title: Dynamics of stable viscous displacement in porous media

abstract:
  We investigate the stabilization mechanisms of the invasion front in
two-dimensional drainage displacement in porous media by using a network
simulator. We focus on the process when the front stabilizes due to the viscous
forces in the liquids. We find that the capillary pressure difference between
two different points along the front varies almost linearly as function of
height separation in the direction of the displacement. The numerical results
support arguments that differ from those suggested earlier for viscous
stabilization. Our arguments are based upon the observation that nonwetting
fluid flows in loopless strands (paths) and we conclude that earlier suggested
theories are not suitable to drainage when nonwetting strands dominate the
displacement process. We also show that the arguments might influence the
scaling behavior between the front width and the injection rate and compare
some of our results to experimental work.


title: Viscous stabilization of 2D drainage displacements with trapping

abstract:
  We investigate the stabilization mechanisms due to viscous forces in the
invasion front during drainage displacement in two-dimensional porous media
using a network simulator. We find that in horizontal displacement the
capillary pressure difference between two different points along the front
varies almost linearly as function of height separation in the direction of the
displacement. The numerical result supports arguments taking into account the
loopless displacement pattern where nonwetting fluid flow in separate strands
(paths). As a consequence, we show that existing theories developed for viscous
stabilization, are not compatible with drainage when loopless strands dominate
the displacement process.


title: Quantum theory of a high harmonic generation as a three-step process

abstract:
  Fully quantum treatment explicitly presents the high harmonic generation as a
three-step process: (i) above threshold ionization (ATI) is followed by (ii)
electron propagation in a laser-dressed continuum. Subsequently (iii)
stimulated (or laser assisted) recombination brings the electron back into the
initial state with emission of a high-energy photon. Contributions of all ATI
channels add up coherently. All three stages of the process are described by
simple, mostly analytical expressions that allow a detailed physical
interpretation. A very good quantitative agreement with the previous
calculations on the harmonic generation by H-minus ion is demonstrated, thus
supplementing the conceptual significance of the theory with its practical
efficiency. The virtue of the present scheme is further supported by a good
accord between the calculations in length and velocity gauges for the
high-energy photon.


title:
Resonant Diffraction Radiation from an Ultrarelativistic Particle Moving
  Close to a Tilted Grating

abstract:
  A simple model for calculating the diffraction radiation characteristics from
an ultrarelativistic charged particle moving close to a tilted ideally
conducting strip is developed. Resonant diffraction radiation (RDR) is treated
as a superposition of the radiation fields for periodically spaced strips. The
RDR characteristics have been calculated as a function of the number of grating
elements, tilted angle, and initial particle energy. An analogy with both the
resonant transition radiation in absorbing medium and the parametric X-ray
radiation is noted.


title:
Exact Dirac equation calculation of ionization induced by
  ultrarelativistic heavy ions

abstract:
  The time-dependent Dirac equation can be solved exactly for ionization
induced by ultrarelativistic heavy ion collisions. Ionization calculations are
carried out in such a framework for a number of representative ion-ion pairs.
For each ion-ion pair, the computed cross section consists of two terms, a
constant energy independent term and a term whose coefficient is ln(gamma).
Scaled values of both terms are found to decrease with increasing Z of the
nucleus that is ionized.


title: Practical Guide to Monte Carlo

abstract:
  I show how to construct Monte Carlo algorithms (programs), prove that they
are correct and document them. Complicated algorithms are build using a handful
of elementary methods. This construction process is transparently illustrated
using graphical representation in which complicated graphs consist of only
several elementary building blocks. In particular I discuss the equivalent
algorithms, that is different MC algorithms, with different arrangements of the
elementary building blocks, which generate the same final probability
distribution. I also show how to transform a given MC algorithm into another
equivalent one and discuss advantages of the various ``architectures''.

categories: physics.comp-ph astro-ph hep-ph physics.data-an


title: Ionospheric HF pump wave triggering of local auroral activation

abstract:
  Experimental results from Tromso HF pumping experiments in the nightside
auroral E region are reported. We found intriguing evidence that a modification
of the ionosphere-magnetosphere coupling, due to the effects of powerful HF
waves beamed into an auroral sporadic E layer, can lead to a local
intensification of the auroral activity. Summarizing multi-instrument
ground-based observations and observations from the IMP 8 and IMP 9 satellites,
one can distinguish the following peculiarities related to this auroral
activation: modification of the auroral arc and its break-up above Tromso;
local changes of the horizontal currents in the vicinity of Tromso; increase of
the electron temperature and ion velocities at altitudes above the HF pump
reflection level; distinctive features in dynamic HF radio scatter Doppler
spectra; pump-induced electron precipitation; substorm activation exactly above
Tromso. The mechanisms of the modification of the ionosphere-magnetosphere
coupling through the excitation of the turbulent Alfven boundary layer between
the base of the ionosphere (~100 km) and the level of sharp increase of the
Alfven velocity (at heights up to one Earth radius), and the formation of a
local magnetospheric current system are discussed. The results suggest that a
possible triggering of local auroral activation requires specific geophysical
conditions.


title: Why the Parity Violation

abstract:
  The sufficient and necessary conditions for a nonzero fermion mass without
Higgs are considered. The Parity Violation is deduced from these conditions.


title: Propulsion Through Electromagnetic Self-Sustained Acceleration

abstract:
  As is known the repulsion of the volume elements of an uniformly accelerating
charge or a charge supported in an uniform gravitational field accounts for the
electromagnetic contribution to the charge's inertial and gravitational mass,
respectively. This means that the mutual repulsion of the volume elements of
the charge produces the resistance to its accelerated motion. Conversely, the
effect of electromagnetic attraction of opposite charges enhances the
accelerated motion of the charges provided that they have been initially
uniformly accelerated or supported in an uniform gravitational field. The
significance of this effect is that it constitutes a possibility of altering
inertia and gravitation.


title: The Fabric of Space-time II: Gravity by Photon Exchange

abstract:
  This is one of a number of papers in which the metric for space-time is
defined on the subatomic level by means of the interchange of photons, and
constrained to be consistent with radar. It is shown that the discrete nature
of particle interactions necessitates a small inherent delay in the radar
method, and hence that the resulting geometry is non- Euclidean. Thus the
forces of gravity and electromagnetism can each be seen as an effect of the
same interaction between elementary particles, and we can identify
gravitational and inertial mass.


title: Inhomogeneity of dusty crystals and plasma diagnostics

abstract:
  Real dusty crystals are inhomogeneous due to the presence of external forces.
We suggest approximations for calculations of different types of inhomogeneous
DC (chain and DC with a few slabs) in the equilibrium state. The results are in
a good agreement with experimental results and can be used as an effective
diagnostic method for many dusty systems.


title: Amplification of External EM-wave by Nonlinear Wake Waves in Cold Plasma

abstract:
  Interaction of external monochromatic, linearly polorized plane EM-wave with
nonlinear one-dimensional wake wave, generated by relativistic electron bunch
moving in cold plasma, is considered. At definite conditions on parameters of
plasma and bunch, nonlinear wake wave can have a pronounced spikes, where
plasma electron density has its maximum value and plasma electron velocities
are nearing wave breaking limit, i.e. velocity of the rigid driving bunch.
Presented calculations show, that external EM-wave, propagating through plasma,
normal to the bunch velocity, at such a conditions can be amplified inside the
spikes, due to interaction with the plasma electrons. EM-wave, Thomson
scattered on spikes, is also amplified. Amplification factors are obtained for
the both cases at different conditions on EM-wave-plasma-electron bunch system
parameters. An additional amplification takes place, when the frequency of
EM-wave is nearing to the spike plasma frequency.


title: Physics of Particle Detection

abstract:
  In this review the basic interaction mechanisms of charged and neutral
particles are presented. The ionization energy loss of charged particles is
fundamental to most particle detectors and is therefore described in more
detail. The production of electromagnetic radiation in various spectral ranges
leads to the detection of charged particles in scintillation, Cherenkov and
transition radiation counters. Photons are measured via the photoelectric
effect, Compton scattering or pair production, and neutrons through their
nuclear interactions. A combination of the various detector methods helps to
identify elementary particles and nuclei. At high energies absorption
techniques in calorimeters provide additional particle identification and an
accurate energy measurement.


title: When do finite sample effects significantly affect entropy estimates ?

abstract:
  An expression is proposed for determining the error caused on entropy
estimates by finite sample effects. This expression is based on the Ansatz that
the ranked distribution of probabilities tends to follow an empirical Zipf law.


title:
Identifying nonlinear wave interactions in plasmas using two-point
  measurements: a case study of Short Large Amplitude Magnetic Structures
  (SLAMS)

abstract:
  A framework is described for estimating Linear growth rates and spectral
energy transfers in turbulent wave-fields using two-point measurements. This
approach, which is based on Volterra series, is applied to dual satellite data
gathered in the vicinity of the Earth's bow shock, where Short Large Amplitude
Magnetic Structures (SLAMS) supposedly play a leading role. The analysis
attests the dynamic evolution of the SLAMS and reveals an energy cascade toward
high-frequency waves.


title: Mecanica Clasica (Classical Mechanics)

abstract:
  First Internet graduate course on Classical Mechanics in Spanish
(Castellano). This is about 80% of the material I covered during the
January-June 1999 semester at IFUG in the Mexican city of Leon. English and
Romanian versions are in (slow) progress and hopefully will be arXived. For a
similar course on Quantum Mechanics, see physics/9808031


title: The Interpretation of Quantum Mechanics (I)

abstract:
  Aiming at providing an objective motion picture for the microscopic object
described by the wave function, new analysis about motion is presented by use
of the point set theory in mathematics, through which we show that a new kind
of motion named quantum discontinuous motion is the general motion mode of the
particle, while classical continuous motion is just one kind of extremely
peculiar motion, and the wave function in quantum mechanics proves to be the
very mathematical complex describing the particle undergoing the quantum
discontinuous motion. Furthermore, Schroedinger equation of the wave function
is shown to be the simplest nonrelativistic evolution equation for the particle
undergoing the new motion, and the consistent axiom system of quantum mechanics
is also deduced out. At last, we demonstrate that present quantum measurement
theories just confirm the existence of the new motion of the microscopic
particle described by the wave function, and the weird displays of the wave
function in microscopic world are also physically explained in terms of the new
motion.


title: The Interpretation of Quantum Mechanics (II)

abstract:
  Aiming at providing an objective picture for the collapse process of wave
function during measurement, further analysis about the quantum discontinuous
motion is presented, when considering general relativity we show that the new
motion is essentially replaced by the quantum jump motion, which naturally
results in the collapse process of the wave function. Furthermore, a concrete
theoretical model is given to interpret the collapse process quantitatively,
and the coincidence between its theoretical prediction and the experimental
evidences is also discussed. At last, the possibility to confirm the collapse
model is analyzed.


title: Serine Proteases: an Ab Initio Molecular Dynamics Study

abstract:
  In serine proteases (SP's), the H-bond between His-57 and Asp-102, and that
between Gly-193 and the transition state intermediate play a crucial role for
enzymatic function. To shed light on the nature of these interactions, we have
carried out ab initio molecular dynamics simulations on complexes representing
adducts between the reaction intermediate and elastase (one protein belonging
to the SP family). Our calculations indicate the presence of a low--barrier
H-bond between His-57 and Asp-102, in complete agreement with NMR experiments
on enzyme--transition state analog complexes. Comparison with an ab initio
molecular dynamics simulation on a model of the substrate--enzyme adduct
indicates that the Gly-193--induced strong stabilization of the intermediate is
accomplished by charge/dipole interactions and not by H-bonding as previously
suggested. Inclusion of the protein electric field in the calculations does not
affect significantly the charge distribution.


title:
Ideal magnetohydrodynamic equilibria with helical symmetry and
  incompressible flows

abstract:
  A recent study on axisymmetric ideal magnetohydrodynamic equilibria with
incompressible flows [H. Tasso and G. N. Throumoulopoulos, Phys. Plasmas {\bf
5}, 2378 (1998)] is extended to the generic case of helically symmetric
equilibria with incompressible flows. It is shown that the equilibrium states
of the system under consideration are governed by an elliptic partial
differential equation for the helical magnetic flux function $\psi$ containing
five surface quantities along with a relation for the pressure. The above
mentioned equation can be transformed to one possessing differential part
identical in form to the corresponding static equilibrium equation, which is
amenable to several classes of analytic solutions. In particular, equilibria
with electric fields perpendicular to the magnetic surfaces and
non-constant-Mach-number flows are constructed. Unlike the case in axisymmetric
equilibria with isothermal magnetic surfaces, helically symmetric $T=T(\psi)$
equilibria are over-determined, i.e., in this case the equilibrium equations
reduce to a set of eight ordinary differential equations with seven surface
quantities. In addition, it is proved the non-existence of incompressible
helically symmetric equilibria with (a) purely helical flows (b) non-parallel
flows with isothermal magnetic surfaces and the magnetic field modulus being a
surface quantity (omnigenous equilibria).


title: Quantum superluminal communication must exist

abstract:
  We show that the quantum superluminal communication based on the quantum
nonlocal influence must exist if a basic principle of science is still valid,
which states that if we have demonstrated the existence of something real, we
can confirm its existence.


title:
Analysis of Water Vapor spatio-temporal structure over the Madrid Area
  using GPS data

abstract:
  We have analyzed Zenith Wet Delay (ZWD) time series from an experiment over
the Madrid (Spain) area obtained from 5 GPS receivers using two different
techniques. In the first case a delay correlation analysis of the ZWD
time-series has been carried out. We show that for this small network (with a
spatial scale of less than 100 km) the correlation between the time series is
very strong, and that using windowing techniques a reliable correlation delay
time series can be produced for each pair of sites (10 such pairs are
available). We use this delay time series together with a frozen flow model to
estimate the velocity of a passing front, and compare the results to
meteorological data and Numerical Weather Prediction output, showing good
agreement. In the second approach, the data is analyzed using Empirical
Orthogonal Functions. We demonstrate that the temporally demeaned and
normalized analysis yields information about the passing of fronts, while the
spatially demeaned data yields orographic information. A common second mode
highlights the underlying wave behavior.


title:
The heat of atomization of sulfur trioxide, SO$_3$ - a benchmark for
  computational thermochemistry

abstract:
  Calibration ab initio (direct coupled cluster) calculations including basis
set extrapolation, relativistic effects, inner-shell correlation, and an
anharmonic zero-point energy, predict the total atomization energy at 0 K of
SO$_3$ to be 335.96 (observed 335.92$\pm$0.19) kcal/mol. Inner polarization
functions make very large (40 kcal/mol with $spd$, 10 kcal/mol with $spdfg$
basis sets) contributions to the SCF part of the binding energy. The molecule
presents an unusual hurdle for less computationally intensive theoretical
thermochemistry methods and is proposed as a benchmark for them. A slight
modification of Weizmann-1 (W1) theory is proposed that appears to
significantly improve performance for second-row compounds.


title: Black-body laws derived from a minimum knowledge of Physics

abstract:
  Starting from the knowledge of the four fundamental quantities length L, mass
M, time T, absolute temperature $\theta$ and accepting the validity of Gauss's
law in all dimensions, we generalize, by the theory of physical dimensions, the
expression of the Stephan-Boltzmann law and of the Planck's formula for the
black-body radiation to a spacetime with one time and n spatial coordinates. In
the particular case n=3 we shall recover the known results.


title: Structure of physical space and nature of electromagnetic field

abstract:
  In the article, on the basis of the author's model of formation of the
observable physical space $R_3$ in the process of dynamics of special discrete
one-dimensional vectorial objects, byuons, while minimizing their potential
energy of interaction in the one-dimensional space $R_1$ formed by them, and
based on the Weyl's geometrical model of the electromagnetic field, the nature
of this field consisting in a suitable variation of byuon interaction periods
in the space $R_1$, is shown.


title: Approach to Equilibrium in the Micromaser

abstract:
  We examine the approach to equilibrium of the micromaser. Analytic methods
are first used to show that for large times (i.e. many atoms) the convergence
is governed by the next to leading eigenvalue of the corresponding discrete
evolution matrix. The model is then studied numerically. The numerical results
confirm the phase structure expected from analytic approximation methods and
agree for large times with the analysis of Elmfors et al in terms of the
continuous master equation. For short times, however, we see evidence for
interesting new structure not previously reported in the literature.


title:
Entropy Decrease in Isolated Systems with an Internal Wall undergoing
  Brownian Motion

abstract:
  We consider an isolated gaseous system, divided in two parts by an adiabatic
movable frictionless internal wall undergoing Brownian motion. We show how this
kind of motion can lead to a substantial decrease of the system entropy. This
surprising result does not violate Boltzmann's H-theorem since the molecular
chaos assumption underlying H-theorem is not fulfilled by our system.


title:
Identification and collapse---the seeds of quantum superluminal
  communication

abstract:
  We deeply analyze the relation between the identification process of the
classical definite states and collapse process of the measured superposition
state of such definite states, and show that these two processes are
essentially irrelevant, which then provides one possibility to achieve quantum
superluminal communication.


title:
Cellular Automata Theory and Physics: A new Paradigm for the Unification
  of Physics

abstract:
  A new paradigm for the unification of physics is described. It is called
Cellular Automata (CA) theory, which is the most massively parallel computer
model currently known to science. We maintain that at the tiniest distance and
time scales the universe is completely deterministic, and utterly simple. Our
universe is a Cellular Automaton consisting of a huge array of cells capable of
storing numeric information. These cells form a vast, 3D 'geometric' CA, where
each cell has 26 surrounding neighboring cells that influence the state of a
given cell. CA theory directly implies that all the laws of physics must result
from interactions that are strictly local, therefore forbidding any form of
action at a distance. CA theory suggests that space, time, matter, energy, and
motion are all the same thing: the end result of information changing state in
the CA. The CA model automatically contains an inherent maximum speed limit for
which information can be moved from place to place.We propose that light
(photon) motion is the fixed, simple shifting of a photon information pattern
from cell to adjacent cell at every 'clock cycle'. Thus photons 'travel' only
at one fixed speed, which is unaffected by any possible source motion. By
adopting absolute CA space and time coordinates for the description of a pair
of observers in inertial reference frames with a relative velocity 'v', then
the Lorentz transformation follows mathematically. We explore the ramifications
of this CA model for all of physics.


title:
Substrate-based atom waveguide using guided two-color evanescent light
  fields

abstract:
  We propose a dipole-force linear waveguide which confines neutral atoms up to
lambda/2 above a microfabricated single-mode dielectric optical guide. The
optical guide carries far blue-detuned light in the horizontally-polarized TE
mode and far red-detuned light in the vertically-polarized TM mode, with both
modes close to optical cut-off. A trapping minimum in the transverse plane is
formed above the optical guide due to the differing evanescent decay lengths of
the two modes. This design allows manufacture of mechanically stable
atom-optical elements on a substrate. We calculate the full vector bound modes
for an arbitrary guide shape using two-dimensional non-uniform finite elements
in the frequency-domain, allowing us to optimize atom waveguide properties. We
find that a rectangular optical guide of 0.8um by 0.2um carrying 6mW of total
laser power (detuning +-15nm about the D2 line) gives a trap depth of 200uK for
cesium atoms (m_F = 0), transverse oscillation frequencies of f_x = 40kHz and
f_y = 160kHz, collection area ~ 1um^2 and coherence time of 9ms. We discuss the
effects of non-zero m_F, surface interactions, heating rate, the substrate
refractive index, and the limits on waveguide bending radius.

categories: physics.atom-ph cond-mat physics.optics quant-ph


title: High Resolution RPC's for Large TOF Systems

abstract:
  Here we report on a particular type of RPC that presents up to 99% efficiency
for minimum ionizing particles and a very sharp time resolution, below 50 ps
sigma in the most optimized conditions. Our 9 cm2 cells, made with glass and
metal electrodes that form accurately spaced gaps of a few hundred micrometers,
are operated at atmospheric pressure in non-flammable gases and can be
economically produced in large quantities, opening perspectives for the
construction of large area time of flight systems.


title:
Two Time-dependent Solutions of Magnetic field Annihilation in Two
  Dimensions

abstract:
  In this paper, two classes of exact analytic time-dependent soultion of
magnetic annihilation for incompressible magnetic fluid, have been obtained by
solving the magnetohydrodynamic (MHD) equations directly. The solutions derived
here possess scaling property with time $t$ as the scale factor. Based on these
two solutions, we find that, for some given inflow fields, the evolution of the
annihilating magnetic field can be described by the solutions of certain
ordinary differential equations whose variables are dilated simply by time $t$.
The relevant evolution characteristics in the process of magnetic annihilation
are also revealed.


title: On the Interpretation of the Redshift in a Static Gravitational Field

abstract:
  The classical phenomenon of the redshift of light in a static gravitational
potential, usually called the gravitational redshift, is described in the
literature essentially in two ways: on the one hand the phenomenon is explained
through the behaviour of clocks which run the faster the higher they are
located in the potential, whereas the energy and frequency of the propagating
photon do not change with height. The light thus appears to be redshifted
relative to the frequency of the clock. On the other hand the phenomenon is
alternatively discussed (even in some authoritative texts) in terms of an
energy loss of a photon as it overcomes the gravitational attraction of the
massive body. This second approach operates with notions such as the
"gravitational mass" or the "potential energy" of a photon and we assert that
it is misleading. We do not claim to present any original ideas or to give a
comprehensive review of the subject, our goal being essentially a pedagogical
one.


title:
Measurements of the radiation hardness of selected scintillating and
  light guide fiber materials

abstract:
  Radiation hardness studies of KURARAY SCSF-78M scintillating fibers and clear
fibers from KURARAY and pol.hi.tech. performed under different dose rate
conditions in proton and electron beams are summarized. For high dose rates
in-situ measurements of the fiber light output were done. During several months
after irradiation all fibers were measured concerning light emission and
transparency.
  Fibers irradiated at high rates to about 1 Mrad are clearly damaged but
recover within a few hours up to several weeks. Using smaller rates up to the
same integral dose a decrease of the light output of scintillating fibers of up
to 30% can not be excluded. Clear fibers seem to be uneffected up to 400 krad.
No significant influence of fiber coverage and atmosphere during irradiation
was found.


title: A Fiber Detector Radiation Hardness Test

abstract:
  An intense 146 MeV/c pion beam was stopped inside a scintillating fiber
detector made out of 12 planes with 16 pixels each, where every pixel consists
out of 8 times 8 scintillating fibers of 500 mkm diameter dense packed. The
detector was irradiated for 52 hours to more than 1 Mrad at its center. Before
and directly after the irradiation the detector has been exposed to a particle
beam to compare the corresponding light output. This study was continued during
the following three months using cosmic rays. No damage was found taking into
account the measurement errors of 5-10 %. In contrast a 9 cm deep lucite
degrader became irreversibly non-transparent in the irradiation region.


title: Synchronization and Inertial Frames

abstract:
  In classical mechanics, a procedure for simultaneous synchronization in all
inertial frames is consistent with the Galilean transformation. However, if one
attempts to achieve such a synchronization utilizing light signals, he will be
facing in the first place the break down of simultaneity, and secondly, a
self-contradictory transformation that has the Lorentz transformation, or its
confinement to the velocity of light, as the only possible ways that resolve
the contradiction. The current work constitutes a smooth transition from
traditional to relativistic vision of mechanics, and therefore is quite
appealing from pedagogical point of view.


title: 2D Numerical Simulation of the Resistive Reconnection Layer

abstract:
  In this paper we present a two-dimensional numerical simulation of a
reconnection current layer in incompressible resistive magnetohydrodynamics
with uniform resistivity in the limit of very large Lundquist numbers. We use
realistic boundary conditions derived consistently from the outside magnetic
field, and we also take into account the effect of the backpressure from the
flow into the separatrix region. We find that within a few Alfven times the
system reaches a steady state consistent with the Sweet--Parker model, even if
the initial state is Petschek-like.


title: Quantum Monte Carlo study of the H- impurity in small helium clusters

abstract:
  We report ground state energies and structural properties for small helium
clusters (4He) containing an H- impurity computed by means of variational and
diffusion Monte Carlo methods. Except for 4He_2H- that has a noticeable
contribution from collinear geometries where the H- impurity lies between the
two 4He atoms, our results show that our 4He_NH- clusters have a compact 4He_N
subsystem that binds the H- impurity on its surface. The results for $N\geq 3$
can be interpreted invoking the different features of the minima of the He-He
and He-H- interaction potentials.


title: Quality control of GEM detectors using scintillation techniques

abstract:
  Non destructive quality control of microstructures at the manufacturing stage
is an important issue in the foreseen use of huge numbers of such gaseous
detectors in the future high luminosity colliders. In this work we report on
the use of the scintillation light emitted by the avalanches in GEM channels
for checking defects in the foils. The test system is described and data on the
relative efficiency of several gaseous mixtures are presented. The foil images
obtained with a low-noise CCD system are analysed and compared with the optical
images obtained with an industrial inspection system of high magnification. The
validity of this test method is established and possible extensions of its use
are discussed.


title: The Fractal Universe: From the Planck to the Hubble Scale

abstract:
  We examine the fractal structure of the physical universe from the large
scale to the smallest scale, including the phenomenon of fractal scaling. This
is explained in terms of a stochastic underpinning for the laws of physics. A
picture in pleasing agreement with experiment and observation at all scales
emerges, very much in the spirit of Wheeler's "Law Without Law". It is argued
that our depiction of the universe is akin to a broad brush delineation of a
jagged coastline, the Compton wavelength being comparable to the thickness of
the brush strokes.


title:
Simple and efficent algorithm for large scale molecular dynamics
  simulation in hard disk systems

abstract:
  A simple and efficient algorithm of the molecular-dynamics simulation of the
hard disk system based on the Event-Driven method is developed. From the
analysis of algorithm, the complexity is O(log N) per 1 event, and the constant
coefficient of the complexity is smaller than conventional efficient algorithm
based on the concept of Cell-Crossing Event. The maximum performance more than
460 millions of collisions per CPU-hour on the Alpha600 compatible in 2500
particle system is achieved. An extension to the infinite-space system based on
this algorithm is also proposed.


title: The Physics Opportunities and Technical Challenges of a Muon Collider

abstract:
  We describe the physics opportunities and technical challenges of a muon
collider as a tool for exploring high energy physics phenomena.


title: Variable Field Bending Magnets for Recirculating Linacs

abstract:
  A lattice of single aperture superconducting variable field bending magnets
is proposed as a cheap and practical way to recirculate the beams in
recirculating linear accelerators. It is shown that the VFBM's can be
configured to provide strong focusing in both transverse planes for the full
range of beam momenta transported by the lattice.


title: A Minimal Model of B-DNA

abstract:
  Recently it has been found that stable and accurate molecular dynamics (MD)
of B-DNA duplexes can be obtained in relatively inexpensive computational
conditions with the bulk solvent represented implicitly, but the minor groove
filled with explicit water (J. Am. Chem. Soc. 1998, 120, 10928). The present
paper further explores these simulation conditions in order to understand the
main factors responsible for the observed surprisingly good agreement with
experimental data. It appears that in the case of the EcoRI dodecamer certain
sequence specific hydration patterns in the minor groove earlier known from
experimental data are formed spontaneously in the course of MD simulations. The
effect is reliably reproduced in several independent computational experiments
in different simulation conditions. With all major groove water removed,
closely similar results are obtained, with even better reproducibility. On the
other hand, without explicit hydration, metastable dynamics around a B-DNA like
state can be obtained which, however, only poorly compares with experimental
data. It appears, therefore, that a right-handed DNA helix with explicitly
hydrated minor groove is a minimal model system where the experimental
properties of B-DNA can be reproduced with non-trivial sequence-dependent
effects. Its small size makes possible virtually exhaustive sampling, which is
a major advantage with respect to alternative approaches. An appendix is
included with a correction to the implicit leapfrog integrator used in internal
coordinate MD.

categories: physics.comp-ph physics.bio-ph physics.chem-ph q-bio.BM


title:
The solar neutrino project HELLAZ : status report on the hardware and
  the simulation

abstract:
  We report the status of the solar neutrino project called HELLAZ. In a high
pressure and cooled TPC filled with helium, the detection of each ionisation
electron of the track produced by the recoil electron from elastic scattering
induced by solar neutrinos, will yield the low energy, high resolution solar
neutrino spectrum. Two topics are presented ; test of Micromegas gas chambers
giving a good discrimination between adjacent ionisation electrons and the
preliminary test of the direction of the primary electron track from the cloud
analysis. These two tests seem rather encouraging.


title: Dielectronic Recombination of Ground-State and Metastable Li+ Ions

abstract:
  Dielectronic recombination has been investigated for Delta-n = 1 resonances
of ground-state Li+(1s^2) and for Delta-n = 0 resonances of metastable Li+(1s2s
^3S). The ground-state spectrum shows three prominent transitions between 53
and 64 eV, while the metastable spectrum exhibits many transitions with
energies < 3.2 eV. Reasonably good agreement of R-matrix, LS coupling
calculations with the measured recombination rate coefficient is obtained. The
time dependence of the recombination rate yields a radiative lifetime of 52.2
+- 5.0 s for the 2 ^3S level of Li+.


title: Perturbation Theory on Top of Optimized Effective Potential Method

abstract:
  We present a perturbative approach within the scope of Kohn-Sham density
functional theory (DFT). The method is based on the exact exchange-only
optimized effective potential method, and correlation is included via
perturbation expansion using Rayleigh-Schrodinger (RS) perturbation theory
(PT). The correlation potential is constructed from Moller-Plesset formulation
of RS calculations. This naturally leads to a new iterative scheme when finite
order perturbation theory is employed. The new iterative procedure can be taken
as a self-consistent parameter-free DFT PT, and, as such, provides correlation
energy which is explicitly functional of the self-consistent orbitals,
eigenvalues and also of the exchange-correlation potential.


title:
Study of the one-dimensional Schroedinger equation generated from the
  hypergeometric equation

abstract:
  Original English Summary. - A systematic method of constructing potentials,
for which the one-variable Schroedinger equation can be solved in terms of the
hypergeometric (HGM) function, is presented. All the potentials, obtained by
energy-independent transformations of the HGM equation, are determined together
with eigenvalues and eigenfunctions. A class of potentials derived from the
confluent HGM equation is found by means of a limit process


title:
A possible explanation for Earth's climatic changes in the past few
  million years

abstract:
  The astronomical theory of Milankovitch relates the changes of Earth' past
climate to variations in insolation caused by oscillations of the orbital
parameters. However, this theory has problems to account for some major
observed phenomena of the past few million years. Here, we present an
alternative explanation for these phenomena. It is based on the idea that the
solar system until quite recently contained an additional massive object of
planetary size. This object, called Z, is assumed to have moved on a highly
eccentric orbit bound to the sun. It influenced Earth's climate through a gas
cloud of evaporated material. Calculations show that more than once during the
last 3.2 Myr it even approached the Earth close enough to provoke a significant
shift of the geographic position of the poles. The last of these shifts
terminated Earth's Ice Age epoch about 11.5 kyr ago. The origin and fate of Z
is also discussed.


title:
Radiative Polarization, Computer Algorithms and Spin Matching in
  Electron Storage Rings

abstract:
  We present a set of notes, meant for quick reference, on radiative spin
polarization, computer algorithms and spin matching in electron storage rings.


title: Design Patterns for Description-Driven Systems

abstract:
  In data modelling, product information has most often been handled separately
from process information. The integration of product and process models in a
unified data model could provide the means by which information could be shared
across an enterprise throughout the system lifecycle from design through to
production. Recently attempts have been made to integrate these two separate
views of systems through identifying common data models. This paper relates
description-driven systems to multi-layer architectures and reveals where
existing design patterns facilitate the integration of product and process
models and where patterns are missing or where existing patterns require
enrichment for this integration. It reports on the construction of a so-called
description-driven system which integrates Product Data Management (PDM) and
Workflow Management (WfM) data models through a common meta-model.


title:
Absorption of radiation by small metallic particles: a general
  self-consistent approach

abstract:
  We introduce a theory for the absorption of electromagnetic radiation by
small metal particles, which generalises the random phase approximation by
incorporating both electric and magnetic dipole absorption within a unified
self-consistent scheme. We demonstrate the equivalence of the new approach to a
superficially dissimilar perturbative approach. We show how to obtain solutions
to the self-consistent equations using a classical approximation, taking into
account the non-locality of the polarisability and the conductivity tensor. We
discuss the nature of the self-consistent solutions for diffusive and ballistic
electron dynamics.


title: Accelerated motion and special relativity transformations

abstract:
  Transformation rules for coordinates, velocities and accelerations in
accelerated reference frames are derived. A generalized approach of the special
relativity is taken for a basis. A 7-dimensional space including projections of
velocity vector as three additional coordinates to time and geometric
coordinates is studied. Turns in pseudoplane (dt,dv) of this 7-space describe
accelerated motion of frame. In addition to the light velocity, the
transformation formulas contain a fundamental constant which has a meaning of
maximal acceleration. It is demonstrated that if a source of light moves with
acceleration with respect to some reference frame, the light velocity in this
frame is less than the constant $c$ and depends on acceleration. The special
relativity relation between energy, impulse, and mass gets changed for particle
in accelerated motion. A generalized wave operator being invariant to the above
transformations is introduced. The components of tensor and of potential of
electromagnetic field get intermixing in transformation relations for
accelerated frame.


title:
Atom focusing by far-detuned and resonant standing wave fields: Thin
  lens regime

abstract:
  The focusing of atoms interacting with both far-detuned and resonant standing
wave fields in the thin lens regime is considered. The thin lens approximation
is discussed quantitatively from a quantum perspective. Exact quantum
expressions for the Fourier components of the density (that include all
spherical aberration) are used to study the focusing numerically. The following
lens parameters and density profiles are calculated as functions of the pulsed
field area $\theta $: the position of the focal plane, peak atomic density,
atomic density pattern at the focus, focal spot size, depth of focus, and
background density. The lens parameters are compared to asymptotic, analytical
results derived from a scalar diffraction theory for which spherical aberration
is small but non-negligible ($\theta \gg 1$). Within the diffraction theory
analytical expressions show that the focused atoms in the far detuned case have
an approximately constant background density $0.5(1-0.635\theta ^{- 1/2})$
while the peak density behaves as $% 3.83\theta ^{1/2}$, the focal distance or
time as $\theta ^{-1}(1+1.27\theta ^{- 1/2})$, the focal spot size as
$0.744\theta ^{-3/4}$, and the depth of focus as $1.91\theta ^{- 3/2}$.
Focusing by the resonant standing wave field leads to a new effect, a Rabi-
like oscillation of the atom density. For the far-detuned lens, chromatic
aberration is studied with the exact Fourier results. Similarly, the
degradation of the focus that results from angular divergence in beams or
thermal velocity distributions in traps is studied quantitatively with the
exact Fourier method and understood analytically using the asymptotic results.
Overall, we show that strong thin lens focusing is possible with modest laser
powers and with currently achievable atomic beam characteristics.


title: Observation of Nonlinear Mode in a Cylindrical Fabry-Perot Cavity

abstract:
  We report the first observation of a nonlinear mode in a cylindrical
nonlinear Fabry-Perot cavity. The field enhancement from cavity buildup, as
well as the large chi3 optical nonlinearity due to resonantly-excited Rb-85
vapor, allows the nonlinear mode to form at low incident optical powers of less
than a milliwatt. The mode is observed to occur for both the self-focusing and
self-defocusing nonlinearity.


title:
Multiple resonance compensation for betatron coupling and its
  equivalence with matrix method

abstract:
  Analyses of betatron coupling can be broadly divided into two categories: the
matrix approach that decouples the single-turn matrix to reveal the normal
modes and the hamiltonian approach that evaluates the coupling in terms of the
action of resonances in perturbation theory. The latter is often regarded as
being less exact but good for physical insight. The common opinion is that the
correction of the two closest sum and difference resonances to the working
point is sufficient to reduce the off-axis terms in the 4X4 single-turn matrix,
but this is only partially true. The reason for this is explained, and a method
is developed that sums to infinity all coupling resonances and, in this way,
obtains results equivalent to the matrix approach. The two approaches is
discussed with reference to the dynamic aperture. Finally, the extension of the
summation method to resonances of all orders is outlined and the relative
importance of a single resonance compared to all resonances of a given order is
analytically described as a function of the working point.


title:
Drag Reduction over Dolphin Skin via the Pondermotive Forcing of Vortex
  Filaments

abstract:
  The skin of Tursiops Truncatus is corrugated with small, quasi-periodic
ridges running circumferentially about the torso. These ridges extend into the
turbulent boundary layer and affect the evolution of coherent structures. The
development and evolution of coherent structures over a surface is described by
the formation and dynamics of vortex filaments. The dynamics of these filaments
over a flat, non-ridged surface is determined analytically, as well as through
numerical simulation, and found to agree with the observations of coherent
structures in the turbulent boundary layer. The calculation of the linearized
dynamics of the vortex filament, successful for the dynamics of a filament over
a flat surface, is extended and applied to a vortex filament propagating over a
periodically ridged surface. The surface ridges induce a rapid parametric
forcing of the vortex filament, and alter the filament dynamics significantly.
A consideration of the contribution of vortex filament induced flow to energy
transport indicates that the behavior of the filament induced by the ridges can
directly reduce surface drag by up to 8%. The size, shape, and distribution of
cutaneous ridges for Tursiops Truncatus is found to be optimally configured to
affect the filament dynamics and reduce surface drag for swimming velocities
consistent with observation.


title: Some Exact Results of Hopfield Neural Networks and Applications

abstract:
  A set of fixed points of the Hopfield type neural network was under
investigation. Its connection matrix is constructed with regard to the Hebb
rule from a highly symmetric set of the memorized patterns. Depending on the
external parameter the analytic description of the fixed points set had been
obtained. And as a conclusion, some exact results of Hopfield neural networks
were gained.


title: Nonlinear Longitudinal Waves in High Energy Stored Beams

abstract:
  We solve the Vlasov equation for the longitudinal distribution function and
find stationary wave patterns when the distribution in the energy error is
Maxwellian. In the long wavelength limit a stability criterion for linear waves
has been obtained, and a Korteweg-de Vries-Burgers equation for the relevant
hydrodynamic quantities has been derived.

categories: physics.acc-ph nlin.PS patt-sol physics.plasm-ph


title:
Non-stationary Characteristics of the instability in a Single-mode Laser
  with Fiber Feedback

abstract:
  Chaotic bursts are observed in a single-mode microchip Nd:YVO$_4$ laser with
fiber feedback. The physical characteristic of the instability is a random
switching between two different dynamical states, i.e., the noise-driven
relaxation oscillation and the chaotic spiking oscillation. As the feedback
strength varied, transition which features the strong interplay between two
states exhibits and the dynamical switching is found to be non-stationary at
the transition.

categories: physics.optics chao-dyn nlin.CD physics.data-an


title: Approximate Solution of the Representability Problem

abstract:
  Approximate solution of the ensemble representability problem for density
operators of arbitrary order is obtained. This solution is closely related to
the ``Q condition'' of A.J.Coleman. The representability conditions are
formulated in orbital representation and are easy to use. They are tested
numerically on the base of CI calculation of simple atomic and molecular
systems. General scheme of construction of the contraction operator right
inverses is proposed and the explicit expression for the right inverse
associated with the expansion operator is derived as an example. Two algorithms
for direct 2-density matrix determination are described.

categories: physics.chem-ph math-ph math.MP quant-ph


title: Classical Electrodynamics: A Tutorial on its Foundations

abstract:
  We will display the fundamental structure of classical electrodynamics.
Starting from the axioms of (1) electric charge conservation, (2) the existence
of a Lorentz force density, and (3) magnetic flux conservation, we will derive
Maxwell's equations. They are expressed in terms of the field strengths
$(E,{\cal B})$, the excitations $({\cal D},H)$, and the sources $(\rho,j)$.
This fundamental set of four microphysical equations has to be supplemented by
somewhat less general constitutive assumptions in order to make it a fully
determined system with a well-posed initial value problem. It is only at this
stage that a distance concept (metric) is required for space-time. We will
discuss one set of possible constitutive assumptions, namely ${\cal D}\sim E$
and $H\sim {\cal B}$. {\em file erik8a.tex, 1999-07-27}

categories: physics.class-ph gr-qc physics.ed-ph physics.gen-ph


title:
Many-body and model-potential calculations of low-energy photoionization
  parameters for Fr

abstract:
  The photoionization cross section $\sigma$, spin-polarization parameters $P$
and $Q$, and the angular-distribution asymmetry parameter $\beta$ are
calculated for the $7s$ state of francium for photon energies below 10 eV. Two
distinct calculations are presented, one based on many-body perturbation theory
and another based on the model potential method. Although predictions of the
two calculations are similar, the detailed energy dependence of the
photoionization parameters from the two calculations differ. From the
theoretical p-wave phase shifts, we infer quantum defects for $p_{1/2}$ and
$p_{3/2}$ Rydberg series, permitting us to calculate positions of
experimentally unknown $p$ states in francium.


title:
Addendum to "...The Relativistic Covariance of the B-Cyclic Relations"
  [Found. Phys. Lett. 10 (1997) 383-391]

abstract:
  In the previous paper we proved that the Evans-Vigier definitions of B^{(0)}
and {\bf B}^{(3)} may be related {\it not} with magnetic fields but with a
4-vector field. In the present {\it Addendum} it is shown that the terms used
in the {\bf B}- Cyclic theorem proposed by M. Evans and J.-P. Vigier may have
various transformation properties with respect to Lorentz transformations. The
fact whether the {\bf B}^{(3)} field is a part of a bi-vector (which is
equivalent to antisymmetric second-rank tensor) or a part of a 4-vector,
depends on the phase factors in the definition of positive- and negative-
frequency solutions of the ({\bf B}, {\bf E}) transverse field. This is closely
connected to our considerations of the Bargmann-Wightman-Wigner
(Gelfand-Tsetlin-Sokolik) Constructs and with the Ahluwalia's recent
consideration of the phase factor related to gravity. The physical relevance of
proposed constructs is discussed.


title: Error Propagation in the Hypercycle

abstract:
  We study analytically the steady-state regime of a network of n error-prone
self-replicating templates forming an asymmetric hypercycle and its error tail.
We show that the existence of a master template with a higher non-catalyzed
self-replicative productivity, a, than the error tail ensures the stability of
chains in which m<n-1 templates coexist with the master species. The stability
of these chains against the error tail is guaranteed for catalytic coupling
strengths (K) of order of a. We find that the hypercycle becomes more stable
than the chains only for K of order of a2. Furthermore, we show that the
minimal replication accuracy per template needed to maintain the hypercycle,
the so-called error threshold, vanishes like sqrt(n/K) for large K and n<=4.


title:
The dynamical Green's function and an exact optical potential for
  electron-molecule scattering including nuclear dynamics

abstract:
  We derive a rigorous optical potential for electron-molecule scattering
including the effects of nuclear dynamics by extending the common many-body
Green's function approach to optical potentials beyond the fixed-nuclei limit
for molecular targets. Our formalism treats the projectile electron and the
nuclear motion of the target molecule on the same footing whereby the dynamical
optical potential rigorously accounts for the complex many-body nature of the
scattering target. One central result of the present work is that the common
fixed-nuclei optical potential is a valid adiabatic approximation to the
dynamical optical potential even when projectile and nuclear motion are
(nonadiabatically) coupled as long as the scattering energy is well below the
electronic excitation thresholds of the target. For extremely low projectile
velocities, however, when the cross sections are most sensitive to the
scattering potential, we expect the influences of the nuclear dynamics on the
optical potential to become relevant. For these cases, a systematic way to
improve the adiabatic approximation to the dynamical optical potential is
presented that yields non-local operators with respect to the nuclear
coordinates.


title: Orthogonal Linear Combinations of Gaussian Type Orbitals

abstract:
  The set of Gaussian Type Orbitals g(n1,n2,n3) of order (n+1)(n+2)/2, of
common n=n1+n2+n3<=7, common center and exponential, is customized to define a
set of 2n+1 linear combinations t(n,m) (-n<=m<=n) such that each t(n,m) depends
on the azimuthal and polar angle of the spherical coordinate system like the
real or imaginary part of the associated Spherical Harmonic. (Results cover
both Hermite and Cartesian Gaussian Type Orbitals.) Overlap, kinetic energy and
Coulomb energy matrix elements are presented for generalized basis functions of
the type r^s*t(n,m) (s=0,2,4,...). In addition, normalization integrals int
|g(n1,n2,n3)|d^3r are calculated up to n=7 and normalization integrals int
|r^s*t(n,m)|d^3r up to n=5.


title: Comment on "Recurrences without closed orbits"

abstract:
  In a recent paper Robicheaux and Shaw [Phys. Rev. A 58, 1043 (1998)]
calculate the recurrence spectra of atoms in electric fields with non-vanishing
angular momentum <L_z> not equal to 0. Features are observed at scaled actions
``an order of magnitude shorter than for any classical closed orbit of this
system.'' We investigate the transition from zero to nonzero angular momentum
and demonstrate the existence of short closed orbits with L_z not equal to 0.
The real and complex ``ghost'' orbits are created in bifurcations of the
``uphill'' and ``downhill'' orbit along the electric field axis, and can serve
to interpret the observed features in the quantum recurrence spectra.


title: 1S-2S Spectrum of a Hydrogen Bose-Einstein Condensate

abstract:
  We calculate the two-photon 1S-2S spectrum of an atomic hydrogen
Bose-Einstein condensate in the regime where the cold collision frequency shift
dominates the lineshape. WKB and static phase approximations are made to find
the intensities for transitions from the condensate to motional eigenstates for
2S atoms. The excited state wave functions are found using a mean field
potential which includes the effects of collisions with condensate atoms.
Results agree well with experimental data. This formalism can be used to find
condensate spectra for a wide range of excitation schemes.


title: On a proposition relative to linear equations

abstract: One of Darboux's seminal results is archived here


title: Dimensionality and Fractals

abstract:
  In this paper we first show that the usual three dimensionality of space,
which is taken for granted, results from the spinorial behaviour of Fermions,
which constitute the material content of the universe. It is shown that the
resulting three dimensionality rests on two factors which have been hitherto
ignored, viz., a Machian or holistic property and the stochastic underpinning
of the universe itself. However the dimensionality is scale dependent in the
sense that at very large scales, or at very small scales, we encounter a
different dimensionality, as indeed is borne out by observation and experiment.
For example the large scale structures in the universe are cellular in nature
on the one hand, and we encounter fractional charges and handedness at very
small scales. Finally it is shown how fractal dimensions can emerge and as an
illustrative example it is shown how this could explain the magnetism of
objects like Planets on the one hand and White Dwarf stars and Pulsars on the
other.


title: Rare-earth loaded liquid scintillator (for LENS experiment)

abstract:
  Rare-earth (Yb/Gd) complexes with neutral organophosphorus ligands are
briefly discussed for their application in liquid scintillation technique. To
evaluate the principle feasibility of a high rare-earth loaded scintillator,
the ytterbium chloride complexes with tri-isoamylphosphine oxides were
synthesized. Relative scintillation efficiency (RSE) for two Yb concentrations
(78 and 88 g/L) was measured by means of the internal conversion electron
exitation from Cs-137. The results obtained were 50 and 40% respectively.


title: New features in non-coalescense of tanget liquid bulks

abstract:
  We had observed a couple of new phenomena in which, two liquid bulks in
contact with each other do not coalesce. The main reason seems to be the motion
of the surface in the place of contact, which forms an air film between the
bulk boundaries. The surface velocities is also estimated and showed to be near
each other and also near the surface velocities in the similar phenomena
reported before.


title: Stability of Plane-Parallel Vibrational Flow In a Two-Layer System

abstract:
  The stability of the interface separating two immiscible incompressible
fluids of different densities and viscosities is considered in the case of
fluids filling a cavity which performs horizontal harmonic oscillation. There
exists a simple basic state which corresponds to the unperturbed interface and
plane-parallel unsteady counter flows; the properties of this state are
examined. A linear stability problem for the interface is formulated and solved
a) for both inviscid and b) for both viscous fluids. A transformation is found
which reduces the linear stability problem under inviscid approximation to the
Mathieu equation. The parametric resonant regions of instability associated
with the intensification of capillary-gravity waves at the interface are
examined and the results are compared to those found in the viscous case in a
fully numerical investigation.


title:
An Explicit Space-time Adaptive Method for Simulating Complex Cardiac
  Dynamics

abstract:
  For plane-wave and many-spiral states of the experimentally based Luo-Rudy 1
model of heart tissue in large (8 cm square) domains, we show that an explicit
space-time-adaptive time-integration algorithm can achieve an order of
magnitude reduction in computational effort and memory - but without a
reduction in accuracy - when compared to an algorithm using a uniform
space-time mesh at the finest resolution. Our results indicate that such an
explicit algorithm can be extended straightforwardly to simulate quantitatively
large-scale three-dimensional electrical dynamics over the whole human heart.


title: The dipole polarizability of the hydrogen molecular ion

abstract:
  A procedure is described for the precise nonrelativistic evaluation of the
dipole polarizabilities of H_2^+ and D_2^+ that avoids any approximation based
on the size of the electron mass relative to the nucleus mass. The procedure is
constructed so that sum rules may be used to assess the accuracy of the
calculation. The resulting polarizabilities are consistent with experiment
within the error bars of the measurements and are far more precise than values
obtained by other theoretical methods.


title: Possibility of Sound Propagation in Vacuums with the Speed of Light

abstract:
  An important question of theoretical physics is whether sound is able to
propagate in vacuums at all and if this is the case, then it must lead to the
reinterpretation of one zero-restmass particle which corresponds to
vacuum-sound waves. Taking the electron-neutrino as the corresponding particle,
its observed non-vanishing rest-energy may only appear for neutrino-propagation
inside material media. The idea may also influence the physics of dense matter,
restricting the maximum speed of sound, both in vacuums and in matter to the
speed of light.


title: Signature of Fermi surface jumps in positron spectroscopy data

abstract:
  A subtractionless method for solving Fermi surface sheets ({\tt FSS}), from
measured $n$-axis-projected momentum distribution histograms by two-dimensional
angular correlation of the positron-electron annihilation radiation ({\tt
2D-ACAR}) technique, is discussed. The window least squares statistical noise
smoothing filter described in Adam {\sl et al.}, NIM A, {\bf 337} (1993) 188,
is first refined such that the window free radial parameters ({\tt WRP}) are
optimally adapted to the data. In an ideal single crystal, the specific jumps
induced in the {\tt WRP} distribution by the existing Fermi surface jumps yield
straightforward information on the resolved {\tt FSS}. In a real crystal, the
smearing of the derived {\tt WRP} optimal values, which originates from
positron annihilations with electrons at crystal imperfections, is ruled out by
median smoothing of the obtained distribution, over symmetry defined stars of
bins. The analysis of a gigacount {\tt 2D-ACAR} spectrum, measured on the
archetypal high-$T_c$ compound $YBa\sb{2}Cu\sb{3}O\sb{7-\delta}$ at room
temperature, illustrates the method. Both electronic {\tt FSS}, the ridge along
$\Gamma X$ direction and the pillbox centered at the $S$ point of the first
Brillouin zone, are resolved.


title: Random Beam Propagation in Accelerators and Storage Rings

abstract:
  A kinetic equation for the joint probability distribution for fixed values of
the classical action, momentum and density has been derived. Further, the
hydrodynamic equations of continuity and balance of momentum density have been
transformed into a Schroedinger-like equation, describing particle motion in an
effective electro-magnetic field and an expression for the gauge potentials has
been obtained.


title:
The quantum quasi-invariant of the time-dependent nonlinear oscillator
  and application to betatron dynamics

abstract:
  Both the classical and quantum approximate invariants are found for the
nonlinar r time-dependent oscillator of sextupole transverse betatron dynamics.
They are represented in terms of the elements of a Lie algebra associated with
powers of phase space coordinates. The first order quantum correction to the
classical quasi-invariant is found.


title:
Teaching statistics in the physics curriculum: Unifying and clarifying
  role of subjective probability

abstract:
  Subjective probability is based on the intuitive idea that probability
quantifies the degree of belief that an event will occur. A probability theory
based on this idea represents the most general framework for handling
uncertainty. A brief introduction to subjective probability and Bayesian
inference is given, with comments on typical misconceptions which tend to
discredit it and comparisons to other approaches.


title: Dark Matter

abstract:
  Gravitational force manifested in its affect on rotational velocity is what
indicates the presence of dark matter in individual galaxies. Newtonian
mechanics is generally used to derive the relationship between rotational
velocity and gravitational force. In Newtonian mechanics, mass is associated
with gravitation. At the same time, in such galaxies there appears to be
insufficient gravitational mass to account for the size of the gravitational
force deduced from rotational velocity. The general theory of relativity
encompasses Newtonian mechanics and also indicates that reference frames
provide the means to develop spacetime curvature that expresses the
gravitational field. It is reasonable to conclude that because of the more
fundamental character of the general theory of relativity, the reference frames
that are a key element of the general theory form the basis for understanding
gravitation, and not mass.


title:
Discussion on Muon Collider Parameters at Center of Mass Energies from
  0.1 TeV to 100 TeV

abstract:
  Some of the potential capabilities and design challenges of muon colliders
are illustrated using self-consistent collider parameter sets at center of mass
energies ranging from 0.1 TeV to 100 TeV.


title: Potential Hazards from Neutrino Radiation at Muon Colliders

abstract:
  High energy muon colliders, such as the TeV-scale conceptual designs now
being considered, are found to produce enough high energy neutrinos to
constitute a potentially serious off-site radiation hazard in the neighbourhood
of the accelerator site. A general characterization of this radiation hazard is
given, followed by an order-of-magnitude calculation for the off-site annual
radiation dose and a discussion of accelerator design and site selection
strategies to minimize the radiation hazard.


title:
Studies for Muon Colliders at Center-of-Mass Energies of 10 TeV and 100
  TeV

abstract:
  Parameter lists are presented for speculative muon colliders at
center-of-mass energies of 10 TeV and 100 TeV. The technological advances
required to achieve the given parameters are itemized and discussed, and a
discussion is given of the design goals and constraints. An important
constraint for multi-TeV muon colliders is the need to minimize neutrino
radiation from the collider ring.


title: Associated Sturm-Liouville systems

abstract: Crum's seminal result of 1955 is archived here


title:
Local Solution Method for Numerical Solving of the Wave Propagation
  Problem

abstract:
  A new method for numerical solving of boundary problem for ordinary
differential equations with slowly varying coefficients which is aimed at
better representation of solutions in the regions of their rapid oscillations
or exponential increasing (decreasing) is proposed. It is based on
approximation of the solution to find in the form of superposition of certain
polynomial- exponential basic functions. The method is studied for the
Helmholtz equation in comparison with the standard finite difference method.
The numerical tests have shown the convergence of the method proposed. In
comparison with the finite difference method the same accuracy is obtained on
substantially rarer mesh. This advantage becomes more pronounced, if the
solution varies very rapidly.


title: Microarrays for Amino Acid Analysis and Protein Sequencing

abstract:
  A method is described where the aminoacyl-tRNA synthetase system is used to
create very small devices for quantitative analysis of the amino acids that
occur in proteins. The basis of the method is that each of the 20 synthetases
and/or a tRNA specific for a different amino acid is separated spatially (e.g.
in tiny chambers or on a surface). The reactions catalyzed by all 20
synthetases are monitored in a spatially resolved manner. Each separately
positioned synthetase or tRNA will signal its cognate amino acid. The
synthetase reactions can be monitored using continuous spectroscopic assays.
Alternatively, since elongation factor Tu;GTP (EF-Tu;GTP) specifically binds
all AA-tRNAs, the aminoacylation reactions catalyzed by the synthetases can be
monitored using ligand assays. Microarrays for amino acid analysis are
suggested. Additionally, it is possible that amino acid analysis arrays can be
integrated with aminopeptidase or carboxypeptidase digestions to produce
miniaturized enzymatic sequenators capable of generating either N- or
C-terminal sequence data at femtomole-attomole levels. The possibility of
parallel processing of many samples in an automated manner is discussed.


title: Density functional calculations of planar DNA base-pairs

abstract:
  We present a systematic Density Functional Theory (DFT) study of geometries
and energies of the nucleic acid DNA bases (guanine, adenine, cytosine and
thymine) and 30 different DNA base-pairs. We use a recently developed
linear-scaling DFT scheme, which is specially suited for systems with large
numbers of atoms. As a first step towards the study of large DNA systems, in
this work: (i) We establish the reliability of the approximations of our method
(including pseudopotentials and basis sets) for the description of the
hydrogen-bonded base pairs, by comparing our results with those of former
calculations. We show that the interaction energies at Hartree-Fock geometries
are in very good agreement with those of second order M{\o}ller-Plesset (MP2)
perturbation theory (the most accurate technique that can be applied at present
for system of the sizes of the base-pairs). (ii) We perform DFT structural
optimizations for the 30 different DNA base-pairs, only three of which had been
previously studied with DFT. Our results provide information on the effect of
correlation on the structure of the other 27 base pairs, for which only
Hartree-Fock geometries were formerly available.

categories: physics.chem-ph cond-mat physics.bio-ph physics.comp-ph q-bio.QM


title:
Track Restore Technique (RST) Applied to Analysis of Waveform of Voltage
  Pulse in SAGE Proportional Counters

abstract:
  A kind of analysis of waveform of voltage pulse in small proportional counter
is described. The technique is based on deconvolution of recorded pulse with a
response function of the counter. It allows one to restore a projection of the
track of initial ionization to the radius of the counter, or a charge
collection function.

categories: physics.data-an astro-ph nucl-ex physics.ins-det


title: The Unified Theory - Electricity, Magnetism, Gravity and Mechanics

abstract:
  This article shows the relations between the electricity, magnetism, gravity
and mechanics by presenting an existing hidden structure in the Maxwell
equations. This hidden structure allows to discover the classical physic from a
new point of view leading to the unified theory (UT).


title:
On the Support that the Special and General Theories of Relativity
  Provide for Rock's Argument Concerning Induced Self-Motion

abstract:
  Though Einstein and other physicists recognized the importance of an observer
being at rest in an inertial reference frame for the special theory of
relativity, the supporting psychological structures were not discussed much by
physicists. On the other hand, Rock, a psychologist, wrote of the factors
involved in the perception of motion, including one's own motion. Rock thus
came to discuss issues of significance to relativity theory, apparently without
any significant understanding of how his theory might be related to relativity
theory. In this paper, connections between Rock's theory on the perception of
one's own motion, as well as empirical work supporting it, and relativity
theory are explored.


title: Physical Parameters for Biconcave Shape Vesicles

abstract:
  The Helfrich's shape equation of axisymmetric vesicles is studied. A
sufficient condition on the physical parameters and some geometric properties
are discovered for the biconcave shape.


title:
A unified approach to the study of temporal, correlational and rate
  coding

abstract:
  We demonstrate that the information contained in the spike occurrence times
of a population of neurons can be broken up into a series of terms, each of
which reflect something about potential coding mechanisms. This is possible in
the coding r{\'e}gime in which few spikes are emitted in the relevant time
window.
  This approach allows us to study the additional information contributed by
spike timing beyond that present in the spike counts; to examine the
contributions to the whole information of different statistical properties of
spike trains, such as firing rates and correlation functions; and forms the
basis for a new quantitative procedure for the analysis of simultaneous
multiple neuron recordings. It also provides theoretical constraints upon
neural coding strategies. We find a transition between two coding r{\'e}gimes,
depending upon the size of the relevant observation timescale. For time windows
shorter than the timescale of the stimulus-induced response fluctuations, there
exists a spike count coding phase, where the purely temporal information is of
third order in time. For time windows much longer than the characteristic
timescale, there can be additional timing information of first order, leading
to a temporal coding phase in which timing information may affect the
instantaneous information rate.
  We study the relative contributions of the dynamic firing rate and
correlation variables to the full temporal information; the interaction of
signal and noise correlations in temporal coding; synergy between spikes and
between cells; and the effect of refractoriness. We illustrate the utility of
the technique by analysis of a few cells from the rat barrel cortex.


title:
Modelling Meso-Scale Diffusion Processes in Stochastic Fluid
  Bio-Membranes

abstract:
  The space-time dynamics of rigid inhomogeneities (inclusions) free to move in
a randomly fluctuating fluid bio-membrane is derived and numerically simulated
as a function of the membrane shape changes. Both vertically placed (embedded)
inclusions and horizontally placed (surface) inclusions are considered. The
energetics of the membrane, as a two-dimensional (2D) meso-scale continuum
sheet, is described by the Canham-Helfrich Hamiltonian, with the membrane
height function treated as a stochastic process. The diffusion parameter of
this process acts as the link coupling the membrane shape fluctuations to the
kinematics of the inclusions. The latter is described via Ito stochastic
differential equation. In addition to stochastic forces, the inclusions also
experience membrane-induced deterministic forces. Our aim is to simulate the
diffusion-driven aggregation of inclusions and show how the external inclusions
arrive at the sites of the embedded inclusions. The model has potential use in
such emerging fields as designing a targeted drug delivery system.


title: Guiding Neutral Atoms

abstract:
  We demonstrate the guiding of neutral atoms by the magnetic fields due to
microfabricated current-carrying wires on a chip. Atoms are guided along a
magnetic field minimum parallel to and above the current-carrying wires. Two
waveguide configurations are demonstrated: one using two wires with an external
magnetic field, and a second using four wires without an external field. These
waveguide geometries can be extended to integrated atom optics circuits,
including beamsplitters.


title: Convergence of two-center expansions in positron-hydrogen collisions

abstract:
  The positron-hydrogen atom scattering system is considered within the S-wave
model. Convergence in the elastic scattering, excitation, ionization, and
positronium formation channels is studied as a function of the number and type
of states used to expand the total wave function. It is found that all
unphysical resonances disappear only if near-complete pseudostate expansions
are applied to both the atomic and positronium centers.


title:
Guiding neutral atoms around curves with lithographically patterned
  current-carrying wires

abstract:
  Laser-cooled neutral atoms from a low-velocity atomic source are guided via a
magnetic field generated between two parallel wires on a glass substrate. The
atoms bend around three curves, each with a 15-cm radius of curvature, while
traveling along a 10-cm-long track. A maximum flux of 2*10^6 atoms/sec is
achieved with a current density of 3*10^4 A/cm^2 in the
100x100-micrometer-cross-section wires. The kinetic energy of the guided atoms
in one transverse dimension is measured to be 42 microKelvin.


title:
Evolutionary implications of a power-law distribution of protein family
  sizes

abstract:
  Current-day genomes bear the mark of the evolutionary processes. One of the
strongest indications is the sequence homology among families of proteins that
perform similar biological functions in different species. The number of
proteins in a family can grow over time as genetic information is duplicated
through evolution. We explore how evolution directs the size distribution of
these families. Theoretical predictions for family sizes are obtained from two
models, one in which individual genes duplicate and a second in which the
entire genome duplicates. Predictions from these models are compared with the
family size distributions for several organisms whose complete genome sequence
is known. We find that protein family size distributions in nature follow a
power-law distribution. Comparing these results to the model systems, we
conclude that genome duplication is the dominant mechanism leading to increased
genetic material in the species considered.


title:
Electric-octupole and pure-electric-quadrupole effects in soft-x-ray
  photoemission

abstract:
  Second-order [O(k^2), k=omega/c] nondipole effects in soft-x-ray
photoemission are demonstrated via an experimental and theoretical study of
angular distributions of neon valence photoelectrons in the 100--1200 eV
photon-energy range. A newly derived theoretical expression for nondipolar
angular distributions characterizes the second-order effects using four new
parameters with primary contributions from pure-quadrupole and octupole-dipole
interference terms. Independent-particle calculations of these parameters
account for a significant portion of the existing discrepancy between
experiment and theory for Ne 2p first-order nondipole parameters.


title: Tight-binding molecular dynamic study of silver clusters

abstract:
  Tight-binding molecular dynamics (TBMD) is used to study the structural and
electronic properties of silver clusters. The ground state structures of Ag
clusters up to 21 atoms are optimized via TBMD combined with genetic algorithm
(GA). The detailed comparison with {\em ab initio} results on small Ag$_n$
clusters (n=3-9) proves the validity of the tight-bind model. The clusters are
found to undergo a transition from ``electronic order'' to ``atomic order'' at
n=10. This is due to s-d mixing at such size. The size dependence of electronic
properties such as density of states (DOS), s-d band separation, HOMO-LUMO gap,
and ionization potentials are discussed. Magic number behavior at Ag$_2$,
Ag$_8$, Ag$_{14}$, Ag$_{18}$, Ag$_{20}$ is obtained, in agreement with the
prediction of electronic ellipsoid shell model. It is suggested that both the
electronic and geometrical shell exist in the coinage metal clusters and they
play a significant role in determining cluster properties.


title: Events registration in a fast neutrons spectrometer

abstract:
  The principle of operation, design, registration system and main
characteristics of a fast neutrons spectrometer are described. The spectrometer
is intended for direct measurements of ultra low fluxes of fast neutrons. It is
sensitive to neutron fluxes of 10^-7 neutrons/(cm^2 s^1) and lower with the
neutron energy above 700 keV. The detection efficiency of fast neutrons with
simultaneous energy measurement is within 0.02-0.06. The neutron spectrometer
was designed taking into account requirements for minimizing the gamma-ray
background. It is a calorimeter based on a pure liquid organic
scintillator-thermalizer with helium proportional counters as capturers of
thermalized neutrons distributed uniformly over the volume. Low-level signal
electronics for the spectrometer were designed with signal-to-noise ratio
optimization and full pulse shape analysis required for efficient rejection of
background events. A data acquisition and processing system is based on fast
(100 MHz) two-channel PC/AT interfaced digital oscilloscope. The acquisition
software was written in the C programming language.


title: Golden Section and the Art of Painting

abstract:
  A statistical study on 565 works of art of different great painters was done
and it was calculated the ratio of the 2 sides of a paintings. Assuming that
all the painters under discussion enter in a statistics with equal weights it
is shown that the average value obtained for the ratio of the sides is 1.34.
This value, determined experimentally is significantly different from the value
of the Golden Section F=1.618, which is a theoretical ratio, obtained from an
abstract, mathematical theory, which supposedly ought to impress on a painting
a supreme harmony.


title: Boundary Conditions on Internal Three-Body Wave Functions

abstract:
  For a three-body system, a quantum wave function $\Psi^\ell_m$ with definite
$\ell$ and $m$ quantum numbers may be expressed in terms of an internal wave
function $\chi^\ell_k$ which is a function of three internal coordinates. This
article provides necessary and sufficient constraints on $\chi^\ell_k$ to
ensure that the external wave function $\Psi^\ell_m$ is analytic. These
constraints effectively amount to boundary conditions on $\chi^\ell_k$ and its
derivatives at the boundary of the internal space. Such conditions find
similarities in the (planar) two-body problem where the wave function (to
lowest order) has the form $r^{|m|}$ at the origin. We expect the boundary
conditions to prove useful for constructing singularity free three-body basis
sets for the case of nonvanishing angular momentum.


title: Properties of Microelectromagnet Mirrors as Reflectors of Cold Rb Atoms

abstract:
  Cryogenically cooled microelectromagnet mirrors were used to reflect a cloud
of free-falling laser-cooled 85Rb atoms at normal incidence. The mirrors
consisted of microfabricated current-carrying Au wires in a periodic serpentine
pattern on a sapphire substrate. The fluorescence from the atomic cloud was
imaged after it had bounced off a mirror. The transverse width of the cloud
reached a local minimum at an optimal current corresponding to minimum mirror
roughness. A distinct increase in roughness was found for mirror configurations
with even versus odd number of lines. These observations confirm theoretical
predictions.


title: Collapsing Bacterial Cylinders

abstract:
  Under special conditions bacteria excrete an attractant and aggregate. The
high density regions initially collapse into cylindrical structures, which
subsequently destabilize and break up into spherical aggregates. This paper
presents a theoretical description of the process, from the structure of the
collapsing cylinder to the spacing of the final aggregates. We show that
cylindrical collapse involves a delicate balance in which bacterial attraction
and diffusion nearly cancel, leading to corrections to the collapse laws
expected from dimensional analysis. The instability of a collapsing cylinder is
composed of two distinct stages: Initially, slow modulations to the cylinder
develop, which correspond to a variation of the collapse time along the
cylinder axis. Ultimately, one point on the cylinder pinches off. At this final
stage of the instability, a front propagates from the pinch into the remainder
of the cylinder. The spacing of the resulting spherical aggregates is
determined by the front propagation.

categories: physics.bio-ph cond-mat.soft nlin.PS patt-sol


title: The Basic Unit System concept and The Principle of Synergy

abstract:
  The purpose of this paper is to present a new proposal to both dualistic and
holistic paradigm, by introducing a complex basic unit system mathematical
concept in which the quantitative and the qualitative aspects of reality
commingle in a unit, and by presenting a new principle, the principle of
synergy, we have then a new framework in which the opposites can become
complementary. The purpose of the Bus is to establish a complex mathematical
unit concept based on Euler relation from which reality, physical reality can
be treated and interpreted, starting from more basic principles or just from a
unified theoretical point of view. The exact simple pendulum formula and the
well-known Schodinger Wave Equation will be the starting point. This approach
will mean a departure from the normal evolution of physical western science had
taken, but its main advantage will not only be a synthesis of that science but
also a unification that will permit validate those great achievements of
figures like Galileo, Newton, Ampere, Faraday, Maxwell, Einstein and Schodinger
by embedding those achievements in a unified mathematical-theoretical
framework. The origin of this work goes back to 1991(copyright in Dec 1991 as
Fisica y Realidad), and then 1997 it had a second version, and in 1999, the
version from which I have taken excerpts to prepare this paper.


title: Gravitational Waves: An Introduction

abstract:
  In this article, I present an elementary introduction to the theory of
gravitational waves. This article is meant for students who have had an
exposure to general relativity, but, results from general relativity used in
the main discussion have been derived and discussed in the appendices. The weak
gravitational field approximation is first considered and the linearized
Einstein's equations are obtained. We discuss the plane wave solutions to these
equations and consider the transverse-traceless (TT) gauge. We then discuss the
motion of test particles in the presence of a gravitational wave and their
polarization. The method of Green's functions is applied to obtain the
solutions to the linearized field equations in presence of a nonrelativistic,
isolated source.


title: Electromagnetism, Relativity and The Basic Unit System concept

abstract:
  This is the second of three papers I will present as an application of the
Basic Unit System concept, a complex mathematical unit presented in The Basic
Unit System concept and The Principle of Synergy. In this case this Bus concept
is used as a powerful tool to obtain again the Lorentz Transformation Groups of
equations, and then to present the emergent proposal that the fundamental is
the magnetic field, and not the charge concept. The need to obtain "waves
solution" is solved concomitant with the Bus concept as we have seen in the
physics/9908040 .


title:
Do Zero-Energy Solutions of Maxwell Equations Have the Physical Origin
  Suggested by A. E. Chubykalo? [Comment on the paper in Mod. Phys. Lett. A13
  (1998) 2139-2146]

abstract:
  Zero-energy solutions of Maxwell's equations have been discovered and
re-discovered many times in this century. In this comment we show that the
paper by A. E. Chubykalo (which, in fact, also comments on the recent papers)
did not explain physical interpretation of this solution and it used doubtful
(up-to-date) postulates. Different explanations of the considered problem are
possible.

categories: physics.class-ph hep-th physics.ed-ph physics.gen-ph


title: Bose-Einstein Condensation of Atomic Hydrogen

abstract:
  This thesis describes the observation and study of Bose-Einstein condensation
of a trapped, dilute gas of atomic hydrogen. The condensate and normal gas are
studied by two-photon spectroscopy of the 1S-2S transition. We condense over
10^9 atoms per second for several seconds, and the peak condensate density is
around 5x10^15 cm^-3. Topics covered in the thesis include a theoretical
analysis of Bose-condensed hydrogen, a description of the cryogenic trapping
cell and the evaporative cooling techniques used to bring the gas to the
condensation point, and an analysis of the condensate.


title: Gravitational Fields and The Basic Unit System concept

abstract:
  This is the third one of three papers I have presented as an application of
the Basic Unit System concept, a complex mathematical unit presented in The
Basic Unit System concept and The Principle of Synergy. In this case this Bus
concept is used as a powerful tool to obtain again those gravitational field
equations of normal planets, deviation from them as that of Mercury, but also a
proposal made by the astronomer Micheal Disney in his book the Hidden Universe
about Dark Matter. The emerging proposal is then to see the cosmic system as a
Steady Open System, state that is continually exchanging energy, matter and
information, and in it Dark gravity bodies can be seen as gravity compensators
of the whole system. But then appear new forces when the whole system is
considered.


title:
How to teach statistical thermal physics in the introductory physics
  course

abstract:
  We report several simulation programs which can be used to teach the
statistical foundation of thermal physics in the introductory college physics
courses. These programs are simple applications of a technique of generating
random configurations of many dice with fixed total value. By simulating dice
throwing only we can demonstrate all the important principles of classical
thermodynamics.


title:
Atomic optical clocks and search for variation of the fine structure
  constant

abstract:
  Theories unifying gravity and other interactions suggest the possibility of
spatial and temporal variation of physical ``constants''. Accuracy achieved for
the atomic optical frequency standards (optical clocks) approaches the level
when possible time evolution of the fine structure constant $\alpha$ can be
studied by comparisons of rates between clocks based on different atomic
transitions in different atoms. The sensitivity to variation of $\alpha$ is due
to relativistic corrections which are different in different atoms ($\sim
Z^2\alpha^2$). We have calculated the values of the relativistic energy shifts
in In II, Tl II, Ba II and Ra II which all can be used as atomic optical
clocks. The results are to be used to translate any change in the clock's rate
into variation of $\alpha$.


title:
Propulsion Without Propellent Mass; a Time-Varying Electromagnetic Field
  Effect

abstract:
  A propulsion generated without propellent mass and external forces using a
well known physics is possible theoretically. To do that, it is proposed to use
two specific time-varying and constrained distributions of electric charges
which own a symmetry axis and are adequately separated in space. Total charge
of each distribution is zero. With a relative temporal phase-shift between
them, an asymmetry into the far fields momentum variation rate distribution
along the symmetry axis can be induced. Consequently, an electromagnetic
propulsive force is generated and applied over both charge distributions in a
same direction along the axis-say. Magnetic part of this force is dissipative
because closely related to energy lost by radiation. But its electric
counterpart gives a conservative contribution to the propulsive force with no
associated energy losses at zero velocity. Momentum conservation law for the
entire system; the two charge distributions and fields, is respected because
all far fields; radiation ones and relativistic correction one, are taken into
account. If radiation and other energy losses could be minimized, such a
conservative propulsive force could help to realize fast and long space
journeys.


title: A Study of an Acrylic Cerenkov Radiation Detector

abstract:
  An experiment investigating the angle of Cerenkov light emitted by 3-MeV
electrons traversing an acrylic detector has been developed for use in the
advanced physics laboratory course at the University of Rochester. In addition
to exploring the experimental phenomena of Cerenkov radiation and total
internal reflection, the experiment introduces students to several experimental
techniques used in actual high energy and nuclear physics experiments, as well
as to analysis techniques involving Poisson statistics. [to be published in Am.
J. Phys. 67 (Oct/Nov 1999).]


title:
A measurement of the absolute neutron beam polarization produced by an
  optically-pumped 3He spin filter

abstract:
  The capability of performing accurate measurements of neutron beam
polarization opens a number of exciting opportunities in fundamental neutron
physics and in neutron scattering. At the LANSCE pulsed neutron source we have
measured the neutron beam polarization with absolute accuracy of 0.3% in the
neutron energy range from 40 meV to 10 eV using an optically-pumped polarized
3He spin filter and a relative transmission measurement technique. 3He was
polarized using the Rb spin-exchange method. We describe the measurement
technique, present our results, and discuss some of the systematic effects
associated with the method.


title: Creation of an Ultracold Neutral Plasma

abstract:
  We report the creation of an ultracold neutral plasma by photoionization of
laser-cooled xenon atoms. The charge carrier density is as high as 2 x 10^9
cm^-3, and the temperatures of electrons and ions are as low as 100 mK and 10
uK, respectively. Plasma behavior is evident in the trapping of electrons by
the positive ion cloud when the Debye screening length becomes smaller than the
size of the sample. We produce plasmas with parameters such that both electrons
and ions are strongly coupled.


title:
The three-century climatic upheaval of c. 2000 BC, and regional
  radiocarbon disparities

abstract:
  Several researchers have previously identified a severe climatic upheaval in
tropical North Africa that began just over 4000 years ago and lasted for about
three centuries. The upheaval is known to have occurred shortly after a
volcanic eruption, and companion work proposes that this eruption was colossal.
Here, we suggest how the eruption acted as a trigger for the upheaval: by
forcing changes in ocean circulation; although the initial (atmospheric)
forcing lasted only a few years, the ocean required three centuries to regain
equilibrium. The suggested triggering mechanism is supported by
palaeoceanographic, palaeoecological, and archaeo-historical data and by
related experiments with a (coupled general-circulation) climate model. We
argue that the changes in ocean circulation forced changes in sea-surface
temperatures that led to a weakening of the south-west North African monsoon.
The upheaval has been proposed to have also encompassed south-western Asia. We
argue that it encompassed most of the Northern Hemisphere: we present a variety
of palaeoecological and palaeoceanographic evidence and describe the principal
underlying climatology. In some areas the upheaval was the most severe since
the ice ages. The full scope of the upheaval has previously been missed in part
because radiocarbon dates from some areas are centuries too early:
palaeoclimatic events in different areas thus appeared asynchronous. (The
erroneous radiocarbon dates also misled searches seeking ice-core and tree-ring
evidence of the eruption.) The cause of the radiocarbon-dating disparities is
identified as a regional deficiency in 14C, and we locate the region's source
of 14C-deficient carbon.


title: Oscar's Physics Phaire: A Collection of Problems

abstract:
  You will find here a number of (mostly) elementary physics problems dealing
mainly with uniform motion kinematics. In preparing this collection I have
tried to create original situations that could help bring motivation to an
introductory course. You are welcome to suggest improvements and ... provide
solutions!


title: Force and Motion Generation of Molecular Motors: A Generic Description

abstract:
  We review the properties of biological motor proteins which move along linear
filaments that are polar and periodic. The physics of the operation of such
motors can be described by simple stochastic models which are coupled to a
chemical reaction. We analyze the essential features of force and motion
generation and discuss the general properties of single motors in the framework
of two-state models. Systems which contain large numbers of motors such as
muscles and flagella motivate the study of many interacting motors within the
framework of simple models. In this case, collective effects can lead to new
types of behaviors such as dynamic instabilities of the steady states and
oscillatory motion.


title: Motion of Three Vortices near Collapse

abstract:
  A system of three point vortices in an unbounded plane has a special family
of self-similarly contracting or expanding solutions: during the motion, vortex
triangle remains similar to the original one, while its area decreases (grows)
at a constant rate. A contracting configuration brings three vortices to a
single point in a finite time; this phenomenon known as vortex collapse is of
principal importance for many-vortex systems. Dynamics of close-to-collapse
vortex configurations depends on the way the collapse conditions are violated.
Using an effective potential representation, a detailed quantitative analysis
of all the different types of near-collapse dynamics is performed when two of
the vortices are identical. We discuss time and length scales, emerging in the
problem, and their behavior as the initial vortex triangle is approaching to an
exact collapse configuration. Different types of critical behaviors, such as
logarithmic or power-law divergences are exhibited, which emphasizes the
importance of the way the collapse is approached. Period asymptotics for all
singular cases are presented as functions of the initial vortices
configurations. Special features of passive particle mixing by a near-collapse
flows are illustrated numerically.

categories: physics.flu-dyn chao-dyn cond-mat nlin.CD physics.gen-ph