February 2000 arXiv papers — page 15

K. Litkowski

As text processing systems expand in scope, they will require ever larger lexicons along with a parsing capability for discriminating among many senses of a word. Existing systems do not incorporate such subtleties in meaning for their lexicons. Ordinary dictionaries contain such information, but are largely untapped. When the contents of dictionaries are sc

V. N. Smolyaninova, X. C. Xie, F. C. Zhang, M. Rajeswari

We report on resistivity measurements in La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ and Nd$_{0.7}$Sr$_{0.3}$MnO$_{3}$ thin films in order to elucidate the underlying mechanism for the CMR behavior. The experimental results are analyzed in terms of quantum phase transition ideas to study the nature of the metal-insulator transition in manganese oxides. Resistivity curve

A. R. Lima, P. M. C. de Oliveira, T. J. P. Penna

We discuss the conceptual differences between the Broad Histogram (BHM) and reweighting methods in general, and particularly the so-called Multicanonical (MUCA) approaches. The main difference is that BHM is based on microcanonical, fixed-energy averages which depends only on the good statistics taken {\bf inside} each energy level. The detailed distribution

J. Kwapien, S. Drozdz, A. A. Ioannides

We adopt the concept of the correlation matrix to study correlations among sequences of time-extended events occuring repeatedly at consecutive time-intervals. As an application we analyse the magnetoencephalography recordings obtained from human auditory cortex in epoch mode during delivery of sound stimuli to the left or right ear. We look into statistical

Eirik G. Flekkoy, Peter V. Coveney, Gianni De Fabritiis

We derive a mesoscopic modeling and simulation technique that is very close to the technique known as dissipative particle dynamics. The model is derived from molecular dynamics by means of a systematic coarse-graining procedure. Thus the rules governing our new form of dissipative particle dynamics reflect the underlying molecular dynamics; in particular al

M. N. Popescu, C. M. Arizmendi, A. L. Salas-Brito, F. Family

The effects of quenched disorder on the overdamped motion of a driven particle on a periodic, asymmetric potential is studied. While for the unperturbed potential the transport is due to a regular drift, the quenched disorder induces a significant additional chaotic ``diffusive'' motion. The spatio-temporal evolution of the statistical ensemble is we

V. M. Krasnov, A. Yurgens, D. Winkler, P. Delsing

We present intrinsic tunneling spectroscopy measurements on small Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ mesas. The tunnel conductance curves show both sharp peaks at the superconducting gap voltage and broad humps representing the $c$-axis pseudo-gap. The superconducting gap vanishes at $T_c$, while the pseudo-gap exists both above and below $T_c$. Our observation i

Gregoire Misguich, Claire Lhuillier

The extension of the Lieb-Schultz-Mattis theorem to dimensions larger than one is discussed. It is explained why the variational wave-function built by the previous authors is of no help to prove the theorem in dimension larger than one. The short range R.V.B. picture of Sutherland, Rokhsar and Kivelson, Read and Chakraborty gives a strong support to the ass

V. Popkov, L. Santen, A. Schadschneider, G. M. Schutz

Boundary-induced phase transitions are one of the surprising phenomena appearing in nonequilibrium systems. These transitions have been found in driven systems, especially the asymmetric simple exclusion process. However, so far no direct observations of this phenomenon in real systems exists. Here we present evidence for the appearance of such a nonequilibr

Jorge Iniguez, Alberto Garcia, J. M. Perez-Mato

We have performed detailed first-principles calculations to determine the eigenvectors of the zone-center modes of hexagonal BaTiO3 and shown that the experimentally relevant low-energy modes (including the non-polar instability) can be represented as suitable combinations of basic local polar distortions associated with the instability of the cubic perovski

Isabelle Cantat, Chaouqi Misbah, Yukio Saito

We study theoretically vesicle locomotion due to haptotaxis. Haptotaxis is referred to motion induced by an adhesion gradient on a substrate. The problem is solved within a local approximation where a Rayleigh-type dissipation is adopted. The dynamical model is akin to the Rousse model for polymers. A powerful gauge-field invariant formulation is used to sol

B. Gerlach, M. A. Smondyrev

We study properties of polarons and excitons confined to a potential generated in a planar semiconductor heterostructure of the $Ga_{1-x}Al_{x}As/GaAs/Ga_{1-x}Al_{x}As$ type. In contrast with results of other authors peaks are found for the exciton energy and the polaron effective mass as functions of the potential width while the polaron energy reveals rath

Matthew A. Bershady, Anna Jangren, Christopher J. Conselice

In this paper we define an observationally robust, multi-parameter space for the classification of nearby and distant galaxies. The parameters include luminosity, color, and the image-structure parameters: size, image concentration, asymmetry, and surface brightness. Based on an initial calibration of this parameter space using the ``normal'' Hubble-

Marek J. Sarna, Ene Ergma, Jelena Antipova

We present a detailed calculation of the evolution of low-mass ($< 0.25~M_\odot $) helium white dwarfs. These white dwarfs (the optical companions to binary millisecond pulsars) are formed via long-term, low-mass binary evolution. After detachment from the Roche lobe, the hot helium cores have a rather thick hydrogen layer with mass between 0.01 to 0.06$~M_\

D. J. Fixsen, S. H. Moseley, R. G. Arendt

The development of sensitive large format imaging arrays for the infrared promises to provide revolutionary capabilities for space astronomy. For example, the Infrared Array Camera (IRAC) on SIRTF will use four 256 x 256 arrays to provide background limited high spatial resolution images of the sky in the 3 to 8 micron spectral region. In order to reach the

J. Pety, E. Falgarone

The cold diffuse interstellar medium must harbor pockets of hot gas to produce the large observed abundances of molecular species, the formation of which require much more energy than available in the bulk of its volume. These hot spots have so far escaped direct detection but observations and modeling severely constrain their phase-space structure i.e. they

Richard G. Arendt, D. J. Fixsen, S. Harvey Moseley

With high sensitivity imaging arrays, accurate calibration is essential to achieve the limits of detection of space observatories. One can simultaneously extract information about the scene being observed and the calibration properties of the detector and imaging system from redundant dithered images of a scene. There are large differences in the effectivene

E. Kerins, B. J. Carr, N. W. Evans, P. Hewett

POINT-AGAPE is an Anglo-French collaboration which is employing the Isaac Newton Telescope (INT) to conduct a pixel-lensing survey towards M31. In this paper we investigate what we can learn from pixel-lensing observables about the MACHO mass and fractional contribution in M31 and the Galaxy for the case of spherically-symmetric near-isothermal haloes. We em

D. Petry, M. Boettcher, V. Connaughton, A. Lahteenmaki

During the observation period 1997, the nearby Blazar Mkn 501 showed extremely strong emission and high variability. We examine multiwavelength aspects of this event using radio, optical, soft and hard X-ray and TeV data. We concentrate on the medium-timescale variability of the broadband spectra, averaged over weekly intervals. We confirm the previously fou

D. L. Khokhlov

It is considered gravitational interaction within the framework of the Newton theory and the quantum field theory. It is introduced the Planck neutrino $ν_{Pl}$. Gravitational interaction of the fields $ψψ$ includes short-range interaction $ψν_{Pl}$ and long-range interaction $ν_{Pl}ν_{Pl}$. Gravitational radiation can be identified with the Planck neutrino.

T. Sako, Y. Matsubara, Y. Muraki, P. V. Ramanamurthy

The gamma-ray pulsar PSR B1509-58 and its surrounding nebulae have been observed with the CANGAROO 3.8m imaging atmospheric Cherenkov telescope. The observations were performed from 1996 to 1998 in Woomera, South Australia, under different instrumental conditions with estimated threshold energies of 4.5 TeV (1996), 1.9 TeV (1997) and 2.5 TeV (1998) at zenith

O. Kessel-Deynet, A. Burkert

A new method for the inclusion of ionizing radiation from uniform radiation fields into 3D Smoothed Particle Hydrodynamics (SPHI) simulations is presented. We calculate the optical depth for the Lyman continuum radiation from the source towards the SPHI particles by ray-tracing integration. The time-dependent ionization rate equation is then solved locally f

Eelco van Kampen

Most phenomenological galaxy formation models show a discrepancy between the predicted Tully-Fisher relation and the luminosity function. We show that this is mainly due to overmerging of galaxy haloes, which is inherent in both the Press-Schechter formalism and dissipationless N-body simulations. This overmerging problem be circumvented by including a speci

G. Efstathiou

I review the basic theory of the cosmic microwave background anisotropies in adiabatic cold dark matter cosmologies. The latest observational results on the CMB power spectrum are consistent with the simplest inflationary models and indicate that the Universe is close to spatially flat with a nearly scale invariant fluctuation spectrum. We are also beginning

Joop Schaye, Tom Theuns, Michael Rauch, George Efstathiou

The thermal evolution of the intergalactic medium (IGM) depends on the reionization history of the universe. Numerical simulations indicate that the low density IGM, which is responsible for the low column density Ly-alpha forest, follows a well defined temperature-density relation. This results in a cut-off in the distribution of line widths as a function o

I. A. Steele, L. Howells

The I-Z colour has been recently shown to be a good temperature indicator for M dwarfs. We present the first IZ photometry of a small sample of L dwarfs ranging in spectral type from L0.5V to L6.0V. We find that the I-Z colour is not a good temperature indicator for objects between L1V and L5V, such objects having colours that overlap with mid M dwarfs. We a

G. Efstathiou

A model of supernovae feedback during disc galaxy formation is developed. The model incorporates infall of cooling gas from a halo and outflow of hot gas from a multiphase interstellar medium and a self-regulated model for star formation. Hot gas is created by thermal evaporation of cold gas clouds in supernovae remnants, and criteria are derived to estimate

A. Marconi, E. Oliva, P. P. van der Werf, R. Maiolino

We present new HST NICMOS observations of NGC 4945, a starburst galaxy hosting a highly obscured active nucleus that is one of the brightest extragalactic sources at 100 keV. The HST data are complemented with ground based [FeII] line and mid--IR observations. A 100pc-scale starburst ring is detected in Pa alpha, while H_2 traces the walls of a super bubble

E. Waxman

The gamma-ray burst (GRB) model for production of ultra-high-energy cosmic-rays (UHECRs) is based on the hypothesis that GRBs arise from the dissipation of the kinetic energy of relativistic fireballs at cosmological distances. Recent GRB afterglow observations support the validity of this hypothesis and provide quantitative support for the model. The inferr

G. Bono, V. Castellani, M. Marconi

We use high precision multiband photometric data of the first overtone RR Lyrae U Com to investigate the predictive capability of full amplitude, nonlinear, convective hydrodynamical models. The main outcome of this investigation is that theoretical predictions properly account for the luminosity variations along a full pulsation cycle. Moreover, we find tha

Daniel Stern, Andrew J. Bunker, Hyron Spinrad, Arjun Dey

We report the serendipitous discovery of two objects close in projection with fairly strong emission lines at long wavelength (~9190 A). One (A) seems not to be hosted by any galaxy brighter than V(555)=27.5, or I(814)=26.7 (Vega-based 3-sigma limits in 1.0 arcsec diameter apertures), while the other line is associated with a faint (I(814)~24.4) red galaxy (

Denis Burgarella, Markus Kissler-Patig, Veronique Buat

In this paper, we are exploring the properties of old, metal-poor globular clusters in galaxies. We investigate whether their properties are related to the properties of their host galaxies, and whether we can constrain their formation. The main result is that the mean metallicities of old GC systems are found to lie in a narrow range -1.7 < [Fe/H] < -1.1 (8

Michael Fellhauer, Pavel Kroupa

We investigate the behaviour of a cluster of young massive star clusters (hereafter super-cluster) in the tidal field of a host galaxy with a high-resolution particle-mesh code, Superbox. Specifically we want to establish if and how such super star-clusters merge and carry out a detailed study of the resulting merger-object. This merger-object shows either t

Koji Hashimoto, Takayuki Hirayama

We study BPS Dirac monopole in U(1) gauge theory on non-commutative spacetime. The corresponding brane configuration is obtained in the equivalent ordinary gauge theory through the map proposed by Seiberg and Witten. This configuration coincides exactly with a tilted D-string as predicted. This study provides an interesting check of the equivalence of the no

G. Cleaver, K. Tanaka

We consider N=2 SU(2) Seiberg-Witten duality theory for models with N_f=2 and N_f=3 quark flavors. We investigate arbitrary large bare mass ratios between the two or three quarks at the singular points. For N_f=2 we explore large bare mass ratios corresponding to a singularity in the strong coupling region. For N_f=3 we determine the location of both strong

S. Ferrara, M. A. Lledó

We investigate some aspects of Moyal-Weyl deformations of superspace and their compatibility with supersymmetry. For the simplest case, when only bosonic coordinates are deformed, we consider a four dimensional supersymmetric field theory which is the deformation of the Wess-Zumino renormalizable theory of a chiral superfield. We then consider the deformatio

Asantha Cooray, Wayne Hu, Max Tegmark

We study the prospects for extracting detailed statistical properties of the Sunyaev-Zel&#39;dovich (SZ) effect associated with large scale structure using upcoming multifrequency CMB experiments. The greatest obstacle to detecting the large-angle signal is the confusion noise provided by the primary anisotropies themselves, and to a lesser degree galactic a

R. Brustein, S. P. de Alwis

If there is a single underlying &#34;theory of everything&#34; which in some limits of its &#34;moduli space&#34; reduces to the five weakly coupled string theories in 10D, and 11D SUGRA, then it is possible that all six of them have some common domain of validity and that they are in the same universality class, in the sense that the 4D low energy physics o

Nakwoo Kim

We study supersymmetric intersecting configurations of D-branes with B-field backgrounds. Noncommutative D-brane or M-brane pairs can intersect supersymmetrically over (p-1)-brane, as well as over (p-2)-brane like ordinary branes. d=10 and d=11 supergravity solutions are obtained and the supersymmetry projection rule is examined. As an application we study a

M. Anselmino, F. Murgia

An azimuthal dependence of pions produced in polarized Deep Inelastic Scattering, gamma^* - p(transv. polarized) -> pion + X, has been recently observed and might be related to the so-called Collins effect. We discuss in details, for a general spin configuration of the nucleon, the kinematics of the process and methods of extracting information on the fragme

A. Cervera, A. Donini, M. B. Gavela, J. J. Gomez Cadenas

The precision and discovery potential of a neutrino factory based on muon storage rings is studied. For three-family neutrino oscillations, we analyse how to measure or severely constraint the angle $θ_{13}$, CP violation, MSW effects and the sign of the atmospheric mass difference $Δm^2_{23}$. We present a simple analytical formula for the oscillation proba

Robert L. Karp, Freydoon Mansouri

We generalize the standard product integral formalism to incorporate Grassmann valued matrices and show that the resulting supersymmetric product integrals provide a natural framework for describing supersymmetric Wilson Lines and Wilson Loops. We use this formalism to establish the supersymmetric version of the non-Abelian Stokes theorem.

K. A. Chikin, V. L. Korotkih, A. P. Kryukov, L. I. Sarycheva

There exist several proposals to use Weizsäcker-Williams photons generated by ultrarelativistic heavy ions to produce exotic particles in $γγ$ fusion reactions. To estimate the background conditions for such reactions we analyze various mechanisms of meson production in very peripheral collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besi

M. Taut

The Schrödinger equation for quantum dot lattices with non-cubic, non-Bravais lattices built up from elliptical dots is investigated. The Coulomb interaction between the dots is considered in dipole approximation. Then only the center of mass (c.m.) coordinates of different dots couple with each other. This c.m. subsystem can be solved exactly and provides m

E. Del Gado, L. de Arcangelis, A. Coniglio

Within a recently introduced model based on the bond-fluctuation dynamics we study the viscoelastic behaviour of a polymer solution at the gelation threshold. We here present the results of the numerical simulation of the model on a cubic lattice: the percolation transition, the diffusion properties and the time autocorrelation functions have been studied. F

A. Alonso Izquierdo, M. A. Gonzalez Leon, J. Mateos Guilarte

The kinks of the (1+1)-dimensional Wess-Zumino model with polynomic superpotential are investigated and shown to be related to real algebraic curves.

MACRO Collaboration

A search for lightly ionizing particles has been performed with the MACRO detector. This search was sensitive to particles with charges between $\fractional{5}$$e$ and close to the charge of an electron, with $β$ between approximately 0.25 and 1.0. Unlike previous searches both single track events and tracks buried within high multiplicity muon showers were

Edson Sardella

In the present work we study an anisotropic layered superconducting film of finite thickness. The film surfaces are considered parallel to the $bc$ face of the crystal. The vortex lines are oriented perpendicular to the film surfaces and parallel to the superconducting planes. We calculate the local field and the London free energy for this geometry. Our cal

A. J. Buras, M. Ciuchini, E. Franco, G. Isidori

We critically analyze recent attempts to include final state interaction (FSI) effects in the calculation of the CP violating ratio epsilon&#39;/epsilon. In particular the approach of using the Muskhelishvili-Omnes equation for the decay amplitudes is examined. We find that the values of the dispersive correction factors are very sensitive to initial conditi

Jesper Sommer-Larsen

Two ways of possibly solving the angular momentum problem plaguing cold dark matter (CDM) ab initio simulations of disk galaxy formation are discussed: 1) Stellar feedback processes and 2) Warm dark matter (WDM) rather than CDM. In relation to the chemical evolution of disk galaxies our simulations indicate that in case 1) the first generation of disk stars

A. Bartl, H. Eberl, S. Kraml, W. Majerotto

We discuss production and decays of stops, sbottoms, tau-sneutrinos, and staus in e+e- annihilation in the energy range \sqrt{s} = 0.5-1 TeV. We present numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates, including one-loop radiative corrections as well as initial state radiation. We also study the impor

Stefano Bertolini

I shortly review the present status of the theoretical estimates of eps&#39;/eps. I consider a few aspects of the theoretical calculations which may be relevant in understanding the present experimental results. In particular, I discuss the role of final state interactions and in general of non-factorizable contributions for the explanation of the Delta I =

Nantel Bergeron, Stefan Mykytiuk, Frank Sottile, Stephanie van Willigenburg

We consider graded representations of the algebra NC of noncommutative symmetric functions on the Z-linear span of a graded poset P. The matrix coefficients of such a representation give a Hopf morphism from a Hopf algebra HP generated by the intervals of P to the Hopf algebra of quasi-symmetric functions. This provides a unified construction of quasi-symmet

A. Sedrakian, A. E. L. Dieperink

We develop a neutrino transport theory, in terms of the real-time non-equilibrium Green&#39;s functions, which is applicable to physical conditions arbitrary far from thermal equilibrium. We compute the coherent neutrino radiation in cores of supernovae by evaluating the two-particle-two-hole (2p-2h) polarization function with dressed propagators. The propag

Romesh K. Kaul, Parthasarathi Majumdar

The exact formula derived by us earlier for the entropy of a four dimensional non-rotating black hole within the quantum geometry formulation of the event horizon in terms of boundary states of a three dimensional Chern-Simons theory, is reexamined for large horizon areas. In addition to the {\it semiclassical} Bekenstein-Hawking contribution to the area obt

Mauricio Bellini

I consider a new semiclassical expansion for the inflaton field in the framework of warm inflation scenario. The fluctuations of the matter field are considered as thermally coupled with the particles of the thermal bath. This coupling parameter depends on the temperature of the bath. The power spectrum remains invariant under this new semiclassical expansio

J. F. Stilck, C. E. Cordeiro, R. L. P. G. do Amaral

The mean square end-to-end distance of a N-step polymer on a Bethe lattice is calculated. We consider semiflexible polymers placed on isotropic and anisotropic lattices. The distance on the Cayley tree is defined by embedding the tree on a sufficiently high dimensional Euclidean space considering that every bend of the polymer defines a direction orthogonal

H. V. Klapdor-Kleingrothaus, H. Päs

Neutrinoless double beta decay belongs to the most sensitive tools for the search of new physics beyond the standard model. The recent half life limit of the Heidelberg-Moscow experiment implies restrictive bounds on the absolute mass scale in the neutrino sector. Possible improvements by the GENIUS project provide a unique possibility to reconstruct the neu

C. Alexandrou, E. Follana, H. Panagopoulos, E. Vicari

We compute the one-loop lattice renormalization of the two-quark operators $\barψ Γψ$, where $Γ$ denotes the generic Dirac matrix, for the lattice formulation of QCD using the overlap-Dirac operator. We also study the renormalization of quark bilinears which are more extended and have better chiral properties. Finally, we present improved estimates of these

M. Glueck, A. R. Kolovsky, H. J. Korsch

The quasienergy spectrum of a Bloch electron affected by dc-ac fields is known to be a fractal function of the so-called electric matching ratio which is the ratio of the ac field frequency and the Bloch frequency. This paper studies a manifestation of the fractal spectrum in the system atom in a standing laser wave, which is a quantum optical realization of

B. W. Hoogenboom, M. Kugler, B. Revaz, I. Maggio-Aprile

We present a detailed study on the behaviour of vortex cores in Bi_2Sr_2CaCu_2O_{8+δ} using scanning tunneling spectroscopy. The very irregular distribution and shape of the vortex cores imply a strong pinning of the vortices by defects and inhomogeneities. The observed vortex cores seem to consist of two or more randomly distributed smaller elements. Even m

Shin-Ichi Ikeda, Yoshiteru Maeno, Satoru Nakatsuji, Masashi Kosaka

We show that single-crystalline Sr3Ru2O7 grown by a floating-zone technique is an isotropic paramagnet and a quasi-two dimensional metal as spin-triplet superconducting Sr2RuO4 is. The ground state is Fermi liquid with very low residual resistivity (3 micro ohm cm for in-plane currents) and a nearly ferromagnetic metal with the largest Wilson ratio Rw>10 amo

H. Zbinden, J. Brendel, W. Tittel, N. Gisin

An experimental test of relativistic wave-packet collapse is presented. The tested model assumes that the collapse takes place in the reference frame determined by the massive measuring detectors. Entangled photons are measured at 10 km distance within a time interval of less than 5 ps. The two apparatuses are in relative motion so that both detectors, each

T. Miyakawa, T. Suzuki, H. Yabu

The behavior of collective oscillations of a trapped boson-fermion mixed condensate is studied in the sum rule approach. Mixing angle of bosonic and fermionic multipole operators is introduced so that the mixing characters of the low-lying collective modes are studied as functions of the boson-fermion interaction strength. For an attractive boson-fermion int

Cornelius Paufler

A vertical exterior derivative is constructed that is needed for a graded Poisson structure on multisymplectic manifolds over nontrivial vector bundles. In addition, the properties of the Poisson bracket are proved and first examples are discussed.

Pablo Mora, Hitoshi Nishino

We propose a class of models in which extended objects are introduced in Chern-Simons supergravity in such a way that those objects appear on the same footing as the target space. This is motivated by the idea that branes are already first quantized object, so that it is desirable to have a formalism that treats branes and their target space in a similar fas

Alexander Moroz

The applicability of the so-called isotropic and anisotropic complete photonic-band-gap (CPBG) models [S. John and J. Wang, Phys. Rev. Lett. {\bf 64}, 2418 (1990)] to capture essential features of the spontaneous emission (SE) of a fluorescent atom or molecule near a band-gap-edge of a CPBG structure is discussed.

O. Yaremchuk

In one-dimensional case, it is shown that the basic principles of quantum mechanics are properties of the set of intermediate cardinality.

Kevin Haglin, Charles Gale

We model J/psi using an effective lagrangian approach and calculate its spectral function in a gas of light mesons at finite temperature. We explore the hadronic landscape estimating cross sections for elastic and inelastic channels. Effects of form factors are tested in a general, but consistently gauge invariant manner. Relevance to heavy ion experiments i

George C. Gellas, Thomas R. Hemmert, Ulf-G. Meißner

We present a complete one-loop analysis of the four nucleon spin polarizabilities in the framework of heavy baryon chiral perturbation theory. The first non-vanishing contributions to the isovector and first corrections to the isoscalar spin polarizabilities are calculated. No unknown parameters enter these predictions. We compare our results to various disp

Krzysztof Sacha, Jakub Zakrzewski, Dominique Delande

We consider the dynamics of Rydberg states of the hydrogen atom driven by a microwave field of elliptical polarization, with a possible additional static electric field. We concentrate on the effect of a resonant weak field - whose frequency is close to the Kepler frequency of the electron around the nucleus - which essentially produces no ionization of the

Bernard Helffer, Mathieu Dutour

Motivated by the paper by J. Berger and K. Rubinstein \cite{BeRu} and other recent studies \cite{GiPh}, \cite{LuPa1}, \cite{LuPa2}, we analyze the Ginzburg-Landau functional in an open bounded set $Ω$. We mainly discuss the bifurcation problem whose analysis was initiated in \cite{Od} and show how some of the techniques developed by the first author in the c

Vyacheslav A. Soroka

A linear odd Poisson bracket realized solely in terms of Grassmann variables is suggested. It is revealed that with the bracket, corresponding to a semi-simple Lie group, both a Grassmann-odd Casimir function and invariant (with respect to this group) nilpotent differential operators of the first, second and third orders are naturally related and enter into

Khaled Abdel-Khalek

We investigate the seven sphere as a soft Lie algebra i.e. an algebra with structure functions instead of structure constants. We calculate its structure functions explicitly and also discuss some relevant points such as the validity of the Jacobi identities. Furthermore, we emphasis some important features such as the pointwise reduction, closure and some o

Khaled Abdel-Khalek

We investigate Clifford Algebras structure over non-ring division algebras. We show how projection over the real field produces the standard Attiyah-Bott-Shapiro classification.

Ludwig Faddeev

Personal view of author on goals and content of Mathematical Physics.

Michael K. Kinyon

On the unit sphere $\mathbb{S}$ in a real Hilbert space $\mathbf{H}$, we derive a binary operation $\odot$ such that $(\mathbb{S},\odot)$ is a power-associative Kikkawa left loop with two-sided identity $\mathbf{e}_0$, i.e., it has the left inverse, automorphic inverse, and $A_l$ properties. The operation $\odot$ is compatible with the symmetric space struct

Eric Leichtnam, John Lott, Paolo Piazza

If M is a compact oriented manifold-with-boundary whose fundamental group is virtually nilpotent or Gromov-hyperbolic, we show that the higher signatures of M are oriented-homotopy invariants.

Duco van Straten, Christian Sevenheck

We investigate deformations of lagrangian manifolds with singularities. We introduce a complex similar to the de Rham-complex whose cohomology calculates deformation spaces. Examples of singular lagrangian varieties are presented and deformations are calculated explicitly.

Valentin Golodets, Sergey Neshveyev

Let a countable amenable group G acts freely and ergodically on a Lebesgue space (X,mu), preserving the measure mu. If T is an automorphism of the equivalence relation defined by G then T can be extended to an automorphism alpha_T of the II_1-factor M=L^\infty(X,μ)\rtimes G. We prove that if T commutes with the action of G then H(alpha_T)=h(T), where H(alpha

Sergey Neshveyev, Erling Stormer

It is shown that if (M,phi,alpha) is a W*-dynamical system with M a type I von Neumann algebra then the entropy of alpha w.r.t. phi equals the entropy of the restriction of alpha to the center of M. If furthermore (N,psi,beta) is a W*-dynamical system with N injective then the entropy of the tensor product system is the sum of the entropies.

Sergey Neshveyev

We prove that some quantized Arnold cat maps are entropic K-systems. This result was formulated by H. Narnhofer[1], but the fact that the optimal decomposition for the multi-channel entropy constructed there is not strictly local was not appropriately taken care of. We propose a strictly local decomposition based on a construction of Voiculescu.

R. E. Borcherds

This is a note constructing a certain weight 4 automorphic form on the moduli space of cubic surfaces, posted here because it is referred to in math.AG/0002066

Sergey Neshveyev

We compute the dynamical entropy of Bogoliubov automorphisms of CAR and CCR algebras with respect to arbitrary gauge-invariant quasi-free states. This completes the research started by Stormer and Voiculescu, and continued in works of Narnhofer-Thirring and Park-Shin.

Tobias Ekholm

Regular homotopy classes of immersions of a 3-sphere in 5-space constitute an infinite cyclic group. The classes containing embeddings form a subgroup of index 24. The obstruction for a generic immersion to be regularly homotopic to an embedding is described in terms of geometric invariants of its self intersection. Geometric properties of self intersections

Tobias Ekholm, Andras Szucs

We give three formulas expressing the Smale invariant of an immersion f of a (4k-1)-sphere into (4k+1)-space. The terms of the formulas are geometric characteristics of any generic smooth map g of any oriented 4k-dimensional manifold, where g restricted to the boundary is an immersion regularly homotopic to f in (6k-1)-space. The formulas imply that if f and

F. Burstall, D. Ferus, K. Leschke, F. Pedit

This is the first comprehensive introduction to the authors&#39; recent attempts toward a better understanding of the global concepts behind spinor representations of surfaces in 3-space. The important new aspect is a quaternionic-valued function theory, whose &#34;meromorphic functions&#34; are conformal maps into quaternions, which extends the classical co

Frédéric Campana, Jean-Pierre Demailly

Andreotti-Vesentini, Ohsawa, Gromov, Kollár, among others, have observed that Hodge theory could be extended to (non compact) Kähler complete manifolds, within the L^2 framework. Also, many vanishing theorems on projective or Kähler manifolds rely on the Kodaira-Bochner-Nakano identity, and thus possess natural L^2 versions. Our goal is to define canonical L

Dana Stanley Fine

Sengupta&#39;s lower bound for the Yang-Mills action on smooth connections on a bundle over a Riemann surface generalizes to the space of connections whose action is finite. In this larger space the inequality can always be saturated. The Yang-Mills critical sets correspond to critical sets of the energy action on a space of paths. This may shed light on Ati

Raúl Ibáñez, Yuli Rudyak, Aleksy Tralle, Luis Ugarte

The paper deals with relations between the Hard Lefschetz property, (non)vanishing of Massey products and the evenness of odd-degree Betti numbers of closed symplectic manifolds. It is known that closed symplectic manifolds can violate all these properties (in contrast with the case of Kaehler manifolds). However, the relations between such homotopy properti

Vadim E. Levit, Eugen Mandrescu

The stability number of a graph G, denoted by alpha(G), is the cardinality of a stable set of maximum size in G. If alpha(G-e) > alpha(G), then e is an alpha-critical edge, and if mu(G-e) < mu(G), then e is a mu-critical edge, where mu(G) is the cardinality of a maximum matching in G. G is a Koenig-Egervary graph if alpha(G) + mu(G) equals its order. Beineke

P. D. Miller, A. Soffer, M. I. Weinstein

We study the solutions of linear Schroedinger equations in which the potential energy is a periodic function of time and is sufficiently localized in space. We consider the potential to be close to one that is time periodic and yet explicitly solvable. A large family of such potentials has been constructed and the corresponding Schroedinger equation solved b

Guillermo Arreaga, Riccardo Capovilla, Jemal Guven

We consider a relativistic brane propagating in Minkowski spacetime described by any action which is local in its worldvolume geometry. We examine the conservation laws associated with the Poincaré symmetry of the background from a worldvolume geometrical point of the view. These laws are exploited to explore the structure of the equations of motion. General

Beatriz Gato-Rivera

In the last six years remarkable developments have taken place concerning the representation theory of N=2 superconformal algebras. Here we present the highlights of such developments.

R. Shaisultanov

Neutrino-photon interactions in the presence of an external homogeneous constant electromagnetic field are studied. The $ννγ$ amplitude is calculated in an electromagnetic field of the general type, when the two field invariants are nonzero.

Z. Bern, L. Dixon, D. C. Dunbar, A. K. Grant

We review some applications of tree-level (classical) relations between gravity and gauge theory that follow from string theory. Together with $D$-dimensional unitarity, these relations can be used to perturbatively quantize gravity theories, i.e. they contain the necessary information for obtaining loop contributions. We also review recent applications of t

Andrew Chamblin, Csaba Csaki, Joshua Erlich, Timothy J. Hollowood

We discuss the properties of black holes in brane-world scenarios where our universe is viewed as a four-dimensional sub-manifold of some higher-dimensional spacetime. We consider in detail such a model where four-dimensional spacetime lies at the junction of several domain walls in a higher dimensional anti-de Sitter spacetime. In this model there may be an

Yonatan Zunger

p-Gerbes are a generalization of bundles that have (p+2)-form field strengths. We develop their properties and use them to show that every theory of p-gerbes can be reinterpreted as a gauge theory containing p-dimensional extended objects. In particular, we show that every closed (p+2)-form with integer cohomology is the field strength for a gerbe, and that

S. Moretti

The process e+e- -> Htt can be exploited at future Linear Colliders to measure the Higgs-top Yukawa coupling. In this note, we estimate the size of the irreducible backgrounds in the channel Htt -> bbbb WW -> bbbb ln qq, for the case of a Standard Model Higgs boson with mass between 100 and 140 GeV.

S. Moretti

The calculation of the tree-level QCD processes e+e- -> qqgggg, qqqqgg and qqqqqq has recently been accomplished. We highlight here the relevance of such reactions for some of the physics at future electron-positron linear accelerators.