October 1995 arXiv papers — page 3

A. V. Bannikov, G. A. Chelkov, Z. K. Silagadze

The usefulness of the $B_s^0 \to D_s^-a_1^+, D_s^- \to ϕπ^- \to K^+K^-π^-, a_1^+ \to ρ^0 π^+ \to π^+ π^- π^+$ decay chain is investigated for the $B_s$-reconstruction in the future ATLAS $B_s$-mixing experiment. It is shown that this decay channel is almost as suitable for this purpose as previously studied $B_s^0 \to D_s^-π^+$.

Nobuhiro Maekawa

We discuss a mechanism which can reduce the S and T parameters in dynamical electroweak symmetry breaking scenario. It is interesting that not only T but also S parameters can be made small even if large isospin violation exists, which can realize the heavy top quark. The point is that if massive vector-like fermions, which have gauge invariant masses, can c

Peter Lepage

This is the Lattice '95 review of recent progress towards accurate QCD simulations using very coarse lattices. This development could have revolutionary implications for low energy (nonperturbative) QCD.

G. M. de Divitiis, R. Frezzotti, M. Guagnelli, M. Masetti

We calculate the effects of including dynamical fermion loops in the lattice QCD estimates of meson decay constants, by extrapolating the results from negative flavour numbers after a suitable matching of the pion and rho mass. For moderately light quarks, the values of the decay constants not corrected for the renormalization constants increase with respect

Masanori Okawa

Recent developments in lattice QCD calculation of flavor singlet nucleon matrix elements are reviewed. Substantial sea quark contributions are found in the $π$-$N\ σ$ term and the quark spin content of the nucleon such that the total magnitude including valence contributions is in reasonable agreement with experiments. Some problems with flavor non-singlet n

L. Guieu, E. Mourre, V. Yu. Ovsienko

We discuss the theorem on the existence of six points on a convex closed plane curve in which the curve has a contact of order six with the osculating conic. (This is the ``projective version'' of the well known four vertices theorem for a curve in the Euclidean plane.) We obtain this classical fact as a corollary of some general Sturm-type theorems.

V. Ovsienko, S. Tabachnikov

We discuss Ghys' theorem on 4 zeroes of the Schwarzian derivative and its relation with flattening points of Legendrian curves and Sturm theory.

C. Gros, W. Wenzel, J. Richter

We present a spin-1/2 bilayer model for the quantum order-disorder transition which (i) can be solved by mean-field theory for bulk quantities, (ii) becomes critical at the transition, and (iii) allows to include intralayer frustration. We present numerical data (for systems with up to 240 sites) and analytical results for the critical coupling strength, gro

Matthias Troyer, Hirokazu Tsunetsugu, T. M. Rice

We have numerically investigated the doped t-J ladder using exact diagonalization. We have studied both the limit of strong inter-chain coupling and isotropic coupling. The ladder scales to the Luther-Emery liquid regime in the strong inter-chain coupling limit. In this strong coupling limit there is a simple picture of the excitation spectrum that can be co

Baowen Li, Marko Robnik

In searching for the manifestations of sensitivity of the eigenfunctions in quantum billiards (with Dirichlet boundary conditions) with respect to the boundary data (the normal derivative) we have performed instead various numerical tests for the Robnik billiard (quadratic conformal map of the unit disk) for 600 shape parameter values, where we look at the s

R. Moessner, R. Brandenberger

Using a modification of the Zel'dovich approximation adapted to hot dark matter, the accretion of such matter onto moving cosmic string loops is studied. It is shown that a large number of $10^{12}M_\odot$ nonlinear objects will be produced by a redshift of $z=4$. These objects could be the hosts of high redshift quasars.

T. Contini, H. Wozniak, E. Davoust, S. Considere

We compare the dense molecular gas content in two barred spiral galaxies, NGC 6764 (classified LINER) and NGC 5430 (a Wolf-Rayet galaxy). We find a significant difference in the proportion of dense molecular gas between the two galaxies. CS(3-2) is detected in NGC 6764 but not in NGC 5430, even though the intensities of CO(2-1) and HCN(1-0) are higher in the

Takahiko Matsubara

The Eulerian and Lagrangian second-order perturbation theories are solved explicitly in closed forms in $Ω\neq 1$ and $Λ\neq 0$ {}Friedmann-Lema\^ıtre models. I explicitly write the second-order theories in terms of closed one-dimensional integrals. In cosmologically interested cases ($Λ= 0$ or $Ω+ λ= 1$), they reduce to elementary functions or hypergeometri

F. X. Timmes, S. E. Woosley, T. A. Weaver

Using recently calculated models for massive stellar evolution and supernovae coupled to a model for Galactic chemical evolution, neutron star and black hole birth functions (number of neutron stars and black holes as a function of their mass) are determined for the Milky Way Galaxy. For those stars that explode as Type II supernovae, the models give birth f

Victor V. Batyrev, Yuri Tschinkel

We prove an asymptotic formula conjectured by Manin for the number of $K$-rational points of bounded height with respect to the anticanonical line bundle for arbitrary smooth projective toric varieties over a number field $K$.

M. C. Ashworth

A Chern-Simons action written with Christoffel Symbols has a natural gauge symmetry of diffeomorphisms. This Chern-Simons action will induce a Wess-Zumio-Witten model on the boundary of the manifold. If we restrict the diffeomorphisms to chiral diffeomorphism, the Wess-Zumio-Witten model is equivalent to a quantum Liouville action.

P. Musgrave, K. Lake

We present the GRjunction package which allows boundary surfaces and thin-shells in general relativity to be studied with a computer algebra system. Implementing the Darmois-Israel thin shell formalism requires a careful selection of definitions and algorithms to ensure that results are generated in a straight-forward way. We have used the package to correct

T. Vojta, D. Belitz, R. Narayanan, T. R. Kirkpatrick

The quantum ferromagnetic transition of itinerant electrons is considered. It is shown that the Landau-Ginzburg-Wilson theory described by Hertz and others breaks down due to a singular coupling between fluctuations of the conserved order parameter. This coupling induces an effective long-range interaction between the spins of the form 1/r^{2d-1}. It leads t

S. V. Goloskokov

It is shown that single and double spin asymmetries in polarized diffractive $Q \bar Q$ production depend strongly on the spin structure of the quark-pomeron vertex. They can be studied in future spin experiments at HERA.

Matthias Blau, Faheem Hussain, George Thompson

We study global aspects of N=2 Kazama-Suzuki coset models by investigating topological G/H Kazama-Suzuki models in a Lagrangian framework based on gauged Wess-Zumino-Witten models. We first generalize Witten's analysis of the holomorphic factorization of bosonic G/H models to models with N=1 and N=2 supersymmetry. We also find some new anomaly-free and s

Mark Dras

Current definitions of notions of lexical density and semantic weight are based on the division of words into closed and open classes, and on intuition. This paper develops a computationally tractable definition of semantic weight, concentrating on what it means for a word to be semantically light; the definition involves looking at the frequency of a word i

B. de Wit, A. Van Proeyen

Special Kahler manifolds are defined by coupling of vector multiplets to $N=2$ supergravity. The coupling in rigid supersymmetry exhibits similar features. These models contain $n$ vectors in rigid supersymmetry and $n+1$ in supergravity, and $n$ complex scalars. Apart from exceptional cases they are defined by a holomorphic function of the scalars. For supe

P. Colangelo, F. De Fazio, P. Santorelli, E. Scrimieri

We use QCD sum rules to calculate the hadronic matrix elements governing the rare decays $B \to K \ell^+ \ell^-$ and $B \to K^* \ell^+ \ell^-$ induced by the flavour changing neutral current $b \to s$ transition. We also study relations among semileptonic and rare $B \to K^{(*)}$ decay form factors. The analysis of the invariant mass distribution of the lept

P. Saracco, G. Chincarini, A. Iovino

Standard models for deep galaxy counts are based on luminosity functions (LF) with relatively flat faint end ($α\sim-1.0$). Galaxy counts in the B--band exceed the prediction of such models by a factor of 2 to more than 5, forcing the introduction of strong luminosity and/or density evolution. Recently Marzke et al. (1994a) using the CfA redshift survey samp

Nobuaki Kodama, Makoto Oka

Properties of the pion are studied at finite temperature with the help of the PCAC and the QCD sum rule. The pionic mode is treated consistently with the thermal pions which consist of the ground state at finite temperature. The temperature dependence of the pion decay constant is estimated for $m_{q}=0$. No consistent solution is found above the critical te

Tohru Eguchi, Sung-Kil Yang

Using recently proposed soliton equations we derive a basic identity for the scaling violation of $N=2$ supersymmetric gauge theories $\sum_i a_i\partial F/\partial a_i-2F=8 πi b_1 u$. Here $F$ is the prepotential, $a_i$'s are the expectation values of the scalar fields in the vector multiplet, $u=1/2\, {\rm Tr}\, \langleϕ^2\rangle$ and $b_1$ is the coef

Hael Collins, Howard Georgi, David Zeltser

We describe a perturbation expansion for the energy and wave function of a weakly bound particle in a short-range potential in one space dimension.

J. A. Harvey, G. Moore

We clarify the role played by BPS states in the calculation of threshold corrections of D=4, N=2 heterotic string compactifications. We evaluate these corrections for some classes of compactifications and show that they are sums of logarithmic functions over the positive roots of generalized Kac-Moody algebras. Moreover, a certain limit of the formulae sugge

Juergen Audretsch, Rainer Mueller, Markus Holzmann

We study the spontaneous de-excitation and excitation of accelerated atoms on arbitrary stationary trajectories (``generalized Unruh effect''). We consider the effects of vacuum fluctuations and radiation reaction separately. We show that radiation reaction is generally not altered by stationary acceleration, whereas the contribution of vacuum fluctu

P. B. Radha, D. J. Dean, S. E. Koonin, T. T. S. Kuo

Shell Model Monte Carlo (SMMC) techniques are used to calculate two-neutrino double beta decay matrix elements. We validate the approach against direct diagonalization for $^{48}$Ca in the complete $pf$-shell using the KB3 interaction. The method is then applied to the decay of $^{76}$Ge in the $(0f_{5/2},1p,0g_{9/2})$ model space using a newly calculated re

Siegfried Böcherer, Rainer Schulze-Pillot

We continue our study of Yoshida's lifting, which associates to a pair of automorphic forms on the adelic multiplicative group of a quaternion algebra a Siegel modular form of degree 2. We consider here the case that the automorphic forms on the quaternion algebra correspond to modular forms of arbitrary even weights and square free levels; in particular

H. Perez Rojas

Bose-Einstein condensation of charged scalar and vector particles may actually occur in presence of a constant homogeneous magnetic field, but there is no critical temperature at which condensation starts. The condensate is described by the statistical distribution. The Meissner effect is possible in the scalar, but not in the vector field case, which exhibi

P. K. Townsend

A review is given of the implications of supersymmetric black holes for the non-perturbative formulation of toroidally compactified superstrings, with particular emphasis on symmetry enhancement at special vacua and S-duality of the heterotic string.

Haru-Tada Sato

We discuss the $q$-Virasoro algebra based on the arguments of the Noether currents in a two-dimensional massless fermion theory as well as in a three-dimensional nonrelativistic one. Some notes on the $q$-differential operator realization and the central extension are also included.

Paul Mansfield

For fields that vary slowly on the scale of the lightest mass the logarithm of the vacuum functional can be expanded as a sum of local functionals. For Yang-Mills theory the leading term in the expansion dominates large distance effects and leads to an area law for the Wilson loop. However, this expansion cannot be expected to converge for fields that vary m

Ziemowit Popowicz

We describe three different approaches to the extended (N=2) supersymmetrization of the multicomponent KP hierarchy. In the first one we utilize only superfermions while in the second only superbosons and in the third superbosons as well as superfermions. It is shown that many soliton equations can be embedded in the supersymmetry theory by using the first a

Serguei B. Isakov, Jon Magne Leinaas

An algebra ${\cal G}$ of symmetric {\em one-particle} operators is constructed for the Calogero model. This is an infinite-dimensional Lie-algebra, which is independent of the interaction parameter $λ$ of the model. It is constructed in terms of symmetric polynomials of raising and lowering operators which satisfy the commutation relations of the $S_N$-{\em

T. Moroi

We study the solution to the Polonyi problem in the framework of no-scale type supergravity. In such a model, Polonyi field can weigh as $O(10{\rm TeV})$ and decay just before the big-bang nucleosynthesis. It is shown that in spite of a large entropy production by the decay of the Polonyi field, one can naturally explain the present value of the baryon-to-en

Johannes Blümlein, Andreas Vogt

The resummation of $O(α_s^{l+1} \ln^{2l} x)$ terms in the evolution kernels of non--singlet combinations of unpolarized and polarized structure functions is investigated. The agreement with complete calculations up to order $α_s^2$ is demonstrated, and the leading small-$x$ contributions to the three--loop non--singlet splitting functions $P^{\pm}$ are deriv

H. C. Eggers, R. Tabti, C. Gale, K. Haglin

We have made a detailed and quantitative study of dilepton production via bremsstrahlung of a virtual photon during pion-pion collisions. Most calculations of electromagnetic radiation from strong interaction processes rely on the soft photon approximation (SPA). The conditions underlying this approximation are generally violated when dilepton spectra are ca

Eric Braaten, Agustin Nieto

Effective-field-theory methods are used to separate the free energy for a nonabelian gauge theory at high temperature $T$ into the contributions from the momentum scales $T$, $gT$, and $g^2T$, where $g$ is the coupling constant at the scale $2 πT$. The effects of the scale $T$ enter through the coefficients in the effective lagrangian for the 3-dimensional e

J. Gluza, M. Zralek

We examine two processes, the neutrino production process e^+e^- ---> Nνand the inverse neutrinoless double-beta decay process e^-e^- --->W^-W^- as possible places for discovering heavy neutrinos in future lepton linear colliders. The heavy neutrino parameters are bound from existing experimental data. We use only one important theoretical input, the lack of

Thomas Mannel, Res Urech

We construct an effective Lagrangian for the hadronic decays of a heavy excited $s$-wave-spin-one quarkonium into its ground state. We show that reasonable fits to the measured invariant mass spectra in the $J/ψ$ and $Υ$ systems can be obtained working in the chiral limit. The mass dependence of the various terms in the Lagrangian is discussed on the basis o

V. M. Braun

I give an overview of the QCD sum rule predictions for the form factors of B-meson weak decays to light hadrons (and leptons)

John Ellis, Marek Karliner

We review the theory of polarized deep inelastic scattering in light of the most recent experimental data. We discuss the nucleon spin decomposition and the Bjorken sum rule. The latter is used for extraction of $\alpha_s(M_Z^2)=0.116^{{+}0.004}_{{-}0.006}$ and as a test case for a new method of analyzing divergent perturbation series in QCD.

W. Mödritsch

Quantum field theory near thresholds of ultra-heavy particles is considered. We focus especially on the top-antitop and the stop-antistop systems. The question of the possible large corrections due to a running width of the top quark could be solved in this work. It was shown that a previously not considered contribution gives rise to large cancellations and

A. Belyaev, E. Boos, L. Dudko

We study the Higgs boson search possibility at the TEVATRON energies. The detailed analysis of the 4-fermion final state reactions is presented. Among the complete set of Feynman diagrams the main contribution to the final states comes from the Higgs signal WH and ZH, from the backgrounds WZ, ZZ and gluonic background Wbb, Zbb with subssiquent decays of W, Z

Keh-Fei Liu

Comments on the recent lattice QCD calculations of the flavor-singlet axial coupling constant $g_A^0$ and individual quark and gluon spin contributions to the proton spin is given. I point out the physics learned from these calculations as well as some of the lessons and pitfalls.

R. Rylko

We show that the kinematic reconstruction of the $e^+e^-\rightarrow W^+W^-\rightarrow jjτ^-\overlineν_τ$\ events have a one-parameter ambiguity when reconstructed from the momentum of all measured $W^-$\ decay products. We propose a {\em hybrid} method of reconstruction of the $e^+e^-\rightarrow W^+W^-\rightarrow jjτ^-\overlineν_τ$\ events. This is based on

Claes R Cramer

We extend the study of the possibility to use the Schwarzschild black hole as a gravitational mirror to the more general case of an uncharged Kerr black hole. We use the null geodesic equation in the equatorial plane to prove a theorem concerning the conditions the impact parameter has to satisfy if there shall exist boomerang photons. We derive an equation

Jorge Griego

Some time ago it was conjectured that the coefficients of an expansion of the Jones polynomial in terms of the cosmological constant could provide an infinite string of knot invariants that are solutions of the vacuum Hamiltonian constraint of quantum gravity in the loop representation. Here we discuss the status of this conjecture at third order in the cosm

Jorge Griego

An analysis of the action of the Hamiltonian constraint of quantum gravity on the Kauffman bracket and Jones knot polynomials is proposed. It is explicitely shown that the Kauffman bracket is a formal solution of the Hamiltonian constraint with cosmological constant ($Λ$) to third order in $Λ$. The calculation is performed in the extended loop representation

A. L. Malvezzi, F. C. Alcaraz

We applied the Density Matrix Renormalization Group to the XXZ spin-1 quantum chain. In studing this model we aim to clarify controversials about the point where the massive Haldane phase appears.

Neeraj Mainkar, D. A. Browne, J. Callaway

We report a first principles, self-consistent, all electron, linear combination of Gaussian orbitals (LCGO) calculation of a comprehensive collection of magneto-optical properties of nickel and iron based on density functional theory. Among the many magneto-optical effects, we have studied the equatorial Kerr effect for absorption in the optical as well as s

A. J. Millis

A classical model for the lattice distortions of $\lax$ is derived and, in a mean field approximation, solved. The model is based on previous work by Kanamori and involves localized Mn d-electrons (which induce tetragonal distortions of the oxygen octahedra surrounding the Mn) and localized holes (which induce breathing distortions). Parameters are determine

Stefan K. Kehrein, Andreas Mielke

We apply the method of infinitesimal unitary transformations recently introduced by Wegner to the Anderson single impurity model. It is demonstrated that this method provides a good approximation scheme for all values of the on-site interaction $U$, it becomes exact for $U=0$. We are able to treat an arbitrary density of states, the only restriction being th

J. M. J. van Leeuwen, M. S. L. du Croo de Jongh, P. J. H. Denteneer

The spin stiffness $ρ_{\rm s}$ of the repulsive Hubbard model that occurs in the hydrodynamic theory of antiferromagnetic spin waves is shown to be the same as the thermodynamically defined stiffness involved in twisting the order parameter. New expressions for $ρ_{\rm s}$ are derived, which enable easier interpretation, and connections with superconducting

S. Giorgini, J. Boronat, J. Casulleras

The ground-state properties of two-dimensional liquid $^4$He at zero temperature are studied by means of a quadratic diffusion Monte Carlo method. As interatomic potential we use a revised version of the HFDHE2 Aziz potential which is expected to give a better description of the interaction between helium atoms. The equation of state is determined with great

F. Dalfovo, S. Stringari

We solve the Gross-Pitaevskii equations for a dilute atomic gas in a magnetic trap, modeled by an anisotropic harmonic potential. We evaluate the wave function and the energy of the Bose Einstein condensate as a function of the particle number, both for positive and negative scattering length. The results for the transverse and vertical size of the cloud of

Pablo Jensen, Albert-László Barabási, Hernán Larralde, Shlomo Havlin

In this paper we briefly review a model that describes the diffusion-controlled aggregation exhibited by particles as they are deposited on a surface. This model allows to understand many experiments of thin film deposition. In the first part, we describe the model, which incorporates deposition, particle and cluster diffusion, and aggregation. In a second p

G. Wendin, V. S. Shumeiko

We study the microscopic structure of the Josephson current in a single-mode tunnel junction with a wide quasiclassical tunnel barrier. In such a junction each Andreev bound state carries a current of magnitude proportional to the {\em amplitude} of the normal electron transmission through the junction. Tremendous enhancement of the bound state current is ca

Melvin Leok Boon Tiong

The correlation dimension and limit capacity serve theoretically as lower and upper bounds, respectively, of the fractal dimension of attractors of dynamic systems. In this paper, we show that estimates of the correlation dimension grow rapidly with increasing noise level in the time-series, while estimates of the limit capacity remain relatively unaffected.

E. Vesperini, D. F. Chernoff

We investigate a population of primordial binaries during the initial stage of evolution of a star cluster. For our calculations we assume that equal mass stars form rapidly in a tidally truncated gas cloud, that $\sim10$\% of the stars are in binaries and that the resulting star cluster undergoes an epoch of violent relaxation. We study the collisional inte

Richard E. Leonard, Robert J. Scherrer

We examine inhomogeneous primordial nucleosynthesis for {\it arbitrary} distributions $f$ of the baryon-to-photon ratio $η$, in the limit where neither particle diffusion nor gravitational collapse is important. By discretizing $f(η)$ and using linear programming, we show that for a set of $m$ constraints on the primordial element abundances, the maximum and

Thomas Buchert, Georgios Karakatsanis, Robert Klaffl, Peter Schiller

We present high--spatial resolution studies of the density field as predicted by Lagrangian perturbation approximations up to the third order. The first--order approximation is equivalent to the ``Zel'dovich approximation'' for the type of initial data analyzed. The study is performed for two simple models which allow studying of typical features

David Merritt, Tema Fridman

Recent work on the equilibrium and stability of ellipsoidal stellar systems is reviewed. The absence of constant-density cores in early-type galaxies implies that chaos and high-order resonances are generic features of the motion in triaxial stellar systems. Bending instabilities are now well understood and may provide the answers to a number of long-standin

Reinaldo Gleiser, Oscar Nicasio, Richard Price, Jorge Pullin

We study the even-parity $\ell=2$ perturbations of a Schwarzschild black hole to second order. The Einstein equations can be reduced to a single linear wave equation with a potential and a source term. The source term is quadratic in terms of the first order perturbations. This provides a formalism to address the validity of many first order calculations of

Eric W. Hirschmann, Dean L. Welch

We report on a new solution to the Einstein-Maxwell equations in 2+1 dimensions with a negative cosmological constant. The solution is static, rotationally symmetric and has a non-zero magnetic field. The solution can be interpreted as a monopole with an everywhere finite energy density.

Sukanta Bose, Jorma Louko, Leonard Parker, Yoav Peleg

We consider the Hamiltonian dynamics and thermodynamics of the two-dimensional vacuum dilatonic black hole in the presence of a timelike boundary with a fixed value of the dilaton field. A~canonical transformation, previously developed by Varadarajan and Lau, allows a reduction of the classical dynamics into an unconstrained Hamiltonian system with one canon

U. Bastolla, G. Parisi

We define a probabilistic scheme to compute the distributions of periods, transients and weigths of attraction basins in Kauffman networks. These quantities are obtained in the framework of the annealed approximation, first introduced by Derrida and Pomeau. Numerical results are in good agreement with the computed values of the exponents of average periods,

J. Fernández-Rossier, C. Tejedor, L. Muñoz, L. Viña

We develop a theory to calculate exciton binding energies of both two- and three-dimensional spin polarized exciton gases within a mean field approach. Our method allows the analysis of recent experiments showing the importance of the polarization and intensity of the excitation light on the exciton luminescence of GaAs quantum wells. We study the breaking o

Derek B. Leinweber

A new Monte-Carlo based uncertainty analysis is introduced to quantitatively determine the predictive ability of QCD sum rules. A comprehensive analysis of ground state rho-meson and nucleon spectral properties is performed. Many of the findings contradict the conventional wisdom of both practitioners and skeptics alike. Associations between the phenomenolog

H. Beer, P. V. Sedyshev, Yu. P. Popov, W. Balogh

At the Karlsruhe pulsed 3.75 MV Van de Graaff accelerator the $^{36}S(n,\gamma)^{37}S(5.05 min)$ cross section was measured by the fast cyclic activation technique via the 3.103 MeV $\gamma$-ray line of the $^{37}$S-decay. Samples of elemental sulfur enriched in $^{36}$S by 5.933 % were irradiated between two gold foils which served as capture standards. The

W. Luecke

A rough overview is given over the most essential structures underlying all working quantum theoretical models as well as axiomatic and algebraic quantum field theory .

K. Behrndt, H. Dorn

We apply the duality transformation relating the heterotic to the IIA string in 6D to the class of exact string solutions described by the chiral null model and derive explicit formulas for all fields after reduction to 4D. If the model is restricted to asymptotically flat black hole type solutions with well defined mass and charges the purely electric solut

S. Dittmaier, D. Schildknecht, G. Weiglein

We investigate the structure of the experimentally significant electroweak bosonic loop corrections to the leptonic weak mixing angle, the leptonic Z-boson decay width, and the W-boson mass. It is shown that the bosonic corrections that have a sizable effect at the present level of experimental accuracy are directly related to the use of the Fermi constant G

G. Cuba, R. Paunov

We analyze the symplectic structure on the dressing group in the \shG\, model by calculating explicitly the Poisson bracket $\{g\x g\}$ where $g$ is the \dg\, element which creates a generic one soliton solution from the vacuum. Our result is that this bracket does not coincide with the Semenov--Tian--Shansky one. The last induces a Lie--Poisson structure on

F. De Jonghe, P. Termonia, W. Troost, S. Vandoren

A recently proposed variation on the usual procedure to perform the topological B-twist in rigid $N=2$ models is applied to the case of the $σ$ model on a Kähler manifold. This leads to an alternative description of Witten's topological $σ$ model, which allows for a proper BRST interpretation and ghost number assignement. We also show that the auxiliary

M. Pierre, J. F. Le Borgne, G. Soucail, J. P. Kneib

We present a deep X-ray ROSAT/HRI observation of the rich cluster-lens Abell 2390 and the analysis of the gas and matter distribution in the cluster. The X-ray centroid coincides with the location of the central cD galaxy, and the core appears to be dominated by a massive cooling flow, one of the strongest ones ever studied. On larger scales, the X-ray distr

Hitoshi Ito

A relativistic equation is proposed for the bound state of two particles, which is in accord with the boundary condition for the propagation of the negative-energy states and reduces to the (one-body)Dirac equation in the infinite limit of one of the constituent mass. It also has the symmetries to assure the existence of the anti-bound-state with the same ma

B. Iványi, Zs. Schram, K. Sailer, W. Greiner

The time dependent pion emission rate and the mean life time of the pion source in the center of mass frame of the two-jet events have been determined for $e^+-e^- \to hadrons$ at $\sqrt{s} = 20 - 50$ GeV by the Dynamical String Model. It was established that the time needed for the creation of the pion source is $5$ fm/c, whereas its life time is $\tau_0 \a

Norihito Sasaki

The system of a closed vortex filament is an integrable Hamiltonian one, namely, a Hamiltonian system with an infinite sequense of constants of motion in involution. An algebraic framework is given for the aim of describing differential geometry of this system. A geometrical structure related to the integrability of this system is revealed. It is not a bi-Ha

A. A. Tseytlin

We provide some additional evidence in favour of the strong - weak coupling duality between the SO(32) heterotic and type I superstring theories by comparing terms quartic in the gauge field strength in their low-energy effective actions. We argue that these terms should not receive higher-loop string corrections so that duality should relate the leading-ord

Johan Linde, Håkan Snellman

We discuss magnetic moments of the $J=3/2$ baryons based on an earlier model for the baryon magnetic moments, allowing for flavor symmetry breaking in the quark magnetic moments as well as a general quark spin structure. From our earlier analysis of the nucleon-hyperon magnetic moments and the measured values of the magnetic moments of $Δ^{++}$ and $Ω^{-}$ w

Yuval Grossman, Zoltan Ligeti, Enrico Nardi

The inclusive $B \to X_s \nu \bar\nu$ decay rate, on which no experimental bound exists to date, can be constrained by searching for large missing energy events in $B$ decays. Carefully examining the experimental and theoretical aspects of such an analysis, we argue that the published ALEPH limit on $\BR(B \to \tau \bar\nu)$ implies, conservatively, the boun

Tanmoy Bhattacharya, Rajan Gupta

We present results of a high statistics study of $f_\pi$, $f_K$, $f_D$, $f_{D_s}$, and $f_V^{-1}$ in the quenched approximation using Wilson fermions at $\beta=6.0$ on $32^3 \times 64$ lattices. We find that the various sources of systematic errors (due to setting the quark masses, renormalization constant, and lattice scale) are now larger than the statisti

E. Caurier, J. M. G. Gomez, V. R. Manfredi, L. Salasnich

The spectral statistics of low--lying states of several $fp$ shell nuclei are studied with realistic shell--model calculations. For Ca isotopes, we find significant deviations from the predictions of the random--matrix theory which suggest that some spherical nuclei are not as chaotic in nature as the conventional view assumes.

M. P. Fry

Lower bounds are placed on the fermionic determinants of Euclidean quantum electrodynamics in two and four dimensions in the presence of a smooth, finite-flux, static, unidirectional magnetic field $B(r) =(0,0,B(r))$, where $B(r) \geq 0$ or $B(r) \leq 0$, and $r$ is a point in the xy-plane.

Claudio Teitelboim

An action principle for spacetimes with the topology of an Euclidean black-hole is given. The gravitational field is described by the ordinary volume degrees of freedom plus additional surface fields at the horizon. The surface degrees of freedom correspond to diffeomorphisms on the sphere at the horizon and a field of ``opening angles''. General covariance

B. M. Zupnik

We consider the harmonic-superspace ($HS$) system of equations that contains superfield $SYM^1_6$ constraints and equations of motion. A dynamical equation in the special $A$-frame is equivalent to the zero-curvature equation corresponding to a covariant conservation of $HS$-analyticity. Properties of a general $SYM^1_6$ solution for the gauge group $SU(2)$

H. Grosse, C. Klimcik, P. Presnajder

We review recent progress in formulating two-dimensional models over noncommutative manifolds where the space-time coordinates enter in the formalism as non-commuting matrices. We describe the Fuzzy sphere and a way to approximate topological nontrivial configurations using matrix models. We obtain an ultraviolet cut off procedure, which respects the symmetr

V. B. Petkova, J. -B. Zuber

In this paper, we pursue the discussion of the connections between rational conformal field theories (CFT) and graphs. We generalize our recent work on the relations of operator product algebra (OPA) structure constants of $sl(2)\,$ theories with the Pasquier algebra attached to the graph. We show that in a variety of CFT built on $sl(n)\,$ -- typically conf

Takeshi Oota

Form factor bootstrap approach is applied for diagonal scattering theories. We consider the ADE theories and determine the functional equations satisfied by the minimal two-particle form factors. We also determine the parameterization of the singularities in two particle form factors. For $A^{(1)}_{2}$ Affine Toda field theory which is the simplest non-self

Mikhail Shifman

Introduction to the Lecture Note Volume "ITEP Lectures in Particle Physics", including 25 years of personal reminiscences.

R. Baur, J. Kambor, D. Wyler

We calculate the electromagnetic corrections to the decays $η\rightarrow 3π$ in next to leading order in the chiral expansion. We find that the corrections are small in accordance with Sutherland's theorem and modify neither rate nor the Dalitz plot distributions noticeably.

Roberto Fiore, Luis Masperi, Ariel Megevand

We describe different electroweak strings with axionic content, including non-topological configurations calculated numerically, and show their possible influence on baryogenesis indicating that they may constitute a mechanism competitive to that of bubble nucleation with two Higgs-doublets.

Paul Hoyer

I review hard photon initiated processes on nuclei. The space-time development of the DIS reaction as viewed in the target rest frame qualitatively describes the nuclear shadowing of quark and gluon distributions, although it may be difficult to understand the very weak $Q^2$ dependence of the low $x$ data. The current jet hadron energy distribution at large

Kostas Philippides, Alberto Sirlin

The pinch technique (PT) is applied to neutral current amplitudes, focusing on the mixing problem. Extending recent arguments due to Papavassiliou and Pilaftsis, it is shown that the use of the PT self-energies does not shift the complex-valued position of the pole through order {\cal O}($g^4$). This leads (to the same accuracy) to a simple interpretation of

J. Hagelin, S. Kelley, Sunil Rawal

We demonstrate that supergravity models containing the Standard Model, dilaton and modulus naturally lead to dynamical symmetry breaking with excellent phenomenology. We assume primordial supersymmetry breaking in the form of a constant contribution to the superpotential. String inspired relations link fundamental couplings to the dilaton vev. We specialize

S. B. Khadkikar, A. Mishra, H. Mishra

We consider here quark matter equation of state in a relativistic harmonic confinement model at zero temperature. The same is considered to study phase transition of neutron matter to quark matter at high densities. This, along with a phenomenological equation of state in the neutron matter sector is used to study hybrid stars. Using Tolman Oppenheimer Volko