April 2000 arXiv papers — page 16

Vyacheslav S. Krushkal

The vanishing of Van Kampen's obstruction is known to be necessary and sufficient for embeddability of a simplicial n-complex into $R^{2n}$ for $n\neq 2$, and it was recently shown to be incomplete for $n=2$. We use algebraic-topological invariants of four-manifolds with boundary to introduce a sequence of higher embedding obstructions for a class of 2-c

Dave Witte, Robert J. Zimmer

Suppose G is a connected, simple, real Lie group with real rank at least two, M is an ergodic G-space with invariant probability measure, and f is a Homeo(T)-valued Borel cocycle, where Homeo(T) denotes the group of homeomorphisms of the circle T. We use an argument of E.Ghys to show that there is a G-invariant probability measure on the skew product of M an

Vadim V. Varlamov

Spinor representations of surfaces immersed into 4-dimensional pseudo-riemannian manifolds are defined in terms of minimal left ideals and tensor decompositions of Clifford algebras. The classification of spinor fields and Dirac operators on the immersed surfaces is given. The Dirac-Hestenes spinor field on surfaces immersed into Lorentzian manifolds and on

Frederic Jouhet, Jiang Zeng

We evaluate the symmetric functions $e_k$, $h_k$ and $p_k$ on the alphabet $\{x_r/(1-tx_r)\}$ by elementary methods and give the related generating functions. Our formulas lead to a new and short proof of an ex-conjecture of Lassalle, which was proved by Lascoux and Lassalle in the framework of $λ$-rings theory.

Laetitia Paoli, Michelle Schatzman

We examine the penalty approximation of the free motion of a material point in an angular domain; we choose an over-damped penalty, and we prove that if the first impact point is not at the vertex, then, the limit of the approximation exists and is described by Moreau's rule for anelastic impacts. The proofs rely on validated asymptotics and use some cla

Erik Koelink, Jasper V. Stokman

In this paper we present an explicit (rank one) function transform which contains several Jacobi-type function transforms and Hankel-type transforms as degenerate cases. The kernel of the transform, which is given explicitly in terms of basic hypergeometric series, thus generalizes the Jacobi function as well as the Bessel function. The kernel is named the A

P. Jolissaint, G. Robertson

Let $n$ be a positive integer. We introduce a concept, which we call the $n$-filling property, for an action of a group on a separable unital $C^*$-algebra $A$. If $A=C(Ω)$ is a commutative unital $C^*$-algebra and the action is induced by a group of homeomorphisms of $Ω$ then the $n$-filling property reduces to a weak version of hyperbolicity. The $n$-filli

Jan B. Thomassen

I study variations of the fermionic determinant for a nonabelian Dirac fermion with external vector and axial vector sources. I consider different regularizations, leading to different chiral anomalies when the variations are chiral transformations. For these different regularizations, I then consider variations associated with Poincare transformations. I fi

G. Dvali

We study some cases in D=4 and in infinite-volume high dimensional theories when unbroken supersymmetry in the vacuum cannot guarantee Fermi-Bose degeneracy among excited states. In 4D we consider an example in which both supersymmetry and $R$ symmetry are unbroken in the vacuum, and the cosmological constant vanishes. However, theory admits solitons that do

Jun Gao, BingAn Li

Theoretical study of anomalous decay mode tau -> omega3pinu is presented.

Guo-Hong Wu

If the mixing angles in each of the seesaw sectors are all small, and the neutrino masses are hierarchical, we study the conditions for large neutrino mixing using triangular matrices. In particular, the implication of the neutrino oscillation data for the mass hierarchy in the heavy Majorana sector is examined, and the heavy Majorana scales are shown to dep

D. T. Son, M. A. Stephanov

We correct a mistake in the calculation of meson masses at large baryon chemical potential made in hep-ph/9910491v2

S. A. Smolyansky, A. V. Prozorkevich, G. Maino, S. G. Mashnik

A generalized quantum kinetic equation (RKE) of the Kadanoff-Baym type is obtained on the basis of the Heisenberg equations of motion where the time evolution and space translation are separated from each other by means of the covariant method. The same approach is used also for a covariant modification of the real-time Green's functions method based on

J. L. Chkareuli, C. D. Froggatt

We argue that the nature of the global conservation laws in Supersymmetric Grand Unified Theories is determined by the basic vacuum configuration in the model rather than its Lagrangian. It is shown that the suppression of baryon number violation in a general (R-parity violating) superpotential can naturally appear in some extended SU(N) SUSY GUTs which, amo

S. Atag, I. T. Cakir

The potential of LC+HERAp based Gamma-p collider to probe WW-Gamma vertex is presented through the discussion of sensitivity to anomalous couplings and P_T distribution of the final quark. The limits of -0.04<Δκ<0.04 and -0.11<λ<0.11 at 95% C.L. can be reached with integrated luminosity 200(1/pb). The limit for Δκis comparable to one which is expected from L

S. Tsujikawa

We consider the dynamics of power-law inflation with a nonminimally coupled scalar field $ϕ$. It is well known that multiple scalar fields with exponential potentials $V(ϕ)=V_0 {\rm exp}(-\sqrt{16π/p m_{\rm pl}^2} ϕ)$ lead to an inflationary solution even if the each scalar field is not capable to sustain inflation. In this paper, we show that inflation can

Y. Sumino

This is an elementary introduction to the recent significant theoretical progress in the field of heavy quarkonium physics. We show how renormalon cancellation takes place in the heavy quarkonium system, such as bottomonium and (remnant of) toponium resonance, and how this notion is useful in extracting the MSbar masses of the bottom and top quarks.

Julien Lesgourgues, Sergio Pastor, Marco Peloso, Lorenzo Sorbo

We provide the first complete analysis of cosmological evolution in the Randall-Sundrum model with stabilized dilaton. We give the exact expansion law for matter densities on the two branes with arbitrary equations of state. The effective four-dimensional theory leads to standard cosmology at low energy. The limit of validity of the low energy theory and pos

Fermilab E706 Collaboration, L. Apanasevich

We present results on the production of omega mesons at high transverse momenta in pi^-Be interactions at 515 GeV/c. The data span the kinematic range 3.5 < p_T < 8 GeV/c. We compare the measured cross section with expectations from Monte Carlo QCD generators. The relative yield of omega to pi^0 mesons is used to extract the ratio of vector to pseudoscalar m

Jiri Bicak

Five classes of radiative solutions of Einstein&#39;s field equations are discussed in the light of some new developments. These are plane waves and their collisions, cylindrical waves, Robinson-Trautman and type N spacetimes, boost-rotation symmetric spacetimes and generalized Gowdy-type cosmological models

J. Fikar, J. Horsky

For the plane symmetry we have found the electro-vacuum exact solutions of the Einstein-Maxwell equations and we have shown that one of them is equivalent to the McVittie solution of a charged infinite thin plane. The analytical extension has been accomplished and the Penrose conformal diagram has been obtained as well.

Robert Shrock

Let $P(G,q)$ be the chromatic polynomial for coloring the $n$-vertex graph $G$ with $q$ colors, and define $W=\lim_{n \to \infty}P(G,q)^{1/n}$. Besides their mathematical interest, these functions are important in statistical physics. We give a comparative discussion of exact calculations of $P$ and $W$ for a variety of recursive families of graphs, includin

Mauro Bologna, Paolo Grigolini, Markos Karagiorgis

We study the problem of entropy increase of the Bernoulli-shift map without recourse to the concept of trajectory and we discuss whether, and under which conditions if it does, the distribution density entropy coincides with the Kolmogorov-Sinai entropy, namely, with the trajectory entropy.

Subir Sachdev, Chiranjeeb Buragohain, Matthias Vojta

We describe the spin dynamics of an arbitrary localized impurity in an insulating two dimensional antiferromagnet, across the host transition from a paramagnet with a spin gap to a Neel state. The impurity spin susceptibility has a Curie-like divergence at the quantum-critical coupling, but with a universal, effective spin which is neither an integer nor a h

Massimiliano Ignaccolo, Paolo Grigolini

We study sporadic randomness by means of a non-extensive form of Lyapunov coefficient. We recover from a different perspective the same conclusion as that of an earlier work, namely, that the ordinary Pesin theorem applies (P.Gaspard and X.-J. Wang, Proc. Natl. Acad. Sci. USA {\bf85}, 4591 (1988)). However, our theoretical analysis allows us to organize the

Yeong E. Kim, Alexander L. Zubarev

We have investigated a general structure of the ground-state wave function for the Schrödinger equation for $N$ identical interacting particles (bosons or fermions) confined in a harmonic anisotropic trap in the limit of large $N$. It is shown that the ground-state wave function can be written in a separable form. As an example of its applications, this form

Niall D. Whelan, Jules P. Carbotte

It has been predicted that the zero frequency density of states of YBCO in the superconducting phase can display interesting anisotropy effects when a magnetic field is applied parallel to the copper-oxide planes, due to the diamagnetic response of the quasi-particles. In this paper we incorporate paramagnetism into the theory and show that it lessens the an

V. T. Petaja, M. J. Alava, H. Rieger

Joint ground states of two directed polymers in a random medium are investigated. Using exact min-cost flow optimization the true two-line ground-state is compared with the single line ground state plus its first excited state. It is found that these two-line configurations are (for almost all disorder configurations) distinct implying that the true two-line

S. Jain, H. Flynn

The spatial distribution of persistent spins at zero-temperature in the pure two-dimensional Ising model is investigated numerically. A persistence correlation length, $ξ(t)\sim t^Z$ is identified such that for length scales $r<<ξ(t)$ the persistent spins form a fractal with dimension $d_f$; for length scales $r>>ξ(t)$ the distribution of persistent spins is

Olivier Deloubriere

We consider the class of Markovian processes defined by the equation $\dd x /\dd t = -βx + \sum_k z_k δ(t-t_k)$. Such processes are encountered in systems (like coalescing systems) where dynamics creates discrete upward jumps at random instants $t_k$ and of random height $z_k$. We observe that the probability for these processes to remain above their mean va

D. W. Wang, A. J. Millis, S. Das Sarma

We present the theoretical basis for analyzing resonant Raman scattering experiments in one-dimensional systems described by the Luttinger liquid fixed point. We make experimentally testable predictions for distinguishing Luttinger liquids from Fermi liquid and argue that presently available quantum wire systems are \textit{not} in the regime where Luttinger

F. Venturini, U. Michelucci, T. P. Devereaux, A. P. Kampf

Although the low frequency electronic Raman response in the superconducting state of the cuprates can be largely understood in terms of a d-wave energy gap, a long standing problem has been an explanation for the spectra observed in the $A_{1g}$ polarization orientations. We present calculations which suggest that the peak position of the observed $A_{1g}$ s

Rudi Podgornik, Per Lyngs Hansen, V. Adrian Parsegian

We study the effect of intersegment interactions on the effective bending and stretching moduli of a semiflexible polymer chain with a finite stretching modulus. For an interaction potential of a screened Debye-H\&#34; uckel type renormalization of the stretching modulus is derived on the same level of approximation as the celebrated Odijk-Skolnick-Fixman re

Adriaan M. J. Schakel

It is pointed out that first, contrary to the claim by Baym et al.[Phys. Rev. Lett 83, 1703 (1999)], the shift in the transition temperature of a weakly interacting Bose gas can be calculated perturbatively. And second, that the regime considered by Huang [Phys. Rev. Lett 83, 3770 (1999)] while addressing the same issue does not describe the Bose-Einstein co

Edward McCann, Vladimir. I. Fal&#39;ko, A. F. Volkov, C. J. Lambert

The classical resistance of a contact between a ferromagnet (F) and a superconductor (S) acquires an additional contact term as compared to the contact between a ferromagnet and a normal metal. The necessity to match spin-polarized current in a ferromagnet to spin-less current in the superconductor results in the accumulation of non-equilibrium polarization

Bernard Jancovici, Emmanuel Trizac

The universal finite-size correction to the free energy of a two-dimensional Coulomb system is checked in the special case of a one-component plasma on a sphere. The correction is related to the known second moment of the short-range part of the direct correlation function for a planar system.

H. R. Krishnamurthy, B. Sriram Shastry, IISc, Bangalore

We present the exact solution of a model of interacting fermions in any dimension with a pure repulsive interaction projecting out a given Cooper channel. The solution rests upon the infinite ranged character of the interaction in real space, leading to a functional integral that is dominated by a Gaussian term. The solution produces strong superconducting e

Yoichi Ando, A. N. Lavrov, Kouji Segawa

We present a study of the in-plane and out-of-plane magnetoresistance (MR) in heavily-underdoped, antiferromagnetic YBa_{2}Cu_{3}O_{6+x}, which reveals a variety of striking features. The in-plane MR demonstrates a &#34;d-wave&#34;-like anisotropy upon rotating the magnetic field H within the ab plane. With decreasing temperature below 20-25 K, the system ac

Yoichi Ando, T. Murayama, S. Ono

Recently we have succeeded in growing a series of high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6} crystals in a wide range of carrier concentrations. The data of ρ_{ab}(T) and R_H(T) of those crystals show behaviors that are considered to be &#34;canonical&#34; to the cuprates. The optimum zero-resistance T_c has been raised to as high as 38 K, which is almost equa

Yoichi Ando, Y. Hanaki, S. Ono, T. Murayama

We measured the thermopower S and the Hall coefficients R_H of Bi_{2}Sr_{2-z}La_{z}CuO_{6+δ} (BSLCO) single crystals in a wide doping range, in an effort to identify the actual hole concentrations per Cu, p, in this system. It is found that the &#34;universal&#34; relation between the room-temperature thermopower and T_c does not hold in the BSLCO system. In

Sandeep K. Joshi, A. M. Jayannavar

A study of statistics of transmission and reflection from a random medium with stochastic amplification as opposed to coherent amplification is presented. It is found that the transmission coefficient $t$, for sample length $L$ less than the critical length $L_c$ grows exponentially with $L$. In the limit $L \to \infty$ transmission decays exponentially as $

Sandeep K. Joshi, Debendranath Sahoo, A. M. Jayannavar

We report a detailed and systematic study of wave propagation through a stochastic absorbing random medium. Stochastic absorption is modeled by introducing an attenuation constant per unit length $α$ in the free propagation region of the one-dimensional disordered chain of delta function scatterers. The average value of the logarithm of transmission coeffici

W. Q. Yu, Shiping Feng, Z. B. Huang, H. Q. Lin

Within the framework of the fermion-spin theory based on the charge-spin separation, the charge dynamics of the doped antiferromagnet on a triangular lattice is studied. The holon part is treated by using the loop expansion to the second order. It is shown that the charge dynamics is mainly caused by charged holons moving in the background of spinon excitati

Kenneth Wood, John Raymond

We have investigated the effects of resonant scattering of emission lines on the image morphology and intensity from coronal loop structures. It has previously been shown that line of sight effects in optically thin line emission can yield loop images that appear uniformly bright at one viewing angle, but show ``looptop sources&#39;&#39; at other viewing ang

Z. Ivezic, J. Goldston, K. Finlator

We present a sample of 148 candidate RR Lyrae stars selected from Sloan Digital Sky Survey (SDSS) commissioning data for about 100 deg2 of sky surveyed twice with Delta(t) = 1.9946 days. Although the faint magnitude limit of the SDSS allows us to detect RR Lyrae stars to large galactocentric distances (about 100 kpc, or r = 21), we find no candidates fainter

B. Paczyński

Contrary to some recent claims the `no torque inner boundary condition&#39; as applied at the marginally stable orbit is correct for geometrically thin disks accreting into black holes.

B. Yanny, H. J. Newberg, S. Kent, S. A. Laurent-Muehleisen

A sample of 4208 objects with magnitude 15 < g* < 22 and colors of main sequence A stars has been selected from 370 square degrees of Sloan Digital Sky Survey (SDSS) commissioning observations. The data is from two long, narrow stripes, each with an opening angle of greater than 60 deg, at Galactic latitudes 36 < abs(b) < 63 on the celestial equator. An exam

M. C. Weisskopf, H. D. Tananbaum, L. P. Van Speybroeck, S. L. O&#39;Dell

The Chandra X-Ray Observatory (CXO), the x-ray component of NASA&#39;s Great Observatories, was launched early in the morning of 1999, July 23 by the Space Shuttle Columbia. The Shuttle launch was only the first step in placing the observatory in orbit. After release from the cargo bay, the Inertial Upper Stage performed two firings, and separated from the o

P. Jean, M. Hernanz, J. Gomez-Gomar, J. Jose

Models of Galactic 1.275 MeV emission produced by the decay of the radionuclide $^{22}$Na have been computed. Several frequency-spatial distributions of novae have been investigated using recent results of nova rates and spatial distributions of novae in our Galaxy. These models allow us to estimate the lower-limit of the $^{22}$Na mass ejected per ONe nova

Pedro F. Gonzalez-Diaz

A generalized quintessence model is presented which corresponds to a richer vacuum structure that, besides a time-dependent, slowly varying scalar field, contains a varying cosmological term. From first principles we determine a number of scalar-field potentials that satisfy the constraints imposed by the field equations and conservations laws, both in the c

V. M. Woolf, C. S. Jeffery

We report new determinations of the radius and mass of the pulsating helium-rich, hydrogen-deficient star LSS 3184 (BX Cir) using measurements of radial velocity and angular radius throughout its pulsation cycle. Measurements of radial velocity, and thus changes in stellar radius, were made using Anglo-Australian Telescope echelle spectra. Hubble Space Teles

R. N. Ogley, S. J. Bell Burnell, R. P. Fender, G. G. Pooley

We present the first detections of the black hole X-ray binary GRS 1915+105 at sub-millimetre wavelengths. We clearly detect the source at 350 GHz on two epochs, with significant variability over the 24 hr between epochs. Quasi-simultaneous radio monitoring indicates an approximately flat spectrum from 2 - 350 GHz, although there is marginal evidence for a m

A. Ray, P. Lundqvist, J. Sollerman, B. Leibundgut

Optical data in the V-band gathered with the 8.2m ESO Very Large Telescope (VLT) at the radio interferometric position of PSR 1706-44 are presented. The pulsar is close to a bright star in projection and was not detected. The pulsar magnitude limit must be fainter than V=24.5 for a distance of $\leq$ 2\farcs0 from the bright star. In the outer gap model for

Brandon Carter, David Langlois, David M. Sedrakian

The frequent glitches (sudden increases of the apparent angular velocity) observed in certain pulsars are generally believed to be attributable to discontinuous angular momentum transfer to the outer neutron star crust from a differentially rotating superfluid layer, but the precise mechanism is not quite elucidated. Most explanations invoke vortex pinning a

P. O. Petrucci, F. Haardt, L. Maraschi, P. Grandi

We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548. The data are well represented by a plane parallel corona with an inclination angle of 30$^{\circ}$, a soft photon temperature of 5 eV and a hot plasma temperature and optical depth of $kT_{\rm e}\simeq$ 360 keV and $τ\simeq$ 0.1, respectively.

Andrea Dieball, Eva K. Grebel, Christian Theis

We present a detailed study of the cluster pair SL 353 & SL 349. This candidate binary cluster is located at the northwestern rim of the LMC bar. Based on photometric data we find that both clusters are coeval with an age of 550 +/- 100 Myr. We use the Ca II triplet in the spectra of individual red giants to derive radial velocities. Both components of the b

P. O. Petrucci, F. Haardt, L. Maraschi, P. Grandi

We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548, allowing for different geometries of the scattering region, different temperatures of the input soft photon field and different viewing angles. We find that the BeppoSAX data are well represented by a plane parallel or hemispherical corona view

D. C. Jewitt, C. A. Trujillo, J. X. Luu

We present a study of Jovian Trojan objects detected serendipitously during the course of a sky survey conducted at the University of Hawaii 2.2-meter telescope. We used a 8192 x 8192 pixel charge-coupled device (CCD) mosaic to observe 20 deg^2 at locations spread over the L4 Lagrangian swarm and reached a limiting magnitude V = 22.5 mag (50% of maximum dete

F. Siddhartha Guzman, Tonatiuh Matos, Dario Nunez, Erandy Ramirez

Through the geodesic analysis of a static and axially symmetric space time, we present conditions on the state equation of an isotropic perfect fluid $p=ωd$, when it is considered as dark matter in spiral galaxies. The main conclusion is that it can be an exotic fluid ($-1<ω<-1/3$) as it is found for Quintessence at cosmological scale.

M. Lutz, W. Florkowski

We analyze the spectra of kaonic atoms using optical potentials withnon-local (gradient) terms. The magnitude of the non-local termsfollows from a self consistent many-body calculation of the kaon selfenergy in nuclear matter, which is based on s-wave kaon nucleoninteractions. The optical potentials exhibit strong non-linearitiesin the nucleon density and si

A. G. Rossberg

A mechanism for the localization of spatially periodic, self-organized patterns in anisotropic media which requires systems extended in all three spatial dimensions is presented: When the anisotropy axis is twisted the pattern becomes localized in planes parallel to the anisotropy axis. An analytic description of the effect is developed and used to interpret

N. Robins, C. Savage, E. Ostrovskaya

We present a model of a cw atom laser based on a system of coupled GP equations. The model incorporates continuous Raman outcoupling, pumping and three-body recombination. The outcoupled field has minimal atomic density fluctuations and is locally monochromatic.

Xiao-Guang Wang

Two-mode nonlinear coherent states are introduced in this paper. The pair coherent states and the two-mode Perelomov coherent states are special cases of the two-mode nonlinear coherent states. The exponential form of the two-mode nonlinear coherent states is given. The photon-added or photon-subtracted two-mode nonlinear coherent states are found to be two-

Bozhidar Z. Iliev

We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one and is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it the Hilbert space of a quantum system (from conventional quantum mechanic

Seth Lloyd

A universal quantum computer can be constructed using abelian anyons. Two qubit quantum logic gates such as controlled-NOT operations are performed using topological effects. Single-anyon operations such as hopping from site to site on a lattice suffice to perform all quantum logic operations. Quantum computation using abelian anyons shares some but not all

M. Lutz, E. Kolomeitsev

We apply the relativistic chiral SU(3) Lagrangian density to kaon-nucleon scattering imposing constraints from the pion-nucleon s- and p-wave threshold parameters at chiral order $Q^2$. The s and u channel decouplet baryon exchange is included explicitly and is found to play a crucial role in understanding the empirical s- and p-wave nuclear kaon dynamics qu

T. Kojima, S. Yamasita

We study the $A_{n-1}^{(1)}$ spin chain at the critical regime $|q|=1$. We give the free boson realizations of the type-I vertex operators and their duals. Using these free boson realizations, we give the integral representations for the correlation functions.

Jaroslaw Kedra

I study flux groups of compact symplectic manifolds. Under some topological assumptions, I give a new estimate of the rank of flux groups and give a method of construcion of compact symplectic aspherical manifolds.

Estelle L. Basor, Harold Widom

The authors of the title proved an elegant identity expressing a Toeplitz determinant in terms of the Fredholm determinant of an infinite matrix which (although not described as such) is the product of two Hankel matrices. The proof used combinatorial theory, in particular a theorem of Gessel expressing a Toeplitz determinant as a sum over partitions of prod

M. Freund, P. Huber, M. Lindner

We discuss and quantify different possibilities to determine matter effects, the value and the sign of $Delta m^2_{31}$, as well as the magnitude of $\sin^2 2θ_{13}$ in very long baseline neutrino oscillation experiments. We study neutrino oscillation at a neutrino factory in the $ν_μ\toν_μ$ disappearance and $ν_e\toν_μ$ appearance channels with and without

S. M. Troshin, N. E. Tyurin

Numerical predictions for the global characteristics of proton-proton interactions are given for the LHC energy. Possibilities for the discovery of the antishadow scattering mode and its physical implications are discussed.

Athar Husain

The collisions between accelerated protons and the photons present in cosmos can be a main source of high-energy neutrinos (E \geq 10^6 GeV) of all flavors above the atmospheric neutrino background. I discuss here the possibility of photohadronic production of high-energy cosmic tau neutrinos in an astrophysical site and study some of the effects of vacuum n

Susumu Koretune

The soft pion theorem in the inclusive reaction at high energy applied to the current induced reaction is explained briefly. A characteristic aspect of this theorem is the charge asymmetry produced by the pole terms in the soft pion limit. The pion charge asymmetry in the central region in the target-virtual-photon center of the mass (CM) frame of the semi-i

M. B. Altaie, Ehab Malkawi

In this paper we investigate the Bose-Einstein condensation of massive spin-1 particles in an Einstein universe. The system is considered under relativistic conditions taking into consideration the possibility of particle-antiparticle pair production. An exact expression for the charge density is obtained, then certain approximations are employed in order to

V. Kurasov

A new simple method for description of the nucleation process on the wide class of heterogeneous centers is given. The nucleation occurs on the heterogeneous centers with different heights of activation barriers. The distribution of the total number of heterogeneous centers over the activation barrier heights is supposed to be a smooth continuous function. T

C. L. Henley, V. Elser, M. Mihalkovic

How, in principle, could one solve the atomic structure of a quasicrystal, modeled as a random tiling decorated by atoms, and what techniques are available to do it? One path is to solve the phase problem first, obtaining the density in a higher dimensional space which yields the_averaged_ scattering density in 3-dimensional space by the usual construction o

Prabodh Shukla

Minor hysteresis loops within the main loop are obtained analytically and exactly in the one-dimensional ferromagnetic random field Ising-model at zero temperature. Numerical simulations of the model show excellent agreement with the analytical results.

G. Bonelli, A. M. Boyarsky

We formulate a topological theory in six dimensions with gauge group SO(3,3) which reduces to gravity on a four dimensional defect if suitable boundary conditions are chosen. In such a framework we implement the reflection automorphism of SO(3,3) as a $\Z2$ symmetry which forbids the appearance of a gravitational cosmological constant. Some temptative specul

K. Itakura, S. Maedan

An investigation of dynamical chiral symmetry breaking on the light front is made in the Nambu--Jona-Lasinio model with one flavor and N colors. Analysis of the model suffers from extraordinary complexity due to the existence of a &#34;fermionic constraint,&#34; i.e., a constraint equation for the bad spinor component. However, to solve this constraint is of

K. Bennaceur, N. Michel, F. Nowacki, J. Okolowicz

We present shell model calculations of both the structure of 17F and the reactions 16O(p,gamma)17F, 16O(p,p)16O. We use the ZBM interaction which provides a good description of the properties of 16O and neighbouring nuclei and, in particular it takes account for the complicated correlations in coexisting low-lying states of 16O.

Alfred Tang, John W. Norbury

Early Chew-Frautschi plots show that meson and baryon Regge trajectoies are approximately linear and non-intersecting. In this paper, we reconstruct all Regge trajectories from the most recent data. Our plots show that meson trajectories are non-linear and intersecting. We also show that all current meson Regge trajectories models are ruled out by data.

S. Pakvasa

If neutrinos have masses and mixings, in general some will decay. In models with new particles and new couplings, some decay modes can be fast enough to be of phenomenological interest.

P. Facchi, V. Gorini, G. Marmo, S. Pascazio

The evolution of a quantum system undergoing very frequent measurements takes place in a subspace of the total Hilbert space (quantum Zeno effect). The dynamical properties of this evolution are investigated and several examples are considered.

J. H. Field

The conventional discussion of the observed distortions of space and time in Special Relativity (the Lorentz-Fitzgerald Contraction and Time Dilatation) is extended by considering observations, from a stationary frame, of : (i) objects moving with constant velocity and uniformly illuminated during a short time $τ_L$ (their `Luminous Proper Time&#39;) in thei

S. J. Lindenbaum, R. S. Longacre

We believe that one can have serious reservations as to whether heavy ion collisions (e.g. 100 GeV/n Au + 100 GeV/n Au) can lead to Thermal and Chemical equilibrium over large regions (particularly if it is assumed this happens whenever QGP is produced at RHIC-that is if it is produced). It is at present not clear that the collision dynamics and times availa

D. Vretenar, G. A. Lalazissis, P. Ring

The neutron distributions of Cs, Ba, Yb and Pb isotopes are described in the framework of relativistic mean-field theory. The self-consistent ground state proton and neutron density distributions are calculated with the relativistic Hartree-Bogoliubov model. The binding energies, the proton and neutron radii, and the quadrupole deformations are compared with

I. Krichever, S Novikov

It is shown that the fourth order real self-adjoint difference operator on the Tivalent Tree admits nontrivial deformations preserving one energy level and therefore defines a nontrinial hierarhy of the completely integrable nonlinear systems representible through the &#39;&#39;L-A-B-triple&#39;&#39;. The Laplace transformations for these operators are also

I. M. Krichever, S. P. Novikov

Commutative rings of one-dimensional difference operators of rank l>1 and their deformations are effectively constructed. Our analytical constructions are based on the so-called &#39;&#39;Tyurin parameters&#39;&#39; for the stable framed holomorphic vector bundles over algebraic curves of the genus equal to g and Chern number equal to lg. These parameters we

Vladimir G. Troitsky

In this paper we develop a version of spectral theory for bounded linear operators on topological vector spaces. We show that the Gelfand formula for spectral radius and Neumann series can still be naturally interpreted for operators on topological vector spaces. Of course, the resulting theory has many similarities to the conventional spectral theory of bou

Feng Luo

Given a finite set of $r$ points in a closed surface of genus $g$, we consider the torsion elements in the mapping class group of the surface leaving the finite set invariant. We show that the torsion elements generate the mapping class group if and only if $(g, r) \neq (2, 5k+4)$ for some integer $k$.

Martin Goldstern

We review a few results concerning interpolation of monotone functions on infinite lattices, emphasizing the role of set-theoretic considerations. We also discuss a few open problems.

Tetsuo Sawada

In order to settle the fundamental question whether the nuclear forces involve the long range components, the S-wave amplitude of the proton-proton scattering is analysed in search for the extra singularity at $ν=0$, which corresponds to the long range force. To facilitate the search, a function, which is free from the singularities in the neighborhood of $ν

Tetsuo Sawada

In the neutron-Pb scattering in the MeV. region, existence of the long range interaction has been known and people have hopefully expected to understand it as the effect of the electric polarization of the neutron. However the precise determination of $α_{n}$ in the very low energy region indicates that the polarizability of the neutron $α_{n}$ is around two

G. Zech

Classical confidence limits are compared to Bayesian error bounds by studying relevant examples. The performance of the two methods is investigated relative to the properties coherence, precision, bias, universality, simplicity. A proposal to define error limits in various cases is derived from the comparison. It is based on the likelihood function only and

George Jaroszkiewicz

A mathematical definition of classical causality over discrete spacetime dynamics is formulated. The approach is background free and permits a definition of causality in a precise way whenever the spacetime dynamics permits. It gives a natural meaning to the concepts of cosmic time, spacelike hypersurfaces and timelike or lightlike flows without assuming the

George Lavrelashvili

There is a single negative mode in the spectrum of small perturbations about the tunneling solutions describing a metastable vacuum decay in flat spacetime. This mode is needed for consistent description of decay processes. When gravity is included the situation is more complicated. An approach based on elimination of scalar field perturbations shows no nega

Dumitru Baleanu, Ayse Karasu

The solution of the Lax tensor equations in the case $L_{αβγ}=-L_{βαγ}$ was analyzed. The Lax tensors on the dual metrics were investigated. We classified all two dimensional metrics having the symmetric Lax tensor $L_{αβγ}$. The Lax tensors of the flat space, Rindler system and its dual were found.

E. C. Bastone, A. S. T. Pires, P. R. Silva

A pseudo-spin model is proposed, as a means to describe some transport properties (resistivity and Hall mobility) in $Bi_2Sr_2(Ca_zPr_{1-z})Cu_2O_{8+y}$. Our model is based in a double-well potential where tunneling in a given site and interaction between different lattice sites are allowed only through the excited states. Doping of the pure system by the ad

M. Tardío, R. Ramírez, R. González, Y. Chen

AC and DC electrical measurements between 273 and 800 K were used to characterize the electrical conductivity of Al_2 O_3:Mg single crystals containing [Mg]^{0} center. At low fields contacts are blocking. At high fields, electrical current flows steadily through the sample and the I-V characteristic corresponds to a directly biased barrier whit a series res

R. Prozorov, R. W. Giannetta, T. Tamegai, P. Guptasarma

The $AC$ magnetic penetration depth $λ(T,H,j)$ was measured in presence of a macroscopic $DC$ (Bean) supercurrent, $j$. In single crystal BSCCO below approximately 28 K, $λ(T,H,j)$ exhibits thermal hysteresis. The irreversibility arises from a shift of the vortex position within its pinning well as $j$ changes. It is demonstrated that below a new irreversibi