September 2001 arXiv papers — page 6

Hans-Andreas Engel, Daniel Loss

We investigate the spin dynamics of a quantum dot with a spin-1/2 ground state in the Coulomb blockade regime and in the presence of a magnetic rf field leading to electron spin resonances (ESR). We show that by coupling the dot to leads, spin properties on the dot can be accessed via the charge current in the stationary and non-stationary limit. We present

Yuval Yaish, Oleg Prus, Evgeny Buchstab, Gidi Ben Yoseph

The magnetotransport of two dimensional holes in a GaAs/AlGaAs heterostructure is studied experimentally and theoretically. Spin-orbit splitting of the heavy hole band is manifested at high carrier densities in two Shubnikov-de Haas frequencies, classical positive magnetoresistance, and weak antilocalization. The latter effect combined with inelastic scatter

M. Ozana, A. Shelankov

We apply the method of two-point quasiclassical Green's function to geometries where the trajectories include interfering paths and loops. For a system of two superconducting layers separated by partially transparent interface, corrections to the quasiclassical solutions for the Green's function are explicitly found as well as the deviation from the

Thereza Paiva, Raimundo R. dos Santos

We study the formation of charge density waves (CDW's) in one-dimensional Hubbard superlattices, modeled by a repeated pattern of repulsive (U>0) and free (U=0) sites. By means of Lanczos diagonalizations for the ground state, we calculate the charge structure factor. Our results show that while the superlattice structure affects the modulation of the ch

Eiji Kaneshita, Masanori Ichioka, Kazushige Machida

Phonon anomalies observed in various high $T_c$ cuprates by neutron experiments are analyzed theoretically in terms of the stripe concept. The phonon self-energy correction is evaluated by taking into account the charge collective modes of stripes, giving rise to dispersion gap, or kink and shadow phonon modes at twice the wave number of spin stripe. These f

E. Cimpoiasu, C. C. Almasan, A. P. Paulikas, B. W. Veal

In-plane and out-of-plane magnetoresistivities (MR) of antiferromagnetic YBa_2Cu_3O_6.25 single crystals were measured in magnetic fields H applied along the (ab) plane. In-plane MR is a superposition of two components: The first component is strongly in-plane anisotropic, changing sign from negative when H is parallel to the electrical current I to positive

Juan Jose Garcia-Ripoll

The moment method is applied to the quantum theory for a trapped dilute gas, obtaining equations for the evolution of the cloud. These equations proof the existence of undamped oscillations in a two-dimensional harmonic trap with radial symmetry. In all other cases we can, with physically reasonable approximations, solve the equations and find the frequencie

C. Jarzynski

A generalization of the free energy perturbation identity is derived, and a computational strategy based on this result is presented. A simple example illustrates the efficiency gains that can be achieved with this method.

Katharina Vollmayr-Lee, Walter Kob, Kurt Binder, Annette Zippelius

We present molecular dynamics simulations of a binary Lennard-Jones mixture at temperatures below the kinetic glass transition. The ``mobility'' of a particle is characterized by the amplitude of its fluctuation around its average position. The 5% particles with the largest/smallest mean amplitude are thus defined as the relatively most mobile/immobi

Alejandro M. F. Rivas, Eduardo R. Mucciolo, Alex Kamenev

The decay rate of quasiparticles in quantum dots is studied through the real time calculation of the single-particle Green function in the self-consistent approximation. The method avoids exact diagonalization, transforming the problem into a system of coupled non-linear integral equations which may be solved iteratively. That allows us to study systems larg

Peter J. Love, Peter V. Coveney, Bruce M. Boghosian

We simulate the dynamics of phase assembly in binary immiscible fluids and ternary microemulsions using a three-dimensional hydrodynamic lattice gas approach. For critical spinodal decomposition we perform the scaling analysis in reduced variables introduced by Jury et al. and Kendon et al. We find a late-stage scaling exponent consistent with the inertial r

Paolo De Los Rios

The probability distribution P(k) of the sizes k of critical trees (branching ratio m=1) is well known to show a power-law behavior k^(-3/2). Such behavior corresponds to the mean-field approximation for many critical and self-organized critical phenomena. Here we show numerically and analytically that also supercritical trees (branching ration m>1) are &#34

H. S. Wio, S. E. Mangioni, R. R. Deza

A system of periodically coupled nonlinear phase oscillators submitted to both additive and multiplicative white noises has been recently shown to exhibit ratchetlike transport, negative zero-bias conductance, and anomalous hysteresis. These features stem from the "asymmetry" of the stationary probability distribution function, arising through a nois

J. A. Revelli, A. D. Sanchez, H. S. Wio

We exploit a simple one-dimensional trapping model introduced before, prompted by the problem of ion current across a biological membrane. The voltage-sensitive channels are open or closed depending on the value taken by an external potential that has two contributions: a deterministic periodic and a stochastic one. Here we assume that the noise source is co

J. Serrano, Ch. Schweitzer, C. T. Lin, K. Reimann

Compared to most tetrahedral semiconductors, the temperature dependence of the absorption edges of the cuprous halides (CuCl, CuBr, CuI) is very small. CuCl and CuBr show a small increase of the gap $E_0$ with increasing temperature, with a change in the slope of $E_0$ vs. $T$ at around 150 K: above this temperature, the variation of $E_0$ with $T$ becomes e

H. S. Wio, S. Bouzat, B. von Haeften

Previous works have shown numerically that the response of a ``stochastic resonator'' is enhanced as a consequence of spatial coupling. Also, similar results have been obtained in a reaction-diffusion model by studying the phenomenon of stochastic resonance (SR) in spatially extended systems using "nonequilibrium potential" (NEP) techniques.

G. F. Zharkov

Based on the self-consistent solution of a nonlinear system of one-dimensional GL-equations, the onset and destruction of superconductivity, the phase transitions and hysteresis phenomena are discussed for a cylinder (radius R) in an axial magnetic field (H) for arbitrary R,kappa,H,m (kappa$ is the GL-parameter, m is the total vorticity of the system). The e

M. Cardona

Kim et al. have reported a dependence of the infrared excitation energies of boron acceptors in diamond on the isotopic mass of the carbon atoms. We show that this change can be quantitatively interpreted as induced by a change in the hole effective mass. Keywords: A. Diamond, A. Stable isotopes, D. Acceptor binding energies, D. Effective masses of holes

M. Koslowski, A. M. Cuitiño, M. Ortiz

An exactly solvable phase-field theory of dislocation dynamics, strain hardening and hysteresis in ductile single crystals is developed. The theory accounts for: an arbitrary number and arrangement of dislocation lines over a slip plane; the long-range elastic interactions between dislocation lines; the core structure of the dislocations resulting from a pie

Yasuo Ohashi, Yoshiaki Ōno

The Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory. The discontinuity in the chemical potential for the change from hole to electron doping is calculated analytically as a function of the on-site Coulomb interaction $U$, and the charge-transfer energy $Δ$ bet

Yishi Duan, Xin Liu, Pengming Zhang

By making use of the $ϕ$-mapping topological current theory, a novel expression of $\nabla \times \vec{V}$ in BEC is obtained, which reveals the inner topological structure of vortex lines characterized by Hopf indices and Brouwer degrees. This expression is just that formula Landau and Feynman expected to find out long time ago. In the case of superconducti

P. Singha Deo

We numerically study the effect of non-symmetry-dictated-nodes (NSDN) on electron correlation effects for spinless electrons. We find that repulsive interaction between electrons can enhance the overlap between nearest neighbors in the tight binding Hamiltonian, in the presence of NSDN. Normally, in the absence of NSDN, attractive interaction between electro

Takeshi Inagaki

In the bilayer quantum Hall system, a spontaneously charge imbalance state appears at the ground energy level. Gap in the collective excitation energy makes it stable against decoherence in macroscopic level. This state behaves as a spin 1/2 representation of SU(2) and can be controlled by applying the interlayer voltage. We suggest this system can be regard

Kaya Mori, Charles J. Hailey, Edward A. Baltz, William W. Craig

We propose a novel antiparticle detector. The gaseous antiparticle spectrometer (GAPS) effects particle identification through the characteristic X-rays emitted by antiparticles when they form exotic atoms in gases. GAPS obtains particularly high grasp (effective area--solid angle product) at lower particle energies, where conventional schemes are most limit

J. Poirier, C. D'Andrea, M. Dunford

Project GRAND has the capability of measuring the angle and identity of single tracks of secondary muons at ground level. The array is comprised of 64 stations each containing eight proportional wire planes with a 50 mm steel absorber plate placed above the bottom two planes in each station. The added steel absorber plate allows muon tracks to be separated f

Alexandre S. Oliveira, J. E. Steiner

HD 45166 was selected as a candidate to the V Sagittae Class. It's spectrum shows quite narrow emission lines of He, C, N, and O, possibly indicating a low inclination for the binary system. We performed high resolution and high stability Coude spectroscopy in order to search for low amplitude radial velocity variations. The orbital period determined fro

Matthew N. Carlson, Jon A. Holtzman

We present a method to derive sizes of marginally resolved star clusters from HST/WFPC2 observations by fitting King models to observations. We describe results on both simulated images and on observations of young compact clusters in NGC 3597 and NGC 1275. From the simulations, we find that we can measure King model concentrations (c) to an accuracy of abou

C. Beisbart, R. Valdarnini, T. Buchert

We explore the morphological and dynamical evolution of galaxy clusters in simulations using scalar and vector-valued Minkowski valuations and the concept of fundamental plane relations. In this context, three questions are of fundamental interest: 1. How does the average cluster morphology depend on the cosmological background model? 2. Is it possible to di

Tammy A. Smecker-Hane, Andrew A. Cole, John S. Gallagher, Peter B. Stetson

Using WFPC2 aboard the Hubble Space Telescope, we have created deep color-magnitude diagrams in the V and I passbands for approximately 100,000 stars in a field at the center of the LMC bar and another in the disk. The main--sequence luminosity functions (LFs) from 19 mag < V < 23.5 mag, the red clump and horizontal branch morphologies, and the differential

S. B. Howell, D. R. Ciardi, M. M. Sirk, A. D. Schwope

We present simultaneous EUV and infrared (J,K) observations of the polar HU Aqr obtained during August 1998 when the star was in a high mass accretion state. EUV and IR light curves and EUV spectra are presented and compared with previous observations. The accretion region on the white dwarf has increased in temperature (124,000K to 240,000K) and radius (0.0

N. Shatsky, A. Tokovinin

The sample of 115 B-type stars in Sco OB2 association is examined for existence of visual companions with ADONIS near-infrared adaptive optics system and coronograph in J and K bands. Practically all components in the separation range 0.3&#34;-6&#34; (45-900 A.U.) were detected, with magnitudes down to K=16. The K and J-K photometry of primaries and differen

T. P. Sasseen, M. Hurwitz, W. V. Dixon, S. Airieau

We have measured the extinction curve in the far-ultraviolet wavelength region of (900 -- 1200 A) using spectra obtained with the Berkeley EUV/FUV spectrometer during the ORFEUS-I and the ORFEUS-II missions in 1993 and 1996. From the complete sample of early-type stars observed during these missions, we have selected pairs of stars with the same spectral typ

S. Arnouts, L. Moscardini, E. Vanzella, S. Colombi

We present an analysis of the evolution of galaxy clustering in the redshift interval 0<z<4.5 in the HDF-S. The HST optical data are combined with infrared ISAAC/VLT observations, and photometric redshifts are used for all the galaxies brighter than I_AB<27.5. The clustering signal is obtained in different redshift bins using two different approaches: a stan

P. N. Appleton, V. Charmandaris, Y. Gao, F. Combes

We describe ISO and BIMA observations of the z=0.04 Seyfert 1 ring galaxy NGC985 which suggest close parallels with some quasar host galaxies. NGC985 contains two closely spaced nuclei embedded in an R$^{1/4}$--law stellar bulge and an outer ring, evidence of an ongoing merger. The system contains \~1.8x10^{10}Msolar of highly disturbed molecular gas which l

Andreas Burkert, Mordecai-Mark Mac Low

The one-point statistics of column density distributions of turbulent molecular cloud models are investigated and compared with observations. In agreement with the observations, the number N of pixels with surface density S is distributed exponentially N(S)=exp(-S/S0) in models of driven compressible supersonic turbulence. However, in contrast to the observa

A. Udalski, L. Wyrzykowski, G. Pietrzynski, O. Szewczyk

We present results of the search for Cepheids in the galaxy IC1613 carried out as a sub-project of the OGLE-II microlensing survey. 138 Cepheids were found in the 14.2x14.2 arcmin region in the center of the galaxy. We present light curves, VI photometry and basic data for all these objects, as well as color-magnitude diagram of the observed field. The Perio

Henk Hoekstra, Marijn Franx, Konrad Kuijken, Pieter G. van Dokkum

We have detected the weak lensing signal induced by the cluster of galaxies MS 2053-04 (z=0.58) from a two-colour mosaic of 6 HST WFPC2 images. The best fit singular isothermal sphere model to the observed tangential distortion yields an Einstein radius r_E=6.2&#34;+-1.8&#34;, which corresponds to a velocity dispersion of 886^{+121}_{-139} km/s. This result

George R. Isaak, Kate G. Isaak

Solar seismology has allowed precision measurements of both the static and dynamic structure of our local star, the Sun. In the near future, seismology of solar-like stars of different ages and masses, necessarily restricted by angular resolution to low l-modes, will allow studies of the internal structure of stars at various stages of evolution. Such studie

A. Buzzoni, M. Chavez, M. L. Malagnini, C. Morossi

The Lick Fe5015, Fe5270, Fe5335, Mgb and Mg2 indices are presented for 139 candidate SMR stars of different luminosity class studied in Malagnini et al. (2000). Evidence is found for a standard (i.e. [Mg/Fe]~0) Mg vs. Fe relative abundance. Both the Worthey et al. (1994) and Buzzoni et al. (1992, 1994) fitting functions are found to suitably match the data a

G. Narayanan, G. Moriarty-Schieven, C. K. Walker, H. M. Butner

We present the detection of kinematic infall signatures towards the Class 0 protostellar system SMM4 in the Serpens cloud core. We have observed the dense molecular gas towards the embedded source using millimeter and submillimeter line transitions of density sensitive molecular tracers. High signal-to-noise ratio maps obtained in HCO+ J=1-0, J=3-2, and J=4-

Stefanie Komossa

It has long been suggested that supermassive black holes in non-active galaxies might be tracked down by occasional tidal disruptions of stars on nearly radial orbits. A tidal disruption event would reveal itself by a luminous flare of electromagnetic radiation. Theorists argued that the convincing detection of such a tidal disruption event would be the obse

S. B. Howell

Recent theoretical efforts have made predictions for the masses of the secondary stars in cataclysmic variables. Accurate observational determinations for M$_2$ are sparse and typically have uncertainties near $\pm$0.1M$_{\odot}$. How well do theory and observation agree?

Kate G. Isaak, Robert S. Priddey, Richard G. McMahon, Alain Omont

We present initial results of a new, systematic search for massive star-formation in the host galaxies of the most luminous and probably most massive z>=4 radio-quiet quasars (M(B) <= -27.5; nuL(nu)(1450Ang)>10^13Lsun). A total of 38 z>=4 radio-quiet quasars have been observed at the JCMT using SCUBA at 850microns: 8 were detected (>3sigma) with S(850microns

M. Rodriguez, R. L. M. Corradi, A. Mampaso

We present low and high resolution long-slit spectra of three bipolar planetary nebulae (PNe) with bright central cores: A79, He2-428 and M1-91. He2-428 and M1-91 have high density (from 10^3.3 to 10^6.5 cm^-3) unresolved nebular cores that indicate that strong mass loss/exchange phenomena are occurring close to their central stars. An F0 star is found at th

L. Magrini, M. Perinotto, R. L. M. Corradi, A. Mampaso

A 34 x 34 arcmin field centred on the spiral galaxy M81 has been searched for emission-line objects using the prime focus wide field camera (WFC) of the 2.54 m Isaac Newton Telescope (La Palma, Spain). A total of 171 candidate planetary nebulae (PNe) are found, 54 of which are in common with the ones detected by Jacoby et al. (1989). The behaviour of PNe exc

M. Cervino, D. Valls-Gabaud, V. Luridiana, J. M. Mas-Hesse

In terms of statistical fluctuations, stellar population synthesis models are only asymptotically correct in the limit of a large number of stars, where sampling errors become asymptotically small. When dealing with stellar clusters, starbursts, dwarf galaxies or stellar populations within pixels, sampling errors introduce a large dispersion in the predicted

H. Navasardian, A. R. Petrosian, M. Turatto, E. Cappellaro

In order to investigate the influence of the environment on the supernova (SN) production we have performed a statistical investigation of the SNe discovered in isolated galaxies, in pairs and in groups of galaxies. 22 SNe in 18 isolated galaxies, 48 SNe in 40 galaxies members of 37 pairs and 211 SNe in 170 galaxies members of 116 groups have been selected a

Kaspar von Braun, Mario Mateo

We report on the discovery and analysis of 14 short-period variable stars in the field of the southern globular cluster NGC 3201, located within roughly two magnitudes on either side of the main-sequence turnoff. 11 of these variable stars are eclipsing binaries, one is an RR Lyrae, and two are thus far unclassified systems. Among the eclipsing binary stars,

James S. Bullock, Andrey V. Kravtsov, Pedro Colin

We compare the specific angular momentum profiles of virialized dark halos in cold dark matter (CDM) and warm dark matter (WDM) models using high-resolution dissipationless simulations. The simulations were initialized using the same set of modes, except on small scales, where the power was suppressed in WDM below the filtering length. Remarkably, WDM as wel

Witold Maciejewski, Peter J. Teuben, Linda S. Sparke, James M. Stone

We report here results of high-resolution hydrodynamical simulations of gas flows in barred galaxies, with a focus on gas dynamics in the central kiloparsec. In a single bar with an Inner Lindblad Resonance, we find either near-circular motion of gas in the nuclear ring, or a spiral shock extending towards the galaxy center, depending on the sound speed in t

Maurice H. P. M. van Putten

Cosmological gamma-ray bursts (GRBs) are probably powered by systems harboring a rotating black hole. These may result from hypernovae or black hole-neutron star coalescence. We identify short/long bursts with hyper- and suspended-accretion states around slowly/rapidly spinning black holes. Baryon poor jets, as input to the observed GRB/afterglow emissions,

Hugo E. Schwarz, Romano L. M. Corradi, Rodolfo Montez

We present [OIII]500.7nm and Halpha+[NII] images and long-slit, high resolution echelle spectra in the same spectral regions of Sa2--237, a possible bipolar planetary nebula. The image shows a bipolar nebula of about 34&#34; extent, with a narrow waist, and showing strong point symmetry about the central object, indicating it&#39;s likely binary nature. The

Michel Zamboni-Rached, Erasmo Recami, Hugo E. Harnandez-Figueroa

By a generalized bidirectional decomposition method, we obtain many new Superluminal localized solutions to the wave equation (for the electromagnetic case, in particular) which are suitable for arbitrary frequency bands; various of them being endowed with finite total energy. We construct, among the others, an infinite family of generalizations of the so-ca

Daniel M. Kaplan

Starting from elementary concepts, muon-beam cooling is defined, and the techniques by which it can be accomplished introduced and briefly discussed.

Eytan Katzav

I analyze the Nonlocal Conserved Kardar-Parisi-Zhang (NCKPZ) equation with spatially correlated noise. This equation is also known as the Nonlocal Molecular Beam Epitaxy (NMBE) equation andv was originally suggested to study the effect of the long-range nature of interactions coupled with spatially correlated noise on the dynamics of a volume conserving surf

Nikita O. Agasian, Dmitri Antonov

The (2+1)D Georgi-Glashow (or Polyakov) model with the additional fundamental massless quarks is explored at finite temperature. In the case of vanishing Yukawa coupling, it is demonstrated that the interaction of a monopole and an antimonopole in the molecule via quark zero modes leads to the decrease of the Berezinsky-Kosterlitz-Thouless critical temperatu

Alexei Borodin, Grigori Olshanski

The infinite-dimensional unitary group U(infinity) is the inductive limit of growing compact unitary groups U(N). In this paper we solve a problem of harmonic analysis on U(infinity) stated in the previous paper math/0109193. The problem consists in computing spectral decomposition for a remarkable 4-parameter family of characters of U(infinity). These chara

Joerg Evers, Christoph H. Keitel

We describe the resonance fluorescence spectrum of an atomic three-level system where two of the states are coupled by a single monochromatic laser field. The influence of the third energy level, which interacts with the two laser-coupled states only via radiative decays, is studied in detail. For a suitable choice of parameters, this system gives rise to a

A. C. Aguilar, A. Mihara, A. A. Natale

We compare phenomenological values of the frozen QCD running coupling constant ($α_s$) with two classes of solutions obtained through nonperturbative Schwinger-Dyson equations. We use these same solutions with frozen coupling constants as well as their respective nonperturbative gluon propagators to compute the QCD prediction for the asymptotic pion form fac

Fran De Aquino

It was demonstrated (gr-qc/9910036) that the gravitational and inertial masses are correlated by an adimensional factor, which depends on the incident (or emitted)radiation upon the particle. There is a direct correlation between the radiation absorbed(or radiated) by the particle and its gravitational mass, independently of the inertial mass. Only in the ab

Olga Choustova

We apply methods of quantum mechanics for mathematical modeling of price dynamics at the financial market. We propose to describe behavioral financial factors (e.g., expectations of traders) by using the pilot wave (Bohmian) model of quantum mechanics. Trajectories of prices are determined by two financial potentials: classical-like $V(q)$ (&#34;hard&#34; ma

Amine Asselah, Pablo A. Ferrari

We consider the symmetric simple exclusion process on Z^d, for d>= 5, and study the regularity of the quasi-stationary measures of the dynamics conditionned on not occupying the origin. For each ρ\in ]0,1[, we establish uniqueness of the density of quasi-stationary measures in L^2(d\nur), where \nur is the stationary measure of density ρ. This, in turn, perm

Oleg Andreev, Tassilo Ott

We compute the one-loop corrections to the tachyon potentials in both, bosonic and supersymmetric, cases by worldsheet methods. In the process, we also get some insight on tachyon condensation from the viewpoint of closed string modes and show that there is an instability due to the closed string tachyon in the bosonic case.

A. B. Henriques, R. G. Moorhouse

The variation of the perturbative 3-curvature parameter, ζ, is investigated in the period of reheating after inflation. The two-field model used has the inflaton, with an extra scalar field coupled to it, and non-linear effects of both fields are included as well as a slow decay mechanism into the hydrodynamic fluid of the radiation era. Changes in ζoccur an

D. H. Correa, G. S. Lozano, E. F. Moreno, F. A. Schaposnik

We study the problem of a charged particle in the presence of a uniform magnetic field plus a vortex in noncommutative planar space considering the two possible non-commutative extensions of the corresponding Hamiltonian, namely the ``fundamental'' and the ``antifundamental'' representations. Using a Fock space formalism we construct eigenfunctions and eigen

S. Nonnenmacher, M. R. Zirnbauer

An attempt is made to clarify the ballistic non-linear sigma model formalism recently proposed for quantum chaotic systems, by the spectral determinant Z(s)=Det(1-sU) of a quantized map U element of U(N). More precisely, we study the correlator omega_U(s)=<|Z(st)|^2> (averaging t over the unit circle). Identifying the group U(N) as one member of a dual pair

D. Wilson, H. Jeong, M. S. Kim

Quantum nonlocality is tested for an entangled coherent state, interacting with a dissipative environment. A pure entangled coherent state violates Bell&#39;s inequality regardless of its coherent amplitude. The higher the initial nonlocality, the more rapidly quantum nonlocality is lost. The entangled coherent state can also be investigated in the framework

Lucia Reining, Valerio Olevano, Angel Rubio, Giovanni Onida

Starting from the many-body Bethe-Salpeter equation we derive an exchange-correlation kernel $f_{xc}$ that reproduces excitonic effects in bulk materials within time-dependent density functional theory. The resulting $f_{xc}$ accounts for both self-energy corrections and the electron-hole interaction. It is {\em static}, {\em non-local} and has a long-range

H. J. W. Müller-Kirsten, Jian-zu Zhang, Yunbo Zhang

A recent analytic test of the instanton method performed by comparing the exact spectrum of the Lam${\acute e}$ potential (derived from representations of a finite dimensional matrix expressed in terms of $su(2)$ generators) with the results of the tight--binding and instanton approximations as well as the standard WKB approximation is commented upon. It is

G. Duplancic, H. Pasagic, M. Praszalowicz, J. Trampetic

Nonleptonic $Ω^{-}$ decay branching ratios are estimated by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate the nonperturbative matrix elements. The model has only one free parameter, namely the Skyrme charge $e$, which is fixed through the experimental values of the octet-decuplet mass splitting $

UKQCD Collaboration, C. M. Maynard

We present results for the leptonic decays of heavy-light mesons in the quenched approximation and a preliminary result for f_Ds with dynamical fermions for Nf=2. We examine the systematic effects of extrapolating the decay constants from the charm to the bottom quark mass, and find this extrapolation to be under control. We present a preliminary result for

Andrew R Liddle, A N Taylor

We consider inflaton potential reconstruction in the context of the simplest braneworld scenario, where both the Friedmann equation and the form of scalar and tensor perturbations are modified at high energies. We derive the reconstruction equations, and analyze them analytically in the high-energy limit and numerically for the general case. As previously sh

Kari Enqvist, Martin S. Sloth

We consider the pre-big bang scenario with a massive axion field which starts to dominate energy density when oscillating in an instanton-induced potential and subsequently reheats the universe as it decays into photons, thus creating adiabatic CMB perturbations. We find that the fluctuations in the axion field can give rise to a nearly flat spectrum of adia

P. Valageas

We investigate the properties of the standard perturbative expansions which describe the early stages of the dynamics of gravitational clustering. We show that for hierarchical scenarios with no small-scale cutoff perturbation theory always breaks down beyond a finite order $q_+$. Besides, the degree of divergence increases with the order of the perturbative

V. E. Lyubovitskij, Th. Gutsche, Amand Faessler, R. Vinh Mau

We apply the perturbative chiral quark model to the study of the low-energy pi-N interaction. Using an effective chiral Lagrangian we reproduce the Weinberg-Tomozawa result for the S-wave pi-N scattering lengths. After inclusion of the photon field we give predictions for the electromagnetic O(p^2) low-energy couplings of the chiral perturbation theory effec

S. M. Kuzenko, I. N. McArthur

The bosonic parts of D3-brane actions in AdS(5) backgrounds are known to have symmetries which are field-dependent extensions of conformal transformations of the worldvolume coordinates. Using the coset space SU(2,2|1)/SO(4,1), we apply the method of nonlinear realizations to construct a four-dimensional N = 1 off-shell supersymmetric action which has a gene

Tatsuhiko Yagasaki

Suppose M is a noncompact connected smooth 2-manifold without boundary and let D(M)_0 denote the identity component of the diffeomorphism group of M with the compact-open C^infty-topology. In this paper we investigate the topological type of D(M)_0 and show that D(M)_0 is a topological ell_2-manifold and it has the homotopy type of the circle if M is the pla

A. J. M. Medved

We consider the dynamical stability of a static brane model that incorporates a three-index antisymmetric tensor field and has recently been proposed as a possible solution to the cosmological constant problem. Ultimately, we are able to establish the existence of time-dependent, purely gravitational perturbations. As a consequence, the static solution of in

H. Nikolic

In a recent paper [Phys. Rev. A 61, 022117 (2000)], quant-ph/9906034, A. Peres argued that quantum mechanics is consistent with special relativity by proposing that the operators that describe time evolution do not need to transform covariantly, although the measurable quantities need to transform covariantly. We discuss the weaknesses of this proposal.

Paul Benioff

Earlier work on modular arithmetic of k-ary representations of length L of the natural numbers in quantum mechanics is extended here to k-ary representations of all natural numbers, and to integers and rational numbers. Since the length L is indeterminate, representations of states and operators using creation and annihilation operators for bosons and fermio

H. E. Tureci, A. D. Stone

We show that when a narrow beam is incident upon a dielectric interface near the critical angle for total internal reflection it will be transmitted into the far-field with an angular deflection from the direction predicted by Snell&#39;s Law, due to a phenomenon we call &#34;Fresnel Filtering&#34;. This effect can be quite large for the parameter range rele

C. L. Korpa, A. E. L. Dieperink, R. G. E. Timmermans

We analyze low-energy hyperon-nucleon scattering using an effective field theory in next-to-leading order. By fitting experimental cross sections for laboratory hyperon momenta below 200 MeV/c and using information from the hypertriton we determine twelve contact-interaction coefficients. Based on these we discuss the low-density expansion of hyperon mass sh

N. Kaiser

We calculate in baryon chiral perturbation theory the relativistic $1/M^2$-corrections to the leading order two-pion exchange diagrams. We give explicit expressions for the corresponding one-loop NN-amplitudes in momentum space. The resulting isovector central and isoscalar spin-spin and tensor NN-amplitudes involve non-static terms proportional to the squar

W. Glockle, H. Kamada, J. Golak, A. Nogga

Some present day results for few-nucleon bound state, two-nucleon correlation functions and scattering observables are briefly reviewed. The old idea of the Coulomb sum rule as a way to extract the pp correlation function is reconsidered. It appears to be an ideal case to probe properties of the density operator and the ground state wave functions without di

K. Krishan, P. Banerjee, R. Bhattacharya

The odd $A$ proton drip line nucleus $^{17}$F has been studied in a semi-microscopic model which couples proton quasiparticle motion to the vibrational motion of the neighbouring even-even $^{18}$Ne core. The experimentally observed low lying excitation spectrum, electric quadrupole moment, magnetic dipole moment, $B(E1)$ and $B(E2)$ values have been fairly

J. L. Nagle

The Relativistic Heavy Ion Collider (RHIC) facility at Brookhaven National Laboratory is the first accelerator specifically constructed for the study of very hot and dense nuclear matter. At sufficiently high temperature, nuclear matter is expected to undergo a phase transition to a quark-gluon plasma. It is the specific goal of the field to study the nature

David Eppstein

We show that geometric thickness and book thickness are not asymptotically equivalent: for every t, there exists a graph with geometric thickness two and book thickness >= t.

Grigori Olshanski

The goal of harmonic analysis on a (noncommutative) group is to decompose the most `natural&#39; unitary representations of this group (like the regular representation) on irreducible ones. The infinite-dimensional unitary group U(infinity) is one of the basic examples of `big&#39; groups whose irreducible representations depend on infinitely many parameters

Bouchta Bouali

In this paper, we discuss when Aut($\cal A$) and Homeo(Prim($\cal A$)) are homeomorphic, where $\cal A$ is a $C^*$-algebra.

Pedro Freitas

We prove that the algebraic connectivity a(G) of a graph embedded on a nonplanar surface satisfies a Heawood-type result. More precisely, it is shown that the algebraic connectivity of a surface S, defined as the supremum of a(G) over all graphs that can be embedded in S, is equal to the chromatic number of S. Furthermore, and with the possible exception of

C. Bouzar, R. Chaili

We show that the multi--quasi-ellipticity is a necessary and sufficient condition for the property of elliptic iterates to be hold for multi-quasi-homogenous differential operators.

Nico M. Temme

Several uniform asymptotics expansions of the Weber parabolic cylinder functions are considered, one group in terms of elementary functions, another group in terms of Airy functions. Starting point for the discussion are asymptotic expansions given earlier by F.W.J. Olver. Some of his results are modified to improve the asymptotic properties and to enlarge t

Amparo Gil, Javier Segura, Nico M. Temme

Integral representations are considered of solutions of the inhomogeneous Airy differential equation $w&#39;&#39;-z w=\pm1/π$. The solutions of these equations are also known as Scorer functions. Certain functional relations for these functions are used to confine the discussion to one function and to a certain sector in the complex plane. By using steepest

D. Burns, S. Halverscheid, R. Hind

We study the canonical complexifications of non-compact Riemannian symmetric spaces G/K by the Grauert tube construction. We determine the maximal such complexification, a domain already constructed in another context by Akhiezer and Gindikin (Math. Ann., 1990), and show that this domain is Stein. We show there is an alternative for a G-invariant complexific

Nico M. Temme, Jose L. Lopez

Many limits are known for hypergeometric orthogonal polynomials that occur in the Askey scheme. We show how asymptotic representations can be derived by using the generating functions of the polynomials. For example, we discuss the asymptotic representation of the Meixner-Pollaczek, Jacobi, Meixner, and Krawtchouk polynomials in terms of Laguerre polynomials

Radu Pantilie, John C. Wood

We give a new construction of Ricci-flat self-dual metrics which is a natural extension of the Gibbons--Hawking ansatz. We also give characterisations of both these constructions, and explain how they come from harmonic morphisms.

J. Tharrats

The distribution of a given sequence in the set of all sequences with n ones and m = M - n zeros are found by relating the problem to the partitions of a natural number in m natural summands, taking into account the order. The formulas obtained have many applications both in Physics and Mathematics. Examples discussed in the present paper are: non Markovian

Peter Polyakov

We prove that for an induced CR structure on a compact, generic, regular 3-pseudoconcave CR submanifold ${\bold M}\subset{\bold G}$, of a complex manifold ${\bold G}$, satisfying condition $\dim H^1({\bold M}, T^{\prime}({\bold G})|_{\bold M})=0$ all the close CR structures are induced by close embeddings.

Jean-Pierre Demailly, Mihai Paun

The goal of this work is give a precise numerical description of the Kähler cone of a compact Kähler manifold. Our main result states that the Kähler cone depends only on the intersection form of the cohomology ring, the Hodge structure and the homology classes of analytic cycles: if $X$ is a compact Kähler manifold, the Kähler cone $\cK$ of $X$ is one of th

R. Aguilar, D. M. Burns

To every real analytic Riemannian manifold M there is associated a complex structure on a neighborhood of the zero section in the real tangent bundle of M. This structure can be uniquely specified in several ways, and is referred to as a Grauert tube. We say that a Grauert tube is entire if the complex structure can be extended to the entire tangent bundle.