October 1999 arXiv papers — page 16

P. A. Marchetti, Jian-Hui Dai, Zhao-Bin Su, Lu Yu

Based on recently proposed U(1)xSU(2) Chern-Simons gauge field theory, an interpretation of the transport and magnetic relaxation properties of underdoped cuprates is proposed, taking into account the short range antiferromagnetic order. The interplay of the doping-dependent spin gap (explicitly derived by us) effect and dissipation due to gauge fluctuations

A. K. Zhuravlev, M. I. Katsnelson

Haldane hypothesis about the universality of Luttinger liquid (LL) behavior in conducting one-dimensional (1D) fermion systems is checked numerically for spinless fermion model with next-nearest-neighbor interactions. It is shown that for large enough interactions the ground state can be gapless (metallic) due to frustrations but not be LL. The exponents of

Maria Serena Causo, Barbara Coluzzi, Peter Grassberger

We study pairs of interacting self-avoiding walks on the 3d simple cubic lattice. They have a common origin and are allowed to overlap only at the same monomer position along the chain. The latter overlaps are indeed favored by an energetic gain. This is inspired by a model introduced long ago by Poland and Sheraga [J. Chem. Phys. {\bf 45}, 1464 (1966)] for

Urs Ledermann, Karyn Le Hur

We study the two-band model of spinless fermions in one dimension for weak repulsive interactions. In this case, the model is equivalent to the weakly interacting spinless two-leg ladder. We obtain analytic expressions for the superconducting pairing correlation function and the charge density correlation function, which show, that a finite interchain hoppin

G. Alvarez, V. Martin-Mayor, J. J. Ruiz-Lorenzo

We show analytically that the perturbative expansion for the free energy of the zero dimensional (quenched) disordered Ising model is Borel-summable in a certain range of parameters, provided that the summation is carried out in two steps: first, in the strength of the original coupling of the Ising model and subsequently in the variance of the quenched diso

M. P. Das, F. Green

In the theory of noise processes for mesoscopic conductors, the relationship between shot noise and hot-electron noise is absolutely fundamental to understanding the underlying microscopic fluctuations. From the vantage point of orthodox microscopics and kinetics, their relation is a long way from being settled. Its resolution calls for the tools of many-bod

W. Pan, H. L. Stormer, D. C. Tsui, L. N. Pfeiffer

We have measured the effective mass ($m^*$) of the four flux composite fermion at Landau level filling factor $ν= 1/4$ ($^4$CF), using the activation energy gaps at the fractional quantum Hall effect (FQHE) states $ν$ = 2/7, 3/11, and 4/15 and the temperature dependence of the Shubnikov-de Haas (SdH) oscillations around $ν= 1/4$. We find that the energy gaps

Monwhea Jeng, Andreas W. W. Ludwig

We analyze the effect of adding quenched disorder along a defect line in the 2D conformal minimal models using replicas. The disorder is realized by a random applied magnetic field in the Ising model, by fluctuations in the ferromagnetic bond coupling in the Tricritical Ising model and Tricritical Three-state Potts model (the $ϕ_{12}$ operator), etc.. We fin

C. T. Shih, Y. C. Chen, T. K. Lee

We reported that the pair-pair correlation function of the two-dimensional t-J model does not have long-range d-wave superconducting correlations in the interesting parameter range of $J/t \leq 0.5$. The power-Lanczos method is used under the assumption of monotonic behavior. This assumption has been well checked in the two-dimensional t-J and attractive Hub

R. Huerta, P. Varona, M. I. Rabinovich, Henry D. I. Abarbanel

Central Pattern Generators (CPGs) in invertebrates are comprised of networks of neurons in which every neuron has reciprocal connections to other members of the CPG. This is a ``closed'' network topology. An ``open'' topology, where one or more neurons receives input but does not send output to other member neurons, is not found in these CPGs

Michael K. -H. Kiessling

The original Jeans dispersion relation and instability criterion are derived by a mathematically well-defined limiting procedure. The procedure highlights Jeans' physical reasoning and vindicates the (in)famous ``Jeans swindle.'' A second, independent procedure is stated which yields the same result.

Richard Ellis

Galaxies represent the visible fabric of the Universe and there has been considerable progress recently in both observational and theoretical studies. The underlying goal is to understand the present-day diversity of galaxy forms, masses and luminosities in the context of theories for the growth of structure. Popular models predict the bulk of the galaxy pop

P. F. Bloser, J. E. Grindlay, T. Narita, J. A. Jenkins

We report on the design and laboratory testing of a prototype imaging CZT detector intended for balloon flight testing in April 2000. The detector tests several key techniques needed for the construction of large-area CZT arrays, as required for proposed hard X-ray astronomy missions. Two 10 mm x 10 mm x 5 mm CZT detectors, each with a 4 x 4 array of 1.9 mm

Sidney van den Bergh

Most of the globular clusters in the main body of the Galactic halo were formed almost simultaneously. However, globular cluster formation in dwarf spheroidal galaxies appears to have extended over a significant fraction of a Hubble time. This suggests that the factors which suppressed late-time formation of globulars in the main body of the Galactic halo we

Judith G. Cohen

The Caltech Faint Galaxy Redshift Survey has collected $\sim$2000 spectra taken with multi-slit masks using the Low Resolution Imaging Spectrograph at the Keck Observatory (Oke et al 1995) in two widely separated fields on the sky, each $\sim$1 x 1 deg$^2$. Most of these objects are faint field galaxies; about 10% are Galactic stars and about 1% are broad-li

Shiho Kobayashi, Re'em Sari

The strong optical flash observed by ROTSE, as well as the radio flare associated with GRB 990123 can be attributed to the emission of the fireball ejecta, initially heated by the reverse shock. We numerically study the evolution of an adiabatic relativistic fireball interacting with an ambient uniform medium, both in the initial energy transfer stage and in

Charles D. Dermer, James Chiang, Kurt E. Mitman

We present detailed calculations of nonthermal synchrotron and synchrotron self-Compton (SSC) spectra radiated by blast waves that are energized by interactions with a uniform surrounding medium. Radio, optical, X-ray and gamma-ray light curves and spectral indices are calculated for a standard parameter set that yields hard GRB spectra during the prompt emi

Shwetabh Singh

Cosmological models involving shear and rotation are considered, first in the General Relat ivistic and then in the Newtonian framework with the aim of investigating singularities in them by using numerical and analytical techniques. The dynamics of these rotating models ar e studied. It is shown that singularities are unavoidable in such models and that the

B. Brandl, W. Brandner, F. Eisenhauer, A. F. J. Moffat

We have observed NGC 3603, the most massive visible HII region known in the Galaxy, with ANTU(VLT1)/ISAAC in the near-infrared (NIR) J_s, H, and K_s bands. Our observations are the most sensitive observations made to date of this dense starburst region, allowing us to investigate with unprecedented quality its low-mass stellar population. Our mass limit to s

Yael Fuchs, F. Mirabel, S. Chaty, A. Claret

Observations at near and mid-infrared wavelengths (1-18 micron) of SGR 1806-20 suggest that it is associated with a cluster of giant massive stars which are enshrouded in a dense cloud of dust. The centre of the best sky position of the gamma-ray source (Hurley et al. 1999) lies on top of the dust cloud at only 7 arcsec (~0.5 pc at a distance of 14.5 kpc) fr

Elena Pian

The spatial and temporal coincidence of a GRB and a supernova explosion (1998bw) on 25 April 1998 has raised conjectures on the physical connection between the two phenomena, and in general on the association of GRBs with supernovae, at least with the most powerful among them (hypernovae or collapsars). In fact, multiwavelength observations of SN 1998bw have

E. Pian, L. Amati, L. A. Antonelli, R. C. Butler

We present BeppoSAX follow-up observations of GRB980425 obtained with the Narrow Field Instruments (NFI) in April, May, and November 1998. The first NFI observation has detected within the 8' radius error box of the GRB an X-ray source positionally consistent with the supernova 1998bw, which exploded within a day of GRB980425, and a fainter X-ray source,

P. J. E. Peebles

This conference shows the impressive rate of advances in the observations and theoretical interpretations of large-scale structure. But to explain my feeling that we may still have a lot to learn I offer some comments on our sociology, informed by social construction, in adopting lines of thought that tend not to follow straightforward readings of what is ob

Shaun Cole, Andrew Benson, Carlton Baugh, Cedric Lacey

The main ingredients of recent semi-analytic models of galaxy formation are summarised. We present predictions for the galaxy clustering properties of a well specified LCDM model whose parameters are constrained by observed local galaxy properties. We present preliminary predictions for evolution of clustering that can be probed with deep pencil beam surveys

Isabella M. Gioia

At z=0.809, RXJ1716.6+6708 is the second most distant X-ray selected cluster so far published and the only one with a large number of spectroscopically determined cluster member velocities. The optical morphology of RXJ1716.6+6708 resembles an inverted S-shape filament with the X-rays coming from the midpoint of the filament. The ROSAT HRI contours have an e

T. Driebe, T. Bloecker, D. Schoenberner

We present a grid of evolutionary tracks for low-mass white dwarfs with helium cores in the mass range from 0.179 to 0.414 M_sun. The lower mass limit is well suited for comparison with white dwarf companions of millisecond pulsars (MSP). The derived cooling ages are of the order of 10^9 yrs due to residual nuclear burning. The cooling ages are consistent wi

Vijay K. Narayanan, David H. Weinberg, E. Branchini, C. S. Frenk

We present the results of reconstruction analysis of the galaxy distribution in a spherical region of radius 50 Mpc/h centered on the Local Group, as mapped by the IRAS Point Source Catalog Redshift Survey (PSCz). We reconstruct it using 15 different models for structure formation in the universe, each consisting of a set of assumptions regarding the value o

Jens Schmalzing, Antonaldo Diaferio

We analyse the redshift space topology and geometry of the nearby Universe by computing the Minkowski functionals of the Updated Zwicky Catalogue (UZC). The UZC contains the redshifts of almost 20,000 galaxies, is 96% complete to the limiting magnitude m_Zw=15.5 and includes the Center for Astrophysics (CfA) Redshift Survey (CfA2). From the UZC we can extrac

S. K. Saha

The current status of the high spatial resolution imaging interferometry in optical astronomy is reviewed in the light of theoretical explanation, as well as of experimental constraints that exist in the present day technology. The basic mathematical interlude pertinent to the interferometric technique and its applications in astronomical observations are pr

Kazushi Sakamoto

The NRO-OVRO CO imaging survey showed that molecular gas was more concentrated to the central kiloparsec in barred spiral galaxies than in their unbarred counterparts. The result provided not only evidence for bar-driven gas transport but also estimates on the mean rate of gas transfer and lower limits to the lifetime of bars. Other lines of evidence for the

Stefan C. Keller, M. S. Bessell, G. S. Da Costa

We have carried out Wide Field Planetary Camera 2 F160BW, F555W and F656N imaging of four young populous clusters: NGC 330 in the Small Magellanic Cloud and NGC 1818, NGC 2004 and NGC 2100 in the Large Magellanic Cloud. We report photometric results for these four clusters, including identification using photometric colours of the cluster Be star population.

Volker Bromm, Paolo S. Coppi, Richard B. Larson

In order to constrain the initial mass function (IMF) of the first generation of stars (Population III), we investigate the fragmentation properties of metal-free gas in the context of a hierarchical model of structure formation. We investigate the evolution of an isolated 3-sigma peak of mass 2x10^6 M_solar which collapses at z_coll=30 using Smoothed Partic

S. Trudolyubov, E. Churazov, M. Gilfanov

We analysed 9 RXTE/PCA observations of GRS 1915+105 in the flaring state, when the hardness of the source spectrum was changing on the time scales from few seconds up to 1000 seconds. The quasi periodic oscillations (QPOs) with the frequency varying between ~ 1 and 12 Hz are associated with the episodes of harder source spectrum. In each observation we found

Carmen J. Gagne, Marcelo Gleiser

We show how to achieve lattice-spacing independent results in numerical simulations of finite-temperature stochastic scalar field theories. We generalize the previous approach of hep-lat/9607026 by obtaining results which are independent of the renormalization scale. As an application of our method, we examine thermal phase mixing in the context of Ginzburg-

Ioannis Kontoyiannis

Suppose A is a finite set equipped with a probability measure P and let M be a ``mass'' function on A. We give a probabilistic characterization of the most efficient way in which A^n can be almost-covered using spheres of a fixed radius. An almost-covering is a subset C_n of A^n, such that the union of the spheres centered at the points of C_n has pr

Vatche Sahakian

We propose a covariant geometrical expression for the c-function for theories which admit dual gravitational descriptions. We state a c-theorem with respect to this quantity and prove it. We apply the expression to a class of geometries, from domain walls in gauged supergravities, to extremal and near extremal Dp branes, and the AdS Schwarzschild black hole.

Mikhail Vasiliev

We review the theory of higher spin gauge fields in 2+1 and 3+1 dimensional anti-de Sitter space and present some new results on the structure of higher spin currents and explicit solutions of the massless equations. A previously obtained d=3 integrating flow is generalized to d=4 and is shown to give rise to a perturbative solution of the d=4 nonlinear high

V. V. Nesterenko, I. G. Pirozhenko

Spectral zeta functions $ζ(s)$ for the massless scalar fields obeying the Dirichlet and Neumann boundary conditions on a surface of an infinite cylinder are constructed. These functions are defined explicitly in a finite domain of the complex plane s containing the closed interval of real axis $-1\le$ Re $s \le 0$. Proceeding from this the spectral zeta func

T. Barreiro, E. J. Copeland, N. J. Nunes

We demonstrate how exponential potentials that could arise in the early Universe as a result of Kaluza-Klein type compactifications of string theory, can lead to cosmological solutions which correspond to the currently observed accelerating Universe. The idea is simple, relying solely on the known scaling properties associated with exponential potentials. In

P. K. Mohanty, Sumathi Rao

We study transport in a class of exactly solvable models of interacting fermions in one dimension. We contrast these models with models of non-interacting fermions in an Aharanov-Bohm ring to which they are superficially similar. We introduce magnetic and non-magnetic impurities at a site, through either a weak $δ$-function potential or through a weak link.

UKQCD Collaboration, K. C. Bowler, P. Boyle, J. Garden

We present a comprehensive study of the masses of pseudoscalar and vector mesons, as well as octet and decuplet baryons computed in O(a) improved quenched lattice QCD. Results have been obtained using the non-perturbative definition of the improvement coefficient c_sw, and also its estimate in tadpole improved perturbation theory. We investigate effects of i

B. Lehmann-Dronke, P. V. Pobylitsa, M. V. Polyakov, A. Schafer

We have calculated the leading order amplitude of hard diffractive electroproduction of two pions in lepton nucleon scattering. At the leading twist level a pion pair can be produced only in an isospin one or zero state. We have shown that isoscalar states are produced dominantly for x_{Bj}>0.3 and with an invariant mass of the two pions close to the thresho

J. -P. Blaizot, E. Iancu, A. Rebhan

Self-consistent approximations allowing the calculation of the entropy and the baryon density of a quark-gluon plasma are presented. These approximations incorporate the essential physics of the hard thermal loops, involve only ultraviolet-finite quantities, and are free from overcounting ambiguities. While being nonperturbative in the strong coupling consta

Silvia Mollerach, Esteban Roulet

We revisit the gravitational lensing phenomenon using a new visualization technique. It consists in projecting the observers sky into the source plane, what gives rise to a folded and stretched surface. This provides a clear graphical tool to visualize some interesting well-known effects, such as the development of multiple images of a source, the structure

Janna Levin

Spinning compact binaries are shown to be chaotic in the Post-Newtonian expansion of the two body system. Chaos by definition is the extreme sensitivity to initial conditions and a consequent inability to predict the outcome of the evolution. As a result, the spinning pair will have unpredictable gravitational waveforms during coalescence. This poses a chall

Hodaka Oda, Kenji Ito, Masashi Naganuma, Norisuke Sakai

An exact solution of domain wall junction is obtained in a four-dimensional N=1 supersymmetric U(1) X U(1)' gauge theory with three pairs of chiral superfields which is motivated by the N=2 SU(2) gauge theory with one flavor perturbed by an adjoint scalar mass. The solution allows us to evaluate various quantities including a new central charge Y_k assoc

Keh-Fei Liu

We formulate the hadronic tensor $W_{μν}$ of deep inelastic scattering in the path-integral formalism. It is shown that there are 3 gauge invariant and topologically distinct contributions. Besides the valence contribution, there are two sources for the sea -- one in the connected insertion and the other in the disconnected insertion. The operator product ex

I. Bars, D. Minic

We discuss the quantum mechanics of a particle in a magnetic field when its position x^μ is restricted to a periodic lattice, while its momentum p^μ is restricted to a periodic dual lattice. Through these considerations we define non-commutative geometry on the lattice. This leads to a deformation of the algebra of functions on the lattice, such that their p

Rong-Gen Cai, Nobuyoshi Ohta

We study the thermodynamics of the large N noncommutative super Yang-Mills theory in the strong 't Hooft coupling limit in the spirit of AdS/CFT correspondence. It has already been noticed that some thermodynamic quantities of near-extremal D3-branes with NS B fields, which are dual gravity configurations of the noncommutative ${\cal N}$=4 super Yang-Mil

Hirokazu Aiba, Toru Suzuki

Properties of the response functions for a two-dimensional quartic oscillator are studied based on the diagonalization of the Hamiltonian in a large model space. In particular, response functions corresponding to a given momentum transfer are studied for different values of the coupling parameter in the Hamiltonian. The latter controls regular or chaotic nat

Christoph Simon, Gregor Weihs, Anton Zeilinger

We show that optimal universal quantum cloning can be realized via stimulated emission. Universality of the cloning procedure is achieved by choosing systems that have appropriate symmetries. We first discuss a scheme based on stimulated emission in certain three-level-systems, e.g. atoms in a cavity. Then we present a way of realizing optimal universal clon

R. Friedberg, T. D. Lee, W. Q. Zhao

We discuss a new relation between the low lying Schroedinger wave function of a particle in a one-dimentional potential V and the solution of the corresponding Hamilton-Jacobi equation with -V as its potential. The function V is $\geq 0$, and can have several minina (V=0). We assume the problem to be characterized by a small anhamornicity parameter $g^{-1}$

H. C. Rosu

This is a Physics World features paper on Chen-Tajima proposal to detect Unruh radiation by means of high-intensity lasers (PRL 83, 256 (1999)).

David Tsiklauri

Kinetic model of three component, weakly ionized, collisional plasma with a beam of neutral particles is developed. New dispersion relations for linear perturbations are derived and analyzed in various limiting cases.

D. Hüber, J. L. Friar, A. Nogga, H. Witala

We include two new three-nucleon-force terms of pion-range - short-range form in our momentum-space calculations for the three-nucleon continuum. These two terms are expected by chiral perturbation theory to be non-negligible. We study the effects of these terms in elastic neutron-deuteron scattering and pay special attention to the neutron vector analyzing

P. Maris, P. C. Tandy

The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the dressed quark-photon vertex to study the low-momentum behavior of the pion electromagnetic form factor. With model gluon parameters previously fixed by the pion mass and decay constant, the pion charge radius $r_π$ is found to be in excell

A. Valor, P. -H. Heenen, P. Bonche

We present in this paper the general framework of a method which permits to restore the rotational and particle number symmetries of wave functions obtained in Skyrme HF+BCS calculations. This restoration is nothing but a projection of mean-field intrinsic wave functions onto good particle number and good angular momentum. The method allows also to mix proje

A. Bianconi, G. Bonomi, E. Lodi Rizzini, L. Venturelli

We set up a plane wave impulse approximation (PWIA) formalism for the analysis of the annihilation cross sections of antinucleons on nuclear targets at very low momenta (below 100 MeV/c), where semiclassical approximations can't be applied. Since, as we test here, PWIA fails in reproducing the unexpected ``inversion'' behavior of the $\bar{p}p$ a

Bao-An Li

Deformation and orientation effects on compression, elliptic flow and particle production in uranium on uranium collisions (UU) at relativistic energies are studied within the transport model ART. The density compression in tip-tip UU collisions is found to be about 30% higher and lasts approximately 50% longer than in body-body or spherical UU reactions. Th

P. -H. Heenen, P. Bonche, S. 'Cwiok, W. Nazarewicz

Two applications of mean-field calculations based on 3D coordinate-space techniques are presented. The first concerns the structure of odd-N superheavy elements that have been recently observed experimentally and shows the ability of the method to describe, in a self-consistent way, very heavy odd-mass nuclei. Our results are consistent with the experimental

David Damanik, Rowan Killip, Daniel Lenz

We study the spectral properties of discrete one-dimensional Schrödinger operators with Sturmian potentials. It is shown that the point spectrum is always empty. Moreover, for rotation numbers with bounded density, we establish purely $α$-continuous spectrum, uniformly for all phases. The proofs rely on the unique decomposition property of Sturmian potential

Robert L. Bryant

This article is a report on the status of the problem of classifying the irriducibly acting subgroups of GL(n,R) that can appear as the holonomy of a torsion-free affine connection. In particular, it contains an account of the completion of the classification of these groups by Chi, Merkulov, and Schwachhofer as well as of the exterior differential systems a

Michel Brion, Michele Vergne

The aim of this article is to generalize in several variables some formulae for Eisenstein series in one variable. For example the formula $2ζ(2k) = (2π)^{2k} \frac{B_{2k}}{(2k)!} = Res_{z=0}(\frac{1}{z^{2k}(1-e^z)})$ for the values of zeta functions at even integers in functions of Bernoulli numbers. A. Szenes proved in several variables a similar residue f

A. W. Peet

Marginally bound systems of two types of branes are considered, such as the prototypical case of Dp+4 branes and Dp branes. As the transverse separation between the two types of branes goes to zero, different behaviour occurs in the supergravity solutions depending on p; no-hair theorems result for p<=1 only. Within the framework of the AdS/CFT correspondenc

Ralph Blumenhagen, Costas Kounnas, Dieter Lust

We consider freely acting orbifold compactifications, which interpolate in two possible decompactification limits between the supersymmetric type II string and the non-supersymmetric type 0 string. In particular we discuss how D-branes are incorporated into these orbifold models. Investigating the open string spectrum on D3-branes, we will show that one can

Matt Visser

We discuss an exotic class of Kaluza-Klein models in which the internal space is neither compact nor even of finite volume. Rather than using the usual compact internal space we consider the case where particles are gravitationally trapped near a four-dimensional submanifold of the higher dimensional spacetime. A specific model exhibiting this phenomenon is

Qaisar Shafi, Zurab Tavartkiladze

By supplementing supersymmetric SO(10) with an anomalous ${\cal U}(1)$ flavor symmetry and additional `matter&#39; superfields carrying suitable ${\cal U}(1)$ charges, we explain the charged fermion mass hierarchies, the magnitudes of the CKM matrix elements, as well as the solar and atmospheric neutrino data. We stress bi-maximal vacuum neutrino mixings, an

Nick Evans, James Hormuzdiar, Stephen D. H. Hsu, Myck Schwetz

We investigate the possible ground states of QCD at asymptotic densities, where the theory is expected to exhibit color superconductivity. We characterize the color-flavor structure of possible diquark condensates, and find those that are energy extrema by solving the weak-coupling Dyson-Schwinger equations, including Landau damping and the Meissner effect.

Wojciech Krolikowski

As an alternative for popular see-saw mechanism, the option of three pseudo% -Dirac neutrinos is discussed, where ${1/2}(m^{(L)} + m^{(R)}) \ll m^{(D)}$ for their Majorana and Dirac masses. The actual neutrino mass matrix is assumed in the form of tensor product $ M^{(ν)} \otimes {(\{array} {cc} λ^{(L)} & 1 1 & λ^{(R)} \{array})}$, where $ M^{(ν)}$ is a neut

D. Roy, T. Morii, H. Toki, A. Titov

The low energy $J/ψ$ photoproduction cross-section has been studied on the basis of the Pomeron model. To incorporate the discrepancy between experimental data and the predictionns by the conventional models, i.e. the sum of the soft Pomeron with intercept 1.08 and the hard Pomeron with intercept 1.418, a Regge trajectory associated with a scalar meson (f,a)

Kenji Fukazawa, Tomohiro Inagaki, Seiji Mukaigawa, Taizo Muta

The mechanism of the chiral symmetry breaking is investigated in the strong-coupling Abelian gauge theories at finite temperature. The Schwinger-Dyson equation in Landau gauge is employed in the real time formalism and is solved numerically within the framework of the instantaneous exchange approximation including the effect of the hard thermal loop for the

Kunio Takamatsu

The results of the analysis of the pi^0 pi^0 scattering amplitudes obtained with pi^- P charge exchange reaction, pi^- P --> pi^0 pi^0 n, data at 9 GeV/c are presented. The pi^0 pi^0 scattering amplitudes show clear f_0(1370) and f_2(1270) signals in the S and D waves, respectively. The pi^0 pi^0 scattering phase shifts have been obtained below Kbar K thresh

Chun Liu

It has been known that the supersymmetric flavor changing neutral current problem can be avoided if the squarks take the following mass pattern, namely the first two generations with the same chirality are degenerate with masses around the weak scale, while the third generation is very heavy. We realize this scenario through the supersymmetric extension of a

R. J. Lindebaum, G. B. Tupper, R. D. Viollier

We examine the phenomenology of a low-energy extension of the Standard Model, based on the gauge group SU(3) x SU(2) x U(1) x SO(3), with SO(3) operating in the shadow sector. This model offers $ν_{e} \to ν_{s}$ and $ν_μ \to ν_τ$ oscillations as the solution of the solar and atmospheric neutrino problems. Moreover, it provides a neutral heavy shadow lepton X

Aurelio Juste, Gonzalo Merino

A feasibility study of the measurement of the top-Higgs Yukawa coupling at a future linear e+e- collider operating at sqrt(s)=800 GeV is presented. As compared to previous existing studies, much effort has been put in a ``realistic simulation&#39;&#39; by including irreducible+reducible backgrounds, realistic detector effects and reconstruction procedures an

Jean-Jacques Dugne, Sverker Fredriksson, Johan Hansson, Enrico Predazzi

A new model for the substructure of quarks, leptons and weak gauge bosons is discussed. It is based on three fundamental and absolutely stable spin-1/2 preons. Its preon flavour SU(3) symmetry leads to a prediction of nine quarks, nine leptons and nine heavy vector bosons. One of the quarks has charge $-4e/3$, and is speculated to be the top quark (whose cha

Alejandro Ayala, Juan Carlos D&#39;Olivo, Manuel Torres

For Dirac neutrinos with magnetic moment, we compute the production rate for right-handed neutrinos in a hot and dense QED plasma containing an initial population of left-handed neutrinos thermally distributed. The most important mechanisms for $ν_L$ depolarization, or production of right-handed neutrinos, are the $ν_L \to ν_R$ chirality flip and the plasmon

Toshinori Abe, representing the SLD Collaboration

We present selected new results on strong interaction physics from the SLD experiment at the SLAC Linear Collider (SLC), symmetry tests of b\bar{b}g vertex, the rate of secondary b\bar{b} production via gluon splitting, the B hadron energy spectrum and rapidity correlations between identified charged hadrons. The parity violation in Z0 --> b\bar{b}g decays i

Richard Hawkings, Klaus Moenig

A future linear collider such as TESLA may be able to run on the Z0 resonance with very high luminosity and polarised electron and positron beams. The possibilities of measuring electroweak quantities with high precision are investigated. Huge improvements with respect to the present precision can be expected, especially for the asymmetries A_LR and A_b wher

Charles W. Misner

A method is described by which a function defined on a cubic grid (as from a finite difference solution of a partial differential equation) can be resolved into spherical harmonic components at some fixed radius. This has applications to the treatment of boundary conditions imposed at radii larger than the size of the grid, following Abrahams, Rezzola, Rupri

Madhavan Varadarajan

Every (1 polarization) cylindrical wave solution of vacuum general relativity is completely determined by a corresponding axisymmetric solution to the free scalar wave equation on an auxilliary 2+1 dimensional flat spacetime. The physical metric at radius R is determined by the energy, $γ(R)$, of the scalar field in a box (in the flat spacetime) of radius R.

Marc Toussaint

A special case of metric-affine gauge theory of gravity (MAG) is equivalent to general relativity with Proca matter as source. We study in detail a corresponding numeric solution of the Reissner-Nordstr&#34;om type. It is static, spherically symmetric, and of electric type. In particular, this solution has no horizon, so it has a naked singularity as its ori

S. Mignemi

We study the general spherical symmetric solutions of dilaton-modulus gravity non-minimally coupled to a Maxwell field, using methods from the theory of dynamical systems. We show that the solutions can be classified by the mass, the electric charge, and a third parameter which we argue can be related to a scalar charge. The global properties of the solution

Antony Lewis, Chris Doran, Anthony Lasenby

We consider topological contributions to the action integral in a gauge theory formulation of gravity. Two topological invariants are found and are shown to arise from the scalar and pseudoscalar parts of a single integral. Neither of these action integrals contribute to the classical field equations. An identity is found for the invariants that is valid for

K. Konno, T. Obata, Y. Kojima

We formulate deformation of relativistic stars due to the magnetic stress, considering the magnetic fields to be perturbations from spherical stars. The ellipticity for the dipole magnetic field is calculated for some stellar models. We have found that the ellipticity becomes large with increase of a relativistic factor for the models with the same energy ra

A. A. Aligia, K. Hallberg, C. D. Batista, G. Ortiz

We determine the quantum phase diagram of the Hubbard chain with electron-hole symmetric correlated hopping at 1/2- and 1/4-filling using geometric concepts and continuum limit field theory. The long distance behavior of various correlation functions show a very rich phase diagram with several insulating, metallic, and superconducting phases, which might be

A. R. Denton, G. Kahl, J. Hafner

Freezing of simple liquid metals and the relative stabilities of competing crystalline solids are investigated using thermodynamic perturbation theory, the interactions between ions being modeled by effective pair potentials derived from pseudopotential theory. The ionic free energy of the solid phase is calculated, to first order in the perturbation potenti

Derek Frydel, William H. Terilla, Kieron Burke

An extremely easy method for accurately calculating the adiabatic connection of density functional theory is presented, and its accuracy tested on both Hooke&#39;s atom and the He atom. The method is easy because calculations are needed only for different values of parameters in the external potential, which can be achieved with almost any electronic structu

Douglas A. Kurtze, Joseph A. Both, Daniel C. Hong

We investigate the formation of ripples on the surface of windblown sand based on the one-dimensional model of Nishimori and Ouchi [Phys. Rev. Lett. 71, 197 (1993)], which contains the processes of saltation and grain relaxation. We carry out a nonlinear analysis to determine the propagation speed of the restabilized ripple patterns, and the amplitudes and p

T. Stein, G. A. Levin, C. C. Almasan, D. A. Gajewski

Transport as well as magnetic relaxation properties of the mixed state were studied on strongly underdoped Y_1-xPr_xBa_2Cu_3O_7-d crystals. We observed two correlated phenomena - a coupling transition and a transition to quantum creep. The distribution of transport current below the coupling transition is highly nonuniform, which facilitates quantum creep. W

Debashish Chowdhury, Ludger Santen, Andreas Schadschneider

In recent years statistical physicists have developed {\it discrete} &#34;particle-hopping&#34; models of vehicular traffic, usually formulated in terms of {\it cellular automata}, which are similar to the microscopic models of interacting charged particles in the presence of an external electric field. Concepts and techniques of non-equilibrium statistical

F. M. Peeters, V. A. Schweigert, B. J. Baelus, P. S. Deo

Phase transitions between different (i.e. giant and multi-vortex) superconducting states and between the superconducting-normal state of mesoscopic disks and rings are studied in the presence of an external magnetic field by solving the two non-linear Ginzburg-Landau equations self-consistently. The flux through a circular disk with a hole in the middle is n

M. B. Walker, M. F. Smith

The quasiparticle lifetime and the related transport relaxation times are the fundamental quantities which must be known in order to obtain a description of the transport properties of the high T_c superconductors. Studies of these quantities have been undertaken previously for the d-wave, high T_c superconductors for the case of temperature-independent elas

Prabodh Shukla, Ratnadeep Roy, Emilia Ray

We analyse hysteresis in a one-dimensional anti-ferromagnetic random field Ising model at zero-temperature. The random field is taken to have a rectangular distribution of width $2 Δ$ centered about the origin. A uniform applied field is varied slowly from $-\infty$ to $+\infty$ and back. Analytic expression for the hysteresis loop is obtained in the case $Δ

Yu. M. Zinoviev

The Onsager formula for the free energy of the two dimensional Ising model with periodic boundary conditions is proved.

Juan M. Lopez

We study surface growth models exhibiting anomalous scaling of the local surface fluctuations. An analytical approach to determine the local scaling exponents of continuum growth models is proposed. The method allows to predict when a particular growth model will have anomalous properties ($α\neq α_{loc}$) and to calculate the local exponents. Several contin

Joachim Krug, Martin Rost

Unstable homoepitaxy on rough substrates is treated within a linear continuum theory. The time dependence of the surface width W(t) is governed by three length scales: The characteristic scale $l_0$ of the substrate roughness, the terrace size $l_D$ and the Ehrlich-Schwoebel length $l_{ES}$. If $l_{ES} \ll l_D$ (weak step edge barriers) and $l_0 \ll l_m \sim

Erwin Müller-Hartmann, Rajiv R. P. Singh, Christian Knetter, Götz S. Uhrig

We study a generalized Shastry-Sutherland model for the material SrCu$_2$(BO$_3$)$_2$. Along a line in the parameter space, we can show rigorously that the model has a first order phase transition between Dimerized and Néel-ordered ground states. Furthermore, when a magnetic field is applied in the Dimerized phase, magnetization plateaus develop at commensur

S. Mazumdar, R. T. Clay, D. K. Campbell

Two-dimensional (2D) strongly correlated electron systems underlie many of the most important phenomena in contemporary condensed matter physics, including the Quantum Hall Effect (QHE), ``high T_c&#39;&#39; superconductivity, and possible exotic conducting states in silicon MOSFETs. We demonstrate the existence of yet another exotic ground state in strongly

Nataliya A. Zimbovskaya, Joseph L. Birman

We propose a theory for the new effects recently observed by Willett et al [1] in the magnetoresistance of a weakly modulated two dimensional electron gas near filling factor 1/2. Minima in transverse magnetoresistance and maxima in longitudinal magnetoresistance at the same magnetic field producing the new resonance structure are reported. The structure occ