January 1994 arXiv papers — page 3

P. Schaller, T. Strobl

We investigate the phase space of a typical model of 1+1 dimensional gravity (Jackiw-Teitelboim model with cylindrical topology) using its reformulation as a non abelian gauge theory based on the sl(2,R) algebra. Modifying the conventional approach we argue that one should take the universal covering of SL(2,R) rather than PSL(2,R) as the gauge group of the

S. W. Hawking

A consistent Euclidean semi classical calculation is given for the superscattering operator $\$ $ in the RST model for states with a constant flux of energy. The $\$ $ operator is CPT invariant. There is no loss of quantum coherence when the energy flux is less than a critical rate and complete loss when the energy flux is critical.

J. M. Figueroa-O'Farrill

In the process of investigating classical realizations of W_3 in terms of free bosons, Romans unveiled a relation to finite-dimensional Jordan algebras with a cubic norm. These algebras have been classified and consist of an infinite series (yielding the ``generic'' realizations) and four sporadic algebras associated to the real division algebras (wh

K. Zarembo

The loop equations in the $U(N)$ lattice gauge theory are represented in the form of constraints imposed on a generating functional for the Wilson loop correlators. These constraints form a closed algebra with respect to commutation. This algebra generalizes the Virasoro one, which is known to appear in one-matrix models in the same way. The realization of t

Jisuke Kubo

In renormalizable theories, we define equal-time commutators (ETC'S) in terms of the equal-time limit and investigate its convergence in perturbation theory. We find that the equal-time limit vanishes for amplitudes with the effective dimension $d_{\em eff} \leq -2$ and is finite for those with $d_{\em eff} =-1$ but without nontrivial discontinuity. Othe

C. P. Burgess, F. Quevedo

We show that bosonization in two dimensions can be derived as a special case of the duality transformations that have recently been used to good effect in string theory. This allows the construction of the bosonic counterpart of any fermionic theory simply by `following your nose' using the standard duality transformation rules. We work through the boson

L. Girardello, A. Zaffaroni

New proves of decoupling of massive fields in several quantum field theories are derived in the effective Lagrangian approach based on Wilson renormalization group. In the most interesting case of gauge theories with spontaneous symmetry breaking, the approach, combined with the quantum action principle, leads to a rather simple proof to all orders.

D. Boyanovsky, H. J. de Vega, R. Holman

We address the issue of whether a region of disordered chiral condensate (DCC), in which the chiral condensate has components along the pion directions, can form. We consider a system going through the chiral phase transition either via a quench, or via relaxation of the high temperature phase to the low temperature one within a given time scale (of order $\

C. E. Carlson, K. E. Lassila

A suggestion is made for distinguishing 2N and 6q short range correlations within the deuteron. The suggestion depends upon observing high momentum backward nucleons emerging from inelastic electromagnetic scattering from a deuteron target. A simple model is worked out to see the size of effects that may be expected.

G. Couture, S. Godfrey

We perform a detailed study of the process $e^+e^-\to μ^+μ^-ν_l\barν_l$ including all contributions. The contributions other than from real gauge boson production leads to a rich phenomenology. We explore the use of the process as a means of precision measurement of the $ZWW$ and $γWW$ vertices. We concentrate on LEP II energies, $\sqrt{s}=200$ GeV, and ener

M. H. Reno

Despite large uncertainties in the $W^\pm$ and $Z^0$ transverse momentum ($q_T$) distributions for $q_T\lsim 10$ GeV, the ratio of the distributions varys little. The uncertainty in the ratio of $W$ to $Z$ $q_T$ distributions is on the order of a few percent, independent of the details of the nonperturbative parameterization.

T. E. Rudy, H. W. Fearing, S. Scherer

The off-shell electromagnetic vertex of a (pseudo-) scalar particle contains, in general, two form factors F and G which depend, in addition to the squared momentum transfer, on the invariant masses associated with the initial and final legs of the vertex. Chiral perturbation theory to one loop is used to calculate the off-shell form factors of pions and kao

Peter Cho, Mark B. Wise

We calculate the rate for $D_s^* \rightarrow D_s π^0$ decay using Chiral Perturbation Theory. This isospin violating process results from $π^0$ - $η$ mixing, and its amplitude is proportional to $(m_d - m_u)/\bigl(m_s-(m_u+m_d)/2 \bigr)$. Experimental information on the branching ratio for $D_s^* \rightarrow D_s π^0$ can provide insight into the pattern of $

H. Heiselberg

The kinetic properties of relativistic quark-gluon and electron-photon plasmas are described in the weak coupling limit. The troublesome Rutherford divergence at small scattering angles is screened by Debye screening for the longitudinal or electric part of the interactions. The transverse or magnetic part of the interactions is effectively screened by Landa

S. Catterall, J. Kogut, R. Renken

We present the results of a high statistics Monte Carlo study of a model for four dimensional euclidean quantum gravity based on summing over triangulations. We show evidence for two phases; in one there is a logarithmic scaling on the mean linear extent with volume, whilst the other exhibits power law behaviour with exponent 1/2. We are able to extract a fi

A. W. Sandvik, D. J. Scalapino

We have studied the antiferromagnetic order -- disorder transition occurring at $T=0$ in a 2-layer quantum Heisenberg antiferromagnet as the inter-plane coupling is increased. Quantum Monte Carlo results for the staggered structure factor in combination with finite-size scaling theory give the critical ratio $J_c = 2.51 \pm 0.02$ between the inter-plane and

Mark M. Millonas, Mark I. Dykman

We present analytic results for the current in a system moving in an arbitrary periodic potential and driven by weak Gaussian noise with an arbitrary power spectrum which are valid to order (t_c/t_r)^2, where t_c is the largest characteristic time of the noise, and t_r is the characteristic intrawell relaxation time. The dependence of the current on the shap

Q. NIu, P. Ao, D. J. Thouless

We calculate the overlap between two many-body wave functions for a superfluid film containing a vortex at shifted positions. Comparing the results to phenomenological theories, which treat vortices as point particles, we find that the results are consistent if the point-particle vortices are considered as under the action of the Magnus force and in weak int

Q. Niu, P. Ao, D. J. Thouless

We calculate the overlap between two many-body wave functions for a superfluid film containing a vortex at shifted positions. Comparing the results to phenomenological theories, which treat vortices as point particles, we find that the results are consistent if the point-particle vortices are considered as under the action of the Magnus force and in weak int

M. Plionis, S. Borgani

We re-estimate the angular 2-point galaxy correlation function from the Lick galaxy catalogue. We argue that the large-scale gradients observed in the Lick catalogue are dominated by real clustering and therefore they should not be subtracted prior to the estimation of the 2-p correlation function. We find that if no such correction is introduced the galaxy

S. R. Kulkarni, D. A. Frail, N. E. Kassim, T. Murakami

Earlier we had suggested that G10.0-0.3, a non-thermal nebula, most likely an old supernova remnant (SNR), was associated with the soft gamma repeater (SGR) SGR 1806-20. Here we present new radio images obtained at the Very Large Array (VLA) of the non-thermal radio nebula G10.0-0.3. The nebula is a plerion with a hierarchy of nested amorphous components cul

Tadeusz Krasinński

We give necessary and sufficient conditions, in the form of matrix identities, for a polynomial f in C[X,Y] to be a component of a polynomial automorphism of C^2 and to be a component of a Keller polynomial mapping of C^2, respectively ((f,g) is a Keller polynomial mapping iff Jac(f,g) = 1).

Alexander Astashkevich, V. Sadov

We compute the quantum cohomology rings of the partial flag manifolds F_{n_1\cdots n_k}=U(n)/(U(n_1)\times \cdots \times U(n_k)). The inductive computation uses the idea of Givental and Kim. Also we define a notion of the vertical quantum cohomology ring of the algebraic bundle. For the flag bundle F_{n_1\cdots n_k}(E) associated with the vector bundle E thi

I. Bigi, B. Blok, M. Shifman, N. Uraltsev

`Anyone who keeps the ability to see beauty never grows old' Franz Kafka. In the last few years considerable progress has been achieved in our understanding of the decays of heavy flavour hadrons. One can now calculate inclusive transition rates in QCD proper through an expansion in inverse powers of the heavy flavour quark mass without recourse to pheno

Stefano Moretti

We study the cross sections for the production of intermediate mass Higgs bosons via the reactions $e^-γ\rightarrow ν_eW^-Φ^0$, $e^-γ\rightarrow ν_eH^-Φ^0$, $e^-γ\rightarrow e^-Z^0Φ^0$ and $e^-γ\rightarrow e^-H^+H^-$ in the Minimal Supersymmetric Standard Model (with $Φ^0=H^0,h^0$ and, where possible, $A^0$) at TeV energies, taking into account $b$--tagging

Sumit R. Das, Sudipta Mukherji

We study black hole formation in a model of two dimensional dilaton gravity and 24 massless scalar fields with a boundary. We find the most general boundary condition consistent with perfect reflection of matter and the constraints. We show that in the semiclassical approximation and for the generic value of the parameter which characterizes the boundary con

Zbigniew Jaskólski, Krzysztof A. Meissner

The first quantization of the relativistic Brink-DiVecchia-Howe-Polyakov (BDHP) string in the range $1<d<25$ is considered. It is shown that using the Polyakov sum over bordered surfaces in the Feynman path integral quantization scheme one gets a consistent quantum mechanics of relativistic 1-dim extended objects in the range $1<d<25$. In particular the BDHP

Shoji Shinmura

Theoretical estimations of production cross sections of light $Λ$ and $Σ$ hypernuclei in $(e,e&#39;K^{+})$ reactions at around CEBAF energies are given. Because of dominant spin-flip amplitudes and large momentum transfers, unnatural parity states and stretched states of hypernuclei are favorably excited. They are compared with quasifree hyperon productions.

Naoki Sasakura

We investigate the neighborhood of Topological Lattice Field Theories (TLFTs) in the parameter space of general lattice field theories in dimension $D\geq 2$, and discuss the phase structures associated to them. We first define a volume-dependent TLFT, and discuss its decomposition to a direct sum of irreducible TLFTs, which cannot be decomposed anymore. Usi

M. Asakawa, C. M. Ko

A double phi peak structure in the dilepton invariant mass spectrum from ultrarelativistic heavy ion collisions is proposed as a signal for the phase transition from the quark-gluon plasma to the hadronic matter. The low mass phi peak results from the decay of phi mesons with reduced in-medium mass during the transition. Furthermore, the measurement of the t

Moti Gitik

We give the optimal conditions for the existence of a club consisting of former regular over an inaccessible and a measurable. The foricing construction based on iteration of distributive posets.

A. A. Vladimirov

Explicit isomorphism is established between quasitriangular Hopf algebras studied recently by O.Ogievetsky and by the present author.

E. Alvarez, J. M. Gracia-Bondía, C. P. Martín

We study the evolution under the renormalization group of the restrictions on the parameters of the standard model coming from Non-Commutative Geometry, namely $m_{top} = 2\,m_W$ and $m_{Higgs} = 3.14 \, m_W$. We adopt the point of view that these relations are to be interpreted as {\it tree level} constraints and, as such, can be implemented in a mass indep

Alok Kumar, Swapna Mahapatra

We obtain new duality transformations relating some exact string backgrounds, by defining the nilpotent duality. We show that the ungauged $SL(2, R)$ WZW model transforms by its action into the three dimensional plane wave geometry. We also give the inverse transformation from the plane wave to the $SL(2, R)$ model and discuss the implications of the results

Taro Kashiwa, Yasushi Takahashi

Contrary to the conventional view point of quantization that breaks the gauge symmetry, a gauge invariant formulation of quantum electrodynamics is proposed. Instead of fixing the gauge, some frame is chosen to yield the locally invariant fields. We show that all the formulations, such as the Coulomb, the axial, and the Lorentz gauges, can be constructed and

Yoshiyuki Watabiki

We propose a new method which analyzes the dynamical triangulation from the viewpoint of the non-critical string field theory. By using the transfer matrix formalism, we construct the non-critical string field theory (including $c>1$ cases) at the discrete level. For pure quantum gravity, we succeed in taking the continuum limit and obtain the $c=0$ non-crit

P. Ramadevi, T. R. Govindarajan, R. K. Kaul

Upto ten crossing number, there are two knots, $9_{42}$ and $10_{71}$ whose chirality is not detected by any of the known polynomials, namely, Jones invariants and their two variable generalisations, HOMFLY and Kauffman invariants. We show that the generalised knot invariants, obtained through $SU(2)$ Chern-Simons topological field theory, which give the kno

G. Bonvicini, L. Randall

The value of the $b$-baryon polarization can be extracted from inclusive data at LEP with better than 10\% precision based on current statistics. We present a new variable by which to measure the polarization, which is the ratio of the average electron energy to the average neutrino energy. This variable is both sensitive to polarization and insensitive to f

H. J. Lu

We analyze various perturbative mechanisms for the production of jet events containing rapidity gaps in $e^+e^-$ annihilation at LEP200 energies. We found that the processes $e^+e^- \to γ^* γ^*, γ^* Z, Z Z, WW \to 4~ jets$ generate gap events at an observable rate. We point out that LEP200 offers a unique opportunity for the study of gap events due to a smal

K. Hagiwara, M. Tanaka, T. Stelzer

We present exact tree level cross sections for the single top production process $e^- e^+ \rightarrow e^- \barν_e t \bar{b} $ at LEP~200. The results reproduce roughly those obtained earlier by using the equivalent real photon approximation and we confirm the observation that detecting a top heavier than half the c.m.~energy is not feasible at LEP~200. The c

Zoltan Kunszt, Adrian Signer, Zoltan Trocsanyi

We describe a general method that enables us to obtain all the singular terms of helicity amplitudes of n-parton processes at one loop. The algorithm uses helicity amplitudes at tree level and simple color algebra. We illustrate the method by calculating the singular part of the one loop helicity amplitudes of all $ 2\to 3$ parton subprocesses. The results a

Wolfgang Lucha, Franz F. Schöberl

We demonstrate that the analytic solution for the set of energy eigenvalues of the semi-relativistic Coulomb problem reported by B. and L. Durand is in clear conflict with an upper bound on the ground-state energy level derived by some straightforward variational procedure.

Johannes Blümlein, James Botts

A next--to--leading order QCD analysis of deep inelastic scattering data is performed allowing for contributions due to a light gluino. We obtain the values of $α_s(M_Z^2) \pm δα_s^{stat} = 0.108 \pm 0.002, 0.124 \pm 0.001, 0.145 \pm 0.009$ for QCD, SUSY QCD with a Majorana gluino and a Dirac gluino respectively. The value of $\alsm$ obtained in SUSY QCD wit

F. Csikor, I. Montvay

The possibility of grand unification of the standard model (SM) with fermion spectrum extended to include mirror fermions is examined. SM gauge couplings do not automatically unify. SO(10) grand unification is studied with one intermediate scale. Renormalization group equations (RGE) for fermion Yukawa couplings and the scalar self-coupling are studied numer

U. M. Heller, Khalil M. Bitar, R. G. Edwards, A. D. Kennedy

We compute the heavy quark potential on configurations generated by the HEMCGC collaboration with dynamical staggered fermions at $6/g^2 = 5.6$ and with dynamical Wilson fermions at $6/g^2 = 5.3$. The computations are done on $16^3 \times 32$ lattices, corresponding to physical sizes of about 1.6 and 2.3 fm, respectively. Up to the distances probed no sign o

Martin Grabenstein

We study the relation between the dynamical critical behavior and the kinematics of stochastic multigrid algorithms. The scale dependence of acceptance rates for nonlocal Metropolis updates is analyzed with the help of an approximation formula. A quantitative study of the kinematics of multigrid algorithms in several interacting models is performed. We find

J. Rizos, K. Tamvakis

We study a general field theory of a scalar field coupled to gravitation through a quadratic Gauss-Bonnet term $ξ(ϕ)$$R_{GB}^2$. We show that, under mild assumptions about the function $ξ(ϕ)$, the classical solutions in a spatially flat FRW background include singularity - free solutions.

H. Waelbroeck

We consider the quantum dynamics of both open and closed two- dimensional universes with ``wormholes&#39;&#39; and particles. The wave function is given as a sum of freely propagating amplitudes, emitted from a network of mapping class images of the initial state. Interference between these amplitudes gives non-trivial scattering effects, formally analogous

H. Waelbroeck, F. Zertuche

We establish the relation between the ISO(2,1) homotopy invariants and the polygon representation of (2+1)-dimensional gravity. The polygon closure conditions, together with the SO(2,1) cycle conditions, are equivalent to the ISO(2,1) cycle conditions for the representa- tions of the fundamental group in ISO(2,1). Also, the symplectic structure on the space

S. DasSarma, C. J. Lanczycki, S. V. Ghaisas, J. M. Kim

Stochastic simulation results, appropriate for Molecular Beam Epitaxy, involving ballistic deposition and thermally activated Arrhenius diffusion of adatoms are presented for one- and two-dimensional substrates, allowing for overhangs and bulk vacancies. The asymptotic Kardar-Parisi- Zhang universality is found to be triggered by a sudden nucleation of large

A. V. Balatsky

Impurity scattering in the unitary limit produces low energy quasiparticles with anisotropic spectrum in a two-dimensional $d$-wave superconductor. We describe a new {\em quasi-one-dimensional } limit of the quasiparticle scattering, which might occur in a superconductor with short coherence length and with {\em finite} impurity potential range. The dc condu

H. -J. Kwon, A. Houghton, J. B. Marston

We investigate fermion liquids interacting with longitudinal and transverse abelian gauge fields via bosonization. In two spatial dimensions we obtain the fermion propagator for the specific case of a Coulomb plus Chern-Simons gauge action. We discuss the relevance of this result to the Halperin-Lee-Read theory of the $ν=1/2$ Landau level and demonstrate how

Ian I. Kogan

We discuss a quantum \qa symmetry in Landau problem, which naturally arises due to the relation between the \qa and the group of magnetic translations. The last one is connected with the \w and area-preserving (symplectic) diffeomorphisms which are the canonical transformations in the two-dimenssional phase space. We shall discuss the hidden quantum symmetry

N. W. Evans, J. Jijina

The measurements of the possible gravitational microlensing events are analysed with a simple yet accurate disc--halo model of the Milky Way Galaxy. This comprises a luminous exponential disc embedded in a flattened dark matter halo with density varying like ${\rm distance}^{-1.8}$. Including a disc has the important effect of lowering the implied masses of

Phung Ho Hai

The dimension of the third homogeneous component of a matrix quantum bialgebra, determined by pair of quantum spaces, is calculated. The Poincaré series of some deformations of $GL(n)$ is calculated. A new deformation of $GL(3)$ with the correct dimension is given.

A. H. Hoang, M. Jeżabek, J. H. Kühn, T. Teubner

The rate for the final state radiation of hadrons in leptonic $Z$ decays is evaluated, using as input experimental data for $σ(e^+e^-\to hadrons)$ in the low energy region. Configurations with a lepton pair of large and a hadronic state of low invariant mass are dominant. A relative rate $Γ_{l\bar l had}/Γ_{l\bar l}=6.3\times 10^{-4}$ is calculated. This res

A. Zhitnitsky

It is shown that there is one-to-one correspondence between two, apparently different problems: \\ 1. The determination of the meanvalues of transverse moments $\la \vec{k}_{\perp}^{2n} \ra $ for the nonperturbative pion wave function $ψ(\k, x)$ and \\ 2. The evaluation of the mixed vacuum condensates $ \la \bar{q}G_{μν}^n q\ra $. eneral properties of the th

B. Nerlo-Pomorska, K. Pomorski

A new formula for the nuclear charge radius is proposed, dependent on the mass number (A) and neutron excess (N-Z) in the nucleus. It is simple and it reproduces all the experimentally available mean square radii and their isotopic shifts of even--even nuclei much better than other frequently used relations.

Lothar Tiator

Photo- and electroproduction of pions and eta-mesons is studied on the nucleon. The formalism of such reactions is presented including polarization degrees of freedom and theoretical approaches are discussed. In particular, the threshold and $Δ$-resonance region of pion photoproduction is considered and recent developments on low energy theorems (LET) and th

Jacobus Verbaarschot

We study the spectrum of the QCD Dirac operator near zero virtuality for $N_c =2$. According to a universality argument, it can be described by a random matrix theory with the chiral structure of QCD, but with $real$ matrix elements. Using results derived by Mehta and Mahoux and Nagao and Wadati, we are able to obtain an analytical result for the microscopic

I. T. Ivanov, U. Lindstrom, M. Rocek

In this note, we construct new representations of D=2, N=4 supersymmetry which do not involve chiral or twisted chiral multiplets. These multiplets may make it possible to circumvent no-go theorems about N=4 superspace formulations of WZWN-models.

Rashmi Ray, Gil Gat

We obtain expressions for the current operator in the lowest Landau level (L.L.L.) field theory, where higher Landau level mixing due to various external and interparticle interactions is sytematically taken into account. We consider the current operators in the presence of electromagnetic interactions, both Coulomb and time-dependent, as well as local four-

A. Dubikovsky, K. Sveshnikov

A set of integral relations for rotational and translational zero modes in the vicinity of the soliton solution are derived from the particle-like properties of the latter and verified for a number of models (solitons in 1+1-dimensions, skyrmeons in 2+1- and 3+1-dimensions, non-abelian monopoles). It is shown, that by consistent quantization within the frame

A. Dubikovsky, K. Sveshnikov

The classical soliton solution, quantized by means of suitable translational and rotational collective coordinates, is embedded into the one-particle irreductible representation of the Poincare group corresponding to a definite spin. It is shown, that within the conventional quasiclassical expansion such embedding leads to a set of nontrivial consistency con

M. Cavicchi

We consider a wide class of two-dimensional models as gauge theories, Gross-Neveu model, $O(N)$ and $CP^{N-1}$-like models using a formalism based on the introduction of bilocal fields that permits to perform easily the large-N expansion of this set of models in a unified and general way. We mainly discuss the $SU(N)$ gauge field theory minimally coupled to

Markus J. Pflaum

It is shown that the principle of locality and noncommutative geometry can be connnected by a sheaf theoretical method. In this framework quantum spaces are introduced and examples in mathematical physics are given. With the language of quantum spaces noncommutative principal and vector bundles are defined and their properties are studied. Important construc

A. V. Batunin, S. M. Sergeev

A transfer matrix method relating the process of refinement of a fractal measure to thermodynamic formalism of an appropriate Ising model is applied to the analysis of intermittency in hadron collisions revealing that underlying dynamics is that of period doublings.

T. Schaefer, E. V. Shuryak

We study hadronic wave functions using an instanton model for the QCD vacuum. The wave functions are defined in terms of gauge invariant Bethe Salpeter amplitudes which we have determined numerically using a Monte Carlo simulation of the instanton ensemble. We find that the pion and the proton, as well as the rho meson and the delta have very similar wave fu

Patrick J. O&#39;Donnell, Q. P. Xu

The exclusive rare decay $B \ra K^\ast γ$ takes place in a region of maximum recoil, $q^{2}=0$, posing a problem for nonrelativistic quark models which are usually thought to be most reliable at zero recoil. The Bauer--Stech--Wirbel (BSW) model, formulated in the infinite--momentum--frame (IMF) formalism, is designed to work at $q^2=0$. We show in this model

Rudolph C. Hwa, C. S. Lam, Jicai Pan

The problem of cluster formation and growth in first-order quark-hadron phase transition in heavy-ion collisions is considered. Behaving as Brownian particles, the clusters carry out random walks and can encounter one another, leading to coalescence and breakup. A simulation of the process in cellular automaton suggests the possibility of a scaling distribut

O. K. Kalashnikov

The nonperturbative equation for the infrared $Π_{44}(0)$-limit is built by using the Slavnov-Taylor identity to define the three-gluon vertex function in the temporal axial gauge. We found that all vertex corrections should be taken into account along with the standard ring graphs to keep the gauge covariance throughout calculations and to give correctly th

E. -M. Ilgenfritz, E. V. Shuryak

A simple model for the instanton ensemble at finite temperature T is proposed, including ``random&#34; and strongly correlated ``molecular&#34; component. T-dependence of fermionic zero modes naturally leads to chiral symmetry restoration, without instanton suppression. Moreover, at $T=(1-2) T_c$ the non-perturbative effects due to ``molecules&#34; are so st

Volker Koch

We study the temperature dependence of quark antiquark correlations in the space like direction. In particular, we predict the temperature dependence of space like Bethe-Salpeter amplitudes using recent Lattice gauge data for the space like string potential. We also investigate the effect of the space like string potential on the screening mass and discuss p

R. F. Alvarez-Estrada, A. Dobado, A. Gomez Nicola

We analyze the finite temperature (T) extension of the Wess-Zumino- Witten functional, discussed in a previous work, to one loop in chiral perturbation theory. As a phenomenological application, we calculate finite temperature corrections to the amplitude of the $π^0$ decay into two photons. This calculation is performed in three limits : i)$T/M_π<<1$, ii)th

T. H. Hansson, M. Sporre, I. Zahed

We extend our earlier work on static color singlet correlators in high T QCD (DeTar correlators) to baryonic and gluonic sources, and estimate the corresponding screening masses using the dimensionally reduced theory. We discuss spin and polarization dependence of meson and baryon masses in the $T \rightarrow \infty$ limit, and possible nonperturbative effec

J. J. de Swart, Th. A. Rijken, R. Timmermans

Invited talk given at the NAN &#39;93 Conference in Moscow, Russia, sept 1993. A review is given of the different ways to describe pbarp scattering. Next the Nijmegen partial wave analyses of the pbarp data as well as the corresponding Nijmegen NbarN database are discussed. These partial wave analyses are finally used as a tool to construct a better NbarN po

C. F. Baillie, K. A. Hawick, D. A. Johnston

We simulate the Ising model on a set of fixed random $ϕ^3$ graphs, which corresponds to a {\it quenched} coupling to 2D gravity rather than the annealed coupling that is usually considered. We investigate the critical exponents in such a quenched ensemble and compare them with measurements on dynamical $ϕ^3$ graphs, flat lattices and a single fixed $ϕ^3$ gra

J. Ambjorn, P. Bialas, J. Jurkiewicz, Z. Burda

We propose a new, very efficient algorithm for sampling of random surfaces in the Monte Carlo simulations, based on so-called baby universe surgery, i.e. cutting and pasting of baby universes. It drastically reduces slowing down as compared to the standard local flip algorithm, thereby allowing simulations of large random surfaces coupled to matter fields. A

D. Weingarten

I review recent work on the calculation of hadron masses, decay constants and wave functions.

H. Chen, J. Sexton, A. Vaccarino, D. Weingarten

We evaluate the infinite volume, continuum limit of $0^{++}$ and $2^{++}$ glueball masses in the valence approximation. We find $m_{0^{++}} = 1740 \pm 71 $~MeV and $m_{2^{++}} = 2359 \pm 128 $~MeV, consistent with the interpretation of $f_0 ( 1710 )$ as the lightest scalar glueball.

Harald F. Muller, Christoph Schmid

The energy density correlation function $C(x,y)=<ρ(x)ρ(y)>-<ρ>^2$ and its Fourier transform generated by the gravitational tidal forces of the inflationary de Sitter expansion are derived for a massless or light ($m<<H$) neutral scalar field $Φ$ without self--interactions, minimally coupled to gravity. The field has no classical background component, $<Φ>=0$

O. Brodbeck, N. Straumann

We prove that static, spherically symmetric, asymptotically flat, regular solutions of the Einstein-Yang-Mills equations are unstable for arbitrary gauge groups. The proof involves the following main steps. First, we show that the frequency spectrum of a class of radial perturbations is determined by a coupled system of radial &#34;Schroedinger equations&#34

Subir Sachdev, T. Senthil, R. Shankar

Consider a $d$-dimensional antiferromagnet with a quantum disordered ground state and a gap to bosonic excitations with non-zero spin. In a finite external magnetic field, this antiferromagnet will undergo a phase transition to a ground state with non-zero magnetization, describable as the condensation of a dilute gas of bosons. The finite temperature proper

Y. C. Chen, T. K. Lee

The spin, charge and pairing correlation functions for the ground state of two-dimensional $t-J$ model are calculated by using the power method which projects out the ground state from a variational wave function. ``Exact&#39;&#39; results are obtained for $10\times10$ and $8\times8$ lattices with low particle densities. The results are surprisingly similar

Frederic Piechon, Anuradha Jagannathan

A numerical study is made of the spectra of a tight-binding hamiltonian on square approximants of the quasiperiodic octagonal tiling. Tilings may be pure or random, with different degrees of phason disorder considered. The level statistics for the randomized tilings follow the predictions of random matrix theory, while for the perfect tilings a new type of l

Hua Chen, Daniel Mattis

We study the stability of the ordinary Landau Fermi liquid phase for interacting, spinless electrons. We require causality and demand that the Pauli principle be obeyed. We find a phase diagram determined by two parameters: the particle density and the interaction strength. We find that the homogeneous, constant density Fermi liquid phase of a spinless Fermi

Alexander G. Ramm, Gennady P. Berman

We consider scattering of a free quantum particle on a singular potential with rather arbitrary shape of the support of the potential. In the classical limit $\hbar=0$ this problem reduces to the well known problem of chaotic scattering. The universal estimates for the stability of the scattering amplitudes are derived. The application of the obtained result

N. J. Cornish, J. W. Moffat

``Reports of my death are greatly exaggerated&#39;&#39; - Mark Twain. We consider the claim by Damour, Deser and McCarthy that nonsymmetric gravity theory has unacceptable global asymptotics. We explain why this claim is incorrect.

R. Paunov

We examine the relation between two known classes of solutions of the sine--Gordon equation, which are expressed by theta functions on hyperelliptic Riemann surfaces. The first one is a consequence of the Fay&#39;s trisecant identity. The second class exists only for odd genus hyperelliptic Riemann surfaces which admit a fixed--point--free automorphism of or

N. Asmar, Stephen J. Montgomery-Smith

In a celebrated paper, Burkholder, Gundy, and Silverstein used Brownian motion to derive a maximal function characterization of H^p spaces for 0 < p < infinity. In this paper, we show that their method extends to higher dimensions and yields a dimension-free weak type (1,1) estimate for a conjugate function on the N-dimensional torus.

V. Mukhanov, A. Wipf

In this paper we show how the well-know local symmetries of Lagrangeans systems, and in particular the diffeomorphism invariance, emerge in the Hamiltonian formulation. We show that only the constraints which are linear in the momenta generate transformations which correspond to symmetries of the corresponding Lagrangean system. The nonlinear constraints (wh

A. Candiello

It is nearly twenty years that there exist computer programs to reduce products of Lie algebra irreps. This is a contribution in the field that uses a modern computer language (``C&#39;&#39;) in a highly structured and object-oriented way. This gives the benefits of high portability, efficiency, and makes it easier to include the functions in user programs.

K. Schoutens, E. Verlinde, H. Verlinde

In this note we consider some consequences of quantum gravity on the process of black hole evaporation. In particular, we will explain the suggestion by &#39;t Hooft that quantum gravitational interactions effectively exclude simultaneous measurements of the Hawking radiation and of the matter falling into the black hole. The complementarity of these measure

R. Antalik, V. E. Lyubovitskij

A description of the NN scattering is constructed starting from the $π, η, η&#39;$ pseudoscalar-, the $ρ, ϕ, ω$ vector-, and the $\varepsilon(600), a_0, f_0(1400)$ scalar - meson-nucleon coupling constants, which we obtain within a relativistic quark model. Working within the Blankenbecler-Sugar-Logunov-Tavkhelidze quasipotential dynamics we thus describe th

A. Ali, V. M. Braun, H. Simma

We carry out a detailed study of exclusive radiative rare $B$-decays in the framework of the QCD sum rules on the light cone, which combines the traditional QCD sum rule technique with the description of final state vector mesons in terms of the light-cone wave functions of increasing twist. The decays considered are: $B_{u,d} \to K^* +γ, B_{u,d}\to ρ+γ, B_d

Peter Cho

Two recently discovered excited charm baryons are studied within the framework of Heavy Hadron Chiral Perturbation Theory. We interpret these new baryons which lie $308 \MeV$ and $340 \MeV$ above the $Λ_c$ as $I=0$ members of a P-wave spin doublet. Differential and total decay rates for their double pion transitions down to the $Λ_c$ ground state are calcula

Chuan Liu, Karl Jansen, Julius Kuti

The first simulation results are presented on Higgs mass calculations in the spontaneously broken phase of the Higgs sector in the minimal Standard Model with higher derivative regulator. A heavy Higgs particle is found in the TeV mass range in the presence of a complex conjugate ghost pair at higher energies. The ghost pair evades easy experimental detectio

T. Neuhaus

We present a new and exploratory approach to determine the $Δβ(β)$-shift in the $O(3)$ nonlinear $σ$-model. The method is based on a scaling hypothesis for a free energy difference, which is assumed to be valid in a situation where the mass gap correlation length $ξ$ is of the order or larger than the linear extent $L$ of the considered square lattice sizes.

She-Sheng Xue, Giuliano Preparata

In the framework of the recently proposed electroweak theory on a Planck lattice, we are able to solve approximately the lattice Dyson equation for the fermion self-energy functions, and obtain the ratio between the masses of the $t-$ and $b-$ quarks in terms of the electroweak coupling constants. The predicted top mass agrees with recent determinations from

R. Brunetti, D. Guido, R. Longo

The Bisognano-Wichmann property on the geometric behavior of the modular group of the von Neumann algebras of local observables associated to wedge regions in Quantum Field Theory is shown to provide an intrinsic sufficient criterion for the existence of a covariant action of the (universal covering of) the Poincaré group. In particular this gives, together