title:
Successful Leptogenesis in SO(10) Unification with a Left-Right
  Symmetric Seesaw Mechanism

abstract:
  We study thermal leptogenesis in a broad class of supersymmetric SO(10)
models with a left-right symmetric seesaw mechanism, taking into account
flavour effects and the contribution of the next-to-lightest right-handed
neutrino supermultiplet. Assuming M_D = M_u and a normal hierarchy of light
neutrino masses, we show that four out of the eight right-handed neutrino mass
spectra reconstructed from low-energy neutrino data can lead to successful
leptogenesis with a reheating temperature in the (10^9 - 10^10) GeV range. In
the remaining four solutions, leptogenesis is dominated by N_2 decays, as in
the type I seesaw case. We find that some of these spectra can generate the
observed baryon asymmetry for reheating temperatures above 10^10 GeV, in
contrast to the type I case. Together with flavour effects, an accurate
description of charged fermion masses turns out to be a crucial ingredient in
the analysis.


title: Diversity-Multiplexing Tradeoffs in MIMO Relay Channels

abstract:
  A multi-hop relay channel with multiple antenna terminals in a quasi-static
slow fading environment is considered. For both full-duplex and half-duplex
relays the fundamental diversity-multiplexing tradeoff (DMT) is analyzed. It is
shown that, while decode-and-forward (DF) relaying achieves the optimal DMT in
the full-duplex relay scenario, the dynamic decode-and-forward (DDF) protocol
is needed to achieve the optimal DMT if the relay is constrained to half-duplex
operation. For the latter case, static protocols are considered as well, and
the corresponding achievable DMT performance is characterized.


title: Constraining the D3-brane effective action

abstract:
  We consider higher derivative corrections of the type D^{2k} R^2 in the
effective action of the D3-brane with trivial normal bundle. Based on the
perturbative disc and annulus amplitudes, and constraints of supersymmetry and
duality, we argue that these interactions are protected, at least for small
values of k. Their coefficient functions receive only a finite number of
perturbative contributions, and non-perturbative contributions from
D-instantons. We propose expressions for these modular forms for low values of
k.


title:
Does The Addition of a Duration Improve the L_iso - E_peak Relation For
  Gamma-Ray Bursts?

abstract:
  Firmani et al. proposed a new Gamma Ray Burst (GRB) luminosity relation that
showed a significant improvement over the L_iso-E_peak relation. The new
proposed relation simply modifies the E_peak value by multiplying it by a power
of T_0.45, where T_0.45 is a particular measure of the GRB duration. We begin
by reproducing the results of Firmani for his 19 bursts. We then test the
Firmani relation for the same 19 bursts except that we use independently
measured values for L_iso, T_0.45, and E_peak, and we find that the relation
deteriorates substantially. We further test the relation by using 60 GRBs with
measured spectroscopic redshifts, and find a relation that has a comparable
scatter as the original L_iso-E_peak relation. That is, a much larger sample of
bursts does not reproduce the small scatter as reported by Firmani et al.
Finally, we investigate whether the Firmani relation is improved by the use of
any of 32 measures of duration in place of T_0.45. The quality of each
alternative duration measure is evaluated with the root mean square of the
scatter between the observed and fitted logarithmic Liso values. Although we
find some durations yield slightly better results than T_0.45, the differences
between the duration measures are minimal. We find that the addition of a
duration does not add any significant improvement to the L_iso-E_peak relation.
We also present a simple and direct derivation of the Firmani relation from
both the L_iso-E_peak and Amati relations. In all we conclude that the Firmani
relation neither has an independent existence nor does it provide any
significant improvement on previously known relations that are simpler.


title:
Hyperbolic conservation laws on the sphere. A geometry-compatible finite
  volume scheme

abstract:
  We consider entropy solutions to the initial value problem associated with
scalar nonlinear hyperbolic conservation laws posed on the two-dimensional
sphere. We propose a finite volume scheme which relies on a web-like mesh made
of segments of longitude and latitude lines. The structure of the mesh allows
for a discrete version of a natural geometric compatibility condition, which
arose earlier in the well-posedness theory established by Ben-Artzi and
LeFloch. We study here several classes of flux vectors which define the
conservation law under consideration. They are based on prescribing a suitable
vector field in the Euclidean three-dimensional space and then suitably
projecting it on the sphere's tangent plane; even when the flux vector in the
ambient space is constant, the corresponding flux vector is a non-trivial
vector field on the sphere. In particular, we construct here "equatorial
periodic solutions", analogous to one-dimensional periodic solutions to
one-dimensional conservation laws, as well as a wide variety of stationary
(steady state) solutions. We also construct "confined solutions", which are
time-dependent solutions supported in an arbitrarily specified subdomain of the
sphere. Finally, representative numerical examples and test-cases are
presented.


title:
Constraining Gravitational and Cosmological Parameters with
  Astrophysical Data

abstract:
  We use astrophysical data to shed light on fundamental physics by
constraining parametrized theoretical cosmological and gravitational models.
  Gravitational parameters are those constants that parametrize possible
departures from Einstein's general theory of relativity. We develop a general
framework to describe torsion in the spacetime around the Earth, and show that
certain observables of the Gravity Probe B experiment can be computed in this
framework. We also search for viable theories of gravity where the Ricci scalar
R in the Lagrangian is replaced by an arbitrary function f(R). Making use of
the equivalence between such theories and scalar-tensor gravity, we find that
models can be made consistent with solar system constraints either by giving
the scalar a high mass or by exploiting the so-called Chameleon Effect.
  Cosmology can successfully describe the evolution of our universe using six
or more adjustable cosmological parameters. There is growing interest in using
3-dimensional neutral hydrogen mapping with the redshifted 21 cm line as a
cosmological probe. We quantify how the precision with which cosmological
parameters can be measured depends on a broad range of assumptions. We present
an accurate and robust method for measuring cosmological parameters that
exploits the fact that the ionization power spectra are rather smooth functions
that can be accurately fit by 7 phenomenological parameters. We find that a
future square kilometer array optimized for 21 cm tomography could have great
potential, improving the sensitivity to spatial curvature and neutrino masses
by up to two orders of magnitude, to Delta-Omega_k ~ 0.0002 and Delta-m_nu ~
0.007 eV, and giving a 4 sigma detection of the spectral index running
predicted by the simplest inflation models.


title:
Lubrication approximation for micro-particles moving along parallel
  walls

abstract:
  Lubrication expressions for the friction coefficients of a spherical particle
moving in a fluid between and along two parallel solid walls are explicitly
evaluated in the low-Reynolds-number regime. They are used to determine
lubrication expression for the particle free motion under an ambient Poiseuille
flow. The range of validity and the accuracy of the lubrication approximation
is determined by comparing with the corresponding results of the accurate
multipole procedure. The results are applicable for thin, wide and long
microchannels, or quasi-two-dimensional systems.


title:
Why many theories of shock waves are necessary. Convergence error in
  formally path-consistent schemes

abstract:
  We are interested in nonlinear hyperbolic systems in nonconservative form
arising in fluid dynamics, and, for solutions containing shock waves, we
investigate the convergence of finite difference schemes applied to such
systems. According to Dal Maso, LeFloch, and Murat's theory, a shock wave
theory for a given nonconservative system requires prescribing a priori a
family of paths in the phase space. In the present paper, we consider schemes
that are formally consistent with a given family of paths, and we investigate
their limiting behavior as the mesh is refined. We generalize to systems a
property established earlier by Hou and LeFloch for scalar conservation laws,
and we prove that nonconservative schemes generate, at the level of the
limiting hyperbolic system, a "convergence error" source-term which, provided
the total variation of the approximations remains uniformly bounded, is a
locally bounded measure. We discuss the role of the equivalent equation
associated with a difference scheme; here, the distinction between scalar
equations and systems appears most clearly since, for systems, the equivalent
equation of a scheme that is formally path-consistent depends upon the
prescribed family of paths. The core of this paper is devoted to investigate
numerically the approximation of several models arising in fluid dynamics. For
systems having nonconservative products associated with linearly degenerate
characteristic fields, the convergence error vanishes. For some other models,
this measure is evaluated very accurately, especially by plotting the shock
curves associated with each scheme under consideration.


title:
Seiberg--Witten maps for $\boldsymbol{SO(1,3)}$ gauge invariance and
  deformations of gravity

abstract:
  A family of diffeomorphism-invariant Seiberg--Witten deformations of gravity
is constructed. In a first step Seiberg--Witten maps for an SO(1,3) gauge
symmetry are obtained for constant deformation parameters. This includes maps
for the vierbein, the spin connection and the Einstein--Hilbert Lagrangian. In
a second step the vierbein postulate is imposed in normal coordinates and the
deformation parameters are identified with the components $\theta^{\mu\nu}(x)$
of a covariantly constant bivector. This procedure gives for the classical
action a power series in the bivector components which by construction is
diffeomorphism-invariant. Explicit contributions up to second order are
obtained. For completeness a cosmological constant term is included in the
analysis. Covariant constancy of $ \theta^{\mu\nu}(x) $, together with the
field equations, imply that, up to second order, only four-dimensional metrics
which are direct sums of two two-dimensional metrics are admissible, the
two-dimensional curvatures being expressed in terms of $\theta^{\mu\nu}$. These
four-dimensional metrics can be viewed as a family of deformed emergent
gravities.


title:
Biexcitons in two-dimensional systems with spatially separated electrons
  and holes

abstract:
  The binding energy and wavefunctions of two-dimensional indirect biexcitons
are studied analytically and numerically. It is proven that stable biexcitons
exist only when the distance between electron and hole layers is smaller than a
certain critical threshold. Numerical results for the biexciton binding
energies are obtained using the stochastic variational method and compared with
the analytical asymptotics. The threshold interlayer separation and its
uncertainty are estimated. The results are compared with those obtained by
other techniques, in particular, the diffusion Monte-Carlo method and the
Born-Oppenheimer approximation.


title: Explicit form of the Mann-Marolf surface term in (3+1) dimensions

abstract:
  The Mann-Marolf surface term is a specific candidate for the "reference
background term" that is to be subtracted from the Gibbons-Hawking surface term
in order make the total gravitational action of asymptotically flat spacetimes
finite. That is, the total gravitational action is taken to be:
  (Einstein-Hilbert bulk term) + (Gibbons-Hawking surface term) - (Mann-Marolf
surface term).
  As presented by Mann and Marolf, their surface term is specified implicitly
in terms of the Ricci tensor of the boundary. Herein I demonstrate that for the
physically interesting case of a (3+1) dimensional bulk spacetime, the
Mann-Marolf surface term can be specified explicitly in terms of the Einstein
tensor of the (2+1) dimensional boundary.


title:
Action and Hamiltonians in higher dimensional general relativity: First
  order framework

abstract:
  We consider $d>4$-dimensional space-times which are asymptotically flat at
spatial infinity and show that, in the first order framework, the action
principle is well-defined \emph{without the need of infinite counter terms.} It
naturally leads to a covariant phase space in which the Hamiltonians generating
asymptotic symmetries provide the total energy-momentum and angular momentum of
the isolated system. This work runs parallel to our previous analysis in four
dimensions \cite{aes}. The higher dimensional analysis is in fact simpler
because of absence of logarithmic and super translation ambiguities.


title: Drug delivery with carbon nanotubes for in vivo cancer treatment

abstract:
  Chemically functionalized single-walled carbon nanotubes (SWNTs) have shown
promise in tumor targeted accumulation in mice and exhibit biocompatibility,
excretion and little toxicity. Here, we demonstrate in-vivo SWNT drug delivery
for tumor suppression in mice. We conjugate paclitaxel (PTX), a widely used
cancer chemotherapy drug to branched polyethylene-glycol (PEG) chains on SWNTs
via a cleavable ester bond to obtain a water soluble SWNT-paclitaxel conjugate
(SWNT-PTX). SWNT-PTX affords higher efficacy in suppressing tumor growth than
clinical Taxol in a murine 4T1 breast-cancer model, owing to prolonged blood
circulation and 10-fold higher tumor PTX uptake by SWNT delivery likely through
enhanced permeability and retention (EPR). Drug molecules carried into the
reticuloendothelial system are released from SWNTs and excreted via biliary
pathway without causing obvious toxic effects to normal organs. Thus, nanotube
drug delivery is promising for high treatment efficacy and minimum side effects
for future cancer therapy with low drug doses.


title: A Four-site Higgsless Model with Wavefunction Mixing

abstract:
  Motivated by models of holographic technicolor, we discuss a four-site
deconstructed Higgsless model with nontrivial wavefunction mixing. We compute
the spectrum of the model, the electroweak triple gauge boson vertices, and,
for brane-localized fermions, the electroweak parameters to O(M^2_W/M^2_rho).
We discuss the conditions under which "S" vanishes (even for brane-localized
fermions) and the (distinct but overlapping) conditions under which the
phenomenologically interesting decay a_1 to W gamma is non-zero and suppressed
by only one power of M_W/M_rho.


title:
Test of Particle-Assisted Tunneling for Strongly Interacting Fermions in
  an Optical Superlattice

abstract:
  Fermions in an optical lattice near a wide Feshbach resonance are expected to
be described by an effective Hamiltonian of the general Hubbard model with
particle-assisted tunneling rates resulting from the strong atomic interaction
[Phys. Rev. Lett. 95, 243202 (2005)]. Here, we propose a scheme to
unambiguously test the predictions of this effective Hamiltonian through
manipulation of ultracold atoms in an inhomogeneous optical superlattice. The
structure of the low-energy Hilbert space as well as the particle assisted
tunneling rates can be inferred from measurements of the time-of-flight images.


title: Lower Bounds on the Rate-Distortion Function of LDGM Codes

abstract:
  A recent line of work has focused on the use of low-density generator matrix
(LDGM) codes for lossy source coding. In this paper, wedevelop a generic
technique for deriving lower bounds on the rate-distortion functions of binary
linear codes, with particular interest on the effect of bounded degrees. The
underlying ideas can be viewing as the source coding analog of the classical
result of Gallager, providing bounds for channel coding over the binary
symmetric channel using bounded degree LDPC codes. We illustrate this method
for different random ensembles of LDGM codes, including the check-regular
ensemble and bit-check-regular ensembles, by deriving explicit lower bounds on
their rate-distortion performance as a function of the degrees.


title:
Limits of Binaries That Can Be Characterized by Gravitational
  Microlensing

abstract:
  Due to the high efficiency of planet detections, current microlensing planet
searches focus on high-magnification events. High-magnification events are
sensitive to remote binary companions as well and thus a sample of
wide-separation binaries are expected to be collected as a byproduct. In this
paper, we show that characterizing binaries for a portion of this sample will
be difficult due to the degeneracy of the binary-lensing parameters. This
degeneracy arises because the perturbation induced by the binary companion is
well approximated by the Chang-Refsdal lensing for binaries with separations
greater than a certain limit. For binaries composed of equal mass lenses, we
find that the lens binarity can be noticed up to the separations of $\sim 60$
times of the Einstein radius corresponding to the mass of each lens. Among
these binaries, however, we find that the lensing parameters can be determined
only for a portion of binaries with separations less than $\sim 20$ times of
the Einstein radius.


title:
Structural effects on the spin-state transition in epitaxially strained
  LaCoO$_3$ films

abstract:
  Using density functional theory within the LSDA + U method, we investigate
the effect of strain on the spin state and magnetic ordering in perovskite
lanthanum cobaltite, LaCoO3. We show that, while strain-induced changes in
lattice parameters are insufficient to stabilize a non-zero spin state,
additional heteroepitaxial symmetry constraints -- in particular the
suppression of octahedral rotations -- stabilize a ferromagnetic
intermediate-spin state. By comparing with experimental data for the bulk
material, we calculate an upper bound on the Hubbard U value, and describe the
role that the on-site Coulomb interaction plays in determining the spin-state
configuration.


title: Wigner crystal physics in quantum wires

abstract:
  The physics of interacting quantum wires has attracted a lot of attention
recently. When the density of electrons in the wire is very low, the strong
repulsion between electrons leads to the formation of a Wigner crystal. We
review the rich spin and orbital properties of the Wigner crystal, both in the
one-dimensional and quasi-one-dimensional regime. In the one-dimensional Wigner
crystal the electron spins form an antiferromagnetic Heisenberg chain with
exponentially small exchange coupling. In the presence of leads the resulting
inhomogeneity of the electron density causes a violation of spin-charge
separation. As a consequence the spin degrees of freedom affect the conductance
of the wire. Upon increasing the electron density, the Wigner crystal starts
deviating from the strictly one-dimensional geometry, forming a zigzag
structure instead. Spin interactions in this regime are dominated by ring
exchanges, and the phase diagram of the resulting zigzag spin chain has a
number of unpolarized phases as well as regions of complete and partial spin
polarization. Finally we address the orbital properties in the vicinity of the
transition from a one-dimensional to a quasi-one-dimensional state. Due to the
locking between chains in the zigzag Wigner crystal, only one gapless mode
exists. Manifestations of Wigner crystal physics at weak interactions are
explored by studying the fate of the additional gapped low-energy mode as a
function of interaction strength.


title:
Bounds of concurrence and their relation with fidelity and frontier
  states

abstract:
  The bounds of concurrence in [F. Mintert and A. Buchleitner, Phys. Rev. Lett.
98 (2007) 140505] and [C. Zhang \textit{et. al.}, Phys. Rev. A 78 (2008)
042308] are proved by using two properties of the fidelity. In two-qubit
systems, for a given value of concurrence, the states achieving the maximal
upper bound, the minimal lower bound or the maximal difference upper-lower
bound are determined analytically.


title:
On the application of homotopy perturbation method to differential
  equations

abstract:
  We show that a recent application of homotopy perturbation method to a class
of ordinary differential equations yields either useless or wrong results.


title:
Localization and the Anomalous Hall Effect in a "Dirty" Metallic
  Ferromagnet

abstract:
  We report magnetoresistance measurements over an extensive temperature range
(0.1 K $\leq T \leq$ 100 K) in a disordered ferromagnetic semiconductor (\gma).
The study focuses on a series of metallic \gma~ epilayers that lie in the
vicinity of the metal-insulator transition ($k_F l_e\sim 1$). At low
temperatures ($T < 4$ K), we first confirm the results of earlier studies that
the longitudinal conductivity shows a $T^{1/3}$ dependence, consistent with
quantum corrections from carrier localization in a ``dirty'' metal. In
addition, we find that the anomalous Hall conductivity exhibits universal
behavior in this temperature range, with no pronounced quantum corrections. We
argue that observed scaling relationship between the low temperature
longitudinal and transverse resistivity, taken in conjunction with the absence
of quantum corrections to the anomalous Hall conductivity, is consistent with
the side-jump mechanism for the anomalous Hall effect. In contrast, at high
temperatures ($T \gtrsim 4$ K), neither the longitudinal nor the anomalous Hall
conductivity exhibit universal behavior, indicating the dominance of inelastic
scattering contributions down to liquid helium temperatures.


title:
Almost filling laminations and the connectivity of ending lamination
  space

abstract:
  We show that if S is a finite type orientable surface of negative Euler
characteristic which is not the 3-holed sphere, 4-holed sphere or 1-holed
torus, then the ending lamination space of S is connected, locally path
connected and cyclic.


title: Concurrent Imitation Dynamics in Congestion Games

abstract:
  Imitating successful behavior is a natural and frequently applied approach to
trust in when facing scenarios for which we have little or no experience upon
which we can base our decision. In this paper, we consider such behavior in
atomic congestion games. We propose to study concurrent imitation dynamics that
emerge when each player samples another player and possibly imitates this
agents' strategy if the anticipated latency gain is sufficiently large. Our
main focus is on convergence properties. Using a potential function argument,
we show that our dynamics converge in a monotonic fashion to stable states. In
such a state none of the players can improve its latency by imitating somebody
else. As our main result, we show rapid convergence to approximate equilibria.
At an approximate equilibrium only a small fraction of agents sustains a
latency significantly above or below average. In particular, imitation dynamics
behave like fully polynomial time approximation schemes (FPTAS). Fixing all
other parameters, the convergence time depends only in a logarithmic fashion on
the number of agents. Since imitation processes are not innovative they cannot
discover unused strategies. Furthermore, strategies may become extinct with
non-zero probability. For the case of singleton games, we show that the
probability of this event occurring is negligible. Additionally, we prove that
the social cost of a stable state reached by our dynamics is not much worse
than an optimal state in singleton congestion games with linear latency
function. Finally, we discuss how the protocol can be extended such that, in
the long run, dynamics converge to a Nash equilibrium.


title: Algebraically Special, Real Alpha Geometries

abstract:
  We exploit the spinor description of four-dimensional Walker geometry, and
conformal rescalings of such, to describe the local geometry of
four-dimensional neutral geometries with algebraically degenerate self-dual
Weyl curvature and an integrable distribution of alpha-planes (algebraically
special real alpha-geometry). In particular, we determine the behaviour of
(four-dimensional neutral) Walker geometry under conformal rescalings and
provide a derivation of the hyperheavenly equation from conformal rescaling
formulae.


title:
Histogram-Aware Sorting for Enhanced Word-Aligned Compression in Bitmap
  Indexes

abstract:
  Bitmap indexes must be compressed to reduce input/output costs and minimize
CPU usage. To accelerate logical operations (AND, OR, XOR) over bitmaps, we use
techniques based on run-length encoding (RLE), such as Word-Aligned Hybrid
(WAH) compression. These techniques are sensitive to the order of the rows: a
simple lexicographical sort can divide the index size by 9 and make indexes
several times faster. We investigate reordering heuristics based on computed
attribute-value histograms. Simply permuting the columns of the table based on
these histograms can increase the sorting efficiency by 40%.


title:
Slow long-range decay of bound Hartree-Fock orbitals and enhancement of
  the exchange interaction and tunneling

abstract:
  Exchange interaction strongly influences the long-range behaviour of
localised electron orbitals. It violates the oscillation theorem (creates extra
nodes) and produces a power-law decay instead of the usual exponential decrease
at large distances. For inner orbitals inside molecules decay is 1/r^2, for
macroscopic systems cos(k_f r)/r^n, where k_f is the Fermi momentum and n=3 for
1D, n=3.5 for 2D and n=4 for 3D crystal. Slow decay increases the exchange
interaction between localised spins and the under-barrier tunneling
amplitude.The under-barrier transmission coefficients in solids (e.g. for point
contacts) become temperature-dependent.

categories: cond-mat.mtrl-sci cond-mat.mes-hall physics.atm-clus physics.atom-ph physics.chem-ph


title:
Enhanced heating of salty water and ice under microwaves: Molecular
  dynamics study

abstract:
  By molecular dynamics simulations, we have studied the enhanced heating
process of salty ice and water by the electric field of applied microwaves at
2.5 GHz, and those in the range 2.5-10 GHz for the frequency dependence. We
show that water molecules in salty ice are allowed to rotate in response to the
microwave electric field to the extent comparable to those in pure water,
because the molecules in salty ice are loosely tied by hydrogen bonds with
adjacent molecules unlike the case of rigidly bonded pure ice. The weakening of
hydrogen-bonded network of molecules in salty ice is mainly caused by the
electrostatic effect of salt ions rather than the short-range geometrical (atom
size) effect of salt ions since the presence of salt ions with small radii
results in similar enhanced heating.


title: Abelian ideals with given dimension in Borel subalgebras

abstract:
  A well-known Peterson's theorem says that the number of abelian ideals in a
Borel subalgebra of a rank-$r$ finite dimensional simple Lie algebra is exactly
$2^r$. In this paper, we determine the dimensional distribution of abelian
ideals in a Borel subalgebra of finite dimensional simple Lie algebras, which
is a refinement of the Peterson's theorem capturing more Lie algebra
invariants.


title:
Connectivity Properties of Horospheres in Euclidean Buildings and
  Applications to Finiteness Properties of Discrete Groups

abstract:
  Let G(O_S) be an S-arithmetic subgroup of a connected, absolutely almost
simple linear algebraic group G over a global function field K. We show that
the sum of local ranks of G determines the homological finiteness properties of
G(O_S) provided the K-rank of G is 1. This shows that the general upper bound
for the finiteness length of G(O_S) established in an earlier paper is sharp in
this case.
  The geometric analysis underlying our result determines the conectivity
properties of horospheres in thick Euclidean buildings.


title: Density estimates and concentration inequalities with Malliavin calculus

abstract:
  We show how to use the Malliavin calculus to obtain density estimates of the
law of general centered random variables. In particular, under a non-degeneracy
condition, we prove and use a new formula for the density of a random variable
which is measurable and differentiable with respect to a given isonormal
Gaussian process. Among other results, we apply our techniques to bound the
density of the maximum of a general Gaussian process from above and below;
several new results ensue, including improvements on the so-called
Borell-Sudakov inequality. We then explain what can be done when one is only
interested in or capable of deriving concentration inequalities, i.e. tail
bounds from above or below but not necessarily both simultaneously.


title:
Capacity-achieving Feedback Scheme for Gaussian Finite-State Markov
  Channels with Channel State Information

abstract:
  In this paper, we propose capacity-achieving communication schemes for
Gaussian finite-state Markov channels (FSMCs) subject to an average channel
input power constraint, under the assumption that the transmitters can have
access to delayed noiseless output feedback as well as instantaneous or delayed
channel state information (CSI). We show that the proposed schemes reveals
connections between feedback communication and feedback control.


title: Self-Similar Polytropic Champagne Flows in H II Regions

abstract:
  We explore large-scale hydrodynamics of H II regions for various self-similar
shock flows of a polytropic gas cloud under self-gravity and with
quasi-spherical symmetry. We formulate cloud dynamics by invoking specific
entropy conservation along streamlines and obtain global self-similar
"champagne flows" for a conventional polytropic gas with shocks as a subclass.
Molecular cloud cores are ionized and heated to high temperatures after the
onset of nuclear burning of a central protostar. We model subsequent
evolutionary processes in several ways and construct possible self-similar
shock flow solutions. We may neglect the mass and gravity of the central
protostar. The ionization and heating of the surrounding medium drive outflows
in the inner cloud core and a shock travels outwards, leading to the so-called
"champagne phase" with an expanding outer cloud envelope. Complementarily, we
also consider the expansion of a central cavity around the centre. As the inner
cloud expands plausibly due to powerful stellar winds, a cavity (i.e., `void'
or `bubble') can be created around the centre, and when the cavity becomes
sufficiently large, one may neglect the gravity of the central protostar. We
thus present self-similar shock solutions for "champagne flows" with an
expanding central void. We compare our solutions with isothermal solutions and
find that the generalization to the polytropic regime brings about significant
differences of the gas dynamics, especially for cases of n<1, where n is a key
scaling index in the self-similar transformation. We also compare our global
polytropic self-similar solutions with numerical simulations on the expansion
of H II regions.


title: The Family Problem

abstract:
  We all know that in our family of particle physics we have three generations
but still don't know why - the so-called "family problem". On other hand, in
view of the masses and oscillations, the neutrinos now present some basic
difficulty in the Standard Model. In this note, I propose that on top of the
SU_c(3) \times SU(2) \times U(1) standard model there is an SU_f (3) extension
- a simple SU_c(3) \times SU(2) \times U(1) \times SU_f (3) extended standard
model. The family gauge bosons (familons) are massive through the so-called
"colored" Higgs mechanism while the remaining Higgs particles are also massive.
The three neutrinos, the electron-like, muon-like, and tao-like neutrinos, form
the basic family triplets. Hopefully all the couplings to the "visible" matter
are through the neutrinos, explaining why dark matter (25 %) is more than
visible matter (5 %) in our Universe.


title: On zero-rate error exponent for BSC with noisy feedback

abstract:
  For the information transmission a binary symmetric channel is used. There is
also another noisy binary symmetric channel (feedback channel), and the
transmitter observes without delay all the outputs of the forward channel via
that feedback channel. The transmission of a nonexponential number of messages
(i.e. the transmission rate equals zero) is considered. The achievable decoding
error exponent for such a combination of channels is investigated. It is shown
that if the crossover probability of the feedback channel is less than a
certain positive value, then the achievable error exponent is better than the
similar error exponent of the no-feedback channel.
  The transmission method described and the corresponding lower bound for the
error exponent can be strengthened, and also extended to the positive
transmission rates.


title:
Are dumbbell brightest cluster members signposts to galaxy cluster
  activity?

abstract:
  We assemble a sample of galaxy clusters whose brightest members are dumbbell
galaxies and compare them with a control sample in order to investigate if they
are the result of recent mergers. We show that the dumbbell sample is no more
likely than other clusters to exhibit subclustering. However, they are much
more likely to have at least one dumbbell component possessing a significant
peculiar velocity with respect to the parent cluster than a non-dumbbell
brightest cluster member. We interpret this in the context of seeing the
clusters at various stages of post-merger relaxation.


title:
Why phase diagrams of different underdoped cuprates are remarkably
  different? Disorder versus bilayer

abstract:
  Contrary to a widely accepted view the phase diagrams of
La$_{2-x}$Sr$_x$CuO$_4$ and YBa$_2$Cu$_3$O$\rm_{6+y}$, in spite of similarities
are remarkably different. Both the electric conduction properties and the
commensurate/incommensurate spin ordering properties differ dramatically. It is
argued that the role of disorder in YBCO is insignificant while the bilayer
structure is crucial. On the other hand in LSCO the intrinsic disorder to a
large extent drives the properties of the system. The developed approach
explains the low-temperature magnetic properties of the systems. The most
important point is the difference with respect to the incommensurate spin
ordering, including the difference in the incommensurate pitches. The present
analysis demonstrates that the superconductivity is intimately related to the
incommensurate spin ordering.


title: Stochastic Resonance in an Overdamped Monostable System

abstract:
  We show, the SR can appear in monostable overdamped systems driven by
additive mix of periodical signal and white Gaussian noise. It can be observed
as nonmonotonic dependence of SNR on the input noise intensity. In this sense
it is similar to classical SR observed in overdamped bistable systems with
potential barrier.


title: Fast Scramblers

abstract:
  We consider the problem of how fast a quantum system can scramble
(thermalize) information, given that the interactions are between bounded
clusters of degrees of freedom; pairwise interactions would be an example.
Based on previous work, we conjecture:
  1) The most rapid scramblers take a time logarithmic in the number of degrees
of freedom.
  2) Matrix quantum mechanics (systems whose degrees of freedom are n by n
matrices) saturate the bound.
  3) Black holes are the fastest scramblers in nature.
  The conjectures are based on two sources, one from quantum information
theory, and the other from the study of black holes in String Theory.


title:
A class of compact Poincare-Einstein manifolds: properties and
  construction

abstract:
  We develop a geometric and explicit construction principle that generates
classes of Poincare-Einstein manifolds, and more generally almost Einstein
manifolds. Almost Einstein manifolds satisfy a generalisation of the Einstein
condition; they are Einstein on an open dense subspace and, in general, have a
conformal scale singularity set that is a conformal infinity for the Einstein
metric. In particular, the construction may be applied to yield families of
compact Poincare-Einstein manifolds, as well as classes of almost Einstein
manifolds that are compact without boundary. We obtain classification results
which show that the construction essentially exhausts a class of almost
Einstein (and Poincare-Einstein) manifold. We develop the general theory of
fixed conformal structures admitting multiple compatible almost Einstein
structures. We also show that, in a class of cases, these are canonically
related to a family of constant mean curvature totally umbillic embedded
hypersurfaces.


title:
Evolution of scalar perturbations in cosmology with quintessential dark
  energy

abstract:
  The dynamics of expansion of the Universe and evolution of scalar
perturbations are studied for the quintessential scalar fields $Q$ with the
classical Lagrangian satisfying the additional condition $w=const$ or
$c^2_a=0$. Both quintessential fields are studied for the same cosmological
model. The systems of evolutionary equations for gauge-invariant perturbations
of metrics, matter and quintessence have been analysed analyticaly for the
early stage of the Universe life and numerically up to the present epoch. It is
shown that amplitudes of the adiabatic matter density perturbations grow like
in $\Lambda$CDM-model but time dependences of amplitudes of the quintessence
perturbations are more varied: gauge-invariant variables $D_g^{(Q)}$ and
$D_s^{(Q)}$ decay from initial constant value after entering the particle
horizon while $D^{(Q)}$ and $V^{(Q)}$ grow at the early stage before entering
the horizon and decay after that -- in the quintessence-dominated epoch, when
gravitational potential starts to decay -- so, that at the current epoch they
are approximately two orders lower than matter ones at the supercluster scale.
Therefore, at the subhorizon scales the quintessential scalar fields are
smoothed out while the matter clusters. It is also shown that both
quintessential scalar fields suppress the growth of matter density
perturbations and the amplitude of gravitational potential. In these
QCDM-models -- unlike $\Lambda$CDM ones -- such suppression is scale dependent
and more visible for the quintessence with $c^2_a=0$.


title: All exceptional surgeries on alternating knots are integral surgeries

abstract:
  We show that all exceptional surgeries on hyperbolic alternating knots in the
3-sphere are integral surgeries.


title: Nonlinear Shear-free Radiative Collapse

abstract:
  We study realistic models of relativistic radiating stars undergoing
gravitational collapse which have vanishing Weyl tensor components. Previous
investigations are generalised by retaining the inherent nonlinearity at the
boundary. We transform the boundary condition to an Abel equation of the first
kind. A variety of nonlinear solutions are generated all of which can be
written explicitly. Several classes of infinite solutions exist.


title: A Riccati equation in radiative stellar collapse

abstract:
  We model the behaviour of a relativistic spherically symmetric shearing fluid
undergoing gravitational collapse with heat flux. It is demonstrated that the
governing equation for the gravitational behaviour is a Riccati equation. We
show that the Riccati equation admits two classes of new solutions in closed
form. We regain particular models, obtained in previous investigations, as
special cases. A significant feature of our solutions is the general spatial
dependence in the metric functions which allows for a wider study of the
physical features of the model, such as the behaviour of the causal temperature
in inhomogeneous spacetimes.


title:
Generalized Maxwell-Boltzmann, Bose-Einstein, Fermi-Dirac and
  Acharya-Swamy Statistics and the Polya Urn Model

abstract:
  Generalized probability distributions for Maxwell-Boltzmann, Bose-Einstein
and Fermi-Dirac statistics, with unequal source probabilities $q_i$ for each
level $i$, are obtained by combinatorial reasoning. For equiprobable degenerate
sublevels, these reduce to those given by Brillouin in 1930, more commonly
given as a statistical weight for each statistic. These distributions and
corresponding cross-entropy (divergence) functions are shown to be special
cases of the P\'olya urn model, involving neither independent nor identically
distributed ("ninid") sampling. The most probable P\'olya distribution contains
the Acharya-Swamy intermediate statistic.


title:
Quasielastic and inelastic neutrino reactions in $^{12}C$ at K2K
  energies

abstract:
  In this paper, we present the results of a study made for the effect of
nuclear medium in the charged current induced quasielastic lepton
production(CCQE) and the incoherent and coherent one pion production
(CC1$\pi^+$)processes from $^{12}C$ in the $\nu_\mu$ energy region of 0.4-3GeV.
The theoretical results are compared with the recent experimental results for
the ratio of charged current $\nu_\mu$ induced one pion production cross
section to the quasielastic lepton production cross section reported by K2K
collaboration. We also present the results for the angular and momentum
distributions of leptons and pions produced in these processes.


title: The flipping puzzle on a graph

abstract:
  Let $S$ be a connected graph which contains an induced path of $n-1$
vertices, where $n$ is the order of $S.$ We consider a puzzle on $S$. A
configuration of the puzzle is simply an $n$-dimensional column vector over
$\{0, 1\}$ with coordinates of the vector indexed by the vertex set $S$. For
each configuration $u$ with a coordinate $u_s=1$, there exists a move that
sends $u$ to the new configuration which flips the entries of the coordinates
adjacent to $s$ in $u.$ We completely determine if one configuration can move
to another in a sequence of finite steps.


title: The Compact Structure of Radio-Loud Broad Absorption Line Quasars

abstract:
  We present the results of EVN+MERLIN VLBI polarization observations of 8
Broad Absorption Line (BAL) quasars at 1.6 GHz, including 4 LoBALs and 4 HiBALs
with either steep or flat spectra on VLA scales. Only one steep-spectrum
source, J1122+3124, shows two-sided structure on the scale of 2 kpc. The other
four steep-spectrum sources and three flat-spectrum sources display either an
unresolved image or a core-jet structure on scales of less than three hundred
parsecs. In all cases the marginally resolved core is the dominant radio
component. Linear polarization in the cores has been detected in the range of a
few to 10 percent. Polarization, together with high brightness temperatures
(from 2*10^9-5*10^10 K), suggest a synchrotron origin for the radio emission.
There is no apparent difference in the radio orphologies or polarization
between low-ionization and high-ionization BAL QSOs nor between flat- and
steep-spectrum sources. We discuss the orientation of BAL QSOs with both flat
and steep spectra, and consider a possible evolutionary scenario for BAL QSOs.
In this scenario, BAL QSOs are probably the young population of radio sources,
which are Compact Steep Spectrum or GHz peaked radio source analog at the low
end of radio power.


title: Multiple charge density wave transitions in Gd$_2$Te$_5$

abstract:
  Diffraction measurements performed via transmission electron microscopy and
high resolution X-ray scattering reveal two distinct charge density wave
transitions in Gd$_2$Te$_5$ at $T_{c1}$ = 410(3) and $T_{c2}$ = 532(3) K,
associated with the \textit{on}-axis incommensurate lattice modulation and
\textit{off}-axis commensurate lattice modulation respectively. Analysis of the
temperature dependence of the order parameters indicates a non-vanishing
coupling between these two distinct CDW states.


title: Prolific pair production with high-power lasers

abstract:
  Prolific electron-positron pair production is possible at laser intensities
approaching 10^{24} W/cm^2 at a wavelength of 1 micron. An analysis of electron
trajectories and interactions at the nodes (B=0) of two counter-propagating,
circularly polarised laser beams shows that a cascade of gamma-rays and pairs
develops. The geometry is generalised qualitatively to linear polarisation and
laser beams incident on a solid target.


title:
Non-linear Integral Equations and Determinant Formulae of the Open XXZ
  Spin Chain

abstract:
  We derive a non-linear integral equation for the Bethe-ansatz solvable open
XXZ spin chain of arbitrary length describing the lowest lying state with zero
magnetization. For this case we show how to combine the integral representation
with the known determinant formula of norms and scalar products.


title:
Two Parallel Swendsen-Wang Cluster Algorithms Using Message-Passing
  Paradigm

abstract:
  In this article, we present two different parallel Swendsen-Wang Cluster(SWC)
algorithms using message-passing interface(MPI). One is based on Master-Slave
Parallel Model(MSPM) and the other is based on Data-Parallel Model(DPM). A
speedup of 24 with 40 processors and 16 with 37 processors is achieved with the
DPM and MSPM respectively. The speedup of both algorithms at different
temperature and system size is carefully examined both experimentally and
theoretically, and a comparison of their efficiency is made. In the last
section, based on these two parallel SWC algorithms, two parallel probability
changing cluster(PCC) algorithms are proposed.


title:
Quadrupole Susceptibility and Elastic Softening due to a Vacancy in
  Silicon Crystal

abstract:
  We investigate the electronic states around a single vacancy in silicon
crystal by using the Green's function approach. The triply degenerate vacancy
states within the band gap are found to be extended over a large distance
$\sim20 {\rm \AA}$ from the vacancy site and contribute to the reciprocal
temperature dependence of the quadrupole susceptibility resulting in the
elastic softening at low temperture. The Curie constant of the quadrupole
susceptibility for the trigonal mode ($O_{yz},O_{zx},O_{xy}$) is largely
enhanced as compared to that for the tetragonal mode ($O_{2}^{0},O_{2}^{2}$).
The obtained results are consistent with the recent ultrasonic experiments in
silicon crystal down to 20 mK. We also calculate the dipole and octupole
susceptibilities and find that the octupole susceptibilities are extremely
enhannced for a specific mode.


title:
The main sequence from F to K stars of the solar neighbourhood in SDSS
  colours

abstract:
  For an understanding of Galactic stellar populations in the SDSS filter
system well defined stellar samples are needed. The nearby stars provide a
complete stellar sample representative for the thin disc population. We compare
the filter transformations of different authors applied to the main sequence
stars from F to K dwarfs to SDSS filter system and discuss the properties of
the main sequence. The location of the mean main sequence in colour-magnitude
diagrams is very sensitive to systematic differences in the filter
transformation. A comparison with fiducial sequences of star clusters observed
in g',r',i' show good agreement. Theoretical isochrones from Padua and from
Dartmouth have still some problems especially in (r-i)-colour.


title: The lack of carbon stars in the Galactic bulge

abstract:
  In order to explain the lack of carbon stars in the Galactic bulge, we have
made a detailed study of thermal pulse - asymptotic giant branch stars by using
a population synthesis code. The effects of the oxygen overabundance and the
mass loss rate on the ratio of the number of carbon stars to that of oxygen
stars in the Galactic bulge are discussed. We find that the oxygen
overabundance which is about twice as large as that in the solar neighbourhood
(close to the present observations) is insufficient to explain the rareness of
carbon stars in the bulge. We suggest that the large mass loss rate may serve
as a controlling factor in the ratio of the number of carbon stars to that of
oxygen stars.


title:
Exclusive semileptonic decays of $\Lambda_b \to \Lambda l^{+} l^{-}$ in
  supersymmetric theories

abstract:
  The weak decays of $\Lambda_b \to \Lambda l^{+} l^{-}$ ($l=e, \mu$) are
investigated in Minimal Supersymmetric Standard Model (MSSM) and also in
Supersymmetric (SUSY) SO(10) Grand Unified Models. In MSSM the special
attention is paid to the Neutral Higgs Bosons (NHBs) as they make quite a large
contribution in exclusive $B \to X_{s} l^{+} l^{-}$ decays at large
$\tan{\beta}$ regions of parameter space of SUSY models, since part of SUSY
contributions is proportional to $\tan^{3}{\beta}$. The analysis of decay rate,
forward-backward asymmetries, lepton polarization asymmetries and the
polarization asymmetries of $\Lambda $ baryon in $\Lambda_b \to \Lambda l^{+}
l^{-}$ show that the values of these physical observables are greatly modified
by the effects of NHBs. In SUSY SO(10) GUT model, the new physics contribution
comes from the operators which are induced by the NHBs penguins and also from
the operators having chirality opposite to that of the corresponding SM
operators. SUSY SO(10) effects show up only in the decay $\Lambda_b \to \Lambda
+\tau^{+} \tau^{-}$ where the longitudinal and transverse lepton polarization
asymmetries are deviate significantly from the SM value while the effects in
the decay rate, forward-backward asymmetries and polarization asymmetries of
final state $\Lambda$ baryon are very mild. The transverse lepton polarization
asymmetry in $\Lambda_b \to \Lambda +\tau^{+} \tau^{-}$ is almost zero in SM
and in MSSM model. However, it can reach to -0.1 in SUSY SO(10) GUT model and
could be seen at the future colliders; hence this asymmetry observable will
provide us useful information to probe new physics and discriminate between
different models.


title:
Final-state interactions in the decays $B^0\to\chi_{c0}K^{*0}$ and $B^+
  \to \chi_{c0}K^{*+}$

abstract:
  In this article, we study the final-state rescattering effects in the decays
$B^0\to \chi_{c0}K^{*0}$ and $B^+ \to \chi_{c0}K^{*+}$, and observe the
corrections are zero in the SU(3) limit, which is warranted by the heavy quark
symmetry. It is difficult to accommodate the experimental data without
fine-tuning.


title:
N/O-trends in Late-Type Galaxies: AGB-stars, IMFs, Abundance Gradients
  and the Origin of Nitrogen

abstract:
  Models of galactic chemical evolution (CEMs) show that the shape of the
stellar initial mass function (IMF) and other assumptions regarding star
formation affect the resultant abundance gradients in models of late-type
galaxies. Furthermore, intermediate mass (IM) stars undeniably play an
important role in the buildup of nitrogen abundances in galaxies. Here I
specifically discuss the nitrogen contribution from IM/AGB stars and how it
affects the N/O-gradient. For this purpose I have modelled the chemical
evolution of a few nearby disc galaxies using different IMFs and star formation
prescriptions. It is demonstrated that N/O-gradients may be used to constrain
the nitrogen contribution from IM/AGB-stars.


title: Erdos-Renyi random graphs + forest fires = self-organized criticality

abstract:
  We modify the usual Erdos-Renyi random graph evolution by letting connected
clusters 'burn down' (i.e. fall apart to disconnected single sites) due to a
Poisson flow of lightnings. In a range of the intensity of rate of lightnings
the system sticks to a permanent critical state.


title: Local Hamiltonians in Quantum Computation

abstract:
  In this thesis, I investigate aspects of local Hamiltonians in quantum
computing. First, I focus on the Adiabatic Quantum Computing model, based on
evolution with a time dependent Hamiltonian. I show that to succeed using AQC,
the Hamiltonian involved must have local structure, which leads to a result
about eigenvalue gaps from information theory. I also improve results about
simulating quantum circuits with AQC. Second, I look at classically simulating
time evolution with local Hamiltonians and finding their ground state
properties. I give a numerical method for finding the ground state of
translationally invariant Hamiltonians on an infinite tree. This method is
based on imaginary time evolution within the Matrix Product State ansatz, and
uses a new method for bringing the state back to the ansatz after each
imaginary time step. I then use it to investigate the phase transition in the
transverse field Ising model on the Bethe lattice. Third, I focus on locally
constrained quantum problems Local Hamiltonian and Quantum Satisfiability and
prove several new results about their complexity. Finally, I define a
Hamiltonian Quantum Cellular Automaton, a continuous-time model of computation
which doesn't require control during the computation process, only preparation
of product initial states. I construct two of these, showing that time
evolution with a simple, local, translationally invariant and time-independent
Hamiltonian can be used to simulate quantum circuits.


title: Study of exclusive processes e^+ e^- \to VP

abstract:
  This paper is devoted to consideration of the hard exclusive processes
$e^+e^- \to VP$, where $V=\rho,\phi; P=\eta,\eta'$. Experimental measurement of
the cross section of the process $e^+ e^- \to \phi\eta$ at BaBar collaboration
at large center mass energy $\sqrt s=10.6$ GeV and some low energy experimental
data $\sqrt s \sim 2-4$ GeV give us the possibility to study the cross section
in the broad energy region. As the result, we have determined the asymptotic
behavior of the cross section of $e^+ e^- \to \phi\eta$ in the limit $s \to
\infty$, which is in agreement with perturbative QCD prediction. Assuming that
the same asymptotic behavior is valid for the other processes under
consideration and using low energy experimental data we have predicted the
cross sections of these processes at energies $\sqrt s=3.67,~10.6$ GeV. In
addition, we have calculated the cross sections of these processes at the same
energies within perturbative QCD. Our results are in agreement with available
experimental data.


title: The Maskit embedding of the twice punctured torus

abstract:
  The Maskit embedding M of a surface \Sigma is the space of geometrically
finite groups on the boundary of quasifuchsian space for which the `top' end is
homeomorphic to \Sigma, while the `bottom' end consists of two triply punctured
spheres, the remains of \Sigma when two fixed disjoint curves have been
pinched. As such representations vary in the character variety, the conformal
structure on the top side varies over the Teichm\"uller space T(\Sigma).
  We investigate M when \Sigma is a twice punctured torus, using the method of
pleating rays. Fix a projective measure class [\mu] supported on closed curves
on \Sigma. The pleating ray P_[\mu] consists of those groups in M for which the
bending measure of the top component of the convex hull boundary of the
associated 3-manifold is in [\mu]. It is known that P is a real 1-submanifold
of M. Our main result is a formula for the asymptotic direction of P in M as
the bending measure tends to zero, in terms of natural parameters for the
2-complex dimensional representation space R and the Dehn-Thurston coordinates
of the support curves to [\mu] relative to the pinched curves on the bottom
side. This leads to a method of locating M in R.


title:
Adjoint vector fields and differential operators on representation
  spaces

abstract:
  Let $G$ be a semisimple algebraic group with Lie algebra $\g$. In 1979, J.
Dixmier proved that any vector field annihilating all $G$-invariant polynomials
on $\g$ lies in the $\bbk[\g]$-module generated by the "adjoint vector fields",
i.e., vector fields $\varsigma$ of the form $\varsigma(y)(x)=[x,y]$,
$x,y\in\g$. A substantial generalisation of Dixmier's theorem was found by
Levasseur and Stafford. They explicitly described the centraliser of
$\bbk[\g]^G$ in the algebra of differential operators on $\g$. On the level of
vector fields, their result reduces to Dixmier's theorem. The purpose of this
paper is to explore similar problems in the general context of affine algebraic
groups and their rational representations.


title: Static-light meson masses from twisted mass lattice QCD

abstract:
  We compute the static-light meson spectrum using two-flavor Wilson twisted
mass lattice QCD. We have considered five different values for the light quark
mass corresponding to 300 MeV < m_PS < 600 MeV. We have extrapolated our
results, to make predictions regarding the spectrum of B and B_s mesons.


title: Two-dimensional models of type theory

abstract:
  We describe a non-extensional variant of Martin-L\"of type theory which we
call two-dimensional type theory, and equip it with a sound and complete
semantics valued in 2-categories.


title:
Mathieu functions approach to bidimensional scattering by dielectric
  elliptical cylinders

abstract:
  Two-dimensional scattering by homogeneous and layered dielectric elliptical
cylinders is analyzed following an analytical approach using Mathieu functions.
Closed-form relations for the expansion coefficients of the resulting electric
field in the vicinity of the scatterer are provided. Numerical examples show
the focalizing effect of dielectric elliptical cylinders illuminated normally
to the axis. The influence of the confocal dielectric cover on the resulting
scattered field is envisaged.


title: Monte Carlo studies of extensions of the Blume-Emery-Griffiths model

abstract:
  We extend the Blume-Emery-Griffiths (BEG) model to a two-component BEG model
in order to study 2D systems with two order parameters, such as magnetic
superconductors or two-component Bose-Einstein condensates. The model is
investigated using Monte Carlo simulations, and the temperature-concentration
phase diagram is determined in the presence and absence of an external magnetic
field. This model exhibits a rich phase diagram, including a second-order
transition to a phase where superconductivity and magnetism coexist. Results
are compared with experiments on Cerium-based heavy-fermion superconductors. To
study cold atom mixtures, we also simulate the BEG and two-component BEG models
with a trapping potential. In the BEG model with a trap, there is no longer a
first order transition to a true phase-separated regime, but a crossover to a
kind of phase-separated region. The relation with imbalanced fermi-mixtures is
discussed. We present the phase diagram of the two-component BEG model with a
trap, which can describe boson-boson mixtures of cold atoms. Although there are
no experimental results yet for the latter, we hope that our predictions could
help to stimulate future experiments in this direction.


title:
Data mining and accelerated electronic structure theory as a tool in the
  search for new functional materials

abstract:
  Data mining is a recognized predictive tool in a variety of areas ranging
from bioinformatics and drug design to crystal structure prediction. In the
present study, an electronic structure implementation has been combined with
structural data from the Inorganic Crystal Structure Database to generate
results for highly accelerated electronic structure calculations of about
22,000 inorganic compounds. It is shown how data mining algorithms employed on
the database can identify new functional materials with desired materials
properties, resulting in a prediction of 136 novel materials with potential for
use as detector materials for ionizing radiation. The methodology behind the
automatized ab-initio approach is presented, results are tabulated and a
version of the complete database is made available at the internet web site
http://gurka.fysik.uu.se/ESP/ (Ref.1).


title: Locality, detection efficiencies, and probability polytopes

abstract:
  We present a detailed investigation of minimum detection efficiencies, below
which locality cannot be violated by any quantum system of any dimension in
bipartite Bell experiments. Lower bounds on these minimum detection
efficiencies are determined with the help of linear programming techniques. Our
approach is based on the observation that any possible bipartite quantum
correlation originating from a quantum state in an arbitrary dimensional
Hilbert space is sandwiched between two probability polytopes, namely the local
(Bell) polytope and a corresponding nonlocal no-signaling polytope. Numerical
results are presented demonstrating the dependence of these lower bounds on the
numbers of inputs and outputs of the bipartite physical system.


title:
Collective excitations in two-dimensional antiferromagnet in strong
  magnetic field

abstract:
  We discuss spin-$\frac12$ two-dimensional (2D) Heisenberg antiferromagnet
(AF) on a square lattice at T=0 in strong magnetic field H near its saturation
value $H_c$. A perturbation approach is proposed to obtain spectrum of magnons
with momenta not very close to AF vector in the leading order in small
parameter $(H_c-H)/H_c$. We find that magnons are well-defined quasi-particles
at $H>0.9H_c$ although the damping is quite large near the zone boundary. A
characteristic rotonlike local minimum in the spectrum is observed at ${\bf
k}=(\pi,0)$ accompanied by decrease of the damping near $(\pi,0)$. The
suggested approach can be used in discussion of short-wavelength excitations in
other 2D Bose gases of particles or quasi-particles.


title: Automation of the Dipole Subtraction Method in MadGraph/MadEvent

abstract:
  We present the implementation of the dipole subtraction formalism for the
real radiation contributions to any next-to-leading order QCD process in the
MadGraph/MadEvent framework. Both massless and massive dipoles are considered.
Starting from a specific (n+1)-particle process the package provides a Fortran
code for all possible dipoles to all Born processes that constitute the
subtraction term to the (n+1)-particle process. The output files are given in
the usual "MadGraph StandAlone" style using helicity amplitudes.


title: Is there a redshift cutoff for submillimetre galaxies?

abstract:
  We present new optical and infrared photometry for a statistically complete
sample of seven 1.1 mm selected sources with accurate Submillimetre Array
coordinates. We determine photometric redshifts for four of the seven sources
of 4.47, 4.50, 1.49 and 0.64. Of the other three sources two are undetected at
optical wavelengths down to the limits of very deep Subaru and
Canada-France-Hawaii Telescope images ($\sim$27 mag AB, i band) and the
photometry of the remaining source is corrupted by a bright nearby galaxy. The
sources with the highest redshifts are at higher redshifts than all but one of
the $\sim$200 sources taken from the largest recent 850 $\mu$m surveys, which
may indicate that 1.1 mm surveys are more efficient at finding sources at very
high redshifts than 850 $\mu$m surveys. We investigate the evolution of the
number density with redshift of our sample using a banded $V_{e}/V_{a}$
analysis and find no evidence for a redshift cutoff, although the number of
sources is very small. We also perform the same analysis on a statistically
complete sample of 38 galaxies selected at 850$\mu$m from the GOODS-N field and
find evidence for a drop-off in the number density beyond $z\sim1$ and 2 for
hot and cold dust dominated SMGs respectively, confirming the earlier
conclusion of Wall, Pope & Scott. We also find strong evidence for the
existence of two differently evolving sub-populations separated in luminosity,
with a higher relative density of the high luminosity galaxies at higher
redshifts.


title:
Electric/magnetic duality for chiral gauge theories with anomaly
  cancellation

abstract:
  We show that 4D gauge theories with Green-Schwarz anomaly cancellation and
possible generalized Chern-Simons terms admit a formulation that is manifestly
covariant with respect to electric/magnetic duality transformations. This
generalizes previous work on the symplectically covariant formulation of
anomaly-free gauge theories as they typically occur in extended supergravity,
and now also includes general theories with (pseudo-)anomalous gauge
interactions as they may occur in global or local N=1 supersymmetry. This
generalization is achieved by relaxing the linear constraint on the embedding
tensor so as to allow for a symmetric 3-tensor related to electric and/or
magnetic quantum anomalies in these theories. Apart from electric and magnetic
gauge fields, the resulting Lagrangians also feature two-form fields and can
accommodate various unusual duality frames as they often appear, e.g., in
string compactifications with background fluxes.


title: Kolmogorov-Sinai entropy and black holes

abstract:
  It is shown that stringy matter near the event horizon of a Schwarzschild
black hole exhibits chaotic behavior (the spreading effect) which can be
characterized by the Kolmogorov-Sinai entropy. It is found that the
Kolmogorov-Sinai entropy of a spreading string equals to the half of the
inverse gravitational radius of the black hole. But the KS entropy is the same
for all objects collapsing into the black hole. The nature of this universality
is that the KS entropy possesses the main property of temperature: it is the
same for all bodies in thermal equilibrium with the black hole. The
Kolmogorov-Sinai entropy measures the rate at which information about the
string is lost as it spreads over the horizon. It is argued that it is the
maximum rate allowed by quantum theory. A possible relation between the
Kolmogorov-Sinai and Bekenstein-Hawking entropies is discussed.


title:
Bound-state third-order optical nonlinearities of embedded germanium
  nanocrystals

abstract:
  Embedded germanium nanocrystals (NCs) in a silica host matrix are
theoretically analyzed to identify their third-order bound-state
nonlinearities. A rigorous atomistic pseudopotential approach is used for
determining the electronic structure and the nonlinear optical
susceptibilities. This study characterizing the two-photon absorption,
nonlinear refractive index, and optical switching parameters reveals the full
wavelength dependence from static up to the ultraviolet spectrum and the size
dependence up to a diameter of 3.5 nm. Similar to Si NCs, the
intensity-dependent refractive index increases with decreasing NC diameter. On
the other hand, Ge NCs possess about an order of magnitude smaller nonlinear
susceptibility compared to Si NCs of the same size. It is observed that the
two-photon absorption threshold extends beyond the half band-gap value. This
enables nonlinear refractive index tunability over a much wider wavelength
range free from two-photon absorption.


title: Comments on Scalar-Tensor Representation of $f(R)$ Theories

abstract:
  We propose a scalar-tensor representation of $f(R)$ theories with use of
conformal transformations. In this representation, the model takes the form of
the Brans-Dicke model with a potential function and a non-zero kinetic term for
the scalar field. We show that due to interaction of the scalar field with
matter systems, the corresponding matter stress tensor is not conserved and
test particles experience an anomalous acceleration.


title: X-ray absorption spectroscopy measurement on the LaO1-xFxFeAs system

abstract:
  Results of Fe K-, As K-, and La L3-edge x-ray absorption near edge structure
(XANES) measurements on LaO1-xFxFeAs compounds are presented. The Fe K- edge
exhibits a chemical shift to lower energy, near edge feature modifications, and
pre-edge feature suppression as a result of F substitution for O. The former
two changes provide evidence of electron charge transfer to the Fe sites and
the latter directly supports the delivery of this charge into the Fe-3d
orbitals. The As K- edge measurements show spectral structures typical of
compounds with planes of transition-metal tetrahedrally coordinated to p-block
elements as is illustrated by comparison to other such materials. The
insensitivity of the As-K edge to doping, along with the strong Fe-K doping
response, is consistent with band structure calculations showing essentially
pure Fe-d character near the Fermi energy in these materials. The energy of the
continuum resonance feature above the La-L3 edge is shown to be quantitatively
consistent with the reported La-O inter-atomic separation and with other oxide
compounds containing rare earth elements.


title:
A multi-zone model for simulating the high energy variability of TeV
  blazars

abstract:
  We present a time-dependent multi-zone code for simulating the variability of
Synchrotron-Self Compton (SSC) sources. The code adopts a multi-zone pipe
geometry for the emission region, appropriate for simulating emission from a
standing or propagating shock in a collimated jet. Variations in the injection
of relativistic electrons in the inlet propagate along the length of the pipe
cooling radiatively. Our code for the first time takes into account the
non-local, time-retarded nature of synchrotron self-Compton (SSC) losses that
are thought to be dominant in TeV blazars. The observed synchrotron and SSC
emission is followed self-consistently taking into account light travel time
delays. At any given time, the emitting portion of the pipe depends on the
frequency and the nature of the variation followed. Our simulation employs only
one additional physical parameter relative to one-zone models, that of the pipe
length and is computationally very efficient, using simplified expressions for
the SSC processes. The code will be useful for observers modeling GLAST, TeV,
and X-ray observations of SSC blazars.


title: Fermion Families from Two Layer Warped Extra Dimensions

abstract:
  In extra dimensions, the quark and lepton mass hierarchy can be reproduced
from the same order bulk mass parameters, and standard model fermion families
can be generated from one generation in the high dimensional space. We try to
explain the origin of the same order bulk mass parameters and address the
family replication puzzle simultaneously. We show that they correlate with each
other. We construct models that families are generated from extra dimensional
space, and in the meantime the bulk mass parameters of same order emerge
naturally. The interesting point is that the bulk mass parameters, which are in
same order, correspond to the eigenvalues of a Schr\"{o}dinger-like equation.
We also discuss the problem existing in this approach.


title:
19F nuclear spin relaxation and spin diffusion effects in the single ion
  magnet LiYF4:Ho3+

abstract:
  Temperature and magnetic field dependences of the 19F nuclear spin-lattice
relaxation in a single crystal of LiYF4 doped with holmium are described by an
approach based on a detailed consideration of the magnetic dipole-dipole
interactions between nuclei and impurity paramagnetic ions and nuclear spin
diffusion processes. The observed non-exponential long time recovery of the
nuclear magnetization after saturation at intermediate temperatures is in
agreement with predictions of the spin-diffusion theory in a case of the
diffusion limited relaxation. At avoided level crossings in the spectrum of
electron-nuclear states of the Ho3+ ion, rates of nuclear spin-lattice
relaxation increase due to quasi-resonant energy exchange between nuclei and
paramagnetic ions, in contrast to the predominant role played by electronic
cross-relaxation processes in the low-frequency ac-susceptibility.


title: Theory of Specific Heat in Glass Forming Systems

abstract:
  Experimental measurements of the specific heat in glass-forming systems
reveal anomalies in the temperature dependence of the specific heat, including
the so called "specific heat peak" in the vicinity of the glass transition. The
aim of this paper is to provide theoretical explanations of these anomalies in
general and a quantitative theory in the case of a simple model of
glass-formation. We first present new simulation results for the specific heat
in a classical model of a binary mixture. We show that in addition to the
formerly observed specific heat peak there is a second peak at lower
temperatures which was not observable in earlier simulations. Second, we
present a general relation between the specific heat and the bulk modulus and
thus offer a smooth connection between the liquid and amorphous solid states.
The central result of this paper is a connection between the micro-melting of
clusters in the system and the appearance of specific heat peaks. We relate the
two peaks to changes in the bulk and shear moduli. We propose that the
phenomenon of glass-formation is accompanied by a fast change in the bulk and
the shear moduli, but these fast changes occur in different ranges of the
temperature. Lastly, we demonstrate how to construct a theory of the frequency
dependent complex specific heat, expected from heterogeneous clustering in the
liquid state of glass formers. A specific example is provided in the context of
our model for the dynamics of glycerol. The theoretical frequency dependent
specific heat agrees well with experimental measurements on glycerol. We
conclude the paper by stating that there is nothing universal about the
temperature dependence of the specific heat in glass formers - unfortunately
one needs to understand each case by itself.


title: Misalignment of the microquasar V4641 Sgr (SAX J1819.3--2525)

abstract:
  In the microquasar V4641 Sgr the spin of the black hole is thought to be
misaligned with the binary orbital axis. The accretion disc aligns with the
black hole spin by the Lense-Thirring effect near to the black hole and further
out becomes aligned with the binary orbital axis. The inclination of the radio
jets and the Fe$K\alpha$ line profile have both been used to determine the
inclination of the inner accretion disc but the measurements are inconsistent.
Using a steady state analytical warped disc model for V4641 Sgr we find that
the inner disc region is flat and aligned with the black hole up to about $900
R_{\rm g}$. Thus if both the radio jet and fluorescent emission originates in
the same inner region then the measurements of the inner disc inclination
should be the same.


title: Phase diagram of geometric d-wave superconductor Josephson junctions

abstract:
  We show that a constriction-type Josephson junction realized by an epitactic
thin film of a d-wave superconductor with an appropriate boundary geometry
exhibits intrinsic phase differences between 0 and pi depending on geometric
parameters and temperature. Based on microscopic Eilenberger theory, we provide
a general derivation of the relation between the change of the free energy of
the junction and the current-phase relation. From the change of the free
energy, we calculate phase diagrams and discuss transitions driven by geometric
parameters and temperature.


title: A growing dynamo from a saturated Roberts flow dynamo

abstract:
  Using direct simulations, weakly nonlinear theory and nonlinear mean-field
theory, it is shown that the quenched velocity field of a saturated nonlinear
dynamo can itself act as a kinematic dynamo. The flow is driven by a forcing
function that would produce a Roberts flow in the absence of a magnetic field.
This result confirms an analogous finding by F. Cattaneo & S. M. Tobias
(arXiv:0809.1801) for the more complicated case of turbulent convection,
suggesting that this may be a common property of nonlinear dynamos; see also
the talk given also online at the Kavli Institute for Theoretical Physics
(http://online.kitp.ucsb.edu/online/dynamo_c08/cattaneo). It is argued that
this property can be used to test nonlinear mean-field dynamo theories.


title: An Abundance of Heterotic Vacua

abstract:
  We explicitly construct the largest dataset to date of heterotic vacua
arising from stable vector bundles on Calabi-Yau threefolds. Focusing on
elliptically fibered Calabi-Yau manifolds with spectral cover bundles, we show
that the number of heterotic models with non-zero number of generations is
finite. We classify these models according to the complex base of their
Calabi-Yau threefold and to the unification gauge group that they preserve in
four dimensions. This database of the order of $10^7$ models, which includes
potential Standard Model candidates, is subjected to some preliminary
statistical analyses. The additional constraint that there should be three net
generations of particles gives a dramatic reduction of the number of vacua.


title:
Tidal disruption and ignition of white dwarfs by moderately massive
  black holes

abstract:
  We present a numerical investigation of the tidal disruption of white dwarfs
by moderately massive black holes, with particular reference to the centers of
dwarf galaxies and globular clusters. Special attention is given to the fate of
white dwarfs of all masses that approach the black hole close enough to be
disrupted and severely compressed to such extent that explosive nuclear burning
can be triggered. Consistent modeling of the gas dynamics together with the
nuclear reactions allows for a realistic determination of the explosive energy
release. In the most favorable cases, the nuclear energy release may be
comparable to that of typical type Ia supernovae. Although the explosion will
increase the mass fraction escaping on hyperbolic orbits, a good fraction of
the debris remains to be swallowed by the hole, causing a bright soft X-ray
flare lasting for about a year. Such transient signatures, if detected, would
be a compelling testimony for the presence of a moderately mass black hole
(below $10^5 M_\odot$).


title: Flow Results and Hints of Incomplete Thermalization

abstract:
  We classified $v_2$ measurements according to their sensitivities w.r.t. to
two planes, namely, reaction plane and participant plane. Likewise, in
$v_2/\epsilon$ scaling, we showed that one needs to choose a $\epsilon$ that is
sensitive to the same plane as that $v_2$ is sensitive to. We presented our
$v_2/\epsilon$ as a function of centrality and transverse momentum. We studied
the ratio of $v_4/v_2^2$. We discussed the applicable range for hydrodynamics,
as well as implications to an incomplete thermalization.


title:
Harmonic oscillator eigenfunction expansions, quantum dots, and
  effective interactions

abstract:
  We give a thorough analysis of the convergence properties of the
configuration-interaction method as applied to parabolic quantum dots among
other systems, including \emph{a priori} error estimates. The method converges
slowly in general, and in order to overcome this, we propose to use an
effective two-body interaction well-known from nuclear physics. Through
numerical experiments we demonstrate a significant increase in accuracy of the
configuration interaction method.


title: Superintegrability of the Caged Anisotropic Oscillator

abstract:
  We study "the Caged Anisotropic Harmonic Oscillator", which is a new example
of a superintegrable, or accidentally degenerate Hamiltonian. The potential is
that of the harmonic oscillator with rational frequency ratio (l:m:n), but
additionally with barrier terms describing repulsive forces from the principal
planes. This confines the classical motion to a sector bounded by the principal
planes, or cage. In 3 degrees, there are five isolating integrals of motion,
ensuring that all bound trajectories are closed and strictly periodic. Three of
the integrals are quadratic in the momenta, the remaining two are polynomials
of order 2(l+m-1) and 2(l+n-1). In the quantum problem, the eigenstates are
multiply degenerate, exhibiting multiple copies of the fundamental pattern of
the symmetry group SU(3).

categories: nlin.SI math-ph math.MP nlin.AO nlin.CD nlin.CG


title: Tuning the Charge Density Wave and Superconductivity in CuxTaS2

abstract:
  We report the characterization of layered, 2H-type CuxTaS2, for x between 0
and 0.12. The charge density wave (CDW), at 70 K for TaS2, is destabilized with
Cu doping. The sub-1K superconducting transition in undoped 2H-TaS2 jumps
quickly to 2.5 K at low x, increases to 4.5 K at the optimal composition
Cu0.04TaS2, and then decreases at higher x. The electronic contribution to the
specific heat, first increasing and then decreasing as a function of Cu
content, is 12 mJ mol-1 K-2 at Cu0.04TaS2. Electron diffraction studies show
that the CDW remains present at the optimal superconducting composition, but
with both a changed q vector and decreased coherence length. We present an
electronic phase diagram for the system.


title: Post Common Envelope Binaries from SDSS - III. Seven new orbital periods

abstract:
  We present follow-up spectroscopy and photometry of 11 post common envelope
binary (PCEB) candidates identified from multiple Sloan Digital Sky Survey
(SDSS) spectroscopy in an earlier paper. Radial velocity measurements using the
\Lines{Na}{I}{8183.27,8194.81} absorption doublet were performed for nine of
these systems and provided measurements of six orbital periods in the range
$\Porb= 2.7-17.4$ h. Three PCEB candidates did not show significant radial
velocity variations in the follow-up data, and we discuss the implications for
the use of SDSS spectroscopy alone to identify PCEBs. Differential photometry
confirmed one of our spectroscopic orbital periods and provided one additional
\Porb measurement. Binary parameters are estimated for the seven objects for
which we have measured the orbital period and the radial velocity amplitude of
the low-mass companion star, $K_\mathrm{sec}$. So far, we have published nine
SDSS PCEBs orbital periods, all of them $\Porb<1$ d. We perform Monte-Carlo
simulations and show that $3\sigma$ SDSS radial velocity variations should
still be detectable for systems in the orbital period range of $\Porb\sim1-10$
days. Consequently, our results suggest that the number of PCEBs decreases
considerably for $\Porb>1$ day, and that during the common envelope phase the
orbital energy of the binary star is maybe less efficiently used to expell the
envelope than frequently assumed.


title:
Entangled state for constructing generalized phase space representation
  and its statistical behavior

abstract:
  Based on the conception of quantum entanglement of Einstein-Podolsky-Rosen we
construct generalized phase space representation associated with the entangled
state |Gamma>_{e}, which is endowed with definite physical meaning. The set of
states make up a complete and non-orthogonal representation. The Weyl ordered
form of |Gamma>_{ee}_<Gamma| is derived which clearly exhibit the statistical
behavior of marginal distribution of |Gamma>_{ee}_<Gamma|.The minimum
uncertainty relation obeyed by |Gamma>_{e} is also demonstrated.


title: On the Renormalization of Theories of a Scalar Chiral Superfield

abstract:
  An exact renormalization group for theories of a scalar chiral superfield is
formulated, directly in four dimensional Euclidean space. By constructing a
projector which isolates the superpotential from the full Wilsonian effective
action, it is shown that the nonperturbative nonrenormalization theorem
follows, quite simply, from the flow equation. Next, it is argued that there do
not exist any physically acceptable non-trivial fixed points. Finally, the
Wess-Zumino model is considered, as a low energy effective theory. Following an
evaluation of the one and two loop beta-function coefficients, to illustrate
the ease of use of the formalism, it is shown that the beta-function in the
massless case does not receive any nonperturbative power corrections.


title: Single-particle spectral function for the classical one-component plasma

abstract:
  The spectral function for an electron one-component plasma is calculated
self-consistently using the GW0 approximation for the single-particle
self-energy. In this way, correlation effects which go beyond the mean-field
description of the plasma are contained, i.e. the collisional damping of
single-particle states, the dynamical screening of the interaction and the
appearance of collective plasma modes. Secondly, a novel non-perturbative
analytic solution for the on-shell GW0 self-energy as a function of momentum is
presented. It reproduces the numerical data for the spectral function with a
relative error of less than 10% in the regime where the Debye screening
parameter is smaller than the inverse Bohr radius, kappa<1/a_B. In the limit of
low density, the non-perturbative self-energy behaves as n^(1/4), whereas a
perturbation expansion leads to the unphysical result of a density independent
self-energy [W. Fennel and H. P. Wilfer, Ann. Phys. Lpz._32_, 265 (1974)]. The
derived expression will greatly facilitate the calculation of observables in
correlated plasmas (transport properties, equation of state) that need the
spectral function as an input quantity. This is demonstrated for the shift of
the chemical potential, which is computed from the analytical formulae and
compared to the GW0-result. At a plasma temperature of 100 eV and densities
below 10^21 cm^-3, both approaches deviate less than 10% from each other.


title: High-dimensional Gaussian model selection on a Gaussian design

abstract:
  We consider the problem of estimating the conditional mean of a real Gaussian
variable $\nolinebreak Y=\sum_{i=1}^p\nolinebreak\theta_iX_i+\nolinebreak
\epsilon$ where the vector of the covariates $(X_i)_{1\leq i\leq p}$ follows a
joint Gaussian distribution. This issue often occurs when one aims at
estimating the graph or the distribution of a Gaussian graphical model. We
introduce a general model selection procedure which is based on the
minimization of a penalized least-squares type criterion. It handles a variety
of problems such as ordered and complete variable selection, allows to
incorporate some prior knowledge on the model and applies when the number of
covariates $p$ is larger than the number of observations $n$. Moreover, it is
shown to achieve a non-asymptotic oracle inequality independently of the
correlation structure of the covariates. We also exhibit various minimax rates
of estimation in the considered framework and hence derive adaptiveness
properties of our procedure.


title:
Angular Momentum Projected Configuration Interaction with Realistic
  Hamiltonians

abstract:
  The Projected Configuration Interaction (PCI) method starts from a collection
of mean-field wave functions, and builds up correlated wave functions of good
symmetry. It relies on the Generator Coordinator Method (GCM) techniques, but
it improves the past approaches by a very efficient method of selecting the
basis states. We use the same realistic Hamiltonians and model spaces as the
Configuration Interaction (CI) method, and compare the results with the full CI
calculations in the sd and pf shell. Examples of 24Mg, 28Si, 48Cr, 52Fe and
56Ni are discussed.


title:
Wilson lines - color charge densities correlators and the production of
  eta' in the CGC for pp and pA collisions

abstract:
  We compute the inclusive differential cross section production of the
pseudo-scalar meson eta' in high-energy proton-proton (pp) and proton-nucleus
(pA) collisions. We use an effective coupling between gluons and eta' meson to
derive a reduction formula that relates the eta' production to a field-strength
tensor correlator. For pA collisions we take into account saturation effects on
the nucleus side by using the Color Glass Condensate formalism to evaluate this
correlator. We derive new results for Wilson line - color charges correlators
in the McLerran-Venugopalan model needed in the computation of eta' production.
The unintegrated parton distribution functions are used to characterize the
gluon distribution inside protons. We show that in pp collisions, the cross
section depends on the parametrization of unintegrated parton distribution
functions and thus, it can be used to put constraints on these distributions.
We also demonstrate that in pA collisions, the cross section is sensitive to
saturation effects so it can be utilized to estimate the value of the
saturation scale.


title: Supertwistors, massive superparticles and k-symmetry

abstract:
  We consider a D=4 two-twistor lagrangian for a massive particle that
incorporates the mass-shell condition in an algebraic way, and extend it to a
two-supertwistor model with N=2 supersymmetry and central charge identified
with the mass. In the purely supertwistorial picture the two D=4 supertwistors
are coupled through a Wess-Zumino term in their fermionic sector. We
demonstrate how the kappa-gauge symmetry appears in the purely supertwistorial
formulation and reduces by half the fermionic degrees of freedom of the two
supertwistors; a formulation of the model in terms of kappa-invariant degrees
of freedom is also obtained. We show that the kappa-invariant supertwistor
coordinates can be obtained by dimensional (D=6 -> D=4) reduction from a D=6
supertwistor. We derive as well by 6 -> 4 reduction the N=2, D=4 massive
superparticle model with Wess-Zumino term introduced in 1982. Finally, we
comment on general superparticle models constructed with more than two
supertwistors.


title:
Estimating stellar rotation from starspot detection during planetary
  transits

abstract:
  A new method for determining the stellar rotation period is proposed here,
based on the detection of starspots during transits of an extra-solar planet
orbiting its host star. As the planet eclipses the star, it may pass in front
of a starspot which will then make itself known through small flux variations
in the transit light curve. If we are lucky enough to catch the same spot on
two consecutive transits, it is possible to estimate the stellar rotational
period. This method is successfully tested on transit simulations on the Sun
yielding the correct value for the solar period. By detecting two starspots on
more than one transit of HD 209458 observed by the Hubble Space Telescope, it
was possible to estimate a period of either 9.9 or 11.4 days for the star,
depending on which spot is responsible for the signature in the light curve a
few transits later. Comparison with period estimates of HD209458 reported in
the literature indicates that 11.4 days is the most likely stellar rotation
period.


title:
Multi-Particle Collision Dynamics -- a Particle-Based Mesoscale
  Simulation Approach to the Hydrodynamics of Complex Fluids

abstract:
  In this review, we describe and analyze a mesoscale simulation method for
fluid flow, which was introduced by Malevanets and Kapral in 1999, and is now
called multi-particle collision dynamics (MPC) or stochastic rotation dynamics
(SRD). The method consists of alternating streaming and collision steps in an
ensemble of point particles. The multi-particle collisions are performed by
grouping particles in collision cells, and mass, momentum, and energy are
locally conserved. This simulation technique captures both full hydrodynamic
interactions and thermal fluctuations. The first part of the review begins with
a description of several widely used MPC algorithms and then discusses
important features of the original SRD algorithm and frequently used
variations. Two complementary approaches for deriving the hydrodynamic
equations and evaluating the transport coefficients are reviewed. It is then
shown how MPC algorithms can be generalized to model non-ideal fluids, and
binary mixtures with a consolute point. The importance of angular-momentum
conservation for systems like phase-separated liquids with different
viscosities is discussed. The second part of the review describes a number of
recent applications of MPC algorithms to study colloid and polymer dynamics,
the behavior of vesicles and cells in hydrodynamic flows, and the dynamics of
viscoelastic fluids.


title: Parallel calibrations and minimal submanifolds

abstract:
  Given a parallel calibration $\phi \in \Omega^p(M)$ on a Riemannian manifold
$M$, I prove that the $\phi$--critical submanifolds with nonzero critical value
are minimal submanifolds. I also show that the $\phi$--critical submanifolds
are precisely the integral manifolds of a $\mathscr{C}^\infty(M)$--linear
subspace $\sP \subset \Omega^p(M)$. In particular, the calibrated submanifolds
are necessarily integral submanifolds of the system. (Examples of parallel
calibrations include the special Lagrangian calibration on Calabi-Yau
manifolds, (co)associative calibrations on $G_2$--manifolds, and the Cayley
calibration on $\tSpin(7)$--manifolds.)


title:
NTT follow-up observations of star cluster candidates from the FSR
  catalogue

abstract:
  We are conducting a large program to classify newly discovered Milky Way star
cluster candidates from the list of Froebrich, Scholz & Raftery (2007). Here we
present deep NIR follow-up observations from ESO/NTT of 14 star cluster
candidates. We show that the combined analysis of star density maps and
colour-colour/magnitude diagrams derived from deep near-infrared imaging is a
viable tool to reliably classify new stellar clusters. This allowed us to
identify two young clusters with massive stars, three intermediate age open
clusters, and two globular cluster candidates among our targets. The remaining
seven objects are unlikely to be stellar clusters. Among them is the object
FSR1767 which has previously been identified as a globular cluster using 2MASS
data by Bonatto et al. (2007). Our new analysis shows that FSR1767 is not a
star cluster. We also summarise the currently available follow-up analysis of
the FSR candidates and conclude that this catalogue may contain a large number
of new stellar clusters, probably dominated by old open clusters.


title:
Local energy estimates for the finite element method on sharply varying
  grids

abstract:
  Local energy error estimates for the finite element method for elliptic
problems were originally proved in 1974 by Nitsche and Schatz. These estimates
show that the local energy error may be bounded by a local approximation term,
plus a global "pollution" term that measures the influence of solution quality
from outside the domain of interest and is heuristically of higher order.
However, the original analysis of Nitsche and Schatz is restricted to
quasi-uniform grids. We present local a priori energy estimates that are valid
on shape regular grids, an assumption which allows for highly graded meshes and
which much more closely matches the typical practical situation. Our chief
technical innovation is an improved superapproximation result.


title:
Search for Doubly Charged Higgs Bosons with Lepton-Flavor-Violating
  Decays involving Tau Leptons

abstract:
  We search for pair production of doubly charged Higgs particles followed by
decays into electron-tau and muon-tau pairs using data (350 inverse picobarns)
collected from proton-antiproton collisions at 1.96 TeV by the CDF II
experiment. We search separately for cases where three or four final-state
leptons are detected, and combine results for exclusive decays to left-handed
electron-tau (muon-tau) pairs. We set a lower mass limit of 114 (112) GeV/cc at
the 95% confidence level for left-handed doubly charged Higgs.


title: Tangent Cone of Numerical Semigroup Rings of Embedding Dimension Three

abstract:
  In this paper, we give new characterizations of the Buchsbaum and
Cohen-Macaulay properties of the tangent cone $\gr_\frakm(R)$, where
$(R,\frakm)$ is a numerical semigroup ring of embedding dimension 3. In
particular, we confirm the conjectures raised by Sapko on the Buchsbaumness of
$\gr_\frakm(R)$.


title: The relativistic Scott correction for atoms and molecules

abstract:
  We prove the first correction to the leading Thomas-Fermi energy for the
ground state energy of atoms and molecules in a model where the kinetic energy
of the electrons is treated relativistically. The leading Thomas-Fermi energy,
established in [Sorensen], as well as the correction given here are of
semi-classical nature. Our result on atoms and molecules is proved from a
general semi-classical estimate for relativistic operators with potentials with
Coulomb-like singularities. This semi-classical estimate is obtained using the
coherent state calculus introduced in [Solovej-Spitzer]. The paper contains a
unified treatment of the relativistic as well as the non-relativistic case.


title:
Electron screening and excitonic condensation in double-layer graphene
  systems

abstract:
  We theoretically investigate the possibility of excitonic condensation in a
system of two graphene monolayers separated by an insulator, in which electrons
and holes in the layers are induced by external gates. In contrast to the
recent studies of this system, we take into account the screening of the
interlayer Coulomb interaction by the carriers in the layers, and this
drastically changes the result. Due to a large number of electron species in
the system (two projections of spin, two valleys, and two layers) and to the
suppression of backscattering in graphene, the maximum possible strength of the
screened Coulomb interaction appears to be quite small making the weak-coupling
treatment applicable. We calculate the mean-field transition temperature for a
clean system and demonstrate that its highest possible value
$T_c^\text{max}\sim 10^{-7}\epsilon_F\lesssim 1 \text{mK}$ is extremely small
($\epsilon_F$ is the Fermi energy). In addition, any sufficiently short-range
disorder with the scattering time $\tau \lesssim \hbar /T_c^\text{max}$ would
suppress the condensate completely. Our findings renders experimental
observation of excitonic condensation in the above setup improbable even at
very low temperatures.


title: Higher dimensional Kerr-Schild spacetimes

abstract:
  We investigate general properties of Kerr-Schild (KS) metrics in n>4
spacetime dimensions. First, we show that the Weyl tensor is of type II or more
special if the null KS vector k is geodetic (or, equivalently, if
T_{ab}k^ak^b=0). We subsequently specialize to vacuum KS solutions, which
naturally split into two families of non-expanding and expanding metrics. After
demonstrating that non-expanding solutions are equivalent to the known class of
vacuum Kundt solutions of type N, we analyze expanding solutions in detail. We
show that they can only be of the type II or D, and we characterize optical
properties of the multiple Weyl aligned null direction (WAND) k. In general, k
has caustics corresponding to curvature singularities. In addition, it is
generically shearing. Nevertheless, we arrive at a possible "weak" n>4
extension of the Goldberg-Sachs theorem, limited to the KS class, which matches
previous conclusions for general type III/N solutions. In passing, properties
of Myers-Perry black holes and black rings related to our results are also
briefly discussed.