June 2000 arXiv papers — page 15

W. Gringel, J. Barnstedt, K. S. de Boer, M. Grewing

Absorption lines of interstellar molecular hydrogen in the far ultraviolet (FUV) have been observed in the spectrum of the O9.5 halo star HD 93521, located some 1500 pc from the Galactic plane. During the second flight of the ORFEUS-SPAS mission a spectrum with the Echelle spectrometer has been recorded with a total integration time of 1740 s. The resolution

Debiprosad Duari, Jennifer Hatchell

We have detected the (0,11c,0)J=3-2 and (0,0,0)J=8-7 transitions of HCN towards the S star {chi} Cygni. The excitation requirements of these transitions are too high to be satisfied in the outer envelope of the star, and the emission must originate within {solar}20 stellar radii, ie. the molecule must be forming close to the star. This conclusion is supporte

V. Karas, B. Czerny, Z. Abrassart, M. Abramowicz

The origin and the profile of the iron K-alpha line from active galactic nuclei is being studied. The model with a quasi-spherical distribution of clouds around a compact galactic nucleus is explored in which the intrinsic spectral feature around 6-7 keV is substantially affected by Comptonization of primary X-rays. The predicted spectral profiles are influe

Roger E. Behrend, Paul A. Pearce

Integrable boundary conditions are studied for critical A-D-E and general graph-based lattice models of statistical mechanics. In particular, using techniques associated with the Temperley-Lieb algebra and fusion, a set of boundary Boltzmann weights which satisfies the boundary Yang-Baxter equation is obtained for each boundary condition. When appropriately

Alan Chodos, Erich Poppitz, Dimitrios Tsimpis

We consider deformations of the singular "global cosmic string" compactifications, known to naturally generate exponentially large scales. The deformations are obtained by allowing a constant curvature metric on the brane and correspond to a choice of integration constant. We show that there exists a unique value of the integration constant that give

Axel Brandenburg

A numerical model of isotropic homogeneous turbulence with helical forcing is investigated. The resulting flow, which is essentially the prototype of the alpha^2 dynamo of mean-field dynamo theory, produces strong dynamo action with an additional large scale field on the scale of the box (at wavenumber k=1; forcing is at k=5). This large scale field is nearl

Santiago Peris, Eduardo de Rafael

We present the result for the invariant B_K factor of K0-anti-K0 mixing in the chiral limit and to next-to-leading order in the 1/Nc expansion. We explicitly demonstrate the cancellation of the renormalization scale and scheme dependences between short- and long-distance contributions in the final expression. Numerical estimates are then given, by taking int

C. Dib, R. Rosenfeld

Using recent experimental evidence from E791 on the sigma meson in D \to 3πdecays, we study the relevant couplings in D \to σπand σ\to π pi within the accepted theoretical framework for non leptonic D decays. We also review the linear sigma model, finding that it gives a description which is consistent with the experimental data.

L. Bonora, M. Schnabl, M. M. Sheikh-Jabbari, A. Tomasiello

We study the generalization of noncommutative gauge theories to the case of orthogonal and symplectic groups. We find out that this is possible, since we are allowed to define orthogonal and symplectic subgroups of noncommutative unitary gauge transformations even though the gauge potentials and gauge transformations are not valued in the orthogonal and symp

Marija Zamaklar

We introduce a calculus of the Lie algebra valued functions present in Tseytlin's proposal for the nonabelian DBI action, and apply it to show that the recently found dyonic instanton is a solution of the full nonabelian DBI action. The geometry of this solution exhibits a new effect of ``blowing-up'' of the brane, which was not present in the ca

Ronald E. Cohen, O. Gulseren

We have investigated the thermal equation of state of tantalum from first principles using the Linearized Augmented Plane Wave (LAPW) and pseudopotential methods for pressures up to 300 GPa and temperatures up to 10000 K. The equation of state at zero temperature was computed using LAPW. For finite temperatures, mixed basis pseudopotential computations were

Simon Catterall, Eric Gregory

We report on a study of the supersymmetric anharmonic oscillator computed using a euclidean lattice path integral. Our numerical work utilizes a Fourier accelerated hybrid Monte Carlo scheme to sample the path integral. Using this we are able to measure massgaps and check Ward identities to a precision of better than one percent. We work with a non-standard

H. G. Ballesteros, A. Cruz, L. A. Fernandez, V. Martin-Mayor

We have simulated, using parallel tempering, the three dimensional Ising spin glass model with binary couplings in a helicoidal geometry. The largest lattice (L=20) has been studied using a dedicated computer (the SUE machine). We have obtained, measuring the correlation length in the critical region, a strong evidence for a second-order finite temperature p

J. B. Sokoloff

Several workers have established that the Larkin domains for two three dimensional nonmetallic elastic solids in contact with each other at a disordered interface are enormously large. This implies that there should be negligible static friction per unit area in the macroscopic solid limit. The present work argues that the fluctuations in the heights of the

Tomonori Totani, Tetsu Kitayama

Over half of GeV gamma-ray sources observed by the EGRET experiment have not yet been identified as known astronomical objects. There is an isotropic component of such unidentified sources, whose number is about 60 in the whole sky. Here we calculate the expected number of dynamically forming clusters of galaxies emitting gamma-rays by high energy electrons

H. Heiselberg, A. D. Jackson

Event-by-event fluctuations and correlations between particles produced in relativistic nuclear collisions are studied. The fluctuations in positive, negative, total and net charge are closely related through correlations. In the event of a phase transitions to a quark-gluon plasma, fluctuations in total and net charge can be enhanced and reduced respectivel

G. Buchalla, G. Hiller, G. Isidori

The rare decays $B\to K^{(*)}\ell^+\ell^-$, $B\to K^{(*)}ν\barν$ and $B_s\toμ^+μ^-$ are analyzed in a generic scenario where New Physics effects enter predominantly via $Z$ penguin contributions. We show that this possibility is well motivated on theoretical grounds, as the $\bar sbZ$ vertex is particularly susceptible to non-standard dynamics. In addition,

Steffen Hein

Typical features of the Transmission Line Matrix (TLM) algorithm in connection with stub loading techniques and prone to be hidden in common frequency domain formulations are elucidated within the propagator approach to TLM. In particular, the latter reflects properly the perturbative character of the TLM scheme and its relation to gauge field models. Intern

M. Caselle, F. Gliozzi, S. Necco

We discuss a new class of identities between correlation functions which arise from a local Z_2 invariance of the partition function of the q-state Potts model on general graphs or lattices. Their common feature is to relate the thermal operators of the Potts model to some topological properties of the Fortuin-Kasteleyn clusters. In particular it turns out t

Peter F. Kolb, Josef Sollfrank, Ulrich Heinz

We use (3+1)-dimensional hydrodynamics with exact longitudinal boost-invariance to study the influence of collision centrality and initial energy density on the transverse flow pattern and the angular distributions of particles emitted near midrapidity in ultrarelativistic heavy-ion collisions. We concentrate on radial flow and the elliptic flow coefficient

S. Kasuya, M. Kawasaki

We obtain a new type of a stable Q ball in the context of gauge-mediated supersymmetry breaking in minimal supersymmetric standard model. It is so-called gravity-mediation type of Q ball, but stable against the decay into nucleons, since the energy per unit charge is equal to gravitino mass m_{3/2}, which can be smaller than nucleon mass in the gauge-mediati

V. Ravindran, W. L. van Neerven

The revised version contains two additional references i.e. [13], [14] w.r.t. to the original paper. Furthermore Eq. (33) in [11] at the end of the paragraph below (3.17) must be Eq. (33) in [10]. Misprints in the list of references are corrected.

Shengjun Wu, Xuemei Chen, Yongde Zhang

We present a necessary and sufficient condition for the separability of multipartite quantum states, this criterion also tells us how to write a multipartite separable state as a convex sum of separable pure states. To work out this criterion, we need to solve a set of equations, actually it is easy to solve these quations analytically if the density matrix

Rong Lu, Yi Zhou, Jia-Lin Zhu, Bing-Lin Gu

The phenomenon of quantum nucleation is studied in a nanometer-scale antiferromagnet with biaxial symmetry in the presence of a magnetic field at an arbitrary angle. Within the instanton approach, we calculate the dependence of the rate of quantum nucleation and the crossover temperature on the orientation and strength of the field for bulk solids and two-di

H. Eschrig, W. E. Pickett

The Hohenberg-Kohn theorem of density functional theory (DFT) for the case of electrons interacting with an external magnetic field (that couples to spin only) is examined in more detail than previously. A unexpected generalization is obtained: in certain cases (which include half metallic ferromagnets and magnetic insulators) the ground state, and hence the

Jens H. Gundlach, Stephen M. Merkowitz

We measured Newton's gravitational constant G using a new torsion balance method. Our technique greatly reduces several sources of uncertainty compared to previous measurements: (1) it is insensitive to anelastic torsion fiber properties; (2) a flat plate pendulum minimizes the sensitivity due to the pendulum density distribution; (3) continuous attracto

A. Ashikhmin, S. Litsyn, M. A. Tsfasman

Using algebraic geometry codes we give a polynomial construction of quantum codes with asymptotically non-zero rate and relative distance.

S. Mazzucchi

A reference frame F is described by the element g of the Poincare' group P which connects F with a given fixed frame F_0. If F is a quantum frame, defined by a physical object following the laws of quantum physics, the parameters of g have to be considered as quantum observables. However, these observables are not compatible and some of them, namely the

Yu-xi Liu, C. P. Sun, S. X. Yu

For the excitons in the quantum well placed within a leaky cavity, the quantum decoherence of a mesoscopically superposed states is investigated based on the factorization theory for quantum dissipation. It is found that the coherence of the exciton superposition states will decrease in an oscillating form when the cavity field interacting with the exciton i

R. F. Werner, K. G. H. Vollbrecht

We give an explicit counterexample to an entanglement inequality suggested in a recent paper [quant-ph/0005126] by Benatti and Narnhofer. The inequality would have had far-reaching consequences, including the additivity of the entanglement of formation.

Jens G Jensen, Ruediger Schack

Starting from Barnum's recent proposal to use entanglement and catalysis for quantum secure identification [quant-ph/9910072], we describe a protocol for quantum authentication and authenticated quantum key distribution. We argue that our scheme is secure even in the presence of an eavesdropper who has complete control over both classical and quantum cha

Fabio Cardarelli, Silvano Simula

The effects of SU(6) breaking on the nucleon elastic form factors are investigated within the constituent quark model formulated on the light-front. It is shown that the kinematical SU(6) breaking caused by the Melosh rotations of the quark spins as well as the dynamical SU(6) breaking due to the mixed-symmetry component generated in the nucleon wave functio

A. V. Avdeenkov, S. P. Kamerdzhiev

General equations for one- particle Green function in non- magic nuclei have been derived where a pairing mechanism, which is analogous to the Bardeen- Cooper- Schrieffer one, has been singled out explicitely. A "refining" procedure for the phenomenological single- particle energies and pairing gaps is formulated to avoid double counting of the phono

WA98 Collaboration, M. M. Aggarwal

A measurement of direct photon production in 208Pb + 208Pb collisions at 158 A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval 0.5 < p_T < 4 GeV/c. A significant direct photon signal, compared to statistical and systematical err

WA98 Collaboration, M. M. Aggarwal

A measurement of direct photon production in 208Pb + 208Pb collisions at 158 A GeV has been carried out in the CERN WA98 experiment. The invariant yield or upper limit of direct photons as a function of transverse momentum in the interval 0.5 < p_T < 4 GeV/c is presented. A significant direct photon excess is observed at p_T > 1.5 GeV/c in central collisions

B. V. Chirikov, V. G. Davidovsky

The results of numerical experiments on chaotic (&#39;turbulent&#39;) dynamics of the second sound in helium II are presented and discussed based on a very simple model proposed and theoretically studied recently by Khalatnikov and Kroyter. Using a powerful present-day techniques for the studying nonlinear phenomena, we confirm their results on the stationar

Adolfo R. Ordonez

It is proved that, in the Misra-Prigogine-Courbage Theory of Irreversibility using the Internal Time superoperator, fixing its associated non-unitary transformation $Λ$, amounts to rigging the corresponding Hilbert-Liouville space. More precisely, it is demonstrated that any $Λ$ determinates three canonical riggings of the Liouville space $\QTR{cal}{L}$: a f

J. A. de Azcarraga, A. J. Macfarlane

This paper deals with the striking fact that there is an essentially canonical path from the $i$-th Lie algebra cohomology cocycle, $i=1,2,... l$, of a simple compact Lie algebra $\g$ of rank $l$ to the definition of its primitive Casimir operators $C^{(i)}$ of order $m_i$. Thus one obtains a complete set of Racah-Casimir operators $C^{(i)}$ for each $\g$ an

Doug Pickrell, Eugene Z. Xia

We prove that the mapping class group of a closed surface acts ergodically on connected components of the representation variety corresponding to a connected compact Lie group.

Eric M. Rains

We show that the correlation functions associated to symmetrized increasing subsequence problems can be expressed as pfaffians of certain antisymmetric matrix kernels, thus generalizing the result of math.RT/9907127 for the unsymmetrized case.

T. Chinburg, G. Pappas, M. J. Taylor

We study equivariant Arakelov-Euler characteristics of hermitian sheaves on arithmetic varieties which support a tame action by a finite group G. The tameness of the group action allows us to produce an equivariant Arakelov-Euler characteristic in a particularly fine &#34;projective&#34; arithmetic class group. We then show that the equivariant Arakelov-Eule

Stefano Bianchini

We consider a hyperbolic system of conservation laws u_t + f(u)_x = 0 and u(0,\cdot) = u_0, where each characteristic field is either linearly degenerate or genuinely nonlinear. Under the assumption of coinciding shock and rarefaction curves and the existence of a set of Riemann coordinates $w$, we prove that there exists a semigroup of solutions $u(t) = \ma

Michael Baake, John A. G. Roberts

Toral automorphisms, represented by unimodular integer matrices, are investigated with respect to their symmetries and reversing symmetries. We characterize the symmetry groups of GL(n,Z) matrices with simple spectrum through their connection with unit groups in orders of algebraic number fields. For the question of reversibility, we derive necessary conditi

Juan Fernando Ospina Giraldo

The Wess-Zumino actions for generalized orientifold planes (GOp-planes) and y-deformed orientifold planes (yOp-planes) are presented and two series power expantions are realized from whiches processes that involves GOp-planes,yOp-planes, RR-forms, gravitons and gaugeons, are obtained. Finally non-standard GOp-planes and y-Op-planes are showed.

M. Bordag, V. Skalozub

The temperature phase transition in scalar $ϕ^4(x)$ field theory with spontaneous symmetry breaking is investigated in a partly resummed perturbative approach. The second Legendre transform is used and the resulting gap equation is considered in the extrema of the free energy functional. It is found that the phase transition is of first order in the super da

N. A. Obers, B. Pioline

Three-dimensional string theories with 16 supersymmetries are believed to possess a non-perturbative U-duality symmetry $SO(8,24,\Zint)$. By covariantizing the heterotic one-loop amplitude under U-duality, we propose an exact expression for the $(\partial ϕ)^4$ amplitude, that reproduces known perturbative limits. The weak-coupling expansion in either of the

Dongsu Bak, Sung Ku Kim, Kwang-Sup Soh, Jae Hyung Yee

We consider two model field theories on a noncommutative plane that have smooth commutative limits. One is the single-component fermion theory with quartic interaction that vanishes identically in the commutative limit. The other is a scalar-fermion theory, which extends the scalar field theory with quartic interaction by adding a fermion. We compute the bou

Kenichi Konishi

Several distinct mechanisms of confinement and dynamical symmetry breaking (DSB) are identified, in a class of supersymmetric $SU(n_c)$, $USp(2n_c)$ and $SO(n_c)$ gauge theories. In some of the vacua, the magnetic monopoles carrying nontrivial flavor quantum numbers condense, causing confinement and symmetry breaking simultaneously. In more general classes o

Bernd A. Berg

I consider infinitesimal translations $x&#39;^α=x^α+δx^α$ and demand that Noether&#39;s approach gives a symmetric electromagnetic energy-momentum tensor as it is required for gravitational sources. This argument determines the transformations of the electromagnetic potentials under infinitesimal translations to be $A&#39;_γ (x&#39;) = A_γ(x)+\partial_γ [δx_

M. Bleicher, H. Stöcker

A sign reversal of the directed flow parameter $v_1$ in the central rapidity region in Au+Au collisions at $\sqrt s =200$~AGeV is predicted. This anti-flow is shown to be linked to the expansion of the hot matter created. In line with this observation the predicted elliptic flow parameter $v_2$ of various particle species is predicted and linked to the mean

Marcela Carena, Debajyoti Choudhury, Chris Quigg, Sreerup Raychaudhuri

To explore the discovery possibilities of a high-energy muon-proton collider, we examine signals that could arise from direct-channel formation of supersymmetric-particle resonances through operators that do not respect R-parity.

A. V. Belitsky, A. Freund, D. Müller

We outline a formalism used for a construction of two-loop flavor singlet exclusive evolution kernels in the MS bar scheme. The approach is based on the known pattern of conformal symmetry breaking in MS bar as well as constraints arising from the superconformal algebra of the N = 1 super Yang-Mills theory.

Ernest Ma

I discuss the connection between neutrino masses and leptogenesis. I use three prime examples: (1) canonical seesaw, (2) triplet Higgs, and (3) $R$ parity violation.

Anjan S. Joshipura, Rishikesh D. Vaidya, Sudhir K. Vempati

The patterns of $R$ violation resulting from imposition of a gauged U(1) horizontal symmetry on the minimal supersymmetric standard model are systematically analyzed. We concentrate on class of models with integer U(1) charges chosen to reproduce the quark masses and mixings as well as charged lepton masses exactly or approximately. The U(1) charges are furt

Jai Sam Kim, Kyungsoo Lee

We introduce an integrated algorithm for full scale investigation of the earth regeneration effect of solar neutrinos with all three active neutrinos. We illustrate that the earth effect on low energy solar neutrinos ($E_ν< 20$ MeV) causes large variations in the survival probabilities for large values of the mixing angle $θ_{12}$ for a given value of $θ_{13

D. Becirevic, D. Meloni, A. Retico, V. Gimenez

We present the results of a quenched lattice calculation of the operator matrix elements relevant for predicting the Bs width difference. Our main result is (ΔΓ_Bs/Γ_Bs)= (4.7 +/- 1.5 +/- 1.6) 10^(-2), obtained from the ratio of matrix elements, R(m_b)=<\bar B_s^0|Q_S|B_s^0>/<\bar B_s^0|Q_L|B_s^0>=-0.93(3)^(+0.00)_(-0.01). R(m_b) was evaluated from the two r

K. Gallmeister, B. Kampfer, O. P. Pavlenko

The data of direct single-photon measurements of the WA98 collaboration in the reaction Pb(158 AGeV) + Pb are analyzed within a thermal model with a minimum number of parameters adjusted to the dilepton data obtained by the CERES and NA50 collaborations in the reactions Pb(158 AGeV) + Au, Pb. The agreement of our model with the WA98 data points to a unique l

Petros D. Draggiotis, Ronald Kleiss

We present an enumeration of all possible amplitudes that contribute to an n-jet process in QCD. We estimate the number of amplitudes for large number of jets and determine the actual number of amplitudes to be calculated, which is smaller due to relabelling among (massless) quark flavours.

Robert Fleischer

After a brief look at CP violation in kaon decays, a short overview of CP violation in the $B$-meson system and of strategies to determine the angles of the unitarity triangles of the CKM matrix is given. Both general aspects and some recent developments are discussed, including $B_c^\pm\to D^\pm_s D$ and $B\toπK$ decays, as well as the $B_d\toπ^+π^-$, $B_s\

A. Bacchetta, P. J. Mulders

We analyze one-particle inclusive DIS in the case when a spin-1 hadron (such as a vector meson) is observed in the final state. We consider only leading order contributions in 1/Q, but we include transverse momentum of partons. Several new fragmentation functions appear in cross sections. One of them can be measured in connection with the transverse-spin dis

D. Falcone

Two topics are covered in this paper. In the first part the relation between quark mass matrices and observable quantities in gauge theories. In the second part neutrino masses and mixings in a seesaw framework.

Joe Sato

Stimulated by the idea of PRISM, a very high intensity muon ring with rather low energy, we consider possibilities of observing CP-violation effects in neutrino oscillation experiments. Destructive sum of matter effect and CP-violation effect can be avoided with use of initial $ν_{\rm e}$ beam. We finally show that the experiment with (a few) $\times$ 100 Me

I. M. Dremin

This talk at Fradkin conference is devoted to brief description of latest results in two topics I worked on during last years. The multiresolution analysis and fast wavelet transform became a standard procedure for pattern recognition and I describe how it has been used for analysis of high energy nucleus-nucleus interactions. Latest QCD results on multiplic

M. Beneke, G. Buchalla, M. Neubert, C. T. Sachrajda

We provide a rigorous basis for factorization for a large class of non-leptonic two-body $B$-meson decays in the heavy-quark limit. The factorization formula incorporates elements of the naive factorization approach and the hard-scattering approach, but allows us to compute systematically radiative (``non-factorizable&#39;&#39;) corrections to naive factoriz

H. Athar, G. Parente, E. Zas

We study prospects for the observations of high-energy cosmic tau neutrinos (E \geq 10^6 GeV) originating from proton acceleration in the cores of active galactic nuclei. We consider the possibility that vacuum flavor neutrino oscillations induce a tau to muon neutrino flux ratio greatly exceeding the rather small value expected from intrinsic production. Th

H. Jung

The structure of the virtual photon and its contribution to small x processes in deep inelastic scattering at HERA is discussed.

F. Boehm, J. Busenitz, B. Cook, G. Gratta

The yield of neutrons produced by cosmic ray muons at a shallow depth of 32 meters of water equivalent has been measured. The Palo Verde neutrino detector, containing 11.3 tons of Gd loaded liquid scintillator and 3.5 tons of acrylic served as a target. The rate of one and two neutron captures was determined. Modeling the neutron capture efficiency allowed u

Fredrik Ståhl

This paper is concerned with two themes: imprisoned curves and the b-length functional. In an earlier paper by the author, it was claimed that an endless incomplete curve partially imprisoned in a compact set admits an endless null geodesic cluster curve. Unfortunately, the proof was flawed. We give an outline of the problem and remedy the situation by provi

Fredrik Ståhl

One of the known mathematical descriptions of singularities in General Relativity is the b-boundary, which is a way of attaching endpoints to inextendible endless curves in a spacetime. The b-boundary of a manifold M with connection is constructed by forming the Cauchy completion of the frame bundle LM equipped with a certain Riemannian metric, the b-metric

Filipe Bonjour, P. S. Letelier

By considering full-field string solutions of the Abelian--Higgs model, we modify the model of a fluid of strings (which is composed of Nambu strings) to obtain a model for a ``fluid of vortices.&#39;&#39; With this model, and following closely Soleng&#39;s proposal of a fluid of strings as the source of a Milgrom-type correction to the Newton dynamics, we d

Paweł Nurowski, David C. Robinson

We apply Cartan&#39;s method of equivalence to construct invariants of a given null hypersurface in a Lorentzian space-time. This enables us to fully classify the internal geometry of such surfaces and hence solve the local equivalence problem for null hypersurface structures in 4-dimensional Lorentzian space-times.

P. Breitenlohner, P. Forgács, D. Maison

Numerical evidence is presented for the existence of a new family of static, globally regular `cosmological&#39; solutions of the spherically symmetric Einstein-Yang-Mills-Higgs equations. These solutions are characterized by two natural numbers ($m\geq 1$, $n\geq 0$), the number of nodes of the Yang-Mills and Higgs field respectively. The corresponding spac

Marcus Ansorg

In this paper, solutions to the Ernst equation are investigated that depend on two real analytic functions defined on the interval [0,1]. These solutions are introduced by a suitable limiting process of Backlund transformations applied to seed solutions of the Weyl class. It turns out that this class of solutions contains the general relativistic gravitation

B. Coll, S. R. Hildebrandt, J. M. M. Senovilla

We study continuous groups of generalized Kerr-Schild transformations and the vector fields that generate them in any n-dimensional manifold with a Lorentzian metric. We prove that all these vector fields can be intrinsically characterized and that they constitute a Lie algebra if the null deformation direction is fixed. The properties of these Lie algebras

Adwait Ratnaparkhi

We present three systems for surface natural language generation that are trainable from annotated corpora. The first two systems, called NLG1 and NLG2, require a corpus marked only with domain-specific semantic attributes, while the last system, called NLG3, requires a corpus marked with both semantic attributes and syntactic dependency information. All sys

Pierre Nugues

We first discuss respective advantages of language interaction in virtual worlds and of using 3D images in dialogue systems. Then, we describe an example of a verbal interaction system in virtual reality: Ulysse. Ulysse is a conversational agent that helps a user navigate in virtual worlds. It has been designed to be embedded in the representation of a parti

Neil J. Gunther

The latest implementations of commercial UNIX to offer mainframe style capacity management on enterprise servers include: AIX Workload Manager (WLM), HP-UX Process Resource Manager (PRM), Solaris Resource Manager (SRM), as well as SGI and Compaq. The ability to manage server capacity is achieved by making significant modifications to the standard UNIX operat

M. D. Lumsden, G. E. Granroth, D. Mandrus, S. E. Nagler

The phase transition in the compound LiVGe2O6 has been proposed as a unique example of a spin-Peierls transition in an S=1 antiferromagnetic chain. We report neutron and x-ray diffraction measurements of LiVGe2O6 above and below the phase transition at T=24 K. No evidence is seen for any structural distortion associated with the transition. The neutron resul

Nir Gov

We propose a new model for the nature of the low temperature phase of a geometrically frustrated antiferromgnet (AFM) with a Kagome lattice, SrCr$_{8-x}$Ga$_{4+x}$O$_{19}$. We propose that the long-range dipolar interaction between the magnetic Cr$^{3+}$ ions introduces correlations in their dynamics. The dipolar ground-state has the spins performing correla

T. Franosch, M. Fuchs, A. Latz

The light scattering spectra of molecular liquids are derived within a generalized hydrodynamics. The wave vector and scattering angle dependences are given in the most general case and the change of the spectral features from liquid to solidlike is discussed without phenomenological model assumptions for (general) dielectric systems without long-ranged orde

Haye Hinrichsen

We demonstrate that first-order phase transitions in 1+1-dimensional nonequilibrium systems with fluctuating ordered phases are impossible, provided that there are no additional conservation laws, long-range interactions, macroscopic currents, or special boundary conditions. Since minority islands in the ordered phase of such systems can only shrink by short

A. Venimadhav, M. S. Hegde, R. Rawat, I. Das

Thin films of Pr0.7Ca 0.3MnO3, Nd-0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3 have been fabricated. by pulse laser deposition. Magnetic and electrical transport properties of these films were compared with their bulk solids. All the films grow in (101) direction on LaAlO3(100). Electrical transport measurements carried out with and without magnetic field has shown dr/dT

A. Chattopadhyay, A. J. Millis

We formulate a theory of double perovskite coumpounds such as Sr$_2$FeReO$_6$ and Sr$_2$FeMoO$_6$ which have attracted recent attention for their possible uses as spin valves and sources of spin polarized electrons. We solve the theory in the dynamical mean field approximation to find the magnetic transition temperature $T_c$. We find that $T_c$ is determine

A. V. Nikolaev, K. H. Michel

We present a theoretical model of the &#34;isostructural&#34; γ-αphase transition in Ce which is based on quadrupolar interactions due to coupled charge density fluctuations of 4f electrons and of conduction electrons. Conduction electrons are treated in tight-binding approximation. The γ-αtransition is described as an orientational ordering of quadrupolar e

Peixun Luo, K. Y. Michael Wong

Using the cavity method we consider the learning of noisy teacher-generated examples by a nonlinear student perceptron. For insufficient examples and weak weight decay, the activation distribution of the training examples exhibits a gap for the more difficult examples. This illustrates that the outliers are sacrificed for the overall performance. Simulation

M. I. Katsnelson, A. V. Trefilov, K. Yu. Khromov

The dispersion in the entire Brillouin zone and the temperature dependence (right up to the melting temperature) of the anharmonic frequency shift and phonon damping in a number of fcc metals is investigated on the basis of microscopic calculations. It is found that the anharmonic effects depend sharply on the wave vector in the directions $Γ$-X, X-W, and $Γ

D. H. E. Gross

Phase transitions in nuclei, small atomic clusters and self-gravitating systems demand the extension of thermo-statistics to ``Small&#39;&#39; systems. The main obstacle is the thermodynamic limit. It is shown how the original definition of the entropy by Boltzmann as the volume of the energy-manifold of the N-body phase space allows a {\em geometrical} defi

Mai Suan Li, Marek Cieplak, Nazar Sushko

The dynamical chaos in Lennard-Jones toy models of heteropolymers is studied by molecular dynamics simulations. It is shown that two nearby trajectories quickly diverge from each other if the heteropolymer corresponds to a random sequence. For good folders, on the other hand, two nearby trajectories may initially move apart but eventually they come together.

A. Contursi, J. Lequeux, C. Cesarsky

We present observations with the mid-infrared camera ISOCAM on board ISO of the major star-forming region N66 in the Small Magellanic Cloud and of its surroundings. These observations were performed with broad filters and the CVF giving a spectral resolution of about 40. In addition, CO(2-1) data are presented, allowing us to identify and study how hot dust

Ilian T. Iliev, Paul R. Shapiro

An analytical model for the postcollapse equilibrium structure of virialized objects which condense out of the cosmological background universe is described and compared with observations and simulations of cosmological halos. The model is based upon the assumption that virialized halos are isothermal, which leads to a prediction of a unique nonsingular isot

Yancy L. Shirley, Neal J. Evans, Jonathan M. C. Rawlings, Erik M. Gregersen

We have obtained 850 and 450 micron continuum maps of 21 low mass cores with SED&#39;s ranging from pre-protostellar to Class I (18K < Tbol < 370K), using SCUBA at the JCMT. In this paper we present the maps, radial intensity profiles, and photometry. Pre-protostellar cores do not have power-law intensity profiles, whereas the intensity profiles of Class 0 a

Ravi Sankrit, W. P. Blair, J. C. Raymond, K. S. Long

We present a spatially-resolved ultraviolet spectrum of a non-radiative shock front in the Cygnus Loop, obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The spectrum covers the wavelength range 1118 - 1716 angstroms, with an effective spectral resolution of ~12 angstroms. The 0.1&#34; spatial resolution

Terry Matilsky

We propose an additional term in the classical gravitational force law, which is repelling in nature, and which may solve the dark matter problem. As an inverse cube field interaction, it operates over 4 real spatial dimensions and its effect on our observable 3-D space may account both for flat rotation curves and standard Newtonian dynamics at small radial

T. Kinman, F. Castelli, C. Cacciari, A. Bragaglia

New spectroscopic observations (R=15000 and 40000) are given for 31 nearby (V < 11) BHB star candidates. IUE low-resolution spectra are available for most of them. New determinations of temperature, gravity, reddening and abundances were obtained from these data using models computed by Castelli with an updated version of the ATLAS9 code. A summary of the vi

P. Bonifacio, S. Monai, T. C. Beers

We report photoelectric UBV data for 268 metal-poor candidates chosen from the northern HK objective-prism/interference-filter survey of Beers and colleagues. Over 40 % of the stars have been observed on more than one night, and most have at least several sets of photometric measurements. Reddening estimates, preliminary spectroscopic measurements of abundan

F. La Franca, I. Matute, C. Gruppioni, D. Alexander

We present the first preliminary estimate of the evolution of type 1 AGNs at 15 um. A new sample of sources selected from the ELAIS-S1 survey has been used together with the RMS sample. The ELAIS-S1 survey covers an effective area of 2.2 deg^2 (total: 4 deg^2) down to 1.2 mJy at 15 um. Spectroscopic identifications have been carried out in the range 17.2<R<2

Dimitri Pourbaix, Alain Jorissen

The Intermediate Astrometric Data (IAD) and Transit Data (TD) made available by ESA after the Hipparcos mission make it possible to re-process the observations of any Hipparcos entry. This paper illustrates how TD and IAD may be used in conjunction with the orbital parameters of spectroscopic binaries to improve the astrometric parameters of binaries conside

G. Clementini, S. Di Tomaso, L. Di Fabrizio, A. Bragaglia

We report the discovery of a new double-mode RR Lyrae variable (RRd) in the field of our Galaxy: CU Comae. CU Comae is the sixth such RRd identified to date and is the most metal-poor RRd ever detected. Based on BVI CCD photometry spanning eleven years of observations, we find that CU Comae has periods P0=0.5441641 +/-0.0000049d and P1=0.4057605 +/-0.0000018

A. Edery, A. A. Méthot, M. B. Paranjape

Conformal gravity has been proposed as an alternative theory of gravity which can account for flat galactic rotation curves without recourse to copious quantities of dark matter. However it was shown that for the usual choice of the metric, the result is catastrophic for null or highly relativistic geodesics, the effect is exactly the opposite yielding an ef

Sang-Hyeon Ahn, Hee-Won Lee, Hyung-Mok Lee

We developed a Monte Carlo code that describes the resonant Lyman alpha line transfer in an optically thick, dusty, and static medium. The code was tested against the analytic formula derived by Neufeld (1990). We explain the line transfer mechanism for a wide range of line center optical depths by tracing histories of photons in the medium. We find that pho