title: Flicker noise in high-speed p-i-n photodiodes

abstract:
  The microwave signal at the output of a photodiode that detects a modulated
optical beam contains the phase noise phi(t) and the amplitude noise alpha(t)
of the detector. Beside the white noise, which is well understood, the spectral
densities S_phi(f) and S_alpha(f) show flicker noise, proportional to 1/f.
  We report on the measurement of the phase and amplitude noise of high-speed
p-i-n photodiodes. The main result is that the flicker coefficient of the
samples is approximately 1E-12 rad^2/Hz (-120dB) for phase noise, and
approximately 1E-12 Hz^-1 (-120dB) for amplitude noise. These values could be
observed only after solving a number of experimental problems and in a
protected environment. By contrast, in ordinary conditions insufficient EMI
isolation, and also insufficient mechanical isolation, are responsible for
additional noise to be taken in. This suggests that if package and EMC are
revisited, applications can take the full benefit from the surprisingly low
noise of the p-i-n photodiodes.


title:
Scaling laws for the movement of people between locations in a large
  city

abstract:
  Large scale simulations of the movements of people in a ``virtual'' city and
their analyses are used to generate new insights into understanding the dynamic
processes that depend on the interactions between people. Models, based on
these interactions, can be used in optimizing traffic flow, slowing the spread
of infectious diseases or predicting the change in cell phone usage in a
disaster. We analyzed cumulative and aggregated data generated from the
simulated movements of 1.6 million individuals in a computer (pseudo
agent-based) model during a typical day in Portland, Oregon. This city is
mapped into a graph with $181,206$ nodes representing physical locations such
as buildings. Connecting edges model individual's flow between nodes. Edge
weights are constructed from the daily traffic of individuals moving between
locations. The number of edges leaving a node (out-degree), the edge weights
(out-traffic), and the edge-weights per location (total out-traffic) are fitted
well by power law distributions. The power law distributions also fit subgraphs
based on work, school, and social/recreational activities. The resulting
weighted graph is a ``small world'' and has scaling laws consistent with an
underlying hierarchical structure. We also explore the time evolution of the
largest connected component and the distribution of the component sizes. We
observe a strong linear correlation between the out-degree and total
out-traffic distributions and significant levels of clustering. We discuss how
these network features can be used to characterize social networks and their
relationship to dynamic processes.


title:
Power-law distributions in economics: a nonextensive statistical
  approach

abstract:
  The cornerstone of Boltzmann-Gibbs ($BG$) statistical mechanics is the
Boltzmann-Gibbs-Jaynes-Shannon entropy $S_{BG} \equiv -k\int dx f(x)\ln f(x)$,
where $k$ is a positive constant and $f(x)$ a probability density function.
This theory has exibited, along more than one century, great success in the
treatment of systems where short spatio/temporal correlations dominate. There
are, however, anomalous natural and artificial systems that violate the basic
requirements for its applicability. Different physical entropies, other than
the standard one, appear to be necessary in order to satisfactorily deal with
such anomalies. One of such entropies is $S_q \equiv k (1-\int dx
[f(x)]^q)/(1-q)$ (with $S_1=S_{BG}$), where the entropic index $q$ is a real
parameter. It has been proposed as the basis for a generalization, referred to
as {\it nonextensive statistical mechanics}, of the $BG$ theory. $S_q$ shares
with $S_{BG}$ four remarkable properties, namely {\it concavity} ($\forall
q>0$), {\it Lesche-stability} ($\forall q>0$), {\it finiteness of the entropy
production per unit time} ($q \in \Re$), and {\it additivity} (for at least a
compact support of $q$ including $q=1$). The simultaneous validity of these
properties suggests that $S_q$ is appropriate for bridging, at a macroscopic
level, with classical thermodynamics itself. In the same natural way that
exponential probability functions arise in the standard context,power-law
tailed distributions, even with exponents {\it out} of the L\'evy range, arise
in the nonextensive framework. In this review, we intend to show that many
processes of interest in economy, for which fat-tailed probability functions
are empirically observed, can be described in terms of the statistical
mechanisms that underly the nonextensive theory.


title: Thermal radiation of conducting nanoparticles

abstract:
  The thermal radiation of small conducting particles was investigated in the
region where the Stephan-Boltzmann law is not valid and strongly overestimates
radiation losses. The new criterion for the particle size, at which black body
radiation law fails, was formulated. The approach is based on the magnetic
particle polarization, which is valid until very small sizes (cluster size)
where due to drop of particle conductivity the electric polarization prevails
over the magnetic one. It was also shown that the radiation power of clusters,
estimated on the basis of the experimental data, is lower than that given by
the Stephan-Boltzmann law.


title: Review of Nonlinear Methods and Modelling

abstract:
  The first part of this Review describes a few of the main methods that have
been employed in non-linear time series analysis with special reference to
biological applications (biomechanics). The second part treats the physical
basis of posturogram data (human balance) and EMG (electromyography, a measure
of muscle activity).


title: Why does the Standard GARCH(1,1) model work well?

abstract:
  The AutoRegressive Conditional Heteroskedasticity (ARCH) and its generalized
version (GARCH) family of models have grown to encompass a wide range of
specifications, each of them is designed to enhance the ability of the model to
capture the characteristics of stochastic data, such as financial time series.
The existing literature provides little guidance on how to select optimal
parameters, which are critical in efficiency of the model, among the infinite
range of available parameters. We introduce a new criterion to find suitable
parameters in GARCH models by using Markov length, which is the minimum time
interval over which the data can be considered as constituting a Markov
process. This criterion is applied to various time series and results support
the known idea that GARCH(1,1) model works well.


title:
A General Systems Theory for Chaos, Quantum Mechanics and Gravity for
  Dynamical Systems of all Space-Time Scales

abstract:
  Non-local connections, i. e. long-range space-time correlations intrinsic to
the observed subatomic dynamics of quantum systems is also exhibited by
macro-scale dynamical systems as selfsimilar fractal space-time fluctuations
and is identified as self-organized criticality. The author has developed a
general systems theory for the observed self-organized criticality applicable
to dynamical systems of all space-time scales based on the concept that spatial
integration of enclosed small-scale fluctuations results in the formation of
large eddy circulation. The eddy energy spectrum therefore represents the
statistical normal distribution according to the Central Limit Theorem. The
additive amplitudes of eddies, when squared (variance or eddy kinetic energy),
represent the statistical normal (probability) distribution, a result observed
in the subatomic dynamics of quantum systems. The model predicts Kepler's laws
of planetary motion for eddy circulation dynamics. Inverse square law of
gravitation therefore applies to the eddy continuum ranging from subatomic to
macro-scale dynamical systems, e.g. weather systems. The model is similar to a
superstring model for subatomic dynamics which unifies quantum mechanical and
classical concepts and manifestation of matter is visualised as vibrational
modes in string-like energy flow patterns. The cumulative sum of centripetal
forces in a hierarchy of vortex circulations may result in the observed inverse
square law form for gravitational attraction between inertial masses of the
eddies.


title: Dust acoustic wave in a strongly magnetized pair-dust plasma

abstract:
  The existence of the dust acoustic wave (DAW) in a strongly magnetized
electron-positron (pair)-dust plasma is demonstrated. In the DAW, the restoring
force comes from the pressure of inertialess electrons and positrons, and the
dust mass provides the inertia. The waves could be of interest in astrophysical
settings such as the supernovae and pulsars, as well as in cluster explosions
by intense laser beams in laboratory plasmas.


title: The Yo-yo Oscillator (Analysis of a Nonlinear System using Spice)

abstract:
  Unlike the simplest (Hooke's law spring) oscillator, where the restoring
force is in magnitude proportional to the displacement; the yo-yo oscillator
has a constant force-magnitude. In other words, its potential energy function
is linear, as contrasted to the quadratic (harmonic) potential of the simple
harmonic oscillator. The linear potential is responsible for a nonlinear
equation of motion which yields many surprising solutions. Rich in complexity,
these solutions are in some cases chaotic. Numerical solutions to the equation
of motion are presently obtained using the 'simulation program for integrated
circuit engineering' (Spice). The circuit employed involves operational
amplifiers and solid state switches.


title:
Competitive Advantage for Multiple-Memory Strategies in an Artificial
  Market

abstract:
  We consider a simple binary market model containing $N$ competitive agents.
The novel feature of our model is that it incorporates the tendency shown by
traders to look for patterns in past price movements over multiple time scales,
i.e. {\em multiple memory-lengths}. In the regime where these memory-lengths
are all small, the average winnings per agent exceed those obtained for either
(1) a pure population where all agents have equal memory-length, or (2) a mixed
population comprising sub-populations of equal-memory agents with each
sub-population having a different memory-length. Agents who consistently play
strategies of a given memory-length, are found to win more on average --
switching between strategies with different memory lengths incurs an effective
penalty, while switching between strategies of equal memory does not. Agents
employing short-memory strategies can outperform agents using long-memory
strategies, even in the regime where an equal-memory system would have favored
the use of long-memory strategies. Using the many-body `Crowd-Anticrowd'
theory, we obtain analytic expressions which are in good agreement with the
observed numerical results. In the context of financial markets, our results
suggest that multiple-memory agents have a better chance of identifying price
patterns of unknown length and hence will typically have higher winnings.


title: Characterization of Etched Glass Surfaces by Wave Scattering

abstract:
  The roughness of glass surfaces after different stages of etching is
investigated by reflection measurements with a spectrophotometer, light
scattering, and atomic-force microscopy (in small scale), and Talysurf (in
large scale). The results suggest, there are three regimes during etching,
according to their optical reflectivity and roughness. The first and second
regimes are studied by the Kirchhoff theory and the third one is studied by the
geometric theory. Also, we compare the roughness obtained by the optical
scattering to the AFM results.


title: Coherent Beamstrahlung at the International Linear Collider

abstract:
  Although we believe most of the results presented here are correct, they are
correct only in the limit of negligible beam disruption, which is not the ILC
case. Also, the paper needs a convincing treatment of beam pipe shielding
effects, though we believe that these effects will be proven to be small
eventually.


title:
Noise-induced Transition between Dynamic Attractors in the
  Parametrically Excited Magneto-optical Trap

abstract:
  We have investigated noise-induced transition of atoms between double or
triple phase-space attractors that are produced in the parametrically driven
magneto-optical trap. The transition rates between two or three dynamic
attractors, measured for various modulation frequencies and amplitudes, are in
good agreement with theoretical calculations and Monte-Carlo simulations based
on the Langevin equations. Our experiment may be useful to study nonlinear
dynamic problems involving transitions between states far from equilibrium.


title: A geostrophic-like model for large Hartmann number flows

abstract:
  A flow of electrically conducting fluid in the presence of a steady magnetic
field has a tendency to become quasi two-dimensional, i.e. uniform in the
direction of the magnetic field, except in thin so-called Hartmann boundary
layers. The condition for this tendency is that of a strong magnetic field,
corresponding to large values of the dimensionless Hartmann number (Ha >> 1).
This is analogous to the case of low Ekman number rotating flows, with Ekman
layers replacing Hartmann layers. This has been at the origin of the
homogeneous model for flows in a rotating frame of reference, with its rich
structure: geostrophic contours and shear layers of Stewartson, Munk and
Stommel. In magnetohydrodynamics, the characteristic surfaces introduced by
Kulikovskii play a role similar to the role of the geostrophic contours.
However, a general theory for quasi two-dimensional magnetohydrodynamics is
lacking. In this paper, a model is proposed which provides a general framework
for quasi two-dimensional magnetohydrodynamic flows. Not only can this model
account for otherwise disconnected past results, but it is also used to predict
a new type of shear layer, of typical thickness Ha^{-1/4}.


title: Finding local community structure in networks

abstract:
  Although the inference of global community structure in networks has recently
become a topic of great interest in the physics community, all such algorithms
require that the graph be completely known. Here, we define both a measure of
local community structure and an algorithm that infers the hierarchy of
communities that enclose a given vertex by exploring the graph one vertex at a
time. This algorithm runs in time O(d*k^2) for general graphs when $d$ is the
mean degree and k is the number of vertices to be explored. For graphs where
exploring a new vertex is time-consuming, the running time is linear, O(k). We
show that on computer-generated graphs this technique compares favorably to
algorithms that require global knowledge. We also use this algorithm to extract
meaningful local clustering information in the large recommender network of an
online retailer and show the existence of mesoscopic structure.


title: Effect of the troposphere on surface neutron counter measurements

abstract:
  Surface neutron counter data are often used as a proxy for atmospheric
ionisation from cosmic rays in studies of extraterrestrial effects on climate.
Neutron counter instrumentation was developed in the 1950s and relationships
between neutron counts, ionisation and meteorological conditions were
investigated thoroughly using the techniques available at the time; the
analysis can now be extended using modern data. Whilst surface neutron counts
are shown to be a good proxy for ionisation rate, the usual meteorological
correction applied to surface neutron measurements, using surface atmospheric
pressure, does not completely compensate for tropospheric effects on neutron
data. Residual correlations remain between neutron counts, atmospheric pressure
and geopotential height, obtained from meteorological reanalysis data. These
correlations may be caused by variations in the height and temperature of the
atmospheric layer at ~100hPa. This is where the primary cosmic rays interact
with atmospheric air, producing a cascade of secondary ionising particles.


title: Visco-magnetic torque at the core mantle boundary

abstract:
  A magneto-hydrodynamic model of boundary layers at the Core-Mantle Boundary
(CMB) is derived and used to compute the viscous and electromagnetic torques
generated by the Earth's nutation forcing. The predicted electromagnetic torque
alone cannot account for the dissipation estimated from the observations of the
free core nutation. The presence of a viscous boundary layer in the
electromagnetic skin layer at the CMB, with its additional dissipative torques,
may explain the geodetic data. An apparent Ekman number at the top of the core
between 3 and $5 10^{-11}$ is inferred depending on the electrical conductivity
of the mantle.


title:
A planar magneto-inductive lens for three-dimensional subwavelength
  imaging

abstract:
  A planar near-field magnetoinductive lens operating in the microwave range is
presented. The proposed device consists of two parallel planar arrays of
metallic broadside coupled (BC-) split ring resonators (SRRs), or BC-SRRs.
Power coming from a point-like source located in front of the lens is focused
into a receiver located in free space behind the device. This focus is clearly
removed from the back side of the lens, and has a size which is an order of
magnitude smaller than the free space wavelength of the incoming radiation. The
imaging properties of the device mainly relies on the excitation of
magnetoinductive surface waves on the BC-SRR arrays. By simply scaling the
BC-SRRs size, as well as the arrays periodicity, the frequency of operation of
the device can be tuned over a wide frequency range. Thus the proposed design
is potentially useful for many applications ranging from megahertzs to
terahertzs.


title:
Inference of a nonlinear stochastic model of the cardiorespiratory
  interaction

abstract:
  A new technique is introduced to reconstruct a nonlinear stochastic model of
the cardiorespiratory interaction. Its inferential framework uses a set of
polynomial basis functions representing the nonlinear force governing the
system oscillations. The strength and direction of coupling, and the noise
intensity are simultaneously inferred from a univariate blood pressure signal,
monitored in a clinical environment. The technique does not require extensive
global optimization and it is applicable to a wide range of complex dynamical
systems subject to noise.


title: Localization of light in a random grating array in a single mode fiber

abstract:
  We investigate light propagation in randomly spaced fiber gratings in a
single mode fiber, and demonstrate the localization effect. Localization of
light in random media resembles that of electrons in disordered solids,
resulting from a subtle wave interference formation. We measured the light
transmission after each additional grating fabrication and found an exponential
decay that follows the localization theory. An important feature of the random
array is its similarity to ordered gratings in the transmission and reflection
behavior at the long array regime. Besides the basic interest in localization
in one-dimensional systems, random grating arrays have potential applications,
utilizing the possibility to fabricate long structures with strong and
broadband reflections.


title: Acoustic black holes

abstract:
  We discuss some general aspects of acoustic black holes. We begin by
describing the associated formalism with which acoustic black holes are
established, then we show how to model arbitrary geometries by using a de Laval
nozzle. It is argued that even though the Hawking temperature of these black
holes is too low to be detected, acoustic black holes have interesting
classical properties, some of which are outlined here, that should be explored.

categories: physics.flu-dyn astro-ph gr-qc physics.class-ph


title:
A Computational Fluid Model for Investigation of Plasma Waves and
  Instabilities

abstract:
  A computational fluid model is developed to study waves and instabilities. A
new technique involving initial perturbations in configuration space have been
implemented to excite the plasma waves; i.e. the perturbations acting similar
to a random velocity distribution in particle in cell (PIC) codes. This forms a
new powerful tool for investigation of many waves arising in both thermal and
cold plasmas and as such will allow investigation of problems demanding scales
and resolution not yet possible by PIC codes. The model predicts Langmuir
waves, two stream instabilities, nonlinear wave-wave interaction, and the Debye
screening effects. The agreement between theory and simulation where analytic
results are available are excellent.


title:
Reduction of Coincident Photomultiplier Noise Relevant to Astroparticle
  Physics Experiment

abstract:
  In low background and low threshold particle astrophysics experiments using
observation of Cherenkov or scintillation light it is common to use pairs or
arrays of photomultipliers operated in coincidence. In such circumstances, for
instance in dark matter and neutrino experiments, unexpected PMT noise events
have been observed, probably arising from generation of light from one PMT
being detected by one or more other PMTs. We describe here experimental
investigation of such coincident noise events and development of new techniques
to remove them using novel pulse shape discrimination procedures. When applied
to data from a low background NaI detector with facing PMTs the new procedures
are found to improve noise rejection by a factor of 20 over conventional
techniques, with significantly reduced loss of signal events.


title: Thermal Equilibrium Calorimeters -- An Introduction

abstract:
  Near-equilibrium thermal detectors operate as classical calorimeters, with
energy deposition and internal equilibration times short compared to the
thermal time constant of the device. Advances in fabrication techniques,
cryogenics, and electronics have made it practical to measure deposited energy
with unprecedented sensitivity and precision. In this chapter we discuss
performance considerations for these devices, including optimal filtering and
energy resolution calculations. We begin with the basic theory of simple
equilibrium calorimeters with ideal resistive thermometers. This provides a
starting point for a brief discussion of electrothermal feedback, other noise
sources, various non-ideal effects, and nonlinearity. We then describe other
types of thermometers and show how they fit into this theoretical framework and
why they may require different optimizations and figures of merit. Most of this
discussion is applicable also to power detectors, or bolometers, where the
detector time constants may be short compared to variations in the incident
signal power.


title:
Translation of Einstein's Attempt of a Unified Field Theory with
  Teleparallelism

abstract:
  We present the first English translation of Einstein's original papers
related to the teleparallel ('absolute parallelism', 'distant parallelism' and
the German 'Fernparallelismus' are synonyms) attempt of an unified field theory
of gravitation and electromagnetism. Our collection contains the summarizing
paper in Math. Annal. 102 (1930) pp. 685-697 and 2 reports published in
'Sitzungsberichte der Preussischen Akademie der Wissenschaften' on June 7th,
1928 (pp. 217-221), June 14th, 1928 (pp. 224-227) and a precursor report (July
9th, 1925 pp. 414-419). To ease understanding, literature on tensor analysis is
quoted in the footnotes.


title:
Contribution to harmonic balance calculations of periodic oscillation
  for self-sustained musical instruments with focus on single-reed instruments

abstract:
  The harmonic balance method (HBM) was originally developed for finding
periodic solutions of electronical and mechanical systems under a periodic
force, but has later been adapted to self-sustained musical instruments. Unlike
time-domain methods, this frequency-domain method does not capture transients
and so is not adapted for sound synthesis. However, its independence of time
makes it very useful for studying every periodic solution of the model, whether
stable or unstable without care of initial conditions. A computer program for
solving general problems involving nonlinearly coupled exciter and resonator,
Harmbal, has been developed based on the HBM. The method as well as convergence
improvements and continuations facilities are thorougly presented and discussed
in the present paper. Application of the method is demonstrated on various
problems related to a common model of the clarinet: a reed modelled as a simple
spring with and without mass and damping, a nonlinear coupling and a cubic
simplification of it, and a cylindrical bore with or without dissipation and
dispersion as well as a bore formed as a stepped cone.


title:
High order stimulated Brillouin scattering in single-mode fibers with
  strong feedback

abstract:
  We present an experimental and theoretical study of cascaded high order
Stimulated Brillouin Scatterings (SBS) in single mode fibers. It is shown that
because of the back-scattering nature of the process, feedback in the input
port is needed for obtaining a significant cascaded effect in nonresonant
systems. We also discuss similarities to nonlinear photorefractive processes.


title: Spice Modeling of the Vilnius Chaotic Oscillator

abstract:
  ``A simple chaotic oscillator for educational purposes'' was recently
described in the literature [1]. In addition to their hardware description, the
authors of this paper generated a bifurcation diagram from the model equations
presented in their paper. In the present treatment of their circuit the
`simulation program for integrated circuit engineering' (Spice) has been used
to generate some insightful graphs that were not shown by the Lithuania group.


title:
Simultaneous Least Squares Treatment of Statistical and Systematic
  Uncertainties

abstract:
  We present a least squares method for estimating parameters from measurements
of event yields in the presence of background and crossfeed. We adopt a unified
approach to incorporating the statistical and systematic uncertainties on the
experimental measurements input to the fit. We demonstrate this method with a
fit for absolute hadronic D meson branching fractions, measured in e+e- ->
\psi(3770) -> D\bar D$ transitions.


title:
On the behavior of liquid drops on a solid surface. 1. The sliding of
  drops on an inclined surface

abstract:
  The idea of contact angle was generalized by using the principle of minimum
total energy. The problems of the shape of the two-dimensional sessile drop and
the drop on an inclined surface are considered. The differential equations
describing the drop shapes are found in both cases. A case of good wetting is
considered to determine the profiles of the sessile and inclined drops. The
generalization of the boundary conditions for the contact angle hysteresis of
the drop on an inclined surface is discussed. The limit of the inclination
angle at which the drop begins to run down the inclined plane is found. The
models of the drop detachment from the solid and the motion of liquid inside of
the drop are discussed. This is not an original text.


title:
Remote Stimulated Triggering of Quantum Entangled Photoluminescent
  Molecules of Strontium Aluminate

abstract:
  We report experiments in which two photoluminescent samples of Strontium
Aluminate pigments and Zinc Sulfide pebbles were quantum entangled via
photoexcitation with entangled photons from a mercury lamp and a CRT screen.
After photo-excitation, remote triggering of one of the sample with infrared
(IR) photons yielded stimulated light variation from the quantum entangled
other sample located 4 m away. The initial half-life of Strontium Aluminate is
approximately one minute. However, molecules with a longer half-life may be
found in the future. These experiments demonstrate that useful quantum
information could be transferred through quantum channels via de-excitation of
one sample of photoluminescent material quantum entangled with another.


title:
Nonlinear Statistical Modelling and Model Discovery for
  Cardiorespiratory Data

abstract:
  We present a Bayesian dynamical inference method for characterizing
cardiorespiratory (CR) dynamics in humans by inverse modelling from blood
pressure time-series data. This new method is applicable to a broad range of
stochastic dynamical models, and can be implemented without severe
computational demands. A simple nonlinear dynamical model is found that
describes a measured blood pressure time-series in the primary frequency band
of the CR dynamics. The accuracy of the method is investigated using surrogate
data with parameters close to the parameters inferred in the experiment. The
connection of the inferred model to a well-known beat-to-beat model of the
baroreflex is discussed.


title: On the behavior of micro-spheres in a hydrogen pellet target

abstract:
  A pellet target produces micro-spheres of different materials, which are used
as an internal target for nuclear and particle physics studies. We will
describe the pellet hydrogen behavior by means of fluid dynamics and
thermodynamics. In particular one aim is to theoretically understand the
cooling effect in order to find an effective method to optimize the working
conditions of a pellet target. During the droplet formation the evaporative
cooling is best described by a multi-droplet diffusion-controlled model, while
in vacuum, the evaporation follows the (revised) Hertz-Knudsen formula.
Experimental observations compared with calculations clearly indicated the
presence of supercooling, the effect of which is discussed as well.


title: Optimal superluminal systems

abstract:
  We demonstrate that significant effects in the "superluminal propagation"of
light-pulses cannot be observed without involving systems whose gain explodes
outside the pulse spectrum. We explicitly determine the minimum norm of the
gain to attain given superluminal effects and the transfer function of the
corresponding optimal system. The gain-norms which would be required with the
most efficient systems considered up to now (dispersive media, photonic
barriers) to attain the same effects are shown to exceed the minimum by several
orders of magnitude. We finally estimate the largest superluminal advances
which could be attained in a realistic experiment.

categories: physics.optics physics.class-ph physics.gen-ph quant-ph


title: Recurrence time analysis, long-term correlations, and extreme events

abstract:
  The recurrence times between extreme events have been the central point of
statistical analyses in many different areas of science. Simultaneously, the
Poincar\'e recurrence time has been extensively used to characterize nonlinear
dynamical systems. We compare the main properties of these statistical methods
pointing out their consequences for the recurrence analysis performed in time
series. In particular, we analyze the dependence of the mean recurrence time
and of the recurrence time statistics on the probability density function, on
the interval whereto the recurrences are observed, and on the temporal
correlations of time series. In the case of long-term correlations, we verify
the validity of the stretched exponential distribution, which is uniquely
defined by the exponent $\gamma$, at the same time showing that it is
restricted to the class of linear long-term correlated processes. Simple
transformations are able to modify the correlations of time series leading to
stretched exponentials recurrence time statistics with different $\gamma$,
which shows a lack of invariance under the change of observables.


title: Chirality Selection in Open Flow Systems and in Polymerization

abstract:
  As an attempt to understand the homochirality of organic molecules in life, a
chemical reaction model is proposed where the production of chiral monomers
from achiral substrate is catalyzed by the polymers of the same enatiomeric
type. This system has to be open because in a closed system the enhanced
production of chiral monomers by enzymes is compensated by the associated
enhancement in back reaction, and the chiral symmetry is conserved. Open flow
without cross inhibition is shown to lead to the chirality selection in a
general model. In polymerization, the influx of substrate from the ambience and
the efflux of chiral products for purposes other than the catalyst production
make the system necessarily open. The chiral symmetry is found to be broken if
the influx of substrate lies within a finite interval. As the efficiency of the
enzyme increases, the maximum value of the enantiomeric excess approaches unity
so that the chirality selection becomes complete.


title:
Stabilization of three--dimensional light bullets by a transverse
  lattice in a Kerr medium with dispersion management

abstract:
  We demonstrate a possibility to stabilize three-dimensional spatiotemporal
solitons ("light bullets") in self--focusing Kerr media by means of a
combination of dispersion management in the longitudinal direction (with the
group-velocity dispersion alternating between positive and negative values) and
periodic modulation of the refractive index in one transverse direction, out of
the two. The analysis is based on the variational approximation (results of
direct three-dimensional simulations will be reported in a follow-up work). A
predicted stability area is identified in the model's parameter space. It
features a minimum of the necessary strength of the transverse modulation of
the refractive index, and finite minimum and maximum values of the soliton's
energy. The former feature is also explained analytically.


title: Levy statistical fluctuations from a Random Amplifying Medium

abstract:
  We report the studies of emission from a novel random amplifying medium that
we term a ``Levy Laser'' due to the non-Gaussian statistical nature of its
emission over the ensemble of random realizations. It is observed that the
amplification is dominated by certain improbable events that are ``larger than
rare'', which give the intensity statistics a Levy like ``fat tail''. This, to
the best of our knowledge, provides the first experimental realization of Levy
flight in optics in a random amplifying medium.


title:
Ultraslow light propagation in an inhomogeneously broadened rare-earth
  ion-doped crystal

abstract:
  We show that Coherent Population Oscillations effect allows to burn a narrow
spectral hole (26Hz) within the homogeneous absorption line of the optical
transition of an Erbium ion-doped crystal. The large dispersion of the index of
refraction associated with this hole permits to achieve a group velocity as low
as 2.7m/s with a ransmission of 40%. We especially benefit from the
inhomogeneous absorption broadening of the ions to tune both the transmission
coefficient, from 40% to 90%, and the light group velocity from 2.7m/s to
100m/s.


title:
Construction of bipartite and unipartite weighted networks from
  collections of journal papers

abstract:
  This work presents a model that allows the study of research specialties
through the manifestations of the specialty's social and epistemological
processes in a collection of journal papers. Collections of papers are modeled
as coupled bipartite networks interlinking 7 types of entities. Matrix-based
link weight functions are introduced to calculate weighted bipartite networks
and weighted unipartite co-occurrence networks in the collection of papers.
These weight calculation methods, when used in conjunction with unweighted
bipartite growth models, produce simple growth models for weighted networks in
collections of papers.


title: Derivation of QFT Dynamics

abstract:
  The perturbative dynamics of quantum field theories is described by a
recursive expansion similar to the well known loop expansion. The equivalent
formulation based on low-energy dynamics via an expansion in derivatives is
well known in the literature; this is described by terms from low energy to
high energy. The coefficients of these terms are presented in a simplified
algebraic manner. In general, the dynamics of any bare Lagrangian, including
additional higher dimension terms, is found by iteration in a discrete
algorithm. Inversion of the quantized dynamics to the fundamental theory is
possible.


title: Modeling spatiotemporal noise covariance for MEG/EEG source analysis

abstract:
  We propose a new model for approximating spatiotemporal noise covariance for
use in MEG/EEG source analysis. Our model is an extension of an existing model
[1,2] that uses a single Kronecker product of a pair of matrices - temporal and
spatial covariance; we employ a series of Kronecker products in order to
construct a better approximation of the full covariance. In contrast to the
single-pair model that assumes the same temporal structure for all spatial
components, the proposed model allows for distinct, independent time courses at
each spatial component. This model better describes spatially and temporally
correlated background activity. At the same time, inversion of the model is
fast which makes it useful in the inverse analysis. We have explored two
versions of the model. One is based on orthogonal spatial components of the
background. The other, more general model, is based on independent spatial
components. Performance of the new and previous models is compared in inverse
solutions to a large number of single dipole problems with simulated time
courses and background from authentic MEG data.


title: The Transition from Anti-Parallel to Component Magnetic Reconnection

abstract:
  We study the transition between anti-parallel and component collisionless
magnetic reconnection with 2D particle-in-cell simulations. The primary finding
is that a guide field \approx 0.1 times as strong as the asymptotic
reconnecting field -- roughly the field strength at which the electron Larmor
radius is comparable to the width of the electron current layer -- is
sufficient to magnetize the electrons in the vicinity of the x-line, thus
causing significant changes to the structure of the electron dissipation
region. This implies that great care should be exercised before concluding that
magnetospheric reconnection is antiparallel. We also find that even for such
weak guide fields strong inward-flowing electron beams form in the vicinity of
the magnetic separatrices and Buneman-unstable distribution functions arise at
the x-line itself. As in the calculations of {\it Hesse et al.} [2002] and {\it
Yin and Winske} [2003], the non-gyrotropic elements of the electron pressure
tensor play the dominant role in decoupling the electrons from the magnetic
field at the x-line, regardless of the magnitude of the guide field and the
associated strong variations in the pressure tensor's spatial structure.
Despite these changes, and consistent with previous work, the reconnection rate
does not vary appreciably with the strength of the guide field as it changes
between 0 and a value equal to the asymptotic reversed field.


title: The BTeV RICH Front End Electronics

abstract:
  We report on the design and testing of novel mixed analog and digital front
end ASICs custom made for the single photon detectors considered for the BTeV
RICH system. The key features are reviewed, as well as results achieved using
electronics bench tests and beam studies.


title: Invariant Variation Problems

abstract:
  The problems in variation here concerned are such as to admit a continuous
group (in Lie's sense); the conclusions that emerge from the corresponding
differential equations find their most general expression in the theorems
formulated in Section 1 and proved in following sections. Concerning these
differential equations that arise from problems of variation, far more precise
statements can be made than about arbitrary differential equations admitting of
a group, which are the subject of Lie's researches. What is to follow,
therefore, represents a combination of the methods of the formal calculus of
variations with those of Lie's group theory. For special groups and problems in
variation, this combination of methods is not new; I may cite Hamel and
Herglotz for special finite groups, Lorentz and his pupils (for instance
Fokker), Weyl and Klein for special infinite groups. Especially Klein's second
Note and the present developments have been mutually influenced by each other,
in which regard I may refer to the concluding remarks of Klein's Note.


title:
Structural phase transitions and out-of-plane dust lattice instabilities
  in vertically confined plasma crystals

abstract:
  The formation of plasma crystals confined in an external one-dimensional
parabolic potential well is simulated for a normal experimental environment
employing a computer code called BOXITREE. Under appropriate conditions,
crystals were found to form layered systems. The system's structural phase
transitions, including transitions between crystals with differing numbers of
layers and the same number of layers but different intralayer structures, were
investigated and found to agree with previous theoretical and experimental
research results. One- to two-layer transitions were examined in detail and
shown to start at the point where the out-of-plane lattice instability appears.
The resulting three layer system caused by this instability was observed at the
center of the system. Finally, growth rates for this out-of-plane lattice
instability were obtained using the BOXITREE simulation with these results
shown to agree with those obtained from analytical theory.


title: Fast growing double tearing modes in a tokamak plasma

abstract:
  Configurations with nearby multiple resonant surfaces have broad spectra of
linearly unstable coupled tearing modes with dominant high poloidal mode
numbers m. This was recently shown for the case of multiple q = 1 resonances
[Bierwage et al., Phys. Rev. Lett. 94 (6), 65001 (2005)]. In the present work,
similar behavior is found for double tearing modes (DTM) on resonant surfaces
with q >= 1. A detailed analysis of linear instability characteristics of DTMs
with various mode numbers m is performed using numerical simulations. The mode
structures and dispersion relations for linearly unstable modes are calculated.
Comparisons between low- and higher-m modes are carried out, and the roles of
the inter-resonance distance and of the magnetic Reynolds number S_Hp are
investigated. High-m modes are found to be destabilized when the distance
between the resonant surfaces is small. They dominate over low-m modes in a
wide range of S_Hp, including regimes relevant for tokamak operation. These
results may be readily applied to configurations with more than two resonant
surfaces.


title: Images in Christmas Balls

abstract:
  We describe light-reflection properties of spherically curved mirrors, like
balls in the Christmas tree. In particular, we study the position of the image
which is formed somewhere beyond the surface of a spherical mirror, when an eye
observes the image of a pointlike light source. The considered problem,
originally posed by Abu Ali Hasan Ibn al-Haitham -- alias Alhazen -- more than
a millennium ago, turned out to have the now well known analytic solution of a
biquadratic equation, being still of great relevance, e.g. for the
aberration-free construction of telescopes. We do not attempt to perform an
exhaustive survey of the rich historical and engineering literature on the
subject, but develop a simple pedagogical approach to the issue, which we
believe to be of continuing interest in view of its maltreating in many
high-school textbooks.


title:
Interaction between incoherent light beams propagating in excited atomic
  hydrogen; applications in astrophysics

abstract:
  While it is generally assumed that several light beams propagate
independently in a refracting medium, the exception of laser beams may be
extended to usual time-incoherent light provided that conditions of
space-coherence are fulfilled. Very few molecules have convenient properties,
the simplest one being atomic hydrogen in 2S and 2P states (called H* here).
  The interaction increases the entropy of a set of beams without a permanent
excitation of H*, a loss of energy by a beam having a high Planck's temperature
producing a decrease of its frequency, and the thermal radiation getting
energy.
  Atomic hydrogen in its ground state is pumped to H* by Lyman alpha
absorptions, producing a redshift of the light. The combination of the Lyman
absorptions and the redshifts they produce, induce oscillations which generate
a spectrum in which the lines deduce from each other by relative frequency
shifts which are products of an integer by a constant z_b=0.062.
  These purely physical results may be applied in astrophysics, searching where
H* may appear. In particular, the computed spectra of the accreting neutron
stars, remarkably identical to the spectra of the quasars, may explain that
these stars seem never observed. The too high frequencies of the radio signals
from the Pioneer probes may result from a transfer of energy from the solar
light allowed by a cooling of the solar wind able to produce H*. A similar
transfer to the CMB may explain its anisotropy bound to the ecliptic.


title:
Macroscopic coherence effects in a mesoscopic system: Weak localization
  of thin silver films in an undergraduate lab

abstract:
  We present an undergraduate lab that investigates weak localization in thin
silver films. The films prepared in our lab have thickness, $a$, between 60-200
\AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing
length for electrons, $L_{\phi}$, exceeds the thickness of the film ($L_{\phi}
\gg a$), and the films are then quasi-2D in nature. In this situation, theory
predicts specific corrections to the Drude conductivity due to coherent
interference between conducting electrons' wavefunctions, a macroscopically
observable effect known as weak localization. This correction can be destroyed
with the application of a magnetic field, and the resulting magnetoresistance
curve provides information about electron transport in the film. This lab is
suitable for Junior or Senior level students in an advanced undergraduate lab
course.


title: Creating chaos and the Life

abstract:
  In this short report the first attempt of a new approach to the still
mysterious phenomenon of the life, and its peak, the human being, is presented
from the view point of the natural sciences, i.e. of the physics in the broad
sense of the word. This idea has come to my mind about 10 years ago when doing
a completely different problem I suddenly have noticed to my surprise (see [1],
p.20) a wonderful relation between a very complicated human (physical)
conception {\it creation} and the relatively simple mathematical theorem due to
Alekseev - Brudno (see for instance [2]) in an almost unknown for physicists
field of the so-called {\it symbolic dynamics} and {\it algorithmic chaos},
which one I have immediately christen {\it the creating chaos}.


title: Generalized Set of Boussinesq equations for Surf Zone Region

abstract:
  In this report, generalized wave breaking equations are developed using three
dimensional fully nonlinear extended Boussinesq equations to encompass
rotational dynamics in wave breaking zone. The derivation for vorticity
distributions are developed from Reynold based stress equations.


title:
Devils staircase like behavior of the range of random time series
  associated with the tangled nature of evolution

abstract:
  We present empirical evidence that the range of random time series associated
with the tangled nature model of evolution exhibits a devils staircase like
behavior characterized by logarithmic trend and the universal multi-affine
spectrum of scaling exponents xi_c of q leq q_c moments of q-order
height-height correlations, whereas for q > q_c the moments behaves
logarithmically.


title: On "gauge renormalization" in classical electrodynamics

abstract:
  In this paper we pay attention to the inconsistency in the derivation of the
symmetric electromagnetic energy-momentum tensor for a system of charged
particles from its canonical form, when the homogeneous Maxwell equations are
applied to the symmetrizing gauge transformation, while the non-homogeneous
Maxwell equations are used to obtain the motional equation. Applying the
appropriate non-homogeneous Maxwell equation to both operations, we have
revealed an additional symmetric term in the tensor, named as "compensating
term". Analyzing the structure of this "compensating term", we suggested a
method of "gauge renormalization, which allows transforming the divergent terms
of classical electrodynamics (infinite self-force, self-energy and
self-momentum) to converging integrals. The motional equation obtained for a
non-radiating charged particle does not contain its self-force, and the mass
parameter includes the sum of mechanical and electromagnetic masses. The
motional equation for a radiating particle also contains the sum of mechanical
and electromagnetic masses, and does not yield any "runaway solutions". It has
been shown that the energy flux in a free electromagnetic field is guided by
the Poynting vector, whereas the energy flux in a bound EM field is described
by the generalized Umov vector, defined in the paper. The problem of "Poincare
stresses" is also examined. It has been shown that the presence of the
"compensating term" in the electromagnetic energy-momentum tensor allows a
solution of the "4/3 problem", where the total observable mass of the electron
is completely determined by the Poincare stresses and hence the conventional
relativistic relationship between the energy and momentum is recovered.


title: Systematic analysis of group identification in stock markets

abstract:
  We propose improved methods to identify stock groups using the correlation
matrix of stock price changes. By filtering out the marketwide effect and the
random noise, we construct the correlation matrix of stock groups in which
nontrivial high correlations between stocks are found. Using the filtered
correlation matrix, we successfully identify the multiple stock groups without
any extra knowledge of the stocks by the optimization of the matrix
representation and the percolation approach to the correlation-based network of
stocks. These methods drastically reduce the ambiguities while finding stock
groups using the eigenvectors of the correlation matrix.


title: On existence of resistive magnetohydrodynamic equilibria

abstract:
  A necessary condition for existence of general dissipative
magnetohydrodynamic equilibria is derived. The ingredients of the derivation
are Ohm's law and the existence of magnetic surfaces, only in the sense of KAM
theorem. All other equations describing the system matter exclusively for the
evaluation of the condition in a concrete case.


title: Towards a New Democracy: Consensus Through Quantum Parliament

abstract:
  We compare different actual forms of democracy and analyse in which way they
are variations of a 'natural consensus decision process'. We analyse how
'consensus decision followed by majority voting' is open to 'false play' by the
majority, and investigate how other types of false play appear in alternative
types of democratic decision procedures. We introduce the combined notion of
'quantum parliament' and 'quantum decision procedure', and prove it to be the
only one, when applied after consensus decision, that is immune to false play.


title:
Little Black Holes as Dark Matter Candidates with Feasible Cosmic and
  Terrestrial Interactions

abstract:
  Little black holes (LBH) contribute to the accelerated expansion of the
Universe, and interact with stars, neutron stars, and planets. A range of
proposals are reviewed in which LBH are considered to be a component of dark
matter/dark energy. A LBH is a candidate for the 1908 devastation of Tungus
Siberia, as important LBH interactions were overlooked. LBH passing through
neutron star pulsars are capable of causing a change in. Energy input due to
the passage of LBH through the earth, sun, and neutron stars is examined to
determine if they could initiate tremors and quakes in such bodies. In
encounters with the earth.s atmosphere, LBH can manifest themselves as the core
energy source of ball lightning (BL). Relating the LBH incidence rate on earth
to BL occurrence has the potential of shedding light on the distribution of LBH
in the universe, and their velocities relative to the earth. Most BL features
can be explained by a testable LBH model. The total number of degrees of
freedom of a d-dimensional body in n-space is derived so that equipartition of
energy may be applied in the early universe. Blackbody and Hawking radiation
are generalized to n-space. The entropy of LBH and of the universe are
examined. The largest possible attractive force, repulsive force, and
luminosity in nature are considered in the context of LBH. A question is raised
as to whether the Planck scale is truly fundamental. The gravitational fine
structure constant is re-examined.


title: Performance of the LiF-TEA Ring Imaging Cherenkov Detector at CLEO

abstract:
  We describe the particle identification capability of the CLEO RICH system.
This system consists of a 1 cm thick LiF radiator coupled to a photon detector
that uses wire proportional chambers filled with a mixture of CH$_4$ and TEA.
We discuss the yield of photoelectrons observed per ring and the angular
resolution. We show the efficiencies achieved for particle identification and
the associated fake rates from data collected with both CLEO III and CLEO-c
detectors. Finally we show examples of the particle separation ability which is
excellent for both CLEO III and CLEO-c data.


title: A New Knot Invariant

abstract:
  A polynomial is presented that models a topological knot in a unique manner.
It distinguishes all types of knots including the orientation and has a group
theory interpretation. The topologies may be labeled via a number, which upon a
base 2 expansion generate the polynomial; the equivalent numbers via
Reidemeister moves are grouped into a superset polynomial with coefficients
labeling the equivalent knots.


title: On the crystal structure of lithium peroxide, Li2O2

abstract:
  The two published lithium peroxide structures, both ascribed to the hexagonal
P -6 space group, were subjected to reinterpretation and another more symmetric
structure, now belonging to the P 63/m m c space group, was found. Detailed
density-functional quantum mechanical calculations and crystal structure
optimisations were carried out on both structures and the energetic arguments
obtained therewith helped to rule out one of them.


title: Stability of Rotating Viscous and Inviscid flows

abstract:
  Flow instability and turbulent transition can be well explained using a new
proposed theory--Energy gradient theory [1]. In this theory, the stability of a
flow depends on the relative magnitude of energy gradient in streamwise
direction and that in transverse direction, if there is no work input. In this
note, it is shown based on the energy gradient theory that inviscid non-uniform
flow is unstable if the energy in transverse direction is not constant. This
new finding breaks the classical linear theory from Rayleigh that inviscid flow
is unstable if the velocity profile has an inflection point in parallel flows
and inviscid flow is stable if the velocity profile has no inflection point in
parallel flow. Then, stability of rotating viscous and inviscid flows is
studied, and two examples of rotating flows (rotating rigid body motion and
free vortex motion) are shown, respectively.


title: Ettore Majorana's course on Theoretical Physics: a recent discovery

abstract:
  We analyze in some detail the course of Theoretical Physics held by Ettore
Majorana at the University of Naples in 1938, just before his mysterious
disappearance. In particular we present the recently discovered "Moreno Paper",
where all the lecture notes are reported. Six of these lectures are not present
in the collection of the original manuscripts conserved at the Domus Galilaeana
in Pisa, consisting of only ten lectures.


title: Heider Balance in Human Networks

abstract:
  Recently, a continuous dynamics was proposed to simulate dynamics of
interpersonal relations in a society represented by a fully connected graph.
Final state of such a society was found to be identical with the so-called
Heider balance (HB), where the society is divided into two mutually hostile
groups. In the continuous model, a polarization of opinions was found in HB.
Here we demonstrate that the polarization occurs also in Barabasi-Albert
networks, where the Heider balance is not necessarily present. In the second
part of this work we demonstrate the results of our formalism, when applied to
reference examples: the Southern women and the Zachary club.


title: Semiconductor Thermistors

abstract:
  Semiconductor thermistors operating in the variable range hopping conduction
regime have been used in thermal detectors of all kinds for more than fifty
years. Their use in sensitive bolometers for infrared astronomy was a highly
developed empirical art even before the basic physics of the conduction
mechanism was understood. Today we are gradually obtaining a better
understanding of these devices, and with improvements in fabrication
technologies thermometers can now be designed and built with predictable
characteristics. There are still surprises, however, and it is clear that the
theory of their operation is not yet complete. In this chapter we give an
overview of the basic operation of doped semiconductor thermometers, outline
performance considerations, give references for empirical design and
performance data, and discuss fabrication issues.


title: Aggregation in Charged Nano Suspensions

abstract:
  In order to control aggregation phenomena in suspensions of nanoparticles,
one often charges the particles electrically, e.g. by triboelectric charging.
Stabilization of suspensions against aggregation of particles is an important
issue, which may be realized by monopolar charging, where particles repel each
other. Contrarily, bipolar charging may be used in coating processes, where
smaller particles of one material coat larger particles of another material.
When the two particle fractions are charged oppositely, aggregation between
equally charged particles is hindered whereas aggregation between oppositely
charged particles is preferred, thereby improving the coating process. We study
various aspects of these two situations by theoretical investigations and
computer simulations.


title: 2D Detectors for Particle Physics and for Imaging Applications

abstract:
  The demands on detectors for particle detection as well as for medical and
astronomical X-ray imaging are continuously pushing the development of novel
pixel detectors. The state of the art in pixel detector technology to date are
hybrid pixel detectors in which sensor and read-out integrated circuits are
processed on different substrates and connected via high density interconnect
structures. While these detectors are technologically mastered such that large
scale particle detectors can be and are being built, the demands for improved
performance for the next generation particle detectors ask for the development
of monolithic or semi-monolithic approaches. Given the fact that the demands
for medical imaging are different in some key aspects, developments for these
applications, which started as particle physics spin-off, are becomming rather
independent. New approaches are leading to novel signal processing concepts and
interconnect technologies to satisfy the need for very high dynamic range and
large area detectors. The present state in hybrid and (semi-)monolithic pixel
detector development and their different approaches for particle physics and
imaging application is reviewed.


title:
Diffraction Problem and Amplitudes-Phases Dispersion of Eigen Fields of
  a Nonlinear Dielectric Layer

abstract:
  The open nonlinear electrodynamic system - nonlinear transverse
non-homogeneous dielectric layer, is an example of inorganic system having the
properties of self-organization, peculiar to biological systems. The necessary
precondition of effects of self-organization is the presence of a flow of
energy acting in system from an external source, due to which the system gets
ability to independent formation of structures. On an example of the transverse
non-homogeneous, isotropic, nonmagnetic, linearly polarized, nonlinear (a
Kerr-like dielectric nonlinearity) dielectric layer the constructive approach
of the analysis of amplitudes-phases dispersion of eigen oscillation-wave
fields of nonlinear object are shown. The norm of an eigen field is defined
from the solution of a diffraction problem of plane waves or excitation of
point or compact source of a nonlinear layer.


title: Melting Transition of Directly-Linked Gold Nanoparticle DNA Assembly

abstract:
  DNA melting and hybridization is a fundamental biological process as well as
a crucial step in many modern biotechnology applications. DNA confined on
surfaces exhibits different behavior from that in free solutions. The system of
DNA-capped gold nanoparticles exhibits unique phase transitions and represents
a new class of complex fluids. Depending on the sequence of the DNA, particles
can be linked to each other through direct complementary DNA sequences or via a
``linker'' DNA whose sequence is complementary to the sequence attached to the
gold nanoparticles. We observed different melting transitions for these two
distinct systems.


title:
Orientational instabilities in nematics with weak anchoring under
  combined action of steady flow and external fields

abstract:
  We study the homogeneous and the spatially periodic instabilities in a
nematic liquid crystal layer subjected to steady plane {\em Couette} or {\em
Poiseuille} flow. The initial director orientation is perpendicular to the flow
plane. Weak anchoring at the confining plates and the influence of the external
{\em electric} and/or {\em magnetic} field are taken into account. Approximate
expressions for the critical shear rate are presented and compared with
semi-analytical solutions in case of Couette flow and numerical solutions of
the full set of nematodynamic equations for Poiseuille flow. In particular the
dependence of the type of instability and the threshold on the azimuthal and
the polar anchoring strength and external fields is analysed.


title: Electronic structure of clusters (LiBC)_n: n=1, 2, 4

abstract:
  A crystalline form of LiBC is known which has been predicted to be
superconducting, with a Tc comparable to that of MgB_2. In both compounds,
superconductivity is enhanced by the presence of two electronic bands, one of
which is close to a dimensional crossover. Here, we take a quantum chemical
approach, and investigate the structural and electronic properties of small
clusters (LiBC)_n (n=1-4). With increasing cluster size, we find that several
properties of crystalline LiBC evolve naturally from the corresponding
properties of the clusters. In particular, one may recognize the origin of the
solid bilayered structure, typical of magnesium diboride, and the character of
the electronic sigma-band, arising from the overlap of the atomic orbitals in
the in-plane BC rings. Two aspects especially emphasized are (a) the HOMO-LUMO
gap as function of n and (b) the role of different spin multiplicity.


title:
Polarization modulation instability in liquid crystals with spontaneous
  chiral symmetry breaking

abstract:
  We present a theoretical model which describes the polarization modulated and
layer undulated structure of the B7 phase and gives the phase transition from
the synclinic ferroelectric B2 phase to the B7 phase as observed
experimentally. The system is driven into the modulated phase due to the
coupling between the polarization splay and the tilt of the molecules with
respect to the smectic layer normal. The modulation wavelength and the width of
the wall between two domains of opposite chirality are estimated.


title: Navier-Stokes' equations for radial and tangential accelerations

abstract:
  The Navier-Stokes equations are considered by the use of the method of
Lagrangians with covariant derivatives (MLCD) over spaces with affine
connections and metrics. It is shown that the Euler-Lagrange equations appear
as sufficient conditions for the existence of solutions of the Navier-Stokes
equations over (pseudo) Euclidean and (pseudo) Riemannian spaces without
torsion. By means of the corresponding (n-1)+ 1 projective formalism the
Navier-Stokes equations for radial and tangential accelerations are found.


title: Questions Concerning Schwarzschild's Solution of Einstein's Equations

abstract:
  Now that an English translation of Schwarzschild's original work exists, that
work has become accessible to more people. Here his original solution to the
Einstein field equations is examined and it is noted that it does not contain
the mathematical singularity normally associated with the existence of a black
hole. Einstein's own views on this subject are considered also and it is seen
that, at the very least, grave questions exist over the possible existence of
these somewhat esoteric stellar objects.


title: Noise sensitivity of an atomic velocity sensor

abstract:
  We use Bloch oscillations to accelerate coherently Rubidium atoms. The
variation of the velocity induced by this acceleration is an integer number
times the recoil velocity due to the absorption of one photon. The measurement
of the velocity variation is achieved using two velocity selective Raman
pi-pulses: the first pulse transfers atoms from the hyperfine state 5S1/2 |F=2,
mF=0> to 5S1/2, |F=1, mF = 0> into a narrow velocity class. After the
acceleration of this selected atomic slice, we apply the second Raman pulse to
bring the resonant atoms back to the initial state 5S1/2, |F=2, mF = 0>. The
populations in (F=1 and F=2) are measured separately by using a one-dimensional
time-of-flight technique. To plot the final velocity distribution we repeat
this procedure by scanning the Raman beam frequency of the second pulse. This
two pi-pulses system constitutes then a velocity sensor. Any noise in the
relative phase shift of the Raman beams induces an error in the measured
velocity. In this paper we present a theoretical and an experimental analysis
of this velocity sensor, which take into account the phase fluctuations during
the Raman pulses.


title: Gel Electrophoresis of DNA Knots in Weak and Strong Electric Fields

abstract:
  Gel electrophoresis allows to separate knotted DNA (nicked circular) of equal
length according to the knot type. At low electric fields, complex knots being
more compact, drift faster than simpler knots. Recent experiments have shown
that the drift velocity dependence on the knot type is inverted when changing
from low to high electric fields. We present a computer simulation on a lattice
of a closed, knotted, charged DNA chain drifting in an external electric field
in a topologically restricted medium. Using a simple Monte Carlo algorithm, the
dependence of the electrophoretic migration of the DNA molecules on the type of
knot and on the electric field intensity was investigated. The results are in
qualitative agreement with electrophoretic experiments done under conditions of
low and high electric fields: especially the inversion of the behavior from low
to high electric field could be reproduced. The knot topology imposes on the
problem the constrain of self-avoidance, which is the final cause of the
observed behavior in strong electric field.


title: Ultra-low voltage resonant tunnelling diode electroabsorption modulator

abstract:
  Embedding a double barrier resonant tunnelling diode (RTD) in an unipolar
InGaAlAs optical waveguide gives rise to a very low driving voltage
electroabsorption modulator (EAM) at optical wavelengths around 1550 nm. The
presence of the RTD within the waveguide core introduces high non-linearity and
negative differential resistance in the current-voltage (I-V) characteristic of
the waveguide. This makes the electric field distribution across the waveguide
core strongly dependent on the bias voltage: when the current decreases from
the peak to the valley there is an increase of the electric field across the
depleted core. The electric field enhancement in the core-depleted layer causes
the Franz-Keldysh absorption band-edge to red shift, which is responsible for
the electroabsorption effect. High frequency ac signals as low as 100 mV can
induce electric field high speed switching, producing substantial light
modulation (up to 15 dB) at photon energies slightly lower than the waveguide
core band-gap energy. The key difference between this device and conventional
p-i-n EAMs is that the tunnelling characteristics of the RTD are employed to
switch the electric field across the core depleted region; the RTDEAM has in
essence an integrated electronic amplifier and therefore requires considerably
less switching power.


title:
Public transport systems in Poland: from Bialystok to Zielona Gora by
  bus and tram using universal statistics of complex networks

abstract:
  We have examined a topology of 21 public transport networks in Poland. Our
data exhibit several universal features in considered systems when they are
analyzed from the point of view of evolving networks. Depending on the assumed
definition of a network topology the degree distribution can follow a power law
p(k) ~ k^(-\gamma) or can be described by an exponential function p(k)
\~exp(-\alpha k). In the first case one observes that mean distances between
two nodes are a linear function of logarithms of their degrees product.


title: Analysis of band-gap formation in squashed arm-chair CNT

abstract:
  The electronic properties of squashed arm-chair carbon nanotubes are modeled
using constraint free density functional tight binding molecular dynamics
simulations. Independent from CNT diameter, squashing path can be divided into
{\it three} regimes. In the first regime, the nanotube deforms with negligible
force. In the second one, there is significantly more resistance to squashing
with the force being $\sim 40-100$ nN/per CNT unit cell. In the last regime,
the CNT looses its hexagonal structure resulting in force drop-off followed by
substantial force enhancement upon squashing. We compute the change in band-gap
as a function of squashing and our main results are: (i) A band-gap initially
opens due to interaction between atoms at the top and bottom sides of CNT. The
$\pi-$orbital approximation is successful in modeling the band-gap opening at
this stage. (ii) In the second regime of squashing, large $\pi-\sigma$
interaction at the edges becomes important, which can lead to band-gap
oscillation. (iii) Contrary to a common perception, nanotubes with broken
mirror symmetry can have {\it zero} band-gap. (iv) All armchair nanotubes
become metallic in the third regime of squashing. Finally, we discuss both
differences and similarities obtained from the tight binding and density
functional approaches.


title: Microscopic and Macroscopic Simulation of Competition between Languages

abstract:
  The similarity of the evolution of human languages (or alphabets, bird songs,
>...) to biological evolution of species is utilized to study with up to $10^9$
people the rise and fall of languages either by macroscopic differential
equations similar to biological Lotka-Volterra equation, or by microscopic
Monte Carlo simulations of bit-strings incorporating the birth, maturity, and
death of every individual. For our bit-string model, depending on parameters
either one language comprises the majority of speakers (dominance), or the
population splits into many languages having in order of magnitude the same
number of speakers (fragmentation); in the latter case the size distribution is
log-normal, with upward deviations for small sizes, just as in reality for
human languages. On a lattice two different dominating languages can coexist in
neighbouring regions, without being favoured or disfavoured by different
status. We deal with modifications and competition for existing languages, not
with the evolution or learning of one language.


title: La aventura de la fisica

abstract:
  Con la intencion de realizar una pequena aportacion en la celebracion del ano
2005, proclamado como Ano Internacional de la Fisica, el cuerpo academico de
Particulas, Campos y Astrofisica de la Universidad Autonoma de Zacatecas
presenta un pequeno esbozo de los trabajos realizados por Einstein en 1905, asi
como un conjunto de ensayos sobre electrodinamica clasica, el grupo de Lorentz,
neutrinos y relatividad general, todos estos relacionados con los temas de
investigacion que realizamos.
  -----
  The Astrophysics, Particles and Fields Unit of the Zacatecas University
presents a brief essay of the Einstein historical works (1905) and a set of
essays on modern development in the classical electrodynamics, the Lorentz
group, neutrinos and the general relativity. The aim is to contribute to the
special issue of the UAEM Journal, which is dedicated to the International Year
of Physics. The corresponding topics of the article are related to the research
work of the authors.


title:
Measurement of the electric fluctuation spectrum of magnetohydrodynamic
  turbulence

abstract:
  Magnetohydrodynamic (MHD) turbulence in the solar wind is observed to show
the spectral behavior of classical Kolmogorov fluid turbulence over an inertial
subrange and departures from this at short wavelengths, where energy should be
dissipated. Here we present the first measurements of the electric field
fluctuation spectrum over the inertial and dissipative wavenumber ranges in a
$\beta \gtrsim 1$ plasma. The $k^{-5/3}$ inertial subrange is observed and
agrees strikingly with the magnetic fluctuation spectrum; the wave phase speed
in this regime is shown to be consistent with the Alfv\'en speed. At smaller
wavelengths $k \rho_i \geq 1$ the electric spectrum is softer and is consistent
with the expected dispersion relation of short-wavelength kinetic Alfv\'en
waves. Kinetic Alfv\'en waves damp on the solar wind ions and electrons and may
act to isotropize them. This effect may explain the fluid-like nature of the
solar wind.


title:
Direct frequency comb measurements of absolute optical frequencies and
  population transfer dynamics

abstract:
  A phase-stabilized femtosecond laser comb is directly used for
high-resolution spectroscopy and absolute optical frequency measurements of
one- and two-photon transitions in laser-cooled \rb atoms. Absolute atomic
transition frequencies, such as the 5S$_{1/2}$ F=2 \ra 7S$_{1/2}$ F"=2
two-photon resonance measured at 788 794 768 921(44) kHz, are determined
without \textit{a priori} knowledge about their values. Detailed dynamics of
population transfer driven by a sequence of pulses are uncovered and taken into
account for the measurement of the 5P states via resonantly enhanced two-photon
transitions.


title: Random trading market: Drawbacks and a realistic modification

abstract:
  We point out some major drawbacks in random trading market models and propose
a realistic modification which overcomes such drawbacks through `sensible
trading'. We apply such trading policy in different situations: a) Agents with
zero saving factor b) with constant saving factor and c) with random saving
factor --in all the cases the richer agents seem to follow power laws in terms
of their wealth (money) distribution which support Pareto's observation.


title:
Thermodynamics and Relativity, A Condensed Explanation of their Close
  Connection

abstract:
  Although its practical efficiency is unquestionable, it is well known that
thermodynamics presents conceptual difficulties from the theoretical point of
view. It is shown that the problem comes from an imperfect compatibility
between the first law and the second law. The solution suggested consists of
connecting thermodynamics with relativity (and, by extension, with gravitation)
through the Einstein mass-energy relation.


title:
Renormalization Theory in the Electrostatic and Vector Potential
  Calculation

abstract:
  In this work we attempt to show in a clear and simple manner the fundamental
ideas of the Renormalization Theory. With that intention we use two well-known
problems of the Physic and Engeneering undergraduate students, the calculation
of the electrostatic and vector potential of a infinite line charge density and
current, respectively. We still employ different regularization methods
(cut-off, dimensional and zeta function) and the arising of the scale parameter
is consider.


title:
On the interaction between a current density and a vector potential:
  Amp\`{e}re force, Helmholtz tension and Larmor torque

abstract:
  Several mathematical formulae are used nowadays in order to compute a
magnetic torque. We demonstrate that its more general expression is the
vectorial product of the current density with the vector potential. We
associate this Larmor's torque with Amp\`{e}re's force and more specifically
with Helmholtz mechanical tension, which is at the origin of the longitudinal
stresses in "open" circuits carrying current. We show that Amp\`{e}re's force
enters into the realm of Newtonian Electrodynamics and we explain the absence
of contradiction with special relativity. Hence, we provide for the first time
a theoretical basis for the numerous experiments, which claimed to have
demonstrated the existence of the longitudinal mechanical tension starting with
the historical Amp\`{e}re's hairpin demonstration and the more modern ones of
the Graneaus and of Saumont.


title: Elastic lever arm model for myosin V

abstract:
  We present a mechanochemical model for myosin V, a two-headed processive
motor protein. We derive the properties of a dimer from those of an individual
head, which we model both with a 4-state cycle (detached, attached with ADP.Pi,
attached with ADP and attached without nucleotide) and alternatively with a
5-state cycle (where the power stroke is not tightly coupled to the phosphate
release). In each state the lever arm leaves the head at a different, but
fixed, angle. The lever arm itself is described as an elastic rod. The chemical
cycles of both heads are coordinated exclusively by the mechanical connection
between the two lever arms. The model explains head coordination by showing
that the lead head only binds to actin after the power stroke in the trail head
and that it only undergoes its power stroke after the trail head unbinds from
actin. Both models (4- and 5-state) reproduce the observed hand-over-hand
motion and fit the measured force-velocity relations. The main difference
between the two models concerns the load dependence of the run length, which is
much weaker in the 5-state model. We show how systematic processivity
measurement under varying conditions could be used to distinguish between both
models and to determine the kinetic parameters.


title: Masses and Interactions in Quantum Chromodynamics

abstract:
  Correlations of composites corresponding to baryons and mesons are composed
within the derivative expansion. The expansion in energy scales permits a
quantitative, algebraic description at various energy scales in QCD. The masses
in QCD are derived utilizing a proposed line interaction, with explicit checks
of the masses up to the baryonic decuplet.


title: Accuracy of an Atomic Microwave Power Standard

abstract:
  We have built an atomic microwave power standard based on the electromagnetic
interaction with laser-cooled atoms. The atoms traversed a waveguide
transmission line, and under the effect of the radiation, the internal state
populations underwent a Rabi flopping oscillation. Measurement of the
oscillation frequency allowed the determination of the incident microwave
power. As many of 60 oscillations were observed over a dynamic range of 20 dB
and the standard deviation of the measurements was about 0.02%. The measured
frequency was compared to a calculated one and an agreement of 1.3% with an
uncertainty of 5% (rectangular) was found.


title: Realizing a stable magnetic double-well potential on an atom chip

abstract:
  We discuss design considerations and the realization of a magnetic
double-well potential on an atom chip using current-carrying wires. Stability
requirements for the trapping potential lead to a typical size of order microns
for such a device. We also present experiments using the device to manipulate
cold, trapped atoms.


title: Channeling as a method of making nanosized beams of particles

abstract:
  Particle channeling in a bent crystal lattice has led to an efficient
instrument for beam steering at accelerators, demonstrated from MeV to TeV
energies. In particular, crystal focusing of high energy protons to micron size
has been demonstrated at IHEP with the results well in match with Lindhard
(critical angle) prediction. Channeling in crystal microstructures has been
proposed as a unique source of a microbeam of high-energy particles. Channeling
in nanostructures (single-wall and multi-wall nanotubes) offers the
opportunities to produce ion beams on nanoscale. Particles channeled in a
nanotube (with typical diameter of about 1 nanometer) are trapped in two
dimensions and can be steered (deflected, focused) with the efficiency similar
to that of crystal channeling or better. This technique has been a subject of
computer simulations, with experimental efforts under way in several high
energy labs, including IHEP. We present the theoretical outlook for making
channeling-based nanoscale ion beams and report the experience with
crystal-focused microscale proton beams.


title:
DNA-based Artificial Nanostructures: Fabrication, Properties, and
  Applications

abstract:
  Table of Content
  1. Introduction
  2. DNA fundamentals
  3. Attachment of DNA to surface
  4. Fabrication of nanostructures using DNA
  4.1 Nanostructures of pure DNA
  4.2 DNA-based assembly of metal nanoparticles
  4.3 Construction of semiconductor particle arrays using DNA
  4.4 DNA-directed nanowires
  4.5 DNA-functionalized carbon nanotubes
  4.6 Field-transistor based on DNA
  4.7 Nanofabrication using artificial DNA
  5. DNA-based nanostructures as biosensors
  6. Properties of DNA-linked gold nanoparticles
  6.1 Aggregation of DNA-modified gold nanoparticles
  6.2 Melting of DNA-linked gold nanoparticle aggregations
  6.3 Effects of external variables on the melting properties
  7. Conclusion


title: Sociophysics Simulations II: Opinion Dynamics

abstract:
  Individuals have opinions but can change them under the influence of others.
The recent models of Sznajd (missionaries), of Deffuant et al. (negotiators),
and of Krause and Hegselmann (opportunists) are reviewed here, while the voter
and Ising models, Galam's majority rule and the Axelrod multicultural model
were dealt with by other lecturers at this 8th Granada Seminar.


title: Comment on "New Methods for Old Coulomb Few-Body Problems"

abstract:
  In this Comment on the above mentioned paper by F. E. Harris, A. M. Frolov,
and V. H. Smith, we briefly review our contributions to development of new
methods for solution of the Coulomb four-body problem. We show that our
research group, headed by Prof. T. K. Rebane, had a priority in using the fully
correlated exponential basis for variational calculations of four-body systems.
We also draw attention to the fact that our group subsequently implemented a
more advanced method, which uses highly efficient exponential-trigonometric
basis functions for solution of the same problem.


title: Transverse Kinematics of Ion Stored in an Electrostatic Ion Beam Trap

abstract:
  We present experimental results, as well as numerical simulations, for the
transverse velocity distribution of ions stored in an electrostatic ion beam
trap. The measurements indicate that the transverse velocity spread is about 1%
of the longitudinal velocity, and that the ions fill the whole transverse
stable phase space. We also demonstrate that ion losses from the trap due to
multiple scattering with molecules from the residual gas is an important factor
limiting the lifetime of the beam.


title: Observation of 2nd band vortex solitons in 2D photonic lattices

abstract:
  We demonstrate second-band bright vortex-array solitons in photonic lattices.
This constitutes the first experimental observation of higher-band solitons in
any 2D periodic system. These solitons possess complex intensity and phase
structures, yet they can be excited by a simple highly-localized vortex-ring
beam. Finally, we show that the linear diffraction of such beams exhibits
preferential transport along the lattice axes.


title: Global Warming: some back-of-the-envelope calculations

abstract:
  We do several simple calculations and measurements in an effort to gain
understanding of global warming and the carbon cycle. Some conclusions are
interesting: (i) There has been global warming since the end of the "little ice
age" around 1700. There is no statistically significant evidence of
acceleration of global warming since 1940. (ii) The increase of CO_2 in the
atmosphere, beginning around 1940, accurately tracks the burning of fossil
fuels. Burning all of the remaining economically viable reserves of oil, gas
and coal over the next 150 years or so will approximately double the
pre-industrial atmospheric concentration of CO_2. The corresponding increase in
the average temperature, due to the greenhouse effect, is quite uncertain:
between 1.3 and 4.8K. This increase of temperature is (partially?) offset by
the increase of aerosols and deforestation. (iii) Ice core samples indicate
that the pre-historic CO_2 concentration and temperature are well correlated.
We conclude that changes in the temperatures of the oceans are probably the
cause of the changes of pre-historic atmospheric CO_2 concentration. (iv) Data
suggests that large volcanic explosions can trigger transitions from glacial to
interglacial climates. (v) Most of the carbon fixed by photosynthesis in the
Amazon basin returns to the atmosphere due to aerobic decay.


title: Realization of a Laser Cooled Microwave Power Standard

abstract:
  We demonstrate the feasibility of a novel microwave power standard based on
the electromagnetic interaction with laser-cooled atoms. Under the effect of
the radiation, the internal state populations undergo a Rabi flopping
oscillation. Measurement of the oscillation frequency allows the determination
of the electromagnetic field strength. The measurements are made over a dynamic
range of 18 dB and the standard deviation of the measurements is about 0.3%.
The field strength was linear with the Rabi frequency within the accuracy of
our measurements.


title: An open cavity formed with a photonic crystal of negative refraction

abstract:
  A novel open cavity formed by three 60-degree wedges of a photonic crystal
with negative effective index is designed and studied. The quality factor of
the open cavity can be larger than 2000. The influence of the interface
termination on the resonant frequency and the quality factor is studied.


title: A Millimeter-Wave Achromatic Half Wave Plate

abstract:
  We have constructed an achromatic half wave plate (AHWP) suitable for the
millimeter wavelength band. The AHWP was made from a stack of three sapphire
a-cut birefringent plates with the optical axes of the middle plate rotated by
50.5 degrees with respect to the aligned axes of the other plates. The measured
modulation efficiency of the AHWP at 110 GHz was $96 \pm 1.5$%. In contrast,
the modulation efficiency of a single sapphire plate of the same thickness was
$43 \pm 4$%. Both results are in close agreement with theoretical predictions.
The modulation efficiency of the AHWP was constant as a function of incidence
angles between 0 and 15 degrees. We discuss design parameters of an AHWP in the
context of astrophysical broad band polarimetry at the millimeter wavelength
band.


title:
A comparison between the styles Romanian and American students use to
  approach an E&M physics problem

abstract:
  Although Physics is the same worldwide, students belonging to different
learning systems as well as different cultural environments may develop
different styles of approaching and reasoning out Physics problems. In a first
experiment we compare student physics problem-solving styles between two
different student populations: a group of typical American students (from an
OSU calculus-based introductory course) and a group of Romanian students (from
a second-year class at Bucharest University). We discuss one of the problems
given in a short E&M survey, in which students from both populations were
presented with a point charge in a region containing a uniform magnetic field.
We asked students to determine the force on the charge for different initial
conditions. In a second experiment, three American physics students and three
Romanian physics students were given the same problem and were asked to explain
loudly their answer to each question. Their answers were tape-recorded.
Students' answers depend on an understanding of the Lorentz force and their
general knowledge from classical mechanics. Observed similarities and
differences in approach between these student groups are discussed, and our
study's results described.


title:
Cultural differences in answering physics questions: Could they arise
  from the difference between reasoning expected in answering exam questions in
  those cultures?

abstract:
  In many ways, the American learning system is unique in its reliance on
testing using multiple-choice questions. Learning in physics, as well as in any
other subject, is a context-dependent process. In this paper, I consider a
broader problem of where differences in understanding arise; often styles of
answering questions arise from the way the questions are posed. I speculate on
the long-run effects a multiple-choice based learning system might have on the
reasoning structure of the student compared to one based on more open-ended
questions. I present some differences in answer styles observed between two
populations of students, US students (mostly exposed to multiple-choice type
exams), and Romanian students (mostly exposed to open-end type exams). Finally,
I suggest some possible ways of checking whether my predictions have any
validity.


title: On the ratchet effect

abstract:
  While the dependence of the directed transport on each of the
ratchet-controlling parameters has been individually investigated
experimentally, theoretically, and numerically, there is still no general
criterion to apply to the whole set of these parameters to optimally control
directed transport in general systems. We report that, to optimally enhance
directed transport, there exists a universal force waveform which can be
understood as the result of two competing fundamental mechanisms: the increase
of the degree of breaking of symmetries and the decrease of the force impulse.
We demonstrate that this universal waveform explains all the previous
experimental, theoretical, and numerical results for a great diversity of
systems, including motor enzymes.


title:
A Common Market Measure for Libor and Pricing Caps, Floors and Swaps in
  a Field Theory of Forward Interest Rates

abstract:
  The main result of this paper that a martingale evolution can be chosen for
Libor such that all the Libor interest rates have a common market measure; the
drift is fixed such that each Libor has the martingale property. Libor is
described using a field theory model, and a common measure is seen to be emerge
naturally for such models. To elaborate how the martingale for the Libor
belongs to the general class of numeraire for the forward interest rates, two
other numeraire's are considered, namely the money market measure that makes
the evolution of the zero coupon bonds a martingale, and the forward measure
for which the forward bond price is a martingale. The price of an interest rate
cap is computed for all three numeraires, and is shown to be numeraire
invariant. Put-call parity is discussed in some detail and shown to emerge due
to some non-trivial properties of the numeraires. Some properties of swaps, and
their relation to caps and floors, are briefly discussed.


title: Tumor growth instability and the onset of invasion

abstract:
  Motivated by experimental observations, we develop a mathematical model of
chemotactically directed tumor growth. We present an analytical study of the
model as well as a numerical one. The mathematical analysis shows that: (i)
tumor cell proliferation by itself cannot generate the invasive branching
behaviour observed experimentally, (ii) heterotype chemotaxis provides an
instability mechanism that leads to the onset of tumor invasion and (iii)
homotype chemotaxis does not provide such an instability mechanism but enhances
the mean speed of the tumor surface. The numerical results not only support the
assumptions needed to perform the mathematical analysis but they also provide
evidence of (i), (ii) and (iii). Finally, both the analytical study and the
numerical work agree with the experimental phenomena.


title: Sociophysics Simulations IV: Hierarchies of Bonabeau et al

abstract:
  The model of Bonabeau et al explains social hierarchies as random: People
keep a memory of recent fights, and winners have a higher probability to win
again. The question of phase transition and the generalization from square
lattices to networks is reviewed here.


title: Symmetry in a Perturbed Optical System

abstract:
  This paper investigates the effects that perturbations to an optical system,
such as translations or rotations of the optical elements, have on the final
location where a light ray strikes a detector. Symmetry arguments are employed
to give selection rules for the combinations of those perturbations that can
affect the light ray. It is shown that a ``Transverse Parity'' can be assigned
to each type of perturbation and that only combinations with an overall odd
parity will produce an effect. Some examples of how these results can be
applied to undergraduate classroom or laboratory courses are given.


title: Time domain deBroglie wave interferometry along a magnetic guide

abstract:
  Time domain deBroglie wave interferometry [Cahn et al, Phys. Rev. Lett. 79,
784] is applied to Rb87 atoms in a magnetic guide. A standing wave light field
is carefully aligned along the guiding direction of the magnetic trapping
potential from a soft-ferromagnetic 4-foil structure. A sequence of two
standing wave pulses is applied to the magnetically trapped atoms. The
backscattered light at the atomic density grating revival time is collected and
detected via a heterodyning technique. In addition to the observed recoil
oscillations that fit the interferometer theory for atoms in free space, we
observe a decay of the interferometer contrast on a millisecond time scale with
unexpected millisecond-scale oscillations. We find that the oscillating decay
is explained by a residual variation of the linear trapping potential along the
standing wave direction.


title:
Variational analysis of self-focusing of intense ultrashort pulses in
  gases

abstract:
  By using perturbation theory we derive an expression for the electrical field
of a Gaussian laser pulse propagating in a gas medium. This expression is used
as a trial solution in a variational method to get quasianalytical solutions
for the width, intensity and self-focusing distance of ultrashort pulse. The
approximation gives an improved agreement with results of numerical simulations
for a broad range of values of the input power of the pulse than previous
analytical results available in the literature.


title: General students' misconceptions related to Electricity and Magnetism

abstract:
  Electromagnetism, being much less intuitive than mechanics, where a lot of
sources of misconceptions have been documented, has in addition to the common
sources of misconceptions borrowed from mechanics other sources related to the
abstract new concepts of electric and magnetic fields. This paper is the first
general overview of the most important documented misconceptions related to
E&M. New sources of misconceptions are also suggested. The shape of Lorentz
law, tempting analogies between magnetic and electric fields, the connection
between the Maxwell's equations and the derived laws (Ampere's law, the
Biot-Savart law, Faraday's law and the Coulomb's law for the electric forces)
and mathematics related misconceptions are among the suggested areas of
misconceptions. A possible explanation of some student E&M related
misconceptions using p-prims is given in the end of the paper.


title: Matter-antimatter asymmetry and chiral behavior in perturbed atom H

abstract:
  Recently, we showed that that band as well as line spectra, reveal a
left-right symmetry in 4- and 2-fermion systems. We now show how a
mass-conjugation explains the difference between atom- and antiatom-states in a
stable 2-unit charge Coulomb system. For the electron-proton system in natural
H, this difference (an anomaly) between states belonging to the hydrogen
(matter) and the antihydrogen (antimatter) anti-world is governed by number
2m(e)/m(H) = 0.0011. This is verified with the H-line spectrum. Classical
physics can describe the parity effects for matter-antimatter asymmetry. An
internal mass-conjugation (internal algebra) extends and generalizes Dirac's
fermion-antifermion symmetry and defies Einstein's Special Theory of Relativity
(STR).


title: Some comments on extreme value statistics

abstract:
  The question of whether extreme value statistics should be introduced into
courses for physics students has been broached recently. Here it is argued that
the topic should be taught but the many and varied physical applications should
be stressed; emphasis should not be confined purely to abstract theory.