August 1995 arXiv papers — page 7

K. Varga, Y. Suzuki

Precise variational solutions are given for problems involving diverse fermionic and bosonic $N=2-7$-body systems. The trial wave functions are chosen to be combinations of correlated Gaussians, which are constructed from products of the single-particle Gaussian wave packets through an integral transformation, thereby facilitating fully analytical calculatio

David B. Jaffe

This research announcement describes in very rough terms methods and a computer language under development, which can be used to prove the nonexistence of binary linear codes. Over a hundred new results have been obtained by the author. For example, there is no [29,11,10] code. The proof of this is roughly outlined.

Jie Wu

We give a combinatorial description of homotopy groups of $ΣK(π,1)$. In particular, all of the homotopy groups of the $3$-sphere are combinatorially given.

Harumi Tanigawa

Grafting is a surgery on Riemann surfaces introduced by Thurston which connects hyperbolic geometry and the theory of projective structures on surfaces. We will discuss the space of projective structures in terms of the Thurston's geometric parametrization given by grafting. From this approach we will prove that on any compact Riemann surface with genus

Hiroshige Shiga, Harumi Tanigawa

Let $K(X)$ denote the set of projective structures on a compact Riemann surface $X$ whose holonomy representations are discrete. We will show that each component of the interior of $K(X)$ is holomorphically equivalent to a complex submanifold of the product of Teichmüller spaces and the holonomy representation of every projective structure in the interior of

H. Banerjee

Definition of the determinant of Euclidean Dirac operator in the nontrivial sector of gauge fields suffers from an inherent ambiguity. The popular Osterwalder-Schrader (OS) recipe for the conjugate Dirac field leads to the option of a vanishing determinant. We propose a novel representation for the conjugate field which depends linearly on the Dirac field an

Ashoke Sen, Cumrun Vafa

Using a $U$-duality symmetry of type II compactification on $T^4$ represented by triality action on the $T$-duality group, and applying the adiabatic argument we construct dual pairs of type II compactifications in lower dimensions. The simplicity of this construction makes it an ideal set up for testing various conjectures about string dualities. In some of

Eqab M. Rabei

The link between the treatment of singular lagrangians as field systems and the general approch is studied. It is shown that singular Lagrangians as field systems are always in exact agreement with the general approch. Two examples and the singular Lagrangian with zero rank Hessian matrix are studied. The equations of motion in the field systems are equivale

S. Ichinose

Two dimensional quantum R$^2$-gravity is formulated in the semiclassical method. The thermodynamic properties,such as the equation of state, the temperature and the entropy, are explained. The topology constraint and the area constraint are properly taken into account. A total derivative term and an infrared regularization play important roles. The classical

S. Ichinose, N. Tsuda, T. Yukawa

We analyse MINBU distribution of 2 dimensional quantum gravity. New data of R$^2$-gravity by the Monte Carlo simulation and its theoretical analysis by the semiclassical approach are presented. The cross-over phenomenon takes place at some size of the baby universe where the randomness competes with the smoothing force of $R^2$-term. The dependence on the ce

Mirjam Cvetič, Donam Youm

We summarize results for all four-dimensional Bogomol'nyi-Sommerfield-Prasat (BPS) saturated and non-extreme solutions of the ($4+n$)-dimensional Abelian Kaluza-Klein theory. Within effective N=4 supersymmetric string vacua, parameterized in terms of fields of the heterotic string on a six-torus, we then present a class of BPS saturated states and the co

A. Ayala, J. Jalilian--Marian, L. Mclerran, R. Venugopalan

We compute the quantum corrections to the gluon distribution function in the background of a non--Abelian Weizsäcker--Williams field. These corrections are valid to all orders in the effective coupling $α_s μ$, where $μ^2$ denotes the average valence quark color charge squared per unit area. We find $\ln(1/x)$ logarithmic corrections to the classical gluon d

I. I. Bigi

The recent progress in our understanding of heavy-flavour decays allows us to define more reliably which future measurements on charm decays are needed to further advance our understanding of QCD and to get our theoretical tools ready for treating beauty decays. After sketching the theoretical landscape I list those required measurements. I argue that some -

Biswajoy Brahmachari, Rabindra N. Mohapatra

We review various ways of obtaining consistency between the idea of supersymmetric grand unification and an apparent low value of $α_s \sim 0.112$ indicated by several low energy experiments. We argue that to reconcile the low value of $α_s$ with the predictions of supersymmetric GUTs, we need to go beyond the standard minimal supersymmetric GUT scenario and

Glennys R. Farrar

When SUSY breaking produces only dimension-2 terms in the minimal supersymmetric standard model, the parameters of the theory can be rather well constrained. This paper deals with strategies for the detection of the new hadrons predicted in the 1-3 GeV mass range. Some limits are obtained. New signatures for squarks are also given. Squark masses as small as

Glennys R. Farrar

I explore an economical variant on supersymmetric standard models which may be indicated on cosmological grounds and is shown to have no SUSY-CP problem. Demanding radiative electroweak symmetry breaking suggests that the Higgs is light; other scalar masses may be ~ 100-200 GeV or less. In this case the gluino and photino, while massless at tree level, have

Yoshiharu Kawamura

From general supergravity theory with unified gauge symmetry, we obtain the low-energy effective Lagrangian by taking the flat limit and integrating out the superheavy fields in model-independent manner. The scalar potential possesses some excellent features. Some light fields classified by using supersymmetric fermion mass, in general, would get intermediat

Martin Bäker

The principle of indirect elimination states that an algorithm for solving discretized differential equations can be used to identify its own bad-converging modes. When the number of bad-converging modes of the algorithm is not too large, the modes thus identified can be used to strongly improve the convergence. The method presented here is applicable to any

J. Greensite

It is shown that the classical field equations pertaining to gravity coupled to other bosonic fields are equivalent to a single geodesic equation, describing the free fall of a point particle in superspace. Some implications for quantum gravity are discussed.

Peter D. D'Eath, Giampiero Esposito

The problem of boundary conditions in a supersymmetric theory of quantum cosmology is studied, with application to the one-loop prefactor in the quantum amplitude. Our background cosmological model is flat Euclidean space bounded by a three-sphere, and our calculations are based on the generalized Riemann zeta-function. One possible set of supersymmetric loc

E. J. Copeland, Amitabha Lahiri

We demonstrate that under plausible assumptions the entropy and temperature associated with the small oscillations on a circular loop of radius $R$ and a black hole of mass $M=R/2G$ are identical.

Giampiero Esposito

The necessary and sufficient condition for the existence of $α$-surfaces in complex space-time manifolds with nonvanishing torsion is derived. For these manifolds, Lie brackets of vector fields and spinor Ricci identities contain explicitly the effects of torsion. This leads to an integrability condition for $α$-surfaces which does not involve just the self-

Yasunori Fujii

Based on our previous attempt, we propose a better way to understand a small but nonzero cosmological constant, as indicated by a number of recent observational studies. We re-examine the assumptions of our model of two scalar fields, trying to explain the basic mechanism resulting in a series of mini-inflations occuring nearly periodically with respect to $

Inkang Kim

In this paper we show that if the limit set is not small ,marked length spectrum determines geometric structure of rank one locally symmetric manifolds.

Maxim Braverman, Michael Farber

We generalize the Novikov inequalities for 1-forms in two different directions: first, we allow non-isolated critical points (assuming that they are non-degenerate in the sense of R.Bott), and, secondly, we strengthen the inequalities by means of twisting by an arbitrary flat bundle. The proof uses Bismut's modification of the Witten deformation of the d

T. P. Pareek, P. Singha Deo, A. M. Jayannavar

We have considered an open system consisting of a metallic ring coupled to two electron reservoirs. We have recently shown that in the presence of a transport current, circulating currents can flow in such a ring even in the absence of magnetic field. This is related to the current magnification effect in the ring. In our present work we have studied the eff

S. Khlebnikov

We study the effect of interlayer tunneling in the gauge theory describing a quasi-two-dimensional paramagnetic metal close to a second-order or weakly first-order antiferromagnetic phase boundary. In that theory, two species of fermions have opposite (rather than equal) charges with respect to the gauge field. We find that single-particle interlayer tunneli

Stephan Haas, Elbio Dagotto

Applying numerical techniques to a model recently proposed for the one dimensional spin-Peierls compound CuGeO_3, we calculate dynamical properties that can be directly compared with inelastic neutron scattering data and angle-resolved photoemission experiments. The momentum and energy dependence of the dynamical structure factor S(q,omega) are discussed, as

Nguyen Hong Quang, Nguyen Minh Khue

The dynamical aspects of the phonoriton state in highly-photoexcited semiconductors is studied theoretically. The effect of the exciton-exciton interaction and nonbosonic character of high-density excitons are taken into account. Using Green's function method and within the Random Phase Approximation it is shown that the phonoriton dispersion and damping

D. W. Koerner, C. J. Chandler, A. I. Sargent

We have detected the T~Tauri star, DO Tauri, in a 0.6$''$-resolution VLA map of 43.3 GHz ($λ$ = 7 mm) continuum emission. The 43 GHz flux density lies on the same power-law slope defined by 89 to 232 GHz measurements, F$_ν$ $\propto ν^α$ with index $α$ = 2.39$\pm$0.23, confirming that the 43.3 GHz emission is thermal radiation from circumstellar dust

N. Itzhaki

We use the weak field approximation to show that information is lost in principle in quantum gravity.

L. Girardello, M. Porrati, A. Zaffaroni

Since T-duality has been proved only perturbatively and most of the heterotic states map into solitonic, non-perturbative, type II states, the 6-dimensional string-string duality between the heterotic string and the type II string is not sufficient to prove the S-duality of the former, in terms of the known T-duality of the latter. We nevertheless show in de

Klaus Kirsten, David J. Toms

We examine the occurrence of Bose-Einstein condensation in both nonrelativistic and relativistic systems with no self-interactions in a general setting. A simple condition for the occurrence of Bose-Einstein condensation can be given if we adopt generalized $ζ$-functions to define the quantum theory. We show that the crucial feature governing Bose-Einstein c

F. Kazemi Tabatabaei

We study the static properties of hadrons, assuming quantum group symmetry. We calculate the magnetic moment, axial form factor and A-symmetry, using $SU_q(2)$ and $SU_q(3)$ quantum groups. The results are fitted with experimental data, giving an interval of $0.9<q<1.1$. Some of the implications for the deformation parameter are discussed.

N. M. Khue, Le Ngoc Minh, Tran Tri Lan, Do Huu Nha

Effect of geometry on the superconductivity is considered. It is shown that the for nearly two dimensional BCS systems the critical temperature is rapidly increased with decreasing the thickness of the layer. The result is expected to be useful in the explanation of high-Tc conductivity of the ceramic compounds.

Robert Port, Fred Cummins, Michael Gasser

It is proposed that the theory of dynamical systems offers appropriate tools to model many phonological aspects of both speech production and perception. A dynamic account of speech rhythm is shown to be useful for description of both Japanese mora timing and English timing in a phrase repetition task. This orientation contrasts fundamentally with the more f

Harel Primack, Holger Schanz, Uzy Smilansky, Iddo Ussishkin

We study diffraction corrections to the semiclassical spectral density of dispersing (Sinai) billiards. They modify the contributions of periodic orbits (PO&#39;s), with at least one segment which is almost tangent to the concave part of the boundary. Given a wavenumber $k$, all the PO&#39;s with length up to the Heisenberg length $O(k)$ are required for qua

Jan Vacter Yang

In 1994, Witten has defined a monopole invariant and he has shown the equivalence of this invariant with Donaldson&#39;s polynomial using his result in \( \SS \)-duality. This new invariant is very powerful because the gauge group is abelian. By using such an invariant, many new results are found in the smooth, Kähler and even the symplectic categories. Howe

S. P. de Alwis

We discuss some issues related to the definition of different effective actions, in connection with the work on supersymmetric theories by Seiberg and collaborators. We also comment on the possibility of extending this work to broken supersymmetric theories.

Roberto Zucchini

A lagrangian euclidean model of Drinfeld--Sokolov (DS) reduction leading to general $W$--algebras on a Riemann surface of any genus is presented. The background geometry is given by the DS principal bundle $K$ associated to a complex Lie group $G$ and an $SL(2,\Bbb C)$ subgroup $S$. The basic fields are a hermitian fiber metric $H$ of $K$ and a $(0,1)$ Koszu

O. Miyamura, S. Origuchi

Pseudoscalar correlator is measured in a singular (monopole dominant) and a regular (photon dominant) parts of a maximal abelian field on SU(2) lattice. In the abelian field and its singular part, light pseudoscalar boson are observed similar to that in SU(2) field. On the other hand , the correlator in the regular part behaves like a product of free quark a

Arturo Trujillo

The paper presents a prototype lexicalist Machine Translation system (based on the so-called `Shake-and-Bake&#39; approach of Whitelock (1992) consisting of an analysis component, a dynamic bilingual lexicon, and a generation component, and shows how it is applied to a range of MT problems. Multi-Lexeme translations are handled through bi-lexical rules which

G. F. Lewis, M. J. Irwin, P. C. Hewett

Several macrolensed systems exhibit photometric variability consistent with microlensing due to objects of stellar mass located in the lens. The degree of microlensing amplification is dependent upon the size of the source, with smaller sources being more amplified. In general, amplification of sources larger than an Einstein radius projected onto the source

W. N. Brandt, A. C. Fabian, K. A. Pounds

We present spatial, temporal and spectral analyses of ROSAT Position Sensitive Proportional Counter (PSPC) observations of the infrared loud quasar IRAS 13349+2438. IRAS 13349+2438 is the archetypal highly-polarized radio-quiet QSO and has an optical/infrared luminosity of about 2E46 erg/s. We detect variability in the ROSAT count rate by a factor of 4.1 in

Nima Arkani-Hamed, Hsin-Chia Cheng, L. J. Hall

The gauge interactions of any supersymmetric extension of the standard model involve new flavor mixing matrices. The assumptions involved in the construction of minimal supersymmetric models, both $SU(3) \times SU(2) \times U(1)$ and grand unified theories, force a large degree of triviality on these matrices. However, the requirement of realistic quark and

M. J. Savage, R. P. Springer

We investigate the weak kaon-nucleon (NNK) S-wave and P-wave interactions using heavy baryon chiral perturbation theory. The leading 1-loop SU(3) breaking contributions to the $ppK$, $pnK$, and $nnK$ couplings are computed. We find that they suppress all NNK amplitudes by $30\%$ to $50\%$. The ratio of neutron-induced to proton-induced hypernuclear decay wid

V. E. R. Lemes, A. L. M. A. Nogueira, J. A. Helayël-Neto

The supersymmetric generalization of a recently proposed Abelian axial gauge model with antisymmetric tensor matter fields is presented.

Anne Schilling

General fermionic expressions for the branching functions of the rational coset conformal field theories $\widehat{su}(2)_{M}\times \widehat{su}(2)_N/\widehat{su}(2)_{M+N}$ are given. The equality of the bosonic and fermionic representations for the branching functions is proven by introducing polynomial truncations of these branching functions which are the

Theodore Voronov

We define generalized bialgebras and Hopf algebras and on this basis we introduce quantum categories and quantum groupoids. The quantization of the category of linear (super)spaces is constructed. We establish a criterion for the classical value of the dimension of the polynomial function algebra on the full subcategory of this quantum category specified by

Reinhard Schlickeiser, Charles D. Dermer

The broadband emission observed from radio galaxies, BL Lac objects and quasars is thought to be produced by energetic electrons confined in plasma blobs which are ejected from supermassive black holes at relativistic speeds. The lower energy radio-through-optical component is almost certainly nonthermal electron synchrotron radiation, while the higher-energ

K. Sellgren, M. W. Werner, L. J. Allamandola

We present a survey for extended 2.2 $\mu$m emission in 20 new visual reflection nebulae, illuminated by stars with temperatures of 3,600 --- 33,000 K. We detect extended 2.2 $\mu$m emission in 13 new nebulae, illuminated by stars with temperatures of 6,800 -- 33,000 K. For most of these 13 nebulae we have measured $J-K$, $H-K$, and $K-L'$, as well as obtain

Stephen R. Lau

In a thorough paper Kuchar has examined the canonical reduction of the most general action functional describing the geometrodynamics of the maximally extended Schwarzschild geometry. This reduction yields the true degrees of freedom for (vacuum) spherically symmetric general relativity. The essential technical ingredient in Kuchar&#39;s analysis is a canoni

Adrian Patrascioiu, Erhard Seiler

We point out that existing numerical data on the correlation length and magnetic susceptibility suggest that the two dimensional $O(3)$ model with standard action has critical exponent $η=1/4$, which is inconsistent with asymptotic freedom. This value of $η$ is also different from the one of the Wess-Zumino-Novikov-Witten model that is supposed to correspond

A. Yelkhovsky

The first in m/M and fourth in Zα(pure recoil) correction to a hydrogen energy level is found. This correction comprises two contributions, one coming from the atomic scale, the other from distances of the Compton wavelength order. Two different perturbation schemes are used to calculate the former. One of them exploits as unperturbed the solution to the Dir

A. Bartl, H. Eberl, K. Hidaka, T. Kon

We calculate the supersymmetric ${\cal O}(α_s)$ QCD corrections to the width of the decay $H^+ \rightarrow \st\bar{\sb}$ within the Minimal Supersymmetric Standard Model. We find that the QCD corrections are significant, but that they do not invalidate our previous conclusionat tree-level on the dominance of the $\st\bar{\sb}$ mode in a wide parameter region

Gordon Baym, Christopher Pethick

We give a quantitative account of the ground-state properties of the dilute magnetically trapped $^{87}$Rb gas recently cooled and Bose-Einstein condensed at nanokelvin-scale temperatures. Using simple scaling arguments, we show that at large particle number the kinetic energy is a small perturbation, and find a spatial structure of the cloud of atoms and it

G. Janssen, K. Holinde, J. Speth

We evaluate the contribution to the nucleon-nucleon interaction due to correlated $πρ$ exchange in the $π$, $ω$, and $A_1$/$H_1$ channels by means of dispersion-theoretic methods based on a realistic meson exchange model for the interaction between $π$ and $ρ$ mesons. These processes have substantial effects: In the pionic channel it counterbalances the supp

C. Schütz, K. Holinde

We determine the $πNN$ and $πNΔ$ formfactors from the $P_{11}$ resp. $P_{33}$ partial wave of $πN$ scattering by dressing corresponding bare vertices with the help of $πN$ non--pole contributions. The underlying model is based on meson exchange, and involves nucleon and delta--isobar pole and crossed--pole terms together with correlated $ππ$--exchange in the

Fernando Lombardo, Francisco Mazzitelli

We consider a $λϕ^4$ theory in Minkowski spacetime. We compute a &#34;coarse grained effective action&#34; by integrating out the field modes with wavelength shorter than a critical value. From this effective action we obtain the evolution equation for the reduced density matrix (master equation). We compute the diffusion coefficients of this equation and an

Carlos E. Laciana

A physical system composed by a scalar field minimally coupled to gravity and a thermal reservoir, as in thermo field dynamics, all of them in curved space time, is considered. When the formalism of thermo field dynamics is generalized to the above mentioned case, an amplification in the number of created particles is predicted.

Fernando T Brandt, Josif Frenkel

Following an argument advanced by Feynman, we consider a method for obtaining the effective action which generates the sum of tree diagrams with external physical particles. This technique is applied, in the unbroken λϕ^4 theory, to the derivation of the threshold amplitude for the production of $n$ scalar particles by $n$ initial particles. The leading cont

R. Ragazzon, D. Treleani

We discuss the inclusive cross section to produce two minijets with a large separation in rapidity in high energy hadronic collisions. The contribution to the inclusive cross section from the exchange of a BFKL Pomeron is compared with the contribution from the exchange of two BFKL Pomerons, which is induced by the unitarization of the semi-hard interaction.

I. Bojak, M. Ernst

The BFKL equation and the kT-factorization theorem are used to obtain predictions for F2 in the small Bjorken-x region over a wide range of Q**2. The dependence on the parameters, especially on those concerning the infrared region, is discussed. After a background fit to recent experimental data obtained at HERA and at Fermilab (E665 experiment), we find tha

G. Haran, G. A. Gehring

The phase diagram of superconducting $U\!Pt_{3}$ in pressure-temperature plane, together with the neutron scattering data is studied within a two component superconducting order parameter scenario. In order to give a qualitative explanation to the experimental data a set of two linearly independent antiferromagnetic moments which emerge appropriately at the

T. Xiang, J. M. Wheatley

Proximity effect and pair tunneling models are applied as alternative scenarios to explain the recently measured $ab$-plane and $c$-axis components of the superfluid tensor in Copper-Oxide superconductors which contain chains, such as $YBa_2Cu_3O_{6.95}$. It is argued that conventional proximity effect models, which couple chains and planes via single electr

J. C. Le Guillou, E. Ragoucy

In the framework of constrained systems, we give the classical Hamiltonian formulation of slave-particle models and their correct quantization. The electron-momentum distribution function in the t-J and Hubbard models is then studied in the framework of slave-particle approaches and within the decoupling scheme. We show that criticisms that have been address

G. George Batrouni, Alex Hansen, Brond Larson

We study the multifractal properties of the current distribution of the three-dimensional random resistor network at the percolation threshold. For lattices ranging in size from $8^3$ to $80^3$ we measure the second, fourth and sixth moments of the current distribution, finding {\it e.g.\/} that $t/ν=2.282(5)$ where $t$ is the conductivity exponent and $ν$ i

Gerhard Hummer

A closed form of the electrostatic potential of a homogeneously charged cube is derived by integration. The exact result is compared with multipole expansions for the exterior and interior of the cube. The electrostatic potential of a homogeneously charged square in two-dimensional electrostatics is also determined.

R. J. A. G. Huveneers, F. Verhulst

In this paper we study a Hamiltonian system with a spatially asymmetric potential. We are interested in the effects on the dynamics when the potential becomes symmetric slowly in time. We focus on a highly simplified non-trivial model problem (a metaphor) to be able to pursue explicit calculations as far as possible. Using the techniques of averaging and adi

Asher Peres

A quantum system is described, whose wave function has a complexity which increases exponentially with time. Namely, for any fixed orthonormal basis, the number of components required for an accurate representation of the wave function increases exponentially.

K. Sellgren, T. Y. Brooke, R. G. Smith

A new 3.2--3.5~$μ$m spectrum of the protostar Mon~R2/IRS-3 confirms our previous tentative detection of a new absorption feature near 3.25 $μ$m. The feature in our new spectrum has a central wavelength of 3.256 $μ$m (3071 cm$^{-1}$) and has a full-width at half maximum of 0.079 $μ$m (75 cm$^{-1}$). We explore a possible identification with aromatic hydrocarb

Rashid Faizullin

In the present paper some geometrical and mechanical regularities are introduced, which constitute certain puzzles of distribution of the nearest stars of $O,B,AO$ classes (brighter than $6.0^m$) and of the brightest galactic objects; the regularities appear when considering in the natural, moment related ($l,b$), ($α,δ$), ($λ,β$) coordinate planes. Also, th

Sukanta Bose, Leonard Parker, Yoav Peleg

We find a family of exact solutions to the semi-classical equations (including back-reaction) of two-dimensional dilaton gravity, describing infalling null matter that becomes outgoing and returns to infinity without forming a black hole. When a black hole almost forms, the radiation reaching infinity in advance of the original outgoing null matter has the p

Gaetano Fiore, Peter Schupp

We propose a solution to the problem of compatibility of Bose-Fermi statistics with symmetry transformations implemented by compact quantum groups of Drinfel&#39;d type. We use unitary transformations to conjugate multi-particle symmetry postulates, so as to obtain a twisted realization of the symmetric groups S_n.

B. S. Acharya

We construct the heterotic dual theory in four dimensions of eleven dimensional supergravity compactified on a particular Joyce manifold, $J$. In particular, $J$ is constructed from resolving fixed point singularities of orbifolds of the seven torus in such a way that one is forced to consider a generalised orbifold on the heterotic side. We conjecture that

Troy Shinbrot

Exact wave functions are is derived from an azimuthally periodic a self-consistent quantum Hamiltonian in 2+1 dimensions using both the Klein-Gordon and the Schroedinger equations. It isWe shown that, curiously, for both relativistic and non-relativistic equations, integer spin wave equations necessarily produce half-integer angular momentum in this potentia

V. B. Belyaev, A. K. Motovilov, W. Sandhas

It is widely accepted that in molecular systems the nuclear interaction plays a negligible role, because of the strong Coulomb repulsion of the nuclei at small distances. We are going to show that this is not always true. The existence of an extended nuclear resonance may lead to considerably enhanced nuclear reaction rates in appropriately prepared molecule

Sebastian Eggert

Data from susceptibility measurements on Sr_2CuO_3 are compared with recent theoretical predictions for the magnetic susceptibility of the antiferromagnetic spin-1/2 Heisenberg chain. The experimental data fully confirms the theoretical predictions and in turn we establish that Sr_2CuO_3 behaves almost perfectly like a one-dimensional antiferromagnet with an

P. Braun-Munzinger, J. Stachel, J. P. Wessels, N. Xu

The currently available set of hadron abundances at the SPS for central S+Au(W,Pb) collisions is compared to predictions from a scenario assuming local thermal and hadrochemical equilibrium. The data are consistent with a freeze-out temperature T = 160-170 MeV. Spectra are consistent with this temperature range and a moderate transverse expansion. The freeze

R. Foot, R. R. Volkas

We re-examine the big bang nucleosynthesis (BBN) bounds on the mixing of neutrinos with sterile species. These bounds depend on the assumption that the relic neutrino asymmetry $L_ν$ is very small. We show that for $L_ν$ large enough (greater than about $10^{-5}$) the standard BBN bounds do not apply. We apply this result to the sterile neutrino solution to

Vahid Karimipour, Ali Mostafazadeh

The lattice definition of the two-dimensional topological quantum field theory [Fukuma, {\em et al}, Commun.~Math.~Phys.\ {\bf 161}, 157 (1994)] is generalized to arbitrary (not necessarily orientable) compact surfaces. It is shown that there is a one-to-one correspondence between real associative $*$-algebras and the topological state sum invariants defined

V. S. Olkhovsky, E. Recami, F. Raciti, A. Zaichenko

In a recent review paper [{\em Phys. Reports} {\bf 214} (1992) 339] we proposed, within conventional quantum mechanics, new definitions for the sub-barrier tunnelling and reflection times. \ Aims of the present paper are: \ (i) presenting and analysing the results of various numerical calculations (based on our equations) on the penetration and return times

Vyjayanthi Chari, Andrew Pressley

We give several formulas for the character of an arbitrary irreducible finite--dimensional representation for the Yangian of sl_2.

L. P. Csernai, J. Németh, G. Papp

The evolution of dynamical perturbations is examined in nuclear multifragmentation in the frame of Vlasov equation. Both plane wave and bubble type of perturbations are investigated in the presence of surface (Yukawa) forces. An energy condition is given for the allowed type of instabilities and the time scale of the exponential growth of the instabilities i

A. Mengoni, T. Otsuka, M. Ishihara

The neutron direct radiative capture (DRC) process is investigated, highlighting the role of incident p-wave neutrons. A set of calculations is shown for the 12-C(n,gamma) process at incoming neutron energies up to 500 keV, a crucial region for astrophysics. The cross section for neutron capture leading to loosely bound s, p and d orbits of 13-C is well repr

Ramzi R. Khuri, Robert C. Myers

In a recent paper, Duff and Rahmfeld argued that certain massive $N_R=1/2$ states of the four-dimensional heterotic string correspond to extreme black hole solutions. We provide further, dynamical, evidence for this identification by comparing the scattering of these elementary string states with that of the corresponding extreme black holes, in the limit of

S. Bellucci

We report the results of the working group on ``Pion (Kaon) and Sigma Polarizabilities&#39;&#39;. Interesting possibilities to measure these polarizabilities include the radiative pion photoproduction in the MAMI experiment at Mainz, as well as at the GRAAL facility (actually the latter is being considered for an experimental determination of the pion polari

S. Bellucci, V. Faraoni

The available tests of the equivalence principle constrain the mass of the Higgs-like boson appearing in extended supergravity theories. We determine the constraints imposed by the present and future high precision experiments on the antigravity fields arising from $N=2,8$ supergravity.

Peter Arnold, Laurence G. Yaffe

In quantum electrodynamics, static electric fields are screened at non-zero temperatures by charges in the plasma. The inverse screening length, or Debye mass, may be analyzed in perturbation theory and is of order $eT$ at relativistic temperatures. An analogous situation occurs when non-Abelian gauge theories are studied perturbatively, but the perturbative

Igor R. Klebanov, Karl M. Westerberg

We study strange dibaryons based on the SU(2)-embedded B=2 toroidal soliton. Treating the excursions of the soliton into strange directions as small rigid oscillations, we obtain a good approximation to the bound state approach. We calculate the dibaryon mass formula to order 1/N and find that the doubly strange I=J=0 dibaryon is bound by about 90 MeV.

W. M. Alberico, S. M. Bilenky, C. Giunti, C. Maieron

Elastic scattering of neutrinos and antineutrinos on nucleons is considered. It is shown that the measurement of the neutrino-antineutrino asymmetry would allow to obtain model independent informations on the strange axial and vector form factors. The ratio of the magnetic form factors of the proton and neutron, on which the asymmetry depends, is investigate

D. Kharzeev, H. Satz

We study charmonium production in hadron-nucleus collisions through the intermediate next-to-leading Fock space component $|(\bar{c}c)_8 g>$, formed by a colour octet $\bar{c}c$ pair and a gluon. We estimate the size of this state and show that its interaction with nucleons accounts for the observed charmonium suppression in nuclear interactions.

Lawrence Gibbons

A preliminary analysis of exclusive $\btou$ decays to the final states $π^\pm\ellν$, $π^0\ellν$, $ρ^\pm\ellν$, $ρ^0\ellν$\ and $ω\ellν$ based on $2.2\e{6}$ $\bbar$ decays collected at CLEO is presented. We have measured the first exclusive $\btou$ branching fraction $\bbpi=[1.19\pm0.41\pm0.21\pm0.19]\e{-4}$ ($[1.70\pm0.51\pm0.31\pm0.27]\e{-4}$), with the ISG

J. Pullin

We give a brief summary of results and ongoing research in the application of linearized theory to the study of black hole collisions in the limit in which the holes start close to each other. This approximation can be a valuable tool for comparison and code-checking of full numerical relativity computations. The approximation works quite well for the head-o

Joao A. N. Filipe, Geoff J. Rodgers

We consider a model for random deposition of monomers on a line with extrinsic precursor states. As the adsorbate coverage increases, the system develops non-trivial correlations due to the diffusion mediated deposition mechanism. In a numeric simulation, we study various quantities describing the evolution of the island structure. We propose a simple, self-

B. M. Elrick, A. E. Jacobs

We report numerical results for the single-hole properties in the $t$-$J$ model and the strong-coupling approximation to the Hubbard model in two dimensions. Using the hopping basis with over $10^6$ states we discuss (for an infinite system) the bandwidth, the leading Fourier coefficients in the dispersion, the band masses, and the spin-spin correlations nea

E. Marinari, G. Parisi, F. Ritort, J. Ruiz-Lorenzo

By numerical simulations of the $3d$ Ising spin glass we find evidence that spontaneous replica symmetry breaking theory and not the droplet model describes with good accuracy the equilibrium behavior of the system.

J. Müllers, A. Schmid

The I-V characteristics of a Josephson junction shunted by an Ohmic resistor shows sharp peaks when levels in neighbouring wells are crossing. We consider the shape and size of these peaks using a double-well model where the wells are given in parabolic approximation. The friction of arbitrary strength is included by the help of a bath of infinitely many deg

K. Vollmayr, W. Kob, K. Binder

Using molecular dynamics computer simulations we investigate the dependence of bulk properties of a Lennard-Jones glass on the cooling rate with which the glass was produced. By studying the clusters formed by the nearest neighbor shells of the particles, we show that the internal structure of the glass depends on the cooling rate and that the cooling rate d

Frederic Mila, Didier Poilblanc

We present numerical evidence that the hopping of electrons between chains described by the $t-J$ model is coherent in the integrable cases ($J=0$ and $J=2$) and essentially incoherent otherwise. This effect is {\it not} related to the value of the exponent $α$, (which is restricted to the interval [0,1/8] when $0\le J\le 2$), and we propose that enhanced co