June 2000 arXiv papers — page 18

A. Alzati, E. Ballico, G. Ottaviani

The theorem of Mather on generic projections of smooth algebraic varieties is also proved for the singular ones.

Juan Gonzalez-Meneses, Luis Paris

We show that Vassiliev invariants separate braids on a closed oriented surface, and we exhibit an universal Vassiliev invariant for these braids in terms of chord diagrams labeled by elements of the fundamental group of the considered surface.

Mark Hovey

(This is an updated version; following an idea of Voevodsky, we have strengthened our results so all of them apply to one form of motivic homotopy theory). We give two general constructions for the passage from unstable to stable homotopy that apply to the known example of topological spaces, but also to new situations, such as motivic homotopy theory of sch

Eugene Lerman

We describe a contact analog of the symplectic cut construction. As an application we show that the group of contactomorphisms for a particular overtwisted contact structure on the three sphere contains countably many nonconjugate two tori.

Justin Khoury, Paul J. Steinhardt, Daniel Waldram

We consider the cosmology of a pair of domain walls bounding a five-dimensional bulk space-time with negative cosmological constant, in which the distance between the branes is not fixed in time. Although there are strong arguments to suggest that this distance should be stabilized in the present epoch, no such constraints exist for the early universe and th

S. -H. Henry Tye, Ira Wasserman

We consider a model with two parallel (positive tension) 3-branes separated by a distance $L$ in 5-dimensional spacetime. If the interbrane space is anti-deSitter, or is not precisely anti-deSitter but contains no event horizons, the effective 4-dimensional cosmological constant seen by observers on one of the branes (chosen to be the visible brane) becomes

G. J. Stephenson,, T. Goldman, B. H. J. McKellar

The interference of charge-changing interactions, weaker than the V-A Standard Model (SM) interaction and having a different Lorentz structure, with that SM interaction, can, in principle, produce effects near the end point of the Tritium beta decay spectrum which are of a different character from those produced by the purely kinematic effect of neutrino mas

K. Maltman, C. E. Wolfe

Strong isospin-breaking (IB) effects in CP-even and CP-odd K-->pi pi decays are computed to next-to-leading order (NLO) in the chiral expansion. The impact of these corrections on the magnitude of the Delta I=1/2 Rule and on the size of the IB correction, Omega_IB, to the gluonic penguin contribution to epsilon'/epsilon are discussed.

K. Dick, M. Freund, P. Huber, M. Lindner

We discuss the potential to determine leading oscillation parameters, the value and the sign of Δm^2_{31}, as well as the magnitude of \sin^2 2θ_{13} using a conventional wide band neutrino beam pointing to water or ice Cherenkov neutrino detectors known as ``Neutrino Telescopes''. We find that precision measurements of Δm^2_{31} and θ_{23} are possi

Egor Babaev

In this paper we discuss symmetry breakdown in NJL model at low N_c. In particular we propose a modified NJL model that displays a symmetry breakdown and also at finite temperatures under certain conditions the chiral fluctuations in this model give rise to a phase analogous to pseudogap phase of strong-coupling and low carrier density superconductors.

V. V. Anisovich, V. A. Nikonov

In the framework of the dispersion relation N/D-approach, we restore the low-energy pi-pi (IJ^{PC}=00^{++})-wave amplitude sewing it with the previously obtained K-matrix solution for the region 450-1900 MeV. The restored N/D-amplitude has a pole on the second sheet of the complex-s plane near the pi-pi threshold, that is the light sigma meson.

Hai-Yang Cheng, B. Tseng

For hadronic two-body decays of charmed mesons involving $η$ or $η'$, resonance-induced final-state interactions (FSI) that mimic the W-exchange or the W-annihilation topology can play an essential role. In particular, the decays $D^0\to\bar K^0η'$ and $D^+\toπ^+η$, which are largely suppressed in the absence of FSI, are enhanced dramatically by reso

Jonathan Dorfan

In this report, the status of the PEP-II machine and the BaBar detector are presented. Performance will be presented as of the Lepton Photon Conference (August 1999) with subsequent performance levels footnoted as appropriate.

Beate Naroska

New results on elastic (exclusive) production of vector mesons are presented, mainly on J/ψand phi mesons with emphasis on an interpretation of the data within pQCD.

Yasusada Nambu

We investigated the back reaction of cosmological perturbations on the evolution of the universe using the second order perturbation of the Einstein's equation. To incorporate the back reaction effect due to the inhomogeneity into the framework of the cosmological perturbation, we used the renormalization group method. The second order zero mode solution

Manny Rayner, Beth Ann Hockey, Frankie James, Elizabeth O. Bratt

Systems now exist which are able to compile unification grammars into language models that can be included in a speech recognizer, but it is so far unclear whether non-trivial linguistically principled grammars can be used for this purpose. We describe a series of experiments which investigate the question empirically, by incrementally constructing a grammar

Beth Ann Hockey, Manny Rayner, Frankie James

When people develop something intended as a large broad-coverage grammar, they usually have a more specific goal in mind. Sometimes this goal is covering a corpus; sometimes the developers have theoretical ideas they wish to investigate; most often, work is driven by a combination of these two main types of goal. What tends to happen after a while is that th

Manny Rayner, Beth Ann Hockey, Frankie James

We describe an architecture for spoken dialogue interfaces to semi-autonomous systems that transforms speech signals through successive representations of linguistic, dialogue, and domain knowledge. Each step produces an output, and a meta-output describing the transformation, with an executable program in a simple scripting language as the final result. The

Frankie James, Manny Rayner, Beth Ann Hockey

Speech is becoming increasingly popular as an interface modality, especially in hands- and eyes-busy situations where the use of a keyboard or mouse is difficult. However, despite the fact that many have hailed speech as being inherently usable (since everyone already knows how to talk), most users of speech input are left feeling disappointed by the quality

Manny Rayner, Beth Ann Hockey, Frankie James

We describe an architecture for implementing spoken natural language dialogue interfaces to semi-autonomous systems, in which the central idea is to transform the input speech signal through successive levels of representation corresponding roughly to linguistic knowledge, dialogue knowledge, and domain knowledge. The final representation is an executable pr

J. D. Naud, Leonid P. Pryadko, S. L. Sondhi

We study edge dynamics in the presence of interlayer tunneling, parallel magnetic field, and various types of disorder for two infinite sequences of quantum Hall states in symmetric bilayers. These sequences begin with the 110 and 331 Halperin states and include their fractional descendants at lower filling factors; the former is easily realized experimental

C. J. Olson, C. Reichhardt, R. T. Scalettar, G. T. Zimanyi

We examine metastable and transient effects both above and below the first-order disorder driven decoupling line in a 3D simulation of magnetically interacting pancake vortices. We observe pronounced transient and history effects as well as supercooling and superheating between the ordered and disordered phases. In the disordered supercooled state as a funct

Haranath Ghosh, Alok Shukla, Sumit Mazumdar

Electron-electron interactions in general lead to both ground state and excited state confinement. We show, however, that in phenyl-substituted polyacetylenes electron-electron interactions cause enhanced delocalization of quasiparticles in the optically excited state from the backbone polyene chain into the phenyl groups, which in turn leads to enhanced con

Lev I. Deych, A. Yamilov, A. A. Lisyansky

We analytically study optical properties of several types of defects in Bragg multiple quantum well structures. We show that a single defect leads to two local polariton modes in the photonic band gap. These modes lead to peculiarities in reflection and transmission spectra. Detailed recommendations for experimental observation of the studied effects are giv

Michael Holicki, Holger Fehske, Ralph Werner

Within the random phase approximation to the spin-Peierls transition two parameter regimes of phonon softening and hardening are present. Magneto-elastic excitations are discussed in detail for phonons coupled to the exactly solvable model of XY spin chains for both regimes, leading to a modified interpretation of the 30 cm$^{-1}$ mode in CuGeO$_3$. Frustrat

Ralph Werner

A regularization method is presented to deduce dynamic correlation functions from exact diagonalization calculations. It is applied to dimer-dimer correlation functions in quantum spin chains relevant for the description of spin-Peierls systems. Exact results for the XY model are presented. The analysis draws into doubt that the dimer-dimer correlation funct

Revaz Ramazashvili

I study the quasiparticle level correlations in a grain of a weakly disordered d-wave superconductor, and show that, in a wide intermediate energy range, they are characterized by a novel type of universal behavior.

Andrea Montanari, Marc Mezard

We introduce a model of thermalized conformations in space of RNA -or single stranded DNA- molecules, which includes the possibility of hairpin formation. This model contains the usual secondary structure information, but extends it to the study of one element of the ternary structure, namely the end-to-end distance. The computed force-elongation characteris

Niels Boye Olsen, Tage Christensen, Jeppe C. Dyre

Dielectric relaxation measurements on supercooled triphenyl phosphite show that at low temperatures time-temperature superposition (TTS) is accurately obeyed for the primary (alpha) relaxation process. Measurements on 6 other molecular liquids close to the calorimetric glass transition indicate that TTS is linked to an $ω^{-1/2}$ high-frequency decay of the

Doriano Brogioli, Alberto Vailati

Recent experimental and theoretical works have shown that giant fluctuations are present during diffusion in liquid systems. We use linearized fluctuating hydrodynamics to calculate the net mass transfer due to these non equilibrium fluctuations. Surprisingly the mass flow turns out to coincide with the usual Fick's one. The renormalization of the hydrod

Ludovic Berthier, Jean-Louis Barrat, Jorge Kurchan

We investigate the dynamics of spin glasses from the `rheological' point of view, in which aging is suppressed by the action of small, non-conservative forces. The different features can be expressed in terms of the scaling of relaxation times with the magnitude of the driving force, which plays the role of the critical parameter. Stated in these terms,

Margit Steiner, Robert A Smith

We develop a consistent treatment of disorder effects in strong coupling superconductors. We use two different approaches, starting either from above or below the transition temperature, and show their equivalence. The normal state approach is a natural extension of a recently developed non-perturbative resummation technique. For the superconducting state we

J. Neuefeind, H. E. Fischer, W. Schröer

We present hard X-ray and neutron diffraction measurements on the polar fluorocarbons HCF3 and H3CF under supercritical conditions and for a range of molecular densities spanning about a factor of ten. The Levesque-Weiss-Reatto inversion scheme has been used to deduce the site-site potentials underlying the measured partial pair distribution functions. The o

J. Takeya, I. Tsukada, Yoichi Ando, T. Masuda

The thermal conductivity κof Cu_1-xMg_xGeO_3 is measured in magnetic fields up to 16 T. At the transition field H_c to the high-field incommensurate (I) phase, κabruptly decreases. While κof the pure CuGeO_3 is enhanced with the application of higher magnetic fields, an anomalous plateau feature shows up in the κ(H) profile in the I phase of the Mg-doped sam

Masao Sako, Steven M. Kahn, Frits Paerels, Duane A. Liedahl

We present a detailed X-ray spectral analysis of the Circinus Galaxy using archival data obtained with the ASCA satellite. The spectrum shows numerous emission lines in the soft X-ray band from highly ionized ions, as well as Compton reflection and fluorescent lines from neutral or near-neutral matter. We analyze the spectrum in the context of a self-consist

Daniel Stern

I discuss two programs to study radio-loud quasars at high (z>4) redshift. Quasars are the most luminous, non-transient objects known and are observed to the earliest cosmic epochs. At lower redshifts, radio-loud quasars are associated with host galaxies having deVaucoleurs profiles. By association, identifying and studying a sample of high-redshift, radio-l

Rory Barnes, Thomas Quinn

Because of the high eccentricities (~0.3) of two of the possible planets about the star Upsilon Andromeda, the stability of the system requires careful study. We present results of 1000 numerical simulations which explore the orbital parameter space as constrained by the observations. The orbital parameters of each planet are chosen from a Gaussian error dis

L. A. Anchordoqui, T. P. McCauley, T. Paul, S. Reucroft

We present a detailed simulation of the performance of water Cerenkov detectors suitable for use in the Pierre Auger Observatory. Using {\sc geant4}, a flexible object-oriented simulation program, including all known physics processes, has been developed. The program also allows interactive visualization, and can easily be modified for any experimental setup

L. Chen, M. Geffert, J. J. Wang, K. Reif

We present the first proper motion study of M10 (NGC6254). Absolute proper motions of about 532 stars in the field of the globular cluster M10 were determined with respect to Hipparcos and ACT reference stars. In addition to photographic plates of Bonn and Shanghai also wide field CCD observations as second epoch plates were used. The wide field CCD observat

Saleem Zaroubi

Galaxy peculiar velocity data provide important dynamical clues to the structures obscured by the Zone of Avoidance (hereafter, ZOA) with resolution >~ 500km/s. This indirect probe complements the very challenging approach of directly mapping of the distribution of galaxies behind the Milky Way. In this work, the Wiener filter method is applied to reconstruc

F. Douchin, P. Haensel

The boundary between the solid crust, assumed to be in complete thermodynamic equilibrium (cold catalyzed matter), and the liquid core of a neutron star is studied using Skyrme SLy effective N-N interactions. An approximate value of the density at the inner edge of the crust is obtained from the threshold for the instability of homogeneous $npe$ matter with

V. R. Chitnis, P. N. Bhat

Atmospheric Čerenkov Technique is an established methodology to study $TeV$ energy gamma rays. However the challenging problem has always been the poor signal to noise ratio due to the presence of abundant cosmic rays. Several ingenious techniques have been employed to alleviate this problem, most of which are centred around the Čerenkov image characteristic

G. D. Chagelishvili, A. G. Tevzadze, M. Goossens

In this paper we report on the nonresonant conversion of convectively unstable linear gravity modes into acoustic oscillation modes in shear flows. The convectively unstable linear gravity modes can excite acoustic modes with similar wave-numbers. The frequencies of the excited oscillations may be qualitatively higher than the temporal variation scales of th

Yan-Jie Xue, Xiang-Ping Wu

We present an extensive study of the double beta model for the X-ray surface brightness profiles of clusters, and derive analytically the gas density and total masses of clusters under the hydrostatic equilibrium hypothesis. It is shown that the employment of the double beta model instead of the conventional single beta model can significantly improve the go

H. J. Deeg, F. Favata, Eddington Science Team

From simulations of transit observations, it is found that the detectability of extrasolar planets depends only on two parameters: The signal-to-noise ratio during a transit, and the number of data points observed during transits. All other physical parameters describing transit configurations (planet and star size, orbital period, orbital half axis, latitud

J. F. Desmurs, V. Bujarrabal, F. Colomer, J. Alcolea

We have performed VLBA observations of the SiO v=1 and v=2 J=1-0 masers in two AGB stars, TX Cam and IRC +10011. We confirm the ring-like spatial distribution, previously found in several AGB objects, as well as the tangential polarization pattern, already reported for TX Cam. Both properties, that seem to be systematic in this kind of objects, are character

T. Furusho, N. Y. Yamasaki, T. Ohashi, Y. Saito

ASCA observation of a region containing a Class 0 protostar, IRAS 20386+6751 in the L1157 dark cloud, has been carried out. The protostar was not detected, and the 95% upper limit to the luminosity depends on assumed Nh : Lx(0.5-10 keV) < 1.1e31 erg/s for Nh = 1e23 cm^-2. A Class I protostar in L1152, IRAS 20353+6742, in the same field was also undetected wi

Patrick A. Woudt, Renee C. Kraan-Korteweg

A deep optical galaxy search behind the southern Milky Way and a subsequent redshift survey of the identified obscured galaxies traces clusters and superclusters into the deepest layers of Galactic foreground extinction (A_B <= 3^m - 5^m). In the Great Attractor region, we have identified a low-mass cluster (the Centaurus-Crux cluster) at (l, b, v, sigma) =

Xiang-Ping Wu, Yan-Jie Xue

The cusped NFW universal density profile suggested by typical CDM models has been challenged in recent years by the discoveries of the soft cores for a broad range of masses from dwarf galaxies to clusters of galaxies. It is thus desirable that a new, analytic model would instead become available for virialized dark halos. One promising candidate is probably

Xiang-Ping Wu

(Abridged)We present a combined analysis of mass estimates in the central cores of galaxy clusters from the strong lensing, the X-ray measurements and the universal density profile (NFW). Special attention is paid to the questions (1)whether the previously claimed mass discrepancy between the strong lensing and X-ray measurements is associated with the prese

Yanqin Wu, Christopher D. Matzner, Phil Arras

Rossby waves (r-modes) have been suggested as a means to regulate the spin periods of young or accreting neutron stars, and also to produce observable gravitational wave radiation. R-modes involve primarily transverse, incompressive motions of the star&#39;s fluid core. However, neutron stars gain crusts early in their lives: therefore, r-modes also imply sh

J. Dyks, B. Rudak

We use Monte Carlo approach to study the energetics of electrons accelerated in a pulsar polar gap. As energy-loss mechanisms we consider magnetic Compton scattering of thermal X-ray photons and curvature radiation. The results are compared with previous calculations which assumed that changes of electron energy occurred smoothly according to approximations

Jose Miguel Pasini, Patricio Cordero

We study a 1-D granular gas of point-like particles not subject to gravity between two walls at temperatures T_left and T_right. The system exhibits two distinct regimes, depending on the normalized temperature difference Delta = (T_right - T_left)/(T_right + T_left): one completely fluidized and one in which a cluster coexists with the fluidized gas. When D

Rajesh Gopakumar, Shiraz Minwalla, Nathan Seiberg, Andrew Strominger

Open string theories can be decoupled from closed strings and gravity by scaling to the critical electric field. We propose dual descriptions for the strong coupling limit of these NCOS (Non-Commutative Open String) theories in six or fewer spacetime dimensions. In particular, we conjecture that the five-dimensionsal NCOS theory at strong coupling, is a theo

Konstantin N. Borozdin, William C. Priedhorsky

Using ROSAT PSPC data, we have performed several tests aimed at understanding the origin of the soft X-ray spectral component detected from the bulge of M31. We find that a significant soft component in the spectrum of the bulge is spatially correlated with the unresolved X-ray emission near the core of M31, which is probably a hot interstellar medium or per

Zurab Kakushadze

We consider a recent proposal to solve the cosmological constant problem within the context of brane world scenarios with infinite volume extra dimensions. In such theories bulk can be supersymmetric even if brane supersymmetry is completely broken. The bulk cosmological constant can therefore naturally be zero. Since the volume of the extra dimensions is in

M. Novello, J. Barcelos-Neto, J. M. Salim

We present a model for a spacetime dependent cosmological {\it constant}. We make a realization of this model based on a possible quantum aspects of the initial stage of the universe and relate the cosmological constant with the chiral anomaly.

Ue-Li Pen, Jounghun Lee, Uros Seljak

We report a tentative detection of spin correlations in the Tully catalogue of nearby galaxies. We define a simple but nontrivial spin correlation function, and find an analytic estimate of it in the frame of the linear perturbation theory. Then, we present the observed spin correlation signal from the Tully galaxies with error bars. The three dimensional sp

J. M. Lawrence, P. S. Riseborough, C. H. Booth, J. L. Sarrao

We compare the results of measurements of the magnetic susceptibility Chi(T), the linear coefficient of specific heat Gamma(T)=C(T)/T and 4f occupation number nf(T) for the intermediate valence compounds YbXCu4 (X = Ag, Cd, In, Mg, Tl, Zn) to the predictions of the Anderson impurity model, calculated in the non-crossing approximation (NCA). The crossover fro

Christoph Simon, Caslav Brukner, Anton Zeilinger

It has recently been questioned whether the Kochen-Specker theorem is relevant to real experiments, which by necessity only have finite precision. We give an affirmative answer to this question by showing how to derive hidden-variable theorems that apply to real experiments, so that non-contextual hidden variables can indeed be experimentally disproved. The

H. Ding, J. R. Engelbrecht, Z. Wang, J. C. Campuzano

In conventional superconductors, the pairing energy gap (Δ) and superconducting phase coherence go hand-in-hand. As the temperature is lowered, both the energy gap and phase coherence appear at the transition temperature T_c. In contrast, in underdoped high-T_c superconductors (HTSCs), a pseudogap appears at a much higher temperature T^*, smoothly evolving i

K. G. McClements, A. Thyagaraja

Magnetohydrodynamic (MHD) and two-fluid quasi-neutral equilibria with azimuthal symmetry, gravity and arbitrary ratios of (nonrelativistic) flow speed to acoustic and Alfven speeds are investigated. In the two-fluid case, the mass ratio of the two species is arbitrary, and the analysis is therefore applicable to electron-positron plasmas. The methods of deri

S. T. Scully, F. W. Stecker

It has been suggested that cosmological gamma-ray bursts (GRBs) can produce the observed flux of cosmic rays at the highest energies. However, recent studies of GRBs indicate that their redshift distribution likely follows that of the average star formation rate and that GRBs were more numerous at high redshifts. As a consequence, we show that photomeson pro

A. L. Rakhmanov, K. I. Kugel, Ya. M. Blanter, M. Yu. Kagan

A simple model is proposed to calculate resistivity, magnetoresistance, and noise spectrum in non-metallic phase-separated manganites containing small metallic droplets (magnetic polarons). The system is taken to be far from the percolation transition into a metallic state. It is assumed that the charge transfer occurs due to electron tunneling from one drop

A. Barrat, J. Kurchan, V. Loreto, M. Sellitto

Can one construct a thermodynamics for compact, slowly moving powders and grains? A few years ago, Edwards proposed a possible step in this direction, raising the fascinating perspective that such systems have a statistical mechanics of their own, different from that of Maxwell, Boltzmann and Gibbs, allowing us to have some information while still ignoring d

John N. Bahcall, Plamen I. Krastev, Alexei Yu. Smirnov

Neutrino oscillation scenarios predict correlations, and zones of avoidance, among measurable quantities such as spectral energy distortions, total fluxes, time dependences, and flavor content. The comparison of observed and predicted correlations will enhance the diagnostic power of solar neutrino experiments. A general test of all presently-allowed (two ne

Ansar Fayyazuddin, Douglas J. Smith

We study a Hanany-Witten set-up relevant to N = 2 superconformal field theories. We find the exact near-horizon solution for this 11-dimensional system which involves intersecting M5-branes. The metric describes a warped product of AdS_5 with a manifold with SU(2) x U(1) isometry.

Yu. S. Kalashnikova, D. S. Kuzmenko

The large distance behaviour of the adiabatic hybrid potentials is studied in the framework of the QCD string model. The calculated spectra are shown to be the result of interplay between potential-type longitudinal and string-type transverse vibrations.

Berthold Stech

A model is considered in which the scale of the heavy singlet neutrinos is a few orders of magnitude below the grand unification scale and where right-handed vector bosons play still a negligible role. In a basis with diagonal up-quark and Dirac-neutrino mass matrices it is assumed that the heavy neutrino mass matrix has only zero elements in its diagonal, i

Maarten Baes, Herwig Dejonghe, Sven De Rijcke

Observations have demonstrated the presence of substantial amounts of interstellar dust in elliptical galaxies, most of which is believed to be distributed diffusely over the galaxy. Absorption by dust grains has a major impact on the transfer of stellar radiation, and affects the projection of each physical (and kinematic) quantity. In a previous paper, we

Gert Brodin, Mattias Marklund, Peter K. S. Dunsby

We consider the interactions of a strong gravitational wave with electromagnetic fields using the 1+3 orthonormal tetrad formalism. A general system of equations are derived, describing the influence of a plane fronted parallel (pp) gravitational wave on a cold relativistic multi-component plasma. We focus our attention on phenomena that are induced by terms

R. Folch, T. Tóth-Katona, Á. Buka, J. Casademunt

We study viscous fingering of an air-nematic interface in a radial Hele-Shaw cell when periodically switching on and off an electric field, which reorients the nematic and thus changes its viscosity, as well as the surface tension and its anisotropy (mainly enforced by a single groove in the cell). We observe undulations at the sides of the fingers which cor

R. G. Bower, A. J. Benson, C. G. Lacey, C. M. Baugh

We present a new model for the X-ray properties of the intracluster medium that explicitly includes heating of the gas by the energy released during the evolution of cluster galaxies. We calculate the evolution of clusters by combining the semi-analytic model of galaxy formation of Cole et al. with a simple model for the radial profile of the intracluster ga

P. Shukla, A. K. Mohanty, S. K. Gupta, Marcelo Gleiser

The effect of subcritical hadron bubbles on a first-order quark-hadron phase transition is studied. These subcritical hadron bubbles are created due to thermal fluctuations, and can introduce a finite amount of phase mixing (quark phase mixed with hadron phase) even at and above the critical temperature. For reasonable choices of surface tension and correlat

Shijun Yoshida, Umin Lee

We investigate the properties of $r$-mode oscillations of a slowly rotating neutron star with a solid crust, by taking account of the effects of the Coriolis force. For the modal analysis we employ three-component neutron star models that are composed of a fluid core, a solid crust and a surface fluid ocean. For the three-component models, we find that there

Seiji Terashima

In this paper we explicitly show the equivalence between the non-Abelian Born-Infeld action, which was proposed by Tseytlin as an effective action on several D-branes, and its noncommutative counterpart for slowly varying fields. This confirms the equivalence between the two descriptions of the D-branes using an ordinary gauge theory with a constant B field

Yu. S. Kalashnikova, A. V. Nefediev

Strong mesonic decays are studied in the framework of the &#39;t Hooft model for the two-dimensional QCD in the axial gauge. Special attention is payed to the processes with pions in the final state involved and the low energy theorems have been checked including the &#34;Adler zero&#34;. It is demonstrated explicitly that in the chiral limit any three-meson

Y. M. Cho, D. G. Pak

The one-loop effective action of QED obtained by Euler and Heisenberg and by Schwinger has been expressed by an asymptotic perturbative series which is divergent. In this letter we present a non-perturbative but convergent series of the effective action. With the convergent series we establish the existence of the manifest electric-magnetic duality in the on

Sanefumi Moriyama

It is widely believed that via the Seiberg-Witten map, the linearly realized BPS equation in the non-commutative space is related to the non-linearly realized BPS equation in the commutative space in the zero slope limit. We show that the relation also holds without taking the zero slope limit as is expected from the arguments of the BPS equation for the non

Vassily S. Beskin, Leonid Malyshkin

A magnetohydrodynamic model is constructed for a cylindrical jet immersed in an external uniform magnetic field. It is shown that, as in the force-free case, the total electric current within the jet can be zero. The particle energetics and the magnetic field structure are determined in a self-consistent way; all jet parameters depend on the physical conditi

M. Fleischhauer

The recently proposed idea to generate entanglement between photon states via exchange interactions in an ensemble of atoms (J.D. Franson and T.B. Pitman, Phys. Rev. A 60, 917 (1999) and J.D. Franson et al., (quant-ph/9912121)) is discussed using an S-matix approach. It is shown that if the nonlinear response of the atoms is negligible and no additional atom

F. Saif, G. Alber, V. Savichev, W. P. Schleich

Quantum revivals are investigated for the dynamics of an atom in a driven gravitational cavity. It is demonstrated that the external driving field influences the revival time significantly. Analytical expressions are presented which are based on second order perturbation theory and semiclassical secular theory. These analytical results explain the dependence

G. Alber, A. Delgado, I. Jex

Universal two-particle entanglement processes are analyzed in arbitrary dimensional Hilbert spaces. On the basis of this analysis the class of possible optimal universal entanglement processes is determined whose resulting output states do not contain any separable states. It is shown that these processes form a one-parameter family. For all Hilbert space di

Dong Pyo Chi, Jinsoo Kim, Soojoon Lee

We construct a quantum algorithm that performs function-dependent phase transform and requires no initialization of an ancillary register. The algorithm recovers the initial state of an ancillary register regardless of whether its state is pure or mixed. Thus we can use any qubits as an ancillary register even though they are entangled with others and are oc

Bao-Sen Shi, Yun-Kun Jiang, Guang-Can Guo

In this paper, we present a scheme for quantum key distribution, in which different-frequency photons are used to encode the key. Thses different-frequency photons are produced by an acoustic-optical modulator and two kinds of narrow filters . This scheme may be implementable in practice.

G. M. Tosi-Beleffi, M. Presi, C. Palma, D. Boschi

We demonstrate experimentally that in a centrosymmetric paraelectric non-stationary boundary conditions can dynamically halt the intrinsic instability of quasi-steady-state photorefractive self-trapping, driving beam evolution into a stable oscillating two-soliton-state configuration.

Amir H. Abbassi, Amir M. Abbassi

A specific form of the inertial law is presented by which we can have some deeper insight into the essence of mass and inertia. In this modified theory, there is no need to keep the concept of absolute space and Newton&#39;s third law as principles. By introducing a convenient form for gravitational law the coupling constant G becomes a function of inertial

Martin Servin, Gert Brodin

In the presence of an external magnetic field, wake fields generated by a short laser pulse can propagate out of the plasma, and thereby provide information about the electron density profile. A method for reconstructing the density profile from a measured wake field spectrum is proposed and a numerical example is given. Finally, we compare our proposal with

M. Gyulassy, P. Levai, I. Vitev

A systematic expansion of the induced inclusive gluon radiation associated with jet production in a dense QCD plasma is derived using a reaction operator formalism. Analytic expressions for the transverse momentum and light-cone momentum distributions are derived to all orders in powers of the gluon opacity of the medium, $Nσ_g/A=L/λ_g$. The reaction operato

G. I. Barenblatt, M. Bertsch, A. E. Chertock, V. M. Prostokishin

The equation $$ \partial_tu=u\partial^2_{xx}u-(c-1)(\partial_xu)^2 $$ is known in literature as a qualitative mathematical model of some biological phenomena. Here this equation is derived as a model of the groundwater flow in a water absorbing fissurized porous rock, therefore we refer to this equation as a filtration-absorption equation. A family of self-s

Estelle L. Basor, Yang Chen, Harold Widom

The purpose of this paper is to compute asymptotically Hankel determinants for weights that are supported in a semi-infinite interval.The main idea is to reduce the problem to determinants of other operators whose determinant asymptotics are well known.

Vassil M. Vassilev

In the case of transversely only loaded shallow shells, the nonlinear Donnell-Mushtari-Vlasov theory for large deflection of isotropic thin elastic shells leads to a system of two coupled nonlinear forth-order partial differential equations known as Marguerre&#39;s equations. This system involves two arbitrary elements -- the curvature tensor of the shell mi

Arturo Magidin

We study the strong, weak, and special amalgamation bases in the varieties of nilpotent groups of class two and exponent n, where n is odd. The main result is a characterization of the special amalgamation bases for these varieties. We also characterize the weak and strong bases. For special amalgamation bases, we show that there are groups which are special

B. M. Brown, M. S. P. Eastham

We are concerned with the Sturm-Liouville problem on the half line. We show that when the potential $q$ is subject only to power decay at infinity the $L^2$ solution may be continued into a sector of the so-called un-physical sheet. This gives rise to resonance free regions and the numerical estimation of resonances outside these regions.

Alexander V. Karabegov, Martin Schlichenmaier

We give a complete identification of the deformation quantization which was obtained from the Berezin-Toeplitz quantization on an arbitrary compact Kaehler manifold. The deformation quantization with the opposite star-product proves to be a differential deformation quantization with separation of variables whose classifying form is explicitly calculated. Its

Z. Petric

It is proved that MacLane&#39;s coherence results for monoidal and symmetric monoidal categories can be extended to some other categories with multiplication; namely, to relevant, affine and cartesian categories. All results are formulated in terms of natural transformations equipped with ``graphs&#39;&#39; (g-natural transformations), and corresponding morp

Marco A. Farinati

We study the derived invariance of the cohomology theories $Hoch^*$, $H^*$ and $HC^*$ associated to coalgebras over a field. We prove a theorem characterizing derived equivalences. As particular cases, it describes the two following situations: 1) $f:C\to D$ a quasi-isomorphism of differential graded coalgebras, 2) the existence of a &#34;cotilting&#34; bico

Massimo Gobbino, Maria Giovanna Mora

We approximate functionals depending on the gradient of $u$ and on the behaviour of $u$ near the discontinuity points, by families of non-local functionals where the gradient is replaced by finite differences. We prove pointwise convergence, $Γ$-convergence, and a compactness result which implies, in particular, the convergence of minima and minimizers.

Stephen D. Miller

We develop a partial trace formula which circumvents some technical difficulties in computing the Selberg trace formula for the quotient $SL_3({\Z})\backslash SL_3({\R})/SO_3({\R})$. As applications, we establish the Weyl asymptotic law for the discrete Laplace spectrum and prove that almost all of its cusp forms are tempered at infinity. The technique shows

Maks A. Akivis, Vladislav V. Goldberg

An n-dimensional submanifold X of a projective space P^N (C) is called tangentially degenerate if the rank of its Gauss mapping γ: X ---> G (n, N) satisfies 0 < rank γ< n. The authors systematically study the geometry of tangentially degenerate submanifolds of a projective space $P^N (\mathbf{C})$. By means of the focal images, three basic types of submanifo