title: Multiplicity of young stars in and around R Corona Australis

abstract:
  The R CrA star-forming region has a small dark cloud with quite a number of
protostars, T Tauri stars, and some Herbig Ae/Be stars, plus a number of
weak-line T Tauri stars around the cloud found by ROSAT follow-up observations.
  We searched for multiples among the young stars in and around the R CrA cloud
in order to investigate multiplicity in this region.
  We performed interferometric and imaging observations with the speckle camera
SHARP I at the ESO 3.5m NTT and adaptive optics observation with ADONIS at the
ESO 3.6m telescope, all in the near-infrared bands JHK obtained in the years
1995, 2000, and 2001.
  We found 13 new binaries among the young stars in CrA between 0.13 arcsec
(the diffraction limit) and 6 arcsec (set as an upper separation limit to avoid
contamination by chance alignments). While most multiples in CrA are binaries,
there are also one quadruple (TY CrA), and one triple (HR 7170) which may form
a quintuple together with the binary HR 7169. One of the newly detected
companions with a large magnitude difference found near the M3-5 type T Tauri
star [MR 81] Ha 17 could be a brown dwarf or an infrared companion with an
edge-on disk. Among seven Herbig Ae/Be stars in CrA, six are multiple.
  The multiplicity frequency in CrA is as high as in similar star forming
regions. By comparing with the period distribution of main-sequence stars and
extrapolating to separations not probed in this survey, we conclude that the
companion-star frequency is 95+/-23 %; i.e. the average number of companions
per primary is 0.95.


title: Financial Time Series Analysis of SV Model by Hybrid Monte Carlo

abstract:
  We apply the hybrid Monte Carlo (HMC) algorithm to the financial time sires
analysis of the stochastic volatility (SV) model for the first time. The HMC
algorithm is used for the Markov chain Monte Carlo (MCMC) update of volatility
variables of the SV model in the Bayesian inference. We compute parameters of
the SV model from the artificial financial data and compare the results from
the HMC algorithm with those from the Metropolis algorithm. We find that the
HMC decorrelates the volatility variables faster than the Metropolis algorithm.
We also make an empirical analysis based on the Yen/Dollar exchange rates.


title:
Ratchet effect in inhomogeneous inertial systems: II. The square-wave
  drive case

abstract:
  The underdamped Langevin equation of motion of a particle, in a symmetric
periodic potential and subjected to a symmetric periodic forcing with mean zero
over a period, with nonuniform friction, is solved numerically. The particle is
shown to acquire a steady state mean velocity at asymptotically large time
scales. This net particle velocity or the ratchet current is obtained in a
range of forcing amplitudes $F_0$ and peaks at some value of $F_0$ within the
range depending on the value of the average friction coefficient and
temperature of the medium. At these large time scales the position dispersion
grows proportionally with time, $t$, allowing for calculating the steady state
diffusion coefficient $D$ which, interestingly, shows a peaking behaviour
around the same $F_0$. The ratchet current, however, turns out to be largely
coherent. At intermediate time scales, which bridge the small time scale
behaviour of dispersion$\sim t^2$ to the large time one, the system shows, in
some cases, periodic oscillation between dispersionless and steeply growing
dispersion depending on the frequency of the forcing. The contribution of these
different dispersion regimes to ratchet current is analysed.


title:
Any multipartite entangled state violating Mermin-Klyshko inequality can
  be distilled for almost all bipartite splits

abstract:
  We study the explicit relation between violation of Bell inequalities and
bipartite distillability of multi-qubit states. It has been shown that even
though for $N\ge 8$ there exist $N$-qubit bound entangled states which violates
a Bell inequality [Phys. Rev. Lett. {\bf 87}, 230402 (2001)], for all the
states violating the inequality there exists at least one splitting of the
parties into two groups such that pure-state entanglement can be distilled
[Phys. Rev. Lett. {\bf 88}, 027901 (2002)]. We here prove that for all
$N$-qubit states violating the inequality the number of distillable bipartite
splits increases exponentially with $N$, and hence the probability that a
randomly chosen bipartite split is distillable approaches one exponentially
with $N$, as $N$ tends to infinity. We also show that there exists at least one
$N$-qubit bound entangled state violating the inequality if and only if $N\ge
6$.


title:
High-Precision Measurement of the Laser-Trapping Frequencies for
  $^{209,210,211}$Fr Atoms

abstract:
  We present the accurate measurement of the frequency of the $7S-7P$
laser-trapping transition for three francium isotopes. Our approach is based on
an interferometric comparison to deduce the unknown laser frequency from a
secondary laser frequency-standard. After careful investigation of systematics,
with samples of about 100 atoms the final accuracy reaches 8 MHz, an order of
magnitude better than the best previous measurement for $^{210}$Fr, and opens
the way to improved tests of the theoretical computation of Fr atomic
structure.


title: Euclidean Methods and the entropy function

abstract:
  We review results of articles hep-th/0607056, hep-th/0610163 and 0704.1405
[hep-th]. Here we focus on establish the connection between the entropy
functional formalism of Sen and the standard Euclidean formalism taken at zero
temperature. We find that Sen's entropy function $f$ (on-shell) matches the
zero temperature limit of the Euclidean action. Moreover, Sen's near horizon
angular and electric fields agree with the chemical potentials that are defined
from the zero-temperature limit of the Euclidean formalism. Connection with the
Dual CFT thermodynamics is briefly discussed.


title: Conception of quantum cosmology

abstract:
  Quantum cosmology describes universe as a relativistic object with an
evolution defined by an equation for the energy density corresponding to the
least action principle: (Taganov, 2008). In quantum cosmology this equation
plays the same role as the Planck equation does in quantum physics. Universe
evolution consists of not only the space expansion but also a deceleration of
the course of physical time. Durations of all processes, measured by
decelerating physical time, are always longer, than corresponding durations,
measured by a scale of the invariable uniform Newtonian time. Quantum
interpretation of the redshift phenomenon enables to estimate the Hubble
parameter by means of fundamental physical constants. In the course of
evolution, the universe retains the self-similarity defined by the constancy of
the characteristic scale relations for micro- and mega worlds with an average
fractal dimension of the typical cosmic large-scale structures D=2. Quantum
cosmology advances new relations for the microwave background parameters,
apparent stellar magnitudes and redshifts; formulae for the cosmological
increase of the macroscopic space- and time- characteristics and evaluation of
quasar redshifts and luminosities.


title: Semiclassical Quantization of Spinning Strings in AdS_4 x CP^3

abstract:
  We derive the one-loop correction to the space-time energy of a folded string
in AdS_4 x CP^3 carrying spin S in AdS_4 and angular momentum J in CP^3 in the
long string approximation. From this general result in the limit J << log S we
obtain the one-loop correction to the cusp anomalous dimension which turns out
to be -5 log 2/(2\pi). This value appears to be in conflict with the prediction
from the recently conjectured all-loop Bethe ansatz.


title: Blow-up estimates at horizontal points and applications

abstract:
  Horizontal points of smooth submanifolds in stratified groups play the role
of singular points with respect to the Carnot-Carathe'odory distance. When we
consider hypersurfaces, they coincide with the well known characteristic
points. In two step groups, we obtain pointwise estimates for the Riemannian
surface measure at all horizontal points of $C^{1,1}$ smooth submanifolds. As
an application, we establish an integral formula to compute the spherical
Hausdorff measure of any $C^{1,1}$ submanifold. Our technique also shows that
$C^2$ smooth submanifolds everywhere admit an intrinsic blow-up and that the
limit set is an intrinsically homogeneous algebraic variety.


title:
The turbulent destruction of clouds - I. A k-epsilon treatment of
  turbulence in 2D models of adiabatic shock-cloud interactions

abstract:
  The interaction of a shock with a cloud has been extensively studied in the
literature, where the effects of magnetic fields, radiative cooling and thermal
conduction have been considered. However, the formation of fully developed
turbulence has often been prevented by the artificial viscosity inherent in
hydrodynamical simulations, and a uniform post-shock flow has been assumed in
all previous single-cloud studies. In reality, the flow behind the shock is
also likely to be turbulent, with non-uniform density, pressure and velocity
structure created as the shock sweeps over inhomogenities upstream of the
cloud. To address these twin issues we use a sub-grid compressible k-epsilon
turbulence model to estimate the properties of the turbulence generated in
shock-cloud interactions and the resulting increase in the transport
coefficients that the turbulence brings. A detailed comparison with the output
from an inviscid hydrodynamical code puts these new results into context.
  We find that cloud destruction in inviscid and k-epsilon models occurs at
roughly the same speed when the post-shock flow is smooth and when the density
contrast between the cloud and inter-cloud medium is less than 100. However,
there are increasing and significant differences as this contrast increases.
Clouds subjected to strong ``buffeting'' by a highly turbulent post-shock
environment are destroyed significantly quicker. Additional calculations with
an inviscid code where the post-shock flow is given random, grid-scale, motions
confirms the more rapid destruction of the cloud.
  Our results clearly show that turbulence plays an important role in
shock-cloud interactions, and that environmental turbulence adds a new
dimension to the parameter space which has hitherto been studied (abridged).


title: Stability of Quadratic Modules

abstract:
  A finitely generated quadratic module or preordering in the real polynomial
ring is called stable, if it admits a certain degree bound on the sums of
squares in the representation of polynomials. Stability, first defined
explicitly by Powers and Scheiderer, is a very useful property. It often
implies that the quadratic module is closed; furthermore it helps settling the
Moment Problem, solves the Membership Problem for quadratic modules and allows
applications of methods from optimization to represent nonnegative polynomials.
  We provide sufficient conditions for finitely generated quadratic modules in
real polynomial rings of several variables to be stable. These conditions can
be checked easily. For a certain class of semi-algebraic sets, we obtain that
the nonexistence of bounded polynomials implies stability of every
corresponding quadratic module. As stability often implies the non-solvability
of the Moment Problem, this complements Schmuedgen's result which uses bounded
polynomials to check the solvability of the Moment Problem by dimensional
induction.
  We also use stability to generalize a result on the Invariant Moment Problem
by Cimpric, Kuhlmann and Scheiderer.


title:
Gap anisotropy and universal pairing scale in a spin fluctuation model
  for cuprates

abstract:
  We consider the evolution of d-wave pairing, mediated by nearly critical spin
fluctuations, with the coupling strength. We show that the onset temperature
for pairing, T*, smoothly evolves between weak and strong coupling, passing
through a broad maximum at intermediate coupling. At strong coupling, T* is of
order the magnetic exchange energy J. We argue that for all couplings, pairing
is confined to the vicinity of the Fermi surface. We also find that thermal
spin fluctuations only modestly reduce T*, even at criticality, but they
substantially smooth the gap anisotropy. The latter evolves with coupling,
being the largest at weak coupling.


title: Gauge Theory in Riem(M)

abstract:
  In the geometrodynamical setting of general relativity in Lagrangian form,
the objects of study are the {\it Riemannian} metrics (and their time
derivatives) over a given 3-manifold $M$. It is our aim in this paper to study
the gauge properties that the space Riem(M) of all metrics over $M$ possesses,
specially as they relate to the constraints of geometrodynamics. For instance,
the Hamiltonian constraint does not generate a group, and it is thus hard to
view its action in Riem(M) in a gauge setting. However, in view of the recent
results representing GR as a dual theory, invariant under foliation preserving
3--diffeomorphisms and 3D conformal transformations, but not under
refoliations, we are justified in considering the gauge structure pertaining
only to the groups $\mathcal{D}$ of diffeomorphisms of $M$, and $\mathcal{C}$,
of conformal diffeomorphisms on $M$. For these infinite-dimensional symmetry
groups, Riem(M) has a natural principal fiber bundle (PFB) structure, which
renders the gravitational field amenable to the full range of gauge-theoretic
treatment. We discuss some of these structures and construct explicit formulae
for supermetric-induced gauge connections. To apply the formalism, we compute
general properties for a specific connection bearing strong resemblance to the
one naturally induced by the deWitt supermetric, showing it has desirable
relationalist properties. Finally, we find that the group of conformal
diffeomorphisms solves the pathologies inherent in the $\DD$ group and also
brings it closer to Horava gravity and the dual conformal theory called Shape
Dynamics.


title:
Error Estimates for Approximate Solutions of the Riccati Equation with
  Real or Complex Potentials

abstract:
  A method is presented for obtaining rigorous error estimates for approximate
solutions of the Riccati equation, with real or complex potentials. Our main
tool is to derive invariant region estimates for complex solutions of the
Riccati equation. We explain the general strategy for applying these estimates
and illustrate the method in typical examples, where the approximate solutions
are obtained by glueing together WKB and Airy solutions of corresponding
one-dimensional Schrodinger equations. Our method is motivated by and has
applications to the analysis of linear wave equations in the geometry of a
rotating black hole.


title: Dynamical Casimir-Polder force between an atom and a conducting wall

abstract:
  The time-dependent Casimir-Polder force arising during the time evolution of
an initially bare two-level atom, interacting with the radiation field and
placed near a perfectly conducting wall, is considered. Initially the
electromagnetic field is supposed to be in the vacuum state and the atom in its
ground state. The analytical expression of the force as a function of time and
atom-wall distance, is evaluated from the the time-dependent atom-field
interaction energy. Physical features and limits of validity of the results are
discussed in detail.


title:
Multiple Gaps and Superfluid Density from Interband Pairing in Iron
  Oxypnictides

abstract:
  We study a four-band model for the iron oxypnictides, in which the
superconducting properties are assumed to be determined by the interband
coupling between hole-like and electron-like Fermi sheets. We show that
reasonable parameters can account for the angle-resolved photoemission spectra
showing multiple gaps in Ba$_{1-x}$K$_x$Fe$_2$As$_2$, and for the temperature
dependence of the superfluid density. At the same time, the zero-temperature
value of the superfluid density shows a conventional scaling with the number of
carriers.


title:
An Algorithm for Detecting Hopf-Birfucation Varieties of Nonlinear
  Polynomial Systems

abstract:
  An algorithm is presented here, for discovering Hopf-Bifurcation varieties of
polynomial dynamical systems. It is based on the expression of specific
polynomials, as sums of products of first degree polynomials, with parametrical
coefficients. By giving to these parameters certain values, we ensure the
positiveness of some quantities, constructing thereby proper Lyapunov
functions, which guarantee the stability of the equilibrium point. The points
where the afore mentioned positiveness fails, define the Hopf-Bifurcation
varieties upon discussion.


title:
Unified description of 0+ states in a large class of nuclear collective
  models

abstract:
  A remarkably simple regularity in the energies of 0+ states in a broad class
of collective models is discussed. A single formula for all 0+ states in
flat-bottomed infinite potentials that depends only on the number of dimensions
and a simpler expression applicable to all three IBA symmetries in the large
boson number limit are presented. Finally, a connection between the energy
expression for 0+ states given by the X(5) model and the predictions of the IBA
near the critical point is explored.


title:
Critical Scaling of the Magnetization and Magnetostriction in the Weak
  Itinerant Ferromagnet UIr

abstract:
  The weak itinerant ferromagnet UIr is studied by magnetization and
magnetostriction measurements. Critical behavior, which surprisingly extends up
to several Tesla, is observed at the Curie temperature $T_C\simeq45$ K and is
analyzed using Arrott and Maxwell relations. Critical exponents are found that
do not match with any of the well-known universality classes. The
low-temperature magnetization $M_s\simeq0.5$ $\mu_B \cong const.$ below 3 T
rises towards higher fields and converges asymptotically around 50 T with the
magnetization at $T_C$. From the magnetostriction and magnetization data, we
extract the uniaxial pressure dependences of $T_C$, using a new method
presented here, and of $M_s$. These results should serve as a basis for
understanding spin fluctuations in anisotropic itinerant ferromagnets.


title:
On next-to-eikonal corrections to threshold resummation for the
  Drell-Yan and DIS cross sections

abstract:
  We study corrections suppressed by one power of the soft gluon energy to the
resummation of threshold logarithms for the Drell-Yan cross section and for
Deep Inelastic structure functions. While no general factorization theorem is
known for these next-to-eikonal (NE) corrections, it is conjectured that at
least a subset will exponentiate, along with the logarithms arising at leading
power. Here we develop some general tools to study NE logarithms, and we
construct an ansatz for threshold resummation that includes various sources of
NE corrections, implementing in this context the improved collinear evolution
recently proposed by Dokshitzer, Marchesini and Salam (DMS). We compare our
ansatz to existing exact results at two and three loops, finding evidence for
the exponentiation of leading NE logarithms and confirming the predictivity of
DMS evolution.


title: 2+1 dimensional solution of Einstein Cartan equations

abstract:
  In this work a static solution of Einstein-Cartan (EC) equations in 2+1
dimensional space-time is given by considering classical spin-1/2 field as
external source for torsion of the space-time. Here, the torsion tensor is
obtained from metricity condition for the connection and the static spinor
field is determined as the solution of Dirac equation in 2+1 spacetime with
non-zero cosmological constant and torsion. The torsion itself is considered as
a non-dynamical field.


title: Hardy's non-locality and generalized non-local theory

abstract:
  Hardy's non-locality theorem for multiple two-level systems is explored in
the context of generalized nonlocal theory. We find nonlocal but non-signaling
probabilities, providing Hardy's nonlocal argument, which are higher than those
in Quantum Mechanics. Maximum probability of success of Hardy's argument is
obtained for three two-level systems in quantum as well as in a more
generalized theory. Interestingly, the maximum in the nonlocal generalized
theory for both the cases turns out to be same.


title: Viscosity solutions for systems of parabolic variational inequalities

abstract:
  In this paper, we first define the notion of viscosity solution for the
following system of partial differential equations involving a subdifferential
operator:\[\{[c]{l}\dfrac{\partial u}{\partial
t}(t,x)+\mathcal{L}_tu(t,x)+f(t,x,u(t,x))\in\partial\phi (u(t,x)),\quad
t\in[0,T),x\in\mathbb{R}^d, u(T,x)=h(x),\quad x\in\mathbb{R}^d,\] where
$\partial\phi$ is the subdifferential operator of the proper convex lower
semicontinuous function $\phi:\mathbb{R}^k\to (-\infty,+\infty]$ and
$\mathcal{L}_t$ is a second differential operator given by
$\mathcal{L}_tv_i(x)={1/2}\operatorname
{Tr}[\sigma(t,x)\sigma^*(t,x)\mathrm{D}^2v_i(x)]+< b(t,x),\nabla v_i(x)>$,
$i\in\bar{1,k}$. We prove the uniqueness of the viscosity solution and then,
via a stochastic approach, prove the existence of a viscosity solution
$u:[0,T]\times\mathbb{R}^d\to\mathbb{R}^k$ of the above parabolic variational
inequality.


title: Coordinated motion design on Lie groups

abstract:
  The present paper proposes a unified geometric framework for coordinated
motion on Lie groups. It first gives a general problem formulation and analyzes
ensuing conditions for coordinated motion. Then, it introduces a precise method
to design control laws in fully actuated and underactuated settings with simple
integrator dynamics. It thereby shows that coordination can be studied in a
systematic way once the Lie group geometry of the configuration space is well
characterized. This allows among others to retrieve control laws in the
literature for particular examples. A link with Brockett's double bracket flows
is also made. The concepts are illustrated on SO(3), SE(2) and SE(3).


title:
On Introspection, Metacognitive Control and Augmented Data Mining Live
  Cycles

abstract:
  We discuss metacognitive modelling as an enhancement to cognitive modelling
and computing. Metacognitive control mechanisms should enable AI systems to
self-reflect, reason about their actions, and to adapt to new situations. In
this respect, we propose implementation details of a knowledge taxonomy and an
augmented data mining life cycle which supports a live integration of obtained
models.


title: On quasiconformal maps with identity boundary values

abstract:
  Quasiconformal homeomorphisms of the unit ball $B^n$ of ${\mathbb R}^n, n \ge
3,$ onto itself with identity boundary values are studied. A spatial analogue
of Teichm\"uller's theorem is proved.


title: The Fermi surface reconstruction in stripe phases of cuprates

abstract:
  Mean-field study of the stripe structures is conducted for a hole-doped
Hubbard model. For bond-directed stripes, the Fermi surface consists of
segments of an open surface and the boundaries of the hole pockets which appear
in the diagonal region of momenta under certain conditions. Segments of the
first type are due to one-dimensional bands of states localized on the domain
walls. The relation of bands to the doping and temperature dependences of the
Hall constant is discussed. In connection with the observation of quantum
magnetic oscillations, a systematic search for the electron pockets has been
carried out. It is shown that the formation of such pockets in bilayer models
is quite possible.


title:
Sampling bias in systems with structural heterogeneity and limited
  internal diffusion

abstract:
  Complex systems research is becomingly increasingly data-driven, particularly
in the social and biological domains. Many of the systems from which sample
data are collected feature structural heterogeneity at the mesoscopic scale
(i.e. communities) and limited inter-community diffusion. Here we show that the
interplay between these two features can yield a significant bias in the global
characteristics inferred from the data. We present a general framework to
quantify this bias, and derive an explicit corrective factor for a wide class
of systems. Applying our analysis to a recent high-profile survey of conflict
mortality in Iraq suggests a significant overestimate of deaths.


title:
Third Level Trigger for the Fluorescence Telescopes of the Pierre Auger
  Observatory

abstract:
  The trigger system for the Auger fluorescence telescopes is implemented in
hard- and software for an efficient selection of fluorescence light tracks
induced by high-energy extensive air showers. The algorithm of the third stage
uses the multiplicity signal of the hardware for fast rejection of lightning
events with above 99% efficiency. In a second step direct muon hits in the
camera and random triggers are rejected by analyzing the space-time correlation
of the pixels. The trigger algorithm was tested with measured and simulated
showers and implemented in the electronics of the fluorescence telescopes. A
comparison to a prototype trigger without multiplicity shows the superiority of
this approach, e.g. the false rejection rate is a factor 10 lower.


title:
Current induced resistance change of magnetic tunnel junctions with
  ultra-thin MgO tunnel barriers

abstract:
  Ultra-thin magnetic tunnel junctions with low resistive MgO tunnel barriers
are prepared to examine their stability under large current stress. The devices
show magnetoresistance ratios of up to 110 % and an area resistance product of
down to 4.4 ohm micrometer squared. If a large current is applied, a reversible
resistance change is observed, which can be attributed to two different
processes during stressing and one relaxation process afterwards. Here, we
analyze the time dependence of the resistance and use a simple model to explain
the observed behavior. The explanation is further supported by numerical fits
to the data in order to quantify the timescales of the involved phenomena.


title: Low-rank optimization for semidefinite convex problems

abstract:
  We propose an algorithm for solving nonlinear convex programs defined in
terms of a symmetric positive semidefinite matrix variable $X$. This algorithm
rests on the factorization $X=Y Y^T$, where the number of columns of Y fixes
the rank of $X$. It is thus very effective for solving programs that have a low
rank solution. The factorization $X=Y Y^T$ evokes a reformulation of the
original problem as an optimization on a particular quotient manifold. The
present paper discusses the geometry of that manifold and derives a second
order optimization method. It furthermore provides some conditions on the rank
of the factorization to ensure equivalence with the original problem. The
efficiency of the proposed algorithm is illustrated on two applications: the
maximal cut of a graph and the sparse principal component analysis problem.


title: Using Dimensional Reduction for Hadronic Collisions

abstract:
  We discuss how to apply regularization by dimensional reduction for computing
hadronic cross sections at next-to-leading order. We analyze the infrared
singularity structure, demonstrate that there are no problems with
factorization, and show how to use dimensional reduction in conjunction with
standard parton distribution functions. We clarify that different versions of
dimensional reduction with different infrared and factorization behaviour have
been used in the literature. Finally, we give transition rules for translating
the various parts of next-to-leading order cross sections from dimensional
reduction to other regularization schemes.


title: Stochastic bifurcations: a perturbative study

abstract:
  We study a noise-induced bifurcation in the vicinity of the threshold by
using a perturbative expansion of the order parameter, called the
Poincar\'e-Lindstedt expansion. Each term of this series becomes divergent in
the long time limit if the power spectrum of the noise does not vanish at zero
frequency. These divergencies have a physical consequence: they modify the
scaling of all the moments of the order parameter near the threshold and lead
to a multifractal behaviour. We derive this anomalous scaling behaviour
analytically by a resummation of the Poincar\'e-Lindstedt series and show that
the usual, deterministic, scalings are recovered when the noise has a low
frequency cut-off. Our analysis reconciles apparently contradictory results
found in the literature.


title: Magnetic QED

abstract:
  A non-Hermitian form of QED is presented which describes interacting Dirac
monopoles. The theory is related by a canonical transformation to a model
proposed by Milton. As in Hermitian QED an abelian gauge potential is coupled
to a four-component fermion. Under proper Lorentz transformations and
time-reversal the fermion field transforms like a Dirac spinor but has a
non-standard parity transformation. This implements the property that magnetic
charge, unlike electric charge, is parity-odd. A consequence of the
non-Hermiticity is that there is an attractive force between identical charged
particles, at least in the weakly coupled regime. This effect can be understood
even at the classical level; a simple calculation of the force between
classical Dirac monopoles is presented which shows that like charge monopoles
attract and opposite charges repel.


title:
Controlled light-matter coupling for a single quantum dot embedded in a
  pillar microcavity using far-field optical lithography

abstract:
  Using far field optical lithography, a single quantum dot is positioned
within a pillar microcavity with a 50 nm accuracy. The lithography is performed
in-situ at 10 K while measuring the quantum dot emission. Deterministic
spectral and spatial matching of the cavity-dot system is achieved in a single
step process and evidenced by the observation of strong Purcell effect.
Deterministic coupling of two quantum dots to the same optical mode is
achieved, a milestone for quantum computing.


title: Implications of non-analytical f(R) gravity at Solar-System scales

abstract:
  We motivate and analyze the weak-field limit of a non-analytical Lagrangian
for the gravitational field. After investigating the parameter space of the
model, we impose constraints on the parameters characterizing this class of
theories imposed by Solar-System data, i.e. we establish the validity range
where this solution applies and refine the constraints by the comparison with
planetary orbits. As a result, we claim that this class of models is viable
within different astrophysical scales.


title:
Ab initio lattice dynamics simulations and inelastic neutron scattering
  spectra for studying phonons in BaFe2As2: Effect of structural phase
  transition, structural relaxation and magnetic ordering

abstract:
  We have performed extensive ab initio calculations to investigate phonon
dynamics and their possible role in superconductivity in BaFe2As2 and related
systems. The calculations are compared to inelastic neutron scattering data
that offer improved resolution over published data [Mittal et al., PRB 78
104514 (2008)], in particular at low frequencies. Effects of structural phase
transition and full/partial structural relaxation, with and without magnetic
ordering, on the calculated vibrational density of states are reported. Phonons
are best reproduced using either the relaxed magnetic structures or the
experimental cell. Several phonon branches are affected by the subtle
structural changes associated with the transition from the tetragonal to the
orthorhombic phase. Effects of phonon induced distortions on the electronic and
spin structure have been investigated. It is found that for some vibrational
modes, there is a significant change of the electronic distribution and spin
populations around the Fermi level. A peak at 20 meV in the experimental data
falls into the pseudo-gap region of the calculation. This was also the case
reported in our recent work combined with an empirical parametric calculation
[Mittal et al., PRB 78 104514 (2008)]. The combined evidence for the coupling
of electronic and spin degrees of freedom with phonons is relevant to the
current interest in superconductivity in BaFe2As2 and related systems.


title:
Linearly recurrent subshifts have a finite number of non-periodic
  subshift factors

abstract:
  A minimal subshift $(X,T)$ is linearly recurrent if there exists a constant
$K$ so that for each clopen set $U$ generated by a finite word $u$ the return
time to $U$, with respect to $T$, is bounded by $K|u|$. We prove that given a
linearly recurrent subshift $(X,T)$ the set of its non-periodic subshift
factors is finite up to isomorphism. We also give a constructive
characterization of these subshifts.


title:
The Principle of Least Action for Fields Containing Higher Order
  Derivatives

abstract:
  When generalizing the principle of least action for fields containing higher
order derivatives, in general, it is not possible not to take into account the
surface integrated term since it gives direct contribution to the forms of the
equations of motion,of the energy-momentum tensor and of the angular-momentum
tensor. This result is applied to two examples. In two dimensional gravity, it
is essential to supplement Dirichclet condition for the surface integrated
terms to vanish. On the contrary, in Hamiltonian description of the open rigid
string, the equation of motion is modified by surface integrated terms.
Boundary conditions are classified according to forms of certain equations of
motion.


title:
Transport anomalies across the quantum limit in semimetallic
  Bi$_{0.96}$Sb$_{0.04}$

abstract:
  We report on a study of electronic transport in semi-metallic
Bi$_{0.96}$Sb$_{0.04}$. At zero field, the system is a very dilute Fermi liquid
displaying a T$^{2}$ resistivity with an enhanced prefactor. Quantum
oscillations in resistivity as well as in Hall, Nernst and Seebeck responses of
the system are detectable and their period quantifies the shrinking of the
Fermi surface with antimony doping. For a field along the trigonal axis, the
quantum limit was found to occur at a field as low as 3T. An ultraquantum
anomaly at twice this field was detected in both charge transport and Nernst
response. Its origin appears to lie beyond the one-particle picture and linked
to unidentified many-body effects.


title: The World-Trade Web: Topological Properties, Dynamics, and Evolution

abstract:
  This paper studies the statistical properties of the web of import-export
relationships among world countries using a weighted-network approach. We
analyze how the distributions of the most important network statistics
measuring connectivity, assortativity, clustering and centrality have
co-evolved over time. We show that all node-statistic distributions and their
correlation structure have remained surprisingly stable in the last 20 years --
and are likely to do so in the future. Conversely, the distribution of
(positive) link weights is slowly moving from a log-normal density towards a
power law. We also characterize the autoregressive properties of
network-statistics dynamics. We find that network-statistics growth rates are
well-proxied by fat-tailed densities like the Laplace or the asymmetric
exponential-power. Finally, we find that all our results are reasonably robust
to a few alternative, economically-meaningful, weighting schemes.


title: Phase separation in imbalanced fermion superfluids beyond mean-field

abstract:
  The density distributions of the two components of a trapped, ultracold Fermi
gas with population imbalance reveal the effect of imbalance on superfluid
pairing. We develop a path-integral derivation of the density, that takes into
account both fluctuations beyond mean-field and effects of nonzero temperature.
The calculated density profiles compare favorably to the measured density
profiles, and illustrate the necessity to incorporate both quantum fluctuations
and finite temperature effects. The temperature dependence of the density
profiles, especially near the superfluid-normal interface, allows determining
the temperature of the superfluid core in current experiments.


title:
Phase transitions in fullerenes: Fragmentation and reassembly of the
  carbon cage

abstract:
  Phase transition in fullerenes C60 and C240 are investigated by means of
constant-temperature molecular dynamics simulations. In the phase transition
region, the assembly (and fragmentation) of the C60 cage from (and to) the
gaseous state is demonstrated via the dynamical coexistence of two phases. In
this critical region, the fullerene system is seen to continuously oscillate
between the carbon cage (the solid phase) and the state of carbon dimers and
short chains (the gas phase). These oscillations correspond to consecutive
disintegration and formation of the fullerene. Furthermore, the
temperature-dependent heat capacity of the fullerene features a prominent peak,
signifying the finite system analogue of a first-order phase transition. The
simulations were conducted for 500 ns using a topologically-constrained
pairwise forcefield which was developed for this work. Results of the
simulations were supplemented by a statistical mechanics analysis to account
for entropy and pressure corrections, corresponding to experimental conditions.
These corrections lead to a phase transition temperature of 3800-4200 K for
pressure 10-100 kPa, in good agreement with available experimental values.


title:
Reinventing College Physics for Biologists: Explicating an
  epistemological curriculum

abstract:
  The University of Maryland Physics Education Research Group (UMd-PERG)
carried out a five-year research project to rethink, observe, and reform
introductory algebra-based (college) physics. This class is one of the Maryland
Physics Department's large service courses, serving primarily life-science
majors. After consultation with biologists, we re-focused the class on helping
the students learn to think scientifically -- to build coherence, think in
terms of mechanism, and to follow the implications of assumptions. We designed
the course to tap into students' productive conceptual and epistemological
resources, based on a theoretical framework from research on learning. The
reformed class retains its traditional structure in terms of time and
instructional personnel, but we modified existing best-practices curricular
materials, including Peer Instruction, Interactive Lecture Demonstrations, and
Tutorials. We provided class-controlled spaces for student collaboration, which
allowed us to observe and record students learning directly. We also scanned
all written homework and examinations, and we administered pre-post conceptual
and epistemological surveys. The reformed class enhanced the strong gains on
pre-post conceptual tests produced by the best-practices materials while
obtaining unprecedented pre-post gains on epistemological surveys instead of
the traditional losses.


title: Anti-symmetrization reveals hidden entanglement

abstract:
  Two-photon anti-bunching at a beamsplitter is only possible if the photons
are entangled in a specific state, anti-symmetric in the spatial modes. Thus,
observation of anti-bunching is an indication of entanglement in a degree of
freedom which might not be easily accessible in an experiment. We
experimentally demonstrate this concept in the case of the interference of two
frequency entangled photons with continuous frequency detunings. The principle
of anti-symmetrisation of the spatial part of a wavefunction and subsequent
detection of hidden entanglement via anti-bunching at a beamsplitter may
facilitate the observation of entanglement in other systems, like atomic
ensembles or Bose-Einstein condensates. The analogue for fermionic systems
would be to observe bunching.


title:
High Field ESR in the Two-Dimensional Triangular Lattice Antiferromagnet
  NiGa2S4

abstract:
  In this Letter, we report the results of ESR measurements in high magnetic
fields up to about 53 T on single crystals of NiGa2S4 to clarify the spin
dynamics in more detail. We have found that the dynamics of Z2 vortices affects
the temperature dependence of the ESR absorption linewidth and the frequency
dependence of the ESR resonance fields at 1.3 K is well explained by a
conventional spin wave theory. These results suggest an occurrence of Z2
vortex-induced topological transition.


title: Measure of submanifolds in the Engel group

abstract:
  We find all intrinsic measures of $C^{1,1}$ smooth submanifolds in the Engel
group, showing that they are equivalent to the corresponding $d$-dimensional
spherical Hausdorff measure restricted to the submanifold. The integer $d$ is
the degree of the submanifold. These results follow from a different approach
to negligibility, based on a blow-up technique.


title:
Unusual decoherence in qubit measurements with a Bose-Einstein
  condensate

abstract:
  We consider an electrostatic qubit located near a Bose-Einstein condensate
(BEC) of noninteracting bosons in a double-well potential, which is used for
qubit measurements. Tracing out the BEC variables we obtain a simple analytical
expression for the qubit's density-matrix. The qubit's evolution exhibits a
slow ($\propto1/\sqrt{t}$) damping of the qubit's coherence term, which however
turns to be a Gaussian one in the case of static qubit. This stays in contrast
to the exponential damping produced by most classical detectors. The
decoherence is, in general, incomplete and strongly depends on the initial
state of the qubit.


title: Magnetic Ordering and Negative Thermal Expansion in PrFeAsO

abstract:
  We report the structure and magnetism of PrOFeAs, one of the parent phases of
the newly discovered Fe-As superconductors, as measured by neutron powder
diffraction. In common with other REOFeAs materials, a tetragonal-orthorhombic
phase transition is found on cooling below 136 K and striped Fe magnetism with
$k =$(1,0,1) is detected below $\sim$ 85 K. Our magnetic order parameter
measurements show that the ordered Fe moment along the a axis reaches a maximum
at $\sim$ 40 K, below which an anomalous expansion of the c axis sets in, which
results in a negative thermal volume expansion of 0.015 % at 2 K. We propose
that this effect, which is suppressed in superconducting samples, is driven by
a delicate interplay between Fe and Pr ordered moments.


title: Dynamics of domain wall networks with junctions

abstract:
  We use a combination of analytic tools and an extensive set of the largest
and most accurate three-dimensional field theory numerical simulations to study
the dynamics of domain wall networks with junctions. We build upon our previous
work and consider a class of models which, in the limit of large number $N$ of
coupled scalar fields, approaches the so-called `ideal' model (in terms of its
potential to lead to network frustration). We consider values of $N$ between
N=2 and N=20, and a range of cosmological epochs, and we also compare this
class of models with other toy models used in the past. In all cases we find
compelling evidence for a gradual approach to scaling, strongly supporting our
no-frustration conjecture. We also discuss the various possible types of
junctions (including cases where there is a hierarchy of them) and their roles
in the dynamics of the network. Finally, we revise the Zel'dovich bound and
provide an updated cosmological bound on the energy scale of this type of
defect network: it must be lower than $10 {\rm keV}$.


title: Spontaneous symmetry breaking in a bridge model fed by junctions

abstract:
  We introduce a class of 1D models mimicking a single-lane bridge with two
junctions and two particle species driven in opposite directions. The model
exhibits spontaneous symmetry breaking (SSB) for a range of
injection/extraction rates. In this phase the steady state currents of the two
species are not equal. Moreover there is a co-existence region in which the
symmetry broken phase co-exists with a symmetric phase. Along a path in which
the extraction rate is varied, keeping the injection rate fixed and large,
hysteresis takes place. The mean field phase diagram is calculated and
supporting Monte-Carlo simulations are presented. One of the transition lines
exhibits a kink, a feature which cannot exist in transition lines of
equilibrium phase transitions.


title:
Swift observations of SAX J1808.4-3658: monitoring the return to
  quiescence

abstract:
  The transient accreting millisecond pulsar SAX J1808.4-3658 has shown several
outbursts to date but the transition from outburst to quiescence has never been
investigated in detail. Thanks to the Swift observing flexibility, we monitored
for the first time the decay to quiescence during the 2005 outburst. At
variance with other transients, wide luminosity variations are observed. In
addition, close to quiescence, SAX J1808.4-3658 seems to switch between two
different states. We interpret them in terms of the accretion states accessible
to a magnetized, fast rotating neutron star.


title:
Magnetoelectric bistabilities in ferromagnetic resonant tunneling
  structures

abstract:
  The conditions for the occurrence of pronounced magnetoelectric bistabilities
in the resonant tunneling through a ferromagnetic quantum well are
theoretically investigated. The bistability appears due to the mutual feedback
of the carriers Coulomb interaction and the carriers exchange coupling with
magnetic impurities in the well. It is shown that the well Curie temperature
depends strongly on the relative alignment of the quantum well level and the
reservoirs chemical potentials, which can be modified electrically. Switching
between a "current-on/magnetism-off" and a "current-off/magnetism-on" mode
becomes possible, if the well temperature lies in-between the bistable values
of the well Curie temperature.


title: Construction of Minimal Bracketing Covers for Rectangles

abstract:
  We construct explicit $\delta$-bracketing covers with minimal cardinality for
the set system of (anchored) rectangles in the two dimensional unit cube. More
precisely, the cardinality of these $\delta$-bracketing covers are bounded from
above by $\delta^{-2} + o(\delta^{-2})$. A lower bound for the cardinality of
arbitrary $\delta$-bracketing covers for $d$-dimensional anchored boxes from
[M. Gnewuch, Bracketing numbers for axis-parallel boxes and applications to
geometric discrepancy, J. Complexity 24 (2008) 154-172] implies the lower bound
$\delta^{-2}+O(\delta^{-1})$ in dimension $d=2$, showing that our constructed
covers are (essentially) optimal.
  We study also other $\delta$-bracketing covers for the set system of
rectangles, deduce the coefficient of the most significant term $\delta^{-2}$
in the asymptotic expansion of their cardinality, and compute their cardinality
for explicit values of $\delta$.


title:
Exactly separable version of the Bohr Hamiltonian with the Davidson
  potential

abstract:
  An exactly separable version of the Bohr Hamiltonian is developed using a
potential of the form u(beta)+u(gamma)/beta^2, with the Davidson potential
u(beta)= beta^2 + beta_0^4/beta^2 (where beta_0 is the position of the minimum)
and a stiff harmonic oscillator for u(gamma) centered at gamma=0. In the
resulting solution, called exactly separable Davidson (ES-D), the ground state
band, gamma band and 0_2^+ band are all treated on an equal footing. The
bandheads, energy spacings within bands, and a number of interband and
intraband B(E2) transition rates are well reproduced for almost all
well-deformed rare earth and actinide nuclei using two parameters (beta_0,
gamma stiffness). Insights regarding the recently found correlation between
gamma stiffness and the gamma-bandhead energy, as well as the long standing
problem of producing a level scheme with Interacting Boson Approximation SU(3)
degeneracies from the Bohr Hamiltonian, are also obtained.


title:
Simulation of Cosmic Ray propagation in the Galactic Centre Ridge in
  Accordance with Observed VHE gamma-ray Emission

abstract:
  Diffuse VHE gamma radiation from the Galactic Centre ridge observed by the
H.E.S.S. telescope has been convincingly linked with the propagation of
recently accelerated cosmic rays that interact with molecular hydrogen clouds
during their diffusion. Through a series of time-dependent simulations of that
diffusion for different propagation parameters we have obtained the most
probable values of the diffusion coefficient for the Galactic Centre region.
Assuming that the diffusion coefficient is of the form kappa(E) =
kappa_0*(E/E_0)^delta, then for different optimal combinations of kappa_0 and
delta its value is obtained for cosmic rays originating from a central point
(possibly Sgr A East) 10 kyr ago.


title:
Self-similar solution of a nonsteady problem of nonisothermal vapour
  condensation on a droplet growing in diffusion regime

abstract:
  This paper presents a mathematically exact self-similar solution to the joint
nonsteady problems of vapour diffusion towards a droplet growing in a
vapour-gas medium and of removal of heat released by a droplet into a
vapour-gas medium during vapour condensation. An equation for the temperature
of the droplet is obtained; and it is only at that temperature that the
self-similar solution exists. This equation requires the constancy of the
droplet temperature and even defines it unambiguously throughout the whole
period of the droplet growth. In the case of strong display of heat effects,
when the droplet growth rate decreases significantly, the equation for the
temperature of the droplet is solved analytically. It is shown that the
obtained temperature fully coincides with the one that settles in the droplet
simultaneously with the settlement of its diffusion regime of growth. At the
obtained temperature of the droplet the interrelated nonsteady vapour
concentration and temperature profiles of the vapour-gas medium around the
droplet are expressed in terms of initial (prior to the nucleation of the
droplet) parameters of the vapour-gas medium. The same parameters are used to
formulate the law in accordance with which the droplet is growing in diffusion
regime, and also to define the time that passes after the nucleation of the
droplet till the settlement of diffusion regime of droplet growth, when the
squared radius of the droplet becomes proportionate to time. For the sake of
completeness the case of weak display of heat effects is been studied.


title: Candy-passing Games on General Graphs, I

abstract:
  We undertake the first study of the candy-passing game on arbitrary connected
graphs. We obtain a general stabilization result which encompasses the first
author's results (arXiv:0709.2156) for candy-passing games on n-cycles with at
least 3n candies.


title: Generalized Kac-Moody Algebras from CHL dyons

abstract:
  We provide evidence for the existence of a family of generalized
Kac-Moody(GKM) superalgebras, G_N, whose Weyl-Kac-Borcherds denominator formula
gives rise to a genus-two modular form at level N, Delta_{k/2}(Z), for
(N,k)=(1,10), (2,6), (3,4), and possibly (5,2). The square of the automorphic
form is the modular transform of the generating function of the degeneracy of
CHL dyons in asymmetric Z_N-orbifolds of the heterotic string compactified on
T^6. The new generalized Kac-Moody superalgebras all arise as different
`automorphic corrections' of the same Lie algebra and are closely related to a
generalized Kac-Moody superalgebra constructed by Gritsenko and Nikulin. The
automorphic forms, Delta_{k/2}(Z), arise as additive lifts of Jacobi forms of
(integral) weight k/2 and index 1/2. We note that the orbifolding acts on the
imaginary simple roots of the unorbifolded GKM superalgebra, G_1 leaving the
real simple roots untouched. We anticipate that these superalgebras will play a
role in understanding the `algebra of BPS states' in CHL compactifications.


title: Evolution of tidal disruption candidates discovered by XMM-Newton

abstract:
  It has been demonstrated that active galactic nuclei are powered by gas
accretion onto supermassive black holes located at their centres. The paradigm
that the nuclei of inactive galaxies are also occupied by black holes was
predicted long ago by theory. In the last decade, this conjecture was confirmed
by the discovery of giant-amplitude, non-recurrent X-ray flares from such
inactive galaxies and explained in terms of outburst radiation from stars
tidally disrupted by a dormant supermassive black hole at the nuclei of those
galaxies. Due to the scarcity of detected tidal disruption events, the
confirmation and follow-up of each new candidate is needed to strengthen the
theory through observational data, as well as to shed new light on the
characteristics of this type of events. Two tidal disruption candidates have
been detected with XMM-Newton during slew observations. Optical and X-ray
follow-up, post-outburst observations were performed on these highly variable
objects in order to further study their classification and temporal evolution.
We show that the detected low-state X-ray emission for these two candidates has
properties such that it must still be related to the flare. The X-ray
luminosity of the objects decreases according to theoretical predictions for
tidal disruption events. At present, optical spectra of the sources do not
present any evident signature of the disruption event. In addition, the tidal
disruption rate as derived from the XMM-Newton slew survey has been computed
and agrees with previous studies.


title:
Modification of Born impurity scattering near the surface of d-wave
  superconductors and influence of external magnetic field

abstract:
  We study the influence of Born impurity scattering on the zero-energy Andreev
bound states near the surface of a d-wave superconductor with and without an
externally applied magnetic field. Without an external magnetic field we show
that the effect of Born impurity scattering is stronger at the surface than in
the bulk. In the presence of an external magnetic field the splitting of the
zero-energy Andreev bound states is shown to have a nonmonotonous temperature
dependence. Born impurity scattering does not wash out the peak splitting, but
instead the peak splitting is shown to be quite robust against impurities. We
also show that a nonzero gap renormalization appears near the surface.


title:
Paris nucleon-antinucleon potential constrained by recent
  antiprotonic-atom data and antineutron-proton total cross sections

abstract:
  We report on an updated Paris nucleon-antinucleon optical potential. The
long- and intermediate-range real parts are obtained by G-parity transformation
of the Paris nucleon-nucleon potential based on a theoretical
dispersion-relation treatment of the correlated and uncorrelated two-pion
exchange. The short-range imaginary potential parametrization results from the
calculation of the nucleon-antinucleon annihilation box diagram into two mesons
with a nucleon-antinucleon intermediate state in the crossed channel. The
parametrized real and imaginary short range parts are determined by fitting not
only the existing experimental data included in the 1999 version of the Paris
nucleon-antinucleon potential, but also the recent antiprotonic-hydrogen data
and antineutron-proton total cross sections. The description of these new
observables is improved. Only this readjusted potential generates an isospin
zero 1S0, 52 MeV broad quasibound state at 4.8 MeV below the threshold. Recent
BES data on J/psi decays could support the existence of such a state.


title: Boundary regularity via Uhlenbeck-Rivi\`ere decomposition

abstract:
  We prove that weak solutions of systems with skew-symmetric structure, which
possess a continuous boundary trace, have to be continuous up to the boundary.
This applies, e.g., to the H-surface system with bounded H and thus extends an
earlier result by P. Strzelecki and proves the natural counterpart of a
conjecture by E. Heinz. Methodically, we use estimates below natural exponents
of integrability and a recent decomposition result by T.Rivi\`ere.


title: An X-ray survey of low-mass stars in Trumpler 16 with Chandra

abstract:
  We identify and characterize low-mass stars in the ~3 Myr old Trumpler 16
(Tr16) region by means of a deep Chandra X-ray observation, and study their
optical and near-IR properties. We compare X-ray activity of Tr16 stars with
known characteristics of Orion and Cygnus OB2 stars. We analyzed a 88.4 ksec
Chandra ACIS-I observation pointed at the center of Tr16. Because of diffuse
X-ray emission, source detection was performed using the PWDetect code for two
different energy ranges: 0.5-8.0 keV and 0.9-8.0 keV. Results were merged into
a single final list. We positionally correlate X-ray sources with optical and
2MASS catalogues. Source events were extracted with the IDL-based routine
ACIS-Extract. X-ray variability was characterized using the Kolmogorov-Smirnov
test and spectra were fitted by using XSPEC. X-ray spectra of early-type,
massive stars were analyzed individually. Our list of X-ray sources consists of
1035 entries, 660 of which have near-IR counterparts and are probably
associated with Tr16 members. From near-IR color-color and color-magnitudes
diagrams we compute individual masses of stars and their Av values. About 15%
of the near-IR counterparts show disk-induced excesses. X-ray variability is
found in 77 sources. X-ray emission from OB stars appear softer than the
low-mass stars. The Tr16 region has a very rich population of low-mass X-ray
emitting stars. An important fraction of its circumstellar disks survive the
intense radiation field of its massive stars. Stars with masses 1.5-2.5 Mo
display X-ray activity similar to that of stars in Cyg OB2 but much less
intense than observed for Orion Nebula Cluster members.


title:
Towards a nonequilibrium thermodynamics: a self-contained macroscopic
  description of driven diffusive systems

abstract:
  In this paper we present a self-contained macroscopic description of
diffusive systems interacting with boundary reservoirs and under the action of
external fields. The approach is based on simple postulates which are suggested
by a wide class of microscopic stochastic models where they are satisfied. The
description however does not refer in any way to an underlying microscopic
dynamics: the only input required are transport coefficients as functions of
thermodynamic variables, which are experimentally accessible. The basic
postulates are local equilibrium which allows a hydrodynamic description of the
evolution, the Einstein relation among the transport coefficients, and a
variational principle defining the out of equilibrium free energy. Associated
to the variational principle there is a Hamilton-Jacobi equation satisfied by
the free energy, very useful for concrete calculations. Correlations over a
macroscopic scale are, in our scheme, a generic property of nonequilibrium
states. Correlation functions of any order can be calculated from the free
energy functional which is generically a non local functional of thermodynamic
variables. Special attention is given to the notion of equilibrium state from
the standpoint of nonequilibrium.


title:
Observation of a near-threshold enhancement in the e+e-
  -->Lambda_c+Lambda_c- cross section using initial-state radiation

abstract:
  We report a measurement of the exclusive e+e- -->Lambda_c+ Lambda_c- cross
section as a function of center-of-mass energy near the Lambda_c+ Lambda_c-
threshold. A clear peak with a significance of 8.2 sigma is observed in the
Lambda_c+ Lambda_c- invariant mass distribution just above threshold. With an
assumption of a resonance origin for the observed peak, a mass and width of
M=(4634^{+8}_{-7}(stat.)^{+5}_{-8}(sys.))Mev/c2 and
Gamma_tot=(92^{+40}_{-24}(stat.)}^{+10}_{-21}(sys.))MeV are determined. The
analysis is based on a study of events with initial-state-radiation photons in
a data sample collected with the Belle detector at the \Upsilon(4S) resonance
and nearby continuum with an integrated luminosity of 695/fb at the KEKB
asymmetric-energy e+e- collider.


title:
Identification of competing ultrafast all-optical switching mechanisms
  in Si woodpile photonic crystals

abstract:
  We present a systematic study of ultrafast all-optical switching of Si
photonic band gap woodpile crystals using broadband tunable nondegenerate
pump-probe spectroscopy. At pump-probe coincidence, we investigate the behavior
the differential reflectivity at the blue edge of the stopband for a wide range
of pump- and probe frequencies. Both dispersive and absorptive features are
observed from the probe spectra at coincidence. As the pump frequency is tuned
through half the electronic bandgap of Si, the magnitude of both these features
increases. For the first time we unambiguously identify this dispersive effect
with the electronic Kerr effect in photonic crystals, and attribute the the
absorptive features to nondegenerate two photon absorption. The dispersive and
absorptive nonlinear coefficients are extracted, and are found to agree well
with literature. Finally, we propose a nondegenerate figure of merit (NFOM),
which defines the quality of switching for all nondegenerate optical switching
processes.


title:
Bound-free $\mathbf{e}^+ \mathbf{e}^-$ pair creation with a linearly
  polarized laser field and a nuclear field

abstract:
  The process of bound-free pair production of electrons and positrons in
combined laser and Coulomb fields is investigated. It is assumed that an ion
collides at relativistic speed with an intense x-ray laser beam of linear
polarization. The process proceeds nonlinearly due to simultaneous absorption
of a few laser photons. The capture of the electron into the ground state and
the $L$-shell is considered. The scaling of the total rate, the angular
distributions of the emitted positrons and a comparison to the competing
free-free channel are surveyed. Numerical results of pair production rates for
parameters for the planned x-ray free electron lasers at DESY and SLAC are
presented. We find that pair production with these laser facilities can become
observable in the near future.


title: The precision electroweak data in warped extra-dimension models

abstract:
  The Randall-Sundrum scenario with Standard Model fields in the bulk and a
custodial symmetry is considered. We determine the several minimal quark
representations allowing to address the anomalies in the forward-backward
b-quark asymmetry A^b_FB, while reproducing the bottom and top masses via wave
function overlaps. The calculated corrections of the Zbb coupling include the
combined effects of mixings with both Kaluza-Klein excitations of gauge bosons
and new b'-like states. It is shown that the mechanism, in which the
left-handed doublet of third generation quarks results from a mixing on the UV
boundary of introduced fields Q_1L and Q_2L, is necessary for phenomenological
reasons. Within the obtained models, both the global fit of R_b with A^b_FB [at
the various center of mass energies] and the fit of last precision electroweak
data in the light fermion sector can simultaneously be improved significantly
with respect to the pure Standard Model case, for M_KK = 3,4,5 TeV (first KK
gauge boson) and a best-fit Higgs mass m_h > 115 GeV i.e. compatible with the
LEP2 direct limit. The quantitative analysis of the oblique parameters S,T,U
even shows that heavy Higgs mass values up to ~500 GeV may still give rise to
an acceptable quality of the electroweak data fit, in contrast with the
Standard Model. The set of obtained constraints on the parameter space, derived
partly from precision electroweak data, is complementary of a future direct
exploration of this parameter space at the LHC. In particular, we find that
custodians, like b' modes, can be as light as ~1200 GeV i.e. a mass lying
possibly in the potential reach of LHC.


title:
Riemannian Metric and Geometric Mean for Positive Semidefinite Matrices
  of Fixed Rank

abstract:
  This paper introduces a new metric and mean on the set of positive
semidefinite matrices of fixed-rank. The proposed metric is derived from a
well-chosen Riemannian quotient geometry that generalizes the reductive
geometry of the positive cone and the associated natural metric. The resulting
Riemannian space has strong geometrical properties: it is geodesically
complete, and the metric is invariant with respect to all transformations that
preserve angles (orthogonal transformations, scalings, and pseudoinversion). A
meaningful approximation of the associated Riemannian distance is proposed,
that can be efficiently numerically computed via a simple algorithm based on
SVD. The induced mean preserves the rank, possesses the most desirable
characteristics of a geometric mean, and is easy to compute.


title: Approximate Multipartite Version of the Hajnal--Szemer\'edi Theorem

abstract:
  Let $q$ be a positve integer, and $G$ be a $q$-partite simple graph on $qn$
vertices, with $n$ vertices in each vertex class. Let $\delta={k_q \over
k_q+1}$, where $k_q=q+O(\log{q})$. If each vertex of $G$ is adjacent to at
least $\delta n$ vertices in each of the other vertex classes, $q$ is bounded
and $n$ is large enough, then $G$ has a $K_q$-factor.


title: Exclusive Diffractive Processes within the Dipole Picture

abstract:
  We discuss two different models for the impact parameter dependent dipole
cross section: one based on DGLAP evolution and the other inspired by the
Balitsky-Kovchegov equation. The parameters are determined from fits to data on
the total gamma* p cross section measured at HERA. The impact parameter
dependent saturation scale is extracted. Predictions are then confronted with
HERA data on exclusive diffractive vector meson production and deeply virtual
Compton scattering. Finally, predictions are given for the cross sections of
exclusive photoproduced J/psi and Upsilon mesons, and Z^0 bosons, expected at
the Tevatron and LHC.


title:
Solution of the Percus-Yevick equation for hard hyperspheres in even
  dimensions

abstract:
  We solve the Percus-Yevick equation in even dimensions by reducing it to a
set of simple integro-differential equations. This work generalizes an approach
we developed previously for hard discs. We numerically obtain both the pair
correlation function and the virial coefficients for a fluid of hyper-spheres
in dimensions $d=4,6$ and 8, and find good agreement with available exact
results and Monte-Carlo simulations. This paper confirms the alternating
character of the virial series for $d \ge 6$, and provides the first evidence
for an alternating character for $d=4$. Moreover, we show that this sign
alternation is due to the existence of a branch point on the negative real
axis. It is this branch point that determines the radius of convergence of the
virial series, whose value we determine explicitly for $d=4,6,8$. Our results
complement, and are consistent with, a recent study in odd dimensions [R.D.
Rohrmann et al., J. Chem. Phys. 129, 014510 (2008)].

categories: cond-mat.stat-mech cond-mat.dis-nn cond-mat.mtrl-sci cond-mat.soft


title:
What can we learn from the Interacting Boson Model in the limit of large
  boson numbers?

abstract:
  Over the years, studies of collective properties of medium and heavy mass
nuclei in the framework of the Interacting Boson Approximation (IBA) model have
focused on finite boson numbers, corresponding to valence nucleon pairs in
specific nuclei. Attention to large boson numbers has been motivated by the
study of shape/phase transitions from one limiting symmetry of IBA to another,
which become sharper in the large boson number limit, revealing in parallel
regularities previously unnoticed, although they survive to a large extent for
finite boson numbers as well. Several of these regularities will be discussed.
It will be shown that in all of the three limiting symmetries of the IBA [U(5),
SU(3), and O(6)], energies of 0+ states grow linearly with their ordinal
number. Furthermore, it will be proved that the narrow transition region
separating the symmetry triangle of the IBA into a spherical and a deformed
region is described quite well by the degeneracies E(0_2^+)=E(6_1^+), E(0_3^+)
=E(10_1^+), E(0_4^+)=E(14_1^+), the energy ratio E(6_1^+) /E(0_2^+) turning out
to be a simple, empirical, easy-to-measure effective order parameter,
distinguishing between first- and second-order transitions. The energies of 0+
states near the point of the first order shape/phase transition between U(5)
and SU(3) will be shown to grow as n(n+3), where n is their ordinal number, in
agreement with the rule dictated by the relevant critical point symmetries
studied in the framework of special solutions of the Bohr Hamiltonian. The
underlying dynamical and quasi-dynamical symmetries are also discussed.


title: Deep Westerbork observations of Abell 2256 at 350 MHz

abstract:
  Deep polarimetric Westerbork observations of the galaxy cluster Abell 2256
are presented, covering a frequency range of 325-377 MHz. The central halo
source has a diameter of the order of 1.2 Mpc (18'), which is somewhat larger
than at 1.4 GHz. With alpha=-1.61+/-0.04, the halo spectrum between 1.4 GHz and
22.25 MHz is less steep than previously thought. The centre of the ultra steep
spectrum source in the eastern part of the cluster exhibits a spectral break
near 400 MHz. It is estimated to be at least 51 million years old, but possibly
older than 125 million years. A final measurement requires observations in the
10-150 MHz range. It remains uncertain whether the source is a radio tail of
Fabricant galaxy 122, situated in the northeastern tip of the source. Faraday
rotation measure synthesis revealed no polarized flux at all in the cluster.
The polarization fraction of the brightest parts of the relic area is less than
1%. The RM-synthesis nevertheless revealed 9 polarized sources in the field
enabling an accurate measurement of the Galactic Faraday rotation (-33+/-2 rad
m^{-2} in front of the relic). Based on its depolarization on longer
wavelengths, the line-of-sight magnetic field in relic filament G is estimated
to be between 0.02 and 2 uG. A value of 0.2 uG appears most reasonable given
the currently available data.


title: The cosmological BCS mechanism and the Big Bang Singularity

abstract:
  We provide a novel mechanism that resolves the Big Bang Singularity present
in FRW space-times without the need for ghost fields. Building on the fact that
a four-fermion interaction arises in General Relativity when fermions are
covariantly coupled, we show that at early times the decrease in scale factor
enhances the correlation between pairs of fermions. This enhancement leads to a
BCS-like condensation of the fermions and opens a gap dynamically driving the
Hubble parameter $H$ to zero and results in a non-singular bounce, at least in
some special cases.


title: The Phase Diagram of Hadronic Matter

abstract:
  We interpret the phase structure of hadronic matter in terms of the basic
dynamical and geometrical features of hadrons. Increasing the density of
constituents of finite spatial extension, by increasing the temperature T or
the baryochemical potential mu, eventually "fills the box" and eliminates the
physical vacuum. We determine the corresponding transition as function of T and
mu through percolation theory. At low baryon density, this means a fusion of
overlapping mesonic bags to one large bag, while at high baryon density, hard
core repulsion restricts the spatial mobility of baryons. As a consequence,
there are two distinct limiting regimes for hadronic matter. We compare our
results to those from effective chiral model studies.


title: New triple systems in the RasTyc sample of stellar X-ray sources

abstract:
  During the study of a large set of late-type stellar X-ray sources, we
discovered a large fraction of multiple systems. In this paper we investigate
the orbital elements and kinematic properties of three new spectroscopic triple
systems as well as spectral types and astrophysical parameters (T_eff, log g,
vsin i, log N(Li)) of their components. We conducted follow-up optical
observations, both photometric and spectroscopic at high resolution, of these
systems. We used a synthetic approach and the cross-correlation method to
derive most of the stellar parameters. We estimated reliable radial velocities
and deduced the orbital elements of the inner binaries. The comparison of the
observed spectra with synthetic composite ones, obtained as the weighted sum of
three spectra of non-active reference stars, allowed us to determine the
stellar parameters for each component of these systems. We found all are only
composed of main sequence stars. These three systems are certainly stable
hierarchical triples composed of short-period inner binaries plus a tertiary
component in a long-period orbit. From their kinematics and/or Lithium content,
these systems result to be fairly young.


title: Mesoscopic lattice Boltzmann modeling of flowing soft systems

abstract:
  A mesoscopic multi-component lattice Boltzmann model with short-range
repulsion between different species and short/mid-ranged attractive/repulsive
interactions between like-molecules is introduced. The interplay between these
composite interactions gives rise to a rich configurational dynamics of the
density field, exhibiting many features of disordered liquid dispersions
(micro-emulsions) and soft-glassy materials, such as long-time relaxation due
to caging effects, anomalous enhanced viscosity, ageing effects under moderate
shear and flow above a critical shear rate.


title: Disk Truncation and Planet Formation in gamma Cephei

abstract:
  The $\gamma$ Cephei system is one of the most closely bound binary planet
hosts known to date. The companion ($\gamma$ Cep B) to the planet-hosting star
($\gamma$ Cep A) should have truncated any protoplanetary disk around $\gamma$
Cep A, possibly limiting planet formation in the disk. We explore this problem
by calculating the truncation radii of protoplanetary disk models around
$\gamma$ Cep A to determine whether or not there is sufficient material
remaining in the disk to form a planet. We vary the accretion rate and
viscosity parameter of the disk models to cover a range of reasonable
possibilities for the disks properties and determine that for accretion rates
of $\geq 10^{-7}$ M$_{\sun}$/yr and low viscosity parameter, sufficient
material in gas and solids exist for planet formation via core accretion to be
possible. Disk instability is less favored, as this can only occur in the most
massive disk model with an extremely high accretion rate.


title: Dynamics and self-similarity in min-driven clustering

abstract:
  We study a mean-field model for a clustering process that may be described
informally as follows. At each step a random integer $k$ is chosen with
probability $p_k$, and the smallest cluster merges with $k$ randomly chosen
clusters. We prove that the model determines a continuous dynamical system on
the space of probability measures supported in $(0,\infty)$, and we establish
necessary and sufficient conditions for approach to self-similar form. We also
characterize eternal solutions for this model via a Levy-Khintchine formula.
The analysis is based on an explicit solution formula discovered by Gallay and
Mielke, extended using a careful choice of time scale.


title: Deeply virtual Compton scattering on a virtual pion target

abstract:
  We study deeply virtual Compton scattering on a virtual pion that is emitted
by a proton. Using a range of models for the generalized parton distributions
of the pion, we evaluate the cross section, as well as the beam spin and beam
charge asymmetries in the leading-twist approximation. Studying Compton
scattering on the pion in suitable kinematics puts high demands on both beam
energy and luminosity, and we find that the corresponding requirements will
first be met after the energy upgrade at Jefferson Laboratory. As a by-product
of our study, we construct a parameterization of pion generalized parton
distributions that has a non-trivial interplay between the x and t dependence
and is in good agreement with form factor data and lattice calculations.


title:
Source separation techniques for characterising cosmic ray transients
  from neutron monitor networks

abstract:
  The analysis of weak variations in the energetic particle flux, as detected
by neutron or muon monitors, can often be considerably improved by analysing
data from monitor networks and thereby exploiting the spatial coherence of the
flux. We present a statistical framework for carrying out such an analysis and
discuss its physical interpretation. Two other applications are also presented:
filling data gaps and removing trends. This study focuses on the method and its
various uses.


title:
Circumnuclear HI disks in radio galaxies: The case of Cen A and B2
  0258+35

abstract:
  New HI observations of the nearby radio-loud galaxies Centaurus A and B2
0258+35 show broad absorption (Delta_v=400km/s) against the unresolved nuclei.
Both sources belong to the cases where blue- and redshifted absorption is
observed at the same time. In previous Cen A observations only a relative
narrow range of redshifted absorption was detected. We show that the data
suggest in both cases the existence of a circumnuclear disk. For Cen A the
nuclear absorption might be the atomic counterpart of the molecular
circumnuclear disk that is seen in CO and H_2. Higher resolution observations
are now needed to locate the absorption and to further investigate the
structure and kinematics of the central region of the AGN and the way the AGN
are fueled.


title:
Locating the inner edge of neutron star crust using terrestrial nuclear
  laboratory data

abstract:
  Within both dynamical and thermodynamical approaches using the equation of
state for neutron-rich nuclear matter constrained by the recent isospin
diffusion data from heavy-ion reactions in the same sub-saturation density
range as the neutron star crust, the density and pressure at the inner edge
separating the liquid core from the solid crust of neutron stars are determined
to be 0.040 fm$^{-3}$ $\leq \rho_{t}\leq 0.065$ fm$^{-3}$ and 0.01 MeV/fm$^{3}$
$\leq P_{t}\leq 0.26$ MeV/fm$^{3}$, respectively. These together with the
observed minimum crustal fraction of the total moment of inertia allow us to
set a new limit for the radius of the Vela pulsar significantly different from
the previous estimate. It is further shown that the widely used parabolic
approximation to the equation of state of asymmetric nuclear matter leads
systematically to significantly higher core-crust transition densities and
pressures, especially with stiffer symmetry energy functionals.


title:
An Image-Based Sensor System for Autonomous Rendez-Vous with
  Uncooperative Satellites

abstract:
  In this paper are described the image processing algorithms developed by
SENER, Ingenieria y Sistemas to cope with the problem of image-based,
autonomous rendez-vous (RV) with an orbiting satellite. The methods developed
have a direct application in the OLEV (Orbital Life Extension Extension
Vehicle) mission. OLEV is a commercial mission under development by a
consortium formed by Swedish Space Corporation, Kayser-Threde and SENER, aimed
to extend the operational life of geostationary telecommunication satellites by
supplying them control, navigation and guidance services. OLEV is planned to
use a set of cameras to determine the angular position and distance to the
client satellite during the complete phases of rendez-vous and docking, thus
enabling the operation with satellites not equipped with any specific
navigational aid to provide support during the approach. The ability to operate
with un-equipped client satellites significantly expands the range of
applicability of the system under development, compared to other competing
video technologies already tested in previous spatial missions, such as the
ones described here below.


title:
FiEstAS sampling -- a Monte Carlo algorithm for multidimensional
  numerical integration

abstract:
  This paper describes a new algorithm for Monte Carlo integration, based on
the Field Estimator for Arbitrary Spaces (FiEstAS). The algorithm is discussed
in detail, and its performance is evaluated in the context of Bayesian
analysis, with emphasis on multimodal distributions with strong parameter
degeneracies. Source code is available upon request.


title:
Higgs and Z-boson FCNC decays correlated with B-meson decays in littlest
  Higgs model with T-parity

abstract:
  In the littlest Higgs model with T-parity (LHT) new flavor-changing
interactions between mirror fermions and the Standard Model (SM) fermions can
induce various FCNC decays for B-mesons, Z-boson and Higgs boson. Since all
these decays induced in the LHT model are correlated, we in this work perform a
collective study for these decays, namely the Z-boson decay Z -> b s_bar, the
Higgs boson decay h -> b s_bar, and the B-meson decays B -> X_s \gamma, B_s ->
\mu^+\mu^- and B -> X_s \mu^+ \mu^-. We find that under the current
experimental constraints from the B-decays, the branching ratios of both Z -> b
s_bar and h -> b s_bar can still deviate from the SM predictions significantly.
In the parameter space allowed by the B-decays, the branching ratio of Z -> b
s_bar can be enhanced to 10^{-7} (about one order above the SM prediction)
while h -> b s_bar can be much suppressed relative to the SM prediction (about
one order below the SM prediction).


title: The Nonperturbative Quantum de Sitter Universe

abstract:
  The dynamical generation of a four-dimensional classical universe from
nothing but fundamental quantum excitations at the Planck scale is a
long-standing challenge to theoretical physicists. A candidate theory of
quantum gravity which achieves this goal without invoking exotic ingredients or
excessive fine-tuning is based on the nonperturbative and
background-independent technique of Causal Dynamical Triangulations. We
demonstrate in detail how in this approach a macroscopic de Sitter universe,
accompanied by small quantum fluctuations, emerges from the full gravitational
path integral, and how the effective action determining its dynamics can be
reconstructed uniquely from Monte Carlo data. We also provide evidence that it
may be possible to penetrate to the sub-Planckian regime, where the Planck
length is large compared to the lattice spacing of the underlying
regularization of geometry.


title:
Schrodinger dynamics as a two-phase conserved flow: an alternative
  trajectory construction of quantum propagation

abstract:
  It is shown that the Schrodinger equation can be cast in the form of two
coupled real conservation equations, in Euclidean spacetime in the free case
and in a five-dimensional Eisenhart geometry in the presence of an external
potential. This implies a novel two-phase quantum hydrodynamic model whose
Lagrangian picture provides an exact scheme to calculate the time-dependent
wavefunction from a continuum of deterministic trajectories where two points
are linked by at most two orbits. Properties of the model are examined,
including the appearance of entangled trajectories in separable states.
Wavefunction constructions employing alternative two-phase models are proposed.


title:
Assigning confidence to inspiral gravitational wave candidates with
  Bayesian model selection

abstract:
  Bayesian model selection provides a powerful and mathematically transparent
framework to tackle hypothesis testing, such as detection tests of
gravitational waves emitted during the coalescence of binary systems using
ground-based laser interferometers. Although its implementation is
computationally intensive, we have developed an efficient probabilistic
algorithm based on a technique known as nested sampling that makes Bayesian
model selection applicable to follow-up studies of candidate signals produced
by on-going searches of inspiralling compact binaries. We discuss the
performance of this approach, in terms of "false alarm rate" and "detection
probability" of restricted second post-Newtonian inspiral waveforms from
non-spinning compact objects in binary systems. The results confirm that this
approach is a viable tool for detection tests in current searches for
gravitational wave signals.


title:
Taxes in a simple wealth distribution model by inelastically scattering
  particles

abstract:
  In this work we use an inelastic scattering process of particles to propose a
model able to reproduce the salient features of the wealth distribution in an
economy by including taxes to each trading process and redistributing that
collected among the population according to a given criterion. Additionally, we
show that different optimal levels of taxes may exist depending on the
redistribution criterion.


title:
Dissociation of Relativistic Projectiles with the Continuum-Discretized
  Coupled-Channels Method

abstract:
  Relativistic effects in the breakup of weakly-bound nuclei at intermediate
energies are studied by means of the continuum-discretized coupled-channels
method with eikonal approximation. Nuclear coupling potentials with Lorentz
contraction are newly included and those effects on breakup cross sections are
investigated. We show that relativistic corrections lead to larger breakup
cross sections. Coupled-channel effects on the breakup cross sections are also
discussed.


title:
Colored scalar particles production in $pp$-collisions and possible mass
  limits for scalar gluons from future LHC data

abstract:
  Cross sections of the colored scalar particle production in $pp$-collisions
are calculated and differential and total cross sections of the corresponding
parton subprocesses are obtained. The total cross section of scalar gluon
production in $pp$-collisions at the LHC is estimated and the dominant decays
of scalar gluons are discussed. The production cross section of scalar gluons
$F$ with masses $m_F\lesssim 1300$ GeV is shown to be sufficient for the
effective production of these particles at the LHC.


title: Deconstructing active region AR10961 using STEREO, Hinode, TRACE & SOHO

abstract:
  Active region 10961 was observed over a five day period (2007 July 2-6) by
instrumentation on-board STEREO, Hinode, TRACE and SOHO. As it progressed from
Sun centre to the solar limb a comprehensive analysis of the EUV, X-ray and
magnetic field data reveals clearly observable changes in the global nature of
the region.
  Temperature analyses undertaken using STEREO EUVI double filter ratios and
XRT single and combined filter ratios demonstrate an overall cooling of the
region from between 1.6 - 3.0 MK to 1.0 - 2.0 MK over the five days. Similarly,
Hinode EIS density measurements show a corresponding increase in density of
27%. Moss, cool (1 MK) outer loop areas and hotter core loop regions were
examined and compared with potential magnetic field extrapolations from SOHO
MDI magnetogram data. In particular it was found that the potential field model
was able to predict the structure of the hotter X-ray loops and that the larger
cool loops seen in 171 Angstrom images appeared to follow the separatrix
surfaces. The reasons behind the high density moss regions only observed on one
side of the active region are examined further.


title:
Determination of anisotropic Hc2 up to 60 T in (Ba0.55K0.45)Fe2As2
  single crystals

abstract:
  The radio frequency penetration depth was measured in the superconductor
(Ba$_{0.55}$K$_{0.45}$)Fe$_{2}$As$_{2}$ under pulsed magnetic fields extending
to 60 tesla and down to 14 K. Using these data we are able to infer a
$H_{c2}(T)$, $H-T$ phase diagram, for applied fields parallel and perpendicular
to the crystallographic c-axis. The upper critical field curvature is different
for the respective orientations but they each remain positive down to 14 K. The
upper critical field anisotropy is moderate, $\approx 3.5$ close to $T_c$, and
drops with the decrease of temperature, reaching $\approx 1.2$ at $14 K$. These
data and analysis indicate that (i) (Ba$_{0.55}$K$_{0.45}$)Fe$_{2}$As$_{2}$
anisotropy diminishes with temperature and has an unusual temperature
dependence, (ii) $H_{c2} (T=0)$ for this compound may easily approach fields of
75 tesla.


title: The nature of the magnetic order in Ca3Co2O6

abstract:
  We present a detailed powder and single crystal neutron diffraction study of
the spin chain compound Ca3Co2O6. Below 25 K, the system orders magnetically
with a modulated partially disordered antiferromagnetic structure. We give a
description of the magnetic interactions in the system which is consistent with
this magnetic structure. Our study also reveals that the long-range magnetic
order co-exists with a shorter range order with a correlation length scale of
180 A in the ab plane. Remarkably, on cooling, the volume of material
exhibiting short range order increases at the expense of the long-range order.


title: Studies on the Role of Entanglement in Mixed-state Quantum Computation

abstract:
  In this thesis, I look at the role of quantum entanglement in mixed-state
quantum computation. The model we consider is the DQC1 or `power of one qubit'
model. I show that there is minimal bipartite entanglement in a typical
instance of the DQC1 circuit and even put an upper bound on the possible amount
of entanglement. This limited amount of entanglement, however, does not imply
that the system is classically simulatable. A matrix product state (MPS)
algorithm for a typical instance of the DQC1 system requires exponential
classical resources. This exposes a gap between the amount of entanglement and
the amount of purely nonclassical correlations in a quantum system. This gap, I
suggest, can be filled by quantum discord. I calculate it in a typical instance
of the DQC1 circuit and find that the amount of discord is a constant fraction
of the maximum possible discord for a system of that size. This allows an
interpretation of quantum discord as the resource that drives mixed-state
quantum computation. I also study quantum discord as a quantity of independent
interest. Its role in the phenomenon of entanglement distribution is studied
through an easily comprehensible example.
  This thesis also contains discussions on the relation between the complexity
classes P, BQP and DQC1. Additional material is presented on the connections
between the DQC1 model, Jones polynomials and statistical mechanics. The thesis
concludes with a discussion of a few open problems related to the DQC1 model,
the quantum discord and their scope in quantum information science.


title: Experimental Summary Moriond QCD 2008

abstract:
  2008 was a vintage year for the QCD Moriond meeting. Plenty of new data from
Tevatron, HERA, B-Factories and other experiments have been reported. Some
brand new results became public just before or even during the conference. A
few new hints for New Physics came up in Winter 2008, but these await further
scrutiny. This paper is the write-up of the experimental summary talk given at
the Moriond QCD March meeting.


title: Shape/Phase Transitions and Critical Point Symmetries in Atomic Nuclei

abstract:
  Shape/phase transitions in atomic nuclei have first been discovered in the
framework of the Interacting Boson Approximation (IBA) model. Critical point
symmetries appropriate for nuclei at the transition points have been introduced
as special solutions of the Bohr Hamiltonian, stirring the introduction of
additional new solutions describing wide ranges of nuclei. A short review of
these recent developments will be attempted.


title:
Search for the Higgs boson produced with $Z \to \ell^+\ell^-$ in
  $p\bar{p}$ collisions at $\sqrt{s}=$ 1.96 TeV

abstract:
  We present a search for the Higgs boson in the process $q\bar{q} \to ZH \to
\ell^+\ell^- b\bar{b}$. The analysis uses an integrated luminosity of 1
fb$^{-1}$ of $p\bar{p}$ collisions produced at $\sqrt{s} =$ 1.96 TeV and
accumulated by the upgraded Collider Detector at Fermilab (CDF II). We employ
artificial neural networks both to correct jets mismeasured in the calorimeter,
and to distinguish the signal kinematic distributions from those of the
background. We see no evidence for Higgs boson production, and set 95% CL upper
limits on $\sigma_{ZH} \cdot {\cal B}(H \to b\bar{b}$), ranging from 1.5 pb to
1.2 pb for a Higgs boson mass ($m_H$) of 110 to 150 GeV/$c^2$.


title: Fast, exact (but unstable) spin spherical harmonic transforms

abstract:
  In many applications data are measured or defined on a spherical manifold;
spherical harmonic transforms are then required to access the frequency content
of the data. We derive algorithms to perform forward and inverse spin spherical
harmonic transforms for functions of arbitrary spin number. These algorithms
involve recasting the spin transform on the two-sphere S^2 as a Fourier
transform on the two-torus T^2. Fast Fourier transforms are then used to
compute Fourier coefficients, which are related to spherical harmonic
coefficients through a linear transform. By recasting the problem as a Fourier
transform on the torus we appeal to the usual Shannon sampling theorem to
develop spherical harmonic transforms that are theoretically exact for
band-limited functions, thereby providing an alternative sampling theorem on
the sphere. The computational complexity of our forward and inverse spin
spherical harmonic transforms scale as O(L^3) for any arbitrary spin number,
where L is the harmonic band-limit of the spin function on the sphere.
Numerical experiments are performed and unfortunately the forward transform is
found to be unstable for band-limits above L~32. The instability is due to the
poorly conditioned linear system relating Fourier and spherical harmonic
coefficients. The inverse transform is expected to be stable, although it is
not possible to verify this hypothesis.


title: Information filtering based on transferring similarity

abstract:
  In this Brief Report, we propose a new index of user similarity, namely the
transferring similarity, which involves all high-order similarities between
users. Accordingly, we design a modified collaborative filtering algorithm,
which provides remarkably higher accurate predictions than the standard
collaborative filtering. More interestingly, we find that the algorithmic
performance will approach its optimal value when the parameter, contained in
the definition of transferring similarity, gets close to its critical value,
before which the series expansion of transferring similarity is convergent and
after which it is divergent. Our study is complementary to the one reported in
[E. A. Leicht, P. Holme, and M. E. J. Newman, Phys. Rev. E {\bf 73} 026120
(2006)], and is relevant to the missing link prediction problem.


title: Rank functions on rooted tree quivers

abstract:
  The free abelian group R(Q) on the set of indecomposable representations of a
quiver Q, over a field K, has a ring structure where the multiplication is
given by the tensor product. We show that if Q is a rooted tree (an oriented
tree with a unique sink), then the ring $R(Q)_{red}$ is a finitely generated
$\Z$-module (here $R(Q)_{red}$ is the ring R(Q) modulo the ideal of all
nilpotent elements). We will describe the ring $R(Q)_{red}$ explicitly, by
studying functors from the category Rep(Q) of representations of Q over K to
the category of finite dimensional K-vector spaces. We also present an open
problem for future direction.


title: Smooth metrics on jet bundles and applications

abstract:
  Following a suggestion made by J.-P. Demailly, for each $k\ge 1$, we endow,
by an induction process, the $k$-th (anti)tautological line bundle $\mathcal
O_{X_k}(1)$ of an arbitrary complex directed manifold $(X,V)$ with a natural
smooth hermitian metric. Then, we compute recursively the Chern curvature form
for this metric, and we show that it depends (asymptotically -- in a sense to
be specified later) only on the curvature of $V$ and on the structure of the
fibration $X_k\to X$. When $X$ is a surface and $V=T_X$, we give explicit
formulae to write down the above curvature as a product of matrices. As an
application, we obtain a new proof of the existence of global invariant jet
differentials vanishing on an ample divisor, for $X$ a minimal surface of
general type whose Chern classes satisfy certain inequalities, without using a
strong vanishing theorem of Bogomolov.


title:
Analysis of a stochastic chemical system close to a SNIPER bifurcation
  of its mean-field model

abstract:
  A framework for the analysis of stochastic models of chemical systems for
which the deterministic mean-field description is undergoing a saddle-node
infinite period (SNIPER) bifurcation is presented. Such a bifurcation occurs
for example in the modelling of cell-cycle regulation. It is shown that the
stochastic system possesses oscillatory solutions even for parameter values for
which the mean-field model does not oscillate. The dependence of the mean
period of these oscillations on the parameters of the model (kinetic rate
constants) and the size of the system (number of molecules present) is studied.
Our approach is based on the chemical Fokker-Planck equation. To get some
insights into advantages and disadvantages of the method, a simple
one-dimensional chemical switch is first analyzed, before the chemical SNIPER
problem is studied in detail. First, results obtained by solving the
Fokker-Planck equation numerically are presented. Then an asymptotic analysis
of the Fokker-Planck equation is used to derive explicit formulae for the
period of oscillation as a function of the rate constants and as a function of
the system size.


title: Echo Phenomena in Large Systems of Coupled Oscillators

abstract:
  As exemplified by the Kuramoto model, large systems of coupled oscillators
may undergo a transition to phase coherence with increasing coupling strength.
It is shown that below the critical coupling strength for this transition such
systems may be expected to exhibit `echo' phenomena: a stimulation by two
successive pulses separated by a time interval tau leads to the spontaneous
formation of response pulses at a time tau, 2 tau, 3 tau ..., after the second
stimulus pulse. Analysis of this phenomenon, as well as illustrative numerical
experiments, are presented. The theoretical significance and potential uses of
echoes in such systems are discussed.