title: Optimizing the Source Distribution in Fluid Mixing

abstract:
  A passive scalar is advected by a velocity field, with a nonuniform spatial
source that maintains concentration inhomogeneities. For example, the scalar
could be temperature with a source consisting of hot and cold spots, such that
the mean temperature is constant. Which source distributions are best mixed by
this velocity field? This question has a straightforward yet rich answer that
is relevant to real mixing problems. We use a multiscale measure of
steady-state enhancement to mixing and optimize it by a variational approach.
We then solve the resulting Euler--Lagrange equation for a perturbed uniform
flow and for simple cellular flows. The optimal source distributions have many
broad features that are as expected: they avoid stagnation points, favor
regions of fast flow, and their contours are aligned such that the flow blows
hot spots onto cold and vice versa. However, the detailed structure varies
widely with diffusivity and other problem parameters. Though these are model
problems, the optimization procedure is simple enough to be adapted to more
complex situations.


title: Interactions and dynamics in Li + Li_2 ultracold collisions

abstract:
  A potential energy surface for the lowest quartet electronic state of lithium
trimer is developed and used to study spin-polarized Li + Li_2 collisions at
ultralow kinetic energies. The potential energy surface allows barrierless atom
exchange reactions. Elastic and inelastic cross sections are calculated for
collisions involving a variety of rovibrational states of Li_2. Inelastic
collisions are responsible for trap loss in molecule production experiments.
Isotope effects and the sensitivity of the results to details of the potential
energy surface are investigated. It is found that for vibrationally excited
states the cross sections are only quite weakly dependent on details of the
potential energy surface.


title: Highly Confined Optical Modes in Nanoscale Metal-Dielectric Multilayers

abstract:
  We show that a stack of metal-dielectric nanolayers, in addition to the long-
and short-range plasmons, guides also an entire family of modes strongly
confined within the multilayer - the bulk plasmon modes. We propose the
classification scheme that reflects specific properties of these modes. We
report experimental verification of the bulk plasmon modes by measuring modal
indices in a structure made of three pairs of silica(29nm)/gold(25nm) layers.


title: Narrow-line phase-locked quantum cascade laser in the 9.2 micron range

abstract:
  We report on the operation of a 50 mW continuous wave quantum cascade laser
(QCL) in the 9.2 micrometer range, phase locked to a single mode CO2 laser with
a tunable frequency offset. The wide free running emission spectrum of the QCL
(3-5 MHz) is strongly narrowed down to the kHz range making it suitable for
high resolution molecular spectroscopy.


title:
The Intrinsic Electric Dipole Moment and the "Time-Space" Intrinsic
  Angular Momentum

abstract:
  In this paper it is found that the spin four-tensor $S^{ab}$ can be
decomposed into two 4-vectors, the usual ``space-space'' intrinsic angular
momentum $S^{a}$ and a new one, the ``time-space'' intrinsic angular momentum
$Z^{a}$, which are both equally well physical quantities. It is shown that an
electric dipole moment (EDM) of a fundamental particle, as a four-dimensional
geometric quantity, is determined by $Z^{a}$ and not, as generally accepted, by
the spin $\mathbf{S}$. Also it is proved that neither the $T$ inversion nor the
$P$ inversion are good symmetries in the 4D spacetime. In our geometric
approach only the world parity $W$, $% x^{a}\to -x^{a}$, is well-defined in the
4D spacetime. The consequences for elementary particle theories and experiments
that search for EDM are briefly discussed.


title:
Fluctuation-Enhanced Sensing of Molecules with Biased Carbon Nanotubes,
  or Nanowires, and Adsorption-Desorption Fluctuations

abstract: A new nanoscale device for fluctuation-enhanced sensing is proposed.


title: Research News -- Meson scattering at high precision

abstract:
  A fascinating new generation of experiments has determined certain meson
scattering parameters at high precision. A confluence of highly sophisticated
theory as well as new experimental ideas have led to this state of affairs,
which sheds important light on the properties of the strong interactions. A
brief review of the experiments and the theory is presented.

categories: physics.pop-ph hep-ex hep-ph physics.ed-ph


title:
Feedback control of probability amplitudes for two-level atom in optical
  field

abstract:
  We demonstrate the possibility to stabilize the probability amplitude of the
upper level for a single quantum two-level atom in a classical optical field
with feedback control scheme.


title: An example of anti-dynamo conformal Arnold metric

abstract:
  A 3D metric conformally related to Arnold cat fast dynamo metric:
${ds_{A}}^{2}=e^{-{\lambda}z}dp^{2}+e^{{\lambda}z}dq^{2}+dz^{2}$ is shown to
present a behaviour of non-dynamos where the magnetic field exponentially decay
in time. The Riemann-Christoffel connection and Riemann curvature tensor for
the Arnold and its conformal counterpart are computed. The curvature decay as
z-coordinates increases without bounds. Some of the Riemann curvature
components such as $R_{pzpz}$ also undergoes dissipation while component
$R_{qzqz}$ increases without bounds. The remaining curvature component
$R_{pqpq}$ is constant on the torus surface. The Riemann curvature invariant
$K^{2}=R_{ijkl}R^{ijkl}$ is found to be 0.155 for the ${\lambda}=0.75$. A
simple solution of Killing equations for Arnold metric yields a stretch Killing
vector along one direction and compressed along other direction in order that
the modulus of the Killing vector is not constant along the flow. The flow is
shown to be untwisted. The stability of the two metrics are found by examining
the sign of their curvature tensor components.


title: A universal model for languages and cities, and their lifetimes

abstract:
  Present human languages display slightly asymmetric log-normal (Gauss)
distribution for size [1-3], whereas present cities follow power law
(Pareto-Zipf law)[4]. Our model considers the competition between languages and
that between cities in terms of growing (multiplicative noise process)[5] and
fragmentation [6]; where, relevant parameters are (naturally) different for
languages and cities. We consider lifetime distribution for old and living
languages and that for old and living cities. We study also the effect of
random elimination (punctuation) within time evolution of languages and cities.
Finally, we assume decreasing exponential distribution for cities over size
with independent random amplitude and random (negative) exponent; and show
that, this gives the Pareto-Zipf law.


title:
Force Equation That Describes the Quantum States of a Relativistic
  Spinless Particle

abstract:
  Newton's second law may be used to obtain a wave equation, which reduces to
Schrodinger's equation in the nonrelativistic limit and for a conservative
force.


title:
Short wavelength electromagnetic propagation in magnetized quantum
  plasmas

abstract:
  The quantum electrodynamical (QED) short wavelength correction on plasma wave
propagation for a non-relativistic quantum plasma is investigated. A general
dispersion relation for a thermal multi-component quantum plasma is derived. It
is found that the classical dispersion relation for any wave mode can be
modified to include quantum and short wavelength QED effects by simple
substitutions of the thermal velocity and the plasma frequency. Furthermore,
the dispersion relation has been modified to include QED effects of strong
magnetic fields. It is found that strong magnetic fields together with the
short wavelength QED correction will induce dispersion both in vacuum and in
otherwise non-dispersive plasma modes. Applications to laboratory and
astrophysical systems are discussed.


title:
Nuclear signatures in high-harmonic generation from laser-driven muonic
  atoms

abstract:
  High-harmonic generation from muonic atoms exposed to intense laser fields is
considered. Our particular interest lies in effects arising from the finite
nuclear mass and size. We numerically perform a fully quantum mechanical
treatment of the muon-nucleus dynamics by employing modified soft-core and
hard-core potentials. It is shown that the position of the high-energy cutoff
of the harmonic spectrum depends on the nuclear mass, while the height of the
spectral plateau is sensitive to the nuclear radius. We also demonstrate that
$\gamma$-ray harmonics can be generated from muonic atoms in ultrastrong VUV
fields, which have potential to induce photo-nuclear reactions.


title: Accuracy Evaluation of an Optical Lattice Clock with Bosonic Atoms

abstract:
  We report the first accuracy evaluation of an optical lattice clock based on
the 1S0 - 3P0 transition of an alkaline earth boson, namely 88Sr atoms. This
transition has been enabled using a static coupling magnetic field. The clock
frequency is determined to be 429 228 066 418 009(32) Hz. The isotopic shift
between 87Sr and 88Sr is 62 188 135 Hz with fractional uncertainty 5.10^{-7}.
We discuss the conditions necessary to reach a clock accuracy of 10^{-17} or
less using this scheme.


title:
Quantum state-resolved probing of strong-field-ionized xenon atoms using
  femtosecond high-order harmonic transient absorption spectroscopy

abstract:
  Femtosecond high-order harmonic transient absorption spectroscopy is used to
resolve the complete |j,m> quantum state distribution of Xe+ produced by
optical strong-field ionization of Xe atoms at 800nm. Probing at the Xe N_4/5
edge yields a population distribution rho_j,|m| of rho_3/2,1/2 : rho_1/2,1/2 :
rho_3/2,3/2 = 75 +- 6 : 12 +- 3 : 13 +- 6 %. The result is compared to a tunnel
ionization calculation with the inclusion of spin-orbit coupling, revealing
nonadiabatic ionization behavior. The sub-50-fs time resolution paves the way
for table-top extreme ultraviolet absorption probing of ultrafast dynamics.


title:
Curvature-induced radiation of surface plasmon polaritons propagating
  around bends

abstract:
  We present a theoretical study of the curvature-induced radiation of surface
plasmon polaritons (SPPs) propagating around bends at metal-dielectric
interfaces. We explain qualitatively how the curvature leads to distortion of
the phase front, causing the fields to radiate energy away from the
metal-dielectric interface. We then quantify, both analytically and
numerically, radiation losses and energy transmission efficiencies of SPPs
propagating around bends with varying radii- as well as sign-of-curvature.


title: Physics based calculation of the fine structure constant

abstract:
  We assume that the coupling between particles and photons is defined by a
surface area and a temperature, and that the square of the temperature is the
inverse of the surface area (h_bar=c=1). By making assumptions regarding
stimulated emission and effects associated with the finite length of a string
that forms the particle surface, the fine structure constant is calculated to
be ~1/137.04. The corresponding calculated fundamental unit of charge is
1.6021E-19 C.


title:
Efficient generation of correlated random numbers using
  Chebyshev-optimal magnitude-only IIR filters

abstract:
  We compare several methods for the efficient generation of correlated random
sequences (colored noise) by filtering white noise to achieve a desired
correlation spectrum. We argue that a class of IIR filter-design techniques
developed in the 1970s, which obtain the global Chebyshev-optimum minimum-phase
filter with a desired magnitude and arbitrary phase, are uniquely suited for
this problem but have seldom been used. The short filters that result from such
techniques are crucial for applications of colored noise in physical
simulations involving random processes, for which many long random sequences
must be generated and computational time and memory are at a premium.


title:
Reduction of time-resolved space-based CCD photometry developed for MOST
  Fabry Imaging data

abstract:
  The MOST (Microvariability & Oscillations of STars) satellite obtains
ultraprecise photometry from space with high sampling rates and duty cycles.
Astronomical photometry or imaging missions in low Earth orbits, like MOST, are
especially sensitive to scattered light from Earthshine, and all these missions
have a common need to extract target information from voluminous data cubes.
They consist of upwards of hundreds of thousands of two-dimensional CCD frames
(or sub-rasters) containing from hundreds to millions of pixels each, where the
target information, superposed on background and instrumental effects, is
contained only in a subset of pixels (Fabry Images, defocussed images,
mini-spectra). We describe a novel reduction technique for such data cubes:
resolving linear correlations of target and background pixel intensities. This
stepwise multiple linear regression removes only those target variations which
are also detected in the background. The advantage of regression analysis
versus background subtraction is the appropriate scaling, taking into account
that the amount of contamination may differ from pixel to pixel. The
multivariate solution for all pairs of target/background pixels is minimally
invasive of the raw photometry while being very effective in reducing
contamination due to, e.g., stray light. The technique is tested and
demonstrated with both simulated oscillation signals and real MOST photometry.


title: String Theory: a mere prelude to non-Archimedean Space-Time Structures?

abstract:
  It took two millennia after Euclid and until in the early 1880s, when we went
beyond the ancient axiom of parallels, and inaugurated geometries of curved
spaces. In less than one more century, General Relativity followed. At present,
physical thinking is still beheld by the yet deeper and equally ancient
Archimedean assumption which entraps us into the limited view of "only one
walkable world". In view of that, it is argued with some rather easily
accessible mathematical support that Theoretical Physics may at last venture
into the Non-Archimedean realms.


title:
Supercontinuum generation of ultrashort laser pulses in air at different
  central wavelengths

abstract:
  Supercontinuum generation by femtosecond filaments in air is investigated for
different laser wavelengths ranging from ultraviolet to infrared. Particular
attention is paid on the role of third-harmonic generation and temporal
steepening effects, which enlarge the blue part of the spectrum. A
unidirectional pulse propagation model and nonlinear evolution equations are
numerically integrated and their results are compared. Apart from the choice of
the central wavelength, we emphasize the importance of the saturation intensity
reached by self-guided pulses, together with their temporal duration and
propagation length as key players acting on both supercontinuum generation of
the pump wave and emergence of the third harmonics. Maximal broadening is
observed for large wavelengths and long filamentation ranges.


title:
Strategy bifurcation and spatial inhomogeneity in a simple model of
  competing sellers

abstract:
  We present a simple one-parameter model for spatially localised evolving
agents competing for spatially localised resources. The model considers selling
agents able to evolve their pricing strategy in competition for a fixed market.
Despite its simplicity, the model displays extraordinarily rich behavior. In
addition to ``cheap'' sellers pricing to cover their costs, ``expensive''
sellers spontaneously appear to exploit short-term favorable situations. These
expensive sellers ``speciate'' into discrete price bands. As well as variety in
pricing strategy, the ``cheap'' sellers evolve a strongly correlated spatial
structure, which in turn creates niches for their expensive competitors. Thus
an entire ecosystem of coexisting, discrete, symmetry-breaking strategies
arises.


title:
Relativistic velocity addition law derived from a machine gun analogy
  and time dilation only

abstract:
  We consider a scenario that involves a machine gun, the bullets it fires and
a moving target, considered from the rest frame of the machine gun and from the
rest frame of the target respectively. Involving the special relativity via its
two postulates and the time dilation formula we derive the relativistic
velocity addition law showing that it leads to the Lorentz transformations for
the space-time coordinates of the same event.


title: A high resolution scintillating fiber tracker with SiPM readout

abstract:
  A novel modular high-resolution charged-particle tracking detector design
using $250\mu m$ diameter, round, scintillating fibers and SiPM arrays for
readout is presented. The fiber modules consist of 8 layers of 128 fibers,
mechanically sta bilized by a carbon fiber / Rohacell foam structure. A
prototype using scintillating fibers with a diameter of $300\mu m$ and two typ
es of silicon photomultipliers has been tested in a $10GeV$ proton beam in late
October 2006 at the T9 PS-beamline, CERN. We present the measured spatial
resolu tion, efficiency and signal-over-noise for this setup. The advantage of
this tra cker concept is a compact and modular design with low material budget
and only little or no cooling requirements depending on the quality of the
silicon photomultiplieres.


title: Belief Propagation and Bethe approximation for Traffic Prediction

abstract:
  We define and study an inference algorithm based on "belief propagation" (BP)
and the Bethe approximation. The idea is to encode into a graph an a priori
information composed of correlations or marginal probabilities of variables,
and to use a message passing procedure to estimate the actual state from some
extra real-time information. This method is originally designed for traffic
prediction and is particularly suitable in settings where the only information
available is floating car data. We propose a discretized traffic description,
based on the Ising model of statistical physics, in order to both reconstruct
and predict the traffic in real time. General properties of BP are addressed in
this context. In particular, a detailed study of stability is proposed with
respect to the a priori data and the graph topology. The behavior of the
algorithm is illustrated by numerical studies on a simple traffic toy model.
How this approach can be generalized to encode superposition of many traffic
patterns is discussed.


title: SigSpec - I. Frequency- and Phase-Resolved Significance in Fourier Space

abstract:
  Identifying frequencies with low signal-to-noise ratios in time series of
stellar photometry and spectroscopy, and measuring their amplitude ratios and
peak widths accurately, are critical goals for asteroseismology. These are also
challenges for time series with gaps or whose data are not sampled at a
constant rate, even with modern Discrete Fourier Transform (DFT) software. Also
the False-Alarm Probability introduced by Lomb and Scargle is an approximation
which becomes less reliable in time series with longer data gaps. A rigorous
statistical treatment of how to determine the significance of a peak in a DFT,
called SigSpec, is presented here. SigSpec is based on an analytical solution
of the probability that a DFT peak of a given amplitude does not arise from
white noise in a non-equally spaced data set. The underlying Probability
Density Function (PDF) of the amplitude spectrum generated by white noise can
be derived explicitly if both frequency and phase are incorporated into the
solution. In this paper, I define and evaluate an unbiased statistical
estimator, the "spectral significance", which depends on frequency, amplitude,
and phase in the DFT, and which takes into account the time-domain sampling. I
also compare this estimator to results from other well established techniques
and demonstrate the effectiveness of SigSpec with a few examples of ground- and
space-based photometric data, illustratring how SigSpec deals with the effects
of noise and time-domain sampling in determining significant frequencies.


title: Polymeric filament thinning and breakup in microchannels

abstract:
  The effects of elasticity on filament thinning and breakup are investigated
in microchannel cross flow. When a viscous solution is stretched by an external
immiscible fluid, a low 100 ppm polymer concentration strongly affects the
breakup process, compared to the Newtonian case. Qualitatively, polymeric
filaments show much slower evolution, and their morphology features multiple
connected drops. Measurements of filament thickness show two main temporal
regimes: flow- and capillary-driven. At early times both polymeric and
Newtonian fluids are flow-driven, and filament thinning is exponential. At
later times, Newtonian filament thinning crosses over to a capillary-driven
regime, in which the decay is algebraic. By contrast, the polymeric fluid first
crosses over to a second type of flow-driven behavior, in which viscoelastic
stresses inside the filament become important and the decay is again
exponential. Finally, the polymeric filament becomes capillary-driven at late
times with algebraic decay. We show that the exponential flow thinning behavior
allows a novel measurement of the extensional viscosities of both Newtonian and
polymeric fluids.


title: The GOES Microburst Windspeed Potential Index

abstract:
  A suite of products has been developed and evaluated to assess hazards
presented by convective downbursts to aircraft in flight derived from the
current generation of Geostationary Operational Environmental Satellite (GOES)
(11-12). The existing suite of GOES microburst products employs the GOES
sounder to calculate risk based on conceptual models of favorable environmental
profiles for convective downburst generation. A GOES sounder-derived wet
microburst severity index (WMSI) product to assess the potential magnitude of
convective downbursts, incorporating convective available potential energy
(CAPE) as well as the vertical theta-e difference (TeD) between the surface and
mid-troposphere has been developed and implemented. Intended to supplement the
use of the GOES WMSI product over the United States Great Plains region, a GOES
Hybrid Microburst Index (HMI) product has also evolved. The HMI product infers
the presence of a convective boundary layer by incorporating the sub-cloud
temperature lapse rate as well as the dew point depression difference between
the typical level of a convective cloud base and the sub-cloud layer. It is
proposed to merge the WMSI and HMI into a Microburst Windspeed Potential Index
(MWPI) algorithm for implementation in the GOES-R Advanced Baseline Imager
(ABI).


title: Limits to differences in active and passive charges

abstract:
  We explore consequences of a hypothetical difference between active charges,
which generate electric fields, and passive charges, which respond to them. A
confrontation to experiments using atoms, molecules, or macroscopic matter
yields limits on their fractional difference at levels down to 10^-21, which at
the same time corresponds to an experimental confirmation of Newtons third law.


title: Cultural route to the emergence of linguistic categories

abstract:
  Categories provide a coarse grained description of the world. A fundamental
question is whether categories simply mirror an underlying structure of nature,
or instead come from the complex interactions of human beings among themselves
and with the environment. Here we address this question by modelling a
population of individuals who co-evolve their own system of symbols and
meanings by playing elementary language games. The central result is the
emergence of a hierarchical category structure made of two distinct levels: a
basic layer, responsible for fine discrimination of the environment, and a
shared linguistic layer that groups together perceptions to guarantee
communicative success. Remarkably, the number of linguistic categories turns
out to be finite and small, as observed in natural languages.


title:
Application of the multiple-scattering method to analysis of systems
  with semi-infinite photonic waveguides

abstract:
  We propose a technique of compensating the spurious reflections implied by
the multiple-scattering (MS) method, commonly used for analyzing finite
photonic crystal (PC) systems, to obtain exact values of characteristic
parameters, such as reflection and transmission coefficients, of PC functional
elements. Rather than a modification of the MS computational algorithm, our
approach involves postprocessing of results obtained by the MS method. We
derive analytical formulas for the fields excited in a finite system, taking
explicitly into account the spurious reflections occurring at the artificial
system boundaries. The intrinsic parameters of the investigated functional
element are found by fitting the results of MS simulations to those obtained
from the formulas derived. Devices linked with one and two semi-infinite
waveguides are analyzed explicitly; possible extensions of the formalism to
more complex circuits are discussed as well. The accuracy of the proposed
method is tested in a number of systems; the results of our calculations prove
to be in good agreement with those obtained independently by other authors.


title:
Observation of a Dynamic Crossover in RNA Hydration Water which Triggers
  the Glass Transition in the Biopolymer

abstract:
  High-resolution quasi-elastic neutron scattering spectroscopy was used to
measure H2O and D2O hydrated RNA samples. The contribution of scattering from
RNA was subtracted out by taking the difference of the signals between the two
samples. The measurements were made at a series of temperatures from 270 K down
to 180 K. The Relaxing-Cage Model was used to analyze the difference
quasi-elastic spectra. We observed clear evidence of a fragile-to-strong
dynamic crossover (FSC) at TL = 220 K in RNA hydration water. We further show
that the mean-square displacement of the hydrogen atoms in both RNA and its
hydration water exhibit a sharp change in slope at approximately the same
temperature 220 K. This latter fact suggests that the dynamic transition (or
the glass transition) in RNA is triggered by the abrupt change of mobility of
the hydration water at its FSC temperature TL.


title:
Comment on "Flow of temperature-dependent viscous fluid between parallel
  heated walls: Exact analytical solutions in the presence of viscous
  dissipation", by K.S. Adegbie and F.I. Alao

abstract:
  In the above paper an analysis has been carried out to obtain results in the
Couette flow of a Newtonian fluid with viscous dissipation and temperature
dependent viscosity. The fluid viscosity is an exponential function of
temperature. Exact analytical solutions are obtained for the calculation of
velocity and temperature. However, there are some fundamental errors in this
paper which are presented herein.


title:
Effects of nonintegrability on stabilization of Feshbach molecules in
  atom waveguides

abstract:
  Deactivation of broad quasi-one-dimensional dibosonic molecules is analyzed.
Within integrable Lieb-Liniger-McGuire (LLMG) model an exact expression does
not demonstrate suppression of the deactivation at low collision energies.
Solution of Faddeev equations demonstrates that when a Feshbach resonance lifts
the symmetry of the LLMG model the deactivation becomes suppressed. This effect
shows a way for formation of a stable gas of dibosonic Feshbach molecules.


title: Femtosecond laser Fourier transform absorption spectroscopy

abstract:
  A femtosecond mode-locked laser is used for the first time as a broadband
infrared source for high resolution Fourier transform absorption spectroscopy.
Demontration is made with a Cr^4+:YAG laser. The entire nu_1+nu_3
vibration-rotation band region of acetylene, observed after passing through a
single pass 80-cm long cell, is simultaneously recorded between 1480 and 1600
nm, in 7.9 s with a signal to noise ratio equal to 1000. Two hot bands of the
most abundant acetylene isotopologue and the n1+n3 band of the ^13C^12CH_2 are
also present. The noise equivalent absorption coefficient at one second
averaging is equal to 7 10^{-7} cm^{-1}.Hz^{-1/2} per spectral element.


title: The ATLAS pixel detector

abstract:
  After a ten years planning and construction phase, the ATLAS pixel detector
is nearing its completion and is scheduled to be integrated into the ATLAS
detector to take data with the first LHC collisions in 2007. An overview of the
construction is presented with particular emphasis on some of the major and
most recent problems encountered and solved.


title: Optical approximation in the theory of geometric impedance

abstract:
  In this paper we introduce an optical approximation into the theory of
impedance calculation, one valid in the limit of high frequencies. This
approximation neglects diffraction effects in the radiation process, and is
conceptually equivalent to the approximation of geometric optics in
electromagnetic theory. Using this approximation, we derive equations for the
longitudinal impedance for arbitrary offsets, with respect to a reference
orbit, of source and test particles. With the help of the Panofsky-Wenzel
theorem we also obtain expressions for the transverse impedance (also for
arbitrary offsets). We further simplify these expressions for the case of the
small offsets that are typical for practical applications. Our final
expressions for the impedance, in the general case, involve two dimensional
integrals over various cross-sections of the transition. We further
demonstrate, for several known axisymmetric examples, how our method is applied
to the calculation of impedances. Finally, we discuss the accuracy of the
optical approximation and its relation to the diffraction regime in the theory
of impedance.


title:
Implementation of a double-scanning technique for studies of the Hanle
  effect in Rubidium vapor

abstract:
  We have studied the resonance fluorescence of a room-temperature rubidium
vapor exited to the atomic 5P3/2 state (D2 line) by powerful single-frequency
cw laser radiation (1.25 W/cm^2) in the presence of a magnetic field. In these
studies, the slow, linear scanning of the laser frequency across the hyperfine
transitions of the D2 line is combined with a fast linear scanning of the
applied magnetic field, which allows us to record frequency-dependent Hanle
resonances from all the groups of hyperfine transitions including V- and Lambda
- type systems. Rate equations were used to simulate fluorescence signals for
85Rb due to circularly polarized exciting laser radiation with different mean
frequency values and laser intensity values. The simulation show a dependance
of the fluorescence on the magnetic field. The Doppler effect was taken into
account by averaging the calculated signals over different velocity groups.
Theoretical calculations give a width of the signal peak in good agreement with
experiment.


title:
A quantum mechanical derivation of the Schwarzschild radius and its
  quantum correction using a model density distribution: Skin of a black hole

abstract:
  Using a single particle density distribution for a system of self-gravitating
particles which ultimately forms a black hole, we from a condensed matter point
of view derive the Schwarzschild radius and by including the quantum mechanical
exchange energy we find a small correction to the Schwarzschild radius, which
we designate as the skin of the black hole.


title:
Exciton-photon coupling in a ZnSe based microcavity fabricated using
  epitaxial liftoff

abstract:
  We report the observation of strong exciton-photon coupling in a ZnSe based
microcavity fabricated using epitaxial liftoff. Molecular beam epitaxial grown
ZnSe/Zn$_{0.9}$Cd$_{0.1}$Se quantum wells with a one wavelength optical length
at the exciton emission were transferred to a SiO$_2$/Ta$_2$O$_5$ mirror with a
reflectance of 96% to form finesse matched microcavities. Analysis of our angle
resolved transmission spectra reveals key features of the strong coupling
regime: anticrossing with a normal mode splitting of $23.6 meV$ at $20 K$;
composite evolution of the lower and upper polaritons; and narrowing of the
lower polariton linewidth near resonance. The heavy hole exciton oscillator
strength per quantum well is also deduced to be $1.78 \times 10^{13} cm^{-2}$.


title:
A quantum mechanical relation connecting time, temperature, and
  cosmological constant of the universe: Gamow's relation revisited as a
  special case

abstract:
  Considering our expanding universe as made up of gravitationally interacting
particles which describe particles of luminous matter and dark matter and dark
energy which is described by a repulsive harmonic potential among the points in
the flat 3-space, we derive a quantum mechanical relation connecting,
temperature of the cosmic microwave background radiation, age, and cosmological
constant of the universe. When the cosmological constant is zero, we get back
the Gamow's relation with a much better coefficient. Otherwise, our theory
predicts a value of the cosmological constant $2.0 10^{-56} {\rm {cm^{-2}}}$
when the present values of cosmic microwave background temperature of 2.728 K
and age of the universe 14 billion years are taken as input.


title: Imaging with the invisible light

abstract:
  We describe a UV photo-detector with single photon(electron) counting and
imaging capability. It is based on a CsI photocathode, a GEM charge multiplier
and a self triggering CMOS analog pixel chip with 105k pixels at 50 micron
pitch. The single photoelectron produced by the absorption of a UV photon is
drifted to and multiplied inside a single GEM hole. The coordinates of the GEM
avalanche are reconstructed with high accuracy (4 micron rms) by the pixel
chip. As a result the map of the GEM holes, arranged on a triangular pattern at
50micron pitch, is finely imaged.


title:
On the occurrence of Balmer spectra in expanding microplasmas from laser
  irradiated liquid hydrogen

abstract:
  Balmer spectra are investigated which are obtained from hydrogen droplets
irradiated by ultra-short intense laser pulses. A unified quantum statistical
description of bremsstrahlung, the Stark broadening and the van der Waals
profile of hydrogen spectral lines is used, which allows to include
many-particle effects. Analyzing the line profiles, a low ionization degree of
a dense plasma is inferred, where the main contribution to the spectral line
shape originates from the interaction with the neutral components. Effective
temperatures and densities of the radiating microplasma are deduced. A
dynamical description is given within plasma hydrodynamics, explaining the
formation of excited atomic states in the expanding system and the occurrence
of the observed Balmer lines only below a critical density.


title:
A Quantum Similarity Study of Atomic Density Functions: Insights from
  Information Theory and the Role of Relativistic Effects

abstract:
  A novel quantum similarity measure (QSM) is constructed based on concepts
from information theory. In an application of QSM to atoms, the new QSM and its
corresponding quantum similarity index (QSI) are evaluated throughout the
periodic table, using the atomic electron densities and shape functions
calculated in the Hartree-Fock approximation. The periodicity of Mendeleev's
table is regained for the first time through the evaluation of a QSM.
Evaluation of the information theory based QSI demonstrates, however, that the
patterns of periodicity are lost due to the renormalization of the QSM,
yielding chemically less appealing results for the QSI. A comparison of the
information content of a given atom on top of a group with the information
content of the elements in the subsequent rows reveals another periodicity
pattern. Relativistic effects on the electronic density functions of atoms are
investigated. Their importance is quantified in a QSI study by comparing for
each atom, the density functions evaluated in the Hartree-Fock and Dirac-Fock
approximations. The smooth decreasing of the relevant QSI along the periodic
table illustrates in a quantitative way the increase of relativistic
corrections with the nuclear charge.


title:
Detrended Fluctuation analysis of Bach's Inventions and Sinfonias
  pitches

abstract:
  Detrended Fluctuation Analysis (DFA), suitable for the analysis of
nonstationary time series, is used to investigate power law in some of the
Bach's pitches series. Using DFA method, which also is a well-established
method for the detection of long-range correlations, frequency series of Bach's
pitches have been analyzed. In this view we find same Hurts exponents in the
range (0.7-0.8) in his Inventions and sinfonia.


title:
A Closed-Form Approximation of Likelihood Functions for Discretely
  Sampled Diffusions: the Exponent Expansion

abstract:
  In this paper we discuss a closed-form approximation of the likelihood
functions of an arbitrary diffusion process. The approximation is based on an
exponential ansatz of the transition probability for a finite time step $\Delta
t$, and a series expansion of the deviation of its logarithm from that of a
Gaussian distribution. Through this procedure, dubbed {\em exponent expansion},
the transition probability is obtained as a power series in $\Delta t$. This
becomes asymptotically exact if an increasing number of terms is included, and
provides remarkably accurate results even when truncated to the first few (say
3) terms. The coefficients of such expansion can be determined
straightforwardly through a recursion, and involve simple one-dimensional
integrals.
  We present several examples of financial interest, and we compare our results
with the state-of-the-art approximation of discretely sampled diffusions
[A\"it-Sahalia, {\it Journal of Finance} {\bf 54}, 1361 (1999)]. We find that
the exponent expansion provides a similar accuracy in most of the cases, but a
better behavior in the low-volatility regime. Furthermore the implementation of
the present approach turns out to be simpler.
  Within the functional integration framework the exponent expansion allows one
to obtain remarkably good approximations of the pricing kernels of financial
derivatives. This is illustrated with the application to simple path-dependent
interest rate derivatives. Finally we discuss how these results can also be
used to increase the efficiency of numerical (both deterministic and
stochastic) approaches to derivative pricing.

categories: physics.soc-ph cond-mat.other math.ST physics.comp-ph q-fin.ST stat.TH


title: Least Squares Importance Sampling for Monte Carlo Security Pricing

abstract:
  We describe a simple Importance Sampling strategy for Monte Carlo simulations
based on a least squares optimization procedure. With several numerical
examples, we show that such Least Squares Importance Sampling (LSIS) provides
efficiency gains comparable to the state of the art techniques, when the latter
are known to perform well. However, in contrast to traditional approaches, LSIS
is not limited to the determination of the optimal mean of a Gaussian sampling
distribution. As a result, it outperforms other methods when the ability to
adjust higher moments of the sampling distribution, or to deal with
non-Gaussian or multi-modal densities, is critical to achieve variance
reductions.

categories: physics.soc-ph cond-mat.other math.ST physics.comp-ph q-fin.CP stat.TH


title: Lake Titicaca - Physics of an Inherited Hydropower Macroproject Proposal

abstract:
  Shared almost evenly by Peru and Bolivia, Lake Titicaca is situated on an
Altiplano endorheic region of the northern Andes Mountains. Rio Desaguadero is
the lake only outlet. From 1908, several macro-engineers speculated on the
creation of a second, completely artificial, outlet for Lake Titicaca
freshwater. Here we reconsider several 20th Century macroproject proposals,
with the goal of examining and enhancing this technically interesting South
American 21st Century Macro-engineering inheritance.


title: Dark Energy and Life's Ultimate Future

abstract:
  The discovery of the present accelerated expansion of space changed
everything regarding cosmology and life's ultimate prospects. Both the
optimistic scenarios of an ever (but decelerated) expanding universe and of a
collapsing universe seem to be no longer available. The final future looks
deadly dark. However, the fate of the universe and intelligence depends
crucially on the nature of the still mysterious dark energy which drives the
accelerated expansion. Depending on its - perhaps time-dependent - equation of
state, there is a confusing number of different models now, popularly called
Big Rip, Big Whimper, Big Decay, Big Crunch, Big Brunch, Big Splat, etc. This
paper briefly reviews possibilities and problems. It also argues that even if
our universe is finally doomed, perhaps that doesn't matter ultimately because
there might be some kind of eternal recurrence. - Key words: Cosmology,
Universe, Dark Energy, Cosmological Constant, Quintessence, Phantom Energy,
Inflation, Quantum Gravity, Far Future, Life, Intelligence


title: Extremal transmission at the Dirac point of a photonic band structure

abstract:
  We calculate the effect of a Dirac point (a conical singularity in the band
structure) on the transmission of monochromatic radiation through a photonic
crystal. The transmission as a function of frequency has an extremum at the
Dirac point, depending on the transparencies of the interfaces with free space.
The extremal transmission $T_{0}=\Gamma_{0} W/L$ is inversely proportional to
the longitudinal dimension $L$ of the crystal (for $L$ larger than the lattice
constant and smaller than the transverse dimension $W$). The interface
transparencies affect the proportionality constant $\Gamma_{0}$, and they
determine whether the extremum is a minimum or a maximum, but they do not
affect the ``pseudo-diffusive'' 1/L dependence of $T_{0}$.


title:
Translational invariance and the space-time Lorentz transformation with
  arbitrary spatial coordinates

abstract:
  Translational invariance requires that physical predictions are independent
of the choice of spatial coordinate system used. The time dilatation effect of
special relativity is shown to manifestly respect this invariance.
Consideration of the space-time Lorentz transformation with arbitrary spatial
coordinates shows that the spurious `length contraction' and `relativity of
simultaneity' effects --the latter violating translational invariance-- result
from the use of a different spatial coordinate system to describe each of two
spatially separated clocks at rest in a common inertial frame


title:
A position- and time-sensitive photon-counting detector with delay-line
  read-out

abstract:
  We have developed image intensifier tubes with delay-anode read-out for time-
and position-sensitive photon counting. The timing precision is better than 1
ns with 1000x1000 pixels position resolution and up to one megacounts/s
processing rate. Large format detectors of 40 and 75 mm active diameter with
internal helical-wire delay-line anodes have been produced and specified. A
different type of 40 and 25 mm tubes with semi-conducting screen for image
charge read-out allow for an economic and robust tube design and for placing
the read-out anodes outside the sealed housing. Two types of external
delay-line anodes, i.e. pick-up electrodes for the image charge, have been
tested. We present tests of the detector and anode performance. Due to the low
background this technique is well suited for applications with very low light
intensity and especially if a precise time tagging for each photon is required.
As an example we present the application of scintillator read-out in
time-of-flight (TOF) neutron radiography. Further applications so far are
Fluorescence Life-time Microscopy (FLIM) and Astronomy


title:
Long-term variations in solar meridional circulation from geomagnetic
  data: implications for solar dynamo theory

abstract:
  Geomagnetic activity has two main peaks in the 11-year sunspot cycle caused
by two types of solar agents: coronal mass ejections and high speed solar wind
streams, whose variations in number and intensity are related to the variations
in solar toroidal and poloidal fields, respectively. From the long-term
variations in the lag between the two aa-index peaks we derive the long-term
variations in solar meridional circulation. We use these relations to test the
flux-transport solar dynamo theory and to explain some well known
characteristics of the solar cycle. Based on these relations, we give a
prediction for the amplitude (125) and epoch of the maximum (April 2011) of
sunspot cycle 24.


title:
Impedance Calculations of Non-Axisymmetric Transitions Using the Optical
  Approximation

abstract:
  In a companion report, we have derived a method for finding the impedance at
high frequencies of vacuum chamber transitions that are short compared to the
catch-up distance, in a frequency regime that (in analogy to geometric optics
for light) we call the optical regime. In this report we apply the method to
various non-axisymmetric geometries such as irises/short collimators in a beam
pipe, step-in transitions, step-out transitions, and more complicated
transitions of practical importance. Most of our results are analytical, with a
few given in terms of a simple one dimensional integral. Our results are
compared to wakefield simulations with the time-domain, finite-difference
program ECHO, and excellent agreement is found.


title: Paradoxical Way for Losers in a Dating Game

abstract:
  We study the dating market decision problem in which men and women repeatedly
go out on dates and learn about each other. We consider a model for the dating
market that takes into account progressive mutual learning. This model consists
of a repeated game in which agents gain an uncertain payoff from being matched
with a particular person on the other side of the market in each time period.
Players have a list of preferred partners on the other set. The players that
reach higher rank levels on the other set preferences list have also higher
probability to be accepted for dating. A question can be raised, as considered
in this study: Can the less appreciated players do better? Two different kinds
of dating game are combined "a la Parrondo" to foster the less attractive
players. Optimism seems to be highly recommendable, especially for losers.


title: Unitary Fermi Gas in a Harmonic Trap

abstract:
  We present an {\it ab initio} calculation of small numbers of trapped,
strongly interacting fermions using the Green's Function Monte Carlo method
(GFMC). The ground state energy, density profile and pairing gap are calculated
for particle numbers $N = 2 \sim 22$ using the parameter-free "unitary"
interaction. Trial wave functions are taken of the form of correlated pairs in
a harmonic oscillator basis. We find that the lowest energies are obtained with
a minimum explicit pair correlation beyond that needed to exploit the
degeneracy of oscillator states. We find that energies can be well fitted by
the expression $a_{TF} E_{TF} + \Delta {\rm mod}(N,2)$ where $E_{TF}$ is the
Thomas-Fermi energy of a noninteracting gas in the trap and $\Delta$ is a
pairing gap. There is no evidence of a shell correction energy in the
systematics, but the density distributions show pronounced shell effects. We
find the value $\Delta= 0.7\pm 0.2\omega$ for the pairing gap. This is smaller
than the value found for the uniform gas at a density corresponding to the
central density of the trapped gas.


title: The Expansion of the Universe and the Cosmological Constant Problem

abstract:
  The discovery that the expansion of the universe is accelerating in time is a
major discovery which still awaits adequate explanation. It is generally agreed
that this implies a cosmic repulsion as a result of the existence of a
cosmological constant . However, estimates of the cosmological constant, based
on calculations of the zero-point fluctuations of quantum fields are too large
by over a hundred orders of magnitude. This result is obtained by summing the
zero-point energies up to a large cutoff energy, based on the Planck scale.
Since there is no compelling reason for this choice, we argue that since all
known quantum electrodynamic (QED) effects involves interaction with matter, a
preferred choice should be based on causality and other considerations, leading
to a much lower value for the cosmological constant .


title: Dissipative Boussinesq equations

abstract:
  The classical theory of water waves is based on the theory of inviscid flows.
However it is important to include viscous effects in some applications. Two
models are proposed to add dissipative effects in the context of the Boussinesq
equations, which include the effects of weak dispersion and nonlinearity in a
shallow water framework. The dissipative Boussinesq equations are then
integrated numerically.

categories: physics.class-ph math.AP nlin.SI physics.ao-ph


title: Network Topology of the Austrian Airline Flights

abstract:
  The information of the Austrian airline flights was collected and
quantitatively analyzed by the concepts of complex network. It displays some
features of small-world networks, namely large clustering coefficient and small
average shortest-path length. The degree distributions of the networks reveal
power law behavior with exponent value of 2 $\sim$ 3 for the small degree
branch but a flat tail for the large degree branch. Similarly, the flight
weight distributions show power-law behavior for the small weight branch.
Furthermore, we found that the clustering coefficient $C$, 0.206, of this
flight network is greatly larger than that of a random network, 0.01, which has
the same numbers of the airports ($N$) and mean degree ($<k>$), and the
diameter $D$, 2.383, of the flight network is significantly smaller than the
value of the same random network, 18.67. In addition, the degree-degree
correlation analysis shows the network has disassortative behavior, i.e. the
large airports are likely to link to smaller airports. Furthermore, the
clustering coefficient analysis indicates that the large airports reveal the
hierarchical organization.


title: Reciprocal Symmetric and Origin of Quantum Statistics

abstract:
  Boltzmann's differential equation is replaced by the corresponding reciprocal
symmetric finite difference equation. Finite difference translates discreteness
of energy. Boltzmann's function, then, splits into two reciprocally related
functions. One of them gives Planck's radiation relation and the other one
gives the corresponding Fermi-Dirac relation.


title:
Implementation of the LANS-alpha turbulence model in a primitive
  equation ocean model

abstract:
  This paper presents the first numerical implementation and tests of the
Lagrangian-averaged Navier-Stokes-alpha (LANS-alpha) turbulence model in a
primitive equation ocean model. The ocean model in which we work is the Los
Alamos Parallel Ocean Program (POP); we refer to POP and our implementation of
LANS-alpha as POP-alpha. Two versions of POP-alpha are presented: the full
POP-alpha algorithm is derived from the LANS-alpha primitive equations, but
requires a nested iteration that makes it too slow for practical simulations; a
reduced POP-alpha algorithm is proposed, which lacks the nested iteration and
is two to three times faster than the full algorithm. The reduced algorithm
does not follow from a formal derivation of the LANS-alpha model equations.
Despite this, simulations of the reduced algorithm are nearly identical to the
full algorithm, as judged by globally averaged temperature and kinetic energy,
and snapshots of temperature and velocity fields. Both POP-alpha algorithms can
run stably with longer timesteps than standard POP.
  Comparison of implementations of full and reduced POP-alpha algorithms are
made within an idealized test problem that captures some aspects of the
Antarctic Circumpolar Current, a problem in which baroclinic instability is
prominent. Both POP-alpha algorithms produce statistics that resemble
higher-resolution simulations of standard POP.
  A linear stability analysis shows that both the full and reduced POP-alpha
algorithms benefit from the way the LANS-alpha equations take into account the
effects of the small scales on the large. Both algorithms (1) are stable; (2)
make the Rossby Radius effectively larger; and (3) slow down Rossby and gravity
waves.


title:
Efficient form of the LANS-alpha turbulence model in a
  primitive-equation ocean model

abstract:
  The Lagrangian-Averaged Navier-Stokes alpha (LANS-alpha) model is a
turbulence parameterization that has been shown to capture some of the most
important features of high resolution ocean modeling at lower resolution.
Simulations using LANS-alpha in the POP primitive-equation ocean model resemble
doubled-resolution simulations of standard POP in statistics like kinetic
energy, eddy kinetic energy, and potential temperature fields. The
computational cost of adding LANS-alpha is only 27% for our most efficient
implementation, as compared to a factor of 8-10 for a doubling of resolution.
  The LANS-alpha model improves turbulence statistics with an additional
nonlinear term and a smoothed advecting velocity. In this work we investigate
different kinds of smoothing techniques and their effect on the LANS-alpha
model's results and efficiency. We show that we can substitute convolution
filters for full Hemlholtz inversions and produce similar results at a
significantly lower expense.
  When constructing filters for LANS-alpha in a primitive-equation ocean model
the filter weights must be chosen carefully, otherwise a pressure-velocity
instability will be excited. We show analytically that certain ranges of filter
weights are unstable, and confirm this with numerical experiments. Our
stability criterion also guarantees that the kinetic energy is well defined,
and that the filtered velocity is smoother that the original velocity.


title:
Comment on "Three papers published by Subhas Abel and his co-workers in
  International Journal of Non-Linear Mechanics and International Journal of
  Thermal Sciences

abstract:
  The above paper concerns the boundary layer flow of a visco-elastic fluid
along a stretching sheet immersed in a porous medium. The plate temperature is
different from that of the ambient medium and the fluid viscosity is a function
of temperature while the other fluid properties are assumed to be constant. The
boundary layer equations are transformed into ordinary ones and subsequently
are solved using the shooting method with Runge-Kutta integration algorithm.
However, there are two fundamental errors in this paper which are presented
below.


title:
How Difficult is it to Develop a Perfect Spell-checker? A
  Cross-linguistic Analysis through Complex Network Approach

abstract:
  The difficulties involved in spelling error detection and correction in a
language have been investigated in this work through the conceptualization of
SpellNet - the weighted network of words, where edges indicate orthographic
proximity between two words. We construct SpellNets for three languages -
Bengali, English and Hindi. Through appropriate mathematical analysis and/or
intuitive justification, we interpret the different topological metrics of
SpellNet from the perspective of the issues related to spell-checking. We make
many interesting observations, the most significant among them being that the
probability of making a real word error in a language is propotionate to the
average weighted degree of SpellNet, which is found to be highest for Hindi,
followed by Bengali and English.


title:
First study of radiation hardness of lead tungstate crystals at low
  temperatures

abstract:
  The electromagnetic calorimeter of PANDA at the FAIR facility will rely on an
operation of lead tungstate (PWO) scintillation crystals at temperatures near
-25 deg.C to provide sufficient resolution for photons in the energy range from
8 GeV down to 10 MeV. Radiation hardness of PWO crystals was studied at the
IHEP (Protvino) irradiation facility in the temperature range from room
temperature down to -25 deg.C. These studies have indicated a significantly
different behaviour in the time evolution of the damaging processes well below
room temperature. Different signal loss levels at the same dose rate, but at
different temperatures were observed. The effect of a deep suppression of the
crystal recovery process at temperatures below
  0 deg.C has been seen.


title: Entanglement of neutrino states

abstract:
  Muon and muon antineutrino born in the decay of charged pion form the
entangled spin state. The decay of muon with the left helicity triggers the
left helicity for muon antineutrino to preserve the null total angular momentum
of muon and muon antineutrino. This is forbidden for antineutrino hence one
cannot detect the muon antineutrino after the decay of muon. This effect may
explain the deficit of muon neutrino flux in the Super-Kamiokande, K2K, MINOS
experiments.


title: Economic Inequality: Is it Natural?

abstract:
  Mounting evidences are being gathered suggesting that income and wealth
distribution in various countries or societies follow a robust pattern, close
to the Gibbs distribution of energy in an ideal gas in equilibrium, but also
deviating significantly for high income groups. Application of physics models
seem to provide illuminating ideas and understanding, complimenting the
observations.

categories: physics.soc-ph cond-mat.stat-mech physics.data-an q-fin.GN


title: Microcanonical and canonical approach to traffic flow

abstract:
  A system of identical cars on a single-lane road is treated as a
microcanonical and canonical ensemble. Behaviour of the cars is characterized
by the probability of car velocity as a function of distance and velocity of
the car ahead. The calculations a performed on a discrete 1D lattice with
discrete car velocities.
  Probability of total velocity of a group of cars as a function of density is
calculated in microcanonical approach. For a canonical ensemble, fluctuations
of car density as a function of total velocity is found. Phase transitions
between free and jammed flow for large deceleration rate of cars and formation
of queues of cars with the same velocity for low deceleration rate are
described.


title: Superstability of Surface Nanobubbles

abstract:
  Shock wave induced cavitation experiments and atomic force microscopy
measurements of flat polyamide and hydrophobized silicon surfaces immersed in
water are performed. It is shown that surface nanobubbles, present on these
surfaces, do not act as nucleation sites for cavitation bubbles, in contrast to
the expectation. This implies that surface nanobubbles are not just stable
under ambient conditions but also under enormous reduction of the liquid
pressure down to −6MPa. We denote this feature as superstability.


title:
Total Differential Errors in One-Port Network Analyzer Measurements with
  Application to Antenna Impedance

abstract:
  The objective was to study uncertainty in antenna input impedance resulting
from full one-port Vector Network Analyzer (VNA) measurements. The VNA process
equation in the reflection coefficient p of a load, its measurement m and three
errors Es -determinable from three standard loads and their measurements- was
considered. Differentials were selected to represent measurement inaccuracies
and load uncertainties (Differential Errors). The differential operator was
applied on the process equation and the total differential error dp for any
unknown load (Device Under Test DUT) was expressed in terms of dEs and dm,
without any simplification. Consequently, the differential error of input
impedance Z -or any other physical quantity differentiably dependent on p- is
expressible. Furthermore, to express precisely a comparison relation between
complex differential errors, the geometric Differential Error Region and its
Differential Error Intervals were defined. Practical results are presented for
an indoor UHF ground-plane antenna in contrast with a common 50 Ohm DC resistor
inside an aluminum box. These two built, unshielded and shielded, DUTs were
tested against frequency under different system configurations and measurement
considerations. Intermediate results for Es and dEs characterize the
measurement system itself. A number of calculations and illustrations
demonstrate the application of the method.


title:
Kinetically-balanced Gaussian Basis Set Approach to Relativistic Compton
  Profiles of Atoms

abstract:
  Atomic Compton profiles (CPs) are a very important property which provide us
information about the momentum distribution of atomic electrons. Therefore, for
CPs of heavy atoms, relativistic effects are expected to be important,
warranting a relativistic treatment of the problem. In this paper, we present
an efficient approach aimed at ab initio calculations of atomic CPs within a
Dirac-Hartree-Fock (DHF) formalism, employing kinetically-balanced Gaussian
basis functions. The approach is used to compute the CPs of noble gases ranging
from He to Rn, and the results have been compared to the experimental and other
theoretical data, wherever possible. The influence of the quality of the basis
set on the calculated CPs has also been systematically investigated.


title: Short-range interaction of strongly nonlocal spatial optical solitons

abstract:
  A novel phenomenon is discovered that the short-range interaction between
strongly nonlocal spatial solitons depends sinusoidally on their phase
difference. The two neighbouring solitons at close proximate can be
inter-trapped via the strong nonlocality, and propagate together as a whole.
The trajectory of the propagation is a straight line with its slope controlled
by the phase difference. The experimental results carried out in nematic liquid
crystals agree quantitatively with the prediction. Our study suggests that the
phenomenon to steer optical beams by controlling the phase difference could be
used in all-optical information processing.


title: The Study of a Fibre Z-Pinch

abstract:
  This thesis presents the results of fibre Z-pinch experiments carried out on
the Z-150 device at the CTU in Prague. The generator that was used to drive the
experiments consisted of one capacitor of 3e-6 F capacitance. In the case of 20
kV charging voltage, the current was peaking at 80 kA with a 850 ns quarter
period. The Z-pinch was formed from carbon fibres of 15 micrometer diameter and
1 cm length. The discharge was observed by a large number of diagnostic tools.
This comprehensive set of diagnostics enabled us to describe the gross dynamics
of the Z-pinch. It was found out that after the breakdown a low density coronal
plasma was formed while the fibre diameter remained almost unchanged. This low
density corona was carrying almost all the current of the order of 10 kA. When
the current had built up, the implosion of the corona onto the central fibre
occurred. The implosion velocity approached the value of 2e5 m/s. When the
imploded corona had reached the fibre, the dip in dI/dt, voltage peak up to 10
kV, and XUV pulse of a 10-30 ns width were observed. XUV radiation was emitted
from several bright spots which corresponded to the interaction of m=0
instability necks with the dense core. The electron temperature and density
were approximately 80 eV and 10e25 per cubic meter, respectively. Although the
presence of a fibre did not significantly suppress MHD instabilities, they were
not disruptive. After the fibre ablation, i.e. after 500 ns, material
evaporated from electrodes started to play a dominant role. The observed plasma
column seemed to be MHD unstable and when m=0 instabilities had developed,
X-ray pulses were emitted from several hot spots, particularly near the anode.
At that time the voltage peak of up to 30 kV was detected.


title:
Statistical properties of short term price trends in high frequency
  stock market data

abstract:
  We investigated distributions of short term price trends for high frequency
stock market data. A number of trends as a function of their lengths was
measured. We found that such a distribution does not fit to results following
from an uncorrelated stochastic process. We proposed a simple model with a
memory that gives a qualitative agreement with real data.


title: Three-dimensional photography by holography

abstract:
  Color encoding of depth is shown to occur naturally in holograms that are
reconstructed under white light illumination. It can be registered in a common
color photograph, allowing a simple method of visual decoding by means of
ordinary colored 3-D spectacles. The fundamental holographic equations and the
photographic procedure required for maximum fidelity in three-dimensional
reproduction are described. The result is a new kind of photograph that shows
all of the views of the object in a continuous sequence. It permits an animated
photographic representation and also makes it possible to adjust the degree of
depth visualization when observed as a stereoscopic representation.


title: Asymmetric, helical and mirror-symmetric travelling waves in pipe flow

abstract:
  New families of three-dimensional nonlinear travelling waves are discovered
in pipe flow. In contrast to known waves (Faisst & Eckhardt Phys. Rev. Lett.
91, 224502 (2003), Wedin & Kerswell, J. Fluid Mech. 508, 333 (2004)), they
possess no rotational symmetry and exist at much lower Reynolds numbers.
Particularly striking is an `asymmetric mode' which has one slow streak
sandwiched between two fast streaks located preferentially to one side of the
pipe. This family originates in a pitchfork bifurcation from a mirror-symmetric
travelling wave which can be traced down to a Reynolds number of 773. Helical
and non-helical rotating waves are also found emphasizing the richness of phase
space even at these very low Reynolds numbers. The delay in Reynolds number
from when the laminar state ceases to be a global attractor to turbulent
transition is then even larger than previously thought.


title: A Compact High-Energy Neutron Spectrometer

abstract:
  A compact liquid organic neutron spectrometer (CLONS) based on a single NE213
liquid scintillator (5 cm diam. x 5 cm) is described. The spectrometer is
designed to measure neutron fluence spectra over the energy range 2-200 MeV and
is suitable for use in neutron fields having any type of time structure.
Neutron fluence spectra are obtained from measurements of two-parameter
distributions (counts versus pulse height and pulse shape) using the Bayesian
unfolding code MAXED. Calibration and test measurements made using a pulsed
neutron beam with a continuous energy spectrum are described and the
application of the spectrometer to radiation dose measurements is discussed.


title:
Diffusion and dispersion of passive tracers: Navier-Stokes versus MHD
  turbulence

abstract:
  A comparison of turbulent diffusion and pair-dispersion in homogeneous,
macroscopically isotropic Navier-Stokes (NS) and nonhelical magnetohydrodynamic
(MHD) turbulence based on high-resolution direct numerical simulations is
presented. Significant differences between MHD and NS systems are observed in
the pair-dispersion properties, in particular a strong reduction of the
separation velocity in MHD turbulence as compared to the NS case. It is shown
that in MHD turbulence the average pair-dispersion is slowed down for
$\tau_\mathrm{d}\lesssim t\lesssim 10 \tau_\mathrm{d}$, $\tau_\mathrm{d}$ being
the Kolmogorov time, due to the alignment of the relative Lagrangian tracer
velocity with the local magnetic field. Significant differences in turbulent
single-particle diffusion in NS and MHD turbulence are not detected. The fluid
particle trajectories in the vicinity of the smallest dissipative structures
are found to be characterisically different although these comparably rare
events have a negligible influence on the statistics investigated in this work.


title: On the orientation of Roman towns in Italy

abstract:
  As is well known, several Roman sources report on the existence of a town
foundation ritual, inherited from the Etruscans, which allegedly included
astronomical references. However, the possible existence of astronomical
orientations in the layout of Roman towns has never been tackled in a
systematic way. As a first step in this direction, the orientation of virtually
all Roman towns in Italy (38 cities) is studied here. Non-random orientation
patterns emerge from these data, aiming at further research in this field.


title: Representation-independent manipulations with Dirac matrices and spinors

abstract:
  Dirac matrices, also known as gamma matrices, are defined only up to a
similarity transformation. Usually, some explicit representation of these
matrices is assumed in order to deal with them. In this article, we show how it
is possible to proceed without any such assumption. Various important
identities involving Dirac matrices and spinors have been derived without
assuming any representation at any stage.


title: Nonlinear phase shift from photon-photon scattering in vacuum

abstract:
  We show that QED nonlinear effects imply a phase correction to the linear
evolution of electromagnetic waves in vacuum. We provide explicit solutions of
the modified Maxwell's equations for the propagation of a superposition of two
plane waves, and calculate analytically and numerically the corresponding phase
shift. This provides a new framework for the search of all-optical signatures
of photon-photon scattering in vacuum. In particular, we propose an experiment
for measuring the phase shift in projected high-power laser facilities.


title: Parametric instability of the helical dynamo

abstract:
  We study the dynamo threshold of a helical flow made of a mean (stationary)
plus a fluctuating part. Two flow geometries are studied, either (i) solid body
or (ii) smooth. Two well-known resonant dynamo conditions, elaborated for
stationary helical flows in the limit of large magnetic Reynolds numbers, are
tested against lower magnetic Reynolds numbers and for fluctuating flows (zero
mean). For a flow made of a mean plus a fluctuating part the dynamo threshold
depends on the frequency and the strength of the fluctuation. The resonant
dynamo conditions applied on the fluctuating (resp. mean) part seems to be a
good diagnostic to predict the existence of a dynamo threshold when the
fluctuation level is high (resp. low).


title:
Properties of a simple bilinear stochastic model: estimation and
  predictability

abstract:
  We analyze the properties of arguably the simplest bilinear stochastic
multiplicative process, proposed as a model of financial returns and of other
complex systems combining both nonlinearity and multiplicative noise. By
construction, it has no linear predictability (zero two-point correlation) but
a certain nonlinear predictability (non-zero three-point correlation). It can
thus be considered as a paradigm for testing the existence of a possible
nonlinear predictbility in a given time series. We present a rather exhaustive
study of the process, including its ability to produce fat-tailed distribution
from Gaussian innovations, the unstable characteristics of the inversion of the
key nonlinear parameters and of the two initial conditions necessary for the
implementation of a prediction scheme and an analysis of the associated
super-exponential sensitivity of the inversion of the innovations in the
presence of a large impluse. Our study emphasizes the conditions under which a
degree of predictability can be achieved and describes a number of different
attempts, which overall illuminates the properties of the process. In
conclusion, notwithstanding its remarkable simplicity, the bilinear stochastic
process exhibits remarkably rich and complex behavior, which makes it a serious
candidate for the modeling of financial times series and of other complex
systems.


title:
Analysis of the structure of complex networks at different resolution
  levels

abstract:
  Modular structure is ubiquitous in real-world complex networks, and its
detection is important because it gives insights in the structure-functionality
Modular structure is ubiquitous in real-world complex networks, and its
detection is important because it gives insights in the structure-functionality
relationship. The standard approach is based on the optimization of a quality
function, modularity, which is a relative quality measure for a partition of a
network into modules. Recently some authors [1,2] have pointed out that the
optimization of modularity has a fundamental drawback: the existence of a
resolution limit beyond which no modular structure can be detected even though
these modules might have own entity. The reason is that several topological
descriptions of the network coexist at different scales, which is, in general,
a fingerprint of complex systems. Here we propose a method that allows for
multiple resolution screening of the modular structure. The method has been
validated using synthetic networks, discovering the predefined structures at
all scales. Its application to two real social networks allows to find the
exact splits reported in the literature, as well as the substructure beyond the
actual split.

categories: physics.data-an cond-mat.other cs.DM physics.soc-ph q-bio.QM


title:
Nonsequential double ionization: a comparison of classical simulations
  and $S$-matrix results

abstract:
  In a fully classical simulation, we investigate the recollision mechanism of
non-sequential double ionization (NSDI) and its manifestation in the
end-of-pulse electron momentum distributions. We compare two different
electron-electron potentials: a soft-core Coulombic potential and a Yukawa
potential. We also implement the strong-field approximation (SFA), which is
commonly made in quantum-mechanical $S$-matrix calculations, in our classical
simulations and study its consequences. We find that, regardless of the form of
the e-e potential, the SFA modifies the momentum distributions and recollision
dynamics significantly, but more so for the long-range than for the short-range
e-e interaction. Surprisingly, our classical results, especially those obtained
with the Yukawa potential under the SFA, agree well with the results from the
$S$-matrix calculations with a contact e-e interaction. This implies that the
recollision dynamics initiated by a quantum tunneling process and a purely
classical process do not deviate much from each other. Furthermore, our
classical predictions of travel times are consistent with the results from the
simple-man model, and the most probable thermalization time is found to be
within 0.15 and 0.25 laser periods.


title: Scientific reticence and sea level rise

abstract:
  I suggest that a "scientific reticence" is inhibiting communication of a
threat of potentially large sea level rise. Delay is dangerous because of
system inertias that could create a situation with future sea level changes out
of our control. I argue for calling together a panel of scientific leaders to
hear evidence and issue a prompt plain-written report on current understanding
of the sea level change issue.


title: Joining inner space to outer space

abstract:
  The purpose of this paper is to demonstrate that it is possible, in
principle, to obtain knowledge of the entire universe at the present time, even
if the radius of the universe is much larger than the radius of the observable
universe.


title:
Demonstrated convergence of the equilibrium ensemble for a fast
  united-residue protein model

abstract:
  Due to the time-scale limitations of all-atom simulation of proteins, there
has been substantial interest in coarse-grained approaches. Some methods, like
"Resolution Exchange," [E. Lyman et al., Phys. Rev. Lett. 96, 028105 (2006)]
can accelerate canonical all-atom sampling, but require properly distributed
coarse ensembles. We therefore demonstrate that full sampling can indeed be
achieved in a sufficiently simplified protein model, as verified by a recently
developed convergence analysis. The model accounts for protein backbone
geometry in that rigid peptide planes rotate according to atomistically defined
dihedral angles, but there are only two degrees of freedom (phi and psi
dihedrals) per residue. Our convergence analysis indicates that small proteins
(up to 89 residues in our tests) can be simulated for more than 50 "structural
decorrelation times" in less than a week on a single processor. We show that
the fluctuation behavior is reasonable, as well as discussing applications,
limitations, and extensions of the model.


title:
A Topological Pattern of Urban Street Networks: Universality and
  Peculiarity

abstract:
  In this paper, we derive a topological pattern of urban street networks using
a large sample (the largest so far to the best of our knowledge) of 40 U.S.
cities and a few more from elsewhere of different sizes. It is found that all
the topologies of urban street networks based on street-street intersection
demonstrate a small world structure, and a scale-free property for both street
length and connectivity degree. More specifically, for any street network,
about 80% of its streets have length or degrees less than its average value,
while 20% of streets have length or degrees greater than the average. Out of
the 20%, there are less than 1% of streets which can form a backbone of the
street network. Based on the finding, we conjecture that the 20% streets
account for 80% of traffic flow, and the 1% streets constitute a cognitive map
of the urban street network. We illustrate further a peculiarity about the
scale-free property.


title: Emerging technologies in physics education

abstract:
  Three emerging technologies in physics education are evaluated from the
interdisciplinary perspective of cognitive science and physics education
research. The technologies - Physlet Physics, the Andes Intelligent Tutoring
System (ITS), and Microcomputer-Based Laboratory (MBL) Tools - are assessed
particularly in terms of their potential at promoting conceptual change,
developing expert-like problem-solving skills, and achieving the goals of the
traditional physics laboratory. Pedagogical methods to maximize the potential
of each educational technology are suggested.


title: Entropic effects in large-scale Monte Carlo simulations

abstract:
  The efficiency of Monte Carlo samplers is dictated not only by energetic
effects, such as large barriers, but also by entropic effects that are due to
the sheer volume that is sampled. The latter effects appear in the form of an
entropic mismatch or divergence between the direct and reverse trial moves. We
provide lower and upper bounds for the average acceptance probability in terms
of the Renyi divergence of order 1/2. We show that the asymptotic finitude of
the entropic divergence is the necessary and sufficient condition for
non-vanishing acceptance probabilities in the limit of large dimensions.
Furthermore, we demonstrate that the upper bound is reasonably tight by showing
that the exponent is asymptotically exact for systems made up of a large number
of independent and identically distributed subsystems. For the last statement,
we provide an alternative proof that relies on the reformulation of the
acceptance probability as a large deviation problem. The reformulation also
leads to a class of low-variance estimators for strongly asymmetric
distributions. We show that the entropy divergence causes a decay in the
average displacements with the number of dimensions n that are simultaneously
updated. For systems that have a well-defined thermodynamic limit, the decay is
demonstrated to be n^{-1/2} for random-walk Monte Carlo and n^{-1/6} for Smart
Monte Carlo (SMC). Numerical simulations of the LJ_38 cluster show that SMC is
virtually as efficient as the Markov chain implementation of the Gibbs sampler,
which is normally utilized for Lennard-Jones clusters. An application of the
entropic inequalities to the parallel tempering method demonstrates that the
number of replicas increases as the square root of the heat capacity of the
system.


title: Infrared absorbing electron in ice-Ih is trapped by a water vacancy

abstract:
  Ionization of polar liquids and glasses often yields metastable electron
centers collectively known as weakly bound (wb) electrons that absorb to the
red of the ground state of the solvated/trapped electron. Formation of these
species is thought to be the initial stage of electron localization in such
media. Although these commonly occurring species have distinctive absorption
spectra, no insight into their structure currently exists. In this Letter, we
address the structure of the wb electron in low-temperature ice-Ih
theoretically, using a combination of mixed quantum-classical (MQC) floating
set of Gaussian orbitals (FSGO) - Metropolis Monte Carlo (MC) method and
embedded cluster density functional theory (DFT) post treatment. The comparison
with the observed properties of the wb electron in ice suggests that this
species is an s-like wavefunction filling a water vacancy.


title:
A distributional approach to the geometry of dislocations at the
  mesoscale

abstract:
  We develop a theory to represent dislocated single crystals at the mesoscopic
scale by considering concentrated effects, governed by the distribution theory
combined with multiple-valued kinematic fields. Our approach gives a new
understanding of the continuum theory of defects as developed by Kroener (1980)
and other authors. Fundamental 2D identities relating the incompatibility
tensor to the Frank and Burgers vectors are proved under global strain
assumptions relying on the geometric measure theory, thereby giving rise to
rigorous homogenisation from mesoscopic to macroscopic scale.


title: Relativity and quantum mechanics: Jorgensen revisited

abstract:
  We first define the functions which ensure the transformation of momentum and
energy of a tardyon, the transformation of the wave vector and the frequency of
the associated wave. Having done this, we show that they ensure the
relativistic invariance of the quotient between momentum and wave vector and
between energy and frequency if the product between particle velocity u and
phase velocity w is a relativistic invariant (uw=c^2), a condition which is a
natural combination of special relativity theory and quantum mechanics.


title:
The Normalized Radial Basis Function Neural Network and its Relation to
  the Perceptron

abstract:
  The normalized radial basis function neural network emerges in the
statistical modeling of natural laws that relate components of multivariate
data. The modeling is based on the kernel estimator of the joint probability
density function pertaining to given data. From this function a governing law
is extracted by the conditional average estimator. The corresponding
nonparametric regression represents a normalized radial basis function neural
network and can be related with the multi-layer perceptron equation. In this
article an exact equivalence of both paradigms is demonstrated for a
one-dimensional case with symmetric triangular basis functions. The
transformation provides for a simple interpretation of perceptron parameters in
terms of statistical samples of multivariate data.


title: Removal of surface plasmon polariton eigenmodes degeneracy

abstract:
  The effect of the tilt angle of metal film on the transmissivity of
subwavelength holes in optically thick metal film is investigated. The
transmission efficiency is found can be highly dependent on the tilt angle. It
is also found that when the input photons are polarized not along the eigenmode
directions of surface plasmon polariton, a birefringent phenomenon is observed
when the array with periodic of subwavelength holes is tilted. Linear
polarization states can be changed to elliptical polarization states and a
phase can be added between two eigenmodes. The phase is changed with the tilt
angle. A model based on surface plasmon polariton eigenmodes degeneracy is
presented to explain these experimental results.


title:
Analytical Solution Describing the Periodicity of the Elements in the
  Periodic System

abstract:
  Mathematical formula describing the periodicity of the elements in the
periodic system is presented.


title: The cyclotron gas stopper project at the NSCL

abstract:
  Gas stopping is becoming the method of choice for converting beams of rare
isotopes obtained via projectile fragmentation and in-flight separation into
low-energy beams. These beams allow ISOL-type experiments, such as mass
measurements with traps or laser spectroscopy, to be performed with projectile
fragmentation products. Current gas stopper systems for high-energy beams are
based on linear gas cells filled with 0.1-1 bar of helium. While already used
successfully for experiments, it was found that space charge effects induced by
the ionization of the helium atoms during the stopping process pose a limit on
the maximum beam rate that can be used. Furthermore, the extraction time of
stopped ions from these devices can exceed 100 ms causing substantial decay
losses for very short-lived isotopes. To avoid these limitations, a new type of
gas stopper is being developed at the NSCL/MSU. The new system is based on a
cyclotron-type magnet with a stopping chamber filled with Helium buffer gas at
low pressure. RF-guiding techniques are used to extract the ions. The space
charge effects are considerably reduced by the large volume and due to a
separation between the stopping region and the region of highest ionization.
Cyclotron gas stopper systems of different sizes and with different magnetic
field strengths and field shapes are presently investigated.


title: Exciton Transfer Integrals Between Polymer Chains

abstract:
  The line-dipole approximation for the evaluation of the exciton transfer
integral, $J$, between conjugated polymer chains is rigorously justified. Using
this approximation, as well as the plane-wave approximation for the exciton
center-of-mass wavefunction, it is shown analytically that $J \sim L$ when the
chain lengths are smaller than the separation between them, or $J\sim L^{-1}$
when the chain lengths are larger than their separation, where $L$ is the
polymer length. Scaling relations are also obtained numerically for the more
realistic standing-wave approximation for the exciton center-of-mass
wavefunction, where it is found that for chain lengths larger than their
separation $J \sim L^{-1.8}$ or $J \sim L^{-2}$, for parallel or collinear
chains, respectively. These results have important implications for the
photo-physics of conjugated polymers and self-assembled molecular systems, as
the Davydov splitting in aggregates and the F\"orster transfer rate for exciton
migration decreases with chain lengths larger than their separation. This
latter result has obvious deleterious consequences for the performance of
polymer photovoltaic devices.


title:
Effects of orientation and alignment in high-harmonic generation and
  above threshold ionization

abstract:
  When molecules interact with intense light sources of femtosecond or shorter
duration the rotational degrees of freedom are frozen during the response to
the strong nonperturbative interaction. We show how the frozen degrees of
freedom affect the measurable signals in high-harmonic generation and above
threshold ionization. High-harmonic generation exhibits optical coherence in
the signal from different orientations of the molecule. For ionization, the
contributions from different orientations are added incoherently. The effects
are demonstrated for realistic alignment and orientation schemes.


title: Dynamo action in cylindrical annulus

abstract:
  We study numerically the induction mechanisms generated from an array of
helical motions distributed along a cylinder. Our flow is a very idealized
geometry of the columnar structure that has been proposed for the convective
motion inside the Earth core. Using an analytically prescribed flow, we apply a
recently introduced iterative numerical scheme to solve the induction equation
and analyze the flow response to externally applied fields with simple
geometries (azimuthal, radial, etc.). Symmetry properties allow us to build
selected induction modes whose interactions lead to dynamo mechanisms. Using an
induction operator formalism, we show how dipole and quadrupole dynamos can be
envisioned from such motions.


title:
Guiding the surgical gesture using an electro-tactile stimulus array on
  the tongue: A feasibility study

abstract:
  Under conventional "open-" surgery, the physician has to take care of the
patient, interact with other clinicians and check several monitoring devices.
Nowadays, the Computer Assisted Surgery proposes to integrate 3D cameras in the
operating theatre in order to assist the surgeon in performing minimal-invasive
surgical punctures. The cameras localize the needle and the computer guides the
surgeon towards an intracorporeal clinically-defined target. A visualization
system (screen) is employed to provide the surgeon with indirect visual spatial
information about the intracorporeal positions of the needle. The present work
proposes to use another sensory modality to guide the surgeon thus keeping the
visual modality fully dedicated to the surgical gesture. For this, the sensory
substitution paradigm using the Bach-y-Rita's "Tongue Display Unit" (TDU) is
exploited to provide to the surgeon information of the position tool. The TDU
device is composed of a 6x6 matrix of electrodes transmitting electrotactile
information on the tongue surface. The underlying idea consists in transmitting
information about the deviation of the needle movement with regard to a
pre-planned "optimal" trajectory. We present an experiment assessing the
guidance effectiveness of an intracorporeal puncture under TDU guidance with
respect to the performance evidenced under a usual visual guidance system.


title:
Scattering in crystals with effective radiation length in the micron
  range

abstract:
  In computer simulations we find that particles can scatter in bent crystal
lattices with effective radiation length down to a few micron or 300-700 times
shorter than in the corresponding amorphous materials. We derive a theoretical
estimate independent of energy for the effective radiation length that is in
agreement with our simulations for C, Si, Ge, and W crystal lattices. We show
that in the ongoing collimation experiment at the Tevatron a crystal-based
smart scattering material could outperform a channeling crystal in efficiency
of collimation reducing the local background rate by a factor of 40.


title: Efficient Uncertainty Minimization for Fuzzy Spectral Clustering

abstract:
  Spectral clustering uses the global information embedded in eigenvectors of
an inter-item similarity matrix to correctly identify clusters of irregular
shape, an ability lacking in commonly used approaches such as k-means and
agglomerative clustering. However, traditional spectral clustering partitions
items into hard clusters, and the ability to instead generate fuzzy item
assignments would be advantageous for the growing class of domains in which
cluster overlap and uncertainty are important. Korenblum and Shalloway [Phys.
Rev. E 67, 056704 (2003)] extended spectral clustering to fuzzy clustering by
introducing the principle of uncertainty minimization. However, this posed a
challenging non-convex global optimization problem that they solved by a
brute-force technique unlikely to scale to data sets having more than O(10^2)
items. Here we develop a new method for solving the minimization problem, which
can handle data sets at least two orders of magnitude larger. In doing so, we
elucidate the underlying structure of uncertainty minimization using multiple
geometric representations. This enables us to show how fuzzy spectral
clustering using uncertainty minimization is related to and generalizes
clustering motivated by perturbative analysis of almost-block-diagonal
matrices. Uncertainty minimization can be applied to a wide variety of existing
hard spectral clustering approaches, thus transforming them to fuzzy methods.


title: Replika Mirrors - Nearly Loss-Free Guides For Ultracold Neutrons

abstract:
  The reflectivity of ultracold neutron (UCN) guides produced with a dedicated
technique called {\sc Replika} has been studied. The guides are made of nickel,
where the surface quality was copied from a glass layer. This results in a
surface roughness smaller than 10 \AA. The reflectivity was measured to be
99.9% or higher. Those guides can be used at present or future UCN sources to
transport UCN over long distances to the respective experiments without
significant losses.


title: Swimming, Pumping and Gliding at low Reynolds numbers

abstract:
  Simple, linear equations relate microscopic swimmers to the corresponding
gliders and pumps. They have the following set of consequences: The swimming
velocity of free swimmers can be inferred from the force on the tethered
swimmer and vice versa; A tethered swimmer dissipates more energy than a free
swimmer; It is possible to swim with arbitrarily high efficiency, but it is
impossible to pump with arbitrarily high efficiency and finally that pumping is
geometric. We also solve several optimization problems associated with swimming
and pumping: The problem of optimal anchoring for a certain class of swimmers
that includes the Purcell swimmer and the three linked spheres and the optimal
geometries of helices considered as swimmers and pumps.


title: Does the Earth show up an impending mega-earthquake?

abstract:
  In line of the intermediate-term monitoring of seismic activity aimed at
prediction of the world largest earthquakes the seismic dynamics of the Earth's
lithosphere is analysed as a single whole, which is the ultimate scale of the
complex hierarchical non-linear system. The present study demonstrates that the
lithosphere does behave, at least in intermediate-term scale, as non-linear
dynamic system that reveals classical symptoms of instability at the approach
of catastrophe, i.e., mega-earthquake. These are: (i) transformation of
magnitude distribution, (ii) spatial redistribution of seismic activity, (iii)
rise and acceleration of activity, (iv) change of dependencies across
magnitudes of different types, and other patterns of collective behaviour. The
observed global scale seismic behaviour implies the state of criticality of the
Earth lithosphere in the last decade.


title:
Expansion of a Formalism of Classical Mechanics for Nonequilibrium
  Systems

abstract:
  The expansion of a classical Hamilton formalism consisting in adaptation of
it to describe the nonequilibrium systems is offered. Expansion is obtained by
construction of formalism on the basis of the dynamics equation of the
equilibrium subsystems by which the nonequilibrium system is represented. It
has allowed removing restrictions on dynamics of the subsystems, which dictated
by the requirement of monogenic and potentiality of the forces between
subsystems. Modified Lagrange, Hamilton and Liouville equations are obtained.
Some features of dynamics of nonequilibrium systems are considered. Connection
between the equation of interaction of subsystems and a thermodynamic principle
of energy is analyzed.


title:
Micromegas TPC studies at high magnetic fields using the charge
  dispersion signal

abstract:
  The International Linear Collider (ILC) Time Projection Chamber (TPC)
transverse space-point resolution goal is 100 microns for all tracks including
stiff 90 degree tracks with the full 2 meter drift. A Micro Pattern Gas
Detector (MPGD) readout TPC can achieve the target resolution with existing
techniques using 1 mm or narrower pads at the expense of increased detector
cost and complexity. The new MPGD readout technique of charge dispersion can
achieve good resolution without resorting to narrow pads. This has been
demonstrated previously for 2 mm x 6 mm pads with GEMs and Micromegas in cosmic
ray tests and in a KEK beam test in a 1 Tesla magnet. We have recently tested a
Micromegas-TPC using the charge dispersion readout concept in a high field
super-conducting magnet at DESY. The measured Micromegas gain was found to be
constant within 0.5% for magnetic fields up to 5 Tesla. With the strong
suppression of transverse diffusion at high magnetic fields, we measure a flat
50 micron resolution at 5 Tesla over the full 15 cm drift length of our
prototype TPC.


title:
Shear and Vorticity in Inflationary Brans-Dicke Cosmology with
  Lambda-Term

abstract:
  We find a solution for exponential inflation in Brans-Dicke cosmology endowed
with a cosmological term, which includes time-varying shear and vorticity. We
find that the scalar field and the scale factor increase exponentialy while
shear, vorticity, energy density, cosmic pressure and the cosmological term
decay exponentialy for beta < 0, where beta is defined in the text.


title:
An instrumented tracer for Lagrangian measurements in Rayleigh-B\'enard
  convection

abstract:
  We have developed novel instrumentation for making Lagrangian measurements of
temperature in diverse fluid flows. A small neutrally buoyant capsule is
equipped with on-board electronics which measure temperature and transmit the
data via a wireless radio frequency link to a desktop computer. The device has
80 dB dynamic range, resolving milli-Kelvin changes in temperature with up to
100 ms sampling time. The capabilities of these "smart particles" are
demonstrated in turbulent thermal convection in water. We measure temperature
variations as the particle is advected by the convective motion, and analyse
its statistics. Additional use of cameras allow us to track the particle
position and to report here the first direct measurement of Lagrangian heat
flux transfer in Rayleigh-B{\'e}nard convection. The device shows promise for
opening new research in a broad variety of fluid systems.


title: Microstructure of neat alcohols

abstract:
  Formation of microstructure in homogeneous associated liquids is analysed
through the density-density pair correlation functions, both in direct and
reciprocal space, as well as an effective local one-body density function. This
is illustrated through a molecular dynamics study of two neat alcohols, namely
methanol and \emph{tert}-butanol, which have a rich microstructure: chain-like
molecular association for the former and micelle-like for the latter. The
relation to hydrogen bonding interaction is demonstrated. The apparent failure
to find microstructure in water -a stronger hydrogen bonding liquid- with the
same tools, is discussed.


title: The CNGS Neutrino Beam

abstract:
  The CERN to Gran Sasso Neutrino beam (CNGS) was commissioned at CERN in early
August 2006 and was first sent at low intensity to Gran Sasso on August 17,
2006. The Borexino, LVD and OPERA experiments continued the commissioning of
their detectors and started taking data with practically no dead time. The CNGS
collected several hundred events with clean time distributions.