July 1999 arXiv papers — page 16

A. Dedes, A. E. Faraggi

The emergence of free fermionic string models with solely the MSSM charged spectrum below the string scale provides further evidence to the assertion that the true string vacuum is connected to the Z_2 x Z_2 orbifold in the vicinity of the free fermionic point in the Narain moduli space. An important property of the Z_2 x Z_2 orbifold is the cyclic permutati

E. Lunghi

We study the semileptonic decays B -> Xs e+ e-, B -> Xs mu+ mu- in generic supersymmetric extensions of the Standard Model. SUSY effects are parameterized using the mass insertion approximation formalism and differences with MSSM results are pointed out. Constraints on SUSY contributions coming from other processes (e.g. b -> s gamma) are taken into account.

Xiao-Jun Bi, Yuan-Ben Dai, Xiao-Yuan Qi

The ${\cal O}(α_s)$ QCD corrections to the three-body decay width of the charged Higgs $Γ$($H^+\to W^+b\bar{b}$) are discussed in the MSSM model. Our calculations indicate that the standard QCD corrections to the three-body decay mode raise the width by about 12% and the supersymmetric QCD corrections(due to $\tilde{g}, \tilde{t}, \tilde{b}$ exchanges) can b

Wei Zhu, Hongwei Xiong, Jianhong Ruan

A consistent and intuitive description of the twist-4 corrections to the hadron structure functions is presented in a QCD-improved parton model using time-ordered perturbative theory, where the collinear singularities are naturally eliminated. We identify the special propagators with the backward propagators of partons in time order.

N. Hammon, H. Stöcker, W. Greiner, A. Dumitru

We calculate the yields of a variety of hadrons for RHIC and LHC energies assuming thermodynamical equilibration of the produced minijets, and using as input results from pQCD for the energy densities at midrapidity. In the calculation of the production of partons and of transverse energy one has to account for nuclear shadowing. By using two parametrization

Pablo Achard

A preliminary study of double tag events using the L3 detector at center of mass energy sqrt{s}=189 GeV has been performed. The cross-section of gamma* gamma* collisions is measured at average <Q2>=14.5 GeV2. The results are in agreement with predictions based on perturbative QCD, while the Quark Parton Model alone is insufficient to describe the data. The m

The CHORUS Collaboration

The present results on the $\numtonut$ oscillation search by the CHORUS experiment at CERN are summarized. A fraction of the neutrino interactions collected in 1994-1997 has been analysed, searching for $ν_τ$ charged current interactions followed by the $τ$ lepton decay into a negative hadron, electron, or into a muon. A sample of 126,229 events with an iden

A. Alavi-Harati

We report on a search for the decay K_L -> pi^0 nu nubar, carried out as a part of E799-II, a rare K_L decay experiment at Fermilab. Within the Standard Model, the K_L -> pi^0 nu nubar decay is dominated by direct CP violating processes, and thus an observation of the decay implies confirmation of direct CP violation. Due to theoretically clean calculations,

Patricio S. Letelier

The well-known ``displace, cut, and reflect&#39;&#39; method used to generate cold disks from given solutions of Einstein equations is extended to solutions of Einstein-Maxwell equations. Four exact solutions of the these last equations are used to construct models of hot disks with surface density, azimuthal pressure, and azimuthal current. The solutions ar

J. Bicak, J. Podolsky

In a suitably chosen essentially unique frame tied to a given observer in a general spacetime, the equation of geodesic deviation can be decomposed into a sum of terms describing specific effects: isotropic (background) motions associated with the cosmological constant, transverse motions corresponding to the effects of gravitational waves, longitudinal moti

J. Bicak, J. Podolsky

All non-twisting Petrov-type N solutions of vacuum Einstein field equations with cosmological constant Lambda are summarized. They are shown to belong either to the non-expanding Kundt class or to the expanding Robinson-Trautman class. Invariant subclasses of each class are defined and the corresponding metrics are given explicitly in suitable canonical coor

A. V. Toporensky, V. O. Ustiansky

The dynamics of the Bianchi IX cosmological model with minimally coupled massive real scalar field is studied. The possibility of non-singular transition from contraction to expansion is shown. A set of initial conditions that lead to non-singular solutions is studied numerically.

Hai Halevi

Uncompactified KK universes are so intrinsically connected to the otherwise only empirically required &#34;missing&#34; Dark Matter (DM), that: 1) They yield a simple prediction which explains both the enigma of the extra-dimensions&#39; (XD) unobservability and the enigma of the present DM. The two enigmas are &#34;annihilated&#34; into the hypothesis of &#

C. G. Bezerra, J. M. de Araujo, C. Chesman, E. L. Albuquerque

We study numerically the magnetic properties (magnetization and magnetoresistance) of ultra-thin magnetic films (Fe/Cr) grown following the Fibonacci sequence. We use a phenomenological model which includes Zeeman, cubic anisotropy, bilinear and biquadratic exchange energies. Our physical parameters are based on experimental data recently reported, which con

Anupam Garg

A discrete WKB method is developed for calculating tunnel splittings in spin problems. The method is then applied to the issue of how nuclear spins affect the macroscopic quantum coherence of the total magnetic moment in small magnetic particles. The results are compared with numerical work, and with previous instanton based analytic approaches.

Anupam Garg

A discrete version of the WKB method is developed and applied to calculate the tunnel splittings between classically degenerate states of spin Hamiltonians. The results for particular model problems are in complete accord with those previously found using instanton methods. The discrete WKB method is more elementary and also yields wavefunctions.

O. V. Patsahan, M. P. Kozlovskii, R. S. Melnyk

A microscopic approach to the investigation of the behaviour of a symmetrical binary fluid mixture in the vicinity of the vapour-liquid critical point is proposed. It is shown that the problem can be reduced to the calculation of the partition function of a 3D Ising model in an external field. For a square-well symmetrical binary mixture we calculate the par

A. A. Golubov

Results of theoretical study of spin-polarized tunneling in ferromagnet/superconductor junctions are presented. Spin and charge currents are calculated as a function of applied voltage and spin polarization in a ferromagnet. The model takes into account the splitting of different spin subbands in a ferromagnet and impurity scattering in the contact. The exce

Dirk K. Morr, Rachel Wortis

We argue that nuclear magnetic resonance experiments are a site-sensitive probe for the electronic spectrum in the mixed state of the high-$T_c$ cuprates. Within a spin-fermion model, we show that the Doppler-shifted electronic spectrum arising from the circulating supercurrent changes the low-frequency behavior of the imaginary part of the spin-susceptibili

Mei-Rong Li, P. J. Hirschfeld, P. Woelfle

We reply to a recent comment by Bhattacharya et. al. (cond-mat/9812290) on our previous Letter (PRL 81, 5640 (1998)).

V. I. Yukalov, M. G. Cottam, M. R. Singh

Nonlinear spin motion in ferromagnets is considered with nonlinearity due to three factors: (i) the sample is prepared in a strongly nonequilibrium state, so that evolution equations cannot be linearized as would be admissible for spin motion not too far from equilibrium, (ii) the system considered consists of interacting electron and nuclear spins coupled w

C. A. Ullrich, G. Vignale

Recent photoabsorption measurements have revealed a rich fine structure in the collective charge-density excitation spectrum of few-electron quantum dots in the presence of magnetic fields. We have performed systematic computational studies of the far-infrared density response of quantum dots, using time-dependent density-functional theory in the linear regi

Jiri Hoogland, Dimitri Neumann

This article is the second one in a series on the use of scaling invariance in finance. In the first article (cond-mat/9906048), we introduced a new formalism for the pricing of derivative securities, which focusses on tradable objects only, and which completely avoids the use of martingale techniques. In this article we show the use of the formalism in the

F. Guinea, G. Gomez-Santos, D. Arovas

The generic changes of the electronic compressibility in systems which show magnetic instabilities is studied. It is shown that, when going into the ordered phase, the compressibility is reduced by an amount comparable to the its original value, making charge instabilities also possible. We discuss, within this framework, the tendency towards phase separatio

K. Tanaka, F. Marsiglio

Motivated by recent experiments on Al nanoparticles, we have studied the effects of fixed electron number and small size in nanoscale superconductors, by applying the canonical BCS theory for the attractive Hubbard model in two and three dimensions. A negative ``gap&#39;&#39; in particles with an odd number of electrons as observed in the experiments is obta

A. Mourachkine

The symmetries of the order parameter (OP) responsible for pairing and the OP responsible for phase coherence in hole-doped cuprates are discussed. We analyze angle-resolved tunneling, ARPES, Raman scattering and torque measurements performed on hole-doped cuprates. We conclude that, most likely, the OP responsible for phase coherence has the d-wave symmetry

J. K. Viljas, E. V. Thuneberg

The flow of superfluid 3He-B through a 65 x 65 array of nanometer size apertures has been measured recently by Backhaus et al. They find in the current--phase relation a new branch, so-called pi state. We study two limiting cases which show that the pi state arises from coupling of the phase degree of freedom to the spin-orbit rotation. The pi state exists i

S. B. Dugdale, M. A. Alam, I. Wilkinson, R. J. Hughes

The rare earth nickel borocarbides, with the generic formula $R$Ni$_{2}$B$_{2}$C, have recently been shown to display a rich variety of phenomena. Most striking has been the competition between, and even coexistence of, antiferromagnetism and superconductivity. We have measured the Fermi surface (FS) of LuNi$_{2}$B$_{2}$C, and shown that it possesses nesting

T. Kawata, Y. Iguchi, T. Itoh, K. Takahata

The resistivity and thermopower of Na$_{1+x}$Co$_2$O$_4$ and Na$_{1.1-x}$Ca$_x$Co$_2$O$_4$ are measured and analyzed. In Na$_{1+x}$Co$_2$O$_4$, whereas the resistivity increases with $x$, the thermopower is nearly independent of $x$. This suggests that the excess Na is unlikely to supply carriers, and decreases effective conduction paths in the sample. In Na

Valeri N. Kotov, Oleg P. Sushkov

We analyze the spectrum of the 2D S=1/2 frustrated Heisenberg model near the transition from the spontaneously dimerized spin-liquid phase into the Neel ordered phase. Two excitation branches: the triplet magnon, and the collective singlet mode, both become gapless at the transition point. However we find that the length scales associated with these modes ar

Scott W. Sides, Gary S. Grest, Martin-D. Lacasse

Evidence for capillary waves at a liquid/vapor interface are presented from extensive molecular dynamics simulations of a system containing up to 1.24 million Lennard-Jones particles. Careful measurements show that the total interfacial width depends logarithmically on $L_\parallel$, the length of the simulation cell parallel to the interface, as predicted t

Martin J. Bünner, Marco Ciofini, Antonino Giaquinta, Rainer Hegger

High-dimensional chaos displayed by multi-component systems with a single time-delayed feedback is shown to be accessible to time series analysis of a scalar variable only. The mapping of the original dynamics onto scalar time-delay systems defined on sufficiently high dimensional spaces is thoroughly discussed. The dimension of the ``embedding&#39;&#39; spa

N. V. Antonov

The field theoretic renormalization group and operator product expansion are applied to the problem of a passive scalar advected by the Gaussian nonsolenoidal velocity field with finite correlation time, in the presence of large-scale anisotropy. The energy spectrum of the velocity in the inertial range has the form $E(k)\propto k^{1-ε}$, and the correlation

Vahe Petrosian, Timothy Q. Donaghy

The aim of this paper is to investigate the spatial structure of the impulsive phase hard X-ray emission from solar flares. This work is motivated by the YOHKOH and the forthcoming HESSI observations. Summarizing past results, it is shown that the transport effects can account for the observations by inhomogeneous loops where there is a strong field converge

K. Hurley, M. Feroci, M. -N. Cinti, E. Costa

We have added the BeppoSAX Gamma-Ray Burst Monitor to the 3rd Interplanetary Network of burst detectors. We analyze 16 bursts whose positions are known to good accuracy from measurements at other wavelengths. We show that there is excellent agreement between the Ulysses/BeppoSAX triangulation annuli and the known positions of these events, and that these ann

D. Proga, J. M. Stone, J. E. Drew

We describe an efficient method of calculating the radiation pressure due to spectral lines, including all the terms in the velocity gradient tensor. We apply this method to calculate the two-dimensional, time-dependent structure of winds from luminous disks. Qualitative features of our new models are very similar to those we calculated including only the do

Cornelia C. Lang, Don F. Figer, W. M. Goss, Mark Morris

VLA images of the Sickle and Pistol H II regions near the Galactic center at 3.6 and 6 cm reveal six point sources in the region where the dense Quintuplet stellar cluster is located. The spectral indices of five of these sources between 6 cm and 3.6 cm have values of alpha = +0.5 to +0.8, consistent with the interpretation that the radio sources correspond

Tsevi Mazeh, Shay Zucker, Andrea Dalla Torre, Floor van Leeuwen

We present an analysis of Hipparcos astrometric measurements of Upsilon Andromedae, a nearby main-sequence star around which three planet candidates have recently been discovered by means of radial-velocity measurements. The stellar orbit associated with the outermost candidate has a period of 1269 +/- 9 days and a minimum semi-major axis of 0.6 milli-arc-se

Peter M. Woods, Chryssa Kouveliotou, Jan van Paradijs, Mark H. Finger

We have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observations of the pulsed emission from SGR 1900+14 during September 1996, June - October 1998, and early 1999. Using these measurements and results reported elsewhere, we construct a period history of this source for 2.5 years. We find significant deviations from a steady spin-down tre

E. Baron, David Branch, Peter H. Hauschildt, Alexei V. Filippenko

We present detailed non-local thermodynamic equilibrium (NLTE) synthetic spectra for comparison with a time series of observed optical spectra of the Type Ic supernova 1994I which occurred in M51. With the exceptions of Si I and S I, we treat the important species in the formation of the spectrum in full NLTE. We present results for both a hydrodynamic model

Elisabeth Vangioni-Flam, Michel Casse, Jean Audouze

The origin and evolution of Lithium-Beryllium-Boron is a crossing point between different astrophysical fields : optical and gamma spectroscopy, non thermal nucleosynthesis, Big Bang and stellar nucleosynthesis and finally galactic evolution. We describe the production and the evolution of Lithium-Beryllium-Boron from Big Bang up to now through the interacti

Ignas Snellen, Richard Schilizzi

Gigahertz Peaked Spectrum (GPS) sources and Compact Symmetric Objects (CSO) are selected in very different ways, but have a significant overlap in properties. Ever since their discovery it has been speculated that they are young objects, but only recently, strong evidence has been provided indicating that GPS sources and CSOs are indeed the young counterpart

Z. Paragi, R. C. Vermeulen, I. Fejes, R. T. Schilizzi

We present multi-frequency VLBA+VLA observations of SS433 at 1.6, 5 and 15 GHz. These observations provide the highest angular resolution radio spectral index maps ever made for this object. Motion of the components of SS433 during the observation is detected. In addition to the usual VLBI jet structure, we detect two radio components in the system at an ano

Sidney A. Bludman

We review the cosmological evidence for a low matter density universe and a cosmological constant or dynamical vacuum energy and address the cosmolog$ coincidence problem: why is the matter density about one-half the vacuum energy {\em now}. This is reasonble, following the anthropic argument of Efstathiou and of Martel, Schapiro & Weinberg.

Z. -Q. Shen, P. G. Edwards, J. E. J. Lovell, K. Fujisawa

We present a high resolution 1.6 GHz VSOP image of the southern blazar PKS 1921-293. The image shows a typical core-jet morphology, consistent with ground-based VLBI images. However, the addition of data from the space antenna has greatly improved the angular resolution (especially along the north-south direction for this source), and thus allowed us to clea

Janna Levin, Imogen Heard

We provide an informal discussion of pattern formation in a finite universe. The global size and shape of the universe is revealed in the pattern of hot and cold spots in the cosmic microwave background. Topological pattern formation can be used to reconstruct the geometry of space, just as gravitational lensing is used to reconstruct the geometry of a lens.

Srdjan Samurovic, Milan M. Cirkovic, Vesna Milosevic-Zdjelar

We discuss the tight interconnection between microlensing optical depths, flattening of dark haloes and low-to-intermediate redshift baryonic census. By analysing plots of the microlensing optical depth as a function of galactic coordinates for different values of axis ratio $q$ of the galactic MACHO halo, we have shown that observations are best described b

Daniel Schaerer

Wolf-Rayet (WR) galaxies provide detailed information on massive star populations in starbursts and thereby represent ideal objects to determine accurate ages for young systems, to measure the burst duration, and to probe the upper end of the IMF. WR galaxies play also a particular role in a variety of studies on star formation in Seyfert2/LINERS, dust produ

S. S. Larsen

A detailed description is given of the data analysis leading to the discovery of young massive star clusters (YMCs) in a sample of 21 nearby galaxies. A new useful tool, ishape, for the derivation of intrinsic shape parameters of compact objects is presented, and some test results are shown. Completeness tests for the cluster samples are discussed, and ishap

Raymond R. Volkas, Yvonne Y. Y. Wong

It has been proposed that the annihilation process $ν\barν \to e^{-}e^{+} \to γγ$ may be responsible for the generation of gamma-ray bursts (GRBs). The incipient neutrino--antineutrino pairs carry virtually all of the gravitational binding energy available from the central engine. However, gamma-ray bursters proposed to date are inevitably surrounded by an e

O. Civitarese, A. Ray

The temperature dependence of the energy centroids and strength distributions for Gamow-Teller (GT) $1^+$ excitations in several fp-shell nuclei is studied. The quasiparticle random phase approximations (QRPA) is extended to describe GT states at finite temperature. A shift to lower energies of the GT$^+$ strength is found, as compared to values obtained at

A. Santangeo, A. Segreto, S. Giarrusso, D. Dal Fiume

The recurrent hard pulsating X-ray transient §was observed with \B on March 19, when the source was at a 2--10 keV flux level of $\sim$310~mCrab. We report on the high energy spectrum of the source, concentrating on cyclotron resonant scattering features. The spectrum is strongly pulse phase dependent and absorption features are detected at virtually all pha

Mousumi Das, Chanda J. Jog

In this paper we propose that the compressive tidal field in the centers of flat-core early type galaxies and ultraluminous galaxies compresses molecular clouds producing dense gas obseved in the centers of these galaxies. The effect of galactic tidal fields is usually considered disruptive in the literature. However, for some galaxies, the mass profile flat

D. Hurley-Keller, M. Mateo, E. Grebel

Color-magnitude diagrams from deep, wide-field CCD photometry of the Sculptor dwarf spheroidal galaxy reveal that the red horizonal branch (RHB) stars are strongly concentrated towards the center of the galaxy relative to the dominant old population in Sculptor, confirming an earlier claim of such a gradient (Da Costa et al. 1996). Since we find no radial gr

Carlos Allende Prieto, Ramon J. Garcia Lopez, David L. Lambert, Bengt Gustafsson

Chemical analyses of late-type stars are usually carried out following the classical recipe: LTE line formation and homogeneous, plane-parallel, flux-constant, and LTE model atmospheres. We review different results in the literature that have suggested significant inconsistencies in the spectroscopic analyses, pointing out the difficulties in deriving indepe

Mie Ishii, Mariko Kato, Munetaka Ueno

We have recalculated interior structure of very massive stars of uniform chemical composition with the OPAL opacity. Very massive stars are found to develop a core-halo structure with a extended radiative-envelope. With the core-halo structure, a more massive star has a more extended envelope, then the track of upper zero-age main-sequence (ZAMS) curves redw

Jan Verschelde

Numerical homotopy continuation methods for three classes of polynomial systems are presented. For a generic instance of the class, every path leads to a solution and the homotopy is optimal. The counting of the roots mirrors the resolution of a generic system that is used to start up the deformations. Software and applications are discussed.

Mar Bastero-Gil, Biswajoy Brahmachari

We make a comprehensive analysis of an extended supersymmetric model(ESSM) obtained by adding a pair of vector-like families to the minimal supersymmetric standard model and having specific forms of 5 x 5 fermion mass matrices. The singlet Higgs couplings which link the ordinary to vector-like generations do not have the renormalization effects of the gauge

Fu-Guang Cao, A. I. Signal

Two phenomenological models which give opposite predictions for the $s$-${\bar s}$ asymmetry in the nucleon sea are re-analyzed carefully. It is pointed out that although the quantitative results in both models depend dramatically on the parameters, the predictions for the shape of $s(x)-{\bar s}(x)$ in the two models are parameter independent and opposite.

Alessio Filippetti, Warren E. Pickett

The Mn-terminated (001) surface of the stable anti-ferromagnetic insulating phase of cubic perovskite CaMnO$_3$ is found to undergo a magnetic reconstruction consisting on a spin-flip process at surface: each Mn spin at the surface flips to pair with that of Mn in the subsurface layer. In spite of very little Mn-O charge transfer at surface, the surface beha

L. B. Okun, K. G. Selivanov, V. L. Telegdi

The classical phenomenon of the redshift of light in a static gravitational potential, usually called the gravitational redshift, is described in the literature essentially in two ways: on the one hand the phenomenon is explained through the behaviour of clocks which run the faster the higher they are located in the potential, whereas the energy and frequenc

J. Park, R. Rabadan, A. M. Uranga

In this paper we study the N=1 supersymmetric field theories realized on the world-volume of type IIB D3-branes sitting at orientifolds of non-orbifold singularities (conifold and generalizations). Several chiral models belong to this family of theories. These field theories have a T-dual realization in terms of type IIA configurations of relatively rotated

Shahar Hod

It is well known that the late-time behaviour of gravitational collapse is {\it dominated} by an inverse power-law decaying tail. We calculate {\it higher-order corrections} to this power-law behaviour in a spherically symmetric gravitational collapse. The dominant ``contamination&#39;&#39; is shown to die off at late times as $M^2t^{-4}\ln(t/M)$. This decay

G. Arutyunov, S. Frolov

All cubic couplings in type IIB supergravity on $AdS_5\times S^5$ that involve two scalar fields $s^I$ that are mixtures of the five form field strength on $S^5$ and the trace of the graviton on $S^5$ are derived by using the covariant equations of motion and the quadratic action for type IIB supergravity on $AdS_5\times S^5$. All corresponding three-point f

Max Zucker

We give an off-shell formulation of N=2 Poincare supergravity in five dimensions

Yair N. Minsky

We examine the internal geometry of a Kleinian surface group and its relations to the asymptotic geometry of its ends, using the combinatorial structure of the complex of curves on the surface. Our main results give necessary conditions for the Kleinian group to have `bounded geometry&#39; (lower bounds on injectivity radius) in terms of a sequence of coeffi

Giovanni Felder, Alexander Varchenko

The elliptic gamma function is a generalization of the Euler gamma function and is associated to an elliptic curve. Its trigonometric and rational degenerations are the Jackson q-gamma function and the Euler gamma function, respectively. The elliptic gamma function appears in Baxter&#39;s formula for the free energy of the eight-vertex model and in the hyper

B. Machet

The standard model seeming at a loss to account for the present experimental average rate for the rare decay K+ -> Pi+ neutrino antineutrino, I tackle the question with the extension of the Glashow-Salam-Weinberg model to an SU(2)left x U(1) gauge theory of J=0 mesons proposed by the author in [Phys. Lett. B 385 (1996) 198], in which, in addition, the neutri

W. Chen

The principal innovative idea in this paper is to transform the original complex nonlinear modeling problem into a combination of linear problem and very simple nonlinear problems. The key step is the generalized linearization of nonlinear terms. This paper only presents the introductory strategy of this methodology. The practical numerical experiments will

M. A. Braun, J. Dias de Deus, C. Pajares

The generalization of the Glauber formula for cumulative production events is derived. On its basis the multiplicity distribution in such events is related to the one in the minimum bias events. As compared to the rare events of type $C$, the formula involves a shift in the arguments determined by the multiplicity from a collision with a cluster of several n

Hiroaki Kusunose, Yoshio Kuramoto

Entanglement of spin and orbital Kondo effect is investigated on the basis of a Kondo-type exchange model with twofold orbital degeneracy. By using Wilson&#39;s numerical renormalization-group method, we examine dynamical and thermal properties respecting the difference in time-reversal property of multipole operators. In the presence of particle-hole symmet

H. Moya-Cessa, S. M. Dutra, A. Vidiella-Barranco, J. A. Roversi

We propose a realistic scheme to determine the quantum state of a single mode cavity field even after it has started to decay due to the coupling with an environment. Although dissipation destroys quantum coherences, we show that at zero temperature enough information about the initial state remains, in an observable quantity, to allow the reconstruction of

K. V. Krutitsky, F. Burgbacher, J. Audretsch

We present the rigorous microscopic quantum theory of the interaction of ultracold Bose and Fermi gases with the electromagnetic field of vacuum and laser photons. The main attention has been paid to the consistent consideration of dynamical dipole-dipole interactions. The theory developed is shown to be consistent with the general principles of the canonica

S. Gov, S. Shtrikman, H. Thomas

Recently, we developed a method for calculating the lifetime of a particle inside a magnetic trap with respect to spin flips, as a first step in our efforts to understand the quantum-mechanics of magnetic traps. The 1D toy model that was used in this study was physically unrealistic because the magnetic field was not curl-free. Here, we study, both classical

Ye. M. Hakobyan, G. S. Pogosyan, A. N. Sissakian, S. I. Vinitsky

The Schrödinger equation is thoroughly analysed for the isotropic oscillator in the three-dimensional space of constant positive curvature in the spherical and cylindrical systems of coordinates. The expansion coefficients between the spherical and cylindrical bases of the oscillator are calculated. It is shown that the relevant coefficients are expressed th

A. C. Hayes, I. S. Towner

Neutrino reaction cross-sections, $(ν_μ,μ^-)$, $(ν_e,e^-)$, $μ$-capture and photoabsorption rates on $^{12}$C are computed within a large-basis shell-model framework, which included excitations up to $4\hbarω$. When ground-state correlations are included with an open $p$-shell the predictions of the calculations are in reasonable agreement with most of the e

Urs Achim Wiedemann

In this review talk, I first summarize the conclusions which can be drawn from a particle interferometric analysis of CERN SPS data and then I address related questions which are relevant for the upcoming experiments at RHIC.

G. P. Kamuntavicius, P. Navratil, B. R. Barrett, G. Sapragonaite

The charge-dependent realistic nuclear Hamiltonian for a nucleus, composed of neutrons and protons, can be successfully approximated by a charge-independent one. The parameters of such a Hamiltonian, i.e., the nucleon mass and the NN potential, depend upon the mass number A, charge Z and isospin quantum number T of state of the studied nucleus.

C. Nonaka, N. Sasaki, S. Muroya, O. Miyamura

We numerically solve fully (3+1)-dimensional relativistic hydrodynamical equation with the baryon number conservation law. For realistic initial conditions we adopt the results from the event generator (URASiMA). Using this model we discuss collective flow.

C. Nonaka, S. Muroya, O. Miyamura

We numerically solve fully (3+1)-dimensional relativistic hydrodynamical equation coupled with the baryon number conservation law without spatial symmetry. We discuss the effect of transverse expansion based on the deviation our numerical result from Bjorken&#39;s scaling solution. We analyze the space-time evolution of the QGP gas in the case of non cylindr

Z. Papp, S. L. Yakovlev

For solving the $2\to 2,3$ three-body Coulomb scattering problem the Faddeev-Merkuriev integral equations in discrete Hilbert-space basis representation are considered. It is shown that as far as scattering amplitudes are considered the error caused by truncating the basis can be made arbitrarily small. By this truncation also the Coulomb Green&#39;s operato

John S. Caughman, IV, Bruce E. Sagan

Let Y denote a symmetric association scheme which is Q-polynomial with respect to an ordering E_0,...,E_D of the primitive idempotents. Bannai and Ito conjectured that the associated sequence of multiplicities m_0,...,m_D is unimodal. We prove that if Y is dual-thin in the sense of Terwilliger, then the sequence of multiplicities satisfies m_i <= m_{i+1} and

David D. Gebhard, Bruce E. Sagan

Greene and Zaslavsky proved that the number of acyclic orientations of a graph with a unique sink is, up to sign, the linear coefficient of the chromatic polynomial. We give three new proofs of this result using pure induction, noncommutative symmetric functions, and an algorithmic bijection.

David D. Gebhard, Bruce E. Sagan

Stanley associated with a graph G a symmetric function X_G which reduces to G&#39;s chromatic polynomial under a certain specialization of variables. He then proved various theorems generalizing results about the chromatic polynomial, as well as new ones that cannot be interpreted at that level. Unfortunately, X_G does not satisfy a Deletion-Contraction Law

Peter A. Linnell

Let G be a group, let U(G) denote the set of unbounded operators on L^2(G) which are affiliated to the group von Neumann algebra W(G) of G, and let D(G) denote the division closure of CG in U(G). Thus D(G) is the smallest subring of U(G) containing CG which is closed under taking inverses. If G is a free group then D(G) is a division ring, and in this case w

J. Migliore, U. Nagel, C. Peterson

We define very proper intersections of modules and projective subschemes. It turns out that equidimensional locally Cohen-Macaulay modules intersect very properly if and only if they intersect properly. We prove a Bezout theorem for modules which meet very properly. Furthermore, we show for equidimensional subschemes $X$ and $Y$: If they intersect properly i

Paolo Salvatore

Let M be an n-manifold, and let A be a space with a partial sum behaving as an n-fold loop sum. We define the space C(M;A) of configurations in M with summable labels in A via operad theory. Some examples are symmetric products, labelled configuration spaces, and spaces of rational curves. We show that C(I^n,dI^n;A) is an n-fold delooping of C(I^n;A), and fo

Theodore Stanford

We use a variation on the commutator collection process to characterize those pure braids which become trivial when any one strand is deleted, or, more generally, those pure braids which become trivial when all the strands in any one of a list of sets of strands is deleted.

Theodore B. Stanford

Delta finite-type invariants are defined analogously to finite-type invariants, using delta moves instead of crossing changes. We show that they are closely related to the lower central series of the commutator subgroup of the pure braid group.

F. J. Plaza Martín

It is shown that it is possible to write down tau functions for the $n$-component KP hierarchy in terms of non-abelian theta functions. This is a generalization of the rank 1 situation; that is, the relation of theta functions of Jacobians and tau functions for the KP hierarchy.

A. D. King, A. H. Schofield

The moduli space M(r,d) of stable, rank r, degree d vector bundles on a smooth projective curve of genus g>1 is shown to be birational to M(h,0) x A, where h=hcf(r,d) and A is affine space of dimension (r^2-h^2)(g-1). The birational isomorphism is compatible with fixing determinants in M(r,d) and M(h,0) and we obtain as a corollary that the moduli space of b

A. Caranti, M. R. Vaughan-Lee

We describe the isomorphism classes of certain infinite-dimensional graded Lie algebras of maximal class, generated by an element of weight one and an element of weight two, over fields of odd characteristic.

B. Enriquez

We give proofs of the PBW and duality theorems for the quantum Kac-Moody algebras and quantum current algebras, relying on Lie bialgebra duality. We also show that the classical limit of the quantum current algebras associated with an untwisted affine Cartan matrix is the enveloping algebra of a quotient of the corresponding toroidal algebra; this quotient i

Alexander Polishchuk

This note is a continuation of our paper with E. Zaslow &#34;Categorical mirror symmetry: the elliptic curve&#34;, math.AG/9801119. We compare some triple Massey products on elliptic curve with the corresponding Fukaya products on the symplectic torus and recover the classical identity due to Kronecker. We also compute some triple Fukaya products such that t

P. Di Francesco, E. Guitter, C. Kristjansen

We introduce and solve a family of discrete models of 2D Lorentzian gravity with higher curvature, which possess mutually commuting transfer matrices, and whose spectral parameter interpolates between flat and curved space-times. We further establish a one-to-one correspondence between Lorentzian triangulations and directed Random Walks. This gives a simple

Jesús Puente Peñalba

A matrix model for type 0 strings is proposed. It consists in making a non-supersymmetric orbifold projection in the Yang-Mills theory and identifying the infrared configurations of the system at infinite coupling with strings. The correct partition function is calculated. Also, the usual spectrum of branes is found. Both type A and B models are constructed.

Luca Lusanna

A review is given of the status and developments of the research program aiming to reformulate the physics of the four interactions at the classical level in a unified way in terms of Dirac-Bergmann observables with special emphasis on the open mathematical, physical and interpretational problems.

Paul J. Steinhardt

We argue that the brane-world picture with matter-fields confined to 4-d domain walls and with gravitational interactions across the bulk disallows adding an arbitrary constant to the low-energy, 4-d effective theory -- which finesses the usual cosmological constant problem. The analysis also points to difficulties in stabilizing moduli fields; as an alterna

Dan Solomon

A common assumption in quantum field theory is that the energy-momentum 4-vector of any quantum state must be timelike. It will be proven that this is not the case for a Dirac-Maxwell field. In this case quantum states can be shown to exist whose energy-momentum is spacelike. This implies that there must exist quantum states with less energy than the vacuum

R. C. Hwa, Y. Wu

The soft production problem in hadronic collisions as described in the eikonal color mutation branching model is improved in the way that the initial parton distribution is treated. Furry branching of the partons is considered as a means of describing the nonperturbative process of parton reproduction in soft interaction. The values of all the moments, <n> a