June 2000 arXiv papers — page 7

Christian Krattenthaler, Anthony J. Guttmann, Xavier G. Viennot

We derive new results for the number of star and watermelon configurations of vicious walkers in the presence of an impenetrable wall by showing that these follow from standard results in the theory of Young tableaux, and combinatorial descriptions of symmetric functions. For the problem of $n$-friendly walkers, we derive exact asymptotics for the number of

Gustavo Dotti

The classical moduli space M of a supersymmetric gauge theory with trivial superpotential can be stratified according to the unbroken gauge subgroup at different vacua. We apply known results about this stratification to obtain the W \neq 0 theory classical moduli space M^W \subset M, working entirely with the composite gauge invariant operators X that span

C. Bagnuls, C. Bervillier, D. I. Meiron, B. G. Nickel

This note is intended to emphasize the existence of estimated Feynman integrals in three dimensions for the free energy of the O(1) scalar theory up to five loops which may be useful for other work. We also correct some misprints of the published paper.

S. Haffner, D. M. Brammeier, C. G. Olson, L. L. Miller

In angle-resolved photoelectron spectra of the antiferromagnetic insulators Ca2CuO2Cl2 and Sr2CuO2Cl2 a sharp drop of the spectral intensity of the lowest-lying band is observed along a line in k space equivalent to the Fermi surface of the optimally doped high-temperature superconductors. This was interpreted as a signature of the existence of a remnant Fer

Stefano Forte, Lorenzo Magnea, Andrea Piccione, Giovanni Ridolfi

We define truncated Mellin moments of parton distributions by restricting the integration range over the Bjorken variable to the experimentally accessible subset x_0 < x < 1 of the allowed kinematic range 0 < x < 1. We derive the evolution equations satisfied by truncated moments in the general (singlet) case in terms of an infinite triangular matrix of anom

Alexander Altland, B. D. Simons, M. R. Zirnbauer

The physics of low-energy quasi-particle excitations in disordered d-wave superconductors is a subject of ongoing intensive research. Over the last decade, a variety of conceptually and methodologically different approaches to the problem have been developed. Unfortunately, many of these theories contradict each other, and the current literature displays a l

Dmitriy Uvarov

By considering the superembedding equation for the Type II superstring we derive the classical relation between the NSR string and the Type II GS superstring Grassmannian variables. The connection between the actions of these two models is also established. Then introducing the proper twistor-like Lorentz harmonic variables we fix $κ-$symmetry of the GS form

P. Haas, E. Griesshaber, B. Gorshunov, D. Schweitzer

Optical reflection measurements within the highly conducting (a,b)-plane of the organic metal (BEDT-TTF)_4[Ni(dto)_2] reveal the gradual development of a sharp feature at around 200 cm as the temperature is reduced below 150 K. Below this frequency a narrow Drude-like response is observed which accounts for the metallic behavior. Since de Haas-von Alphen osc

L. V. Fil&#39;kov, V. L. Kashevarov, E. S. Konobeevski, M. V. Mordovskoy

The analysis of new experimental data, obtained at the Proton Linear Accelerator of INR, with the aim to search for supernarrow dibaryons in the $pd\to ppX_1$ and $pd\to pdX_2$ reactions is presented. Narrow peaks with an experimental width of 5 MeV at masses of 1904$\pm 2$, 1926$\pm 2$, and 1942$\pm 2$ MeV have been observed in missing mass $M_{pX_1}$ spect

Jong-Phil Lee, Chun Liu, H. S. Song

The mass spectrum of the L=1 orbitally excited heavy baryons with light quarks in the spin-flavor symmetric representation is studied by the $1/N_c$ expansion method in the framework of the heavy quark effective theory. The mixing effect from the baryons in the mixed representation is considered. The general pattern of the spectrum is predicted which will be

Daigen Fukayama, Tohru Nakano, Alexander Bershadskii, Toshiyuki Gotoh

Using a generalization of extended self-similarity we have studied local scaling properties of 3D turbulence in a direct numerical simulation. We have found that these properties are consistent with lognormal-like behavior of energy dissipation fluctuations with moderate amplitudes for space scales $r$ beginning from Kolmogorov length $η$ up to the largest s

Rosy Teh

Some exact static solutions of the SU(2) Yang-Mills-Higgs theory are presented. These solutions satisfy the first order Bogomol&#39;nyi equations, and possess infinite energies. They are axially symmetric and could possibly represent monopoles and an antimonopole sitting on the z-axis.

W. C. Haxton, Wei Lin

We calculate the thermal flux of low-energy solar neutrinos and antineutrinos of all flavors arising from a variety of neutrino pair processes: Compton production (including plasmon-pole diagrams), neutral current decay of thermally populated nuclear states, plasmon decay, and electron transitions from free to atomic bound states. The resulting flux density

Dik Bouwmeester

An optical scheme for the reliable transfer of quantum information through a noisy quantum channel is proposed. The scheme is inspired by quantum error-correction protocols, but it avoids the currently infeasible requirement for a controlled-NOT operation between single photons. The quantum communication scheme presented here rejects single bit-flip errors i

Suranjana Rai, Jagdish Rai

We provide a group-theoretical classification of the entangled states of N identical particles. The connection between quantum entanglement and the exchange symmetry of the states of N identical particles is made explicit using the duality between the permutation group and the simple unitary group. Each particle has n-levels and spans the n-dimensional Hilbe

Diana Duplij, Steven Duplij

A three-dimensional model of the genetic vocabulary is proposed in terms of determinative degree, an introduced characteristic of nucleotide, which reflects absolute difference between purin and pyrimidin bases in one DNA strand. In the fremework of this model manifest symmetry and group properties are described. It is proposed to use the determinative degre

Jacek Piskozub, Piotr J. Flatau, J. V. R. Zaneveld

A Monte Carlo model was used to study the scattering error of an absorption meter with a divergent light beam and a limited acceptance angle of the receiver. Reflections at both ends of the tube were taken into account. Calculations of the effect of varying optical properties of water, as well as the receiver geometry, were performed. A weighting function sh

Piotr J. Flatau, Maria Flatau, J. R. V. Zaneveld, Curtis D. Mobley

We report on the influence of submerged bubble clouds on the remote sensing properties of water. We show that the optical effect of bubbles on radiative transfer and on the estimate of the ocean color is significant. We present a global map of the volume fraction of air in water derived from daily wind speed data. This map, together with the parameterization

Jun Wang, Wei Wang

The folding characteristics of sequences reduced with a possibly simplified representation of five types of residues are shown to be similar to their original ones with the natural set of residues (20 types or 20 letters). The reduced sequences have a good foldability and fold to the same native structure of their optimized original ones. A large ground stat

Jean Ringot, Pascal Szriftgiser, Jean-Claude Garreau, Dominique Delande

This paper presents the first experimental evidence of the transition from dynamical localization to delocalization under the influence of a quasi-periodic driving on a quantum system. A quantum kicked rotator is realized by placing cold atoms in a pulsed, far-detuned, standing wave. If the standing wave is periodically pulsed, one observes the suppression o

Murray Peshkin

Mugnai et al. have reported an experiment in which microwave packets appear to travel in air with a speed substantially greater than c. They calculate the group velocity of their packets and find that it agrees with their experimental result. That calculation is incorrect. A correct calculation gives a group velocity less than c. The reported experimental re

P. N. Bibikov

A computer algebra algoritm for solving the quantum Yang-Baxter equation is presented. It is based on the Taylor expansion of R-matrix which is developed up to the order λ^6. As an example the classification of 4x4 R-matrices is given.

L. Martina, Kur. Myrzakul, R. Myrzakulov, G. Soliani

A few years ago, some of us devised a method to obtain integrable systems in (2+1)-dimensions from the classical non-Abelian pure Chern-Simons action via reduction of the gauge connection in Hermitian symmetric spaces. In this paper we show that the methods developed in studying classical non-Abelian pure Chern-Simons actions, can be naturally implemented by

Tokuzo Shimada, Kengo Kikuchi

We revisit the globally coupled map lattice (GCML). We show that in the so called turbulent regime various periodic cluster attractor states are formed even though the coupling between the maps are very small relative to the non-linearity in the element maps. Most outstanding is a maximally symmetric three cluster attractor in period three motion (MSCA) due

J. Lieberum

We consider vector spaces H(n,l) and F(n,l) spanned by the degree-n coefficients in power series forms of the Homfly and Kauffman polynomials of links with l components. Generalizing previously known formulas, we determine the dimensions of the spaces H(n,l), F(n,l) and H(n,l)+F(n,l) for all values of n and l. Furthermore, we show that for knots the algebra

Liviu I. Nicolaescu

We prove that the mod Z reduction of the torsion of a rational homology 3-sphere is completely determined by three data: a certain canonical spin^c structure, the linking form and a Q/Z-valued constant c. This constant is a new topological invariant of the rational homology sphere. Experimentations with lens spaces suggest this constant may be as powerful an

Anders Kock

In the context of synthetic differential geometry, we study the Laplace operator an a Riemannian manifold. The main new aspect is a neighbourhood of the diagonal, smaller than the second neighbourhood usually required as support for second order differential operators. The new neighbourhood has the property that a function is affine on it if and only if it i

Stefan Schraml, Julius Wess

The three-dimensional quantum Euclidean space is an example of a non-commutative space that is obtained from Euclidean space by $q$-deformation. Simultaneously, angular momentum is deformed to $so_q(3)$, it acts on the $q$-Euclidean space that becomes a $so_q(3)$-module algebra this way. In this paper it is shown, that this algebra can be realized by differe

Anatoly Vershik

The new model for the free solvable groups of level two is given; this helps to calculate the Poisson-Furstenberg boundary of the group.

Daniel Bertrand, Wadim Zudilin

It is a classical fact that the elliptic modular functions satisfies an algebraic differential equation of order 3, and none of lower order. We show how this generalizes to Siegel modular functions of arbitrary degree. The key idea is that the partial differential equations they satisfy are governed by Gauss--Manin connections, whose monodromy groups are wel

Joseph Lykken, Robert C. Myers, Jing Wang

We consider a brane-world construction which incorporates a finite region of flat space, ``the box,&#39;&#39; surrounded by a region of anti-de Sitter space. This hybrid construction provides a framework which interpolates between the scenario proposed by Arkani-Hamed, Dimopoulos and Dvali, and that proposed by Randall and Sundrum. Within this composite fram

P. Y. Casteill, G. Valent

We study the principal sigma-models defined on any group manifold GL x GR/GD with breaking of GR, and their T-dual transforms. For abritary breaking we can express the torsion and Ricci tensor of the dual model in terms of the frame geometry of the initial principal model. Using these results, we give necessary and sufficient conditions for the dual model to

Matej Pavsic

A brane world model is investigated, in which there are many branes that may intersect and self intersect. One of the branes, being a 3-brane, represents our spacetime, while the other branes, if they intersect our brane world, manifest themselves as matter in our 3-brane. It is shown that such a matter encompasses dust of point particles and higher dimensio

M. Bonini, E. Tricarico

We use the Wilson renormalization group (RG) formulation to solve the fine-tuning procedure needed in renormalization schemes breaking the gauge symmetry. To illustrate this method we systematically compute the non-invariant couplings of the ultraviolet action of the SU(2) pure Yang-Mills theory at one-loop order.

A. Martinez, J. J. Torres, R. Flores-Mendieta, A. Garcia

We obtain a model-independent expression for the Dalitz plot of semileptonic decays of polarized hyperons including radiative corrections to order alpha and neglecting terms of order (alpha q)/(pi M_1), where q is the four-momentum transfer and M_1 is the mass of the decaying hyperon. We specialize our results to exhibit the correlation between the charged-l

D. R. Tovey

An effective mass scale Meffsusy for supersymmetric particles is defined and techniques for its measurement at the LHC discussed. Monte Carlo results show that, for jets + ETmiss events, a variable constructed from the scalar sum of the transverse momenta of all reconstructed jets together with ETmiss provides in most cases the most accurate model independen

Manuel Drees, David Wright

It has been suggested that a sterile neutrino ν_s which mixes with standard neutrinos can form nonthermal ``cool&#39;&#39; Dark Matter if its mass and mixing angle fall in the ranges 0.1 keV \lsim m_s \lsim 10 keV and 10^{-10} \lsim \sin^2 θ\lsim 10^{-4}, respectively. We point out that the required mixing makes these heavy neutrinos unstable. The dominant d

K. Maltman, J. Kambor

New finite energy sum rules (FESR's) for extracting m_s from hadronic tau decay data are constructed which (1) significantly reduce potential theoretical uncertainties present in existing sum rule analyses and (2) remove problems associated with both the poor convergence of the OPE representation of the longitudinal part of the $us$ vector and axial vector c

Andrei I. Onishchenko

We perform a detailed study of semileptonic form-factors for the doubly heavy baryons in the framework of three-point NRQCD sum rules. The analyis of spin symmetry relations as well as numerical results on various exclusive decay modes of doubly heavy baryons are given.

Stefan Weinzierl

These lectures given to graduate students in high energy physics, provide an introduction to Monte Carlo methods. After an overview of classical numerical quadrature rules, Monte Carlo integration together with variance-reducing techniques is introduced. A short description on the generation of pseudo-random numbers and quasi-random numbers is given. Finally

Fukuko Yuasa, Tadashi Ishikawa, Setsuya Kawabata, Denis Perret-Gallix

With an integrated software package {\tt GRACE}, it is possible to generate Feynman diagrams, calculate the total cross section and generate physics events automatically. We outline the hybrid method of parallel computation of the multi-dimensional integration of {\tt GRACE}. We used {\tt MPI} (Message Passing Interface) as the parallel library and, to impro

G. Morpurgo

Stimulated by a recent paper by Buchmann and Lebed,a comparison is presented of the two methods mentioned in the title for treating hadron properties in QCD.Doubts arise on the equivalence of the large N(c) description to real QCD.[PACS:12.38.Aw;11.15.Pg;12.40.Yx;13.40.Dk]

The CDF Collaboration

This report describes a measurement of the top quark mass in $\ppbar$ collisions at a center of mass energy of 1.8 TeV. The data sample was collected with the CDF detector during the 1992--95 collider run at the Fermilab Tevatron, and corresponds to an integrated luminosity of 106 \pb. Candidate $t\bar{t}$ events in the ``lepton+jets&#39;&#39; decay channel

Lee Samuel Finn

This paper has been withdrawn due to a crucial error in combining the two probability sectors represented in equations 13 and 14. Corrected, one can recover, in the limit of no background, the results of Allen et al. The general result that an analysis allowing for a background permits a substantial improvement of the limit still holds, though the presentati

S. Capozziello, G. Lambiase, Diego F. Torres

We explore the possibility that a charged particle moving in the gravitational field generated by a scalar star could radiate energy via a recently proposed gravitational Čerenkov mechanism. We numerically prove that this is not possible for stable boson stars. We also show that soliton stars could have Čerenkov radiation for particular values of the boson m

Victor Berezin, Maxim Okhrimenko

The self-gravitating, spherically symmetric thin shells built of orbiting particles are sstudied. Two new features are found. One is the minimal possible value for an angular momentum of particles, above which elleptic orbits become possible. The second is the coexistence of both the wormhole solutions and the elleptic or hyperbolic orbits for the same value

Jan-Georg Smaus, Patricia M. Hill, Andy King

We present verification methods for logic programs with delay declarations. The verified properties are termination and freedom from errors related to built-ins. Concerning termination, we present two approaches. The first approach tries to eliminate the well-known problem of speculative output bindings. The second approach is based on identifying the predic

Gregory Grefenstette, Julien Nioche

The World Wide Web has grown so big, in such an anarchic fashion, that it is difficult to describe. One of the evident intrinsic characteristics of the World Wide Web is its multilinguality. Here, we present a technique for estimating the size of a language-specific corpus given the frequency of commonly occurring words in the corpus. We apply this technique

Imseok Yang, Sergej Y. Savrasov, Gabriel Kotliar

We calculate magnetic anisotropy energy of Fe and Ni by taking into account the effects of strong electronic correlations, spin-orbit coupling, and non-collinearity of intra-atomic magnetization. The LDA+U method is used and its equivalence to dynamical mean-field theory in the static limit is emphasized. Both experimental magnitude of MAE and direction of m

Allan Griffin

This is based on 4 lectures given at the 13th Australian Physics Summer School, Australia National University, Canberra, Jan 17-28, 2000. The main topic is the theory of collective modes in a trapped Bose gas at finite temperatures. A generalized Gross-Pitaevskii equation is derived at finite temperatures, which is used to discuss a new mechanism for damping

J. P. Rodriguez

The nature of decoupling in the mixed phase of extremely type-II layered superconductors is studied theoretically through a duality transformation of the layered XY model with frustration. In the limit of weak coupling, we generally find that the Josephson effect is absent if and only if the phase correlations within isolated layers are short range. In the c

David J. Bergman

A recently developed self-consistent effective medium approximation, for composites with a columnar microstructure, is applied to such a three-constituent mixture of isotropic normal conductor, perfect insulator, and perfect conductor, where a strong magnetic field {\bf B} is present in the plane perpendicular to the columnar axis. When the insulating and pe

M. G. Vavilov, P. W. Brouwer, V. Ambegaokar, C. W. J. Beenakker

Random-matrix theory is used to study the mesoscopic fluctuations of the excitation gap in a metal grain or quantum dot induced by the proximity to a superconductor. We propose that the probability distribution of the gap is a universal function in rescaled units. Our analytical prediction for the gap distribution agrees well with exact diagonalization of a

Stefan Boettcher

An introduction to Extremal Optimization written for the Computer Simulation Column in ``Computing in Science and Engineering&#39;&#39; (CISE).

Horacio Castillo, Pierre Le Doussal

A particle in a random potential with logarithmic correlations in dimensions $d=1,2$ is shown to undergo a dynamical transition at $T_{dyn}>0$. In $d=1$ exact results demonstrate that $T_{dyn}=T_c$, the static glass transition temperature, and that the dynamical exponent changes from $z(T)=2 + 2 (T_c/T)^2$ at high temperature to $z(T)= 4 T_c/T$ in the glass

Tairan Wang, Jonathan Miller, Ned S. Wingreen, Chao Tang

Native protein folds often have a high degree of symmetry. We study the relationship between the symmetries of native proteins, and their designabilities -- how many different sequences encode a given native structure. Using a two-dimensional lattice protein model based on hydrophobicity, we find that those native structures that are encoded by the largest n

M. R. Trunin, Yu. A. Nefyodov, D. V. Shovkun, A. A. Zhukov

The c-axis penetration depth $λ_c$ in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO) single crystals as a function of temperature has been determined using three high-frequency techniques, namely: (i) measurements of the ac-susceptibility at a frequency of 100 kHz for different sample alignments with respect to the ac magnetic field; (ii) measurements of the surface

H. Enriquez, N. Bontemps, A. A. Zhukov, D. V. Shovkun

The first penetration field H_{J}(T) of Josephson vortices is measured through the onset of microwave absorption in the locked state, in slightly overdoped $\rm{Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}}$ single crystals (T_{c} ~ 84 K). The magnitude of H_{J}(T) is too large to be accounted for by the first thermodynamic critical field H_{c1}(T). We discuss the possibilit

S. Das Sarma, Jaroslav Fabian, Xuedong Hu, Igor Zutic

We review from a theoretical perspective the emerging field of spintronics where active control of spin transport and dynamics in electronic materials may provide novel device application possibilities. In particular, we discuss the quantum mechanical principles underlying spintronics applications, emphasizing the formidable challenges involving spin decoher

D. V. Shovkun, M. R. Trunin, A. A. Zhukov, Yu. A. Nefyodov

The $c$-axis penetration depth $Δλ_c$ in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO) single crystals as a function of temperature has been determined using two techniques, namely, measurements of the ac-susceptibility at a frequency of 100 kHz and the surface impedance at 9.4 GHz. Both techniques yield an almost linear function $Δλ_c(T)\propto T$ in the temperatur

L. I. Korovin, I. G. Lang D. A. Contreras-Solorio, S. T. Pavlov

The theory of a response of a two-energy-level system, irradiated by symmetrical light pulses, has been developed.(Suchlike electronic system approximates under the definite conditions a single ideal quantum well (QW) in a strong magnetic field {\bf H}, directed perpendicularly to the QW&#39;s plane, or in magnetic field absence.) The general formulae for th

Alexander Altland, Alex Kamenev

The level statistics of disordered metallic grains with broken time reversal invariance is obtained from a saddle point analysis of the Keldysh nonlinear sigma-model.

G. Hackenbroich

This is a review of the phase coherent transmission through interacting mesoscopic conductors. As a paradigm we study the transmission amplitude and the dephasing rate for electron transport through a quantum dot in the Coulomb blockade regime. We summarize experimental and theoretical work devoted to the phase of the transmission amplitude. It is shown that

Paul Fendley

I survey the kinds of critical behavior believed to be exhibited in two-dimensional disordered systems. I review the different replica sigma models used to describe the low-energy physics, and discuss how critical points appear because of WZW and theta terms.

V. V. Kabanov, J. Demsar, D. Mihailovic

A model is developed for photoinduced absorption from localized states observed in femtosecond pump-probe experiments in high-Tc superconductors and other materials. The dynamics of localized carriers are described in terms of phenomenological approach similar to that originaly proposed by Rothwarf and Taylor. Expanding the relaxation rate in powers of the o

M. Ya. Amusia, V. R. Shaginyan

It is argued that there exists the only one inverse of the linear response function $χ$, i.e. $χ^{-1}$, which depends symmetrically of its spatial-times variables, see M.K. Harbola, and A. Banerjee, Phys. Rev. A {\bf 60}, 5101 (1999). Some brief comments on this consideration are presented. We show instead, that it is possible to construct the causal inverse

S. Brazovski

Topologically nontrivial states are common in symmetry broken phases at macroscopic scales. Low dimensional systems bring them to a microscopic level where solitons emerge as single particles. The earliest and latest applications are conducting polymers and spin-Peierls chains. After a history introduction, we shall discuss the topological aspects of element

C. Aebischer, D. Baeriswyl, R. M. Noack

We study the Mott transition as a function of interaction strength in the half-filled Hubbard chain with next-nearest-neighbor hopping t&#39; by calculating the response to an external electric field using the Density Matrix Renormalization Group. The electric susceptibility chi diverges when approaching the critical point from the insulating side. We show t

Federico Becca, Luca Capriotti, Sandro Sorella

We use a recently developed technique, which allows to perform few Lanczos steps on a given wavefunction even for large system sizes, to investigate the $t{-}J$ model in the physical parameter region and to check the stability of the BCS d-wave variational wavefunction. Our statistical Lanczos algorithm, which extends and improves the one Lanczos step, has b

Zhen Ye, Haoran Hsu

Wave localization is a ubiquitous phenomenon. It refers to situations that transmitted waves in scattering media are trapped in space and remain confined in the vicinity of the initial site until dissipated. Here we report a phase transition from acoustically extended to localized states in arrays of identical air-filled bubbles in water. It is shown that th

Yicheng Zhong, M. P. Sarachik, Jae Yoo, D. N. Hendrickson

We report point by point measurements below the blocking temperature of the magnetic relaxation of Mn$_{12}$-acetate as a function of magnetic field applied along the easy axis of magnetization. Unexpectedly complex structure is observed which we attribute to the effect of higher-order terms of the spin Hamiltonianon on the tunneling process.

Jochen L. Deetjen

We present an analysis of the subdwarf O star Feige 67 with a fully metal-line blanketed NLTE model atmosphere based on high-resolution Far-UV (912-2000 A) and Near-UV (2000-3400 A) spectra from new ORFEUS II echelle observations and the IUE final archive. The Far-UV spectra are heavily blanketed by iron and nickel lines, preventing the detection of the stel

J. Kuraszkiewicz, B. J. Wilkes, B. Czerny, S. Mathur

We study the UV spectra of narrow-line Seyfert~1 (NLSy1) galaxies and compare them with ``normal&#39;&#39; AGN. Similar to their optical lines, the NLSy1s show narrower UV lines. They are also characterized by weaker CIV 1549, CIII] 1909, and stronger AlIII 1857 emission. These UV line properties add to the optical and X-ray properties known to be part of th

K. Nandra, T. Le, R. A. Edelson, I. M. George

We present a spectral analysis of a 30d, near-continuous observation of the Seyfert 1 galaxy NGC 7469 with RXTE. Daily integrations show strong spectral changes during the observation. Ourmain result is that we find the X-ray spectral index to be correlated with the UV flux. Furthermore, the broad-band X-ray photon flux is also correlated with the UV continu

J. L. Deetjen, S. Dreizler, T. Rauch, K. Werner

We present the first attempt to determine the iron abundance in hot central stars of planetary nebulae. We perform an analysis with fully metal-line blanketed NLTE model atmospheres for a sample of ten stars (T_eff >= 70.000 K) for which high-resolution UV spectra are available from the IUE archive. In all cases lines of Fe VI or Fe VII can be identified. As

J. Mayo Greenberg, Chuanjian Shen

The past century of interstellar dust has brought us from first ignoring it to finding that it plays an important role in the evolution of galaxies. Current observational results in our galaxy provide a complex physical and chemical evolutionary picture of interstellar dust starting with the formation of small refractory particles in stellar atmospheres to t

Å. Nordlund, R. F. Stein

We present a formalism for investigating the interaction between pmode oscillations and convection by analyzing realistic, three-dimensional simulations of the near-surface layers of the solar convection zone. By choosing suitable definitions for fluctuations and averages, we obtain a separation that retains exact equations. The equations for the horizontal

J. J. M. in &#39;t Zand, J. Halpern, M. Eracleous, M. McCollough

We have discovered with the Wide Field Cameras on board BeppoSAX the weak transient X-ray source SAXJ2239.3+6116 whose position coincides with that of 4U2238+60/3A2237+608 and is close to that of the fast transient AT2238+60 and the unidentified EGRET source 3EG2227+6122. The data suggest that the source exhibits outbursts that last for a few weeks and peak

Thomas Zeltwanger, Neil F. Comins, Richard V. E. Lovelace

Observations of lopsided spiral galaxies motivated us to explore whether the rapid passage of a companion galaxy could cause them. We examine whether the center of mass of the visible matter becomes displaced from the center of mass of the dark halo during the intruder&#39;s passage, thereby causing an asymmetric response and asymmetric structure. Two dimens

P. Giommi, M. Perri, F. Fiore

We present the results of a 2-10 keV BeppoSAX survey based on 140 high galactic latitude MECS fields, 12 of which are deep exposures of ``blank&#39;&#39; parts of the sky. The limiting sensitivity is 5 10^-14 erg cm^-2 s^-1 where about 25% of the Cosmic X-ray Background (CXB) is resolved into discrete sources. The logN-logS function, built with a statistical

Sujan Sengupta

Considering Joule heating caused by the dissipation of the magnetic field in the neutron star crust to be an efficient mechanism in maintaining a relatively high surface temperature in very old neutron stars, the role of general relativity is investigated. It is found that, although the effect of space-time curvature produced by the intense gravitational fie

A. M. Mickaelian, A. C. Goncalves, M. -P. Veron-Cetty, P. Veron

In Paper I (Mickaelian et al. 1999), we compared the surface density of QSOs in the Bright Quasar Survey (BQS) and in the First Byurakan Survey (FBS) and concluded that the completeness of the BQS is of the order of 70% rather than 30-50% as suggested by several authors. A number of new observations recently became available, allowing a re-evaluation of this

Kenneth F. Nicholson

Given the dimensions(including thickness) of an axisymmetric galaxy, Newton&#39;s law is used in integral form to find the density distributions required to match a wide range of orbital speed profiles. Newton&#39;s law is not modified and no dark-matter halos are required. The speed distributions can have extreme shapes if they are reasonably smooth. Severa

Kohji Tomisaka

Dynamical contraction of a slowly-rotating magnetized cloud is studied using the magnetohydrodynamical (MHD) simulations. In the isothermal stage ($n \la n_{\rm A} \sim 10^{10}{\rm cm}^{-3}$), the cloud evolves similarly to that expected from Larson-Penston self-similar solution and experiences the run-away collapse. However, after the central density exceed

S. Malhotra, D. Hollenbach, G. Helou, N. Silbermann

Four IRAS-detected early type galaxies were observed with ISO. With the exception of the 15 micron image of NGC1052, the mid-IR emission from NGC1052, NGC1155, NGC5866 and NGC6958 at 4.5, 7 and 15 microns show extended emission. Mid-IR emission from NGC1052, NGC1155, and NGC6958 follows a de Vaucouleurs profile. The ratio of 15/7 micron flux decreases with r

A. A. Cole, T. A. Smecker-Hane, J. S. Gallagher

We report new metallicity determinations for 39 red giants in a 220 square arcminute region, 1.8 degrees southwest of the bar of the Large Magellanic Cloud. These abundance measurements are based on spectroscopy of the Ca II infrared triplet. The metallicity distribution function (MDF) shows a strong peak at [Fe/H] = -0.57 +/- 0.04. Half the red giants in ou

M. Uemura, T. Kato, K. Matsumoto, H. Yamaoka

We discovered the optical counterpart about 13 mag of a soft X-ray transient, XTE J1118+480 on 2000 March 30. We perform astrometry and provide the accurate position as R.A. = 11h18m10s.85, Decl. = +48o02&#39;12&#34;.9. The outbursting object is identified with a 18.8 mag star in USNO catalog. Our pre-discovery data shows another outburst during 2000 January

M. Pohlen, R. -J. Dettmar, R. Luetticke

We present the analysis of a CCD survey of 31 nearby (<= 110 Mpc) edge-on spiral galaxies. The three-dimensional one-component best fit models provide their disk-scalelengths h and for the first time their disk cut-off radii R_{co}. We confirm for this sample the existence of such sharp truncations, and find a significantly lower mean value of the distance i

Gunnar S. Bali

Potentials between static colour sources in eight different representations are computed in four dimensional SU(3) gauge theory. The simulations have been performed with the Wilson action on anisotropic lattices where the renormalised anisotropies have been determined non-perturbatively. After an extrapolation to the continuum limit we are able to exclude an

E. Gabrielli, S. Khalil, C. Munoz, E. Torrente-Lujan

The neutralino-nucleon cross section in the context of the MSSM with universal soft supersymmetry-breaking terms is compared with the limits from dark matter detectors. Our analysis is focussed on the stability of the corresponding cross sections with respect to variations of the initial scale for the running of the soft terms, finding that the smaller the s

Roman Scoccimarro, Ravi K. Sheth, Lam Hui, Bhuvnesh Jain

We study galaxy clustering using halo models, where gravitational clustering is described in terms of dark matter halos. At small scales, clustering statistics are dominated by halo density profiles, whereas at large scales, correlations are the result of combining non-linear perturbation theory with halo biasing. Galaxies are assumed to follow the dark matt

S. T. Chui, V. N. Ryzhov, E. E. Tareyeva

The vortex configurations in the Bose-Einstein condensate of the mixture of two different spin states |F=1,m_f=-1> and |2,1> of ^{87}Rb atoms corresponding to the recent experiments by Matthews et. al. (Phys. Rev. Lett. 83, 2498 (1999)) are considered in the framework of the Thomas-Fermi approximation as functions of N_2/N_1, where N_1 is the number of atoms

J. Fuchs, C. Schweigert

We develop a systematic approach to boundary conditions that break bulk symmetries in a general way such that left and right movers are not necessarily connected by an automorphism. In the context of string compactifications, such boundary conditions typically include non-BPS branes. Our formalism is based on two dual fusion rings, one for the bulk and one f

D. F. Agterberg, Kun Yang

We derive the Ginzburg-Landau theory of unconventional singlet superconductors in the presence of a Zeeman field and impurities, in order to examine the resulting Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases. We show that the behavior of the FFLO phases in unconventional superconductors in the presence of impurities is qualitatively different from that fou

Roman R. Rafikov, Bruce T. Draine

It has been proposed that the Galaxy might contain a population of cold clouds in numbers sufficient to account for a substantial fraction of the total mass of the Galaxy. These clouds would have masses of the order of 10^{-3} Solar mass and sizes of the order of 10 AU. We consider here the lensing effects of such clouds on the light from background stars. A

Massimo Bianchi, Jose F. Morales

We discuss the interpaly between IR and UV divergences in theories with open and unoriented strings in view of the AdS/CFT correspondence. We start by deriving general formulas for the computation of threshold corrections to gauge couplings in generic configurations with open and unoriented strings. These allow us to discuss the IR/UV correspondence between

Renata Kallosh, Lev Kofman, Andrei Linde, Antoine Van Proeyen

We introduce the general N=1 gauge theory superconformally coupled to supergravity. The theory has local SU(2,2|1) symmetry and no dimensional parameters. The superconformal origin of the Fayet-Iliopoulos terms is clarified. The phase of this theory with spontaneously broken conformal symmetry gives various formulations of N=1 supergravity interacting with m

D. Monier, L. Fruchter

We present simulations of the dynamic critical state for a 2D superconductor with strong pinning centers, corresponding to a matching field twice the applied magnetic field. The sharp crossover between the plastic regime, at low current density and temperature, and the fluid flow regime for flux motion is characterized by the activation energy for flux motio

Sergey V. Barabash, David J. Bergman, D. Stroud

Scaling theory, duality symmetry, and numerical simulations of a random network model are used to study the magnetoresistance of a metal/insulator/perfect conductor composite with a disordered columnar microstructure. The phase diagram is found to have a critical line which separates regions of saturating and non-saturating magnetoresistance. The percolation

George Triantaphyllou, George Zoupanos

The method of coset-space dimensional reduction is employed in order to proceed from a gauged E_8 * E_8&#39; unified theory defined in 10 dimensions to 4 dimensions. The resulting theory comprises the Standard Model along with a strongly-interacting fermion sector which breaks the electroweak symmetry dynamically at the right scale.