December 1999 arXiv papers — page 22

Ying-Qing Wu

Steinhaus conjectured that every closed oriented $C^1$-curve has a pair of anti-parallel tangents. Porter disproved the conjecture by showing that there exist curves with no anti-parallel tangents. Colin Adams rised the question of whether there exists a nontrivial knot in $\R^3$ which has no parallel or antiparallel tangents. The main result of this paper s

Ying-Qing Wu

Let $F$ be a proper essential immersed surface in a hyperbolic 3-manifold $M$ with boundary disjoint from a torus boundary component $T$ of $M$. Let $α$ be the set of coannular slopes of $F$ on $T$. The main theorem of the paper shows that there is a constant $K$ and a finite set of slopes $Λ$ on $T$, such that if $β$ is a slope on $T$ with $Δ(β, α_i) > K$ f

Vadim E. Levit, Eugen Mandrescu

The stability number alpha(G) of a graph G is the cardinality of a maximum stable set in G, xi(G) denotes the size of core(G), where core(G) is the intersection of all maximum stable sets of G. In this paper we prove that for a graph G without isolated vertices, the following assertions are true: (i) if xi(G)< 2, then G is quasi-regularizable; (ii) if G is o

Sergei Ivashkovich, Vsevolod Shevchishin

This are the notes of a course, given by the first author for the Graduiertenkollegs (=graduate students) at the Ruhr-University Bochum, in December 1997. These lectures pursued two main tasks: FIRST - to give a systematic and self-contained introduction to the Gromov theory of pseudoholomorphic curves. This is done in Chapters I,II,III. SECOND - to explain

Tien-Cuong DINH

Let f and g two rational functions having the same Julia set J_f. Lets suppose that f has a rational indifferent periodic point and that the critical set of f is disjoint of J_f. Then or J_f has to be equal to P^1, a circle, an arc of a circle for some cordinate or f and g has to verify an equation of the type: $$f^{m_1}\circ g\circ f^{m_2}\circ\cdotc\circ f

Tomas L. Gomez, Francisco Presas

Unitary representations of the fundamental group of a Kahler manifold correspond to polystable vector bundles (with vanishing Chern classes). Semisimple linear representations correspond to polystable Higgs bundles. In this paper we find the objects corresponding to affine representations: the linear part gives a Higgs bundle and the translation part corresp

Roger Alperin

We give a hierarchial set of axioms for mathematical origami. The hierachy gives the fields of Pythagorean numbers, first discussed by Hilbert, the field of Euclidean constructible numbers which are obtained by the usual constructions of straightedge and compass, and the Origami numbers, which is also the field generated from the intersections of conics or e

B. Lian, K. Liu, S. T. Yau

We generalize the theorems in {\it Mirror Principle I} and {\it II} to the case of general projective manifolds without the convexity assumption. We also apply the results to balloon manifolds, and generalize to higher genus.

Kirill Saraikin

We consider the free field approach or bosonization technique for the Wess-Zumino-Novikov-Witten model with arbitrary Kac-Moody algebra on Riemann surface of genus zero. This subject was much studied previously, and the paper can be partially taken as a brief survey. The way to obtain well-known Schechtman-Varchenko solutions of the Knizhnik-Zamolodchikov eq

Helmuth Huffel, Gerald Kelnhofer

Based on a generalization of the stochastic quantization scheme we recently proposed a generalized, globally defined Faddeev-Popov path integral density for the quantization of Yang-Mills theory. In this talk first our approach on the whole space of gauge potentials is shortly reviewed; in the following we discuss the corresponding global path integral on th

J. C. Fabris, A. M. Pelinson, I. L. Shapiro

We consider vacuum quantum effects in the Early Universe, which may lead to inflation. The inflation is a direct consequence of the supposition that, at high energies, all the particles can be described by the weakly interacting, massless, conformally invariant fields. We discuss, from the effective field theory point of view, the stability of inflation, tra

Noboru Nakanishi, Izumi Ojima

It is pointed out that the essential parts of some recent papers by Mebarki {\it et al.} (hep-th/9911045, hep-th/9911046, hep-th/9911048, hep-th/9911049, dated 6 Nov.1999) are taken from a book written by Nakanishi and Ojima, published in 1990.

Richard Easther, Gerald Guralnik, Stephen Hahn

We test the Sinc function representation, a novel method for numerically evaluating Feynman diagrams, by using it to evaluate the three-loop master diagrams. Analytical results have been obtained for all these diagrams, and we find excellent agreement between our calculations and the exact values. The Sinc function representation converges rapidly, and it is

A. D. Martin, J. Outhwaite, M. G. Ryskin

We review the determination of the QED coupling at the Z pole, which is a crucial parameter for electroweak theory. We include recent e+e- -> hadron data from Novosibirsk and Beijing to re-evaluate alpha (M_Z^2). We find 1/alpha (M_Z^2) = 128.973 +/- 0.035 or 128.934 +/- 0.040 according, respectively, to whether inclusive or exclusive e+e- -> hadron data are

Mark Smith

Bose-Einstein symmetrization can lead to correlations between out going identical particles which reflect the space-time extent of the collision process. At LEP and LEPII these correlations have been studied as a function of a single variable Q, the invariant momentum separation. Assuming a simple form for the correlation function the experiments find source

A. Dedes, S. Heinemeyer, P. Teixeira-Dias, G. Weiglein

The upper limit on the lightest CP-even Higgs boson mass, mh, is analyzed within the MSSM as a function of tan(beta) for fixed mtop and Msusy. The impact of recent diagrammatic two-loop results on this limit is investigated. We compare the MSSM theoretical upper bound on mh with the lower bound obtained from experimental searches at LEP. We estimate that wit

V. A. Petrov, A. V. Prokudin

The proton structure function $F_2^p(x,Q^2)$ is described in the framework of the off-shell extention of the Regge-eikonal approach which automatically takes into account off-shell unitarity. We achieved a good quality of description for $x<10^{-2}$ and we argue that the data on $F_2^p(x,Q^2)$ measured at HERA can be fairly described with classical universal

Robert H. Brandenberger, Joao Magueijo

We review a few off-the-beaten-track ideas in cosmology. They solve a variety of fundamental problems; also they are fun. We start with a description of non-singular dilaton cosmology. In these scenarios gravity is modified so that the Universe does not have a singular birth. We then present a variety of ideas mixing string theory and cosmology. These solve

Barbara Szczerbinska, Wojciech Broniowski

Chiral restoration at finite temperatures is studied in chiral quark models with non-local regulators. At the leading-N_c level we find transition temperatures of the order of 100MeV. Meson-loop contributions are also analyzed and found to have a very small effect.

D. T. Son, M. A. Stephanov

We derive the effective Lagrangian for the low-energy massive meson excitations of the color-flavor-locking (CFL) phase of QCD with 3 flavors of light quarks. We compute the decay constants, the maximum velocities, and the masses of the mesons at large baryon chemical potential mu. The decay constants are linear in mu. The meson maximum velocities are close

D. A. Demir

Two well-known extended supersymmetric models, Z&#39; models and NMSSM, are comparatively analyzed in the limit of large trilinear Higgs couplings. The two models are found to have distinguishable Higgs spectra at both tree- and loop- levels. Higgs production through Bjorken processes at an $e^+e^-$ collider is shown to discriminate between the two models.

S. Dalley

I review a new treatment of an old idea for light-front quantization of lattice gauge theories and give new results from some illustrative calculations: [I] transverse lattice gauge theory; [II] pure glue; [III] heavy sources and winding modes; [IV] an example -- large-N QCD in 2+1 dimensions.

Norman H. Christ

The architecture and capabilities of the computers currently in use for large-scale lattice QCD calculations are described and compared. Based on this present experience, possible future directions are discussed.

JLQCD Collaboration, S. Aoki, M. Fukugita, S. Hashimoto

We present a study for the pion decay constant $f_π$ in the quenched approximation to lattice QCD with the Kogut-Susskind (KS) quark action, with the emphasis given to the renormalization problems. Numerical simulations are carried out at the couplings $β= 6.0$ and 6.2 on $32^3\times 64$ and $48^3\times 64$ lattices, respectively. The pion decay constant is

A. J. Schwartz

HERA-B is a hadroproduction experiment located at DESY in Hamburg, Germany. The experiment produces B mesons and baryons by inserting thin wire targets into the halo of the proton beam circulating in the HERA storage ring. The B decays are studied to search for evidence of CP violation and constrain the angle $β$ and possibly $γ$ and $α$ of the CKM unitarity

Michele Gallinaro

We present the latest results from the CDF experiment at the Tevatron Collider in \ppbar collisions at $\sqrt{s} = 1.8$ TeV. The large data sample collected during Run 1, from 1992 until 1995, allows measurements in many domains of high-energy physics. Here, we report on the first measurement of $\sin(2β)$, a CP violation parameter, and on an improved measur

Myung Ho Kim

This decade has seen a great deal of progress in the development of information retrieval systems. Unfortunately, we still lack a systematic understanding of the behavior of the systems and their relationship with documents. In this paper we present a completely new approach towards the understanding of the information retrieval systems. Recently, it has bee

M. O. Dzero, L. P. Gor&#39;kov, V. Z. Kresin

The phase diagram and low temperature properties of the doped manganites A1-xBxMnO3 are discussed for the concentrations x < 0.4. The transition from insulating antiferromagnetic to metallic ferromagnetic state at x_cr = 0.16 is treated by means of percolation theory. The unifying description of insulating and metallic states is presented. The undoped mangan

A. A. Ovchinnikov, M. Ya. Ovchinnikova

Angular dependence of gap, seen in photoemission, its evolution with doping and temperature are interpreted on base t-t&#39;-U Hubbard model in which a pseudogap is a working function for electrons removing from dielectric segments of zone boundary. Tunnel spectra in one-particle approximation display only superconducting gap and too large asymmetry in regio

H. Wahlen, H. Rieger

By means of molecular dynamics simulations we examine the aging process of a strong glass former, a silica melt modeled by the BKS potential. The system is quenched from a temperature above to one below the critical temperature, and the potential energy and the scattering function C(t_w,t+t_w) for various waiting times t_w after the quench are measured. We f

Y. -C. Lin, N. Kawashima, F. Igloi, H. Rieger

The quantum critical behavior and the Griffiths-McCoy singularities of random quantum Ising ferromagnets are studied by applying a numerical implementation of the Ma-Dasgupta-Hu renormalization group scheme. We check the procedure for the analytically tractable one-dimensional case and apply our code to the quasi-one-dimensional double chain. For the latter

H. -P. Eckle, H. Johannesson, C. A. Stafford

We study the influence of a magnetic impurity or ultrasmall quantum dot on the charge persistent current of a mesoscopic ring. The system consists of electrons in a one-dimensional ring threaded by spin-dependent Aharonov-Bohm/Casher fluxes, coupled via an antiferromagnetic exchange interaction to a localized electron. By passing to a basis of electron state

Lapo Casetti, Marco Pettini, E. G. D. Cohen

This paper is a review of results which have been recently obtained by applying mathematical concepts drawn, in particular, from differential geometry and topology, to the physics of Hamiltonian dynamical systems with many degrees of freedom of interest for statistical mechanics. The first part of the paper concerns the applications of methods used in classi

V. V. Moshchalkov, V. A. Ivanov

We have analysed the effect of intrinsic doping inhomogeneity and the presence of stripes in high-T_c superconductors on coupling λby using a simple analytically solvable model with an angular dependent λ(ϕ) represented by a square-well form. We have found that the introduction of the Coulomb repulsion λ_C, increasing the &#39;&#39;contrast&#39;&#39; | λ| +

S L A de Queiroz

Finite-size corrections to scaling of critical correlation lengths and free energies of Ising and three-state Potts ferromagnets are analysed by numerical methods, on strips of width $N$ sites of square, triangular and honeycomb lattices. Strong evidence is given that the amplitudes of the ``analytical&#39;&#39; correction terms, $N^{-2}$, are identically ze

F. Zambelli, L. P. Pitaevskii, D. M. Stamper-Kurn, S. Stringari

The dynamic structure factor of a trapped Bose-Einstein condensed gas is investigated at zero temperature in the framework of Bogoliubov theory. Different values of momentum transfer are considered, ranging from the phonon to the single-particle regime. Various approximated schemes are discussed, including the local density approximation, where the system is

C. Furtlehner

We propose a Lifshitz argument in order to analyse the low energy spectrum of an electron moving in a strong magnetic field and scattered by randomly distributed repulsive zero-range impurities. The typical configurations of disorder which give rise to low energy states are identified as clusters of impurities. This allows for an interpretation of low-lying

I. S. Gorban, M. M. Bilyi, I. M. Dmitruk, O. A. Yeshchenko

Tokunaga et al. [Phys. Rev. B Vol. 59, R7837 (1999)] claim the first successful observation of the inverse exciton M series in the emission spectrum of excitonic molecules. We assert that actually such a series was observed as early as 1989 in the beta-ZnP_2 crystal. We show that the objections of Tokunaga et al. against the biexciton nature of the inverse e

Pierpaolo Bruscolini, Lapo Casetti

We define a lattice model for the interaction of a polymer with water. We solve the model in a suitable approximation. In the case of a non-polar homopolymer, for reasonable values of the parameters, the polymer is found in a non-compact conformation at low temperature; as the temperature grows, there is a sharp transition towards a compact state, then, at h

Kirill Kavokin

Spins of charge carriers, paramagnetic centers, and nuclei in semiconductor structures are known to be oriented if circular-polarized light is shined upon the structure. This is due to transfer of angular momentum from photons to various excitations in the semiconductor. What would happen if the structure is anisotropic, so that the angular momentum is not c

O. Entin-Wohlman, A. Aharony, Y. Imry, Y. Levinson

The transmission of two electrons through a region where they interact is found to be enhanced by a renormalization of the repulsive interaction. For a specific example of the single-particle Hamiltonian, which includes a strongly attractive potential, the renormalized interaction becomes attractive, and the transmission has a pronounced maximum as function

R. J. F. Leote de Carvalho, E. Trizac, J. -P. Hansen

Swollen stacks of finite-size disc-like Laponite clay platelets are investigated within a Wigner-Seitz cell model. Each cell is a cylinder containing a coaxial platelet at its centre, together with an overall charge-neutral distribution of microscopic co and counterions, within a primitive model description. The non-linear Poisson-Boltzmann (PB) equation for

Ph. Blanchard, B. Cessac, T. Krueger

We develop a dynamical system approach for the Zhang&#39;s model of Self-Organized Criticality, for which the dynamics can be described either in terms of Iterated Function Systems, or as a piecewise hyperbolic dynamical system of skew-product type. In this setting we describe the SOC attractor, and discuss its fractal structure. We show how the Lyapunov exp

Subhasis Sinha

We investigate the collective magnetoplasmon excitations in a quantum dot containing finite number of electrons in the high magnetic field limit. We consider the electrons in the lowest Landau level and neglect mixing between the higher Landau levels. The dispersion relation of these edge modes are estimated following the energy weighted sum-rule approach. I

Subhasis Sinha

We investigate different types of collective excitations in a quantum dot containing finite number of electrons at zero magnetic field. To estimate the excitation energies analytically we follow the energy weighted sum-rule approach. We consider the most general multipole excitation with angular momentum l, and the breathing mode excitation (monopole excitat

Robert Joynt

A theory is put forward that the electronic phase transition at 0.2 K in Ni-doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ is result of the formation of a spin density wave in the system of Ni impurities. The driving force for the transition is the exchange interaction between the impurity spins and the spins of the conduction electrons. This creates a small gap at

Jae Dong Noh

We propose a group model for correlations in stock markets. In the group model the markets are composed of several groups, within which the stock price fluctuations are correlated. The spectral properties of empirical correlation matrices reported in [Phys. Rev. Lett. {\bf 83}, 1467 (1999); Phys. Rev. Lett. {\bf 83}, 1471 (1999.)] are well understood from th

Y. A. Dimashko, C. Morais Smith, N. Hasselmann, A. O. Caldeira

We study the transversal dynamics of a charged stripe (quantum string) and show that zero temperature quantum fluctuations are able to depin it from the lattice. If the hopping amplitude t is much smaller than the string tension J, the string is pinned by the underlying lattice. At t>>J, the string is depinned and allowed to move freely, if we neglect the ef

C. Morais Smith, N. Hasselmann, Yu. A. Dimashko, A. H. Castro Neto

We study the influence of disorder and lattice pinning on the dynamics of a charged stripe. Starting from a phenomenological model of a discrete quantum string, we determine the phase diagram for this system. Three regimes are identified, the free phase, the flat phase pinned by the lattice, and the disorder pinned phase. In the absence of impurities, the sy

Boldizsar Janko

In order to test the recently proposed connection between the neutron resonance and the specific heat anomaly in cuprates, the experimental specific heat data on $YBa_2Cu_3O_{6.93}$ and a theoretical estimate of the single particle fermionic contribution to the specific heat is used to provide an upper bound for the intensity of the neutron peak. The deduced

B. Arnaud, M. Alouani

We have implemented the so called GW approximation (GWA) based on an all-electron full-potential Projector Augmented Wave (PAW) method. For the screening of the Coulomb interaction W we tested three different plasmon-pole dielectric function models, and showed that the accuracy of the quasiparticle energies is not sensitive to the the details of these models

A. H. Castro Neto

In this paper we review the current experimental and theoretical situation of the description of non-Fermi liquid behavior (NFL) in U and Ce intermetallics. We focus on the magnetic and thermodynamic properties. We also discuss a recent theoretical interpretation of this behavior in terms of Griffiths-McCoy singularities close to the magnetic quantum critica

N. Berglund

We review some properties of dynamical systems with slowly varying parameters, when a parameter is moved through a bifurcation point of the static system. Bifurcations with a single zero eigenvalue may create hysteresis cycles, whose area scales in a nontrivial way with the adiabatic parameter. Hopf bifurcations lead to the delayed appearance of oscillations

F. Legrand

It has been suggested that a continuous low star formation rate has been the dominant regime in IZw 18 and in dwarf galaxies for the lifetime of these objects (Legrand et al. 1999). Here, we discuss and model various star-forming histories for IZw 18. Particularly, we show that if the metallicity observed in IZw 18 results from starburst events only, the obs

D. T. Frayer, N. Z. Scoville

We present observations of the luminous population of high-redshift sub-mm galaxies taken at the OVRO Millimeter Array. Studies of sub-mm galaxies are vital to our understanding of the formation and early evolution of galaxies since this population could account for a significant fraction of the total amount of star formation and AGN activity at high redshif

Edward F. Brown, Greg Ushomirsky

Recent observations suggest that neutron stars in low-mass X-ray binaries rotate within a narrow range of spin frequencies clustered around 300 Hz. A proposed explanation for this remarkable fact is that gravitational radiation from a steady-state r-mode oscillation in the neutron star&#39;s core halts the spin-up due to accretion. For the neutron star trans

Andrew Gould, Hans-Walter Rix

If supermassive black holes (BHs) are generically present in galaxy centers, and if galaxies are built up through hierarchical merging, BH binaries are at least temporary features of most galactic bulges. Observations suggest, however, that binary BHs are rare, pointing towards a binary lifetime far shorter than the Hubble time. We show that, regardless of t

Craig J. Hogan

A brief but broad survey is presented of the flows, forms and large-scale transformations of mass-energy in the universe, spanning a range of about twenty orders of magnitude (m_{Planck}/m_{proton}) in space, time and mass. Forms of energy considered include electromagnetic radiation, magnetic fields, cosmic rays, gravitational energy and gravitational radia

R. de Grijs, R. W. O&#39;Connell, J. S. Gallagher

We present high-resolution optical and near-infrared HST observations of two adjacent regions in the fossil starburst region in M82, B1 and B2. Age estimates date the cluster population in the fossil starburst between ~2 x 10^8 and ~10 x 10^9 years, assuming solar metallicity. The star cluster population in B2 is more heavily affected by internal extinction

Craig J. Hogan

A fair and complete accounting of cosmic baryons now appears possible, because most of them are in states which are either directly observable or reliably constrained by indirect arguments. More than three-quarters of the baryons are probably in hot ionized gas clustering, along with galaxies and dark matter, in the cosmic web. The rest are in galaxies, roug

F. W. Stecker, M. H. Salamon, C. Done

In this paper, we suggest a new hypothesis for explaining the spectrum of the extragalactic MeV gamma-ray background as observed by COMPTEL and SMM. We propose that both the flux level and spectrum can be accounted for as a superposition of non-thermal MeV tails in the spectra of Seyfert galaxies and other AGN. Although present detectors are not sensitive en

O. Lahav, S. L. Bridle, M. P. Hobson, A. N. Lasenby

Recently several studies have jointly analysed data from different cosmological probes with the motivation of estimating cosmological parameters. Here we generalise this procedure to take into account the relative weights of various probes. This is done by including in the joint χ^2 function a set of `Hyper-Parameters&#39;, which are dealt with using Bayesia

P. G. Perez-Gonzalez, J. Zamorano, J. Gallego, A. Gil de Paz

We present Johnson B CCD photometry for the whole sample of galaxies of the Universidad Complutense de Madrid (UCM) Survey Lists I and II. They constitute a well-defined and complete sample of galaxies in the Local Universe with active star formation. The data refer to 191 S0 to Irr galaxies at an averaged redshift of 0.027, and complement the already publis

P. Uttley, I. M. McHardy, I. E. Papadakis, I. Cagnoni

We present a flux variability study of simultaneous RXTE and EUVE observations of the highly variable Seyfert galaxy NGC4051. We find a strong correlation between variability in the EUV and medium energy X-ray bands,indicating that both are sampling the same power-law continuum. The lag between the two bands is less than 20 ks and, depending on model assumpt

A. W. Strong, I. V. Moskalenko, O. Reimer

Galactic diffuse continuum gamma-ray emission is intricately related to cosmic-ray physics and radio astronomy. We describe recent results from an approach which endeavours to take advantage of this. Information from cosmic-ray composition constrains the propagation of cosmic rays; this in turn can be used as input for gamma-ray models. The GeV gamma-ray exc

Shmuel Balberg, Stuart L. Shapiro, Luca Zampieri

If a black hole formed in a core-collapse supernova is accreting material from the base of the envelope, the accretion luminosity could be observable in the supernova light curve. We present results of a fully relativistic numerical investigation of the fallback of matter onto a black hole in a supernova and examine conditions which would be favorable for de

A. W. Strong, I. V. Moskalenko

Models for the diffuse Galactic continuum emission and synchrotron radiation show that it is difficult to reproduce observations of both of these from the same population of cosmic-ray electrons. This indicates that an important contributor to the emission below 10 MeV could be an unresolved point-source population. We suggest that these could be Crab-like s

J. B. Hutchings, M. L. Balogh

This paper reports maps of the cD galaxy in the rich z=0.23 cluster Abell 2390 at UV, [OII], L alpha and H alpha wavelengths. Spatially resolved UV and optical spectra were obtained with STIS on the Hubble Space Telescope; the 2 arcsec wide slit was aligned close to the long axis and blue lane of the galaxy and includes all the inner bright features seen in

Cesario Lia, Giovanni Carraro

We describe a new implementation of a parallel Tree-SPH code with the aim to simulate Galaxy Formation and Evolution. The code has been parallelized using SHMEM, a Cray proprietary library to handle communications between the 256 processors of the Silicon Graphics T3E massively parallel supercomputer hosted by the Cineca Supercomputing Center (Bologna, Italy

Martin C. Weisskopf

Significant advances in science inevitably occur when the state of the art in instrumentation improves. NASA&#39;s newest Great Observatory, the Chandra X-Ray Observatory (CXO) -- formally known as the Advanced X-Ray Astrophysics Facility (AXAF) -- launched on July 23, 1999 and represents such an advance. The CXO is designed to study the x-ray emission from

A. Udalski, I. Soszynski, M. Szymanski, M. Kubiak

We present the Catalog of Cepheids from the SMC which contains data for 2049 objects detected in the 2.4 square degree area of central parts of the SMC. For each object period, BVI photometry, astrometry, and R_21, \phi_21 parameters of the Fourier decomposition of I-band light curve are provided. The Catalog is based on observations collected during the OGL

W. E. Harris, J. J. Kavelaars, D. A. Hanes, J. E. Hesser

Deep HST/WFPC2 (V,I) photometry is used to investigate the globular cluster system (GCS) in NGC 4874, the central cD galaxy of the Coma cluster. The luminosity function of the clusters displays its normal Gaussian-like shape and turnover level. Other features of the system are surprising: the GCS is (a) spatially extended, with core radius r_c = 22 kpc, (b)

F. -J. Zickgraf, J. M. Alcala, E. Covino, J. Krautter

We investigated the properties of the late-type stellar component in the RASS at high-galactic latitude |b| based on an optically identified sample of ROSAT All-Sky Survey (RASS) X-ray sources. The stellar sample comprises ~250 objects in six study areas covering 685 deg^2 at |b|> 20 deg. We spectroscopically detected a significant fraction of lithium-rich p

Franz-Josef Zickgraf

The characteristics of the various types of B[e] stars are discussed and compared with those of classical Be stars. Both groups of stars are characterized by the presence of emission lines in their spectra, in particular of hydrogen. However, there are also significant differences between these classes. Classical Be stars lack hot circumstellar dust and stro

L. W. Looney, M. J. Hardcastle

We present the results of sub-arcsecond 108 GHz continuum interferometric observations toward the radio luminous galaxy 3C123. Using multi-array observations, we utilize the high u,v dynamic range of the BIMA millimeter array to sample fully spatial scales ranging from 0.5&#34; to 50&#34;. This allows us to make one-to-one comparisons of millimeter-wavelengt

P. J. Outram, R. F. Carswell, T. Theuns

Recent numerical simulations have lead to a paradigm shift in our understanding of the intergalactic medium, and the loss of a physical justification for Voigt profile fitting of the Lyman-alpha forest. Many individual lines seen in simulated spectra have significant departures from the Voigt profile, yet could be well fitted by a blend of two or more such l

A. Kucinskas, V. Vansevicius, M. Sauvage, T. Tanabé

We report ISO (Infrared Space Observatory) observations of a new infrared source discovered in the vicinity of the young populous cluster NGC 330 in the Small Magellanic Cloud. The object was observed with ISOCAM at 4.5, 6.75 and 11.5 $μ$m and shows a prominent mid-infrared excess, indicating the presence of a dust shell. The available observations of the op

Joel R. Primack

The cosmological parameters that I will emphasize are the Hubble parameter $H_0 \equiv 100 h$ km s$^{-1}$ Mpc$^{-1}$, the age of the universe $t_0$, the average matter density $Ω_m$, the baryonic matter density $Ω_b$, the neutrino density $Ω_ν$, and the cosmological constant $Ω_Λ$. The evidence currently favors $t_0 \approx 13$ Gyr, $h \approx 0.65$, $Ω_m \a

Pierre-Henri Chavanis

We develop the idea proposed by Barge & Sommeria (1995) and Tanga et al. (1996) that large-scale vortices present in the solar nebula can concentrate dust particles and facilitate the formation of planetesimals and planets. We introduce an exact vortex solution of the incompressible 2D Euler equation and study the motion of dust particles in that vortex. In

F. Palla, R. Bachiller, L. Stanghellini, M. Tosi

We present the results of a study aimed at determining the 12C/13C ratio in two samples of planetary nebulae (PNe) by means of millimeter wave observations of 12CO and 13CO. The first group includes six PNe which have been observed in the 3He+ hyperfine transition by Balser et al. (1997); the other group consists of 22 nebulae with rich molecular envelopes.

Ken-ichi Oohara, Takashi Nakamura

We develop a 3 dimensional computer code to study a coalescing neutron star binary. The code can currently follow the evolution up to two stars begin to merge from two spherical stars of mass 1 solar mass and radius 8.9km with separation 35.4km. As for coordinate conditions, we use conformal slicing and pseudo-minimal distortion conditions. The evolution equ

Yoshihiro Ueda

We present main results from X-ray surveys performed with ASCA, focusing on the ASCA Large Sky Survey (LSS), the Lockman Hole deep survey, and the ASCA Medium Sensitivity Survey (AMSS or the GIS catalog project). The log N-log S relations, spectral properties of sources, and results of optical identification are summarized. We discuss implications of these r

Yang Sun, Mike Guidry, Lian-Ao Wu, Cheng-Li Wu

This paper has been withdrawn by the author due to incomplete interpretation for the results.

Luis Bento, Petteri Keränen, Jukka Maalampi

Active galactic nuclei (AGN) have been suggested to be sources of very high energy neutrinos. We consider the possibility of using AGN neutrinos to test neutrino mixings. From the atmospheric, solar and laboratory data on neutrino oscillations we derive the flavour composition of the AGN neutrino flux in different neutrino mixing schemes. We show that most o

P. Deines-Jones, M. L. Cherry, A. Dabrowska, R. Holynski

Charged particle multiplicities from high multiplicity central interactions of 158 GeV/nucleon Pb ions with Pb target nuclei have been measured in the central and far forward projectile spectator regions using emulsion chambers. Multiplicities are significantly lower than predicted by Monte Carlo simulations. We examine the shape of the pseudorapidity distri

D. V. Pakhnin, A. I. Sokolov

The renormalization-group (RG) functions for the three-dimensional n-vector cubic model are calculated in the five-loop approximation. High-precision numerical estimates for the asymptotic critical exponents of the three-dimensional impure Ising systems are extracted from the five-loop RG series by means of the Pade-Borel-Leroy resummation under n = 0. These

H. B. Benaoum

A U(1) BF-Yang-Mills theory on noncommutative ${\mathbb{R}}^4$ is presented and in this formulation the U(1) Yang-Mills theory on noncommutative ${\mathbb{R}}^4$ is seen as a deformation of the pure BF theory. Quantization using BRST symmetry formalism is discussed and Feynman rules are given. Computations at one-loop order have been performed and their reno

Vladimir P. Gerdt, Yuri A. Blinkov

In this paper we present an algorithm for construction of minimal involutive polynomial bases which are Groebner bases of the special form. The most general involutive algorithms are based on the concept of involutive monomial division which leads to partition of variables into multiplicative and non-multiplicative. This partition gives thereby the self-cons

Yang Ze-sen, Li Xianhui, Zhou Zhining, Zhong Yushu

Based on the renormalisability of the SU(n) theory with massive gauge bosons, we start with the path integral of the generating functional for the renormalized Green functions and develop a method to construct the scattering matrix so that the unitarity is evident. By using as basical variables the renormalized field functions and defining the unperturbed Ha

A. Mary Selvam, A. S. Ramachandra Murty, Bh. V. Ramanamurty

A simple model which can explain the observed vertical distribution and size spectrum of atmospheric aerosol has been proposed. The model is based on a new physical hypothesis for the vertical mass exchange between the troposphere and the stratosphere. The vertical mass excange takes place through a gravity wave feedback mechanism. There is a close agreement

Steven Finch

We study a specific convex maximization problem in the space of continuous functions defined on a semi-infinite interval. An unexplained connection to the discrete version of this problem is investigated.

Steven Finch

We study a specific convex maximization problem in n-dimensional space. The conjectured solution is proved to be a vertex of the polyhedral feasible region, but only a partial proof of local maximality is known. Integer sequences with interesting patterns arise in the analysis, owing to the number theoretic origin of the problem.

E. Tevelev

The paper deals with the configuration of subalgebras in generic $n$-dimensional $k$-argument anticommutative algebras and ``regular&#39;&#39; anticommutative algebras.

Bertrand Toen

This is the integral text of my thesis. The first part is an expanded version of &#34;Riemann-Roch theorems for Deligne-Mumford stacks&#34;, where I deal with Artin stacks over general bases. In the second part, I prove some Riemann-Roch statment for D-modules on Deligne-Mumford stacks, and I also consider the problem of algebraization of analytic stacks.

Pierre van Baal

We review results of the last two years concerning caloron solutions of unit charge with non-trivial holonomy, revealing the constituent monopole nature of these instantons. For SU(n) there are n such BPS constituents. New is the presentation of the exact values for the Polyakov loop at the three constituent locations for the SU(3) caloron with arbitrary hol

A. Ya. Berdnikov, Ya. A. Berdnikov, A. N. Ivanov, V. F. Kosmach

An abundance of the strangeness that can be induced in a thermalized quark-gluon plasma (QGP) is considered as a signal of the QGP phase appearing in the intermediate state of ultra-relativistic heavy-ion collisions. As a quantitative characteristic of this signal we take the ratio R_{K^+ K^-} = N_{K^+}/N_{K^-} of the multiplicities of the production of K^+_

V. A. Petrov, A. V. Prokudin

We develop an off-shell extention of the Regge-eikonal approach which automatically takes into account off-shell unitarity. We argue that exclusive vector-meson production cross-sections measured at HERA can be fairly described with classical universal Regge trajectories. No extra ``hard&#39;&#39; trajectories of high intercept are needed for that.

Afsar Abbas

Very recently, it has been shown by the author that the Standard Model Higgs cannot be a physical particle. Here, on most general grounds it is established that as per the Standard Model there is no electric charge above the electro-weak phase transition temperature. Hence there was no electric charge present in the early universe. The Superstring Theories a

Afsar Abbas

It is shown that in the Standard Model, the property of charge quantization holds for a Higgs with arbitrary isospin and hypercharge. These defining quantum numbers of the Higgs remain unconstrained while the whole basic and fundamental structure of the Standard Model remains intact. Hence it is shown that the Higgs cannot be a physical particle. Higgs is th

Joao P Silva, Abner Soffer

Several methods have been devised to measure the weak phase gamma using decays of the type B+- --> D K+-, where it is assumed that there is no mixing in the D0-D0bar system. However, when using these methods to uncover new physics, one must entertain the real possibility that the measurements are affected by new physics effects in the D0-D0bar system. We sho