title:
On some consequences of the Snyder-Sidharth deformation of Special
  Relativity

abstract:
  The hypothesis on a minimal scale existence in the Universe leads to
noncommutative geometry of Spacetime and thence to a modification of the
Special Relativity constraint. Sidharth has deduced that this is equivalent to
the Lorentz symmetry violation. This latter consideration was also used by
Glashow, Coleman and other scholars though based on purely phenomenological
models that have been suggested by the observation of Ultra High Energy Cosmic
Rays and Gamma Bursts. On the other hand a parallel development has been the
proposal of a small but nonzero photon mass $m_\gamma>0$ by some authors
including Sidharth, such a mass being within experimentally allowable limits.
This too leads to a small violation of the Lorentz symmetry observable in
principle in very high energy gamma rays, as in fact is claimed. In this paper
we study the Snyder--Sidharth Hamiltonian and briefly comment the
Dirac--Sidharth Hamiltonian, that is a possible explanation for observable
violation of the Lorentz symmetry.

categories: hep-th astro-ph math-ph math.MP physics.class-ph


title: Manifest spin 2 duality with electric and magnetic sources

abstract:
  We extend the formulation of spin 2 fields on Minkowski space which makes the
action manifestly invariant under duality rotations to the case of interactions
with external electric and magnetic sources by adding suitable potentials for
the longitudinal and trace parts. In this framework, the string singularity of
the linearized Taub-NUT solution is resolved into a Coulomb-like solution.
Suitable surface charges to measure energy-momentum and angular momentum of
both electric and magnetic type are constructed.


title: Flow invariants in the classification of Leavitt path algebras

abstract:
  We analyze in the context of Leavitt path algebras some graph operations
introduced in the context of symbolic dynamics by Williams, Parry and Sullivan,
and Franks. We show that these operations induce Morita equivalence of the
corresponding Leavitt path algebras. As a consequence we obtain our two main
results: the first gives sufficient conditions for which the Leavitt path
algebras in a certain class are Morita equivalent, while the second gives
sufficient conditions which yield isomorphisms. We discuss a possible approach
to establishing whether or not these conditions are also in fact necessary. In
the final section we present many additional operations on graphs which
preserve Morita equivalence (resp., isomorphism) of the corresponding Leavitt
path algebras.


title:
Index Theory for Boundary Value Problems via Continuous Fields of
  C*-algebras

abstract:
  We prove an index theorem for boundary value problems in Boutet de Monvel's
calculus on a compact manifold X with boundary. The basic tool is the tangent
semigroupoid $\cT^-X$ generalizing the tangent groupoid defined by Connes in
the boundaryless case, and an associated continuous field C*_r(\cT^-X) of
C*-algebras over [0,1]. Its fiber in h=0, C*_r(T^-X), can be identified with
the symbol algebra for Boutet de Monvel's calculus; for h\not=0 the fibers are
isomorphic to the algebra K of compact operators. We therefore obtain a natural
map K_0(C*_r(T^-X))=K_0(C_0(T*X)) -> K_0(K)=Z. Using deformation theory we show
that this is the analytic index map. On the other hand, using ideas from
noncommutative geometry, we construct the topological index map and prove that
it coincides with the analytic index map.


title: Statistical properties of intermittent maps with unbounded derivative

abstract:
  We study the ergodic and statistical properties of a class of maps of the
circle and of the interval of Lorenz type which present indifferent fixed
points and points with unbounded derivative. These maps have been previously
investigated in the physics literature. We prove in particular that
correlations decay polynomially, and that suitable Limit Theorems (convergence
to Stable Laws or Central Limit Theorem) hold for H\"older continuous
observables. We moreover show that the return and hitting times are in the
limit exponentially distributed.


title:
Perpetual American vanilla option pricing under single regime change
  risk. An exhaustive study

abstract:
  Perpetual American options are financial instruments that can be readily
exercised and do not mature. In this paper we study in detail the problem of
pricing this kind of derivatives, for the most popular flavour, within a
framework in which some of the properties |volatility and dividend policy| of
the underlying stock can change at a random instant of time, but in such a way
that we can forecast their final values. Under this assumption we can model
actual market conditions because most relevant facts usually entail sharp
predictable consequences. The effect of this potential risk on perpetual
American vanilla options is remarkable: the very equation that will determine
the fair price depends on the solution to be found. Sound results are found
under the optics both of finance and physics. In particular, a parallelism
among the overall outcome of this problem and a phase transition is
established.


title:
Computation of Casimir forces for dielectrics or intrinsic
  semiconductors based on the Boltzmann transport equation

abstract:
  The interaction between drifting carriers and traveling electromagnetic waves
is considered within the context of the classical Boltzmann transport equation
to compute the Casimir-Lifshitz force between media with small density of
charge carriers, including dielectrics and intrinsic semiconductors. We expand
upon our previous work [Phys. Rev. Lett. {\bf 101}, 163203 (2008)] and derive
in some detail the frequency-dependent reflection amplitudes in this theory and
compute the corresponding Casimir free energy for a parallel plate
configuration. We critically discuss the the issue of verification of the
Nernst theorem of thermodynamics in Casimir physics, and explicity show that
our theory satisfies that theorem. Finally, we show how the theory of drifting
carriers connects to previous computations of Casimir forces using spatial
dispersion for the material boundaries.


title:
Abundances in the Galactic bulge: results from planetary nebulae and
  giant stars

abstract:
  Our understanding of the chemical evolution of the Galactic bulge requires
the determination of abundances in large samples of giant stars and planetary
nebulae (PNe). We discuss PNe abundances in the Galactic bulge and compare
these results with those presented in the literature for giant stars. We
present the largest, high-quality data-set available for PNe in the direction
of the Galactic bulge (inner-disk/bulge). For comparison purposes, we also
consider a sample of PNe in the Large Magellanic Cloud (LMC). We derive the
element abundances in a consistent way for all the PNe studied. By comparing
the abundances for the bulge, inner-disk, and LMC, we identify elements that
have not been modified during the evolution of the PN progenitor and can be
used to trace the bulge chemical enrichment history. We then compare the PN
abundances with abundances of bulge field giant. At the metallicity of the
bulge, we find that the abundances of O and Ne are close to the values for the
interstellar medium at the time of the PN progenitor formation, and hence these
elements can be used as tracers of the bulge chemical evolution, in the same
way as S and Ar, which are not expected to be affected by nucleosynthetic
processes during the evolution of the PN progenitors. The PN oxygen abundance
distribution is shifted to lower values by 0.3 dex with respect to the
distribution given by giants. A similar shift appears to occur for Ne and S. We
discuss possible reasons for this PNe-giant discrepancy and conclude that this
is probably due to systematic errors in the abundance derivations in either
giants or PNe (or both). We issue an important warning concerning the use of
absolute abundances in chemical evolution studies.


title: WIMPonium and Boost Factors for Indirect Dark Matter Detection

abstract:
  We argue that WIMP dark matter can annihilate via long-lived "WIMPonium"
bound states in reasonable particle physics models of dark matter (DM).
WIMPonium bound states can occur at or near threshold leading to substantial
enhancements in the DM annihilation rate, closely related to the Sommerfeld
effect. Large "boost factor" amplifications in the annihilation rate can thus
occur without large density enhancements, possibly preferring colder less dense
objects such as dwarf galaxies as locations for indirect DM searches. The
radiative capture to and transitions among the WIMPonium states generically
lead to a rich energy spectrum of annihilation products, with many distinct
lines possible in the case of 2-body decays to $\gamma\gamma$ or $\gamma Z$
final states. The existence of multiple radiative capture modes further
enhances the total annihilation rate, and the detection of the lines would give
direct over-determined information on the nature and self-interactions of the
DM particles.


title:
Nets in groups, minimum length $g$-adic representations, and minimal
  additive complements

abstract:
  The number theoretic analogue of a net in metric geometry suggests new
problems and results in combinatorial and additive number theory. For example,
for a fixed integer g > 1, the study of h-nets in the additive group of
integers with respect to the generating set A_g = {g^i:i=0,1,2,...} requires a
knowledge of the word lengths of integers with respect to A_g. A g-adic
representation of an integer is described that algorithmically produces a
representation of shortest length. Additive complements and additive asymptotic
complements are also discussed, together with their associated minimality
problems.


title:
Time evolution of correlations in strongly interacting fermions after a
  quantum quench

abstract:
  Using the adaptive time-dependent density matrix renormalization group, we
study the time evolution of density correlations of interacting spinless
fermions on a one-dimensional lattice after a sudden change in the interaction
strength. Over a broad range of model parameters, the correlation function
exhibits a characteristic light-cone-like time evolution representative of a
ballistic transport of information. Such behavior is observed both when
quenching an insulator into the metallic region and also when quenching within
the insulating region. However, when a metallic state beyond the quantum
critical point is quenched deep into the insulating regime, no indication for
ballistic transport is observed. Instead, stable domain walls in the density
correlations emerge during the time evolution, consistent with the predictions
of the Kibble-Zurek mechanism.


title: Higher Order Decompositions of Ordered Operator Exponentials

abstract:
  We present a decomposition scheme based on Lie-Trotter-Suzuki product
formulae to represent an ordered operator exponential as a product of ordinary
operator exponentials. We provide a rigorous proof that does not use a
time-displacement superoperator, and can be applied to non-analytic functions.
Our proof provides explicit bounds on the error and includes cases where the
functions are not infinitely differentiable. We show that Lie-Trotter-Suzuki
product formulae can still be used for functions that are not infinitely
differentiable, but that arbitrary order scaling may not be achieved.


title:
The Electrostatic Component of the Disjoining Pressure and the Pore
  Creation Rate in Electroporation Models and Theory

abstract:
  Under externally applied electric fields, lipid membranes tend to permeate
and change their electrical resistance by the combined processes of pore
creation and pore evolution (expansion or contraction). This study is focused
on the pore creation process, represented by an empirical expression currently
used in the electroporation (EP) models, for which an alternative theoretically
based expression was provided. The choice of this expression was motivated by
the role the DLVO's (disjoining) pressures may play in the process of EP. The
electrostatic energy effects on each sides of a lipid membrane were evaluated
in terms of the electrostatic component of the disjoining pressure. Thus the
pore creation energy considerations in the current EP models, associated with
the necessity of an idealized non conducting circular pre-pore were avoided. As
a result, a new expression for the onset of the electroporation was proposed.
It was found that this new theoretically determined expression is in good
agreement with the one estimated from an experiment that specifically targeted
the pore nucleation by eliminating the pore evolution process. Furthermore, the
proposed expression is dependent on the electrolyte and the lipid properties
and should provide better predictability than the currently used pore creation
EP model, which is only temperature dependent.


title: Provenance Traces

abstract:
  Provenance is information about the origin, derivation, ownership, or history
of an object. It has recently been studied extensively in scientific databases
and other settings due to its importance in helping scientists judge data
validity, quality and integrity. However, most models of provenance have been
stated as ad hoc definitions motivated by informal concepts such as "comes
from", "influences", "produces", or "depends on". These models lack clear
formalizations describing in what sense the definitions capture these intuitive
concepts. This makes it difficult to compare approaches, evaluate their
effectiveness, or argue about their validity.
  We introduce provenance traces, a general form of provenance for the nested
relational calculus (NRC), a core database query language. Provenance traces
can be thought of as concrete data structures representing the operational
semantics derivation of a computation; they are related to the traces that have
been used in self-adjusting computation, but differ in important respects. We
define a tracing operational semantics for NRC queries that produces both an
ordinary result and a trace of the execution. We show that three pre-existing
forms of provenance for the NRC can be extracted from provenance traces.
Moreover, traces satisfy two semantic guarantees: consistency, meaning that the
traces describe what actually happened during execution, and fidelity, meaning
that the traces "explain" how the expression would behave if the input were
changed. These guarantees are much stronger than those contemplated for
previous approaches to provenance; thus, provenance traces provide a general
semantic foundation for comparing and unifying models of provenance in
databases.


title: Time turns the universal kaleidoscope

abstract:
  This (withdrawn) creative essay intended to consider the appearance of time's
arrow in a fully symmetric universe compatible with "pilot wave" or
transactional interpretations (D. Bohm or J.G. Kramer, respectively). The
(unstated) hypothesis was that, despite unitary time evolution, the inherent
Hilbert transform operator found in the energy operator of the Schrodinger
equation and in commutation relations of Fourier observables indicates
dissipation and seemingly, entropy increase.


title:
Application of Conformal Mapping to the determination of Magnetic Moment
  Distributions in typical Antidot Film Nanostructures

abstract:
  There has been an increasing technological interest on magnetic thin films
containing antidot arrays of hexagonal or square symmetry. Part of this
interest is related to the possibility of domain formation and pinning at the
antidots boundaries. In this paper, we develop a method for the calculation of
the magnetic moment distribution for such arrays which concentrates on the
immediate vicinity of each antidot. For each antidot distribution (square or
hexagonal) a suitable system of coordinates is defined to exploit the shape of
the unit-cells of the overall nanostructure. The Landau-Lifshitz-Gilbert-Brown
equations that govern the distribution of moments are rewritten in terms of
these coordinates. The equilibrium moments orientation is calculated for each
position in a Cartesian grid defined for these new coordinate systems, and then
a conformal transformation is applied to insert the moment vectors into the
actual unit-cell. The resulting vector maps display quite clearly regions of
different moment orientation around the antidots, which can be associated with
nanoscale domains. These results are similar to the ones obtained by other
authors[1-4] using the NIST oommf method.


title: The ensemble of random Markov matrices

abstract:
  The ensemble of random Markov matrices is introduced as a set of Markov or
stochastic matrices with the maximal Shannon entropy. The statistical
properties of the stationary distribution pi, the average entropy growth rate
$h$ and the second largest eigenvalue nu across the ensemble are studied. It is
shown and heuristically proven that the entropy growth-rate and second largest
eigenvalue of Markov matrices scale in average with dimension of matrices d as
h ~ log(O(d)) and nu ~ d^(-1/2), respectively, yielding the asymptotic relation
h tau_c ~ 1/2 between entropy h and correlation decay time tau_c = -1/log|nu| .
Additionally, the correlation between h and and tau_c is analysed and is
decreasing with increasing dimension d.


title: Special features of the KdV-Sawada-Kotera equation

abstract:
  The KdV-Sawada-Kotera equation has single-, two- and three-soliton solutions.
However, it is not known yet whether it has N-soliton solutions for any N.
Viewing it as a perturbed KdV equation, the asymptotic expansion of the
solution is developed through third order within the framework of a Normal Form
analysis. It is shown that the equation is asymptotically integrable through
the order considered. Focusing on the soliton sector, it is shown that the
higher-order corrections in the Normal Form expansion represent purely
inelastic KdV-soliton-collision processes, and vanish identically in the
single-soliton limit. These characteristics are satisfied by the exact
two-soliton solution of the KdV-Sawada-Kotera equation: The deviation of this
solution from its KdV-type two-soliton approximation describes a purely
inelastic scattering process: The incoming state is the faster KdV soliton. It
propagates until it hits a localized perturbation, which causes its
transformation into the outgoing state, the slower soliton. In addition, the
effect of the perturbation on the exact two-soliton solution vanishes
identically in the single-soliton limit (equal wave numbers for the two
solitons).


title: Spatial random permutations with small cycle weights

abstract:
  We consider the distribution of cycles in two models of random permutations,
that are related to one another. In the first model, cycles receive a weight
that depends on their length. The second model deals with permutations of
points in the space and there is an additional weight that involves the length
of permutation jumps. We prove the occurrence of infinite macroscopic cycles
above a certain critical density.


title:
Fermions in higher representations. Some results about SU(2) with
  adjoint fermions

abstract:
  We discuss the lattice formulation of gauge theories with fermions in
arbitrary representations of the color group, and present the implementation of
the RHMC algorithm for simulating dynamical Wilson fermions. A first dataset is
presented for the SU(2) gauge theory with two fermions in the adjoint
representation, which has been proposed as a possible technicolor candidate.
Simulations are performed on 8^3x16 lattices, at fixed lattice spacing. The
PCAC mass, the pseudoscalar, vector and axial meson masses, the pseudoscalar
meson decay constant are computed. The extrapolation to the chiral limit is
discussed. However more extensive investigations are needed in order to control
the systematic errors in the numerical results, and then understand in detail
the phase structure of these theories.


title: Modification of Graphene Properties due to Electron-Beam Irradiation

abstract:
  The authors report micro-Raman investigation of changes in the single and
bilayer graphene crystal lattice induced by the low and medium energy
electron-beam irradiation (5 and 20 keV). It was found that the radiation
exposures results in appearance of the strong disorder D band around 1345 1/cm
indicating damage to the lattice. The D and G peak evolution with the
increasing radiation dose follows the amorphization trajectory, which suggests
graphene's transformation to the nanocrystalline, and then to amorphous form.
The results have important implications for graphene characterization and
device fabrication, which rely on the electron microscopy and focused ion beam
processing.


title:
Solving three-body scattering problem in the momentum lattice
  representation

abstract:
  A brief description of the novel approach towards solving few-body scattering
problems in a finite-dimensional functional space of the $L_2$-type is
presented. The method is based on the complete few-body continuum
discretization in the basis of stationary wave packets. This basis, being
transformed to the momentum representation, leads to the cell-lattice-like
discretization of the momentum space. So the initial scattering problem can be
formulated on the multi-dimensional momentum lattice which makes it possible to
reduce the solution of any scattering problem above the breakup threshold
(where the integral kernels include, in general, some complicated moving
singularities) to convenient simple matrix equations which can be solved on the
real energy axis. The phase shifts and inelasticity parameters for the
three-body $nd$ elastic scattering with MT I-III $NN$ potential both below and
above the three-body breakup threshold calculated with the proposed wave-packet
technique are in a very good agreement with the previous accurate benchmark
calculation results.


title:
Application of a dynamical two-box surface-atmosphere model to the Mount
  Pinatubo cooling event

abstract:
  We analyze the global temperature change due to the Mt. Pinatubo eruption
using a simple two-layer model of the atmosphere and surface to obtain results
consistent with satellite data. Through analytic and numerical analysis we find
a principal characteristic response time of 5 to 8 months and a climate
sensitivity of 0.17 to 0.20 C/(W/m^2), corresponding to a negative
instantaneous feedback. Our solutions were fit to the data, reproducing the
results of a one-box model, and providing somewhat more detailed information
about the feedbacks related to surface layer temperature. The formalism for
coupling of the surface layer to the thermocline is set up but not applied.


title:
The Muisca Calendar: An approximation to the timekeeping system of the
  ancient native people of the northeastern Andes of Colombia

abstract:
  The aim of this project is to review and expand upon the model proposed by
Father Jose Domingo Duquesne de la Madrid (1745-1821) regarding the calendar of
the ancient Muisca culture of the central Colombia. This model was dismissed by
scholars in the late 19th century, calling it just a simple invention of a
clergyman; however, a detailed analysis of Duquesne's work shows that his
interpretation of the timekeeping system was based on information given to him
by indigenous informers. Based on his work, we can be derive somewhat
indirectly, some aspects of the calendar that apparently were not understood by
the priest. This confirms that such a system was not his own invention.
Ethnohistorical and archaeological evidence provide support for Duquesne's
calendar model. Massive Muisca ceremonies described by 16th century Spanish
chroniclers, is examined and; the occurrence of such ceremonies seem to match
the astronomical cycle of conjunctions of the planets Jupiter and Saturn, wich
also agrees with the 60-year span described by Duquesne as the Muisca Acrotom
Century. Archaeological artifacts, such as a carved stone found in the village
of Choachi (Cundinamarca) that shows numerical elements supports Duquesne's
model that suggests this stone was a calendar calculation tool for Muisca
priests.


title:
Obtaining the diffusion coefficient for cosmic ray propagation in the
  Galactic Centre Ridge through time-dependent simulations of their gamma-ray
  emission

abstract:
  Recent observations by the H.E.S.S. collaboration of the Galactic Centre
region have revealed what appears to be gamma-ray emission from the decay of
pions produced by interactions of recently accelerated cosmic rays with local
molecular hydrogen clouds. Synthesizing a 3-D hydrogen cloud map from the
available data and assuming a diffusion coefficient of the form kappa(E) =
kappa_0(E/E0)^delta, we performed Monte Carlo simulations of cosmic ray
diffusion for various propagation times and values of kappa_0 and delta. By
fitting the model gamma-ray spectra to the observed one we were able to infer
the value of the diffusion coefficient in that environment (kappa = 3.0 +/- 0.2
kpc^2 Myr^-1 for E = 10^12.5 eV and for total propagation time 10^4 yr) as well
as the source spectrum (2.1 < gamma < 2.3). Also, we found that proton losses
can be substantial, which justifies our approach to the problem.


title: kappa-Minkowski spacetime as the result of Jordanian twist deformation

abstract:
  Two one-parameter families of twists providing kappa-Minkowski * -product
deformed spacetime are considered: Abelian and Jordanian. We compare the
derivation of quantum Minkowski space from two perspectives. The first one is
the Hopf module algebra point of view, which is strictly related with
Drinfeld's twisting tensor technique. The other one relies on an appropriate
extension of "deformed realizations" of nondeformed Lorentz algebra by the
quantum Minkowski algebra. This extension turns out to be de Sitter Lie
algebra. We show the way both approaches are related. The second path allows us
to calculate deformed dispersion relations for toy models ensuing from
different twist parameters. In the Abelian case one recovers kappa-Poincar'e
dispersion relations having numerous applications in doubly special relativity.
Jordanian twists provide a new type of dispersion relations which in the
minimal case (related to Weyl-Poincar'e algebra) takes an energy-dependent
linear mass deformation form.


title: Quantization of the Jackiw-Teitelboim model

abstract:
  We study the phase space structure of the Jackiw-Teitelboim model in its
connection variables formulation where the gauge group of the field theory is
given by local SL(2,R) (or SU(2) for the Euclidean model), i.e. the de Sitter
group in two dimensions. In order to make the connection with two dimensional
gravity explicit, a partial gauge fixing of the de Sitter symmetry can be
introduced that reduces it to spacetime diffeomorphisms. This can be done in
different ways. Having no local physical degrees of freedom, the reduced phase
space of the model is finite dimensional. The simplicity of this gauge field
theory allows for studying different avenues for quantization, which may use
various (partial) gauge fixings. We show that reduction and quantization are
noncommuting operations: the representation of basic variables as operators in
a Hilbert space depend on the order chosen for the latter. Moreover, a
representation that is natural in one case may not even be available in the
other leading to inequivalent quantum theories.


title:
NLO Higgs boson production via gluon fusion matched with shower in
  POWHEG

abstract:
  We present a next-to-leading order calculation of Higgs boson production via
gluon fusion interfaced to shower Monte Carlo programs, implemented according
to the POWHEG method. A detailed comparison with MC@NLO and PYTHIA is carried
out for several observables, for the Tevatron and LHC colliders. Comparisons
with next-to-next-to-leading order results and with resummed ones are also
presented.


title: Weak solution of the Hele-Shaw problem: shocks and viscous fingering

abstract:
  In Hele-Shaw flows, boundaries between fluids develop unstable viscous
fingers. At vanishing surface tension, the fingers further evolve to cusp-like
singularities. We show that the problem admits a {\it weak solution} where
shock fronts triggered by a singularity propagate together with a fluid. Shocks
form a growing, branching tree of a mass deficit, and a line distribution of
vorticity where pressure and velocity of the fluid have finite discontinuities.
Imposing that the flow remain curl-free at macroscale determines the shock
graph structure. We present a self-similar solution describing shocks emerging
from a generic (2,3)-cusp singularity -- an elementary branching event.


title:
Gauge Invariance in Field Theory and Statistical Physics in Operator
  Formalism

abstract:
  We obtain the Ward identities and the gauge-dependence of Green's functions
in non-Abelian gauge theories by using only the canonical commutation relations
and the equations of motion for the Heisenberg operators. The consideration is
applicable to theories both with and without spontaneous symmetry breaking. We
present a definition of a generalized statistical average which ensures that
the Fourier images of temperature Green's functions of the Fermionic fields
have only even-valued frequencies. This makes it possible to set up a procedure
of gauge-invariant statistical averaging in terms of the Hamiltonian and the
field operators.


title: Pushing BitTorrent Locality to the Limit

abstract:
  Peer-to-peer (P2P) locality has recently raised a lot of interest in the
community. Indeed, whereas P2P content distribution enables financial savings
for the content providers, it dramatically increases the traffic on inter-ISP
links. To solve this issue, the idea to keep a fraction of the P2P traffic
local to each ISP was introduced a few years ago. Since then, P2P solutions
exploiting locality have been introduced. However, several fundamental issues
on locality still need to be explored. In particular, how far can we push
locality, and what is, at the scale of the Internet, the reduction of traffic
that can be achieved with locality? In this paper, we perform extensive
experiments on a controlled environment with up to 10 000 BitTorrent clients to
evaluate the impact of high locality on inter-ISP links traffic and peers
download completion time. We introduce two simple mechanisms that make high
locality possible in challenging scenarios and we show that we save up to
several orders of magnitude inter-ISP traffic compared to traditional locality
without adversely impacting peers download completion time. In addition, we
crawled 214 443 torrents representing 6 113 224 unique peers spread among 9 605
ASes. We show that whereas the torrents we crawled generated 11.6 petabytes of
inter-ISP traffic, our locality policy implemented for all torrents would have
reduced the global inter-ISP traffic by 40%.


title:
A case study of an Hamilton-Jacobi equation by the Adomian
  decompositional method

abstract:
  We present a study of the Adomian's Decomposition Method (ADM) applied to the
Hamilton-Jacobi equations ut + H (ux) = 0. We recall the well known
characteristics methods in the case of this type of equations to justify the
existence or not of solutions. This yields that the ADM gives efficient
solutions in time only in ]0; T *[, where T * is the critical time of our
equation.


title: Cross-Calibration of Cluster Mass-Observables

abstract:
  This paper is a first step towards developing a formalism to optimally
extract dark energy information from number counts using multiple cluster
observation techniques. We use a Fisher matrix analysis to study the
improvements in the joint dark energy and cluster mass-observables constraints
resulting from combining cluster counts and clustering abundances measured with
different techniques. We use our formalism to forecast the constraints in
Omega_{DE} and w from combining optical and SZ cluster counting on a 4000 sq.
degree patch of sky. We find that this cross-calibration approach yields ~2
times better constraints on Omega_{DE} and w compared to simply adding the
Fisher matrices of the individually self-calibrated counts. The
cross-calibrated constraints are less sensitive to variations in the mass
threshold or maximum redshift range. A by-product of our technique is that the
correlation between different mass-observables is well constrained without the
need of additional priors on its value.


title: Local control of ultrafast dynamics in magnetic nanoparticles

abstract:
  Using the local control theory we derive analytical expressions for magnetic
field pulses that steer the magnetization of a monodomain magnetic nanoparticle
to a predefined state. Finite-temperature full numerical simulations confirm
the analytical results and show that a magnetization switching or freezing is
achievable within few precessional periods and that the scheme is exploitable
for fast thermal switching.


title:
Implications of primordial black holes on the first stars and the origin
  of the super--massive black holes

abstract:
  If the cosmological dark matter has a component made of small primordial
black holes, they may have a significant impact on the physics of the first
stars and on the subsequent formation of massive black holes. Primordial black
holes would be adiabatically contracted into these stars and then would sink to
the stellar center by dynamical friction, creating a larger black hole which
may quickly swallow the whole star. If these primordial black holes are heavier
than $\sim 10^{22} {\rm g}$, the first stars would likely live only for a very
short time and would not contribute much to the reionization of the universe.
They would instead become $10 - 10^3 M_\odot$ black holes which (depending on
subsequent accretion) could serve as seeds for the super--massive black holes
seen at high redshifts as well as those inside galaxies today.


title: Type I Planet Migration in Nearly Laminar Disks

abstract:
  We describe 2D hydrodynamic simulations of the migration of low-mass planets
($\leq 30 M_{\oplus}$) in nearly laminar disks (viscosity parameter $\alpha <
10^{-3}$) over timescales of several thousand orbit periods. We consider disk
masses of 1, 2, and 5 times the minimum mass solar nebula, disk thickness
parameters of $H/r = 0.035$ and 0.05, and a variety of $\alpha$ values and
planet masses. Disk self-gravity is fully included. Previous analytic work has
suggested that Type I planet migration can be halted in disks of sufficiently
low turbulent viscosity, for $\alpha \sim 10^{-4}$. The halting is due to a
feedback effect of breaking density waves that results in a slight mass
redistribution and consequently an increased outward torque contribution. The
simulations confirm the existence of a critical mass ($M_{cr} \sim 10
M_{\oplus}$) beyond which migration halts in nearly laminar disks. For $\alpha
\ga 10^{-3}$, density feedback effects are washed out and Type I migration
persists. The critical masses are in good agreement with the analytic model of
Rafikov (2002). In addition, for $\alpha \la 10^{-4}$ steep density gradients
produce a vortex instability, resulting in a small time-varying eccentricity in
the planet's orbit and a slight outward migration. Migration in nearly laminar
disks may be sufficiently slow to reconcile the timescales of migration theory
with those of giant planet formation in the core accretion model.


title:
Electron- and neutrino-nucleus scattering from the quasielastic to the
  resonance region

abstract:
  We present a model for electron- and neutrino-scattering off nucleons and
nuclei focussing on the quasielastic and resonance region. The lepton-nucleon
reaction is described within a relativistic formalism that includes, besides
quasielastic scattering, the excitation of 13 N* and Delta resonances and a
non-resonant single-pion background. Recent electron-scattering data is used
for the state-of-the-art parametrizations of the vector form factors; the axial
couplings are determined via PCAC and, in the case of the Delta resonance, the
axial form factor is refitted using neutrino-scattering data. Scattering off
nuclei is treated within the GiBUU framework that takes into account various
nuclear effects: the local density approximation for the nuclear ground state,
mean-field potentials and in-medium spectral functions. Results for inclusive
scattering off Oxygen are presented and, in the case of electron-induced
reactions, compared to experimental data and other models.


title: A Cheap Levitating Gas/Load Pipeline

abstract:
  Design of new cheap aerial pipelines, a large flexible tube deployed at high
altitude, for delivery of natural (fuel) gas, water and other payload over a
long distance is delineated. The main component of the natural gas is methane
which has a specific weight less than air. A lift force of one cubic meter of
methane equals approximately 0.5 kg (1 pound). The lightweight film flexible
pipeline can be located in air at high altitude and, as such, does not damage
the environment. Using the lift force of this pipeline and wing devices
payloads of oil, water, or other fluids, or even solids such as coal, cargo,
passengers can be delivered cheaply at long distance. This aerial pipeline
dramatically decreases the cost and the time of construction relative to
conventional pipelines of steel which saves energy and greatly lowers the
capital cost of construction. The article contains a computed project for
delivery 24 billion cubic meters of gas and tens of million tons of oil, water
or other payload per year.


title: Bound States and Superconductivity in Dense Fermi Systems

abstract:
  A quantum field theoretical approach to the thermodynamics of dense Fermi
systems is developed for the description of the formation and dissolution of
quantum condensates and bound states in dependence of temperature and density.
As a model system we study the chiral and superconducting phase transitions in
two-flavor quark matter within the NJL model and their interrelation with the
formation of quark-antiquark and diquark bound states. The phase diagram of
quark matter is evaluated as a function of the diquark coupling strength and a
coexistence region of chiral symmetry breaking and color superconductivity is
obtained at very strong coupling. The crossover between Bose-Einstein
condensation (BEC) of diquark bound states and condensation of diquark
resonances (Cooper pairs) in the continuum (BCS) is discussed as a Mott effect.
This effect consists in the transition of bound states into the continuum of
scattering states under the influence of compression and heating. We explain
the physics of the Mott transition with special emphasis on role of the Pauli
principle for the case of the pion in quark matter.

categories: hep-ph cond-mat.supr-con nucl-th physics.plasm-ph


title: A Fast Potential and Self-Gravity Solver for Non-Axisymmetric Disks

abstract:
  Disk self-gravity could play an important role in the dynamic evolution of
interaction between disks and embedded protoplanets. We have developed a fast
and accurate solver to calculate the disk potential and disk self-gravity
forces for disk systems on a uniform polar grid. Our method follows closely the
method given by Chan et al. (2006), in which an FFT in the azimuthal direction
is performed and a direct integral approach in the frequency domain in the
radial direction is implemented on a uniform polar grid. This method can be
very effective for disks with vertical structures that depend only on the disk
radius, achieving the same computational efficiency as for zero-thickness
disks. We describe how to parallelize the solver efficiently on distributed
parallel computers. We propose a mode-cutoff procedure to reduce the parallel
communication cost and achieve nearly linear scalability for a large number of
processors. For comparison, we have also developed a particle-based fast
tree-code to calculate the self-gravity of the disk system with vertical
structure. The numerical results show that our direct integral method is at
least two order of magnitudes faster than our optimized tree-code approach.


title:
Impact of star formation inhomogeneities on merger rates and
  interpretation of LIGO results

abstract:
  Within the next decade, ground based gravitational wave detectors are in
principle capable of determining the compact object merger rate per unit volume
of the local universe to better than 20% with more than 30 detections. We argue
that the stellar models are sensitive to heterogeneities (in age and
metallicity at least) in such a way that the predicted merger rates are subject
to an additional 30-50% systematic errors unless these heterogeneities are
taken into account. Without adding new electromagnetic constraints on massive
binary evolution or relying on more information from each merger (e.g., binary
masses and spins), as few as the $\simeq 5$ merger detections could exhaust the
information available in a naive comparison to merger rate predictions. As a
concrete example, we use a nearby-universe catalog to demonstrate that no one
tracer of stellar content can constrain merger rates without introducing a
systematic error of order $O(30%)$ at 90% confidence. More generally, we argue
that theoretical binary evolution can depend sufficiently sensitively on
star-forming conditions -- even assuming no uncertainty in binary evolution
model -- that the \emph{distribution} of star forming conditions must be
incorporated to reduce the systematic error in merger rate predictions below
roughly 40%. (Abridged)


title: Evolution of Lyman Alpha Galaxies: Stellar Populations at z ~ 0.3

abstract:
  We present the results of a stellar population analysis of 30 Lyman alpha
emitting galaxies (LAEs) at z ~ 0.3, previously discovered with the Galaxy
Evolution Explorer (GALEX). With a few exceptions, we can accurately fit model
spectral energy distributions to these objects, representing the first time
this has been done for a large sample of LAEs at z < 3, a gap of ~ 8 Gyr in the
history of the Universe. From the 26/30 LAEs which we can fit, we find an age
and stellar mass range of 200 Myr - 10 Gyr and 10^9 - 10^11 Msol, respectively.
These objects thus appear to be significantly older and more massive than LAEs
at high-redshift. We also find that these LAEs show a mild trend towards higher
metallicity than those at high redshift, as well as a tighter range of dust
attenuation and interstellar medium geometry. These results suggest that
low-redshift LAEs have evolved significantly from those at high redshift.


title: Origin of the Mott Gap

abstract:
  We show exactly that the only charged excitations that exist in the
strong-coupling limit of the half-filled Hubbard model are gapped composite
excitations generated by the dynamics of the charge $2e$ boson that appears
upon explicit integration of the high-energy scale. At every momentum, such
excitations have non-zero spectral weight at two distinct energy scales
separated by the on-site repulsion $U$. The result is a gap in the spectrum for
the composite excitations accompanied by a discontinuous vanishing of the
density of states at the chemical potential when $U$ exceeds the bandwidth.
Consequently, we resolve the long-standing problem of the cause of the charge
gap in a half-filled band in the absence of symmetry breaking.


title: A Minimal Poset Resolution of Stable Ideals

abstract:
  We use the theory of poset resolutions to construct the minimal free
resolution of an arbitrary stable monomial ideal in the polynomial ring whose
coefficients are from a field. This resolution is recovered by utilizing a
poset of Eliahou-Kervaire admissible symbols associated to a stable ideal. The
structure of the poset under consideration is quite rich and in related
analysis, we exhibit a regular CW complex which supports a minimal cellular
resolution of a stable monomial ideal.


title: Thermal Hall Effect in 2D model for paramagnetic dielectrics

abstract:
  Phonon polarization in a magnetic field is analyzed in 2D model. It is shown,
that at presence of spin-phonon interaction phonon possess elliptic
polarization which causes the appearance of heat flux component perpendicular
both to temperature gradient and magnetic field.


title: A Deformation of Quantum Dynamics through the Phase Space Path Integral

abstract:
  Using a regularised construction of the phase space path integral due to
Ingrid Daubechies and John Klauder which involves a time scale ultimately taken
to vanish, and motivated by the general programme towards a noncommutative
space(time) geometry, physical consequences of assuming this time parameter to
provide rather a new fundamental time scale are explored in the context of the
one dimensional harmonic oscillator. Some tantalising results are achieved,
which raise intriguing prospects when extrapolated to the quantum field theory
and gravitational contexts.


title:
Gamma Rays from Clusters and Groups of Galaxies: Cosmic Rays versus Dark
  Matter

abstract:
  Clusters of galaxies have not yet been detected at gamma-ray frequencies;
however, the recently launched Fermi Gamma-ray Space Telescope, formerly known
as GLAST, could provide the first detections in the near future. Clusters are
expected to emit gamma rays as a result of (1) a population of high-energy
primary and re-accelerated secondary cosmic rays (CR) fueled by structure
formation and merger shocks, active galactic nuclei and supernovae, and (2)
particle dark matter (DM) annihilation. In this paper, we ask the question of
whether the Fermi telescope will be able to discriminate between the two
emission processes. We present data-driven predictions for a large X-ray flux
limited sample of galaxy clusters and groups. We point out that the gamma ray
signals from CR and DM can be comparable. In particular, we find that poor
clusters and groups are the systems predicted to have the highest DM to CR
emission at gamma-ray energies. Based on detailed Fermi simulations, we study
observational handles that might enable us to distinguish the two emission
mechanisms, including the gamma-ray spectra, the spatial distribution of the
signal and the associated multi-wavelength emissions. We also propose optimal
hardness ratios, which will help to understand the nature of the gamma-ray
emission. Our study indicates that gamma rays from DM annihilation with a high
particle mass can be distinguished from a CR spectrum even for fairly faint
sources. Discriminating a CR spectrum from a light DM particle will be instead
much more difficult, and will require long observations and/or a bright source.
While the gamma-ray emission from our simulated clusters is extended,
determining the spatial distribution with Fermi will be a challenging task
requiring an optimal control of the backgrounds.


title:
Preference Games and Personalized Equilibria, with Applications to
  Fractional BGP

abstract:
  We study the complexity of computing equilibria in two classes of network
games based on flows - fractional BGP (Border Gateway Protocol) games and
fractional BBC (Bounded Budget Connection) games. BGP is the glue that holds
the Internet together and hence its stability, i.e. the equilibria of
fractional BGP games (Haxell, Wilfong), is a matter of practical importance.
BBC games (Laoutaris et al) follow in the tradition of the large body of work
on network formation games and capture a variety of applications ranging from
social networks and overlay networks to peer-to-peer networks.
  The central result of this paper is that there are no fully polynomial-time
approximation schemes (unless PPAD is in FP) for computing equilibria in both
fractional BGP games and fractional BBC games. We obtain this result by proving
the hardness for a new and surprisingly simple game, the fractional preference
game, which is reducible to both fractional BGP and BBC games.
  We define a new flow-based notion of equilibrium for matrix games --
personalized equilibria -- generalizing both fractional BBC and fractional BGP
games. We prove not just the existence, but the existence of rational
personalized equilibria for all matrix games, which implies the existence of
rational equilibria for fractional BGP and BBC games. In particular, this
provides an alternative proof and strengthening of the main result in [Haxell,
Wilfong]. For k-player matrix games, where k = 2, we provide a combinatorial
characterization leading to a polynomial-time algorithm for computing all
personalized equilibria. For k >= 5, we prove that personalized equilibria are
PPAD-hard to approximate in fully polynomial time. We believe that the concept
of personalized equilibria has potential for real-world significance.


title: OGLE2-TR-L9: An extrasolar planet transiting a fast-rotating F3 star

abstract:
  Context: Photometric observations for the OGLE-II microlens monitoring
campaign have been taken in the period 1997-2000. All light curves of this
campaign have recently been made public. Our analysis of these data has
revealed 13 low-amplitude transiting objects among ~15700 stars in three Carina
fields towards the galactic disk. One of these objects, OGLE2-TR-L9 (P~2.5
days), turned out to be an excellent transiting planet candidate.
  Aims: In this paper we report on our investigation of the true nature of
OGLE2-TR-L9, by re-observing the photometric transit with the aim to determine
the transit parameters at high precision, and by spectroscopic observations, to
estimate the properties of the host star, and to determine the mass of the
transiting object through radial velocity measurements.
  Methods: High precision photometric observations have been obtained in g',
r', i', and z' band simultaneously, using the new GROND detector, mounted on
the MPI/ESO 2.2m telescope at La Silla. Eight epochs of high-dispersion
spectroscopic observations were obtained using the fiber-fed FLAMES/UVES
Echelle spectrograph, mounted on ESO's Very Large Telescope at Paranal.
  Results: The photometric transit, now more than 7 years after the last
OGLE-II observations, was re-discovered only ~8 minutes from its predicted
time. The primary object is a fast rotating F3 star, with vsini=39.33+-0.38
km/s, T=6933+-58 K, log g = 4.25+-0.01, and [Fe/H] = -0.05+-0.20. The
transiting object is an extrasolar planet with M_p=4.5+-1.5 M_Jup and
R_p=1.61+-0.04 R_Jup. The rejection of possible blend scenarios was based on a
quantitative analysis of the multi-color photometric data [abridged].


title: The Experimental Status of Glueballs

abstract:
  Glueballs and other resonances with large gluonic components are predicted as
bound states by Quantum Chromodynamics (QCD). The lightest (scalar) glueball is
estimated to have a mass in the range from 1 to 2 GeV/c**2; a pseudoscalar and
tensor glueball are expected at higher masses. Many different experiments
exploiting a large variety of production mechanisms have presented results in
recent years on light mesons with J(PC) = 0(++), 0(-+), and 2(++) quantum
numbers. This review looks at the experimental status of glueballs. Good
evidence exists for a scalar glueball which is mixed with nearby mesons, but a
full understanding is still missing. Evidence for tensor and pseudoscalar
glueballs are weak at best. Theoretical expectations of phenomenological models
and QCD on the lattice are briefly discussed.


title: Polynomial relations among principal minors of a 4x4-matrix

abstract:
  The image of the principal minor map for n x n-matrices is shown to be
closed. In the 19th century, Nansen and Muir studied the implicitization
problem of finding all relations among principal minors when n=4. We complete
their partial results by constructing explicit polynomials of degree 12 that
scheme-theoretically define this affine variety and also its projective closure
in $\PP^{15}$. The latter is the main component in the singular locus of the 2
x 2 x 2 x 2-hyperdeterminant.


title: Intergalactic Baryons in the Local Universe

abstract:
  Simulations predict that shocks from large-scale structure formation and
galactic winds have reduced the fraction of baryons in the warm, photoionized
phase (the Lya forest) from nearly 100% in the early universe to less than 50%
today. Some of the remaining baryons are predicted to lie in the warm-hot
ionized medium (WHIM) phase at T=10^5-10^7 K, but the quantity remains a highly
tunable parameter of the models. Modern UV spectrographs have provided
unprecedented access to both the Lya forest and potential WHIM tracers at z~0,
and several independent groups have constructed large catalogs of far-UV IGM
absorbers along ~30 AGN sight lines. There is general agreement between the
surveys that the warm, photoionized phase makes up ~30% of the baryon budget at
z~0. Another ~10% can be accounted for in collapsed structures (stars,
galaxies, etc.). However, interpretation of the ~100 high-ion (OVI, etc)
absorbers at z<0.5 is more controversial. These species are readily created in
the shocks expected to exist in the IGM, but they can also be created by
photoionization and thus not represent WHIM material. Given several pieces of
observational evidence and theoretical expectations, I argue that most of the
observed OVI absorbers represent shocked gas at T~300,000 K rather than
photoionized gas at T<30,000 K, and they are consequently valid tracers of the
WHIM phase. Under this assumption, enriched gas at T=10^5-10^6 K can account
for ~10% of the baryon budget at z<0.5, but this value may increase when bias
and incompleteness are taken into account and help close the gap on the 50% of
the baryons still "missing".


title:
First measurement of the magnetic field on FK Com and its relation to
  the contemporaneous starspot locations

abstract:
  In this study we present simultaneous low-resolution longitudinal magnetic
field measurements and high-resolution spectroscopic observations of the cool
single giant FK Com. The variation of the magnetic field over the rotational
period of 2.4 days is compared with the starspot location obtained using
Doppler imaging techniques, V-band photometry and V-I colours. The
chromospheric activity is studied simultaneously with the photospheric activity
using high resolution observations of the Halpha, Hbeta and Hgamma line
profiles. Both the maximum (272 +/- 24 G) and minimum (60 +/- 17 G) in the mean
longitudinal magnetic field, <Bz>, are detected close to the phases where cool
spots appear on the stellar surface. A possible explanation for such a
behaviour is that the active regions at the two longitudes separated by 0.2 in
phase have opposite polarities.


title:
Space-time picture of the string fragmentation and the fusion of colour
  strings

abstract:
  It is shown that naive two stage scenario of the soft multiparticle
production in hadronic and nuclear collisions at high energy, when at first
stage the colour strings are formed and at the second stage these strings, or
some other (higher colour) strings formed due to fusion of primary strings, are
decaying, emitting observed particles, encounters some difficulties at the
attempt to analyse the space-time picture of the process. Simple analysis shows
the dominant is the process when the formation and the decay of a string occur
in parallel - a string breaks into two parts already at rather small length
(about 1-2 fm in its c.m. system), then the process repeats in the pieces and
so on. Nevertheless it is proved to be possible to agree the string fusion idea
with the space-time picture of a string decay. In the framework of the
Artru-Mennessier model of a string fragmentation the simple interpretation of
the homogeneity of the rapidity distribution for hadrons produced from the
decay of a single string at high energy is presented and the analytical
estimate for the density of this rapidity distribution is obtained.


title: The Production of Time

abstract:
  I suggest that measurement in quantum theory should be regarded as a sense of
time (of things happening), which is as important as the conventional
relativistic notion of time. A key question -- of basic physical interest
whether one accepts the arguments here or not -- is, What physical criteria
determine when a measurement takes place? I suggest a way in which the answer
to this may be bound up with the resolution of some pathologies associated with
the stress-energy operator, and may at the same time determine the cosmic flow
of time. The problem of reconciling the quantum sense of time (measurement) and
the conventional relativistic one gives some indication that the the correct
"quantization" of gravity is essentially different from that of other fields.


title: Time reversal in thermoacoustic tomography - an error estimate

abstract:
  The time reversal method in thermoacoustic tomography is used for
approximating the initial pressure inside a biological object using
measurements of the pressure wave made on a surface surrounding the object.
This article presents error estimates for the time reversal method in the cases
of variable, non-trapping sound speeds.


title:
Dilation, smoothed distance, and minimization diagrams of convex
  functions

abstract:
  We study Voronoi diagrams for distance functions that add together two convex
functions, each taking as its argument the difference between Cartesian
coordinates of two planar points. When the functions do not grow too quickly,
then the Voronoi diagram has linear complexity and can be constructed in
near-linear randomized expected time. Additionally, the level sets of the
distances from the sites form a family of pseudocircles in the plane, all cells
in the Voronoi diagram are connected, and the set of bisectors separating any
one cell in the diagram from each of the others forms an arrangement of
pseudolines in the plane. We apply these results to the smoothed distance or
biotope transform metric, a geometric analogue of the Jaccard distance whose
Voronoi diagrams can be used to determine the dilation of a star network with a
given hub. For sufficiently closely spaced points in the plane, the Voronoi
diagram of smoothed distance has linear complexity and can be computed
efficiently. We also experiment with a variant of Lloyd's algorithm, adapted to
smoothed distance, to find uniformly spaced point samples with exponentially
decreasing density around a given point.


title:
Small-world of communities: communication and correlation of the
  meta-network

abstract:
  Given a network and a partition in n communities, we address the issues ``how
communities influence each other'' and ``when two given communities do
communicate''. We prove that, for a small-world network, among communities, a
simple superposition principle applies and each community plays the role of a
microscopic spin governed by a sort of effective TAP (Thouless, Anderson and
Palmer) equations. The relative susceptibilities derived from these equations
calculated at finite or zero temperature (where the method provides an
effective percolation theory) give us the answers to the above issues. As for
the already studied case n=1, these equations are exact in the paramagnetic
regions (at T=0 this means below the percolation threshold) and provide
effective approximations in the other regions. However, unlike the case n=1,
asymmetries among the communities may lead, via the TAP-like structure of the
equations, to many metastable states whose number, in the case of negative
short-cuts among the communities, may grow exponentially fast with n and glassy
scenarios with a remarkable presence of abrupt jumps take place. Furthermore,
as a byproduct, from the relative susceptibilities a natural and efficient
method to detect the community structure of a generic network emerges.


title:
Degenerate Sklyanin algebras and Generalized Twisted Homogeneous
  Coordinate rings

abstract:
  In this work, we introduce the point parameter ring B, a generalized twisted
homogeneous coordinate ring associated to a degenerate version of the
three-dimensional Sklyanin algebra. The surprising geometry of these algebras
yields an analogue to a result of Artin-Tate-van den Bergh, namely that B is
generated in degree one and thus is a factor of the corresponding degenerate
Sklyanin algebra.


title:
Simultaneous Continuation of Infinitely Many Sinks Near a Quadratic
  Homoclinic Tangency

abstract:
  We prove that the $C^3$ diffeomorphisms on surfaces, exhibiting infinitely
many sinksnear the generic unfolding of a quadratic homoclinic tangency of a
dissipative saddle, can be perturbed along an infinite dimensional manifold of
$C^3$ diffeomorphisms such that infinitely many sinks persist simultaneously.
On the other hand, if they are perturbed along one-parameter families that
unfold generically the quadratic tangencies, then at most a finite number of
those sinks have continuation.


title:
Asymmetries involving dihadron fragmentation functions: from DIS to e+e-
  annihilation

abstract:
  Using a model calculation of dihadron fragmentation functions, we fit the
spin asymmetry recently extracted by HERMES for the semi-inclusive pion pair
production in deep-inelastic scattering on a transversely polarized proton
target. By evolving the obtained dihadron fragmentation functions, we make
predictions for the correlation of the angular distributions of two pion pairs
produced in electron-positron annihilations at BELLE kinematics. Our study
shows that the combination of two-hadron inclusive deep-inelastic scattering
and electron-positron annihilation measurements can provide a valid alternative
to Collins effect for the extraction of the quark transversity distribution in
the nucleon.


title: Central exclusive production at the Tevatron

abstract:
  In CDF we have observed several exclusive processes: 2-photon --> e+e- and
--> mu+mu-, photon+pomeron --> J/psi and psi(2S), and pomeron+pomeron -->
chi_c. The cross sections agree with QED, HERA photoproduction data, and
theoretical estimates of gg --> chi_c with another gluon exchanged to screen
the color. This observation of exclusive chi_c, together with earlier
observations of exclusive dijets and exclusive 2-photon candidates, support
some theoretical predictions for p+p --> p+H+p at the LHC. Exclusive dileptons
offer the best means of precisely calibrating forward proton spectrometers.


title: Minimum Bias Triggers at ATLAS, LHC

abstract:
  In the first phase of LHC data-taking ATLAS will measure the charged-particle
density at the initial center-of-mass energy of 10 TeV and then at 14 TeV. This
will allow us improve our knowledge of soft QCD models and pin-down
cross-sections of different classes of inelastic collisions at LHC energies. In
particular, the dominant non-diffractive interaction is a key process to
understanding QCD backgrounds when we reach higher luminosities. We highlight
two minimum-bias triggers, sensitive to particles in complementary ranges in
pseudo-rapidity, one based on signals from the Inner Detector, the other
explicitly designed to trigger on inelastic processes. Studies of their trigger
efficiencies as well as possible trigger biases are presented.


title: Flavor content of the nucleon in an unquenched quark model

abstract:
  We discuss the flavor content of the nucleon in an unquenched quark model in
which the effects of quark-antiquark pairs (up, down and strange) are taken
into account in an explicit form. It is shown that the inclusion of
quark-antiquark pairs leads to an excess of anti-d over anti-u quarks in the
proton and to a large contribution of orbital angular momentum to the spin of
the proton.


title: Unramified cohomology of finite groups of Lie type

abstract:
  We prove vanishing results for unramified stable cohomology of finite groups
of Lie type.


title: Veneziano Amplitudes, Spin Chains and String Models

abstract:
  In a series of recently published papers we reanalyzed the existing
treatments of Veneziano and Veneziano-like amplitudes and the models associated
with these amplitudes. In this work we demonstrate that the already obtained
new partition function for these amplitudes can be exactly mapped into that for
the Polychronakos-Frahm (P-F) spin chain model. This observation allows us to
recover many of the existing string-theoretic models, including the most recent
ones.


title:
The Capacity Region of the Cognitive Z-interference Channel with One
  Noiseless Component

abstract:
  We study the discrete memoryless Z-interference channel (ZIC) where the
transmitter of the pair that suffers from interference is cognitive. We first
provide upper and lower bounds on the capacity of this channel. We then show
that, when the channel of the transmitter-receiver pair that does not face
interference is noiseless, the two bounds coincide and therefore yield the
capacity region. The obtained results imply that, unlike in the Gaussian
cognitive ZIC, in the considered channel superposition encoding at the
non-cognitive transmitter as well as Gel'fand-Pinsker encoding at the cognitive
transmitter are needed in order to minimize the impact of interference. As a
byproduct of the obtained capacity region, we obtain the capacity result for a
generalized Gel'fand-Pinsker problem.


title: Thermodynamics of Chaplygin gas

abstract:
  We clarify thermodynamics of the Chaplygin gas by introducing the
integrability condition. All thermal quantities are derived as functions of
either volume or temperature. Importantly, we find a new general equation of
state, describing the Chaplygin gas completely. We confirm that the Chaplygin
gas could show a unified picture of dark matter and energy which cools down
through the universe expansion without any critical point (phase transition).


title:
Fast approximation of solutions of SDE's with oblique reflection on an
  orthant

abstract:
  We consider the discrete "fast" penalization scheme for SDE's driven by
general semimartingale on orthant $\mathbb{R}_{+}^{d}$ with oblique reflection.


title:
Simplified Vacuum Energy Expressions for Radial Backgrounds and Domain
  Walls

abstract:
  We extend our previous results of simplified expressions for functional
determinants for radial Schr\"odinger operators to the computation of vacuum
energy, or mass corrections, for static but spatially radial backgrounds, and
for domain wall configurations. Our method is based on the zeta function
approach to the Gel'fand-Yaglom theorem, suitably extended to higher
dimensional systems on separable manifolds. We find new expressions that are
easy to implement numerically, for both zero and nonzero temperature.


title:
Channel Estimation and Linear Precoding in Multiuser Multiple-Antenna
  TDD Systems

abstract:
  Traditional approaches in the analysis of downlink systems decouple the
precoding and the channel estimation problems. However, in cellular systems
with mobile users, these two problems are in fact tightly coupled. In this
paper, this coupling is explicitly studied by accounting for channel training
overhead and estimation error while determining the overall system throughput.
The paper studies the problem of utilizing imperfect channel estimates for
efficient linear precoding and user selection. It presents precoding methods
that take into account the degree of channel estimation error.
Information-theoretic lower and upper bounds are derived to evaluate the
performance of these precoding methods. In typical scenarios, these bounds are
close.


title: Remarks on Feedforward Circuits, Adaptation, and Pulse Memory

abstract:
  This note studies feedforward circuits as models for perfect adaptation to
step signals in biological systems. A global convergence theorem is proved in a
general framework, which includes examples from the literature as particular
cases. A notable aspect of these circuits is that they do not adapt to pulse
signals, because they display a memory phenomenon. Estimates are given of the
magnitude of this effect.


title: The mean curvature of cylindrically bounded submanifolds

abstract:
  We give an estimate of the mean curvature of a complete submanifold lying
inside a closed cylinder $B(r)\times\R^{\ell}$ in a product Riemannian manifold
$N^{n-\ell}\times\R^{\ell}$. It follows that a complete hypersurface of given
constant mean curvature lying inside a closed circular cylinder in Euclidean
space cannot be proper if the circular base is of sufficiently small radius. In
particular, any possible counterexample to a conjecture of Calabion complete
minimal hypersurfaces cannot be proper. As another application of our method,
we derive a result about the stochastic incompleteness of submanifolds with
sufficiently small mean curvature.


title: A Frobenius theorem for Cartan geometries, with applications

abstract:
  We prove analogues for Cartan geometries of Gromov's major theorems on
automorphisms of rigid geometric structures. The starting point is a Frobenius
theorem, which says that infinitesimal automorphisms of sufficiently high order
integrate to local automorphisms. Consequences include a stratification theorem
describing the configuration of orbits for local Killing fields in a compact
real-analytic Cartan geometry, and an open-dense theorem in the smooth case,
which says that if there is a dense orbit, then there is an open, dense,
locally homogeneus subset. Combining the Frobenius theorem with the embedding
theorem of Bader, Frances, and the author gives a representation theorem that
relates the fundamental group of the manifold with the automorphism group.


title:
Formation of complex Langmuir and Langmuir-Blodgett films of water
  soluble rosebengal

abstract:
  This communication reports the formation of complex Langmuir monolayer at the
air-water interface by charge transfer types of interaction with the water
soluble N- cetyl N, N, N trimethyl ammonium bromide (CTAB) molecules doped with
rosebengal (RB), with the stearic acid (SA) molecules of a preformed SA
Langmuir monolayer. The reaction kinetics of the formation of RB-CTAB-SA
complex monolayer was monitored by observing the increase in surface pressure
with time while the barrier was kept fixed. Completion of interaction kinetics
was confirmed by FTIR study. This complex Langmuir films at the air-water
interface was transferred onto solid substrates at a desired surface pressure
to form multilayered Langmuir-Blodgett films. Spectroscopic characterizations
reveal some molecular level interactions as well as formation of
microcrystalline aggregates depending upon the molar ratios of CTAB and RB
within the complex LB films. Presence of two types of species in the complex LB
films was confirmed by fluorescence spectroscopy.


title: On the Hydrogen Atom via Wigner-Heisenberg Algebra

abstract:
  We extend the usual Kustaanheimo-Stiefel $4D\to 3D$ mapping to study and
discuss a constrained super-Wigner oscillator in four dimensions. We show that
the physical hydrogen atom is the system that emerges in the bosonic sector of
the mapped super 3D system.


title: Predicted field-induced hexatic structure in an ionomer membrane

abstract:
  Coarse-grained molecular-dynamics simulations were used to study the
morphological changes induced in a Nafion$^{\tiny
  \textregistered}$-like ionomer by the imposition of a strong electric field.
We observe the formation of novel structures aligned along the direction of the
applied field. The polar head groups of the ionomer side chains aggregate into
clusters, which then form rod-like formations which assemble into a hexatic
array aligned with the direction of the field. Occasionally these lines of
sulfonates and protons form a helical structure. Upon removal of the electric
field, the hexatic array of rod-like structures persists, and has a lower
calculated free energy than the original isotropic morphology.


title: Eta-eta' mixing from V->Pgamma and J/psi->VP decays

abstract:
  The $\eta$-$\eta^\prime$ pseudoscalar mixing angle and the gluonium content
of the $\eta^\prime$ meson are deduced from an updated phenomenological
analysis of $V\to P\gamma$ and $J/\psi\to VP$ decays. In absence of gluonium,
the value of the mixing angle in the quark-flavour basis is found to be
$\phi_P=(41.5\pm 1.2)^\circ$ from $V\to P\gamma$ and $\phi_P=(40.5\pm
2.4)^\circ$ from $J/\psi\to VP$. In presence of gluonium, the values for the
mixing angle and the gluonic content of the $\eta^\prime$ wave function are
$\phi_P=(41.4\pm 1.3)^\circ$ and $Z^2_{\eta^\prime}=0.04\pm 0.09$ from $V\to
P\gamma$ and $\phi_P=(44.5\pm 4.3)^\circ$ and $Z^2_{\eta^\prime}=0.28\pm 0.21$
from $J/\psi\to VP$, respectively.


title: Dynamic spectrum sharing game by lease

abstract:
  We propose and analyze a dynamic implementation of the property-rights model
of cognitive radio. A primary link has the possibility to lease the owned
spectrum to a MAC network of secondary nodes, in exchange for cooperation in
the form of distributed space-time coding (DSTC). The cooperation and
competition between the primary and secondary network are cast in the framework
of sequential game. On one hand, the primary link attempts to maximize its
quality of service in terms of signal-to-interference-plus-noise ratio (SINR);
on the other hand, nodes in the secondary network compete for transmission
within the leased time-slot following a power control mechanism. We consider
both a baseline model with complete information and a more practical version
with incomplete information, using the backward induction approach for the
former and providing approximate algorithm for the latter. Analysis and
numerical results show that our models and algorithms provide a promising
framework for fair and effective spectrum sharing, both between primary and
secondary networks and among secondary nodes.


title:
The Uniqueness Problem of Sequence Product on Operator Effect Algebra
  $\varepsilon (H)$

abstract:
  A quantum effect is an operator on a complex Hilbert space $H$ that satisfies
$0\leq A\leq I$. We denote the set of all quantum effects by ${\cal E}(H)$. In
this paper we prove, Theorem 4.3, on the theory of sequential product on ${\cal
E}(H)$ which shows, in fact, that there are sequential products on ${\cal
E}(H)$ which are not of the generalized L\"{u}ders form. This result answers a
Gudder's open problem negatively.

categories: math-ph math.MP math.OA math.QA quant-ph


title:
On the origin of double main-sequence turn-offs in star clusters of the
  Magellanic Clouds

abstract:
  Recent observational studies of intermediate-age star clusters (SCs) in the
Large Magellanic Cloud (LMC) have reported that a significant number of these
objects show double main-sequence turn-offs (DMSTOs) in their color-magnitude
diagrams (CMDs). One plausible explanation for the origin of these DMSTOs is
that the SCs are composed of two different stellar populations with age
differences of ~ 300 Myr. Based on analytical methods and numerical
simulations, we explore a new scenario in which SCs interact and merge with
star-forming giant molecular clouds (GMCs) to form new composite SCs with two
distinct component populations. In this new scenario, the possible age
differences between the two different stellar populations responsible for the
DMSTOs are due largely to secondary star formation within GMCs interacting and
merging with already-existing SCs in the LMC disk. The total gas masses being
converted into new stars (i.e., the second generation of stars) during GMC-SC
interaction and merging can be comparable to or larger than the masses of the
original SCs (i.e, the first generation of stars) in this scenario. Our
simulations show that the spatial distributions of new stars in composite SCs
formed from GMC-SC merging are more compact than those of stars initially in
the SCs. We discuss both advantages and disadvantages of the new scenario in
explaining fundamental properties of SCs with DMSTOs in the LMC and in the
Small Magellanic Cloud (SMC). We also discuss the merits of various alternative
scenarios for the origin of the DMSTOs.


title:
A New Look at Massive Clusters: weak lensing constraints on the triaxial
  dark matter halos of Abell 1689, Abell 1835, & Abell 2204

abstract:
  Measuring the 3D distribution of mass on galaxy cluster scales is a crucial
test of the LCDM model, providing constraints on the nature of dark matter.
Recent work investigating mass distributions of individual galaxy clusters
(e.g. Abell 1689) using weak and strong gravitational lensing has revealed
potential inconsistencies between the predictions of structure formation models
relating halo mass to concentration and those relationships as measured in
massive clusters. However, such analyses employ simple spherical halo models
while a growing body of work indicates that triaxial 3D halo structure is both
common and important in parameter estimates. We recently introduced a Markov
Chain Monte Carlo (MCMC) method to fit fully triaxial models to weak lensing
data that gives parameter and error estimates that fully incorporate the true
shape uncertainty present in nature. In this paper we apply that method to weak
lensing data obtained with the ESO/MPG Wide-Field Imager for galaxy clusters
A1689, A1835, and A2204, under a range of Bayesian priors derived from theory
and from independent X-ray and strong lensing observations. For Abell 1689,
using a simple strong lensing prior we find marginalized mean parameter values
M_200 = (0.83 +- 0.16)x10^15 M_solar/h and C=12.2 +- 6.7, which are marginally
consistent with the mass-concentration relation predicted in LCDM. The large
error contours that accompany our triaxial parameter estimates more accurately
represent the true extent of our limited knowledge of the structure of galaxy
cluster lenses, and make clear the importance of combining many constraints
from other theoretical, lensing (strong, flexion), or other observational
(X-ray, SZ, dynamical) data to confidently measure cluster mass profiles.
(Abridged)


title: Censored Glauber Dynamics for the mean field Ising Model

abstract:
  We study Glauber dynamics for the Ising model on the complete graph on $n$
vertices, known as the Curie-Weiss Model. It is well known that at high
temperature ($\beta < 1$) the mixing time is $\Theta(n\log n)$, whereas at low
temperature ($\beta > 1$) it is $\exp(\Theta(n))$. Recently, Levin, Luczak and
Peres considered a censored version of this dynamics, which is restricted to
non-negative magnetization. They proved that for fixed $\beta > 1$, the
mixing-time of this model is $\Theta(n\log n)$, analogous to the
high-temperature regime of the original dynamics. Furthermore, they showed
\emph{cutoff} for the original dynamics for fixed $\beta<1$. The question
whether the censored dynamics also exhibits cutoff remained unsettled.
  In a companion paper, we extended the results of Levin et al. into a complete
characterization of the mixing-time for the Currie-Weiss model. Namely, we
found a scaling window of order $1/\sqrt{n}$ around the critical temperature
$\beta_c=1$, beyond which there is cutoff at high temperature. However,
determining the behavior of the censored dynamics outside this critical window
seemed significantly more challenging.
  In this work we answer the above question in the affirmative, and establish
the cutoff point and its window for the censored dynamics beyond the critical
window, thus completing its analogy to the original dynamics at high
temperature. Namely, if $\beta = 1 + \delta$ for some $\delta > 0$ with
$\delta^2 n \to \infty$, then the mixing-time has order $(n /
\delta)\log(\delta^2 n)$. The cutoff constant is $(1/2+[2(\zeta^2 \beta /
\delta - 1)]^{-1})$, where $\zeta$ is the unique positive root of
$g(x)=\tanh(\beta x)-x$, and the cutoff window has order $n / \delta$.


title:
A multipixel silicon APD with ultralow dark count rate at liquid
  nitrogen temperature

abstract:
  The dark count rate of a multipixel photon counter (MPPC) was reduced to less
than 0.2 cps by cooling the counter to 78.5 K. Characteristics of the MPPC
other than the dark count rate were also detemined at 78.5 K and 295 K. The
photodetection efficiency and the timing jitter at 78.5 K were comparable to
those at 295 K. The MPPC had a count rate of up to 50 MHz at 78.5 K and above
100 MHz at 295 K. Detailed measurements were performed for detemining the
afterpulse probability.


title: Analysis of Group Multiuser Detection Based on Coalitional Game

abstract:
  The issue of group-blind multiuser detection in MAC channel among wireless
nodes in the environment of multiple networks coexisting and sharing spectrum
is addressed under the Framework of coalitional game. We investigate the
performance and stability of multiple access channel (MAC) with linear
decorrelating multiuser detection under varying SNR, channel gains and
coalitional structures, in which both single BS and multiple BSs cases were
considered. The main results and conclusion are as follows: (1) the grand
coalition is payoff maximizing under loose SNR; (2) it is in conformity with
group and coalitional rationality forming coalition among nodes that have
comparative channel gains.


title: Partially Unbiased Entangled Bases

abstract:
  In this contribution we group the operator basis for d^2 dimensional Hilbert
space in a way that enables us to relate bases of entangled states with single
particle mutually unbiased state bases (MUB), each in dimensionality d. We
utilize these sets of operators to show that an arbitrary density matrix for
this d^2 dimensional Hilbert space system is analyzed by via d^2+d+1
measurements, d^2-d of which involve those entangled states that we associate
with MUB of the d-dimensional single particle constituents. The number
$d^2+d+1$ lies in the middle of the number of measurements needed for bipartite
state reconstruction with two-particle MUB (d^2+1) and those needed by
single-particle MUB [(d^2+1)^2].


title: A note on large N scalar QCD_2

abstract:
  We review the features of the bound state equation in large N scalar QCD in
two dimensions, the 't Hooft model, and compute the discrete hadron mass
spectrum in this theory. We make the Ansatz that the scalar fields of this
model represent spin zero diquarks and we estimate the minimum allowed mass for
the first radial excitation of the lowest diquark-antidiquark scalar meson. The
discussion is extended to the case of spin one diquarks.


title:
A multiplicative product of distributions and a global formulation of
  the confined Schrodinger equation

abstract:
  A concise derivation of a new multiplicative product of Schwartz
distributions is presented. The new product $\star$ is defined in the vector
space ${\cal A}$ of piecewise smooth functions on $\bkR$ and all their
(distributional) derivatives; it is associative, satisfies the Leibnitz rule
and reproduces the usual product of functions for regular distributions. The
algebra $({\cal A},+,\star)$ yields a sufficiently general setting to address
some interesting problems. As an application we consider the problem of
deriving a global formulation for quantum confined systems.


title: Giambelli, Pieri, and tableau formulas via raising operators

abstract:
  We give a direct proof of the equivalence between the Giambelli and Pieri
type formulas for Hall-Littlewood functions using Young's raising operators,
parallel to joint work with Buch and Kresch for the Schubert classes on
isotropic Grassmannians. We prove several closely related mirror identities
enjoyed by the Giambelli polynomials, which lead to new recursions for Schubert
classes. The raising operator approach is applied to obtain tableau formulas
for Hall-Littlewood functions, theta polynomials, and related Stanley symmetric
functions. Finally, we introduce the notion of a skew element w of the
hyperoctahedral group and identify the set of reduced words for w with the set
of standard k-tableaux on a skew Young diagram.


title:
Combinatorial formulas for Le-coordinates in a totally nonnegative
  Grassmannian

abstract:
  Postnikov constructed a decomposition of a totally nonnegative Grassmannian
into positroid cells. We provide combinatorial formulas that allow one to
decide which cell a given point belongs to and to determine affine coordinates
of the point within this cell. This simplifies Postnikov's description of the
inverse boundary measurement map and generalizes formulas for the top cell
given by Speyer and Williams. In addition, we identify a particular subset of
Pluecker coordinates as a totally positive base for the set of non-vanishing
Pluecker coordinates for a given positroid cell.


title: A Reinvestigation of Moving Punctured Black Holes with a New Code

abstract:
  We report on our code, in which the moving puncture method is applied and an
adaptive/fixed mesh refinement is implemented, and on its preliminary
performance on black hole simulations. Based on the BSSN formulation,
up-to-date gauge conditions and the modifications of the formulation are also
implemented and tested. In this work we present our primary results about the
simulation of a single static black hole, of a moving single black hole, and of
the head-on collision of a binary black hole system. For the static punctured
black hole simulations, different modifications of the BSSN formulation are
applied. It is demonstrated that both the currently used sets of modifications
lead to a stable evolution. For cases of a moving punctured black hole with or
without spin, we search for viable gauge conditions and study the effect of
spin on the black hole evolution. Our results confirm previous results obtained
by other research groups. In addition, we find a new gauge condition, which has
not yet been adopted by any other researchers, which can also give stable and
accurate black hole evolution calculations. We examine the performance of the
code for the head-on collision of a binary black hole system, and the agreement
of the gravitational waveform it produces with that obtained in other works. In
order to understand qualitatively the influence of matter on the binary black
hole collisions, we also investigate the same head-on collision scenarios but
perturbed by a scalar field. The numerical simulations performed with this code
not only give stable and accurate results that are consistent with the works by
other numerical relativity groups, but also lead to the discovery of a new
viable gauge condition, as well as clarify some ambiguities in the modification
of the BSSN formulation.


title: An almost sure limit theorem for super-Brownian motion

abstract:
  We establish an almost sure scaling limit theorem for super-Brownian motion
on $\mathbb{R}^d$ associated with the semi-linear equation $u_t = {1/2}\Delta u
+\beta u-\alpha u^2$, where $\alpha$ and $\beta$ are positive constants. In
this case, the spectral theoretical assumptions that required in Chen et al
(2008) are not satisfied. An example is given to show that the main results
also hold for some sub-domains in $\mathbb{R}^d$.


title: Bass Numbers and Semidualizing Complexes

abstract:
  Let R be a commutative local noetherian ring. We prove that the existence of
a chain of semidualizing R-complexes of length (d+1) yields a degree-d
polynomial lower bound for the Bass numbers of R. We also show how information
about certain Bass numbers of R provide restrictions on the lengths of chains
of semidualizing R-complexes. To make this article somewhat self-contained, we
also include a survey of some of the basic properties of semidualizing modules,
semidualizing complexes and derived categories.


title: Survival Strategies

abstract:
  This paper addresses the theoretical conditions necessary for some subject of
study to survive forever. A probabilistic analysis leads to some prerequisite
conditions for preserving, say, electronic data indefinitely into the future.
The general analysis would also apply to a species, a civilization, or any
subject of study, as long as there is a definition of "survival" available. A
distinction emerges between two approaches to longevity: being many or being
smart. Natural selection relies on the first method, whereas a civilization,
individual, or other singular subject must rely on the latter. A computational
model of survival incorporates the idea of Kolmogorov-type complexity for both
strategies to illustrate the role of data analysis and information processing
that may be required. The survival-through-intelligence strategy has problems
when the subject can self-modify, which is illustrated with a link to Turing's
Halting Problem. The paper concludes with comments on the Fermi Paradox.


title: Quantum communication through anisotropic Heisenberg XY spin chains

abstract:
  We study quantum communication through an anisotropic Heisenberg XY chain in
a transverse magnetic field. We find that for some time $t$ and anisotropy
parameter $\gamma$, one can transfer a state with a relatively high fidelity.
In the strong-field regime, the anisotropy does not significantly affect the
fidelity while in the weak-field regime the affect is quite pronounced. The
most interesting case is the the intermediate regime where the oscillation of
the fidelity with time is low and the high-fidelity peaks are relatively broad.
This would, in principle, allow for quantum communication in realistic
circumstances. Moreover, we calculate the purity, or tangle, as a measure of
the entanglement between one spin and all the other spins in the chain and find
that the stronger the anisotropy and exchange interaction, the more
entanglement will be generated for a given time.


title: Spherically Symmetric Gravitational Collapse

abstract:
  In this paper, we discuss gravitational collapse of spherically symmetric
spacetimes. We derive a general formalism by taking two arbitrary spherically
symmetric spacetimes with $g_{00}=1$. Israel's junction conditions are used to
develop this formalism. The formulae for extrinsic curvature tensor are
obtained. The general form of the surface energy-momentum tensor depending on
extrinsic curvature tensor components is derived. This leads us to the surface
energy density and the tangential pressure. The formalism is applied to two
known spherically symmetric spacetimes. The results obtained show the regions
for the collapse and expansion of the shell.


title:
Lyapunov spectra instability of chaotic dynamo Ricci flows in twisted
  magnetic flux tubes

abstract:
  Previously Casetti, Clementi and Pettini [\textbf{Phys.Rev.E
\textbf{54},6,(1996)}] have investigated the Lyapunov spectrum of Hamiltonian
flows for several Hamiltonian systems by making use of the Riemannian geometry.
Basically the Lyapunov stability analysis was substituted by the Ricci
sectional curvature analysis. In this report we apply Pettini's geometrical
framework to determine the potential energy of a twisted magnetic flux tube,
from its curved Riemannian geometry. Actually the Lyapunov exponents, are
connected to a Riemann metric tensor, of the twisted magnetic flux tubes
(MFTs). The Hamiltonian flow inside the tube is actually given by Perelman
Ricci flows constraints in twisted magnetic flux tubes, where the Lyapunov
eigenvalue spectra for the Ricci tensor associated with the Ricci flow equation
in MFTs leads to a finite-time Lyapunov exponential stretching along the
toroidal direction of the tube and a contraction along the radial direction of
the tube. The Jacobi equation for the MFTs is shown to have a constant
sectional Ricci curvature which allows us to compute the Jacobi-Levi-Civita
(JLC) geodesic deviation for the spread of lines on the tube manifold and
chaotic action through the greatest of its Lyapunov exponents. By analyzing the
spectra of the twisted MFT, it is shown that the greater exponent is positive
and proportional to the random radial flow of the tube, which allows the onset
of chaos is guaranted. The randomness in the twisted flow reminds a discussed
here is similar of a recent work by Shukurov, Stepanov, and Sokoloff on dynamo
action on Moebius flow [\textbf{Phys Rev E 78 (2008)}]. The dynamo action in
twisted flux tubes discussed here may also serve as model for dynamo
experiments in laboratory.


title:
Effects of scattering and dust grain size on the temperature structure
  of protoplanetary discs: A three-layer approach

abstract:
  The temperature in the optically thick interior of protoplanetary discs is
essential for the interpretation of millimeter observations of the discs, for
the vertical structure of the discs, for models of the disc evolution and the
planet formation, and for the chemistry in the discs. Since large icy grains
have a large albedo even in the infrared, the effect of scattering of the
diffuse radiation in the discs on the interior temperature should be examined.
We have performed a series of numerical radiation transfer simulations
including isotropic scattering by grains with various typical sizes for the
diffuse radiation as well as for the incident stellar radiation. We also have
developed an analytic model including isotropic scattering to understand the
physics concealed in the numerical results. With the analytic model, we have
shown that the standard two-layer approach is valid only for grey opacity (i.e.
grain size $\ga10$ \micron) even without scattering. A three-layer
interpretation is required for grain size $\la10$ \micron. When the grain size
is 0.1--10 \micron, the numerical simulations show that isotropic scattering
reduces the temperature of the disc interior. This reduction is nicely
explained by the analytic three-layer model as a result of the energy loss by
scatterings of the incident stellar radiation and of the warm diffuse radiation
in the disc atmosphere. For grain size $\ga10$ \micron (i.e. grey scattering),
the numerical simulations show that isotropic scattering does not affect the
interior temperature. This is nicely explained by the analytic two-layer model;
the energy loss by scattering in the disc atmosphere is exactly offset by the
"green-house effect" due to scattering of the cold diffuse radiation in the
interior.


title: The Seventh Data Release of the Sloan Digital Sky Survey

abstract:
  This paper describes the Seventh Data Release of the Sloan Digital Sky Survey
(SDSS), marking the completion of the original goals of the SDSS and the end of
the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most
of the roughly 2000 deg^2 increment over the previous data release lying in
regions of low Galactic latitude. The catalog contains five-band photometry for
357 million distinct objects. The survey also includes repeat photometry over
250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A
coaddition of these data goes roughly two magnitudes fainter than the main
survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2
in the Northern Galactic Cap, closing the gap that was present in previous data
releases. There are over 1.6 million spectra in total, including 930,000
galaxies, 120,000 quasars, and 460,000 stars. The data release includes
improved stellar photometry at low Galactic latitude. The astrometry has all
been recalibrated with the second version of the USNO CCD Astrograph Catalog
(UCAC-2), reducing the rms statistical errors at the bright end to 45
milli-arcseconds per coordinate. A systematic error in bright galaxy photometr
is less severe than previously reported for the majority of galaxies. Finally,
we describe a series of improvements to the spectroscopic reductions, including
better flat-fielding and improved wavelength calibration at the blue end,
better processing of objects with extremely strong narrow emission lines, and
an improved determination of stellar metallicities. (Abridged)


title: Cluster-tilted algebras of type $D_n$

abstract:
  Let $H$ be a hereditary algebra of Dynkin type $D_n$ over a field $k$ and
$\mathscr{C}_H$ be the cluster category of $H$. Assume that $n\geq 5$ and that
$T$ and $T'$ are tilting objects in $\mathscr{C}_H$. We prove that the
cluster-tilted algebra $\Gamma=\mathrm{End}_{\mathscr{C}_H}(T)^{\rm op}$ is
isomorphic to $\Gamma'=\mathrm{End}_{\mathscr{C}_H}(T')^{\rm op}$ if and only
if $T=\tau^iT'$ or $T=\sigma\tau^jT'$ for some integers $i$ and $j$, where
$\tau$ is the Auslander-Reiten translation and $\sigma$ is the automorphism of
$\mathscr{C}_H$ defined in section 4.


title: Fermi transport of spinors and free QED states in curved spacetime

abstract:
  Fermi transport of spinors can be precisely understood in terms of 2-spinor
geometry. By using a partly original, previously developed treatment of
2-spinors and classical fields, we describe the family of all transports, along
a given 1-dimensional timelike submanifold of spacetime, which yield the
standard Fermi transport of vectors. Moreover we show that this family has a
distinguished member, whose relation to the Fermi transport of vectors is
similar to the relation between the spinor connection and spacetime connection.
Various properties of the Fermi transport of spinors are discussed, and applied
to the construction of free electron states for a detector-dependent QED
formalism introduced in a previous paper.


title:
Monodromy at infinity of $A$-hypergeometric functions and toric
  compactifications

abstract:
  We study $A$-hypergeometric functions introduced by
Gelfand-Kapranov-Zelevinsky and prove a formula for the eigenvalues of their
monodromy automorphisms defined by the analytic continuaions along large loops
contained in complex lines parallel to the coordinate axes. A method of toric
compactifications will be used to prove our main theorem.


title: Construction and Refinement of Coarse-Grained Models

abstract:
  A general scheme, which includes constructions of coarse-grained (CG) models,
weighted ensemble dynamics (WED) simulations and cluster analyses (CA) of
stable states, is presented to detect dynamical and thermodynamical properties
in complex systems. In the scheme, CG models are efficiently and accurately
optimized based on a directed distance from original to CG systems, which is
estimated from ensemble means of lots of independent observable in two systems.
Furthermore, WED independently generates multiple short molecular dynamics
trajectories in original systems. The initial conformations of the trajectories
are constructed from equilibrium conformations in CG models, and the weights of
the trajectories can be estimated from the trajectories themselves in
generating complete equilibrium samples in the original systems. CA calculates
the directed distances among the trajectories and groups their initial
conformations into some clusters, which correspond to stable states in the
original systems, so that transition dynamics can be detected without requiring
a priori knowledge of the states.