June 2000 arXiv papers — page 5

E. Shriberg, A. Stolcke, D. Hakkani-Tur, G. Tur

A crucial step in processing speech audio data for information extraction, topic detection, or browsing/playback is to segment the input into sentence and topic units. Speech segmentation is challenging, since the cues typically present for segmenting text (headers, paragraphs, punctuation) are absent in spoken language. We investigate the use of prosody (in

Wolfgang Ketterle

A recent paper, Quantum backaction of optical observations on Bose-Einstein condensates by U. Leonhardt, T. Kiss, and P. Piwnicki, Eur. Phys. J. D7, 413 (1999), emphasized that the limit of dispersive imaging of Bose-Einstein condensates with off-resonant light is not residual absorption, but a different form of quantum backaction of the probe light. This no

R. Hilfer

A fractional diffusion equation based on Riemann-Liouville fractional derivatives is solved exactly. The initial values are given as fractional integrals. The solution is obtained in terms of $H$-functions. It differs from the known solution of fractional diffusion equations based on fractional integrals. The solution of fractional diffusion based on a Riema

A. Zheludev, M. Kenzelmann, S. Raymond, E. Ressouche

Inelastic neutron scattering is used to study transverse-polarized magnetic excitations in the quasi-one-dimensional S=1/2 antiferromagnet BaCu_2Si_2O_7, where the saturation value for the Néel order parameter is $m_0=0.12 μ_{\rm B}$ per spin. At low energies the spectrum is totally dominated by resolution-limited spin wave-like excitations. An excitation co

Enrico Celeghini, Mario Rasetti

The role of background in bosonic quantum statistics is discussed in the frame of a new approach in terms of coherent states. Bosons are indeed detected in different physical situations where they exhibit different and apparently unconnected properties. Besides Bose gas we consider bosons in particle physics and bosons in harmonic traps. In particle physics

Z. Neda, E. Ravasz, T. Vicsek, Y. Brechet

We discuss in detail a human scale example of the synchronization phenomenon, namely the dynamics of the rhythmic applause. After a detailed experimental investigation, we describe the phenomenon with an approach based on the classical Kuramoto model. Computer simulations based on the theoretical assumptions, reproduce perfectly the observed dynamics. We arg

Alexander D. Mirlin

The supersymmetry method has proven to be a very powerful tool of study of the statistical properties of energy levels and eigenfunctions in disordered and chaotic systems. The aim of these lectures is to present a tutorial introduction to the method, as well as an overview of the recent developments.

Ya. M. Blanter, A. D. Mirlin

We calculate average magnetopolarizability of an isolated metallic sample at frequency $ω$ comparable to the mean level spacing $Δ$. The frequency dependence of the magnetopolarizability is described by a universal function of $ω/Δ$.

J. S. Stiessberger, W. Zwerger

By considering the stability of potential flow of a superfluid around large obstacles of size R, we derive an analytical result for the critical velocity which is of order v_c \sim \hbar / mR, scaling inversely with obstacle size, in contrast to what is obtained from a Landau criterion. Our results are compared with numerical solutions of the Gross-Pitaevski

K. Held, R. Bulla

We show analytically that, under certain assumptions, the periodic Anderson model and the Hubbard model become equivalent within the dynamical mean field theory for quasiparticle weight Z -> 0. A scaling relation is derived which is validated numerically using the numerical renormalization group at zero temperature and quantum Monte Carlo simulations at fini

S. N. Artemenko, S. V. Remizov

We calculate suppression of inter- and intralayer superconducting currents due to equilibrium phase fluctuations and find that, in contrast to a recent prediction, the effect of thermal fluctuations cannot account for linear temperature dependence of the superfluid density in high-Tc superconductors at low temperatures. Quantum fluctuations are found to domi

G. Seibold, J. Lorenzana

We develop a time-dependent Gutzwiller approximation (GA) for the Hubbard model analogous to the time-dependent Hartree-Fock (HF) method. The formalism incorporates ground state correlations of the random phase approximation (RPA) type beyond the GA. Static quantities like ground state energy and double occupancy are in excellent agreement with exact results

S. M. Apenko

We further analyze the recently proposed criterion, according to which a superfluid transition occurs whenever the r.m.s. displacement of a particle from its initial position in imaginary time reaches a certain fraction of the interparticle distance. The critical temperature $T_λ$ is expressed in terms of the single particle mobility. Within the Drude approx

A. Barrat, V. Loreto

Stimulated by recent experimental results, we simulate ``temperature''-cycling experiments in a model for the compaction of granular media. We report on the existence of two types of memory effects: short-term dependence on the history of the sample, and long-term memory for highly compact (aged) systems. A natural interpretation of these results is

J. Albrecht, S. Leonhardt, H. Kronmueller

Low-angle grain boundaries with misorientation angles theta < 5 degrees in optimally doped thin films of YBCO are investigated by magnetooptical imaging. By using a numerical inversion scheme of Biot-Savart&#39;s law the critical current density across the grain boundary can be determined with a spatial resolution of about 5 micrometers. Detailed investigati

E. C. Bastone, P. R. Silva

We use an effective field model (transverse Ising model) to describe the dependence on the temperature of the energy gap of some two-dimensional $(2-D)$ superconducting systems. The order parameter of this model is put in a direct correspondence with that of the Ising model. Then, we use the exact relations for the spontaneous magnetization of the Ising mode

Jizhong Lou, Shaojin Qin, Tai-Kai Ng, Zhaobin Su

The manifestations of topological effects in finite antiferromagnetic Heisenberg chains is examined by density matrix renormalization group technique in this paper. We find that difference between integer and half-integer spin chains shows up in ground state energy per site when length of spin chain is longer than $\simξ$, where $ξ\sim\exp(πS)$ is a spin-spi

J. J. Garcia-Ripoll, V. M. Perez-Garcia

We study the generation of vortices in rotating axially elongated magneto-optical traps, a situation which has been realized in a recent experiment (K. W. Madison, F. Chevy, W. Wohlleben, J. Dalibard, Phys. Rev. Lett. 84, 806 (2000)). We predict that at a critical frequency the condensate experiences a symmetry breaking and changes from a convex cloud to a s

Matthew Shetrone, Eric Sandquist

We have analyzed high-resolution spectra of relatively cool blue stragglers and main sequence turnoff stars in the old open cluster M67 (NGC 2682). We attempt to identify blue stragglers whose spectra are least contaminated by binary effects (contamination by a binary companion or absorption by circumstellar material). These ``best&#39;&#39; stragglers have

George A. Baker,

Recent experimental results find strong indications that the universe is flat, while other experimental results from supernovae Ia observations have been interpreted to show that, not only that there is an accelerating expansion of the universe, but also that the universe is strongly curved. By means of a recently proposed metric, I am able to show that the

V. Hradecky, C. Jones, R. H. Donnelly, S. G. Djorgovski

We constrain the mass-to-light ratios, gas mass fractions, baryon mass fractions and the ratios of total to luminous mass for a sample of eight nearby relaxed galaxy groups and clusters: A262, A426, A478, A1795, A2052, A2063, A2199 and MKW4s. We use ASCA spatially resolved spectroscopic X-ray observations and ROSAT PSPC images to constrain the total and gas

D. G. York

The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g&#39; about 23 magni

Bin Wang, Elcio Abdalla, Takeshi Osada

We calculated the entropy of a class of inhomogeneous dust universes. Allowing spherical symmetry, we proposed a holographic principle by reflecting all physical freedoms on the surface of the apparent horizon. In contrast to flat homogeneous counterparts, the principle may break down in some models, though these models are not quite realistic. We refined fr

J. S. Sanders, A. C. Fabian, S. W. Allen

We present an analysis of X-ray colour maps of the cores of clusters of galaxies, formed from the ratios of counts in different X-ray bands. Our technique groups pixels lying between contours in an adaptively-smoothed image of a cluster. We select the contour levels to minimize the uncertainties in the colour ratios, whilst preserving the structure of the ob

P. O. Petrucci, G. Henri, G. Pelletier

We investigate the effect of pair creation on a shock structure. Actually, particles accelerated by a shock can be sufficiently energetic to boost, via Inverse Compton process for example, surrounding soft photons above the rest mass electron energy and thus to trigger the pair creation process. The increase of the associated pair pressure is thus able to di

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

We test accurate models of Comptonisation spectra over BeppoSAX observations of Seyfert galaxies focusing on the long look at NGC 5548. The hot plasma temperature derived with these models is significantly higher than that obtained fitting the same data with a power law plus high energy cut off model for the continuum. This is due to the fact that in anisotr

R. Falomo, R. Scarpa, A. Treves, C. M. Urry

We report on the optical properties of a sample of 30 BL Lac host galaxies in the redshift range $0.03<z<0.2$, as derived from HST observations. All galaxies are fully resolved in the WFPC2 (F702W filter) images, allowing a quantitative analysis in two dimensions. Most and possibly all these galaxies have characteristics very similar to those of ``normal&#39

M. Tucci, E. Carretti, S. Cecchini, R. Fabbri

We derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36 < l < 10^3 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to l \simeq 10^3 are approximated very well by power laws with slope coefficients \simeq 1.4, quit

P. Marigo

The luminosity evolution of stars with highly condensed cores surrounded by nuclear-burning shell(s) is analytically investigated with the aid of homology relations. With respect to earlier works using a similar approach (e.g. Refsdal & Weigert 1970; Kippenhahn 1981), the major improvement is that we derive all the basic dependences (i.e. on core mass, core

Aurore Bacmann, Philippe Andre, Jean-Loup Puget, Alain Abergel

We present the results of a mid-infrared (7 micron) imaging survey of a sample of 24 starless dense cores carried out at an angular resolution of 6 arcsec with the ISOCAM camera aboard the Infrared Space Observatory (ISO). The targeted cores are believed to be pre-stellar in nature and to represent the initial conditions of low-mass, isolated star formation.

Leo Stodolsky

We briefly discuss the history of suggestions for time- of-flight effects due to non-zero neutrino mass and a recent proposal that such effects can be used to determine the parameters of cosmology. With neutrinos there is potentially a much deeper ``look back time&#39;&#39; than with photons. We note a new point, that if future large scale neutrino detection

G. Chabrier, I. Baraffe

Since the discovery of the first bona-fide brown dwarfs and extra-solar planets in 1995, the field of low mass stars and substellar objects has considerably progressed, both from theoretical and observational viewpoints.Recent developments in the physics entering the modeling of these objects have led to significant improvements in the theory and to a better

Jan B. Rehm, Karsten Jedamzik

We present detailed numerical calculations of the light element abundances synthesized in a Universe consisting of matter- and antimatter- domains, as predicted to arise in some electroweak baryogenesis scenarios. In our simulations all relevant physical effects, such as baryon-antibaryon annihilations, production of secondary particles during annihilations,

Gabriele Giovannini, Luigina Feretti, Federica Govoni

New sensitive VLA observations confirm the existence of halo and relic sources in 6 Abell clusters where a diffuse emission was found in the NVSS. We find evidence that the frequency of clusters with halos and relics is larger in clusters with high X-ray luminosity. The evidence that the occurrence of a halo source is larger at high redshifts is marginal.

Luigina Feretti

The number of known diffuse radio sources in clusters of galaxies has grown in recent years, making it possible to derive statistical properties of these sources and of the hosting clusters. We show that diffuse sources are associated with X-ray luminous clusters which have undergone recent merger processes. The radio and X-ray structures are often similar,

J. G. Robertson, K. Taylor, I. K. Baldry, P. R. Gillingham

We are proposing a new spectrograph (ATLAS) which would revolutionise intermediate-dispersion observations at the AAT. Based on the new technology of Volume Phase Holographic gratings, and using transmission optics, ATLAS offers high throughput and a wide field (24&#39;). It will be ideally suited to extensive surveys of faint objects. It has been designed w

Jing Li, David Jewitt, Barry LaBonte

We use time series observations from the SOHO and Yohkoh spacecraft to study solar polar rays. Contrary to our expectations, we find that the rays are associated with active regions on the sun and are not features of the polar coronal holes. They are extended, hot plasma structures formed in the active regions and projected onto the plane of the sky above th

Andreas Heithausen, Fabian Walter

Using the IRAM 30m radio telescope we have mapped the tidal arm feature south-east of NGC3077 where we recently detected molecular gas in the CO (J=1-0) and (2-1) transitions. We find that the molecular gas is much more extended than previously thought (several kpc). The CO emission can be separated into at least 3 distinct complexes with equivalent radii be

C. Armendariz-Picon, V. Mukhanov, Paul J. Steinhardt

We recently introduced the concept of &#34;k-essence&#34; as a dynamical solution for explaining naturally why the universe has entered an epoch of accelerated expansion at a late stage of its evolution. The solution avoids fine-tuning of parameters and anthropic arguments. Instead, k-essence is based on the idea of a dynamical attractor solution which cause

N. Masetti

We present BVRI light curves of the afterglow of GRB000301C, one of the brightest ever detected at a day time scale interval after GRB trigger. The monitoring started 1.5 days after the GRB and ended one month later. Inspection of the extremely well sampled R band light curve and comparison with BVI data has revealed a complex behavior, with a long term flux

M. J. Konstantinovic, M. Isobe, Y. Ueda

In the ac polarized Raman spectra of NaV2O5 we have found anomalous phonon broadening, and an energy shift of the low-frequency mode as a function of the temperature. These effects are related to the breaking of translational symmetry, caused by electrical disorder that originates from the fluctuating nature of the V {4.5+} valence state of vanadium. The str

P. Mayr

We describe heterotic string and M-theory realizations of the Randall-Sundrum (RS) scenario with $\cx N=2$ and $\cx N=1$ supersymmetry in the bulk. Supersymmetry can be broken only on the world brane, a scenario that has been proposed to account for the smallness of the cosmological constant. An interesting prediction from string duality is the generation of

Ichiro Oda

After presenting string-like solutions with a warp factor to Einstein&#39;s equations, we study localization of various spin fields on a string-like defect in a general space-time dimension from the viewpoint of field theory. It is shown that spin 0 and 2 fields are localized on a defect with the exponentially decreasing warp factor. Spin 1 field can be also

M. Suzuki

We examine the so-called rho-pi puzzle of the psi(2S) decay by incorporating two inputs: One is the relative phase between the one-photon and the gluon decay amplitude, and the other is a possible anomaly in the inclusive nonelectromagnetic decay rate of psi(2S). We propose the possibility that in the psi(2S) decay a hadronic decay process of long distance o

Lowell S. Brown, R. F. Sawyer

We have reexamined the electromagnetic corrections to the weak interaction rates for the transformation of neutrons to protons, and protons to neutrons, in the early universe, before freeze-out. We derive compact expressions for these rates in terms of thermal expectation values of products of fields, and we give explicit constructions of the terms to order

C. Biagini, D. L. Maslov, M. Yu. Reizer, L. I. Glazman

It is shown that a strong magnetic field applied to a bulk metal induces a Luttinger-liquid phase. This phase is characterized by the zero-bias anomaly in tunneling: the tunneling conductance scales as a power-law of voltage or temperature. The tunneling exponent increases with the magnetic field as BlnB. The zero-bias anomaly is most pronounced for tunnelin

S. Barannikov

We introduce a generalization of variations of Hodge structures living over moduli spaces of non-commutative deformations of complex manifolds. Hodge structure associated with a point of such moduli space is an element of Sato type grassmanian of semi-infinite subspaces in H^*(X,C)[[h^{-1},h]]. Periods associated with such semi-infinite Hodge structures serv

J. G. Russo, M. M. Sheikh-Jabbari

We investigate new compactifications of OM theory giving rise to a 3+1 dimensional open string theory with noncommutative $x^0$-$x^1$ and $x^2$-$x^3$ coordinates. The theory can be directly obtained by starting with a D3 brane with parallel (near critical) electric and magnetic field components, in the presence of a RR scalar field. The magnetic parameter pe

Claudio A. Scrucca, Marco Serone

We investigate in the simplest compact D=4 N=1 Type IIB orientifold models the sigma-model symmetry suggested by the proposed duality of these models to heterotic orbifold vacua. This symmetry is known to be present at the classical level, and is associated to a composite connection involving untwisted moduli in the low-energy supergravity theory. In order t

G. German, A. de la Macorra, M. Mondragon

We study a supergravity model of inflation with R-symmetry and a single scalar field, the inflaton, slowly rolling away from the origin. The scales of inflation can be as low as the supersymmetry breaking scale of 10^10 GeV or even the electroweak scale of 10^3 GeV which could be relevant in the context of theories with submillimiter dimensions. Exact analyt

Armen Nersessian, George Pogosyan

It is shown, that oscillators on the sphere and the pseudosphere are related, by the so-called Bohlin transformation, with the Coulomb systems on the pseudosphere. The even states of an oscillator yield the conventional Coulomb system on the pseudosphere, while the odd states yield the Coulomb system on the pseudosphere in the presence of magnetic flux tube

I. Chaudhuri, A. Taraphder, S. K. Ghatak

A model incorporating simultaneous superconducting and lattice instabilities has been studied in detail to estimate the nature of coupling and inter-play between them. The phase diagram is obtained in the temperature-filling plane at different values of the parameters of the model. It is found that a pseudogap develops in the distorted phase that inhibits th

Z. Z. Aydin, A. Kandemir, A. U. Yilmazer

We present an outlook for possible R-parity violating SUSY search at gamma-proton and gamma-electron colliders. Single production of third generation slepton/sneutrino through the lambda&#39;-ijk couplings at a gamma-p collider is investigated and compared with the results of the resonant sfermion productions at the existing colliders. Also single sneutrino

J. X. Lu, S. Roy, H. Singh

We study decoupling limits and S-dualities for noncommutative open string/ Yang-Mills theory in a gravity setup by considering an $SL(2,Z)$ invariant supergravity solution of the form ((F, D1), D3) bound state of type IIB string theory. This configuration can be regarded as D3-branes with both electric and magnetic fields turned on along one of the spatial d

Alejandro Rivero

It is argued that properties of Democritus&#39; atoms parallel those of volume forms in differential geometry. This kind of atoms has not &#34;size&#34; of finite magnitude. ----- Se arguye que las propiedades de los atomos de Democrito son paralelas a las de sus formas de volumen en geometria diferencial. Este tipo de atomos no tiene tamanno de magnitud fin

Joseph O'Rourke

Define a ``slice'' curve as the intersection of a plane with the surface of a polytope, i.e., a convex polyhedron in three dimensions. We prove that a slice curve develops on a plane without self-intersection. The key tool used is a generalization of Cauchy's arm lemma to permit nonconvex ``openings'' of a planar convex chain.

Da-Shin Lee, Kin-Wang Ng

We study the production of photons through the non-equilibrium relaxation of a disoriented chiral condensate. We propose that to search for non-equilibrium photons in the direct photon measurements of heavy-ion collisions can be a potential test of the formation of disoriented chiral condensates.

J. Kwiecinski, B. Ziaja

Spin dependent structure function $g_1^γ(x,Q^2)$ of the polarised photon is analysed within the formalism based upon the unintegrated spin dependent parton distributions incorporating the LO Altarelli-Parisi evolution and the double $ln^2(1/x)$ resummation at low values of Bjorken parameter x. We analyse the effects of the double $ln^2(1/x)$ resummation on t

A. E. Lobanov, O. S. Pavlova

Electromagnetic radiation from an uncharged spin 1/2 particle with an anomalous magnetic moment moving in the classical electromagnetic external field originates from quantum spin-flip transitions. Although this process has a purely quantum nature, it was observed for certain particular external field configurations that, when quantum recoil is neglected, th

Anastasia Doikou

We consider the case of an integrable quantum spin chain with &#34;soliton non-peserving&#34; boundary conditions. This is the first time that such boundary conditions have been considered in the spin chain framework. We construct the transfer matrix of the model, we study its symmetry and we find explicit expressions for its eigenvalues. Moreover, we derive

A. Díaz-Sánchez, A. Pérez-Garrido

The relaxation of the specific heat and the entropy to their equilibrium values is investigated numerically for the three-dimensional Coulomb glass at very low temperatures. The long time relaxation follows a stretched exponential function, $f(t)=f_0\exp[-(t/τ)^β]$, with the exponent $β$ increasing with the temperature. The relaxation time follows an Arrheni

J. Engels, S. Holtmann, T. Mendes, T. Schulze

We investigate numerically the three-dimensional O(2) model on 8^3-160^3 lattices as a function of the magnetic field H. In the low-temperature phase we verify the H-dependence of the magnetization M induced by Goldstone modes and determine M in the thermodynamic limit both by extrapolation and by chiral perturbation theory. This enables us to calculate the

Jun-ichi Inoue

Quantum fluctuation is introduced into the Markov random fields (MRF&#39;s) model for image restoration in the context of Bayesian approach. We investigate the dependence of the quantum fluctuation on the quality of BW image restoration by making use of statistical mechanics. We find that the maximum posterior marginal (MPM) estimate based on the quantum flu

Ulrich Mohrhoff

The ABL rule is derived as a tool of standard quantum mechanics. The ontological significance of the existence of objective probabilities is discussed. Objections by Kastner and others to counterfactual uses of the ABL rule are refuted. Metaphysical presumptions leading to such views as Kastner is defending in her Comment are examined and shown to be unwarra

K. K. Nandi, P. M. Alsing, J. C. Evans, T. B. Nayak

The {\it exact} formulation for the effect of the Brans-Dicke scalar field on the gravitational corrections to the Sagnac delay in the Jordan and Einstein frames is presented for the first time. The results completely agree with the known PPN factors in the weak field region. The calculations also reveal how the Brans-Dicke coupling parameter (appears in var

Fumihiko Nakano

We give a simple proof to derive the optimal flux which minimizes the ground state energy in one dimensional Hubbard model, provided the number of particles is even.

Jun-ichi Inoue, Domenico M. Carlucci

We investigate static and dynamic properties of gray-scale image restoration (GSIR) by making use of the Q-Ising spin glass model, whose ladder symmetry allows to take in account the distance between two spins. We thus give an explicit expression of the Hamming distance between the original and restored images as a function of the hyper-parameters in the mea

Ryutaroh Matsumoto, Tomohiko Uyematsu

We generalize the construction of quantum error-correcting codes from GF(4)-linear codes by Calderbank et al. to p^m-state systems. Then we show how to determine the error from a syndrome. Finally we discuss a systematic construction of quantum codes with efficient decoding algorithms.

David J. Fernandez C

Using the modified factorization method introduced by Mielnik, we construct a new class of radial potentials whose spectrum for l=0 coincides exactly with that of the hydrogen atom. A limiting case of our family coincides with the potentials previously derived by Abraham and Moses

Daniel Braun, Fritz Haake, Walter T. Strunz

We consider environment induced decoherence of quantum superpositions to mixtures in the limit in which that process is much faster than any competing one generated by the Hamiltonian $H_{\rm sys}$ of the isolated system. While the golden rule then does not apply we can discard $H_{\rm sys}$. By allowing for simultaneous couplings to different reservoirs, we

F. Popescu

Using the theoretical model of the optical beam-splitter, the interference of the self-phase modulated ultrashort light pulse (SPM-USP) with the coherent one is investigated. It is found that, the choice of the coefficient of transmission of the beam-splitter allows one to get the spectra of quadrature fluctuations with forms of interest to us. It is shown t

L. Fedichkin, M. Yanchenko, K. A. Valiev

As basic elements of the quantum computer - quantum bits (qubits) we offer semiconductor quantum dots containing one electron each and consisting each of two tunnel-connected parts. The numerical solution of a Schroedinger equation with the account of Coulomb field of adjacent electrons shows, that in such structures the realization of a full set of basic lo

Yuri Ozhigov

Call a spectrum of Hamiltonian sparse if each eigenvalue can be quickly restored with accuracy $ε$ from its rough approximation in within $ε_1$ by means of some classical algorithm. It is shown how a behavior of system with sparse spectrum up to time $T=\frac{1-ρ}{14ε}$ can be predicted with fidelity $ρ$ on quantum computer in time $t=\frac{4}{(1-ρ)ε_1}$ plu

Kirk T. McDonald

An analytic solution to the linearized Navier-Stokes equation is given that describes the radial flow of an incompressible, viscous fluid between two parallel, concentric annular plates.

Marijan Kostrun, Matt Mackie, Robin Cote, Juha Javanainen

We study coherent photoassociation, phenomena analogous to coherent optical transients in few-level systems, which may take place in photoassociation of an atomic Bose-Einstein condensate but not in a nondegenerate gas. We develop a second-quantized Hamiltonian to describe photoassociation, and apply the Hamiltonian both in the momentum representation and in

Piotr J. Flatau

The discrete-dipole approximation (DDA) is a flexible technique for computing scattering and absorption by targets of arbitrary geometry. In this paper we perform systematic study of various non-stationary iterative (conjugate gradient) methods in search for the most efficient one in order to solve the system of equations arising in DDA. We document implemen

R. Palit, J. A. Sheikh, Y. Sun, H. C. Jain

A systematic study of the yrast-band structure for the proton-rich, even-even mass-80 nuclei is carried out using projected shell model approach. We describe the the energy spectra, transition quadrupole moments and gyromagnetic factors. The observed variations in energy spectra and transition quadrupole moments in this mass region are discussed in terms of

A. Deloff

We demonstrate that the kernel of the Lippmann-Schwinger equation, associated with interactions consisting of a sum of the Coulomb plus a short range nuclear potential, below threshold becomes degenerate. Taking advantage of this fact, we present a simple method of calculating the effective range function for negative energies. This may be useful in practice

A. Marinov, S. Gelberg, D. Kolb

The reaction 28Si + 181Ta has been studied at E(Lab) = 125 and 135 MeV. Coincidences between high energy particles and various X- and gamma-rays from abnormally long-lived states were observed. e.g. 7.8 - 8.6 MeV alpha-particles with gamma-rays of a superdeformed band, 5.1 - 5.5 MeV alpha-particles with X- and gamma-rays of W, Re, and Pt, and 3.88 MeV partic

Silviu Olariu, Agata Olariu, Yoshiaki Ito, Takeshi Mukoyama

We report cross sections for the direct excitation of gamma-ray transitions up to 200 keV by the transient electromagnetic fields of electrons from a beam, for incident kinetic energies of 500 keV and 5 MeV. The cross sections for the electron activation of gamma-ray fluorescence are of the order of 300 nanobarns for an electron incident kinetic energy of 50

L. Faybusovich, M. Gekhtman

We introduce a family of compatible Poisson brackets on the space of rational functions with denominator of a fixed degree and use it to derive a multi-Hamiltonian structure for a family of integrable lattice equations that includes both the standard and the relativistic Toda lattices.

A. Dreischuh, D. Neshev, G. G. Paulus, F. Grasbon

Theoretical and experimental results on optical ring dark solitary waves are presented, emphasizing the interplay between initial dark beam contrast, phase-shift magnitude, background-beam intensity and saturation of the nonlinearity are presented. The results are found to confirm qualitatively the existing analytical theory and are in agreement with the num

Jian Zhou

We show how to construct an N=1 superconformal vertex algebra (SCVA) from any Riemannian manifold. When the Riemannian manifold has special holonomy groups, we discuss the extended supersymmetry. When the manifold is complex or Kähler, we also generalize the construction to obtain N=2 SCVA&#39;s. We study the BRST cohomology groups of the topological vertex

Bernhard Kroetz

Let $G$ be a connected Lie group and $\hat G$ its unitary dual. We are interested in the part $Λ\subset\hat G$ which corresponds to the unitary highest weight representations of $G$. Then there are several topologies on $Λ$: The euclidean topology $T_E$ which comes from the identification of $Λ$ with the set of highest weights, the induced topology $T_I$ ind

Mikhail Matveev

We show that a Tychonoff discretely star-Lindelof space can have arbitrarily big extent and note that there are consistent examples of normal discretely star-Lindelof spaces with uncountable extent.

Mikhail Matveev

A space X is star-Lindelof provided for every open cover U there is a finite subset A of X such that St(A,U)=X. We show that a Tychonoff star-Lindelof space can have arbitraryly big extent while the extent of a normal star-Lindelof space can not be greater than c.

Mikhail Matveev

We show that it is consistent that for some uncountable cardinal k, all compactifications of the countable discrete space with remainders homeomorphic to $D^k$ are homeomorphic to each other. On the other hand, there are $2^c$ pairwise non-homeomorphic compactifications of the countable discrete space with remainders homeomorphic to $D^c$ (where c is the car

Mikhail Matveev

We answer a question of Yasui. Morever, we show that if a Tychonoff space Y is countably 1-paracompact in every Tychonoff space X that contains Y as a closed subspace then Y is linearly Lindelof.

Axel Gruenrock

The Cauchy- and periodic boundary value problem for the nonlinear Schroedinger equations in $n$ space dimensions [u_t - iΔu = (\nabla \bar{u})^β, |β|=m \ge 2, u(0)=u_0 \in H^{s+1}_x] is shown to be locally well posed for $s > s_c := \frac{n}{2} - \frac{1}{m-1}$, $s \ge 0$. In the special case of space dimension $n=1$ a global $L^2$-result is obtained for NLS

Peter Ozsvath, Zoltan Szabo

We use Heegaard decompositions and the theta divisor on a Riemannian surface to define a three-manifold invariant for rational homology three-spheres. This invariant is defined on the set of $Spin^c$ structures $$ {\hat θ}\colon Spin^c(Y)\longrightarrow Q. $$ In the first part of the paper, we give the definition of the invariant (which builds on the theory

Peter Ozsvath, Zoltan Szabo

In this paper we study an invariant for oriented three-manifolds with $b_1>0$, which is defined using Heegaard splittings and the theta divisor of a Riemann surface. The paper is divided into two parts, the first of which gives the definition of the invariant, and the second of which identifies it with more classical (torsion) invariants of three-manifolds.

Peter Ozsvath, Zoltan Szabo

We demonstrate an obstruction to finding certain splittings of four-manifolds along sufficiently twisted circle bundles over Riemann surfaces, arising from Seiberg-Witten theory. These obstructions are used to show a non-splitting result for algebraic surfaces of general type.

I. Petras, L. Dorcak, I. Kostial

This paper deals with fractional-order controlled systems and fractional-order controllers in the discrete domain. The mathematical description by the fractional difference equations and properties of these systems are presented. A practical example for modelling the fractional-order control loop is shown and obtained results are discussed in conclusion.

Jan Stevens

A tetragonal canonical curve is the complete intersection of two divisors on a scroll. The equations can be written in `rolling factors&#39; format. For such homogeneous ideals we give methods to compute infinitesimal deformations. Deformations can be obstructed. For the case of quadratic equations on the scroll we derive explicit base equations. They are us

Nicola Grillo

I discuss some issues of perturbative quantum gravity, namely of a theory of self-interacting massless spin-2 quantum gauge fields, the gravitons, on flat space-time, in the framework of causal perturbation theory. The central aspects of this approach lie in the construction of the scattering matrix by means of causality and Poincare covariance and in the an

Fotini Markopoulou

We propose that Kreimer&#39;s method of Feynman diagram renormalization via a Hopf algebra of rooted trees can be fruitfully employed in the analysis of block spin renormalization or coarse graining of inhomogeneous statistical systems. Examples of such systems include spin foam formulations of non-perturbative quantum gravity as well as lattice gauge and sp

Alfredo Iorio

A reliable method to construct Supersymmetric Noether currents is presented. As the most important application the central charge of the N=2 Supersymmetric Yang-Mills effective theory, known as Seiberg-Witten (SW) theory, is computed. The analisys is carried out in the SW low energy U(1) effective Sector, as well as in the SW high energy SU(2) effective Sect

D. Chruscinski

We show that the Hamiltonian dynamics of the self-interacting, abelian p-form theory in D=2p+2 dimensional space-time gives rise to the quasi-local structure. Roughly speaking, it means that the field energy is localized but on closed 2p-dimensional surfaces (quasi-localized). From the mathematical point of view this approach is implied by the boundary value

W. F. Kao

Kaluza-Klein approach in an N(=1+3+D)-dimensional Friedmann-Robertson-Walker type space is often adopted in the literature. We derive a compact expression for the Friedmann equation in a (1+3+D)-dimensional space. The redundancy of the associated field equations due to the Bianchi identity is analyzed. We also study the dilaton gravity theory with higher-der

S. V. Molodtsov, A. M. Snigirev, G. M. Zinovjev

We develop the theory of fermion induced phononlike excitations of the instanton liquid. It suggests a mechanism of current quark mass generation which is easily understandable by calculating the corresponding functional integral in the tadpole approximation. We systematically study the quark condensate excitations influenced by the phononlike modes and rede