June 1999 arXiv papers — page 23

Jin Chengjin, M. A. Garrett, S Nair, R. W. Porcas

We present 8 epochs of 7 mm dual-polarization VLBA observations of the gravitational lens system PKS 1830-211 made over the course of 14 weeks. Clear changes in the relative positions of the cores of up to $80 μ$arcseconds ($μ$as) were observed between epochs (each separated by $\approx 2$ weeks). A comparison with previous 7 mm VLBA maps shows that the sepa

Carlos Feinstein, F. Duccio Macchetto, Andre R. Martel, William B. Sparks

We present results of HST observations of the radio galaxy 3C 299. The broad-band F702W (R) and F555W (V) images (WFPC2/PC) show an elliptical galaxy, with a comet-like structure extending to the NE in the radio jet direction. The [OIII]$λ$5007 emission line map, shows a bi-conical structure centered on the nucleus, that overlaps the structure found in the b

A. Loinger

Only Levi-Civita's electromagnetic interpretation of the characteristic hypersurfaces of Einstein field equations is conceptually correct.

P. Bonifacio, M. Centurion, P. Molaro

High resolution spectra of 5 candidate metal-weak thick-disc stars suggested by Beers & Sommer-Larsen (1995) are analyzed to determine their chemical abundances. The low abundance of all the objects has been confirmed with metallicity reaching [Fe/H]=-2.9. However, for three objects, the astrometric data from the Hipparcos catalogue suggests they are true ha

N. Hayashida, K. Honda, N. Inoue, K. Kadota

Anisotropy in the arrival directions of cosmic rays around 10^{18}eV is studied using data from the Akeno 20 km^2 array and the Akeno Giant Air Shower Array (AGASA), using a total of about 216,000 showers observed over 15 years above 10^{17}eV. In the first harmonic analysis, we have found significant anisotropy of $\sim$ 4 % around 10^{18}eV, corresponding

The Utah Seven Telescope Array collaboration

We have developed the energy measurement method which based on stereoscopic observation with multiple telescopes for TeV gamma rays. Energy resolution obtained by this method was 23 %. The energy spectrum of the gamma-ray flares of Markarian 501 in 1997 was also obtained using this techniques. We have confirmed the bending or the cutoff of the energy spectru

The Utah Seven Telescope Array collaboration

We have investigated TeV gamma-ray emissions from nearby X-ray selected BL Lac objects using the Utah Seven Telescope Array for more than two years. These objects can be considered as potential sources of TeV gamma rays with inverse compton model. The gamma-ray flares from Mrk421 and Mrk501 found in these observation will be reported.

F. Caputo, M. Marconi, V. Ripepi

We discuss the metallicity effect on the theoretical visual and near-infrared PL and PLC relations of classical Cepheids, as based on nonlinear, nonlocal and time--dependent convective pulsating models at varying chemical composition. In view of the two usual methods of averaging (magnitude-weighted and intensity-weighted) observed magnitudes and colors over

George Chapline

In this paper we consider how to organize the sharing of information in a distributed network of sensors and data processors so as to provide explanations for sensor readings with minimal expenditure of energy. We point out that the Minimum Description Length principle provides an approach to information fusion that is more naturally suited to energy minimiz

Saharon Shelah

Part A: A revised version of the guide in "Cardinal Arithmetic" ([Sh:g]), with corrections and expanded to include later works. Part B: Corrections to [Sh:g]. Part C: Contains some revised proof and improved theorems. Part D: Contains a list of relevant references.

Daniel Boer, P. J. Mulders

We consider the color gauge invariance of a factorized description of the Drell-Yan process cross section. In particular, we focus on the next-to-leading twist contributions for polarized scattering and on the cross section differential in the transverse momentum of the lepton pair in the region where the transverse momentum is small compared to the hard sca

T. J. Turner, I. M. George, K. Nandra, D. Turcan

This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in the optical band introduces scatter into the established correlation between X-ray variability and nuclear luminosity. Consideration of the X-ray spectral index

Martin Gremm, Emanuel Katz

We construct three-dimensional N=1 QED with N_f flavors using branes of type IIB string theory. This theory has a mirror, which can be realized using the S-dual brane configuration. As in examples with more supersymmetry, the Higgs branch of the original theory gets mapped into the Coulomb branch of the mirror. We use parity invariance to argue that these br

Richard D. Ball, Stefano Forte

We extract the small x asymptotic behaviour of the Altarelli-Parisi splitting functions from their expansion in leading logarithms of 1/x. We show in particular that the nominally next-to-leading correction extracted from the Fadin-Lipatov kernel is enhanced asymptotically by an extra ln 1\x over the leading order. We discuss the origin of this problem, its

H. H. Asatryan, H. M. Asatrian

We study the inclusive rare decay $B\to X_d+γ$ in the supergravity inspired Minimal Supersymmetric Standard Model and compute the CP-asymmetry in the decay rates. We show that there exist two phenomenologically acceptable sets of SUSY parameters: for one set the CP-asymmetry has the same (positive) sign as in the Standard Model and lies in the range (5-45)%

E. Kiritsis

In these lecture notes duality tests and instanton effects in supersymmetric vacua of string theory are discussed. A broad overview of BPS-saturated terms in the effective actions is first given. Their role in testing the consistency of duality conjectures as well as discovering the rules of instanton calculus in string theory is discussed. The example of he

Emory F. Bunn, Douglas Scott

Large patterns could exist on the microwave sky as a result of various non-standard possibilities for the large-scale Universe -- rotation or shear, non-trivial topology, and single topological defects are specific examples. All-sky (or nearly all-sky) CMB data sets allow us, uniquely, to constrain such exotica, and it is therefore worthwhile to explore a wi

D. Rainwater, D. Zeppenfeld

Weak boson fusion promises to be a copious source of intermediate mass Standard Model Higgs bosons at the LHC. The additional very energetic forward jets in these events provide for powerful background suppression tools. We analyze the H -> W^(*)W^(*) -> e mu pTmiss decay mode for a Higgs boson mass in the 130-200 GeV range. A parton level analysis of the do

Kyungho Oh, Radu Tatar

We consider D3 branes at orbifolded conifold singularities which are not quotient singularities. We use toric geometry and gauged linear sigma model to study the moduli space of the gauge theories on the D3 branes. We find that topologically distinct phases are related by a flop transition. It is also shown that an orbifold singularity can occur in some phas

J. L. Feldman, D. J. Singh, I. I. Mazin, D. Mandrus

The great reduction in thermal conductivity of skutterudites upon filling the ``void'' sites with Rare Earth (RE) ions is key to their favorable thermoelectric properties but remains to be understood. Using lattice dynamic models based on first principles calculations, we address the most popular microscopic mechanism, reduction via rattling ions. Th

Giovanni Jona-Lasinio, Francesca Maria Marchetti

Using a sequence of Bogoliubov transformations, we obtain an exact expression for the vacuum state of a Dirac field in 2+1 dimensions in presence of a constant magnetic field. This expression reveals a peculiar two level pairing structure for any value of the mass m greater than zero. This calculation clarifies the nature of the condensate in the lowest Land

A. N. Vall, S. E. Korenblit, V. M. Leviant, D. V. Naumov

In a nonrelativistic contact four-fermion model we show that simple regularisation prescriptions together with a definite fine-tuning of the cut-off-parameter dependence of ``bare'' quantities give the exact solutions for the two-particle sector and Goldstone modes. Their correspondence with the self-adjoint extension into Pontryagin space is establi

Jian-Ge Zhou

The super 0-brane and GS superstring actions on AdS$_2 \times S^2$ background with 2-form flux are constructed by supercoset approach. We find the super 0-brane action contains two parameters which are interpreted as the electric and magnetic charges of the super 0-brane. The obtained super 0-brane action describes the BPS saturated dyonic superparticle movi

Hiroki Tsuchiura, Yukio Tanaka, Masao Ogata, Satoshi Kashiwaya

The superconducting state around a well isolated nonmagnetic impurity in the high-Tc superconductors is studied using the two-dimensional t-J model. The spatial dependence of the order parameter and the local density of states are obtained from the numerical diagonalization of the Bogoliubov-de Gennes equation derived using the Gutzwiller approximation. We f

Ch. Eslahchi, M. Ghebleh, H. Hajiabolhassan

In this paper uniquely list colorable graphs are studied. A graph G is called to be uniquely k-list colorable if it admits a k-list assignment from which G has a unique list coloring. The minimum k for which G is not uniquely k-list colorable is called the M-number of G. We show that every triangle-free uniquely vertex colorable graph with chromatic number k

Peter Brinkmann

McCammond and Wise have introduced the perimeter of 2-complexes, and they have used it to obtain a sufficient criterion for coherence. We present a new exposition of their main result, as well as some applications.

C. Savkli, J. Tjon, F. Gross

The Feynman-Schwinger representation provides a convenient framework for the cal culation of nonperturbative propagators. In this paper we first investigate an analytically solvable case, namely the scalar QED in 0+1 dimension. With this toy model we illustrate how the formalism works. The analytic result for the self energy is compared with the perturbative

Kenji Tomita

We study the distances and gravitational lensing in spherically symmetric inhomogeneous cosmological models consisting of inner and outer homogeneous regions which are connected by a single shell or double shells at the redshift $z_1 \sim 0.067$. The density and Hubble parameters in the inner region are assumed to be smaller and larger, respectively, than th

Hideo Hasegawa

Numerical investigations have been made of responses of a Hodgkin-Huxley (HH) neuron to spike-train inputs whose interspike interval (ISI) is modulated by deterministic, semi-deterministic (chaotic) and stochastic signals. As deterministic one, we adopt inputs with the time-independent ISI and with time-dependent ISI modulated by sinusoidal signal. The Rössl

N. Dorey

An exact superpotential is derived for the N=1 theories which arise as massive deformations of N=4 supersymmetric Yang-Mills (SYM) theory. The superpotential of the SU(N) theory formulated on R^{3}\times S^{1} is shown to coincide with the complexified potential of the N-body elliptic Calogero-Moser Hamiltonian. This superpotential reproduces the vacuum stru

Margarita A. Man'ko

Some properties of the fractional Fourier transform, which is used in information processing, are presented in connection with the tomography transform of optical signals. Relation of the Green function of the quantum harmonic oscillator to the fractional Fourier transform is elucidated.

J. Dittmann

It is the aim of this article to determine curvature quantities of an arbitrary Riemannian monotone metric on the space of positive matrices resp. nonsingular density matrices. Special interest is focused on the scalar curvature due to its expected quantum statistical meaning. The scalar curvature is explained in more detail for three examples, the Bures met

Yuri Ozhigov

Given a sequence $f_1 (x_1), f_2 (x_1, x_2), ..., f_k (x_1, ..., x_k)$ of Boolean functions, each of which $f_i$ takes the value 1 in a single point of the form $x_1^0, x_2^0, ..., x_i^0, i=1,2,..., k$. A length of all $x_i^0$ is $n, N=2^n$. It is shown how to find $x_k^0 (k\geq 2)$ using \frac{kπ\sqrt{N}}{4\sqrt{2}}$ simultaneous evaluations of functions of

Constantine Yannouleas, Uzi Landman

We show that electronic-entropy effects in the size-evolutionary patterns of relatively small (as small as 20 atoms), simple-metal clusters become prominent already at moderate temperatures. Detailed agreement between our finite-temperature-shell-correction-method calculations and experimental results is obtained for certain temperatures. This agreement incl

T. Levi-Civita

Foreword. While most textbooks of general relativity and research articles discuss at length the relative merits of the pseudo tensors proposed by Einstein and by other authors for representing the energy of the gravitational field, Levi Civita's definition of a true gravitational energy tensor has succumbed to the authority of Einstein and is nearly for

J. M. Richard

We review ideas and speculations concerning possible bound states or resonances of the nucleon--antinucleon system.

T. -S. Park, K. Kubodera, D. -P. Min, M. Rho

Previously, in an effective field theory formulated by us, we have carried out parameter-free calculations of a large number of low-energy two-nucleon properties. An experiment at the Institut Laue-Langevin is currently measuring spin-dependent effects in the polarized np capture process \vec{n}+\vec{p} -> d +γat threshold. Noting that spin-dependent observa

Alexander Kiselev, Yoram Last

Let H be a Schrödinger operator defined on an unbounded domain D in R^d with Dirichlet boundary conditions (D may equal R^d in particular). Let u(x,E) be a solution of the Schrödinger equation (H-E)u(x,E)=0, and let B_R denote a ball of radius R centered at zero. We show relations between the rate of growth of the L^2 norm \|u(x,E)\|_{L^2(B_R \cap D)} of suc

Ryszard Nest, Boris Tsygan

Recently Kontsevich solved the classification problem for deformation quantizations of all Poisson structures on a manifold. In this paper we study those Poisson structures for which the explicit methods of Fedosov can be applied, namely the Poisson structures coming from symplectic Lie algebroids, as well as holomorphic symplectic structures. For deformatio

Noam D. Elkies

We use theta series and modular forms to prove that Z^n is the only integral unimodular lattice of rank n without characteristic vectors of norm <n, i.e. the only integral unimodular lattice not containing a vector w such that (w,w)<n and 2|(v,v+w) for all lattice vectors v. By the work of Kronheimer and others on the Seiberg-Witten equation this yields an a

Saharon Shelah

The present note is an answer to complains of E.Weitz on [Sh:371]. We present a corrected version of a part of chapter VIII of &#34; Cardinal Arithmetic&#34;.

Neil J. Cornish, David N. Spergel

We present a simple algorithm for finding eigenmodes of the Laplacian for arbitrary compact hyperbolic 3-manifolds. We apply our algorithm to a sample of twelve manifolds and generate a list of the lowest eigenvalues. We also display a selection of eigenmodes taken from the Weeks space.

A. Montesinos-Amilibia, J. J. Nuno-Ballesteros

We introduce the self-linking number of a smooth closed curve in R^n with respect to a 3-dimensional vector bundle over the curve, provided that some regularity conditions are satisfied. When n=3, this construction gives the classical self-linking number of a closed embedded curve with non-vanishing curvature. We also look at some interesting particular case

Laurent Bonavero

With the help of Mori theory for projective toric manifolds due to M. Reid, we study non projective toric manifolds which become projective after a single blow up along an invariant curve.

Karl Michael Schmidt

We give a definition of integration by quadratures of first-order ordinary differential equations, and recover a little known result by Maximovic which states that a first-order ordinary differential equation can be integrated by quadratures only if it arises from the linear equation by a diffeomorphic transformation of the dependent variable. In the appendi

M. Ghebleh, R. Khoeilar

The concept of an H-cordial graph is introduced by I. Cahit in 1996 (Bulletin of the ICA). But that paper has some gaps and invalid statements. We try to prove the statements whose proofs in Cahit&#39;s paper have problems, and also we give counterexamples for the wrong statements. We prove necessary and sufficient conditions for H-cordiality of complete gra

M. Ghebleh, E. S. Mahmoodian

Let G be a graph with n vertices and suppose that for each vertex v in G, there exists a list of k colors L(v), such that there is a unique proper coloring for G from this collection of lists, then G is called a uniquely k-list colorable graph. Recently M. Mahdian and E.S. Mahmoodian characterized uniquely 2-list colorable graphs. Here we state some results

Denis V. Juriev

Kaleidoscope-roulettes, a proper class of perception games, is described. Kaleidoscope-roulette is defined as a perception and, hence, verbalizable interactive game, whose hidden dialogue consists of quasirandom sequences of ``words&#39;&#39;. The resonance phenomena in such games and their controlling are discussed.

Tetsuji Miwa, Yoshihiro Takeyama, Vitaly Tarasov

We construct the hypergeometric solutions for the quantized KZ equation with values in a tensor product of vector representations of $U_q(sl_n)$ at $|q|=1$ and give an explicit formula for the corresponding determinant in terms of the double sine function.

Meng Chen

This paper aims to improve a theorem of Janos Kollar. For a given Complex projective threefold X of general type, suppose the plurigenus p_k(X)\ge 2, Kollar proved that the (11k+5)-canonical map is birational. Here we show that either the (7k+3)-canonical map or the (7k+5)-canonical map is birational and that the m-canonical map is stably birational for m\ge

Vicente Muñoz

We determine the Fukaya Floer homology of the three-manifold which is the product of a Riemann surface of genus $g\geq 1$ times the circle. This sets up the groundwork for finding the structure of the Donaldson invariants of four-manifolds not of simple type in the future. We give the following applications: 1) We show that every four-manifold with $b^+>1$ i

Thomas Hoffman-Ostenhof, Peter W. Michor, Nikolai Nadirashvili

For a membrane in the plane the multiplicity of the $k$-th eigenvalue is known to be not greater than $2k-1$. Here we prove that it is actually not greater than $2k-3$, for $k\ge 3$.

P. W. Irwin, M. B. Paranjape

We study the behaviour of Wilson and &#39;t Hooft loop operators for the 2+1 dim. Abelian-Higgs model with Chern-Simons term. The phase of topological symmetry breaking where the vortex field condenses, found by Samuel for the model in the absence of the Chern-Simons term, persists in its presence. In this phase, the topological linking of instantons, which

M. Fleck, H. O. Girotti

The embedding procedure of Batalin, Fradkin, and Tyutin, which allows to convert a second-class system into first-class, is pushed beyond the formal level. We explicitly construct, in all cases, the variables of the converted first-class theory in terms of those of the corresponding second-class one. Moreover, we only conclude about the equivalence between t

Jean Alexandre, Janos Polonyi

It is shown in the framework of the N-component scalar model that the saddle point structure may generate non-trivial renormalization group flow. The spinodal phase separation can be described in this manner and a flat action is found as an exact result which is valid up to any order of the loop expansion. The correlation function is computed in a mean-field

J. A. E. Carrillo, J. A. S. Lima, A. Maia

The spectrum of massless bosonic and fermionic fluids satisfying the equation of state $p=(γ-1)ρ$ is derived using elementary statistical methods. As a limiting case, the Lorentz invariant spectrum of the vacuum ($γ=0, p=-ρ$) is deduced. These results are in agreement with our earlier derivation for bosons using thermodynamics and semiclassical consideration

Mark Strikman, Michail Zhalov

We outline major ideas involved in discussion of color coherence phenomena (CCP) at intermediate energies. We point out that the recent advances in calculating cross sections of hard exclusive processes off light nuclei allow to use the lightest nuclei for sensitive tests of CCP. Consistency of the results of the measurements of color transparency in quasiel

G. D&#39;Ambrosio, G. Miele, P. Migliozzi, P. Santorelli

A novel method for a direct measurement of the exclusive Lambda_c^+ branching ratios is here described. The approach is based on the peculiar topology of the quasi-elastic charm neutrino-induced events on nucleons. The intrinsic potentiality of the method is thoroughly discussed using a &#34;perfect detector&#34;. As an application, the statistical accuracy

Marco Radici

We investigate the properties of interference fragmentation functions arising from the emission of two leading hadrons inside the same jet for semi-inclusive lepton-nucleon deep-inelastic scattering. Using an extended spectator model we give numerical estimates for the example of the fragmentation into a proton-pion pair with its invariant mass on the Roper

D. Schildknecht

We give a brief overview on the present status of Generalized Vector Dominance as appplied to vector-meson production and the total photoabsorption cross section in the region of small x_{bj}. We comment on how GVD originates from QCD notions such as color transparency.

Ehab Malkawi, C. -P. Yuan

We investigate, in detail, a model in which the third family fermions are subjected to an SU(2) dynamics different from the first two families. Constrained by the precision Z-pole data, the heavy gauge boson mass is bounded from below to be about 1.7 TeV at the $2σ$ level. The flavor-changing neutral current (FCNC) in the lepton sector can be significant in

B. Buschbeck, F. Mandl

Results on two-particle angular correlations in jet cones and on multiplicity fluctuations in one- and two- dimensional angular intervals, delivered by three experiments (DELPHI, L3 and ZEUS, at $\sqrt{s}$ from few to 183 GeV) are compared to present existing analytical QCD calculations, using the LPHD hypothesis. Two different types of functions have been t

A. V. Gulov, V. V. Skalozub

The observables useful for the model independent search for signals of the abelian Z&#39; in the processes e^+ e^- \to {\bar f}f are introduced. They are based on the renormalization group relations between the Z&#39; couplings to the Standard Model particles developed recently and extend the variables suggested by Osland, Pankov and Paver. The bounds on the

Jifeng Yang

It is suggested that within the effective potential approach, convexity and spontaneous symmetry breaking(SSB) make the Higgs modes (elementary or effective) complicated in that the normal final states (experimentally identifiable) for Higgs modes could not be analytically defined. This observation might have some nontrivial consequences for the Standard Mod

L. Frankfurt, M. Strikman

The QCD factorization theorem for diffractive processes in DIS is used to derive formulae for the leading twist contribution to the nuclear shadowing of parton distributions in the low thickness limit. Based on the current analyzes of diffraction at HERA we find that the average strength of the interactions which govern diffraction in the gluon sector at $x

P. Zavada

The alternative to the standard formulation of the quark-parton model is proposed. Our relativistically covariant approach is based on the solution of the master equations relating the structure and distribution functions, which consistently takes into account the intrinsic quark motion - in contradistinction to the standard infinite momentum approach, in wh

Iain A. Bertram

The systematic uncertainties of the measurements of the Inclusive Jet Cross Section at the Tevatron and their effect on the chi^2 comparisons between data and theoretical predictions are discussed.

Alfredo Macías, José Socorro

We present the generalized Reissner-Nordström solution of the field equations of metric-affine gravity (MAG), endowed with electric and magnetic charges, as well as with gravito-electric and gravito-magnetic charges and a cosmological constant term. Moreover, the case $M=e_o$, i.e. mass equal to electric charge and $λ=0$, corresponds to an electrically and m

Jose F. Nieves, Palash B. Pal

When neutrinos travel through a normal matter medium, the electron neutrinos couple differently to gravity compared to the other neutrinos, due to the presence of electrons in the medium and the absence of the other charged leptons. The matter-induced gravitational couplings of the neutrinos under such conditions are calculated and their contribution to the

Enrico Montanari, Mirco Calura, Pierluigi Fortini

We have studied the main features of the gravitational radiation generated by an astrophysical system constituted of three compact objects attracting one another (only via gravitational interaction) in such a manner that stable orbits do exist. We have limited our analysis to systems that can be treated with perturbative methods. We show the profile of the g

Shahar Hod

The assimilation of a quantum (finite size) particle by a Reissner-Nordström black hole inevitably involves an increase in the black-hole surface area. It is shown that this increase can be minimized if one considers the capture of the lightest charged particle in nature. The unavoidable area increase is attributed to two physical reasons: the Heisenberg qua

Walter Daelemans, Sabine Buchholz, Jorn Veenstra

We present a memory-based learning (MBL) approach to shallow parsing in which POS tagging, chunking, and identification of syntactic relations are formulated as memory-based modules. The experiments reported in this paper show competitive results, the F-value for the Wall Street Journal (WSJ) treebank is: 93.8% for NP chunking, 94.7% for VP chunking, 77.1% f

Sabine Buchholz, Jorn Veenstra, Walter Daelemans

In this paper we discuss cascaded Memory-Based grammatical relations assignment. In the first stages of the cascade, we find chunks of several types (NP,VP,ADJP,ADVP,PP) and label them with their adverbial function (e.g. local, temporal). In the last stage, we assign grammatical relations to pairs of chunks. We studied the effect of adding several levels to

Melanie Siegel

Particles fullfill several distinct central roles in the Japanese language. They can mark arguments as well as adjuncts, can be functional or have semantic funtions. There is, however, no straightforward matching from particles to functions, as, e.g., GA can mark the subject, the object or an adjunct of a sentence. Particles can cooccur. Verbal arguments tha

John H. Reina, Neil F. Johnson

We propose a practical solid-state system capable of demonstrating quantum teleportation. The set-up exploits recent advances in the optical control of excitons in coupled quantum dots, in order to produce maximally-entangled Bell and Greenberger-Horne-Zeilinger (GHZ) states. Only two unitary transformations are then required: a quantum Controlled-Not gate a

M. Trippenbach, Y. B. Band, M. Edwards, M. Doery

We study the coherence properties of an atom laser, which operates by extracting atoms from a gaseous Bose-Einstein condensate via a two-photon Raman process, by analyzing a recent experiment. We obtain good agreement with the experimental data by solving the time-dependent Gross-Pitaevskii equation in three dimensions both numerically and with a Thomas-Ferm

Leon Balents

Carbon nanotubes provide a remarkably versatile system in which to explore the effects of Coulomb interactions in one dimension. The most dramatic effects of strong electron-electron repulsion are *orthogonality catastrophes*. These orthogonality catastrophes come in different varieties, and can be observed both in low-bias transport and tunneling measuremen

M. Vazquez-Prada, J. B. Gomez, Y. Moreno, A. F. Pacheco

The time to failure, $T$, of dynamical models of fracture for a hierarchical load-transfer geometry is studied. Using a probabilistic strategy and juxtaposing hierarchical structures of height $n$, we devise an exact method to compute $T$, for structures of height $n+1$. Bounding $T$, for large $n$, we are able to deduce that the time to failure tends to a n

Yu. A. Kuznetsov, E. G. Timoshenko

In this paper we complete the study of the phase diagram and conformational states of a stiff homopolymer. It is known that folding of a sufficiently stiff chain results in formation of a torus. We find that the phase diagram obtained from the Gaussian variational treatment actually contains not one, but several distinct toroidal states distinguished by the

Serge F. Mingaleev, Yuri B. Gaididei, Eva Majernikova, Serge Shpyrko

We consider Klein-Gordon models with a $δ$-correlated spatial disorder. We show that the properties of immobile kinks exhibit strong dependence on the assumptions as to their statistical distribution over the minima of the effective random potential. Namely, there exists a crossover from monotonically increasing (when a kink occupies the deepest potential we

V. Celebonovic

This is a short review of the physical ideas,algorithm for calculations and some results of a semiclassical theory of the behaviour of materials under high pressure,proposed by P.Savic and R.Kasanin.The theory has found applications from DAC experiments to studies of planetary interior structure.

Sudhakar Yarlagadda

Recently Wagner et al. [Phys. Rev. Lett. Vol. 81, P. 3980 (1998)] proposed that Mott&#39;s original model be modified to incorporate a hopping barrier which depends on the misorientation between the spins of electrons at the initial and the final states in an elementary process. They further claimed that using the model they can explain the observed scaling

Q. K. K. Liu, N. Moll, M. Scheffler, E. Pehlke

The equilibrium shapes and energies of coherent strained InP islands grown on GaP have been investigated with a hybrid approach that has been previously applied to InAs islands on GaAs. This combines calculations of the surface energies by density functional theory and the bulk deformation energies by continuum elasticity theory. The calculated equilibrium s

Yuri B. Gaididei, Peter L. Christiansen, Serge F. Mingaleev

Three types of nonlinear Schrodinger models with multiple length scales are considered. It is shown that the length-scale competition universally results into arising of new localized stationary states. Multistability phenomena with a controlled switching between stable states become possible.

D. E. Grupp, T. Zhang, G. J. Dolan, Ned S. Wingreen

We have observed anomalous transport properties for a 50 nm Bi dot in the Coulomb-blockade regime. Over a range of gate voltages, Coulomb blockade peaks are suppressed at low bias, and dramatic structure appears in the current at higher bias. We propose that the state of the dot is determined self-consistently with the state of a nearby two-level system (TLS

Ryuzo Azuma, Hajime Takayama

Diffusion properties of a self-avoiding polymer embedded in regularly distributed obstacles with spacing a=20 and confined in two dimensions is studied numerically using the extended bond fluctuation method which we have developed recently. We have observed for the first time to our knowledge, that the mean square displacement of a center monomer $ϕ_{M/2}(t)

Z. A. Xu, Y. Zhang, N. P. Ong

In underdoped YBa_2Cu_3O_x (YBCO) with x = 6.63, the opening of the pseudogap at T^* ~ 160 K has a strong effect on the Hall angle tan(theta). While the Hall response is significantly reduced, the diagonal current is relatively unaffected. The Hall conductivity suppression continues deep into the flux-flow state (from T_c to 40 K), as an anomalous suppressio

E. Ardonne, K. Schoutens

We present a new class of non-abelian spin-singlet quantum Hall states, generalizing Halperin&#39;s abelian spin-singlet states and the Read-Rezayi non-abelian quantum Hall states for spin-polarized electrons. We label the states by (k,M) with M odd (even) for fermionic (bosonic) states, and find a filling fraction $ν=2k/(2kM+3)$. The states with M=0 are bos

Piero Olla

The behavior of a non-spherical particle in a viscous, plane channel flow is studied by means of a combination of analytical technique and geometrical reasoning. An efficient implementation of Lamb&#39;s general solution is adopted, allowing rapid calculation, in the perturbative quasi-spherical regime, of forces and torques coming from the particle interact

M. S. Brotherton, Wil van Breugel, S. A. Stanford, R. J. Smith

We report the discovery of a spectacular ``post-starburst quasar&#39;&#39; UN J1025-0040 (B=19; z=0.634). The optical spectrum is a chimera, displaying the broad Mg II emission line and strong blue continuum characteristic of quasars, but is dominated in the red by a large Balmer jump and prominent high-order Balmer absorption lines indicative of a substanti

William H. Kinney, Pierre Sikivie

The late infall of dark matter onto a galaxy produces structure (such as caustics) in the distribution of dark matter in the halo. We argue that such structure is likely to occur generically on length scales proportional to $l \sim t_0 v_{rot}$, where $t_0$ is the age of the universe and $v_{rot}$ is the rotation velocity of the galaxy. A set of 32 extended

D. C. Backer, R. A. Sramek

Proper motions and radial velocities of luminous infrared stars in the galactic center have provided strong evidence for a dark mass of 2.5 million solar masses in the central 0.05 pc of the galaxy. The leading hypothesis for this mass is a black hole. High angular resolution measurements at radio wavelengths find a compact radio source, Sagittarius (Sgr) A*

David Merritt

The consequences of nuclear black holes for the structure and dynamics of stellar spheroids are reviewed. Slow growth of a black hole in a pre-existing core produces a steep power-law density profile similar to the cusps seen in faint elliptical galaxies. The weaker cusps in bright ellipticals may result from ejection of stars by a coalescing black-hole bina

Helio V. Fagundes, Evelise Gausmann

We present a modified version of the cosmic crystallography method, especially useful for testing closed models of negative spatial curvature. The images of clusters of galaxies in simulated catalogs are ``pulled back&#39;&#39; to the fundamental domain before the set of distances is calculated.

Ph. Podsiadlowski, S. Rappaport

The X-ray binary Cygnus X-2 (Cyg X-2) has recently been shown to contain a secondary that is much more luminous and hotter than is appropriate for a low-mass subgiant. We present detailed binary-evolution calculations which demonstrate that the present evolutionary state of Cyg X-2 can be understood if the secondary had an initial mass of around 3.5 M_sun an

J. -P. Tavernet

We report here observations of the active galactic nucleus Mrk 501, at energies above 250 GeV carried out with the CAT atmospheric imaging telescope from March 1997 to Autumn 1998. This source was in a high state of activity at several different wavelengths in 1997, and the observed flux at TeV energies has been seen to change by a factor of ~ 20 from from 1

A. Musquere

Since 1996, the CAT experiment, operating at the THEMIS site (French Pyrenees), has been collecting Very High Energy (VHE) gamma-ray data from the Crab. The temporal analysis of photon arrival times folded with the pulsar parameters did not reveal any significant pulsation. The upper limit of a steady pulsed flux over the 102.7 hours of observation is 1.5 10

G. Mohanty

We present here results from large zenith-angle observations with the CAT atmospheric Cherenkov imaging telescope, based on data taken on the Crab Nebula and on the blazar Mk501 from 1996 onwards. From Monte Carlo simulations, the threshold energy of the telescope is expected to vary from about 250 GeV at zenith to about 2 TeV at a zenith angle of 60 degrees

P. Goret, C. Gouiffes, E. Nuss, D. C. Ellison

The recent detection of a hard X-ray component in the supernova remnant Cassiopeia A is interpreted as synchrotron emission from electrons accelerated to energies up to 40 TeV (Allen et al., 1997). It is therefore tempting to consider TeV gamma-ray emission from this object through : i) bremsstrahlung and inverse Compton radiation from electrons and/or ii) p

Adrian Jenkins, C. S. Frenk, F. R. Pearce, P. A. Thomas

We have simulated the growth of structure in two 100 Mpc boxes for LCDM and SCDM universes. These N-body/SPH simulations include a gaseous component which is able to cool radiatively. A fraction of the gas cools into cold dense objects which we identify as galaxies. In this article we give a preliminary analysis of the clustering behaviour of these galaxies