title: Supernova VLBI

abstract:
  We review VLBI observations of supernovae over the last quarter century and
discuss the prospect of imaging future supernovae with space VLBI in the
context of VSOP-2. From thousands of discovered supernovae, most of them at
cosmological distances, ~50 have been detected at radio wavelengths, most of
them in relatively nearby galaxies. All of the radio supernovae are Type II or
Ib/c, which originate from the explosion of massive progenitor stars. Of these,
12 were observed with VLBI and four of them, SN 1979C, SN 1986J, SN 1993J, and
SN 1987A, could be imaged in detail, the former three with VLBI. In addition,
supernovae or young supernova remnants were discovered at radio wavelengths in
highly dust-obscured galaxies, such as M82, Arp 299, and Arp 220, and some of
them could also be imaged in detail. Four of the supernovae so far observed
were sufficiently bright to be detectable with VSOP-2. With VSOP-2 the
expansion of supernovae can be monitored and investiated with unsurpassed
angular resolution, starting as early as the time of the supernova's transition
from its opaque to transparent stage. Such studies can reveal, in a movie, the
aftermath of a supernova explosion shortly after shock breakout.


title: Phase diagram of SU(2) with 2 flavors of dynamical adjoint quarks

abstract:
  We report on numerical simulations of SU(2) lattice gauge theory with two
flavors of light dynamical quarks in the adjoint of the gauge group. The
dynamics of this theory is thought to be very different from QCD -- the theory
exhibiting conformal or near conformal behavior in the infrared. We make a high
resolution survey of the phase diagram of this model in the plane of the bare
coupling and quark mass on lattices of size 8^3 \times 16. Our simulations
reveal a line of first order phase transitions extending from beta=0 to
beta=beta_c \sim 2.0. For beta > beta_c the phase boundary is no longer first
order but continues as the locus of minimum meson mass. For beta > 2.0 we
observe the pion and rho masses along the phase boundary to be light,
independent of bare coupling and approximately degenerate. We discuss possible
interpretations of these observations and corresponding continuum limits.


title: On the rich-club effect in dense and weighted networks

abstract:
  For many complex networks present in nature only a single instance, usually
of large size, is available. Any measurement made on this single instance
cannot be repeated on different realizations. In order to detect significant
patterns in a real--world network it is therefore crucial to compare the
measured results with a null model counterpart. Here we focus on dense and
weighted networks, proposing a suitable null model and studying the behaviour
of the degree correlations as measured by the rich-club coefficient. Our method
solves an existing problem with the randomization of dense unweighted graphs,
and at the same time represents a generalization of the rich--club coefficient
to weighted networks which is complementary to other recently proposed ones.


title: Neutrinos and Gamma Rays from Galaxy Clusters

abstract:
  The next generation of neutrino and gamma-ray detectors should provide new
insights into the creation and propagation of high-energy protons within galaxy
clusters, probing both the particle physics of cosmic rays interacting with the
background medium and the mechanisms for high-energy particle production within
the cluster. In this paper we examine the possible detection of gamma-rays (via
the GLAST satellite) and neutrinos (via the ICECUBE and Auger experiments) from
the Coma cluster of galaxies, as well as for the gamma-ray bright clusters
Abell 85, 1758, and 1914. These three were selected from their possible
association with unidentified EGRET sources, so it is not yet entirely certain
that their gamma-rays are indeed produced diffusively within the intracluster
medium, as opposed to AGNs. It is not obvious why these inconspicuous
Abell-clusters should be the first to be seen in gamma-rays, but a possible
reason is that all of them show direct evidence of recent or ongoing mergers.
Their identification with the EGRET gamma-ray sources is also supported by the
close correlation between their radio and (purported) gamma-ray fluxes. Under
favorable conditions (including a proton spectral index of 2.5 in the case of
Abell 85, and sim 2.3 for Coma, and Abell 1758 and 1914), we expect ICECUBE to
make as many as 0.3 neutrino detections per year from the Coma cluster of
galaxies, and as many as a few per year from the Abell clusters 85, 1758, and
1914. Also, Auger may detect as many as 2 events per decade at ~ EeV energies
from these gamma-ray bright clusters.


title: Suppressed FCNC in New Physics with Shared Flavor Symmetry

abstract:
  Many extensions of the Standard Model(SM) generate contributions to Flavor
Changing Neutral Current(FCNC) processes that must have sufficient flavor
suppression to be consistent with experiments, if the new physics (NP) is
associated with a scale of a TeV. Here we present a mechanism for suppressing
the NP effects to FCNC processes. We consider the possibility that the source
of NP contributions to FCNC processes share the same flavor symmetry underlying
the SM source of FCNC processes which are the quark and lepton mass matrices.
We call this the principle of shared flavor symmetry. In the flavor symmetric
limit, the quark and lepton mixing matrices have fixed forms and there are no
NP FCNC processes. In the flavor symmetric limit, we take the quark mixing
matrix to be the identity matrix and the lepton mixing matrix to be given by
tri-bimaximal mixing. Realistic mixing matrices are obtained by the small
breaking of the flavor symmetry. New contributions to FCNC processes arise
because of non universal breaking of the flavor symmetry in the quark and
lepton mass matrices and the NP sources of FCNC processes. In particular, we
will focus on new FCNC effects that arise due to the breaking of flavor
symmetry only in the quark and charged lepton mass matrices but not in the NP
sector. In this scenario, NP contributions to FCNC processes is linked to the
source of flavor symmetry breaking in the quark and charged lepton mass
matrices. To demonstrate the mechanism we use a two higgs doublet model as an
example of beyond the SM physics though one should be able to adapt this
mechanism to other models of new physics.


title: Cech homology for shape recognition in the presence of occlusions

abstract:
  In Computer Vision the ability to recognize objects in the presence of
occlusions is a necessary requirement for any shape representation method. In
this paper we investigate how the size function of a shape changes when a
portion of the shape is occluded by another shape. More precisely, considering
a set $X=A\cup B$ and a measuring function $\phi$ on $X$, we establish a
condition so that
$\ell_{(X,\phi)=\ell_{(A,\phi|_A)}+\ell_{(B,\phi|_B)}-\ell_{(A\cap
B,\phi|_{A\cap B})}$. The main tool we use is the Mayer-Vietoris sequence of
\v{C}ech homology groups. This result allows us to prove that size functions
are able to detect partial matching between shapes by showing a common subset
of cornerpoints.


title: Landau-Zener Transitions in an Adiabatic Quantum Computer

abstract:
  We report an experimental measurement of Landau-Zener transitions on an
individual flux qubit within a multi-qubit superconducting chip designed for
adiabatic quantum computation. The method used isolates a single qubit, tunes
its tunneling amplitude Delta into the limit where Delta is much less than both
the temperature T and the decoherence-induced energy level broadening, and
forces it to undergo a Landau-Zener transition. We find that the behavior of
the qubit agrees to a high degree of accuracy with theoretical predictions for
Landau-Zener transition probabilities for a double-well quantum system coupled
to 1/f magnetic flux noise.


title: Algebraic Independence in SL(3,C) Character Varieties of Free Groups

abstract:
  Let X be the moduli space of SL(3,C) representations of a free group of rank
r. In this paper we describe maximal algebraically independent subsets of
certain minimal sets of coordinate functions on X. These subsets locally
parametrize the moduli space.


title: An Improved Robust Fuzzy Extractor

abstract:
  We consider the problem of building robust fuzzy extractors, which allow two
parties holding similar random variables W, W' to agree on a secret key R in
the presence of an active adversary. Robust fuzzy extractors were defined by
Dodis et al. in Crypto 2006 to be noninteractive, i.e., only one message P,
which can be modified by an unbounded adversary, can pass from one party to the
other. This allows them to be used by a single party at different points in
time (e.g., for key recovery or biometric authentication), but also presents an
additional challenge: what if R is used, and thus possibly observed by the
adversary, before the adversary has a chance to modify P. Fuzzy extractors
secure against such a strong attack are called post-application robust.
  We construct a fuzzy extractor with post-application robustness that extracts
a shared secret key of up to (2m-n)/2 bits (depending on error-tolerance and
security parameters), where n is the bit-length and m is the entropy of W. The
previously best known result, also of Dodis et al., extracted up to (2m-n)/3
bits (depending on the same parameters).


title: Pressure-induced superconductivity in single crystal CaFe2As2

abstract:
  We report pressure-induced superconductivity in a single crystal of CaFe2As2.
At atmospheric pressure, this material is antiferromagnetic below 170 K but
under an applied pressure of 0.69 GPa becomes superconducting, with a
transition temperature Tc exceeding 10 K. The rate of Tc suppression with
applied magnetic field is -0.7 K/T, giving an extrapolated zero-temperature
upper critical field of 10-14T.


title: Supersymmetric models with minimal flavour violation and their running

abstract:
  We revisit the formulation of the principle of minimal flavor violation (MFV)
in the minimal supersymmetric extension of the standard model, both at moderate
and large tan(beta), and with or without new CP-violating phases. We introduce
a counting rule which keeps track of the highly hierarchical structure of the
Yukawa matrices. In this manner, we are able to control systematically which
terms can be discarded in the soft SUSY breaking part of the Lagrangian. We
argue that for the implementation of this counting rule, it is convenient to
introduce a new basis of matrices in which both the squark (and slepton) mass
terms as well as the trilinear couplings can be expanded. We derive the RGE for
the MFV parameters and show that the beta functions also respect the counting
rule. For moderate tan(beta), we provide explicit analytic solutions of these
RGE and illustrate their behaviour by analyzing the neighbourhood (also
switching on new phases) of the SPS-1a benchmark point. We then show that even
in the case of large tan(beta), the RGE remain valid and that the analytic
solutions obtained for moderate tan(beta) still allow us to understand the most
important features of the running of the parameters, as illustrated with the
help of the SPS-4 benchmark point.


title: Semi-classical strings in AdS_4*CP^3

abstract:
  In this paper, we study the semi-classical strings in AdS_4*CP^3 spacetime.
We construct various kinds of string solutions, including the point-like,
circular, folded and pulsating strings. For the circular and folded strings, we
figure out their field theory dual operators. In particular, we discuss the
anomalous dimensions of the corresponding operators from decoupled SU(2)*SU(2)
spin chain. We find that in the large angular momentum limit, the field theory
and string theory results are in very good agreement up to an interpolating
function of coupling constant.


title: Parallel Coupling of Symmetric and Asymmetric Exclusion Processes

abstract:
  A system consisting of two parallel coupled channels where particles in one
of them follow the rules of totally asymmetric exclusion processes (TASEP) and
in another one move as in symmetric simple exclusion processes (SSEP) is
investigated theoretically. Particles interact with each other via hard-core
exclusion potential, and in the asymmetric channel they can only hop in one
direction, while on the symmetric lattice particles jump in both directions
with equal probabilities. Inter-channel transitions are also allowed at every
site of both lattices. Stationary state properties of the system are solved
exactly in the limit of strong couplings between the channels. It is shown that
strong symmetric couplings between totally asymmetric and symmetric channels
lead to an effective partially asymmetric simple exclusion process (PASEP) and
properties of both channels become almost identical. However, strong asymmetric
couplings between symmetric and asymmetric channels yield an effective TASEP
with nonzero particle flux in the asymmetric channel and zero flux on the
symmetric lattice. For intermediate strength of couplings between the lattices
a vertical cluster mean-field method is developed. This approximate approach
treats exactly particle dynamics during the vertical transitions between the
channels and it neglects the correlations along the channels. Our calculations
show that in all cases there are three stationary phases defined by particle
dynamics at entrances, at exits or in the bulk of the system, while phase
boundaries depend on the strength and symmetry of couplings between the
channels. Extensive Monte Carlo computer simulations strongly support our
theoretical predictions.


title:
Duality between normal and superconducting junctions of multiple quantum
  wires

abstract:
  We study junctions of single-channel spinless Luttinger liquids using
bosonisation. We generalize earlier studies by allowing the junction to be
superconducting and find new charge non-conserving low energy fixed points. We
establish the existence of $g \leftrightarrow 1/g$ duality (where $g$ is the
Luttinger Liquid parameter) between the charge conserving (normal) junction and
the charge non-conserving (superconducting) junction by evaluating and
comparing the scaling dimensions of various operators around the fixed points
in normal and superconducting sectors of the theory. For the most general
two-wire junction, we show that there are two conformally invariant
one-parameter families of fixed points which are also connected by a duality
transformation. We also show that the stable fixed point for the two-wire
superconducting junction corresponds to the situation where the crossed Andreev
reflection is perfect between the wires. For the three-wire junction, we study,
in particular, the superconducting analogs of the chiral, $D_P$ and the
disconnected fixed points obtained earlier in the literature in the context of
charge conserving three-wire junctions. We show that these fixed points can be
stabilized for $g < 1$ (repulsive electrons) within the superconducting sector
of the theory which makes them experimentally relevant.


title:
A Comparison Theorem for Gromov-Witten Invariants in the Symplectic
  Category

abstract:
  In this paper we exploit the geometric approach to the virtual fundamental
class, due to Fukaya-Ono and Li-Tian, to compare the virtual fundamental
classes of stable maps to a symplectic manifold and a symplectic submanifold
whenever all constrained stable maps to the former are contained in the latter
to first order. This extends versions of a statement well-known in the
algebraic category to the symplectic category, where it appears to be less
familiar. The latter's inherent flexibility then leads to a confirmation of
Pandharipande's Gopakumar-Vafa prediction for GW-invariants of Fano classes in
6-dimensional symplectic manifolds. In a forthcoming paper, we use a similar
approach to relative Gromov-Witten invariants and the absolute/relative
correspondence in genus~0.


title:
Effective potentials and electrostatic interactions in self-assembled
  molecular bilayers II: the case of biological membranes

abstract:
  We propose a very simple but realistic enough model which allows to include a
large number of molecules in molecular dynamics MD simulations of these
bilayers, but nevertheless taking into account molecular charge distributions,
flexible amphiphilic molecules and a reliable model of water. All these
parameters are essential in a nanoscopic scale study of intermolecular and long
range electrostatic interactions. This model was previously used by us to
simulate a Newton black film and in this paper we extend our investigation to
bilayers of the biological membrane type. The electrostatic interactions are
calculated using Ewald sums and, for the macroscopic long range electrostatic
interactions, we use our previously proposed coarsed fit of the (perpendicular
to the bilayer plane) molecular charge distributions with gaussian
distributions. To study an unique biological membrane (not an stack of
bilayers), we propose a simple effective external potential that takes into
account the microscopic pair distribution functions of water and is used to
simulate the interaction with the surrounding water. The method of effective
macroscopic and external potentials is extremely simple to implement in
numerical simulations, and the spatial and temporal charge inhomogeneities are
then roughly taken into account. Molecular dynamics simulations of several
models of a single biological membrane, of neutral or charged polar
amphiphilics, with or without water (using the TIP5P intermolecular potential
for water) are included.


title: Shortest Paths Avoiding Forbidden Subpaths

abstract:
  In this paper we study a variant of the shortest path problem in graphs:
given a weighted graph G and vertices s and t, and given a set X of forbidden
paths in G, find a shortest s-t path P such that no path in X is a subpath of
P. Path P is allowed to repeat vertices and edges. We call each path in X an
exception, and our desired path a shortest exception-avoiding path. We
formulate a new version of the problem where the algorithm has no a priori
knowledge of X, and finds out about an exception x in X only when a path
containing x fails. This situation arises in computing shortest paths in
optical networks. We give an algorithm that finds a shortest exception avoiding
path in time polynomial in |G| and |X|. The main idea is to run Dijkstra's
algorithm incrementally after replicating vertices when an exception is
discovered.


title: Multiple M2-branes and Generalized 3-Lie algebras

abstract:
  We propose a generalization of the Bagger-Lambert-Gustavsson action as a
candidate for the description of an arbitrary number of M2-branes. The action
is formulated in terms of N=2 superfields in three dimensions and corresponds
to an extension of the usual superfield formulation of Chern-Simons matter
theories. Demanding gauge invariance of the resulting theory does not imply the
total antisymmetry of the underlying 3-Lie algebra structure constants. We
relax this condition and propose a class of examples for these generalized
3-Lie algebras. We also discuss how to associate various ordinary Lie algebras.


title:
Abundances of Sr, Y, and Zr in Metal-Poor Stars and Implications for
  Chemical Evolution in the Early Galaxy

abstract:
  Studies of nucleosynthesis in neutrino-driven winds from nascent neutron
stars show that the elements from Sr through Ag with mass numbers A~88-110 are
produced by charged-particle reactions (CPR) during the alpha-process in the
winds. Accordingly, we have attributed all these elements in stars of low
metallicities ([Fe/H]<-1.5) to low-mass and normal supernovae (SNe) from
progenitors of ~8-11M_sun and ~12-25M_sun, respectively, which leave behind
neutron stars. Using this rule and attributing all Fe production to normal SNe,
we previously developed a phenomenological two-component model, which predicts
that [Sr/Fe]>-0.32 for all metal-poor stars. The high-resolution data now
available on Sr abundances in Galactic halo stars show that there is a great
shortfall of Sr relative to Fe in many stars with [Fe/H]<-3. This is in direct
conflict with the above prediction. The same conflict also exists for two other
CPR elements Y and Zr. The very low abundances of Sr, Y, and Zr observed in
stars with [Fe/H]<-3 thus require a stellar source that cannot be low-mass or
normal SNe. We show that this observation requires a stellar source leaving
behind black holes and that hypernovae (HNe) from progenitors of ~25-50M_sun
are the most plausible candidates. (Abridged)


title:
Reconstructing the history of structure formation using redshift
  distortions

abstract:
  Measuring the statistics of galaxy peculiar velocities using redshift-space
distortions is an excellent way of probing the history of structure formation.
Because galaxies are expected to act as test particles within the flow of
matter, this method avoids uncertainties due to an unknown galaxy density bias.
We show that the parameter combination measured by redshift-space distortions,
$f\sigma_8^{\rm mass}$ provides a good test of dark energy models, even without
the knowledge of bias or $\sigma_8^{\rm mass}$ required to extract $f$ from
this measurement (here $f$ is the logarithmic derivative of the linear growth
rate, and $\sigma_8^{\rm mass}$ is the root-mean-square mass fluctuation in
spheres with radius $8h^{-1}$Mpc). We argue that redshift-space distortion
measurements will help to determine the physics behind the cosmic acceleration,
testing whether it is related to dark energy or modified gravity, and will
provide an opportunity to test possible dark energy clumping or coupling
between dark energy and dark matter. If we can measure galaxy bias in addition,
simultaneous measurement of both the overdensity and velocity fields can be
used to test the validity of equivalence principle, through the continuity
equation.


title: DA495 - an aging pulsar wind nebula

abstract:
  We present a radio continuum study of the pulsar wind nebula (PWN) DA 495
(G65.7+1.2), including images of total intensity and linear polarization from
408 to 10550 MHz based on the Canadian Galactic Plane Survey and observations
with the Effelsberg 100-m Radio Telescope. Removal of flux density
contributions from a superimposed \ion{H}{2} region and from compact
extragalactic sources reveals a break in the spectrum of DA 495 at 1.3 GHz,
with a spectral index ${\alpha}={-0.45 \pm 0.20}$ below the break and
${\alpha}={-0.87 \pm 0.10}$ above it (${S}_\nu \propto{\nu^{\alpha}}$). The
spectral break is more than three times lower in frequency than the lowest
break detected in any other PWN. The break in the spectrum is likely the result
of synchrotron cooling, and DA 495, at an age of $\sim$20,000 yr, may have
evolved from an object similar to the Vela X nebula, with a similarly energetic
pulsar. We find a magnetic field of $\sim$1.3 mG inside the nebula. After
correcting for the resulting high internal rotation measure, the magnetic field
structure is quite simple, resembling the inner part of a dipole field
projected onto the plane of the sky, although a toroidal component is likely
also present. The dipole field axis, which should be parallel to the spin axis
of the putative pulsar, lies at an angle of ${\sim}50\degr$ east of the North
Celestial Pole and is pointing away from us towards the south-west. The upper
limit for the radio surface brightness of any shell-type supernova remnant
emission around DA 495 is $\Sigma_{1 GHz} \sim 5.4 \times 10^{-23}$ OAWatt
m$^{-2}$ Hz$^{-1}$ sr$^{-1}$ (assuming a radio spectral index of $\alpha =
-0.5$), lower than the faintest shell-type remnant known to date.


title:
Truncated Nambu-Poisson Bracket and Entropy Formula for Multiple
  Membranes

abstract:
  We show that there exists a cut-off version of Nambu-Poisson bracket which
defines a finite dimensional Lie 3-algebra. The algebra still satisfies the
fundamental identity and thus produces N=8 supersymmetric BLG type equation of
motion for multiple M2 branes. By counting the number of the moduli and the
degree of freedom, we derive an entropy formula which scales as N^{3/2} as
expected for the multiple M2 branes.


title: On the eigenvalues of the twisted Dirac operator

abstract:
  Given a compact Riemannian spin manifold with positive scalar curvature, we
find a family of connections $\nabla^{A_t}$ for $t\in[0,1]$ on a trivial vector
bundle of sufficiently high rank, such that the first eigenvalue of the twisted
Dirac operator $D_{A_t}$ is nonzero and becomes arbitrarily small as $t\to1$.
However, if one restricts the class of twisting connections considered, then
nonzero lower bounds do exist. We illustrate this fact by establishing a
nonzero lower bound for the Dirac operator twisted by Hermitian-Einstein
connections over Riemann surfaces.


title:
Chemical Evolution of Heavy Elements in the Early Galaxy: Implications
  for Stellar Sources

abstract:
  An overview of the sources for heavy elements in the early Galaxy is given.
It is shown that observations of abundances in metal-poor stars can be used
along with a basic understanding of stellar models to guide the search for the
source of the heavy r-process nuclei (r-nuclei). Observations show that this
source produces very little of the elements from C through Zn including Fe.
This strongly suggests that O-Ne-Mg core-collapse supernovae (SNe) from
progenitors of ~8-11M_sun are the source for the heavy r-nuclei. It is shown
that a two-component model based on the abundances of Fe (from Fe core-collapse
SNe) and Eu (from O-Ne-Mg core-collapse SNe) gives very good quantitative
predictions for the abundances of all the other elements in metal-poor stars.


title:
Momentum dependence of the superconducting gap in NdFeAsO1-xFx single
  crystals measured by angle resolved photoemission spectroscopy

abstract:
  We use angle resolved photoemission spectroscopy (ARPES) to study the
momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals.
We find that the Gamma hole pocket is fully gapped below the superconducting
transition temperature. The value of the superconducting gap is 15 +- 1.5 meV
and its anisotropy around the hole pocket is smaller than 20% of this value.
This is consistent with an isotropic or anisotropic s-wave symmetry of the
order parameter or exotic d-wave symmetry with nodes located off the Fermi
surface sheets. This is a significant departure from the situation in the
cuprates, pointing to possibility that the superconductivity in the iron
arsenic based system arises from a different mechanism.


title: Confinement effects from massive photons

abstract:
  This paper has been withdrawn by the author due to an error in equations 39
and 41.


title:
Classification of irreducible modules of the vertex algebra $V_L^+$ when
  $L$ is a nondegenerate even lattice of an arbitrary rank

abstract:
  In this paper, we first classify all irreducible modules of the vertex
algebra $V_L^+$ when $L$ is a negative definite even lattice of arbitrary rank.
In particular, we show that any irreducible $V_L^+$-module is isomorphic to a
submodule of an irreducible twisted $V_L$-module. We then extend this result to
a vertex algebra $V_L^+$ when $L$ is a nondegenerate even lattice of finite
rank.


title: Nucleosynthesis in Metal-Free and Metal-Poor Stars

abstract:
  There have been a number of important recent developments in theoretical and
observational studies of nucleosynthesis, especially regarding nucleosynthetic
sources at low metallicities. Those selected for discussion here include the
origin of Li6, the primary production of N, the s-process, and the supernova
sources for three groups of metals: (1) C to Zn with mass numbers A<70, (2) Sr
to Ag with A~90-110, and (3) r-process nuclei with A~130 and above.


title: Mechanical rejuvenation and over-aging in the soft glassy rheology model

abstract:
  Mechanical rejuvenation and over-aging of glasses is investigated through
stochastic simulations of the soft glassy rheology (SGR) model. Strain- and
stress-controlled deformation cycles for a wide range of loading conditions are
analyzed and compared to molecular dynamics simulations of a model polymer
glass. Results indicate that deformation causes predominantly rejuvenation,
whereas over-aging occurs only at very low temperature, small strains, and for
high initial energy states. Although the creep compliance in the SGR model
exhibits full aging independent of applied load, large stresses in the
nonlinear creep regime cause configurational changes leading to rejuvenation of
the relaxation time spectrum probed after a stress cycle. During recovery,
however, the rejuvenated state rapidly returns to the original aging trajectory
due to collective relaxations of the internal strain.


title: A spatially shifted beam approach to subwavelength focusing

abstract:
  Although negative-refractive-index metamaterials have successfully achieved
subwavelength focusing, image resolution is limited by the presence of losses.
In this Letter, a metal transmission screen with subwavelength spaced slots is
proposed that focuses the near-field beyond the diffraction limit and
furthermore, is easily scaled from microwave frequencies to the optical regime.
An analytical model based on the superposition of shifted beam patterns is
developed that agrees very well with full-wave simulations and is corroborated
by experimental results at microwave frequencies.


title: On Wiretap Networks II

abstract:
  We consider the problem of securing a multicast network against a wiretapper
that can intercept the packets on a limited number of arbitrary network links
of his choice. We assume that the network implements network coding techniques
to simultaneously deliver all the packets available at the source to all the
destinations. We show how this problem can be looked at as a network
generalization of the Ozarow-Wyner Wiretap Channel of type II. In particular,
we show that network security can be achieved by using the Ozarow-Wyner
approach of coset coding at the source on top of the implemented network code.
This way, we quickly and transparently recover some of the results available in
the literature on secure network coding for wiretapped networks. We also derive
new bounds on the required secure code alphabet size and an algorithm for code
construction.


title:
TERAD91: A Program package for the calculation of the cross sections of
  deep inelastic NC and CC scattering at HERA

abstract:
  We present a brief description of the recently developed Fortran code TERAD91
for semi-analytical calculations of the double differential cross sections of
NC and CC deep inelastic electron-proton scattering and of some related
observables. The code is mainly intended for the calculations at HERA or other
ep-colliders but may be also used for similar processes like muon-proton
scattering in fixed-target experiments.


title: Superconductivity in Co-doped LaFeAsO

abstract:
  Here we report the synthesis and basic characterization of LaFe1-xCoxAsO for
several values of x. The parent phase LaFeAsO orders antiferromagnetically (TN
~ 145 K). Replacing Fe with Co is expected to both electron dope the system and
introduce disorder in the FeAs layer. For x = 0.05 antiferromagnetic order is
destroyed and superconductivity is observed at Tconset = 11.2 K. For x = 0.11
superconductivity is observed at Tc(onset) = 14.3 K, and for x = 0.15 Tc = 6.0
K. Superconductivity is not observed for x = 0.2 and 0.5, but for x = 1, the
material appears to be ferromagnetic (Tc ~ 56 K) as judged by magnetization
measurements. We conclude that Co is an effective dopant to induce
superconductivity. Somewhat surprisingly, the system appears to tolerate
considerable disorder in the FeAs planes.


title: xPert: Computer algebra for metric perturbation theory

abstract:
  We present the tensor computer algebra package xPert for fast construction
and manipulation of the equations of metric perturbation theory, around
arbitrary backgrounds. It is based on the combination of explicit combinatorial
formulas for the n-th order perturbation of curvature tensors and their gauge
changes, and the use of highly efficient techniques of index canonicalization,
provided by the underlying tensor system xAct, for Mathematica. We give
examples of use and show the efficiency of the system with timings plots: it is
possible to handle orders n=4 or n=5 within seconds, or reach n=10 with timings
below 1 hour.


title:
Energy and entropy radiated by a black hole embedded in the de-Sitter
  braneworld

abstract:
  We study the Hawking radiation of (4+n)-dimensional Schwarzschild black hole
imbedded in the space-time with positive cosmological constant. The greybody
and energy emission rates of scalars, fermions, bosons, and gravitons are
calculated in the full range of energy. The valuable information on the
dimensions and curvature of space-time is revealed. Furthermore, we investigate
the entropy radiated and lost by black hole. We find their ratio near unit in
favor of the Bekenstein's conjecture.


title: Yang-Mills gauge theories from fermionic lattice models

abstract:
  A doublet of three-dimensional Dirac fermions can effectively describe the
low energy spectrum of a fermionic cubic lattice. We employ this fermion
doubling to encode a non-Abelian SU(2) charge in the fundamental
representation. We explicitly demonstrate that suitable distortion of the
tunnelling couplings can introduce a scalar and a Yang-Mills field in the
effective low energy description, both coupled to the Dirac fermions. As an
application we simulate Yang-Mills monopoles that give rise to localized
zero-modes and fermion fractionalization. The generation of the non-Abelian
field in the two-dimensional case is also presented.

categories: cond-mat.str-el cond-mat.mes-hall hep-lat hep-th quant-ph


title: New Heterotic Non-Kahler Geometries

abstract:
  New heterotic torsional geometries are constructed as orbifolds of T^2
bundles over K3. The discrete symmetries considered can be freely-acting or
have fixed points and/or fixed curves. We give explicit constructions when the
base K3 is Kummer or algebraic. The orbifold geometries can preserve N=1,2
supersymmetry in four dimensions or be non-supersymmetric.


title: Perturbative QCD at High Energy Colliders

abstract:
  Selected applications of perturbative Quantumchromodynamics (QCD) to
predictions of the Standard Model for processes at high energy colliders are
reviewed with emphasis on past successes and future problems. This is a
personal retrospective is not intended to be a comprehensive review of the
field.


title: Massive Dirac fermions and the zero field quantum Hall effect

abstract:
  Through an explicit calculation for a Lagrangian in quantum electrodynamics
in (2+1)-space--time dimensions (QED$_3$), making use of the relativistic Kubo
formula, we demonstrate that the filling factor accompanying the quantized
electrical conductivity for massive Dirac fermions of a single species in two
spatial dimensions is a half (in natural units) when time reversal and parity
symmetries of the Lagrangian are explicitly broken by the fermion mass term. We
then discuss the most general form of the QED$_3$ Lagrangian, both for
irreducible and reducible representations of the Dirac matrices in the plane,
with emphasis on the appearance of a Chern-Simons term. We also identify the
value of the filling factor with a zero field quantum Hall effect (QHE).


title:
Probing the Spectral Function Using Momentum Resolved Radio Frequency
  Spectroscopy in Trapped Fermi Gases

abstract:
  We address recent momentum resolved radio frequency (RF) experiments on
ultracold trapped Fermi gases of $^{40}$K. We show that momentum resolved RF
probes provide measurements of the centrally important fermionic spectral
function. They also serve to remove ambiguity plaguing the interpretation of
momentum integrated RF experiments by establishing a clear dispersion signature
of pairing. We find that the temperature dependence of the spectral function is
dramatic at unitarity, and, importantly, smooth from above to below $T_c$
throughout BCS-BEC crossover. This should be tested experimentally, given
widespread predictions of first order behavior.


title:
Possible impact of the fourth generation quarks on production of a
  charged Higgs boson at the LHC

abstract:
  We investigate the impact of the fourth generation quarks on production and
decays of the charged Higgs boson at CERN Large Hadron Collider (LHC) with
triple $b$-tagging. The signal is the process $gg\to \bar{u_4}u_4$, followed by
$\bar{u_4}\to W^{-} \bar{b}$ and $u_4\to h^{+} b$ decays with subsequent
$h^{+}\to t \bar{b}$ and corresponding hermitic conjugates. It is shown that,
if $m_{u_{4}}= 400$ GeV, considered process will provide unique opportunity to
discover charged Higgs boson with mass range of 200 to 350 GeV at the first
years of the LHC run.


title: Astroelectrons as Non-Dual Field Solutions

abstract:
  The continuous charge density of the r^{-4} radial astroelectron is found
analytically from the Maxwell-Lorentz equations. The electric charge is not a
basic concept, but is the nonlinear field distribution associated with the
elementary self-energy density. The Poisson equation for the unified field
carrier in non-dual electrodynamics locally relates the post-Coulomb potential
with the energy-charge density. The local Maxwell equations maintain the global
overlap of nonlocal electric energy-charges in the undivided Universe.


title:
Temperature dependent optical conductivity of undoped cuprates with weak
  exchange

abstract:
  The optical conductivity sigma(omega) is calculated at finite temperature T
for CuO_2 chain clusters within a pd-Hubbard model. Data at T = 300 K for
Li_2CuO_2 are reanalyzed within this approach. The relative weights of
Zhang-Rice singlet and triplet charge excitations near 2.5 and 4 eV,
respectively, depend strongly on T, and a rather dramatic dependence of
sigma(omega) on the ratio of the first to second neighbor exchange integrals is
predicted. On the basis of these results, information about exchange
interactionsfor frustrated edge-shared cuprates can be obtained from
T-dependent optical spectra. Our results are also relevant for magnetically
weakly coupled wide-gap insulators in general.


title: Is graphene in vacuum an insulator?

abstract:
  We present evidence, from Lattice Monte Carlo simulations of the phase
diagram of graphene as a function of the Coulomb coupling between
quasiparticles, that graphene in vacuum is likely to be an insulator. We find a
semimetal-insulator transition at $\alpha_g^\text{crit} = 1.11 \pm 0.06$, where
$\alpha_g^{} \simeq 2.16$ in vacuum, and $\alpha_g^{} \simeq 0.79$ on a
SiO$_2^{}$ substrate. Our analysis uses the logarithmic derivative of the order
parameter, supplemented by an equation of state. The insulating phase
disappears above a critical number of four-component fermion flavors $4 <
N_f^{\text{crit}} < 6$. Our data are consistent with a second-order transition.


title:
Long-Term Evolution in Transit Duration of Extrasolar Planets from
  Magnetic Activity in their Parent Stars

abstract:
  Existing upper limits on variations in the photospheric radius of the Sun
during the solar magnetic activity cycle are at a fractional amplitude of
2x10^{-4}. At that level, the transit duration of a close-in planet around a
Sun-like star could change by a fraction of a second per year. This magnitude
of variation is larger than that caused by other studied effects (owing to
proper motion or general-relativistic effects), and should be included in the
analysis of constraints on multi-planet systems from transit timing. A temporal
correlation between the transit duration and spectroscopic measures of stellar
activity can be used to separate the stellar radius change from other effects.
The magnetic activity effect could be significantly larger for late-type stars,
such as M-dwarfs, which are more variable than the Sun. In general, precision
transit measurements provide a new tool for measuring long-term variations of
stellar radii.


title:
A threshold phenomenon for random independent sets in the discrete
  hypercube

abstract:
  Let $I$ be an independent set drawn from the discrete $d$-dimensional
hypercube $Q_d=\{0,1\}^d$ according to the hard-core distribution with
parameter $\lambda>0$ (that is, the distribution in which each independent set
$I$ is chosen with probability proportional to $\lambda^{|I|}$). We show a
sharp transition around $\lambda=1$ in the appearance of $I$: for $\lambda>1$,
$\min\{|I \cap {\cal E}|, |I \cap {\cal O}|\}=0$ asymptotically almost surely,
where ${\cal E}$ and ${\cal O}$ are the bipartition classes of $Q_d$, whereas
for $\lambda<1$, $\min\{|I \cap {\cal E}|, |I \cap {\cal O}|\}$ is
asymptotically almost surely exponential in $d$. The transition occurs in an
interval whose length is of order $1/d$.
  A key step in the proof is an estimation of $Z_\lambda(Q_d)$, the sum over
independent sets in $Q_d$ with each set $I$ given weight $\lambda^{|I|}$
(a.k.a. the hard-core partition function). We obtain the asymptotics of
$Z_\lambda(Q_d)$ for $\lambda>\sqrt{2}-1$, and nearly matching upper and lower
bounds for $\lambda \leq \sqrt{2}-1$, extending work of Korshunov and
Sapozhenko. These bounds allow us to read off some very specific information
about the structure of an independent set drawn according to the hard-core
distribution.
  We also derive a long-range influence result. For all fixed $\lambda>0$, if
$I$ is chosen from the independent sets of $Q_d$ according to the hard-core
distribution with parameter $\lambda$, conditioned on a particular $v \in {\cal
E}$ being in $I$, then the probability that another vertex $w$ is in $I$ is
$o(1)$ for $w \in {\cal O}$ but $\Omega(1)$ for $w \in {\cal E}$.


title: A class of locally conformally flat 4-manifolds

abstract:
  We construct infinite families of non-simply connected locally conformally
flat (LCF) 4-manifolds realizing rich topological types. These manifolds have
strictly negative scalar curvature and the underlying topological 4-manifolds
do not admit any Einstein metrics. Such 4-manifolds are of particular interest
as examples of Bach-flat but non-Einstein spaces in the non-simply connected
case. Besides that the underlying smooth manifolds are examples of spaces that
admit open book decomposition in dimension 4.


title:
Charge fluctuations and their effect on conduction in biological ion
  channels

abstract:
  The effect of fluctuations on the conductivity of ion channels is
investigated. It is shown that modulation of the potential barrier at the
selectivity site due to electrostatic amplification of charge fluctuations at
the channel mouth exerts a leading-order effect on the channel conductivity. A
Brownian dynamical model of ion motion in a channel is derived that takes into
account both fluctuations at the channel mouth and vibrational modes of the
wall. The charge fluctuations are modeled as a short noise flipping the height
of the potential barrier. The wall fluctuations are introduced as a slow
vibrational mode of protein motion that modulates ion conductance both
stochastically and periodically. The model is used to estimate the contribution
of the electrostatic amplification of charge fluctuations to the conductivity
of ion channels.


title: On a Lower Bound for the Time Constant of First-Passage Percolation

abstract:
  We consider the Bernoulli first-passage percolation on $\mathbb Z^d (d\ge
2)$. That is, the edge passage time is taken independently to be 1 with
probability $1-p$ and 0 otherwise. Let ${\mu(p)}$ be the time constant. We
prove in this paper that \[ \mu(p_1)-\mu({p_2})\ge
\frac{\mu(p_2)}{1-p_2}(p_2-p_1)\] for all $ 0\leq p_1<p_2< 1$ by using Russo's
formula.


title:
Enhancement of spatiotemporal regularity in an optimal window of random
  coupling

abstract:
  We investigate the spatiotemporal dynamics of a lattice of coupled chaotic
maps whose coupling connections are dynamically rewired to random sites with
probability p, namely at any instance of time, with probability p a regular
link is switched to a random one. In a range of weak coupling, where
spatiotemporal chaos exists for regular lattices (i.e. for p = 0), we find that
p > 0 yields synchronized periodic orbits. Further we observe that this
regularity occurs over a window of p values, beyond which the basin of
attraction of the synchronized cycle shrinks to zero. Thus we have evidence of
an optimal range of randomness in coupling connections, where spatiotemporal
regularity is efficiently obtained. This is in contrast to the commonly
observed monotonic increase of synchronization with increasing p, as seen for
instance, in the strong coupling regime of the very same system.


title:
Mechanism of recrystallization process in epitaxial GaN under dynamic
  stress field - Atomistic origin of planar defect formation

abstract:
  The mechanism of recrystallization in epitaxial (1000) GaN film, introduced
by indentation technique, is probed by lattice dynamic studies using Raman
spectroscopy. The recrystallized region is identified by Micro-Raman area
mapping. Pop-in bursts in loading lines indicate nucleation of dislocations and
climb of dislocations. These processes set in plastic motion of lattice atoms
under stress field at the center of indentation for the initiation of
recrystallization process. A planar defect migration mechanism is evolved. A
pivotal role of vacancy migration is pointed out, for the first time, as the
rate limiting factor for the dislocation dynamics initiating the
recrystallization process in GaN.


title:
Under what kind of parametric fluctuations is spatiotemporal regularity
  the most robust?

abstract:
  It was observed that the spatiotemporal chaos in lattices of coupled chaotic
maps was suppressed to a spatiotemporal fixed point when some fraction of the
regular coupling connections were replaced by random links. Here we investigate
the effects of different kinds of parametric fluctuations on the robustness of
this spatiotemporal fixed point regime. In particular we study the
spatiotemporal dynamics of the network with noisy interaction parameters,
namely fluctuating fraction of random links and fluctuating coupling strengths.
We consider three types of fluctuations: (i) noisy in time, but homogeneous in
space; (ii) noisy in space, but fixed in time; (iii) noisy in both space and
time. We find that the effect of different kinds of parameteric noise on the
dy- namics is quite distinct: quenched spatial fluctuations are the most
detrimental to spatiotemporal regularity; spatiotemporal fluctuations yield
phenomena similar to that observed when parameters are held constant at the
mean-value; and interestingly, spatiotemporal regularity is most robust under
spatially uniform temporal fluctuations, which in fact yields a larger fixed
point range than that obtained under constant mean-value parameters.


title: A complete Raman mapping of phase transitions in Si under indentation

abstract:
  Crystalline Si substrates are studied for pressure induced phase
transformation under indentation at room temperature using Berkovich tip. Raman
scattering study is used for the identification of the transformed phases.
Raman line as well as area mapping are used for locating the phases in the
indented region. Calculation of pressure contours in the indented region is
used for understanding the phase distribution. We report here a comprehensive
study of all the phases of Si, reported so far, leading to possible
understanding of material properties useful for possible electromechanical
applications. As a major finding, distribution of amorphous phase in the
indented region deviates from the conventional wisdom of being in the central
region alone. We present phase mapping results for both Si(100) and Si(111)
substrates.


title: Surface optical Raman modes in InN nanostructures

abstract:
  Raman spectroscopic investigations are carried out on one-dimensional
nanostructures of InN,such as nanowires and nanobelts synthesized by chemical
vapor deposition. In addition to the optical phonons allowed by symmetry; A1,
E1 and E2(high) modes, two additional Raman peaks are observed around 528 cm-1
and 560 cm-1 for these nanostructures. Calculations for the frequencies of
surface optical (SO) phonon modes in InN nanostructures yield values close to
those of the new Raman modes. A possible reason for large intensities for SO
modes in these nanostructures is also discussed.


title: Symmetry of Quadratic Homogeneous Differential Systems

abstract:
  In this paper, the symmetry group of a differential system of n quadratic
homogeneous first order ODEs of n variables is studied. For this purpose, we
consider the action of both point and contact transformations to signify the
corresponding Lie algebras. We also find the independent differential
invariants of these actions.


title: Symmetries of 2nd order ODE: y'' + G(x)y' + H(x)y = 0

abstract:
  This paper is devoted to study the Lie algebra of linear symmetries of a
homogenous 2nd order ODE, by the method of Kushner, Lychagin and Robstov.


title:
Dynamical CPA and Tight-Binding LMTO Approach to Correlated Electron
  System

abstract:
  Dynamical Coherent-Potential Approximation (CPA) to correlated electrons has
been extended to a system with realistic Hamiltonian which consists of the
first-principles tight-binding Linear Muffintin Orbital (LMTO) bands and
intraatomic Coulomb interactions. Thermodynamic potential and self-consistent
equations for Green function are obtained on the basis of the functional
integral method and the harmonic approximation which neglects the mode-mode
couplings between the dynamical potentials with different frequency. Numerical
calculations have been performed for Fe and Ni within the 2nd-order dynamical
corrections to the static approximation. The band narrowing of the
quasiparticle states and the 6 eV satellite are obtained for Ni at finite
temperatures. The theory leads to the Curie-Weiss law for both Fe and Ni.
Calculated effective Bohr magneton numbers are 3.0 $\mu_{\rm B}$ for Fe and 1.2
$\mu_{\rm B}$ for Ni, explaining the experimental data. But calculated Curie
temperatures are 2020 K for Fe and 1260 K for Ni, being still overestimated by
a factor of two as compared with the experimental ones. Dynamical effects on
electronic and magnetic properties are discussed by comparing with those in the
static approximations.


title:
The local Calderon problem and the determination at the boundary of the
  conductivity

abstract:
  We discuss the inverse problem of determining the, possibly anisotropic,
conductivity of a body $\Omega\subset\mathbb{R}^{n}$ when the so--called
Dirichlet-to-Neumann map is locally given on a non empty portion $\Gamma$ of
the boundary $\partial\Omega$. We extend results of uniqueness and stability at
the boundary, obtained by the same authors in SIAM J. Math. Anal. 33 (2001),
no. 1, 153--171, where the Dirichlet-to-Neumann map was given on all of
$\partial\Omega$ instead. We also obtain a pointwise stability result at the
boundary among the class of conductivities which are continuous at some point
$y\in\Gamma$. Our arguments also apply when the local Neumann-to-Dirichlet map
is available.


title: Electrical and magnetic properties of nano-scale Pi-junctions

abstract:
  The physics of the "Pi" phase shift in ferromagnetic Josephson junctions
enables a range of applications for spin-electronic devices and quantum
computing. In this respect our research is devoted to the evaluation of the
best materials for the development and the realization of the quantum devices
based on superconductors and at the same point towards the reduction of the
size of the employed heterostructures towards and below nano-scale. In this
chapter we report our investigation of transitions from "0" to "Pi" states in
Nb Josephson junctions with strongly ferromagnetic barriers of Co, Ni,
Ni$_{80}$Fe$_{20}$ (Py) and Fe. We show that it is possible to fabricate
nanostructured Nb/ Ni(Co, Py, Fe)/Nb $\pi$-junctions with a nano-scale magnetic
dead layer and with a high level of control over the ferromagnetic barrier
thickness variation. In agreement with the theoretical model we estimate, from
the oscillations of the critical current as function of the ferromagnetic
barrier thickness, the exchange energy of the ferromagnetic material and we
obtain that it is close to bulk ferromagnetic materials implying that the
ferromagnet is clean and S/F roughness is minimal. We conclude that S/F/S
Josephson junctions are viable structures in the development of
superconductor-based quantum electronic devices; in particular Nb/Co/Nb and
Nb/Fe/Nb multilayers with their low value of the magnetic dead layer and high
value of the exchange energy can readily be used in controllable two-level
quantum information systems. In this respect, we discuss applications of our
nano-junctions to engineering magnetoresistive devices such as programmable
pseudo-spin-valve Josephson structures.


title:
Quantum information with single fermions: teleportation and
  fermion-boson entanglement conversion

abstract:
  While single boson entanglement is known to be equivalent to standard
non-identical particle entanglement, the use of fermionic entanglement is
constrained by a parity superselection rule. Nevertheless we show that within
the framework of second quantization, where local modes play the role of
qubits, the analogy with ordinary entanglement holds: two entangled spinless
fermion modes can be used to teleport a single local fermion mode and to
perform standard dense coding. Entanglement concentration and dilution are
possible for fermions. We clarify the meaning of our results by discussing the
connection with quantum reference frames and conversion between spinless
fermion entanglement and spinless boson entanglement.


title: Calculation of neutron background for underground experiments

abstract:
  New generation dark matter experiments aim at exploring the 10e-9 - 10e-10 pb
cross-section region for the WIMP-nucleon scalar interactions. Neutrons
produced in the detector components are one of the main factors that can limit
detector sensitivity. Estimation of the background from this source then
becomes a crucial task for designing future large-scale detectors. Energy
spectra and production rates for neutrons coming from radioactive contamination
are required for all materials in and around the detector. In order to estimate
neutron yields and spectra, the cross-sections of (a,n) reactions and
probabilities of transitions to different excited states should be known.
Cross-sections and transition probabilities have been calculated using
Empire2.19 for several isotopes, and for some isotopes, a comparison with the
experimental data is shown. The results have been used to calculate the neutron
spectra from materials using the code Sources4A. Neutron background event rates
from some detector components in a hypothetical dark matter detector based on
Ge crystals have been estimated. Some requirements for the radiopurity of the
materials have been deduced from the results of these simulations.


title:
Production of ultracold heteronuclear YbRb* molecules by
  photoassociation

abstract:
  We have produced ultracold heteronuclear YbRb$^*$ molecules in a combined
magneto-optical trap by photoassociation. The formation of electronically
excited molecules close to the dissociation limit was observed by trap loss
spectroscopy in mixtures of $^{87}$Rb with $^{174}$Yb and $^{176}$Yb. The
molecules could be prepared in a series of vibrational levels with resolved
rotational structure, allowing for an experimental determination of the
long-range potential in the electronically excited state.


title:
Three-Dimensional Phase-Kink State in Thick Stack of Josephson Junctions
  and Terahertz Radiation

abstract:
  The dynamics of superconductivity phase in thick stack of Josephson junctions
with strong inductive coupling, such as the one realized in layered high-$T_c$
cuprates and possibly the recently discovered FeAs-based superconductors, is
investigated under a c-axis bias voltage and in the absence of an external
magnetic field. The kink state found previously by the present authors is
extended to three dimensions for both rectangular and cylindrical geometries.
The IV characteristics are calculated and the distributions of electromagnetic
field inside the samples are clarified. The solution for a cylindrical mesa
exhibits a higher resonating frequency than that of a square mesa with the same
linear size by a factor of $\sim 2.4$. More importantly, from the radius
dependence of the resonance frequency for the cylinder geometry it is possible
to confirm directly the kink state, and thus to reveal the mechanism of the
strong radiation discovered in recent experiments.


title: Applications of the Gauss-Bonnet theorem to gravitational lensing

abstract:
  In this geometrical approach to gravitational lensing theory, we apply the
Gauss-Bonnet theorem to the optical metric of a lens, modelled as a static,
spherically symmetric, perfect non-relativistic fluid, in the weak deflection
limit. We find that the focusing of the light rays emerges here as a
topological effect, and we introduce a new method to calculate the deflection
angle from the Gaussian curvature of the optical metric. As examples, the
Schwarzschild lens, the Plummer sphere and the singular isothermal sphere are
discussed within this framework.


title: Thermodynamics of SU(3) Gauge Theory in 2 + 1 Dimensions

abstract:
  The pressure, and the energy and entropy densities are determined for the
SU(3) gauge theory in $2 + 1$ dimensions from lattice Monte Carlo calculations
in the interval $0.6 \leq T/T_c \leq 15$. The finite temperature lattices
simulated have temporal extent $N_\tau = 2, 4, 6$ and 8, and spatial volumes
$N_S^2$ such that the aspect ratio is $N_S/N_\tau = 8$. To obtain the
thermodynamical quantities, we calculate the averages of the temporal
plaquettes $P_\tau$ and the spatial plaquettes $P_S$ on these lattices. We also
need the zero temperature averages of the plaquettes $P_0$, calculated on
symmetric lattices with $N_\tau = N_S$. We discuss in detail the finite size
($N_S$-dependent) effects. These disappear exponentially. For the zero
temperature lattices we find that the coefficient of $N_S$ in the exponent is
of the order of the glueball mass. On the finite temperature lattices it lies
between the two lowest screening masses. For the aspect ratio equal to eight,
the systematic errors coming from the finite size effects are much smaller than
our statistical errors. We argue that in the continuum limit, at high enough
temperature, the pressure can be parametrized by the very simple formula
$p=a-bT_c/T$ where $a$ and $b$ are two constants. Using the thermodynamical
identities for a large homogeneous system, this parametrization then determines
the other thermodynamical variables in the same temperature range.


title: Approximation of subharmonic functions in the unit disk

abstract:
  Let u be a subharmonic function in D={|z|<1}. There exist an absolute
constant C and an analytic function f in D such that \int_D |u(z)-log|f(z)||
dm(z)<C where m denotes the plane Lebesgue measure. We also consider uniform
approximation.


title: Organic Matter in Space - an Overview

abstract:
  Organic compounds are ubiquitous in space: they are found in diffuse clouds,
in the envelopes of evolved stars, in dense star-forming regions, in
protoplanetary disks, in comets, on the surfaces of minor planets, and in
meteorites and interplanetary dust particles. This brief overview summarizes
the observational evidence for the types of organics found in these regions,
with emphasis on recent developments. The Stardust sample-return mission
provides the first opportunity to study primitive cometary material with
sophisticated equipment on Earth. Similarities and differences between the
types of compounds in different regions are discussed in the context of the
processes that can modify them. The importance of laboratory astrophysics is
emphasized.


title:
Vector chiral and multipolar orders in the spin-1/2 frustrated
  ferromagnetic chain in magnetic field

abstract:
  We study the one-dimensional spin-1/2 Heisenberg chain with competing
ferromagnetic nearest-neighbor J_1 and antiferromagnetic next-nearest-neighbor
J_2 exchange couplings in the presence of magnetic field. We use both numerical
approaches (the density matrix renormalization group method and exact
diagonalization) and effective field-theory approach, and obtain the
ground-state phase diagram for wide parameter range of the coupling ratio
J_1/J_2. The phase diagram is rich and has a variety of phases, including the
vector chiral phase, the nematic phase, and other multipolar phases. In the
vector chiral phase, which appears in relatively weak magnetic field, the
ground state exhibits long-range order (LRO) of vector chirality which
spontaneously breaks a parity symmetry. The nematic phase shows a quasi-LRO of
antiferro-nematic spin correlation, and arises as a result of formation of
two-magnon bound states in high magnetic fields. Similarly, the higher
multipolar phases, such as triatic (p=3) and quartic (p=4) phases, are formed
through binding of p magnons near the saturation fields, showing quasi-LRO of
antiferro-multipolar spin correlations. The multipolar phases cross over to
spin density wave phases as the magnetic field is decreased, before
encountering a phase transition to the vector chiral phase at a lower field.
The implications of our results to quasi-one-dimensional frustrated magnets
(e.g., LiCuVO_4) are discussed.


title:
Search for charged Higgs bosons decaying to top and bottom quarks in
  ppbar collisions

abstract:
  We describe a search for production of a charged Higgs boson, q \bar{q'} ->
H^+, reconstructed in the t\bar{b} final state in the mass range 180 <= M_{H^+}
<= 300 GeV. The search was undertaken at the Fermilab Tevatron collider with a
center-of-mass energy sqrt{s} = 1.96 TeV and uses 0.9 fb^{-1} of data collected
with the D0 detector. We find no evidence for charged Higgs boson production
and set upper limits on the production cross section in the Types I, II and III
two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H^+},tan\beta)
plane for Type I 2HDM is presented.


title: Towards a controlled study of the QCD critical point

abstract:
  The phase diagram of QCD, as a function of temperature T and quark chemical
potential mu, may contain a critical point (mu_E,T_E) whose non-perturbative
nature makes it a natural object of lattice studies. However, the sign problem
prevents the application of standard Monte Carlo techniques at non-zero baryon
density. We have been pursuing an approach free of the sign problem, where the
chemical potential is taken as imaginary and the results are Taylor-expanded in
mu/T about mu=0, then analytically continued to real mu.
  Within this approach we have determined the sensitivity of the critical
chemical potential mu_E to the quark mass, d(\mu_E)^2/dm_q|_{\mu_E=0}. Our
study indicates that the critical point moves to {\em smaller} chemical
potential as the quark mass {\em increases}. This finding, contrary to common
wisdom, implies that the deconfinement crossover, which takes place in QCD at
mu=0 when the temperature is raised, will remain a crossover in the mu-region
where our Taylor expansion can be trusted. If this result, obtained on a coarse
lattice, is confirmed by simulations on finer lattices now in progress, then we
predict that no {\em chiral} critical point will be found for mu_B \lesssim 500
MeV, unless the phase diagram contains additional transitions.


title:
Functoriality and the Inverse Galois problem II: groups of type B_n and
  G_2

abstract:
  For every finite field F and every positive integer r, there exists a finite
extension F' of F such that either SO(2r+1,F') or its simple derived group can
be realized as a Galois group over Q. If the characteristic of F is 3 or 5 (mod
8), then we can guarantee that the derived group of SO(2r+1,F') can be
realized. Likewise, for every finite field F, there exists a finite extension
F' of F such that the finite simple group G_2(F') can be realized a Galois
group over Q.
  The proof uses automorphic forms to construct Galois representations which
cut out Galois extensions of the desired type.


title: Quantifying Residual Finiteness

abstract:
  We introduce the concept of quantifying the extent to which a finitely
generated group is residually finite. The quantification is carried out for
some examples including free groups, the first Grigorchuk group, finitely
generated nilpotent groups, and certain arithmetic groups such as
$SL_n(\mathbb{Z})$. In the context of finite nilpotent quotients, we find a new
characterization of nilpotent groups.


title: Stellar models with the ML2 theory of convection

abstract:
  The mixing length theory (MLT) used to compute the temperature gradient in
superadiabatic layers of stellar (interior and atmosphere) models contains in
its standard form 4 free parameters. Three parameters are fixed a priori (and
define what we denote as the MLT 'flavour') whereas one (the so-called mixing
length) is calibrated by reproducing observational constraints. The 'classical'
B\"ohm-Vitense flavour is used in all modern MLT-based stellar model
computations and, despite its crude approximations, the resulting $T_{eff}$
scale appears -- perhaps surprisingly -- remarkably realistic, once the mixing
length parameter is calibrated with a solar model. Model atmosphere
computations employ parameter choices different from what is used in stellar
interior modelling, raising the question of whether a single MLT flavour and
mixing length value can be used to compute interiors and atmospheres of stars
of all types. As a first step towards addressing this issue, we study whether
the MLT flavour (the so-called ML2) and mixing length choice that have been
proven adequate to model white dwarf atmospheres, is able to provide, when used
in stellar models, results at least comparable to the use of the 'classical'
B\"ohm-Vitense flavour. We have computed solar models and evolutionary tracks
for both low- and intermediate-mass Population I and II stars, adopting both
solar calibrated B\"ohm-Vitense and ML2 flavours of the MLT in our stellar
evolution code, and state-of-the-art input physics. The two sets of models
provide consistent results, with only minor differences. Both calibrations
reproduce also the $T_{eff}$ of red giants in a sample of Galactic globular
clusters.


title: Removal of Z_3-symmetry breaking from Fermionic Determinants

abstract:
  We consider prescriptions that are free from the direct charge-screening
effects by quark loops and enable us to clarify the confining nature of a
vacuum. We test two candidates for an order parameter, a Polyakov loop ($P$)
evaluated in zero-triality backgrounds and fermionic determinants (${\mathcal
D}_{1,2}$) with non-zero triality. Especially, ${\mathcal D}_{1,2}$ has very
small fluctuations in comparison with a Polyakov loop in zero-triality sector,
and seems to well reflect the characteristic of a vacuum. Such prescriptions
could be still usable for the clarification of the confinement property of a
vacuum.


title:
Pressure effect on high-$T_{c}$ superconductors and Casimir Effect in
  nanometer scale

abstract:
  Considering $CuO_{2}$ conducting layers present in high Tc superconductors as
plasma sheets, we proposed a prescription for the $T_{c}$ pressure behavior
taken into account the Casimir effect. The Casimir energy arises from these
parallel plasma sheets (Cu-O planes) when it take placed in the regime of
nanometer scale (small \textit{d} distance). The charge reservoir layer
supplies carries to the conducting $nCuO_{2}$ layers, which are a source of
superconductivity. The pressure induced charge transfer model (PICTM) makes use
of an intrinsic term, which description is still unclear. Considering Casimir
energy describing the $T_{c}$ for the case of hight-$T_{c}$ superconductors, we
propose an explicit expression to the intrinsic term. Realistic parameters used
in the proposed expression have shown an agreement with experimental intrinsic
term data observed in some high-$T_{c}$ compounds.


title:
On Modelling a Relativistic Hierarchical (Fractal) Cosmology by Tolman's
  Spacetime. I. Theory

abstract:
  This work examines a relativistic model for the observed inhomogeneities of
the large scale structure where the hypothesis that this structure can be
described as being a self-similar fractal system is advanced. The concept of
hierarchical clustering is identified with a fractal distribution and the
problems raised by the use of fractal ideas in a relativistic model are
discussed, as well as their relations to the Copernican and Cosmological
Principles. Voids, clusters and superclusters of galaxies are assumed to be
part of a smoothed-out fractal structure described by a Lemaitre-Tolman
solution. The basic concepts of the Newtonian model presented by Pietronero
(1987) are reinterpreted and applied to this inhomogeneous curved spacetime.
This fractal system is also assumed to have a crossover to homogeneity which
leads to a "Swiss cheese" type model, composed by an interior Lemaitre-Tolman
metric and an exterior dust Friedmann solution. The Darmois junction conditions
between the two spacetimes are calculated, and the observational relations
necessary to compare the model with observations are obtained for the interior
region. The differential equations of the interior spacetime are set up and a
numerical strategy is devised for finding particular Tolman solutions
representing a fractal behaviour along the past light cone.


title:
Meta-stable Supersymmetry Breaking in an N=1 Perturbed Seiberg-Witten
  Theory

abstract:
  In this contribution, we discuss the possibility of meta-stable supersymmetry
(SUSY) breaking vacua in a perturbed Seiberg-Witten theory with
Fayet-Iliopoulos (FI) term. We found meta-stable SUSY breaking vacua at the
degenerated dyon and monopole singular points in the moduli space at the
nonperturbative level.


title: On the Capacity of Pairwise Collaborative Networks

abstract:
  We derive expressions for the achievable rate region of a collaborative
coding scheme in a two-transmitter, two-receiver Pairwise Collaborative Network
(PCN) where one transmitter and receiver pair, namely relay pair, assists the
other pair, namely the source pair, by partially decoding and forwarding the
transmitted message to the intended receiver. The relay pair provides such
assistance while handling a private message. We assume that users can use the
past channel outputs and can transmit and receive at the same time and in the
same frequency band. In this collaborative scheme, the transmitter of the
source pair splits its information into two independent parts. Ironically, the
relay pair employs the decode and forward coding to assist the source pair in
delivering a part of its message and re-encodes the decoded message along with
private message, which is intended to the receiver of the relay pair, and
broadcasts the results. The receiver of the relay pair decodes both messages,
retrieves the private message, re-encodes and transmits the decoded massage to
the intended destination. We also characterize the achievable rate region for
Gaussian PCN. Finally, we provide numerical results to study the rate trade off
for the involved pairs. Numerical result shows that the collaboration offers
gain when the channel gain between the users of the relay pair are strong. It
also shows that if the channel conditions between transmitters or between the
receivers of the relay and source pairs are poor, such a collaboration is not
beneficial.


title:
On Modelling a Relativistic Hierarchical (Fractal) Cosmology by Tolman's
  Spacetime. II. Analysis of the Einstein-de Sitter Model

abstract:
  This paper studies the spatially homogeneous Einstein-de Sitter cosmological
model in the context of a relativistic hierarchical (fractal) cosmology as
developed in paper I (0807.0866). The Einstein-de Sitter model is treated as a
special case of Lemaitre-Tolman's spacetime, obtained by the appropriate choice
of the latter's three arbitrary functions. The observational relations along
the past light cone of the model under consideration are calculated, and an
investigation of whether or not it has fractal behaviour is performed. It was
found that the Einstein-de Sitter model does not seem to remain homogeneous
along the geodesic and that it also has no fractal features along the backward
null cone.


title:
Bulk photons in Asymmetrically Warped Space-times and Non-trivial Vacuum
  Refractive Index

abstract:
  We consider asymmetrically warped brane models, or equivalently brane models
where the background metric is characterized by different time and space warp
factors. The main feature of these models is that 4D Lorentz symmetry is
violated for fields which propagate in the bulk, such as gravitons. In this
paper we examine the case of bulk photons in asymmetrically warped brane
models. Although our results are general, we examine here two specific but
characteristic solutions: 1) AdS-Schwarzschild 5D Black Hole solution and 2)
AdS-Reissner Nordstrom 5D Black Hole solution. We show that the standard
Lorentz invariant dispersion relation for 4D photons is corrected by nonlinear
terms which lead to an Energy-dependent speed of light. Specifically, we obtain
a sub-luminous Energy-dependent refractive index of the form
n_{eff}(\omega)=1+c_{G} \omega^2, where \omega is the energy of the photon, and
the factor c_G is always positive and depends on the free parameters of the
model. Finally, comparing the results with recent data from the MAGIC
Telescope, claiming a delayed arrival of photons from the Active Galactic
Nucleus of Mk501, we impose concrete restrictions to the two sets of models
examined in this work. We shall also discuss briefly other possible
astrophysical constraints on our models.


title:
Tensor products and Correlation Estimates with applications to Nonlinear
  Schr\"odinger equations

abstract:
  We prove new interaction Morawetz type (correlation) estimates in one and two
dimensions. In dimension two the estimate corresponds to the nonlinear diagonal
analogue of Bourgain's bilinear refinement of Strichartz. For the 2d case we
provide a proof in two different ways. First, we follow the original approach
of Lin and Strauss but applied to tensor products of solutions. We then
demonstrate the proof using commutator vector operators acting on the
conservation laws of the equation. This method can be generalized to obtain
correlation estimates in all dimensions. In one dimension we use the
Gauss-Weierstrass summability method acting on the conservation laws. We then
apply the 2d estimate to nonlinear Schr\"odinger equations and derive a direct
proof of Nakanishi's $H^1$ scattering result for every $L^{2}$-supercritical
nonlinearity. We also prove scattering below the energy space for a certain
class of $L^{2}$-supercritical equations.


title: History of the formulas and algorithms for pi

abstract:
  Throughout more than two millennia many formulas have been obtained, some of
them beautiful, to calculate the number pi. Among them, we can find series,
infinite products, expansions as continued fractions and expansions using
radicals. Some expressions which are (amazingly) related to pi have been
evaluated. In addition, a continual battle has been waged just to break the
records computing digits of this number; records have been set using rapidly
converging series, ultra fast algorithms and really surprising ones,
calculating isolated digits. The development of powerful computers has played a
fundamental role in these achievements of calculus.


title:
Effects of Ground-State Correlations on High Energy Scattering off
  Nuclei: the Case of the Total Neutron-Nucleus Cross Section

abstract:
  With the aim at quantitatively investigating the longstanding problem
concerning the effect of short range nucleon-nucleon correlations on scattering
processes at high energies, the total neutron-nucleus cross section is
calculated within a parameter-free approach which, for the first time, takes
into account, simultaneously, central, spin, isospin and tensor nucleon-nucleon
(NN) correlations, and Glauber elastic and Gribov inelastic shadowing
corrections. Nuclei ranging from 4He to 208Pb and incident neutron momenta in
the range 3 GeV/c - 300 GeV/c are considered; the commonly used approach which
approximates the square of the nuclear wave function by a product of one-body
densities is carefully analyzed, showing that NN correlations can play a
non-negligible role in high energy scattering off nuclei.


title: Conformally K\"ahler base metrics for Einstein warped products

abstract:
  A Riemannian metric $\wht{g}$ with Ricci curvature $\wht{\ri}$ is called
nontrivial quasi-Einstein, in the sense of Case, Shu and Wei, if it satisfies
$(-a/f)\wht{\nab} df+\wht{\ri}=\lambda \wht{g}$, for a smooth nonconstant
function $f$ and constants $\lambda$ and $a>0$. If $a$ is a positive integer,
by a result of Kim and Kim, such a metric forms a base for certain warped
Einstein metrics. On a manifold $M$ of real dimension at least six, let
$(g,\t)$ be a pair consisting of a K\"ahler metric $g$ which is locally
K\"ahler irreducible, and a nonconstant Killing potential $\t$. Suppose the
metric $\wht{g}=g/\t^2$ is nontrivial \bee on $M\setminus\t^{-1}(0)$, and the
associated function $f$ is locally a function of $\t$. Then $(g,\t)$ is an \sk\
pair, a notion defined by Derdzinski and Maschler. This implies that $M$ is
biholomorphic to an open set in the total space of a $CP^1$ bundle whose base
manifold admits a K\"ahler-Einstein metric. If $M$ is additionally compact, it
is a total space of such a bundle or complex projective space. Also, the
function $f$ is affine in $\t^{-1}$ with nonzero constants. Conversely, in all
even dimensions $n\geq 4$, there exist \sk pairs $(g,\t)$ and corresponding
nonzero constants $K$ and $L$ for which $g/\t^2$ is nontrivial quasi-Einstein
with $f=K\t^{-1}+L$. Additionally, a result of Case, Shu and Wei on the
K\"ahler reducibility of nontrivial K\"ahler \bers is reproduced in dimension
at least six in a more explicit form.


title: Structural complexity in monodisperse systems of isotropic particles

abstract:
  It has recently been shown that identical, isotropic particles can form
complex crystals and quasicrystals. In order to understand the relation between
the particle interaction and the structure, which it stabilizes, the phase
behavior of a class of two-scale potentials is studied. In two dimensions, the
phase diagram features many phases previously observed in experiment and
simulation. The three-dimensional system includes the sigma phase with 30
particles per unit cell, not grown in simulations before, and an amorphous
state, which we found impossible to crystallize in molecular dynamics. We
suggest that the appearance of structural complexity in monodisperse systems is
related to competing nearest neighbor distances and discuss implications of our
result for the self-assembly of macromolecules.


title:
Nodeless superconducting gap in NdFeAsO$_{0.9}$F$_{0.1}$ single crystals
  from anisotropic penetration depth studies

abstract:
  This paper is no longer active and will NOT appear in print. For new data and
analysis, please see: arXiv:0903.2220


title:
Orbital ordering promotes weakly-interacting S=1/2 dimers in the
  triangular lattice compound Sr3Cr2O8

abstract:
  The weakly interacting S=1/2 dimers system Sr3Cr2O8 has been investigated by
powder neutron diffraction and inelastic neutron scattering. Our data reveal a
structural phase transition below room temperature corresponding to an
antiferro-orbital ordering with nearly 90 degrees arrangement of the occupied
3z^2-r^2 d-orbital. This configuration leads to a drastic reduction of the
inter-dimer exchange energies with respect to the high temperature
orbital-disorder state, as shown by a spin-dimer analysis of the
super-superexchange interactions performed using the Extended Huckel Tight
Binding method. Inelastic neutron scattering reveals the presence of a quasi
non-dispersive magnetic excitation at 5.4 meV, in agreement with the picture of
weakly-interacting dimers.


title: Creation of perfect long-distance quantum communication channel

abstract:
  This paper has been withdrawn by the authors, due a oversimplified
decoherence model. It will be substituted by a new work.


title:
Experimental constraints on a dark matter origin for the DAMA annual
  modulation effect

abstract:
  A claim for evidence of dark matter interactions in the DAMA experiment has
been recently reinforced. We employ a new type of germanium detector to
conclusively rule out a standard isothermal galactic halo of Weakly Interacting
Massive Particles (WIMPs) as the explanation for the annual modulation effect
leading to the claim. Bounds are similarly imposed on a suggestion that dark
pseudoscalars mightlead to the effect. We describe the sensitivity to light
dark matter particles achievable with our device, in particular to
Next-to-Minimal Supersymmetric Model candidates.


title:
Studies of the ABJM Theory in a Formulation with Manifest SU(4)
  R-Symmetry

abstract:
  We examine the three-dimensional N = 6 superconformal Chern--Simons theory
with U(N) X U(N) gauge symmetry, which was recently constructed by Aharony,
Bergman, Jafferis, and Maldacena (ABJM). Using a formulation with manifest
SU(4) R-symmetry and no auxiliary fields, we verify in complete detail both the
Poincare supersymmetry and the conformal supersymmetry of the action. Together,
these imply the complete OSp(6|4) superconformal symmetry of the theory. The
potential, which is sixth order in scalar fields, is recast as a sum of
squares.


title: Two Permanently Congruent Rods May Have Different Proper Lengths

abstract:
  We scrutinize congruence as one of the basic definitions of equality in
geometry and pit it against physics of Special Relativity. We show that two
non-rigid rods permanently kept congruent during their common expansion or
compression may have different instantaneous proper lengths (when measured at
the same time of their respective reference clocks) if they have different mass
distributions over their lengths. Alternatively, their proper lengths can come
out equal only when measured at different but strictly correlated moments of
time of their respective clocks. The derived expression for the ratio of
instantaneous proper lengths of two permanently congruent changing objects
explicitly contains information about the objects mass distribution. The same
is true for the ratio of readings of the two reference clocks, for which the
instantaneous measurements of respective proper lengths produce the same
result. In either case the characteristics usually considered as purely
kinematic depend on mass distribution, which is a dynamic property. This is a
spectacular demonstration of dynamic aspect of geometry already in the
framework of Special Relativity.


title: Ill-posedness of the Navier-Stokes equations in a critical space in 3D

abstract:
  We prove that the Cauchy problem for the three dimensional Navier-Stokes
equations is ill posed in $\dot{B}^{-1,\infty}_{\infty}$ in the sense that a
``norm inflation'' happens in finite time. More precisely, we show that initial
data in the Schwartz class $\mathcal{S}$ that are arbitrarily small in
$\dot{B}^{-1, \infty}_{\infty}$ can produce solutions arbitrarily large in
$\dot{B}^{-1, \infty}_{\infty}$ after an arbitrarily short time. Such a result
implies that the solution map itself is discontinuous in $\dot{B}^{-1,
\infty}_{\infty}$ at the origin.


title: Electronic Properties of Graphene Nanoribbon on Si(001) Substrate

abstract:
  We show by first-principles calculations that the electronic properties of
zigzag graphene nanoribbons (Z-GNRs) adsorbed on Si(001) substrate strongly
depend on ribbon width and adsorption orientation. Only narrow Z-GNRs with even
rows of zigzag chains across their width adsorbed perpendicularly to the Si
dimer rows possess an energy gap, while wider Z-GNRs are metallic due to
width-dependent interface hybridization. The Z-GNRs can be metastably adsorbed
parallel to the Si dimer rows, but show uniform metallic nature independent of
ribbon width due to adsorption induced dangling-bond states on the Si surface.


title: Stability and electronic properties of small BN nanotubes

abstract:
  We report the stability and electronic structures of the boron nitride
nanotubes (BNNTs) with diameters below 4 A by semi-empirical quantum mechanical
molecular dynamics simulations and ab initio calculations. Among them (3,0),
(3,1), (2,2), (4,0), (4,1) and (3,2) BNNTs can be stable well over room
temperature. These small BNNTs become globally stable when encapsulated in a
larger BNNT. It is found that the energy gaps and work functions of these small
BNNTs are strongly dependent on their chirality and diameters. The small zigzag
BNNTs become desirable semiconductors and have peculiar distribution of nearly
free electron states due to strong hybridization effect. When such a small BNNT
is inserted in a larger one, the energy gap of the formed double-walled BNNT
can even be much reduced due to the coupled effect of wall buckling difference
and NFE-pi hybridization.


title: Using polarized maser to detect high-frequency relic gravitational waves

abstract:
  A GHz maser beam with Gaussian-type distribution passing through a homogenous
static magnetic field can be used to detect gravitational waves (GWs) with the
same frequency. The presence of GWs will perturb the electromagnetic (EM)
fields, giving rise to perturbed photon fluxes (PPFs). After being reflected by
a fractal membrane, the perturbed photons suffer little decay and can be
measured by a microwave receiver. This idea has been explored to certain extent
as a method for very high frequency gravitational waves. In this paper, we
examine and develop this method more extensively, and confront the possible
detection with the predicted signal of relic gravitational waves (RGWs). A
maser beam with high linear polarization is used to reduce the background
photon fluxes (BPFs) in the detecting direction as the main noise. As a key
factor of applicability of this method, we give a preliminary estimation of the
sensitivity of a sample detector limited by thermal noise using currently
common technology.
  The minimal detectable amplitude of GWs is found to be
$h_{\rm{min}}\sim10^{-30}$. Comparing with the known spectrum of the RGWs in
the accelerating universe for $\beta=-1.9$, there is still roughly a gap of
$4\sim 5$ orders. However, possible improvements on the detector can further
narrow down the gap and make it a feasible method to detect high frequency
RGWs.


title:
Intrinsic Hyperpolarizabilities as a Figure of Merit for Electro-optic
  Molecules

abstract:
  We propose the scale-invariant intrinsic hyperpolarizability as a measure of
the figure of merit for electrooptic molecules. By applying our analysis to the
best second-order nonlinear-optical molecules that are made using the present
paradigms, we conclude that it should be possible to make dye-doped polymers
with electrooptic coefficients of several thousand picometers per volt.


title: On Cycles in AS Relationships

abstract:
  Several users of our AS relationship inference data
(http://www.caida.org/data/active/as-relationships/), released with cs/0604017,
asked us why it contained AS relationship cycles, e.g., cases where AS A is a
provider of AS B, B is a provider of C, and C is a provider of A, or other
cycle types. Having been answering these questions in private communications,
we have eventually decided to write down our answers here for future reference.


title: Semi-flexible hydrogen-bonded and non-hydrogen bonded lattice polymers

abstract:
  We investigate the addition of stiffness to the lattice model of
hydrogen-bonded polymers in two and three dimensions. We find that, in contrast
to polymers that interact via a homogeneous short-range interaction, the
collapse transition is unchanged by any amount of stiffness: this supports the
physical argument that hydrogen bonding already introduces an effective
stiffness. Contrary to possible physical arguments, favouring bends in the
polymer does not return the model's behaviour to that comparable to the
semi-flexible homogeneous interaction model, where the canonical $\theta$-point
occurs for a range of parameter values. In fact, for sufficiently large bending
energies the crystal phase disappears altogether, and no phase transition of
any type occurs. We also compare the order-disorder transition from the globule
phase to crystalline phase in the semi-flexible homogeneous interaction model
to that for the fully-flexible hybrid model with both hydrogen and non-hydrogen
like interactions. We show that these phase transitions are of the same type
and are a novel polymer critical phenomena in two dimensions. That is, it is
confirmed that in two dimensions this transition is second-order, unlike in
three dimensions where it is known to be first order. We also estimate the
crossover exponent and show that there is a divergent specific heat, finding
$\phi=0.7(1)$ or equivalently $\alpha=0.6(2)$. This is therefore different from
the $\theta$ transition, for which $\alpha=-1/3$.


title: Possible mechanism of Cooper pairing in HTS cuprates

abstract:
  In this study, the possible pairing mechanism based on attraction between
electrons from adjacent CuO2 layers is proposed. Initially, each CuO2 layer was
found to expand the Fermi sphere owing to ridged geometry. When the two layers
are close enough for tunneling, it becomes energetically advantageous to form
correlated quantum states (CQS), reducing the Fermi sphere volume. Cooper
pairs, comprising inter-tunneling electrons, occupy the CQS. The image force is
responsible for the electron-electron attraction. Energy exchange between the
paired electrons happens through photons. Pair-binding energy and the
corresponding effective mass vary in a wide range. At T>0, some heavy pairs do
not condense. Such pairs are responsible for pseudogap. Light pairs get Bose
condensed and are responsible for superconductivity. The proposed mechanism
provides possible explanation of two energy gaps and two characteristic
temperatures in cuprates. It also provides clarification on the unconventional
isotopic effect, Fermi surface pockets, anisotropy of charge transport, and
other properties of HTS cuprates. The pseudogap, calculated within the model,
is close to the experimental values for the two-layer cuprates, such as YBCO,
Bi2212, Tl2212, and Hg1212. It has been shown that the model can be extended to
multiple and single-layer cuprates.


title: A note on interpreting N M2 branes

abstract:
  A new world volume theory with a free scalar field was proposed for Multiple
M2 branes recently. By giving the free scalar a large VEV, we can obtain a
gauge theory of multiple D2 branes with a coupling constant proportional to the
VEV. It is pointed out by Banerjee and Sen that we can get D2 branes by
choosing a compactification in the $\theta$ direction, with radial position
having the same value of the VEV. Following this work, we try to describe the
multiple M2 branes in R^8/Z_K and give a simple provement of g_{YM} \propto {1
\ov \sqrt{K}} in the compactification. We try to interpret T^0 and T^{-1} as
the radial coordinate operator and momentum operator and give some evidences in
geometry and quantum mechanics.


title: The Coin Exchange Problem and the Structure of Cube Tilings

abstract:
  Let k_1,...,k_d be positive integers, and D be a subset of [k_1]x...x[k_d],
whose complement can be decomposed into disjoint sets of the form
{x_1}x...x{x_{s-1}}x[k_s]x{x_{s+1}}x...x{x_d}. We conjecture that the number of
elements of D can be represented as a linear combination of the numbers
k_1,..., k_d with non-negative integer coefficients. A connexion of this
conjecture with the structure of periodical cube tilings is revealed.


title: The driving force behind genomic diversity

abstract:
  Eukaryote genomes contain excessively introns, inter-genic and other
non-genic sequences that appear to have no vital functional role or phenotype
manifestation. Their existence, a long-standing puzzle, is viewed from the
principle of increasing entropy. According to thermodynamics of open systems,
genomes evolve toward diversity by various mechanisms that increase, decrease
and distribute genomic material in response to thermodynamic driving forces.
Evolution results in an excessive genome, a high-entropy ecosystem of its own,
where copious non-coding segments associate with low-level functions and
conserved sequences code coordinated activities. The rate of entropy increase,
equivalent to the rate of free energy decrease, is identified with the
universal fitness criterion of natural selection that governs populations of
genomic entities as well as other species.


title: XIAO: a soft X-ray telescope for the SVOM Mission

abstract:
  The study of Gamma-ray bursts (GRBs) is a key field to expand our
understanding of several astrophysical and cosmological phenomena. SVOM is a
Chinese-French Mission which will permit to detect and rapidly locate GRBs, in
particular those at high redshift, and to study their multiwavelength emission.
The SVOM satellite, to be launched in 2013, will carry wide field instruments
operating in the X/gamma-ray band and narrow field optical and soft X-ray
telescopes. Here we describe a small soft X-ray telescope (XIAO) proposed as an
Italian contribution to the SVOM mission. Thanks to a grazing incidence X-ray
telescope with effective area of ~120 cm^2 and a short focal length, coupled to
a very compact, low noise, fast read out CCD camera, XIAO can substantially
contribute to the overall SVOM capabilities for both GRB and non-GRB science.


title:
N=4 supersymmetric Yang Mills scattering amplitudes at high energies:
  the Regge cut contribution

abstract:
  We further investigate, in the planar limit of N=4 supersymmetric Yang Mills
theories,the high energy Regge behavior of six-point MHV scattering amplitudes.
In particular, for the new Regge cut contribution found in our previous paper,
we compute in the leading logarithmic approximation (LLA) the energy spectrum
of the BFKL equation in the color octet channel, and we calculate explicitly
the two loop corrections to the discontinuities of the amplitudes for the
transitions 2 to 4 and 3 to 3. We find an explicit solution of the BFKL
equation for the octet channel for arbitrary momentum transfers and investigate
the intercepts of the Regge singularities in this channel. As an important
result we find that the universal collinear and infrared singularities of the
BDS formula are not affected by this Regge-cut contribution. Any improvement of
the BDS formula should reproduce this cut to all orders in the coupling.


title: A revisit to agglomerates of early-type Hipparcos stars

abstract:
  We study the spatial structure and sub-structure of regions rich in Hipparcos
stars with blue B_T-V_T colours. These regions, which comprise large stellar
complexes, OB associations, and young open clusters, are tracers of on-going
star formation in the Galaxy. The DBSCAN (Density-Based Spatial Clustering of
Applications with Noise) data clustering algorithm is used to look for spatial
overdensities of early-type stars. Once an overdensity, "agglomerate", is
identified, we carry out a data and bibliographic compilation of their star
member candidates. The actual membership in agglomerate of each early-type star
is studied based on its heliocentric distance, proper motion, and previous
spectro-photometric information. We identify 35 agglomerates of early-type
Hipparcos stars. Most of them are associated to previously known clusters and
OB associations. The previously unknown P Puppis agglomerate is subject of a
dedicated study with Virtual Observatory tools. It is actually a new, nearby,
young open cluster (d ~ 470 pc, age ~ 20 Ma) with a clear radial density
gradient. We list P Puppis and other six agglomerates (including NGC 2451 A,
vdBH 23, and Trumpler 10) as new sites for substellar searches because of their
youth, closeness, and spatial density. We investigate in detail the
sub-structure in the Orion, CMa-Pup and Pup-Vel OB complexes
("super-agglomerates"). We confirm or discover some stellar overdensities in
the Orion complex, like the 25 Ori group, the Horsehead region (including the
sigma Orionis cluster), and the eta Orionis agglomerate. Finally, we derive
accurate parallactic distances to the Pleiades, NGC 2451 A, and IC 2391,
describe several field early-type stars at d < 200 pc, and discuss the
incompleteness of our search.


title: Left-right mixing on leptonic and semileptonic $b\to u$ decays

abstract:
  It has been known that there exists a disagreement emerged between the
determination of $|V_{ub}|$ from inclusive $B \to X_u\ell\nu$ decays and
exclusive $B \to \pi\ell\nu$ decays. In order to solve the mismatch, we
investigate the left-right (LR) mixing effects, denoted by $\xi_u$, in leptonic
and semileptonic $b \to u$ decays. We find that the new interactions
$(V+A)\times (V-A)$ induced via the LR mixing can explain the mismatch between
the values of $|V_{ub}|$ if Re$(\xi_{u})=-(0.14 \pm 0.12)$. Furthermore, we
also find that the LR mixing effects can enhance the branching fractions for $B
\to \tau\nu$ and $B \to \rho\ell\nu$ decays by 30% and 17%, respectively, while
reducing the branching fraction for $B \to \gamma\ell\nu$ decays by 18%.


title:
The seismogenic area in the lithosphere considered as an "Open Physical
  System". Its implications on some seismological aspects. Part - II. Maximum
  expected magnitude determination

abstract:
  The (any) seismogenic area in the lithosphere is considered as an open
physical system. Following its energy balance analysis earlier presented (Part
- I, Thanassoulas, 2008), the specific case when the seismogenic area is under
normal (input energy equals released energy) seismogenic conditions is studied.
In this case the cumulative seismic energy release is a linear time function.
Starting from this linear function a method is postulated for the determination
of the maximum expected magnitude of a future earthquake. The proposed method
has been tested "a posteriori" on real EQs from the Greek territory, USA and
data obtained from the seismological literature. The obtained results validate
the methodology while an analysis is presented that justifies the obtained high
degree of accuracy compared to the corresponding calculated EQ magnitudes with
seismological methods.