title: Structural Flyby Characterization of Nanoporosity

abstract:
  Recently, Ferreira da Silva et al. [3] have performed a gradient pattern
analysis of a canonical sample set (CSS) of scanning force microscopy (SFM)
images of p-Si. They applied the so-called Gradient Pattern Analysis to images
of three typical p-Si samples distinguished by different absorption energy
levels and aspect ratios. Taking into account the measures of spatial
asymmetric fluctuations they interpreted the global porosity not only in terms
of the amount of roughness, but rather in terms of the structural complexity
(e.g., walls and fine structures as slots). This analysis has been adapted in
order to operate in a OpenGL flyby environment (the StrFB code), whose
application give the numerical characterization of the structure during the
flyby real time. Using this analysis we compare the levels of asymmetric
fragmentation of active porosity related to different materials as p-Si and
"porous diamond-like" carbon. In summary we have shown that the gradient
pattern analysis technique in a flyby environment is a reliable sensitive
method to investigate, qualitatively and quantitatively, the complex morphology
of active nanostructures.


title: Properties of the triplet metastable states of the alkaline-earth atoms

abstract:
  The static and dynamic properties of the alkaline-earth atoms in their
metastable state are computed in a configuration interaction approach with a
semi-empirical model potential for the core. Among the properties determined
are the scalar and tensor polarizabilities, the quadrupole moment, some of the
oscillator strengths and the dispersion coefficients of the van der Waals
interaction. A simple method for including the effect of the core on the
dispersion parameters is described.


title: Capillary flow in an evaporating sessile drop

abstract:
  An analytical expression of velocity potential inside an evaporating sessile
drop with pinned contact line is found.


title: The Astumian's Paradox

abstract:
  We discuss some aspects of Astumian suggestions that combination of biased
games (Parrondo's paradox) can explain performance of molecular motors.
Unfortunately the model is flawed by explicit asymmetry overlooked by the
author. In addition, we show that taking into consideration stakes allows to
remove the paradoxical behaviour of Parrondo games.


title: Nonlinear magneto-optical effects in Ba vapor

abstract:
  We report the first measurements of linear and nonlinear magneto-optical
polarization rotation on an intercombination transition of Ba vapor (lambda=
791.1nm). We observe a maximum polarization rotation angle in Faraday
configuration of 15mrad, accompanied by suppression of absorption. A
theoretical treatment of the nonlinear Faraday effect in the limit of a strong
interacting light field is developed.


title:
Boosted Decision Trees as an Alternative to Artificial Neural Networks
  for Particle Identification

abstract:
  The efficacy of particle identification is compared using artificial neutral
networks and boosted decision trees. The comparison is performed in the context
of the MiniBooNE, an experiment at Fermilab searching for neutrino
oscillations. Based on studies of Monte Carlo samples of simulated data,
particle identification with boosting algorithms has better performance than
that with artificial neural networks for the MiniBooNE experiment. Although the
tests in this paper were for one experiment, it is expected that boosting
algorithms will find wide application in physics.


title:
Ultracold atomic collisions in tight harmonic traps: Perturbation
  theory, ionization losses and application to metastable helium atoms

abstract:
  Collisions between tightly confined atoms can lead to ionization and hence to
loss of atoms from the trap. We develop second-order perturbation theory for a
tensorial perturbation of a spherically symmetric system and the theory is then
applied to processes mediated by the spin-dipole interaction. Redistribution
and loss mechanisms are studied for the case of spin-polarized metastable
helium atoms and results obtained for the five lowest s states in the trap and
trapping frequencies ranging from 1 kHz to 10 MHz.


title: Simulation of Special Bubble Detectors for PICASSO

abstract:
  The PICASSO project is a cold dark matter (CDM) search experiment relying on
the superheated droplet technique. The detectors use superheated freon liquid
droplets (active material) dispersed and trapped in a polymerized gel. This
detection technique is based on the phase transition of superheated droplets at
about room temperature and ambient pressure. The phase transition is induced by
nuclear recoils when an atomic nucleus in the droplets interacts with incoming
subatomic particles. This includes CDM particles candidate as the neutralino (a
yet-to-discover particle predicted in extensions of the Standard Model of
particle physics). Simulations performed to understand the detector response to
neutrons and alpha particles are presented along with corresponding data
obtained at the Montreal Laboratory.


title: Minimal mass-size of a stable 3He cluster

abstract:
  The minimal number of 3He atoms required to form a bound cluster has been
estimated by means of a Diffusion Monte Carlo procedure within the fixed-node
approximation. Several importance sampling wave functions have been employed in
order to consider different shell-model configurations. The resulting upper
bound for the minimal number is 32 atoms.


title: Short waves and cyclotron losses in the relativistic gyrokinetic theory

abstract:
  Radiation damping of the motion of charged particles in relativistic,
optically thin plasmas is described within the framework of the covariant
gyrokinetic theory. It involves description of the collisionless
single-particle dynamics as well as the Vlasov and Maxwell equations both
written in the covariant formulation. The damping causes corrections to the
phase-space trajectory of the particle, as well as to the form of the kinetic
equation itself, due to the failure of conditions of the Liouville theorem.
Both effects result independent of the gyrophase, which is retained as an
ignorable variable. In addition, the applicability range of the covariant
gyrokinetic theory is extended to describe short-wavelength perturbations with
the background of zero parallel electric field. The presented theory is
suitable for description of magnetized, relativistic, collisionless plasmas in
the context of astrophysical or laboratory problems. Non-uniquenes of the
gyrokinetic representation and consequences thereof are discussed.


title:
An Improved Weighting Algorithm to Achieve Software Compensation in a
  Fine Grained LAr Calorimeter

abstract:
  An improved weighting algorithm applied to hadron showers has been developed
for a fine grained LAr calorimeter. The new method uses tabulated weights which
depend on the density of energy deposited in individual cells and in a
surrounding cone whose symmetry axis connects the interaction vertex with the
highest energy cluster in the shower induced by a hadron. The weighting of the
visible energy and the correction for losses due to noise cuts are applied in
separate steps. In contrast to standard weighting procedures the new algorithm
allows to reconstruct the total energy as well as the spatial energy deposition
on the level of individual calorimeter cells. The linearity and the energy
resolution of the pion signal in the momentum interval 2 GeV/c <= p <= 20 GeV/c
studied in this analysis are considerably improved in comparison to the
standard weighting algorithm as practiced presently by the H1 collaboration.
Moreover the energy spectra reconstructed with the new method follow in a broad
interval a Gaussian distribution and have less pronounced tails.


title: Open nonradiative cavities as millimeter wave single-mode resonators

abstract:
  Open single-mode metallic cavities operating in nonradiative configurations
are proposed and demonstrated. Starting from well-known dielectric resonators,
possible nonradiative cavities have been established; their behavior on the
fundamental TE011 mode has been predicted on the basis of general
considerations. As a result, very efficient confinement properties are expected
for a wide variety of open structures having rotational invariance. Test
cavities realized having in mind practical millimeter wave constraints have
been characterized at microwave frequencies. The field distribution of some
relevant configurations has been modeled by means of a finite-element numerical
method. The obtained results confirm the expected high performances on widely
open configurations. A possible excitation of the proposed resonators
exploiting their nonradiative character is discussed, and the resulting overall
ease of realization enlightened in view of millimeter wave employments.


title: High Magnetic Field Performance of a GEM-TPC

abstract:
  A large volume time projection chamber (TPC) has been proposed as main
tracking device for a detector at a future linear e+e- collider. Gas electron
multipliers (GEMs) are studied as potential replacement of the conventional
wire based gas amplification system of TPCs. This talk presents recent results
from R&D activities with a small GEM-TPC prototype. The spatial resolution was
measured for different magnetic fields up to 4 T.


title: Beamstrahlung monitoring of the beam beam effects at the Linear Collider

abstract:
  At the Linear Collider mismatches between the two beams will result in an
intense beamstrahlung. We have studied how this beamstrahlung would evolve as a
function of the offset between the two beams and we suggest ways of monitoring
it.


title: A Note on the Dipole Coordinates

abstract:
  A couple of orthogonal coordinates for dipole geometry are proposed for
numerical simulations of plasma geophysics in the Earth's dipole magnetic
field. These coordinates have proper metric profiles along field lines in
contrast to the standard dipole coordinate system that is commonly used in
analytical studies for dipole geometry.


title:
A Method to Separate Stochastic and Deterministic Information from
  Electrocardiograms

abstract:
  In this work we present a new idea to develop a method to separate stochastic
and deterministic information contained in an electrocardiogram, ECG, which may
provide new sources of information with diagnostic purposes. We assume that the
ECG has information corresponding to many different processes related with the
cardiac activity as well as contamination from different sources related with
the measurement procedure and the nature of the observed system itself. The
method starts with the application of an improuved archetypal analysis to
separate the mentioned stochastic and deterministic information. From the
stochastic point of view we analyze Renyi entropies, and with respect to the
deterministic perspective we calculate the autocorrelation function and the
corresponding correlation time. We show that healthy and pathologic information
may be stochastic and/or deterministic, can be identified by different measures
and located in different parts of the ECG.


title: What are the left-handed media and what is interesting about them?

abstract:
  We review the intensively discussed ideas about wave propagation and
refraction in media where both electric permittivity and magnetic permeability
are negative. The criticism against negative refraction as violating the
causality principle is considered. Starting from the initial wave equations,
refraction of beams at the boundary of a left-handed medium is analyzed. The
physics of a perfect lens formed by a flat layer of a left-handed material is
considered.


title: Lithium Ionization by a Strong Laser Field

abstract:
  We study ab initio computations of the interaction of Lithium with a strong
laser field. Numerical solutions of the time-dependent fully-correlated
three-particle Schroedinger equation restricted to the one-dimensional
soft-core approximation are presented. Our results show a clear transition from
non-sequential to sequential double ionization for increasing intensities. Non
sequential double ionization is found to be sensitive to the spin configuration
of the ionized pair. This asymmetry, also found in experiments of
photoionization of Li with synchrotron radiation, shows the evidence of the
influence of the exclusion principle in the underlying rescattering mechanism.


title:
The HERMES Polarized Hydrogen and Deuterium Gas Target in the HERA
  Electron Storage Ring

abstract:
  The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in
use since 1996 with the polarized electron beam of HERA at DESY to study the
spin structure of the nucleon. Polarized atoms from a Stern-Gerlach Atomic Beam
Source are injected into a storage cell internal to the HERA electron ring.
Atoms diffusing from the center of the storage cell into a side tube are
analyzed to determine the atomic fraction and the atomic polarizations. The
atoms have a nuclear polarization, the axis of which is defined by an external
magnetic holding field. The holding field was longitudinal during 1996-2000,
and was changed to transverse in 2001. The design of the target is described,
the method for analyzing the target polarization is outlined, and the
performance of the target in the various running periods is presented.


title:
Nuclear Polarization of Molecular Hydrogen Recombined on a Non-metallic
  Surface

abstract:
  The nuclear polarization of $\mathrm{H}_2$ molecules formed by recombination
of nuclear polarized H atoms on the surface of a storage cell initially coated
with a silicon-based polymer has been measured by using the longitudinal
double-spin asymmetry in deep-inelastic positron-proton scattering. The
molecules are found to have a substantial nuclear polarization, which is
evidence that initially polarized atoms retain their nuclear polarization when
absorbed on this type of surface


title: Classical electrodynamics from the motion of a relativistic fluid

abstract:
  We show that there exists a choice of gauge in which the electromagnetic
4-potential may be written as the difference of two 4-velocity vector fields
describing the motion of a two-component space-filling relativistic fluid.
Maxwell's equations are satisfied immediately, while the Lorentz force equation
follows from the interactions of sources and sinks. The usual electromagnetic
quantities then admit new interpretations as functions of the local
4-velocities. Electromagnetic waves are found to be described by oscillations
of the underlying medium which can therefore be identified with the
`luminiferous aether'. The formulation of electrodynamics in terms of
4-velocities is more general than that of the standard 4-potential in that it
also allows for a classical description of a large class of vacuum energy
configurations. Treated as a self-gravitating fluid, the model can be
explicitly identified with Nelson's stochastic formulation of quantum
mechanics, making it a promising candidate as the classical field theory
unifying gravitation, electromagnetism and quantum theory which Einstein had
sought.


title:
Exact periodic solutions of the Liouville equation and the "snake" of
  density in JET

abstract:
  The "snake" is a persistent density perturbation at the rational q-surfaces
after pellet injection. Together with other phenomena (density pinch and
profile resiliancy) it can be traced back to the extremum of an action
functional for line-vortices in 3D. In a field theoretical formulation this
leads to the Liouville equation. We provide explicit method of calculating
solutions to the Liouville eq. on periodic domains and obtain, in particular,
localised perturbations similar to the experimentally observed "snakes".


title: Resonant modes in triangular dielectric cavities

abstract:
  The resonant optical modes of a high permittivity dielectric prism with an
equilateral triangular cross section are discussed. Eigenmode solutions of the
scalar Helmholtz equation with Dirichlet boundary conditions, appropriate to a
conducting boundary, are applied for this purpose. The particular plane wave
components present in these modes are analyzed for their total internal
reflection behavior and implied mode confinement when the conducting boundary
is replaced by a sharp dielectric mismatch. Improvement in TIR confinement by
adjusting the longitudinal wavevector $k_z$ is also discussed. For
two-dimensional electromagnetic solutions ($k_z=0$), TE polarization leads to
longer lifetime than TM polarization, assuming that escape of evanescent
boundary waves at the corners is the primary decay process.


title: The Aleph Cosmological Principle

abstract:
  A general cosmological principle -- Aleph -- is proposed as a substitute to
the Anthropic principle. Furthermore, the universe, conceived as a world
ensemble, is characterized by many (possibly infinite) X-Life world principles.
The only known X-Life world principle recovers much of the Anthropic
conjecture. The inescapable final conclusion is the formulation of the Strong
Copernicus principle.


title: On Chemotaxis

abstract:
  We compare chemotaxis, the migration of cells and higher animals in reaction
to a chemical stimulus, and similar phenomena originating within gases from
temperature differences. Then we explain two easy mathematical models for
handling experimental data.

categories: physics.comp-ph physics.bio-ph physics.class-ph q-bio.CB


title: Optimal behavior of viscoelastic flow at resonant frequencies

abstract:
  The global entropy generation rate in the zero-mean oscillatory flow of a
Maxwell fluid in a pipe is analyzed with the aim at determining its behavior at
resonant flow conditions. This quantity is calculated explicitly using the
analytic expression for the velocity field and assuming isothermal conditions.
The global entropy generation rate shows well-defined peaks at the resonant
frequencies where the flow displays maximum velocities. It was found that
resonant frequencies can be considered optimal in the sense that they maximize
the power transmitted to the pulsating flow at the expense of maximum
dissipation.


title: The D0 Silicon Track Trigger

abstract:
  The Level-2 Silicon Track Trigger preprocessor (L2 STT) of the D0 detector in
Run II is described. It performs a precise reconstruction of charged particle
tracks in the Central Fiber Tracker (CFT) and the Silicon Microstrip Tracker
(SMT). Events with displaced tracks originating from the decay of long living
particles such as B hadrons are triggered on. The presence of b quarks
contained in such hadrons is relevant for B physics and crucial as signature of
top quark and Higgs boson decays.


title: Suppressing and restoring constants in physical equations

abstract:
  A simple procedure for restoring the constants in physical equations is
introduced by a consistent consideration of the correspondence between the
symbols representing physical quantities and pairs formed by numerical values
and unit symbols. This procedure is applied to the very used unit systems
stressing also the direct relations between the atomic, natural systems and SI.


title: Constrained Molecular Dynamics Simulations of Atomic Ground-States

abstract:
  Constrained molecular dynamics(CoMD) model, previously introduced for nuclear
dynamics, has been extended to the atomic structure and collision calculations.
Quantum effects corresponding to the Pauli and Heisenberg principle are
enforced by constraints, in a parameter-free way. Our calculations for small
atomic system, H, He, Li, Be, F reproduce the ground-state binding energies
within 3%, compared with the results of quantum mechanical Hartree-Fock
calculations.


title:
Probe spectroscopy in an operating magneto-optical trap: the role of
  Raman transitions between discrete and continuum atomic states

abstract:
  We report on cw measurements of probe beam absorption and four-wave-mixing
spectra in a $^{85}$Rb magneto-optical trap taken while the trap is in
operation. The trapping beams are used as pump light. We concentrate on the
central feature of the spectra at small pump-probe detuning and attribute its
narrow resonant structures to the superposition of Raman transitions between
light-shifted sublevels of the ground atomic state and to atomic recoil
processes. These two contributions have different dependencies on trap
parameters and we show that the former is inhomogeneously broadened. The strong
dependence of the spectra on the probe-beam polarization indicates the
existence of large optical anisotropy of the cold-atom sample, which is
attributed to the recoil effects. We point out that the recoil-induced
resonances can be isolated from other contributions, making pump-probe
spectroscopy a highly sensitive diagnostic tool for atoms in a working MOT.


title: Mach's Principle II

abstract:
  The meaning and significance of Mach's Principle and its dependence on ideas
about relativistic rotating frame theory and the celestial sphere is explained
and discussed. Two new relativistic rotation transformations are introduced by
using a linear simulation for the rotating disc situation. The accepted formula
for centrifugal acceleration in general relativity is then analysed with the
use of one of these transformations. It is shown that for this general
relativity formula to be valid throughout all space-time there has to be
everywhere a local standard of absolutely zero rotation. It is then concluded
that the field off all possible space-time null geodesics or photon paths unify
the absolute local non-rotation standard throughout space-time. Thus it is
suggested that Mach's principle holds in the restricted sense that there is a
universal standard of absolute local rotation rate related to the apparent
rotation of the celestial sphere. However this apparent rotation is actually
the earth's rotation relative to a local mapping of null geodesic endpoints
from that time and space distant sphere to the local time in the local
zero-rotation environment. A connection of local inertia with the celestial
sphere is not found.


title:
Collimated, single-pass atom source from a pulsed alkali metal dispenser
  for laser-cooling experiments

abstract:
  We have developed an improved scheme for loading atoms into a magneto-optical
trap (MOT) from a directed alkali metal dispenser in < 10^-10 torr ultra-high
vacuum conditions. A current-driven dispenser was surrounded with a cold
absorbing "shroud" held at < 0 C, pumping rubidium atoms not directed into the
MOT. This nearly eliminates background alkali atoms and reduces the detrimental
rise in pressure normally associated with these devices. The system can be
well-described as a current-controlled, rapidly-switched, two-temperature
thermal beam, and was used to load a MOT with 3 x 10^8 atoms.


title: A Gauge Condition for Studying the Origin of Intrinsic Magnetospheres

abstract:
  We propose an analytical model based on the solution of the
magnetohydrodynamics (MHD) equations for studying the origin of intrinsic
magnetospheres. For this purpose, we reveal a new gauge condition for the
electromagnetic vector potential, which eases the solution of such complex
system of non-linear equations. Using this model, we analyse the deformation of
the terrestrial magnetic field due to the presence of the solar wind. By
comparing with experimental observations, we have found that the geometrical
configuration of the magnetosphere, before, and after the magnetic field of the
Earth started to deviate the solar wind, has not changed notably, and that the
solar wind should have had a finite conductivity. This model can also be used
to perform linear stability analysis of fluid and magnetic instabilities.


title:
Relativistic aberration of light as a corollary of relativity of
  simultaneity

abstract:
  A new derivation of the relativistic aberration formula for a plane-polarized
light wave is presented that does not require any use of the Lorentz
transformation. The method is based on a modification of the Huygens-Fresnel
principle to include the relativistic effects introduced by the relative motion
between the observer and the emitter. The derivation clearly shows that the
aberration formula is a direct consequence of the relative simultaneity.


title: The Doppler effect from a uniformly moving mirror

abstract:
  The formula for the frequency shift of a plane-polarized light wave reflected
from a uniformly moving mirror is derived directly from the constant light
speed postulate and the basic principles of wave optics. Unlike the original
derivation by Einstein, our derivation does not involve Lorentz
transformations. As such, it lies within the scope of a first course in special
relativity.


title: Single-loop interferometer for minimal ellipsometry

abstract:
  We present a simple polarizing Mach-Zehnder interferometer that can be used
for optimal minimal ellipsometry: Only four intensities are measured to
determine the three Stokes parameters, and an optimal choice for the four
polarization projections can be achieved for any sufficiently small wavelength
range of interest.


title:
Spatio-temporal wave propagation in photonic crystals: a
  Wannier-function analysis

abstract:
  A general analysis of undistorted propagation of localized wavepackets in
photonic crystals based on a Wannier-function expansion technique is presented.
Different kinds of propagating and stationary spatio-temporal localized waves
are found from an asymptotic analysis of the Wannier function envelope
equation.


title: Relationship Among Efficiency and Output Power of Heat Energy Converters

abstract:
  Relationship among efficiency and output power of heat-electric energy
converters as well as of any converters for transforming of heat energy into
any other kind of energy is considered. It is shown, that the parameter
efficiency does not determine univocally the output power of a converter. It is
proposed to use another parameter for determination of working ability of heat
energy converters. It is shown, that high output power can not be achieved by
any kind of Stirling-type converters in spite of their high efficiency.


title: Dynamic ultrasound radiation force in fluids

abstract:
  The subject of this paper is to present a theory for the dynamic radiation
force produced by dual-frequency ultrasound beams in lossless and
non-dispersive fluids. A formula for the dynamic radiation force exerted on a
three-dimensional object by a dual-frequency beam is obtained stemming from the
fluid dynamics equations. Dependence of the dynamic radiation force to
nonlinear effects of the medium is analyzed. The developed theory is applied to
calculate the dynamic radiation force exerted on solid elastic (brass and
stainless steel) spheres by a low-amplitude dual-frequency plane wave. The
dynamic radiation force is calculated by solving the dual-frequency plane wave
scattering problem for solid elastic spheres. Results show that the dynamic
radiation force on the analized spheres presents fluctuations similar to those
present in the static radiation force. Furthermore, analysis of the static and
the dynamic radiation forces on the stainless steel sphere shows that they have
approximately the same magnitude.


title:
Non-linear amplification of small spin precession using long range
  dipolar interactions

abstract:
  In measurements of small signals using spin precession the precession angle
usually grows linearly in time. We show that non-linear interactions between
particles can lead to an exponentially growing spin precession angle, resulting
in an amplification of small signals and raising them above the noise level of
a detection system. We demonstrate amplification by a factor of greater than 8
of a spin precession signal due to a small magnetic field gradient in a
spherical cell filled with hyperpolarized liquid $^{129}$Xe. This technique can
improve the sensitivity in many measurements that are limited by the noise of
the detection system, rather then the fundamental spin-projection noise.


title:
Computation of Internal Fluid Flows in Channels Using the CFD Software
  Tool FlowVision

abstract:
  The article describes the CFD software tool FlowVision (OOO "Tesis", Moscow).
The model equations used for this research are the set of Reynolds and
continuity equations and equations of the standard k - e turbulence model. The
aim of the paper was testing of FlowVision by comparing the computational
results for a number of simple internal channel fluid flows with known
experimental data. The test cases are non-swirling and swirling flows in pipes
and diffusers, flows in stationary and rotating bends. Satisfactory
correspondence of results was obtained both for flow patterns and respective
quantitative values.


title:
Fabrication of micro-mirrors with pyramidal shape using anisotropic
  etching of silicon

abstract:
  Gold micro-mirrors have been formed in silicon in an inverted pyramidal
shape. The pyramidal structures are created in the (100) surface of a silicon
wafer by anisotropic etching in potassium hydroxide. High quality micro-mirrors
are then formed by sputtering gold onto the smooth silicon (111) faces of the
pyramids. These mirrors show great promise as high quality optical devices
suitable for integration into MOEMS systems.


title: Critical dimension of Spectral Triples

abstract:
  It is open the possibility of imposing requisites to the quantisation of
Connes' Spectral Triples in such a way that a critical dimension D=26 appears.


title: An advance report on particle invariance in particle physics

abstract:
  Since particle such as molecule, atom and nucleus are composite particle, it
is important to recognize that physics must be invariant for both the composite
particle and its constituent particles, this requirement is called particle
invariance. But difficulties arise immediately because for fermion we use the
Dirac equation, for boson we use the Klein-Gordon equation. Therefore, the
particle invariance demands there is a general wave equation for describing
particle motion regardless particle class. In this paper, three advances in
this subject are reported: (1) momentum-wavefunction relation is a general
relation shared by both fermion and boson, meets the requirement of the
particle invaiance. As a test, the momentum-wavefunction relation was directly
applied to hydrogen atom, and get the correct fine structure and spin effect
for the electron. (2) the Dirac equation and Klein-Gordon equation can be
derived out from the momentum-wavefunction relation when we abandon some higher
order terms. (3) according to the momentum-wavefunction relation a path
integral method was developed, differing from Feynman's path integral, it
simplfies quantum computation.


title:
Relativistic electron beam acceleration by Compton scattering of
  lower-hybrid waves

abstract:
  It has been proved theoetically and numerically that the highly relativistic
electron beam can be accelerated efficiently via the Compton scattering induced
by nonlinear Landau and cyclotron damping of the lower-hybrid waves.


title: Nonlinear cyclotron-resonance accelerations by a generalized EM wave

abstract:
  Particle accelerations by a 1D, EM, dispersive pulse in an external magnetic
field are investigated. It is found that the well-known cyclotron resonance may
be classified into three regimes as the length and/or the amplitude of the
pulse are varied. Namely, as the pulse amplitude increases, the transit-time
cyclotron-resonance acceleration [CRA] evolves to phase trapping, and reflect
particles. The amplitude and wave dispersion as well as the pulse length
strongly affect those accelerations. The interesting phenomena of quantization
of resonance velocities in between the two regimes are also investigated. This
new mechanism may lead to wave amplification at some discrete frequencies other
than the cyclotron frequency.


title:
Arbitrary amplitude inertial Alfven waves in homogeneous magnetized
  electron-positron-ion plasmas

abstract:
  Nonlinear set of equations for inertial or slow shear Alfven wave (SSAW) in
ideal electron-positron-ion (e-p-i) plasmas are presented. The analytical
solution for arbitrary amplitude SSAW in such multi-component plasmas is
obtained using Sagdeev potential approach. The numerical solutions for several
different cases have also been presented for illustrative purpose. It is found
that the electron density dips of SSAW are formed in the super Alfvenic region.
The amplitude and the width of the nonlinear shear Alfven wave reduces with the
increase in the concentration of positrons in electron-ion (e-i) plasmas. The
width of the soliton also depends upon the direction of propagation of the
perturbation in both e-i and e-p-i plasmas.


title:
Discreteness-induced Stochastic Steady State in Reaction Diffusion
  Systems: Self-consistent Analysis and Stochastic Simulations

abstract:
  A self-consistent equation to derive a discreteness-induced stochastic steady
state is presented for reaction-diffusion systems. For this formalism, we use
the so-called Kuramoto length, a typical distance over which a molecule
diffuses in its lifetime, as was originally introduced to determine if local
fluctuations influence globally the whole system. We show that this Kuramoto
length is also relevant to determine whether the discreteness of molecules is
significant or not. If the number of molecules of a certain species within the
Kuramoto length is small and discrete, localization of some other chemicals is
brought about, which can accelerate certain reactions. When this acceleration
influences the concentration of the original molecule species, it is shown that
a novel, stochastic steady state is induced that does not appear in the
continuum limit. A theory to obtain and characterize this state is introduced,
based on the self-consistent equation for chemical concentrations. This
stochastic steady state is confirmed by numerical simulations on a certain
reaction model, which agrees well with the theoretical estimation. Formation
and coexistence of domains with different stochastic states are also reported,
which is maintained by the discreteness. Relevance of our result to
intracellular reactions is briefly discussed.

categories: physics.chem-ph nlin.PS physics.bio-ph q-bio.SC


title:
Photoluminescence and Terahertz Emission from Femtosecond Laser-Induced
  Plasma Channels

abstract:
  Luminescence as a mechanism for terahertz emission from femtosecond
laser-induced plasmas is studied. By using a fully microscopic theory, Coulomb
scattering between electrons and ions is shown to lead to luminescence even for
a spatially homogeneous plasma. The spectral features introduced by the rod
geometry of laser-induced plasma channels in air are discussed on the basis of
a generalized mode-function analysis.


title: Astumian's Paradox revisited

abstract:
  I give a simple analysis of the game that I previously published in
Scientific American which shows the paradoxical behavior whereby two losing
games randomly combine to form a winning game. The game, modeled on a random
walk, requires only two states and is described by a first-order Markov
process.


title:
Between Laws and Models: Some Philosophical Morals of Lagrangian
  Mechanics

abstract:
  I extract some philosophical morals from some aspects of Lagrangian
mechanics. (A companion paper will present similar morals from Hamiltonian
mechanics and Hamilton-Jacobi theory.) One main moral concerns methodology:
Lagrangian mechanics provides a level of description of phenomena which has
been largely ignored by philosophers, since it falls between their accustomed
levels--``laws of nature'' and ``models''. Another main moral concerns
ontology: the ontology of Lagrangian mechanics is both more subtle and more
problematic than philosophers often realize.
  The treatment of Lagrangian mechanics provides an introduction to the subject
for philosophers, and is technically elementary. In particular, it is confined
to systems with a finite number of degrees of freedom, and for the most part
eschews modern geometry. But it includes a presentation of Routhian reduction
and of Noether's ``first theorem''.


title:
Non-linear plane perturbation in a non-ohmic/ohmic fluid interface in a
  vertical electric field

abstract:
  The stability of a non-ohmic/ohmic fluid interface in the presence of a
constant gravitational field and stressed by a vertical stationary electric
field with unipolar injection is studied, focusing on the destabilizing action
of the electric pressure when charge relaxation effects can be ignored. We use
a hydraulic model, whose static equilibrium condition is written and analysed
as a function of the ohmic fluid conductivity when subjected to a non-linear
perturbation. The combined action of the polarization and free interfacial
charges on the pressure instability mechanism is also analysed. The results
show some important peculiarities of the fluid interface behaviour in the
presence of a stationary space charge distribution generated by unipolar
injection in the non-ohmic fluid.


title:
GPS radio occultation with GRACE: Atmospheric profiling utilizing the
  zero difference technique

abstract:
  Radio occultation events recorded on 28-29 July 2004 by a GPS receiver aboard
the GRACE-B satellite are analyzed. The stability of the receiver clock allows
for the derivation of excess phase profiles using a zero difference technique,
rendering the calibration procedure with concurrent observations of a reference
GPS satellite obsolete. 101 refractivity profiles obtained by zero differencing
and 96 profiles calculated with an improved single difference method are
compared with co-located ECMWF meteorological analyses. Good agreement is found
at altitudes between 5 and 30 km with an average fractional refractivity
deviation below 1% and a standard deviation of 2-3%. Results from end-to-end
simulations are consistent with these observations.


title: Influence length and space-time correlation between earthquakes

abstract:
  Short and long range interactions between earthquakes are attracting
increasing interest. Scale invariant properties of seismicity in time, space
and energy argue for the presence of complex triggering mechanisms where, like
a cascade process, each event produces aftershocks. A definitive method to
assess any connection between two earthquakes separated in time and distance
does not exist. Here we propose a novel method of data analysis that, based on
the space-time combined generalization of the correlation integral leads to a
self-consistent visualization and analysis of both spatial and temporal
correlations. When analyzing global seismicity we discovered a universal
relation linking the spatial Influence Length of a given earthquake to the time
elapsed from the event itself. Following an event, time correlations (i.e.
causality effects) exist in a region that shrinks over time, suggesting a
long-range dissipating stress transfer. A different process is acting in the
short-range where events are randomly set, evidencing a sub-diffusive growth of
the seismogenic zone.


title: Triple photoionization of Lithium near threshold

abstract:
  Solving the full classical four-body Coulomb problem numerically using a
Wigner initial distribution we formulate a classical-quantum hybrid approach to
study triple ionization by single photon absorption from the Li ground state in
the threshold region.
  We confirm the Wannier threshold law $\sigma \propto E^{\alpha}$ and we show
that the $\alpha$ determined in the interval between 2-5 eV deviates from the
analytical threshold value of 2.16 which we find in the interval between
$0.1-2$ eV.


title:
On a multi-scale approach to analyze the joint statistics of
  longitudinal and transverse increments experimentally in small scale
  turbulence

abstract:
  We analyze the relationship of longitudinal and transverse increment
statistics measured in isotropic small-scale turbulence. This is done by means
of the theory of Markov processes leading to a phenomenological Fokker-Planck
equation for the two increments from which a generalized Karman equation is
derived. We discuss in detail the analysis and show that the estimated equation
can describe the statistics of the turbulent cascade. A remarkably result is
that the main differences between longitudinal and transverse increments can be
explained by a simple rescaling-symmetry, namely the cascade speed of the
transverse increments is 1.5 times faster than that of the longitudinal
increments. Small differences can be found in the skewness and in a higher
order intermittency term. The rescaling symmetry is compatible with the
Kolmogorov constants and the Karman equation and give new insight into the use
of extended self similarity (ESS) for transverse increments. Based on the
results we propose an extended self similarity for the transverse increments
(ESST).


title: Contactless inductive flow tomography

abstract:
  The three-dimensional velocity field of a propeller driven liquid metal flow
is reconstructed by a contactless inductive flow tomography (CIFT). The
underlying theory is presented within the framework of an integral equation
system that governs the magnetic field distribution in a moving electrically
conducting fluid. For small magnetic Reynolds numbers this integral equation
system can be cast into a linear inverse problem for the determination of the
velocity field from externally measured magnetic fields. A robust
reconstruction of the large scale velocity field is already achieved by
applying the external magnetic field alternately in two orthogonal directions
and measuring the corresponding sets of induced magnetic fields. Kelvin's
theorem is exploited to regularize the resulting velocity field by using the
kinetic energy of the flow as a regularizing functional. The results of the new
technique are shown to be in satisfactory agreement with ultrasonic
measurements.


title: Stability of flow through a slowly diverging pipe

abstract:
  Although the critical Reynolds number for linear instability of the laminar
flow in a straight pipe is infinite, we show that it is finite for a divergent
pipe, and approaches infinity as the inverse of the divergence angle. The
velocity profile at the threshold of inviscid stability is obtained. A
non-parallel analysis yields linear instability at surprisingly low Reynolds
numbers, of about 150 for a divergence of 3 degrees, which would suggest a role
for such instabilities in the transition to turbulence. A multigrid Poisson
equation solver is employed for the basic flow, and an extended eigenvalue
method for the partial differential equations describing the stability.


title:
New experimental and theoretical approach to the 3d D-level lifetimes of
  40Ca+

abstract:
  We report measurements of the lifetimes of the 3d $^2$D$_{5/2}$ and 3d
$^2$D$_{3/2}$ metastable states of a single laser-cooled $^{40}$Ca$^+$ ion in a
linear Paul trap. We introduce a new measurement technique based on
high-efficiency quantum state detection after coherent excitation to the
D$_{5/2}$ state or incoherent shelving in the D$_{3/2}$ state, and subsequent
free, unperturbed spontaneous decay. The result for the natural lifetime of the
D$_{5/2}$ state of 1168(9) ms agrees excellently with the most precise
published value. The lifetime of the D$_{3/2}$ state is measured with a single
ion for the first time and yields 1176(11) ms which improves the statistical
uncertainty of previous results by a factor of four. We compare these
experimental lifetimes to high-precision ab initio all order calculations and
find a very good agreement. These calculations represent an excellent test of
high-precision atomic theory and will serve as a benchmark for the study of
parity nonconservation in Ba$^+$ which has similar atomic structure.


title: Calorimeter clustering with minimal spanning trees

abstract:
  We present a top-down approach to calorimeter clustering. An algorithm based
on minimal spanning tree theory is described briefly.

categories: physics.data-an hep-ex nucl-ex physics.ins-det


title: Comparisons of hadronic shower packages

abstract:
  We report on simulation studies comparing various hadronic shower packages.
Results show that predictions from different models vary significantly,
illustrating the necessity of testbeam data to resolve the situation.

categories: physics.ins-det hep-ex nucl-ex physics.data-an


title:
Variational bounds on the energy dissipation rate in body-forced shear
  flow

abstract:
  A new variational problem for upper bounds on the rate of energy dissipation
in body-forced shear flows is formulated by including a balance parameter in
the derivation from the Navier-Stokes equations. The resulting min-max problem
is investigated computationally, producing new estimates that quantitatively
improve previously obtained rigorous bounds. The results are compared with data
from direct numerical simulations.


title: Gravity and the Fermion Mass

abstract:
  It is shown that gravity generates mass for the fermion. It does so by
coupling directly with the spinor field. The coupling term is invariant with
respect to the electroweak gauge group $ U(1) \otimes SU(2)_L. $ It replaces
the fermion mass term $ m\bar{\psi} \psi $.


title: Positron/Proton Separation Using the AMS-02 TRD

abstract:
  AMS-02 is a cosmic ray experiment that will be placed on the International
Space Station. One of its goals is to search for WIMP Dark Matter, specifically
from anomalous features in the positron spectrum. In order to identify
positrons at high energy from the large background of protons, a Transition
Radiation Detector (TRD) will be used. Here we will present studies of
positron/proton separation using the TRD from the AMS-02 Simulation.


title: Photon localization laser

abstract:
  We demonstrate low-threshold random lasing in random amplifying layered
medium via photon localization. Lasing is facilitated by resonant excitation of
localized modes at the pump laser wavelength, which are peaked deep within the
sample with greatly enhanced intensity. Emission occurs into long-lived
localized modes overlapping the localized gain region. This mechanism overcomes
a fundamental barrier to reducing lasing thresholds in diffusive random lasers,
in which multiple scattering restricts the excitation region to the proximity
of the sample surface.


title:
Configuration interaction calculation of hyperfine and P,T-odd constants
  on ^{207}PbO excited states for the electron EDM experiments

abstract:
  We report first configuration interaction calculations of hyperfine constants
A_\parallel and the effective electric field W_d acting on the electric dipole
moment of the electron, in two excited electronic states of ^{207}PbO. The
obtained hyperfine constants, A_\parallel = -3826 MHz for the a(1) state and
A_\parallel = 4887 MHz for the B(1) state, are in very good agreement with the
experimental data, -4113 MHz and 5000 \pm 200 MHz, respectively. We find W_d =
-(6.1 ^{+1.8}_{-0.6}) 10^{24} Hz/(e cm) for a(1), and W_d = (8.0 \pm 1.6)
10^{24} Hz/(e cm) for B(1). The obtained values are analyzed and compared to
recent relativistic coupled cluster results and a semiempirical estimate of W_d
for the a(1) state.


title:
Collective behavior in the system of self propelling particles with
  nonholonomic constraints

abstract:
  We consider the dynamics of systems of self propelling particles with
nonholonomic constraints. A continuum model for a discrete algorithm used in
works by T. Vicsek et al. is proposed. For a case of planar geometry the finite
flocking behavior is obtained. The circulation of the velocity field is found
not to be conserved as a consequence of the nonholomicity. The stability of
ordered motion with respect to noise is discussed. An analogy with the kinetics
of charges in superconductors is noted.


title:
Numerical study of the normal current density behaviour in a narrow -
  gap glow discharge

abstract:
  A numerical study of normal glow discharge properties was performed in the
case of small electrodes separations (0.05-0.4 cm) and moderate gas pressures
(10-46 Torr). A recently observed new experimental effect of a considerable
reduction in the normal current density for smaller discharge lengths was
analyzed both by means of 2D fluid model and by a minimal 1D drift model of gas
discharge. A good agreement between theoretical and experimental behaviour was
demonstrated. An influence of the electrodes separation and of the gas heating
on the value of the normal current density is discussed.


title:
The detection of single electrons by means of a Micromegas-covered
  MediPix2 pixel CMOS readout circuit

abstract:
  A small drift chamber was read out by means of a MediPix2 readout chip as
direct anode. A Micromegas foil was placed 50 $\mu$m above the chip, and
electron multiplication occurred in the gap. With a He/Isobutane 80/20 mixture,
gas multiplication factors up to tens of thousands were achieved, resulting in
an efficiency for detecting single electrons of better than 90% . We recorded
many frames containing 2D images with tracks from cosmic muons. Along these
tracks, electron clusters were observed, as well as delta-rays.


title: Type inversion in irradiated silicon: a half truth

abstract:
  Charge collection measurements performed on heavily irradiated p-spray dofz
pixel sensors with a grazing angle hadron beam provide a sensitive
determination of the electric field within the detectors. The data are compared
with a complete charge transport simulation of the sensor which includes signal
trapping and charge induction effects. A linearly varying electric field based
upon the standard picture of a constant type-inverted effective doping density
is inconsistent with the data. A two-trap double junction model implemented in
ISE TCAD software can be tuned to produce a doubly-peaked electric field which
describes the data reasonably well at two different fluences. The modeled field
differs somewhat from previous determinations based upon the transient current
technique. The model can also account for the level of signal trapping observed
in the data.


title:
Effective shear and extensional viscosities of cocentrated disordered
  suspensions of rigid particles

abstract:
  We study effective shear viscosity $\mu^\star$ and effective extensional
viscosity $\lambda^\star$ of concentrated non-colloidal suspensions of rigid
spherical particles. The focus is on the spatially disordered arrays. We use
recently developed discrete network approximation techniques to obtain
asymptotic formulas for the viscosities as the typical inter-particle distance
$\delta$ tends to zero. For disordered arrays, the volume fraction alone does
not determine the effective viscosity. Use of the network approximation allows
us to study the dependence of the effective viscosities on variable distances
between neighboring particles. Our analysis can be characterized as global
because it goes beyond the local analysis of the flow between two particles.
The principal conclusion in the paper is that, in general, asymptotic formulas
obtained by global analysis are different from the formulas obtained from local
analysis. In particular, the leading term in the asymptotics of $\mu^\star$ is
of lower order than suggested by the local analysis (weak blow up), while the
order of the leading term in the asymptotics of $\lambda^\star$ depends on the
geometry of the particle array (either weak or strong blow up). We obtain
geometric conditions on a random particle array that lead to the strong blow up
of $\lambda^\star$, and show that these conditions are generic. We also provide
an example of a closely packed particle array for which the leading term in the
asymptotics of $\lambda^\star$ degenerates (weak blow up).


title:
Optical clocks based on ultra-narrow three-photon resonances in alkaline
  earth atoms

abstract:
  A sharp resonance line that appears in three-photon transitions between the
$^{1}S_{0}$ and $^{3}P_{0}$ states of alkaline earth and Yb atoms is proposed
as an optical frequency standard. This proposal permits the use of the even
isotopes, in which the clock transition is narrower than in proposed clocks
using the odd isotopes and the energy interval is not affected by external
magnetic fields or the polarization of trapping light. The method has the
unique feature that the width and rate of the clock transition can be
continuously adjusted from the $MHz$ level to sub-$mHz$ without loss of signal
amplitude by varying the intensities of the three optical beams. Doppler and
recoil effects can be eliminated by proper alignment of the three optical beams
or by point confinement in a lattice trap. The three beams can be mixed to
produce the optical frequency corresponding to the $^{3}P_{0}$ - $^{1}S_{0}$
clock interval.


title:
Heat transport by turbulent Rayleigh-B'enard Convection in cylindrical
  cells with aspect ratio one and less

abstract:
  We present high-precision measurements of the Nusselt number N as a function
of the Rayleigh number R for cylindrical samples of water (Prandtl number sigma
= 4.4) with a diameter D of 49.7 cm and heights L = 116.3, 74.6, and 50.6 cm,
as well as for D = 24.8 cm and L = 90.2 cm. For each aspect ratio Gamma = D/L =
0.28, 0.43, 0.67, and 0.98 the data cover a range of a little over a decade of
R. The maximum R ~= 10^12 and Nusselt number N ~= 600 were reached for Gamma =
0.43 and D = 49.7. The data were corrected for the influence of the finite
conductivity of the top and bottom plates on the heat transport in the fluid to
obtain estimates of N_infty for plates with infinite conductivity. The results
for N_infty and Gamma >= 0.43 are nearly independent of Gamma. For Gamma =
0.275 N_infty falls about 2.5 % below the other data. For R ~<= 10^11, the
effective exponent gamma_eff of N_infty = N_0 R^gamma_eff is about 0.321,
larger than those of the Grossmann-Lohse model with its current parameters by
about 0.01. For the largest Rayleigh numbers covered for Gamma = 0.98, 0.67,
and 0.43, gamma_eff saturates at the asymptotic value gamma = 1/3 of the
Grossmann-Lohse model. The data do not reveal any crossover to a Kraichnan
regime with gamma_eff > 1/3.


title:
Steady-state relaxation and the first passage time distribution of the
  generalized master equation

abstract:
  In principle, the generalized master equation can be used to efficiently
compute the macroscopic first passage time (FPT) distribution of a complex
stochastic system from short-term microscopic simulation data. However,
computing its transition function matrix, Gamma(tau), from such data can be
practically difficult or impossible. We solve this problem by showing that the
FPT moment generating function is a simple function of the (easily computable)
Laplace transform of the local FPT distribution matrix. Physical insight into
this relationship is obtained by analyzing the process of steady-state
relaxation.


title:
Coherent Beam-Beam Tune Shift of Unsymmetrical Beam-Beam Interactions
  with Large Beam-Beam Parameter

abstract:
  Coherent beam-beam tune shift of unsymmetrical beam-beam interactions was
studied experimentally and numerically in HERA where the lepton beam has a very
large beam-beam parameter (up to $\xi_y=0.272$). Unlike the symmetrical case of
beam-beam interactions, the ratio of the coherent and incoherent beam-beam tune
shift in this unsymmetrical case of beam-beam interactions was found to
decrease monotonically with increase of the beam-beam parameter. The results of
self-consistent beam-beam simulation, the linearized Vlasov equation, and the
rigid-beam model were compared with the experimental measurement. It was found
that the coherent beam-beam tune shifts measured in the experiment and
calculated in the simulation agree remarkably well but they are much smaller
than those calculated by the linearized Vlasov equation with the single-mode
approximation or the rigid-beam model. The study indicated that the single-mode
approximation in the linearization of Vlasov equation is not valid in the case
of unsymmetrical beam-beam interactions. The rigid-beam model is valid only
with a small beam-beam parameter in the case of unsymmetrical beam-beam
interactions.


title:
Radiation-hard ASICs for optical data transmission in the ATLAS pixel
  detector

abstract:
  We have developed two radiation-hard ASICs for optical data transmission in
the ATLAS pixel detector at the LHC at CERN: a driver chip for a Vertical
Cavity Surface Emitting Laser (VCSEL) diode for 80 Mbit/s data transmission
from the detector, and a Bi-Phase Mark decoder chip to recover the control data
and 40 MHz clock received optically by a PIN diode. We have successfully
implemented both ASICs in 0.25 mm CMOS technology using enclosed layout
transistors and guard rings for increased radiation hardness. We present
results from circuits of final design and from irradiation studies with 24 GeV
protons up to 62 Mrad (2.3 x 10^15 p/cm^2).


title:
On the probability distribution function of small scale interplanetary
  magnetic field fluctuations

abstract:
  In spite of a large number of papers dedicated to study MHD turbulence in the
solar wind there are still some simple questions which have never been
sufficiently addressed like: a)do we really know how the magnetic field vector
orientation fluctuates in space? b) what is the statistics followed by the
orientation of the vector itself? c) does the statistics change as the wind
expands into the interplanetary space? A better understanding of these points
can help us to better characterize the nature of interplanetary fluctuations
and can provide useful hints to investigators who try to numerically simulate
MHD turbulence. This work follows a recent paper presented by the same authors.
This work follows a recent paper presented by some of the authors which shows
that these fluctuations might resemble a sort of random walk governed by a
Truncated Leevy Flight statistics. However, the limited statistics used in that
paper did not allow final conclusions but only speculative hypotheses. In this
work we aim to address the same problem using a more robust statistics which on
one hand forces us not to consider velocity fluctuations but, on the other hand
allows us to establish the nature of the governing statistics of magnetic
fluctuations with more confidence. In addition, we show how features similar to
those found in the present statistical analysis for the fast speed streams of
solar wind, are qualitatively recovered in numerical simulations of the
parametric instability. This might offer an alternative viewpoint for
interpreting the questions raised above.

categories: physics.space-ph astro-ph nlin.CD physics.data-an physics.plasm-ph


title:
Heuristic approach to a {\em natural} unification of the Quantum Theory
  and the General Theory of Relativity

abstract:
  In non-relativistic as well as in special relativistic quantum theory, {\em
mass} and {\em charge} are {\em pure numbers} appearing in various (quantum)
operators and admit {\em any values}, {\it ie}, values for these quantities are
to be prescribed {\em by hand}. This is, in a theory of probability,
understandable since we need to {\em assume} some {\em intrinsic} properties of
the object we are calculating the probability about. Then, if we {\em specify},
in some satisfactory manner, mass and charge for a point of the space in a
suitable general-relativistic framework, the quantum theoretical framework
could, in principle, be {\em obtainable} within it. Heuristic arguments are
presented to show that a {\em natural unification} of the quantum theory and
the general theory of relativity is achievable in this manner.


title: Exotic atoms

abstract:
  In this paper I review a number of recent results in the field of exotic
atoms. Recent experiments or ongoing experiments with muonic, pionic and
antiprotonic hydrogen, as well as recent measurement of the pion mass are
described. These experiments provide information about nucleon-pion or
nucleon-antinucleon interaction as well as information on the proton structure
(charge or magnetic moment distribution).


title:
Size-Dependent Bruggeman Approach for Dielectric-Magnetic Composite
  Materials

abstract:
  Expressions arising from the Bruggeman approach for the homogenization of
dielectric-magnetic composite materials, without ignoring the sizes of the
spherical particles, are presented. These expressions exhibit the proper limit
behavior. The incorporation of size dependence is directly responsible for the
emergence of dielectric-magnetic coupling in the estimated relative
permittivity and permeability of the homogenized composite material.


title:
Ground State Properties of Fermi Gases in the Strongly Interacting
  Regime

abstract:
  The ground state energies and pairing gaps in dilute superfluid Fermi gases
have now been calculated with the quantum Monte Carlo method without detailed
knowledge of their wave functions. However, such knowledge is essential to
predict other properties of these gases such as density matrices and pair
distribution functions. We present a new and simple method to optimize the wave
functions of quantum fluids using Green's function Monte Carlo method. It is
used to calculate the pair distribution functions and potential energies of
Fermi gases over the entire regime from atomic Bardeen-Cooper-Schrieffer
superfluid to molecular Bose-Einstein condensation, spanned as the interaction
strength is varied.


title:
A Simple Model of Scale-free Networks Driven by both Randomness and
  Adaptability

abstract:
  In this paper, we present a simple model of scale-free networks that
incorporates both preferential & random attachment and anti-preferential &
random deletion at each time step. We derive the degree distribution
analytically and show that it follows a power law with the degree exponent in
the range of (2,infinity). We also find a way to derive an expression of the
clustering coefficient for growing networks and compute the average path length
through simulation.


title: Landau damping in thin films irradiated by a strong laser field

abstract:
  The rate of linear collisionless damping (Landau damping) in a classical
electron gas confined to a heated ionized thin film is calculated. The general
expression for the imaginary part of the dielectric tensor in terms of the
parameters of the single-particle self-consistent electron potential is
obtained. For the case of a deep rectangular well, it is explicitly calculated
as a function of the electron temperature in the two limiting cases of specular
and diffuse reflection of the electrons from the boundary of the
self-consistent potential. For realistic experimental parameters, the
contribution of Landau damping to the heating of the electron subsystem is
estimated. It is shown that for films with a thickness below about 100 nm and
for moderate laser intensities it may be comparable with or even dominate over
electron-ion collisions and inner ionization.


title:
Gamma background and neutron flux measurements at Basic Ecological
  Observatory Moussala

abstract:
  The Basic Ecological Observatory (BEO) Moussala is located at 2925m above sea
level and one of the main activities is connected with gamma background and
neutron dose rate monitoring. The neutron and gamma measurements are carried
out with help of site radiation monitor Harwell Type 3208-1. The dose rate of
ambient gamma background is measured with SBN-90, improved with the embedded
microprocessor system using automatic PC based system. A cross check and inter
calibration with existing TLD (thermo luminescent dosimeters) at BEO Moussala
which is a part of the monitoring network of INRNE is presented. A polyethylene
sphere with a layer of lead serving as a neutron breeder, extending the energy
range from about 40 MeV to several hundred MeV is presented as a project in
development. Another project in development is the construction of active
detector based on SNM-15 detectors for a dose rate measurement of cosmic
neutrons is described. Preliminary study of the performances of the detectors
are carried out. A further project for muonic telescope similar to the yet
developed is discussed.


title: Quantum mechanics in curved space-time

abstract:
  In this paper, the principles of the general relativity are used to formulate
quantum wave equations for spin-0 and spin-1/2 particles. More specifically,
the equations are worked in a Schwarzschild-like metric. As a test, the
hydrogen atom spectrum is calculated. A comparison of the calculated spectrum
with the numerical data of the deuterium energy levels shows a significant
improvement of the accord, and the deviations are almost five times smaller
then the ones obtained with the Dirac theory. The implications of the theory
considering the strong interactions are also discussed.


title:
Statistics of transition times, phase diffusion and synchronization in
  periodically driven bistable systems

abstract:
  The statistics of transitions between the metastable states of a periodically
driven bistable Brownian oscillator are investigated on the basis of a
two-state description by means of a master equation with time-dependent rates.
The results are compared with extensive numerical simulations of the Langevin
equation for a sinusoidal driving force. Very good agreement is achieved both
for the counting statistics of the number of transitions and the residence time
distribution of the process in either state. The counting statistics
corroborate in a consistent way the interpretation of stochastic resonance as a
synchronisation phenomenon for a properly defined generalized Rice phase.


title:
Precision Spectroscopy of Pionic Atoms: From Pion Mass Evaluation to
  Tests of Chiral Perturbation Theory

abstract:
  Preliminary results of the strong interaction shift and width in pionic
hydrogen ($\pi H$) using an X-ray spectrometer with spherically bent crystals
and CCDs as X-ray detector are presented. In the experiment at the Paul
Scherrer Institute three different $(np\to 1s)$ transitions in $\pi H$ were
measured. Moreover the pion mass measurement using the $(5 \to 4)$ transitions
in pionic nitrogen and muonic oxygen is presented


title: Annular Bragg Defect mode Resonators

abstract:
  We propose and analyze a new type of a resonator in an annular geometry which
is based on a single defect surrounded by radial Bragg reflectors on both
sides. We show that the conditions for efficient mode confinement are different
from those of the conventional Bragg waveguiding in a rectangular geometry. A
simple and intuitive approach to the design of optimal radial Bragg reflectors
is proposed and employed, yielding chirped gratings. Small bending radii and
strong control over the resonator dispersion are possible by the Bragg
confinement. A design compromise between large Free Spectral Range (FSR)
requirements and fabrication tolerances is suggested.


title: Low Threshold Two-Dimensional Annular Bragg Lasers

abstract:
  Lasing at telecommunication wavelengths from annular resonators employing
radial Bragg reflectors is demonstrated at room temperature under pulsed
optical pumping. Sub milliwatt pump threshold levels are observed for
resonators with 0.5-1.5 wavelengths wide defects of radii 7-8 mm. The quality
factors of the resonator modal fields are estimated to be on the order of a few
thousands. The electromagnetic field is shown to be guided by the defect. Good
agreement is found between the measured and calculated spectrum.


title:
Periodic orbits of the ensemble of Sinai-Arnold cat maps and
  pseudorandom number generation

abstract:
  We propose methods for constructing high-quality pseudorandom number
generators (RNGs) based on an ensemble of hyperbolic automorphisms of the unit
two-dimensional torus (Sinai-Arnold map or cat map) while keeping a part of the
information hidden. The single cat map provides the random properties expected
from a good RNG and is hence an appropriate building block for an RNG, although
unnecessary correlations are always present in practice. We show that
introducing hidden variables and introducing rotation in the RNG output,
accompanied with the proper initialization, dramatically suppress these
correlations. We analyze the mechanisms of the single-cat-map correlations
analytically and show how to diminish them. We generalize the Percival-Vivaldi
theory in the case of the ensemble of maps, find the period of the proposed RNG
analytically, and also analyze its properties. We present efficient practical
realizations for the RNGs and check our predictions numerically. We also test
our RNGs using the known stringent batteries of statistical tests and find that
the statistical properties of our best generators are not worse than those of
other best modern generators.


title:
Quantum chaos theory and the spectrum of ideal-MHD instabilities in
  toroidal plasmas

abstract:
  In a fully 3-D system such as a stellarator, the toroidal mode number $n$
ceases to be a good quantum number--all $n$s within a given mode family being
coupled. It is found that the discrete spectrum of unstable ideal MHD
(magnetohydrodynamic) instabilities ceases to exist unless MHD is modified
(regularized) by introducing a short-perpendicular-wavelength cutoff. Attempts
to use ray tracing to estimate the regularized MHD spectrum fail due to the
occurrence of chaotic ray trajectories. In quantum chaos theory, strong chaos
in the semiclassical limit leads to eigenvalue statistics the same as those of
a suitable ensemble of random matrices. For instance, the probability
distribution function for the separation between neighboring eigenvalues is as
derived from random matrix theory and goes to zero at zero separation. This
contrasts with the Poissonian distribution found in separable systems, showing
that a signature of quantum chaos is level repulsion. In order to determine
whether eigenvalues of the regularized MHD problem obey the same statistics as
those of the Schr\"odinger equation in both the separable 1-D case and the
chaotic 3-D cases, we have assembled data sets of ideal MHD eigenvalues for a
Suydam-unstable cylindrical (1-D) equilibrium using \emph{Mathematica} and a
Mercier-unstable (3-D) equilibrium using the CAS3D code. In the 1-D case, we
find that the unregularized Suydam-approximation spectrum has an anomalous peak
at zero eigenvalue separation. On the other hand, regularization by restricting
the domain of $\kvec_{\perp}$ recovers the expected Poissonian distribution. In
the 3-D case we find strong evidence of level repulsion within mode families,
but mixing mode families produces Poissonian statistics.


title: Two-step method for precise calculation of core properties in molecules

abstract:
  Precise calculations of core properties in heavy-atom systems which are
described by the operators heavily concentrated in atomic cores, like to
hyperfine structure and P,T-parity nonconservation effects, usually require
accounting for relativistic effects. Unfortunately, completely relativistic
treatment of molecules containing heavy elements is very consuming already at
the stages of calculation and transformation of two-electron integrals with a
basis set of four-component spinors.
  In turn, the relativistic effective core potential (RECP) calculations of
valence (spectroscopic, chemical etc.) properties of molecules are very popular
because the RECP method allows one to treat quite satisfactory the correlation
and relativistic effects for the valence electrons of a molecule and to reduce
significantly the computational efforts. The valence molecular spinors are
usually smoothed in atomic cores and, as a result, direct calculation of
electronic densities near heavy nuclei is impossible.
  In the paper, the methods of nonvariational and variational one-center
restoration of correct shapes of four-component spinors in atomic cores after a
two-component RECP calculation of a molecule are discussed. Their efficiency is
illustrated in correlation calculations of hyperfine structure and parity
nonconservation effects in heavy-atom molecules YbF, BaF, TlF, and PbO.


title:
Regularization of the second-order partial derivatives of the Coulomb
  potential of a point charge

abstract:
  The second-order partial derivatives of the Coulomb potential of a point
charge can be regularized using the Coulomb potential of a charge of the oblate
spheroidal shape that a moving rest-frame-spherical charge acquires by the
Lorentz contraction. This `physical' regularization is shown to be fully
equivalent to the standard delta-function identity involving these derivatives.


title: Optical Velocimetry

abstract:
  This work considers current potential uses of laser Doppler velocimetry. A
discussion of other optical velocimetry techniques is presented and compared
with their practical application to modern shock physics diagnostics, such as
VISAR.


title: Self-organization in turbulence as a route to order in plasma and fluids

abstract:
  Transitions from turbulence to order are studied experimentally in thin fluid
layers and magnetically confined toroidal plasma. It is shown that turbulence
self-organizes through the mechanism of spectral condensation. The spectral
redistribution of the turbulent energy leads to the reduction in the turbulence
level, generation of coherent flow, reduction in the particle diffusion and
increase in the system's energy. The higher order state is sustained via the
nonlocal spectral coupling of the linearly unstable spectral range to the
large-scale mean flow. The similarity of self-organization in two-dimensional
fluids and low-to-high confinement transitions in plasma suggests the
universality of the mechanism.


title: ATLAS RPC Cosmic Ray Teststand at INFN Lecce

abstract:
  We describe the design and functionality of the cosmic ray teststand built at
  INFN Lecce for ATLAS RPC quality control assurance.


title: On Dirac's incomplete analysis of gauge transformations

abstract:
  Dirac's approach to gauge symmetries is discussed. We follow closely the
steps that led him from his conjecture concerning the generators of gauge
transformations {\it at a given time} --to be contrasted with the common view
of gauge transformations as maps from solutions of the equations of motion into
other solutions-- to his decision to artificially modify the dynamics,
substituting the extended Hamiltonian (including all first-class constraints)
for the total Hamiltonian (including only the primary first-class constraints).
We show in detail that Dirac's analysis was incomplete and, in completing it,
we prove that the fulfilment of Dirac's conjecture --in the "non-pathological"
cases-- does not imply any need to modify the dynamics. We give a couple of
simple but significant examples.

categories: physics.hist-ph gr-qc hep-th math-ph math.MP


title:
Lifetime and hyperfine splitting measurements on the 7s and 6p levels in
  rubidium

abstract:
  We present lifetime measurements of the 7S1/2 level and the 6p manifold of
rubidium. We use a timecorrelated single-photon counting technique on a sample
of 85Rb atoms confined and cooled in a magneto-optic trap. The upper state of
the 5P1/2 repumping transition serves as the resonant intermediate level for
twophoton excitation of the 7s level. A probe laser provides the second step of
the excitation, and we detect the decay of atomic fluorescence to the 5P3/2
level at 741 nm. The decay process feeds the 6p manifold that decays to the 5s
ground state emitting UV photons. We measure lifetimes of 88.07 +- 0.40 and
120.7 +- 1.2 ns for the 7S1/2 level and 6p manifold, respectively; the
hyperfine splitting of the 7S1/2 level is 282.6 +- 1.6 MHz. The agreement with
theoretical calculations confirms the understanding of the wave functions
involved and provides confidence on the possibility of extracting weak
interaction constants from a parity nonconservation measurement.


title: Rotary dipole-mode solitons in Bessel photonic lattices

abstract:
  We address Bessel photonic lattices of radial symmetry imprinted in cubic
Kerr-type nonlinear media and show that they support families of stable
dipole-mode solitons featuring two out-of-phase light spots located in
different lattice rings. We show that the radial symmetry of the Bessel
lattices afford a variety of unique soliton dynamics including controlled
radiation-free rotation of the dipole-mode solitons.


title:
Natural radioelement concentration in the Troodos Ophiolite Complex of
  Cyprus

abstract:
  High-resolution gamma-ray spectrometry was exploited to determine naturally
occurring thorium (Th), uranium (U) and potassium (K) elemental concentrations
in the whole area covered by the Troodos Ophiolite Complex of Cyprus. For that
purpose, a total of 59 samples from surface soils and 10 from the main rock
formations of the region of interest were analysed. Elemental concentrations
were determined for Th (range from 2.5x10^-3 ppm to 2.0 ppm), U (from 8.1x10^-4
ppm to 0.6 ppm), and K (from 1.3x10^-4 % to 1.0 %). The average values (A.M +-
S.D.) derived are (0.24 +- 0.34) ppm, (0.10 +- 0.10) ppm and (0.21 +- 0.24) %,
for Th, U, and K, respectively, in the soils, and (0.52 +- 0.17) ppm, (0.17 +-
0.11) ppm and (0.49 +- 0.87) % in the rocks. From these values, a radioactivity
(radioelement) loss of nearly 50% is estimated in the underlying surface soils
due to bleaching and eluviation during weathering of the rocks. The measured
Th/U ratio exhibits values between 2 and 4, whereas the K/Th ratio is highly
variable ranging between 1.5x10^3 and 3.0x10^4.


title:
Theoretical studies of the kinetics of mechanical unfolding of
  cross-linked polymer chains and their implications for single molecule
  pulling experiments

abstract:
  We have used kinetic Monte Carlo simulations to study the kinetics of
unfolding of cross-linked polymer chains under mechanical loading. As the ends
of a chain are pulled apart, the force transmitted by each crosslink increases
until it ruptures. The stochastic crosslink rupture process is assumed to be
governed by first order kinetics with a rate that depends exponentially on the
transmitted force. We have performed random searches to identify optimal
crosslink configurations whose unfolding requires a large applied force
(measure of strength) and/or large dissipated energy (measure of toughness). We
found that such optimal chains always involve cross-links arranged to form
parallel strands. The location of those optimal strands generally depends on
the loading rate. Optimal chains with a small number of cross-links were found
to be almost as strong and tough as optimal chains with a large number of
cross-links. Furthermore, optimality of chains with a small number of
cross-links can be easily destroyed by adding cross-links at random. The
present findings are relevant for the interpretation of single molecule force
probe spectroscopy studies of the mechanical unfolding of load-bearing
proteins, whose native topology often involves parallel strand arrangements
similar to the optimal configurations identified in the study.


title:
Criteria for the experimental observation of multi-dimensional optical
  solitons in saturable media

abstract:
  Criteria for experimental observation of multi-dimensional optical solitons
in media with saturable refractive nonlinearities are developed. The criteria
are applied to actual material parameters (characterizing the cubic
self-focusing and quintic self-defocusing nonlinearities, two-photon loss, and
optical-damage threshold) for various glasses. This way, we identify operation
windows for soliton formation in these glasses. It is found that two-photon
absorption sets stringent limits on the windows. We conclude that, while a
well-defined window of parameters exists for two-dimensional solitons (spatial
or spatiotemporal), for their three-dimensional spatiotemporal counterparts
such a window \emph{does not} exist, due to the nonlinear loss in glasses.


title: Priliminary Modeling of Air Breakdown with the ICEPIC code

abstract:
  Interest in air breakdown phenomena has recently been re-kindled with the
advent of advanced virtual prototyping of radio frequency (RF) sources for use
in high power microwave (HPM) weapons technology. Air breakdown phenomena are
of interest because the formation of a plasma layer at the aperture of an RF
source decreases the transmitted power to the target, and in some cases can
cause significant reflection of RF radiation. Understanding the mechanisms
behind the formation of such plasma layers will aid in the development of
maximally effective sources. This paper begins with some of the basic theory
behind air breakdown, and describes two independent approaches to modeling the
formation of plasmas, the dielectric fluid model and the Particle in Cell (PIC)
approach. Finally we present the results of preliminary studies in numerical
modeling and simulation of breakdown.


title: On the physical origins of the negative index of refraction

abstract:
  The physical origins of negative refractive index are derived from a dilute
microscopic model, producing a result that is generalized to the dense
condensed phase limit. In particular, scattering from a thin sheet of electric
and magnetic dipoles driven above resonance is used to form a fundamental
description for negative refraction. Of practical significance, loss and
dispersion are implicit in the microscopic model. While naturally occurring
negative index materials are unavailable, ferromagnetic and ferroelectric
materials provide device design opportunities.


title: Measuring questions: relevance and its relation to entropy

abstract:
  The Boolean lattice of logical statements induces the free distributive
lattice of questions. Inclusion on this lattice is based on whether one
question answers another. Generalizing the zeta function of the question
lattice leads to a valuation called relevance or bearing, which is a measure of
the degree to which one question answers another. Richard Cox conjectured that
this degree can be expressed as a generalized entropy. With the assistance of
yet another important result from Janos Aczel, I show that this is indeed the
case, and that the resulting inquiry calculus is a natural generalization of
information theory. This approach provides a new perspective on the Principle
of Maximum Entropy.


title: Counterion density profiles at charged flexible membranes

abstract:
  Counterion distributions at charged soft membranes are studied using
perturbative analytical and simulation methods in both weak coupling
(mean-field or Poisson-Boltzmann) and strong coupling limits. The softer the
membrane, the more smeared out the counterion density profile becomes and
counterions pentrate through the mean-membrane surface location, in agreement
with anomalous scattering results. Membrane-charge repulsion leads to a
short-scale roughening of the membrane.


title: Simple Pendulum Revisited

abstract:
  We describe a 8085 microprocessor interface developed to make reliable time
period measurements. The time period of each oscillation of a simple pendulum
was measured using this interface. The variation of the time period with
increasing oscillation was studied for the simple harmonic motion (SHM) and for
large angle initial displacements (non-SHM). The results underlines the
importance of the precautions which the students are asked to take while
performing the pendulum experiment.


title: Accurate, efficient and simple forces with Quantum Monte Carlo methods

abstract:
  Computation of ionic forces using quantum Monte Carlo methods has long been a
challenge. We introduce a simple procedure, based on known properties of
physical electronic densities, to make the variance of the Hellmann-Feynman
estimator finite. We obtain very accurate geometries for the molecules H$_2$,
LiH, CH$_4$, NH$_3$, H$_2$O and HF, with a Slater-Jastrow trial wave function.
Harmonic frequencies for diatomics are also in good agreement with experiment.
An antithetical sampling method is also discussed for additional reduction of
the variance.


title: How Fundamental is Gravitation ?

abstract:
  Based on a Planck scale underpinning for the universe, we deduce an
expression for the gravitational constant which exhibits it as a distributional
effect over all the particles of the universe. This solves a long standing
puzzle, the so called Weinberg formula which gives a microphysical parameter in
terms of a cosmic parameter. This was also discussed on the basis of a
cosmology that correctly predicted a dark energy driven accelerating universe -
the linkage is now established.


title:
The Bubble regime of laser-plasma acceleration: monoenergetic electrons
  and the scalability

abstract:
  The Bubble regime of electron acceleration in ultra-relativistic laser plasma
is considered. It has been shown that the bubble can produce ultra-short dense
bunches of electrons with quasi-monoenergetic energy spectra. The first
experiment in this regime done at LOA has confirmed the peaked electron
spectrum (J. Faure, et al., {\it submitted}, 2004). The generated electron
bunch may have density an order of magnitude higher than that of the background
plasma. The bubble is able to guide the laser pulse over many Rayleigh lengths,
thus no preformed plasma channel is needed for high-energy particle
acceleration in the bubble regime. In the present work we discuss a simple
analytical model for the bubble fields as well as the scaling laws.


title: MHD precursor to disruption in Iran tokamak 1

abstract:
  The purpose of this paper is to further investigate the major disruptions
occurring in low-q(a) discharges in Iran Tokamak 1, and to compare the
theoretical and experimental results for the rate of island growth. The study
of precursor phase of disruption can be predicted and avoided using suitable
control systems. In this paper are described the stability analysis and the
observed growth rates indicate that the rotating modes are tearing modes.


title: Criticality in a Vlasov-Poisson system - a fermionic universality class

abstract:
  A model Vlasov--Poisson system is simulated close the point of marginal
stability, thus assuming only the wave-particle resonant interactions are
responsible for saturation, and shown to obey the power--law scaling of a
second-order phase transition. The set of critical exponents analogous to those
of the Ising universality class is calculated and shown to obey the Widom and
Rushbrooke scaling and Josephson's hyperscaling relations at the formal
dimensionality $d=5$ below the critical point at nonzero order parameter.
However, the two-point correlation function does not correspond to the
propagator of Euclidean quantum field theory, which is the Gaussian model for
the Ising universality class. Instead it corresponds to the propagator for the
fermionic {\it vector} field and to the {\it upper critical dimensionality}
$d_c=2$. This suggests criticality of collisionless Vlasov-Poisson systems as
representative of the {\it universality class} of critical phenomena of {\it a
fermionic} quantum field description.


title: Wholeness as a Conceptual Foundation of Physical Theories

abstract:
  A description of physical reality in which wholeness is the foundation is
discussed along with the motivation for such an attempt. As a possible
mathematical framework within which a physical theory based on wholeness may be
expressed, elementary embeddings along with the Wholeness Axiom are suggested.
It is shown how features of wholeness such as wholeness being indescribable,
more than the sum of parts, locally accessible and giving rise to a
self-similar, or holographic, type of order are reflected in the mathematics.
It is also shown how all the sets in the mathematical universe may be expressed
as emerging from the dynamics of wholeness. Moreover, it is indicated how the
mathematics may be further developed so as to connect up with a physical
interpretation.


title: Topological soliton in magnetohydrodynamics

abstract:
  We use the Hopf mapping to construct a magnetic configuration consisting of
closed field lines, each of which is linked with all the other ones. We obtain
in this way a solution of the equations of magnetohydrodynamics of an ideal
incompressible fluid with infinite conductivity, which describes a localized
topological soliton.


title:
Multi-windowed defocused speckle photographic system for tilt
  measurement

abstract:
  Defocused speckle photography has long been used to measure rotations of
rough surfaces. This paper explains how, by adding a suitably perforated mask,
some measurement properties, such as range or lateral resolution, may be
changed at wish. Particularly, the maximum measurable tilt can be significantly
raised, although at the expense of poorer lateral resolution. Advantages over
previously described techniques include independent tuning of speckle size and
optical system aperture and more extended adaptability to different measuring
needs. The benefits and disadvantages of the new and old techniques are
thoroughly compared.


title: Structure of mesoscopic Coulomb balls

abstract:
  An analysis of the structural properties of three-dimensional Coulomb
clusters confined in a spherical parabolic trap is presented. Based on
extensive high accuracy computer simulations the shell configurations and
energies for particle numbers in the range $60 \le N\le 160$ are reported.
Further, the intrashell symmetry and the lowest metastable configurations are
analyzed for small clusters and a novel type of excited state which does not
involve a change of shell configuration is identified.


title:
Probabilistic temperature forecasting: a summary of our recent research
  results

abstract:
  We summarise the main results from a number of our recent articles on the
subject of probabilistic temperature forecasting.


title:
Making use of the information in ensemble weather forecasts: comparing
  the end to end and full statistical modelling approaches

abstract:
  We discuss how ensemble weather forecasts can be used, and highlight the
advantages and disadvantages of two particular methods.


title: Effect of the Vacuum Energy Density on Graviton Propagation

abstract:
  It is known that the value L of the vacuum energy density affects the
propagation equation for gravitons: A mass term appears in the propagation
equation, such that m^2=-L. As a consequence, the polarization states of
gravitons also change. This effect of the L-term has been confirmed by recent
calculations in a curved background, which is the only proper setting, since
solutions of the classical Einstein equations in the presence of a L-term
represent a space with constant curvature. A real value for the mass (when L<0)
will show up as a slight exponential damping in the gravitational potential,
which is however strongly constrained by astronomical data. The consequences of
an imaginary mass (for L>0) are still unclear; on general grounds, one can
expect the onset of instabilities in this case. This is also confirmed by
numerical simulations of quantum gravity which became recently available. These
properties gain a special interest in consideration of the following. (1) The
most recent cosmological data indicate that L is positive and of the order of
0.1 J/m^3. Is this value compatible with a stable propagation of gravitons? (2)
The answer to the previous question lies perhaps in the scale dependence of the
effective value of L. L may be negative at the small distance/large energy
scale at which the quantum behavior of gravitational fields and waves becomes
relevant. Furthermore, local contributions to the vacuum energy density (in
superconductors in certain states, and in very strong static electromagnetic
fields) can change locally the sign of L, and so affect locally the propagation
and the properties of gravitons. The graviton wavefunction, for different
values of the parameters, may be characterized by superluminal phase velocity
or by unitarity only in imaginary valued time.


title:
Non-Sequential Double Ionization is a Completely Classical Photoelectric
  Effect

abstract:
  We introduce a unified and simplified theory of atomic double ionization. Our
results show that at high laser intensities ($I \ge 10^{14}$ watts/cm$^2$)
purely classical correlation is strong enough to account for all of the main
features observed in experiments to date.


title: Tables of mesoscopic 3D Coulomb balls

abstract:
  Detailed numerical results for the structural properties of three-dimensional
classical Coulomb clusters confined in a spherical parabolic trap are
presented. Based on extensive high accuracy computer simulations the shell
configurations and energies for particle numbers in the range $2 \le N\le 160$
are reported. Further, the mean shell radii and shell widths are calculated.


title: X-Ray Scanner for Atlas Barrel TRT Modules

abstract:
  X-ray scanners for gain mapping of ATLAS Barrel Transition Radiation Tracker
(TRT) modules were developed at Hampton University for quality assurance
purposes. Gas gain variations for each straw of the TRT modules were used to
decide whether wires should be removed or restrung, and to evaluate overall
module quality.


title:
Contemporary Approach for Simulation and Computation of Fluid Flows in
  Centrifugal Hydromachines

abstract:
  The article describes various aspects of mathematical modeling of fluid
flows, both in general and with reference to hydraulic machinery. The article
reviews historical development of corresponding methods of mathematical
modeling. Implementation of these aspects in modern commercial CFD software
tools is described together with advantages and disadvantages of implemented
methods. The conclusion is drawn concerning possibilities of computation of
fluid flows nowadays.


title:
Derivation of the Lorentz Force Law, the Magnetic Field Concept and the
  Faraday-Lenz Law using an Invariant Formulation of the Lorentz Transformation

abstract:
  It is demonstrated how the right hand sides of the Lorentz Transformation
equations may be written, in a Lorentz invariant manner, as 4--vector scalar
products. This implies the existence of invariant length intervals analogous to
invariant proper time intervals. This formalism, making essential use of the
4-vector electromagnetic potential concept, provides a short derivation of the
Lorentz force law of classical electrodynamics, the conventional definition of
the magnetic field, in terms of spatial derivatives of the 4--vector potential
and the Faraday-Lenz Law. An important distinction between the physical
meanings of the space-time and energy-momentum 4--vectors is pointed out.


title:
Possibilities of Simulation of Fluid Flows Using the Modern CFD Software
  Tools

abstract:
  The article reviews fluid flow models implemented in the leading CFD software
tools and designed for simulation of multi-component and multi-phase flows,
compressible flows, flows with heat transfer, cavitation and other phenomena.
The article shows that these software tools (CFX, Fluent, STAR-CD, etc.) allow
for adequate simulation of complex physical effects of different nature, even
for problems where performing of physical experiment is extremely difficult.


title:
Spectroscopy in the Presence of Geometrical Constraints: A Torsional
  Pendulum

abstract:
  We demonstrate that an effect other than anharmonicity can severely distort
the spectroscopic signatures of quantum mechanical systems. This is done
through an analytic calculation of the spectroscopic response of a simple
system, a charged torsional pendulum. One may look for these effects in the
optical data of real systems when for example a significant rocking component
of rigid polyhedra plays a significant role in the lattice dynamics.


title:
Observation of spontaneous self-channelling of light in air below the
  collapse threshold

abstract:
  We report the observation of the self-guided propagation of 120 fs, 0.56 mJ
infrared radiation in air for distances greater than one meter. In contrast to
the known case of filamentation, in the present experiment the laser power is
lower than the collapse threshold. Therefore the counter balance between Kerr
self focussing and ionization induced defocussing as the stabilizing mechanism
is ruled out. Instead, we find evidences of a process in which the transversal
beam distribution reshapes into a form similar to a Townes soliton. We include
numerical support for this conclusion.


title:
Electrodynamical properties of a "grid" volume resonator for travelling
  wave tube and backward wave oscillator

abstract:
  The electrodynamical properties of a volume resonator formed by a perodic
structure built from the metallic threads inside a rectangular waveguide
("grid" volume resonator) is considered for travelling wave tube and backward
wave oscillator operation. Peculiarities of passing of electromagnetic waves
with different polarizations through such volume resonator are discussed.


title: Ropelength of tight polygonal knots

abstract:
  A physical interpretation of the rope simulated by the SONO algorithm is
presented. Properties of the tight polygonal knots delivered by the algorithm
are analyzed. An algorithm for bounding the ropelength of a smooth inscribed
knot is shown. Two ways of calculating the ropelength of tight polygonal knots
are compared. An analytical calculation performed for a model knot shows that
an appropriately weighted average should provide a good estimation of the
minimum ropelength for relatively small numbers of edges.


title: The axial ratio of hcp iron at the conditions of the Earth's inner core

abstract:
  We present ab initio calculations of the high-temperature axial c/a ratio of
hexagonal-close-packed (hcp) iron at Earth's core pressures, in order to help
interpret the observed seismic anisotropy of the inner core. The calculations
are based on density functional theory, which is known to predict the
properties of high-pressure iron with good accuracy. The temperature dependence
of c/a is determined by minimising the Helmholtz free energy at fixed volume
and temperature, with thermal contributions due to lattice vibrations
calculated using harmonic theory. Anharmonic corrections to the harmonic
predictions are estimated from calculations of the thermal average stress
obtained from ab initio molecular dynamics simulations of hcp iron at the
conditions of the inner core. We find a very gradual increase of axial ratio
with temperature. This increase is much smaller than found in earlier
calculations, but is in reasonable agreement with recent high-pressure,
high-temperature diffraction measurements. This result casts doubt on an
earlier interpretation of the seismic anisotropy of the inner core.