March 2000 arXiv papers — page 8

P. Ball, R. Fleischer, G. F. Tartarelli, P. Vikas

We review the prospects for B decay studies at the LHC.

Chung-Pei Ma, J. N. Fry

We present an analytic model for the fully nonlinear power spectrum P and bispectrum Q of the cosmological mass density field. The model is based on physical properties of dark matter halos, with the three main model inputs being analytic halo density profiles, halo mass functions, and halo-halo spatial correlations, each of which has been well studied in th

H. Saleur, B. Wehefritz-Kaufmann

We present the first computation of the thermodynamic properties of the complex su(3) Toda theory. This is possible thanks to a new string hypothesis, which involves bound states that are non self-conjugate solutions of the Bethe equations. Our method provides equivalently the solution of the su(3) generalization of the XXZ chain. In the repulsive regime, we

Kaustubh Agashe

In a previous paper, we presented a model in which the {\em same} modulus field breaks SUSY and a simple GUT gauge group, and which has {\em dynamical} origins for {\em both} SUSY breaking and GUT scales. In this model, the supergravity (SUGRA) and gauge mediated (GM) contributions to MSSM scalar and gaugino masses are comparable - this enables a realistic s

Jaume Gomis, Matthew Kleban, Thomas Mehen, Mukund Rangamani

We show how string theory can be used to reproduce the one-loop two-point photon amplitude in noncommutative U(1) gauge theory. Using a simple realization of the gauge theory in bosonic string theory, we extract from a string cylinder computation in the decoupling limit the exact one loop field theory result. The result is obtained entirely from the region o

G. E. Brown, C. -H. Lee, R. A. M. J. Wijers, H. K. Lee

We present a specific scenario for the link between GRB and hypernovae, based on Blandford-Znajek extraction of black-hole spin energy. Such a mechanism requires a high angular momentum in the progenitor object. The observed association of gamma-ray bursts with type Ibc supernovae leads us to consider massive helium stars that form black holes at the end of

Max S. Zolotorev, Kirk T. McDonald

We consider a linearly polarized electromagnetic wave incident on an opaque screen with square aperture of edge a. An application of Faraday's law to a loop parallel to the screen, on the side away from the source, shows that the wave must have longitudinal components there. The ratio of the longitudinal to transverse field is a measure of the diffractio

Timo Bartsch, Stefan Schippers, Michael Beutelspacher, Sebastian Boehm

Dielectronic recombination(DR) of lithium-like Ti19+(1s2 2s) ions via 2s->2p core excitations has been measured at the Heidelberg heavy ion storage ring TSR. We find that not only external electric fields (0 <= Ey <= 280 V/cm) but also crossed magnetic fields (30 mT <= Bz <= 80 mT) influence the DR via high-n (2p_j nl)-Rydberg resonances. This result confirm

A. F. Volkov, R. Seviour

In this report we analyse three effects which may arise in a mesoscopic multiterminal S/N structure (two normal and two superconducting reservoirs). We show that the Josephson critical current is a non-monotonic function of a voltage between the normal reservoirs. The influence of the spin-polarized electrons on the Josephson critical current was also studie

T. J. Gaetz, Yousaf M. Butt, Richard J. Edgar, Kristoffer A. Eriksen

We present observations of the young, Oxygen-rich supernova remnant 1E0102.2-7219 taken by the Chandra X-ray Observatory during Chandra's Orbital Activation and Checkout phase. The boundary of the blast wave shock is clearly seen for the first time, allowing the diameter of the remnant and the mean blast wave velocity to be determined accurately. The promine

Claus Beisbart, Martin Kerscher

How does the clustering of galaxies depend on their inner properties like morphological type and luminosity? We address this question in the mathematical framework of marked point processes and clarify the notion of luminosity and morphological segregation. A number of test quantities such as conditional mark-weighted two-point correlation functions are intr

Juan M. R. Parrondo, Gregory P. Harmer, Derek Abbott

Based on Brownian ratchets, a counter-intuitive phenomenon has recently emerged -- namely, that two losing games can yield, when combined, a paradoxical tendency to win. A restriction of this phenomenon is that the rules depend on the current capital of the player. Here we present new games where all the rules depend only on the history of the game and not o

Tero T. Heikkila, Frank K. Wilhelm, Gerd Schoen

We consider a mesoscopic normal metal, where the spin degeneracy is lifted by a ferromagnetic exchange field or Zeeman splitting, coupled to two superconducting reservoirs. As a function of the exchange field or the distance between the reservoirs, the supercurrent through this device oscillates with an exponentially decreasing envelope. This phenomenon is s

Daniel Huertas-Hernando, Yu. V. Nazarov, Arne Brataas, Gerrit E. W. Bauer

We study diffusive transport through ferromagnet - normal metal - ferromagnet (F-N-F) systems, with arbitrary but fixed magnetization directions of the ferromagnetic reservoirs and orientations of a magnetic field applied to the normal metal. For non-collinear configurations, the complex mixing conductance describes the transport of spins non-collinear to th

Kiyoshi Kamimura, Joan Simon

T-duality realized on SuperD-brane effective actions probing in constant $G_{mn}$ and $b_{mn}$ backgrounds is studied from a pure world volume point of view. It is proved that requiring {\em T-duality covariance} of such actions ``fixes&#39;&#39; the T-duality transformations of the world volume dynamical fields, and consequently, of the NS-NS and R-R coupli

P. Furlan, L. K. Hadjiivanov, A. P. Isaev, O. V. Ogievetsky

The zero modes of the chiral SU(n) WZNW model give rise to an intertwining quantum matrix algebra A generated by an n x n matrix a=(a^i_α) (with noncommuting entries) and by rational functions of n commuting elements q^{p_i}. We study a generalization of the Fock space (F) representation of A for generic q (q not a root of unity) and demonstrate that it give

M. C. B. Abdalla, A. L. Gadelha, I. V. Vancea

We construct the finite temperature field theory of the two-dimensional ghost-antighost system within the framework of thermo field theory.

B. Bernu, G. Misguich

We have developed a new method for evaluating the specific heat of lattice spin systems. It is based on the knowledge of high-temperature series expansions, the total entropy of the system and the low-temperature expected behavior of the specific heat as well as the ground-state energy. By the choice of an appropriate variable (entropy as a function of energ

D. Kekez, D. Klabucar, M. D. Scadron

We survey various U_A(1) problems and attempt to resolve the two puzzles related to the eta mesons that have experimental verification. Specifically, we first explore the Goldstone structure of the eta and eta&#39; mesons in the context of eta-eta&#39; mixing using ideas based on QCD. Then we study the eta decays eta->3pi0, eta&#39;->3pi0 and eta&#39;->eta p

Sumiyoshi Abe, A. K. Rajagopal

A self-consistent thermodynamic framework is presented for power-law canonical distributions based on the generalized central limit theorem by extending the discussion given by Khinchin for deriving Gibbsian canonical ensemble theory. The thermodynamic Legendre transform structure is invoked in establishing its connection to nonextensive statistical mechanic

Markus Diehl, Thierry Gousset, Bernard Pire

We perform a QCD analysis of the exclusive production of two mesons in gamma^* gamma collisions in the kinematical domain of large photon virtuality Q and small hadronic invariant mass W. This reaction is dominated by a scale invariant mechanism which factorizes into a perturbative subprocess, gamma^* gamma --> q qbar or gamma^* gamma --> g g, and a generali

Masako Bando, Taichiro Kugo, Koichi Yoshioka

A novel relation is found which gives the 2-3 lepton mixing angle in terms of quark masses and CKM mixing: \tanθ_{μτ}=(m_b/m_s)V_{cb}. This relation, which is remarkably in good agreement with the quark data and the large lepton mixing recently observed, is a kind of SO(10) GUT relation similar to the celebrated bottom-tau mass ratio in SU(5). The GUT models

W. F. Kao

In an induced-gravity model, the stability condition of an inflationary slow-rollover solution is shown to be $ϕ_0 \partial_{ϕ_0}V(ϕ_0)=4V(ϕ_0)$. The presence of higher derivative terms will, however, act against the stability of this expanding solution unless further constraints on the field parameters are imposed. We find that these models will acquire a n

M. Tij, E. E. Tahiri, J. M. Montanero, V. Garzó

A model kinetic equation is solved exactly for a special stationary state describing nonlinear Couette flow in a low density system of inelastic spheres. The hydrodynamic fields, heat and momentum fluxes, and the phase space distribution function are determined explicitly. The results apply for conditions such that viscous heating dominates collisional cooli

Enrique Alvarez, Cesar Gomez

A non supersymmetric string background, directly derived from the string soft dilaton theorem, is used to compute, in the semiclassical approximation, the expectation value of Wilson loops in static gauge. The resulting potential shares common features with the one obtained through Schwarzschild-anti de Sitter spacetime metrics. In particular a linear confin

Priyamvada Natarajan, Alexandre Refregier

We propose a new technique to directly measure the shapes of dark matter halos of galaxies using weak gravitational lensing. Extending the standard galaxy-galaxy lensing method, we show that the shape parameters of the mass distribution of foreground galaxies can be measured from the two-dimensional shear field derived from background galaxies. This enables

Lu-Ming Duan, J. I. Cirac, P. Zoller, E. S. Polzik

Protocols for quantum communication between massive particles, such as atoms, are usually based on transmitting nonclassical light, and/or super-high finesse optical cavities are normally needed to enhance interaction between atoms and photons. We demonstrate a surprising result: an unknown quantum state can be teleported from one free-space atomic ensemble

X. X. Yi, C. P. Sun

The stability of Bose-Fermi gases trapped in an isotropic potentials at ultracold temperature is strongly influenced by the interaction between the fermions and the bosons. At zero temperature, the stability criterion is given in this paper using variation method, the results show that whether a fermion-boson mixture is stable depends mainly on the interacti

Kirk T. McDonald, Heinrich Mitter

There is not a unique solution to the electro- or magnetostatic problem where the &#34;boundary condition&#34; is merely a specification of the fields along a line. As a practical example, we consider the case where it is desired to have a magnetic field that that traces a helix about the z axis.

Kirk T. McDonald

A vacuum photodiode driven by a pulsed laser can sustain an average current very similar to that of a continous diode, where the latter is described by Child&#39;s law.

Kirk T. McDonald

In optics, a reflective grating is a conducting surface with a ripple. The typical use of such a grating involves an incident electromagnetic wave with wave vector k in the x-z plane, and interference effects lead to a discrete set of reflected waves also with wave vectors in the x-z plane. Consider, instead, an incident plane electromagnetic wave with wave

Max S. Zolotorev, Kirk T. McDonald

The principle of an electrostatic accelerator is that when a charge e escapes from a conducting plane that supports a uniform electric field of strength E_0, then the charge gains energy e E_0 d as it moves distance d from the plane. Where does this energy come from? We that the mechanical energy gain of the electron is balanced by the decrease in the electr

Kirk T. McDonald

Can the wavelength of a classical electromagnetic field be arbitrarily small, or its electric field strength be arbitrarily large? If we require that the radiation-reaction force on a charged particle in response to an applied field be smaller than the Lorentz force we find limits on the classical electromagnetic field that herald the need for a better theor

Kirk T. McDonald

The Hawking-Unruh effective temperature, hbar a* / 2 pi c k, due to quantum fluctuations in the radiation of an accelerated charged-particle beam can be used to show that transverse oscillations of the beam in a practical linear focusing channel damp to the quantum-mechanical limit. A comparison is made between this behavior and that of beams in a wiggler.

Kirk T. McDonald

We wish to draw attention to a novel view of the effect of the quantum fluctuations during the radiation of accelerated particles, particularly those in storage rings. This view is inspired by the remarkable insight of Hawking that the effect of the strong gravitational field of a black hole on the quantum fluctuations of the surrounding space is to cause th

Kirk T. McDonald, Konstantin Shmakov

The energy and momentum densities of the fields of a free electron in a plane electromagnetic wave include interference terms that are the classical version of the ``dressing&#39;&#39; of the electron the arises in a quantum analysis. The transverse mechanical momentum of the oscillating electron is balanced by the field momentum resulting from the interfere

Max S. Zolotorev, Kirk T. McDonald

We show that a time-reversed formulation of Huygens-Kirchhoff diffraction can be used to deduce the transverse and longitudinal fields of a Gaussian laser beam, starting from a simple assumption of a Gaussian beam profile in the far field. An attempt to apply this technique to the far fields of a Hertzian dipole shows how the laws of diffraction do not permi

Kirk T. McDonald

The sweep speed of an electron beam across the face of an oscilloscope can exceed the velocity of light, although of course the velocity of the electrons does not. Associated with this possibility there should be a kind of Cherenkov radiation, as if the oscilloscope trace were due to a charge moving with superluminal velocity.

Zhong-yu Ma, Nguyen Van Giai, A. Wandelt, D. Vretenar

A fully consistent relativistic RPA calculation is performed for the monopole and dipole compression modes in nuclei. The emphasis is put on the effects of Dirac sea states which are generally neglected in relativistic RPA calculations. It is found that these effects can be quite important for the isoscalar monopole mode. The main contributions from the pair

W. Gloeckle, K. Miyagawa

Using the generalized Pauli principle by adding particle labels to the usual space and spin labels a symmetric Hamiltonian and a corresponding antisymmetric wavefunction is constructed for systems of three baryons in the strangeness sectors $S=-1$ and -2. Applications are the $ΞNN-ΛΛN$ and $NNΛ-NNΣ$ systems. Minimal sets of generalized coupled Faddeev equati

V. Pascalutsa, J. A. Tjon

We develop a relativistic covariant and unitary description of the pion-nucleon interaction in a hadron-exchange model. The model is based on the solution of a dimensionally reduced (quasipotential) Bethe-Salpeter equation for the partial-wave off-shell $πN$ scattering amplitudes with the potential consisting of the field-theoretical $s$- and $u$-channel nuc

M. Locher, N. Chatterjee, F. Marchesoni, W. L. Ditto

We expand on prior results on noise supported signal propagation in arrays of coupled bistable elements. We present and compare experimental and numerical results for kink propagation under the influence of local and global fluctuations. As demonstrated previously for local noise, an optimum range of global noise power exists for which the medium acts as a r

G. W. Patrick

The Landau-Lifshitz equation is derived as the reduction of a geodesic flow on the group of maps into the rotation group. Passing the symmetries of spatial isotropy to the reduced space is an example of semidirect product reduction by stages.

M. A. Lledó

A method for the deformation quantization of coadjoint orbits of semisimple Lie groups is proposed. It is based on the algebraic structure of the orbit. Its relation to geometric quantization and differentiable deformations is explored.

Saharon Shelah, Zoran Spasojević

This paper studies cardinal invariants b_kappa and t_kappa, the natural generalizations of the invariants b and t to a regular cardinal kappa.

Saharon Shelah

Boban Velickovic asked the following question: Is there a nontrivial forcing notion with the Sacks property which is also ccc? A ``definable&#39;&#39; variant of this question has been answered in [Sh:480] (math.LO/9303208): Every nontrivial Souslin forcing notion which has the Sacks property has an uncountable antichain. Here we show that it is consistent t

János Kollár

Let U be an open subset of a unirational variety. We prove that there is rational curve C in U such that the fundamental group of C surjects onto the fundamental group of U. As a consequence we obtain new proofs of the theorems of Harbater and Colliot-Thélène on Galois covers and torsors over the p-adic line. We also obtain examples of pencils of curves of g

Hiroyuki Miyoshi, Toru Tsujishita

In this paper, firstly, we introduce a higher-dimensional analogue of hypergraphs, namely $ω$-hypergraphs. This notion is thoroughly flexible because unlike ordinary $ω$-graphs, an n-dimensional edge called an n-cell has many sources and targets. Moreover, cells have polarity, with which pasting of cells is implicitly defined. As examples, we also give some

Adam Logan

Nigel Boston and Barry Mazur have shown how to determine the natural subspaces of certain S_3-extensions of the rationals, which they term &#34;generic&#34;. We extend some of their results to another class of extensions, called &#34;degenerate&#34;.

A. J. Roberts

I prove that a centre manifold approach to creating finite difference models will consistently model linear dynamics as the grid spacing becomes small. Using such tools of dynamical systems theory gives new assurances about the quality of finite difference models under nonlinear and other perturbations on grids with finite spacing. For example, the advection

A. A. Pavlov

We define N-theory being some analogue of K-theory on the category of von Neumann algebras such that $K_0(A)\subset N_0(A)$ for any von Neumann algebra A. Moreover, it turns out to be possible to construct the extension of the Chern character to some homomorphism from $N_0(A)$ to even Banach cyclic homology of A. Also, we define generalized Lefschetz numbers

W. Fischler, E. Gorbatov, A. Kashani-Poor, R. McNees

We extend a recent computation of the dependence of the free energy, F, on the noncommutative scale $θ$ to theories with very different UV sensitivity. The temperature dependence of $F$ strongly suggests that a reduced number of degrees of freedom contributes to the free energy in the non-planar sector, $F_{\rm np}$, at high temperature. This phenomenon seem

A. H. Chamseddine, W. A. Sabra

Magnetic and Dyonic solutions are constructed for the theory of abelian gauged N=2 gauged four dimensional supergravity coupled to vector multiplets. The solutions found preserve 1/4 of the supersymmetry.

S. Boukraa, J-M. Maillard

We recall the concept of Baxterisation of an R-matrix, or of a monodromy matrix, which corresponds to build, from one point in the $ R$-matrix parameter space, the algebraic variety where the spectral parameter(s) live. We show that the Baxterisation, which amounts to studying the iteration of a birational transformation, is a ``win-win&#39;&#39; strategy: i

J. Ambjorn, K. N. Anagnostopoulos, W. Bietenholz, T. Hotta

We perform Monte Carlo simulations of a supersymmetric matrix model, which is obtained by dimensional reduction of 4D SU(N) super Yang-Mills theory. The model can be considered as a four-dimensional counterpart of the IIB matrix model. We extract the space-time structure represented by the eigenvalues of bosonic matrices. In particular we compare the large N

W. Kornelis, H. G. Dosch

In this work an extension of the Gaussian model of the stochastic vacuum is presented. It consists of including higher cumulants than just the second one in the cluster expansion in QCD. The influence of nonabelian fourth cumulants on the potential of a static quark-antiquarkpair is examined and the formation of flux tubes between a static $q\bar{q}$-pair is

Shijong Ryang

Based on the canonical quantization of open strings ending on D-branes with a background B field, we construct the open string propagator. We demonstrate the relation between the T duality of the underlying string theory and the Morita equivalence of the interpolating general Dirac-Born-Infeld theory on a noncommutative torus in the nonzero modulus Φsector.

Avijit Mukherjee, Mohammad M. Sheikh-Jabbari

This paper has been withdrawn.

S. Liuti, F. Cano

We examine the gluon distributions in nuclei in the asymptotic region defined by $Q^2 \to \infty$, $x \to 0$. An analysis using the Double Asymptotic Scaling variables of Ball and Forte is proposed. New scaling relations are predicted which can help disentangling the different mechanisms of low $x$ perturbative QCD evolution in nuclei.

Apostolos Pilaftsis

We briefly review the phenomenological implications of the minimal supersymmetric standard model (MSSM) with explicit radiative breaking of CP invariance in the Higgs sector for the LEP2 and Tevatron colliders.

Tadeusz Wibig

The alignment of the products of very high energy interactions seen in mountain altitude experiments is one of the most puzzling phenomena in cosmic ray physics for quite a long time. The observations of the Pamir and Chacaltaya emulsion chamber groups and by the Tien-Shan extensive air shower experiment, together with a very clear event seen in the Concorde

Uma Mahanta

In low energy phenomenology to avoid the strong constraints of proton decay it is usually assumed that light ($\approx $ 250 Gev) leptoquarks couple only to quark-lepton pairs and light diquarks couple only to quark pairs. In this paper we present two specific examples where the higgs induced mixing between leptoquarks and diquarks through trilinear interact

Anirban Kundu

In this talk, we point out some of the present and future possible signatures of physics beyond the Standard Model from B-meson decays, taking R-parity conserving and violating supersymmetry as illustrative examples.

F. S. Roux

Using an instanton effective action formalism, we compute the critical coupling for the nonperturbative formation of a dynamical mass via instantons in non-Abelian gauge theories with N_f massless fermions. Only continuous phase transitions are considered. For large values of N_f the critical couplings are found to be much smaller than the equivalent critica

M. Alford, I. T. Drummond, R. R. Horgan, M. Peardon

Using tadpole inproved actions we investigate the consistency between different methods of measuring the aspect ratio renormalization of anisotropic-lattice gluons for bare aspect ratios χ_0=4,6,10 and inverse lattice spacing in the range a_s^{-1}=660-840 MeV. The tadpole corrections to the action, which are established self-consistently, are defined for two

Edward H. Thorndike

On the occasion of a symposium honoring my collegue Adrian Melissinos, I gave an informal, personal review of bottom quark physics. This paper is a writeup of that talk. I first summarize the early days, the decade from the discovery through the determination of the b quark&#39;s rough features. I note a change in objective which occurred around 1990, with t

Mark Burgess

This paper describes necessary elements for constructing theoretical models of network and system administration. Armed with a theoretical model it becomes possible to determine best practices and optimal strategies in a way which objectively relates policies and assumptions to results obtained. It is concluded that a mixture of automation and human, or othe

Gosse Bouma

A finite-state method, based on leftmost longest-match replacement, is presented for segmenting words into graphemes, and for converting graphemes into phonemes. A small set of hand-crafted conversion rules for Dutch achieves a phoneme accuracy of over 93%. The accuracy of the system is further improved by using transformation-based learning. The phoneme acc

L. Fabbian, A. Latz, R. Schilling, F. Sciortino

We present static and dynamic properties of molecular correlation functions S_{lmn,l&#39;m&#39;n&#39;}(q,t) in a simulated supercooled liquid of water molecules, as a preliminary effort in the direction of solving the molecular mode coupling theory (MMCT) equations for supercooled molecular liquids. The temperature and time dependence of various molecular co

A. P. Chikkatur, A. Gorlitz, D. M. Stamper-Kurn, S. Inouye

Impurity atoms propagating at variable velocities through a trapped Bose-Einstein condensate were produced using a stimulated Raman transition. The redistribution of momentum by collisions between the impurity atoms and the stationary condensate was observed in a time-of-flight analysis. The collisional cross section was dramatically reduced when the velocit

Michael R. Swift, Hemant Bokil, Rui D. M. Travasso, Alan J. Bray

Recent work has suggested the existence of glassy behavior in a ferromagnetic model with a four-spin interaction. Motivated by these findings, we have studied the dynamics of this model using Monte Carlo simulations with particular attention being paid to two-time quantities. We find that the system shares many features in common with glass forming liquids.

T. S. Lo, P. M. Hui, N. F. Johnson

We present a theory which describes a recently introduced model of an evolving, adaptive system in which agents compete to be in the minority. The agents themselves are able to evolve their strategies over time in an attempt to improve their performance. The present theory explicitly demonstrates the self-interaction, or so-called market impact, that agents

P. Devillard, J. Ranninger

We describe the approach of the superconducting state as a sequence of cross-over phenomena. As the temperature is decreased, uncorrelated pairing of the electrons leads to the opening of a pseudogap at T_F^*. Upon further lowering the temperature those electron pairs acquire well behaved itinerant features at T_B^*, leading to partial Meissner screening and

R. Bulla

The Numerical Renormalization Group method (NRG) has been developed by Wilson in the 1970&#39;s to investigate the Kondo problem. The NRG allows the non-perturbative calculation of static and dynamic properties for a variety of impurity models. In addition, this method has been recently generalized to lattice models within the Dynamical Mean Field Theory. Th

K. N. Yugay, N. V. Blinov, I. V. Shirokov

Stationary and nonstationary, in particular, chaotic states in long Josephson junctions are investigated. Bifurcation lines on the parametric bias current-external magnetic field plane are calculated. The chaos strip along the bifurcation line is observed. It is shown that transitions between stationary states are the transitions from metastable to stable st

Petrica I. Cristea

The effect of an in-plane magnetic field on resonant tunneling in a symmetric GaAs/AlYGa1-YAs triple-barrier resonant tunneling TBRT structure is presented. The splitting of the resonant lines (and hence the coupling energy vs. magnetic induction) for the ground and the first excited resonant doublet shifts up in energy by increasing the magnetic induction.

Sung-Sik Lee, Sung-Ho Suck Salk

Based on an improved SU(2) slave-boson approach showing coupling between the cha rge and spin degrees of freedom, we derive a phase diagram of high $T_c$ cuprate s which displays both the superconducting and pseudogap phases in the plane of t emperature vs. hole doping rate. It is shown that phase fluctuations in the order parameters results in a closer agre

S. K. Kwon, B. I. Min

Magnetic properties of NiO are investigated by incorporating the spin-orbit interaction in the LSDA+U scheme. It is found that the large part of orbital moment remains unquenched in NiO. The orbital moment contributes about mu_L = 0.29 mu_B to the total magnetic moment of M = 1.93 mu_B, as leads to the orbital-to-spin angular momentum ratio of L/S = 0.36. Th

L. A. Urena-Lopez, T. Matos

In this paper we propose a quintessence model with the potential $V(Φ)=V_{o}[ \sinh {(α\sqrt{κ_{o}}ΔΦ})] ^β$, which asymptotic behavior corresponds to an inverse power-law potential at early times and to an exponential one at late times. We demonstrate that this is a tracker solution and that it could have driven the Universe into its current inflationary st

Ruth Durrer

Structure formation with topological defects is described. The main differences from inflationary models are highlighted. The results are compared with recent observations. It is concluded that all the defect models studied so far are in disagreement with recent observations of CMB anisotropies. Furthermore, present observations do not support &#39;decoheren

Claudia V. Rodrigues, A. Mario Magalhaes

Some isolated Wolf-Rayet stars present random variability in their optical flux and polarization. We make the assumption that such variability is caused by the presence of regions of enhanced density, i.e. blobs, in their envelopes. In order to find the physical characteristics of such regions we have modeled the stellar emission using a Monte Carlo code to

D. Fabricant, M. Franx, P. van Dokkum

We describe the morphological composition of a sample of 518 galaxies in the field of CL1358+62 at z=0.33, drawn from a large HST mosaic covering 53 sq. arcmin. The sample is complete to I=22, corresponding to M_V=-18.5 in the rest frame. The galaxies have been independently classified by the authors of this paper and by Alan Dressler. For galaxies with I<21

J. E. Beckman, M. Rozas, A. Zurita, R. A. Watson

(Abridged) We present evidence that the HII regions of high luminosity in disk galaxies may be density bounded, so that a significant fraction of the ionizing photons emitted by their exciting OB stars escape from the regions. The key piece of evidence is the presence, in the Hαluminosity functions (LFs) of the populations of HII regions, of glitches, local

Amadeu Fernandes

Long slit spectra of the molecular outflow Herbig-Haro (HH) 46/47 has been taken in the J and K near-infrared bands. The observed H2 line emission confirms the existence of a bright and extended redshifted counter-jet outflow southwest of HH46. We show that this outflow seems to be composed of two different emission regions which have distinct heliocentric v

R. Ramaty, V. Tatischeff, J. P. Thibaud, B. Kozlovsky

By introducing a hitherto ignored Li-6 producing process, due to accelerated He-3 reactions with He-4, we show that accelerated particle interactions in solar flares produce much more Li-6 than Li-7. By normalizing our calculations to gamma-ray data we demonstrate that the Li-6 produced in solar flares, combined with photospheric Li-7, can account for the re

Dipak Munshi, Peter Coles

Many recent studies have demonstrated that scaling arguments, such as the so-called hierarchical {\em ansatz}, are extremely useful in understanding the statistical properties of weak gravitational lensing. This is especially true on small angular scales (i.e. at high resolution), where the usual perturbative calculations of matter clustering no longer apply

D. Saumon, T. R. Geballe, S. K. Leggett, M. S. Marley

We present new, high resolution, infrared spectra of the T dwarf Gliese 229B in the J, H, and K bandpasses. We analyze each of these as well as previously published spectra to determine its metallicity and the abundances of NH3 and CO in terms of the surface gravity of Gl 229B, which remains poorly constrained. The metallicity increases with increasing gravi

Yveline Lebreton

During the last decade, the understanding of fine features of the structure and evolution of stars has become possible as a result of enormous progress made in the acquisition of high-quality observational and experimental data and of new developments and refinements in the theoretical description of stellar plasmas. The confrontation of high-quality observa

M. C. Bento, O. Bertolami, R. Rosenfeld, L. Teodoro

Self-interacting dark matter has been suggested in order to overcome the difficulties of the Cold Dark Matter model on galactic scales. We argue that a scalar gauge singlet coupled to the Higgs boson, which could lead to an invisibly decaying Higgs, is an interesting candidate for this self-interacting dark matter particle. We also present estimates on the a

A. M. Perez Garcia J. M. Rodriguez Espinosa

We present mid and far IR ISO data of the CfA Seyfert galaxy sample. These data allow a detailed study of the far IR Spectral Energy Distribution (SED) of these galaxies. A Bayesian inversion method has been used to invert the SED of these sources yielding two fundamental results, namely, that the mid and far IR SED of Seyfert galaxies can be explained solel

F. M. Zerbi, E. Poretti, C. Aerts, G. Handler

The MONS space experiment will be able to verify some of the most important topics in the asteroseismologic studies of Delta Sct and Gamma Dor stars. We discuss how the $γ$ Doradus can be considered possible &#34;bridges&#34; between the opacity driven overstable pulsation and the stochastically excited solar like oscillation. For this reason the possible in

S K Saha, S. Morel

This article is a sort of sequel of the earlier extensive review by Saha (1999a) where emphasis was laid down on the ground based single aperture, as well as on the working long baseline optical interferometers (LBI) situated at the various observatories across the globe that are producing a large amount of astronomical results. Since the future of high reso

D. Rosenthal, J. W. Beeman, N. Geis, L. Looney

We are developing two-dimensional 16 x 25 pixel detector arrays of both unstressed and stressed Ge:Ga photoconductive detectors for far-infrared astronomy from SOFIA. The arrays, based on earlier 5 x 5 detector arrays used on the KAO, will be for our new instrument, the Far Infrared Field Imaging Line Spectrometer (FIFI LS). The unstressed Ge:Ga detector arr

Rosalba Perna, John Raymond

The energy source of the giant HI supershells in nearby galaxies and in our own is still an unsettled issue. Proposed scenarios for production of near-complete ringlike supershells are multiple supernovae (SNe) and gamma-ray bursts (GRBs). In the late phase of evolution it is difficult to tell these models apart. We show that, if a supershell has been powere

Tomas L. Gomez

We prove the irreducibility of the moduli space of rank 2 semistable torsion free sheaves (with a generic polarization and any value of c_2) on a K3 or a del Pezzo surface. In the case of a K3 surface, we need to prove a result on the connectivity of the Brill-Noether locus for singular curves on the surface. In the case of a del Pezzo surface, we reduce the

Bryan Gaensler, John Dickel, Anne Green

We report on radio continuum and HI observations of the radio source G328.4+0.2 using the Australia Telescope Compact Array. Our results confirm G328.4+0.2 to be a filled-center nebula with no surrounding shell, showing significant linear polarization and an almost flat spectral index. These results lead us to conclude that G328.4+0.2 is a Crab-like, or ``pl

Dilip Kumar Ghosh, Sourov Roy

We study the pair production of right selectrons at a 500 GeV $e^-e^-$ collider followed by their decay into an electron and a lightest neutralino. This lightest neutralino decays into multifermion final states in the presence of R-parity-violating couplings. A detailed analysis of possible signals is performed for some important regions of the parameter spa

Shao-Hsuan Chiu, T. K. Kuo, Guo-Hong Wu

We provide a complete and systematic analysis of hermitian, hierarchical quark mass matrices with four texture zeros. Using triangular mass matrices, each pattern of texture zeros is readily shown to lead to a definite relation between the CKM parameters and the quark masses. Nineteen pairs are found to be consistent with present data, and one other is margi

P. Mayr

We use string duality to describe instanton induced spontaneous supersymmetry breaking in string compactifications with additional background fields. Dynamical supersymmetry breaking by space-time instantons in the heterotic string theory is mapped to a tree level breaking in the type II string which can be explicitly calculated by geometric methods. It is a

Remo Garattini

A simple model of spacetime foam, made by $N$ wormholes in a semiclassical approximation, is taken under examination. The Casimir-like energy of the quantum fluctuation of such a model and its probability of being realized are computed. Implications on the Bekenstein-Hawking entropy and the cosmological constant are considered.