June 1997 arXiv papers — page 5

R. Cid Fernandes, R. Terlevich, I. Aretxaga

We draw attention to some intriguing coincident patterns in the optical light curves of NGC 4151 and NGC 5548. Inspecting the light curves of these two classic Seyferts, we find evidence for at least five occurrences of a similar sequence of variations. This pattern consists of a ~ 2 yr long sequence of shorter flares, with a total energy of 3--5 10^{50} erg

Sabine Schindler

X-ray observations of three clusters are presented: RXJ1347.5-1145, Cl0939+47, and Cl0500-24. Although these clusters are the in same redshift range (0.32 - 0.45) and act all as gravitational lenses, they show very different properties. RXJ1347.5-1145 seems to be an old, well relaxed system, with a relaxed morphology, high X-ray luminosity, high temperature,

Sabine Schindler, M. Almudena Prieto

An analysis of a ROSAT/PSPC observation of the galaxy cluster A2634 is presented. The cluster has a luminosity of $7.9\pm0.1\times10^{43}$erg/s in the ROSAT band (0.1-2.4 keV). The temperature profile decreases from about 3 keV in the outer parts to 1.2 keV in the centre. Within a radius of 1.5 Mpc the gas mass of the cluster is 0.51$\times 10^{14}\msol$ and

S. Andreon, S. Zaggia, R. de Carvalho, S. Djorgovski

The CRONA project is a joint enterprise between Caltech and the astronomical observatory of Rome and Naples aimed to the photometric calibration of the Second Palomar Sky Survey (POSS-II) plates and to the construction of a complete photometric and astrometric catalogue of all objects present on the POSS-II. The calibrated final catalogues of objects will be

S. Andreon, J. Annis, J. -C. Cuillandre, E. Davoust

We present an optical and near-infrared survey of galaxies in nearby clusters aimed at determining fundamental quantities of galaxies, such as multivariate luminosity function and color distribution for each Hubble type. The main characteristics of our survey are completeness in absolute magnitude, wide wavelength coverage and faint limiting magnitudes.

A. Levin, M. Olshanetsky

It is proved that the Painlevé VI equation $(PVI_{\al,\be,\ga,\de})$ for the special values of constants $(\al=\frac{ν^2}{4},\be=-\frac{ν^2}{4}, \ga=\frac{ν^2}{4},\de=\f1{2}-\frac{ν^2}{4})$ is a reduced hamiltonian system. Its phase space is the set of flat $SL(2,C)$ connections over elliptic curves with a marked point and time of the system is given by the

Francisco J. Plaza Martín

In this paper we study Prym varieties and their moduli space using the well known techniques of the infinite Grassmannian. There are three main results of this paper: a new definition of the BKP hierarchy over an arbitrary base field (that generalizes the classical one over the complex numbers; a characterization of Prym varieties in terms of dynamical syste

John L. Friedman, Sharon M. Morsink

Perturbations of rotating relativistic stars can be classified by their behavior under parity. For axial perturbations (r-modes), initial data with negative canonical energy is found with angular dependence $e^{imϕ}$ for all values of $m\geq 2$ and for arbitrarily slow rotation. This implies instability (or marginal stability) of such perturbations for rotat

M. M. Tung, J. Bernabeu, J. Penarrocha

We present the full O(alpha_s) longitudinal spin-spin correlations for heavy-quark pair production at e+ e- high-energy colliders in closed analytical form. In such reactions, quark and antiquark have strongly correlated spins, and the longitudinal components are dominant. For the explicit computation of the QCD bremsstrahlung contributions, new phase-space

Norman K. Glendenning

In the first of these two lectures I will discuss the rich constitution of neutron stars as a consequence of the Pauli principle which is engaged by the dominance of gravity over the nuclear force. Three especially interesting phenomena are discussed in this contect--(1) a mechanism for the formation of low-mass black holes distinct in their mass-range from

A. S. Cattaneo, P. Cotta-Ramusino, M. Rinaldi

For any principal bundle $P$, one can consider the subspace of the space of connections on its tangent bundle $TP$ given by the tangent bundle $T{\cal A}$ of the space of connections ${\cal A}$ on $P$. The tangent gauge group acts freely on $T{\cal A}$. Appropriate BRST operators are introduced for quantum field theories that include as fields elements of $T

T. V. Shahbazyan, S. E. Ulloa

We study the structure of 2D electronic states in a strong magnetic field in the presence of a large number of resonant scatterers. For an electron in the lowest Landau level, we derive the exact density of states by mapping the problem onto a zero-dimensional field-theoretical model. We demonstrate that the interplay between resonant and non-resonant scatte

Paolo Sibani

A simple geometrical characterization of configuration space neighborhoods of local energy minima in spin glass landscapes is found by exhaustive search. Combined with previous Monte Carlo investigations of thermal domain growth, it allows a discussion of the connection between real and configuration space descriptions of low temperature relaxational dynamic

D. Harris, F. I. Olness, S. Ritz, M. Albrow

We summarize the studies and discussions of the Structure Function subgroup of the QCD working group of the Snowmass 1996 Workshop: New Directions for High Energy Physics.

Angus F. Nicholson, Dallas C. Kennedy

A perturbative SU(2)_L X U(1)_Y electroweak theory containing W, Z, photon, ghost, lepton and quark fields, but no Higgs or other fields, gives masses to W, Z and the non-neutrino fermions by means of an unconventional choice for the unperturbed Lagrangian and a novel method of renormalisation. The renormalisation extends to all orders. The masses emerge on

V. C. de Andrade, J. G. Pereira

A comparative study between the metric and the teleparallel descriptions of gravitation is made for the case of a scalar field. In contrast to the current belief that only spin matter could detect the teleparallel geometry, scalar matter being able to feel the metric geometry only, we show that a scalar field is able not only to feel anyone of these geometri

Jean M. Quashnock, Daniel E. Vanden Berk

We have analyzed the clustering of C IV and Mg II absorption-line systems on comoving scales from 1 to 16 \hMpc, using an extensive catalog of heavy-element QSO absorbers with mean redshift 2.2 (C IV) and 0.9 (Mg II). We find that, for the C IV sample as a whole, the absorber line-of-sight correlation function is well-fit by a power law with index $\gamma =

G. Aldazabal, A. Font, L. E. Ibanez, A. M. Uranga

We consider D=6, N=1, Z_M orbifold compactifications of heterotic strings in which the usual modular invariance constraints are violated. It is argued that in the presence of non-perturbative effects many of these vacua are nevertheless consistent. The perturbative massless sector can be computed explicitly from the perturbative mass formula subject to an ex

Charles A. Nelson, Brian T. Kress, Marco Lopes, Thomas P. McCauley

The most general Lorentz-invariant decay-density-matrix for $t\to W^{+}b\to (l^{+}ν)b$, or for $t\to W^{+}b\to (j_{\bar d}j_u)b$, is expressed in terms of eight helicity parameters. The parameters are physically defined in terms of partial-width-intensities for polarized-final-states in $t\to W^{+}b$ decay. The parameters are the partial width, the $b$ quark

Kurt Broderix, Paul M. Goldbart, Annette Zippelius

Dynamical properties of vulcanized polymer networks are addressed via a Rouse-type model that incorporates the effect of permanent random crosslinks. The incoherent intermediate scattering function is computed in the sol and gel phases, and at the vulcanization transition between them. At any nonzero crosslink density within the sol phase Kohlrausch relaxati

Daniele Amati

On the basis of recently discovered connections between D-branes and black holes, I show how the information puzzle is solved by superstring theory as the fundamental theory of quantum gravity. The picture that emerges is that a well-defined quantum state does not give rise to a black hole even if the apparent distribution of energy, momenta, charges, etc. w

Satoshi Yukawa, Macoto Kikuchi, Gen Tatara, Hiroshi Matsukawa

The concept of thermal ratchets is extended to the system governed by quantum mechanics. We study a tight-binding model with an asymmetric periodic potential contacting with a heat bath under an external oscillating field as a specific example of quantum ratchet. Dynamics of a density operator of this system is studied numerically by using the quantum Liouvi

Ya. Azimov

Phenomenological CP-violating parameters in decays of neutral B-mesons are discussed with special attention to the degree of their measurability. Important role of the sign of Δm_B is emphasized. We briefly describe how it could be determined experimentally.

Juri Rolf, Tomas Bohr, Mogens H. Jensen

We present strong evidence that a coupled-map-lattice model for spatio-temporal intermittency belongs to the universality class of directed percolation when the updating rules are asynchronous, i.e. when only one randomly chosen site is evolved at each time step. In contrast, when the system is subjected to parallel updating, available numerical evidence sug

E. G. Floratos, G. K. Leontaris

In this letter, we provide evidence for a classical sector of states in the Hilbert space of Finite Quantum Mechanics (FQM). We construct a subset of states whose the minimum bound of position -momentum uncertainty (equivalent to an effective $\hbar$) vanishes. The classical regime, contrary to standard Quantum Mechanical Systems of particles and fields, but

Andreas Blumhofer, Bodo Lampe

The Standard Model is extended by a SU(2)L singlet of vector leptoquarks. An additional SU(4) gauge symmetry between right-handed up quarks and right-handed leptons is introduced to render the model renormalizable. The arrangement is made in such a way that no conflict with low energy restrictions is encountered. The SU(2)L singlet mediates interactions betw

C. S. Kim, G. Cvetic

Based on experimental mass hierarchy, a set of flavor-democratic (FD) quark mass matrices at low energies is discussed. The model predicts CP violation parameters $J_{CP}=(0.3 \pm 0.2) 10^{-4}$ and ${ε'/ε} = (0.6 \pm 0.5) 10^{-3}$. However, this simple FD model also predicts a physical top quark mass not much higher than 100 GeV. As a next step, we assum

Clifford V. Johnson

A duality relationship between certain brane configurations in type IIA and type IIB string theory is explored by exploiting the geometrical origins of each theory in M-theory. The configurations are dual ways of realising the non-perturbative dynamics of a four dimensional N=2 supersymmetric SU(2) gauge theory with four or fewer favours of fermions in the f

S. Raghavan, A. Smerzi, S. Fantoni, S. R. Shenoy

We discuss the coherent atomic oscillations between two weakly coupled Bose-Einstein condensates. The weak link is provided by a laser barrier in a (possibly asymmetric) double-well trap or by Raman coupling between two condensates in different hyperfine levels. The Boson Josephson Junction (BJJ) dynamics is described by the two-mode non-linear Gross-Pitaevs

Won Tae Kim, Myung Seok Yoon

We study the graceful exit problem and the role of the stress-energy-momentum tensors in the two-dimensional string cosmology. The one-loop quantum correction of conformal fields is incorporated in the arbitrary large $N$ limit to ensure exact quantum solvability. The only solution which gives the bounded curvature with the asymptotic flatness is restricted

Shun-Jen Cheng, Victor Kac

In this paper we study a class of modules over infinite-dimensional Lie (super)algebras, which we call conformal modules. In particular we classify and construct explicitly all irreducible conformal modules over the Virasoro and the N=1 Neveu-Schwarz algebras, and over the current algebras.

Suhyoung Choi

An affine manifold is a manifold with an affine structure, i.e. a torsion-free flat affine connection. We show that the universal cover of a closed affine 3-manifold $M$ with holonomy group of shrinkable dimension (or discompacité in French) less than or equal to two is diffeomorphic to $\bR^3$. Hence, $M$ is irreducible. This follows from two results: (i) a

A. A. Deriglazov, A. V. Galajinsky

We suggest a D=11 super Poincaré invariant action for the superstring which has free dynamics in the physical variables sector. Instead of the standard approach based on the searching for an action with local $κ$-symmetry (or, equivalently, with corresponding first class constraints), we propose a theory with fermionic constraints of second class only. Then

Markus Grassl, Thomas Beth

We discuss the quantum search algorithm using complex queries that has recently been published by Grover (quant-ph/9706005). We recall the algorithm adding some details showing which complex query has to be evaluated. Based on this version of the algorithm we discuss its complexity.

John Ellis, N. E. Mavromatos, D. V. Nanopoulos

We discuss recent experimental evidence of decoherence in a laboratory mesoscopic system in a cavity, from which we draw analogies with the decoherence that we argue is induced by microscopic quantum-gravity fluctuations in the space-time background. We emphasize the parallel rôles played in both cases by dissipation through non-trivial vacuum fluctuations t

Luis Gonzalez-Mestres

Special relativity has been tested at low energy with great accuracy, but these results cannot be extrapolated to the very high-energy region. Introducing a critical distance scale, $a$ , below 10E-25 cm (the wavelength scale of the highest-energy observed cosmic rays) allows to consider models, compatible with standard tests of special relativity, where a s

V. M. Shabaev, M. Tomaselli, T. Kühl, A. N. Artemyev

The ground state hyperfine splitting values of high Z hydrogenlike ions are calculated. The relativistic, nuclear and QED corrections are taken into account. The nuclear magnetization distribution correction (the Bohr-Weisskopf effect) is evaluated within the single particle model with the g_{S}-factor chosen to yield the observed nuclear moment. An addition

E. de la Puente, A. Aguado, A. Ayuela, J. M. Lopez

Ab initio Perturbed Ion (PI) calculations are reported for neutral stoichiometric (MgO)n clusters (n<14). An extensive number of isomer structures was identified and studied. For the isomers of (MgO)n (n<8) clusters, a full geometrical relaxation was considered. Correlation corrections were included for all cluster sizes using the Coulomb-Hartree-Fock (CHF)

T. Meissner, E. M. Henley

We use QCD sum rules for the three point function of a pseudoscalar and two nucleonic currents in order to estimate the charge dependence of the pion nucleon coupling constant coming from isospin violation in the strong interaction. The effect can be attributed primarily to the difference of the quark condensates <ubar u> and <dbar d>. Assuming that the pi0

K. Pomorski, K. Dietrich, W. Przystupa, J. Bartel

The fusion process and the competition between fission and n, p and alpha-particle emission is studied. The calculations are performed for nuclei at excitation energies from 80 MeV up to about 300 MeV. The nuclear fission is described by a Langevin equation coupled to the Master equation for particle evaporation. A significant influence of the initial spin d

M. -Th. Huett, A. I. Milstein

The non-resonant (seagull) contribution to the nuclear Compton amplitude at low energies is strongly influenced by nucleon correlations arising from meson exchange. We study this problem in a modified Fermi gas model, where nuclear correlation functions are obtained with the help of perturbation theory. The dependence of the mesonic seagull amplitude on the

Kang Li, Carlos Naon

We study, through path-integral methods, an extension of the massive Thirring model in which the interaction between currents is non-local. By examining the mass-expansion of the partition function we show that this non-local massive Thirring model is equivalent to a certain non-local extension of the sine-Gordon theory. Thus, we establish a non-local genera

Nobuyoshi Ohta, Jian-Ge Zhou

We present a systematic analysis of possible bound states of M-brane solutions (including waves and monopoles) by using the solution generating technique of reduction of M-brane to 10 dimensions, use of T-duality and then lifting back to 11 dimensions. We summarize a list of bound states for one- and two-charge cases including tilted brane solutions. Constru

Samir D. Mathur

When we vary the moduli of a compactification it may become entropically favourable at some point for a state of branes and strings to rearrange itself into a new configuration. We observe that for the elementary string with two large charges such a rearrangement happens at the `correspondence point&#39; where the string becomes a black hole. For smaller cou

Hsin-Chia Cheng, Jonathan L. Feng, Nir Polonsky

Supersymmetric particles at the multi-TeV scale will escape direct detection at planned future colliders. However, such particles induce non-decoupling corrections in processes involving the accessible superparticles through violations of the supersymmetric equivalence between gauge boson and gaugino couplings. In a previous study, we parametrized these viol

Lisa Randall

We review the motivation for Gauge-Mediated Supersymmetry Breaking and discuss some recent advances.

Lisa Randall

We review a class of models of dynamical supersymmetry breaking, and give a unified description of these models.

T. G. Steele, J. C. Breckenridge, M. Benmerrouche, V. Elias

A global fit to the shape of the first QCD Laplace sum rule exhibiting sensitivity to pion-resonance [$Π(1300)$] parameters is performed, leading to predictions for the pion-resonance mass and decay constant. This fit leads to predictions of $M_π = 1.15 \pm 0.15 GeV$ for the pion-resonance mass, and $F_π^2=(4.5\pm 2.1).(f_π^2m_π^4/M_π^4)$ for the pion-resona

V. Elias, A. H. Fariborz, M. A. Samuel, Fang Shi

We consider the first pion excitation as a sub-continuum resonance in the pseudoscalar channel, and we obtain parameters characterizing this resonance through a global fit of the Borel-parameter dependence of the field-theoretical pseudoscalar Laplace sum rule to its hadronic (pion + pion-excitation + QCD-continuum) content. Our analysis incorporates finite-

E. S. Swanson

It has become traditional to assume that the Dirac structure of the phenomenological quark confinement potential is scalar $\otimes$ scalar. We use the heavy quark expansion of the Coulomb gauge QCD Hamiltonian and the Flux Tube model to demonstrate that this is true but in the effective sense only. The demonstration contains some surprises: confinement is a

Stanley J. Brodsky, John Ellis, Einan Gardi, Marek Karliner

We show that the Pade Approximant (PA) approach for resummation of perturbative series in QCD provides a systematic method for approximating the flow of momentum in Feynman diagrams. In the large-$β_0$ limit, diagonal PA&#39;s generalize the Brodsky-Lepage-Mackenzie (BLM) scale-setting method to higher orders in a renormalization scale- and scheme-invariant

Sheldon Stone

A brief description is given of BTeV a proposed program at the Fermilab collider sited at the C0 intersection region. The main goals are measurement of mixing, CP violation and rare decays in both the $b$ and charm systems. The detector is a two arm forward-backward spectrometer capable of triggering on detached vertices and dileptons, and possessing excelle

Markus Finkemeier

We discuss and test the assumptions of the chirally normalized vector meson dominance model (CN-VMD), as it is used for tau decays. We compare the CN-VMD amplitudes with those using on-shell couplings, derived directly from experimental data. We discuss in detail the $3π$, $K K π$ and $2π$ final states. We suggest that the true values for the $K_1$ widths mi

L. Burakovsky, T. Goldman, L. P. Horwitz

By assuming the existence of (quasi)-linear baryon Regge trajectories, we derive new quadratic Gell-Mann-Okubo type baryon mass relations. These relations are used to predict the masses of the charmed baryons absent from the Baryon Summary Table so far, in good agreement with the predictions of many other approaches.

K. G. Chetyrkin, M. Steinhauser

We consider the decay of an intermediate mass Higgs boson into hadrons up to order O(α_s^3). The results from the diagrams containing only light degrees of freedom were recently computed in a previous work by K.G. Ch. (Phys. Lett. B 390 (1997) 309). In this letter the remaining contributions involving the top quark are evaluated analytically using an effecti

Teruaki Watabe, Klaus Goeke

We give a survey of recent development and applications of the chiral quark soliton model (also called the Nambu-Jona-Lasinio soliton model) with $N_f$=2 and $N_f$=3 quark flavors for the structure of baryons. The model is an effective chiral quark model obtained from the instanton liquid model of the quantum chromodynamics. Mesons appear as quark-antiquark

F. W. Bopp, R. Engel, J. Ranft, A. Rostovtsev

Multiple interaction models satisfying $s$-channel unitarity predict that, in contrast to inelastic processes, factorization is violated in diffractive processes. The size of this effect can be characterized in terms of the rapidity gap survival probability. The possibility of its measurement at HERA is pointed out. Furthermore a method to measure photon dif

Richard D. Ball, Stefano Forte

We describe how perturbative QCD may be applied to inelastic e-p scattering at high center-of-mass energies, i.e. at small x and fixed Q^2.

A. Hebecker

In this talk the relation between the semiclassical approach and the concept of diffractive parton densities is discussed. The proton rest frame calculation is organized in a way that exhibits the hard partonic cross section and the diffractive parton density as the two fundamental ingredients. The latter one is a non-perturbative quantity which, in the pres

M. Beneke

A qualitative (and selective) discussion of current activities and problems in the field is given.

A. Bravar, D. von Harrach, A. Kotzinian

We propose to access the gluon polarization $ΔG$ by measuring the cross section spin-asymmetry in semi-inclusive polarized lepton -- nucleon scattering. The photon-gluon fusion sub-process will be tagged by detecting high-$p_T$ correlated hadron pairs in the forward hemisphere. Selecting oppositely charged kaon pairs will allow to suppress the background com

J. Kwiecinski, A. D. Martin, A. Stasto

We introduce a coupled pair of evolution equations for the unintegrated gluon distribution and the sea quark distribution which incorporate both the resummed leading $\ln (1/x)$ BFKL contributions and the resummed leading $\ln (Q^2)$ DGLAP contributions. We solve these unified equations in the perturbative QCD domain. With only two physically motivated param

S. Chiku, T. Hatsuda

Using a novel resummation procedure of thermal loops, real-time correlations in the scalar and pseudo-scalar channels are studied in the O(4) linear sigma model at finite temperature. A threshold enhancement of the spectral function in the scalar channel is shown to be a noticeable precritical phenomenon of the chiral phase transition.

N. Armesto, A. Capella

We review the two main interpretations of $J/ψ$ suppression proposed in the literature. The phase transition (or deconfining) scenario assumes that below some critical value of the local energy density (or of some other geometrical quantity which depends both on the colliding systems and on the centrality of the collision), there is only nuclear absorption.

H. Jallouli, H. Sazdjian

The pionium decay width is evaluated in the framework of chiral perturbation theory and the relativistic bound state formalism of constraint theory. Corrections of order O(α) are calculated with respect to the conventional lowest-order formula, in which the strong interaction amplitude has been calculated to two-loop order with charged pion masses. Strong in

P. Labelle, S. M. Zebarjad, C. P. Burgess

We compute the next-to-leading, O(m alpha^5), contribution to the hyperfine splitting in positronium within the framework of NRQED. When applied to the ground state, our calculation reproduces known results, providing a further test of NRQED techniques. Besides providing a very simple method of calculation of the standard result, we also obtain new expressio

Stephane Willocq

We review recent $B$ physics results obtained in polarized $e^+ e^-$ interactions at the SLC by the SLD experiment. The excellent 3-D vertexing capabilities of SLD are exploited to extract precise $\bu$ and $\bd$ lifetimes, as well as measurements of the time evolution of $B^0_d - \bar{B^0_d}$ mixing.

Anzhong Wang, Jose A. C. Nogales

The stability of the cosmological event horizons found recently by Gregory [Phys. Rev. D54, 4955 (1996)] for a class of non-static global cosmic strings is studied. It is shown that they are not stable to both test particles and physical perturbations. In particular, the back reaction of the perturbations of null dust fluids will turn them into spacetime sin

M. F. A. da Silva, Anzhong Wang, N. O. Santos

The static vacuum plane spacetimes are considered, which have two non-trivial solutions: The Taub solution and the Rindler solution. Imposed reflection symmetry, we find that the source for the Taub solution does not satisfy any energy conditions, which is consistent with previous studies, while the source for the Rindler solution satisfies the weak and stro

Abhay Ashtekar, Troy A. Schilling

States of a quantum mechanical system are represented by rays in a complex Hilbert space. The space of rays has, naturally, the structure of a Kähler manifold. This leads to a geometrical formulation of the postulates of quantum mechanics which, although equivalent to the standard algebraic formulation, has a very different appearance. In particular, states

S. T. R. Pinho, T. A. S. Haddad, S. R. Salinas

We write exact renormalization-group recursion relations for a ferromagnetic Ising model on the diamond hierarchical lattice with an aperiodic distribution of exchange interactions according to a class of generalized two-letter Fibonacci sequences. For small geometric fluctuations, the critical behavior is unchanged with respect to the uniform case. For larg

V. Dobrosavljevic, G. Kotliar

We discuss the successes of the dynamical mean field (DMF) approach to metal insulator transitions in both the clean and the disordered limit. In the latter case, standard DMF equations are generalized in order to incorporate both the physics of strong correlation and Anderson localization effects. The results give new insights into the puzzling features of

Valery I. Rupasov

The degenerate Anderson model with a nonlinear electron dispersion and an energy dependent hybridization is proven to exhibit hidden integrability and is diagonalized by the Bethe ansatz. If the impurity $f$-level energy lies below the conduction band edge, the spectrum of the system is shown to contain pairs of confined ``gap excitations&#39;&#39; and their

F. C. Alcaraz, R. Z. Bariev

The model of strongly correlated electrons with the correlated hopping term and an additional interaction between holes $V$ is solved exactly in one dimension at a special point where the number of hole pairs is conserved. As a function of the interaction $V$ the phase diagram has a rich structure. There exist gapless phases with dominating density-density c

F. C. Alcaraz, R. Z. Bariev

A new generalization of the t-J model with a nearest-neigbor hopping is formulated and solved exactly by the Bethe-ansatz method. The model describes the dynamics of spin-S fermions with isotropic or anisotropic interactions. In the case S=1 the magnetic interaction is biquadratic in the spin operators. In contrast to the SU(N) generalization of the t-J mode

Victor Gurarie, Chetan Nayak

We present an approach to the computation of the non-Abelian statistics of quasiholes in quantum Hall states, such as the Pfaffian state, whose wavefunctions are related to the conformal blocks of minimal model conformal field theories. We use the Coulomb gas construction of these conformal field theories to formulate a plasma analogy for the quantum Hall st

T. Schork, S. Blawid

We investigate a periodic Anderson model with interacting conduction electrons which are described by a Hubbard-type interaction of strength U_c. Within dynamical mean-field theory the total Hamiltonian is mapped onto an impurity model, which is solved by an extended non-crossing approximation. We consider the particle-hole symmetric case at half-filling. Si

Sidney Redner

The time dependence of the survival probability, S(t), is determined for diffusing particles in two dimensions which are also driven by a random unidirectional zero-mean velocity field, v_x(y). For a semi-infinite system with unbounded y and x>0, and with particle absorption at x=0, a qualitative argument is presented which indicates that S(t)~t^{-1/4}. This

A. P. Jauho, Ned S. Wingreen

Recent double-slit interference experiments have demonstrated the possibility of probing the phase of the complex transmission coefficient of a quantum dot via the Aharonov-Bohm effect. We propose an extension of these experiments: an ac voltage imposed on the side gate with the concomitant photonic sidebands leads to additional structure both in the amplitu

A. Smerzi, S. Fantoni, S. Giovanazzi, . R. Shenoy

We study the coherent atomic tunneling between two zero-temperature Bose-Einstein condensates (BEC) confined in a double-well magnetic trap. Two Gross-Pitaevskii equations for the self-interacting BEC amplitudes, coupled by a transfer matrix element, describe the dynamics in terms of the inter-well phase-difference and population imbalance. In addition to th

Marko Robnik, Tomaz Prosen

We comment on the recent paper by Abul-Magd (J.Phys.A: Math.Gen. 29 (1996) 1) concerning the energy level statistics in the mixed regime, i.e. such having the mixed classical dynamics where regular and chaotic regions coexist in the phase space. We point out that his basic assumption on the additive property of the level-repulsion function $r(S)$ (conditiona

Henry A. Kobulnicky, Evan D. Skillman

We present a longslit optical spectrophotometric survey in the irregular &#34;post-starburst&#34; galaxy NGC 1569 to search for chemical gradients and inhomogeneities in the interstellar medium. Despite the presence of two massive evolved starclusters and numerous HII regions, we find no evidence for chemical gradients or inhomogeneities that may be attribut

Mark S. Marley

Stratospheric heating, condensation, convective transport of non-equilibrium species, and deep radiative energy transport are important processes in the atmospheres of the solar jovian planets. They likely affect the atmospheres of extrasolar giant planets and brown dwarfs as well. Stratospheric temperatures control thermal fluxes in strong molecular bands,

Bohdan Paczyński

The energetics of optical and radio afterglows following BeppoSAX and BATSE gamma-ray bursts (GRBs) suggests that gamma-ray emission is not narrowly collimated, but a moderate beaming is possible, so the total energy of a GRB may be in the range 10^{50} - 10^{51} erg. All attempts to generate a fireball powered by neutrino-antineutrino annihilation have fail

M. Boettcher, H. Mause, R. Schlickeiser

We present model calculations reproducing broadband spectra of $γ$-ray blazars by a relativistic leptonic jet, combining the EIC and the SSC model. To this end, the evolution of the particle distribution functions inside a relativistic pair jet and of the resulting photon spectra is investigated. Inverse-Compton scattering of both external (EIC) as well as s

Roelof Bottema

The observed stellar velocity dispersions of galactic discs show that the maximum rotation of a disc is on average 63% of the observed maximum rotation. This criterion can, however, not be applied to small or low surface brightness (LSB) galaxies because such systems show, in general, a continuously rising rotation curve until the outermost measured radial p

Jaume Garriga, Xavier Montes, Misao Sasaki, Takahiro Tanaka

Faddeev and Jackiw&#39;s method for constrained systems is used to derive a gauge invariant formulation of cosmological perturbations in the one bubble inflationary universe. For scalar perturbations in a flat universe, reduction of the action to the one with a single physical degree of freedom has been derived in the literature. A straightforward generaliza

M. Yildiz, N. Kiziloglu

Solar models through evolutionary phases of gravitational contraction, pre-main sequence and MS phases, up to current age 4.5E9 yr. and 4.57E9 yr., were studied adopting different prescriptions for the equation of state (EOS) and different opacity tables. The results are compared with solar models we computed with different radiative opacities (Cox & Stewart

Lawrence M. Krauss

The lower limit on the age of the universe derived from globular cluster dating techniques, which previously strongly motivated a non-zero cosmological constant, has now been dramatically reduced, allowing consistency for a flat matter dominated universe with a Hubble Constant, $H_0 \le 66 km s^{-1} Mpc^{-1}$. The case for an open universe versus a flat univ

Mats Carlsson, Philip G. Judge, Klaus Wilhelm

On 12 March 1996 we obtained observations of the quiet Sun with the SUMER instrument. The observa- tions were sequences of 15-20 second exposures of ultraviolet emission line profiles and of the neighboring continua. These data contain signatures of the dynamics of the solar chromosphere that are uniquely useful because of wavelength coverage, moderate signa

Klaus Altmann, Lutz Hille

Let Q be a finite quiver without oriented cycles. Denote by U --> M the fine moduli space of stable thin sincere representations of Q with respect to the canonical stability notion. We prove Ext^i(U,U) = 0 for all i >0 and compute the endomorphism algebra of the universal bundle U. Moreover, we obtain a necessary and sufficient condition for when this algebr

Hans-Martin Bröker, Peter Grassberger

We reconsider a model introduced by Bak, Chen, and Tang (Phys. Rev. A 38, 364 (1988)) as a supposedly self-organized critical model for forest fires. We verify again that the model is not critical in 2 dimensions, as found also by previous authors. But we find that the model does show anomalous scaling (i.e., is critical in the sense of statistical mechanics

Kailash C. Sahu, Mario Livio, Larry Petro, Howard E. Bond

We present the discovery observations for the optical counterpart of the $γ$-ray burster GRB 970508 and discuss its light curve in the context of the fireball model. We analyze the HST data for this object, and conclude that any underlying galaxy must be fainter than $R$ = 25.5. We also present a detailed analysis of the HST images of GRB 970228 claimed to s

Gustav W. Delius, Christopher Gardner, Mark D. Gould

The structure constants of quantum Lie algebras depend on a quantum deformation parameter q and they reduce to the classical structure constants of a Lie algebra at $q=1$. We explain the relationship between the structure constants of quantum Lie algebras and quantum Clebsch-Gordan coefficients for adjoint x adjoint ---> adjoint. We present a practical metho

A. N. Kvinikhidze, B. Blankleider

We show how to derive relativistic, unitary, gauge invariant, and charge conserving three-dimensional scattering equations for a system of hadrons interacting with an electromagnetic field. In the method proposed, the spectator equations describing the strong interactions of the hadrons are gauged using our recently introduced gauging of equations method. A

O. Megged

Paper withdrawn due to conceptual mistakes. A corrected version will soon be available at the gr-qc archive.

Yi-Zhi Huang, James Lepowsky

We apply the general theory of tensor products of modules for a vertex operator algebra developed in our papers hep-th/9309076, hep-th/9309159, hep-th/9401119, q-alg/9505018, q-alg/9505019 and q-alg/9505020 to the case of the Wess-Zumino-Novikov-Witten models and related models in conformal field theory. We show that for the category of modules for a vertex

Joshua Feinberg, A. Zee

We study localization and delocalization in a class of non-hermitean Hamiltonians inspired by the problem of vortex pinning in superconductors. In various simplified models we are able to obtain analytic descriptions, in particular of the non-perturbative emergence of a forked structure (the appearance of &#34;wings&#34;) in the density of states. We calcula

Lajos Diosi, Walter T. Strunz

We present the non-Markovian generalization of the widely used stochastic Schrodinger equation. Our result allows to describe open quantum systems in terms of stochastic state vectors rather than density operators, without approximation. Moreover, it unifies two recent independent attempts towards a stochastic description of non-Markovian open systems, based

Dimitri Kusnezov

Representation theory is shown to be incomplete in terms of enumerating all integrable limits of quantum systems. As a consequence, one can find exactly solvable Hamiltonians which have apparently strongly broken symmetry. The number of these hidden symmetries depends upon the realization of the Hamiltonian.