February 1994 arXiv papers — page 4

M. Goeckeler, H. A. Kastrup, J. Westphalen, F. Zimmermann

According to a proposal of Luescher it is possible to determine elastic scattering phases in infinite volume from the energy spectrum of two-particle states in a periodic box. We demonstrate the applicability of this method in the broken phase of the four-dimensional O(4) non-linear sigma-model in a Monte Carlo study on finite lattices. This non-perturbative

Warren G. Anderson

We show that the appropriate vacuum state for the interior of a box with reflecting walls being lowered adiabatically into a Schwarzschild black hole is the Boulware state. This is concordant with the results of Unruh and Wald, who used a different approach to obtain the stress-energy inside the box. Some comments about an entropy bound for ordinary matter,

Jerome Martin

We show in this article how the usual hamiltonian formalism of General Relativity should be modified in order to allow the inclusion of the Euclidean classical solutions of Einstein's equations. We study the effect that the dynamical change of signature has on the superspace and we prove that it induces a passage of the signature of the supermetric from

T. R. Kirkpatrick, D. Belitz

The nonlinear $σ$-model for disordered interacting electrons is studied in spatial dimensions $d>4$. The critical behavior at the metal-insulator transition is determined exactly, and found to be that of a standard Landau-Ginzburg-Wilson $ϕ^4$-theory with the single-particle density of states as the order parameter. All static exponents have their mean-field

P. Di Francesco, E. Guitter

The problem of counting the different ways of folding the planar triangular lattice is shown to be equivalent to that of counting the possible 3-colorings of its bonds, a dual version of the 3-coloring problem of the hexagonal lattice solved by Baxter. The folding entropy Log q per triangle is thus given by Baxter's formula q=sqrt(3)(Gamma[1/3])^(3/2)/2p

Afshin Montakhab, J. M. Carlson, Jeremy Levy

We study the response of a recently proposed global coupling model of charge-density waves to a joint ac+dc drive. The model is the standard Fukuyama-Lee-Rice model with an additional global coupling term to account for interaction with (uncondensed) quasi-particles. We find that traditional mode-locking is accompanied by hysteresis on mode-locked steps. The

Toshio Tsuchiya, Tetsuro Konishi, Naoteru Gouda

The microscopic dynamics of one-dimensional self-gravitating many-body systems is studied. We examine two courses of the evolution which has the isothermal and stationary water-bag distribution as initial conditions. We investigate the evolution of the systems toward thermal equilibrium. It is found that when the number of degrees of freedom of the system is

Martin White

We discuss a method for a model independent reconstruction of the CMB temperature fluctuation power spectrum on small and intermediate scales that is geared to individual experiments. The importance of off-diagonal correlations for determining the shape of the power spectrum is emphasized and some examples of a reconstruction method are given. By using this

Martin White, Mark Srednicki

We discuss the applicability and derivation of window functions for cosmic microwave background experiments on large and intermediate angular scales. These window functions describe the response of the experiment to power in a particular mode of the fluctuation spectrum. We give general formulae, illustrated with specific examples, for the most common observ

M. S. Ravi, J. Rosenthal, X. Wang

We compute the degree of the generalized Plücker embedding $κ$ of a Quot scheme $X$ over $\PP^1$. The space $X$ can also be considered as a compactification of the space of algebraic maps of a fixed degree from $\PP^1$ to the Grassmanian $\rm{Grass}(m,n)$. Then the degree of the embedded variety $κ(X)$ can be interpreted as an intersection product of pullbac

Stanley J. Brodsky, L. Frankfurt, J. F. Gunion, A. H. Mueller

We demonstrate that the distinctive features of the forward differential cross section of diffractive leptoproduction of a vector meson can be legitimately calculated in perturbative QCD in terms of the light-cone $q \bar q$ wave function of the vector meson and the gluon distribution of the target. In particular, we calculate the $Q^2$ and nuclear dependenc

A. Zhitnitsky

We discuss the nonleading, ``soft" contribution to the pion form factor at intermediate momentum transfer within operator product expansion approach. We argue, that the corresponding contribution can temporarily {\bf simulate} the leading twist behavior in the extent region of $ Q^2:~~3 GeV^2\leq Q^2\leq 35 GeV^2 $, where $Q^2 F(Q^2)\sim const.$ Such a m

C. Kounnas

We construct a class of superstring solutions in non trivial space-time. The existence of an $N=4$ world-sheet superconformal symmetry stabilizes our solutions under perturbative string loop corrections and implies in target space some unbroken space-time supersymmetries.

Ulrich Ellwanger

Flow equations describe the evolution of the effective action $Γ_k$ in the process of varying an infrared cutoff $k$. The presence of the infrared cutoff explicitly breaks gauge and hence BRS invariance. We derive modified Slavnov-Taylor identities, which are valid for nonvanishing $k$. They guarantee the BRS invariance of $Γ_k$ for $k\to0$, and hence allow

P. A. Shah

The scattering of vortices at a critical value of the coupling constant in the Lagrangian can be approximated by a geodesic motion in the moduli space of classical static configurations of vortices. In this paper we give a scheme for generalising this idea to couplings that are near to the critical value. By perturbing a critically coupled field, we show tha

M. I. Polikarpov, Ken Yee

The fractal dimension $D_f$ of sites resisting Landau or maximal Abelian(MA) gauge fixing in lattice $SU(3)$ gluodynamics is defined and computed. In Landau gauge such sites clump into $D_f\sim 1$ clusters in the confining phase. In the finite temperature phase their dimensionality drops to $D_f < 1$, that is, clustering seems to dissipate. In contrast, MA g

I. Antoniadis, S. Ferrara, C. Kounnas

We construct a new class of exact and stable superstring solutions based on $N=4$ superconformal world-sheet symmetry. In a subclass of these, the full spectrum of string excitations is derived in a modular-invariant way. In the weak curvature limit, our solutions describe a target space with non-trivial metric and topology, and generalize the previously kno

Max Tegmark, Harold S. Shapiro

We study the behavior of infinite systems of coupled harmonic oscillators as t->infinity, and generalize the Central Limit Theorem (CLT) to show that their reduced Wigner distributions become Gaussian under quite general conditions. This shows that generalized coherent states tend to be produced naturally. A sufficient condition for this to happen is shown t

A. A. Tseytlin

We discuss charged string solutions of the effective equations of D=4 heterotic string theory with non-constant dilaton and modulus fields. The effective action contains a generic moduli-dependent coupling function in the gauge field kinetic term and a non-perturbative scalar potential. This is a review of hep-th/9307123 by M. Cvetic and the author. To be pu

M. Matone

We obtain nonperturbative results in the framework of continuous Liouville theory. In particular, we express the specific heat ${\cal Z}$ of pure gravity in terms of an expansion of integrals on moduli spaces of punctured Riemann spheres. The integrands are written in terms of the Liouville action. We show that ${\cal Z}$ satisfies the Painlevé I.

G. Papadopoulos, B. Spence

We give new formulations of the solutions of the field equations of the affine Toda and conformal affine Toda theories on a cylinder and two-dimensional Minkowski space-time. These solutions are parameterised in terms of initial data and the resulting covariant phase spaces are diffeomorphic to the Hamiltonian ones. We derive the fundamental Poisson brackets

J. Baacke, S. Junker

We correct an error in our treatment of the tadpole contribution to the fluctuation determinant of the sphaleron, and also a minor mistake in a previous estimate. Thereby the overall agreement between the two existing exact computations and their consistency with the estimate is improved considerably.

Uwe Grimm

A ``dilute&#39;&#39; generalisation of the Birman--Wenzl--Murakami algebra is considered. It can be ``Baxterised&#39;&#39; to a solution of the Yang--Baxter algebra. The $D^{(2)}_{n+1}$ vertex models are examples of corresponding solvable lattice models and can be regarded as the dilute version of the $B^{(1)}_{n}$ vertex models.

Terry Gannon

The complete classification of WZNW modular invariant partition functions is known for very few affine algebras and levels, the most significant being all levels of $A_1$ and $A_2$ and level 1 of all simple algebras. Here, we address the classification problem for the nicest high rank semi-simple affine algebras: $(A_1^{(1)})^{\oplus_r}$. Among other things,

B. Ananthanarayan, K. S. Babu, Q. Shafi

Within the framework of supersymmetric grand unification, estimates of the $b$ quark mass based on the asymptotic relation $m_b \simeq m_τ$ single out the region with $\tanβ$ close to unity, particularly if $m_t(m_t) \stackrel{_<}{_\sim} 170\ GeV$. We explore the radiative breaking of the electroweak symmetry and the associated sparticle and higgs spectrosco

U. Baur, S. Errede, G. Landsberg

We study the correlation of photon and charged lepton pseudorapidities, $η(γ)$ and $η(\ell)$, $\ell=e,\,μ$, in $p\,\pbar \rightarrow W^\pmγ+X\rightarrow \ell^\pm p\llap/_Tγ+X$. In the Standard Model, the $Δη(γ,\ell)= η(γ) - η(\ell)$ differential cross section is found to exhibit a pronounced dip at $Δη(γ,\ell) \approx \mp 0.3$ ($=0$)in $p\bar p$ ($pp$) colli

Krzysztof Kurek

Improvement of the radiative correction scheme for the deep inelastic scattering on the heavy targets is discussed. Arguments that the contribution of the radiative tail from the elastic peak should be calculated without use of the Born approximation in the case of the heavy target scattering are presented. The semianalytical approach based on the classical

H. Hogaasen, M. Sadzikowski

We explore the influence on the Isgur-Wise function of the colour electric potential between heavy and light quarks in mesons. It is shown that in bag models, its inclusion tends to restore light quark flavour symmetry relative to the MIT bag predictions, and that relative to this model it flattens the Isgur-Wise function. Results compare very well with obse

Jun-ichi Kamoshita, Yasuhiro Okada, Minoru Tanaka

Upper bounds on the three neutral scalar Higgs masses are considered in the supersymmetric standard model with a gauge singlet Higgs field. When the lightest Higgs is singlet-dominated the second lightest Higgs is shown to lie near or below the theoretical upper bound on the lightest Higgs mass. We also consider detectability of these Higgs bosons at a futur

Michael Gronau

This review addresses the question of the chirality of $b$ quark weak couplings from a theoretical and from a purely phenomenological point of view. Due to their small magnitude $b$ decay couplings are subject to possible large corrections from right-handed terms, on the one hand, and do not affect the weak interactions of the first two quark families in any

N. J. Cornish, C. P. Dettmann, N. E. Frankel

We investigate the phase-space for trajectories in multi-black hole spacetimes. We find that complete, chaotic geodesics are well described by Lyapunov exponents, and that the attractor basin boundary scales as a fractal in a diffeomorphism invariant manner.

Marcelo J. Rozenberg, Goetz Moeller, Gabriel Kotliar

We study the metal-to-insulator transition of the Hubbard model at zero temperatures in infinite dimensions. The coexistence of metallic and insulating solutions for a finite range of the interaction is established. It is shown that the metallic solution is lower in energy for any interaction in the coexistence region and that the transition is of second ord

Sergei E. Esipov

We investigate the time behavior of the fragmentation model with Kolmogorov time scales and space contraction resembling the random $β$-model of turbulence. The space averages computed at any instant using the entire spatial realization of the velocity field are shown to fluctuate strongly in time, and in this sense they are not observable. The time averagin

E. Ben-Naim, P. L. Krapivsky, S. Redner

We study a simple aggregation model that mimics the clustering of traffic on a one-lane roadway. In this model, each ``car&#39;&#39; moves ballistically at its initial velocity until it overtakes the preceding car or cluster. After this encounter, the incident car assumes the velocity of the cluster which it has just joined. The properties of the initial dis

R. G. Carlberg, H. K. C. Yee, E. Ellingson

The MS1224+20 cluster of galaxies is a high luminosity X-ray source at z=0.325. To compare the lensing mass to the virial mass we have completed a uniform, high precision redshift survey over a field of $7\arcm\times9\arcm$, obtaining 75 redshifts. The velocity dispersion of 30 cluster galaxies is $775$ \kms\ and the projected harmonic radius is 0.32 \hmpc.

E. Giallongo, S. D&#39;Odorico, A. Fontana, R. G. McMahon

A measure of the average depression between Lyman absorption lines in the spectrum of the faint quasar BR1202-0725 ($z_{em}=4.695$) is presented. The relatively high resolution of the spectrum ($\sim 40$ km s$^{-1}$) allows the selection of regions free of strong absorption lines in the Lyman alpha forest. A reliable evaluation of the continuum shape is base

Yoshiaki SOFUE

We simulate the propagation of a shock front through the galactic halo induced by an explosion and/or a starburst at the galactic center. A huge dumbbell ($Ω$)-shaped shock front produced by an explosion of energy $3\times 10^{56}$ ergs about fifteen million years ago can mimic the radio and X-ray North Polar Spur as well the southern large X-ray spur. The p

Hironobu Ishihara

This paper is an attempt for the classification of polarized manifolds of sectional genus $g=3$ and dimension $n\geq 3$. As in the case of $g\leq 2$,which was classified by T.Fujita,we use Mori-Kawamata theory. The classification result of $g=3$ and $n=2$, which was obtained by H.Maeda,is also used essentially. Although our results are far from being complet

George G. Szpiro

We study sequences of random numbers {Z[1],Z[2],Z[3],...,Z[n]} -- which can be considered random walks with reflecting barriers -- and define their &#34;types&#34; according to whether Z[i] > Z[i+1], (a down-movement), or Z[i] < Z[i+1] (up-movement). This paper examines the means, xi, to which the Zi converge, when a large number of sequences of the same typ

W. Janke, M. Katoot, R. Villanova

We use the single-cluster Monte Carlo update algorithm to simulate the Ising model on two-dimensional Poissonian random lattices with up to 80,000 sites which are linked together according to the Voronoi/Delaunay prescription. In one set of simulations we use reweighting techniques and finite-size scaling analysis to investigate the critical properties of th

L. Berezansky, E. Braverman

The connection of function properties of solutions with exponential stability of linear impulsive differential equation $$\dot{x} (t) - \sum_{k=1}^m {A_k (t) x[h_k(t)]} = r(t),~ t \geq 0, x(ξ) = φ(ξ),~ ξ< 0,$$ $$x(τ_j) = B_j x(τ_j - 0) , ~j=1,2, \dots .$$ The explicit stability results and sufficient conditions for existence of integrable solutions are prese

S. S. Bayin, F. I. Cooperstock, V. Faraoni

We explore the possibility of describing our universe with a singularity--free, closed, spatially homogeneous and isotropic cosmological model, using only general relativity and a suitable equation of state which produces an inflationary era. A phase transition to a radiation--dominated era occurs as a consequence of boundary conditions expressing the assump

P. M. Stevenson

In QCD with 16\half-epsilon massless quark flavours there is an infrared fixed point with alpha_s/pi = (8/321)epsilon in the limit epsilon -> 0+. I develop the idea of Banks and Zaks to expand about N_f=16\half. This expansion is certainly useful for N_f=16, 15, 14, ..., and arguably it can reach the phenomenologically interesting case N_f=2, where it sugges

T. Shigetani, K. Suzuki, H. Toki

We study the deep inelastic structure functions of mesons within the Nambu and Jona-Lasinio model. We calculate the valence quark distributions in $π$, $K $, and $ρ$ mesons at the low energy model scale, which are evoluted to the experimental momentum scale in terms of the Altarelli-Parisi equation. The resulting distribution functions show reasonable agreem

George R. Blumenthal, Kathryn V. Johnston

The Sachs-Wolfe effect is known to produce large angular scale fluctuations in the Cosmic Microwave Background Radiation (CMBR) due to gravitational potential fluctuations. We show how the angular correlation function of the CMBR can be expressed explicitly in terms of the mass autocorrelation function $ξ(r)$ in the Universe. We derive analytic expressions f

L. D. Faddeev, P. N. Pyatov

The non-commutative differential calculus on the quantum groups $SL_q(N)$ is constructed. The quantum external algebra proposed contains the same number of generators as in the classical case. The exterior derivative defined in the constructive way obeys the modified version of the Leibnitz rules.

V. M. Braun, I. Halperin

We propose a simple method to calculate the pion form factor at not very large momentum transfers, which combines the technique of the QCD sum rules with the description of the pion in terms of the set of wave functions of increasing twist. This approach allows one to calculate the soft (end point) contribution to the form factor in a largely model-independe

P. Marziani, W. C. Keel, D. Dultzin--Hacyan, J. W. Sulentic

A detailed study of the mixed-morphology galaxy pair CPG 29 (Arp 119, VV 347) shows spectacular spectroscopic peculiarities in the southern (spiral) component (Mkn 984) including a spatially resolved region, roughly aligned along the minor axis of the galaxy, with multiple emission-line components redshifted by as much as 1300 km s$^{-1}$ with respect to the

Alvaro Arias

In this paper we address some basic questions of the Banach space structure of the nest algebras in the trace class; in particular, we study whether any two of them are isomorphic to each other, and show that the nest algebras in the trace class have bases. We construct three non-isomorphic examples of nest algebras in $c_1$; present a new proof of the prima

Denny H. Leung

Let $M$ be a non-degenerate Orlicz function such that there exist $\ep > 0$ and $0 < s < 1$ with $\su M(\ep s^i)/M(s^i) < \infty$. It is shown that the Orlicz sequence space $h_M$ is isomorphic to a subspace of $C(\om^\om)$. It is also shown that for any non-degenerate Orlicz function $M$, $h_M$ does not embed into $C(\al)$ for any $\al < \om^\om$.

Nigel J. Kalton

We give a simple and explicit example of a complex Banach space which is not isomorphic to its complex conjugate, and hence of two real-isomorphic spaces which are not complex-isomorphic.

Nigel J. Kalton

We consider the problem of complex interpolation of certain Hardy-type subspaces of Köthe function spaces. For example, suppose $X_0$ and $X_1$ are Köthe function spaces on the unit circle $\bold T,$ and let $H_{X_0}$ and $H_{X_1}$ be the corresponding Hardy spaces. Under mild conditions on $X_0,X_1$ we give a necessary and sufficient condition for the compl

W. Bietenholz

A system of Goldstone bosons - stemming from a symmetry breaking $O(N) \to O(N-1)$ - in a finite volume at finite temperature is considered. In the framework of dimensional regularization, the partition function is calculated to 3 loops for 3 and 4 dimensions, where Polyakov&#39;s measure for the functional integration is applied. Although the underlying the

A. Agodi, G. Andronico, M. Consoli

The generally accepted ``triviality&#39;&#39; of $λΦ^4$ theories does not forbid Spontaneous Symmetry Breaking but implies a trivially free shifted field which becomes effectively governed by a quadratic hamiltonian. As a consequence, one expects the one-loop potential to be exact . We present a lattice computation of the effective potential for massless $λΦ

Piotr Podleś

We prove that each action of a compact matrix quantum group on a compact quantum space can be decomposed into irreducible representations of the group. We give the formula for the corresponding multiplicities in the case of the quotient quantum spaces. We describe the subgroups and the quotient spaces of quantum SU(2) and SO(3) groups.

M. Henneaux

Some general techniques and theorems on the spacetime locality of the antifield formalism are illustrated in the familiar cases of the free scalar field, electromagnetism and Yang-Mills theory. The analysis explicitly shows that recent criticisms of the usual approach to dealing with locality are ill-founded.

A. A. Vladimirov

A regular way to define an additive coproduct (or ``coaddition&#39;&#39;) on the q-deformed differential complexes is proposed for quantum groups and quantum spaces related to the Hecke-type R-matrices. Several examples of braided coadditive differential bialgebras (Hopf algebras) are presented.

J. Lopez, D. Nanopoulos

We propose a string-inspired model which correlates several aspects of particle physics and cosmology. Inspired by the flat directions and the absence of adjoint Higgs representations found in typical string models, we consider a no-scale $SU(5)\times U(1)$ supergravity model. This model entails well determined low-energy phenomenology, such as the value of

J. P. Blaizot, A. Krzywicki

We use the linear $σ$ model to analyse the dynamics of a disoriented chiral condensate. For idealized boundary conditions appropriate to high energy collisions, the problem can be reduced to a one dimensional one. The evolution of the chiral state is then that of a simple dynamical system and can be studied analytically.

G. K. Leontaris, J. D. Vergados

In practically all extentions of the standard model, the neutrinos naturally acquire a mass. The neutrino mass matrix, however, contains many parameters which can neither be predicted by the prevailing models nor can be fitted to the data. We propose a fermion mass matrix ansatz in the context of Grand Unified Supersymmetric Theories (GUTs) at the GUT scale

N. G. Stefanis, M. Bergmann

Physical wave functions for the nucleon and the $Δ^{+}$ isobar are presented, which unify the best features of previous models. With these wave functions we can calculate elastic form factors and the decays of the charmonium levels ${}^{3}S_{1}$, ${}^{3}P_{1}$, ${}^{3}P_{2}$ into $p\bar p$ in agreement with the data. A striking scaling behavior between $R=|G

R. J. N. Phillips

Invited review talk at the International Conference on Non-Accelerator Particle Physics (ICNAPP-94), Bangalore, India, 2-9 January 1994. Latex file.

Hitoshi Yamamoto

Hadronic decays of $B$ mesons are reviewed. First, masses of $B$ mesons and observed patterns together with physics behind them are discussed. Then the effective Hamiltonian responsible for major decays is presented and its practical applications are discussed in the context of factorization. Various tests of factorization are then studied. For rare decays,

J. F. Gunion, H. Pois

We explore the prospects for detection of sparticles and Higgs bosons at the Tevatron, LEP-200 and the LHC in the allowed parameter space of a `yukawa unified&#39; ($λ_b(M_U)=λ_τ(M_U)$) minimal supergravity (YUMS) model, where the only non-zero unification scale soft-SUSY-breaking terms are a universal gaugino mass and a Higgs mixing term. In a bottom-up app

J. M. Aroca, H. Fort

It is showed that the very recently introduced Lagrangian $loop$ formulation of the lattice Maxwell theory is equivalent to the Villain form in 2+1 dimensions. A transparent description of the classical $loop$ action is given in pure geometrical terms for the $2+1$ and $3+1$ dimensional cases.

Jacobus Verbaaarschot

Approximating the sum over all gauge field configurations in the QCD partition function by a liquid of instantons, we calculate the spectrum of the Dirac operator for two and three colors and for 0, 1 and 2 flavors. We find a remarkable difference in the spectrum near zero virtuality between 2 and 3 colors, which can be explained in terms of chiral random ma

Riccardo Capovilla, Jemal Guven

We consider the specialization to spatially homogenous solutions of the Jacobson formulation of N=1 canonical supergravity in terms of Ashtekar&#39;s new variables. We find that the classical Poisson algebra of the supersymmetry constraints is preserved by this specialization only for Bianchi type A models. The quantization of supersymmetric Bianchi type A m

Edward Malec

Spherical configurations that are very massive must be surrounded by apparent horizons. These in turn, when placed outside a collapsing body, have a fixed area and must propagate outward with a velocity equal to the velocity of radially outgoing photons. That proves, within the framework of the (1+3) formalism and without resorting to the Birkhoff theorem, t

A. V. Balatsky, P. Monthoux, D. Pines

We consider the influence of planar ``magnetic&#34; imperfections which destroy the local magnetic order, such as Zn impurities or $Cu^{2+}$ vacancies, on the low temperature properties of the cuprate superconductors. In the unitary limit, at low temperatures, for a $d_{x^2-y^2}$ pairing state such imperfections produce low energy quasiparticles with an anis

J. Garcia-Ojalvo, J. M. Sancho, H. Guo

The non-conserved $ϕ^4$ model defined by a Langevin equation with external non-white noise is studied by means of the Dynamic Renormalization Group. The correlation time of the noise changes the critical point location but does not affect the critical exponents up to order $\varepsilon^2$. The same effect is obtained when the correlation length of the noise

Elbio Dagotto, Alexander Nazarenko, Massimo Boninsegni

A model of weakly interacting hole quasiparticles is proposed to describe the normal state of the high temperature superconductors. The effect of strong correlations is contained in the dispersion relation of the holes, which is obtained accurately using a numerical technique and the t-J model on $12\times 12$ clusters. Saddle-points generated by many-body e

Gen Tatara, Hidetoshi Fukuyama

The macroscopic quantum tunneling of a planar domain wall in a ferromagnetic metal is studied by use of an instanton method. Based on the Hubbard model, the effective action of the magnetization is derived within the assumption of slow dependences on space and time. The resulting action is formally similar to that of a ferromagnetic Heisenberg model but with

Andrei Linde

We show that, contrary to the standard belief, primordial monopoles expand exponentially during inflation in the new inflationary universe scenario. Moreover, inflation of monopoles continues without an end even when inflation ends in the surrounding space. Therefore primordial monopoles (as well as other topological defects produced during inflation) can se

Alain Bouquet, Jean Kaplan, Jean-Manuel Verschaeve

Experiments are looking for diffuse brown dwarfs in the dark galactic halo through the gravitational lens effect. If brown dwarfs are clumped in dark clusters, the event rate is not changed, but events are spatially clustered, and stars nearby a micro-lensed one are likely to be micro-lensed in a near future. Therefore, an intensive survey of the region wher

Scott Dodelson, Geza Gyuk, Michael S. Turner

The cold dark matter (CDM) scenario for structure formation in the Universe is very attractive and has many successes; however, when its spectrum of density perturbations is normalized to the COBE anisotropy measurement the level of inhomogeneity predicted on small scales is too large. This can be remedied by a tau neutrino of mass $1\MeV - 10\MeV$ and lifet

A. V. Smilga

We show that $QCD_2$ with adjoint fermions involves instantons due to nontrivial $π_1[SU(N)/Z_N]~=~Z_N$. At high temperatures, quasiclassical approximation works and the action and the form of effective (with account of quantum corrections) instanton solution can be evaluated. Instanton presents a localized configuration with the size $\propto g^{-1}$. At $N

Andreas Albrecht

There are many striking phenomena which are attributed to ``quantum coherence&#39;&#39;. It is natural to wonder if there are new quantum coherence effects waiting to be discovered which could lead to interesting results and perhaps even practical applications. A useful starting point for such discussions is a definition of ``quantum coherence&#39;&#39;. In

Igor Vaysburd

We present a new class of 2d integrable models obtained as perturbations of minimal CFT with W-symmetry by fundamental weight primaries. These models are generalisations of well known $(1,2)$-perturbed Virasoro minimal models. In the large $p$ (number of minimal model) limit they coincide with scalar perturbations of WZW theories. The algebra of conserved ch

A. P. Isaev

The algebraic formulation of the quantum group covariant noncommutative geometry in the framework of the $R$-matrix approach to the theory of quantum groups is given. We consider structure groups taking values in the quantum groups and introduce the notion of the noncommutative connections and curvatures transformed as comodules under the &#34;local&#34; coa

W. de Boer

A review is given on the consistency checks of GUT, which unify the electroweak and strong nuclear forces into a single theory. Such theories predict a new kind of force, which could provide answers to several open questions in cosmology. The possible role of such a ``primeval'' force will be discussed in the framework of the Big Bang Theory. Although such a

B. Grammaticos, A. Ramani, K. M. Tamizhmani

We present an integrability criterion for rational mappings based on two requirements. First, that a given point should have a unique preimage under the mapping and, second, that the spontaneously appearing singularities be confined to a few iteration steps. We present several examples of known integrable mappings that meet these requirements and, also, use

J. Parramore, J. Piekarewicz

We investigate the Lorentz structure of the confinement potential through a study of the meson spectrum using Salpeter&#39;s instantaneous approximation to the Bethe-Salpeter equation. The equivalence between Salpeter&#39;s and a random-phase-approximation (RPA) equation enables one to employ the same techniques developed by Thouless, in his study of nuclear

Ekkard Schnedermann, Ulrich Heinz

We are analyzing the hydrodynamics of 200 A GeV S+S collisions using a new approach which tries to quantify the uncertainties arising from the specific implementation of the hydrodynamical model. Based on a previous phenomenological analysis we use the global hydrodynamics model to show that the amount of initial flow, or initial energy density, cannot be de

Suk-Joon Lee

Nuclear multifragmentation process can be viewed as a recombination of nucleons into clusters of various sizes. In a combinatorial analysis, various moments of cluster size distribution appear to be quite simple in terms of canonical partition functions. This simple model can also describe a branching phenomena and a clusterization phenomena. The possibility

W. Bietenholz, J. J. Giambiagi

We discuss solutions of the spherically symmetric wave equation and Klein Gordon equation in an arbitrary number of spatial and temporal dimensions. Starting from a given solution, we present various procedures to generate futher solutions in the same or in different dimensions. The transition from odd to even or non integer dimensions can be performed by fr

S. Krivonos, A. Sorin

We construct the nonlinear $N=2$ super-$W_3^{(2)}$ algebra with an arbitrary central charge at the classical level in the framework of Polyakov &#34;soldering&#34; procedure. It contains two non-intersecting subalgebras: $N=2$ superconformal algebra and $W_3^{(2)}$ and their closure gives the $N=2$ super-$W_3^{(2)}$ algebra. Besides the currents of $N=2$ sup

Michel Dubois-Violette

We describe a bigraded generalization of the Weil algebra, of its basis and of the characteristic homomorphism which besides ordinary characteristic classes also maps on Donaldson invariants.

M. R. Niedermaier

An elementary proof is given for the existence of infinite dimensional abelian subalgebras in quantum W-algebras. In suitable realizations these subalgebras define the conserved charges of various quantum integrable systems. We consider all principle W-algebras associated with the simple Lie algebras. The proof is based on the more general result that for a

Eduardo Ramos, Sonia Stanciu

We prove that the supersymmetric BKP-hierarchy of Yu (SBKP_2) is hamiltonian with respect to a nonlinear extension of the N=1 Super-Virasoro algebra (W_SBKP) by fields of spin k, where k>3/2 and 2k = 0,3 mod 4. Moreover, we show how to associate in a similar manner an N=1 W-superalgebra with every integrable hierarchy of the SKdV-type. We also show using dre

N. G. Stefanis, M. Bergmann

Invited talk presented at the International Workshop on Hadron Structure &#39;93, Banská \v Stiavnica, Slovakia, 5-10 September, 1993; to be published in the Proceedings.

H. Baer, M. Bisset, C. Kao, X. Tata

We examine prospects for detecting the neutral Higgs bosons of minimal supersymmetric models (MSSM) when their decays into neutralino pairs are kinematically allowed. The best signature appears to be $H_h,H_p\to\tz_2\tz_2\to 4\ell +\eslt$. We argue that Standard Model contributions to this signature are negligible, and examine regions of MSSM parameter space

Jin Dai, James Hughes, Jun Liu

We carry out next-to-leading order (NLO) parton model calculations for the standard hard ``QCD&#39;&#39; processes in the massless Schwinger model. The asymptotic expansion of the exact result for the deep inelastic cross section is used to infer the NLO distribution function. These distribution functions are then used to calculate the NLO Drell-Yan parton m

W. Bietenholz

We discuss fixed point actions for various types of free lattice fermions. The iterated block spin renormalization group transformation yields lines of local but chiral symmetry breaking fixed points. For staggered fermions at least the $U(1) \otimes U(1)$ symmetry can be preserved. This provides a basis for approximating perfect actions for asymptotically f

Patrick R. Brady

An exact one parameter ($α$) family of solutions representing scalar field collapse is presented. These solutions exhibit a type of critical behaviour which has been discussed by Choptuik. The three possible evolutions are outlined. For supercritical evolution (when black holes form) I show that a quantity related to the mass of the black hole exhibits a pow

Hisa-aki SHINKAI, Kei-ichi MAEDA

We study a generality of an inflationary scenario by integrating the Einstein equations numerically in a plane-symmetric spacetime. We consider the inhomogeneous spacetimes due to (i) localized gravitational waves with a positive cosmological constant $Λ$, and (ii) an inhomogeneous inflaton field $Φ$ with a potential $\frac12 m^2 Φ^2$. For the case (i), we f

Werner Kerler, Peter Rehberg

After developing an appropriate iteration procedure for the determination of the parameters, the method of simulated tempering has been successfully applied to the 2D Ising spin glass. The reduction of the slowing down is comparable to that of the multicanonical algorithm. Simulated tempering has, however, the advantages to allow full vectorization of the pr

Bodo Huckestein

Finite size corrections to scaling laws in the centers of Landau levels are studied systematically by numerical calculations. The corrections can account for the apparent non-universality of the localization length exponent $ν$. In the second lowest Landau level the irrelevant scaling index is $y_{\mathrm{irr}}=-0.38\pm0.04$. At the center of the lowest Land

Goetz Moeller, Qimiao Si, Gabriel Kotliar, Marcelo Rozenberg

We introduce a systematic low-energy approach to strongly correlated electron systems in infinite dimensions, and apply it to the problem of the correlation-induced metal-insulator transition in the half-filled Hubbard model. We determine the low-energy scaling functions of the metallic state, including the single-particle Green function and dynamical spin s

A. Malvezzi

Finite-Size-Scaling and Conformal Invariance are used in order to find the phase diagram and critical exponents of a quantum spin chain with spin $S=3/2$. The model has a tetracritical point besides critical lines. The conformal anomaly and anomalous dimensions of some primary operators are calculated at the tetracritical point.

J. Boronat, J. Casulleras, J. Navarro

A Quadratic Diffusion Monte Carlo method has been used to obtain the equation of state of liquid $^4$He including the negative pressure region down to the spinodal point. The atomic interaction used is a renewed version (HFD-B(HE)) of the Aziz potential, which reproduces quite accurately the features of the experimental equation of state. The spinodal pressu