February 2000 arXiv papers — page 10

M. Gluck, E. Reya

A phenomenological ansatz for the flavor-asymmetry of the light sea distributions of the nucleon, based on the Pauli exclusion principle, is proposed. This ansatz is compatible with the measured flavor-asymmetry of the unpolarized sea distributions, $\bar{d}>\bar{u}$, of the nucleon. A prediction for the corresponding polarized flavor-asymmetry is presented

Daniel Wójcik, Andrzej Nowak, Marek Kuś

A method allowing to distinguish interacting from non-interacting systems based on available time series is proposed and investigated. Some facts concerning generalized Renyi dimensions that form the basis of our method are proved. We show that one can find the dimension of the part of the attractor of the system connected with interaction between its parts.

V. G. Bornyakov, D. A. Komarov, M. I. Polikarpov, A. I. Veselov

We perform the careful study of the gauge copies problem for the direct center projection in SU(2) lattice gauge theory. Our results indicate that this gauge is not appropriate for the investigation of the center vortices. We also show that the point-like objects, nexuses, are important for the confinement dynamics.

M. Alimohammadi, N. Ahmadi

We consider a process in which there are two types of particles, A and B, on an infinite one-dimensional lattice. The particles hop to their adjacent sites, like the totally asymmetric exclusion process (ASEP), and have also the following interactions: A+B -> B+B and B+A -> B+B, all occur with equal rate. We study this process by imposing four boundary condi

Zeev Rudnick, Peter Sarnak, Alexandru Zaharescu

We study the distribution of normalized spacings between the fractional parts of an^2, n=1,2,.... We conjecture that if a is "badly approximable" by rationals, then the sequence of fractional parts has Poisson spacings, and give a number of results towards this conjecture. We also present an example of a Diophantine number a for which the higher corr

B. Sathiapalan

We describe a method of writing down interacting equations for all the modes of the bosonic open string. It is a generalization of the loop variable approach that was used earlier for the free, and lowest order interacting cases. The generalization involves, as before, the introduction of a parameter to label the different strings involved in an interaction.

Zoltan Haiman, Joseph J. Mohr, Gilbert P. Holder

We study the expected redshift evolution of galaxy cluster abundance between 0 < z < 3 in different cosmologies, including the effects of the cosmic equation of state parameter w=p/rho. Using the halo mass function obtained in recent large scale numerical simulations, we model the expected cluster yields in a 12 deg^2 Sunyaev-Zeldovich Effect (SZE) survey an

V. I. Man&#39;ko, R. Vilela Mendes

Using the symplectic tomography map, both for the probability distributions in classical phase space and for the Wigner functions of its quantum counterpart, we discuss a notion of Lyapunov exponent for quantum dynamics. Because the marginal distributions, obtained by the tomography map, are always well defined probabilities, the correspondence between class

Dominik Janzing, Pawel Wocjan, Robert Zeier, Rubino Geiss

Landauer&#39;s principle states that the erasure of one bit of information requires the free energy kT ln 2. We argue that the reliability of the bit erasure process is bounded by the accuracy inherent in the statistical state of the energy source (`the resources&#39;) driving the process. We develop a general framework describing the `thermodynamic worth&#3

M. C. de Oliveira, M. H. Y. Moussa, S. S. Mizrahi

Here we consider the continuous pumping of a dissipative QED cavity and derive the time-dependent density operator of the cavity field prepared initially as a superposition of mesoscopic coherent states. The control of the coherence of this superposition is analyzed considering the injection of a beam of two-level Rydberg atoms through the cavity. Our treatm

Anthony Sudbery

This paper is withdrawn by the author. It is superseded by Makhlin&#39;s paper quant-ph/0002045.

A. Mary Selvam

Observations show that geomagnetic field lines follow closely the atmospheric circulation patterns and that geomagnetic field variations are precursors to climate change . The exact mechanism for the observed close relationship between global geomagnetic field and the tropospheric weather patterns is not clear. In this paper a universal theory of atmospheric

B. Maraghechi, B. Farrokhi, J. E. Willett, U. -H. Hwang

An analysis of single-electron orbits in combined coaxial wiggler and axial guide magnetic fields is presented. Solutions of the equations of motion are developed in a form convenient for computing orbital velocity components and trajectories in the radially dependent wiggler. Simple analytical solutions are obtained in the radially-uniform-wiggler approxima

R. Egger, L. Muehlbacher, C. H. Mak

The multilevel blocking algorithm recently proposed as a possible solution to the sign problem in path-integral Monte Carlo simulations has been extended to systems with long-ranged interactions along the Trotter direction. As an application, new results for the real-time quantum dynamics of the spin-boson model are presented.

L. V. Bravina, Amand Faessler, C. Fuchs, E. E. Zabrodin

The centrality dependence of directed and elliptic flow in light and heavy systems of colliding nuclei is studied within two microscopic transport models at energies from 1 AGeV to 160 A GeV. The pion directed flow has negative slope in the midrapidity range irrespective of bombarding energy and mass number of the colliding ions. In contrast, the directed fl

V. Koch, M. Bleicher, A. K. Dutt-Mazumder, C. Gale

We discuss how dilepton production is related to chiral symmetry and its restoration. We then analyse presently available data by the CERES collaboration in this context. We find that the present data do not support any conclusions concerning the restoration of chiral symmetry. We finally provide a prediction for the dilepton spectrum for the just completed

T. -D. Albert, H. Boos, R. Flume, K. Ruhlig

We construct Drinfel&#39;d twists for the rational sl(n) XXX-model giving rise to a completely symmetric representation of the monodromy matrix. We obtain a polarization free representation of the pseudoparticle creation operators figuring in the construction of the Bethe vectors within the framework of the quantum inverse scattering method. This representat

Anil Maybhate, R. E. Amritkar

We consider a dynamic method, based on synchronization and adaptive control, to estimate unknown parameters of a nonlinear dynamical system from a given scalar chaotic time series. We present an important extension of the method when time series of a scalar function of the variables of the underlying dynamical system is given. We find that it is possible to

Anil Maybhate, R. E. Amritkar

We introduce a method to estimate the initial conditions of a mutivariable dynamical system from a scalar signal. The method is based on a modified multidimensional Newton-Raphson method which includes the time evolution of the system. The method can estimate initial conditions of periodic and chaotic systems and the required length of scalar signal is very

S. Yu. Sakovich, Takayuki Tsuchida

A new system of coupled higher-order nonlinear Schroedinger equations is proposed which passes the Painleve test for integrability well. A Lax pair and a multi-field generalization are obtained for the new system.

Gregory Leibon

This paper contains a generalization of the convex ideal case of the Thurston-Andreev theorem when the genus is greater than 1. The heart of the paper concerns taking formal angle data on a surface and ``conformally flowing&#39;&#39; this formal angle data to uniquely associated uniform angle data. This flow turns out to be the gradient of an objective funct

V. K. Kharchenko

We propose a notion of a quantum universal enveloping algebra for an arbitrary Lie algebra defined by generators and relations which is based on the quantum Lie operation concept. This enveloping algebra has a PBW basis that admits the Kashiwara crystalization. We describe all skew primitive elements of the quantum universal enveloping algebra for the classi

T. J. Christiansen, M. S. Joshi

We develop a scattering theory for perturbations of powers of the Laplacian on asymptotically Euclidean manifolds. The (absolute) scattering matrix is shown to be a Fourier integral operator associated to the geodesic flow at time πon the boundary. Furthermore, it is shown that on \Real^n the asymptotics of certain short-range perturbations of Δ^k can be rec

Francisco Martin, Santiago Morales

In 1996, Nadirashvili used Runge&#39;s theorem to produce a complete minimal disc inside a ball in R^3. In this paper we generalize the techniques used by Nadirashvili to obtain new examples of complete minimal surfaces inside a ball in R^3, with the conformal structure of an annulus.

Ignacio Bajo, Said Benayadi, Martin Bordemann

In this note we introduce the notion of $T^*-$extension $T^*{\mathfrak g}$ of a Lie superalgebra ${\mathfrak g}$, i.e. an extension of ${\mathfrak g}$ by its dual space ${\mathfrak g}^*$. The natural pairing induces on $T^*{\mathfrak g}$ an even supersymmetric nondegenerate bilinear form $B$ which is invariant ($B([X,Y],Z)=B(X,[Y,Z])$ for all $X,Y,Z \in T^*{

David Ruelle, Amie Wilkinson

We show that for the C^1-open set of partially hyperbolic diffeomorphisms constructed in (M. Shub and A. Wilkinson, &#34;Pathological foliations and removable zero exponents,&#34; Invent. math. 139 (2000) 3, 495-508), Lebesgue measure on the 3-torus decomposes as atomic measure along the leaves of the central foliation.

G. I. Barenblatt, A. J. Chorin, V. M. Prostokishin

In a turbulent boundary layer over a smooth flat plate with zero pressure gradient, the intermediate structure between the viscous sublayer and the free stream consists of two layers: one adjacent to the viscous sublayer and one adjacent to the free stream. When the level of turbulence in the free stream is low, the boundary between the two layers is sharp a

Riccardo Benedetti, Carlo Petronio

We generalize Turaev&#39;s definition of torsion invariants of pairs (M,x), where M is a 3-dimensional manifold and x is an Euler structure on M (a non-singular vector field up to homotopy relative to bM and local modifications in int(M). Namely, we allow M to have arbitrary boundary and x to have simple (convex and/or concave) tangency circles to the bounda

V. Manuilov

Let $A$ be a separable $C^*$-algebra and let $B$ be a stable $C^*$-algebra with a strictly positive element. We consider the (semi)group $\Ext^{as}(A,B)$ (resp. $\Ext(A,B)$) of homotopy classes of asymptotic (resp. of genuine) homomorphisms from $A$ to the corona algebra $M(B)/B$ and the natural map $i:\Ext(A,B)\ar\Ext^{as}(A,B)$. We show that if $A$ is a su

Sergey Neshveyev

For each β\in(0,+\infty) there exists a canonical measure μ_βon the ring A_f of finite adeles. We show that the positive rationals act ergodically on (A_f,μ_β) for β\in(0,1], and then deduce from this the uniqueness of KMS_β-states for the Bost-Connes system.

Zhenquan Li, A. J. Roberts

In applications of centre manifold theory we need more flexible error estimates than that provided by, for example, the Approximation Theorem~3 by Carr (1981,1983). Here we extend the theory to cover the case where the order of approximation in parameters and that in dynamical variables may be completely different. This allows, for example, the effective eva

Rosa Gini

Some properties of non-orientable 3-manifolds are shown. The semi-group of cobordism of immersions of surfaces in such manifolds is computed and proven actually to be a group. Explicit invariants are provided.

Massimo Bianchi, Jose F. Morales

We show that massless RR tadpoles in vacuum configurations with open and unoriented strings are always related to anomalies. RR tadpoles arising from sectors of the internal SCFT with non-vanishing Witten index are in one-to-one correspondence with conventional irreducible anomalies. The anomalous content of the remaining RR tadpoles can be disclosed by cons

Stephen Hawking, Juan Maldacena, Andrew Strominger

A deSitter brane-world bounding regions of anti-deSitter space has a macroscopic entropy given by one-quarter the area of the observer horizon. A proposed variant of the AdS/CFT correspondence gives a dual description of this cosmology as conformal field theory coupled to gravity in deSitter space. In the case of two-dimensional deSitter space this provides

S. Ferrara

We derive massless and massive representations of all SU(2,2/N) superalgebras by using superfields defined in &#34;harmonic superspace&#34;. This method allows one to easily construct &#34;short superfields&#34; which are relevant in the analysis of the AdS/CFT correspondence.

J. I. Kapusta, S. M. H. Wong

We calculate the change in the effective mass and width of a Z boson in the environment of a quark-gluon plasma under the conditions expected in Pb-Pb collisions at the LHC. The change in width is predicted to be only about 1 MeV at a temperature of 1 GeV, compared to the natural width of 2490$\pm$7 MeV. The mass shift is even smaller. Hence no observable ef

E. Oset, S. Hirenzaki, E. Marco, J. A. Oller

We report on recent results on the decay of the phi into pi^+ pi^- and phi radiative decays into pi^0 pi^0 gamma and pi^0 eta gamma, which require the consideration of the final state interaction of a pair of mesons in a region inaccessible to Chiral Perturbation Theory. By using nonperturbative chiral unitary methods for the meson meson interaction we can o

S. M. H. Wong

We propose a numerical definition for baryon stopping in relativistic heavy ion collisions that is obtainable from final hadron rapidity distributions as well as from bremsstrahlung measurements. Thus a new channel of communication is opened between the two methods.

R. A. Alanakyan

We consider bound states of fermions with an anomalous magnetic moments in the field of charged cylinder.Also we obtain second order equations for axially symmetric $Z_0(r)$-boson field, radial axially symmetric magnetic field, obtain second order equations for case of bound states of fermions in the radial electric and magnetic fields.

Tomislav Prokopec

In this study we examine post-inflationary cosmologies dominated by a scalar field with the equation of state: p_phi=w_phi rho_phi (0 leq w_phi leq 1) in order to facilitate baryogenesis at the electroweak scale. We take a more conventional approach from one in Ref. 1 [Joyce, Prokopec] and assume that the Universe reheats by the scalar field decay before the

T. Blum, S. Sasaki

We give a brief sketch of lattice structure function calculations and review previous results for the axial coupling $g_A$. We outline a new technique for treating fermions on the lattice that preserves chiral symmetry, domain wall fermions. Finally, we give preliminary results for the nucleon spectrum using this new technique. Remarkably, a large mass split

R. Alfieri, F. Di Renzo, E. Onofri, L. Scorzato

The numerical stochastic perturbation method based on Parisi-Wu quantisation is applied to a suite of simple models to test its validity at high orders. Large deviations from normal distribution for the basic estimators are systematically found in all cases (``Pepe effect&#39;&#39;). As a consequence one should be very careful in estimating statistical error

AMS Collaboration

The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 in a 51.7 degree orbit at altitudes between 320 and 390 km. A total of 2.86 * 10^6 helium nuclei were observed in the rigidity range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of <

Y. Shikaze, S. Orito, T. Mitsui, K. Yoshimura

We describe the design and performance of a large-area scintillator hodoscope onboard the BESS rigidity spectrometer; an instrument with an acceptance of 0.3 m^{2}sr. The hodoscope is configured such that 10 and 12 counters are respectively situated in upper and lower layers. Each counter is viewed from its ends by 2.5 inch fine-mesh photomultiplier tubes pl

N. Z. Akopov, A. B. Apyan, S. M. Darbinyan

The possibility to convert the photon beam linear polarization into circular one at photon energies of hundreds GeV with the use of crystals is considered. The energy and orientation dependencies of refractive indexes are investigated in case of diamond, silicon and germanium crystal targets. To maximize the values for figure of merit, the corresponding crys

Filipe C. Mena, Reza Tavakol, Pankaj S. Joshi

By considering families of radial null geodesics, we study the subsets of initial data that lead to naked singularities and black holes in inhomogeneous spherical dust collapse. We introduce the notion of central homogeneity for spherical dust collapse and prove that for the occurrence of naked singularities, the initial data set must in general be centrally

Ming Li, Bin Ma, Lusheng Wang

The problem of finding a center string that is `close&#39; to every given string arises and has many applications in computational biology and coding theory. This problem has two versions: the Closest String problem and the Closest Substring problem. Assume that we are given a set of strings ${\cal S}=\{s_1, s_2, ..., s_n\}$ of strings, say, each of length $

N. F. Maxemchuk, D. H. Shur

We are moving toward a distributed, international, twenty-four hour, electronic stock exchange. The exchange will use the global Internet, or internet technology. This system is a natural application of multicast because there are a large number of receivers that should receive the same information simultaneously. The data requirements for the stock exchange

F. Mancini

The Mott-Hubbard transition is studied in the context of the two-dimensional Hubbard model. Analytical calculations show the existence of a critical value Uc of the potential strength which separates a paramagnetic metallic phase from a paramagnetic insulating phase. Calculations of the density of states and double occupancy show that the ground state in the

Eugene B. Kolomeisky, T. J. Newman, Joseph P. Straley, Xiaoya Qi

The Gross-Pitaevskii approximation is a long-wavelength theory widely used to describe a variety of properties of dilute Bose condensates, in particular trapped alkali gases. We point out that for short-ranged repulsive interactions this theory fails in dimensions d less than or equal to 2, and we propose the appropriate low-dimensional modifications. For d=

David Pines

Following the identification of the pairing state, the major challenge in understanding the cuprate superconductors has been determining the evolution with doping and temperature of their anomalous normal state behavior. Key to this understanding is the experimentally determined magnetic phase diagram for the cuprates, which provides information on the prote

W. A. C. Passos, P. N. Lisboa-Filho, W. A. Ortiz

In this work we study the remanent magnetization exhibited by tridimensional disordered high-Tc Josephson junction arrays excited by an AC magnetic field. The effect, as predicted by numerical simulations and previously verified for a low-Tc array of Nb, occurs in a limited range of temperatures. We also show that the magnetized state can be excited and dete

H. M. Wiseman, Dian Wahyu Utami, He Bi Sun, G. J. Milburn

We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number using a single electron transistor (SET). The measurement is made when the bare tunneling rate though the SET is changed by the occupation number of one of the dots. We show that there is a difference between

G. Munster, A. Strumia, N. Tetradis

First-order phase transitions that proceed via nucleation of bubbles are described by the homogeneous nucleation theory of Langer. The nucleation rate is one of the most interesting parameters of these transitions. In previous works we have computed nucleation rates with two different methods: (A) employing coarse-grained potentials; (B) by means of a saddle

M. N. Kiselev, R. Oppermann

We use the Popov-Fedotov representation of spin operators to construct an effective action for a Kondo lattice model with quenched disorder at finite temperatures. We study the competition between the Kondo effect and frozen spin order in Ising-like spin glass. We present the derivation of new mean-field equations for the spin-glass order parameter and analy

M. L. Chiofalo, M. Polini, M. P. Tosi

We study the dispersion relation of the excitations of a dilute Bose-Einstein condensate confined in a periodic optical potential and its Bloch oscillations in an accelerated frame. The problem is reduced to one-dimensionality through a renormalization of the s-wave scattering length and the solution of the Bogolubov - de Gennes equations is formulated in te

E. V. Sampathkumaran, R. Mallik, P. L. Paulose, Subham Majumdar

A closer look at the temperature (T) dependence of magnetoresistance (MR) of two polycrystalline magnetic compounds, LaMn$_2$Ge$_2$ and SmMn$_2$Ge$_2$, previously reported by us, is made. A common feature for both these compounds is that the low temperature MR is positive (say, below, 30 K) in spite of the fact that both are ferromagnetic at such low tempera

Youichi Yanase, Kosaku Yamada

We theoretically investigate the effect of magnetic field on the pseudogap phenomena in High-Tc cuprates. The obtained results well explain the experimental results including their doping dependences. In our previous paper (J. Phys. Soc. Jpn. 68 (1999) 2999.), we have shown that the pseudogap phenomena observed in High-Tc cuprates are naturally understood as

Y. G. Wang, M. E. Reeves, F. J. Rachford

We use a near-field scanning microwave microscope to simultaneously image the dielectric constant, loss tangent, and topography in a PbTiO_3 crystal. By this method, we study the effects of the local dielectric constant and loss tangent in the geometry of periodic domains on the measured resonant frequency, and quality factor. We also carry out theoretical c

V. Ta Phuoc, A. Ruyter, R. de Sousa, L. Ammor

We report on transport measurements in a Bi-2212 single crystal with columnar defects parallel to the c-axis. The tilt of the magnetic field away from the direction of the tracks is studied for filling factors f=B_z/B_phi<1. Near the Bose Glass transition temperature T_BG, the angular scaling laws are verified and we find the field independent critical expon

M. I. Marques, J. A. Gonzalo, J. Romero, L. F. Fonseca

&#34;Swing&#34; effects at the onset of crossover towards two dimensional behavior in thin Ising films are investigated close to Tc(D) by means of Monte Carlo calculations. We find that the effect is extremely large for the specific heat effective critical exponent, in comparison with the &#34;swing&#34; already noted by Capehart and Fisher for the susceptib

A. M. Song, P. Omling

With unusually slow and high-resolution sweeps of magnetic field, strong, ultra-narrow (width down to $100 {\rm μT}$) resistance peaks are observed in the regime of breakdown of the quantum Hall effect. The peaks are dependent on the directions and even the history of magnetic field sweeps, indicating the involvement of a very slow physical process. Such a p

David Andelman, Roland R. Netz

This chapter deals with various aspects related to the adsorption of long chain-like macromolecules (polymers) onto solid surfaces. Physical aspects of the adsorption mechanism are elaborated mainly at thermodynamical equilibrium. The basic features needed in modeling of this adsorption are discussed. We first discuss the adsorption of a single and long poly

V. I. Yukalov, E. P. Yukalova

The peculiarities of electric current in high-resistance materials, such as semiconductors or semimetals, irradiated by ion beams are considered. It is shown that after ion--beam irradiation an unusual electric current may arise directed against the applied voltage. Such a negative current is a transient effect appearing at the initial stage of the process.

Yoshihiko Nonomura, Xiao Hu

Phase transition between the vortex glass and the Bragg glass phases in high-$T_{\rm c}$ superconductors in $\vec{B}\parallel\vec{c}$ is studied by Monte Carlo simulations in the presence of point pins. A finite latent heat and a $δ$-function peak of the specific heat are observed, which clearly indicates that this is a thermodynamic first-order phase transi

Xiao-jun Li, M. Schick

We consider the role of nonlamellar-forming lipids in biological membranes by examining fluctuations, within the random phase approximation, of a model mixture of two lipids, one of which forms lamellar phases while the other forms inverted hexagonal phases. To determine the extent to which nonlamellar-forming lipids facilitiate the formation of nonlamellar

K. Tanaka, F. Marsiglio

In order to incorporate spatial inhomogeneity due to nonmagnetic impurities, Anderson [1] proposed a BCS-type theory in which single-particle states in such an inhomogeneous system are used. We examine Anderson&#39;s proposal, in comparison with the Bogoliubov-de Gennes equations, for the attractive Hubbard model on a system with surfaces and impurities. [1]

Leon Balents

A tight binding model is introduced to describe the strong interaction limit of excitonic ordering. At stoichiometry, the model reduces in the strong coupling limit to a pseudo-spin model with approximate U(4) symmetry. Excitonic order appears in the pseudo-spin model as in-plane pseudo-magnetism. The U(4) symmetry unifies all possible singlet and triplet or

J. J. M. in &#39;t Zand, A. Bazzano, M Cocchi, R. Cornelisse

Four or five new outbursts were detected of the bright X-ray transient GRS 1747-312 in the globular cluster Terzan 6 between 1996 and 1999, through monitoring campaigns with the Wide Field Cameras (WFCs) on BeppoSAX and the Proportional Counter Array (PCA) on RossiXTE. This is the first time that the source is seen to exhibit recurrent outbursts after the di

Vinod Krishan, Paul J. Wiita, S. Ramadurai

We show that a certain class of flare models for variability from accretion disk coronae are subject to beam-plasma instabilities. These instabilities can prevent significant direct acceleration and greatly reduce the variable X-ray emission argued to arise via inverse Compton scattering involving relativistic electrons in beams and soft photons from the dis

W. A. Barkhouse, H. K. C. Yee, O. Lopez-Cruz

We have recently completed a comprehensive photometric survey of 27 Abell clusters with the 8k mosaic camera on the KPNO 0.9m telescope. Preliminary luminosity functions and dwarf-to-giant galaxy ratios have been calculated for five galaxy clusters (A1185, A1656, A2151, A2152, and A2197). A significant increase in the faint end slope between the inner (0.0-0

A. M. Gilbert, J. R. Graham, I. S. McLean, E. E. Becklin

We present infrared spectroscopy of the Antennae Galaxies (NGC 4038/4039) with NIRSPEC at the W. M. Keck Observatory. We imaged the star clusters in the vicinity of the southern nucleus (NGC 4039) in 0.39&#34; seeing in K-band using NIRSPEC&#39;s slit-viewing camera. The brightest star cluster revealed in the near-IR (M_K(0) = -17.9) is insignificant optical

Anil K. Pradhan

Recent advances in theoretical atomic physics have enabled large-scale calculation of atomic parameters for a variety of atomic processes with high degree of precision. The development and application of these methods is the aim of the Iron Project. At present the primary focus is on collisional processes for all ions of iron, Fe I- FeXXVI, and other iron-pe

G. Ghisellini

The radiation we observe from blazars is most likely the product of the transformation of bulk kinetic energy into random energy. This process must have a relatively small efficiency (e.g. 10%) if jets are to power the extended radio-structures. Recent results suggest that the average power reaching the extended radio regions and lobes is of the same order o

B. Stelzer, R. Neuhaeuser, V. Hambaryan

We present results of a systematic search for X-ray flares on young stars observed during ROSAT PSPC observations of the Taurus-Auriga-Perseus region. All pointed PSPC observations currently available from the ROSAT Public Data Archive with known T Tauri stars, Pleiads, or Hyads in the field are analyzed in order to study the evolution of coronal activity. 3

Jose Dias do Nascimento, Sylvie Theado, Sylvie Vauclair

The application to main-sequence stars of the rotation-induced mixing theory in the presence of mu-gradients leads to partial mixing in the lithium destruction region, not visible in the atmosphere. The induced lithium depletion becomes visible in the sub-giant phase as soon as the convective zone deepens enough. This may explain why the observed &#34; lithi

Sylvie Theado, Sylvie Vauclair

It has been known for a long time (Mestel~1953) that the meridional circulation velocity in stars, in the presence of mu-gradients, is the sum of two terms, one due to the classical thermal imbalance (Omega-currents) and the other one due to the induced horizontal mu-gradients (mu-induced currents, or mu-currents in short). In the most general cases, mu-curr

Sylvie Vauclair

The observations of light elements in the Sun and Solar type stars give special clues for understanding the hydrodynamical processes at work in stellar interiors. In the Sun 7Li is depleted by 140 while 3He has not increased by more than 10% in 3 Gyrs. Meanwhile the inversion of helioseismic modes lead to a precision on the sound velocity of about .1%. The m

M. R. Merrifield, D. A. Forbes, A. I. Terlevich

We present evidence that there is a significant correlation between the fraction of a galaxy&#39;s mass that lies in its central black hole and the age of the galaxy&#39;s stellar population. Since the absorption line indices that are used to estimate the age are luminosity weighted, they essentially measure the time since the last significant episode of sta

Conny Aerts, Laurent Eyer

We review the current status of different mode-identification techniques based on observed line-profile variations. Three basic methods are currently available to identify the non-radial pulsation modes. These three methods are described, together with their different variants. We further present applications to real data, focusing especially on delta Scuti

D. Dal Fiume, N. Masetti, C. Bartolini, S. Del Sordo

The X-ray source 4U1700+24/HD154791 is one of the few galactic sources whose counterpart is an evolved M star. In X-rays the source shows extreme erratic variability and a complex and variable spectrum. While this strongly suggests accretion onto a compact object, no clear diagnosis of binarity was done up to now. We report on ASCA and BeppoSAX X-ray broad b

M. E. Dieckmann, K. G. McClements, S. C. Chapman, R. O. Dendy

Observations of synchrotron radiation across a wide range of wavelengths provide clear evidence that electrons are accelerated to relativistic energies in supernova remnants (SNRs). However, a viable mechanism for the pre-acceleration of such electrons to mildly relativistic energies has not yet been established. In this paper an electromagnetic particle-in-

D. Dal Fiume, Filippo Frontera, Nicola Masetti, Mauro Orlandini

The systematic search for the presence of cyclotron lines in the spectra of accreting X-ray pulsars is being carried on with the BeppoSAX satellite since the beginning of the mission. These highly successful observations allowed the detection of cyclotron lines in many of the accreting X-ray pulsars observed. Some correlations between the different measured

J. S. Kaastra, R. Mewe, D. A. Liedahl, S. Komossa

We present for the first time a high-resolution X-ray spectrum of a Seyfert galaxy. The Chandra-LETGS spectrum of NGC 5548 shows strong, narrow absorption lines from highly ionised species (the H-like and He-like ions of C, N, O, Ne, Na, Mg, Si, as well as Fe XIV--XXI). The lines are blueshifted by a few hundred km/s. The corresponding continuum absorption e

Masaru Kajisawa, Toru Yamada, Ichi Tanaka, Toshinori Maihara

We have investigated the optical and near-infrared colors of K&#39;-selected galaxies in clusters at z ~ 1.2 near to the radio galaxy 3C 324 using images obtained with the Subaru telescope and archival HST data. The distribution of colors of the galaxies in the cluster region is found to be fairly broad, and it may imply significant scatter in their star-for

Masaru Kajisawa, Toru Yamada, Ichi Tanaka, Toshinori Maihara

We investigate the $K$-band luminosity distribution of galaxies in the region of clusters at $z\sim1.2$ near to the radio galaxy 3C 324. The imaging data were obtained during the commissioning period of the Subaru telescope. There is a significant excess of the surface number density of the galaxies with $K =$ 17--20 mag in the region within $\sim$ 40&#39;&#

M. Pozzo, R. D. Jeffries, T. Naylor, E. J. Totten

We report the serendipitous discovery of a population of low mass, pre-main sequence stars (PMS) in the direction of the Wolf-Rayet/O-star binary system gamma^{2} Vel and the Vela OB2 association. We argue that gamma^{2} Vel and the low mass stars are truly associated, are approximately coeval and that both are at distances between 360-490 pc, disagreeing at

B. J. Mochejska, J. Kaluzny, I. Thompson

We present the results of a search for variable stars in the faint sparse globular cluster E3. We have found two variable stars: an SX Phe variable (V1) and a W UMa eclipsing binary (V2). We have applied period-luminosity and period-color-luminosity relations to the variables to obtain their distance moduli. V1 seems to be a blue straggler belonging to E3, b

Michael D. Gladders, H. K. C. Yee

The Toronto Red-Sequence Cluster Survey (TRCS) is a new galaxy cluster survey designed to provide a large sample of optically selected 0.1 < z < 1.4 clusters. The planned survey data is 100 square degrees of two color (R and z&#39;) imaging, with a 5-sigma depth ~2 mag past M* at z=1. The primary scientific drivers of the survey are a derivation of Omega_m a

Achim Feldmeier, Isaac Shlosman

Line-driven winds from hot stars and accretion disks are thought to adopt a unique, critical solution which corresponds to maximum mass loss rate and a particular velocity law. We show that in the presence of negative velocity gradients, radiative-acoustic (Abbott) waves can drive shallow wind solutions towards larger velocities and mass loss rates. Perturba

Daniel Stern, Hyron Spinrad, Peter Eisenhardt, Andrew J. Bunker

We present observations of RD J030117+002025, a quasar at z=5.50 discovered from deep, multi-color, ground-based observations covering 74 square arcmin. This is the most distant quasar or AGN currently known. The object was targeted as an R-band dropout, with R(AB)>26.3 (3-sigma limit in a 3 arcsec diameter region), I(AB)=23.8, and z(AB)=23.4. The Keck/LRIS

K. Iwamoto, F. Brachwitz, K. Nomoto, N. Kishimoto

We calculate explosive nucleosynthesis in Chandrasekhar mass models for Type Ia Supernovae(SNe Ia) to obtain new constraints on the rate of matter accretion onto the progenitor white dwarf and on the ignition density of central carbon deflagration. The calculated abundance of the Fe-group neutron-rich nuclei is highly sensitive to the electron captures takin

James E. Larkin, Ian S. McLean, James R. Graham, E. E. Becklin

This paper presents infrared spectra taken with the newly commissioned NIRSPEC spectrograph on the Keck II Telescope of the High Redshift Radio Galaxy MRC 2025-218 (z=2.63) These observations represent the deepest infrared spectra of a radio galaxy to date and have allowed for the detection of Hbeta, [OIII] (4959/5007), [OI] (6300), Halpha, [NII] (6548/6583)

Vladimir V. Usov, Jonathan I. Katz

Gamma-ray bursts, if they are generated in the process of interaction between relativistic strongly magnetized winds and an ambient medium, may be accompanied by very short pulses of low-frequency radio emission. The bulk of this emission is expected to be at the frequencies of $\sim 0.1-1$ MHz and cannot be observed. However, the high-frequency tail of the

Michael D. Gregg, Lutz Wisotzki, Robert Becker, Jose Maza

In the course of a Cycle 8 snapshot survey, we have discovered that the z=1.565 quasar HE 0512-3329 is a double with image separation 0.644&#34;, almost certainly due to gravitational lensing. The two components differ in brightness by only 0.4 magnitudes and a high signal-to-noise ground-based composite optical spectrum shows no trace of any stellar feature

J. W. Maluf, J. F. da Rocha-Neto

We establish the Hamiltonian formulation of the teleparallel equivalent of general relativity, without fixing the time gauge condition, by rigorously performing the Legendre transform. The time gauge condition, previously considered, restricts the teleparallel geometry to the three-dimensional spacelike hypersurface. Geometrically, the teleparallel geometry

Tsuguhiko Asakawa, Isao Kishimoto

We construct noncommutative gauge theories based on the notion of the Weyl bundle, which appears in Fedosov&#39;s construction of deformation quantization on an arbitrary symplectic manifold. These correspond to D-brane worldvolume theories in non-constant B-field and curved backgrounds in string theory. All such theories are embedded into a &#34;universal&#

Gian F. Giudice, Riccardo Rattazzi, James D. Wells

We investigate the properties of scalar fields arising from gravity propagating in extra dimensions. In the scenario of large extra dimensions, proposed by Arkani-Hamed, Dimopoulos and Dvali, graviscalar Kaluza-Klein excitations are less important than the spin-2 counterparts in most processes. However, there are important exceptions. The Higgs boson can mix

Craig J. Hogan, Julianne J. Dalcanton

We examine the effect of primordial dark matter velocity dispersion and/or particle self-interactions on the structure and stability of galaxy halos, especially with respect to the formation of substructure and central density cusps. Primordial velocity dispersion is characterised by a ``phase density&#39;&#39; $Q\equiv ρ/<v^2>^{3/2}$, which for relativistic

Ben Moore, Sergio Gelato, Adrian Jenkins, F. R. Pearce

We compare the structure and substructure of dark matter halos in model universes dominated by collisional, strongly self interacting dark matter (SIDM) and collisionless, weakly interacting dark matter (CDM). While SIDM virialised halos are more nearly spherical than CDM halos, they can be rotationally flattened by as much as 20% in their inner regions. Sub