January 2001 arXiv papers — page 20

F. M. L. Almeida, Y. A. Coutinho, J. A. Martins Simões, M. A. B. do Vale

The possibility of detecting single heavy Dirac and Majorana neutrinos at LEP II is investigated for heavy neutrino masses in the range $M_N=(\sqrt s/2, \sqrt s)$. We study the process $e^+e^- \longrightarrow ν_{\ell} \ell q_i \bar q_j $ as a clear signature for heavy neutrinos. Numerical estimates for cross sections and distributions for the signal and the

Hsiao-Ping Hsu, Simon C. Lin, Chin-Kun Hu

Percolation models with multiple percolating clusters have attracted much attention in recent years. Here we use Monte Carlo simulations to study bond percolation on $L_{1}\times L_{2}$ planar random lattices, duals of random lattices, and square lattices with free and periodic boundary conditions, in vertical and horizontal directions, respectively, and wit

H. H. Wen, S. L. Li, G. H. Chen, X. S. Ling

Current-voltage $I-V$ curves have been carefully measured for YBa$_2$Cu$_3$O$_{7-δ}$ thin films by following different thermal or field annealing procedures. Although all data can be described quite well by the vortex-glass theory, it is found that the dissipation in a small region just above the vortex-glass transition is history dependent: the dissipation

L. Hedin, J. D. Lee

New expressions are derived for photoemission, which allow experimental electron energy loss data to be used for estimating losses in photoemission. The derivation builds on new results for dielectric response and mean free paths of strongly correlated systems of two dimensional layers. Numerical evaluations are made for $Bi_{2}Sr_{2}CaCu_{2}O_{8}$ (Bi2212)

Z. Junhao

In this paper we prove the following: (1) The basic error of time-dependent perturbation theory is using the sum of first finite order of perturbed solutions to substitute the exact solution in the divergent interval of the series for calculating the transition probability. In addition quantum mechanics neglects the influence of the normality condition in th

H. Kowata, M. Arima

The excitation spectrum of the nucleon with the spin 1/2 is examined by using the Friedberg-Lee model containing the constituent quark and the scalar meson. An appropriate way of quantization for the non-linear meson field is employed by taking account of the non-topological soliton existed in the classical level. Our model space for the nucleon resonances i

W. C. Haxton, C. -P. Liu, M. J. Ramsey-Musolf

Standard analyses of low-energy NN and nuclear parity-violating observables have been based on a pi-, rho-, and omega-exchange model capable of describing all five independent s-p partial waves. Here a parallel analysis is performed for the one-body, exchange-current, and nuclear polarization contributions to the anapole moments of 133Cs and 205Tl. The resul

A. P. Kobushkin

It is considered how spin-orbit potential for two nucleons is changed when one of them is imbedded in nuclear matter. It is emphasized that there appears new tipe of potential antisymmetric under nucleon spins which is proportional to mass difference between free and imbedded nucleons. The longest range behaviour of such potential is estimated.

Glen D. Granzow, Hermann Riecke

In a Ginzburg-Landau model for parametrically driven waves a transition between a state of ordered and one of disordered spatio-temporal defect chaos is found. To characterize the two different chaotic states and to get insight into the break-down of the order, the trajectories of the defects are tracked in detail. Since the defects are always created and an

T. Gorin, T. H. Seligman

In order to analyze the effect of chaos or order on the rate of decoherence in a subsystem we aim to distinguish effects of the two types of dynamics from those depending on the choice of the wave packet. To isolate the former we introduce a random matrix model that permits to vary the coupling strength between the subsystems. The case of strong coupling is

T. -D. Albert, K. Ruhlig

We present a detailed construction of a completely symmetric representation of the monodromy matrix by the use of Drinfel'd twists for the rational $sl(3)$ Heisenberg model without refering to the special symmetry of the model. With the help of this representation we are able to resolve the hierarchy of the nested Bethe wavevectors for the $sl(3)$ invari

Viktor Kravchenko, Vladislav Kravchenko, Benjamin Williams

A quaternionic partial differential equation is shown to be a generalisation of the Riccati ordinary differential equation and its relationship with the Schrodinger equation is established. Various approaches to the problem of finding particular solutions are explored, and the generalisations of two theorems of Euler on the Riccati differential equation, whi

J. Samuel Jiang, Hans G. Kaper, Gary K. Leaf

This article addresses a problem of micromagnetics: the reversal of magnetic moments in layered spring magnets. A one-dimensional model is used of a film consisting of several atomic layers of a soft material on top of several atomic layers of a hard material. Each atomic layer is taken to be uniformly magnetized, and spatial inhomogeneities within an atomic

Margaret M. Bayer, Aaron M. Bruening, Joshua Stewart

Bisztriczky defines a multiplex as a generalization of a simplex, and an ordinary polytope as a generalization of a cyclic polytope. This paper presents results concerning the combinatorics of multiplexes and ordinary polytopes. The flag vector of the multiplex is computed, and shown to equal the flag vector of a many-folded pyramid over a polygon. Multiplex

Margaret M. Bayer, Gabor Hetyei

A partially ordered set is r-thick if every nonempty open interval contains at least r elements. This paper studies the flag vectors of graded, r-thick posets and shows the smallest convex cone containing them is isomorphic to the cone of flag vectors of all graded posets. It also defines a k-analogue of the Mobius function and k-Eulerian posets, which are 2

Roger C. Alperin, Benson Farb, Guennadi A. Noskov

In this paper we give a criterion for pairs of isometries of a nonpositively curved metric space to generate a free group. This criterion holds only in singular spaces, for example in Euclidean buildings. The original motivation for our criterion was to prove that the four dimensional Burau representation is faithful. Although we do not settle this question,

Hjalmar Rosengren

We prove a multivariable elliptic analogue of Jackson's 8W7 summation formula, which was recently conjectured by S.O.Warnaar.

Robert Carroll

It is shown how formulas of the author for general operator transmutation can be adapted to a quantum group context

Grigori Litvinov, Viktor Maslov, Anatoli Rodionov

A unifying approach to software and hardware design generated by ideas of Idempotent Mathematics is discussed. The so-called idempotent correspondence principle for algorithms, programs and hardware units is described. A software project based on this approach is presented.

Jean-Francois Burnol

Weil has generalized the Riemann-von Mangoldt explicit formula linking the prime numbers with the zeros of the zeta function to the set-up of a general algebraic number field K and Dirichlet-Hecke L-function, revealing in the process the role played by the completions (finite and infinite) of K. We show how the local terms of these explicit formulae are expl

Jeffrey C. Lagarias, Colin L. Mallows, Allan R. Wilks

The Descartes circle theorem states that if four circles are mutually tangent with disjoint intersion, then their curvatures (or "bends) b_j = 1/r_j satisfy the relation (b_1 + b_2 + b_3 + b_4)^2 = 2(b_1^2 + b_2^2 + b_3^2 + b_4^2). We show that similar relations hold involving the centers of the circles in such a configuration, coordinatized as complex n

Mihai Ciucu, Christian Krattenthaler

We evaluate the determinant $\det_{1\leq i,j\leq n}(\binom{x+y+j}{x-i+2j}-\binom{x+y+j}{x+i+2j})$, which gives the number of lozenge tilings of a hexagon with cut off corners. A particularly interesting feature of this evaluation is that it requires the proof of a certain hypergeometric identity which we accomplish by using Gosper's algorithm in a non-au

Tom Braden, Robert MacPherson

We describe a method of computing equivariant and ordinary intersection cohomology of certain varieties with actions of algebraic tori, in terms of structure of the zero- and one-dimensional orbits. The class of varieties to which our formula applies includes Schubert varieties in flag varieties and affine flag varieties. We also prove a monotonicity result

G. Hatayama, A. Kuniba, M. Okado, T. Takagi

Solvable vertex models in a ferromagnetic regime give rise to soliton cellular automata at q=0. By means of the crystal base theory, we study a class of such automata associated with the quantum affine algebra U_q(g_n) for non exceptional series g_n = A^{(2)}_{2n-1}, A^{(2)}_{2n}, B^{(1)}_n, C^{(1)}_n, D^{(1)}_n and D^{(2)}_{n+1}. They possess a commuting fa

Jon Magne Leinaas

A uniformly accelerated system will get thermally excited due to interactions with the vacuum fluctuations of the quantum fields. This is the Unruh effect. Also a system accelerated in a circular orbit will be heated, but in this case complications arise relative to the linear case. An interesting question is in what sense the real quantum effects for orbita

A. Bassetto, S. Nicoli, F. Vian

We show that keeping only the topologically trivial contribution to the average of a class function on U(N) amounts to integrating over its algebra. The goal is reached first by decompactifying an expansion over the instanton basis and then directly, by means of a geometrical procedure.

Michael Engelhardt

QCD(1+1) in the limit of a large number of flavours N_F and a large number of colours N_C is examined in the small N_F/N_C regime. Using perturbation theory in N_F/N_C, stringent results for the leading behaviour of the spectrum departing from N_F/N_C = 0 are obtained. These results provide benchmarks in the light of which previous truncated treatments of QC

Davide Fabbri, Pietro Frè

We discuss a general feature of Freund Rubin compactifications that was previously overlooked. It consist in a curious pairing, which we call a shadow relation, of completely different (in terms of spin and mass) fields of the dimensionally reduced theory. Particularly interesting is the case where the compactification preserves a certain amount of supersymm

S. Kretzer, F. I. Olness, R. J. Scalise, R. S. Thorne

The first measurements of Delta- xF3 are higher than current theoretical predictions. We investigate the sensitivity of these theoretical predictions upon a variety of factors including: renormalization scheme and scale, quark mass effects, higher twist, isospin violation, and PDF uncertainties.

Allen C. Caldwell, Mara S. Soares

We apply the Golec-Biernat Wuesthoff model in the calculation of vector meson photo- and electroproduction. Starting from very simple non-relativistic wave functions we show that the model provides a good description of $J/Ψ$ cross sections in wide $Q^2$ and $W$ ranges. For the light mesons one obtains the approximately correct $W$ dependence and ratio of lo

Nick van Eijndhoven, Wouter Wetzels

A method is presented for the reconstruction of both the background and signal in invariant-mass analyses for two-photon decays. The procedure does not make use of event mixing techniques and as such is based exclusively on an event-by-event analysis. Consequently, topological correlations of the event (e.g. jet structures) are automatically taken into accou

M. M. Mühlleitner, M. Krämer, M. Spira, P. M. Zerwas

The heavy neutral Higgs bosons H, A in the minimal supersymmetric extension of the Standard Model can be produced as single resonances at high-energy gamma gamma colliders. We have studied the prospects of the search for these particles in b\bar b and neutralino-pair final states. The Higgs bosons can be found with masses up to 70-80% of the initial e^\pm e^

S. Dawson, L. Reina

We discuss associated production of a Higgs boson with a pair of $t {\bar t}$ quarks at a future high energy $e^+e^-$ collider. The process $e^+e^-\to t {\bar t}h$ is particularly sensitive to the presence of new physics and we consider the MSSM and models with extra dimensions at the $TeV$ scale as examples.

Felipe J. Llanes-Estrada, Stephen R. Cotanch

We represent QCD at the hadronic scale by means of an effective Hamiltonian, $H$, formulated in the Coulomb gauge. As in the Nambu-Jona-Lasinio model, chiral symmetry is explicity broken, however our approach is renormalizable and also includes confinement through a linear potential with slope specified by lattice gauge theory. This interaction generates an

A. De Roeck

Recent results on total cross-section measurements in gamma-gamma and gamma*-gamma* collisions at LEP are reported. Phenomenological fits to the data are presented.

A. De Roeck

Prospects for QCD studies in two-photon interactions at a future linear e+e- and gamma-gamma collider are discussed.

Maurizio Lusignoli

A discussion of several exotic models and how well they are able to describe the data, with particular emphasis on atmospheric neutrinos.

K. Kubota, H. Terao

Dynamical symmetry breaking in three dimensional QED with $N$ flavors, which has been mostly analyzed by solving the Schwinger-Dyson equations, is investigated by means of the approximated Wilson, or non-perturbative, renormalization group (RG). We study the RG flows of the gauge coupling and the general four-fermi couplings allowed by the symmetry with conc

R. Ugoccioni, J. Dias de Deus

We analyse recent results on charged particle pseudo-rapidity densities from RHIC in the framework of the Dual String Model, in particular when including string fusion. The model, in a simple way, agrees with all the existing data and is consistent with the presence of the percolation transition to the Quark-Gluon Plasma already at the CERN-SPS. It leads to

O. V. Selyugin

New methods have been developed for extracting the parameters of diffraction scattering amplitude, $σ_{tot}$ and $ρ=Re F_N/Im F_N$, from experimental data. The latter determines these parameters with less errors and without the knowledge of the normalization coefficient. The impact of additional information from the measurement of the spin-dependence cross s

E. Rizvi, T. Sloan

Measurements of the structure function xF3(gamma-Z) are now becoming available in charged lepton deep inelastic scattering at HERA. The correction factors which are necessary to compare these with measurements of xF3(nu N) in neutrino-nucleon scattering are deduced and a comparison is made between the H1 and the CCFR data. A sum rule is derived for the struc

Roh S. Tung

We present a gauge theory of the super SL(2,C) group. The gauge potential is a connection of the Super SL(2,C) group. A MacDowell-Mansouri type of action is proposed where the action is quadratic in the Super SL(2,C) curvature and depends purely on gauge connection. By breaking the symmetry of the Super SL(2,C) topological gauge theory to SL(2,C), a metric i

Seth A. Major

Two operators for quantum gravity, angle and quasilocal energy, are briefly reviewed. The requirements to model semi-classical angles are discussed. To model semi-classical angles it is shown that the internal spins of the vertex must be very large, ~10^20.

Lorenzo Iorio, Erricos C. Pavlis

The tiny general relativistic Lense-Thirring effect can be measured by means of a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. This observable is affected, among other factors, by the Earth' s solid and ocean tides. They induce long-period orbital perturbations that, over observational p

Daniel Braun, Etienne Hofstetter, Gilles Montambaux, Angus MacKinnon

We study the influence of boundary conditions transverse to the transport direction for disordered mesoscopic conductors both at the Anderson metal-insulator transition and in the metallic regime. We show that the boundary conditions strongly influence the conductance distribution exactly at the metal-insulator transition and we discuss implications for the

A. M. Lacasta, J. M. Sancho, F. Sagues, G. Oshanin

We study propagation dynamics of a particle phase in a single-file pore connected to a reservoir of particles (bulk liquid phase). We show that the total mass $M(t)$ of particles entering the pore up to time $t$ grows as $M(t) = 2 m(J,ρ_F) \sqrt{D_0 t}$, where $D_0$ is the "bare" diffusion coefficient and the prefactor $m(J,ρ_F)$ is a non-trivial fun

O. Benichou, A. M. Cazabat, J. De Coninck, M. Moreau

In the present paper we overview our recent results on intrinsic frictional properties of adsorbed monolayers, composed of mobile hard-core particles undergoing continuous exchanges with a vapor phase. Within the framework of a dynamical master equation approach, describing the time evolution of the system, we determine in the most general form the terminal

O. Benichou, G. Oshanin

We study the dynamics of a charged tracer particle (TP) on a two-dimensional lattice all sites of which except one (a vacancy) are filled with identical neutral, hard-core particles. The particles move randomly by exchanging their positions with the vacancy, subject to the hard-core exclusion. In case when the charged TP experiences a bias due to external el

Oliver Biermann, Erich Haedicke, Sebastian Koltzenburg, Michael Seufert

Molecular dynamics simulations of diluted (~2.5 weight percent) aqueous solutions of two polyelectrolytes, namely sodium carboxy methyl cellulose (CMC) and sodium poly(acrylate) (PAA) have been performed. Water and counterions were taken into account explicitly. For CMC the substitution pattern and starting conformation is all-important. Two simulations of C

S. Stringari

A trapped Bose-Einstein condensed atomic gas containing a quantized vortex is predicted to exhibit precession after a sudden rotation of the confining potential. The equations describing the motion of the condensate are derived and the effects of superfluidity explicitly pointed out. The dependence of the precession frequency on the relevant parameters of th

Moshe Schwartz, Avishay Efrat, James L. Monroe

We consider Ising systems where all the many-spin couplings $J_A$ are positive. We show that the absolute value of all the many-spin correlations does not increase when the value of any of the couplings is reduced, taking any value in the interval $[-J_A,J_A]$. Results of this type are motivated by work in systems such as random field Ising models.

Avishay Efrat, Moshe Schwartz

Random bond Ising systems on a general hierarchical lattice are considered. Interesting inequalities between eigenvalues of the Jacobian renormalization matrix at the pure fixed point are obtained. These lead to upper bounds on the crossover exponents $\{ϕ_i\}$.

Kasper Astrup Eriksen, Per Hedegaard, Henrik Bruus

To study composite fermions around an even denominator fraction, we adapt the phase space single-particle path integral technique for interacting electrons in zero magnetic field developed recently by D.S. Golubev and A.D. Zaikin, Phys. Rev. B {\bf 59}, 9195 (1999). This path integral description gives an intuitive picture of composite fermion propagation ve

Jianmin Yuan

Supercell method is used to study the relaxation and screening effects during the Auger transition in metals. In order to make the interaction between the core-holes sited at different atoms negligible, the real metal is simulated by supercells repeated periodically. The electronic states concerned by the Auger transition are calculated by using FLAPW method

W. Wernsdorfer

Nanometer-sized magnetic particles have generated continuous interest as the study of their properties has proved to be scientifically and technologically very challenging. In this article we reviewed the most important theories and experimental results concerning the magnetization reversal of single-domain particles,clusters and molecular clusters. Sect.1 r

Liang-Xin Li, Sophia Sun, Y. C. Chang

The theoretical studies of optical properties of Ga$_{1-x}$In$_x$As self-assembled quantum-wires (QWR's) made of short-period superlattices with strain-induced lateral ordering are presented. Valence-band anisotropy, band mixing, and effects due to local strain distribution at the atomistic level are all taken into account. Using realistic material param

Nie Luo

We consider a model of three electrons and one hole confined in a two-dimensional (2D) plane, interacting with one another through Coulomb forces. Using a Ritz variational method we find an upper bound of \approx -0.0112me^4/8π^2 ε^2 \hbar ^2 for the ground-state energy of such a system when the particles are near one another. The possible connections of suc

David N. Spergel

The challenge for optical detection of terrestial planet is the 25 magnitude brightness contrast between the planet and its host star. This paper introduces a new pupil design that produces a very dark null along its symmetry axis. By changing the shape of the pupil, we can control the depth and location of this null. This null can be further enhanced by com

Greg Ushomirsky, Robert E. Rutledge

Transiently accreting neutron stars in quiescence (Lx<10^34 erg/s) have been observed to vary in intensity by factors of few, over timescales of days to years. If the quiescent luminosity is powered by a hot NS core, the core cooling timescale is much longer than the recurrence time, and cannot explain the observed, more rapid variability. However, the non-e

E. Gueron, P. S. Letelier

The Newtonian as well as the special relativistic dynamics are used to study the stability of orbits of a test particle moving around a black hole plus a dipolar halo. The black hole is modeled by either the usual monopole potential or the Paczynki-Wiita pseudo-Newtonian potential. The full general relativistic similar case is also considered. The Poincare s

Joseph D. Adams, John R. Stauffer, David G. Monet, Michael F. Strutskie

We present the results of a large scale search for new members of the Pleiades star cluster using 2MASS near-infrared photometry and proper motions derived from POSS plates digitized by the USNO PMM program. The search extends to a 10 degree radius around the cluster, well beyond the presumed tidal radius, to a limiting magnitude of R ~ 20, corresponding to

B. Rudak

Highly magnetised rapidly spinning neutron stars are widely considered to be natural sites for acceleration of charged particles. Powerful acceleration mechanism due to unipolar induction is thought to operate in the magnetospheres of isolated neutron stars, bringing the particles to ultrarelativistic energies at the expense of the neutron star rotational en

Ilse van Bemmel, Frank Bertoldi

In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mm observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find that the 1.2 mm emission is dominated by non-thermal emission. An extrapolation of the non-thermal radio spectrum indicates

Lee Lindblom

Gravitational radiation (GR) drives an instability in certain modes of rotating stars. This instability is strong enough in the case of the r-modes to cause their amplitudes to grow on a timescale of tens of seconds in rapidly rotating neutron stars. GR emitted by these modes removes angular momentum from the star at a rate which would spin it down to a rela

L. van Zee

The results of UBV and H alpha imaging of a large sample of isolated dwarf irregular galaxies are interpreted in the context of composite stellar population models. The observed optical colors are best fit by composite stellar populations which have had approximately constant star formation rates for at least 10 Gyr. The galaxies span a range of central surf

G. Bertone, G. Sigl, J. Silk

Annihilations of weakly interacting dark matter particles provide an important signature for the possibility of indirect detection of dark matter in galaxy halos. These self-annihilations can be greatly enhanced in the vicinity of a massive black hole. We show that the massive black hole present at the centre of our galaxy accretes dark matter particles, cre

M. H. Heyer, J. M. Carpenter, R. L. Snell

A summary of global properties and an evaluation of the equilibrium state of molecular regions in the outer Galaxy are presented from the decomposition of the FCRAO Outer Galaxy Survey and targeted 12CO and 13CO observations of four giant molecular cloud complexes. The ensemble of identified objects includes both small, isolated clouds and clumps within larg

William H. Lee

We show the results of dynamical simulations of the coalescence of black hole-neutron star binaries. We use a Newtonian Smooth Particle Hydrodynamics code, and include the effects of gravitational radiation back reaction with the quadrupole approximation for point masses, and compute the gravitational radiation waveforms. We assume a polytropic equation of s

J. -Ch. Hamilton, K. M. Ganga

We present a correlation between the ACME/SP94 CMB anisotropy data at 25 to 45 GHz with the IRAS/DIRBE data and the Haslam 408 MHz data. We find a marginal correlation between the dust and the Q-band CMB data but none between the CMB data and the Haslam map. While the amplitude of the correlation with the dust is larger than that expected from naive models o

Y. Mellier, L. van Waerbeke, R. Maoli, P. Schneider

Gravitational weak shear produced by large-scale structures of the universe induces a correlated ellipticity distribution of distant galaxies. The amplitude and evolution with angular scale of the signal depend on cosmological models and can be inverted in order to constrain the power spectrum and the cosmological parameters. We present our recent analysis o

Reza Samadi, Marie-Jo Goupil, Yveline Lebreton, Annie Baglin

The acoustic power injected by turbulent convection into solar-like oscillations depends on the details of the turbulent spectrum. A theoretical formulation for the oscillation power is developed which generalizes previous ones. The formulation is first calibrated on a solar model in such a way as to reproduce the solar seismic data. This allows to investiga

Reza Samadi, Guenter Houdek

Recent observations and theoretical studies support the theory that solar-type oscillations are intrinsically stable but excited stochastically by the turbulent convection in the outer layers of the star. The acoustic noise generated by the convective motion depends on the details of the turbulent energy spectrum. In this paper we present a general formulati

P. J. E. Peebles

Advances in theoretical ideas on how galaxies formed have not been strongly influenced by the advances in observations of what might be in the voids between the concentrations of ordinary optically selected galaxies. The theory and observations are maturing, and the search for a reconciliation offers a promising opportunity to improve our understanding of co

Wojtek Pych, Janusz Kaluzny, Wojtek Krzeminski, A. Schwarzenberg-Czerny

We present CCD photometry of SX Phe variables in the field of the globular cluster M 55. We have discovered 27 variables, three of which are probable members of the Sagittarius dwarf galaxy. All of the SX Phe stars in M 55 lie in the blue straggler region of the cluster color-magnitude diagram. Using period ratio information we have identified the radial pul

Jacco Th. van Loon, Albert A. Zijlstra, Valentin Bujarrabal, Lars-Ake Nyman

We have searched for 22 GHz H2O and 43/86/129 GHz SiO masers in bright IRAS point sources in the SMC and LMC, to test whether the kinematics of the mass loss from these stars depends on metallicity. H2O masers were detected in the red supergiants IRAS04553-6825 and IRAS05280-6910, and tentatively in the luminous IR object IRAS05216-6753 and the AGB star IRAS

G. Nelemans, S. F. Portegies Zwart, F. Verbunt, L. R. Yungelson

We study two models for AM CVn stars: white dwarfs accreting (i) from a helium white dwarf companion and (ii) from a helium-star donor. We show that in the first model possibly no accretion disk forms at the onset of mass transfer. The stability and the rate of mass transfer then depend on the tidal coupling between the accretor and the orbital motion. In th

F. Gianotti, M. Trifoglio

The ESA Packet Telemetry and Telecommand Standards accommodate the requirements of a great variety of scientific space missions, thus providing a standard basis for cost-effective and technically compatible developments of on-board and on-ground data handling systems for a wide range of projects. This paper describes the design and the implementation of a de

J. B. Stephen, L. Foschini

The INTEGRAL satellite is an observatory-class gamma-ray telescope due for launch in early 2002. It comprises two main instruments, one optimised for imaging (IBIS) and the other for spectroscopy (SPI). The PICsIT telescope is the high energy (150 keV - 10 MeV) plane of the IBIS imager and consists of 8 individual modules of 512 detection elements. The modul

Frank Krennrich

The field of TeV gamma-ray astronomy is reviewed with emphasis on its relation to the origin of cosmic rays. The discovery of TeV photons from supernova remnants and active galaxies has provided the first direct observational link between specific astrophysical objects and particle production at the TeV scale. TeV gamma-ray observations constrain the high en

Thomas Matheson, Alexei V. Filippenko, Weidong Li, Douglas C. Leonard

We present 84 spectra of Type Ib/c and Type IIb supernovae (SNe), describing the individual SNe in detail. The relative depths of the helium absorption lines in the spectra of the SNe Ib appear to provide a measurement of the temporal evolution of the SN, with He I 5876 and He I 7065 growing in strength relative to He I 6678 over time. Light curves for three

K. J. Borkowski, J. P. Harrington

Spectroscopic observations of a proto-planetary nebula He 3-1475 with the Space Telescope Imaging Spectrograph (STIS) reveal the kinematics of its high (1200 km/s) velocity jets. The jets are formed at a large (0.15 pc) distance from its central star by collimation of an asymmetric stellar wind in a pair of conical shocks seen in Wide Field Planetary Camera

Eduardo Lima, Burt Ovrut, Jaemo Park, René Reinbacher

A formalism for calculating the open supermembrane contribution to the non-perturbative superpotential of moduli in heterotic M-theory is presented. This is explicitly applied to the Calabi-Yau (1,1)-moduli and the separation modulus of the end-of-the-world BPS three-branes, whose non-perturbative superpotential is computed. The role of gauge bundles on the

A. A. Aligia

In recent scanning tunneling microscopy experiments, confinement in an elliptical corral has been used to project the Kondo effect from one focus to the other one. I solve the Anderson model at arbitrary temperatures, for an impurity hybridized with eigenstates of an elliptical corral, each of which has a resonant level width delta. This width is crucial. If

T. P. Cheng, Ling-Fong Li

One way to detect the presence of new particles in theories beyond the standard model is through their contribution to electroweak loop effects. We comment on the importance of a consistent inclusion of their mixing angles to ensure that the physical requirement of heavy particle decoupling is fulfilled. We illustrate our points by a detailed discussion of t

Shantanu Basu, Chigurupati Murali

We discuss constraints on the rates of stirring and dissipation of MHD turbulence in molecular clouds. Recent MHD simulations suggest that turbulence in clouds decays rapidly, thus providing a significant source of energy input, particularly if driven at small scales by, for example, bipolar outflows. We quantify the heating rates by combining the linewidth-

Martin Makler, Takeshi Kodama, Mauricio O. Calvao

We present a comparative analysis of several methods, known as local Lagrangian approximations, which are aimed to the description of the nonlinear evolution of large-scale structure. We have investigated various aspects of these approximations, such as the evolution of a homogeneous ellipsoid, collapse time as a function of initial conditions, and asymptoti

Xuedong Hu, S. Das Sarma

In a quantum computer the hardware and software are intrinsically connected because the quantum Hamiltonian (or more precisely its time development) is the code that runs the computer. We demonstrate this subtle and crucial relationship by considering the example of electron-spin-based solid state quantum computer in semiconductor quantum dots. We show that

Lexie Davison, David Sherrington, Juan P. Garrahan, Arnaud Buhot

In this article we study a simple spin model which has a non-interacting Hamiltonian but constrained dynamics. The model, which is a simplification of a purely toplogical cellular model, displays glassy behaviour, involves activated processes and exhibits two-step relaxation. This is a consequence of the existence of annihilation-diffusion processes on two d

Reza Samadi, Marie-Jo Goupil, Yveline Lebreton

Acoustic power and oscillation amplitudes of radial oscillations computed for a solar model are compared with solar seismic observations. The oscillations are assumed stochastically excited by turbulence. The numerical computations are based upon a theoretical formulation of the power going into solar like oscillation modes as proposed by Samadi et al. (2000

Reza Samadi, Marie-Jo Goupil

Stochatic excitation of stellar oscillations by turbulent convection is investigated and an expression for the power injected into the oscillations by the turbulent convection of the outer layers is derived which takes into account excitation through turbulent Reynolds stresses and turbulent entropy fluctuations. This formulation generalizes results from pre

D. E. Jaffe, CLEO Collaboration

We have measured the charge asymmetry in like-sign dilepton yields from B^0 B^0-bar meson decays using the CLEO detector at the Cornell Electron Storage Ring. We find a_ll = [N(l+l+) - N(l-l-)]/[N(l+l+) + N[l-l-)] = +0.013 +/- 0.050 +/- 0.005 . We combine this result with a previous, independent measurement and obtain Re(epsilon_B)/(1+|epsilon_B|^2) = +0.003

Y. Sidis, C. Ulrich, P. Bourges, C. Bernhard

Commensurate antiferromagnetic ordering has been observed in the superconducting high-$Tc$ cuprate ${\rm YBa_{2}Cu_{3}O_{6.5}}$ (${\rm T_{c}}$=55 K) by polarized and unpolarized elastic neutron scattering. The magnetic peak intensity exhibits a marked enhancement at $T_{c}$. Zero-field $μ$SR experiments demonstrate that the staggered magnetization is not tru

G. W. Carter, E. V. Shuryak

We consider the $N_c\to\infty$ limit of QCD using a toy model in which instantons exchange color-singlet scalar fields which do not self-interact. Our main observation is that collective attraction leads the formation of large clusters containing $O(N_c)$ nonperturbative objects. We further show that this clustering of instantons is limited due to a non-triv

Roya Mohayaee, Attilio L. Stella, Carlo Vanderzande

The minimal energy variations of a directed polymer with tilted columnar disorder in two dimensions are shown numerically to obey a multiscaling at short distances which crosses over to global simple scaling at large distances. The scenario is analogous to that of structure functions in bifractal Burgers&#39; turbulence. Some scaling properties are predicted

L. Biferale, M. Cencini, A. Lanotte, D. Vergni

The problem of inverse statistics (statistics of distances for which the signal fluctuations are larger than a certain threshold) in differentiable signals with power law spectrum, $E(k) \sim k^{-α}$, $3 \le α< 5$, is discussed. We show that for these signals, with random phases, exit-distance moments follow a bi-fractal distribution. We also investigate two

D. Bagrets, A. Bagrets, A. Vedyayev, B. Dieny

We propose the two-band s-d model to describe theoretically a diffuse regime of the spin-dependent electron transport in magnetic tunnel junctions (MTJ&#39;s) of the form F/O/F where F&#39;s are 3d transition metal ferromagnetic layers and O is the insulating spacer. We aim to explain the strong interface sensitivity of the tunneling properties of MTJ&#39;s

C. Vogt

We derive an explicit and model-independent representation for the skewed quark distribution of the pion in the limit of large momentum transfer. Our result is expressed in terms of the conventional pion distribution amplitudes and complies with known properties of skewed parton distributions such as symmetry and polynomiality conditions. The continuity of t

M. Hassaïne, P. A. Horváthy

The relativistic generalization of the Chaplygin gas, put forward by Jackiw and Polychronakos, is derived in Duval&#39;s Kaluza-Klein framework, using a universal quadratic Lagrangian. Our framework yields a simplified proof of the field-dependent Poincaré symmetry Our action is related to the usual Nambu-Goto action [world volume] of $d$-branes in the same

P. Facchi, S. Pascazio, A. Scardicchio, L. S. Schulman

The dynamics of a quantum system undergoing frequent measurements (quantum Zeno effect) is investigated. Using asymptotic analysis, the system is found to evolve unitarily in a proper subspace of the total Hilbert space. For spatial projections, the generator of the &#34;Zeno dynamics&#34; is the Hamiltonian with Dirichlet boundary conditions.

Hyunchul Nha, Kyungwon An

We investigate the fluorescence spectrum of a two-level atom in a cavity when the atom is driven by a classical field. We show that forbidden dipole transitions in the Jaynes-Cummings Ladder structure are induced in the presence of the cavity damping, which deteriorates the degree of otherwise perfect destructive interference among the transition channels. W