinates

abstract:
  Under consideration of coordinate conditions, we get the
Schwarzschild-Beltrami-de Sitter (S-BdS) metric solution of the Einstein field
equations with a cosmological constant $\Lambda$. A brief review to the de
Sitter invariant special relativity (dS-SR), and de Sitter general relativity
(dS-GR, or GR with a $\Lambda$) is presented. The Beltrami metric $B_{\mu\nu}$
provides inertial reference frame for the dS-spacetime. By examining the
Schwarzschild-de Sitter (S-dS) metric $g_{\mu\nu}^{(M)}$ existed in literatures
since 1918, we find that the existed S-dS metric $g_{\mu\nu}^{(M)}$ describes
some mixing effects of gravity and inertial-force, instead of a pure gravity
effect arisen from "solar mass" $M$ in dS-GR. In this paper, we solve the
vacuum Einstein equation of dS-GR, with the requirement of gravity-free metric
$g_{\mu\nu}^{(M)}|_{M\rightarrow 0}=B_{\mu\nu}$. In this way we find S-BdS
solution of dS-GR, written in inertial Beltrami coordinates. This is a new form
of S-dS metric. Its physical meaning and possible applications are discussed.


title: Frequency-domain algorithm for the Lorenz-gauge gravitational self-force

abstract:
  State-of-the-art computations of the gravitational self-force (GSF) on
massive particles in black hole spacetimes involve numerical evolution of the
metric perturbation equations in the time-domain, which is computationally very
costly. We present here a new strategy, based on a frequency-domain treatment
of the perturbation equations, which offers considerable computational saving.
The essential ingredients of our method are (i) a Fourier-harmonic
decomposition of the Lorenz-gauge metric perturbation equations and a numerical
solution of the resulting coupled set of ordinary equations with suitable
boundary conditions; (ii) a generalized version of the method of extended
homogeneous solutions [Phys. Rev. D {\bf 78}, 084021 (2008)] used to circumvent
the Gibbs phenomenon that would otherwise hamper the convergence of the Fourier
mode-sum at the particle's location; and (iii) standard mode-sum
regularization, which finally yields the physical GSF as a sum over regularized
modal contributions. We present a working code that implements this strategy to
calculate the Lorenz-gauge GSF along eccentric geodesic orbits around a
Schwarzschild black hole. The code is far more efficient than existing
time-domain methods; the gain in computation speed (at a given precision) is
about an order of magnitude at an eccentricity of 0.2, and up to three orders
of magnitude for circular or nearly circular orbits. This increased efficiency
was crucial in enabling the recently reported calculation of the long-term
orbital evolution of an extreme mass ratio inspiral [Phys. Rev. D {\bf 85},
061501(R) (2012)]. Here we provide full technical details of our method to
complement the above report.


title:
A Link Between Star Formation Quenching and Inner Stellar Mass Density
  in SDSS Central Galaxies

abstract:
  We study the correlation between galaxy structure and the quenching of star
formation using a sample of SDSS central galaxies with stellar masses 9.75< log
M_*/M_sun<11.25 and redshifts z<0.075. GALEX UV data are used to cleanly divide
the sample into star-forming and quenched galaxies, and to identify galaxies in
transition (the green valley). Despite a stark difference in visual appearance
between blue and red galaxies, their average radial stellar mass density
profiles are remarkably similar (especially in the outer regions) at fixed
mass. The inner stellar mass surface density within a radius of 1 kpc,
\Sigma_1, is used to quantify the growth of the bulge as galaxies evolve. When
galaxies are divided into narrow mass bins, their distribution in the
color-\Sigma_1 plane at fixed mass forms plausible evolutionary tracks.
\Sigma_1 seems to grow as galaxies evolve through the blue cloud, and once it
crosses a threshold value, galaxies are seen to quench at fixed \Sigma_1. The
\Sigma_1 threshold for quenching grows with stellar mass, \Sigma_1 ~
M_*^{0.64}. However, the existence of some star-forming galaxies above the
threshold \Sigma_1 implies that a dense bulge is necessary but not sufficient
to quench a galaxy fully. This would be consistent with a two-step quenching
process in which gas within a galaxy is removed or stabilized against star
formation by bulge-driven processes (such as a starburst, AGN feedback, or
morphological quenching), whereas external gas accretion is suppressed by
separate halo-driven processes (such as halo gas shock heating). Quenching thus
depends on an interplay between the inner structure of a galaxy and its
surrounding dark matter halo, and lack of perfect synchrony between the two
could produce the observed scatter in color vs. \Sigma_1. (Abridged)


title: Elastic and transition form factors of the \Delta(1232)

abstract:
  Predictions obtained with a confining, symmetry-preserving treatment of a
vector-vector contact interaction at leading-order in a widely used truncation
of QCD's Dyson-Schwinger equations are presented for \Delta and \Omega baryon
elastic form factors and the \gamma N -> \Delta transition form factors. This
simple framework produces results that are practically indistinguishable from
the best otherwise available, an outcome which highlights that the key to
describing many features of baryons and unifying them with the properties of
mesons is a veracious expression of dynamical chiral symmetry breaking in the
hadron bound-state problem. The following specific results are of particular
interest. The \Delta elastic form factors are very sensitive to m_\Delta.
Hence, given that the parameters which define extant simulations of
lattice-regularised QCD produce \Delta-resonance masses that are very large,
the form factors obtained therewith are a poor guide to properties of the
\Delta(1232). Considering the \Delta-baryon's quadrupole moment, whilst all
computations produce a negative value, the conflict between theoretical
predictions entails that it is currently impossible to reach a sound conclusion
on the nature of the \Delta-baryon's deformation in the infinite momentum
frame. Results for analogous properties of the \Omega baryon are less
contentious. In connection with the N->\Delta transition, the Ash-convention
magnetic transition form factor falls faster than the neutron's magnetic form
factor and nonzero values for the associated quadrupole ratios reveal the
impact of quark orbital angular momentum within the nucleon and \Delta; and,
furthermore, these quadrupole ratios do slowly approach their anticipated
asymptotic limits.


title: The Influence of Ram Pressure on the Evolution of Tidal Dwarf Galaxies

abstract:
  The formation mechanism of tidal dwarf galaxies means they are expected to
contain little or no dark matter. As such, they might be expected to be very
sensitive to their environment. We investigate the impact of ram pressure on
tidal dwarf galaxies in a parameter study, varying dwarf galaxy properties and
ram pressures. We submit model tidal dwarf galaxies to wind-tunnel style tests
using a toy ram pressure model. The effects of ram pressure are found to be
substantial. If tidal dwarf galaxies have their gas stripped, they may be
completely destroyed. Ram pressure drag causes acceleration of our dwarf galaxy
models, and this further enhances stellar losses. The dragging can also cause
stars to lie in a low surface brightness stellar stream that points in the
opposite direction to the stripped gas, in a manner distinctive from tidal
streams. We investigate the effects of ram pressure on surface density
profiles, the dynamics of the stars, and discuss the consequences for dynamical
mass measurements.


title:
Surfaces of colloidal PbSe nanocrystals probed by thin-film positron
  annihilation spectroscopy

abstract:
  Positron annihilation lifetime spectroscopy (PALS) and positron-electron
momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs),
supported by transmission electron microscopy (TEM), show that positrons are
strongly trapped at NC surfaces, where they provide insight into the surface
composition and electronic structure of PbSe NCs. Our analysis indicates
abundant annihilation of positrons with Se electrons at the NC surfaces and
with O electrons of the oleic ligands bound to Pb ad-atoms at the NC surfaces,
which demonstrates that positrons can be used as a sensitive probe to
investigate the surface physics and chemistry of nanocrystals inside
multilayers. Ab-initio electronic structure calculations provide detailed
insight in the valence and semi-core electron contributions to the
positron-electron momentum density of PbSe. Both lifetime and PEMD are found to
correlate with changes in the particle morphology characteristic of partial
ligand removal.


title: The Fermi Bubbles as a Scaled-up Version of Supernova Remnants

abstract:
  In this study, we treat the Fermi bubbles as a scaled-up version of supernova
remnants (SNRs). The bubbles are created through activities of the
super-massive black hole (SMBH) or starbursts at the Galactic center (GC).
Cosmic-rays (CRs) are accelerated at the forward shocks of the bubbles like
SNRs, which means that we cannot decide whether the bubbles were created by the
SMBH or starbursts from the radiation from the CRs. We follow the evolution of
CR distribution by solving a diffusion-advection equation, considering the
reduction of the diffusion coefficient by CR streaming. In this model,
gamma-rays are created through hadronic interaction between CR protons and the
gas in the Galactic halo. In the GeV band, we can well reproduce the observed
flat distribution of gamma-ray surface brightness, because some amount of gas
is left behind the shock. The edge of the bubbles is fairly sharp owing to the
high gas density behind the shock and the reduction of the diffusion
coefficient there. The latter also contributes the hard gamma-ray spectrum of
the bubbles. We find that the CR acceleration at the shock has started when the
bubbles were small, and the time-scale of the energy injection at the GC was
much smaller than the age of the bubbles. We predict that if CRs are
accelerated to the TeV regime, the apparent bubble size should be larger in the
TeV band, which could be used to discriminate our hadronic model from other
leptonic models. We also present neutrino fluxes.


title:
The Spectrum of Thorium from 250 nm to 5500 nm: Ritz Wavelengths and
  Optimized Energy Levels

abstract:
  We have made precise observations of a thorium-argon hollow cathode lamp
emission spectrum in the region between 350 nm and 1175 nm using a
high-resolution Fourier transform spectrometer. Our measurements are combined
with results from seven previously published thorium line lists (Giacchetti et
al. 1974; Zalubas & Corliss 1974; Zalubas 1976; Palmer & Engleman 1983;
Engleman et al. 2003; Lovis & Pepe 2007; Kerber et al. 2008) to re-optimize the
energy levels of neutral, singly-, and doubly-ionized thorium (Th I, Th II, and
Th III). Using the optimized level values, we calculate accurate Ritz
wavelengths for 19874 thorium lines between 250 nm and 5500 nm (40000 1/cm to
1800 1/cm). We have also found 102 new thorium energy levels. A systematic
analysis of previous measurements in light of our new results allows us to
identify and propose corrections for systematic errors in Palmer & Engleman
(1983) and typographical errors and incorrect classifications in Kerber et al.
(2008). We also found a large scatter in the thorium line list of Lovis & Pepe
(2007). We anticipate that our Ritz wavelengths will lead to improved
measurement accuracy for current and future spectrographs that make use of
thorium-argon or thorium-neon lamps as calibration standards.


title:
Magnetic field amplification by cosmic-ray-driven turbulence: I.
  isotropic CR diffusion

abstract:
  We have performed magnetohydrodynamical simulations to study the
amplification of magnetic fields in the precursors of shock waves. Strong
magnetic fields are required in the precursors of the strong shocks that occur
in supernova remnants. Observations also suggest that magnetic field
amplification takes place in the weak shocks that occur in galaxy clusters and
that produce so-called radio relics. Here, we extend the study of magnetic
field amplification by cosmic-ray driven turbulence to weak shocks. The
amplification is driven by turbulence that is produced by the cosmic-ray
pressure acting on the density inhomogeneities in the upstream fluid. The
clumping that has been inferred from X-ray data for the outskirts of galaxy
clusters could provide some of the seed inhomogeneities. Magnetic field power
spectra and Faraday maps are produced. Furthermore, we investigate how the
synchrotron emission in the shock precursor can be used to verify the existence
of this instability and constrain essential plasma parameters.


title:
Causal connection in parsec-scale relativistic jets: results from the
  MOJAVE VLBI survey

abstract:
  We report that active galactic nucleus (AGN) jets are causally connected on
parsec scales, based on 15 GHz Very Long Baseline Array (VLBA) data from a
sample of 133 AGN jets. This result is achieved through a new method for
measuring the product of the jet Lorentz factor and the intrinsic opening angle
Gamma*theta_j from measured apparent opening angles in flux density limited
samples of AGN jets. The Gamma*theta_j parameter is important for jet physics
because it is related to the jet-frame sidewise expansion speed and causal
connection between the jet edges and its symmetry axis. Most importantly, the
standard model of jet production requires that the jet be causally connected
with its symmetry axis, implying that Gamma*theta_j < 1. When we apply our
method to the MOJAVE flux density limited sample of radio loud objects, we find
Gamma*theta_j = 0.2, implying that AGN jets are causally connected. We also
find evidence that AGN jets viewed very close to the line of sight effectively
have smaller intrinsic opening angles compared with jets viewed more off-axis,
which is consistent with Doppler beaming and a fast inner spine/slow outer
sheath velocity field. Notably, gamma-ray burst (GRB) jets have a typical
Gamma*theta_j that is two orders of magnitude higher, suggesting that different
physical mechanisms are at work in GRB jets compared to AGN jets. A useful
application of our result is that a jet's beaming parameters can be derived.
Assuming Gamma*theta_j is approximately constant in the AGN jet population, an
individual jet's Doppler factor and Lorentz factor (and therefore also its
viewing angle) can be determined using two observable quantities: apparent jet
opening angle and the apparent speed of jet components.


title:
Sturm und Drang: Supernova-Driven Turbulence, Magnetic Fields, and
  Cosmic Rays in the Chaotic Starburst Interstellar Medium

abstract:
  Frequent supernova explosions in compact starburst regions are a main shaper
of these regions' interstellar media (ISM). In most starbursts, the supernova
remnants blast open a hot phase that fills the regions and launches a
superwind. Denser starbursts are too overpressured for hot wind formation, but
supernovae still stir up the ISM. I argue that supernovae power ubiquitous
turbulence through each of the starburst ISM phases, including the hot wind,
and that a fluctuation dynamo amplifies magnetic fields until they are in
equipartition with the turbulence. Supernovae can drive turbulence with speeds
of ~1000 km/s in the hot wind and ~20 km/s in the cold molecular gas, depending
on the outer scale. I predict magnetic field strengths of 70 muG in the
Galactic Center starburst, 300 muG in M82 and NGC 253, and 2 mG in Arp 220's
nuclei. The mean magnetic field strengths are a few times stronger in molecular
gas than in hot winds, but do not vary strongly with density within a
starburst. I explain how the dominance of supernova-driven turbulence leads to
near equipartition between the components of starburst ISM. I also consider
implications for cosmic ray (CR) diffusion in starbursts. The high amounts of
power cascading to small scales could confine CRs very effectively in
starbursts, so much that CR transport is dominated by the flow of gas rather
than diffusion through the gas. In addition, I discuss the effects of
turbulence on X-ray line width, the far-infrared--radio correlation, observed
radio polarization, and Faraday rotation measures. Finally, I discuss the many
questions raised regarding the physics of turbulence in starbursts.


title: Eta Products, BPS States and K3 Surfaces

abstract:
  Inspired by the multiplicative nature of the Ramanujan modular discriminant,
Delta, we consider physical realizations of certain multiplicative products
over the Dedekind eta-function in two parallel directions: the generating
function of BPS states in certain heterotic orbifolds and elliptic K3 surfaces
associated to congruence subgroups of the modular group. We show that they are,
after string duality to type II, the same K3 surfaces admitting Nikulin
automorphisms. In due course, we will present some identities arising from
q-expansions as well as relations to the sporadic Mathieu group M24.


title:
The missing GeV {\gamma}-ray binary: Searching for HESS J0632+057 with
  Fermi-LAT

abstract:
  The very high energy (VHE; >100 GeV) source HESS J0632+057 has been recently
confirmed as a \gamma-ray binary, a subclass of the high mass X-ray binary
(HMXB) population, through the detection of an orbital period of 321 days. We
performed a deep search for the emission of HESS J0632+057 in the GeV energy
range using data from the Fermi Large Area Telescope (LAT). The analysis was
challenging due to the source being located in close proximity to the bright
\gamma-ray pulsar PSR J0633+0632 and lying in a crowded region of the Galactic
plane where there is prominent diffuse emission. We formulated a Bayesian block
algorithm adapted to work with weighted photon counts, in order to define the
off-pulse phases of PSR J0633+0632. A detailed spectral-spatial model of a 5
deg circular region centred on the known location of HESS J0632+057 was
generated to accurately model the LAT data. No significant emission from the
location of HESS J0632+057 was detected in the 0.1-100 GeV energy range
integrating over ~3.5 years of data; with a 95% flux upper limit of F_{0.1-100
GeV} < 3 x 10-8 ph cm-2 s-1. A search for emission over different phases of the
orbit also yielded no significant detection. A search for source emission on
shorter timescales (days--months) did not yield any significant detections. We
also report the results of a search for radio pulsations using the 100-m Green
Bank Telescope (GBT). No periodic signals or individual dispersed bursts of a
likely astronomical origin were detected. We estimated the flux density limit
of < 90/40 \mu Jy at 2/9 GHz. The LAT flux upper limits combined with the
detection of HESS J0632+057 in the 136-400 TeV energy band by the MAGIC
collaboration imply that the VHE spectrum must turn over at energies <136 GeV
placing constraints on any theoretical models invoked to explain the \gamma-ray
emission.


title: Fundamental properties of T dwarfs from model fits to FIRE spectra

abstract:
  We fit a sample of 49 R=6000 NIR (0.9 - 2.5 micron) T dwarf spectra obtained
with Magellan's FIRE spectrograph with two different atmospheric model sets to
compare the derived physical parameters such as Teff, log g, cloud opacity, and
rotational velocity between the models, as well as their reliability. Many of
our T dwarfs have distance measurements, which allows us to calculate their
radii during the fitting, which can be compared to evolutionary models to
determine age, mass and potentially the presence of unseen companions. We
present our spectral sample and model fits, and comment on the measured
fundamental properties of these T dwarfs. Our analysis allows us to identify
global deviations between models and observed spectra, and hence provides
important feedback for the next generation of substellar atmospheric models.


title: Exponential Galaxy Disks from Stellar Scattering

abstract:
  Stellar scattering off of orbiting or transient clumps is shown to lead to
the formation of exponential profiles in both surface density and velocity
dispersion in a two-dimensional non-self gravitating stellar disk with a fixed
halo potential. The exponential forms for both nearly-flat rotation curves and
near-solid body rotation curves. The exponential does not depend on initial
conditions, spiral arms, bars, viscosity, star formation, or strong shear.
After a rapid initial development, the exponential saturates to an
approximately fixed scale length. The inner exponential in a two-component
profile has a break radius comparable to the initial disk radius; the outer
exponential is primarily scattered stars.