October 1994 arXiv papers — page 8

Hyunggyu Park, Meesoon Ha, In-mook Kim

Surface structure of a restricted ballistic deposition(RBD) model is examined on a one-dimensional staircase with free boundary conditions. In this model, particles can be deposited only at the steps of the staircase. We set up recurrence relations for the surface fluctuation width $W$ using generating function method. Steady-state solutions are obtained exa

U. Nowak, A. Hucht

Recently, a new memory effect was found in the metamagnetic domain structure of the diluted Ising antiferromagnet $Fe_x Mg_{1-x} Cl_2$ by domain imaging with Faraday contrast. Essential for this effect is the dipole interaction. We simulate the low temperature behavior of diluted Ising-antiferromagnets by a Monte Carlo simulation considering long range inter

Tomo Munehisa, Yasuko Munehisa

We propose a new algorithm which works effectively in global updates in Monte Carlo study. We apply it to the quantum spin chain with next-nearest-neighbor interactions. We observe that Monte Carlo results are in excellent agreement with numerically exact ones obtained by the transfer matrix method.

Susan E. Brennan, Marilyn Walker Friedman, Carl J. Pollard

In this paper we present a formalization of the centering approach to modeling attentional structure in discourse and use it as the basis for an algorithm to track discourse context and bind pronouns. As described in Grosz, Joshi and Weinstein (1986), the process of centering attention on entities in the discourse gives rise to the intersentential transition

J. W. Sulentic, P. Marziani, T. Zwitter, M. Calvani

We obtained a new spectrum for the radio galaxy Pictor~A in December 1993. Comparison with previous data obtained in 1983 and 1987 shows that the broad component of the Balmer lines has increased considerably in strength and complexity. The Balmer lines now show a boxy, double peaked profile with FWZI$\sim$24000 \kms. Although the 1993 H\a\ profile is remini

Haret C. Rosu

A short discussion is provided on the hypothesis of strange quark dust of low specific charge in the terrestrial magnetosphere. We suggest by means of rough estimates the possible existence of a strangelet belt in the magnetosphere.

A. A. Akhundov, S. Gerzon, S. Kananov, M. A. Moinester

We use the semi-analytical program RCFORGV to evaluate radiative corrections to one-photon radiative emission in the high-energy scattering of pions in the Coulomb field of a nucleus with atomic number Z. It is shown that radiative corrections can simulate a pion polarizability effect. The average effect was estimated for pion energies 40-600 GeV. We also st

Victor Ginzburg

In this paper differential operators on various moduli spaces (e.g. of holomorphic vector bundles) are described in a canonical way in terms of the geometry of a certain distinguished completion of an appropriate configuration space.

David J. Gross, Andrei Matytsin

Large $N$ two-dimensional QCD on a cylinder and on a vertex manifold (a sphere with three holes) is investigated. The relation between the saddle-point description and the collective field theory of QCD$_2$ is established. Using this relation, it is shown that the Douglas--Kazakov phase transition on a cylinder is associated with the presence of a gap in the

E. H. Lieb

The conjecture is verified that the optimum, energy minimizing magnetic flux for a half-filled band of electrons hopping on a planar, bipartite graph is $π$ per square plaquette. We require {\it only} that the graph has periodicity in one direction and the result includes the hexagonal lattice (with flux 0 per hexagon) as a special case. The theorem goes bey

Zhan-Ning Hu

The Abelian current algebra on the lattice is given from a series of the independent Weyl pairs and the shift operator is constructed by this algebra. So the realization of the operators of the braid group is obtained. For $|q|\neq 1$ the shift operator is the product of the theta functions of the generators $w_n$ of the current algebra. For $|q|=1$ it can b

P V Landshoff

A wide variety of experimental data in hadronic reactions are described in terms of the exchange of an object called the soft pomeron. It is nonperturbative in origin and is perhaps associated with glueballs. The HERA measurements of $νW_2$ at small $x$ suggest the possibility that there is also a hard pomeron, which is perturbative. I review the experimenta

P. Coleman

I summarize some of the key questions to have emerged during the 1994 conference on ``Strongly Correlated Electron Systems'', held in Amsterdam, August 1994. Issues addressed include: Hunds rule interactions and how they renormalize; the Luttinger sum rule and metamagnetism; heavy fermion insulators, the nature of the charge gap, spectral weight transfer in

E. Sezgin

The requirement of an $SL(2)$ duality symmetry, mixing the worldvolume field equations with Bianchi identities, leads to a highly nonlinear equation involving the transformation parameters and certain worldvolume currents. In general, this equation seems to admit a solution only for a two parameter subgroup of the seeked $SL(2)$. These transformations also l

V. V. Mangazeev, S. M. Sergeev, Yu. G. Stroganov

In this paper we formulate a new N-state spin integrable model on a three-dimensional lattice with spins interacting round each elementary cube of the lattice. This model can be also reformulated as a vertex type model. Weight functions of the model satisfy tetrahedron equations.

C. Fu, S. Doniach

Revised to reflect the differences between the second order perturbation theory method developed by Scheitzer and Czycholl, and followed by us, and the iterated perturbation theory (IPT)of Georges and Kotliar, et al. Because of our domain of interest, this does not materially change our conclusions, but it is important to realize that the method used here fa

Ruth Gregory, Raymond Laflamme

We investigate the stability of the extremal black p-brane which contains a n-form and a dilaton. We show that the instability due to the s-mode, which was present in the uncharged and non-extremal p-brane, disappears in the extreme case. This is shown to be consistent with an entropy argument which shows that the zero entropy of the extremal black hole is a

C. O. Lousto

We stress the strongly observer-dependent nature of the fine-grained black hole entropy as computed by usual methods. From the point of view of a fiducial observer, the 1-loop renormalized energy-momentum tensor diverges at the horizon. Considering, more consistently, the computation of the black hole entropy in the back-reaction-corrected curved background

S. Laporta

The contributions to the (g-2) of the electron from the corner-ladder graphs in sixth-order (three-loop) QED perturbation theory are evaluated in closed analytical form. The results obtained are in excellent agreement with the most precise numerical evaluations already existing in the literature. Our results allows one to reduce the numerical uncertainty of

Geir Ellingsrud, Lothar Göttsche

The paper determines the change of moduli spaces of rank $2$ sheaves on surfaces with $p_g=0$ under change of polarization and the corresponding change of the Donaldson invariants. In this revised version we have made some minor stylistic changes in the previous text. In addition we have added a final chapter of about 20 pages (announced in the previous vers

E. Quack, P. Zhuang, Y. Kalinovsky, S. P. Klevansky

The $s$-wave $π-π$ scattering lengths $a^I(T)$ at finite temperature $T$ and isospin $I=0,2$ are calculated within the SU(2) Nambu--Jona-Lasinio model. $a^2(T)$ displays a singularity at the Mott temperature $T_M$, defined as $m_π(T_M) = 2m_q(T_M)$, while $a^0(T)$ is singular in addition at the lower temperature $T_d$, where $m_σ(T_d) = 2m_π(T_d)$, $m_σ$ and

G. Q. Li, C. M. Ko, B. A. Li

The flow of kaons, i.e., the average kaon transverse momentum as a function of rapidity, and the associated flow parameter in heavy-ion collisions at SIS/GSI energies is investigated in the relativistic transport model. It is found that the pattern of kaon flow at the final stage is sensitive to the kaon potential used in the model and is thus a useful probe

E. Kwa{ś}niewicz, H. Herndl, H. Oberhummer

Spectroscopic amplitudes are calculated for one--nucleon transfer between low--lying, normal--parity states of nuclei in the lower part of the 1p$0\,$f--shell. Calculations are performed using shell--model wave functions obtained from the diagonalization procedure of a nuclear Hamiltonian in the space given by the complete set of states generated from the 1p

S. G. Rajeev, O. T. Turgut

We formulate the canonical structure of Yang--Mills theory in terms of Poisson brackets of gauge invariant observables analogous to Wilson loops. This algebra is non--trivial and tractable in a light--cone formulation. For U(N) gauge theories the result is a Lie algebra while for SU(N) gauge theories it is a quadratic algebra. We also study the identities sa

Edward Witten

This paper is devoted to the construction of a family of linear sigma models with $(0,4)$ supersymmetry which should flow in the infrared to the stringy version of Yang-Mills instantons on ${\bf R}^4$. The family depends on the full set of expected parameters and is obtained by using the data that appear in the ADHM construction of instantons.

I. A. B. Strachan

A new Lax equation is introduced for the KP hierarchy which avoids the use of pseudo-differential operators, as used in the Sato approach. This Lax equation is closer to that used in the study of the dispersionless KP hierarchy, and is obtained by replacing the Poisson bracket with the Moyal bracket. The dispersionless limit, underwhich the Moyal bracket col

I. A. B. Strachan

An important example of a multi-dimensional integrable system is the anti-self-dual Einstein equations. By studying the symmetries of these equations, a recursion operator is found and the associated hierarchy constructed. Owing to the properties of the recursion operator one may construct a hierarchy of symmetries and find the algebra generated by them. In

M. J. Duff

The Kaluza-Klein idea of extra spacetime dimensions continues to pervade current attempts to unify the fundamental forces, but in ways somewhat different from that originally envisaged. We present a modern perspective on the role of internal dimensions in physics, focussing in particular on superstring theory. A novel result is the interpretation of Kaluza-K

D. R. Grigore

A general discussion of the construction of free fields based on Weinberg anszatz is provided and various applications appearing in the litterature are considered.

Roberto Soldati

It is shown that the quantization of the unphysical degrees of freedom, which leads to the Mandelstam--Leibbrandt prescription for the infrared spurious singularities in the continuum light cone gauge, does indeed suggest some quite natural recipe to treat the zero modes in the Discretized Light Front Quantization of gauge theories.

M. Cadoni, S. Mignemi

A four-dimensional dilaton-gravity action whose spherical reduction to two dimensions leads to the Jackiw-Teitelboim theory is presented. A nonsingular black hole solution of the theory is obtained and its physical interpretation is discussed. The classical and semiclassical properties of the solution and of its 2d counterpart are analysed. The 2d theory is

V. F Müller

In two space-time dimensions a class of classical multicomponent scalar field theories with discrete, in general non-Abelian global symmetry is considered. The corresponding soliton solutions are given for the cases of 2, 3, and 4 components.

M. G. Olsson, S. Veseli

The Relativistic Flux Tube model is used to calculate of the Isgur-Wise functions describing the exclusive semileptonic decays of $\bar{B}$ and $\bar{B}_{s}$ mesons. The light quark mass dependence is investigated and the predicted universal function agrees well with the results of lattice simulations, and with the experimental data. Recent experimental meas

Herbert Nachbagauer

We present a self--consistent solution of the finite temperature gap--equation for $λΦ^4$ theory beyond the Hartree-Fock approximation using a composite operator effective action. We find that in a spontaneously broken theory not only the so--called daisy and superdaisy graphs contribute to the resummed mass, but also resummed non--local diagrams are of the

Nick Evans

We argue that in dynamical models of fermion masses, which explain the three mass scales of the generations of fermions with three separate heavy scales above the electroweak symmetry breaking scale, the off diagonal CKM matrix elements must be generated at a fourth scale. The simplest form for the additional mass generation is a mechanism that has an $SU(3)

W. Grimus, H. Neufeld

We perform a quantum theoretical calculation of transition radiation by neutral particles with spin 1/2 equipped with magnetic moments and/or electric dipole moments. The limit of vanishing masses is treated exactly for arbitrary refraction index. Finally we apply our result to the solar neutrino flux.

Michael H. Seymour

We formulate the first order corrections to processes involving the scattering or annihilation of quarks in a form in which the QCD and electroweak parts are exactly factorised. This allows for a straightforward physical interpretation of effects such as lepton-hadron correlations, and a simpler Monte Carlo treatment. The postscript file for this paper can a

Manu Mathur, Rajiv V. Gavai

We study the three dimensional fundamental-adjoint $SU(2)$ lattice gauge theory at non-zero temperatures by Monte Carlo simulations. On an $8^3 \times 2$ lattice, at $β_A = 1.1$, where $β_A$ is the adjoint coupling, we find no evidence of any transition at the location of a previously known bulk phase transition around $β= 1.33$. Moreover, the deconfinement

Sergey Sushkov

It is considered the quantum complex scalar field which obeys the authomorphic condition in the two-dimensional spacetime with closed timelike curves and the chronology horizon. The renormalized stress-energy tensor is obtained. It is shown that the value of the stress-energy tensor is regular at the chronology horizon for specific authomorphic parameters. T

Takahiro Tanaka

We consider fundamental problems on the understanding of the tunneling phenomena in the context of the multi-dimensional wave function. In this paper, we reconsider the quantum state after tunneling and extend our previous formalism to the case when the quantum state before tunneling is in a squeezed state. Through considering this problem, we reveal that th

P. COLEMAN, E. Miranda

What is the character of the gapless quasiparticles in heavy fermion superconductors (HFSC)? We discuss an odd-frequency pairing interpretation of HFSC which leads to a two component model for the quasiparticle excitations. In this picture, line zeroes of unpaired electrons may coexist with gapless surfaces of paired electrons, with vanishing spin and charge

J-P. Bouchaud, D. S. Dean

We present a detailed study of simple `tree' models for off equilibrium dynamics and aging in glassy systems. The simplest tree describes the landscape of a random energy model, whereas multifurcating trees occur in the solution of the Sherrington-Kirkpatrick model. An important ingredient taken from these models is the exponential distribution of deep f

Yeong-Lieh Lin, Franco Nori

We study quantum interference effects due to electron motion on the Kagomé lattice in a perpendicular magnetic field. These effects arise from the interference between phase factors associated with different electron closed-paths. From these we compute, analytically and numerically, the superconducting-normal phase boundary for Kagomé superconducting wire ne

Jaime Ferrer

The characterization and evolution of a Spin Density Wave into the Quantum Neel ground state is considered in the context of a weak coupling theory of the half-filled Hubbard model. Magnetic properties obtained from this weak coupling approach in one dimension compare favorably with exact results from Bethe ansatz (BA). A study of the evolution of several le

Sudhansu S. Mandal, S. Ramaswamy, V. Ravishankar

We study Chern-Simons (CS) superconductivity in the presence of uniform external magnetic field of {\it arbitrary strength} for a system of fermions in two spatial dimensions, which are minimally coupled both to the CS and Maxwell gauge fields. We have carried out the computation within the mean field ansatz. Analysing only the mean field (i.e., ignoring the

F. V. Kusmartsev

In systems with the spin-charge separation, the period of the Aharonov-Bohm (AB) oscillation becomes half of the flux quantum. This effect is at least related to the fact that for the creation of the holons (spinons) are needed two electrons. The effect is illustrated on the example of the Hubbard Hamiltonian with the aid of the bosonization including topolo

K. Jedamzik, G. M. Fuller

We study big bang nucleosynthesis in the presence of large mass-scale, non-linear entropy fluctuations. Overdense regions, with masses above the local baryon-Jeans mass, are expected to collapse and form condensed objects. Surviving nucleosynthesis products therefore tend to originate from underdense regions. We compute expected surviving light element ($^2$

Walter Dehnen

A technique for the construction of axisymmetric distribution functions for individual galaxies is presented. It starts from the observed surface bright- ness distribution, which is deprojected to gain the axisymmetric luminosity density, from which follows the stars' gravitational potential. After adding dark mass components, such as a central black hol

Christopher D. Carone, Elizabeth H. Simmons, Yumian Su

We consider the radiative decay $b\rightarrow s γ$, and the correction to the $Zb\overline{b}$ vertex in technicolor models with scalars. In these models, the scalar develops a vacuum expectation value when the technifermions condense, and the ordinary fermions develop masses via Yukawa couplings. Since the symmetry breaking sector involves both a fundamenta

C. Steidel, M. Dickinson, S. E. Persson

We present some of the results of a large survey aimed at establishing the properties of galaxies selected by their having produced detectable Mg~II $\lambda\lambda 2796$, 2803 absorption in the spectra of background QSOs. The present sample covers the redshift range $0.2 \le z \le 1.0 $, with $\langle z \rangle = 0.65$. From an extensive program of optical

D. J. Broadhurst, A. G. Grozin

Heavy--light QCD currents are matched with HQET currents at two loops and leading order in $1/m$. A single formula applies to all current matchings. As a by--product, a master formula for the two--loop anomalous dimension of the QCD current $\bar{q}γ^{[μ_1}\ldotsγ^{μ_n]}q$ is obtained, yielding a new result for the tensor current. The dependence of matching

Julian Borrill, Marcelo Gleiser

The dynamics of first order phase transitions are studied in the context of (3+1)-dimensional scalar field theories. Particular attention is paid to the question of quantifying the strength of the transition, and how `weak' and `strong' transitions have different dynamics. We propose a model with two available low temperature phases separated by an e

Bruce Allen, Robert Caldwell, Scott Koranda

Primordial gravitational waves are created during the de Sitter phase of an exponentially-expanding (inflationary) universe, due to quantum zero-point vacuum fluctuations. These waves produce fluctuations in the temperature of the Cosmic Background Radiation (CBR). We calculate the multipole moments of the correlation function for these temperature fluctuati

G. 't Hooft

Early developments leading to renormalizable non-Abelian gauge theories for the weak, electromagnetic and strong interactions, are discussed from a personal viewpoint. They drastically improved our view of the role of field theory, symmetry and topology, as well as other branches of mathematics, in the world of elementary particles.

E. W. N. Glover, M. R. Sutton

The ${\cal O}(α_s^2)$ coefficient of the energy-energy correlation function (EEC) has been calculated by four groups with differing results. This discrepancy has lead to some confusion over how to measure the strong coupling constant using the EEC and the asymmetry of the energy-energy correlation function (AEEC) in electron-positron annihilation at the $Z$

Debashis Ghoshal, Camillo Imbimbo, Sunil Mukhi

We investigate Landau-Ginzburg string theory with the singular superpotential X^{-1} on arbitrary Riemann surfaces. This theory, which is a topological version of the c=1 string at the self-dual radius, is solved using results from intersection theory and from the analysis of matter Landau-Ginzburg systems, and consistency requirements. Higher-genus amplitud

M. J. M. de Jong, C. W. J. Beenakker

The transport properties of a ferromagnet-superconductor (FS) junction are studied in a scattering formulation. Andreev reflection at the FS interface is strongly affected by the exchange interaction in the ferromagnet. The conductance G_FS of a ballistic point contact between F and S can be both larger or smaller than the value G_FN with the superconductor

Kemal Oflazer

This paper presents an approach to spelling correction in agglutinative languages that is based on two-level morphology and a dynamic programming based search algorithm. Spelling correction in agglutinative languages is significantly different than in languages like English. The concept of a word in such languages is much wider that the entries found in a di

Kai Hencken, Dirk Trautmann, Gerhard Baur

Effective photon-photon luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding photon-photon luminosities at electron-positron and future Photon Linear Colliders (PLC). Higher order corrections as wel

Hungchong Kim, C. J. Horowitz, M. R. Frank

Inclusive quasielastic response functions are calculated for electron scattering in a relativistic model including momentum dependent scalar and vector mean fields. The momentum dependence of the mean fields is taken from Dirac optical fits to proton nucleus scattering and is important in describing data at momentum transfers of 1 GeV/c or larger. Our simple

Ulrich Meyer

Associated to the standard $SU_{q}(n)$ R-matrices, we introduce quantum spheres $S_{q}^{2n-1}$, projective quantum spaces $CP_{q}^{n-1}$, and quantum Grassmann manifolds $G_{k}(C_{q}^{n})$. These algebras are shown to be homogeneous quantum spaces of standard quantum groups and are also quantum principle bundles in the sense of T Brzezinski and S. Majid (Com

Andre LeClair

It is known that classical electromagnetic radiation at a frequency in resonance with energy splittings of atoms in a dielectric medium can be described using the classical sine-Gordon equation. In this paper we quantize the electromagnetic field and compute quantum corrections to the classical results by using known results from the sine-Gordon quantum fiel

V. Chari, A. N. Pressley

We continue our study of minimal affinizations for algebras of type D, E.

A. N. Theron, F. A. Schaposnik, F. G. Scholtz, H. B. Geyer

We present a derivation of abelian and non-abelian bosonization in a path integral setting by expressing the generating functional for current-current correlation functions as a product of a $G/G$-coset model, which is dynamically trivial, and a bosonic part which contains the dynamics. A BRST symmetry can be identified which leads to smooth bosonization in

A. Yu. Umnikov, L. P. Kaptari, K. Yu. Kazakov, F. C. Khanna

The nuclear effects in the spin-dependent structure functions $g_1^D$ and $b_2^D$ are calculated in the relativistic approach based on the Bethe-Salpeter equation with a realistic meson-exchange potential. The results of calculations are compared with the non-relativistic calculations. The problem of extraction of the neutron spin structure function, $g_1^n$

S. Frankel, W. Frati

The A dependence of the production of hadrons in inelastic muon scattering and of the production of dimuons in high $Q^2$ proton interactions are simply related. Feynman x distributions and z scaling distributions in nuclei are compared with energy loss models. Suggestions for new data analyses are presented.

Wai-Keung Tang

Measurements of the polarization of $\jp$ produced in pion-nucleus collisions are in disagreement with leading twist QCD prediction where $\jp$ is observed to have negligible polarization whereas theory predicts substantial polarization. We argue that this discrepancy cannot be due to poorly known structure functions nor the relative production rates of $\jp

M. Vänttinen, P. Hoyer, S. J. Brodsky, W. -K. Tang

In the limit of heavy quark mass, the production cross section and polarization of quarkonia can be calculated in perturbative QCD. We study the $p_\perp$-averaged production of charmonium states in $πN$ collisions at fixed target energies. The data on the relative production rates of $\jp$ and $χ_J$ is found to disagree with leading twist QCD. The polarizat

Michael Gronau

We review the present status of the Standard Model of CP violation, which is based on a complex phase in the Cabibbo-Kobayashi- Maskawa (CKM) matrix. So far CP violation has been observed only in $K^0-\Kbar$ mixing, consistent with a sizable phase. The implications of future CP nonconserving measurements in $K$ and $B$ decays are discussed within the model.

John Terning

I consider the possibility that electroweak symmetry is broken by a strongly interacting chiral gauge theory. I argue that some of the discrepancies between precision electroweak measurements and the predictions of QCD-like technicolor models can be resolved if technicolor is a chiral gauge theory. I present a toy technicolor model which demonstrates this id

F. A. Berends, A. I. Davydychev, V. A. Smirnov, J. B. Tausk

An algorithm is constructed to derive a small momentum expansion for two-loop two-point diagrams in all cases where, due to the presence of physical thresholds, there are singularities at zero external momentum. The coefficients of this ``zero-threshold'' expansion are calculated analytically for arbitrary masses. Numerical examples, using diagrams o

Nir Polonsky, Alex Pomarol

Potentially large non-universal corrections to the soft supersymmetry breaking parameters arise from their evolution between the Planck and the grand-unification scales. We detail typical patterns of non-universality in GUT models, as well as elaborate on their propagation to the weak scale and on their low-energy implications. Possible corrections to the di

G. Couture, C. Hamzaoui, H. König

We present the results of the gluino and scalar quarks contribution to the flavour changing top quark decay into a charm quark and a photon, gluon or a $Z^0$\ boson within the minimal supersymmetric standard model. We include the mixing of the scalar partners of the left and right handed top quark. This mixing has several effects, the most important of which

Ahmed Sayed HASSAN, Masahiro IMACHI, Hiroshi YONEYAMA

U(1) lattice gauge theory with $θ$-term is investigated by real space renormalization group approach. Flows of renormalized coupling constants are analyzed. For each $θ$, renormalization flows converge to a single trajectory irrespective of bare coupling constants of real action. For $θ\not= π$ the system is in the confinement phase controlled by an infrared

Paul F. Derwent

Using data collected during the 1992-1993 collider run at Fermilab, CDF has made measurements of correlated $b$ quark cross sections where one $b$ is detected from the lepton from semileptonic decay and the second $b$ is detected with secondary vertex techniques. We report on measurements of the cross section as a function of the momentum of the second $b$ a

James B. Hartle, Raymond Laflamme, Donald Marolf

We investigate conservation laws in the quantum mechanics of closed systems. We review an argument showing that exact decoherence implies the exact conservation of quantities that commute with the Hamiltonian including the total energy and total electric charge. However, we also show that decoherence severely limits the alternatives which can be included in

M. Benakli, M. Gabay, W. M. Saslow

The row model is used to study the commensurate-incommensurate (C-IC) an isotropic (FFTXY) transitions of the frustrated 2D XY model on the triangular lattice. New relevant variables clarify the physics of these transitions: phase and chiral variables are coupled so that spin waves generate long range polar interactions. The resulting dielectric constan dive

J. Dewitz, W. Hubner, K. H. Bennemann

Using classical electrodynamics we determine the angular dependence of the light intensities radiated in second and third harmonic generation by spherical metal clusters. Forward and backward scattering is analyzed in detail. Also resonance effects in the integrated intensities are studied. Our work treats the case of intermediate cluster sizes. Thus it comp

Jean-Rene ROY, Daniel KUNTH

Stellar and nebular abundance indicators reveal that there exists significant abundance fluctuations in the interstellar medium (ISM) of gas-rich galaxies. It is shown that at the present observed solar level of O/H $\sim 6 \times 10^{-4}$, abundance differences of a factor of two, such as existing between the Sun and the nearby Orion Nebula, are many times

Anatoly Klypin, Stefano Borgani, Jon Holtzman, Joel Primack

Damped Ly$α$ systems provide possibly the most significant evidence for early structure formation, and thus a stringent constraint on the Cold + Hot Dark Matter (CHDM) cosmology. Using the numbers of halos in N-body simulations to normalize Press-Schechter (PS) estimates of the number densities of protogalaxies as a function of redshift, we find that CHDM wi

Michael A. Nowak, Robert V. Wagoner

The high state of black hole candidates is characterized by a quasi- thermal emission component at $kT \sim 1$ keV. In addition, this state tends to have very low variability which indicates that it is relatively stable, at least on {\it short} time scales. Most models of the high state imply that the bulk of the emission comes from an optically thick accret

David Gieseker, Jun Li

This is the revised version of our previous preprint. In this paper, we establish a generic smoothness result for moduli space of semistable sheaves of arbitrary rank over surfaces provided that the second Chern class of the sheaves is sufficiently large. The theorem is proved using degeneration theory.

D. A. R. Dalvit, F. D. Mazzitelli

We consider the non-local energy-momentum tensor of quantum scalar and spinor fields in $2 w$-dimensional curved spaces. Working to lowest order in the curvature we show that, while the non-local terms proportional to $\Box {\cal R}$, $\Box \Box{\cal R}$, $\ldots, \Box^{w-2} {\cal R}$ are fully determined by the early-time behaviour of the heat kernel, the t

Vasily E. Tarasov

The dissipative models in string theory can have more broad range of application: 1) Noncritical strings are dissipative systems in the "coupling constant" phase space. 2) Bosonic string in the affine-metric curved space is dissipative system. But the quantum descriptions of the dissipative systems have well known ambiguities. In order to solve the p

Ariel R. Zhitnitsky

We discuss a few, apparently different (but actually, tightly related) problems: 1. The relation between QCD and valence quark model, 2. The evaluation of the nonlocal condensate $ \la \bar{q}(x)q(0)\ra $, its relation to heavy-light $\bar{q}Q$ quark system and to constituent quark mass, 3. The asymptotic behavior of the nonperturbative pion wave function $ψ

Jacek Dziarmaga

We show that delinking of Z-string loops changes helicity and thus violates baryon number. The key point is that an unlinked vortex loop can not be twisted. Helicity of an eventual magnetic twist when averaged in time is zero.

M. Anazawa, A. Ishikawa, H. Itoyama

An explicit expression for continuum annulus amplitudes having boundary lengths $\ell_{1}$ and $\ell_{2}$ is obtained from the two-matrix model for the case of the unitary series; $(p,q) = (m + 1, m)$. In the limit of vanishing cosmological constant, we find an integral representation of these amplitudes which is reproduced, for the cases of the $m = 2~(c=0)

Kenzo Inoue

The three chiral generations of quarks and leptons may be generated through a spontaneous breakdown of the noncompact horizontal gauge symmetry $G_{H}$ which governs, together with the standard gauge symmetry ${SU(3) \times SU(2) \times U(1)}$, the world in a vectorlike manner. In a framework of supersymmetric theory, the simplest choice ${G_{H}=SU(1,1)}$ wo

J. L. Forest, V. R. Pandharipande, J. Carlson, R. Schiavilla

In relativistic Hamiltonians the two-nucleon interaction is expressed as a sum of $\tilde{v}_{ij}$, the interaction in the ${\bf P}_{ij}=0$ rest frame, and the ``boost interaction'' $δv({\bf P}_{ij})$ which depends upon the total momentum ${\bf P}_{ij}$ and vanishes in the rest frame. The $δv$ can be regarded as a sum of four terms: $δv_{RE}$, $δv_{L

Joseph N. Ginocchio, Calvin W. Johnson

After a brief review of various mappings of fermion pairs to bosons, we rigorously derive a general approach. Following the methods of Marumori and Otsuka, Arima, and Iachello, our approach begins with mapping states and constructs boson representations that preserve fermion matrix elements. In several cases these representations factor into finite, Hermitia

J. L. Forest, V. R. Pandharipande, J. L. Friar

Relativistic Hamiltonians are defined as the sum of relativistic one-body kinetic energies, two- and many-body interactions and their boost corrections. We review the calculation of the boost correction of the two-body interaction from commutation relations of the Poincare group and show that its important terms can be easily understood from classical relati

Mihai Horoi

A simple superfluid model with an effective four body interaction of monopole pairing type is used to explain the staggering of the charge radii in the isotope chains. The contribution of deformation and of the particle number projection are analyzed for the Sn isotopes. Good results are obtained for the staggering parameters and neutron pairing energies.

Mihai Horoi

The $γ$-circular polarizations ($P_γ$) and asymmetries ($A_γ$) of the parity forbidden M1 + E2 $γ$-decays: $^{36}Cl^{\ast} (J^π = 2^{-}; T = 1; E_{x} = 1.95 $ MeV) $\rightarrow$ $^{36}Cl (J^π = 2^{+}; T = 1; g.s.)$ and $^{36}Ar^{\ast} (J^π = 2^{-}; T = 0; E_{x} = 4.97 $ MeV) $\rightarrow$ $^{36}Ar^{\ast} (J^π = 2^{+}; T = 0; E_{x} = 1.97 $ MeV) are investiga

Mihai Horoi, Vladimir Zelevinsky, B. Alex Brown

Generic signatures of quantum chaos found in realistic shell model calculations are compared with thermal statistical equilibrium. We show the similarity of the informational entropy of individual eigenfunctions in the mean field basis to the thermodynamical entropy found from the level density. Mean occupation numbers of single-particle orbitals agree with

Karl Grün, Rudolf Pichler, Heinz Oberhummer

The $({\rm n},γ)$--cross sections for neutron--rich oxygen isotopes have been calculated in the direct capture model. The experimental data for ${^{18}{\rm O}}({\rm n},γ){^{19}{\rm O}}$ can be reproduced using this model. Compared to previous work the cross section for ${^{19-21}{\rm O}}({\rm n},γ){^{20-22}{\rm O}}$ are enhanced considerably by factors betwe

Sadhan K. Adhikari, Lauro Tomio

The relativistic effect on differential cross sections, nucleon-to-nucleon and nucleon-to-deuteron polarization transfer coefficients, and the spin correlation function, of nucleon-deuteron elastic scattering is investigated employing several three-dimensional relativistic three-body equations and several nucleon-nucleon potentials. The polarization transfer

Doron Gepner

We revisit the solvable lattice models described by Andrews Baxter and Forrester and their generalizations. The expressions for the local state probabilities were shown to be related to characters of the minimal models. We recompute these local state probabilities by a different method. This yields generalized Rogers Ramanujan identities, some of which recen

Ashok Das, Marcelo Hott

The solubility of a general two dimensional model, which reduces to various models in different limits, is studied within the path integral formalism. Various subtleties and interesting features are pointed out.

Miguel E. Ortiz

The definition of matter states on spacelike hypersurfaces of a 1+1 dimensional black hole spacetime is considered. Because of small quantum fluctuations in the mass of the black hole, the usual approximation of treating the gravitational field as a classical background on which matter is quantized, breaks down near the black hole horizon. On any hypersurfac

L. Dolan, P. Goddard, P. Montague

An account is given of the structure and representations of chiral bosonic meromorphic conformal field theories (CFT's), and, in particular, the conditions under which such a CFT may be extended by a representation to form a new theory. This general approach is illustrated by considering the untwisted and $Z_2$-twisted theories, $H(Λ)$ and $\tilde H(Λ)$