August 1998 arXiv papers — page 12

S. A. Rakityansky, S. A. Sofianos

Recently, we proposed an exact method for direct calculation of the Jost function for central potentials (which may have Coulombic tails) and the Jost matrix for non-central short range potentials. This method works for all real or complex momenta of physical interest, including the spectral points corresponding to bound and Siegert states. In this work we e

Jonathan Beck, Vyjayanthi Chari, Andrew Pressley

The canonical basis for quantized universal enveloping algebras associated to the finite--dimensional simple Lie algebras, was introduced by Lusztig. The principal technique is the explicit construction (via the braid group action) of a lattice over $\bz[q^{-1}]$. This allows the algebraic characterization of the canonical basis as a certain bar-invariant ba

A. M. Khvedelidze, H. -P. Pavel

The unconstrained system equivalent to SU(2) Yang-Mills field theory is obtained in the framework of the generalized Hamiltonian formalism using the method of Hamiltonian reduction. The reduced system is expressed in terms of fields which transform as spin zero and spin two under spatial rotations.

Gary T. Horowitz, Robert C. Myers

We examine the AdS/CFT correspondence when the gauge theory is considered on a compactified space with supersymmetry breaking boundary conditions. We find that the corresponding supergravity solution has a negative energy, in agreement with the expected negative Casimir energy in the field theory. Stability of the gauge theory would imply that this supergrav

Mirjam Cvetic, Lisa Everett, Jing Wang

We determine the units and numerical values for a class of couplings in the effective theory of perturbative heterotic string vacua, with the emphasis on the correct translation between the canonical gauge coupling g and Planck scale M_Planck ~ 1.2 x 10^19 GeV as used in the effective theory description and the string coupling g_string and string tension alp

E. R. Berger, O. Nachtmann

Total and differential cross sections for high energy and small momentum transfer elastic hadron-hadron scattering are studied in QCD using a functional integral approach. The hadronic amplitudes are governed by vacuum expectation values of lightlike Wegner-Wilson loops, for which a matrix cumulant expansion is derived. The cumulants are evaluated within the

Joao Pulido

The distortion of the energy spectrum of recoil electrons in SuperKamiokande resulting from several solar magnetic field profiles that are consistent with data and standard solar models is investigated. The aim is to provide a test of the general common features of these field profiles derived in a previous work on the basis of the resonant spin flip flavour

D. Falcone, P. Santorelli, N. Tancredi, F. Tramontano

The form factors for the weak currents between B and light mesons are studied by relating them to the corresponding D form factors at q^2_{max} according to HQET, by evaluating them at q^2=0 by QCD sum rules, and by assuming a polar q^2 dependence. The results found are consistent with the information obtained from exclusive non-leptonic two-body decays and,

Hong-Yi Zhou, Yu-Ping Kuang, Chong-Xing Yue, Hua Wang

Pseudo-Goldstone boson contributions to $t\bar{t}$ production rates in technicolor models with and without topcolor at the $\sqrt{s}=0.5 and 1.5$ TeV photon colliders and hadron colliders are reviewed. For reasonable ranges of the parameters, the contributions are large enough to be experimentally observable. Models with topcolor, without topcolor and the MS

F. del Aguila, M. Perez-Victoria

The scope of constrained differential renormalization is to provide renormalized expressions for Feynman graphs, preserving at the same time the Ward identities of the theory. It has been shown recently that this can be done consistently at least to one loop for abelian and non-abelian gauge theories. We briefly review these results, evaluate as an example t

V. B. Semikoz, S. Pastor, J. W. F. Valle

If neutrino conversions within the Sun result in partial polarization of initial solar neutrino fluxes, then a new opportunity arises to observe the anti-ν_e's in future neutrino experiments in the low energy region (such as BOREXINO or HELLAZ) and thus to probe the Majorana nature of the neutrinos. The ν_e -> anti-ν_e conversions may take place for low

Changhao Jin

The study of inclusive semileptonic decays of $B$ mesons is analyzed from the viewpoint of probing hadron structure and strong interactions. General formulas for the differential decay rates are given in terms of the structure functions in arbitrary frame of reference, taking into account the finite charged lepton mass. These formulas can be used for structu

I. G. Aznauryan, S. G. Stepanyan

Within the fixed-t dispersion relation approach we have analysed the TJNAF and DESY data on the exclusive p(e,e'p)π^0 reaction in order to find the P_{33}(1232) resonance contribution into the multipole amplitudes M_{1+}^{3/2},E_{1+}^{3/2},S_{1+}^{3/2}. As an input for the resonance and nonresonance contributions into these amplitudes the earlier obtaine

Andrei V. Afanasev

First, I define generalized Bloom-Gilman duality and Bjorken-like scaling for inclusive photoproduction of pions, relating Quark-Parton Model description in the deep-inelastic region to the properties of exclusive resonance excitation. Secondly, connection between inclusive and exclusive processes is established in the formalism of Nonforward Parton Densitie

The OPAL Collaboration, K. Ackerstaff et al

The production of charged hadrons and K_s mesons in the collisions of quasi-real photons has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass energies of 161 and 172 GeV. The differential cross-sections as a function of the transverse momentum and the pseudorapidity of the charged hadrons and K_s mesons have been compa

Wu Zhong Chao

Creation of a black hole in quantum cosmology is the third way of black hole formation. In contrast to the gravitational collapse from a massive body in astrophysics or from the quantum fluctuation of matter fields in the very early universe, in quantum cosmology scenario the black hole is essentially created from nothing. The black hole originates from a co

G. Modanese

It is known that the action of Euclidean Einstein gravity is not bounded from below and that the metric of flat space does not correspond to a minimum of the action. Nevertheless, perturbation theory about flat space works well. The deep dynamical reasons for this reside in the non perturbative behaviour of the system and have been clarified in part by numer

James P. Crutchfield, Cosma Rohilla Shalizi

Thermodynamic depth is an appealing but flawed structural complexity measure. It depends on a set of macroscopic states for a system, but neither its original introduction by Lloyd and Pagels nor any follow-up work has considered how to select these states. Depth, therefore, is at root arbitrary. Computational mechanics, an alternative approach to structural

S. C. Dultz, H. W. Jiang, W. J. Schaff

By tracking the delocalized states of the two-dimensional hole gas in a p-type GaAs/AlGaAs heterostructure as a function of magnetic field, we mapped out a phase diagram in the density-magnetic-field plane. We found that the energy of the delocalized state from the lowest Landau level flattens out as the magnetic field tends toward zero. This finding is diff

Christopher L. Martin

An extension to the multiple-histogram method (sometimes referred to as the Ferrenberg-Swendsen method) for use in quantum Monte Carlo simulations is presented. This method is shown to work well for the 2D repulsive Hubbard model, allowing measurements to be taken over a continuous region of parameters. The method also reduces the error bars over the range o

A. I. Belousov, S. A. Verzakov, Yu. E. Lozovik

A lattice boson model is used to study ordering phenomena in regular 2D array of superconductive mesoscopic granules, Josephson junctions or pores filled with a superfluid helium. Phase diagram of the system, when quantum fluctuations of both the phase and local superfluid density are essential, is analyzed both analytically and by quantum Monte Carlo techni

Chandan Dasgupta, Oriol T. Valls

The topography of the free energy landscape in phase space of a dense hard sphere system characterized by a discretized free energy functional of the Ramakrishnan-Yussouff form is investigated numerically using a ``microcanonical'' Monte Carlo procedure. We locate a considerable number of glassy local minima of the free energy and analyze the distrib

M. A. Moore, Hemant Bokil, Barbara Drossel

We have studied the Parisi overlap distribution for the three dimensional Ising spin glass in the Migdal-Kadanoff approximation. For temperatures T around 0.7Tc and system sizes upto L=32, we found a P(q) as expected for the full Parisi replica symmetry breaking, just as was also observed in recent Monte Carlo simulations on a cubic lattice. However, for low

Andre Wobst, Dietmar Weinmann

The curvatures of two-particle energy levels with respect to the enclosed magnetic flux in mesoscopic disordered rings are investigated numerically. We find that the typical value of the curvatures is increased by interactions in the localised regime and decreased in the metallic regime. This confirms a prediction by Akkermans and Pichard (Eur. Phys. J. B 1,

Xiangyang Huang, Weidong Yang, Ulrich Eckern

The electronic structure of VO$_2$ is studied in the frameworks of local density approximation (LDA) and LDA+$U$ to give a quantitative description of the metal-insulator (MI) transition in this system. It is found that, both structural distortion and the local Coulomb interaction, play important roles in the transition. An optical gap, comparable to the exp

M. E. Cates, J. P. Wittmer, J. -P. Bouchaud, P. Claudin

We present simple models of particulate materials whose mechanical integrity arises from a jamming process. We argue that such media are generically "fragile", that is, they are unable to support certain types of incremental loading without plastic rearrangement. In such models, fragility is naturally linked to the marginal stability of force chain n

Bernd Ludwig, Guenther Goerz, Heinrich Niemann

We present work in progress on abstracting dialog managers from their domain in order to implement a dialog manager development tool which takes (among other data) a domain description as input and delivers a new dialog manager for the described domain as output. Thereby we will focus on two topics; firstly, the construction of domain descriptions with descr

Hideaki Aoyama, John Constable

Recent observations in the theory of verse and empirical metrics have suggested that constructing a verse line involves a pattern-matching search through a source text, and that the number of found elements (complete words totaling a specified number of syllables) is given by dividing the total number of words by the mean number of syllables per word in the

A. M. Selvam, Suvarna Fadnavis

Cantorian fractal spacetime fluctuations characterize quantumlike chaos in atmospheric flows. The macroscale atmospheric flow structure behaves as a unified whole quantum system, where, the superimposition of a continuum of eddies results in the observed global weather patterns with long-range spatiotemporal correlations such as that of the widely investigat

Richard B. Larson

It has frequently been suggested that the stellar IMF in galaxies was top-heavy at early times. This would be plausible physically if the IMF depends on a mass scale such as the Jeans mass that was higher at earlier times because of the generally higher temperatures that were present then. In this paper it is suggested, on the basis of current evidence and t

Peter Widerin, Christoph Schmid

Can a violent process like sudden reheating after supercooling at the onset of a first-order QCD transition improve the possibility of primordial black hole formation? Underdensities reheat earlier than overdensities, there is a short period of huge pressure differences, hence fluid acceleration. Density perturbations on scales far below the Hubble radius $λ

C. M. Rudge, D. J. Raine

We propose that the scatter in line width versus luminosity of the BLR of AGN arises from a dependence on the line of sight to an axially symmetric BLR. Adopting a simple model for the line width as a function of luminosity and angle, and convolving this with the observed luminosity function, allows us to predict a line width distribution consistent with the

Shantanu Basu

We use magnetic collapse models to place some constraints on the formation and angular momentum evolution of circumstellar disks which are embedded in magnetized cloud cores. Previous models have shown that the early evolution of a magnetized cloud core is governed by ambipolar diffusion and magnetic braking, and that the core takes the form of a nonequilibr

Gerard Gilmore, M. Unavane

We exclude hydrogen burning stars, of any mass above the hydrogen-burning limit and any metallicity, as significant contributors to the massive halos deduced from rotation curves to dominate the outer parts of spiral galaxies. We present and analyse images of 4 nearly edge-on bulgeless spiral galaxies (UGC711, NGC2915, UGC12426, UGC1459) obtained with ISOCAM

Richard W. Pogge, Paul B. Eskridge

A significant number of S0 galaxies with a detectable ISM show some level of on-going massive-star formation activity in the form of visible HII regions. A rich ISM, however, does not guarantee star formation: a similar number of gas-rich S0s have no detectable HII regions down to the level of regions ionized by single O stars. The H-alpha luminosities of st

Eli Waxman, Abraham Loeb

SN1998bw is the most luminous radio supernova ever observed. Previous discussions argued that its exceptional radio luminosity, 4e38 erg/s, must originate from a highly relativistic shock which is fully decoupled from the supernova ejecta. Here we present an alternative model in which the radio emission originates from a sub-relativistic shock with a velocit

Alexis von Hoensbroech

Using polarimetric radio profiles of 84 pulsars at a wavelength of 6 cm, we present a correlation between the polarization and characteristic age of pulsars. Considering the large error connected with the value of the characteristic age, we speculate about the possibility of identifying young pulsars through their polarimetric properties. Using this method w

R. Civelek, N. Kiziloglu

In recent years, white dwarf stars are receiving increasing attension. The recent studies on the relation of M-R for the WDs are those of Wood (1990), Vennes et al. (1995) and Althaus and Benvenuto (1997, 1998). Vennes et al. (1995) computed static M-R relation for masses between 0.4 $M_\odot$ and 0.7 $M_\odot$ assuming non zero temperature effects. They ass

Bruno Altieri, Leo Metcalfe, Jean-Paul Kneib, Brian Mc Breen

We present the first results of mid-infrared (MIR) ultra-deep observations towards the lensing cluster Abell 2390 using the ISOCAM infrared camera on-board ESA's Infrared Space Observatory (ISO) satellite. They reveal a large number of luminous MIR sources. Optical and near-infrared (NIR) cross-identification suggests that almost all 15 microns sources a

Chung-Pei Ma

This paper presents a detailed theoretical study of the two-point correlation function $ξ$ for both dark matter halos and the matter density field in five cosmological models with varying matter density $Ω_m$ and neutrino fraction $Ω_ν$. The objectives of this systematic study are to evaluate the nonlinear gravitational effects on $ξ$, to contrast the behavi

R. J. Protheroe, Todor Stanev

We have examined cutoffs and pile-ups due to various processes in the spectra of particles produced by shock acceleration, and found that, even in the absence of energy losses, the shape of the spectrum of accelerated particles at energies well below the nominal maximum energy depends strongly on the energy dependence of the diffusion coefficient. This has i

H. C. Rosu, C. Castro

We present a version of q-deformed calculus based on deformed counterparts of Darboux intertwining operators. The case in which the deformed transformation function is of the vacuum type is detailed, but the extension to counterparts of excited states used as Darboux transformation functions is also formally discussed. The method leads to second-order Fokker

Steven S. Gubser, Igor R. Klebanov

Coincident D3-branes placed at a conical singularity are related to string theory on $AdS_5\times X_5$, for a suitable five-dimensional Einstein manifold $X_5$. For the example of the conifold, which leads to $X_5=T^{1,1}=(SU(2)\times SU(2))/U(1)$, the infrared limit of the theory on $N$ D3-branes was constructed recently. This is ${\cal N}=1$ supersymmetric

Ben Craps, Frederik Roose

We compute scattering amplitudes involving both R-R and NS-NS fields in the presence of a D-brane or orientifold plane. These provide direct evidence for the anomalous couplings in the D-brane and orientifold actions. The D9-brane and O9-plane are found to couple to the first Pontrjagin class with the expected relative strength.

Jeremy S. Heyl, Lars Hernquist

We examine the timing history of several anomalous X-ray pulsars (AXPs), and find that they exhibit spin down irregularities statistically similar to those of radio pulsars. We propose that these irregularities are simply glitches like those of radio pulsars and fit glitching spin down solutions to the data available for 1E~2259+586, 1E~1048.1-5937 and 4U~01

W. Vincent Liu

We suggest that the 2+1 dimensional Gross-Neveu model can give an effective field theory description of low-energy quasiparticles in high temperature superconductors. The magnetic catalysis of dynamical symmetry breaking is examined. The model shows that a magnetic field can induce a phase transition associated with parity breaking. In particular, it is inte

Sushan Konar, Dipankar Bhattacharya

We investigate the evolution of the magnetic field of isolated pulsars and of neutron stars in different kinds of binary systems, assuming the field to be originally confined to the crust. Our results for the field evolution in isolated neutron stars helps us to constrain the physical parameters of the crust. Modelling the full evolution of a neutron star in

J. Cleymans, K. Redlich

It is shown that the chemical freeze-out parameters obtained at CERN/SPS, BNL/AGS and GSI/SIS energies all correspond to a unique value of 1 GeV per hadron in the local rest frame of the system, independent of the beam energy and of the target and beam particles.

P. Hernández, K. Jansen, M. Lüscher

The gauge covariant lattice Dirac operator D which has recently been proposed by Neuberger satisfies the Ginsparg-Wilson relation and thus preserves chiral symmetry. The operator also avoids a doubling of fermion species, but its locality properties are not obvious. We now prove that D is local (with exponentially decaying tails) if the gauge field is suffic

Yukitoshi Motome, Masatoshi Imada

Roles of Coulomb interaction, orbital degeneracy and Jahn-Teller coupling in double-exchange models are examined for Mn perovskite oxides. We study the undoped Mott insulator as well as metal-insulator transitions by hole doping, and especially strong incoherence of ferromagnetic metal. We derive models where all the spins are fully polarized in two-dimensio

K. Zioutas, D. J. Thompson, E. A. Paschos

Orbiting $γ$-detectors combined with the magnetic field of the Earth or the Sun can work parasitically as cosmic axion telescopes. The relatively short field lengths allow the axion-to-photon conversion to be coherent for $m_{axion} \sim 10^{-4}$ eV, if the axion kinetic energy is above $\sim 500$ keV (Earth's field), or, $\sim 50$ MeV (Sun's field),

Robert H. Brandenberger, Xinmin Zhang

We propose a new mechanism for the generation of primordial magnetic fields, making use of the magnetic fields which are induced by anomalous global strings which couple to electromagnetism via Wess-Zumino type interactions. This mechanism can be realized in QCD by utilizing pion strings, global vortices which appear in the linear sigma model which describes

B. G. Sidharth

In this paper, starting from vortices we are finally lead to a treatment of Fermions as Kerr-Newman type Black Holes wherein we identify the horizon at the particle's Compton wavelength periphery. A naked singularity is avoided and the singular processes inside the horizon of the Black Hole are identified with Quantum Mechanical effects within the Compto

Milos V. Lokajicek

It has been shown that the predictions of some new phenomena (e.g., teleportation and cryptography) are based on some assumptions added to the quantum-mechanical model or modifying some of its basic axioms. The hitherto experiments presented as a support of the mentioned phenomena may be hardly regarded as sufficient, as they may be interpreted alternatively

K. Yabana, G. F. Bertsch

The time-dependent local-density approximation (TDLDA) is applied to the optical response of conjugated carbon molecules in the energy range of 0-30 eV, with calculations given for carbon chains, polyenes, retinal, benzene and C_60. The major feature of the spectra, the collective pi-pi* transition, is seen at energies ranging from below 2 to 7 eV, and is re

Jan M. L. Martin, Peter R. Taylor

A benchmark ab initio study on the thermochemistry of the trans-HNNH, cis-HNNH, and H$_2$NN isomers of diazene has been carried out using the CCSD(T) coupled cluster method, basis sets as large as $[7s6p5d4f3g2h/5s4p3d2f1g]$, and extrapolations towards the 1-particle basis set limit. The effects on inner-shell correlation and of anharmonicity in the zero-poi

Jan M. L. Martin

By judicious use of extrapolations to the 1-particle basis set limit and $n$-particle calibration techniques, total atomization energies of molecules with up to four heavy atoms can be obtained with calibration accuracy (1 kJ/mol or better, on average) without any empirical correction. For the SCF energy a 3-point geometric extrapolation is the method of cho

Jan M. L. Martin

The quartic force field of SO$_3$ was computed fully ab initio using coupled cluster (CCSD(T)) methods and basis sets of up to $spdfgh$ quality. The effect of inner-shell correlation was taken into account. The addition of tight $d$ functions is found to be essential for accurate geometries and harmonic frequencies. The equilibrium geometry and vibrational f

Alexey K. Mazur

Internal coordinate molecular dynamics (ICMD) is an efficient method for studying biopolymers, but it is readily applicable only to molecules with tree topologies, that is with no internal flexible rings. Common examples violating this condition are prolines and loops closed by S-S bridges in proteins. The most important such case, however, is nucleic acids

Ziwei Lin, Xin-Nian Wang

We study the dimuon yield from open charm decays in the intermediate mass region(IMR) in heavy-ion collisions at the CERN-SPS energy. We find that final state rescatterings which broaden the $m_T$ spectrum of charmed mesons can enrich the part of the phase space covered by the NA50 experiment, thus leading to an apparent enhancement of IMR dileptons within t

C. M. Ko, X. N. Wang, X. F. Zhang

Charmonium production from the hadron gas formed in ultra-relativistic heavy-ion collisions is studied. Using the $J/ψ$-hadron absorption cross section determined from the nonperturbative quark-exchange model, which has a peak value similar to that used in the comover model for $J/ψ$ suppression and a thermally averaged value consistent from that extracted f

W. Poeschl, B. Mueller

We describe the dynamics of gluons and quarks in a relativistic nuclear collision, within the framework of classical mean-field transport theory, by the coupled equations for the classical Yang-Mills field and a collection of colored point particles. The particles represent the valence quarks in the colliding nuclei. We explore the time evolution of the gaug

Michael Penkava, Lynelle Weldon

In this paper we give some examples of generalized Massey products, arising from deformations of A-infinity and L-infinity algebras. The generalized Massey products are given by certain graded commutative algebra structures, depending on the deformation problem considered. We show that the formal deformations of infinity algebras give rise to the same algebr

Andrzej Roslanowski, Saharon Shelah

We address several questions of Donald Monk related to irredundance and spread of Boolean algebras, gaining both some ZFC knowledge and consistency results. We show in ZFC that irr(B_0 times B_1)= max(irr(B_0),irr(B_1)). We prove consistency of the statement ``there is a Boolean algebra B such that irr(B)<s(B otimes B)&#39;&#39; and we force a superatomic Bo

Paul Vojta

This paper proves a finiteness result for families of integral points on a semiabelian variety minus a divisor, generalizing the corresponding result of Faltings for abelian varieties. Combined with the main theorem of the first part of this paper, this gives a finiteness statement for integral points on a closed subvariety of a semiabelian variety, minus a

Joseph Donin, Dmitry Gurevich, Steve Shnider

We study one and two parameter quantizations of the function algebra on a semisimple orbit in the coadjoint representation of a simple Lie group subject to the condition that the multiplication on the quantized algebra is invariant under action of the Drinfeld-Jimbo quantum group. We prove that the corresponding Poisson bracket must be the sum of the so-call

Aaron Robertson, Doron Zeilberger

We prove that the minimum number (asymptotically) of monochromatic Schur triples that a 2-coloring of [1,n] can have is (n^2)/22 + O(n). This was solved independently by Tomasz Schoen.

Matthew J. Strassler

As shown in hep-th/9709081, non-BPS saturated solitons play an important role in the duality transformations of N=1 supersymmetric gauge theories. In particular, a massive spinor in an SO(N) gauge theory with massless matter in the vector representation appears in the dual description as a magnetic monopole with a Z_2 charge. This claim is supported by numer

H. Gustafsson, U. Lindstrom

We describe new $N$-extended 2D supergravities on a $(p+1)$-dimensional (bosonic) space. The fundamental objects are moving frame densities that equip each $(p+1)$-dimensional point with a 2D ``tangent space&#39;&#39;. The theory is presented in a $[p+1, 2]$ superspace. For the special case of $p=1$ we recover the 2D supergravities in an unusual form. The fo

M. Perez-Victoria

We renormalize QCD to one loop in coordinate space using constrained differential renormalization, and show explicitly that the Slavnov-Taylor identities are preserved by this method.

Ignatios Antoniadis, Pawel O. Mazur, Emil Mottola

We compute the intrinsic Hausdorff dimension of spacetime at the infrared fixed point of the quantum conformal factor in 4D gravity. The fractal dimension is defined by the appropriate covariant diffusion equation in four dimensions and is determined by the coefficient of the Gauss-Bonnet term in the trace anomaly to be generally greater than 4. In addition

C. M. Hull, R. R. Khuri

Dualities link M-theory, the 10+1 dimensional strong coupling limit of the IIA string, to other 11-dimensional theories in signatures 9+2 and 6+5, and to type II string theories in all 10-dimensional signatures. We study the Freund-Rubin-type compactifications and brane-type solutions of these theories, and find that branes with various world-volume signatur

Alex Lewis

We find the critical charge for a topologically massive gauge theory for any gauge group, generalising our earlier result for SU(2). The relation between critical charges in TMGT, singular vectors in the WZNW model and logarithmic CFT is investigated.

A. Jaramillo, P. Mansfield

We show how to compute vacuum expectation values from derivative expansions of the vacuum wave functional. Such expansions appear to be valid only for slowly varying fields, but by exploiting analyticity in a complex scale parameter we can reconstruct the contribution from rapidly varying fields.

Sho Tanaka

In order to get the general framework describing a nonlocalizable object beyond the bilocal field theory early proposed by Markov and Yukawa, the quantization of space-time is reconsidered and further developed. Space-time quantities are there not only noncommutative with U-field describing the nonlocalizable object, as in the bilocal field theory, but also

Nemanja Kaloper

This note is a summary of the work reported in hep-th/9801073. We give a brief discussion of the fine tuning problem in pre-big bang cosmology. We use the flatness problem as our test case, and in addition to the exact numerical limits on initial conditions, we highlight the differences between pre-big bang and standard inflation. The main difference is that

Eric W. Hirschmann, Steven L. Liebling

We consider the collapse of a global &#34;Hopf&#34; texture and examine the conjecture, disputed in the literature, that monopole-antimonopole pairs can be formed in the process. We show that such monopole-antimonopole pairs can indeed be nucleated in the course of texture collapse given appropriate initial conditions. The subsequent dynamics include the rec

I. Akushevich

The electromagnetic radiative correction to the cross section of the vector meson electroproduction is calculated. Explicit covariant formulae for the observed cross section are obtained. The dependence of the radiative correction on the experimental resolution and on the inelasticity cut is discussed. FORTRAN code DIFFRAD based on both exact (ultrarelativis

Xiaofeng Guo

Using the Drell-Yan process in hadron-nucleus collisions and deeply inelastic lepton-nucleus scattering (DIS) as examples, I show that the transverse momentum broadening can be expressed in terms of four-parton correlation functions. I argue that jet broadening in DIS provide an excellent measurement of the four-parton correlation functions and a test of QCD

Wojciech Krolikowski

The existence of two sterile neutrinos $ν_s$ and $ν&#39;_s$ (blind to all Standard-Model interactions) is shown to be implied by a model of fermion &#34;texture&#34; that we develop since some time. They may mix nearly maximally with two of three conventional neutrinos, say $ν_e$ and $ν_μ$, thus leading to neutrino oscillations, say $ν_e \to ν_s$ and $ν_μ\to

M. Napsuciale

Meson properties are considered within a U(3)\times U(3) Linear Sigma Model(LSM). The importance of the U_A(1)-breaking term and the OZI rule violating term in the generation of meson masses and mixing angles is stressed. The LSM parameters are fitted to the pseudoscalar meson spectrum thus giving predictions for scalar meson properties. The model predicts a

R. Johnson, M. Teper

We discuss the problem of constructing operators of arbitrary continuum angular momentum on a spatial lattice. We illustrate one simple approach and estimate the lightest J=4 glueball mass in the D=2+1 SU(2) gauge theory.

R. Frezzotti, K. Jansen

We give a detailed description of the so-called Polynomial Hybrid Monte Carlo (PHMC) algorithm. The effects of the correction factor, which is introduced to render the algorithm exact, are discussed, stressing their relevance for the statistical fluctuations and (almost) zero mode contributions to physical observables. We also investigate rounding-error effe

A. Di Giacomo, D. Martelli, G. Paffuti

The 3d Heisenberg model is studied from a dual point of view. It is shown that the disordered phase corresponds to condensation of vortices in the vacuum, and the critical indices are computed from the corresponding disorder parameter.

K. Rajesh Nayak, C. V. Vishveshwara

We study the phenomenon of gyroscopic precession and the analogues of inertial forces within the framework of general relativity. Covariant connections between the two are established for circular orbits in stationary spacetimes with axial symmetry. Specializing to static spacetimes, we prove that gyroscopic precession and centrifugal force both reverse at t

Gary T. Horowitz, Saul A. Teukolsky

Black holes are among the most intriguing objects in modern physics. Their influence ranges from powering quasars and other active galactic nuclei, to providing key insights into quantum gravity. We review the observational evidence for black holes, and briefly discuss some of their properties. We also describe some recent developments involving cosmic censo

Joerg P. Kottmann, Adriaan M. J. Schakel

The dynamics of vortices in a superfluid film at the absolute zero of temperature is studied. The quantum-mechanical, i.e., ``first-quantized&#39;&#39; description is compared to a recently proposed quantum-field-theoretic, i.e., ``second-quantized&#39;&#39; description. The theory, consisting of the nonrelativistic effective action of phonons linearly coupl

N. Markovic, C. Christiansen, A. M. Goldman

The superconductor-insulator transition in ultrathin films of amorphous Bi was tuned by an applied magnetic field. A finite size scaling analysis has been carried out to determine the critical exponent product vz=0.7 for five films of different thicknesses and normal state resistances. This result differs from the exponents found in previous experiments on I

A. Jaster, J. Mainville, L. Schuelke, B. Zheng

Comprehensive Monte Carlo simulations of the short-time dynamic behaviour are reported for the three-dimensional Ising model at criticality. Besides the exponent $θ$ of the critical initial increase and the dynamic exponent $z$, the static critical exponents $ν$ and $β$ as well as the critical temperature are determined from the power-law scaling behaviour o

Keir E. Novik, Peter V. Coveney

We discuss algorithms applicable to the numerical solution of second-order ordinary differential equations by finite-differences. We make particular reference to the solution of the dissipative particle dynamics fluid model, and present extensive results comparing one of the algorithms discussed with the standard method of solution. These results show the su

J. M. Pitarke, I. Campillo

A survey is presented of the theoretical status of quadratic response theories for the understanding of nonlinear aspects in the interaction of charged particles with matter. In the frame of the many-body perturbation theory we study the interaction of charged particles with the electron gas, within the random-phase approximation (RPA). In particular, nonlin

Gernot Stollhoff

Electronic correlations in the ground state of an idealized infinite-layer high-Tc compound are computed using the ab-initio method of local ansatz. Comparisons are made with the local-density approximation (LDA) results, and the correlation functions are analyzed in detail. These correlation functions are used to determine the effective atomic-interaction p

V. A. Grigoryan

The measurements of temperature dependence of AC magnetic susceptibility were used to study the influence of inhomogeneities on intragranular superconducting properties of YBa2Cu3-xMxOy (M=Fe,x=0.005; Al,x=0.01; Cr,x=0.01), Bi1.7Pb0.2Sb0.1Sr2Ca2Cu3Oy and Bi1.5Pb0.3Sb0.2Sr2Ca2Cu3Oy ceramics. It is found that step-like regions are revealed on AC magnetic field

Giancarlo Jug, Boris N. Shalaev

We study phase transitions in uniformly frustrated SU(N)-symmetric $(2+ε)$-dimensional lattice models describing type-II superconductors near the upper critical magnetic field $H_{c2}(T)$. The low-temperature renormalization-group approach is employed for calculating the beta-function $β(T,f)$ with $f$ an arbitrary rational magnetic frustration. The phase-bo

A. I. Belousov, S. A. Verzakov, Yu. E. Lozovik

The phase diagram of a two-dimensional Josephson array of mesoscopic objects is examined. Quantum fluctuations in both the modulus and phase of the superconducting order parameter are taken into account within a lattice boson Hubbard model. Modulating the average occupation number $n_0$ of the sites in the system leads to changes in the state of the array, a

Ryuzo Azuma, Hajime Takayama

We present a new computational methodology for the investigation of gel electrophoresis of polyelectrolytes. We have developed the method initially to incorporate sliding motion of tight parts of a polymer pulled by an electric field into the bond fluctuation method (BFM). Such motion due to tensile force over distances much larger than the persistent length

Toru Aonishi

Studies have been made on the phase transition phenomena of an oscillator network model based on a standard Hebb learning rule like the Hopfield model. The relative phase informations---the in-phase and anti-phase, can be embedded in the network. By self-consistent signal-to-noise analysis (SCSNA), it was found that the storage capacity is given by $α_c = 0.

R. J. Baxter

This is the third in a series of papers in which we set up and discuss the functional relations for the ``split rapidity line&#39;&#39; correlation function in the N - state chiral Potts model. The order parameters of the model can be obtained from this function. Here we consider the case N = 3 and write the equations explicitly in terms of the hyperelliptic

Martin Siegert

The formation of pyramid-like structures in thin-film growth on substrates with a quadratic symmetry, e.g., {001} surfaces, is shown to exhibit anisotropic scaling as there exist two length scales with different time dependences. Analytical and numerical results indicate that for most realizations coarsening of mounds is described by an exponent n=0.2357. Ho

E. A. Cornell, D. S. Hall, M. R. Matthews, C. E. Wieman

We have begun a series of experiments on mixed bosonic quantum fluids. Our system is mixed Bose-Einstein condensates in dilute Rb-87. By simultaneously trapping the atoms in two different hyperfine states, we are able to study the dynamics of component separation and of the relative quantum phase of two interpenetrating condensates. Population can be convert