May 1999 arXiv papers — page 10

Reinhard Alkofer, Steven Ahlig, Lorenz von Smekal

A closed system of equations for the propagators of Landau gauge QCD is obtained in a truncation scheme for their Dyson-Schwinger equations which implements the Slavnov-Taylor identities for the 3-point vertex functions while neglecting contributions from irreducible 4-point correlations. In the pure gauge theory without quarks, non-perturbative solutions fo

O. Borisenko, V. Kushnir

We extend our previous analysis to arbitrary two dimensional SU(N) principal chiral model in a link formulation. A general expression for the second order coefficient of fixed distance correlation function is given in terms of Green functions. This coefficient is calculated for distance 1 and is proven to be path independent. We also study the weak coupling

Mario Campanelli

Driven by new experimental results, in the latest period several new neutrino oscillation experiments have been proposed. I will outline the main ideas behind the different proposals, in particular concerning atmospheric neutrinos and neutrinos from accelerated beams.

S. E. Vigdor

I review progress toward the experimental study of polarized proton collisions at RHIC, at center-of-mass energies of several hundred GeV. The tools under development for these experiments are summarized, with emphasis on the complementarity for the spin program of the two major detectors, PHENIX and STAR. The proposed research program includes measurements

Mark Hayes

Differential cross sections, $dσ/d x_γ^{\rm OBS}$, for dijet photoproduction events with a tagged $D^*$ meson are presented, where $x_γ^{\rm OBS}$ is the fraction of the photon energy contributing to the two highest transverse energy jets. Results on open beauty cross sections (from semileptonic decays) compared to LO Monte Carlo predictions are also present

J. -F. Pascual-Sánchez

Due to the resemblance between Maxwell and the gravitomagnetic equations obtained in the weak field and slow motion limit of General Relativity, one can ask if it is possible to amplify a seed intrinsic rotation or spin motion by a gravitomagetic dynamo, in analogy with the well-known dynamo effect. Using the Galilean limits of the gravitomagnetic equations,

Stefan Riezler

We present a probabilistic model for constraint-based grammars and a method for estimating the parameters of such models from incomplete, i.e., unparsed data. Whereas methods exist to estimate the parameters of probabilistic context-free grammars from incomplete data (Baum 1970), so far for probabilistic grammars involving context-dependencies only parameter

Franz Beil, Glenn Carroll, Detlef Prescher, Stefan Riezler

The paper describes an extensive experiment in inside-outside estimation of a lexicalized probabilistic context free grammar for German verb-final clauses. Grammar and formalism features which make the experiment feasible are described. Successive models are evaluated on precision and recall of phrase markup.

Mats Rooth, Stefan Riezler, Detlef Prescher, Glenn Carroll

We present a technique for automatic induction of slot annotations for subcategorization frames, based on induction of hidden classes in the EM framework of statistical estimation. The models are empirically evalutated by a general decision test. Induction of slot labeling for subcategorization frames is accomplished by a further application of EM, and appli

Iwan Jensen, Anthony J Guttmann

We have developed an improved algorithm that allows us to enumerate the number of self-avoiding polygons on the square lattice to perimeter length 90. Analysis of the resulting series yields very accurate estimates of the connective constant $μ=2.63815852927(1)$ (biased) and the critical exponent $α= 0.5000005(10)$ (unbiased). The critical point is indisting

F. M. Munteanu, Yongmin Kim, C. H. Perry, D. G. Rickel J. A. Simmons

The magnetophotoluminescence (MPL) behavior of a GaAs/Al(0.3)Ga(0.7)As single heterojunction has been investigated to 60T. We observed negatively charged singlet and triplet exciton states that are formed at high magnetic fields beyond the nu=1 quantum Hall state. The variation of the charged exciton binding energies are in good agreement with theoretical pr

H. Schiessel, J. Rudnick, R. Bruinsma, W. M. Gelbart

We present results relevant to the equilibrium organization of DNA strands of arbitrary length interacting with a spherical organizing center, suggestive of DNA-histone complexation in nucleosomes. We obtain a rich phase diagram in which a wrapping state is transformed into a complex multi-leafed, rosette structure as the adhesion energy is reduced. The stat

R. MacKenzie, J. M. Cline

A model unifying superconductivity and antiferromagnetism using an underlying approximate SO(5) symmetry has injected energy into the field of high-temperature superconductivity. This model might lead to a variety of interesting solitons. In this paper, the idea that superconducting vortices may have antiferromagnetic cores is presented, along with the resul

I. S. Aranson, N. B. Kopnin, V. M. Vinokur

We show that vortex nucleation in superfluid $^3$He by rapid thermal quench in the presence of superflow is dominated by a transverse instability of the moving normal-superfluid interface. Exact expressions for the instability threshold as a function of supercurrent density and the front velocity are found. The results are verified by numerical solution of t

M. v. Zimmermann, J. P. Hill, Doon Gibbs, M. Blume

We report resonant x-ray scattering studies of charge and orbital order in Pr_{1-x}Ca_{x}MnO_3 with x=0.4 and 0.5. Below the ordering temperature, T_O=245 K, the charge and orbital order intensities follow the same temperature dependence, including an increase at the antiferromagnetic ordering temperature, T_N. High resolution measurements reveal, however, t

Valeriy V. Ginzburg, Feng Qiu, Marco Paniconi, Gongwen Peng

We simulate the motion of spherical particles in a phase-separating binary mixture. By combining cell dynamical equations with Langevin dynamics for particles, we show that the addition of hard particles significantly changes both the speed and the morphology of the phase separation. At the late stage of the spinodal decomposition process, particles signific

N. G. Almarza, E. Enciso

The fluid - crystal equilibria of polydisperse mixtures of hard spheres have been studied by computer simulation of the solid phase and using an accurate equation of state for the fluid. A new scheme has been developed to evaluate the composition of crystalline phases in equilibrium with a given polydisperse fluid. Some common assumptions in theoretical appr

M. Acharyya, U. Nowak, K. D. Usadel

Motivated by the recent experimental observations [Phys Rev B 57 R11051 (1998)] of transverse spin ordering in FeBr_2 induced by a magnetic field with oblique angle to the easy axis of the system, we performed extensive Monte Carlo simulations of a classical anisotropic Heisenberg model. We have calculated the specific heat and the parallel and perpendicular

Achod Aradian, Elie Raphael, Pierre-Gilles de Gennes

A few years ago, Bouchaud al. introduced a phenomenological model to describe surface flows of granular materials [J. Phys. Fr. I, 4, 1383 (1994)]. According to this model, one can distinguish between a static phase and a rolling phase that are able to exchange grains through an erosion/accretion mechanism. Boutreux et al. [Phys. Rev. E, 58, 4692 (1998)] pro

L. V. Gasparov, D. B. Tanner, D. B. Romero, H. D. Drew

We present infrared and Raman measurements of magnetite (Fe_3O_4). This material is known to undergo a metal-insulator and a structural transition (Verwey transition) at T_V=120K. At temperatures below T_V, we observe a strong gap-like suppression of the optical conductivity below 1000 cm^-1. The structural aspect of the Verwey transition demonstrates itself

Claude de Calan, Flavio S. Nogueira

The gauge dependence of the renormalization group functions of the Ginzburg-Landau model is investigated. The analysis is done by means of the Ward-Takahashi identities. After defining the superconducting order parameter, it is shown that its exponent $β$ is in fact gauge independent. This happens because in d=3 the Landau gauge is the only gauge having a ph

A. Cuccoli, A. Fort, A. Rettori, E. Adam

We study the magnetic relaxation of a system of localized spins interacting through weak dipole interactions, at a temperature large with respect to the ordering temperature but low with respect to the crystal field level splitting. The relaxation results from quantum spin tunneling but is only allowed on sites where the dipole field is very small. At low ti

Hiroki Nakano, Yukitoshi Motome, Masatoshi Imada

Taking the orbital degeneracy of $e_g$ conduction bands and the Coulomb interaction into account in a double-exchange model, we investigate charge dynamics of perovskite Mn oxides by the Lancz$\ddot{\rm o}$s diagonalization method. In the metallic phase near the Mott insulator, it is found that the optical conductivity for a spin-polarized two-dimensional sy

Yutaka Okabe

We apply the exchange Monte Carlo method to the ordering dynamics of the three-state Potts model with the conserved order parameter. Even for the deeply quenched case to low temperatures, we have observed a rapid domain growth; we have proved the efficiency of the exchange Monte Carlo method for the ordering process. The late-stage growth law has been found

A. Satou, Y. O. Nakamura

The ground state property of the alternating spin ladder is studied in the case that the system involves an antiferromagnetic intra-chain interaction as well as two kinds of inter-chain interactions; one is between spins of the same magnitude and the other is between spins with different magnitudes. The calculation has been carried out by the exact diagonali

Yongmin Kim, F. M. Munteanu, C. H. Perry, X. Lee

Coulomb driven, magneto-optically induced electron and hole bound states from a series of heavily doped GaAs/Al(0.3)Ga(0.7)As single heterojunctions (SHJ) are revealed in high magnetic fields. At low magnetic fields (nu > 2), the photoluminescence spectra display Shubnikov de-Haas type oscillations associated with the empty second subband transition. In the

V. S L'vov, Yu. V. L'vov, A. Pomyalov

We found universal anizopropic spectra of acoustic turbulence with the linear dispersion law \bbox{$ω(k) =ck$} within the framework of generalized kinetic equation which takes into account the finite time of three-wave interactions. This anisotropic spectra can assume both scale-invariant and non scale-invariant form. The implications for the evolution of th

Victor S. L'vov, Anna Pomyalov, Itamar Procaccia

The Taylor hypothesis which allows surrogating spatial measurements requiring many experimental probes by time series from one or two probes is examined on the basis of a simple analytic model of turbulent statistics. The main points are as follows: (i) The Taylor hypothesis introduces systematic errors in the evaluation of scaling exponents. (ii) When the m

J. J. Mohr, J. E. Carlstrom, G. P. Holder, W. L. Holzapfel

Interferometric observations of the Sunyaev-Zel'dovich Effect (SZE) toward clusters of galaxies provide sensitive cosmological probes. We present results from 1 cm observations (at BIMA and OVRO) of a large, intermediate redshift cluster sample. In addition, we describe a proposed, higher sensitivity array which will enable us to survey large portions of

J. E. Carlstrom, M. K. Joy, L. Grego, G. P. Holder

We report on results of interferometric imaging of the Sunyaev-Zel'dovich Effect (SZE) with the OVRO and BIMA mm-arrays. Using low-noise cm-wave receivers on the arrays, we have obtained high quality images for 27 distant galaxy clusters. We review the use of the SZE as a cosmological tool. Gas mass fractions derived from the SZE data are given for 18 of

P. Newbury, G. G. Fahlman

We propose a new, two-stage algorithm for inverting strong gravitational lenses. The key to the algorithm is decoupling the effects of lens magnification and intrinsic structure in the background source in the appearance of lensed arcs. First, the distribution of mass on the deflector plane and the geometry of the source-deflector-observer optical system are

Pasquale Blasi

Clusters of galaxies are revealing themselves as powerful sources of non thermal radiation in a wide range of wavelengths. In order to account for these multifrequency observations equipartition of cosmic rays (CRs) with the thermal gas in clusters of galaxies is often invoked. This condition might suggest a dynamical role played by cosmic rays in the virial

D. Palle

We study an area distance in the Riemannian spacetime with expansion, vorticity and acceleration. It is shown that this observable depends on expansion, deceleration and acceleration parameters to third order in redshift, as well as on vorticity. Thus, the considerable acceleration or vorticity of the Universe can substantially influence the standard astrono

Scott M. Croom, A. Ratcliffe, Q. A. Parker, T. Shanks

We present results from a continuing campaign to secure deep multi-colour CCD sequences for photometric calibration in UK Schmidt fields with galactic latitudes |b|>50deg. In this paper we present UBVR photometry in 12 fields and BR photometry in a further 14 fields observed within UK Schmidt survey fields centred at declination=-30deg. Photometric errors ar

Andrew W. Blain

It is difficult to identify the distant galaxies selected in existing submillimeter (submm)-wave surveys, because their positional accuracy is only several arcseconds. Currently, centimeter-wave VLA observations are required in order to determine sub-arcsec positions, and so to make reliable optical identifications. Carilli & Yun (1999) pointed out that the

Adrianne Slyz, Kevin H. Prendergast

We incorporate a time-independent gravitational field into the BGK scheme for numerical hydrodynamics. In the BGK scheme the gas evolves via an approximation to the collisional Boltzmann equation, namely the Bhatnagar-Gross-Krook (BGK) equation. Time-dependent hydrodynamical fluxes are computed from local solutions of the BGK equation. By accounting for part

A. Owens, T. Oosterbroek, A. N. Parmar, R. Schulz

We report broad-band X-ray measurements of the Be star Gamma Cassiopeiae by the BeppoSAX X-ray astronomy satellite. The observations took place on 1998 July, 18-23. The 0.1-200 keV X-ray spectrum is reasonably well fit by an optically thin thermal plasma model of temperature 12.5 +/- 0.6 keV with significant residuals around 0.3 keV and 1 keV. The former is

D. Barrado y Navascues, E. De Castro, M. J. Fernandez-Figueroa, M. Cornide

We present a study of the lithium abundances of a sample of evolved components of Chromospherically Active Binary Systems. We show that a significant part of them have lithium excesses, independently of their mass and evolutionary stage. Therefore, it can be concluded that Li abundance does not depend on age for giant components of CABS. These overabundances

D. Barrado y Navascues

We have recomputed the kinematic properties of several of dozens nearby stars, to try to verify if Castor has a cohort of stars sharing the same space motion and age. We used kinematics, the location of the stars in CM diagrams, their lithium abundances, and their activity, to establish that the moving group seems to be real and to reject several stars which

D. Barrado y Navascues, J. R. Stauffer, I. Song, J-P. Caillault

We have reanalyzed data for the proposed moving group associated with beta Pic in order to determine if the group (or part of it) is real, and, if so, to derive an improved age estimate for beta Pic. By using new, more accurate proper motions from PPM and Hipparcos and a few new radial velocities, we conclude that on kinematic grounds, two M dwarfs have spac

Shai Kaspi, Hagai Netzer

We present a new scheme for modeling the broad line region in active galactic nuclei (AGNs). It involves photoionization calculations of a large number of clouds, in several pre-determined geometries, and a comparison of the calculated line intensities with observed emission line light curves. Fitting several observed light curves simultaneously provides str

Gustavo Medina Tanco, Alan A. Watson

Several explanations for the existence of Ultra High Energy Cosmic Rays (UHECR) invoke the idea that they originate from the decay of massive particles created in the reheating following inflation. It has been suggested that the decay products can explain the observed isotropic flux of UHECR. We have calculated the anisotropy expected for various models of t

Gustavo Medina Tanco

The Ultra-high energy cosmic ray energy spectrum summarized by the AGASA collaboration indicates clearly that the cosmic ray spectrum extends well beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off at \sim 5 x 10^19 eV. Furthermore, despite the small number statistics involved, some structure in the spectrum may be emerging. Using numerical simulations, it is

Tomas Dahlen, Claes Fransson

Using observed star formation rates at redshifts up to z ~ 5, we calculate cosmic supernova rates for core collapse and Type Ia supernovae. Together with supernova statistics and detailed light curves, we estimate the number of supernovae, and their distribution in redshift, that should be detectable in different filters with various instruments, including b

Jean-Pierre Luminet, Boudewijn F. Roukema

``One could imagine that as a result of enormously extended astronomical experience, the entire universe consists of countless identical copies of our Milky Way, that the infinite space can be partitioned into cubes each containing an exactly identical copy of our Milky Way. Would we really cling on to the assumption of infinitely many identical repetitions

J. M. Mas-Hesse, D. Kunth

We have analyzed the properties of the star formation episodes taking place in a sample of Blue Compact and Irregular galaxies by comparing their multiwavelength observational properties with the predictions of evolutionary population synthesis models. This method has allowed us to constrain the age, star formation regime (instantaneous or extended) and Init

Matthias W. Reinsch

A simple expression is derived for the terms in the Baker-Campbell-Hausdorff series. One formulation of the result involves a finite number of operations with matrices of rational numbers. Generalizations are discussed.

Alexander Schmedding, Oleg Yakovlev

We study the pion form factor F^{πγγ^*}(Q^2) in the light-cone sum rule approach, accounting for radiative corrections and higher twist effects. Comparing the results to the CLEO experimental data on F^{πγγ^*}(Q^2), we extract the the pion distribution amplitude of twist-2. The deviation of the distribution amplitude from the asymptotic one is small and is e

Michael Creutz

I discuss the connection between the Hamiltonian and path integral approaches for fermionic fields. I show how the temporal Wilson projection operators appear naturally in a lattice action. I also carefully treat the insertion of a chemical potential term.

Z. Chacko, R. N. Mohapatra

If Nature has chosen the vacuum oscillation solution to the Solar neutrino puzzle, a key theoretical challenge is to understand the extreme smallness of the $Δm^2_{ν_e-ν_X}$ ($\sim 10^{-10} eV^2$) required for the purpose. We find that in a class of models such as [SU(3)]^3 or its parent group E_6, which contain one sterile neutrino, $ν_{is}$ for each family

Gunnar S. Bali

We find that perturbation theory fails to describe the short range static potential as obtained from quenched lattice simulations, at least for source separations r > 1/(6 GeV). The difference between the non-perturbatively determined potential and perturbation theory at short distance is well parameterised by a linear term with a slope of approximately 1.2

Zurab Kakushadze, Tomasz R. Taylor

We discuss higher loop corrections to gauge coupling renormalization in the context of gauge coupling unification via Kaluza-Klein thresholds. We show that in the case N=1 supersymmetric compactifications the one-loop threshold contributions are dominant, while the higher loop correction are subleading. This is due to the fact that at heavy Kaluza-Klein leve

J. M. Campbell, R. K. Ellis

We present numerical results (including full one-loop QCD corrections) for the processes p p-bar and pp -> W+ W-, W+/- Z/gamma* and Z/gamma* Z/gamma* followed by the decay of the massive vector bosons into leptons. In addition to their intrinsic importance as tests of the standard model, these processes are also backgrounds to conjectured non-standard model

C. J. Horowitz

High energy solar neutrinos can come from the hep reaction ^3He(p,\nue^+)^4He with a large end point energy of 18.8 MeV. Understanding the hep reaction may be important for interpreting solar neutrino spectra. We calculate the contribution of the axial charge transition $^3P_0\to ^1S_0$ to the hep thermonuclear S factor using a one-body reaction model involv

A. P. Balachandran, E. Batista, I. P. Costa e Silva, P. Teotonio-Sobrinho

The topology of orientable (2 + 1)d spacetimes can be captured by certain lumps of non-trivial topology called topological geons. They are the topological analogues of conventional solitons. We give a description of topological geons where the degrees of freedom related to topology are separated from the complete theory that contains metric (dynamical) degre

Pascal Baseilhac

The 2-dimensional space-time sine-Gordon field theory is extended algebraically within the n-dimensional space of extended complex numbers. This field theory is constructed in terms of an adapted extension of standard vertex operators. A whole set of non-local conserved charges is constructed and studied in this framework. Thereby, an algebraic non-perturbat

D. Fabbri, P. Fre`, L. Gualtieri, P. Termonia

In this paper we fill a necessary gap in order to realize the explicit comparison between the Kaluza Klein spectra of supergravity compactified on AdS_4 x X^7 and superconformal field theories living on the world volume of M2-branes. On the algebraic side we consider the superalgebra Osp(N|4) and we study the double interpretation of its irreducible represen

Georg M. Bruun, Charles W. Clark

We discuss collective excitations of a trapped dilute Fermi gas within a hydrodynamic approximation. Analytical results are derived for both high- and low-temperature limits and are applied to $^{40}$K and $^6$Li systems of current experimental interest. We identify spectral signatures which can be used to detect the onset of Fermi degeneracy. Also, we find

Weonjong Lee, Stephen Sharpe

We study the leading discretization errors for staggered fermions by first constructing the continuum effective Lagrangian including terms of O(a^2), and then constructing the corresponding effective chiral Lagrangian. The terms of O(a^2) in the continuum effective Lagrangian completely break the SU(4) flavor symmetry down to the discrete subgroup respected

A. Duviryak

Classical description of relativistic pointlike particle with intrinsic degrees of freedom such as isospin or colour is proposed. It is based on the Lagrangian of general form defined on the tangent bundle over a principal fibre bundle. It is shown that the dynamics splits into the external dynamics which describes the interaction of particle with gauge fiel

Gregoire Ribordy, Jean-Daniel Gautier, Nicolas Gisin, Olivier Guinnard

Some guidelines for the comparison of different quantum key distribution experiments are proposed. An improved 'plug & play' interferometric system allowing fast key exchange is then introduced. Self-alignment and compensation of birefringence remain. Original electronics implementing the BB84 protocol and allowing user-friendly operation is presente

Teruhiko Kawano, Kazumi Okuyama

We explicitly calculate a Witten diagram with general spinor field exchange on $(d+1)$-dimensional Euclidean Anti-de Sitter space, which is necessary to evaluate four-point correlation functions with spinor fields when we make use of the AdS/CFT correspondence, especially in supersymmetric cases. We also show that the amplitude can be reduced to a scalar exc

Jan Tobochnik

Inelastic collapse is found in a two-dimensional system of inelastic hard disks confined between two walls which act as an energy source. As the coefficient of restitution is lowered, there is a transition between a state containing small collapsed clusters and a state dominated by a large collapsed cluster. The transition is analogous to that of a percolati

C. Terquem, J. Papaloizou, R. Nelson

We review results about protoplanetary disk models, protoplanet migration and formation of giant planets with migrating cores. We first model the protoplanetary nebula as an \alpha-accretion disk and present steady state calculations for different values of \alpha and gas accretion rate through the disk. We then review the current theories of protoplanet mig

A. Surdo

The flux of low energy atmospheric neutrinos (E_nu ~ 4 GeV) has been studied with the MACRO detector at Gran Sasso by detecting nu_mu interactions inside the apparatus, and by upward-going stopping muons. The updated analysis of the data collected until now with the complete apparatus will be presented. The results show a deficit of the measured number of ev

Kanehisa Takasaki

We show that various models of the elliptic Calogero-Moser systems are accompanied with an isomonodromic system on a torus. The isomonodromic partner is a non-autonomous Hamiltonian system defined by the same Hamiltonian. The role of the time variable is played by the modulus of the base torus. A suitably chosen Lax pair (with an elliptic spectral parameter)

Anthony Challinor, Matthew Ford, Anthony Lasenby

We derive analytic expressions for the leading-order corrections to the polarization induced in the cosmic microwave background (CMB) due to scattering off hot electrons in galaxy clusters along the line of sight. For a thermal distribution of electrons with a kinetic temperature of 10 keV and a bulk peculiar velocity of 1000 km/s, the dominant corrections t

Y. M. Cho

It has been conjectured that the Abelian projection of QCD is responsible for the confinement of color. Using a gauge independent definition of the Abelian projection which does {\it not} employ any gauge fixing, we provide a strong evidence for the Abelian dominance in Wilson loop integral. In specific we prove that the gauge potential which contributes to

Yuji Ohta

This paper studies the dual form of Witten-Dijkgraaf-Verlinde-Verlinde (WDVV) equations in N=2 supersymmetric Yang-Mills theory by applying a duality transformation to WDVV equations. The dual WDVV equations called in this paper are non-linear differential equations satisfied by dual prepotential and are found to have the same form with the original WDVV equ

S. Ghosh, G. Kar, A. Roy

This paper has been withdrawn temporarily.

S. Gov, S. Shtrikman, H. Thomas

We study, both classically and quantum-mechanically, the problem of a neutral particle with spin S, mass m and magnetic moment mue, moving in two-dimensions in an inhomogeneous magnetic field given by B_x=B'*x; B_y=-B'*y; B_z=B; We identify K, the ratio between the precessional frequency of the particle and its vibration frequency, as the relevant pa

M. Abolhasani, M. Golshani

We try to obtain Born's principle as a result of a subquantum heat death, using classical ${\cal H}$-theorem and the definition of a proper quantum ${\cal H}$-theorem, within the framwork of Bohm's theory. We shall show the possibility of solving the problem of action-reaction asymmetry present in Bohm's theory and the arrow of time problem in ou

Samuel L. Braunstein, Christopher A. Fuchs, Daniel Gottesman, Hoi-Kwong Lo

We analyze a generalization of Huffman coding to the quantum case. In particular, we notice various difficulties in using instantaneous codes for quantum communication. Nevertheless, for the storage of quantum information, we have succeeded in constructing a Huffman-coding inspired quantum scheme. The number of computational steps in the encoding and decodin

S. Gov, S. Shtrikman

We calculate exactly the modes of motion of the Time-averaged Orbiting Potential (TOP) trap with its four degrees of freedom, namely the three translations and the spin, taken into account. We find that, when gravity is neglected, there are two parameters in the problem namely, the angular velocity of the rotating field and its strength. We present the stabi

Ovidiu Costin, Joel L. Lebowitz, Alexander Rokhlenko

We prove that a model atom having one bound state will be fully ionized by a time periodic potential of arbitrary strength $r$ and frequency $ω$. The survival probability is for small $r$ given by $e^{-Γt}$ for times of order $Γ^{-1} \sim r^{-2n}$, where $n$ is the number of ``photons'' required for ionization, with enhanced stability at resonances.

Bao-An Li, Andrew T. Sustich

A strong differential transverse collective flow is predicted for the first time to occur in heavy-ion collisions at balance energies. We also give a novel explanation for the disappearance of the total transverse collective flow at the balance energies. It is further shown that the differential flow especially at high transverse momenta is a useful microsco

H. -W. Hammer

We apply the effective field theory approach to the three-nucleon system. In particular, we consider neutron-deuteron scattering and the triton. Precise predictions for S=3/2 scattering are obtained in a straightforward way. In the S=1/2 channel, however, a unique nonperturbative renormalization takes place which requires the introduction of a three-body for

J. E. Amaro, M. B. Barbaro, J. A. Caballero, T. W. Donnelly

A new non-relativistic expansion in terms of the nucleon's momentum inside nuclear matter of the current for isobar electro-excitation from the nucleon is performed. Being exact with respect to the transferred energy and momentum, this yields new current operators which retain important aspects of relativity not taken into account in the traditional non-

A. Gokalp, O. Yilmaz

We employ the light cone QCD sum rules to calculate $ΔπN$ coupling constant by studying the two point correlation function between the vacuum and the pion state. Our result is consistent with the traditional QCD sum rules calculations and it is in agreement with the experimental value.

Jennifer Slimowitz

We use the criteria of Lalonde and McDuff to determine a new class of examples of length minimizing paths in the group $Ham(M)$. For a compact symplectic manifold $M$ of dimension two or four, we show that a path in $Ham(M)$, generated by an autonomous Hamiltonian and starting at the identity, which induces no non-constant closed trajectories of points in $M

B. Fantechi, R. Pandharipande

We construct a natural branch divisor for equidimensional projective morphisms where the domain has lci singularities and the target is nonsingular. The method involves generalizing a divisor contruction of Mumford from sheaves to complexes. The construction is valid in flat families. The generalized branch divisor of a stable map to a nonsingular curve X yi

George Thompson

The group SL(2) acts on the space of cohomology groups of any hyper-Kahler manifold X. The χ_{y} genus of a hyper-Kahler X is shown to have a geometric interpretation as the super trace of an element of SL(2). As a by product one learns that the generalized Casson invariant for a mapping torus is essentially the χ_{y} genus.

D. Arnaudon, J. Avan, L. Frappat, M. Rossi

Scaling limits when q tends to 1 of the elliptic vertex algebras A_qp(sl(N)) are defined for any N, extending the previously known case of N=2. They realise deformed, centrally extended double Yangian structures DY_r(sl(N)). As in the quantum affine algebras U_q(sl(N)), and quantum elliptic affine algebras A_qp(sl(N)), these algebras contain subalgebras at c

Kiran S. Kedlaya

We present a variation and generalization of a determinant evaluation of Wilf (math.CO/9809120). His result concerns a matrix whose entries are the coefficients of powers of a given power series; we replace the powers by repeated compositions and obtain similar results.

Joaquim Roe

We address the problem of determining the degree a plane curve must have in order to pass with multiplicity m through r points in general position. A conjecture of Nagata states that one must have d > m \sqrt{r}. We prove the inequalities d \geq m(r-1)\prod_{i=2}^{r-1}(1-i/(i^2+r-1)) and d > m (\sqrt{r-1} - π/8).

M. Garcia Perez, A. Gonzalez-Arroyo, C. Pena, P. van Baal

We give a unified description of self-dual SU(2) gauge fields on tori of size lt x ls^3 based on a mixture of analytical and numerical methods using the Nahm transformation, extended to the case of twisted boundary conditions. We show how torus calorons (lt/ls small) are Nahm dual to the torus instantons (lt/ls large). Holonomies are dual to the locations of

Ashok Das, Sergio A. Pernice

The breaking of supersymmetry due to singular potentials in supersymmetric quantum mechanics is critically analyzed. It is shown that, when properly regularized, these potentials respect supersymmetry, even when the regularization parameter is removed.

A. Campbell-Smith, N. E. Mavromatos, J. Papavassiliou

Using superfield Dyson-Schwinger equations, we compute the infrared dynamics of the semi-amputated full vertex, corresponding to the effective running gauge coupling, in N-flavour {\mathcal N}=1 supersymmetric QED(3). It is shown that the presence of a supersymmetry-preserving mass for the matter multiplet stabilizes the infrared gauge coupling against oscil

M. M. Deminov, A. A. Slavnov

The one loop gluon - W-meson amplitude is calculated by means of the gauge-invariant generalized Pauli-Villars regularization and with the help of dimensional regularization. It is shown that in the former case the amplitude satisfies Generalized Ward Identities, whereas in the latter case the amplitude differs from the first one by the constant.

K. G. Selivanov

This is a short and simple introduction into perturbiners, that is, the solutions of field equations which are generating functions for tree amplitudes. The perturbiners have been constructed in Yang-Mills, in SUSY Yang-Mills, in gravity, and in sin(h)-Gordon.

F. Landry, R. Brock, G. Ladinsky, C. -P. Yuan

We update the non-perturbative function of the Collins-Soper- Sterman resummation formalism in hadron collisions. Two functional forms in impact parameter space are considered, one with a pure Gaussian form with two parameters and the other with an additional linear term. The results for the two parameter fit are found to be g1=0.24+0.08-0.07 GeV^2, g2=0.34+

Z. Chacko, Markus A. Luty, Ivan Maksymyk, Eduardo Ponton

We consider supersymmetry breaking communicated entirely by the superconformal anomaly in supergravity. This scenario is naturally realized if supersymmetry is broken in a hidden sector whose couplings to the observable sector are suppressed by more than powers of the Planck scale, as occurs if supersymmetry is broken in a parallel universe living in extra d

L. Pasquali, M. H. Reno, I. Sarcevic

We evaluate the fluxes of neutrinos and muons from charmed particles produced by cosmic ray interactions with air nuclei. Using next-to-leading order perturbative QCD, we compare our results with calculations based on a PYTHIA Monte Carlo evaluation of charm production. We investigate the sensitivity of our results to the choice of parton distribution functi

M. Grazzini

I consider the singular behaviour of tree-level QCD amplitudes when the momenta of three partons become simultaneously parallel and I discuss the universal factorization formula that controls the singularities of the multiparton matrix elements in this collinear limit.

A. Ringwald, F. Schrempp

We give a brief status report on our on-going investigation of the prospects to discover QCD instantons in deep inelastic scattering (DIS) at HERA. A recent high-quality lattice study of the topological structure of the QCD vacuum is exploited to provide crucial support of our predictions for DIS, based on instanton perturbation theory.

A. Kolchuzhkin, A. Potylitsyn, A. Bogdanov, I. Tropin

Kinetic equations for the process of multiphoton bremsstrahlung of electron in a matter have been used to derive the equations for the moments of distributions of electrons over the number of emitted photons and over the energy loss. The equations for the moments have been solved in continuous slowing down approximation. It has been shown that the moments of

Cong-Feng Qiao, Han-Wen Huang, Kuang-Ta Chao

We present the results of a study of heavy-light-quark bound states in the context of the reduced Bethe-Salpeter equation with relativistic vector and scalar interactions. We find that satisfactory fits may also be obtained when the retarded effect of the quark-antiquark interaction is concerned.

J. A. Casas, J. R. Espinosa, A. Ibarra, I. Navarro

If neutrinos are to play a relevant cosmological role, they must be essentially degenerate with a mass matrix of the bimaximal mixing type. We study this scenario in the MSSM framework, finding that if neutrino masses are produced by a see-saw mechanism, the radiative corrections give rise to mass splittings and mixing angles that can accommodate the atmosph

J. Matias

The computation of the polarized amplitudes and cross section of the processes $γν\toγγν$, $γγ\to γν\barν$ and $ν\barν\to γγγ$ is described. We used an effective lagrangian approach for energies below the threshold for $e^+e^-$ pair production and the complete computation at higher energies for application in supernova dynamics. Leading contributions of phys

J. Fleischer, M. Yu. Kalmykov, A. V. Kotikov

A set of recurrence relations for on-shell two-loop self-energy diagrams with one mass is presented, which allows to reduce the diagrams with arbitrary indices (powers of scalar propagators) to a set of the master integrals. The SHELL2 package is used for the calculation of special types of diagrams. A method of calculation of higher order ε-expansion of mas