July 1998 arXiv papers — page 10

Edgardo T. Garcia Alvarez, Fabian H. Gaioli

A many particle Hamiltonian, where the interaction term conserves the number of particles, is considered. A master equation for the populations of the different levels is derived in an exact way. It results in a local equation with time-dependent coefficients, which can be identified with the transition probabilities in the golden rule approximation. A reint

Ron Rubin, Nathan Salwen

We present here a canonical quantization for the baker's map. The method we use is quite different from that used in Balazs and Voros (ref. \QCITE{cite}{}{BV}) and Saraceno (ref. \QCITE{cite}{}{S}). We first construct a natural ``baker covering map'' on the plane $\QTO{mathbb}{\mathbb{R}}^{2}$. We then use as the quantum algebra of observables th

Anna Okopińska

The application of the optimized expansion for the quantum-mechanical propagation in the anharmonic potential $λx^4$ is discussed for real and imaginary time. The first order results in the imaginary time formalism provide approximations to the free energy and particle density which agree well with the exact results in the whole range of temperatures.

J. Oppenheim, B. Reznik, W. G. Unruh

Although one can show formally that a time-of-arrival operator cannot exist, one can modify the low momentum behaviour of the operator slightly so that it is self-adjoint. We show that such a modification results in the difficulty that the eigenstates are drastically altered. In an eigenstate of the modified time-of-arrival operator, the particle, at the pre

Giulio Ruffini, Lidia Cucurull, Alex Flores, Antonio Rius

We develop the formalism for a PIM-based functional for stochastic tomography with a Kalman filter, in which the inversion problem associated with four-dimensional ionospheric stochastic tomography is regularized. For consistency, GPS data is used to select dynamically the best PIM parameters, in a 3DVAR fashion. We demonstrate the ingestion of GPS (IGS and

A. Delfino, M. Chiapparini, W. A. Colchete

By scaling the mesonic masses in the Walecka model, to the inverse of the hadronic effective mass in medium, we generate the Zimanyi-Moszkowski (ZM) models added to a surface term. For infinite nuclear matter, the surface term vanishes and this new model becomes equivalent to the usual ZM model. For finite nuclei calculations, the surface contribution change

E. J. V. de Passos, A. F. R. de Toledo Piza, F. Krmpotić

The dynamical effects of ground state correlations for excitation energies and transition strengths near the superfluid phase transition are studied in the soluble two level pairing model, in the context of the particle-particle self consistent Random Phase Approximation (SCRPA). Exact results are well reproduced across the transition region, beyond the coll

K. Morawetz, H. S. Köhler

The formation of correlations due to collisions in an interacting nucleonic system is investigated shortly after a disturbance. Results from one-time kinetic equations are compared with the Kadanoff and Baym two-time equation with collisions included in second order Born approximation. A reasonable agreement is found for a proposed approximation of the memor

R. S. Mackintosh, S. G. Cooper, V. I. Kukulin

We present the first successful potential model description of Li-6 -- He-4 scattering. The differential cross-sections for three energies and the vector analyzing powers for two energies were fitted by a single potential with energy dependent imaginary components. An essential ingredient is a set of Majorana terms in each component. The potential was determ

Partha Guha

In this paper we study generalized classes of volume preserving multidimensional integrable systems via Nambu-Poisson mechanics. These integrable systems belong to the same class of dispersionless KP type equation. Hence they bear a close resemblance to the self dual Einstein equation. Recently Takasaki-Takebe provided the twistor construction of dispersionl

Nik Weaver

Basic aspects of differential geometry can be extended to various non-classical settings: Lipschitz manifolds, rectifiable sets, sub-Riemannian manifolds, Banach manifolds, Weiner space, etc. Although the constructions differ, in each of these cases one can define a module of measurable 1-forms and a first-order exterior derivative. We give a general constru

Shuzhou Wang

We determine the quantum automorphism groups of finite spaces and find they are all compact quantum groups in the sense of Woronowicz. This solves a problem of Connes for finite spaces.

Don A. Jones, Steve Shkoller

We prove that under certain stability and smoothing properties of the semi-groups generated by the partial differential equations that we consider, manifolds left invariant by these flows persist under $C^1$ perturbation. In particular, we extend well known finite-dimensional results to the setting of an infinite-dimensional Hilbert manifold with a semi-grou

Edgardo T. Garcia Alvarez, Fabian H. Gaioli

The genesis of Feynman's original approach to QED is reviewed. The main ideas of his original presentation at the Pocono Conference are discussed and compared with the ones involved in his action-at-distance formulation of classical electrodynamics. The role of the de Sitter group in Feynman's visualization of space-time processes is pointed out.

Fabian H. Gaioli, Edgardo T. Garcia Alvarez

A great effort has been devoted to formulate a classical relativistic theory of spin compatible with quantum relativistic wave equations. The main difficulty in order to connect classical and quantum theories rests in finding a parameter which plays the role of proper time at a purely quantum level. We present a partial review of several proposals of classic

Edgardo T. Garcia Alvarez, Fabian H. Gaioli

The hyperplane and proper time formalisms are discussed mainly for the spin-half particles in the quantum case. A connection between these covariant Hamiltonian formalisms is established. It is showed that choosing the space-like hyperplanes instantaneously orthogonal to the direction of motion of the particle the proper time formalism is retrieved on the ma

V. I. Tkach, J. Socorro, J. J. Rosales, J. A. Nieto

In this work we present a new hidden symmetry in gravity for the scale factor in the FRW model, for $k=0$. This exact symmetry vanishes the cosmological constant. We interpret this hidden symmetry as a dual symmetry in the sense that appears in the string theory.

Giampiero Esposito

A review is presented of some recent progress in spectral geometry on manifolds with boundary: local boundary-value problems where the boundary operator includes the effect of tangential derivatives; application of conformal variations and other functorial methods to the evaluation of heat-kernel coefficients; conditions for strong ellipticity of the boundar

Dirk Kreimer

We summarize recent results connecting multiloop Feynman diagram calculations to different parts of mathematics, with special attention given to the Hopf algebra structure of renormalization.

R. Balbinot, A. Fabbri

Recently proposed 2D anomaly induced effective actions for the matter-gravity system are critically reviewed. Their failure to correctly reproduce Hawking's black hole radiation or the stability of Minkowski space-time led us to a modification of the relevant ``quantum'' matter stress energy tensor that allows physically meaningful results to be

W. Kummer, G. Tieber

It is well-known that all 2d models of gravity---including theories with nonvanishing torsion and dilaton theories---can be solved exactly, if matter interactions are absent. An absolutely (in space and time) conserved quantity determines the global classification of all (classical) solutions. For the special case of spherically reduced Einstein gravity it c

M. Bordag, K. Scharnhorst

The leading radiative correction to the Casimir energy for two parallel penetrable mirrors is calculated within QED perturbation theory. It is found to be of the order $α$ like the known radiative correction for ideally reflecting mirrors from which it differs only by a monotonic, powerlike function of the frequency at which the mirrors become transparent. T

Defu Hou, Enke Wang, Ulrich Heinz

We study $n$-point functions at finite temperature in the closed time path formalism. With the help of two basic column vectors and their dual partners we derive a compact decomposition of the time-ordered $n$-point functions with $2^n$ components in terms of $2^{n-1} -1$ independent retarded/advanced $n$-point functions. This representation greatly simplifi

T. Blazek

Study of the MSSM in large tan$β$ regime has to include correlations between the constraints presented by the low energy values of the b quark mass and $BR(b\to sγ)$. Both quantities receive SUSY contributions enhanced by tan$β$ and have a major impact on the MSSM analysis. Here we summarize the results of such a study constrained by minimal SO(10) unificati

Masayasu Harada, Akihiro Shibata

We study the chiral phase transition of QCD at finite temperature and density by numerically solving Schwinger-Dyson equation for the quark propagator with the improved ladder approximation in the Landau gauge. Using the solution we calculate a pion decay constant from a generalized version of Pagels-Stokar formula. Chiral phase transition point is determine

Jerrold Franklin

The importance of exchange currents, and of conserving isotopic spin at both the quark and baryon levels in application of the chiral quark model to any calculation of baryon magnetic moments is emphasized.

I. Bojak, M. Stratmann

We present all relevant details of our calculation of the complete next-to-leading order (O(alpha_s^2 alpha)) QCD corrections to heavy flavor photoproduction with longitudinally polarized point-like photons and hadrons. In particular we provide analytical results for the virtual plus soft gluon cross section. We carefully address the relevance of remaining t

S. S. Agaev

Single pseudoscalar and vector mesons hard semi-inclusive photoproduction $γh \to MX" via higher twist (HT) mechanism is calculated using the QCD running coupling constant method. The structure of infrared renormalon singularities of the HT subprocess cross section and the Borel sum for it are found. The problem of normalization of HT process cross secti

R. M. Godbole

After giving a very brief introduction to the resolved photon processes, I will summarise the latest experimental information from HERA, on resolved photon contribution to large pt jet production as well as to direct photon production. I will point out the interesting role that resolved photon processes can play in increasing our understanding of the dynamic

Sachiko Takeuchi

The symmetric and antisymmetric spin-orbit forces (SLS and ALS) in the YN interaction are investigated for relative P-wave systems by a valence quark model with the instanton-induced interaction (III). The size of the adiabatic potential at the zero range is shown for each of the YN channels. The nonlocal RGM potential of the LS and ALS forces are also shown

M. Hasenbusch

We propose various improvements of finite step-size updating for full QCD on the lattice that might turn finite step-size updating into a viable alternative to the hybrid Monte Carlo algorithm. These improvements are noise reduction of the noisy estimator of the fermion determinant, unbiased inclusion of the hopping parameter expansion and a multi-level Metr

D0 Collaboration, B. Abbott

We have made a precise measurement of the central inclusive jet cross section at sqrt(s) = 1.8 TeV. The measurement is based on an integrated luminosity of 92 pb-1 collected at the Fermilab Tevatron pbar-p Collider with the D-Zero detector. The cross section, reported as a function of jet transverse energy (ET >= 60 GeV) in the pseudorapidity interval |eta|

D. J. Miller

The LEP experiments are making real progress in understanding the structure of the photon, though the results do not yet give such clear demonstrations of QCD in action as the proton structure has done. Other new results are reported, including QED related effects and $γγ\to Resonances$, from LEP and from CLEO II.

Luciano Rezzolla, Andrew M. Abrahams, Richard A. Matzner, Mark E. Rupright

We present results from a new technique which allows extraction of gravitational radiation information from a generic three-dimensional numerical relativity code and provides stable outer boundary conditions. In our approach we match the solution of a Cauchy evolution of the nonlinear Einstein field equations to a set of one-dimensional linear equations obta

Masaru Shibata, Misao Sasaki

We investigate the innermost stable circular orbit (ISCO) of a test particle moving on the equatorial plane around rotating relativistic stars such as neutron stars. First, we derive approximate analytic formulas for the angular velocity and circumferential radius at the ISCO making use of an approximate relativistic solution which is characterized by arbitr

Bernard Jancewicz

We present pictorial means of distinguishing contravariant vectors (or simply vectors) from covariant vectors (or linear forms). When one depicts vector as the directed segment, then the pictorial image of a linear form is a family of equidistant parallel planes with an arrow joining the neighbouring planes and showing the direction of increase of the form.

E. Marinari

We study numerically a disordered model that interpolates among the Sherrington-Kirkpatrick mean field model and the three dimensional Edwards-Anderson spin glass. We find that averages over the disorder of powers of the overlap and of the full $P(q)$ are smooth, and do not show any discontinuity. Different lattice sizes are used to provide evidence for a sm

s. Bogdanovich, D. Simonian, S. V. Kravchenko, M. P. Sarachik

Using uniaxial stress to tune the critical density near that of the sample, we have studied in detail the low-temperature conductivity of p-type Si:B in the insulating phase very near the metal-insulator transition. For all values of temperature and stress, the conductivity collapses onto a single universal scaling curve. For large values of the argument, th

C. K. Law, H. Pu, N. P. Bigelow

We examine the internal structure of the ground states of a trapped Bose-Einstein condensate in which atoms have three internal hyperfine spins. We determine a set of collective spin states which minimize the interaction energy between condensate atoms. We also examine the internal dynamics of an initially spin polarized condensate. The time scale of spin-mi

C. Rascon, A. O. Parry

We consider phase coexistence and criticality in a thin-film Ising magnet with opposing surface fields and non-planar (corrugated) walls. We show that the loss of translational invariance has a strong and unexpected non-linear influence on the interface structure and phase diagram. We identify 4 non-thermodynamic singularities where there is a qualitative ch

M. Latkovic, A. Bjelis

We study the Landau model for uniaxial incommensurate-commensurate systems of the I class by keeping Umklapp terms of third and fourth order in the expansion of the free energy. It applies to systems in which the soft mode minimum lies between the corresponding commensurate wave numbers. The minimization of the Landau functional leads to the sine-Gordon equa

Peter Horsch, Janez Jaklic, Frank Mack

Recent optical conductivity $σ(ω)$ experiments have revealed an anomalous spectral distribution in the ferromagnetic phase of the perovskite system $La_{1-x}Sr_xMnO_3$. Using finite temperature diagonalization techniques we investigate $σ(ω)$ for a model that contains only the $e_g$-orbital degrees of freedom. Due to strong correlations the orbital model app

Ya. M. Blanter, M. Buttiker

We investigate the transition from sub-Poissonian to super-Poissonian values of the zero-temperature shot noise power of a resonant double barrier of macroscopic cross-section. This transition occurs for driving voltages which are sufficiently strong to bring the system near an instability threshold. It is shown that interactions in combination with the ener

G. Lang, E. Paladino, U. Weiss

We study the dynamical equilibrium correlation function of the polaron-dressed tunneling operator in the dissipative two-state system. Unlike the position operator, this coherence operator acts in the full system-plus-reservoir space. We calculate the relevant modified influence functional and present the exact formal expression for the coherence correlation

T. Antal, M. Droz, J. Magnin, Z. Racz

Theoretical models of the Liesegang phenomena are studied and simple expressions for the spacing coefficients characterizing the patterns are derived. The emphasis is on displaying the explicit dependences on the concentrations of the inner- and the outer-electrolytes. Competing theories (ion-product supersaturation, nucleation and droplet growth, induced so

Zheng Weihong, J. Oitmaa, C. J. Hamer

We study antiferromagnetic, $S=1/2$ Heisenberg models with nearest and second neighbor interactions on the one-fifth depleted square lattice which describes the spin degrees of freedom in the spin-gap system CaV$_4$O$_9$. The meta-plaquette expansion for the triplet excitation spectrum is extended to fifth order, and the results are compared with experimenta

Klaus Morawetz, Václav Špička, Pavel Lipavský

The formation of binary correlations in plasma is studied from the quantum kinetic equation. It is shown that this formation is much faster than dissipation due to collisions, in hot (dense) plasma the correlations form on the timescale of inverse plasma frequency (Fermi energy). This hierarchy of characteristic times is used to derive analytical formulae fo

Wojciech Skut, Thorsten Brants, Brigitte Krenn, Hans Uszkoreit

In this paper, we report on the development of an annotation scheme and annotation tools for unrestricted German text. Our representation format is based on argument structure, but also permits the extraction of other kinds of representations. We discuss several methodological issues and the analysis of some phenomena. Additional focus is on the tools develo

Wojciech Skut, Thorsten Brants

We describe a stochastic approach to partial parsing, i.e., the recognition of syntactic structures of limited depth. The technique utilises Markov Models, but goes beyond usual bracketing approaches, since it is capable of recognising not only the boundaries, but also the internal structure and syntactic category of simple as well as complex NP's, PP&#3

Wojciech Skut, Thorsten Brants

This paper describes a partial parser that assigns syntactic structures to sequences of part-of-speech tags. The program uses the maximum entropy parameter estimation method, which allows a flexible combination of different knowledge sources: the hierarchical structure, parts of speech and phrasal categories. In effect, the parser goes beyond simple bracketi

John Larcheveque

A derivation step in a Graph Interpolation Grammar has the effect of scanning an input token. This feature, which aims at emulating the incrementality of the natural parser, restricts the formal power of GIGs. This contrasts with the fact that the derivation mechanism involves a context-sensitive device similar to tree adjunction in TAGs. The combined effect

Hang Li, Naoki Abe

We address the problem of clustering words (or constructing a thesaurus) based on co-occurrence data, and using the acquired word classes to improve the accuracy of syntactic disambiguation. We view this problem as that of estimating a joint probability distribution specifying the joint probabilities of word pairs, such as noun verb pairs. We propose an effi

N. Berglund, H. Kunz

This article deals with dynamical systems depending on a slowly varying parameter. We present several physical examples illustrating memory effects, such as metastability and hysteresis, which frequently appear in these systems. A mathematical theory is outlined, which allows to show existence of hysteresis cycles, and determine related scaling laws.

Lam Hui, Albert Stebbins, Scott Burles

In this Letter we explore a version of the test of cosmological geometry proposed by Alcock and Paczynski (1979), using observations of the Lyman-alpha forest in the spectra of close quasar pairs. By comparing the correlations in absorption in one quasar spectrum with correlations between the spectra of neighboring quasars one can determine the relation of t

Vahe' Petrosian

We describe the classical cosmological tests, such as the Log$N$-Log$S$, redshift-magnitude and angular diameter tests, and propose some new tests of the evolution of galaxies and the universe. Most analyses of these tests treat the problem in terms of a luminosity function and its evolution which can lead to incorrect conclusions when dealing with high reds

R. C. Kennicutt

As a byproduct of its search for the first star forming galaxies, NGST will obtain high-quality spectra for thousands of galaxies in the redshift range z = 0 - 6 and beyond. Most of the galaxies will possess strong emission-line spectra, and these spectra will provide a wealth of information on their star formation rates, reddening, metal abundances, interna

Robert C. Kennicutt,

Observations of star formation rates (SFRs) in galaxies provide vital clues to the physical nature of the Hubble sequence, and are key probes of the evolutionary properties of galaxies. The focus of this review is on the broad patterns in the star formation properties of galaxies along the Hubble sequence, and their implications for understanding galaxy evol

A. G. Agnese, R. Festa

The Old Quantum Mechanics actions discretization rules for periodic motions on the atomic scale (Bohr-Sommerfeld) have been suitably modified in order to account the gravitational field instead of the electrostatic one. The new rules are used to calculate a few mechanical quantities pertinent to the periodic motions of celestial bodies. Several values have b

A. M. Newsam, J. F. L. Simmons, M. A. Hendry, I. J. Coleman

It has already been shown that microlensing can give rise to a non-zero variable polarisation signal. Here we use realistic simulations to demonstrate the additional information that can be gained from polarimetric observations of lensing events.

M. Bruggen

The general relativistic effects on spin-flavor oscillations above the core of type II supernovae are investigated. The evolution equation is derived and the relative magnitudes of the terms in the Hamiltonian, which arise from the weak, electromagnetic and gravitational interaction, are compared. The effects on the resonance position and the adiabaticity ar

Randal C. Telfer, Gerard A. Kriss, Wei Zheng, Arthur F. Davidsen

We have analyzed the broad absorption line system of the bright (V=16.5) high-redshift (z=2.361) QSO SBS1542+541 using UV spectra from the HST FOS along with optical data from the MMT and the Steward Observatory 2.3m telescope. These spectra give continuous wavelength coverage from 1200 to 8000 Angstroms, corresponding to 340 to 2480 Angstroms in the QSO res

V. K. Dubrovich, A. A. Lipovka

New class of low- ionization BAL quasars (Becker et al. 1997), represented by QSO 1556+3517, 0840+3633 and 0059-2735, is considered. Their optical spectra are completely dominated by absorption features, whereas emission lines are weak or absent. Possibility to explain these exclusive features of their spectra by existence of molecular shells, responsible fo

D. Burgarella, R. Bouwens, T. Broadhurst, V. Buat

This paper presents the results of simulated NGST observations. The goal of this work is to study the detectability of very high redshift galaxies and to try to characterize Wide Deep-Field observations. The main points made in this paper are 1) high-z galaxies observable by NGST would be similar to local starburst galaxies 2) even if they exist, large spira

Jens C. Astor, Christoph Adami

We present a model of decentralized growth for Artificial Neural Networks (ANNs) inspired by the development and the physiology of real nervous systems. In this model, each individual artificial neuron is an autonomous unit whose behavior is determined only by the genetic information it harbors and local concentrations of substrates modeled by a simple artif

Howard Georgi, Sheldon L. Glashow

We discuss a class of models in which CP is violated softly in a heavy sector adjoined to the standard model. Heavy-sector loops produce the observed CP violation in kaon physics, yielding a tiny and probably undetectable value for $ε^\prime$. All other CP-violating parameters in the effective low-energy standard model, including the area of the unitarity tr

Edward F. Brown, Lars Bildsten, Robert E. Rutledge

Nuclear reactions occurring deep in the crust of a transiently accreting neutron star efficiently maintain the core at a temperature >5e7 K. When accretion halts, the envelope relaxes to a thermal equilibrium set by the flux from the hot core, as if the neutron star were newly born. For the time-averaged accretion rates typical of low-mass X-ray transients,

Silas R. Beane

Sigma models in which the integer coefficient of the Wess-Zumino term vanishes are easy to construct. This is the case if all flavor symmetries are vectorlike. We show that there is a subset of SU(N)XSU(N) vectorlike sigma models in which the Wess-Zumino term vanishes for reasons of symmetry as well. However, there is no chiral sigma model in which the Wess-

Gianguido Dall'Agata, Davide Fabbri, Christophe Fraser, Pietro Fre'

Our goal is to study the supermembrane on an $AdS_4 \times \cal M_7$ background, where $\cal M_7$ is a 7--dimensional Einstein manifold with $N$ Killing spinors. This is a direct way to derive the $Osp(N|4)$ singleton field theory with all the additional properties inherited from the geometry of the internal manifold. As a first example we consider the maxim

Dumitru Baleanu, Sorin Codoban

In this paper we study the symmetries of the dual Taub-NUT metrics. Generic and non-generic symmetries of dual Taub-NUT metrics are investigated. The existence of the Runge-Lenz type symmetry is analyzed for dual Taub-NUT metrics. We find that in some cases the symmetries of the dual metrics are the same with the symmetries of Taub-NUT metric.

Thibault Damour, Bernard Pichon

Big Bang Nucleosynthesis (BBN) is studied within the framework of a two-parameter family of tensor-scalar theories of gravitation, with nonlinear scalar-matter coupling function a(phi). We run a BBN code modified by tensor-scalar gravity, and impose that the theoretically predicted BBN yields of Deuterium, Helium and Lithium lie within some conservative obse

D0 Collaboration, B. Abbott

Using the DZero detector at the 1.8 TeV pbarp Fermilab Tevatron collider, we have measured the inclusive dijet mass spectrum in the central pseudorapidity region |eta_jet| < 1.0 for dijet masses greater than 200 Gev/c^2. We have also measured the ratio of spectra sigma(|eta_jet| < 0.5)/sigma(0.5 < |eta_jet| < 1.0). The order alpha_s^3 QCD predictions are in

Friedemann Brandt, Joaquim Gomis, David Mateos, Joan Simón

We show that each rigid symmetry of a D-string action is contained in a family of infinitely many symmetries. In particular, kappa-invariant D-string actions have infinitely many supersymmetries. The result is not restricted to standard D-string actions, but holds for any two-dimensional action depending on an abelian world-sheet gauge field only via the fie

A. M. M. Pruisken, B. Skoric, M. A. Baranov

The concepts of an instanton vacuum and F-invariance are used to derive a complete effective theory of massless edge excitations in the quantum Hall effect. We establish, for the first time, the fundamental relation between the instanton vacuum approach and the theory of chiral edge bosons. Two longstanding problems of smooth disorder and Coulomb interaction

G. Johansson, E. N. Bratus, V. S. Shumeiko, G. Wendin

We investigate the properties of subharmonic gap structure (SGS) in superconducting quantum contacts with normal-electron resonances. We find two distinct new features of the SGS in resonant junctions which distinguish them from non-resonant point contacts: (i) The odd-order structures on the current-voltage characteristics of resonant junctions are strongly

H. Bechmann-Pasquinucci, N. Gisin

All incoherent as well as 2- and 3-qubit coherent eavesdropping strategies on the 6 state protocol of quantum cryptography are classified. For a disturbance of 1/6, the optimal incoherent eavesdropping strategy reduces to the universal quantum cloning machine. Coherent eavesdropping cannot increase Eve&#39;s Shannon information, neither on the entire string

Marco Andreatta, Gianluca Occhetta

Let E be an ample vector bundle of rank r on a complex projective manifold X such that there exists a section $s \in Γ(\cal E)$ whose zero locus Z = (s = 0) is a smooth submanifold of the expected dimension dim X - r: = n -r. Assume that Z is not minimal; we investigate the hypothesis under which the extremal contractions of Z can be lifted to X. Finally we

S. Mizoguchi, N. Ohta

It has been known that D=5 simple supergravity resembles D=11 supergravity in many respects. We present their further resemblances in (1) the duality groups upon dimensional reduction, and (2) the worldsheet structure of the solitonic string of the D=5 supergravity. We show that the D=3, G_{2(+2)}/SO(4) (bosonic) nonlinear sigma model is obtained by using Fr

Tomohiro Harada

The final fate of the spherically symmetric collapse of a perfect fluid which follows the $γ$-law equation of state and adiabatic condition is investigated. Full general relativistic hydrodynamics is solved numerically using a retarded time coordinate, the so-called observer time coordinate. Thanks to this coordinate, the causal structure of the resultant sp

Jongsoo Yoon, C. C. Li, D. Shahar, D. C. Tsui

We report the transport properties of a low disorder two-dimensional hole system (2DHS) in the GaAs/AlGaAs heterostructure, which has an unprecedentedly high peak mobility of $7\times 10^5cm^2/Vs$, with hole density of $4.8\times 10^9 cm^{-2}<p<3.72\times 10^{10}cm^{-2}$ in the temperature range of $50mK<T<1.3K$. From their T, p, and electric field dependenc

H. B. Nersisyan

The analytical and numerical investigations of the energy loss rate of the test particle in a magnetized electron plasma are developed on the basis of the Vlasov-Poisson equations, and the main results are presented. The Larmor rotation of a test particle in a magnetic field is taken into account. The analysis is based on the assumption that the energy varia

Lennart B. Karlsson, Ingemar Ragnarsson, Sven Aberg

A detailed theoretical investigation of polarization effects in superdeformed nuclei is performed. In the pure harmonic oscillator potential it is shown that when one particle (or hole) with the mass single-particle quadrupole moment q_{nu} is added to a superdeformed core, the change of the electric quadrupole moment can be parameterized as q_{eff}=e(bq_{nu

L. A. Ferreira, J. F. Gomes, A. V. Razumov, M. V. Saveliev

We associate to an arbitrary $\mathbb Z$-gradation of the Lie algebra of a Lie group a system of Riccati-type first order differential equations. The particular cases under consideration are the ordinary Riccati and the matrix Riccati equations. The multidimensional extension of these equations is given. The generalisation of the associated Redheffer--Reid d

Harri Ojanen

Numerical optimization is used to construct new orthonormal compactly supported wavelets with Sobolev regularity exponent as high as possible among those mother wavelets with a fixed support length and a fixed number of vanishing moments. The increased regularity is obtained by optimizing the locations of the roots the scaling filter has on the interval (pi/

Maks A. Akivis, Vladislav V. Goldberg

We consider real isotropic geodesics on manifolds endowed with a pseudoconformal structure and their applications to the theory of lightlike hypersurfaces on such manifolds, the geometry of four-dimensional conformal structures of Lorentzian type, and a classification of the Einstein spaces.

Jerrold E. Marsden, Steve Shkoller

This paper concerns the development and application of the multisymplectic Lagrangian and Hamiltonian formalism for nonlinear partial differential equations. In this theory, solutions of a PDE are sections of a fiber bundle $Y$ over a base manifold $X$ of dimension $n$$+$1, typically taken to be spacetime. Given a connection on $Y$, a covariant Hamiltonian d

Harri Ojanen

Weighted norm estimates and representation formulas are proved for non-homogeneous singular integrals with no regularity condition on the kernel and only an L log L integrability condition. The representation formulas involve averages over a star-shaped set naturally associated with the kernel. The proof of the norm estimates is based on the representation f

B. G. Konopelchenko, U. Pinkall

Generalizations of the classical affine Lelieuvre formula to surfaces in projective three-dimensional space and to hypersurfaces in multi- dimensional projective space are given. A discrete version of the projective Lelieuvre formula is presented too.

Miles Reid

The text of an oration to present Prof Andrew Wiles for the degree of Doctor of Science, Honoris Causa, at the University of Warwick

Amer Iqbal

In a recent paper DeWolfe et al. have shown how to use the self-intersection number of junctions to constrain the BPS spectrum of N=2, D=4 theories with ADE flavor symmetry arising on a single D3-brane probe in a 7-brane background. Motivated by the existence of more general N=2, D=4 theories arising on the worldvolume of multiple D3-brane probes we show how

James A. Feigenbaum

Previous work involving Born-regulated gravity theories in two dimensions is extended to four dimensions. The action we consider has two dimensionful parameters. Black hole solutions are studied for typical values of these parameters. For masses above a critical value determined in terms of these parameters, the event horizon persists. For masses below this

Diego A. R. Dalvit

In this Thesis we study quantum corrections to the classical dynamics for mean values in field theory. To that end we make use of the formalism of the closed time path effective action to get real and causal equations of motion. We introduce a coarse grained effective action, which is useful in the study of phase transitions in field theory. We derive an exa

Hatem Widyan, A. Mukherjee, N. Panchapakesan, R. P. Saxena

Scalar field theory with an asymmetric potential is studied at zero temperature and high-temperature for phi^4 theory with both phi and phi^3 symmetry breaking. The equations of motion are solved numerically to obtain O(4) symmetric and O(3) cylindrical symmetric bounce solutions. These solutions control the rates for tunneling from the false vacuum to the t

Mohammad R. Ahmady, Emi Kou

We calculate the branching ratio and direct CP asymmetry in nonleptonic two body B decays B^+- ->π^+- η&#39;. It is shown that the tree diagram and gluon fusion mechanism via penguin diagram have comparable contributions to these decays which, as a result, could provide an interesting venue for investigating CP violation. Our estimate shows that the direct C

Alan M. Nathan

We discuss the physics motivation for a program of Real Compton Scattering on the proton in the regime where both the incident energy and the transverse momentum transfer are large. It is shown that such a program can test which of the various hard scattering mechanisms is dominant and can allow a measurement of a new generalized form factor that is sensitiv

B. G. Zakharov

We study the quark energy loss in an expanding quark-gluon plasma. The expanding plasma produced in high energy AA-collision is described by Bjorken&#39;s model. The dependence of the energy loss on the infrared cutoff for the radiated gluons, on the quark mass, and on the initial conditions of QCD plasma is investigated.

E. Matsinos

Recent analyses of low-energy pion-nucleon experimental data have provided clear evidence for the violation of the isospin symmetry of the strong interaction. In the present work, it is shown that the single-charge-exchange reaction is the culprit for the effect. Given the present experimental uncertainties, no evidence for isospin breaking was found in the

Philip G. Ratcliffe

SU(3) breaking in hyperon semi-leptonic decays is discussed. The SU(3) parameters $F$ and $D$, relevant to the ``proton-spin puzzle&#39;&#39;, are extracted and a prediction is presented for the decay Xi0 -> Sigma+ e anti-neutrino, currently under study by the KTeV collaboration. The values found are g1/f1 = 1.16+/-0.03+/-0.01 and Gamma = (0.80+/-0.03+/-0.01

B. Tseng

Using the next-to-leading order QCD-corrected effective Hamiltonian, charmless exclusive nonleptonic decays of the $B_s$ meson into $η$ or $η&#39;$ are calculated within the generalized factorization approach. Nonfactorizable contributions, which can be parametrized in terms of the effective number of colors $N_c^{\rm eff}$ for $P P$ and $V P$ decay modes, a

Hsiang-nan Li

We derive the evolution equations of parton distribution functions appropriate in different kinematic regions in a unified and simple way using the resummation technique. They include the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation for large momentum transfer $Q$, the Balitskii-Fadin-Kuraev-Lipatov equation for a small Bjorken variable $x$, and the C

Tao Huang, HongYing Jin, Ailin Zhang

The $0^{++}$ glueball mass is analyzed in the QCD sum rules. We show that in order to determine the $0^{++}$ glueball mass by using the QCD sum rules method, it is necessary to clarify the following three ingredients: (1) to choose the appropriate moment with acceptable parameters which satisfy all of the criteria; (2) to take account into the radiative corr