title:
Internal solitary waves in the ocean: Analysis using the periodic,
  inverse scattering transform

abstract:
  The periodic, inverse scattering transform (PIST) is a powerful analytical
tool in the theory of integrable, nonlinear evolution equations. Osborne
pioneered the use of the PIST in the analysis of data form inherently nonlinear
physical processes. In particular, Osborne's so-called nonlinear Fourier
analysis has been successfully used in the study of waves whose dynamics are
(to a good approximation) governed by the Korteweg--de Vries equation. In this
paper, the mathematical details and a new application of the PIST are
discussed. The numerical aspects of and difficulties in obtaining the nonlinear
Fourier (i.e., PIST) spectrum of a physical data set are also addressed. In
particular, an improved bracketing of the "spectral eigenvalues" (i.e., the
+/-1 crossings of the Floquet discriminant) and a new root-finding algorithm
for computing the latter are proposed. Finally, it is shown how the PIST can be
used to gain insightful information about the phenomenon of soliton-induced
acoustic resonances, by computing the nonlinear Fourier spectrum of a data set
from a simulation of internal solitary wave generation and propagation in the
Yellow Sea.


title: A Modified Synchrotron Model for Knots in the M87 Jet

abstract:
  For explaining the broadband spectral shape of knots in the M87 jet from
radio through optical to X-ray, we propose a modified synchrotron model that
considers the integrated effect of particle injection from different
acceleration sources in the thin acceleration region. This results in two break
frequencies at two sides of which the spectral index of knots in the M87 jet
changes. We discuss the possible implications of these results for the physical
properties in the M87 jet. The observed flux of the knots in the M87 jet from
radio to X-ray can be satisfactorily explained by the model, and the predicted
spectra from ultraviolet to X-ray could be further tested by future
observations. The model implies that the knots D, E, F, A, B, and C1 are
unlikely to be the candidate for the TeV emission recently detected in M87.


title: A Remark on Hypercontractive Semigroups and Operator Ideals

abstract:
  In this note, we answer a question raised by Johnson and Schechtman
\cite{JS}, about the hypercontractive semigroup on $\{-1,1\}^{\NN}$. More
generally, we prove the folllowing theorem. Let $1<p<2$. Let $(T(t))_{t>0}$ be
a holomorphic semigroup on $L_p$ (relative to a probability space). Assume the
following mild form of hypercontractivity: for some large enough number $s>0$,
$T(s)$ is bounded from $L_p$ to $L_2$. Then for any $t>0$, $T(t)$ is in the
norm closure in $B(L_p)$ (denoted by $\bar{\Gamma_2}$) of the subset (denoted
by ${\Gamma_2}$) formed by the operators mapping $L_p$ to $L_2$ (a fortiori
these operators factor through a Hilbert space).


title: A perfect stratification of M_g for g at most 5

abstract:
  We find for g at most 5 a stratification of depth g-2 of the moduli space of
curves M_g with the property that its strata are affine and the classes of
their closures provide a Q-basis for the Chow ring of M_g. The first property
confirms a conjecture of one of us. The way we establish the second property
yields new (and simpler) proofs of theorems of Faber and Izadi which, taken
together, amount to the statement that in this range the Chow ring is generated
by the lambda-class.


title:
Mathematical problems on generalized functions and the canonical
  Hamiltonian formalism

abstract:
  This text is addressed to mathematicians who are interested in generalized
functions and unbounded operators on a Hilbert space. We expose in detail (in a
"formal way" - as done by Heisenberg and Pauli - i.e. without mathematical
definitions and then, of course, without mathematical rigour) the
Heisenberg-Pauli calculations on the simplest model close to physics. The
problem for mathematicians is to give a mathematical sense to these
calculations, which is possible without any knowledge in physics, since they
mimick exactly usual calculations on infinitely differentiable functions and on
bounded operators, and can be considered at a purely mathematical level,
ignoring physics in a first step. The mathematical tools to be used are
nonlinear generalized functions, unbounded operators on a Hilbert space and
computer calculations.


title: Sally modules of rank one

abstract:
  The structure of Sally modules of $\fkm$-primary ideals $I$ in a
Cohen-Macaulay local ring $(A, \m)$ satisfying the equality
$\e_1(I)=\e_0(I)-\ell_A(A/I)+1$ is explored, where $\e_0(I)$ and $\e_1(I)$
denote the first two Hilbert coefficients of $I$.


title: Meson masses at large N_c

abstract:
  We analyze the meson spectrum in SU(N_c) lattice gauge theory. We use Wilson
quarks to measure the pseudoscalar and vector masses in SU(2), SU(3), SU(4) and
SU(6), and extrapolate to the large-N_c limit. We find that finite-N_c
corrections are small at all values of the quark mass.


title:
A new renormalization approach to the Dirichlet Casimir effect for
  \phi^4 theory in (1+1) dimensions

abstract:
  The next to the leading order Casimir effect for a real scalar field, within
$\phi^4$ theory, confined between two parallel plates is calculated in one
spatial dimension. Here we use the Green's function with the Dirichlet boundary
condition on both walls. In this paper we introduce a systematic perturbation
expansion in which the counterterms automatically turn out to be consistent
with the boundary conditions. This will inevitably lead to nontrivial position
dependence for physical quantities, as a manifestation of the breaking of the
translational invariance. This is in contrast to the usual usage of the
counterterms, in problems with nontrivial boundary conditions, which are either
completely derived from the free cases or at most supplemented with the
addition of counterterms only at the boundaries. We obtain \emph{finite}
results for the massive and massless cases, in sharp contrast to some of the
other reported results. Secondly, and probably less importantly, we use a
supplementary renormalization procedure in addition to the usual regularization
and renormalization programs, which makes the usage of any analytic
continuation techniques unnecessary.


title: Coherent laser control of the current through molecular junctions

abstract:
  The electron tunneling through a molecular junction modeled by a single site
weakly coupled to two leads is studied in the presence of a time-dependent
external field using a master equation approach. In the case of small bias
voltages and high carrier frequencies of the external field, we observe the
phenomenon of coherent destruction of tunneling, i.e. the current through the
molecular junction vanishes completely for certain parameters of the external
field. In previous studies the tunneling within isolated and open multi-site
systems was suppressed; it is shown here that the tunneling between a single
site and electronic reservoirs, i.e. the leads, can be suppressed as well. For
larger bias voltages the current does not vanish any more since further
tunneling channels participate in the electron conduction and we also observe
photon-assisted tunneling which leads to steps in the current-voltage
characteristics. The described phenomena are demonstrated not only for
monochromatic fields but also for laser pulses and therefore could be used for
ultrafast optical switching of the current through molecular junctions.


title: Twelve bridges from a reductive group to its Langlands dual

abstract:
  These notes are based on lectures given in Wuhan (China) in July 2007. Their
aim is to provide an introduction to Langlands philosophy.


title: Toric dynamical systems

abstract:
  Toric dynamical systems are known as complex balancing mass action systems in
the mathematical chemistry literature, where many of their remarkable
properties have been established. They include as special cases all deficiency
zero systems and all detailed balancing systems. One feature is that the steady
state locus of a toric dynamical system is a toric variety, which has a unique
point within each invariant polyhedron. We develop the basic theory of toric
dynamical systems in the context of computational algebraic geometry and show
that the associated moduli space is also a toric variety. It is conjectured
that the complex balancing state is a global attractor. We prove this for
detailed balancing systems whose invariant polyhedron is two-dimensional and
bounded.


title: Switching the current through molecular wires

abstract:
  The influence of Gaussian laser pulses on the transport through molecular
wires is investigated within a tight-binding model for spinless electrons
including correlation. Motivated by the phenomenon of coherent destruction of
tunneling for monochromatic laser fields, situations are studied in which the
maximum amplitude of the electric field fulfills the conditions for the
destructive quantum effect. It is shown that, as for monochromatic laser
pulses, the average current through the wire can be suppressed. For parameters
of the model, which do not show a net current without any optical field, a
Gaussian laser pulse can establish a temporary current. In addition, the effect
of electron correlation on the current is investigated.


title:
Coherent destruction of the current through molecular wires using short
  laser pulses

abstract:
  A molecular wire coupled to two electron reservoirs is investigated within a
tight-binding approach including spin and Coulomb interaction. Under the
assumption of weak coupling to the electron reservoirs a quantum master
equation can be derived for the electron transport through the wire. Motivated
by the phenomenon of coherent destruction of tunneling for monochromatic laser
fields, the influence of Gaussian laser pulses on the transport through the
wires is studied. For situations in which the maximum amplitude of the electric
field fulfills the conditions for the destructive quantum effect the average
current through the system can be suppressed even for a wire consisting of only
one site. Turning on the electron correlation does not destroy the suppression
of the current by the laser.


title: Some counterexamples in dynamics of rational semigroups

abstract:
  We give an example of two rational functions with non-equal Julia sets that
generate a rational semigroup whose completely invariant Julia set is a closed
line segment. We also give an example of polynomials with unequal Julia sets
that generate a non nearly Abelian polynomial semigroup with the property that
the Julia set of one generator is equal to the Julia set of the semigroup.
These examples show that certain conjectures in the field of dynamics of
rational semigroups do not hold as stated and therefore require the allowance
of certain exceptional cases.


title: On the Dreaded Right Bousfield Localization

abstract:
  I verify the existence of right Bousfield localizations of right semimodel
categories, and I apply this to construct a model of the homotopy limit of a
left Quillen presheaf as a right semimodel category.


title: High-density Skyrmion matter and Neutron Stars

abstract:
  We examine neutron star properties based on a model of dense matter composed
of B=1 skyrmions immersed in a mesonic mean field background. The model
realizes spontaneous chiral symmetry breaking non-linearly and incorporates
scale-breaking of QCD through a dilaton VEV that also affects the mean fields.
Quartic self-interactions among the vector mesons are introduced on grounds of
naturalness in the corresponding effective field theory. Within a plausible
range of the quartic couplings, the model generates neutron star masses and
radii that are consistent with a preponderance of observational constraints,
including recent ones that point to the existence of relatively massive neutron
stars with mass M 1.7 Msun and radius R (12-14) km. If the existence of neutron
stars with such dimensions is confirmed, matter at supra-nuclear density is
stiffer than extrapolations of most microscopic models suggest.


title:
Anomalous dispersion of optical phonons at the neutral-ionic transition:
  Evidence from diffuse X-ray scattering

abstract:
  Diffuse X-ray data for mixed stack organic charge-transfer crystals
approaching the neutral-ionic phase transition can be quantitatively explained
as due to the softening of the optical phonon branch. The interpretation is
fully consistent with vibrational spectra, and underlines the importance of
electron-phonon coupling in low-dimensional systems with delocalized electrons.


title: Alternative Method for Studying Color Centers in CsCl Thin Films

abstract:
  The optical properties of cesium chloride (CsCl) are changed with presence of
vacancies in the crystal structure giving rise to what is called as "color
centers". We have unconventionally adopted Tauc's method to determine the
characteristic color centers and have modeled the correlation among the film
optical properties and lattice size, highlighting the interrelation between the
structural and optical properties of alkali halide films.


title:
Global strings in extra dimensions: a full map of solutions, matter
  trapping and the hierarchy problem

abstract:
  We consider (d_0+2)-dimensional configurations with global strings in the two
extra dimensions and a flat metric in d_0 dimensions, endowed with a warp
factor e^{2\gamma} depending on the distance l from the string center. All
possible regular solutions to the field equations are classified by the
behavior of the warp factor and the extra-dimensional circular radius r(l).
Solutions with r\to \infty and r\to \const >0 as l\to \infty are interpreted in
terms of thick brane world models. Solutions with r \to 0 as l \to l_c > 0,
i.e., those with a second center, are interpreted as either multi-brane systems
(which is appropriate for large enough distances l_c between the centers) or as
Kaluza-Klein type configurations with extra dimensions invisible due to their
smallness. For the case of the Mexican-hat symmetry breaking potential, we
build a full map of regular solutions on the (\epsilon,\Gamma) parameter plane,
where \epsilon acts as an effective cosmological constant while \Gamma
characterizes the strength of gravity. The trapping properties of candidate
brane worlds for test scalar fields are discussed. Good trapping properties for
massive fields are found for models with growing warp factors. Kaluza-Klein
type models are shown to possess nontrivial warp factor behaviors, leading to
matter particle mass spectra which seem promising from the standpoint of
hierarchy problems.


title: Stability and nonlinear adjustment of vortices in Keplerian flows

abstract:
  We investigate the stability, nonlinear development and equilibrium structure
of vortices in a background shearing Keplerian flow. We make use of
high-resolution global two-dimensional compressible hydrodynamic simulations.
We introduce the concept of nonlinear adjustment to describe the transition of
unbalanced vortical fields to a long-lived configuration. We discuss the
conditions under which vortical perturbations evolve into long-lived persistent
structures and we describe the properties of these equilibrium vortices. The
properties of equilibrium vortices appear to be independent from the initial
conditions and depend only on the local disk parameters. In particular we find
that the ratio of the vortex size to the local disk scale height increases with
the decrease of the sound speed, reaching values well above the unity. The
process of spiral density wave generation by the vortex, discussed in our
previous work, appear to maintain its efficiency also at nonlinear amplitudes
and we observe the formation of spiral shocks attached to the vortex. The
shocks may have important consequences on the long term vortex evolution and
possibly on the global disk dynamics. Our study strengthens the arguments in
favor of anticyclonic vortices as the candidates for the promotion of planetary
formation. Hydrodynamic shocks that are an intrinsic property of persistent
vortices in compressible Keplerian flows are an important contributor to the
overall balance. These shocks support vortices against viscous dissipation by
generating local potential vorticity and should be responsible for the eventual
fate of the persistent anticyclonic vortices. Numerical codes have be able to
resolve shock waves to describe the vortex dynamics correctly.


title:
Generalized Cauchy identities, trees and multidimensional Brownian
  motions. Part II: Combinatorial differential calculus

abstract:
  We present an analogue of the differential calculus in which the role of
polynomials is played by certain ordered sets and trees. Our combinatorial
calculus has all nice features of the usual calculus and has an advantage that
the elements of the considered ordered sets might carry some additional
information. In this way an analytic proof of generalized Cauchy identities
from the previous work of the second author can be directly reformulated in our
new language of the combinatorial calculus; furthermore the additional
information carried by vertices determines uniquely the bijections presented in
Part I of this series.


title: Differential Gerstenhaber algebras associated to nilpotent algebras

abstract:
  This article provides a complete description of the differential Gerstenhaber
algebras of all nilpotent complex structures on any real six-dimensional
nilpotent algebra. As an application, we classify all pseudo-K\"ahlerian
complex structures on six-dimensional nilpotent algebras such that the
differential Gerstenhaber algebra of its complex structure is quasi-isomorphic
to that of its symplectic structure. In a weak sense of mirror symmetry, it is
a classification of pseudo-K\"ahler structures on six-dimensional nilpotent
algebras whose mirror images are themselves.


title: The special cuts of 600-cell

abstract:
  A polytope is called {\em regular-faced} if every one of its facets is a
regular polytope. The 4-dimensional regular-faced polytopes were determined by
G. Blind and R. Blind \cite{BlBl2,roswitha,roswitha2}. The last class of such
polytopes is the one which consists of polytopes obtained by removing a set of
non-adjacent vertices (an independent set) of the 600-cell. These independent
sets are enumerated up to isomorphism and it is determined that the number of
polytopes in this last class is $314,248,344$.


title: PROMPT Observations of the Early-Time Optical Afterglow of GRB 060607A

abstract:
  PROMPT (Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes)
observed the early-time optical afterglow of GRB 060607A and obtained a densely
sampled multiwavelength light curve that begins only tens of seconds after the
GRB. Located at Cerro Tololo Inter-American Observatory in Chile, PROMPT is
designed to observe the afterglows of gamma-ray bursts using multiple automated
0.4-m telescopes that image simultaneously in many filters when the afterglow
is bright and may be highly variable. The data span the interval from 44
seconds after the GRB trigger to 3.3 hours in the Bgri filters. We observe an
initial peak in the light curve at approximately three minutes, followed by
rebrightenings peaking around 40 minutes and again at 66 minutes. Although our
data overlap with the early Swift gamma-ray and x-ray light curves, we do not
see a correlation between the optical and high-energy flares. We do not find
evidence for spectral evolution throughout the observations. We model the
variations in the light curves and find that the most likely cause of the
rebrightening episodes is a refreshment of the forward shock preceded by a
rapidly fading reverse shock component, although other explanations are
plausible.


title:
Modeling the chemical evolution of Omega Centauri using
  three-dimensional hydrodynamical simulations

abstract:
  We present a hydrodynamical and chemical model for the globular cluster Omega
Cen, under the assumption that it is the remnant of an ancient dwarf spheroidal
galaxy (dSph), the bulk of which was disrupted and accreted by our Galaxy ~10
Gyr ago. We highlight the very different roles played by Type II and Type Ia
supernovae (SNe) in the chemical enrichment of the inner regions of the
putative parent dSph. While the SNe II pollute the interstellar medium rather
uniformly, the SNe Ia ejecta may remain confined inside dense pockets of gas as
long as succesive SNe II explosions spread them out. Stars forming in such
pockets have lower alpha-to-iron ratios than the stars forming elsewhere. Owing
to the inhomogeneous pollution by SNe Ia, the metal distribution of the stars
in the central region differs substantially from that of the main population of
the dwarf galaxy, and resembles that observed in Omega Cen. This inhomogeneous
mixing is also responsible for a radial segregation of iron-rich stars with
depleted [alpha/Fe] ratios, as observed in some dSphs. Assuming a star
formation history of ~1.5 Gyr, our model succeeds in reproducing both the iron
and calcium distributions observed in Omega Cen and the main features observed
in the empirical alpha/Fe versus Fe/H plane. Finally, our model reproduces the
overall spread of the color-magnitude diagram, but fails in reproducing the
morphology of the SGB-a and the double morphology of the main sequence.
However, the inhomogeneous pollution reduces (but does not eliminate) the need
for a significantly enhanced helium abundance to explain the anomalous position
of the blue main sequence. Further models taking into account the dynamical
interaction of the parent dwarf galaxy with the Milky Way and the effect of AGB
pollution will be required.


title: Multi and Independent Block Approach in Public Cluster

abstract:
  We present extended multi block approach in the LIPI Public Cluster. The
multi block approach enables a cluster to be divided into several independent
blocks which run jobs owned by different users simultaneously. Previously, we
have maintained the blocks using single master node for all blocks due to
efficiency and resource limitations. Following recent advancements and
expansion of node\'s number, we have modified the multi block approach with
multiple master nodes, each of them is responsible for a single block. We argue
that this approach improves the overall performance significantly, for
especially data intensive computational works.


title:
Strings in SU(N) gauge theories in 2+1 dimensions: beyond the
  fundamental representation

abstract:
  We calculate energies and tensions of closed k-strings in (2+1)-dimensional
SU(N) gauge theories with N=4,5,6,8. When we study the dependence of the ground
state energy on the string length, we find that it is well described by a
Nambu-Goto (NG) free bosonic string for large lengths. At shorter lengths we
see deviations which we fit, and this allows us to control the systematic error
involved in extracting the tension. We compare the resulting string tensions
with Casimir scaling, which we find to be lower than our data by 1%-4%.
Extrapolating our results to N=oo we see that our data fits more naturally to
1/N rather than 1/N^2 corrections. Finally, we see that the full spectrum of
the k-string states falls into sectors that belong to particular irreducible
representations of SU(N).


title: The host of GRB 060206: kinematics of a distant galaxy

abstract:
  We present early (starting 1.6h after the burst) WHT/ISIS optical
spectroscopy of the afterglow of the gamma-ray burst GRB 060206 detecting a
range of metal absorption lines and their fine-structure transitions.
Additional information is provided by the afterglow lightcurve. The resolution
and wavelength range of the spectra and the bright afterglow facilitate a
detailed study and fitting of the absorption line systems in order to derive
column densities. We also use deep imaging to detect the host galaxy and probe
the nature of an intervening system at z = 1.48 seen in absorption in the
afterglow spectra. We detect four discrete velocity systems in the resonant
metal absorption lines, best explained by shells within and/or around the host
created by starburst winds. The fine-structure lines have no less than three
components with strengths decreasing from the redmost components. We therefore
suggest that the fine-structure lines are best explained to be produced by UV
pumping from which follows that the redmost component is the one closest to the
burst where also NV was detected. The host is detected in deep HST imaging with
F814W_AB = 27.48 +- 0.19 mag and a 3 sigma upper limit of H = 20.6 mag (Vega)
is achieved. A candidate counterpart for the intervening absorption system is
detected as well, which is quite exceptional for an absorber in the sightline
towards a GRB afterglow. The intervening system shows no temporal evolution as
claimed by Hao et al. (2007) which we prove from our WHT spectra taken before
and Subaru spectra taken during the observations from Hao et al.


title:
On Local Behavior of Holomorphic Functions Along Complex Submanifolds of
  C^N

abstract:
  In this paper we establish some general results on local behavior of
holomorphic functions along complex submanifolds of $\Co^{N}$. As a corollary,
we present multi-dimensional generalizations of an important result of Coman
and Poletsky on Bernstein type inequalities on transcendental curves in
$\Co^{2}$.


title:
Mediation of Long-Range Attraction Selectively between
  Negatively-Charged Colloids on Surfaces by Solvation

abstract:
  We propose a mean-field analytical model to account for the observed
asymmetry in the ability to form long-range attraction by the negatively
charged colloidal particles and not their equivalently charged positive
counterpart. We conjecture that this asymmetry is due to solvation effects, and
we phenomenologically capture its physics by considering the relative strength
of this water-induced short-range repulsion between the different charge
species. We then apply our model to the colloidal system of negatively charged
disks that are neutralized by a sea of counterions and strongly absorbed to an
interface in a compressible binary system. We demonstrate the resulting
coexistence between a dilute isotropic ionic phase and a condensed hexagonal
lattice phase as a function of density and interaction strength.


title: Diophantine subsets of function fields of curves

abstract:
  We consider diophantine subsets of function fields of curves and show,
roughly speaking, that they are either very small or very large. In particular,
this implies that the ring of polynomials $k[t]$ is a not a diophantine subset
of the field of rational functions $k(t)$ for many fields $k$.


title: Scattering on D3-branes

abstract:
  In a direct open string approach we analyze scattering of massless states on
a stack of D3-branes. First we construct vertex operators on the D-branes. The
4+6 splitting for the fermionic part is made possible by inserting
appropriately defined projection operators. With the vertex operators
constructed we compute various tree amplitudes. The results are then compared
with the corresponding field theory computations of the $\N=4$ SYM with
$\a'$-corrections: agreements are found. We comment on applications to AdS/CFT.


title: Asymptotic behavior of the rate of adaptation

abstract:
  We consider the accumulation of beneficial and deleterious mutations in large
asexual populations. The rate of adaptation is affected by the total mutation
rate, proportion of beneficial mutations and population size $N$. We show that
regardless of mutation rates, as long as the proportion of beneficial mutations
is strictly positive, the adaptation rate is at least
$\mathcal{O}(\log^{1-\delta}N)$ where $\delta$ can be any small positive
number, if the population size is sufficiently large. This shows that if the
genome is modeled as continuous, there is no limit to natural selection, that
is, the rate of adaptation grows in $N$ without bound.


title:
First-person visualizations of the special and general theory of
  relativity

abstract:
  Visualizations that adopt a first-person point of view allow observation and,
in the case of interactive simulations, experimentation with relativistic
scenes. This paper gives examples of three types of first-person
visualizations: watching objects that move at nearly the speed of light, being
a high-speed observer looking at a static environment and having a look-around
near a compact object. I illustrate and explain the main aspects of the visual
observations, outline their use in teaching relativity and report on teaching
experiences. For teaching purposes, our visualization work is available on the
web site http://www.spacetimetravel.org and its German counterpart
http://www.tempolimit-lichtgeschwindigkeit.de . This paper assumes some basic
knowledge about relativity on the part of the reader. It addresses instructors
of physics at the undergraduate and advanced secondary school level as well as
their students.


title: On the Range of Validity of the Dipole Picture

abstract:
  We derive correlated bounds on ratios of deep inelastic structure functions
from the dipole picture of photon-hadron scattering at high energies. In
particular we consider ratios of the longitudinal structure function, the total
structure function and the charm part of the latter. We also consider ratios of
total structure functions taken at the same energy but at three different
photon virtualities. It is shown that by confronting these bounds with
experimental data we can significantly constrain the range of validity of the
dipole picture.


title: Index theorems for quantum graphs

abstract:
  In geometric analysis, an index theorem relates the difference of the numbers
of solutions of two differential equations to the topological structure of the
manifold or bundle concerned, sometimes using the heat kernels of two
higher-order differential operators as an intermediary. In this paper, the case
of quantum graphs is addressed. A quantum graph is a graph considered as a
(singular) one-dimensional variety and equipped with a second-order
differential Hamiltonian H (a "Laplacian") with suitable conditions at
vertices. For the case of scale-invariant vertex conditions (i.e., conditions
that do not mix the values of functions and of their derivatives), the constant
term of the heat-kernel expansion is shown to be proportional to the trace of
the internal scattering matrix of the graph. This observation is placed into
the index-theory context by factoring the Laplacian into two first-order
operators, H =A*A, and relating the constant term to the index of A. An
independent consideration provides an index formula for any differential
operator on a finite quantum graph in terms of the vertex conditions. It is
found also that the algebraic multiplicity of 0 as a root of the secular
determinant of H is the sum of the nullities of A and A*.


title:
Enhanced Group Analysis and Exact Solutions of Variable Coefficient
  Semilinear Diffusion Equations with a Power Source

abstract:
  A new approach to group classification problems and more general
investigations on transformational properties of classes of differential
equations is proposed. It is based on mappings between classes of differential
equations, generated by families of point transformations. A class of variable
coefficient (1+1)-dimensional semilinear reaction-diffusion equations of the
general form $f(x)u_t=(g(x)u_x)_x+h(x)u^m$ ($m\ne0,1$) is studied from the
symmetry point of view in the framework of the approach proposed. The singular
subclass of the equations with $m=2$ is singled out. The group classifications
of the entire class, the singular subclass and their images are performed with
respect to both the corresponding (generalized extended) equivalence groups and
all point transformations. The set of admissible transformations of the imaged
class is exhaustively described in the general case $m\ne2$. The procedure of
classification of nonclassical symmetries, which involves mappings between
classes of differential equations, is discussed. Wide families of new exact
solutions are also constructed for equations from the classes under
consideration by the classical method of Lie reductions and by generation of
new solutions from known ones for other equations with point transformations of
different kinds (such as additional equivalence transformations and mappings
between classes of equations).


title: First Law, Counterterms and Kerr-AdS_5 Black Holes

abstract:
  We apply the counterterm subtraction technique to calculate the action and
other quantities for the Kerr--AdS black hole in five dimensions using two
boundary metrics; the Einstein universe and rotating Einstein universe with
arbitrary angular velocity. In both cases, the resulting thermodynamic
quantities satisfy the first law of thermodynamics. We point out that the
reason for the violation of the first law in previous calculations is that the
rotating Einstein universe, used as a boundary metric, was rotating with an
angular velocity that depends on the black hole rotation parameter. Using a new
coordinate system with a boundary metric that has an arbitrary angular
velocity, one can show that the resulting physical quantities satisfy the first
law.


title: Bulk viscosity of gauge theory plasma at strong coupling

abstract:
  We propose a lower bound on bulk viscosity of strongly coupled gauge theory
plasmas. Using explicit example of the N=2^* gauge theory plasma we show that
the bulk viscosity remains finite at a critical point with a divergent specific
heat. We present an estimate for the bulk viscosity of QGP plasma at RHIC.


title:
First-principles study of a single-molecule magnet Mn_{12} monolayer on
  the Au(111) surface

abstract:
  The electronic structure of a monolayer of single-molecule magnets Mn$_{12}$
on a Au(111) surface is studied using spin-polarized density-functional theory.
The Mn$_{12}$ molecules are oriented such that the magnetic easy axis is normal
to the surface, and the terminating ligands in the Mn$_{12}$ are replaced by
thiol groups (-SH) where the H atoms are lost upon adsorption onto the surface.
This sulfur-terminated Mn$_{12}$ molecule has a total magnetic moment of 18
$\mu_B$ in the ground state, in contrast to 20$\mu_B$ for the standard
Mn$_{12}$. The Mn$_{12}$ molecular orbitals broaden due to the interaction of
the molecule with the gold surface and the broadening is of the order of 0.1
eV. It is an order of magnitude less than the single-electron charging energy
of the molecule so the molecule is weakly bonded to the surface. Only electrons
with majority spin can be transferred from the surface to the sulfur-terminated
Mn$_{12}$ since the gold Fermi level is well above the majority lowest
unoccupied molecular orbital (LUMO) but below the minority LUMO. The amount of
the charge transfer is calculated to be 1.23 electrons, dominated by the tail
in the electronic distribution of the gold surface. A calculation of level
shift upon charging provides 0.28 electrons being transferred. The majority of
the charge transfer occurs at the S, C, and O atoms close to the surface. The
total magnetic moment also changes from 18 $\mu_B$ to 20 $\mu_B$, due to
rearrangements of the magnetic moments on the S and Mn atoms upon adsorption
onto the surface. The magnetic anisotropy barrier is computed including
spin-orbit interaction self-consistently in density-functional theory. The
barrier for the Mn$_{12}$ on the gold surface decreases by 6 K in comparison to
that for an isolated Mn$_{12}$ molecule.


title:
Quaternion-Octonion Analyticity for Abelian and Non-Abelian Gauge
  Theories of Dyons

abstract:
  Einstein- Schroedinger (ES) non-symmetric theory has been extended to
accommodate the Abelian and non-Abelian gauge theories of dyons in terms of the
quaternion-octonion metric realization. Corresponding covariant derivatives for
complex, quaternion and octonion spaces in internal gauge groups are shown to
describe the consistent field equations and generalized Dirac equation of
dyons. It is also shown that quaternion and octonion representations extend the
so-called unified theory of gravitation and electromagnetism to the Yang-Mill's
fields leading to two SU(2) gauge theories of internal spaces due to the
presence of electric and magnetic charges on dyons.


title:
Search for pulsed multi-TeV gamma rays from the Crab pulsar using the
  Tibet-III air shower array

abstract:
  We searched for pulsed gamma-ray emissions from the Crab pulsar using data of
the Tibet-III air shower array from November 1999 through November 2005. No
evidence for the pulsed emissions was found in our analysis. Upper limits at
different energies were calculated for a $3 \sigma$ confidence level in the
energy range of multi-TeV to several hundred TeV.


title: A Neural Networks Model of the Venezuelan Economy

abstract:
  Besides an indicator of the GDP, the Central Bank of Venezuela generates the
so called Monthly Economic Activity General Indicator. The a priori knowledge
of this indicator, which represents and sometimes even anticipates the
economy's fluctuations, could be helpful in developing public policies and in
investment decision making. The purpose of this study is forecasting the IGAEM
through non parametric methods, an approach that has proven effective in a wide
variety of problems in economics and finance.


title:
A Non Parametric Study of the Volatility of the Economy as a Country
  Risk Predictor

abstract:
  This paper intends to explain Venezuela's country spread behavior through the
Neural Networks analysis of a monthly economic activity general index of
economic indicators constructed by the Central Bank of Venezuela, a measure of
the shocks affecting country risk of emerging markets and the U.S. short term
interest rate. The use of non parametric methods allowed the finding of non
linear relationship between these inputs and the country risk. The networks
performance was evaluated using the method of excess predictability.


title:
An Early Warning System for Bankruptcy Prediction: lessons from the
  Venezuelan Bank Crisis

abstract:
  During 1993-94 Venezuela experienced a severe banking crisis which ended up
with 18 commercial banks intervened by the government. Here we develop an early
warning system for detecting credit related bankruptcy through discriminant
functions developed on financial and macroeconomic data predating the crisis. A
robustness test performed on these functions shows high precision in error
estimation. The model calibrated on pre-crisis data could detect abnormal
financial tension in the late Banco Capital many months before it was
intervened and liquidated.


title: Photoionization of Clustered Halos by the First Stars

abstract:
  We present numerical simulations of the photoevaporation of cosmological
halos clustered around a 120 M$_\odot$ primordial star, confining our study to
structures capable of hosting Population III star formation. The calculations
include self-consistent multifrequency conservative transfer of UV photons
together with nine-species primordial chemistry and all relevant radiative
processes. The ultimate fates of these halos varies with central density and
proximity to the central source but generally fall into one of four categories.
Diffuse halos with central densities below 2 - 3 cm$^{-3}$ are completely
ionized and evaporated by the central star anywhere in the cluster. More
evolved halo cores at densities above 2000 cm$^{-3}$ are impervious to both
ionizing and Lyman-Werner flux at most distances from the star and collapse of
their cores proceeds without delay. Radiative feedback in halos of intermediate
density can be either positive or negative, depending on how the I-front
remnant shock both compresses and deforms the core and enriches it with H$_2$.
We find that the 120 M$_\odot$ star photodissociates H$_2$ in most halos within
the cluster but that catalysis by H- rapidly restores molecular hydrogen within
a few hundred Kyr after the death of the star, with little delay in star
formation. Our models exhibit significant departures from previous
one-dimensional spherically-symmetric simulations, which are prone to serious
errors due to unphysical geometric focusing effects.


title: Analytical modelling of terminal properties in industrial growth

abstract:
  In this pedagogical study, carried out by adopting standard mathematical
methods of nonlinear dynamics, we have presented some simple analytical models
to understand terminal behaviour in industrial growth. This issue has also been
addressed from a dynamical systems perspective, with especial emphasis on the
concept of the Balanced Scorecard. Our study enables us to make the general
claim that although the fortunes of an industrial organization can rise with
exponential rapidity on relatively short time scales, its growth will
ultimately and inevitably be saturated on long time scales by various factors
which are nonlinear in character. We have mathematically demonstrated the
likely occurrence of this feature under various possible circumstances,
including the Red Ocean and the Blue Ocean. Finally and most importantly, our
arguments and their associated mathematical modelling have received remarkable
support from the growth pattern indicated by empirical data gathered from a
well-recognized global company like IBM.


title: Weak ferromagnetism and spin glass state with nano-sized nickel carbide

abstract:
  Ni3C nanoparticles of about 40 nm have been studied experimentally to exhibit
weak ferromagnetic (FM), spin-glass (SG) and paramagnetic (PM) properties. The
freezing temperature of the SG phase at zero applied field is determined as,
TF0 ~ 11.0 K. At T > TF0, a very weak ferromagnetism has been observed over a
PM background. The Curie temperature, TC, is shown to exceed 300 K and the
ferromagnetism at 300 K is determined as about 0.02 emu/g (~6.7*10^{-4}mu_B per
Ni3C formula unit) by subtracting the background paramagnetism. An anomalous
dip appears in the temperature dependent coercivity, HC(T), near the freezing
temperature, TF0. It reflects a distortedly reduced coercivity in the M(H)
hysteresis loop measured at T = TF0 with the applied sweeping field around H =
0. This is attributable to the exchange coupling effect between the SG and the
weak FM phases. The possible origin of the magnetic moments that account for
the observed FM, SG and PM properties is discussed.


title:
Electronic structure of self-assembled InAs/InP quantum dots: A
  Comparison with self-assembled InAs/GaAs quantum dots

abstract:
  We investigate the electronic structure of the InAs/InP quantum dots using an
atomistic pseudopotential method and compare them to those of the InAs/GaAs
QDs. We show that even though the InAs/InP and InAs/GaAs dots have the same dot
material, their electronic structure differ significantly in certain aspects,
especially for holes: (i) The hole levels have a much larger energy spacing in
the InAs/InP dots than in the InAs/GaAs dots of corresponding size. (ii)
Furthermore, in contrast with the InAs/GaAs dots, where the sizeable hole $p$,
$d$ intra-shell level splitting smashes the energy level shell structure, the
InAs/InP QDs have a well defined energy level shell structure with small $p$,
$d$ level splitting, for holes. (iii) The fundamental exciton energies of the
InAs/InP dots are calculated to be around 0.8 eV ($\sim$ 1.55 $\mu$m), about
200 meV lower than those of typical InAs/GaAs QDs, mainly due to the smaller
lattice mismatch in the InAs/InP dots. (iii) The widths of the exciton $P$
shell and $D$ shell are much narrower in the InAs/InP dots than in the
InAs/GaAs dots. (iv) The InAs/GaAs and InAs/InP dots have a reversed light
polarization anisotropy along the [100] and [1$\bar{1}$0] directions.


title:
Effects of mode degeneracy in the LIGO Livingston Observatory recycling
  cavity

abstract:
  We analyze the electromagnetic fields in a Pound-Drever-Hall locked,
marginally unstable, Fabry-Perot cavity as a function of small changes in the
cavity length during resonance. More specifically, we compare the results of a
detailed numerical model with the behavior of the recycling cavity of the Laser
Interferometer Gravitational-wave Observatory (LIGO) detector that is located
in Livingston, Louisiana. In the interferometer's normal mode of operation, the
recycling cavity is stabilized by inducing a thermal lens in the cavity mirrors
with an external CO2 laser. During the study described here, this thermal
compensation system was not operating, causing the cavity to be marginally
optically unstable and cavity modes to become degenerate. In contrast to stable
optical cavities, the modal content of the resonating beam in the uncompensated
recycling cavity is significantly altered by very small cavity length changes.
This modifies the error signals used to control the cavity length in such a way
that the zero crossing point is no longer the point of maximum power in the
cavity nor is it the point where the input beam mode in the cavity is
maximized.


title: Structure of the Roper Resonance with Diquark Correlations

abstract:
  We study electromagnetic properties of the nucleon and Roper resonance in a
chiral quark-diquark model including two kinds of diquarks needed to describe
the nucleon: scalar and axial-vector diquarks. The nucleon and Roper resonance
are described as superpositions of two quark-diquark bound states of a quark
and a scalar diquark and of a quark and an axial-vector diquark.
Electromagnetic form factors of the nucleon and Roper resonance are obtained
from one-loop diagrams where the quark and diquarks are coupled by a photon. We
include the effects of intrinsic properties of the diquarks: the intrinsic form
factors both of the diquarks and the anomalous magnetic moment of the
axial-vector diquark. The electric form factors of the proton and neutron
reasonably agree with the experiments due to the inclusions of the diquark
sizes, while the magnetic moments become smaller than the experimental values
because of the scalar dominance in the nucleon. The charge radii of the Roper
resonance are almost comparable with those of the nucleon.


title:
Empirical distributions of Chinese stock returns at different
  microscopic timescales

abstract:
  We study the distributions of event-time returns and clock-time returns at
different microscopic timescales using ultra-high-frequency data extracted from
the limit-order books of 23 stocks traded in the Chinese stock market in 2003.
We find that the returns at the one-trade timescale obey the inverse cubic law.
For larger timescales (2-32 trades and 1-5 minutes), the returns follow the
Student distribution with power-law tails. With the decrease of timescale, the
tail becomes fatter, which is consistent with the vibrational theory.


title: Geodesic plasma flows instabilities of Riemann twisted solar loops

abstract:
  Riemann and sectional curvatures of magnetic twisted flux tubes in Riemannian
manifold are computed to investigate the stability of the plasma astrophysical
tubes. The geodesic equations are used to show that in the case of thick
magnetic tubes, the curvature of planar (Frenet torsion-free) tubes have the
effect ct of damping the flow speed along the tube. Stability of geodesic flows
in the Riemannian twisted thin tubes (almost filaments), against constant
radial perturbations is investigated by using the method of negative sectional
curvature for unstable flows. No special form of the flow like Beltrami flows
is admitted, and the proof is general for the case of thin magnetic flux tubes.
In the magnetic equilibrium state, the twist of the tube is shown to display
also a damping effect on the toroidal velocity of the plasma flow. It is found
that for positive perturbations and angular speed of the flow, instability is
achieved, since the sectional Ricci curvature of the magnetic twisted tube
metric is negative. Solar flare production may appear from these geometrical
instabilities of the twisted solar loops.


title: Nonlinear control of chaotic walking of atoms in an optical lattice

abstract:
  Centre-of-mass atomic motion in an optical lattice near the resonance is
shown to be a chaotic walking due to the interplay between coherent internal
atomic dynamics and spontaneous emission. Statistical properties of chaotic
atomic motion can be controlled by the single parameter, the detuning between
the atomic transition frequency and the laser frequency. We derive a
Fokker-Planck equation in the energetic space to describe the atomic transport
near the resonance and demonstrate numerically how to manipulate the atomic
motion varying the detuning.


title:
Optical sum rule anomalies in the cuprates: interplay between strong
  correlation and electronic bandstructures

abstract:
  We theoretically analyze some of the anomalies of the optical sumrules in the
high-temperature superconductors. In particular we address the particularly
strong dependence on temperature of the sumrule in the normal state. Both
electron-electron correlations and the presence of a Van-Hove singularity have
been shown to enhance such a dependence. Here we consider both effects
simultaneously by means of Dynamical Mean-Field Theory for a two dimensional
Hubbard model with realistic parameters for different cuprates, and we find
that the two effects are not cooperative, as they appear to compete one another
in the region of parameters relevant for the experiments.


title: Mean Field Theory for Pedestrian Outflow through an Exit

abstract:
  An average pedestrian flow through an exit is one of the most important index
in evaluating pedestrian dynamics. In order to study the flow in detail, the
floor field model, which is a crowd model by using cellular automaton, is
extended by taking into account a realistic behavior of pedestrians around the
exit. The model is studied by both numerical simulations and cluster analysis
to obtain a theoretical expression of an average pedestrian flow through the
exit. It is found quantitatively that the effect of exit door width, a wall,
and pedestrian's mood of competition or cooperation significantly influence the
average flow. The results show that there is suitable width of the exit and
position according to pedestrian's mood.


title: The Church Synthesis Problem with Parameters

abstract:
  For a two-variable formula ψ(X,Y) of Monadic Logic of Order (MLO) the
Church Synthesis Problem concerns the existence and construction of an operator
Y=F(X) such that ψ(X,F(X)) is universally valid over Nat.
  B\"{u}chi and Landweber proved that the Church synthesis problem is
decidable; moreover, they showed that if there is an operator F that solves the
Church Synthesis Problem, then it can also be solved by an operator defined by
a finite state automaton or equivalently by an MLO formula. We investigate a
parameterized version of the Church synthesis problem. In this version ψ
might contain as a parameter a unary predicate P. We show that the Church
synthesis problem for P is computable if and only if the monadic theory of
<Nat,<,P> is decidable. We prove that the B\"{u}chi-Landweber theorem can be
extended only to ultimately periodic parameters. However, the MLO-definability
part of the B\"{u}chi-Landweber theorem holds for the parameterized version of
the Church synthesis problem.


title: Feedback from Multiple Supernova Explosions inside a Wind-Blown Bubble

abstract:
  We study the evolution of multiple supernova (SN) explosions inside a
pre-exiting cavity blown by winds from massive progenitor stars. Hydrodynamic
simulations in one-dimensional spherical geometry, including radiative cooling
and thermal conduction, are carried out to follow first the development of the
wind-blown bubble during the main sequence and then the evolution of the
SN-driven bubble. We find the size and mass of the SN-driven bubble shell
depend on the structure of the pre-existing wind bubble as well as the SN
explosion energy E_{SN} (= N_{SN} 10^{51} ergs). The hot cavity inside the
bubble is 2-3 times bigger in volume and hotter than that of a bubble created
by SNe exploded in a uniform interstellar medium (ISM). For an association with
10 massive stars in the average ISM, the SN-driven shell has an outer radius of
R_{ss} ~ (85 pc) N_{SN}^{0.1} and a mass of M_{ss} ~ (10^{4.8} Msun)
N_{SN}^{0.3}at 10^6 years after the explosion. By that time most of the
explosion energy is lost via radiative cooling, while ~10% remains as kinetic
energy and ~10% as thermal energy. We also calculate the total integrated
spectrum of diffuse radiation emitted by the shock-heated gas of the SN bubble.
For the models with 0.1 solar metalicity, the radiative energy loss is smaller
and the fraction of non-ionizing photons is larger, compared to those with
solar metalicity. We conclude the photoionization/heating by diffuse radiation
is the most dominant form of feedback from SN explosions into the surrounding
medium.


title:
Possible nodeless superconductivity in the noncentrosymmetric
  superconductor Mg_(12-delta)Ir_19B_16

abstract:
  We measured the resistivity, diamagnetization, and low-temperature specific
heat of the newly discovered noncentrosymmetric superconductor
Mg_(12-delta)Ir_19B_16. The temperature dependence of specific heat is
consistent with the model of an isotropic s-wave gap with value Delta_0 = 0.94
meV for the sample Tc = 5.7 K, and the ratio Delta_0/k_BTc = 1.91 indicates a
slightly moderate coupling for the superconductivity. The correlations among
the normal state Sommerfeld constant gamma_n, the slope -dHc2(T)/dT near Tc,
and the condensation energy Ec are all consistent with the slightly moderate
coupling picture. Based on the data of phonon contribution, Tc and the McMillan
formula, we obtained an electron-phonon coupling strength lambda_(e-ph) = 0.66,
which suggests that the superconductivity here is induced by the
electron-phonon coupling.


title: On the Theory of Surfaces in the Four-dimensional Euclidean Space

abstract:
  For a two-dimensional surface in the four-dimensional Euclidean space we
introduce an invariant linear map of Weingarten type in the tangent space of
the surface, which generates two invariants k and kappa.
  The condition k = kappa = 0 characterizes the surfaces consisting of flat
points. The minimal surfaces are characterized by the equality kappa^2=k. The
class of the surfaces with flat normal connection is characterized by the
condition kappa = 0. For the surfaces of general type we obtain a geometrically
determined orthonormal frame field at each point and derive Frenet-type
derivative formulas.
  We apply our theory to the class of the rotational surfaces, which prove to
be surfaces with flat normal connection, and describe the rotational surfaces
with constant invariants.


title: Formation of Multipartite Entanglement Using Random Quantum Gates

abstract:
  The formation of multipartite quantum entanglement by repeated operation of
one and two qubit gates is examined. The resulting entanglement is evaluated
using two measures: the average bipartite entanglement and the Groverian
measure. A comparison is made between two geometries of the quantum register: a
one dimensional chain in which two-qubit gates apply only locally between
nearest neighbors and a non-local geometry in which such gates may apply
between any pair of qubits. More specifically, we use a combination of random
single qubit rotations and a fixed two-qubit gate such as the controlled-phase
gate. It is found that in the non-local geometry the entanglement is generated
at a higher rate. In both geometries, the Groverian measure converges to its
asymptotic value more slowly than the average bipartite entanglement. These
results are expected to have implications on different proposed geometries of
future quantum computers with local and non-local interactions between the
qubits.


title: Designing a Spin Channel for Perfect Quantum Communication

abstract:
  We propose a scheme for using a spin chain with fixed symmetry interaction as
a channel for perfect quantum communication. The perfect quantum communication
is determined by the eigenvalues that form a special arithmetical progression,
the concrete interaction parameter $J_i$ is obtained as a function of integer
and perfect transmission time $t_p$. There are infinite choices of $J_i$ for
perfect transmission and one can design the channel according to the
requirement of $t_p$. This scheme will provide more choices of spin chain for
future experiment in quantum communication.


title: An Ideal Channel of Long Distance Entanglement in Spin Systems

abstract:
  We propose a scheme for using spin chain to realize an ideal channel of long
distance entanglement. The results show that there has different entanglement
in different Hilbert subspace, the anisotropic parameter $\Delta$ will
frustrate the entanglement and the magnetic field affect the entanglement
through changing the ground state, the boundary entanglement $C_{1N}$ has the
simplest expression in the simplest subspace and it only depend on the first
item of the ground state, that item can be increased when a local magnetic
field is introduced. Our propose can be handled easily because it only needs a
uniform XX open chain initialized in the simplest Hilbert subspace and a bulk
magnetic field that absent for the boundary qubits.


title: (p,q)-string in matrix-regularized membrane and type IIB duality

abstract:
  We consider a lightcone wrapped supermembrane compactified on 2-torus in the
matrix regularization. We examine the double dimensional reduction technique
and deduce the free matrix string of (p,q)-string in type IIB superstring
theory explicitly from the matrix-regularized wrapped supermembrane. In
addition we obtain the (2+1)-dimensional super Yang-Mills action in curved
background. We also examine the duality.


title:
Unparticle decay of neutrinos and it's effect on ultra high energy
  neutrinos

abstract:
  The unparticle is proposed by Georgi as a conceptual new physics beyond the
standard model to describe the low energy sector of a nontrivial scale
invariant sector of an effective theory. We consider the neutrino decay in
unparticle scenario and investigate the effect of such decay for the case of
ultra high energy neutrinos from GRB. The effect on the detection yield of
these neutrinos are also probed for a kilometer scale ice-Cerenkov detector.


title: On topological spaces possessing uniformly distributed sequences

abstract:
  Two classes of topological spaces are introduced on which every probability
Radon measure possesses a uniformly distributed sequence or a uniformly tight
uniformly distributed sequence. It is shown that these classes are stable under
multiplication by completely regular Souslin spaces


title: Threadbare Parallel Port DAQ Card

abstract:
  A very simple Data acquisition card was developed in our under-graduate class
for interfacing with the parallel port of a standard computer. It was developed
with the intention to enable students to do various physics experiments with
the computer sparing them from knowing the details of the electronics required.
The article is a summary of our experience and ends with a request for
suggestions to improve the circuit without losing its simplicity.


title:
Magnetometry Based on Nonlinear Magneto-Optical Rotation with
  Amplitude-Modulated Light

abstract:
  We report on an all-optical magnetometric technique based on nonlinear
magneto-optical rotation with amplitude-modulated light. The method enables
sensitive magnetic-field measurements in a broad dynamic range. We demonstrate
the sensitivity of $4.3\times10^{-9}$ G/$\sqrt{\text{Hz}}$ at 10 mG and the
magnetic field tracking in a range of 40 mG. The fundamental limits of the
method sensitivity and factors determining current performance of the
magnetometer are discussed.


title: Extrema of low eigenvalues of the Dirichlet-Neumann Laplacian on a disk

abstract:
  We study extrema of the first and the second mixed eigenvalues of the
Laplacian on the disk among some families of Dirichlet-Neumann boundary
conditions. We show that the minimizer of the second eigenvalue among all mixed
boundary conditions lies in a compact 1-parameter family for which an explicit
description is given. Moreover, we prove that among all partitions of the
boundary with bounded number of parts on which Dirichlet and Neumann conditions
are imposed alternately, the first eigenvalue is maximized by the uniformly
distributed partition.


title:
Two-Dimensional Spectroscopy of Photospheric Shear Flows in a Small
  delta Spot

abstract:
  In recent high-resolution observations of complex active regions,
long-lasting and well-defined regions of strong flows were identified in major
flares and associated with bright kernels of visible, near-infrared, and X-ray
radiation. These flows, which occurred in the proximity of the magnetic neutral
line, significantly contributed to the generation of magnetic shear. Signatures
of these shear flows are strongly curved penumbral filaments, which are almost
tangential to sunspot umbrae rather than exhibiting the typical radial
filamentary structure. Solar active region NOAA 10756 was a moderately complex,
beta-delta sunspot group, which provided an opportunity to extend previous
studies of such shear flows to quieter settings. We conclude that shear flows
are a common phenomenon in complex active regions and delta spots. However,
they are not necessarily a prerequisite condition for flaring. Indeed, in the
present observations, the photospheric shear flows along the magnetic neutral
line are not related to any change of the local magnetic shear. We present
high-resolution observations of NOAA 10756 obtained with the 65-cm vacuum
reflector at Big Bear Solar Observatory (BBSO). Time series of
speckle-reconstructed white-light images and two-dimensional spectroscopic data
were combined to study the temporal evolution of the three-dimensional vector
flow field in the beta-delta sunspot group. An hour-long data set of consistent
high quality was obtained, which had a cadence of better than 30 seconds and
sub-arcsecond spatial resolution.


title: Equation of State of Wet Granular Matter

abstract:
  A theory is derived for the nonequilibrium probability currents of the
capillary interaction which determines the pair correlation function near
contact. This yields an analytic expression for the equation of state, P =
P(N/V,T), of wet granular matter for D=2 dimensions, valid in the complete
density range from gas to jamming. Driven wet granular matter exhibits a
van-der-Waals-like unstable branch at granular temperatures T<T_c corresponding
to a first order segregation transition of clusters. For the realistic rupture
length of the liquid bridge, s_crit=0.07 d, the critical point is located at
T_c = 0.274 E_cb. While the critical temperature weakly depends on the rupture
length, the critical density phi_c is shown to scale with s_crit according to
s_crit = 4d (sqrt(phi_J / phi_c) -1). The segregation transition is closely
related to the precipitation of granular droplets reported for the free cooling
of one-dimensional wet granular matter [Phys. Rev. Lett. 97, 078001 (2006)],
and extends the effect to higher dimensional systems. Since the limiting case
of sticky bonds, E_cb >> T, is of relevance for aggregation in general,
simulations have been performed which show very good agreement with the
theoretically predicted coordination K of capillary bonds as a function of the
bond length s_crit. This result implies that particles that stick at the
surface, s_crit=0, form isostatic clusters.


title: The Variability of Polarized Radiation from Sgr A*

abstract:
  Sgr A* is variable at radio and submillimeter wavelengths on hourly time
scales showing time delays between the peaks of flare emission as well as
linearly polarized emission at millimeter and sub-mm wavelengths. To determine
the polarization characteristics of this variable source at radio frequencies,
we present VLA observations of Sgr A* and report the detection of polarized
emission at a level of 0.77\pm0.01% and 0.2\pm0.01% at 43 and 22 GHz,
respectively. The change in the time averaged polarization angle between 22 and
43 GHz corresponds to a RM of -2.5\pm0.6 x10^3 rad m{-2} with no phase wrapping
(or \sim 5x10^4 rad m^2 with 2\pi phase wrap). We also note a rise and fall
time scale of 1.5 -- 2 hours in the total polarized intensity. The light curves
of the degree of linearly polarized emission suggests a a correlation with the
variability of the total intensity at 43 GHz. The available polarization data
at radio and sub-mm wavelengths suggest that the rotation measure decreases
with decreasing frequency. This frequency dependence, and observed changes in
polarization angle during flare events, may be caused by the reduction in
rotation measure associated with the expansion of synchrotron-emitting blobs.


title:
Best network chirplet-chain: Near-optimal coherent detection of
  unmodeled gravitation wave chirps with a network of detectors

abstract:
  The searches of impulsive gravitational waves (GW) in the data of the
ground-based interferometers focus essentially on two types of waveforms: short
unmodeled bursts and chirps from inspiralling compact binaries. There is room
for other types of searches based on different models. Our objective is to fill
this gap. More specifically, we are interested in GW chirps with an arbitrary
phase/frequency vs. time evolution. These unmodeled GW chirps may be considered
as the generic signature of orbiting/spinning sources. We expect quasi-periodic
nature of the waveform to be preserved independent of the physics which governs
the source motion. Several methods have been introduced to address the
detection of unmodeled chirps using the data of a single detector. Those
include the best chirplet chain (BCC) algorithm introduced by the authors. In
the next years, several detectors will be in operation. The joint coherent
analysis of GW by multiple detectors can improve the sight horizon, the
estimation of the source location and the wave polarization angles. Here, we
extend the BCC search to the multiple detector case. The method amounts to
searching for salient paths in the combined time-frequency representation of
two synthetic streams. The latter are time-series which combine the data from
each detector linearly in such a way that all the GW signatures received are
added constructively. We give a proof of principle for the full sky blind
search in a simplified situation which shows that the joint estimation of the
source sky location and chirp frequency is possible.


title:
Fidelity Between Partial States as Signature of Quantum Phase
  Transitions

abstract:
  We introduce a partial state fidelity approach to quantum phase transitions.
We consider a superconducting lattice with a magnetic impurity inserted at its
centre, and look at the fidelity between partial (either one-site or two-site)
quantum states. In the vicinity of the point of the quantum phase transition,
we observe a sudden drop of the fidelity between two one-site partial states
corresponding to the impurity location and its close vicinity. In the case of
two-site states, the fidelity reveals the transition point as long as one of
the two electron sites is located at the impurity, while the other lies
elsewhere in the lattice. We also determine the Uhlmann mixed state geometric
phase, recently introduced in the study of the structural change of the system
state eigenvectors in the vicinity of the lines of thermal phase transitions,
and find it to be trivial, both for one- and two-site partial states, except
when an electron site is at the impurity. This means that the system partial
state eigenvectors do not contribute significantly to the enhanced state
distinguishability around the point of this quantum phase transition. Finally,
we use the fidelity to analyze the total amount of correlations contained
within a composite system, showing that, even for the smallest two-site states,
it features an abrupt quantitative change in the vicinity of the point of the
quantum phase transition.


title:
Study of the young stellar population of NGC 4214 using the Hubble Space
  Telescope

abstract:
  We present an original study of the dwarf starburst galaxy NGC 4214. We use
archival optical and UV images obtained with WFPC2 and STIS on-board the Hubble
Space Telescope. We explain the process followed to obtain high-quality
photometry and astrometry of the stellar and cluster populations of this
galaxy. We describe the procedure used to transform magnitudes and colours into
physical parameters using spectral energy distributions. We analyze several
aspects of the astrophysics of NGC 4214: we briefly describe the stellar
populations in its inner structure with emphasis in the determination of the
ratio of blue-to-red supergiants. We study the stellar extinction and we find
it consistent with previous studies of the nebular extinction. The extinction
associated to the stellar population is found to be rather low (E(B-V) < 0.1
mag). We make a complete research of the initial mass function (IMF) of the
stars with masses between 20 and 100 Mo using a photometric method. We find
that this dwarf galaxy has a steeper IMF than Salpeter. We analyze several
extended structures distributed throughout the central regions of NGC 4214. We
infer their properties, such as age, mass, and extinction. Some of the clusters
that we study are likely to disappear because of "infant mortality". We discuss
the interaction between massive stars and their environment. We argue that star
formation in NGC 4214 could take place in several stages.


title: Threshold effect and \pi^\pm \psi(2S) peak

abstract:
  A resonance-like structure in the $\pi^\pm \psi(2S)$ mass spectrum arising in
$B \to K \pi^\pm \psi(2S)$ has recently been reported. It is noted that the
mass of this structure, $4433 \pm 4 \pm 1$ MeV, is not far from the threshold
for production of $D^* \bar{D}_1(2420)$. A proposed mechanism for production of
this state is suggested, and tests are suggested.


title:
A Mechanism for Kaluza-Klein Number Violation in UED and Implications
  for LHC

abstract:
  If the Higgs does not propagate into an otherwise universal extra dimension,
then tree-level Kaluza-Klein number is not conserved in the Yukawa
interactions. This leads to mixing between zero-mode fermions and their
associated Kaluza-Klein excitations. The effect can be quite large for the top
quark, since its mass (171.4 plus or minus 2.1 GeV) is approximately one-half
the current Tevatron mass bound (about 350-400 GeV) for Kaluza-Klein
excitations of quarks with one universal extra dimension. In contrast to the
SM, the bi-unitary transformation that diagonalizes the mass matrix does not
diagonalize the effective 4D Yukawa coupling matrix because of the presence of
the 5D kinetic terms. This leads to violation of tree-level Kaluza-Klein number
conservation in the gauge sector due to a unique feature of the 5D theory. This
allows Kaluza-Klein excitations of the fermions to be produced singly, and
opens up new decay channels in the gauge sector. We compute the cross section
for the production of the lowest-lying Kaluza-Klein excitations of the top and
bottom quarks in the non-universal Higgs model at the Large Hadron Collider,
and consider their subsequent decays. The effect is quite large: For example,
pair production of Kaluza-Klein excitations of the bottom quark will lead to a
pair of top quarks plus a pair of charged weak gauge bosons. Since the
production is via the strong interaction, such final states stand out well
against the Standard Model background, and are observable at the LHC for a wide
range of compactification scales. Finally, we discuss the effects that such a
model has on the T- parameter, and propose a model with maximal mixing where
the compactification scale may be as large as a universal extra dimension.


title: Voltage Controlled Resistance

abstract:
  The paper discusses an application of the field effected transistor (FET) as
a voltage controlled resistance which can be done in under-graduate labs either
as a routine experiment or as a project.


title: Comparison of Tree-Child Phylogenetic Networks

abstract:
  Phylogenetic networks are a generalization of phylogenetic trees that allow
for the representation of non-treelike evolutionary events, like recombination,
hybridization, or lateral gene transfer. In this paper, we present and study a
new class of phylogenetic networks, called tree-child phylogenetic networks,
where every non-extant species has some descendant through mutation. We provide
an injective representation of these networks as multisets of vectors of
natural numbers, their path multiplicity vectors, and we use this
representation to define a distance on this class and to give an alignment
method for pairs of these networks. To the best of our knowledge, they are
respectively the first true distance and the first alignment method defined on
a meaningful class of phylogenetic networks strictly extending the class of
phylogenetic trees. Simple, polynomial algorithms for reconstructing a
tree-child phylogenetic network from its path multiplicity vectors, for
computing the distance between two tree-child phylogenetic networks, and for
aligning a pair of tree-child phylogenetic networks, are provided, and they
have been implemented as a Perl package and a Java applet, and they are
available at http://bioinfo.uib.es/~recerca/phylonetworks/mudistance


title:
Monte Carlo simulation of the nuclear medium: Fermi gases, nuclei and
  the role of Pauli potentials

abstract:
  The role of Pauli potentials in the semiclassical simulation of Fermi gases
at low temperatures is investigated. An alternative Pauli potential to the
usual bivariate Gaussian form by Dorso et al. is proposed. This new Pauli
potential allows for a simultaneous good reproduction of not only the kinetic
energy per particle but also the momentum distribution and the two-body
correlation function. The reproduction of the binding energies in finite nuclei
in the low and medium mass range is also analyzed. What is found is that given
a reasonable short-range atractive nuclear interaction one can include
correlation effects in a suitable chosen density dependent Pauli potential.


title: The Meaning Of The Fine Structure Constant

abstract:
  A possible explanation is offered for the longstanding mystery surrounding
the meaning of the fine structure constant. The reasoning is based on a
discrete self-similar cosmological paradigm that has shown promise in
explaining the general scaling properties of nature's global hierarchy. The
discrete scale invariance of the paradigm implies that "strong gravity" governs
gravitational interactions within atomic scale systems. Given the revised
gravitational coupling constant and Planck mass, one can demonstrate that the
fine structure constant is the ratio of the strengths of the unit
electromagnetic interaction and the unit gravitational interaction within
atomic scale systems. [Abridged]


title: Child mortality in Penna ageing model

abstract:
  Assuming the deleterious mutations in the Penna ageing model to affect mainly
the young ages, we get an enhanced mortality at very young age, followed by a
minimum of the mortality, and then the usual exponential increase of mortality
with age.


title: On the theorem of M.Golomb

abstract:
  Let $X_{1},...,X_{n}$ be compact spaces and $X=X_{1}\times ... \times X_{n}.$
Consider the approximation of a function $f\in C(X)$ by sums $g_{1}(x_{1})+...
g_{n}(x_{n}),$ where $g_{i}\in C(X_{i}),$ $i=1,...,n.$ In [8], M.Golomb
obtained a formula for the error of this approximation in terms of measures
constructed on special points of $X$, called "projection cycles". However, his
proof had a gap, which was pointed out by Marshall and O'Farrell [15]. But the
question if the formula was correct, remained open. The purpose of the paper is
to prove that Golomb's formula holds in a stronger form.


title:
Anisotropic conductivity of disordered 2DEGs due to spin-orbit
  interactions

abstract:
  We show that the conductivity tensor of a disordered two-dimensional electron
gas becomes anisotropic in the presence of both Rashba and Dresselhaus
spin-orbit interactions (SOI). This anisotropy is a mesoscopic effect and
vanishes with vanishing charge dephasing time. Using a diagrammatic approach
including zero, one, and two-loop diagrams, we show that a consistent
calculation needs to go beyond a Boltzmann equation approach. In the absence of
charge dephasing and for zero frequency, a finite anisotropy \sigma_{xy}
e^2/lhpf arises even for infinitesimal SOI.


title:
Gaze as a Supplementary Modality for Interacting with Ambient
  Intelligence Environments

abstract:
  We present our current research on the implementation of gaze as an efficient
and usable pointing modality supplementary to speech, for interacting with
augmented objects in our daily environment or large displays, especially
immersive virtual reality environments, such as reality centres and caves. We
are also addressing issues relating to the use of gaze as the main interaction
input modality. We have designed and developed two operational user interfaces:
one for providing motor-disabled users with easy gaze-based access to map
applications and graphical software; the other for iteratively testing and
improving the usability of gaze-contingent displays.


title:
Stability Analysis of Continuous Waves in Nonlocal Random Nonlinear
  Media

abstract:
  On the basis of the competing cubic-quintic nonlinearity model, stability
(instability) of continuous waves in nonlocal random non-Kerr nonlinear media
is studied analytically and numerically. Fluctuating media parameters are
modeled by the Gaussian white noise. It is shown that for different response
functions of a medium nonlocality suppresses, as a rule, both the growth rate
peak and bandwidth of instability caused by random parameters. At the same
time, for a special form of the response functions there can be an
''anomalous'' subjection of nonlocality to the instability development which
leads to further increase of the growth rate. Along with the second-order
moments of the modulational amplitude, higher-order moments are taken into
account.


title: Relativistic Tunneling Through Two Successive Barriers

abstract:
  We study the relativistic quantum mechanical problem of a Dirac particle
tunneling through two successive electrostatic barriers. Our aim is to study
the emergence of the so-called \emph{Generalized Hartman Effect}, an effect
observed in the context of nonrelativistic tunneling as well as in its
electromagnetic counterparts, and which is often associated with the
possibility of superluminal velocities in the tunneling process. We discuss the
behavior of both the phase (or group) tunneling time and the dwell time, and
show that in the limit of opaque barriers the relativistic theory also allows
the emergence of the Generalized Hartman Effect. We compare our results with
the nonrelativistic ones and discuss their interpretation.


title:
The young stellar population of NGC 4214 as observed with HST. I. Data
  and methods

abstract:
  We present the data and methods that we have used to perform a detailed
UV-optical study of the nearby dwarf starburst galaxy NGC 4214 using
multifilter HST/WFPC2+STIS photometry. We explain the process followed to
obtain high-quality photometry and astrometry of the stellar and cluster
populations of this galaxy. We describe the procedure used to transform
magnitudes and colors into physical parameters using spectral energy
distributions. The data show the existence of both young and old stellar
populations that can be resolved at the distance of NGC 4214 (2.94 Mpc) and we
perform a general description of those populations.


title: Modeling polymerization of microtubules: a quantum mechanical approach

abstract:
  In this paper a quantum mechanical description of the assembly/disassembly
process for microtubules is proposed. We introduce creation and annihilation
operators that raise or lower the microtubule length by a tubulin layer.
Following that, the Hamiltonian and corresponding equations of motion for the
quantum fields are derived that describe the dynamics of microtubules. These
Heisenberg-type equations are then transformed to semi-classical equations
using the method of coherent structures. We find that the dynamics of a
microtubule can be mathematically expressed via a cubic-quintic nonlinear
Schr\"{o}dinger (NLS) equation. We show that a vortex filament, a generic
solution of the NLS equation, exhibits linear growth/shrinkage in time as well
as temporal fluctuations about some mean value which is qualitatively similar
to the dynamic instability of microtubules.


title:
The young stellar population of NGC 4214 as observed with HST. II.
  Results

abstract:
  We present the results of a detailed UV-optical study of the nearby dwarf
starburst galaxy NGC 4214 using multifilter HST/WFPC2+STIS photometry. The
stellar extinction is found to be quite patchy, with some areas having values
of E(4405-5495)< 0.1 mag and others, associated with star forming regions, much
more heavily obscured, a result which is consistent with previous studies of
the nebular extinction. We determined the ratio of blue-to-red supergiants and
found it to be consistent with theoretical models for the metallicity of the
SMC. The stellar IMF of the field in the range 20-100 solar masses is found to
be steeper than Salpeter. A number of massive clusters and associations with
ages between a few and 200 million years are detected and their properties are
discussed.


title:
Formulation of a constrained system in terms of extended Lagrangian and
  its local symmetries

abstract:
  It is shown that an arbitrary singular Lagrangian theory (with first and
second class constraints up to $N$-th stage in the Hamiltonian formulation) can
be reformulated as a theory with at most third-stage constraints. The
corresponding Lagrangian $\tilde L$ can be obtained by pure algebraic methods,
its manifest form in terms of quantities of the initial formulation is found.
Local symmetries of $\tilde L$ are obtained in closed form. All the first class
constraints of the initial Lagrangian turn out to be gauge symmetry generators
for $\tilde L$.


title: An estimate for the location of QCD critical end point

abstract:
  It is proposed that a study of the ratio of shear viscosity to entropy
density $\frac{\eta}{s}$ as a function of the baryon chemical potential
$\mu_B$, and temperature T, provides a dynamic probe for the critical end point
(CEP) in hot and dense QCD matter. An initial estimate from an elliptic flow
excitation function gives $\mu^{\text{cep}}_B \sim 150-180$ MeV and
$T_{\text{cep}} \sim 165 - 170$ MeV for the location of the the CEP. These
values place the CEP in the range for "immediate" validation at RHIC.


title: Computational complexity of quantum optimal control landscapes

abstract:
  We study the Hamiltonian-independent contribution to the complexity of
quantum optimal control problems. The optimization of controls that steer
quantum systems to desired objectives can itself be considered a classical
dynamical system that executes an analog computation. The system-independent
component of the equations of motion of this dynamical system can be integrated
analytically for various classes of discrete quantum control problems. For the
maximization of observable expectation values from an initial pure state and
the maximization of the fidelity of quantum gates, the time complexity of the
corresponding computation belongs to the class continuous log (CLOG), the
lowest analog complexity class, equivalent to the discrete complexity class NC.
The simple scaling of the Hamiltonian-independent contribution to these
problems with quantum system dimension indicates that with appropriately
designed search algorithms, quantum optimal control can be rendered efficient
even for large systems.


title: Characteristic 2 approach to bivariate interpolation problems

abstract:
  We investigate bivariate interpolation problems in characteristic 2. Given a
nonnegative integer $t$, we describe all the sub-linear systems generated by
monomials, in which there is no curve passing through a general point with
multiplicity at least $2^t$. As an application, we show that a certain linear
system of plane curves with 10 base points is non-special.


title: Intransitive geometries and fused amalgams

abstract:
  We study geometries that arise from the natural $G_2(K)$ action on the
geometry of one-dimensional subspaces, of nonsingular two-dimensional
subspaces, and of nonsingular three-dimensional subspaces of the building
geometry of type $C_3(K)$ where $K$ is a perfect field of characteristic 2. One
of these geometries is intransitive in such a way that the non-standard
geometric covering theory by the first and the last author is not applicable.
In this paper we introduce the concept of fused amalgams in order to extend the
geometric covering theory so that it applies to that geometry. This yields an
interesting new amalgamation result for the group $G_2(K)$.


title:
Annihilation Rate of Heavy 0^{++} P-wave Quarkonium in Relativistic
  Salpeter Method

abstract:
  Two-photon and two-gluon annihilation rates of P-wave scalar charmonium and
bottomonium up to third radial excited states are estimated in the relativistic
Salpeter method. We solved the full Salpeter equation with a well defined
relativistic wave function and calculated the transition amplitude using the
Mandelstam formalism. Our model dependent estimates for the decay widths:
$\Gamma(\chi_{c0} \to 2\gamma)=3.78$ keV, $\Gamma(\chi'_{c0} \to 2\gamma)=3.51$
keV, $\Gamma(\chi_{b0} \to 2\gamma)=48.8$ eV and $\Gamma(\chi'_{b0} \to
2\gamma)=50.3$ eV. We also give estimates of total widths by the two-gluon
decay rates: $\Gamma_{tot}(\chi_{c0})=10.3$ MeV,
$\Gamma_{tot}(\chi'_{c0})=9.61$ MeV, $\Gamma_{tot}(\chi_{b0})=0.887$ MeV and
$\Gamma_{tot}(\chi'_{b0})=0.914$ MeV.


title: Sparse inverse covariance estimation with the lasso

abstract:
  We consider the problem of estimating sparse graphs by a lasso penalty
applied to the inverse covariance matrix. Using a coordinate descent procedure
for the lasso, we develop a simple algorithm that is remarkably fast: in the
worst cases, it solves a 1000 node problem (~500,000 parameters) in about a
minute, and is 50 to 2000 times faster than competing methods. It also provides
a conceptual link between the exact problem and the approximation suggested by
Meinhausen and Buhlmann (2006). We illustrate the method on some cell-signaling
data from proteomics.


title:
A Look at the Abandoned Contributions to Cosmology of Dirac, Sciama and
  Dicke

abstract:
  The separate contributions to cosmology of the above researchers are
revisited and a cosmology encompassing their basic ideas is proposed. We study
Dirac's article on the large number hypothesis (1938), Sciama's proposal of
realizing Mach's principle (1953), and Dicke's considerations (1957) on a
flat-space representation of general relativity with a variable speed of light
(VSL). Dicke's tentative theory can be formulated in a way which is compatible
with Sciama's hypothesis on the gravitational constant G. Additionally, such a
cosmological model is shown to satisfy Dirac's second `large number' hypothesis
on the total number of particles in the universe being proportional to the
square of the epoch. In the same context, Dirac's first hypothesis on an
epoch-dependent G-contrary to his prediction- does not necessarily produce a
visible time dependence of G. While Dicke's proposalreproduces the classical
tests of GR in first approximation, the cosmological redshift is described by a
shortening of measuring rods rather than an expansion of space. Since the
temporal evolution of the horizon R is governed by \dot R(t) =c(t), the
flatness and horizon problems do not arise in the common form.


title: Photons inside a waveguide as massive particles

abstract:
  In the paper, we show that there exists a close analogy between the behavior
of de Broglie matter waves and that of electromagnetic waves inside a hollow
waveguide, such that the guided photons can be treated as free massive
particles subject to a relativistic quantum-mechanical equation. Inspired by
the effective rest mass of guided photons and the zitterbewegung phenomenon of
the Dirac electron, at variance with the well-known Higgs mechanism we present
some different heuristic ideas on the origin of mass.


title:
Prisoner's Dilemma in One-Dimensional Cellular Automata: Visualization
  of Evolutionary Patterns

abstract:
  The spatial Prisoner's Dilemma is a prototype model to show the emergence of
cooperation in very competitive environments. It considers players, at site of
lattices, that can either cooperate or defect when playing the Prisoner's
Dilemma with other z players. This model presents a rich phase diagram. Here we
consider players in cells of one-dimensional cellular automata. Each player
interacts with other z players. This geometry allows us to vary, in a simple
manner, the number of neighbors ranging from one up to the lattice size,
including self-interaction. This approach has multiple advantages. It is simple
to implement numerically and we are able to retrieve all the previous results
found in the previously considered lattices, with a faster convergence to
stationary values. More remarkable, it permits us to keep track of the
spatio-temporal evolution of each player of the automaton. Giving rise to
interesting patterns. These patterns allow the interpretation of
cooperation/defection clusters as particles, which can be absorbed and collided
among themselves. The presented approach represents a new paradigm to study the
emergence and maintenance of cooperation in the spatial Prisoner's Dilemma.


title: A novel operation associated with Gauss' arithmetic-geometric means

abstract:
  The arithmetic mean is the mean for addition and the geometric mean is that
for multiplication. Then what kind of binary operation is associated with the
arithmetic-geometric mean (AGM) due to C. F. Gauss? If it is possible to
construct an arithmetic operation such that AGM is the mean for this operation,
it can be regarded as an intermediate operation between addition and
multiplication in view of the meaning of AGM. In this paper such an operation
is introduced and several of its algebraic properties are proved.


title:
Bounding the Betti numbers and computing the Euler-Poincar\'e
  characteristic of semi-algebraic sets defined by partly quadratic systems of
  polynomials

abstract:
  Let $\R$ be a real closed field, $ {\mathcal Q} \subset
\R[Y_1,...,Y_\ell,X_1,...,X_k], $ with $ \deg_{Y}(Q) \leq 2, \deg_{X}(Q) \leq
d, Q \in {\mathcal Q}, #({\mathcal Q})=m,$ and $ {\mathcal P} \subset
\R[X_1,...,X_k] $ with $\deg_{X}(P) \leq d, P \in {\mathcal P}, #({\mathcal
P})=s$, and $S \subset \R^{\ell+k}$ a semi-algebraic set defined by a Boolean
formula without negations, with atoms $P=0, P \geq 0, P \leq 0, P \in {\mathcal
P} \cup {\mathcal Q}$. We prove that the sum of the Betti numbers of $S$ is
bounded by \[ \ell^2 (O(s+\ell+m)\ell d)^{k+2m}. \] This is a common
generalization of previous results on bounding the Betti numbers of closed
semi-algebraic sets defined by polynomials of degree $d$ and 2, respectively.
  We also describe an algorithm for computing the Euler-Poincar\'e
characteristic of such sets, generalizing similar algorithms known before. The
complexity of the algorithm is bounded by $(\ell s m d)^{O(m(m+k))}$.


title:
Polarized neutron scattering study on antiferromagnetic states in
  CeRh0.6Co0.4In5

abstract:
  Polarized neutron scattering experiments were performed on mixed compound
CeRh0.6Co0.4In5 to clarify the nature of the low-temperature ordered states.
Three nonequivalent Bragg peaks, characterized by the wave vectors of q_h ~
(1/2,1/2,0.3), q_1 ~ (1/2,1/2,0.4) and q_c=(1/2,1/2,1/2), were observed at 1.4
K. These Bragg peaks are found to occur entirely in spin-flip channel. This
indicates that these Bragg peaks originate from the magnetic scattering, i.e.,
the antiferromagnetic orders with three different modulations appear in this
compound.


title: The nanoscale phase separation in hole-doped manganites

abstract:
  A macroscopic phase separation, in which ferromagnetic clusters are observed
in an insulating matrix, is sometimes observed, and believed to be essential to
the colossal magnetoresistive (CMR) properties of manganese oxides. The
application of a magnetic field may indeed trigger large magnetoresistance
effects due to the percolation between clusters allowing the movement of the
charge carriers. However, this macroscopic phase separation is mainly related
to extrinsic defects or impurities, which hinder the long-ranged charge-orbital
order of the system. We show in the present article that rather than the
macroscopic phase separation, an homogeneous short-ranged charge-orbital order
accompanied by a spin glass state occurs, as an intrinsic result of the
uniformity of the random potential perturbation induced by the solid solution
of the cations on the $A$-sites of the structure of these materials. Hence the
phase separation does occur, but in a more subtle and interesting nanoscopic
form, here referred as ``homogeneous''. Remarkably, this ``nanoscale phase
separation'' alone is able to bring forth the colossal magnetoresistance in the
perovskite manganites, and is potentially relevant to a wide variety of other
magnetic and/or electrical properties of manganites, as well as many other
transition metal oxides, in bulk or thin film form as we exemplify throughout
the article.


title: Gauge invariance and time symmetry breaking

abstract:
  Employing an arbitrary velocity gauge transformation this contribution argues
that the breaking of time symmetry is a natural consequence of irreversibility.


title: 1/N_c corrections to the magnetic susceptibility of the QCD vacuum

abstract:
  We investigate the magnetic susceptibility of the QCD vacuum with the $1/N_c$
corrections taken into account, based on the instanton vacuum. Starting from
the instanton liquid model we derive the gauged light-quark partition function
in the presence of the current quark mass as well as of external Abelian vector
and tensor fields. We consider the $1/N_c$ meson-loop corrections which are
shown to contribute to the magnetic susceptibility by around 15% for the up
(and down) quarks. We also take into account the tensor terms of the
quark-quark interaction from the instanton vacuum as well as the finite-width
effects, both of which are of order $\mathcal{O}(1/N_c)$. The effects of the
tensor terms and finite width turn out to be negligibly small. The final
results for the up-quarks are given as: $\chi< i\psi^\dagger \psi>_0 \simeq
35-40 \mathrm{MeV}$ with the quark condensate $<i\psi^\dagger \psi>_0$. We also
discuss the pion mass dependence of the magnetic susceptibility in order to
give a qualitative guideline for the chiral extrapolation of lattice data.


title:
Science-Based Comparative Culture: A New Theme of Experiment for
  Freshmen in Tohoku University

abstract:
  In 2004, Tohoku University created a new introductory science experimental
course for freshmen. The course is a compulsory subject for students in all
natural science fields. The course is not designed for a professional
education, but as a liberal education, in which students are trained to become
familiar with nature and to discover natural laws for themselves. We present
here one of 12 themes - "science and culture: vibration of string instrument
and music", in which we expect students to study two aspects: 1) the
universality of natural laws and 2) the variety of value judgments from the
evidence.


title:
Determination of Penetration Depth of Transverse Spin Current in
  Ferromagnetic Metals by Spin Pumping

abstract:
  Spin pumping in nonmagnetic/ferromagnetic metal multilayers is studied both
theoretically and experimentally. We show that the line widths of the
ferromagnetic resonance (FMR) spectrum depend on the thickness of the
ferromagnetic metal layers, which must not be in resonance with the oscillating
magnetic field. We also show that the penetration depths of the transverse spin
current in ferromagnetic metals can be determined by analyzing the line widths
of their FMR spectra. The obtained penetration depths in NiFe, CoFe and CoFeB
were 3.7 [nm], 2.5 [nm] and 12.0 [nm], respectively.


title:
Tuning Co valence state in cobalt oxyhydrate superconductor by post
  reduction

abstract:
  We report a successful tuning of Co valence state in cobalt oxyhydrate
superconductor via a facile post reduction using NaOH as reducing agent. The
change in Co valence was precisely determined by measuring the volume of the
released oxygen. The possible hydronium-incorporation was greatly suppressed in
concentrated NaOH solution, making the absolute Co valence determinable. As a
result, an updated superconducting phase diagram was obtained, which shows that
the superconducting transition temperature increases monotonically with
increasing Co valence in a narrow range from +3.58 to +3.65.


title: Gravity localization on thick branes: a numerical approach

abstract:
  We introduce a numerical procedure to investigate the spectrum of massive
modes and its contribution for gravity localization on thick branes. After
considering a model with an analytically known Schroedinger potential, we
present the method and discuss its applicability. With this procedure we can
study several models even when the Schroedinger potential is not known
analytically. We discuss both the occurrence of localization of gravity and the
correction to the Newtonian potential given by the massive modes.