February 1999 arXiv papers — page 19

David O. Caldwell

There is a puzzling contradiction: direct observations favor a low-mass density universe, but the only model which fits universe structure over more than three orders of magnitude in distance scale has a mix of hot (neutrino) and cold dark matter consistuting a critical density universe. If all present indications for neutrino mass are valid, that hot dark m

Jeffrey E. Mandula

We discuss global gauge fixing on the lattice, specifically to the lattice Landau gauge, with the goal of understanding the question of why the process becomes extremely slow for large lattices. We construct an artificial "gauge-fixing" problem which has the essential features encountered in actuality. In the limit in which the size of the system to

Owe Philipsen, Hartmut Wittig

We compute the static potential in three-dimensional SU(2) Yang Mills Theory with adjoint sources using numerical simulations. By employing a variational approach involving string and gluelump operators, we obtain clear evidence for string breaking in the adjoint potential. The breaking scale r_b is computed and extrapolated to the continuum limit. The resul

Amir H. Abbassi

The Schwarzschild-deSitter metric is the known solution of Einstein field equations with cosmological constant term for vacuum spherically symmetric space around a point mass M. Recently it has been reported that in a $Lamda$-dominant world the Schwarzschild type coordinate systems are disqualified by redshift-magnitude test as a proper frame of reference(gr

Shahar Hod, Tsvi Piran

We study the gravitational collapse of a self-gravitating charged scalar-field. Starting with a regular spacetime, we follow the evolution through the formation of an apparent horizon, a Cauchy horizon and a final central singularity. We find a null, weak, mass-inflation singularity along the Cauchy horizon, which is a precursor of a strong, spacelike singul

Paul Vitanyi

Genetic fitness optimization using small populations or small population updates across generations generally suffers from randomly diverging evolutions. We propose a notion of highly probable fitness optimization through feasible evolutionary computing runs on small size populations. Based on rapidly mixing Markov chains, the approach pertains to most types

Harry Buhrman, Matthew Franklin, Juan A. Garay, Jaap-Henk Hoepman

We introduce a search problem called ``mutual search'' where $k$ \agents, arbitrarily distributed over $n$ sites, are required to locate one another by posing queries of the form ``Anybody at site $i$?''. We ask for the least number of queries that is necessary and sufficient. For the case of two \agents using deterministic protocols we obtai

Eric Lease Morgan

This paper describes the Alex Catalogue of Electronic Texts, the only Internet-accessible collection of digital documents allowing the user to 1) dynamically create customized, typographically readable documents on demand, 2) search the content of one or more documents from the collection simultaneously, 3) create sets of documents from the collection for re

Eric Lease Morgan

The paper describes an extensible model for implementing a user-centered, customizable interface to a library's collection of information resources. This model, called MyLibrary, integrates the principles of librarianship (collection, organization, dissemination, and evaluation) with globally networked computing resources creating a dynamic, customer-dri

A. Mobius, B. Freisleben, P. Merz, M. Schreiber

A procedure is presented which considerably improves the performance of local search based heuristic algorithms for combinatorial optimization problems. It increases the average `gain' of the individual local searches by merging pairs of solutions: certain parts of either solution are transcribed by the related parts of the respective other solution, cor

Bernard Derrida, Susanna C. Manrubia, Damian H. Zanette

We analyse the statistical properties of genealogical trees in a neutral model of a closed population with sexual reproduction and non-overlapping generations. By reconstructing the genealogy of an individual from the population evolution, we measure the distribution of ancestors appearing more than once in a given tree. After a transient time, the probabili

J. Röhler, C. Friedrich, T. Granzow, E. Kaldis

The dimpling in the CuO_2 planes of overdoped Y_{1-y}Ca_yBa_2Cu_3 O_{6.96-6.98} (y=0.02-0.2) has been measured by x-ray absorption-fine- structure spectroscopy (Y-K EXAFS). A step-like decrease around 12% Ca indicates a percolation threshold for distorted sites of 5 cells, and thus phase segregation. We conclude the charge carriers added by substitution of Y

Paul Bartlett, Patrick B. Warren

The effect of polydispersity on the freezing transition of hard spheres is examined within a moment description. At low polydispersities a single fluid-to-crystal transition is recovered. With increasing polydispersity we find a density above which the crystal melts back into an amorphous phase. The range of densities over which the crystalline phase is stab

Chi-Yong Lin, A. F. R. de Toledo Piza

Using many-body theory we develop a set of formally exact kinetic equations for inhomogeneous condensate and one-body observables. The method is illutrated for phi^4 field theory in 1+1 dimensions. These equations, when computed with the help of time-dependent projection technique, lead to a systematic mean-field expansion. The lowest and the higher order te

Carsten Honerkamp, Katsunori Wakabayashi, Manfred Sigrist

We compare different scenarios for the low temperature splitting of the zero-energy peak in the local density of states at (110) surfaces of d_{x^2-y^2}-wave superconductors, observed by Covington et al. (Phys.Rev.Lett.79 (1997), 277). Using a tight binding model in the Bogolyubov-de Gennes treatment we find a surface phase transition towards a time-reversal

S. B. Goryachev

Rutenberg [cond-mat/9411016] claimed erroneously that I incorrectly apply only global conservation constraint to systems with local conservation embodied by continuity equation [PRL vol.72, p.1850 (1994)]. I reply that my theory describes the order parameter (OP) evolution of all three types of systems: without conservation law, with global one and with loca

S. C. Gallagher, W. N. Brandt, R. M. Sambruna, S. Mathur

We present the analysis and interpretation of a sample of eight ASCA observations of Broad Absorption Line Quasi-Stellar Objects (BALQSOs). This is the first moderate-sized sample of sensitive BALQSO observations above 2 keV, and the BALQSOs in our sample are among the optically brightest known (B=14.5-18.5). Despite the ability of 2-10 keV X-rays to penetra

A. Dey, J. R. Graham, R. J. Ivison, I. Smail

We present new near-IR and optical spectroscopic observations which confirm the redshift of the z=1.44 extremely red object ERO J164502+4626.4 (object 10 of Hu & Ridgway 1994) and a HST image which reveals a reflected-S-shaped morphology at (rest-frame) near-UV wavelengths. The contrast between the rest-frame far-red (8200-9800A) and near-UV (2900-3900A) mor

K. D. Gordon, M. M. Hanson, G. C. Clayton, G. H. Rieke

We have thoroughly characterized the ultraviolet to near-infrared (0.15 - 2.2 micron) spectral energy distribution (SED) of the central parsec of the M33 nucleus through new infrared photometry and optical/near-infrared spectroscopy, combined with ultraviolet/optical observations from the literature and the HST archive. The SED shows evidence for a significa

F. Halzen

Surrounded by stunning Algarve landscapes not far from where Henry the Navigator organized the voyages that mapped the Earth, particle astrophysicists discussed new initiatives to explore the cosmos. While first generation experiments opened new voyages of the mind with evidence for neutrino mass and a cosmological constant, much of the discussion focussed o

Elihu Boldt

Forty years have passed since the first Explorer orbiting observatory - the 1958 mission used to discover the Van Allen radiation belts outside the atmosphere - ushered in the modern age of space science. Even though in situ observations of outer space are still restricted to measurements made within the solar system, we now have access to a wide range of co

J. Alvarez-Muniz, F. Halzen

Because of the limited size of the satellite-borne instruments, it has not been possible to observe the flux of gamma ray bursts (GRB) beyond GeV energy. We here show that it is possible to detect the GRB radiation of TeV energy and above, by detecting the muon secondaries produced when the gamma rays shower in the Earth's atmosphere. Observation is made

A. C. Edge, R. J. Ivison, Ian Smail, A. W. Blain

We present 850-um observations with the SCUBA submillimetre (sub-mm) camera of the central galaxies in seven concentrated clusters of galaxies at redshifts between 0.19 and 0.41. We detect sub-mm emission from the central galaxies in the rich clusters A1835 and A2390, and present upper limits for the central galaxies in the remaining five clusters. The two g

Eberhard Grün, Harald Krüger, Markus Landgraf

Dust measurements in the outer solar system are reviewed. Only the plasma wave instrument on board Voyagers 1 and 2 recorded impacts in the Edgeworth-Kuiper belt (EKB). Pioneers 10 and 11 measured a constant dust flux of 10-micron-sized particles out to 20 AU. Dust detectors on board Ulysses and Galileo uniquely identified micron-sized interstellar grains pa

D. M. Neumann

We present ROSAT HRI data of the distant and X-ray luminous (L_x(bol)=2.6^ {+0.4}_{-0.2} 10^{45}erg/sec) cluster of galaxies 3C 295. We fit both a one-dimensional and a two-dimensional isothermal beta-model to the data, the latter one taking into account the effects of the point spread function (PSF). For the error analysis of the parameters of the two-dimen

John Magorrian

The deprojection of the surface brightness distribution of an axisymmetric galaxy does not have a unique solution unless the galaxy is viewed precisely edge-on. I present an algorithm that finds the full range of smooth axisymmetric density distributions consistent with a given surface brightness distribution and inclination angle, and use it to investigate

John Magorrian, Scott Tremaine

There is strong evidence for some kind of massive dark object in the centres of many galaxy bulges. The detection of flares from tidally disrupted stars could confirm that these objects are black holes (BHs). Here we present calculations of the stellar disruption rates in detailed dynamical models of real galaxies, taking into account the refilling of the lo

Knut A. G. Olsen

We present results on the analysis of background field stars found in HST WFPC2 observations of six of the old globular clusters of the Large Magellanic Cloud. Treated as contaminants by the globular cluster analysts, we produce V-I,V color-magnitude diagrams of the field stars and use them to explore the LMC's star formation history. The photometry appr

Re'em Sari, Tsvi Piran

We compare the ongoing observations of the remarkable burst GRB990123, the mother of all bursts, with the predictions of the afterglow theory. We show that the observations agree with the recent prediction that a reverse shock propagating into the ejecta would produce a very strong prompt optical flash. This reverse shock has also produced the 8.46GHz radio

E. E. Fenimore, E. Ramirez-Ruiz, Bobing Wu

GRB990123 was a long complex gamma-ray burst with an optical transient that started early within the gamma-ray phase. The peak and power law decay of the early optical emission strongly indicates the presence of a decelerating relativistic shell during that phase. Prior to this burst, it was not known if the shell decelerated during the burst, so an external

Miguel A. de Avillez

Gas that escapes from the Galactic disk, rises into the halo, cools and falls back, constitutes a "Galactic Fountain". Three-Dimensional simulations show that such a fountain model reproduces many of the features that have been observed in the Galaxy and other galaxies such as M31 and M33. Here, these results are reported.

Sergei V. Shabanov, John R. Klauder

We propose a modification of the Faddeev-Popov procedure to construct a path integral representation for the transition amplitude and the partition function for gauge theories whose orbit space has a non-Euclidean geometry. Our approach is based on the Kato-Trotter product formula modified appropriately to incorporate the gauge invariance condition, and ther

Wentao Lu, M. Rose, K. Pance, S. Sridhar

The quantum resonances of classically chaotic n-disk geometries were studied experimentally utilizing thin 2-D microwave geometries. The experiments yield the frequencies and widths of low-lying resonances, which are compared with semiclassical calculations. The longtime or small energy behavior of the wave-vector auto-correlation gives information about the

Debra J. Searles, Denis J. Evans

Green-Kubo and Einstein expressions for the transport coefficients of a fluid in a nonequilibrium steady state can be derived using the Fluctuation Theorem and by assuming the probability distribution of the time-averaged dissipative flux is Gaussian. These expressions are consistent with those obtained using linear response theory and are valid in the linea

C. Murali, P. Arras, I. Wasserman

We establish constraints on the mass and abundance of black holes in the Galactic halo by determining their impact on globular clusters which are conventionally considered to be little evolved. Using detailed Monte Carlo simulations and simple analytic estimates, we conclude that, at Galactocentric radius R~8 kpc, black holes with masses M_bh >~(1-3) x 10^6

M. J. Werner, A. Imamoglu

Dissipation-free photon-photon interaction at the single photon level is studied in the context of cavity electromagnetically induced transparency (EIT). For a single multilevel atom exhibiting EIT in the strong cavity-coupling regime, the anharmonicity of the atom-cavity system has an upper bound determined by single atom-photon coupling strength. Photon bl

E. Solano, R. L. de Matos Filho, N. Zagury

We present a method for the deterministic generation of all the electronic Bell states of two trapped ions. It involves the combination of a purely dispersive with a resonant laser excitation of vibronic transitions of the ions. In contrast to other methods presented up to now, our proposal does not require differential laser addressing of the individual ion

M. Cappi, M. Persic, S. Mariani, L. Bassani

New BeppoSAX observations of the nearby prototypical starburst galaxies NGC 253 and M82 are presented. A companion paper (Cappi et al. 1998;astro-ph/9809325) shows that the hard (2-10 keV) spectrum of both galaxies, extracted from the source central regions, is best described by a thermal emission model with kT ~ 6-9 keV and abundances ~ 0.1-0.3 solar. The s

V. I. Perel, B. I. Shklovskii

Screening of a macroion by multivalent counterions is considered. It is shown that ions form strongly correlated liquid at the macroion surface. Cohesive energy of this liquid leads to strong additional attraction of counterions to the surface. Away from the surface this attraction is taken into account by a new boundary condition for the Poisson-Boltzmann e

P. W. Stephenson

The roughly linear rise of the potential found between adjoint sources in SU(N) in lattice simulations is expected to saturate into a state of two `gluelumps' due to gluonic screening. We examine this in SU(2) in 2+1 dimensions. Crossover between string-like and broken states is clearly seen by the mixing-matrix technique, using different operators to pr

R. A. Burenin, A. A. Vikhlinin, M. R. Gilfanov, O. V. Terekhov

We present a GRANAT/SIGMA observation of the soft gamma-ray afterglow immediately after GRB 920723. The main burst is very bright. After ~6 s, the burst light curve makes a smooth transition into an afterglow where flux decays as t^{-0.7}. The power-law decay lasts for at least 1000 s; beyond this time, the afterglow emission is lost in the background fluctu

V. N. Pervushin, V. I. Smirichinski

The paper is devoted to the formulation of quantum field theory for an early universe in General Relativity considered as the Dirac general constrained system. The main idea is the Hamiltonian reduction of the constrained system in terms of measurable quantities of the observational cosmology: the world proper time, cosmic scale factor, and the density of ma

R. Siddharthan, B. S. Shastry, A. P. Ramirez, A. Hayashi

Pyrochlore magnets are candidates for spin-ice behavior. We present theoretical simulations of relevance for the pyrochlore family R2Ti2O7 (R= rare earth) supported by magnetothermal measurements on selected systems. By considering long ranged dipole-dipole as well as short-ranged superexchange interactions we get three distinct behaviours: (i) an ordered do

E. Alvarez, C. Gomez

String vacua for non critical strings satisfying the requirements of Zig-Zag invariance are constructed. The Liouville mode is shown to play the rôle of scale in the Renormalization Group operation. Differences and similarities with the D-brane near horizon approach to non supersymmetric gauge theories are discussed as well.

A. Fring, C. Korff, B. J. Schulz

We investigate the thermodynamic Bethe ansatz (TBA) equations for a system of particles which dynamically interacts via the scattering matrix of affine Toda field theory and whose statistical interaction is of a general Haldane type. Up to the first leading order, we provide general approximated analytical expressions for the solutions of these equations fro

Norihiro Muramoto, Minoru Takahashi

An exact solution for an XXZ chain with four-body interactions is obtained and its phase diagram is determined. The model can be reduced to two chains coupled by four-body interactions, and it is shown that the ground state of the two-chain model is magnetized in part. Furthermore, a twisted four-body correlation function of the anti-ferromagnetic Heisenberg

E. Prodan

The problem of spontaneous pair creation in static external fields is reconsidered. A weak version of the conjecture proposed by G Nenciu (1980) is seated and proved. The method reduces the proof of the general conjecture to the study of the evolution, associated with a time dependent Hamiltonian, of a vector which is eigenvector of this Hamiltonian at some

Bernhard G. Bodmann, John R. Klauder

A Wiener-regularized path integral is presented as an alternative way to formulate Berezin-Toeplitz quantization on a toroidal phase space. Essential to the result is that this quantization prescription for the torus can be constructed as an induced representation from anti-Wick quantization on its covering space, the plane. When this construction is express

Liu Yu-Xi, Cao Chang-Qi

The effect of the non-linear interaction between the high density Wannier excitons is analysed. We use the Fokker-Planck equation in the positive P presentation and the corresponding stochastic differential equation to study the composite system of a single mode cavity field and exciton under classical field pumping. The small fluctuation approximation is ma

C. Leger, F. Argoul, M. Z. Bazant

Experiments on the diffusion-limited corrosion of porous copper clusters in thin gap cells containing cupric chloride are reported. By carefully comparing corrosion front velocities and concentration profiles obtained by phase-shift interferometry with theoretical predictions, it is demonstrated that this process is well-described by a one-dimensional mean-f

R. Hasson, S. J. Swithenby

This paper extends the work of Clarke [1] on the Bayesian foundations of the biomagnetic inverse problem. It derives expressions for the expectation and variance of the a posteriori source current probability distribution given a prior source current probability distribution, a source space weight function and a data set. The calculation of the variance enab

M. L. Perl

During the past one hundred years three related elementary particles - the electron, the muon, and the tau - were discovered by very different scientific techniques. The author, who received the Wolf Prize and the Nobel Prize for the discovery of the tau, uses this history to discuss certainty and uncertainty in the practice of science. While the emphasis is

Todd Kapitula, Jonathan Rubin

We consider the existence and stability of the hole, or dark soliton, solution to a Ginzburg-Landau perturbation of the defocusing nonlinear Schroedinger equation (NLS), and to the nearly real complex Ginzburg-Landau equation (CGL). By using dynamical systems techniques, it is shown that the dark soliton can persist as either a regular perturbation or a sing

T. Gaitanos, C. Fuchs, H. H. Wolter

An detailed study of the thermodynamical state of nuclear matter in transport calculations of heavy--ion reactions is presented. In particular we determine temperatures from an analysis of the local momentum space distribution on one hand, and from a fit to fragment energy spectra in terms of a blast model with radial flow and temperature on the other. We ap

H. Blum, R. Brockmann

The stability of the nuclear matter system with respect to density fluctuations is examined exploring in detail the pole structure of the electro-nuclear response functions. Making extensive use of the method of dispersion integrals we calculate the full polarization propagator not only for real energies in the spacelike and timelike regime but also in the w

T. Kunihiro

We discuss how the possible changes of hadron properties can be tested, associated with the chiral transition in nuclear medium; the hadrons discussed are the vector mesons,the $σ$ meson and the chiral partner of the nucleon. We emphasize that the proper quantity is the spectral function which describes the nuclear medium having a hadron; the analysis of ele

E. Oset, J. A. Oller, J. R. Pelaez, A. Ramos

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a stand

J. Bryce McLeod, Chie Bing Wang

In this paper we give a mathematical proof of the existence of the time independent and spherically symmetric solution to the 't Hooft-Polyakov model of magnetic monopole by using 2D-shooting method.

J. Brian Conrey, Steven M. Gonek

The authors describe a general approach which, in principal, should produce the correct (conjectural) formula for every even integer moment of the Riemann zeta function. They carry it out for the sixth and eigth powers; in the case of sixth powers this leads to the formula conjectured by Conrey and Ghosh, and in the case of eighth powers is new.

Matt Jones, Martin Scharlemann

It has been shown elsewhere that a strongly irreducible Heegaard splitting surface Q of a compact orientable 3-manifold M can, under reasonable side conditions, intersect a ball or a solid torus in M in only a few possible ways. Here we extend those results to describe how Q can intersect a handlebody in M.

I. P. Goulden, D. M. Jackson

An explicit expression is obtained for the generating series for the number of ramified coverings of the sphere by the torus, with elementary branch points and prescribed ramification type over infinity. This proves a conjecture of Goulden, Jackson and Vainshtein for the explicit number of such coverings.

Martin Scharlemann, Jennifer Schultens

We prove that the tunnel number of the sum of n knots is at least n.

G. Godefroy, N. Kalton, D. Li

We provide an unified approach of results of L. Dor on the complementation of the range, and of D. Alspach on the nearness from isometries, of small into isomorphisms of L1. We introduce the notion of small subspace of L1 and show lifting theorems for operators between quotients of L1 by small subspaces. We construct a subspace of L1 which shows that extensi

Bernard Leclerc

We obtain some simple relations between decomposition numbers of quantized Schur algebras at an n-th root of unity (over a field of characteristic 0). These relations imply that every decomposition number for such an algebra occurs as a decomposition number for some Hecke algebra of type A. We prove similar relations between coefficients of the canonical bas

Bogdan Alexandrov, Gueo Grantcharov, Stefan Ivanov

We consider the Dolbeault operator of $K^{1/2}$ -- the square root of the canonical line bundle which determines the spin structure of a compact Hermitian spin surface (M,g,J). We prove that the Dolbeault cohomology groups of $K^{1/2}$ vanish if the scalar curvature of g is non-negative and non-identically zero. Moreover, we estimate the first eigenvalue of

Rainer H. Kaenders

Given a compact Riemann surface $\bar{X}$ of genus $g$ and a point $q$ on $\bar{X}$, we consider $X:=\bar{X}\setminus\{q\}$ with a basepoint $p\in X$. The extension of mixed Hodge structures, given by the weights -1 and -2, of the mixed Hodge structure on the fundamental group (in the sense of Hain) is studied. We show that it naturally corresponds on the on

Yogish I. Holla

In this paper we use Weil conjectures (Deligne's theorem) to calculate the Betti numbers of the moduli spaces of semi-stable parabolic bundles on a curve. The quasi parabolic analogue of the Siegel formula, together with the method of Harder-Narasimhan filtration gives us a recursive formula for the Poincaré polynomials of the moduli. We solve the recurs

Jean-Francois Burnol

I apply the set-up of Lax-Phillips Scattering Theory to a non-archimedean local field. It is possible to choose the outgoing space and the incoming space to be Fourier transforms of each other. Key elements of the Lax-Phillips theory are seen to make sense and to have the expected interrelations: the scattering matrix S, the projection K to the interacting s

Bernard Leclerc, Jean-Yves Thibon

We show that the Littlewood-Richardson coefficients are values at 1 of certain parabolic Kazhdan-Lusztig polynomials for affine symmetric groups. These q-analogues of Littlewood-Richardson multiplicities coincide with those previously introduced in terms of ribbon tableaux.

Yuri N. Bespalov, Bernhard Drabant

The subject of this article are cross product bialgebras without co-cycles. We establish a theory characterizing cross product bialgebras universally in terms of projections and injections. Especially all known types of biproduct, double cross product and bicross product bialgebras can be described by this theory. Furthermore the theory provides new families

Geoffrey Dixon

The link of the Division Algebras to 10-dimensional spacetime and one leptoquark family is extended to 26-dimensional spacetime and three leptoquark families.

Herbert Neuberger

For two decades it was believed that chiral symmetries cannot be realized in lattice field theory but this has changed now. Highlights of these new developments will be presented with emphasis on the mathematical structure of the so called ``overlap''.

R. Amorim, J. Barcelos-Neto

It has been shown in literature that a possible mechanism of mass generation for gauge fields is through a topological coupling of vector and tensor fields. After integrating over the tensor degrees of freedom, one arrives at an effective massive theory that, although gauge invariant, is nonlocal. Here we quantize this nonlocal resulting theory both by path

Ali Kaya

It is shown that, under certain conditions, the existence of a Killing spinor on a bosonic background of a supergravity theory implies that the Einstein equations are also satisfied. As an application of the theorem, we obtain a new black fivebrane solution of D=11 supergravity, which has $K3\times R$ topology and preserves 1/4'th supersymmetries of the

Michael R. Douglas

This is a write-up of lectures given at the 1998 Spring School at the Abdus Salam ICTP. We give a conceptual introduction to D-geometry, the study of geometry as seen by D-branes in string theory, and to noncommutative geometry as it has appeared in D-brane and Matrix theory physics.

Sergey Prokushkin, Mikhail Vasiliev

This paper is a letter-type version of hep-th/9806236. We discuss properties of non-linear equations of motion which describe higher-spin gauge interactions for massive spin-0 and spin-1/2 matter fields in 2+1 dimensional anti-de Sitter space. The model is shown to have N=2 supersymmetry and to describe higher-spin interactions of d3 N=2 massive hypermultipl

T. G. Steele, V. Elias

The perturbative series used to extract $α_s(M_τ)$ from the $τ$ hadronic width exhibits slow convergence. Asymptotic Pade-approximant and Pade summation techniques provide an estimate of these unknown higher-order effects, leading to values for $α_s(M_τ)$ that are about 10% smaller than current estimates. Such a reduction improves the agreement of $α_s(M_τ)$

E. R. Takano Natti, Chi-Yong Lin, A. F. R. de Toledo Piza, P. L. Natti

We investigate the physics of elementary excitations for the so called relativistic scalar plasma system. Following the standard many-body procedure we have obtained the RPA equations for this model by linearizing the TDHFB equations of motion around equilibrium and shown that these oscillation modes give one-meson and two-fermion state of the theory. The re

K. R. Schubert

Neutrino oscillations with three lepton families are described with a unitary mixing matrix U in analogy to the quark mixing matrix V(CKM). If U contains a nontrivial phase, there will be CP- and T-violating asymmetries at distances large compared to E/D**2, where D**2 is the largest difference of neutrino mass squares. The paper presents explicit expression

Stefano Moretti

The process $e^+e^-\to H t\bar t$ can be used at the Next Linear Collider to measure the Higgs-top Yukawa coupling. In this paper, we compute $2\to 8$ processes of the form $e^+e^-\to b\bar b b\bar b W^+W^-\to b\bar b b\bar b \ell^\pmν_\ell q\bar q'$, accounting for the Higgs-top-antitop signal as well as several irreducible backgrounds in the semi-lepto

D. Espriu

This is the written version of the lecture on deep inelastic scattering and related topics in QCD, delivered in the course of the XXVI International Meeting on Fundamental Physics to an audience of young experimentalists. The aim is fundamentally pedagogical. I review the theoretical setting of the Altarelli-Parisi equations, discuss recent determinations of

W. J. Stirling

We present an overview of the theory of high--Q^2 deep inelastic scattering. We focus in particular on the theoretical uncertainties in the predictions for neutral and charged current cross sections obtained by extrapolating from lower Q^2.

Vittorio Del Duca

Dijet production with a rapidity gap between the jets is considered as a test ground for the production of a heavy Higgs boson via weak-boson fusion at hadron supercolliders. It is argued that in order to perform a detailed analysis of dijet production with a rapidity gap we need an ${\cal O}(\al_s^4)$ calculation including the relevant collinear enhancement

J. Marteau

We perform a calculation of the absolute charged current neutrino- oxygen events rates relevant in the atmospheric neutrino experiments. The inclusive reaction cross-section is split into exclusive channels, which are classified according to the number of Čerenkov rings they produce. The model includes the effects of residual interaction in a RPA scheme with

Hidenori Sonoda

Bose condensation is usually a low temperature phenomenon due to a low particle number density. When the number density is kept large compared to the inverse Compton volume, Bose condensation can occur at a temperature much higher than the mass of the particle. We can then use a three dimensional effective theory to study the thermal properties. We compute t

E. M. Lipmanov

In the recent note we argued that most of the available positive and negative neutrino oscillation data can be incorporated in a four-neutrino weak interaction model with one physical condition: thorough maximal mixing of the neutrino components in each of the two mass doublets. On the level of CP-invariance an extended Pontecorvo analogy between the neutrin

Afsar Abbas, Lina Paria, Samar Abbas

The ideas of "local" and "global" colour-singletness are not well understood within QCD. We use a group theoretical technique to project out the partition function for a system of quarks, antiquarks and gluons to a particular representation of the internal symmetry group $SU(3)_c$: colour-singlet, colour-octet and colour 27-plet at finite tem

S. Bilke

We analyze a model of hypercubic random surfaces with an extrinsic curvature term in the action. We find a first order phase transition at finite coupling separating a branched polymer from a stable flat phase.

Vladimir G. Baryshevsky, Olga M. Lugovskaya

The PXR spectral-angular and angular distributions in Si and LiH crystals for Bragg geometry are presented. PXR for both the forward and backward diffraction is studied. It is shown that for Bragg geometry the contributions of both the slow and the fast waves in radiation intensity are comparable and only their joint account allows to describe the experiment

Alexander Vilenkin

The stochastic approach to inflation suffers from ambiguities due to the arbitrary choice of the time variable and due to the choice of the factor ordering in the corresponding Fokker-Planck equation. Here it is shown that both ambiguities can be removed if we require that the factor ordering should be set in such a way that physical results are invariant wi

Oscar A. Reula

It is shown that during expanding phases of flat homogeneous cosmologies all small enough non-linear perturbations decay exponentially. This result holds for a large class of perfect fluid equations of state, but notably not for very ``stiff'' fluids as the pure radiation case.

Mustapha Azreg-Ainou

We solve the eigenvalue problem of general relativity for the case of charged black holes in two-dimensional heterotic string theory, derived by McGuigan et al. For the case of $m^{2}>q^{2}$, we find a physically acceptable time-dependent growing mode; thus the black hole is unstable. The extremal case $m^{2}=q^{2}$ is stable.

Marco Cavaglia, Carlo Ungarelli

We discuss the quantisation of a class of string cosmology models that are characterized by scale factor duality invariance. We compute the amplitudes for the full set of classically allowed and forbidden transitions by applying the reduce phase space and the path integral methods. We show that these approaches are consistent. The path integral calculation c

Takeshi Chiba

We study numerically the inhomogeneous pre-big-bang inflation in a spherically symmetric space-time. We find that a large initial inhomogeneity suppresses the onset of the pre-big-bang inflation. We also find that even if the pre-big-bang inflationary stage is realized, the initial inhomogeneities are not homogenized. Namely, during the pre-big-bang inflatio

Lior M. Burko

We study the linear metric perturbations of the Reissner-Nordström solution for the case of axial perturbation modes. We find that the well-known perturbative analysis fails for the case of dipole $(l=1)$ perturbations, although valid for higher multipoles. We define new radial functions, with which the perturbation formalism is generalized to all multipole

Kuang-hua Chen

The amount of electronic documents in the Internet grows very quickly. How to effectively identify subjects for documents becomes an important issue. In past, the researches focus on the behavior of nouns in documents. Although subjects are composed of nouns, the constituents that determine which nouns are subjects are not only nouns. Based on the assumption

L. Capriotti, A. Cuccoli, V. Tognetti, P. Verrucchi

The classical XXZ triangular-lattice antiferromagnet (TAF) shows both an Ising and a BKT transition, related to the chirality and the in-plane spin components, respectively. In this paper the quantum effects on the thermodynamic quantities are evaluated by means of the pure-quantum self-consistent harmonic approximation (PQSCHA), that allows one to deal with

Anthony Roberts

A method of modelling the three-dimensional microstructure of random isotropic two-phase materials is proposed. The information required to implement the technique can be obtained from two-dimensional images of the microstructure. The reconstructed models share two-point correlation and chord-distribution functions with the original composite. The method is

Shay Wolfling, Yacov Kantor

Distribution of loops in a one-dimensional random walk (RW), or, equivalently, neutral segments in a sequence of positive and negative charges is important for understanding the low energy states of randomly charged polymers. We investigate numerically and analytically loops in several types of RWs, including RWs with continuous step-length distribution. We

P. R. Broussard, S. B. Qadri, V. M. Browning, V. C. Cestone

We have grown thin films of (100) oriented La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} on (100) NdGaO_{3} substrates by off-axis sputtering. We have looked at the changes in the resistivity and magnetoresistance of the samples as the Ca/Sr ratio was varied. We find that as the calcium fraction is decreased, the lattice match to the substrate decreases, and the f