title: Ground Motion Model of the SLAC Site

abstract:
  We present a ground motion model for the SLAC site. This model is based on
recent ground motion studies performed at SLAC as well as on historical data.
The model includes wave-like, diffusive and systematic types of motion. An
attempt is made to relate measurable secondary properties of the ground motion
with more basic characteristics such as the layered geological structure of the
surrounding earth, depth of the tunnel, etc. This model is an essential step in
evaluating sites for a future linear collider.


title: Simulation Studies of the NLC with Improved Ground Motion Models

abstract:
  The performance of various systems of the Next Linear Collider (NLC) have
been studied in terms of ground motion using recently developed models. In
particular, the performance of the beam delivery system is discussed. Plans to
evaluate the operation of the main linac beam-based alignment and feedback
systems are also outlined.


title: Measurement and Correction of Cross-Plane Coupling in Transport Lines

abstract:
  In future linear colliders the luminosity will depend on maintaining the
small emittance aspect ratio delivered by damping rings. Correction of
cross-plane coupling can be important in preventing dilution of the beam
emittance. In order to minimize the vertical emittance, especially for a flat
beam, it is necessary to remove all cross-plane (x-y) correlations. This paper
studies emittance measurement and correction for coupled beams in the presence
of realistic measurement errors. The results of simulations show that
reconstruction of the full 4x4 beam matrix can be misleading in the presence of
errors. We suggest more robust tuning procedures for minimizing linear
coupling.


title: Investigations of Slow Motions of the SLAC Linac Tunnel

abstract:
  Investigations of slow transverse motion of the linac tunnel of the Stanford
Linear Collider have been performed over period of about one month in December
1999 -- January 2000. The linac laser alignment system, equipped with a
quadrant photodetector, allowed submicron resolution measurement of the motion
of the middle of the linac tunnel with respect to its ends. Measurements
revealed two major sources responsible for the observed relative motion.
Variation of the external atmospheric pressure was found to be the most
significant cause of short wavelength transverse motion of the tunnel. The long
wavelength component of the motion has been also observed to have a large
contribution from tidal effects. The measured data are essential for
determination of parameters for the Next Linear Collider.


title: A Second-Order Stochastic Leap-Frog Algorithm for Langevin Simulation

abstract:
  Langevin simulation provides an effective way to study collisional effects in
beams by reducing the six-dimensional Fokker-Planck equation to a group of
stochastic ordinary differential equations. These resulting equations usually
have multiplicative noise since the diffusion coefficients in these equations
are functions of position and time. Conventional algorithms, e.g. Euler and
Heun, give only first order convergence of moments in a finite time interval.
In this paper, a stochastic leap-frog algorithm for the numerical integration
of Langevin stochastic differential equations with multiplicative noise is
proposed and tested. The algorithm has a second-order convergence of moments in
a finite time interval and requires the sampling of only one uniformly
distributed random variable per time step. As an example, we apply the new
algorithm to the study of a mechanical oscillator with multiplicative noise.


title: RF Processing of X-band Accelerator Structures at the NLCTA

abstract:
  During the initial phase of operation, the linacs of the Next Linear Collider
(NLC) will contain roughly 5000 X-Band accelerator structures that will
accelerate beams of electrons and positrons to 250 GeV. These structures will
nominally operate at an unloaded gradient of 72 MV/m. As part of the NLC R&D
program, several prototype structures have been built and operated at the Next
Linear Collider Test Accelerator (NLCTA) at SLAC. Here, the effect of high
gradient operation on the structure performance has been studied. Significant
progress was made during the past year after the NLCTA power sources were
upgraded to reliably produce the required NLC power levels and beyond. This
paper describes the structures, the processing methodology and the observed
effects of high gradient operation.


title:
Fabrication and Tolerance Issues and their Influence on Multi-Bunch Bbu
  and Emittance Dilution in the Construction of X-Band RDDS Linacs for the NLC

abstract:
  The main linacs of the Next Linear Collider (NLC) will contain several
thousand X-band RDDS (Rounded Damped Detuned Structures). The transverse
wakefield in the structures is reduced by detuning the modal frequencies such
that they destructively interfere and by four damping manifolds per structure
which provide weak damping. Errors in the fabrication of the individual cells
and in the alignment of the cells will reduce the cancellation of the modes.
Here, we calculate the tolerances on random errors in the synchronous
frequencies of the cells and the cell-to-cell alignment.


title: Pulsed SC Proton Linac

abstract:
  The superconducting (SC) proton linac is proposed in the JAERI/KEK Joint
Project for a high-intensity proton accelerator in the energy region from 400
to 600 MeV. Highly stable fields in the SC cavities are required under the
dynamic Lorentz force detuning. A new model describing the dynamic Lorentz
detuning has been developed and the validity has been confirmed experimentally.
The model has been applied successfully to the rf control simulation of the SC
proton linac.


title:
Multiresolution Representations for Solutions of Vlasov-Maxwell-Poisson
  Equations

abstract:
  We present the applications of variational-wavelet approach for computing
multiresolution/multiscale representation for solution of some approximations
of Vlasov-Maxwell-Poisson equations.

categories: physics.acc-ph math-ph math.MP nlin.PS physics.comp-ph


title:
Applications of Time Domain Simulation to Coupler Design for Periodic
  Structures

abstract:
  We present numerical procedures for analyzing the properties of periodic
structures and associated couplers based upon time domain simulation. Simple
post processing procedures are given for determining Brillouin diagrams and
complex field distributions of the traveling wave solutions, and the reflection
coefficient of the traveling waves by the input and output. The availability of
the reflection coefficient information facilitates a systematic and efficient
procedure for matching the input and output. The method has been extensively
applied to coupler design for a wide variety of structures and to a study
directed towards elimination of the surface field enhancement commonly
experienced in coupler cells.


title:
An Investigation of Optimised Frequency Distributions for Damping
  Wakefields in X-Band Linacs for the NLC

abstract:
  In the NLC (Next Linear Collider) small misalignments in each of the
individual accelerator structures (or the accelerator cells) will give rise to
wakefields which kick the beam from its electrical axis. This wakefield can
cause BBU (Beam Break Up) or at the very least it will dilute the emittance of
the beam. Several Gaussian detuned structures have been designed and tested [1]
at SLAC and in this paper we explore new distributions with possibly better
damping properties. The progress of the beam through approximately 5,000
structures is monitored in phase space and results on this are presented.
  [1] J.W. Wang et al, TUA03, LINAC2000


title:
Comparisons Of Equivalent Circuit Predictions With Measurements For
  Short Stacks Of Rdds1 Discs, And Their Potential Application To Improved
  Wakefield Prediction

abstract:
  In fabricating the first X-Band RDDS (Rounded Damped Detuned Structure)
accelerator structure, microwave measurements are made on short groups of discs
prior to bonding the discs of the entire structure. The design dispersion
curves are compared with the frequency measurements. The theory utilised is
based on a circuit model adapted to a short stack of slowly varying non-uniform
discs. The model reveals the nature of the modes in the structure and may also
be used to refit the experimental data to the parameters in a model of the
wakefield given earlier [1]. This method allows a more faithful determination
of the wakefield that a beam will experience as it traverses the structure.
Results obtained on the frequencies are compared to the original design.
  [1] R.M.Jones, et al, EPAC96 (also SLAC-PUB-7187)


title: New Development in RF Pulse Compression

abstract:
  Several pulse compression systems have been proposed for future linear
collider. Most of these systems require hundreds of kilometers of low-loss
waveguide runs. To reduce the waveguide length and improve the efficiency of
these systems, components for multimoding, active switches and non-reciprocal
elements are being developed. In the multimoded systems a waveguide is utilized
several times by sending different signals over different modes. The multimoded
components needed for these systems have to be able to handle hundreds of
megawatts of rf power at the X-band frequency and above. Consequently, most of
these components are overmoded. We present the development of multimoded
components required for such systems. We also present the development efforts
towards overmoded active component such as switches and overmoded
non-reciprocal components such as circulators and isolators.


title: Impedance of a Beam Tube with Small Corrugations

abstract:
  In accelerator projects involving the use of very short bunches, such as the
Linac Coherent Light Source (LCLS)-where the rms bunch length in the undulator
section is 30 micron-, it appears that even submicron imperfections in the beam
tube surface can generate an impedance that is unacceptably large. We consider
two periodic models of an imperfect, rough surface, one with small rectangular
corrugations, the other with smooth sinusoidal oscillations. We compare the
impedance of these two models.


title: Compression of High-Charge Electron Bunches

abstract:
  The A0 Photoinjector at Fermilab can produce high charge (10-14 nC) electron
bunches of low emittance (20 pi mm-mrad for 12 nC). We have undertaken a study
of the optimal compression conditions. Off-crest acceleration in the 9-cell
capture cavity induces an energy-time correlation, which is rotated by the
compressor chicane (4 dipoles). The bunch length is measured using streak
camera images of optical transition radiation. We present measurements under
various conditions, including the effect of the laser pulse length (2 ps sigma
Gaussian vs. 10 ps FWHM flat top). The best compression to date is for a 13.2
nC bunch with sigma = 0.63 mm (1.89 ps), which corresponds to a peak current of
2.8 kA.


title:
Electro-Optic Sampling of Transient Fields from the passage of
  High-Charge Electron Bunches

abstract:
  When a relativistic electron bunch traverses a structure, strong electric
fields are induced in its wake. We present measurements of the electric field
as a function of time as measured at a fixed location in the beam line. For a
12 nC bunch of duration 4.2 ps FWHM, the peak field is measured >0.5 MV/m. Time
resolution of ~5 ps is achieved using electro-optic sampling with a lithium
tantalate (LiTaO_3) crystal and a short-pulse infrared laser synchronized to
the beam. We present measurements under several different experimental
conditions and discuss the influence of mode excitation in the structure.


title: Efficient Design Scheme of Superconducting Cavity

abstract:
  For many next-generation high intensity proton accelerator applications
including the Spallation Neutron Source (SNS), superconducting (SC) RF provides
the technology of choice for the linac. In designing the superconducting
cavity, several features, such as peak fields, inter-cell coupling, mechanical
stiffness, field flatness, external Q, manufacturability, shunt impedance,
higher order mode (HOM), etc., should be considered together. A systematic
approach to determine the optimum cavity shape by exploring the entire
geometric space of the cavity has been found. The most efficient use of RF
energy can be accomplished by adjusting the cell shape. A small region in
parameter space satisfying all reasonable design criteria has been found. With
this design procedure, choosing the optimum shape is simplified. In this paper,
the whole design procedure of this optimisation scheme is explained and applied
to the SNS cavity design.


title: Structural Analysis of Superconducting Accelerator Cavities

abstract:
  The static and dynamic structural behavior of superconducting cavities for
various projects was determined by finite element structural analysis. The b =
0.61 cavity shape for the Neutron Science Project was studied in detail and
found to meet all design requirements if fabricated from five millimeter thick
material with a single annular stiffener. This 600 MHz cavity will have a
Lorentz coefficient of -1.8 Hz/(Mv/meter)2 and a lowest structural resonance of
more than 100 Hz. Cavities at b = 0.48, 0.61, and 0.77 were analyzed for a
Neutron Science Project concept which would incorporate 7-cell cavities. The
medium and high beta cavities were found to meet all criteria but it was not
possible to generate a b = 0.48 cavity with a Lorentz coefficient of less than
-3 Hz/(Mv/meter) 2.


title: CW Performance of the Triumf 8 Meter Long RFQ for Exotic Ions

abstract:
  The ISAC 35 MHz RFQ is designed to accelerate ions of A/q up to 30 from
2keV/u to 150keV/u in cw mode. The RFQ structure is 8 meters long and the
vane-shaped rods are supported by 19 rings spaced 40 cm apart. An unusual
feature of the design is the constant synchronous phase of -25; the buncher and
shaper sections are eliminated in favor of an external multi-harmonic buncher.
All 19 rings are installed with quadrature positioning of the four rod
electrodes aligned to +/- 0.08 mm. Relative field variation and quadruple
asymmetry along the 8 meters of the RFQ was measured to be within +/- 1%. Early
operation at peak inter-electrode voltage (75kV) was restricted by the rapid
growth of dark currents due to field emission; the nominal operating power of
75 kW increased to 100 kW in a few hours. A program of high power pulsing,
followed by cw operation have all but eliminated the problem leading to a
successful 150 hour test at full power. Successful beam test results confirm
beam dynamics and rf designs.


title:
Local and Fundamental Mode Coupler Damping of the Transverse Wakefield
  in RDDS1 Linacs

abstract:
  In damping the wakefield generated by an electron beam traversing several
thousand X-band linacs in the NLC we utilise a Gaussian frequency distribution
of dipole modes to force the modes to deconstructively interfere, supplemented
with moderate damping achieved by coupling these modes to four attached
manifolds. Most of these modes are adequately damped by the manifolds. However,
the modes towards the high frequency end of the lower dipole band are not
adequately damped because the last few cells are, due to mechanical fabrication
requirements, not coupled to the manifolds. To mitigate this problem in the
present RDDS1 design, the output coupler for the accelerating mode has been
designed so as to also couple out those dipole modes which reach the output
coupler cell. In order to couple out both dipole mode polarizations, the output
coupler has four ports. We also report on the results of a study of the
benefits which can be achieved by supplementing manifold damping with local
damping for a limited number of cells at the downstream end of the structure.


title: An Overview of the Spallation Neutron Source Project

abstract:
  The Spallation Neutron Source (SNS) is being designed, constructed, installed
and commissioned by the staff of six national laboratories, Argonne National
Laboratory, Brookhaven National Laboratory, Jefferson National Accelerator
Laboratory, Lawrence Berkeley National Laboratory, Los Alamos National
Laboratory, and Oak Ridge National Laboratory. The accelerator systems are
designed to deliver a 695 ns proton-pulse onto a mercury target at a 60-Hz
repetition rate and an average power of 2-MW. Neutron moderators that will
convert the spallation neutrons into slow neutrons for material science
research will surround the target. The Front-End systems are designed to
generate an H- beam of minipulses, 68% beam on, 32% beam off every 965 ns, at
2.5 MeV for 1 ms, 60 times a second. The Front-End systems include a RF driven,
volume-production ion source, beam chopping system, RFQ, and beam transport.
The ion source will have to achieve about 65 mA to deliver 52 mA at the input
to the linac. The linac consists of a drift tube linac up to 86.8 MeV, a
coupled-cell linac to 185 MeV, and a superconducting RF linac to the nominal
energy of 1 GeV. The design of the superconducting section includes 11
cryomodules with three, 0.61-beta cavities per cryomodule and 17 cryomodules
with four, 0.81-beta cavities per cryomodule, with space to install four more
0.81-beta cryomodules. The accumulator ring is designed for charge exchange
injection at full energy. The peak charge per bunch at the end of the
accumulation cycle will reach 2.08x10**14 for 2-MW operation. The goal is to
control beam losses to less than 1x10**-4.


title: Design of 11.8 MHZ Buncher for Isac at Triumf

abstract:
  The high energy beam transport (HEBT) line for the ISAC radioactive beam
facility at TRIUMF requires an 11.8 MHz buncher. The main requirements of the
buncher are to operate in cw mode with a velocity acceptance of 2.2% and an
effective voltage of 100 kV, which for a three gap buncher gives a drift tube
voltage of 30 kV. A lumped element circuit is more suitable than a distributed
rf structure for this low frequency of operation. The resonant frequency of
11.8 MHz is obtained by an inductive coil in parallel with the capacitance of
the drift tube. The coil is housed in a dust free box at atmospheric pressure
whereas the drift tube is placed in a vacuum chamber and an rf feedthrough
connects them. Two design of this feedthrough, one using disk and one using
tubular ceramics, operating at 30 kV rf, are described in this paper. MAFIA and
SUPERFISH codes are used to simulate the fields in the feedthroughs,
particularly around the ceramic metal interfaces. Test results of the prototype
feedthroughs are presented and the choice of the proposed final solution is
outlined.


title:
Predictions about the behaviour of diamond, silicon, SiC and some AIIIBV
  semiconductor materials in hadron fields

abstract:
  The utilisation of crystalline semiconductor materials as detectors and
devices operating in high radiation environments, at the future particle
colliders, in space applications, in medicine and industry, makes necessary to
obtain radiation harder materials. Diamond, SiC and different AIIIBV compounds
(GaAs, GaP, InP, InAs, InSb) are possible competitors for silicon to different
electronic devices for the up-mentioned applications. The main goal of this
paper is to give theoretical predictions about the behaviour of these
semiconductors in hadron fields (pions, protons). The effects of the
interaction between the incident particle and the semiconductor are
characterised in the present paper both from the point of view of the
projectile, the relevant quantity being the energy loss by nuclear
interactions, and of the target, using the concentration of primary radiation
induced defects on unit particle fluence. Some predictions about the damage
induced by hadrons in these materials in possible applications in particle
physics and space experiments are done.

categories: physics.ins-det astro-ph cond-mat.mtrl-sci hep-ex


title:
Laser spectroscopy of simple atoms and precision tests of bound state
  QED

abstract:
  We present a brief overview of precision tests of bound state QED and mainly
pay our attention to laser spectroscopy as an appropriate tool for these tests.
We particularly consider different precision tests of bound state QED theory
based on the laser spectroscopy of optical transitions in hydrogen, muonium and
positronium and related experiments.


title: New Method of Dispersion Correction in the Pep-II Low Energy Ring

abstract:
  The sextupole magnets in the Low Energy Ring (LER) of PEP-II are grouped in
pairs with a phase advance of 180 degrees. Displacing the magnets or moving the
orbit to displace the beam in the magnets in an antisymmetric way creates a
dispersion wave around the ring. This can be used to correct the vertical
dispersion in LER without changing the local coupling. Results from simulations
are shown.


title: SNS Front End Diagnostics

abstract:
  The Front End of the Spallation Neutron Source (SNS) extends from the Ion
Source (IS), through a 65 keV LEBT, a 402.5 MHz RFQ, a 2.5 MeV MEBT, ending at
the entrance to the DTL. The diagnostics suite in this space includes stripline
beam position and phase monitors (BPM), toroid beam current monitors (BCM), and
an emittance scanner. Provision is included for beam profile measurement,
either gas fluorescence, laser-based photodissociation, or a crawling wire.
Mechanical and electrical design and prototyping of BPM and BCM subsystems are
proceeding. Significant effort has been devoted to packaging the diagnostic
devices in minimal space. Close ties are maintained to the rest of the SNS
effort, to ensure long term compatibility of interfaces and in fact share some
design work and construction. The data acquisition, digital processing, and
control system interface needs for the BPM, BCM, and LEBT diagnostic are
similar, and we are committed to using an architecture common with the rest of
the SNS collaboration.


title:
High Power Model Fabrication of Biperiodic L-Support Disk-and-Washer
  Structure

abstract:
  The high power test model of biperiodic L-support disk-and- washer was
fabricated. Among some trouble in the fabrication, the main one was a vacuum
leak in a brazing process. The repair test of the leak showed a good result;
four units were recovered out of five leak units (recover rate 80%). While an
accelerating mode frequency was tuned at an operating frequency of 2857 MHz by
squeezing method, a coupling mode frequency of 2847MHz and the 3.4% field
flatness (peak to peak ratio) were achieved.


title: Integral methods for shallow free-surface flows with separation

abstract:
  We study laminar thin film flows with large distortions in the free surface
using the method of averaging across the flow. Two concrete problems are
studied: the circular hydraulic jump and the flow down an inclined plane. For
the circular hydraulic jump our method is able to handle an internal eddy and
separated flow. Assuming a variable radial velocity profile like in
Karman-Pohlhausen's method, we obtain a system of two ordinary differential
equations for stationary states that can smoothly go through the jump where
previous studies encountered a singularity. Solutions of the system are in good
agreement with experiments. For the flow down an inclined plane we take a
similar approach and derive a simple model in which the velocity profile is not
restricted to a parabolic or self-similar form. Two types of solutions with
large surface distortions are found: solitary, kink-like propagating fronts,
obtained when the flow rate is suddenly changed, and stationary jumps,
obtained, e.g., behind a sluice gate. We then include time-dependence in the
model to study stability of these waves. This allows us to distinguish between
sub- and supercritical flows by calculating dispersion relations for
wavelengths of the order of the width of the layer.


title: Binary Representations of ABCD Matrices

abstract:
  The ABCD matrix is one of the essential mathematical instruments in optics.
It is the two-by-two representation of the group Sp(2), which is applicable to
many branches of physics, including squeezed states of light, special
relativity and coupled oscillators. It is pointed out that the shear
representation is oriented to binary logic which may be friendly to computer
applications. While this is a future possibility, it is known that para-axial
lens optics is based on the shear representation of the Sp(2) group. It is
pointed out that the most general form of the ABCD matrix can be written in
terms of six shear matrices, which correspond to lens and translation matrices.
The parameter for each shear matrix is computed in terms of the three
independent parameters of the ABCD matrix.


title:
Investigations of Amplitude and Phase Excitation Profiles in Femtosecond
  Coherence Spectroscopy

abstract:
  We present an effective linear response approach to pump-probe femtosecond
coherence spectroscopy in the well separated pulse limit. The treatment
presented here is based on a displaced and squeezed state representation for
the non-stationary states induced by an ultrashort pump laser pulse or a
chemical reaction. The subsequent response of the system to a delayed probe
pulse is modeled using closed form non-stationary linear response functions,
valid for a multimode vibronically coupled system at arbitrary temperature.
When pump-probe signals are simulated using the linear response functions, with
the mean nuclear positions and momenta obtained from a rigorous moment analysis
of the pump induced (doorway) state, the signals are found to be in excellent
agreement with the conventional third order response approach. The key
advantages offered by the moment analysis based linear response approach
include a clear physical interpretation of the amplitude and phase of
oscillatory pump-probe signals, a dramatic improvement in computation times, a
direct connection between pump-probe signals and equilibrium absorption and
dispersion lineshapes, and the ability to incorporate coherence such as those
created by rapid non-radiative surface crossing. We demonstrate these aspects
using numerical simulations, and also apply the present approach to the
interpretation of experimental amplitude and phase measurements on reactive and
non-reactive samples of the heme protein Myoglobin. The role played by
inhomogeneous broadening in the observed amplitude and phase profiles is
discussed in detail. We also investigate overtone signals in the context of
reaction driven coherent motion.


title: P-Loop Oscillator on Clifford Manifolds and Black Hole Entropy

abstract:
  A new relativity theory, or more concretely an extended relativity theory,
actively developed by one of the authors incorporated 3 basic concepts. They
are the old idea of Chew about bootstrapping, Nottale's scale relativity, and
enlargement of the conventional time-space by inclusion of noncommutative
Clifford manifolds where all p-branes are treated on equal footing. The latter
allowed one to write a master action functional. The resulting functional
equation is simplified and applied to the p-loop oscillator. Its respective
solution is a generalization of the conventional point oscillator. In addition
, it exhibits some novel features: an emergence of two explicit scales
delineating the asymptotic regimes (Planck scale region and a smooth region of
a conventional point oscillator). In the most interesting Planck scale regime,
the solution reproduces in an elementary fashion the basic relations of string
theory (including string tension quantization). In addition, it is shown that
comparing the massive (super) string degeneracy with the p-loop degeneracy one
is arriving at the proportionality between the Shannon entropy of a p-loop
oscillator in D-dimensional space and the Bekenstein-Hawking entropy of the
black hole of a size comparable with a string scale.


title: New complex variables for equations of ideal barotropic fluid

abstract:
  We propose new construction of dependent variables for equations of an ideal
barotropic fluid. This construction is based on a direct generalization of the
known connection between Schroedinger equation and a system of Euler-type
equations. The system for two complex-valued functions is derived that is
equivalent to Euler equations. Possible advantages of the proposed formulation
are discussed.


title: Challenges in Affecting U.S. Attitudes Towards Space Science

abstract:
  Space Science enjoys broad public support in the US. People say they follow
developments with interest, and that the programs are worth their cost. This
attitude seems to arise in part because of the intrinsic accessibility and
appeal of the subject matter. Yet at the same time the public is often
disturbingly ignorant about basic facts. In this article I summarize recent
survey results, including attitudes towards basic research, and also consider
some of the criticisms of the polling methods. I argue that the results imply
vigorous and innovative education and outreach programs can and should be made
even more effective -- but that the consequences of success for Space Science
research itself are not obvious. I outline two popular education programs which
address some of the new challenges facing Space Science outreach.


title: The easiest way to Heaviside ellipsoid

abstract:
  The formula for the electric field of a point charge moving with constant
velocity is derived using the symmetry properties of Maxwell's equations - its
Lorentz invariance. In contrast to conventional treatments, the derivation
presented does not use retarded integrals or relativity transformations.


title: Circular Orbits Inside the Sphere of Death

abstract:
  A wheel or sphere rolling without slipping on the inside of a sphere in a
uniform gravitational field can have stable circular orbits that lie wholly
above the "equator", while a particle sliding freely cannot.


title: The Rolling Motion of a Disk on a Horizontal Plane

abstract:
  Recent interest in the old problem of the motion of a coin spinning on a
tabletop has focused on mechanisms of dissipation of energy as the angle alpha
of the coin to the table decreases, while the angular velocity Omega of the
point of contact increases. Following a review of the general equations of
motion of a thin disk rolling without slipping on a horizontal surface, we
present results of simple experiment on the time dependence of the motion that
indicate the dominant dissipative power loss to be proportional to the Omega^2
up to and including the last observable cycle.


title:
Entropy Shows that Global Warming Should Cause Increased Variability in
  the Weather

abstract:
  Elementary physical reasoning seems to leave it inevitable that global
warming would increase the variability of the weather. The first two terms in
an approximation to the global entropy are used to show that global warming has
increased the free energy available to drive the weather, and that the variance
of the weather should increase correspondingly.


title: The birth of special relativity. "One more essay on the subject"

abstract:
  Special relativity was discovered at the eve of the century, but finds its
roots in the 19th century efforts to understand the optics and electromagnetism
of moving bodies. These roots are reviewed in Parts 1 and 2, the latter being
specially devoted to the works of Lorentz and of Poincare up to 1904. Part 3
contains a detailed comparison of the works of Einstein and of Poincare in
1905. It is shown that both authors succeeded in constructing a coherent and
fully relativistic theory, although their ideas about the ether were radically
different. In Part 4, the question of the respective merits of the three
potential fathers of special relativity (i.e. Lorentz, Poincare, Einstein) is
discussed again, at the light of the preceding analysis and of the "post-1905"
developments of the theory.


title: Limit on Lorentz and CPT Violation of the Proton Using a Hydrogen Maser

abstract:
  We present a new measurement constraining Lorentz and CPT violation of the
proton using a hydrogen maser double resonance technique. A search for hydrogen
Zeeman frequency variations with a period of the sidereal day (23.93 h) sets a
clean limit on violation of Lorentz and CPT symmetry of the proton at the
10^{-27} GeV level.

categories: physics.atom-ph hep-ex hep-ph physics.gen-ph


title: Purine-pyrimidine symmetry, determinative degree and DNA

abstract:
  Various symmetries connected with purine-pyrimidine content of DNA sequences
are studied in terms of the intruduced determinative degree, a new
characteristics of nucleotide which is connected with codon usage. A
numerological explanation of CG pressure is proposed. A classification of DNA
sequences is given. Calculations with real sequences show that
purine-pyrimidine symmetry increases with growing of organization. A new small
parameter which characterizes the purine-pyrimidine symmetry breaking is
proposed for the DNA theory.


title: Minimum Entropy Aproach to Word Segmentation Problems

abstract:
  Given a sequence composed of a limit number of characters, we try to "read"
it as a "text". This involves to segment the sequence into "words". The
difficulty is to distinguish good segmentation from enormous number of random
ones.Aiming at revealing the nonrandomness of the sequence as strongly as
possible, by applying maximum likelihood method, we find a quantity called
Segmentation Entropy that can be used to fulfill the duty. Contrary to
commonplace where maximum entropy principle was applied to obtain good
solution, we choose to {\em minimize} the segmentation entropy to obtain good
segmentation. The concept developed in this letter can be used to study the
noncoding DNA sequences, e.g., for regulatory elements prediction, in eukaryote
genomes.

categories: physics.bio-ph cond-mat.stat-mech physics.data-an q-bio


title: Fast and Flexible CCD Driver System Using Fast DAC and FPGA

abstract:
  We have developed a completely new type of general-purpose CCD data
acquisition system which enables one to drive any type of CCD using any type of
clocking mode. A CCD driver system widely used before consisted of an analog
multiplexer (MPX), a digital-to-analog converter (DAC), and an operational
amplifier. A DAC is used to determine high and low voltage levels and the MPX
selects each voltage level using a TTL clock. In this kind of driver board, it
is difficult to reduce the noise caused by a short of high and low level in MPX
and also to select many kinds of different voltage levels. Recent developments
in semiconductor IC enable us to use a very fast sampling ($\sim$ 10MHz) DAC
with low cost. We thus develop the new driver system using a fast DAC in order
to determine both the voltage level of the clock and the clocking timing. We
use FPGA (Field Programmable Gate Array) to control the DAC. We have
constructed the data acquisition system and found that the CCD functions well
with our new system. The energy resolution of Mn K$\alpha$ has a full-width at
half-maximum of $\simeq$ 150 eV and the readout noise of our system is $\simeq$
8 e$^-$.


title: On the Possibility of Local SR Construction

abstract:
  The violation of the invariance of the speed of light in Special Relativity
has been made. The version of the theory (LSR) has been constructed in which
the possibility of the superluminal motions are permitted. Some predictions of
this theory are available for experimental check, for example, the measurements
of aberration angles, the observation of distinctions between the redshifts in
radio and optical ranges of a spectrum, the detection of superluminal objects
in astrophysics and in time-flight experiments.


title: Emergence of Bulk CsCl Structure in (CsCl)nCs+ Cluster Ions

abstract:
  The emergence of CsCl bulk structure in (CsCl)nCs+ cluster ions is
investigated using a mixed quantum-mechanical/semiempirical theoretical
approach. We find that rhombic dodecahedral fragments (with bulk CsCl symmetry)
are more stable than rock-salt fragments after the completion of the fifth
rhombic dodecahedral atomic shell. From this size (n=184) on, a new set of
magic numbers should appear in the experimental mass spectra. We also propose
another experimental test for this transition, which explicitely involves the
electronic structure of the cluster. Finally, we perform more detailed
calculations in the size range n=31--33, where recent experimental
investigations have found indications of the presence of rhombic dodecahedral
(CsCl)32Cs+ isomers in the cluster beams.


title: Equilibrium solutions of the shallow water equations

abstract:
  A statistical method for calculating equilibrium solutions of the shallow
water equations, a model of essentially 2-d fluid flow with a free surface, is
described. The model contains a competing acoustic turbulent {\it direct}
energy cascade, and a 2-d turbulent {\it inverse} energy cascade. It is shown,
nonetheless that, just as in the corresponding theory of the inviscid Euler
equation, the infinite number of conserved quantities constrain the flow
sufficiently to produce nontrivial large-scale vortex structures which are
solutions to a set of explicitly derived coupled nonlinear partial differential
equations.


title: Higher Dipole Bands in the NLC Accelerating Structure

abstract:
  We show that scattering matrix calculations for dipole modes between 23-43
GHz for the 206 cell detuned structure (DS) are consistent with finite element
calculations and results of the uncoupled model. In particular, the rms sum
wake for these bands is comparable to that of the first dipole band.
  We also show that for RDDS1 uncoupled wakefield calculations for higher bands
are consistent with measurements. In particular, a clear 26 GHz signal in the
short range wake is found in both results.


title:
Transitions Induced by the Discreteness of Molecules in a Small
  Autocatalytic System

abstract:
  Autocatalytic reaction system with a small number of molecules is studied
numerically by stochastic particle simulations. A novel state due to
fluctuation and discreteness in molecular numbers is found, characterized as
extinction of molecule species alternately in the autocatalytic reaction loop.
Phase transition to this state with the change of the system size and flow is
studied, while a single-molecule switch of the molecule distributions is
reported. Relevance of the results to intracellular processes are briefly
discussed.

categories: physics.bio-ph cond-mat.stat-mech nlin.AO q-bio.SC


title:
Comments on "Effective Core Potentials" [M.Dolg, Modern Methods and
  Algorithms of Quantum Chemistry (Ed. by J.Grotendorst, John von Neumann
  Institute for Computing, J\"ulich, NIC Series, Vol.1, ISBN 3-00-005618-1,
  pp.479-508, 2000)]

abstract:
  The recent paper of M.Dolg is discussed and his critical remarks with respect
to the Generalized Relativistic Effective Core Potential (GRECP) method are
shown to be incorrect. Some main features of GRECP are discussed as compared
with the ``energy-consistent/adjusted'' pseudopotential and with the
conventional shape-consistent RECP.


title: A simple unbreakable code

abstract:
  A simple unbreakable cipher system is presented which uses the concept of
"pseudo-bits" that has never been used in either classical or quantum
cryptography.


title: Rotation in liquid $^4$He: Lessons from a toy model

abstract:
  This paper presents an analysis of a model problem, consisting of two
interacting rigid rings, for the rotation of molecules in liquid $^4$He. Due to
Bose symmetry, the excitation of the rotor corresponding to a ring of N helium
atoms is restricted to states with integer multiples of N quanta of angular
momentum. This minimal model shares many of the same features of the rotational
spectra that have been observed for molecules in nanodroplets of $\approx 10^3
- 10^4$ helium atoms. In particular, this model predicts, for the first time,
the very large enhancement of the centrifugal distortion constants that have
been observed experimentally. It also illustrates the different effects of
increasing rotational velocity by increases in angular momentum quantum number
or by increasing the rotational constant of the molecular rotor. It is found
that fixed node, diffusion Monte Carlo and a hydrodynamic model provide upper
and lower bounds on the size of the effective rotational constant of the
molecular rotor when coupled to the helium.


title: Status of the RFD Linac Structure Developement

abstract:
  The Proof-of-Principle (POP) prototype of the Rf-Focused Drift tube (RFD)
linac structure is currently under test at Linac Systems, after years of delay
due to a variety of technical problems. A discussion of these technical
problems and their solutions will be presented. The status of these tests will
be reported. Plans for future development of this linac structure will be
revealed. Potential uses of this linac structure for a variety of scientific,
medical, and industrial applications will be described, including: proton linac
injectors for proton synchrotrons, compact proton linacs for PET isotope
production, epithermal neutron sources for the BNCT application, energy
boosters for proton therapy, compact portable neutron sources for thermal
neutron radiography, and pulsed cold neutron sources for cold neutron physics
and related applications.


title:
Simulation of the Beam-Beam Effects in $e^+e^-$ Storage Rings with a
  Method of Reducing the Region of Mesh

abstract:
  A highly accurate self-consistent particle code to simulate the beam-beam
collision in $e^+e^-$ storage rings has been developed. It adopts a method of
solving the Poisson equation with an open boundary. The method consists of two
steps: assigning the potential on a finite boundary using the Green's function,
and then solving the potential inside the boundary with a fast Poisson solver.
Since the solution of the Poisson's equation is unique, our solution is exactly
the same as the one obtained by simply using the Green's function. The method
allows us to select much smaller region of mesh and therefore increase the
resolution of the solver. The better resolution makes more accurate the
calculation of the dynamics in the core of the beams. The luminosity simulated
with this method agrees quantitatively with the measurement for the PEP-II
B-factory ring in the linear and nonlinear beam current regimes, demonstrating
its predictive capability in detail.


title:
Compactification of the moduli space in symplectization and hidden
  symmetries of its boundary

abstract:
  In this paper, we establish the compactification of the moduli space in
symplectization and and studied the hidden symmetries of its boundary.


title: The Approach to Ergodicity in Monte Carlo Simulations

abstract:
  The approach to the ergodic limit in Monte Carlo simulations is studied using
both analytic and numerical methods. With the help of a stochastic model, a
metric is defined that enables the examination of a simulation in both the
ergodic and non-ergodic regimes. In the non-ergodic regime, the model implies
how the simulation is expected to approach ergodic behavior analytically, and
the analytically inferred decay law of the metric allows the monitoring of the
onset of ergodic behavior. The metric is related to previously defined measures
developed for molecular dynamics simulations, and the metric enables the
comparison of the relative efficiencies of different Monte Carlo schemes.
Applications to Lennard-Jones 13-particle clusters are shown to match the model
for Metropolis, J-walking and parallel tempering based approaches. The relative
efficiencies of these three Monte Carlo approaches are compared, and the decay
law is shown to be useful in determining needed high temperature parameters in
parallel tempering and J-walking studies of atomic clusters.


title:
Wave packet evolution approach to ionization of hydrogen molecular ion
  by fast electrons

abstract:
  The multiply differential cross section of the ionization of hydrogen
molecular ion by fast electron impact is calculated by a direct approach, which
involves the reduction of the initial 6D Schr\"{o}dinger equation to a 3D
evolution problem followed by the modeling of the wave packet dynamics. This
approach avoids the use of stationary Coulomb two-centre functions of the
continuous spectrum of the ejected electron which demands cumbersome
calculations. The results obtained, after verification of the procedure in the
case atomic hydrogen, reveal interesting mechanisms in the case of small
scattering angles.


title:
Optimal Control of Molecular Motion Expressed Through Quantum Fluid
  Dynamics

abstract:
  A quantum fluid dynamic control formulation is presented for optimally
manipulating atomic and molecular systems. In quantum fluid dynamic the control
quantum system is expressed in terms of the probability density and the quantum
current. This choice of variables is motivated by the generally expected slowly
varying spatial-temporal dependence of the fluid dynamical variables. The
quantum fluid dynamic approach is illustrated for manipulation of the ground
electronic state dynamics of HCl induced by an external electric field.


title: Measurement of persistence in 1D diffusion

abstract:
  Using a novel NMR scheme we observed persistence in 1-D gas diffusion.
Analytical approximations and numerical simulations have indicated that for an
initially random array of spins undergoing diffusion, the probability p(t) that
the average spin magnetization in a given region has not changed sign (i.e.,
``persists'') up to time t follows a power law t^{-\theta}, where \theta\
depends on the dimensionality of the system. Using laser-polarized ^{129}Xe
gas, we prepared an initial ``quasirandom'' 1D array of spin magnetization and
then monitored the ensemble's evolution due to diffusion using real-time NMR
imaging. Our measurements are consistent with analytical and numerical
predictions of \theta \approx 0.12.


title: Comment on "Degenerate Wannier Theory for Multiple Ionization"

abstract:
  Recent Letter of T.Pattard and J.M.Rost (Phys.Rev.Lett 80, 5081 (1998))
suggests that there exist logarithmic corrections to the near threshold cross
section for the processes of break up of a particle into several charged
fragments. This comment shows that it is incorrect, the logarithmic terms never
exist. The cross section for all processes behaves as some power of the
above-threshold energy, similarly to the known Wannier problem.


title:
Statistically Significant Strings are Related to Regulatory Elements in
  the Promoter Regions of Saccharomyces cerevisiae

abstract:
  Finding out statistically significant words in DNA and protein sequences
forms the basis for many genetic studies. By applying the maximal entropy
principle, we give one systematic way to study the nonrandom occurrence of
words in DNA or protein sequences. Through comparison with experimental
results, it was shown that patterns of regulatory binding sites in
Saccharomyces cerevisiae(yeast) genomes tend to occur significantly in the
promoter regions. We studied two correlated gene family of yeast. The method
successfully extracts the binding sites varified by experiments in each family.
Many putative regulatory sites in the upstream regions are proposed. The study
also suggested that some regulatory sites are a ctive in both directions, while
others show directional preference.

categories: physics.bio-ph cond-mat.soft physics.data-an q-bio


title: Noise Delays Bifurcation in a Positively Coupled Neural Circuit

abstract:
  We report a noise induced delay of bifurcation in a simple pulse-coupled
neural circuit. We study the behavior of two neural oscillators, each
individually governed by saddle-node dynamics, with reciprocal excitatory
synaptic connections. In the deterministic circuit, the synaptic current
amplitude acts as a control parameter to move the circuit from a mono-stable
regime through a bifurcation into a bistable regime. In this regime stable
sustained anti-phase oscillations in both neurons coexist with a stable rest
state. We introduce a small amount of random current into both neurons to model
possible randomly arriving synaptic inputs. We find that such random noise
delays the onset of bistability, even though in decoupled neurons noise tends
to advance bifurcations and the circuit has only excitatory coupling. We show
that the delay is dependent on the level of noise and suggest that a curious
stochastic ``anti-resonance'' is present.


title: The beryllium atom and beryllium positive ion in strong magnetic fields

abstract:
  The ground and a few excited states of the beryllium atom in external uniform
magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for
field strengths ranging from zero up to 2.35*10^9T. With changing field
strength the ground state of the Be atom undergoes three transitions involving
four different electronic configurations which belong to three groups with
different spin projections S_z=0,-1,-2. For weak fields the ground state
configuration arises from the 1s^2 2s^2, S_z=0 configuration. With increasing
field strength the ground state evolves into the two S_z=-1 configurations
1s^22s 2p_{-1} and 1s^2 2p_{-1}3d_{-2}, followed by the fully spin polarised
S_z=-2 configuration 1s2p_{-1}3d_{-2}4f_{-3}. The latter configuration forms
the ground state of the beryllium atom in the high field regime \gamma>4.567.
The analogous calculations for the Be^+ ion provide the sequence of the three
following ground state configurations: 1s^22s and 1s^22p_{-1} (S_z=-1/2) and
1s2p_{-1}3d_{-2} (S_z=-3/2).


title: Beam-based Feedback Simulations for the NLC Linac

abstract:
  Extensive beam-based feedback systems are planned as an integral part of the
Next Linear Collider (NLC) control system. Wakefield effects are a significant
influence on the feedback design, imposing both architectural and algorithmic
constraints. Studies are in progress to assure the optimal selection of devices
and to refine and confirm the algorithms for the system design. We show the
results of initial simulations, along with evaluations of system response for
various conditions of ground motion and other operational disturbances.


title:
Theory of sub-10 fs Generation in Kerr-lens Mode-locked Solid-State
  Lasers with a Coherent Semiconductor Absorber

abstract:
  The results of the study of ultra-short pulse generation in continuous-wave
Kerr-lens mode-locked (KLM) solid-state lasers with semiconductor saturable
absorbers are presented. The issues of extremely short pulse generation are
addressed in the frames of the theory that accounts for the coherent nature of
the absorber-pulse interaction. We developed an analytical model that bases on
the coupled generalized Landau-Ginzburg laser equation and Bloch equations for
a coherent absorber. We showed, that in the absence of KLM semiconductor
absorber produces 2pi - non-sech-pulses of self-induced transparency, while the
KLM provides an extremely short sech-shaped pulse generation. 2pi- and
pi-sech-shaped solutions and variable-area chirped pulses have been found. It
was shown, that the presence of KLM removes the limitation on the minimal
modulation depth in absorber. An automudulational stability and self-starting
ability were analyzed, too.


title: Breaking of vortex lines - a new mechanism of collapse in hydrodynamics

abstract:
  A new mechanism of the collapse in hydrodynamics is suggested, due to
breaking of continuously distributed vortex lines. Collapse results in
formation of the point singularities of the vorticity field $|{\bf\Omega}|$. At
the collapse point, the value of the vorticity blows up as $(t_0-t)^{-1}$ where
$t_0$ is a collapse time. The spatial structure of the collapsing distribution
approaches a pancake form: contraction occurs by the law $l_1\sim(t_0-t)^{3/2}$
along the "soft" direction, the characteristic scales vanish like
$l_2\sim(t_0-t)^{1/2}$ along two other ("hard") directions. This scenario of
the collapse is shown to take place in the integrable three-dimensional
hydrodynamics with the Hamiltonian ${\cal H}=\int|{\bf\Omega}|d{\bf r}$. Most
numerical studies of collapse in the Euler equation are in a good agreement
with the proposed theory.


title: One way to Characterize the compact structures of lattice protein model

abstract:
  On the study of protein folding, our understanding about the protein
structures is limited. In this paper we find one way to characterize the
compact structures of lattice protein model. A quantity called Partnum is given
to each compact structure. The Partnum is compared with the concept
Designability of protein structures emerged recently. It is shown that the
highly designable structures have, on average, an atypical number of local
degree of freedom. The statistical property of Partnum and its dependence on
sequence length is also studied.

categories: physics.bio-ph cond-mat.soft cond-mat.stat-mech q-bio


title:
Soliton Generation and Picosecond Collapse in Solid-State Lasers with
  Semiconductor Saturable Absorber

abstract:
  Based on self - consistent field theory we study a soliton generation in cw
solid-state lasers with semiconductor saturable absorber. Various soliton
destabilizations, i.e. the switch from femtosecond to picosecond generation
(''picosecond collapse''), an automodulation regime, breakdown of soliton
generation and hysteresis behavior, are predicted.


title: Psychophysical quantum-string Weltdrama

abstract:
  Hypothesis of an existence of the universal quantum string field for all
interactive phenomena is formulated. Its practical value is clarified.


title:
Orientational melting of two-shell carbon nanoparticles: molecular
  dynamics study

abstract:
  The energetic characteristics of two-shell carbon nanoparticles ("onions")
with different shapes of second shell are calculated. The barriers of relative
rotation of shells are found to be surprisingly small; therefore, free relative
rotation of shells can take place at room temperature. The intershell
orientational melting of the nanoparticle $C_{60}@C_{240}$ is studied by
molecular dynamics. The parameters of Arrhenius formula for jump rotational
intershell diffusion are calculated. The definition of orientational melting
temperature is proposed as the temperature when the transition probability over
barrier between equivalent potential minima is equal to 1/2. The temperature of
orientational melting of the nanoparticle $C_{60}@C_{240}$ is about 60 K.


title:
Test of Cosmic Spatial Isotropy for Polarized Electrons Using a
  Rotatable Torsion Balance

abstract:
  To test the cosmic spatial isotropy, we use a rotatable torsion balance
carrying a transversely spin-polarized ferrimagnetic Dy_{6}Fe_{23} mass. With a
rotation period of one hour, the period of anisotropy signal is reduced from
one sidereal day by about 24 times, and hence the 1/f noise is greatly reduced.
Our present experimental results constrain the cosmic anisotropy Hamiltonian H
= C_{1} sigma_{1} + C_{2} sigma_{2} + C_{3} sigma_{3} (sigma_{3} is in the axis
of earth rotation) to (C_{1}^{2} +C_{2}^{2})^{1/2} = (1.8 +- 5.3) X 10^{-21} eV
and | C_{3} | = (1.2 +- 3.5) X 10^{-19} eV. This improves the previous limits
on (C_{1},C_{2}) by 120 times and C_{3} by a factor of 800.


title:
Rotatable-Torsion-Balance Equivalence Principleexperiment for the
  Spin-Polarized Hofe_{3}

abstract:
  We use a rotatable torsion balance to perform an equivalence principle test
on a magnetically shielded spin-polarized body of HoFe_{3}. With a rotation
period of one hour, the period of possible signal is reduced from one solar day
by 24 times, and hence the 1/f noise is greatly reduced. Our present
experimental results gives a limit (0.25 +- 1.26) X 10^{-9} on the Eotvos
parameter \eta of equivalence of the polarized body compared with unpolarized
aluminium-brass cylinders in the solar gravitional field, and a limit (0.34 +-
0.52) X 10^{-9} in the earth gravitional fields. This improves the previous
limit on polarized bodies by a factor of 45 for solar field and by a factor of
11 for earth field.


title:
Alarming Oxygen Depletion Caused by Hydrogen Combustion and Fuel Cells
  and their Resolution by Magnegas$^{TM}$

abstract:
  We recall that hydrogen combustion does resolve the environmental problems of
fossil fuels due to excessive emission of carcinogenic substances and carbon
dioxide. However, hydrogen combustion implies the permanent removal from our
atmosphere of directly usable oxygen, a serious environmental problem called
oxygen depletion, since the combustion turns oxygen into water whose separation
to restore the original oxygen is prohibitive due to cost. We then show that a
conceivable global use of hydrogen in complete replacement of fossil fuels
would imply the permanent removal from our atmosphere of 2.8875x10^7 metric
tons O_2/day. Fuel cells are briefly discussed to point out similarly serious
environmental problems, again, for large uses. We propose the possibility of
resolving these problems by upgrading hydrogen to the new combustible fuel
called magnegas^TM, whose chemical structure is composed by the new chemical
species of magnecules, whose energy content and other features are beyond the
descriptive capacities of quantum chemistry. In fact, magnegas contains up to
50% hydrogen, while having combustion exhaust with: 1) a positive oxygen
balance (releasing more oxygen in the exhaust than that used in the
combustion); 2) no appreciable carcinogenic or toxic substances; 3)
considerably reduced carbon dioxide as compared to fossil fuels; 4)
considerably reduced nitrogen oxides; and 5) general reduction of pollutants in
the exhaust up to 96% of current EPA standards.


title: Perfectly secure cipher system

abstract:
  We present a perfectly secure cipher system based on the concept of fake bits
which has never been used in either classical or quantum cryptography.


title: Second law versus variation principles

abstract:
  The field-dependent equilibrium thermodynamics is derived with two methods:
either by using the potential formalism either by the statistical method.
Therefore, Pontrjagin's extremum principle of control theory is applied to an
extended ensemble average. This approach allows to derive the grand partition
function of thermodynamics as a result of a control problem with the Hamilton
energy. Furthermore, the maximum entropy principle follows and the second law
in a modified form. The derivation can predict second law violations if cycles
with irreversibilities in varying potential fields are included into
consideration. This conclusion is supported indirectly by experimental data
from literature. The upper maximum gain efficiency of a cycle with a known
polymer solution as dielectrics was estimated to less than 1 promille per
cycle. Note added in proof 28th October 2003: Comparing this preprint work with
an analogous ferrofluidic system discrepancies are is found which show that the
concrete model proposed here in section 4 is insufficient to settle the
question. A way to solve the problem is proposed.


title:
On the sensitivity of wave channeling of X-ray beam to the shape of
  interface channels

abstract:
  The effect of transmission of x-ray beams through submicron capillaries was
investigated with account for diffraction and roughness scattering. Possible
explanation of anomalous energy dependence of transmission through thin Cr/C/Cr
channeles was given due to effect of periodic deformations.


title:
Two-time Green function method in quantum electrodynamics of high-Z
  few-electron atoms

abstract:
  The two-time Green function method in quantum electrodynamics of high-Z
few-electron atoms is described in detail. This method provides a simple
procedure for deriving formulas for the energy shift of a single level and for
the energies and wave functions of degenerate and quasi-degenerate states. It
also allows one to derive formulas for the transition and scattering
amplitudes. Application of the method to resonance scattering processes yields
a systematic theory for the spectral line shape. The practical ability of the
method is demonstrated by deriving formulas for the QED and
interelectronic-interaction corrections to energy levels and transition and
scattering amplitudes in one-, two-, and three-electron atoms. Numerical
calculations of the Lamb shift, the hyperfine splitting, the bound-electron g
factor, and the radiative recombination cross section in heavy ions are also
reviewed.


title: A Generalization of the Maximum Noise Fraction Transform

abstract:
  A generalization of the maximum noise fraction (MNF) transform is proposed.
Powers of each band are included as new bands before the MNF transform is
performed. The generalized MNF (GMNF) is shown to perform better than the MNF
on a time dependent airborne electromagnetic (AEM) data filtering problem.


title: Automodulations in Kerr-lens Modelocked Solid-State Lasers

abstract:
  Nonstationary pulse regimes associated with self modulation of a Kerr-lens
modelocked Ti:sapphire laser have been studied experimentally and
theoretically. Such laser regimes occur at an intracavity group delay
dispersion that is smaller or larger than what is required for stable
modelocking and exhibit modulation in pulse amplitude and spectra at
frequencies of several hundred kHz. Stabilization of such modulations, leading
to an increase in the pulse peak power by a factor of ten, were accomplished by
weakly modulating the pump laser with the self-modulation frequency. The main
experimental observations can be explained with a round trip model of the fs
laser taking into account gain saturation, Kerr lensing, and second- and
third-order dispersion.


title: Dirac and Majorana Constructs

abstract:
  The present work is a brief review of the recent development in the
relativistic quantum mechanics in the $(1/2)\oplus (0,1/2)$ representation
space. It can be useful for graduate students in particle physics and quantum
field theory.


title: Highlights of AAC 2000 Workshop

abstract:
  The Advanced Accelerator Concepts 2000 (AAC2K) Workshop was held in Santa Fe
in June, 2000, and included a wide array of conceptual and theoretical advances
at the frontier of accelerator physics. This paper reviews the highlights of
the workshop, with subjects ranging from acceleration using lasers, plasmas and
microstructures, to the beam physics of muon colliders. Particular emphasis is
given to the topics which are relevant to research at existing linear
accelerator facilities, and the effect of this research on the capabilities of
such facilities.


title:
Experimental Evidence of Near-field Superluminally Propagating
  Electromagnetic Fields

abstract:
  A simple experiment is presented which indicates that electromagnetic fields
propagate superluminally in the near-field next to an oscillating electric
dipole source. A high frequency 437MHz, 2 watt sinusoidal electrical signal is
transmitted from a dipole antenna to a parallel near-field dipole detecting
antenna. The phase difference between the two antenna signals is monitored with
an oscilloscope as the distance between the antennas is increased. Analysis of
the phase vs distance curve indicates that superluminal transverse electric
field waves (phase and group) are generated approximately one-quarter
wavelength outside the source and propagate toward and away from the source.
Upon creation, the transverse waves travel with infinite speed. The outgoing
transverse waves reduce to the speed of light after they propagate about one
wavelength away from the source. The inward propagating transverse fields
rapidly reduce to the speed of light and then rapidly increase to infinite
speed as they travel into the source. The results are shown to be consistent
with standard electrodynamic theory.


title: Local Momentum and a Three-Body Gauge

abstract:
  In recent years researchers have attempted to improve the continuum state
three-body wavefunction for three, mutually interacting Coulomb particles by
including, so called, local momentum effects, which depend upon the logarithmic
gradient of the continuum, two-body Coulomb waves. Using the exact three-body
wavefunction in the region where two of the three particles remain close, a
revised description of these local momenta, is attained which predicts that a
quantum-mechanical impulse may develop in the reaction zone, causing
like-sign-charged particles to decrease their radial separation and
opposite-sign-charged particles to increase their radial separation. The
consequences of these predictions are investigated through both quantum and
semi-classical techniques where the total energy of a two-body continuum
Coulomb system in the presence of a third, mutually interacting body are
analyzed. Numerical calculations confirm that while ignoring these local
effects for light-ion-atom processes, may be appropriate, three-body effects
may dominate in the reaction zone for heavy-ion-atom processes. This hypothesis
is investigated and it is shown that a real-valued, position-dependent phase is
added to the wavefunction. Further analysis shows that one may detect
asymptotic variations in the scattering amplitudes for massive systems at
near-threshold energies. These results provide convincing theoretical and
physical evidence for a formal three-body gauge.


title:
Design, fabrication and measurement of the first rounded damped detuned
  accelerator structure (RDDS1)

abstract:
  As a joint effort in the JLC/NLC research program, we have developed a new
type of damped detuned accelerator structure with optimized round-shaped
cavities (RDDS). This paper discusses some important R&D aspects of the first
structure in this series (RDDS1). The design aspects covered are the cell
design with sub-MHz precision, HOM detuning, coupling and damping technique and
wakefield simulation. The fabrication issues covered are ultra-precision cell
machining with micron accuracy, assembly and diffusion bonding technologies to
satisfactorily meet bookshelf, straightness and cell rotational alignment
requirements. The measurements described are the RF properties of single
cavities and complete accelerator section, as well as wakefields from the ASSET
tests at SLAC. Finally, future improvements are also discussed.


title:
Stable, Strongly Attractive, Two-State Mixture of Lithium Fermions in an
  Optical Trap

abstract:
  We use an all-optical trap to confine a strongly attractive two-state mixture
of lithium fermions. By measuring the rate of evaporation from the trap, we
determine the effective elastic scattering cross section (4 PI a^2) to show
that the magnitude of the scattering length |a| is very large, in agreement
with predictions. We show that the mixture is stable against inelastic decay
provided that a small bias magnetic field is applied. For this system, the
s-wave interaction is widely tunable at low magnetic field, and can be turned
on and off rapidly via a Raman PI pulse. Hence, this mixture is well suited for
fundamental studies of an interacting Fermi gas.


title: Magnetospheric disturbances, and the GPS operation

abstract:
  We have investigated a dependence of the relative density of phase slips in
the GPS navigation system on the disturbance level of the Earth's
magnetosphere. The study is based on using Internet-available selected data
from the global GPS network, with the simultaneously handled number of
receiving stations ranging from 160 to 323. The analysis used four days from
the period 1999-2000, with the values of the geomagnetic field disturbance
index Dst from 0 to -300 nT. During strong magnetic storms, the relative
density of phase slips on mid latitudes exceeds the one for magnetically quiet
days by one-two orders of magnitude as a minimum, and reaches a few and (for
some of the GPS satellites) even ten percent of the total density of
observations. Furthermore, the level of phase slips for the GPS satellites
located on the sunward side of the Earth was by a factor of 5-10 larger
compared with the opposite side of the Earth. The high positive correlation of
an increase in the density of phase slips and the intensity of ionospheric
irregularities during geomagnetic disturbances as detected in this study points
to the fact that the increase is slips is caused by the scattering of the GPS
signal from ionospheric irregularities.


title: Slice Sampling

abstract:
  Markov chain sampling methods that automatically adapt to characteristics of
the distribution being sampled can be constructed by exploiting the principle
that one can sample from a distribution by sampling uniformly from the region
under the plot of its density function. A Markov chain that converges to this
uniform distribution can be constructed by alternating uniform sampling in the
vertical direction with uniform sampling from the horizontal `slice' defined by
the current vertical position, or more generally, with some update that leaves
the uniform distribution over this slice invariant. Variations on such `slice
sampling' methods are easily implemented for univariate distributions, and can
be used to sample from a multivariate distribution by updating each variable in
turn. This approach is often easier to implement than Gibbs sampling, and more
efficient than simple Metropolis updates, due to the ability of slice sampling
to adaptively choose the magnitude of changes made. It is therefore attractive
for routine and automated use. Slice sampling methods that update all variables
simultaneously are also possible. These methods can adaptively choose the
magnitudes of changes made to each variable, based on the local properties of
the density function. More ambitiously, such methods could potentially allow
the sampling to adapt to dependencies between variables by constructing local
quadratic approximations. Another approach is to improve sampling efficiency by
suppressing random walks. This can be done using `overrelaxed' versions of
univariate slice sampling procedures, or by using `reflective' multivariate
slice sampling methods, which bounce off the edges of the slice.


title:
Time-Symmetric ADI and Causal Reconnection: Stable Numerical Techniques
  for Hyperbolic Systems on Moving Grids

abstract:
  Moving grids are of interest in the numerical solution of hydrodynamical
problems and in numerical relativity. We show that conventional integration
methods for the simple wave equation in one and more than one dimension exhibit
a number of instabilities on moving grids. We introduce two techniques, which
we call causal reconnection and time-symmetric ADI, which together allow
integration of the wave equation with absolute local stability in any number of
dimensions on grids that may move very much faster than the wave speed and that
can even accelerate. These methods allow very long time-steps, are fully
second-order accurate, and offer the computational efficiency of
operator-splitting.


title: The influence of a metallic sheet on an evanescent mode atomic mirror

abstract:
  A theory of evanescent mode atomic mirrors utilising a metallic sheet on a
dielectric substrate is described. The emphasis here is on the role of the
metallic sheet and on the evaluation of atomic trajectories using the field-
dipole orientation picture. At low intensity, the atomic reflection process is
controlled by two separate mechanisms both of which are modified by the
presence of the metallic sheet and influenced by the use of the field-dipole
orientation picture. The first mechanism involves the spontaneous force which
accelerates the atom parallel to the sheet plane. The second mechanism involves
the combined dipole plus van der Waals force which acts to repel the atom from
the surface, decelerating its motion until it attains an instantaneous halt
before changing direction away from the surface at an appr opriate turning
point in the trajectory. Various quantitative features arising from varying the
controllable parameters of the system, including screening effects as well as
desirable enhancement effects, are pointed out and discussed.


title: Design of the JLC/NLC RDDS Structure Using Parallel Eigensolver Omega3p

abstract:
  The complexity of the Round Damped Detuned Structue (RDDS) for the JLC/NLC
main linac is driven by the considerations of rf efficiency and dipole
wakefield suppression. As a time and cost saving measure for the JLC/NLC, the
dimensions of the 3D RDDS cell are being determined through computer modeling
to within fabrication precision so that no tuning may be needed once the
structures are assembled. The tolerances on the frequency errors for the RDDS
structure are about one MHz for the fundamental mode and a few MHz for the
dipole modes. At the X-band frequency, these correspond to errors of a micron
level on the major cell dimensions. Such a level of resolution requires highly
accurate field solvers and vast amount of computer resources. A parallel
finite-element eigensolver Omega3P was developed at SLAC that runs on massively
parallel computers such as the Cray T3E at NERSC. The code was applied in the
design of the RDDS cell dimensions that are accurate to within fabrication
precision. We will present the numerical approach of using these codes to
determine the RDDS dimensions and compare the numerical predictions with the
cold test measurements on RDDS prototypes that are diamond-turned using these
dimensions.


title: Information theory and learning: a physical approach

abstract:
  We try to establish a unified information theoretic approach to learning and
to explore some of its applications. First, we define {\em predictive
information} as the mutual information between the past and the future of a
time series, discuss its behavior as a function of the length of the series,
and explain how other quantities of interest studied previously in learning
theory - as well as in dynamical systems and statistical mechanics - emerge
from this universally definable concept. We then prove that predictive
information provides the {\em unique measure for the complexity} of dynamics
underlying the time series and show that there are classes of models
characterized by {\em power-law growth of the predictive information} that are
qualitatively more complex than any of the systems that have been investigated
before. Further, we investigate numerically the learning of a nonparametric
probability density, which is an example of a problem with power-law
complexity, and show that the proper Bayesian formulation of this problem
provides for the `Occam' factors that punish overly complex models and thus
allow one {\em to learn not only a solution within a specific model class, but
also the class itself} using the data only and with very few a priori
assumptions. We study a possible {\em information theoretic method} that
regularizes the learning of an undersampled discrete variable, and show that
learning in such a setup goes through stages of very different complexities.
Finally, we discuss how all of these ideas may be useful in various problems in
physics, statistics, and, most importantly, biology.

categories: physics.data-an cond-mat.dis-nn cs.LG nlin.AO


title:
Bayesian Blocks: Divide and Conquer, MCMC, and Cell Coalescence
  Approaches

abstract:
  Identification of local structure in intensive data -- such as time series,
images, and higher dimensional processes -- is an important problem in
astronomy. Since the data are typically generated by an inhomogeneous Poisson
process, an appropriate model is one that partitions the data space into cells,
each of which is described by a homogeneous (constant event rate) Poisson
process. It is key that the sizes and locations of the cells are determined by
the data, and are not predefined or even constrained to be evenly spaced. For
one-dimensional time series, the method amounts to Bayesian changepoint
detection. Three approaches to solving the multiple changepoint problem are
sketched, based on: (1) divide and conquer with single changepoints, (2)
maximum posterior for the number of changepoints, and (3) cell coalescence. The
last method starts from the Voronoi tessellation of the data, and thus should
easily generalize to spaces of higher dimension.


title: Has superluminal light propagation been observed?

abstract:
  It says in the report$^1$ by Wang et al. that a negative group velocity
$u=-c/310$ is obtained and that a pulse advancement shift 62-ns is measured.
The authors claim that the negative group velocity is associated with
superluminal light propagation and that the pulse advancement is not at odds
with causality or special relativity. However, it is shown here that their
conclusions above are not true. Furthermore, I give some suggestion concerning
a re-definition of group-velocity and a new explanation in special relativity
of causality.


title:
Binding Energies and Scattering Observables in the 4Helium3 Atomic
  System

abstract:
  The 4He3 system is investigated using a hard-core version of the Faddeev
differential equations and realistic 4He-4He interactions. We calculate the
binding energies of the 4He trimer but concentrate in particular on scattering
observables. The atom-diatom scattering lengths are calculated as well as the
atom-diatom phase shifts for center of mass energies up to 2.45 mK.


title: Exotic Ion-Beams, Targets and Sources

abstract:
  Exotic beams of short-lived radioisotopes are produced in nuclear reactions
such as thermal neutron induced fission, target or projectile fragmentation and
fusion reactions. For a given radioactive ion beam (RIB), different production
modes are in competition. For each of them the cross section, the intensity of
the projectile beam and the target thickness define an upper production rate.
The final yield relies on the optimisation of the ion-source, which should be
fast and highly efficient in view of the limited production cross section, and
on obtaining a minimum diffusion time out of the target matrix or fragment
catcher to reduce decay losses. Eventually, either chemical or isobaric
selectivity is needed to confine unwanted elements near to the production site.
These considerations are discussed for pulsed or dc-driven RIB facilities and
the solutions to some of the technical challenges will be illustrated by
examples of currently produced near-drip-line elements.


title:
Influence of guiding magnetic field on emission of stimulated photons in
  generators utilizing periodic slow-wave structures

abstract:
  Effect of guiding magnetic field on evolution of stimulated emission is
considered. It is shown that the transverse dynamics of electrons contributes
to generation process and that contribution decreases with the magnetic field
grows. The equation of generation for stimulated radiation of electron beam
passing over periodic medium in magnetic field of arbitrary value is derived.
The critical value of guiding field for which the transverse dynamics of
electron don't contribute to emission is determined. It is shown, that
transverse dynamics of electron modifies the boundary conditions. It follows
from the derived generation equation that transverse dynamics yields to ~25%
increase of the increment magnitude in high gain regime. In the limit of small
signal the generation gain twice increases when transverse dynamics evolves.
Obtained results are valid for every FEL system, which use the mechanism of
waves slowing in the slow-wave structures for generation.


title: Relativistic recoil corrections to the atomic energy levels

abstract:
  The quantum electrodynamic theory of the nuclear recoil effect in atoms to
all orders in \alpha Z and to first order in m/M is considered. The complete
\alpha Z - dependence formulas for the relativistic recoil corrections to the
atomic energy levels are derived in a simple way. The results of numerical
calculations of the recoil effect to all orders in \alpha Z are presented for
hydrogenlike and lithiumlike atoms. These results are compared with analytical
results obtained to lowest orders in \alpha Z. It is shown that even for
hydrogen the numerical calculations to all orders in \alpha Z provide most
precise theoretical predictions for the relativistic recoil correction of first
order in m/M.


title: Numerical Studies on Locally Damped Structures

abstract:
  In the JLC/NLC X-band linear collider, it is essential to reduce the
long-range dipole wakefields in the accelerator structure to prevent beam break
up (BBU) and emittance degradation. The two methods of reducing the long-range
wakefields are detuning and damping. Detuning reduces the wakefields rapidly as
the dipole modes de-cohere but, with a finite number of modes, the wakefield
will grow again as the modes re-cohere. In contrast, damping suppresses the
wakefields at a longer distance. There are two principal damping schemes:
synchronous damping using HOM manifolds such as that used in the RDDS1
structure and local damping similar to that used in the CLIC structure. In a
locally damped scheme, one can obtain almost any Q value, however, the damping
can have significant effects on the accelerating mode. In this paper, we
present a medium local-damping scheme where the wakefields are controlled to
meet the BBU requirement while minimizing the degradations of the fundamental
rf parameters. We will address the load design and pulse heating issues
associated with the medium damping scheme.


title: Mirror modes: Nonmaxwellian distributions

abstract:
  We perform direct analysis of mirror mode instabilities from the general
dielectric tensor for several model distributions, in the longwavelength limit.
The growth rate at the instability threshold depends on the derivative of the
distribution for zero parallel energy. The maximum growth rate is always $\sim
k_\parallel v_{T\parallel}$ and the instability is of nonresonant kind. The
instability growth rate and its dependence on the propagation angle depend on
the shape of the ion and electron distribution functions.


title:
Charged-Surface Instability Development in Liquid Helium; Exact
  Solutions

abstract:
  The nonlinear dynamics of charged-surface instability development was
investigated for liquid helium far above the critical point. It is found that,
if the surface charge completely screens the field above the surface, the
equations of three-dimensional (3D) potential motion of a fluid are reduced to
the well-known equations describing the 3D Laplacian growth process. The
integrability of these equations in 2D geometry allows the analytic description
of the free-surface evolution up to the formation of cuspidal singularities at
the surface.


title: Relativistic Geometry and Quantum Electrodynamics

abstract:
  Excitations of a relativistic geometry are used to represent the theory of
quantum electrodynamics. The connection excitations and the frame excitations
reduce, respectively, to the electromagnetic field operator and electron field
operator. Because of the inherent geometric algebraic structure these operators
obey the standard commutation rules of QED. If we work with excitations, we
need to use statistical theory when considering the evolution of microscopic
subsystems. The use of classical statistics, in particular techniques of
irreversible thermodynamics, determine that the probability of absorption or
emission of a geometric excitation is a function of the classical energy
density. Emission and absorption of geometric excitations imply discrete
changes of certain physical variables, but with a probability determined by its
wave energy density. Hence, this geometric theory, without contradicting the
fundamental aspects of quantum physics, provides a geometric foundation for the
theory.


title: From Superluminal Velocity To Time Machines?

abstract:
  Various experiments have shown superluminal group and signal velocities
recently. Experiments were essentials carried out with microwave tunnelling,
with frustrated total internal reflection, and with gain-assisted anomalous
dispersion. According to text books a superluminal signal velocity violates
Einstein causality implying that cause and effect can be changed and time
machines known from science fiction could be constructed. This naive analysis,
however, assumes a signal to be a point in the time dimension neglecting its
finite duration. A signal is not presented by a point nor by its front, but by
its total length. On the other hand a signal energy is finite thus its
frequency band is limited, the latter is a fundamental physical property in
consequence of field quantization with quantum $h \nu$. All superluminal
experiments have been carried out with rather narrow frequency bands. The
narrow band width is a condition sine qua non to avoid pulse reshaping of the
signal due to the dispersion relation of the tunnelling barrier or of the
excited gas, respectively. In consequence of the narrow frequency band width
the time duration of the signal is long so that causality is preserved.
However, superluminal signal velocity shortens the otherwise luminal time span
between cause and effect.


title: Universal Tunnelling Time in photonic Barriers

abstract:
  Tunnelling transit time for a frustrated total internal reflection in a
double-prism experiment was measured using microwave radiation. We have found
that the transit time is of the same order of magnitude as the corresponding
transit time measured either in an undersized waveguide (evanescent modes) or
in a photonic lattice. Moreover we have established that in all such
experiments the tunnelling transit time is approximately equal to the
reciprocal 1/f of the corresponding frequency of radiation.


title: Relativistic Geometry and Weak Interactions

abstract:
  Geometric interactions in a new relativistic geometric unified theory include
interactions other than gravitation and electromagnetism. In a low energy limit
one of these interactions leads essentially to a Fermi type theory of weak
interactions including the Hamiltonian and coupling constant.


title:
Average observed properties of the Earth's quasi-perpendicular and
  quasi-parallel bow shock

abstract:
  We present a statistical analysis of 132 dayside (LT 0700-1700) bow shock
crossings of the AMPTE/IRM spacecraft. We perform a superposed epoch analysis
of plasma and magnetic field parameters as well as of low frequency magnetic
power spectra some minutes upstream and downstream of the bow shock by dividing
the events into categories depending on the angle between bow shock normal and
interplanetary magnetic field and on the plasma-beta, i.e., the ratio of plasma
to magnetic pressure.
  Downstream of the quasi-perpendicular low-beta (beta < 0.5) bow shock we find
a dominance of the left-hand polarized component at frequencies just below the
ion cyclotron frequency with amplitudes of about 3 nT. These waves are
identified as ion cyclotron waves which grow in a low-beta regime due to the
proton temperature anisotropy. We find a strong correlation of this anisotropy
with the intensity of the left-hand polarized component. Downstream of some
nearly perpendicular high-beta (beta > 1.0) crossings mirror waves are
identified. However, there are also cases where the conditions for mirror modes
are met downstream of the nearly perpendicular shock, but no mirror waves are
observed.


title: The Longitudinal Polarimeter at HERA

abstract:
  The design, construction and operation of a Compton back-scattering laser
polarimeter at the HERA storage ring at DESY are described. The device measures
the longitudinal polarization of the electron beam between the spin rotators at
the HERMES experiment with a fractional systematic uncertainty of 1.6%. A
measurement of the beam polarization to an absolute statistical precision of
0.01 requires typically one minute when the device is operated in the
multi-photon mode. The polarimeter also measures the polarization of each
individual electron bunch to an absolute statistical precision of 0.06 in
approximately five minutes. It was found that colliding and non-colliding
bunches can have substantially different polarizations. This information is
important to the collider experiments H1 and ZEUS for their future
longitudinally polarized electron program because those experiments use the
colliding bunches only.


title: Balanced Branching in Transcription Termination

abstract:
  The theory of stochastic transcription termination based on free-energy
competition requires two or more reaction rates to be delicately balanced over
a wide range of physical conditions. A large body of work on glasses and large
molecules suggests that this should be impossible in such a large system in the
absence of a new organizing principle of matter. We review the experimental
literature of termination and find no evidence for such a principle but many
troubling inconsistencies, most notably anomalous memory effects. These suggest
that termination has a deterministic component and may conceivably be not
stochastic at all. We find that a key experiment by Wilson and von Hippel
allegedly refuting deterministic termination was an incorrectly analyzed
regulatory effect of Mg2+ binding.


title:
Single-bubble sonoluminescence: Shape stability analysis of collapse
  dynamics in a semianalytical approach

abstract:
  This paper theoretically analyzes the hydrodynamic shape stability problem
for sonoluminescing bubbles. We present a semianalytical approach to describe
the evolution of shape perturbations in the strongly nonlinear regime of
violent collapse. The proposed approximation estimating the damping rate
produced by liquid viscosity is used to elucidate the influence of the collapse
phase on subsequent evolution of the Rayleigh-Taylor instability. We
demonstrate that time derivatives of shape perturbations grow significantly as
the bubble radius vanishes, forming the dominant contribution to
destabilization during the ensuing bounce phase. By this effect the
Rayleigh-Taylor instability can be enhanced drastically, yielding a viable
explanation of the upper threshold of driving pressure experimentally observed
by Barber et al. [Phys. Rev. Lett. 72, 1380 (1994)].


title:
Formation of Root Singularities on the Free Surface of a Conducting
  Fluid in an Electric Field

abstract:
  The formation of singularities on a free surface of a conducting ideal fluid
in a strong electric field is considered. It is found that the nonlinear
equations of two-dimensional fluid motion can be solved in the small-angle
approximation. This enables us to show that for almost arbitrary initial
conditions the surface curvature becomes infinite in a finite time.


title: The Alpha Constant from Relativistic Groups

abstract:
  The value of the alpha constant, known to be equal to an algebraic expression
in terms of pi and entire numbers related to certain group volumes, is derived
from the relativistic structure group of a geometric unified theory, its
subgroups and corresponding symmetric space quotients.


title:
A Program for the Geometric Classification of Particles and Relativistic
  Interactions

abstract:
  Geometric relativistc interactions in a new geometric unified theory are
classified using the dynamic holonomy groups of the connection. Physical
meaning may be given to these interactions if the frame excitations represent
particles. These excitations have algebraic and topological quantum numbers.
The proton, electron and neutrino may be associated to the frame excitations of
the three dynamical holonomy subgroups. In particular, the proton excitation
has a dual mathematical structure of a triplet of subexcitations. Hadronic,
leptonic and gravitational interactions correspond to the same subgroups. The
background geometry determines non trivial fiber bundles where excitations
live, introducing topological quantum numbers that classify families of
excitations. From these three particles, the only stable ones, it may be
possible, as suggested by Barut, to build the rest of the particles. The
combinations of the three fundamental excitations display SU(3)xSU(2)xU(1)
symmetries.


title: Cold collisions between atoms in optical lattices

abstract:
  We have simulated binary collisions between atoms in optical lattices during
Sisyphus cooling. Our Monte Carlo Wave Function simulations show that the
collisions selectively accelerate mainly the hotter atoms in the thermal
ensemble, and thus affect the steady state which one would normally expect to
reach in Sisyphus cooling without collisions.


title:
Low-frequency method for magnetothermopower and Nernst effect
  measurements on single crystal samples at low temperatures and high magnetic
  fields

abstract:
  We describe an AC method for the measurement of the longitudinal (Sxx) and
transverse (Sxy, i.e. Nernst) thermopower of mm-size single crystal samples at
low temperatures (T<1 K) and high magnetic fields (B>30 T). A low-frequency (33
mHz) heating method is used to increase the resolution, and to determine the
temperature gradient reliably in high magnetic fields. Samples are mounted
between two thermal blocks which are heated by a sinusoidal frequency f0 with a
p/2 phase difference. The phase difference between two heater currents gives a
temperature gradient at 2f0. The corresponding thermopower and Nernst effect
signals are extracted by using a digital signal processing method due. An
important component of the method involves a superconducting link, YBa2Cu3O7+d
(YBCO), which is mounted in parallel with sample to remove the background
magnetothermopower of the lead wires. The method is demonstrated for the quasi
two-dimensional organic conductor a-(BEDT-TTF)2KHg(SCN)4, which exhibits a
complex, magnetic field dependent ground state above 22.5 T at low
temperatures.


title: Apparent Superluminal Behavior

abstract:
  The apparent superluminal propagation of electromagnetic signals seen in
recent experiments is shown to be the result of simple and robust properties of
relativistic field equations. Although the wave front of a signal passing
through a classically forbidden region can never move faster than light, an
attenuated replica of the signal is reproduced ``instantaneously'' on the other
side of the barrier. The reconstructed signal, causally connected to the
forerunner rather than the bulk of the input signal, appears to move through
the barrier faster than light.

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


title: Mathematical ultrashort-pulse laser physics

abstract:
  The analytical and numerical approaches to the analysis of the
ultrashort-pulse solid-state lasers are presented. The unique self-consistent
method of the laser dynamics analysis is based on the symbolical, numerical,
programming, and graphical capacities of Maple 6. The algorithmization of the
basic conceptions as well as sophisticated research methods is of interest to
both students and experts in the laser physics and the nonlinear dynamics


title: Sonoluminescence: Nature's Smallest BlackBody

abstract:
  The Spectrum of the light emitted by a sonoluminescing bubble is extremely
well fit by the spectrum of a blackbody. Furthermore the radius of emission can
be smaller than the wavelength of the light. Consequences, for theories of
sonoluminescence are discussed.


title:
Transport control by coherent zonal flows in the core/edge transitional
  regime

abstract:
  3D Braginskii turbulence simulations show that the energy flux in the
core/edge transition region of a tokamak is strongly modulated - locally and on
average - by radially propagating, nearly coherent sinusoidal or solitary zonal
flows. The flows are geodesic acoustic modes (GAM), which are primarily driven
by the Stringer-Winsor term. The flow amplitude together with the average
anomalous transport sensitively depend on the GAM frequency and on the magnetic
curvature acting on the flows, which could be influenced in a real tokamak,
e.g., by shaping the plasma cross section. The local modulation of the
turbulence by the flows and the excitation of the flows are due to wave-kinetic
effects, which have been studied for the first time in a turbulence simulation.


title: Efficiency of different numerical methods for solving Redfield equations

abstract:
  The numerical efficiency of different schemes for solving the Liouville-von
Neumann equation within multilevel Redfield theory has been studied. Among the
tested algorithms are the well-known Runge-Kutta scheme in two different
implementations as well as methods especially developed for time propagation:
the Short Iterative Arnoldi, Chebyshev and Newtonian propagators. In addition,
an implementation of a symplectic integrator has been studied. For a simple
example of a two-center electron transfer system we discuss some aspects of the
efficiency of these methods to integrate the equations of motion. Overall for
time-independent potentials the Newtonian method is recommended. For
time-dependent potentials implementations of the Runge-Kutta algorithm are very
efficient.


title: Convergence improvement for coupled cluster calculations

abstract:
  Convergence problems in coupled-cluster iterations are discussed, and a new
iteration scheme is proposed. Whereas the Jacobi method inverts only the
diagonal part of the large matrix of equation coefficients, we invert a matrix
which also includes a relatively small number of off-diagonal coefficients,
selected according to the excitation amplitudes undergoing the largest change
in the coupled cluster iteration. A test case shows that the new IPM (inversion
of partial matrix) method gives much better convergence than the
straightforward Jacobi-type scheme or such well-known convergence aids as the
reduced linear equations or direct inversion in iterative subspace methods.


title: Shafranov's virial theorem and magnetic plasma confinement

abstract:
  Shafranov's virial theorem implies that nontrivial magnetohydrodynamical
equilibrium configurations must be supported by externally supplied currents.
Here we extend the virial theorem to field theory, where it relates to
Derrick's scaling argument on soliton stability. We then employ virial
arguments to investigate a realistic field theory model of a two-component
plasma, and conclude that stable localized solitons can exist in the bulk of a
finite density plasma. These solitons entail a nontrivial electric field which
implies that purely magnetohydrodynamical arguments are insufficient for
describing stable, nontrivial structures within the bulk of a plasma.


title: Two exact derivations of the mass/energy relationship, E=mc^2

abstract:
  The E=mc^2 relationship is not unique to special relativity. Einstein
published one exact derivation from special relativity and two approximate
derivations that used general extensions to Newtonian mechanics, and an exact
derivation is also possible if we use a "first-order" Doppler equation instead
of special relativity's "relativistic Doppler" formula. We present two sample
derivations based on different non-transverse Doppler relationships, and
briefly look at the two diverging systems of physics that result.