April 1996 arXiv papers — page 6

S. Catani, M. L. Mangano, P. Nason, L. Trentadue

We compute the effects of soft gluon resummation for the production of high mass systems in hadronic collisions. We carefully analyse the growth of the perturbative expansion coefficients of the resummation formula. We propose an expression consistent with the known leading and next-to-leading resummation results, in which the coefficients grow much less tha

Mats Dahlbom, Anders Irbäck

This paper is withdrawn.

D-H Lee, Yu. A. Krotov, J. Gan, S. A. Kivelson

We show that at electronic filling factor $ν=1/2$, the lowest Landau level constraint implies that at any temperature, and in the presence of {\it any} amount of particle-hole symmetric disorder, the {\it composite fermion} Hall conductivity is precisely $-e^2/2h$. (The electronic Hall conductivity is $e^2/2h$.) This is inconsistent with the response of a co

M. Belkacem, P. F. Mastinu, V. Latora, A. Bonasera

Within the framework of Classical Molecular Dynamics, we study the collision Au + Au at an incident energy of 35 MeV/nucleon. It is found that the system shows a critical behaviour at peripheral impact parameters, revealed through the analysis of conditional moments of charge distributions, Campi Scatter Plot, and the occurrence of large fluctuations in the

M Hjorth-Jensen, A Polls, A Ramos, H Muether

The self--energy of the strange baryon $Λ$ in $^{17}$O is calculated using a microscopic many--body approach which accounts for correlations beyond the mean--field or Hartree--Fock approximation. The non-locality and energy-dependence of the $Λ$ self--energy is discussed and the effects on the bound and scattering states are investigated. For the nucleon--hy

Z. Papp, W. Plessas

We demonstrate the feasibility and efficiency of the Coulomb-Sturmian separable expansion method for generating accurate solutions of the Faddeev equations. Results obtained with this method are reported for several benchmark cases of bosonic and fermionic three-body systems. Correct bound-state results in agreement with the ones established in the literatur

F. Aldabe

T-duality has been shown to arise from a gauge symmetry in some string theories. However, in the case of \IIA\ compactified on a circle, it is not possible to show that this is the case. This situation is rather uncomfortable since string string duality suggests that all T-dualities should arise from a gauge symmetry. Here we show that the T-duality of \IIA\

Claudia Daboul

I give a relatively elementary proof of the symmetric space theorem, due to Goddard, Nahm and Olive \cite{GNO}. Unlike their original proof, which involves the quark-model construction, I only use elementary algebraic techniques.

F. Aldabe

We show that the open membrane action on $T^3\times S^1/Z^2$ is equivalent to the closed membrane action on K3. The main difference between the two actions is that one generates the KK modes in the worldvolume action which is the strong coupling limit of \IIA\ while the other action generates the KK modes in a worldsheet action. Thus explaining membrane-stri

L. Burakovsky, L. P. Horwitz

We prove the uncertainty relation $T_{\triangle V}\triangle m\stackrel{>}{\sim }2π\hbar /c^2,$ which is realized on a statistical mechanical level for an ensemble of events in $(1+D)$-dimensional spacetime with motion parametrized by an invariant ``proper time'' $τ,$ where $T_{\triangle V}$ is the average passage interval in $τ$ for the events which

M. Bauer, A. Coste, C. Itzykson, P. Ruelle

We examine the proposal made recently that the su(3) modular invariant partition functions could be related to the geometry of the complex Fermat curves. Although a number of coincidences and similarities emerge between them and certain algebraic curves related to triangular billiards, their meaning remains obscure. In an attempt to go beyond the su(3) case,

E. S. Ackleh, T. Barnes, E. S. Swanson

Open-flavor strong decays are mediated by $q\bar q$ pair production, which is known to occur dominantly with \3p0 quantum numbers. The relation of the phenomenological \3p0 model of these decays to ``microscopic" QCD decay mechanisms has never been clearly established. In this paper we investigate $q\bar q$ meson decay amplitudes assuming pair production

P. Kroll, M. Schuermann, K. Passek, W. Schweiger

The reactions gamma p -> K+ Lambda and gamma p -> K* Lambda are analyzed within perturbative QCD, allowing for diquarks as quasi-elementary constituents of baryons. The diquark-model parameters and the quark-diquark distribution amplitudes of proton and Lambda are taken from previous investigations of electromagnetic baryon form factors and Compton-scatterin

Christopher Balzereit, Thorsten Ohl

We present a new calculation of the renormalized HQET Lagrangian at order O(1/m_Q^2) and discuss the consequences of the BRST invariance of QCD and the reparameterization invariance of HQET. Our result corrects earlier, conflicting calculations and sets the stage for the calculation of the renormalized currents at order O(1/m_Q^2).

M. A. Braun

Within the hard pomeron approach it is shown that the triple pomeron interaction gives no contribution to the cross-section for a projectile with large enough virtuality $g^{2}\ln Q^{2}\sim 1$. For small virtualities $g^{2}\ln Q^{2}<<1$ its contribution is essential.

Thomas DeGrand, Anna Hasenfratz, Decai Zhu

We construct a few parameter approximate fixed point action for SU(2) pure gauge theory and subject it to scaling tests, via Monte Carlo simulation. We measure the critical coupling for deconfinement for lattices of temporal extent $N_t=2$, 3, 4, the torelon mass at fixed physical volume, and the string tension (and heavy quark potential) from Wilson loops.

Bas van den Heuvel

We consider the effective theory for the low-energy modes of SU(2) gauge theory on the three-sphere. By explicitely integrating out the high-energy modes, the one-loop correction to the hamiltonian for this problem is obtained. We calculate the influence of this correction on the glueball spectrum.

Tereza Mendes, Andrea Pelissetto, Alan D. Sokal

We introduce a variant of the multi-grid Monte Carlo (MGMC) method, based on the embedding of an $XY$ model into the target model, and we study its mathematical properties for a variety of nonlinear $σ$-models. We then apply the method to the two-dimensional $O(N)$-symmetric nonlinear $σ$-models (also called $N$-vector models) with $N=3,4,8$ and study its dy

Werner M. Vieira, Patricio S. Letelier

A solution of the Einstein&#39;s equations that represents the superposition of a Schwarszchild black hole with both quadrupolar and octopolar terms describing a halo is exhibited. We show that this solution, in the Newtonian limit, is an analog to the well known Hénon-Heiles potential. The integrability of orbits of test particles moving around a black hole

Heinz-Dieter Conradi

The meaning of `tunneling&#39; in a timeless theory such as quantum cosmology is discussed. A recent suggestion of `tunneling&#39; of the macroscopic universe at the classical turning point is analyzed in an anisotropic and inhomogeneous toy model. This `inhomogeneous tunneling&#39; is a local process which cannot be interpreted as a tunneling of the univers

E. J. Vlachynsky, R. Tresguerres, Yu. N. Obukhov, F. W. Hehl

We present an exact stationary {\it axially symmetric} vacuum solution of metric-affine gravity (MAG) which generalises the recently reported spherically symmetric solution. Besides the metric, it carries nonmetricity and torsion as post-Riemannian geometrical structures. The parameters of the solution are interpreted as mass and angular momentum and as dila

Daniel Boies, Claude Bourbonnais, A. -M. S. Tremblay

The stability of the Luttinger liquid to small transverse hopping has been studied from several points of view. The renormalization group approach in particular has been criticized because it does not take explicitly into account the difference between spin and charge velocities and because the interaction should be turned-on before the transverse hopping if

D. F. Wang

In this work, the ground states of the Hubbard model on complete graph are studied, for a finite lattice size $L$ and arbitrary on-site energy $U$. We construct explicitly the ground states of the system when the number of the electrons $N_e \ge L+1$. In particular, for $N_e=L+1$, the ground state is ferromagnetic with total spin $s_g=(N_e-2)/2$.

Ana Achucarro, Juan L. Manes

Following Bogomolnyi&#39;s classical treatment of vortices, we develop a method for finding rigorous lower bounds to the Landau-Ginzburg free energy describing unconventional superconductors in the absence of external magnetic fields. This allows a more precise description of the magnetic instabilities previously considered in these systems. In particular, w

Alex Buchel, James P. Sethna

Nonlinear elastic theory studies the elastic constants of a material (such as Young&#39;s modulus or bulk modulus) as a power series in the applied load. The inverse bulk modulus K, for example depends on the compression P: $ {1/ K(P)} = c_0 + c_1 P + c_2 P^2 \cdots + c_n P^n + \cdots $. Elastic materials that allow cracks are unstable at finite temperature

Uwe Grimm, Michael Baake

We consider several aspects of non-periodic Ising models in one and two dimensions. Here we are not interested in random systems, but rather in models with intrinsic long-range aperiodic order. The most prominent examples in one dimension are sequences generated by substitution rules on a finite alphabet. The classical one-dimensional Ising chain as well as

Robert Dale, Ehud Reiter

Grice&#39;s maxims of conversation [Grice 1975] are framed as directives to be followed by a speaker of the language. This paper argues that, when considered from the point of view of natural language generation, such a characterisation is rather misleading, and that the desired behaviour falls out quite naturally if we view language generation as a goal-ori

Péter Pollner, Gábor Vattay

The topological pressure introduced by Ruelle and similar quantities describe dynamical multifractal properties of dynamical systems. These are important characteristics of mesoscopic systems in the classical regime. Original definition of these quantities are based on the symbolic description of the dynamics. It is hard or impossible to find symbolic descri

Jaroslaw Kwapien, Wojciech Slomczynski, Karol Zyczkowski

Coherent states (CS) quantum entropy can be split into two components. The dynamical entropy is linked with the dynamical properties of a quantum system. The measurement entropy, which tends to zero in the semiclassical limit, describes the unpredictability induced by the process of a quantum approximate measurement. We study the CS--measurement entropy for

V. Emsellem, L. Kadanoff, D. Lohse, P. Tabeling

Previous analysis of a Paris turbulence experiment \cite{zoc94,tab95} shows a transition at the Taylor Reynolds number $\rel \approx 700$. Here correlation function data is analyzed which gives further evidence for this transition. It is seen in both the power spectrum and in structure function measurements. Two possible explanations may be offered for this

M. Ostrowski, R. Schlickeiser

In the present paper we discuss the modifications introduced into the first-order Fermi shock acceleration process due to a finite extent of diffusive regions near the shock or due to boundary conditions leading to an increased particle escape upstream and/or downstream the shock. In the considered simple example of the planar shock wave we idealize the esca

J. I. Katz

Sillanpää, {\it et al.} (1996) have demonstrated that the AGN OJ287 has intensity peaks which recur with a period of about 12 years. I suggest that this is the result of the sweeping of a precessing relativistic beam across our line of sight. In analogy to Her~X-1 and SS433, precession is attributed to the torque exerted by a companion mass on an accretion d

R. D. Blum, K. Sellgren, D. L. DePoy

J, H, K, and L photometry for the stars in the central 2&#39; (5 pc) of the Galaxy are presented. Using the observed J-H, H-K, and K-L colors and assumed intrinsic colors, we determine the interstellar extinction at 2.2 mic (A_K) for approximately 1100 individual stars. The mean A_K (= 3.3 mag) is similar to previous results, but we find that the reddening i

Ulrich Lindner, Jaan Einasto, Maret Einasto, Klaus J. Fricke

We introduce Void Hierarchy as an important property of the Large--Scale Structure in the Universe and demonstrate how it can be used to interpret observations. Moreover the void hierarchy constraints any realistic galaxy and structure formation scenario.

Ulrich Lindner, Uta Fritze - von Alvensleben, Klaus J. Fricke

We have made an attempt to compile all currently available data on optically identified QSO absorber systems (Lindner et al. 1996) to establish the status quo of absorber galaxy data as a basis for the investigation of galaxy evolution. We present a first comparison with results from our galaxy evolutionary synthesis models to demonstrate the potential power

Jane C. Charlton, Christopher W. Churchill

Quasar absorption lines provide detailed information on the chemical, kinematic, and ionization conditions in galaxies and their environments, and provide a means for studying the evolution of these conditions back to the epoch of the first quasars. Among the collection of absorbing structures along the lines of sight to quasars there is an evolutionary sequ

Andrew R Liddle

A brief account is given of large-scale structure modelling based on the assumption that the initial perturbations arise from inflation. A recap is made of the implications of inflation for large-scale structure; under the widely applicable slow-roll paradigm inflation adds precisely two extra parameters to the normal scenarios, which can be taken to be the

D. Reimers, S. Jordan, D. Koester, N. Bade

Four magnetic white dwarfs have been found in the course of the Hamburg/ESO Survey for bright QSOs. The objects have been selected as QSO candidate on the basis of its blue continuum and the apparent absence of strong hydrogen or helium lines. One star, HE1211-1707, shows a rather fast spectral variability: both the strength and the position of the shallow a

Takahiro T. Nakamura, Ewan D. Stewart

We derive general analytic formulae for the power spectrum and spectral index of the curvature perturbation produced during inflation driven by a multi-component inflaton field, up to the second order in the slow-roll approximation. We do not assume any specific properties of the potential or the metric on the scalar field space, except for the slow-roll con

M. Hernanz, J. Jose, A. Coc, J. Isern

The production of ^7 Li and ^7 Be during the explosive hydrogen-burning that occurs in nova explosions is computed by means of a hydrodynamic code able to treat both the accretion and the explosion stages. Large overproduction factors with respect to solar abundances are obtained, the exact value depending mainly on the chemical composition of the envelope.

Sangjin Lee

The origin and nature of ultrahigh energy cosmic rays with energies above $10^{20}\,$eV is a puzzle for the physics and astrophysics of cosmic rays which is still unresolved. In this paper, I report on an extensive study on the propagation of extragalactic nucleons, $γ$-rays, and electrons in the energy range between $10^8\,$eV and $10^{23}\,$eV. I have devi

Nicole P. Vogt, Duncan A. Forbes, Andrew C. Phillips, Caryl Gronwall

Spatially resolved velocity profiles are presented for nine faint field galaxies in the redshift range 0.1 < z < 1, based on moderate-resolution spectroscopy obtained with the Keck 10 m telescope. These data were augmented with high-resolution HST images from WFPC2, which provided V and I photometry, galaxy type, orientation, and inclination. The effects of

Bo-Qiang Ma

The strange sea quarks distributions of nucleons obtained by two global analyses based on available structure function data of muon and neutrino deep inelastic scatterings are different from the strange sea quark distribution measured by the CCFR Collaboration from dimuon events in neutrino scattering. We discuss possible contributions to this discrepancy fr

Marc Davis, Adi Nusser, Jeff Willick

We consider a measure of the peculiar velocity field derived from the Mark III compilation of 2900 spiral galaxies (Willick \etal 1996b), using an analysis that is substantially free of bias (Nusser and Davis 1995). We expand the velocity field in a set of orthogonal, smooth modes, reducing the data to a set of 56 coefficients fitted to a maximum redshift of

Tomasz Brzezinski

We show how the method of separation of variables can be used to construct integrable models corresponding to curves describing vacuum structure of four-dimensional ${\cal N} = 2$ SUSY Yang-Mills theories. We use this technique to construct models corresponding to $SU(N)$ Yang-Mills theory with $N_f<2N$ matter hypermultiplets by generalising the periodic Tod

Andre&#39; Leclair

We consider a fibrillar medium with a continuous distribution of two-level atoms coupled to quantized electromagnetic fields. Perturbation theory is developed based on the current algebra satisfied by the atomic operators. The one-loop corrections to the dispersion relation for the polaritons and the dielectric constant are computed. Renormalization group eq

Gabor Takacs

The RSOS restriction of the Zhiber-Mikhailov-Shabat (ZMS) model is investigated. It is shown that in addition to the usual RSOS restriction, corresponding to $Φ_{(1,2)}$ and $Φ_{(2,1)}$ perturbations of minimal CFT, there is another one which yields $Φ_{(1,5)}$ perturbations of non-unitary minimal models. The new RSOS restriction is carried out and the parti

Sergio Ferrara, Ruben Minasian, Augusto Sagnotti

We elucidate the interplay between gauge and supersymmetry anomalies in six-dimensional $N=1$ supergravity with generalized couplings between tensor and vector multiplets. We derive the structure of the five-dimensional supergravity resulting from the $S_1$ reduction of these models and give the constraints on Chern-Simons couplings that follow from duality

J. -G. Zhou, Y. -G. Miao, J. -Q. Liang, H. J. W. Mueller-Kirsten

The constraint structure of 2D-gravity with the Weyl and area-preserving diffeomorphism invariances is analysed in the ADM formulation. It is found that when the area-preserving diffeomorphism constraints are kept, the usual conformal gauge does not exist, whereas there is the possibility to choose the so-called ``quasi-light-cone'' gauge, in which besides t

T. Feuster, U. Mosel

An effective Lagrangian calculation of pion photoproduction including all nucleon resonances up to $\sqrt s = 1.7$ GeV is presented. We compare our results to recent calculations and show the influence of different width parametrizations and offshell cutoffs on the photoproduction multipoles. We determine the electromagnetic couplings of the resonances from

P. Lombardo, J. Schmalian, M. Avignon, K. -H. Bennemann

Using the Hubbard Hamiltonian for transition metal-3d and oxygen-2p states with perovskite geometry, we present a dynamical mean field theory which becomes exactin the limit of large coordination numbers or equivalently large spatial dimensions $D$. The theory is based on a new description of these systems for large $D$ using a selective treatment of differe

Shuhei Yamaji, Fedor A. Ivanyuk, Helmut Hofmann

We study slow collective motion at finite thermal excitations on the basis of linear response theory applied to the locally harmonic approximation. The transport coefficients for average motion, friction γ, inertia M and the local stiffness C are computed along a fission path of Th-224 within a quasi-static picture. The inverse relaxation time β=γ/M and the

Brian D. Fields, Grant J. Mathews, David N. Schramm

We present a schematic model for the formation of baryonic galactic halos and hot gas in the Local Group and the intergalactic medium. We follow the dynamics, chemical evolution, heat flow and gas flows of a hierarchy of scales, including: protogalactic clouds, galactic halos, and the Local Group itself. Within this hierarchy, the Galaxy is built via mergers

K. Yonemitsu, M. Imada

Asymptotic properties of nearly-half-filled one-dimensional conductors coupled with phonons are studied through a renormalization group method. Due to spin-charge coupling via electron-phonon interaction, the spin correlation varies with filling as well as the charge correlation. Depending on the relation between cut-off energy scales of the Umklapp process

David E. Brahm

The $\Zbb$ excess, $\Zcc$ deficit, and low left-right asymmetry $A_b$ may be explained by a single term $\lam C^c B^c B^{\prime c}$ in the superpotential. This operator violates R-parity and requires a sequential 4th generation. 1-loop diagrams involving squark exchange interfere with the tree-level processes to give an excess of right-handed $b$ quarks, and

D. T. Son

We consider a simple model for the Universe reheating, which consists of a single self--interacting scalar field in Minkowskian space--time. Making use of the existence of an additional small parameter proportional to the amplitude of the initial spatially homogeneous field oscillations, we show that the behavior of the field can be found reliably. We descri

E. Alfinito, M. Leo, R. A. Leo, M. Palese

The Estabrook-Wahlquist prolongation method is applied to the (compact and noncompact) continuous isotropic Heisenberg model in 1 + 1 dimensions. Using a special realization (an algebra of the Kac-Moody type) of the arising incomplete prolongation Lie algebra, a whole family of nonlinear field equations containing the original Heisenberg system is generated.

R. Cenni, F. Conte, P. Saracco

The nuclear response is evaluated in the frame of the bosonic loop expansion in a purely nucleonic dynamical scheme, which seems to be reliable in handling those channels where a direct excitation of a $Δ$-resonance is not allowed. It is shown that the response strongly depends upon the effective interaction in the spin-transverse isovector channel. New expe

Y. Kondo, S. Saito, Y. Tanushi, M. Uehara

Strong pion and kaon couplings to hyperons are given in the bound-state approach to the Skyrme model.

Ofer Aharony

We analyze how string theory dualities may be described in M theory. T dualities arise from scalar-vector dualities in the worldvolume of the membrane of M theory. ``Electric-magnetic&#39;&#39; dualities arise from a duality transformation in M theory compactified on a 3-torus, which takes the membrane into a fivebrane wrapped around the 3-torus.

Artemio Gonzalez-Lopez, Niky Kamran, Peter J. Olver

We first establish some general results connecting real and complex Lie algebras of first-order differential operators. These are applied to completely classify all finite-dimensional real Lie algebras of first-order differential operators in $R^2$. Furthermore, we find all algebras which are quasi-exactly solvable, along with the associated finite-dimension

Harald W. Griesshammer, Alex C. Kalloniatis

We characterise a class of SU(2) gluonic field configurations in the modified axial gauge where a zero mode component vanishes at some space point but the global Haar measure remains non-zero. The consequence of this is that gluonic wavefunctionals need not vanish at the boundary of the fundamental modular domain, which itself permits $θ$ dependence in QCD(3

Andre Lukas, Alexander Niemeyer, Masahiro Yamaguchi

We analyze the behaviour of moduli fields in string effective models between the end of inflation and reheating. The effective moduli potential during this era is derived for a class of simple models. We argue that this potential significantly stabilizes the modulus at its high energy minimum, if some restrictions on modular weights are met. Two mechanisms t

Marcos Jardim

In this paper we derive in a coordinate-free manner the field equations for a lagrangean consisting of Yang-Mills kinetical term plus Chern-Simons self-coupling term. This equation turns out to be an eigenvalue equation for the covariant laplacian.

Fernando Falceto, Krzysztof Gawedzki

We work out finite-dimensional integral formulae for the scalar product of genus one states of the group $G$ Chern-Simons theory with insertions of Wilson lines. Assuming convergence of the integrals, we show that unitarity of the elliptic Knizhnik-Zamolodchikov-Bernard connection with respect to the scalar product of CS states is closely related to the Beth

V. Karimipour

We prove that the dynamical system charaterized by the Hamiltonian $ H = λN \sum_{j}^{N} p_j + μ\sum_{j,k}^{N} {{(p_j p_k)}^{1\over 2}} \{ cos [ ν( q_j - q_k)] \} $ proposed and studied by Calogero [1,2] is equivalent to a system of {\it non-interacting} harmonic oscillators. We find the explicit form of the conserved currents which are in involution. We als

S. Groote, J. G. Körner, O. I. Yakovlev

We present results on the two-loop anomalous dimensions of the heavy baryon HQET currents $J=(q^TCΓτq)Γ&#39;Q$ with arbitrary Dirac matrices $Γ$ and $Γ&#39;$. From our general result we obtain the two-loop anomalous dimensions for currents with quantum numbers of the ground state heavy baryons $Λ_Q$, $Σ_Q$ and $Σ_Q^*$. As a by-product of our calculation and

Jari Häkkinen

We show that experimental data are in very good agreement with predictions from the string fragmentation model by Bowler and Morris. We present a physical interpretation and discuss the relation to results obtained from Perturbative QCD and Local Hadron Parton Duality (LPHD). We also present implications for B$π$ correlations and the possibility to use these

C. Friberg, G. Gustafson, J. Häkkinen

We have a very limited knowledge about how the confinement mechanism works in processes like $\epea\epe\ra\epq\epqa\ggn\ldots\ggn$, when there are identical colour charges. In this case the partons can be connected by a string or a cluster chain in several different ways. We do not know if in such a situation Nature chooses a particular configuration at rand

Piotr Zenczykowski

Within the standard model, CP-violating asymmetries A(Λ^0_-) and A(Ξ^-_-) have been estimated in short-distance calculations to occur at the level of a few times 10^{-5}. We show here that in this model the dispersive contribution tends to give asymmetries of similar size.

B. Badelek, J. Bartels, N. Brook, A. De Roeck

We summarize the developments on the structure of the proton that were studied at the Workshop on &#34;HERA Physics&#34; that was held in Durham in September 1995. We survey the latest structure function data; we overview the QCD interpretations of the measurements of the structure functions and of final state processes; we discuss charm production and the s

Giampiero Passarino

The status of the standard model is briefly reviewed in the light of the most recent set of experimental data, with particular emphasis to the limits on the Higgs boson mass. The search for a light Higgs boson at LEP~2 is also briefly analyzed.

K. Tamvakis

We study $R$-parity violation in the framework of GUTs, focusing on the case that $R$-parity is broken exclusively through $ΔB=1$, $ΔL=0$ effective interactions. We construct two such models, an $SU(5)$ and an $SU(5)\times U(1)_{X}$ model, in which $R$-parity breaking is induced through interactions with extra supermassive fields. The presence of only the Ba

Michael E. Peskin

If Nature is supersymmetric at the weak interaction scale, what can we hope to learn from experiments on supersymmetric particles? The most mysterious aspect of phenomenological supersymmetry is the mechanism of spontaneous supersymmetry breaking. This mechanism ties the observable pattern of supersymmetric particle masses to aspects of the underlying unifie

Karl Jansen, Beat Jegerlehner, Chuan Liu

Three topics concerning fermion simulation algorithms are discussed: 1.) A performance comparison of the multiboson technique to simulate dynamical fermions and the Kramers equation algorithm, 2.) the question of reversibility in the Hybrid Monte Carlo algorithm and 3.) the implementation of Symanzik&#39;s improvement program for dynamical Wilson fermions.

U. Glässner, S. Güsken, H. Hoeber, Th. Lippert

We present a lattice calculation of the interquark potential between static quarks in a ``full&#39;&#39; QCD simulation with 2 flavours of dynamical Wilson-quarks at three intermediate sea-quark masses. We work at $β= 5.6$ on lattice size of $16^3 \times 32$ with 100 configurations per sea-quark mass. We compare the full QCD potential with its quenched count

Rainer Pietig, Franz J. Wegner

We prove the existence of an ordered low temperature phase in a model of soft-self-avoiding closed random surfaces on a cubic lattice by a suitable extension of Peierls contour method. The statistical weight of each surface configuration depends only on the mean extrinsic curvature and on an interaction term arising when two surfaces touch each other along s

Mario Castagnino

It is demonstrated how a convenient choice of the mathematical structure of the quantum cosmology superspace, precisely the definition of a convenient regular state superspace and the restriction of the dynamics to this space, yields directly to an irreversible evolution, in the classical (and semiclassical) phase of the universe, where: Decoherence and corr

Roberto Longo, John E. Roberts

In which a theory of dimension related to the Jones index and based on the notion of conjugation is developed. An elementary proof of the additivity and multiplicativity of the dimension is given and there is an associated trace. Applications are given to a class of endomorphisms of factors and to the theory of subfactors. An important role is played by a no

N. B. Wilding, M. Mueller, K. Binder

We report grand canonical Monte Carlo simulations of the critical point properties of homopolymers within the Bond Fluctuation model. By employing Configurational Bias Monte Carlo methods, chain lengths of up to N=60 monomers could be studied. For each chain length investigated, the critical point parameters were determined by matching the ordering operator

Kikuo Harigaya

Variations in the band structures of C60-polymers are studied, when conjugation conditions and the electron number are changed. We use a semiempirical model with the Su-Schrieffer-Heeger type electron-phonon interactions. In the neutral one-dimensional C60-polymer, electronic structures change among direct-gap insulators and the metal, depending on the degre

N. Persky, I. Kanter, S. Solomon

In simulations of some infinite range spin glass systems with finite connectivity, it is found that for any resonable computational time, the saturatedenergy per spin that is achieved by a cluster algorithm is lowered in comparison to that achieved by Metropolis dynamics.The gap between the average energies obtained from these two dynamics is robust with res

M. S. Li, T. Nattermann, H. Rieger, M. Schwartz

The stability of the ordered phase of the three-dimensional XY-model with random phase shifts is studied by considering the roughening of a single stretched vortex line due to the disorder. It is shown that the vortex line may be described by a directed polymer Hamiltonian with an effective random potential that is long range correlated. A Flory argument est

A. M. Somoza, U. Marini Bettolo Marconi, P. Tarazona

We present a theoretical study for the intermediate stages of the growth of membranes and vesicles in supersaturated solutions of amphiphilic molecules. The problem presents important differences with the growth of droplets in the classical theory of Lifshitz-Slyozov-Wagner, because the aggregates are extensive only in two dimensions, but still grow in a thr

J. P. Rodriguez, Pascal Lederer

By exploiting the internal gauge-invariance intrinsic to a spin-charge separated electron, we show that such degrees of freedom must be confined in two-dimensional superconductors experiencing strong inter-electron repulsion. We also demonstrate that incipient confinement in the normal state can prevent chiral spin-fluctuations from destroying the cross-over

Masanori Yamanaka, Masaki Oshikawa, Seiji Miyashita

We study ground state properties of the $S=2$ quantum antiferromagnetic chain with a bond alternation \[ H = \sum_{j} [ 1 + δ(-1)^j ] \mbox{\boldmath $S$}_{j} \cdot \mbox{\boldmath $S$}_{j+1} \] by a Quantum Monte Carlo calculation. We find that the hidden $Z_2 \times Z_2$ symmetry is broken for $0.3 < |δ| < 0.5$ while it is unbroken in the other regions. Th

Thorsten Brants

This paper investigates model merging, a technique for deriving Markov models from text or speech corpora. Models are derived by starting with a large and specific model and by successively combining states to build smaller and more general models. We present methods to reduce the time complexity of the algorithm and report on experiments on deriving languag

M. H. van Kerkwijk, T. R. Geballe, D. L. King, M. van der Klis

We present orbital-phase resolved I and K-band spectroscopy of Cygnus X-3. All spectra show emission lines characteristic of Wolf-Rayet stars of the WN subclass. On time scales longer than about one day, the line strengths show large changes, both in flux and in equivalent width. In addition, the line ratios change, corresponding to a variation in spectral s

Joshua S. Bloom, Edward E. Fenimore, Jean in 't Zand

Recent analysis of relativistically expanding shells of cosmological gamma-ray bursts has shown that if the bursts are cosmological, then most likely total energy (E_0) is standard and not peak luminosity (L_0). Assuming a flat Friedmann cosmology (q_o = 1/2, Lambda = 0) and constant rate density (rho_0) of bursting sources, we fit a standard candle energy t

M. Teresa Ceballos, Xavier Barcons

We analyse the ROSAT PSPC hardness ratio and the 0.5-2 keV to 2-10 keV flux ratio of 65 Active Galactic Nuclei (AGN) for which there are both ROSAT archival observations available and 2-10 keV fluxes, mostly from the HEAO-1 MC-LASS survey. We conclude that the simplest spectral model for the AGN that can accommodate the variety of X-ray colours obtained is a

M. Rovinsky

I prove that for any complex projective variety $X$ and a sufficiently large integer $N$ all the fibers of Albanese map of the $N$-th configuration space of $X$ are dominated by smooth connected projective varieties with vanishing ${\rm H}^1$.

A. Amatuni

The perturbative approach for describing the underdense plasma--ultrarelativistic electron bunch system is developed, using the ratio $\frac{n_0}{n_b}$ as a small parameter ($n_b$--bunch,$n_0$--plasma electron densities). Focusing of the electron bunch emerged in the first approximation of the perturbative procedure as a result of the plasma electrons redist

Liviu Tătaru, Ion V. Vancea

A method for the calculation of the BRST cohomology, recently developed for 2D gravity theory and the bosonic string in the Beltrami parametrization,is generalised to the superstring theories quantized in super-Beltrami parametrization.

Guenter Sigl, Sangjin Lee, Paolo Coppi

We explore scenarios where the highest energy cosmic rays (HECR) are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic cosmic and gamma-ray propagation, we show the existence of a significant parameter space for which such scenarios are consistent with all observational constraints. An av

I. R. Klebanov, A. A. Tseytlin

We carry out a thorough survey of entropy for a large class of $p$-branes in various dimensions. We find that the Bekenstein-Hawking entropy may be given a simple world volume interpretation only for the non-dilatonic $p$-branes, those with the dilaton constant throughout spacetime. The entropy of extremal non-dilatonic $p$-branes is non-vanishing only for t

Stuart Samuel

Analytical solutions are obtained to the nonlinear equations describing neutrino oscillations when explicit neutrino-antineutrino asymmetries are present. Such a system occurs in the early Universe if neutrinos have a non-zero chemical potential. Solutions to the equations lead to a new type of coherent behavior governed by two modes. These bimodal solutions

M. B. Voloshin

It is shown that the absolute rate of the semileptonic decays of the $Ξ_c$ baryons can be as much as two times higher than the semileptonic decay rate of $Λ_c$ due to the Pauli interference of the strange quark. This interference effect is still larger in the semileptonic decay rate of $Ω_c$. An experimental measurement of the difference of these rates would

Bruce Allen

A world-wide effort is now underway to build gravitational wave detectors based on highly-sensitive laser interferometers. When data from detectors at different sites is properly combined, it will permit highly-sensitive searches for a stochastic background of relic gravitational radiation. These lectures (from the Les Houches School in October 1995) review

E. Atzmon

In a one-dimensional lattice, the induced metric (from a noncommutative geometry calculation) breaks translation invariance. This leads to some inconsistencies among different spectator frames, in the observation of the hoppings of a test particle between lattice sites. To resolve the inconsistencies between the different spectator frames, we replace the tes

Yaroslav M. Blanter

The inelastic quasiparticle lifetime due to the electron-electron interaction (out-scattering time in the kinetic equation formalism) is calculated for finite metallic diffusive systems (quantum dots) in the whole range of parameters. Both cases of ``continuous&#39;&#39; (the inelastic level broadening much exceeds the mean level spacing) and ``discrete&#39;