title: The 2008 May burst activation of SGR 1627-41

abstract:
  In May 2008 the soft gamma-ray repeater SGR 1627-41 resumed its bursting
activity after nearly a decade of quiescence. After detection of a bright
burst, Swift pointed its X-ray telescope in the direction of the source in less
than five hours and followed it for over five weeks. In this paper we present
an analysis of the data from these Swift observations and an XMM-Newton one
performed when SGR 1627-41 was still in a quiescent state. The analysis of the
bursts detected with Swift/BAT shows that their temporal and spectral
properties are similar to those found in previous observations of SGR 1627-41
and other soft gamma-ray repeaters. The maximum peak luminosity of the bursts
was about 2E+41 erg/s. Our data show that the outburst was accompanied by a
fast flux enhancement and by a hardening of the spectrum with respect to the
persistent emission.


title: Vector valued reproducing kernel Hilbert spaces and universality

abstract:
  This paper is devoted to the study of vector valued reproducing kernel
Hilbert spaces. We focus on two aspects: vector valued feature maps and
universal kernels. In particular we characterize the structure of translation
invariant kernels on abelian groups and we relate it to the universality
problem.


title: Color neutrality effects in the phase diagram of the PNJL model

abstract:
  The phase diagram of a two-flavor Polyakov loop Nambu-Jona-Lasinio model is
analyzed imposing the constraint of color charge neutrality. Main effects of
this constraint are a shrinking of the chiral symmetry breaking (chiSB) domain
in the T-mu plane, a shift of the critical point to lower temperatures and a
coexistence of chiSB and two-flavor superconducting phases. The effects can be
understood in view of the presence of a nonvanishing color chemical potential
mu_8, which is necessary to compensate the color charge density rho_8 induced
by the nonvanishing Polyakov-loop mean field phi_3.


title: 2+1 Flavor Lattice QCD toward the Physical Point

abstract:
  We present the first results of the PACS-CS project which aims to simulate
2+1 flavor lattice QCD on the physical point with the nonperturbatively
$O(a)$-improved Wilson quark action and the Iwasaki gauge action. Numerical
simulations are carried out at the lattice spacing of $a=0.0907(13)$fm on a
$32^3\times 64$ lattice with the use of the DDHMC algorithm to reduce the
up-down quark mass. Further algorithmic improvements make possible the
simulation whose ud quark mass is as light as the physical value. The resulting
PS meson masses range from 702MeV down to 156MeV, which clearly exhibit the
presence of chiral logarithms. An analysis of the PS meson sector with SU(3)
ChPT reveals that the NLO corrections are large at the physical strange quark
mass. In order to estimate the physical ud quark mass, we employ the SU(2)
chiral analysis expanding the strange quark contributions analytically around
the physical strange quark mass. The SU(2) LECs ${\bar l}_3$ and ${\bar l}_4$
are comparable with the recent estimates by other lattice QCD calculations. We
determine the physical point together with the lattice spacing employing
$m_\pi$, $m_K$ and $m_\Omega$ as input. The hadron spectrum extrapolated to the
physical point shows an agreement with the experimental values at a few % level
of statistical errors, albeit there remain possible cutoff effects. We also
find that our results of $f_\pi=134.0(4.2)$MeV, $f_K=159.4(3.1)$MeV and
$f_K/f_\pi=1.189(20)$ with the perturbative renormalization factors are
compatible with the experimental values. For the physical quark masses we
obtain $m_{\rm ud}^\msbar=2.527(47)$MeV and $m_{\rm s}^\msbar=72.72(78)$MeV
extracted from the axial-vector Ward-Takahashi identity with the perturbative
renormalization factors.


title: A note on two-positive Ricci curvature and positive Einstein curvature

abstract:
  In this short note we discuss some recent results about two-positive Ricci
curvature and their applications to positive Einstein curvature.


title:
Complexity of 2D random laser modes at the transition from weak
  scattering to Anderson localization

abstract:
  The spatial extension and complexity of the eigenfunctions of an open
finite-size two-dimensional (2D) random system are systematically studied for a
random collection of systems ranging from weakly scattering to localized. The
eigenfunctions are obtained by introducing gain in the medium and pumping just
above threshold. All lasing modes are found to correspond to quasimodes of the
passive system, for all regimes of propagation. We demonstrate the existence of
multipeaked quasimodes or necklace states in 2D at the transition from
localized to diffusive, resulting from the coupling of localized states.


title: Quasi-K\"ahler manifolds with trivial Chern Holonomy

abstract:
  In this paper we study almost complex manifolds admitting a quasi-K\"ahler
Chern-flat metric (Chern-flat means that the holonomy of the Chern connection
is trivial). We prove that in the compact case such manifolds are all
nilmanifolds. Some partial classification results are established and we prove
that a quasi-K\"ahler Chern-flat structure can be tamed by a symplectic form if
and only if the ambient space is isomorphic to a flat torus.


title:
Properties of the Milky Way stellar disks in the direction of the Draco
  dSph galaxy

abstract:
  We present the first results of a study where we determine the metallicity
distribution function in the Galactic disks as a function of height above the
Galactic plane. Observations in the Stromgren photometric system enables us to
identify the dwarf stars and derive metallicities for them. The resulting
metallicity distribution functions at 0.5 and 2.0 kpc above the Galactic plane
are significantly broader and more metal-rich than is anticipated from standard
models such as the Besancon model. Our results can be explained by invoking a
smaller scale height and larger local normalisation for the thick disk than is
commonly used in the models. These results are compatible with recent
determinations of the thick disk scale height based e.g. on SDSS data.
  The age of the stellar populations as a function of height above the Galactic
plane is also investigated by studying the turn-off colour and metallicity. We
tentatively find that at 2.0 kpc above the Galactic plane there exist an
intermediate age population.


title: Flux interactions on D-branes and instantons

abstract:
  We provide a direct world-sheet derivation of the couplings of NS-NS and R-R
fluxes to various types of D-branes (including instantonic ones) by evaluating
disk amplitudes among two open string vertex operators at a generic brane
intersection and one closed string vertex representing the background fluxes.
This world-sheet approach is in full agreement with the derivation of the flux
couplings in the brane effective actions based on supergravity methods, but it
is applicable also to more general brane configurations involving fields with
twisted boundary conditions. As an application, we consider an orbifold
compactification of Type IIB string theory with fractional D-branes preserving
N=1 supersymmetry and study the flux-induced fermionic mass terms both on
space-filling branes and on instantonic ones. Our results show the existence of
a relation between the soft supersymmetry breaking and the lifting of some
instanton fermionic zero-modes, which may lead to new types of non-perturbative
couplings in brane-world models.


title:
Quasi-Mandelbrot sets for perturbed complex analytic maps: visual
  patterns

abstract:
  We consider perturbations of the complex quadratic map $ z \to z^2 +c$ and
corresponding changes in their quasi-Mandelbrot sets. Depending on particular
perturbation, visual forms of quasi-Mandelbrot set changes either sharply (when
the perturbation reaches some critical value) or continuously. In the latter
case we have a smooth transition from the classical form of the set to some
forms, constructed from mostly linear structures, as it is typical for
two-dimensional real number dynamics. Two examples of continuous evolution of
the quasi-Mandelbrot set are described.


title: Overview of the SIM PlanetQuest Light (SIM-Lite) mission concept

abstract:
  The Space Interferometry Mission PlanetQuest Light (or SIM-Lite) is a new
concept for a space borne astrometric instrument, to be located in a solar
Earth-trailing orbit. SIM-Lite utilizes technology developed over the past ten
years for the SIM mission. The instrument consists of two Michelson stellar
interferometers and a precision telescope. The first interferometer chops
between the target star and a set of Reference stars. The second interferometer
monitors the attitude of the instrument in the direction of the target star.
The telescope monitors the attitude of the instrument in the other two
directions.
  SIM-Lite will be capable of one micro-arc-second narrow angle astrometry on
magnitude 6 or brighter stars, relative to magnitude 9 Reference stars in a two
degree field. During the 5 year mission, SIM-Lite would search 65 nearby stars
for planets of masses down to one Earth mass, in the Habitable Zone, which have
orbit periods of less than 3 years. SIM-Lite will also perform global
astrometry on a variety of astrophysics objects, reaching 4.5 micro-arc-seconds
absolute position and parallax measurements. As a pointed instrument, SIM-Lite
will be capable of achieving 8 micro-arc-second astrometric accuracy on 19th
visual magnitude objects and 15 micro-arc-second astrometric accuracy on 20th
visual magnitude objects after 100 hours of integration.
  This paper will describe the instrument, how it will do its astrometric
measurements and the expected performance based on the current technology.


title: Coinductive Formal Reasoning in Exact Real Arithmetic

abstract:
  In this article we present a method for formally proving the correctness of
the lazy algorithms for computing homographic and quadratic transformations --
of which field operations are special cases-- on a representation of real
numbers by coinductive streams. The algorithms work on coinductive stream of
M\"{o}bius maps and form the basis of the Edalat--Potts exact real arithmetic.
We use the machinery of the Coq proof assistant for the coinductive types to
present the formalisation. The formalised algorithms are only partially
productive, i.e., they do not output provably infinite streams for all possible
inputs. We show how to deal with this partiality in the presence of syntactic
restrictions posed by the constructive type theory of Coq. Furthermore we show
that the type theoretic techniques that we develop are compatible with the
semantics of the algorithms as continuous maps on real numbers. The resulting
Coq formalisation is available for public download.


title: $gamma$ measurements at LHCb

abstract:
  The LHCb collaboration has studied various promising ways to determine the
Unitarity Triangle angle $\gamma$. Three complementary methods will be
considered. The potential of the $B \to DK^{(*)}$ decays has been studied by
employing the combined Gronau-London-Wyler (GLW) and the Atwood-Dunietz-Soni
(ADS) methods, making use of a large sample of simulated data. $\gamma$ can
also be extracted with a time-dependent analysis of $B_s \to D_s K$ decays,
provided that the $B_s$ mixing phase is measured independently. In addition,
the combined measurement of the $B^0 \to \pi^+ \pi^-$ and $B^0_s \to K^+K^-$
time-dependent CP asymmetries allows the determination of $\gamma$, up to
U-spin flavour symmetry breaking corrections. For each method the expected
sensitivities to the angle $\gamma$ are presented.


title:
First-passage and extreme-value statistics of a particle subject to a
  constant force plus a random force

abstract:
  We consider a particle which moves on the x axis and is subject to a constant
force, such as gravity, plus a random force in the form of Gaussian white
noise. We analyze the statistics of first arrival at point $x_1$ of a particle
which starts at $x_0$ with velocity $v_0$. The probability that the particle
has not yet arrived at $x_1$ after a time $t$, the mean time of first arrival,
and the velocity distribution at first arrival are all considered. We also
study the statistics of the first return of the particle to its starting point.
Finally, we point out that the extreme-value statistics of the particle and the
first-passage statistics are closely related, and we derive the distribution of
the maximum displacement $m={\rm max}_t[x(t)]$.


title: Distinctive subdynamic features of bipartite systems

abstract:
  There are several important bipartite systems of great interest in condensed
matter physics and in quantum information science. In condensed matter systems,
the subsystems are examined traditionally by using the Green function and
mean-field-like methods based on the Heisenberg representation. In quantum
information science, the subsystems are handled by composite density matrix,
its marginals describing the subsystems, and the Kraus representation to
elucidate the subsystem properties. In this work, a relationship is first
established between the two techniques which appear to be distinct at first
sight. This will be illustrated in detail by presenting the two methods in the
case of the celebrated exactly soluable Jaynes - Cummings model (1963) of a
two-state atom interacting with a one-mode quantized electromagnetic field. The
dynamics of this system was treated in the Heisenberg representation by
Ackerhalt and Rzazewski (1975). We present here the corresponding subdynamics
using Kraus representation. A relationship between the two approaches is
established and the relative merits of the two techniques are discussed in
elucidating the distinctive features of the subdynamics. The striking effects
of interaction and entanglement are made transparent in two illustrative
examples: the transformations that manifest in non-interacting number and spin
representations due to interactions in their respective subspaces.


title:
Structural Chemistry, Spin Order, and the Distinction Between the
  Cuprate and Pnictide High-Temperature Superconductors

abstract:
  In the cuprate and iron-pnictide systems, valence changes induce
high-temperature superconductivity while the local structural chemistry and
local spin order both independently generate the attractive interactions
responsible for the high transition temperature. We argue that together they
favor d-wave singlet superconductivity in the cuprates but s-wave singlet in
the pnictides. This difference arises from the existence of a large on-site
repulsion between carriers in the cuprates largely absent in the pnictides.
Fluorine is responsible for raising Tc significantly in some pnictides and in
the cuprates to 155K-168K, the highest achieved at ambient pressure. We propose
an experimental procedure for finding and fabricating the fluorinated cuprate
phase having that exceptional property.


title:
Type Ib Supernova 2008D associated with the Luminous X-ray Transient
  080109: An Energetic Explosion of a Massive Helium Star

abstract:
  We present a theoretical model for supernova (SN) 2008D associated with the
luminous X-ray transient 080109. The bolometric light curve and optical spectra
of the SN are modelled based on the progenitor models and the explosion models
obtained from hydrodynamic/nucleosynthetic calculations. We find that SN 2008D
is a more energetic explosion than normal core-collapse supernovae, with an
ejecta mass of Mej = 5.3 +- 1.0 Msun and a kinetic energy of E = 6.0 +- 2.5 x
10^{51} erg. The progenitor star of the SN has a 6-8 Msun He core with
essentially no H envelope (< 5 x 10^{-4} Msun) prior to the explosion. The
main-sequence mass of the progenitor is estimated to be Mms =20-25 Msun, with
additional systematic uncertainties due to convection, mass loss, rotation, and
binary effects. These properties are intermediate between those of normal SNe
and hypernovae associated with gamma-ray bursts. The mass of the central
remnant is estimated as 1.6 - 1.8 Msun, which is near the boundary between
neutron star and black hole formation.


title: Classes of Monomial Ideals

abstract:
  In this thesis, we focus on the study of some classes of monomial ideals,
namely lexsegment ideals and monomial ideals with linear quotients.


title: Percolation of arbitrary words in one dimension

abstract:
  We consider a type of long-range percolation problem on the positive
integers, motivated by earlier work of others on the appearance of (in)finite
words within a site percolation model. The main issue is whether a given
infinite binary word appears within an iid Bernoulli sequence at locations that
satisfy certain constraints. We settle the issue in some cases, and provide
partial results in others.


title: The Hexatangle

abstract:
  We are interested in knowing what type of manifolds are obtained by doing
Dehn surgery on closed pure 3-braids in the 3-sphere. In particular, we want to
determine when we get the 3-sphere by surgery on such a link. We consider links
which are small closed pure 3-braids; these are the closure of 3-braids of the
form $({\sigma_1}^{2e_1})({\sigma_2}^{2f_1})(\sigma_2\sigma_1\sigma_2)^{2e}$,
where $\sigma_1$, $\sigma_2$ are the generators of the 3-braid group and $e_1$,
$f_1$, $e$ are integers. We study Dehn surgeries on these links, and determine
exactly which ones admit an integral surgery producing the 3-sphere. This is
equivalent to determining the surgeries of some type on a certain six component
link $L$ that produce $S^3$. The link $L$ is strongly invertible and its
exterior double branch covers a certain configuration of arcs and spheres,
which we call the Hexatangle. Our problem is equivalent to determine which
fillings of the spheres by integral tangles produce the trivial knot, which is
what we explicitly solve. This hexatangle is a generalization of the Pentangle,
which is studied by Gordon and Luecke.


title:
Performance Comparison of Graphene Nanoribbon FETs with Schottky
  Contacts and Doped Reservoirs

abstract:
  We present an atomistic 3D simulation study of the performance of graphene
nanoribbon (GNR) Schottky barrier (SB) FETs and transistors with doped
reservoirs (MOSFETs) by means of the self-consistent solution of the Poisson
and Schrodinger equations within the non-equilibrium Green's function (NEGF)
formalism. Ideal MOSFETs show slightly better electrical performance, for both
digital and THz applications. The impact of non-idealities on device
performance has been investigated, taking into account the presence of single
vacancy, edge roughness and ionized impurities along the channel. In general,
MOSFETs show more robust characteristics than SBFETs. Edge roughness and single
vacancy defect largely affect performance of both device types.


title:
A modified logarithmic Sobolev inequality for the Hamming cube and some
  applications

abstract:
  The logarithmic Sobolev inequality for the Hamming cube {0,1}^n states that
for any real-valued function f on the cube holds E(f,f) \ge 2 Ent(f^2), where
E(f,f) is the appropriate Dirichlet form (also known as "sum of influences").
  We show that the constant C = 2 at the right hand side of this inequality can
be replaced by a function C(rho) depending on rho = Ent(f^2) / (n Ef^2). The
function C is an increasing convex function taking [0,log 2] to [2, 2/log 2].
  We present some applications of this modified inequality. In particular, it
is used to obtain a discrete version of the Faber-Krahn inequality for small
subsets of the Hamming cube, answering a question of Friedman and Tillich. We
introduce, following the approach of Friedman and Tillich, the notion of a
fractional edge-boundary size of a subset of {0,1}^n, and show Hamming balls of
radius at most n/2 - O(n^{3/4}) to be sets with (asymptotically) the smallest
fractional edge-boundary for their size.


title: Nuclear shadowing and prompt photons at relativistic hadron colliders

abstract:
  The production of prompt photons at high energies provides a direct probe of
the dynamics of the strong interactions. In particular, one expect that it
could be used to constrain the behavior of the nuclear gluon distribution in
$pA$ and $AA$ collisions. In this letter we investigate the influence of
nuclear effects in the production of prompt photons and estimate the transverse
momentum dependence of the nuclear ratios $R_{pA} = {\frac{d\sigma (pA)}{dy d^2
p_T}} / A {\frac{d\sigma (pp)}{dy d^2 p_T}}$ and $R_{AA} = {\frac{d\sigma
(AA)}{dy d^2 p_T}} / A^2 {\frac{d\sigma (pp)}{dy d^2 p_T}}$ at RHIC and LHC
energies. We demonstrate that the study of these observables can be useful to
determine the magnitude of the shadowing and antishadowing effects in the
nuclear gluon distribution.


title: The Eyring-Kramers law for potentials with nonquadratic saddles

abstract:
  The Eyring-Kramers law describes the mean transition time of an overdamped
Brownian particle between local minima in a potential landscape. In the
weak-noise limit, the transition time is to leading order exponential in the
potential difference to overcome. This exponential is corrected by a prefactor
which depends on the principal curvatures of the potential at the starting
minimum and at the highest saddle crossed by an optimal transition path. The
Eyring-Kramers law, however, does not hold whenever one of these principal
curvatures vanishes, since it would predict a vanishing or infinite transition
time. We derive the correct prefactor up to multiplicative errors that tend to
one in the zero-noise limit. As an illustration, we discuss the case of a
symmetric pitchfork bifurcation, in which the prefactor can be expressed in
terms of modified Bessel functions, as well as bifurcations with two vanishing
eigenvalues. The corresponding transition times are studied in a full
neighbourhood of the bifurcation point. These results extend work by Bovier,
Eckhoff, Gayrard and Klein, who rigorously analysed the case of quadratic
saddles, using methods from potential theory.


title:
Study of the hadronic production of kaon pairs below the threshold for
  the phi meson

abstract:
  The near threshold production of K+K- pairs in proton-proton collisions has
been investigated at the cooler synchrotron COSY below and above the threshold
for the $\phi$ meson using the COSY-11 and ANKE facilities, respectively. The
excitation function determined for the pp-->ppK+K- reaction revealed a
statistically significant enhancement close to the threshold which may
plausibly be assigned to the influence of the K-p interaction. In addition,
observed consistently by both groups, a strong enhancement at low values of the
ratio of the K-p to K+p invariant mass distributions shows that the proton
interacts much stronger with K- than with K+. In this report we focus on the
measurements performed by the COSY-11 collaboration. We explain the
experimental method used and present main results of completed analyses as well
as a new qualitative elaboration of the ppK+K- events population on the
Goldhaber plot. We conclude with the observation that event densities increase
at the region where the influence from the K+K- interaction is expected.


title:
Study of the Hubbard model on the triangular lattice using dynamical
  cluster approximation and dual fermion methods

abstract:
  We investigate the Hubbard model on the triangular lattice at half-filling
using the dynamical cluster approximation (DCA) and dual fermion (DF) methods
in combination with continuous-time quantum Monte carlo (CT QMC) and
semiclassical approximation (SCA) methods. We study the one-particle properties
and nearest-neighbor spin correlations using the DCA method. We calculate the
spectral functions using the CT QMC and SCA methods. The spectral function in
the SCA and obtained by analytic continuation of the Pade approximation in CT
QMC are in good agreement. We determine the metal-insulator transition (MIT)
and the hysteresis associated with a first-order transition in the double
occupancy and nearest-neighbor spin correlation functions as a function of
temperature. As a further check, we employ the DF method and discuss the
advantages and limitation of the dynamical mean field theory (DMFT), DCA and
recently developed DF methods by comparing Green's functions. We find an
enhancement of antiferromagnetic (AF) correlations and provide evidence for
magnetically ordered phases by calculating the spin susceptibility.


title: Young measures, Cartesian maps, and polyconvexity

abstract:
  We consider the variational problem consisting of minimizing a polyconvex
integrand for maps between manifolds. We offer a simple and direct proof of the
existence of a minimizing map. The proof is based on Young measures.


title:
Convergence of the law of the Environment Seen by the Particle for
  Directed Polymers in Random Media in the $L^2$ region

abstract:
  We consider the model of Directed Polymers in an i.i.d. gaussian or bounded
Environment in the $L^2$ region. We prove the convergence of the law of the
environment seen by the particle. As a main technical step, we establish a
lower tail concentration inequality for the partition function for bounded
environments. Our proof is based on arguments developed by Talagrand in the
context of the Hopfield Model. This improves in some sense a concentration
inequality obtained by Carmona and Hu for gaussian environments. We use this
and a Local Limit Theorem to prove the $L^1$ convergence of the density of the
law of the environment seen by the particle with respect to the product
measure.


title:
Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation
  Diagnostics

abstract:
  While the strong anti-correlation between chromospheric activity and age has
led to the common use of the Ca II H & K emission index (R'_HK = L_HK/L_bol) as
an empirical age estimator for solar type dwarfs, existing activity-age
relations produce implausible ages at both high and low activity levels. We
have compiled R'_HK data from the literature for young stellar clusters, richly
populating for the first time the young end of the activity-age relation.
Combining the cluster activity data with modern cluster age estimates, and
analyzing the color-dependence of the chromospheric activity age index, we
derive an improved activity-age calibration for F7-K2 dwarfs (0.5 < B-V < 0.9
mag). We also present a more fundamentally motivated activity-age calibration
that relies on conversion of R'_HK values through the Rossby number to rotation
periods, and then makes use of improved gyrochronology relations. We
demonstrate that our new activity-age calibration has typical age precision of
~0.2 dex for normal solar-type dwarfs aged between the Hyades and the Sun
(~0.6-4.5 Gyr). Inferring ages through activity-rotation-age relations accounts
for some color-dependent effects, and systematically improves the age estimates
(albeit only slightly). We demonstrate that coronal activity as measured
through the fractional X-ray luminosity (R_X = L_X/L_bol) has nearly the same
age- and rotation-inferring capability as chromospheric activity measured
through R'_HK. As a first application of our calibrations, we provide new
activity-derived age estimates for the nearest 100 solar-type field dwarfs (d <
15 pc).


title: Update: Accurate Determinations of alpha_s from Realistic Lattice QCD

abstract:
  We use lattice QCD simulations, with MILC configurations (including vacuum
polarization from u, d, and s quarks), to update our previous determinations of
the QCD coupling constant. Our new analysis uses results from 6 different
lattice spacings and 12 different combinations of sea-quark masses to
significantly reduce our previous errors. We also correct for
finite-lattice-spacing errors in the scale setting, and for nonperturbative
chiral corrections to the 22 short-distance quantities from which we extract
the coupling. Our final result is alpha_V(7.5GeV,nf=3) = 0.2120(28), which is
equivalent to alpha_msbar(M_Z,n_f=5)= 0.1183(8). We compare this with our
previous result, which differs by one standard deviation.


title: Magnetic properties of undoped and 15%F doped SmFeAsO compounds

abstract:
  In this paper the magnetic behaviour of SmFeAsO and SmFeAs(O0.85F0.15)
samples is presented and discussed. Molar susceptibility of SmFeAsO exhibits a
local peak at T around 140K due to the establishment of a long range
antiferromagnetic ordering of the Fe moments in Fe-As layers. This feature has
already been observed with different techniques, and frequently ascribed to the
onset of a Spin Density Wave (SDW). At TN around 6K another peak, which we
attribute to the establishment of antiferromagnetic ordering of Sm ion
sublattice, is observed. Furthermore, a temperature independent signal (Pauli
paramagnetism, Landau and core diamagnetism...) is also present in the magnetic
behaviour of this sample. In SmFeAs(O0.85F0.15) the antiferromagnetic ordering
in Fe-As plane is suppressed and superconductivity occurs at T = 52 K, whereas
the antiferromagnetic ordering of Sm ions at low temperature persists, leading
to the coexistence and competition between superconducting and magnetic
orderings. Above the transition temperature, after the subtraction of the Sm
ion sublattice paramagnetic contribution and of the temperature independent
contribution to the experimental susceptibility data, a Curie-Weiss behaviour
for Fe is observed, with a magnetic moment of 1.4 Bohr magneton.


title: Bimetric varying speed of light theories and primordial fluctuations

abstract:
  We exhibit a varying speed of light (VSL) theory that implements the recently
proposed decaying speed of sound mechanism for generating density fluctuations.
We avail ourselves of bimetric VSL theories, where the speed of gravity differs
from that of light. We first show that a Dirac-Born-Infeld (DBI) type of
$K$-essence has the necessary speed of sound profile to produce (near)
scale-invariant fluctuations. We then examine the map between bimetric and
$K$-essence models: typically the bi-scalar connecting the two metrics is a
$K$-essence field in one of them. Remarkably, the DBI model is found to
perturbatively represent the minimal bimetric model, where the bi-scalar is
Klein-Gordon in the matter frame. But the full non-perturbative bimetric
structure is even simpler: the bi-scalar dynamics should be simply driven by a
cosmological constant in the matter frame, balanced by an opposite cosmological
constant in the gravity frame. Thus the problem of structure formation receives
an elegant and universal solution within bimetric VSL theories, which are known
to also solve the flatness and entropy problems and evade a plethora of
causality concerns.


title: Feynman motives of banana graphs

abstract:
  We consider the infinite family of Feynman graphs known as the "banana
graphs" and compute explicitly the classes of the corresponding graph
hypersurfaces in the Grothendieck ring of varieties as well as their
Chern-Schwartz-MacPherson classes, using the classical Cremona transformation
and the dual graph, and a blowup formula for characteristic classes. We outline
the interesting similarities between these operations and we give formulae for
cones obtained by simple operations on graphs. We formulate a positivity
conjecture for characteristic classes of graph hypersurfaces and discuss
briefly the effect of passing to noncommutative spacetime.


title:
The role of particle interactions in a many-body model of Feshbach
  molecular formation in bosonic systems

abstract:
  In this paper, we investigate the atom-molecule conversion dynamics of a
generalized many-body model that includes the atom-atom, atom-molecule, and
molecule-molecule interactions, emphasizing the efficiency of the Feshbach
molecular formation. We show that the picture of two-body molecular production
depicted by the Landau-Zener model is significantly altered: The energy levels
are dramatically distorted and the conversion efficiency is suppressed by the
particle interactions. According to the rule of constant action and with the
help of phase-space analysis, we derive an analytical expression for the
conversion efficiency in the adiabatic limit. It shows a ceiling for the
conversion efficiency when the interaction strength is larger than a critical
value. We further derive a closed equation for the conversion efficiency with
the stationary phase approximation. In the sudden limit, the conversion
efficiency is twice that predicted by the two-body Landau-Zener formula. Our
analytical formula has been confirmed by numerical calculations.


title:
Search for anomalous $\boldmath{Wtb}$ couplings in single top quark
  production

abstract:
  In 0.9 fb$^{-1}$ of $p \bar p$ collisions, D0 has observed an excess of
events with an isolated lepton, missing transve rse momentum, and two to four
jets. This excess is consistent with single top quark production. We examine
these data to study the Lorentz structure of the $Wtb$ coupling. The standard
model predicts a left-handed vector coupling at the $Wt b$ vertex. The most
general lowest dimension, CP-conserving Lagrangian admits right-handed vector
and left- or right-h anded tensor couplings as well. We find that the data
prefer the left-handed vector coupling and set upper limits on the anomalous
couplings. These are the first direct constraints on a general $Wtb$
interaction and the first direct limits on left- and right-handed tensor
couplings.


title: Numerical simulations of galaxy evolution in cosmological context

abstract:
  Large volume cosmological simulations succeed in reproducing the large-scale
structure of the Universe. However, they lack resolution and may not take into
account all relevant physical processes to test if the detail properties of
galaxies can be explained by the CDM paradigm. On the other hand, galaxy-scale
simulations could resolve this in a robust way but do not usually include a
realistic cosmological context.
  To study galaxy evolution in cosmological context, we use a new method that
consists in coupling cosmological simulations and galactic scale simulations.
For this, we record merger and gas accretion histories from cosmological
simulations and re-simulate at very high resolution the evolution of baryons
and dark matter within the virial radius of a target galaxy. This allows us for
example to better take into account gas evolution and associated star
formation, to finely study the internal evolution of galaxies and their disks
in a realistic cosmological context.
  We aim at obtaining a statistical view on galaxy evolution from z = 2 to 0,
and we present here the first results of the study: we mainly stress the
importance of taking into account gas accretion along filaments to understand
galaxy evolution.


title: Floer homology in disc bundles and symplectically twisted geodesic flows

abstract:
  We show that if K: P \to R is an autonomous Hamiltonian on a symplectic
manifold (P,\Omega) which attains 0 as a Morse-Bott nondegenerate minimum along
a symplectic submanifold M, and if c_1(TP)|_M vanishes in real cohomology, then
the Hamiltonian flow of K has contractible periodic orbits with bounded period
on all sufficiently small energy levels. As a special case, if the geodesic
flow on the cotangent bundle of M is twisted by a symplectic magnetic field
form, then the resulting flow has contractible periodic orbits on all low
energy levels. These results were proven by Ginzburg and G\"urel when \Omega|_M
is spherically rational, and our proof builds on their work; the argument
involves constructing and carefully analyzing at the chain level a version of
filtered Floer homology in the symplectic normal disc bundle to M.


title:
The metamorphosis of Supernova SN2008D/XRF080109: a link between
  Supernovae and GRBs/Hypernovae

abstract:
  The only supernovae (SNe) to have shown early gamma-ray or X-ray emission
thus far are overenergetic, broad-lined Type Ic SNe (Hypernovae - HNe).
Recently, SN 2008D shows several novel features: (i) weak XRF, (ii) an early,
narrow optical peak, (iii) disappearance of the broad lines typical of SNIc
HNe, (iv) development of He lines as in SNeIb. Detailed analysis shows that SN
2008D was not a normal SN: its explosion energy (KE ~ 6*10^{51} erg) and
ejected mass (~7 Msun) are intermediate between normal SNeIbc and HNe. We
derive that SN 2008D was originally a ~30Msun star. When it collapsed a black
hole formed and a weak, mildly relativistic jet was produced, which caused the
XRF. SN 2008D is probably among the weakest explosions that produce
relativistic jets. Inner engine activity appears to be present whenever massive
stars collapse to black holes.


title: The invariant factor of the chiral determinant

abstract:
  The coupling of spin 0 and spin 1 external fields to Dirac fermions defines a
theory which displays gauge chiral symmetry. Quantum mechanically, functional
integration of the fermions yields the determinant of the Dirac operator, known
as the chiral determinant. Its modulus is chiral invariant but not so its
phase, which carries the chiral anomaly through the Wess-Zumino-Witten term.
Here we find the remarkable result that, upon removal from the chiral
determinant of this known anomalous part, the remaining chiral invariant factor
is just the square root of the determinant of a local covariant operator of the
Klein-Gordon type. This procedure bypasses the integrability obstruction
allowing to write down a functional that correctly reproduces both the modulus
and the phase of the chiral determinant. The technique is illustrated by
computing the effective action in two dimensions at leading order in the
derivative expansion. The results previously obtained by indirect methods are
indeed reproduced.


title:
Investigation of solutions of boundary value problems for a composite
  type equation with non-local boundary conditions

abstract:
  Since the order of elliptic type model equation (Laplace equation) is two
[1], [2], then it is natural the order of composite type model equation must be
[3] [4] [5] three. At each point of the domain under consideration these
equations have both real and complex characteristics. Notice that a boundary
value problem for a composite type equation of second order first appeared in
the paper [6]. The method for investigating the Fredholm property of boundary
value problems is distinctive and belongs to one of the authors of the present
paper.


title:
Deciphering the Pulsations of G 29-38 with Optical Time Series
  Spectroscopy

abstract:
  We present optical time series spectroscopy of the pulsating white dwarf star
G29-38 taken at the Very Large Telescope (VLT). By measuring the variations in
brightness, Doppler shift, and line shape of each spectrum, we explore the
physics of pulsation and measure the spherical degree ($\ell$) of each stellar
pulsation mode. We measure the physical motion of the g-modes correlated with
the brightness variations for three of the eight pulsation modes in this data
set. The varying line shape reveals the spherical degree of the pulsations, an
important quantity for properly modeling the interior of the star with
asteroseismology. Performing fits to the H$\beta$, H$\gamma$, and H$\delta$
lines, we quantify the changing shape of the line and compare them to models
and previous time series spectroscopy of G~29-38. These VLT data confirm
several $\ell$ identifications and add four new values, including an additional
$\ell$=2 and a possible $\ell$=4. In total from both sets of spectroscopy of
G29-38, eleven modes now have known spherical degrees.


title:
Inherent flexibility determines the transition mechanisms of the
  EF-hands of Calmodulin

abstract:
  We explore how inherent flexibility of a protein molecule influences the
mechanism controlling the kinetics of allosteric transitions using a
variational model inspired from work in protein folding. The striking
differences in the predicted transition mechanism for the opening of the two
domains of calmodulin (CaM) emphasizes that inherent flexibility is key to
understanding the complex conformational changes that occur in proteins. In
particular, the C-terminal domain of CaM (cCaM) which is inherently less
flexible than its N-terminal domain (nCaM) reveals "cracking" or local partial
unfolding during the open/closed transition. This result is in harmony with the
picture that cracking relieves local stresses due to conformational
deformations of a sufficiently rigid protein. We also compare the
conformational transition in a recently studied "even-odd" paired fragment of
CaM. Our results rationalize the different relative binding affinities of the
EF-hands in the engineered fragment compared to the intact "odd-even" paired
EF-hands (nCaM and cCaM) in terms of changes in flexibility along the
transition route. Aside from elucidating general theoretical ideas about the
cracking mechanism, these studies also emphasize how the remarkable intrinsic
plasticity of CaM underlies conformational dynamics essential for its diverse
functions.


title:
Optimal approximation of harmonic growth clusters by orthogonal
  polynomials

abstract:
  Interface dynamics in two-dimensional systems with a maximal number of
conservation laws gives an accurate theoretical model for many physical
processes, from the hydrodynamics of immiscible, viscous flows (zero
surface-tension limit of Hele-Shaw flows, [1]), to the granular dynamics of
hard spheres [2], and even diffusion-limited aggregation [3]. Although a
complete solution for the continuum case exists [4, 5], efficient
approximations of the boundary evolution are very useful due to their practical
applications [6]. In this article, the approximation scheme based on orthogonal
polynomials with a deformed Gaussian kernel [7] is discussed, as well as
relations to potential theory.

categories: math-ph cond-mat.stat-mech math.MP nlin.SI


title:
High energy photoelectron diffraction: model calculations and future
  possibilities

abstract:
  We discuss the theoretical modelling of x-ray photoelectron diffraction (XPD)
with hard x-ray excitation at up to 20 keV, using the dynamical theory of
electron diffraction to illustrate the characteristic aspects of diffraction
patterns resulting from such localized emission sources in a multi-layer
crystal.
  We show via dynamical calculations for diamond, Si, and Fe that the dynamical
theory well predicts available current data for lower energies around 1 keV,
and that the patterns for energies above about 1 keV are dominated by Kikuchi
bands which are created by the dynamical scattering of electrons from lattice
planes. The origin of the fine structure in such bands is discussed from the
point of view of atomic positions in the unit cell. The profiles and positions
of the element-specific photoelectron Kikuchi bands are found to be sensitive
to lattice distortions (e.g. a 1% tetragonal distortion) and the position of
impurities or dopants with respect to lattice sites. We also compare the
dynamical calculations to results from a cluster model that is more often used
to describe lower-energy XPD. We conclude that hard XPD (HXPD) should be
capable of providing unique bulk-sensitive structural information for a wide
variety of complex materials in future experiments.


title:
Evidence of a Curved Synchrotron Spectrum in the Supernova Remnant SN
  1006

abstract:
  A joint spectral analysis of some Chandra ACIS X-ray data and Molonglo
Observatory Synthesis Telescope radio data was performed for 13 small regions
along the bright northeastern rim of the supernova remnant SN 1006. These data
were fitted with a synchrotron radiation model. The nonthermal electron
spectrum used to compute the photon emission spectra is the traditional
exponentially cut off power law, with one notable difference: The power-law
index is not a constant. It is a linear function of the logarithm of the
momentum. This functional form enables us to show, for the first time, that the
synchrotron spectrum of SN 1006 seems to flatten with increasing energy. The
effective power-law index of the electron spectrum is 2.2 at 1 GeV (i.e., radio
synchrotron-emitting momenta) and 2.0 at about 10 TeV (i.e., X-ray
synchrotron-emitting momenta). This amount of change in the index is
qualitatively consistent with theoretical models of the amount of curvature in
the proton spectrum of the remnant. The evidence of spectral curvature implies
that cosmic rays are dynamically important instead of being "test" particles.
The spectral analysis also provides a means of determining the critical
frequency of the synchrotron spectrum associated with the highest-energy
electrons. The critical frequency seems to vary along the northeastern rim,
with a maximum value of 1.1e17 (0.6e17 - 2.1e17) Hz. This value implies that
the electron diffusion coefficient can be no larger than a factor of ~4.5-21
times the Bohm diffusion coefficient if the velocity of the forward shock is in
the range 2300-5000 km/s. Since the coefficient is close to the Bohm limit,
electrons are accelerated nearly as fast as possible in the regions where the
critical frequency is about 1.0e17 Hz.


title: On Self-Sustained Dynamo Cycles in Accretion Discs

abstract:
  (abridged) MHD turbulence is known to exist in shearing boxes with either
zero or nonzero net magnetic flux. However, the way turbulence survives in the
zero-net-flux case is not explained by linear theory and appears as a purely
numerical result. Aims: We look for a nonlinear mechanism able to explain the
persistence of MHD turbulence in shearing boxes with zero net magnetic flux,
and potentially leading to large-scale dynamo action. Method: Spectral
nonlinear simulations of the magnetorotational instability are shown to exhibit
a large-scale axisymmetric magnetic field, maintained for a few orbits. The
generation process of this field is investigated using the results of the
simulations and an inhomogeneous linear approach. Results: The mechanism by
which turbulence is sustained in zero-net-flux shearing boxes is shown to be
related to the existence of a large-scale azimuthal field, surviving for
several orbits. In particular, it is shown that MHD turbulence in shearing
boxes can be seen as a dynamo process coupled to a magnetorotational-type
instability.


title: Convenient Categories of Smooth Spaces

abstract:
  A "Chen space" is a set X equipped with a collection of "plots" - maps from
convex sets to X - satisfying three simple axioms. While an individual Chen
space can be much worse than a smooth manifold, the category of all Chen spaces
is much better behaved than the category of smooth manifolds. For example, any
subspace or quotient space of a Chen space is a Chen space, and the space of
smooth maps between Chen spaces is again a Chen space. Souriau's "diffeological
spaces" share these convenient properties. Here we give a unified treatment of
both formalisms. Following ideas of Dubuc, we show that Chen spaces,
diffeological spaces, and even simplicial complexes are examples of "concrete
sheaves on a concrete site". As a result, the categories of such spaces are
locally cartesian closed, with all limits, all colimits, and a weak subobject
classifier. For the benefit of differential geometers, our treatment explains
most of the category theory we use.


title:
Universal, Continuous-Discrete Nonlinear Yau Filtering I: Affine, Linear
  State Model with State-Independent Diffusion Matrix

abstract:
  The continuous-discrete filtering problem requires the solution of a partial
differential equation known as the Fokker-Planck-Kolmogorov forward equation
(FPKfe). In this paper, it is pointed out that for a state model with an
affine, linear drift and state-independent diffusion matrix the fundamental
solution can be obtained using only linear algebra techniques. In particular,
no differential equations need to be solved. Furthermore, there are no
restrictions on the size of the time step size, or on the measurement model.
Also discussed are important computational aspects that are crucial for
potential real-time implementation for higher-dimensional problems. The
solution is universal in the sense that the initial distribution may be
arbitrary.


title: An explanation of the solar transition region

abstract:
  Prompted by high resolution observations, I propose an explanation for the
40+ year old problem of structure and energy balance in the solar transition
region. The ingredients are simply cross-field diffusion of neutral atoms from
cool threads extending into the corona, and the subsequent excitation,
radiation and ionization of these atoms via electron impact. The processes
occur whenever chromospheric plasma is adjacent to coronal plasma, and are
efficient even when ion gyro-frequencies exceed collision frequencies. Cool
threads - fibrils and spicules perhaps - grow slowly in thickness as a neutral,
ionizing front expands across the magnetic field into coronal plasma. Radiative
intensities estimated for H L$\alpha$ are within an order of magnitude of those
observed, with no ad-hoc parameters - only thermal parameters and geometric
considerations are needed. I speculate that the subsequent dynamics of the
diffused material might also explain observed properties of trace elements.


title:
Quasi-Homogeneous Backward-Wave Plasmonic Structures: Theory and
  Accurate Simulation

abstract:
  Backward waves and negative refraction are shown to exist in plasmonic
crystals whose lattice cell size is a very small fraction of the vacuum
wavelength (less than 1/40th in an illustrative example). Such
``quasi-homogeneity'' is important, in particular, for high-resolution imaging.
Real and complex Bloch bands are computed using the recently developed
finite-difference calculus of ``Flexible Local Approximation MEthods'' (FLAME)
that produces linear eigenproblems, as opposed to quadratic or nonlinear ones
typical for other techniques. FLAME dramatically improves the accuracy by
incorporating local analytical approximations of the solution into the
numerical scheme.


title: Formation of regular structures in the process of phase separation

abstract:
  Phase separation under directional quenching has been studied in a
Cahn-Hilliard model. In distinct contrast to the disordered patterns which
develop under a homogeneous quench periodic stripe patterns are generated
behind the quench front. Their wavelength is uniquely defined by the velocity
of the quench interface in a wide range. Numerical simulations match perfectly
analytical results obtained in the limit of small and large velocities of the
quench interface. Additional periodic modulation of the quench interface may
lead to cellular patterns. The quenching protocols analyzed in this paper are
expected to be an effective tool in technological applications to design
nanostructured materials.


title:
Modeling of Spin Metal-Oxide-Semiconductor Field-Effect-Transistor: A
  Non-Equilibrium Green's Function Approach with Spin Relaxation

abstract:
  A spin metal-oxide-semiconductor field-effect-transistor (spin MOSFET), which
combines a Schottky-barrier MOSFET with ferromagnetic source and drain
contacts, is a promising device for spintronic logic. Previous simulation
studies predict that this device should display a very high magnetoresistance
(MR) ratio (between the cases of parallel and anti-parallel magnetizations) for
the case of half-metal ferromagnets (HMF). We use the non-equilibrium Green's
function (NEGF) formalism to describe tunneling and carrier transport in this
device and to incorporate spin relaxation at the HMF-semiconductor interfaces.
Spin relaxation at interfaces results in non-ideal spin injection. Minority
spin currents arise and dominate the leakage current for anti-parallel
magnetizations. This reduces the MR ratio and sets a practical limit for spin
MOSFET performance. We found that MR saturates at a lower value for smaller
source-to-drain bias. In addition, spin relaxation at the detector side is
found to be more detrimental to MR than that at the injector side, for drain
bias less than the energy difference of the minority spin edge and the Fermi
level.


title: Dynamical Analysis of the Structure of Neutron Star Critical Collapses

abstract:
  Jin et al reported that axisymmetric simulations of NS-like objects with
polytropic EOS undergo critical gravitational collapse. As the critical
collapse observed via fine-tuning of the adiabatic index $\Gamma$, they
conjecture that critical phenomena may occur in realistic astrophysical
scenarios. To clarify the implications this numerical observation has on
realistic astrophysical scenarios, here, we perform dynamical analysis on the
structure of the critical collapse observed in the former work. We report the
time scales and oscillation frequencies exhibited by the critical solution and
compare these results with values obtained from analytic perturbative mode
analysis of equilibrium TOV configurations. We also establish the universality
of the critical solution with respect to a 1-parameter family of initial data
as well as the phase space manifold of the critical collapse.


title: Three findings to model a quantum-gravitational theory

abstract:
  In 1967 Zeldovich expressed the cosmological constant lambda in terms of G, m
and h, the gravitational constant, the mass of a fundamental particle and
Plancks constant. In 1972 Weinberg expressed m in terms of h, G, the speed of
light c and the Hubble parameter H. We proved that both expressions are
identical. We also found proportionality between c and H. The critical mass
balancing the outward quantum mechanical spreading of the wave function, and
its inward gravitational collapse, has been recently estimated. We identify
this mass with Zeldovich and Weinberg mass. A semi classical gravity model is
reinforced and provides an insight for the modelling of a quantum-gravitational
theory. The time evolution of the peak probability density for a free particle,
a wave function initially filling the whole Universe, explains the later
geometrical properties of the fundamental particles. We prove that they end up
acquiring a constant size given by their Compton wavelength. The size of the
fundamental particles, as well as their mass, is explained. The three findings
converge: Newton laws of motion and gravitation, while explaining Zeldovich and
Weinberg relations, also define the mass and size of the fundamental particles
when using the Schrodinger-Newton equation.


title: Thermodynamics of G.A mispairs in DNA: continuum electrostatic model

abstract:
  An analysis of the stability of a duplex containing G.A mispairs or G.A/A.G
tandem during DNA melting has revealed that duplex stability depends on both
DNA sequences and on the conformations of the G.A mispairs. The thermodynamics
of single pair opening for G(anti).A(syn) and G(anti).A(anti) conformations
adopted by G.A mispairs is found to strongly correlate with that of the
canonical base pairs, while for sheared conformation a significant difference
is observed.


title: Asymptotics in ASEP with Step Initial Condition

abstract:
  In previous work the authors considered the asymmetric simple exclusion
process on the integer lattice in the case of step initial condition, particles
beginning at the positive integers. There it was shown that the probability
distribution for the position of an individual particle is given by an integral
whose integrand involves a Fredholm determinant. Here we use this formula to
obtain three asymptotic results for the positions of these particles. In one an
apparently new distribution function arises and in another the distribuion
function F_2 arises. The latter extends a result of Johansson on TASEP to ASEP.


title: Integrality theorems in the theory of topological strings

abstract:
  We give a simplified derivation of the expression of instanton numbers and of
mirror map in terms of Frobenius map on p-adic cohomology and use this
expression to prove integrality theorems. Modifying this proof we verify that
the Aganagic-Vafa formulas for the number of holomorphic disks can be expressed
in terms of Frobenius map on p-adic relative cohomology; this expression
permits us to prove integrality of this number.


title:
Evolution Families and the Loewner Equation II: complex hyperbolic
  manifolds

abstract:
  We prove that evolution families on complex complete hyperbolic manifolds are
in one to one correspondence with certain semicomplete non-autonomous
holomorphic vector fields, providing the solution to a very general Loewner
type differential equation on manifolds.


title: The GIT-stability of Polarised Varieties via discrepancy

abstract:
  We prove that various GIT semistabilities of polarized varieties imply
semi-log-canonicity.


title:
Diameters and albedos of three sub-kilometer Near Earth Objects derived
  from Spitzer observations

abstract:
  Near Earth Objects (NEOs) are fragments of remnant primitive bodies that date
from the era of Solar System formation. At present, the physical properties and
origins of NEOs are poorly understood. We have measured thermal emission from
three NEOs -- (6037) 1988 EG, 1993 GD, and 2005 GL -- with Spitzer's IRAC
instrument at 3.6, 4.5, 5.8, and 8.0 microns (the last object was detected only
at 5.8 and 8.0 microns). The diameters of these three objects are 400 m, 180 m,
and 160 m, respectively, with uncertainties of around 20% (including both
observational and systematic errors). For all three the geometric albedos are
around 0.30, in agreement with previous results that most NEOs are S-class
asteroids. For the two objects detected at 3.6 and 4.5 microns, diameters and
albedos based only on those data agree with the values based on modeling the
data in all four bands. This agreement, and the high sensitivity of IRAC, show
the promise of the Spitzer Warm Mission for determining the physical parameters
for a large number of NEOs.


title: Coherent imaging of extended objects

abstract:
  When used with coherent light, optical imaging systems, even
diffraction-limited, are inherently unable to reproduce both the amplitude and
the phase of a two-dimensional field distribution because their impulse
response function varies slowly from point to point (a property known as
non-isoplanatism). For sufficiently small objects, this usually results in a
phase distortion and has no impact on the measured intensity. Here, we show
that the intensity distribution can also be dramatically distorted when objects
of large extension or of special shapes are imaged. We illustrate the problem
using two simple examples: the pinhole camera and the aberration-free thin
lens. The effects predicted by our theorical analysis are also confirmed by
experimental observations.


title: Sur la classification de quelques phi-modules simples

abstract:
  This note is an appendix to a preprint by E. Hellmann. We give a complete
classification of simple objects of the category of vector spaces D over K =
Fpbar((u)) equipped with an endomorphism phi whose image generates D and that
are semi-linear with respect to the ring morphism sending u to u^b (b > 1 is an
integer) and acting on elements of k through a fixed automorphism. Some of
these phi-modules are involved in the classification of finite flat group
schemes over ring of integers of p-adic fields.


title: Resource Allocation Strategies for In-Network Stream Processing

abstract:
  In this paper we consider the operator mapping problem for in-network stream
processing applications. In-network stream processing consists in applying a
tree of operators in steady-state to multiple data objects that are continually
updated at various locations on a network. Examples of in-network stream
processing include the processing of data in a sensor network, or of continuous
queries on distributed relational databases. We study the operator mapping
problem in a ``constructive'' scenario, i.e., a scenario in which one builds a
platform dedicated to the application buy purchasing processing servers with
various costs and capabilities. The objective is to minimize the cost of the
platform while ensuring that the application achieves a minimum steady-state
throughput. The first contribution of this paper is the formalization of a set
of relevant operator-placement problems as linear programs, and a proof that
even simple versions of the problem are NP-complete. Our second contribution is
the design of several polynomial time heuristics, which are evaluated via
extensive simulations and compared to theoretical bounds for optimal solutions.


title: Physics of reverse annealing in high-resistivity Chandra ACIS CCDs

abstract:
  After launch, the Advanced CCD Imaging Spectrometer (ACIS), a focal plane
instrument on the Chandra X-ray Observatory, suffered radiation damage from
exposure to soft protons during passages through the Earth's radiation belts.
An effect of the damage was to increase the charge transfer inefficiency (CTI)
of the front illuminated CCDs. As part of the initial damage assessment, the
focal plane was warmed from the operating temperature of -100C to +30C which
unexpectedly further increased the CTI. We report results of ACIS CCD
irradiation experiments in the lab aimed at better understanding this reverse
annealing process. Six CCDs were irradiated cold by protons ranging in energy
from 100 keV to 400 keV, and then subjected to simulated bakeouts in one of
three annealing cycles. We present results of these lab experiments, compare
them to our previous experiences on the ground and in flight, and derive limits
on the annealing time constants.


title:
Stability and mode analysis of solar coronal loops using thermodynamic
  irreversible energy principles II. Modes in twisted non--isothermal magnetic
  field configurations

abstract:
  We study the stability and the modes of non -- isothermal coronal loop models
with different intensity values of the equilibrium twisted magnetic field.We
use an energy principle obtained via non -- equilibrium thermodynamic
arguments. The principle is expressed in terms of Hermitian operators and
allows to consider together the coupled system of equations: the balance of
energy equation and the equation of motion, to obtain modes and eigenmodes in a
spectrum ranging from short to long--wavelength disturbances without having to
use weak varying approximations of the equilibrium parameters. Long--wavelength
perturbations introduce additional difficulties because the inhomogeneous
nature of the medium determines disturbances leading to continuous intervals of
eigenfrequencies which cannot be considered as purely sinusoidal.We analyze the
modification of periods, modes structure and stability when the helicity, the
magnetic field strength and the radius of the fluxtube are varied. The
efficiency of the damping due to the resonant absorption mechanism is analyzed
in a context of modes that can either impulsively release or storage magnetic
energy.We find that the onset of the instability is associated to a critical
value of the helicity and that the magnetic energy content has a determinant
role on the instability of the system with respect to the stabilizing effect of
the resonant absorption mechanism.


title: Open-flow mixing: Experimental evidence for strange eigenmodes

abstract:
  We investigate experimentally the mixing dynamics in a channel flow with a
finite stirring region undergoing chaotic advection. We study the
homogenization of dye in two variants of an eggbeater stirring protocol that
differ in the extent of their mixing region. In the first case, the mixing
region is separated from the side walls of the channel, while in the second it
extends to the walls. For the first case, we observe the onset of a permanent
concentration pattern that repeats over time with decaying intensity. A
quantitative analysis of the concentration field of dye confirms the
convergence to a self-similar pattern, akin to the strange eigenmodes
previously observed in closed flows. We model this phenomenon using an
idealized map, where an analysis of the mixing dynamics explains the
convergence to an eigenmode. In contrast, for the second case the presence of
no-slip walls and separation points on the frontier of the mixing region leads
to non-self-similar mixing dynamics.


title:
Artificial Intelligence Approach to the Determination of Physical
  Properties of Eclipsing Binaries. I. The EBAI Project

abstract:
  Achieving maximum scientific results from the overwhelming volume of
astronomical data to be acquired over the next few decades will demand novel,
fully automatic methods of data analysis. Artificial intelligence approaches
hold great promise in contributing to this goal. Here we apply neural network
learning technology to the specific domain of eclipsing binary (EB) stars, of
which only some hundreds have been rigorously analyzed, but whose numbers will
reach millions in a decade. Well-analyzed EBs are a prime source of
astrophysical information whose growth rate is at present limited by the need
for human interaction with each EB data-set, principally in determining a
starting solution for subsequent rigorous analysis. We describe the artificial
neural network (ANN) approach which is able to surmount this human bottleneck
and permit EB-based astrophysical information to keep pace with future data
rates. The ANN, following training on a sample of 33,235 model light curves,
outputs a set of approximate model parameters (T2/T1, (R1+R2)/a, e sin(omega),
e cos(omega), and sin i) for each input light curve data-set. The whole sample
is processed in just a few seconds on a single 2GHz CPU. The obtained
parameters can then be readily passed to sophisticated modeling engines. We
also describe a novel method polyfit for pre-processing observational light
curves before inputting their data to the ANN and present the results and
analysis of testing the approach on synthetic data and on real data including
fifty binaries from the Catalog and Atlas of Eclipsing Binaries (CALEB)
database and 2580 light curves from OGLE survey data. [abridged]


title: Coherence measures for heralded single-photon sources

abstract:
  Single-photon sources (SPSs) are mainly characterized by the minimum value of
their second-order coherence function, viz. their $g^{(2)}$ function. A precise
measurement of $g^{(2)}$ may, however, require high time-resolution devices, in
whose absence, only time-averaged measurements are accessible. These
time-averaged measures, standing alone, do not carry sufficient information for
proper characterization of SPSs. Here, we develop a theory, corroborated by an
experiment, that allows us to scrutinize the coherence properties of heralded
SPSs that rely on continuous-wave parametric down-conversion. Our proposed
measures and analysis enable proper standardization of such SPSs.


title: Axion Cosmology and the Energy Scale of Inflation

abstract:
  We survey observational constraints on the parameter space of inflation and
axions and map out two allowed windows: the classic window and the inflationary
anthropic window. The cosmology of the latter is particularly interesting;
inflationary axion cosmology predicts the existence of isocurvature
fluctuations in the CMB, with an amplitude that grows with both the energy
scale of inflation and the fraction of dark matter in axions. Statistical
arguments favor a substantial value for the latter, and so current bounds on
isocurvature fluctuations imply tight constraints on inflation. For example, an
axion Peccei-Quinn scale of 10^16 GeV excludes any inflation model with energy
scale > 3.8*10^14 GeV (r > 2*10^(-9)) at 95% confidence, and so implies
negligible gravitational waves from inflation, but suggests appreciable
isocurvature fluctuations.


title: Physical Conditions of Accreting Gas in T Tauri Star Systems

abstract:
  We present results from a low resolution (R~300) near-infrared spectroscopic
variability survey of actively accreting T Tauri stars (TTS) in the
Taurus-Auriga star forming region. Paschen and Brackett series H I
recombination lines were detected in 73 spectra of 15 classical T Tauri
systems. The values of the Pan/PaB, Brn/BrG, and BrG/Pan H I line ratios for
all observations exhibit a scatter of < 20% about the weighted mean, not only
from source to source, but also for epoch-to-epoch variations in the same
source. A representative or `global' value was determined for each ratio in
both the Paschen and Brackett series as well as the BrG/Pan line ratios. A
comparison of observed line ratio values was made to those predicted by the
temperature and electron density dependent models of Case B hydrogen
recombination line theory. The measured line ratios are statistically well-fit
by a tightly constrained range of temperatures (T < 2000 K) and electron
densities 1e9 < n_e < 1e10 cm^-3. A comparison of the observed line ratio
values to the values predicted by the optically thick and thin local
thermodynamic equilibrium cases rules out these conditions for the emitting H I
gas. Therefore, the emission is consistent with having an origin in a non-LTE
recombining gas. While the range of electron densities is consistent with the
gas densities predicted by existing magnetospheric accretion models, the
temperature range constrained by the Case B comparison is considerably lower
than that expected for accreting gas. The cooler gas temperatures will require
a non-thermal excitation process (e.g., coronal/accretion-related X-rays and UV
photons) to power the observed line emission.


title: Mechanical feedback in the molecular ISM of luminous IR galaxies

abstract:
  Aims: Molecular emission lines originating in the nuclei of luminous
infra-red galaxies are used to determine the physical properties of the nuclear
ISM in these systems.
  Methods: A large observational database of molecular emission lines is
compared with model predictions that include heating by UV and X-ray radiation,
mechanical heating, and the effects of cosmic rays.
  Results: The observed line ratios and model predictions imply a separation of
the observedsystems into three groups: XDRs, UV-dominated high-density (n>=10^5
cm-3) PDRs, and lower-density (n=10^4.5 cm-3) PDRs that are dominated by
mechanical feedback.
  Conclusions: The division of the two types of PDRs follows naturally from the
evolution of the star formation cycle of these sources, which evolves from
deeply embedded young stars, resulting in high-density (n>=10^5 cm-3) PDRs, to
a stage where the gas density has decreased (n=10^4.5 cm-3) and mechanical
feedback from supernova shocks dominates the heating budget.


title: Textures and Semi-Local Strings in SUSY Hybrid Inflation

abstract:
  Global topological defects may account for the large cold spot observed in
the Cosmic Microwave Background. We explore possibilities of constructing
models of supersymmetric F-term hybrid inflation, where the waterfall fields
are globally SU(2)-symmetric. In contrast to the case where SU(2) is gauged,
there arise Goldstone bosons and additional moduli, which are lifted only by
masses of soft-supersymmetry breaking scale. The model predicts the existence
of global textures, which can become semi-local strings if the waterfall fields
are gauged under U(1)_X. Gravitino overproduction can be avoided if reheating
proceeds via the light SU(2)-modes or right-handed sneutrinos. For values of
the inflaton- waterfall coupling >=10^-4, the symmetry breaking scale imposed
by normalisation of the power spectrum generated from inflation coincides with
the energy scale required to explain the most prominent of the cold spots. In
this case, the spectrum of density fluctuations is close to scale-invariant
which can be reconciled with measurements of the power spectrum by the
inclusion of the sub-dominant component due to the topological defects.


title:
Observation of a robust peak in the glue function of the high-Tc
  cuprates in the 50-60 meV range

abstract:
  We take advantage of the connection between the free carrier optical
conductivity and the glue function in the normal state, to reconstruct from the
infrared optical conductivity the glue-spectrum of ten different high-Tc
cuprates revealing a robust peak in the 50-60 meV range and a broad continuum
at higher energies for all measured charge carrier concentrations and
temperatures up to 290 K. We observe an intriguing correlation between the
doping trend of the experimental glue spectra and the critical temperature.


title:
Binary formation and mass function variations in fragmenting discs with
  short cooling times

abstract:
  Accretion discs at sub-pc distances around supermassive black holes are
likely to cool rapidly enough that self-gravity results in fragmentation. Here,
we use high-resolution hydrodynamic simulations of a simplified disc model to
study how the outcome of fragmentation depends upon numerical resolution and
cooling time, and to investigate the incidence of binary formation within
fragmenting discs. We investigate a range of cooling times, from the relatively
long cooling time-scales that are marginally unstable to fragmentation down to
highly unstable cooling on a time-scale that is shorter than the local
dynamical time. The characteristic mass of fragments decreases with reduced
cooling time, though the effect is modest and dependent upon details of how
rapidly bound clumps radiate. We observe a high incidence of capture binaries,
though we are unable to determine their final orbits or probability of
survival. The results suggest that faster cooling in the parent disc results in
an increased binary fraction, and that a high primordial binary fraction may
result from disc fragmentation. We discuss our results in terms of the young
massive stars close to the Galactic Centre, and suggest that observations of
some stellar binaries close to the Galactic Centre remain consistent with
formation in a fragmenting accretion disc.


title:
Absence of resonant decay for metastable vacua in gauge theories of
  scalar fields

abstract:
  We prove the impossibility of resonant decay of a metastable vacuum in a
theory of a scalar field coupled to a gauge field. Our result extends to gauge
theories of scalar fields a recent no go theorem for resonant tunneling in a
pure scalar field theory.


title:
Nonlinear perturbation theory with halo bias and redshift-space
  distortions via the Lagrangian picture

abstract:
  The nonlinear perturbation theory of gravitational instability is extended to
include effects of both biasing and redshift-space distortions, which are
inevitable in predicting observable quantities in galaxy surveys. The precise
determination of scales of baryon acoustic oscillations is crucial to
investigate the nature of dark energy by galaxy surveys. We find that a local
Lagrangian bias and redshift-space distortions are naturally incorporated in
our formalism of perturbation theory with a resummation technique via the
Lagrangian picture. Our formalism is applicable to any biasing scheme which is
local in Lagrangian space, including the halo bias as a special case. Weakly
nonlinear effects on halo clustering in redshift space are analytically
given.We assume only a fundamental idea of the halo model: haloes form
according to the extended Press-Schechter theory, and the spatial distributions
are locally biased in Lagrangian space. There is no need for assuming the
spherical collapse model to follow the dynamical evolution, which is
additionally assumed in standard halo prescriptions. One-loop corrections to
the power spectrum and correlation function of haloes in redshift space are
explicitly derived and presented. Instead of relying on expensive numerical
simulations, our approach provides an analytic way of investigating the weakly
nonlinear effects, simultaneously including the nonlinear biasing and nonlinear
redshift-space distortions. Nonlinearity introduces a weak scale dependence in
the halo bias. The scale dependence is a smooth function in Fourier space, and
the bias does not critically change the feature of baryon acoustic oscillations
in the power spectrum. The same feature in the correlation function is less
affected by nonlinear effects of biasing.


title:
Faster Sequential Search with a Two-Pass Dynamic-Time-Warping Lower
  Bound

abstract:
  The Dynamic Time Warping (DTW) is a popular similarity measure between time
series. The DTW fails to satisfy the triangle inequality and its computation
requires quadratic time. Hence, to find closest neighbors quickly, we use
bounding techniques. We can avoid most DTW computations with an inexpensive
lower bound (LB_Keogh). We compare LB_Keogh with a tighter lower bound
(LB_Improved). We find that LB_Improved-based search is faster for sequential
search. As an example, our approach is 3 times faster over random-walk and
shape time series. We also review some of the mathematical properties of the
DTW. We derive a tight triangle inequality for the DTW. We show that the DTW
becomes the l_1 distance when time series are separated by a constant.


title:
Spectroscopy of Bright QUEST RR Lyrae Stars: Velocity Substructures
  toward Virgo

abstract:
  Using a sample of 43 bright (V<16.1, distance <13 kpc) RR Lyrae stars (RRLS)
from the QUEST survey with spectroscopic radial velocities and metallicities,
we find that several separate halo substructures contribute to the Virgo
overdensity (VOD). While there is little evidence for halo substructure in the
spatial distribution of these stars, their distribution in radial velocity
reveals two moving groups. These results are reinforced when the sample is
combined with a sample of blue horizontal branch stars that were identified in
the SDSS, and the combined sample provides evidence for one additional moving
group. These groups correspond to peaks in the radial velocity distribution of
a sample of F type main-sequence stars that was recently observed in the same
directon by SEGUE, although in one case the RRLS and F star groups may not lie
at the same distance. One of the new substructures has a very narrow range in
metallicity, which is more consistent with it being the debris from a destroyed
globular cluster than from a dwarf galaxy. A small concentration of stars have
radial velocities that are similar to the Virgo Stellar Stream (VSS) that was
identified previously in a fainter sample of RRLS. Our results suggest that
this feature extends to distances as short as ~12 kpc from its previous
detection at ~19 kpc. None of the new groups and only one star in the sample
have velocities that are consistent with membership in the leading tidal stream
from the Sagittarius Dwarf Spheroidal Galaxy, which some authors have suggested
is the origin of the VOD.


title: The Mobius function is strongly orthogonal to nilsequences

abstract:
  We show that the Mobius function mu(n) is strongly asymptotically orthogonal
to any polynomial nilsequence n -> F(g(n)L). Here, G is a simply-connected
nilpotent Lie group with a discrete and cocompact subgroup L (so G/L is a
nilmanifold), g : Z -> G is a polynomial sequence and F: G/L -> R is a
Lipschitz function. More precisely, we show that the inner product of mu(n)
with F(g(n)L) over {1,...,N} is bounded by 1/log^A N, for all A > 0. In
particular, this implies the Mobius and Nilsequence conjecture MN(s) from our
earlier paper "Linear equations in primes" for every positive integer s. This
is one of two major ingredients in our programme, outlined in that paper, to
establish a large number of cases of the generalised Hardy-Littlewood
conjecture, which predicts how often a collection \psi_1,...,\psi_t : Z^d -> Z
of linear forms all take prime values. The proof is a relatively quick
application of the results in our recent companion paper on the distribution of
polynomial orbits on nilmanifolds.
  We give some applications of our main theorem. We show, for example, that the
Mobius function is uncorrelated with any bracket polynomial. We also obtain a
result about the distribution of nilsequences n -> a^nxL as n ranges only over
the primes.


title:
The gravity dual to a quantum critical point with spontaneous symmetry
  breaking

abstract:
  We consider zero temperature solutions to the Abelian Higgs model coupled to
gravity with a negative cosmological constant. With appropriate choices of
parameters, the geometry contains two copies of anti-de Sitter space, one
describing conformal invariance in the ultraviolet, and one in the infrared.
The effective speed of signal propagation is smaller in the infrared. Green's
functions and associated transport coefficients can have unusual power law
scaling in the infrared. We provide an example in which the real part of the
conductivity scales approximately as omega^3.5 for small omega.


title:
Gravitationally distorted P-Cygni profiles from outflows near compact
  objects

abstract:
  We consider resonant absorption in a spectral line in the outflowing plasma
within several tens of Schwarzschild radii from a compact object. We take into
account both Doppler and gravitational shifting effects and re-formulate the
theory of P-Cygni profiles in these new circumstances. It is found that a
spectral line may have multiple absorption and emission components depending on
how far the region of interaction is from the compact object and what is the
distribution of velocity and opacity. Profiles of spectral lines produced near
a neutron star or a black hole can be strongly distorted by Doppler blue-, or
red-shifting, and gravitational red-shifting. These profiles may have both red-
and blue-shifted absorption troughs. The result should be contrasted with
classical P-Cygni profiles which consist of red-shifted emission and
blue-shifted absorption features.
  We suggest this property of line profiles to have complicated narrow
absorption and emission components in the presence of strong gravity may help
to study spectroscopically the innermost parts of an outflow.


title:
Restoration of the residue factorizability in the bound-state pole by
  instanton-antiinstanton configurations

abstract:
  The instanton-antiinstnton contributions to the $q\overline{q}$ bound state
pole in the four-point Green function in the Schwinger Model are calculated. It
is shown that these configurations, thanks to the cancellation of all unwanted
terms, are responsible for the restoration of the perfect factorizability of
the residue.


title:
Mechanical and Electronic Properties of Ferromagnetic GaMnAs Using
  Ultrafast Coherent Acoustic Phonons

abstract:
  Ultrafast two-color pump-probe measurements, involving coherent acoustic
phonon (CAP) waves, have provided information simultaneously on the mechanical
properties and on the electronic structure of ferromagnetic GaMnAs. The elastic
constant C11 of Ga1-xMnxAs (0.03<x<0.07) are observed to be systematically
smaller than those of GaAs. Both C11 and Vs of GaMnAs are found to increase
with temperature (78 K<T<295 K), again in contrast to the opposite behavior in
GaAs. In addition, the fundamental bandgap (at E0 critical point) of Ga1-xMnxAs
is found to shift slightly to higher energies with Mn concentration.


title: The Majorana Project

abstract:
  Building a \BBz experiment with the ability to probe neutrino mass in the
inverted hierarchy region requires the combination of a large detector mass
sensitive to \BBz, on the order of 1-tonne, and unprecedented background
levels, on the order of or less than 1 count per year in the \BBz signal
region. The MAJORANA Collaboration proposes a design based on using high-purity
enriched Ge-76 crystals deployed in ultra-low background electroformed Cu
cryostats and using modern analysis techniques that should be capable of
reaching the required sensitivity while also being scalable to a 1-tonne size.
To demonstrate feasibility, the collaboration plans to construct a prototype
system, the MAJORANA DEMONSTRATOR, consisting of 30 kg of 86% enriched \Ge-76
detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to
deploy and evaluate two different Ge detector technologies, one based on a
p-type configuration and the other on n-type.


title: Splotch: Visualizing Cosmological Simulations

abstract:
  We present a light and fast, public available, ray-tracer {\tt Splotch}
software tool which supports the effective visualization of cosmological
simulations data. We describe the algorithm it relies on, which is designed in
order to deal with point-like data, optimizing the ray-tracing calculation by
ordering the particles as a function of their ``depth'' defined as a function
of one of the coordinates or other associated parameter. Realistic
three-dimensional impressions are reached through a composition of the final
color in each pixel properly calculating emission and absorption of individual
volume elements. We describe several scientific as well as public applications
realized with {\tt Splotch}. We emphasize how different datasets and
configurations lead to remarkable different results in terms of the images and
animations. A few of these results are available online.


title:
Neutron diffraction on antiferromagnetic ordering in single-crystal
  BaFe2As2

abstract:
  Neutron diffraction experiments have been carried out on a Sn-flux grown
BaFe2As2 single crystal, the parent compound of the A-122 family of FeAs-based
high-Tc superconductors. A tetragonal to orthorhombic structural phase
transition and a three dimensional long-range antiferromagnetic ordering of the
iron moment, with a unique magnetic propagation wavevector k = (1, 0, 1), have
been found to take place at ~90 K. The magnetic moments of iron are aligned
along the long a axis in the low temperature orthorhombic phase (Fmmm with
b<a<c). Our results thus demonstrate that the magnetic structure of BaFe2As2
single crystal is the same as those in other A-122 iron pnictides compounds. We
argue that the tin incorporation in the lattice is responsible for a smaller
orthorhombic splitting and lower Neel temperature T_N observed in the
experiment.


title:
Red Nuggets at z~1.5: Compact passive galaxies and the formation of the
  Kormendy Relation

abstract:
  We present the results of NICMOS imaging of a sample of 16 high mass
passively evolving galaxies with 1.3<z<2, taken primarily from the Gemini Deep
Deep Survey. Around 80% of galaxies in our sample have spectra dominated by
stars with ages >1 Gyr. Our rest-frame R-band images show that most of these
objects have compact regular morphologies which follow the classical R^1/4 law.
These galaxies scatter along a tight sequence in the Kormendy relation. Around
one-third of the massive red objects are extraordinarily compact, with
effective radii under one kiloparsec. Our NICMOS observations allow the
detection of such systems more robustly than is possible with optical
(rest-frame UV) data, and while similar systems have been seen at z>2, this is
the first time such systems have been detected in a rest-frame optical survey
at 1.3<z<2. We refer to these compact galaxies as "red nuggets". Similarly
compact massive galaxies are completely absent in the nearby Universe. We
introduce a new "stellar mass Kormendy relation" (stellar mass density vs size)
which isolates the effects of size evolution from those of luminosity and color
evolution. The 1.1 < z < 2 passive galaxies have mass densities that are an
order of magnitude larger then early type galaxies today and are comparable to
the compact distant red galaxies at 2 < z < 3. We briefly consider mechanisms
for size evolution in contemporary models focusing on equal-mass mergers and
adiabatic expansion driven by stellar mass loss. Neither of these mechanisms
appears able to transform the high-redshift Kormendy relation into its local
counterpart. <ABRIDGED>


title:
Massive Star Formation in the Molecular Ring Orbiting the Black Hole at
  the Galactic Center

abstract:
  A ring of dense molecular gas extending 2-7 pc orbits the supermassive black
hole Sgr A* at the center of our Galaxy. Using the Green Bank Telescope, we
detected water maser lines and both narrow (0.35 km/s) and broad (30 - 50 km/s)
methanol emission from the molecular ring. Two of the strongest methanol lines
at 44 GHz are confirmed as masers by interferometric observations. These class
I methanol masers are collisionally excited and are signatures of early phases
of massive star formation in the disk of the Galaxy, suggesting that star
formation in the molecular ring is in its early phase. Close inspection of the
kinematics of the associated molecular clumps in the HCN (J=1-0) line reveals
broad red-shifted wings indicative of disturbance by protostellar outflows from
young (few times 10^4 yr), massive stars embedded in the clumps. The thermal
methanol profile has a similar shape, with a narrow maser line superimposed on
a broad, red-shifted wing. Additional evidence for the presence of young
massive protostars is provided by shocked molecular hydrogen and a number of
striking ionized and molecular linear filaments in the vicinity of methanol
sources suggestive of 0.5-pc scale protostellar jets. Given that the
circumnuclear molecular ring is kinematically unsettled and thus is likely be
the result of a recent capture, the presence of both methanol emission and
broad, red-shifted HCN emission suggests that star formation in the
circumnuclear ring is in its infancy.


title: Exotic Implications of Electron and Photon Final States

abstract:
  New resonances with masses of order a few ${\rm TeV}$ might be discovered at
the LHC. We show that no resonance that couples to electrons only through
Standard Model interactions can decay to both $e^+e^-$and $\gamma \gamma$ with
significant branching ratios. This means that finding both electron-positron
and two-photon final states is evidence that electrons couple directly to the
new physics associated with the resonance and furthermore that the resonance is
not spin-1. The least fine-tuned such examples involve electron compositeness.
One such example, Kaluza Klein excitations of the graviton in the version of
the Randall Sundrum Model where Standard Model matter is located on the ${\rm
TeV}$ brane, can be distinguished from other possibilities by its predicted
branching fractions into the two modes.


title: The n-body problem in spaces of constant curvature

abstract:
  We generalize the Newtonian n-body problem to spaces of curvature k=constant,
and study the motion in the 2-dimensional case. For k>0, the equations of
motion encounter non-collision singularities, which occur when two bodies are
antipodal. This phenomenon leads, on one hand, to hybrid solution singularities
for as few as 3 bodies, whose corresponding orbits end up in a
collision-antipodal configuration in finite time; on the other hand, it
produces non-singularity collisions, characterized by finite velocities and
forces at the collision instant. We also point out the existence of several
classes of relative equilibria, including the hyperbolic rotations for k<0. In
the end, we prove Saari's conjecture when the bodies are on a geodesic that
rotates elliptically or hyperbolically. We also emphasize that fixed points are
specific to the case k>0, hyperbolic relative equilibria to k<0, and Lagrangian
orbits of arbitrary masses to k=0--results that provide new criteria towards
understanding the large-scale geometry of the physical space.


title: Landau-Zener tunnelling in dissipative circuit QED

abstract:
  We investigate the influence of temperature and dissipation on the
Landau-Zener transition probability in circuit QED. Dissipation is modelled by
coupling the transmission line to a bath of harmonic oscillators. The reduced
description for the density operator is treated within Bloch-Redfield theory. A
phase-space representation allows an efficient numerical implementation of the
resulting master equation. It provides reliable results which are valid even
for rather low temperatures. We find that the spin-flip probability as a
function of temperature and dissipation strength exhibits a non-monotonic
behaviour. Our numerical results are complemented by analytical solutions for
zero temperature and for vanishing dissipation strength.


title: Discrete Anomalies of Binary Groups

abstract:
  We derive the discrete anomaly conditions for the binary tetrahedral group T'
as well as the binary dihedral groups Q_2n. The ambiguities of embedding these
finite groups into SU(2) and SU(3) lead to various possible definitions of the
discrete indices which enter the anomaly equations. We scrutinize the different
choices and show that it is sufficient to consider one particular assignment
for the discrete indices. Thus it is straightforward to determine whether or
not a given model of flavor is discrete anomaly free.


title:
A Markovian growth dynamics on rooted binary trees evolving according to
  the Gompertz curve

abstract:
  Inspired by biological dynamics, we consider a growth Markov process taking
values on the space of rooted binary trees, similar to the Aldous-Shields
model. Fix $n\ge 1$ and $\beta>0$. We start at time 0 with the tree composed of
a root only. At any time, each node with no descendants, independently from the
other nodes, produces two successors at rate $\beta(n-k)/n$, where $k$ is the
distance from the node to the root. Denote by $Z_n(t)$ the number of nodes with
no descendants at time $t$ and let $T_n = \beta^{-1} n \ln(n /\ln 4) + (\ln
2)/(2 \beta)$. We prove that $2^{-n} Z_n(T_n + n \tau)$, $\tau\in\bb R$,
converges to the Gompertz curve $\exp (- (\ln 2) e^{-\beta \tau})$. We also
prove a central limit theorem for the martingale associated to $Z_n(t)$.

categories: q-bio.CB math-ph math.MP q-bio.QM stat.OT


title: Characterization of agostic interactions in theory and computation

abstract:
  Agostic interactions are covalent intramolecular interactions between an
electron deficient metal and a sigma-bond in close geometrical proximity to the
metal atom. While the classic cases involve CH sigma-bonds close to early
transition metals like titanium, many more agostic systems have been proposed
which contain CH, SiH, BH, CC and SiC sigma-bonds coordinated to a wide range
of metal atoms. Recent computational studies of a multitude of agostic
interactions are reviewed in this contribution. It is highlighted how several
difficulties with the theoretical description of the phenomenon arise because
of the relative weakness of this interaction. The methodology used to compute
and interpret agostic interactions is presented and different approaches such
as atoms in molecules (AIM), natural bonding orbitals (NBO) or the electron
localization function (ELF) are compared and put into context. A brief overview
of the history and terminology of agostic interactions is given in the
introduction and fundamental differences between alpha, beta; and other agostic
interactions are explained.


title: A New Spiral Arm of the Galaxy: The Far 3-Kpc Arm

abstract:
  We report the detection in CO of the far-side counterpart of the well-known
expanding 3-Kpc Arm in the central region of the Galaxy. In a CO
longitude-velocity map at b = 0 deg the Far 3-Kpc Arm can be followed over at
least 20 deg of Galactic longitude as a faint lane at positive velocities
running parallel to the Near Arm. The Far Arm crosses l = 0 deg at +56 km/s,
quite symmetric with the -53 km/s expansion velocity of the Near Arm. In
addition to their symmetry in longitude and velocity, we find that the two arms
have linewidths (~21 km/s), linear scale heights (~103 pc FWHM), and H2 masses
per unit length (~4.3 x 10^6 Mo/kpc) that agree to 26% or better. Guided by the
CO, we have also identified the Far Arm in high-resolution 21 cm data and find,
subject to the poorly known CO-to-H2 ratio in these objects, that both arms are
predominately molecular by a factor of 3-4. The detection of these symmetric
expanding arms provides strong support for the existence of a bar at the center
of our Galaxy and should allow better determination of the bar's physical
properties.


title: The cost of probabilistic gathering in oblivious robot networks

abstract:
  In this paper we address the complexity issues of two agreement problems in
oblivious robot networks namely gathering and scattering. These abstractions
are fundamental coordination problems in cooperative mobile robotics. Moreover,
their oblivious characteristics makes them appealing for self-stabilization
since they are self-stabilizing with no extra-cost. Given a set of robots with
arbitrary initial location and no initial agreement on a global coordinate
system, gathering requires that all robots reach the exact same but not
predetermined location while scattering aims at scatter robots such that no two
robots share the same location. Both deterministic gathering and scattering
have been proved impossible under arbitrary schedulers therefore probabilistic
solutions have been recently proposed. The contribution of this paper is
twofold. First, we propose a detailed complexity analysis of the existent
probabilistic gathering algorithms in both fault-free and fault-prone
environments. We consider both crash and byzantine-prone environments.
Moreover, using Markov chains tools and additional assumptions on the
environment we prove that the gathering convergence time can be reduced from
O(n^2) (the best known tight bound) to O(nln(n)). Additionally, we prove that
in crash-prone environments gathering is achieved in O(nln(n)+2f). Second,
using the same technique we prove that the best known scattering strategy
converges in fault-free systems is O(n) (which is one to optimal) while in
crash-prone environments it needs O(n-f). Finally, we conclude the paper with a
discussion related to different strategies to gather oblivious robots.


title: On a New 4-Vector Cosmological Field Theory

abstract:
  The original Dirac Equation is modified in the simplest imaginable and most
trivial manner to include a universal 4-Vector Cosmological Field term in the
space and time dimensions. This cosmological field leads to a modified Dirac
Equation capable of explaining why the Universe appears to be made up chiefly
of matter. It is seen that this 4-Vector Cosmological Field is actually a
particle field and this particle field can possibly be identified with the
darkmatter and darkenergy field. Further, this 4-Vector Cosmological Field is
seen to give spacetime the desired quantum mechanical properties of randomness.
Furthermore, it is seen that in the emergent Universe, the position coordinates
of a particle in space -- contrary to the widely accepted belief that the
position of a particle in space has no physical significance, we see that that
opposite is true - namely that the position of a particle has physical
significance. We further note that the 4-Vector Cosmological Field modification
to the Dirac Equation leads us to a vacuum model redolent but different from
that of Quantum Electrodynamics (QED). This new vacuum model is without virtual
particles but darkparticles. We dare to make the suggestion that these
darkparticles may possibly explain the current mystery of what really is
darkmatter and darkenergy.