July 2000 arXiv papers — page 14

E791 Collaboration

From a sample of $1172 \pm 61$ $D^+ \to π^- π^+ π^+$ decay, we find $Γ(D^+ \to π^- π^+ π^+) / Γ(D^+ \to K^- π^+ π^+) = 0.0311 \pm 0.0018 ^{+0.0016}_{-0.0026}$. Using a coherent amplitude analysis to fit the Dalitz plot of this decays, we find strong evidence that a scalar resonance of mass $478^{+24}_{-23} \pm 17$ MeV/$c^2$ and width $324^{+42}_{-40} \pm 21$

E791 Collaboration

From a sample of 848 $\pm$ 44 $D_s^+ \to π^- π^+ π^+$ decays, we find $Γ(D_s^+ \to π^- π^+ π^+) / Γ(D_s^+ \to ϕπ^+) = 0.245 \pm 0.028^{+0.019}_{-0.012} $. Using a Dalitz plot analysis of this three body decay, we find significant contributions from the channels $ρ^0(770)π^+$, $ρ^0(1450)π^+$, $f_0(980)π^+$, $f_2(1270)π^+$, and $f_0(1370)π^+$. We present also

Z. Fodor, S. D. Katz

The clustering of ultra high energy (above 10^20 eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. Statistical analysis of Dubovsky et al. (Phys. Rev. Lett. 85 (2000) 1154) estimated the source density. We extend their analysis to give also the confidence intervals for the number of sources using a.) no assumptions on the relati

Peter Grassberger

We argue that the mean crossing number of a random polymer configuration is simply a measure of opacity, without being closely related to entanglement as claimed by several authors. We present an easy way of estimating its asymptotic behaviour numerically. These estimates agree for random walks (theta polymers), self-avoiding walks, and for compact globules

S. Klose, B. Stecklum, N. Masetti, E. Pian

We report near-infrared and optical follow-up observations of the afterglow of the Gamma-Ray Burst 000418 starting 2.5 days after the occurrence of the burst and extending over nearly seven weeks. GRB 000418 represents the second case for which the afterglow was initially identified by observations in the near-infrared. During the first 10 days its R-band af

F. Anselmo, J. Ellis, D. V. Nanopoulos, G. Volkov

We present results from an inductive algebraic approach to the systematic construction and classification of the `lowest-level' CY3 spaces defined as zeroes of polynomial loci associated with reflexive polyhedra, derived from suitable vectors in complex projective spaces. These CY3 spaces may be sorted into `chains' obtained by combining lower-dimens

K. C. Bowler, L. Del Debbio, J. M. Flynn, G. N. Lacagnina

The decay constants of B, D and K mesons are computed in quenched lattice QCD at two different values of the coupling. The action and operators are O(a) improved with non-perturbative coefficients. The results are f_B=195(6)(+24/-23) MeV, f_D=206(4)(+17/-10) MeV, f_B_s=220(6)(+23/-28) MeV, f_D_s=229(3)(+23/-12) MeV and f_K= 150(3)(+12/-8) MeV. Systematic err

A. Bartl, W. Porod, D. Restrepo, J. Romao

We discuss the phenomenology of the lightest neutralino in models where an effective bilinear term in the superpotential parametrizes the explicit breaking of R-parity. We consider supergravity scenarios where the lightest supersymmetric particle (LSP) is the lightest neutralino and which can be explored at LEP2. We present a detailed study of the LSP decay

Donam Youm

We construct a q-deformed version of the conformal quantum mechanics model of de Alfaro, Fubini and Furlan for which the deformation parameter is complex and the unitary time evolution of the system is preserved. We also study differential calculus on the q-deformed quantum phase space associated with such system.

A. Acin, E. Jane, W. Dur, G. Vidal

We present the optimal local protocol to distill a Greenberger-Horne-Zeilinger (GHZ) state from a single copy of any pure state of three qubits.

C. Giunti, M. C. Gonzalez-Garcia, C. Pena-Garay

We perform a fit of solar neutrino data in the framework of the two four-neutrino schemes that are compatible with the results of all neutrino oscillation experiments. These schemes allow simultaneous transitions of solar nu_e's into active nu_mu's, nu_tau's and sterile nu_s. The data imply that the SMA solution is valid for any combination of nu

T. -D. Albert, K. Ruhlig

Employing a change of basis, the so-called factorizing Drinfel'd twist, we construct polarization-free and completely symmetric creation operators for a face type model equivalent to the Belavin model. A resolution of the nested structure of the Bethevectors is achieved.

Alex Kleiner, Sebastian Eggert

Primary metallic, or small gap semiconducting nanotubes, are tubes with band gaps that arise solely from breaking the bond symmetry due to the curvature. We derive an analytic expression for these gaps by considering how a general symmetry breaking opens a gap in nanotubes with a well defined chiral wrapping vector. This approach provides a straightforward w

O. Újsághy, G. Zaránd, A. Zawadowski

The Kondo effect may develop in those cases where there are non-commuting operators describing the interaction between the conduction electrons and impurities or defects with internal degrees of freedom. This interaction may involve spin or orbital variables. There are cases where the conduction electrons have conserved quantum numbers that do not appear in

Alok Kumar, Aalok Misra

We apply the string-triality\cite{duffetal} to argue the existence of the string-networks of solitonic T and U-strings in the heterotic theory on T^6, S and T-strings in IIB on K3 x T^2 and, S and U-strings in IIA on K3 x T^2. We then show the existence of the above heterotic string networks by analyzing the supersymmetry property of the supergravity solutio

Congjun Wu, Tao Xiang, Zhao-Bin Su

The c-axis tunneling matrix of high-Tc superconductors is shown to depend strongly on the in-plane momentum of electrons and vanish along the four nodal lines of the d(x^2-y^2)-wave energy gap. This anisotropic tunneling matrix suppresses completely the contribution of the most extended quasiparticles in the vortex core to the c-axis tunneling current and le

D. J. Broadhurst, A. L. Kataev, C. J. Maxwell

The single renormalon-chain contribution to the correlator of scalar currents in QCD is calculated in the $\bar{MS}$-scheme in the limit of a large $N_f$. We find that in the factorial growth of the coefficients due to renormalons takes over almost immediatelly in the euclidean region. The essential differences between the large-order growth of coefficients

M. Cvetic, H. Lu, C. N. Pope

We obtain new consistent Kaluza-Klein embeddings of the gauged supergravities with half of maximal supersymmetry in dimensions D=7, 6, 5 and 4. They take the form of warped embeddings in type IIA, type IIB, M-theory and type IIB respectively, and are obtained by performing Kaluza-Klein circle reductions or T-duality transformations on Hopf fibres in S^3 subm

L. Angelani, R. Di Leonardo, G. Ruocco, A. Scala

We numerically investigate the supercooled dynamics of two simple model liquids exploiting the partition of the multi-dimension configuration space in basins of attraction of the stationary points (inherent saddles) of the potential energy surface. We find that the inherent saddles order and potential energy are well defined functions of the temperature T. M

D. R. Lamm, S. R. Valluri, U. D. Jentschura, E. J. Weniger

Complete results were obtained by us in [Can. J. Phys. 71, 389 (1993)] for convergent series representations of both the real and the imaginary part of the QED effective action; these derivations were based on correct intermediate steps. In this comment, we argue that the physical significance of the "logarithmic correction term" found by Cho and Pak

Dongsu Bak, Kimyeong Lee

We discuss the characteristic properties of noncommutative solitons moving with constant velocity. As noncommutativity breaks the Lorentz symmetry, the shape of moving solitons is affected not just by the Lorentz contraction along the velocity direction, but also sometimes by additional `elongation' transverse to the velocity direction. We explore this i

Rong-Gen Cai, Nobuyoshi Ohta

We discuss the properties of the bound state (F1, D1, D3) in IIB supergravity in three different scaling limits and the $SL(2,{\bf Z})$ transformation of the resulting theories. In the simple decoupling limit with finite electric and magnetic components of NS $B$ field, the worldvolume theory is the ${\cal N}$=4 super Yang-Mills (SYM) and the supergravity du

Amitava Datta, Anirban Kundu, Abhijit Samanta

Motivated by the possibilities of $b-τ$ or $t-b-τ$ Yukawa unification in the supersymmetric Grand Unified Theories, we consider the dangerous directions of the supersymmetric potential for large values of $\tanβ(\geq 30)$, in two versions of the minimal supergravity model with and without common soft breaking scalar masses at the GUT scale, where the potenti

Iwan Jensen

We have developed an improved algorithm that allows us to enumerate the number of site animals on the square lattice up to size 46. We also calculate the number of lattice trees up to size 44 and the radius of gyration of both lattice animals and trees up to size 42. Analysis of the resulting series yields an improved estimate, $λ= 4.062570(8)$, for the grow

Diederik Aerts, Sven Aerts, Jan Broekaert, Liane Gabora

We show that Bell inequalities can be violated in the macroscopic world. The macroworld violation is illustrated using an example involving connected vessels of water. We show that whether the violation of inequalities occurs in the microworld or in the macroworld, it is the identification of nonidentical events that plays a crucial role. Specifically, we pr

John M. Myers, A. F. Fahmy, S. J. Glaser, R. Marx

We offer an improved method for using a nuclear-magnetic-resonance quantum computer (NMRQC) to solve the Deutsch-Jozsa problem. Two known obstacles to the application of the NMRQC are exponential diminishment of density-matrix elements with the number of bits, threatening weak signal levels, and the high cost of preparing a suitable starting state. A third o

Diederik Aerts, Ellie D'Hondt, Liane Gabora

The quantum logical `or' is analyzed from a physical perspective. We show that it is the existence of EPR-like correlation states for the quantum mechanical entity under consideration that make it nonequivalent to the classical situation. Specifically, the presence of potentiality in these correlation states gives rise to the quantum deviation from the c

Martin Markl, Steve Shnider

Coherence phenomena appear in two different situations. In the context of category theory the term `coherence constraints' refers to a set of diagrams whose commutativity implies the commutativity of a larger class of diagrams. In the context of algebra coherence constrains are a minimal set of generators for the second syzygy, that is, a set of equation

D. Bear, R. E. Stoner, R. L. Walsworth, V. Alan Kostelecky

A search for sidereal variations in the frequency difference between co-located 129-Xe and 3-He Zeeman masers sets the most stringent limit to date on leading-order Lorentz and CPT violation involving the neutron, consistent with no effect at the level of 10^{-31} GeV.

B. P. Anderson, M. A. Kasevich

Low intensity white light was used to increase the loading rate of $^{87}$Rb atoms into a vapor cell magneto-optic trap by inducing non-thermal desorption of Rb atoms from the stainless steel walls of the vapor cell. An increased Rb partial pressure reached a new equilibrium value in less than 10 seconds after switching on the broadband light source. After t

G. Van Hooydonk

A comment on a recent paper by P. Froelich et. al., Phys. Rev. Lett., 84, 4577 (2000) on hydrogen-antihydrogen collisions and on matter-antimatter reactions in general. The center of mass of a stable HHbar system has prochiral character. It is not necessary to look for large scale anti-matter domains at distances Mpc away or at the cosmological horizon.

A. G. Khachatryan

The diffraction broadening of the intense laser radiation restricts its efficient use in many applications. Proposed in the present work is a method for laser radiation guiding in a density channel formed in plasma by a relativistic electron beam. The conditions and parameters of the relativistic beam ensuring the guiding by means of the proposed method have

A. Lovell, K. Amos

Fixed energy inverse scattering theory has been used to define central and spin-orbit Schrödinger potentials for the scattering of 5 eV polarized electrons from Xe atoms. The results are typical for a range of such data; including energies above threshold when the potentials become complex. The phase shifts obtained from an analysis of the measured different

M. Ferrario, P. R. Bolton, J. E. Clendenin, D. H. Dowell

We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that lead to the discovery of a new effective working point for a split RF photoinjector. We consider the emittance compensation regime of a space charge beam: by increasing the solenoid strength, the emittance evolution shows a double minimum beh

A. Bulgac, E. M. Henley, G. A. Miller, M. J. Savage

This document is a summary of the physics research carried out by the Nuclear Theory Group at the University of Washington during the last twelve-month period, 1999-2000.

D. Zschiesche, L. Gerland, S. Schramm, J. Schaffner-Bielich

Compelling evidence for a new form of matter has been claimed to be formed in Pb+Pb collisions at SPS. We critically review two suggested signatures for this new state of matter: First the suppression of the J/$Ψ$, which should be strongly suppressed in the QGP by two different mechanisms, the color-screening and the QCD-photoeffect. Secondly the measured pa

A. W. Thomas

We briefly review the status of our understanding of hadron structure based on QCD. This includes the role of symmetries, especially chiral symmetry, and the insights provided by lattice QCD. The main focus is on baryon structure and especially the nucleon, but this cannot be treated realistically without reference to spectroscopy. Our aim is to highlight re

A. Lovell, K. Amos

A Newton-Sabatier fixed energy inversion scheme has been used to equate inherently non-local p-${}^{12}$C potentials at a variety of energies to pion threshold, with exactly phase equivalent local ones. Those energy dependent local potentials then have been recast in the form of non-local Frahn-Lemmer interactions.

Rashmi Raniwala, Sudhir Raniwala, Yogendra Pathak Viyogi

A method is suggested to deduce the anisotropy in neutral pions by measuring the azimuthal anisotropy of photons in ultra-relativistic nuclear collisions. The ratio of the estimated anisotropy in photons to the anisotropy in neutral pions is seen to scale with a parameter which depends on photon multiplicity and anisotropy. This parameter can be determined f

S. A. Denisov

Discovered by M.G.Krein analogy between polinomials orthogonal on the unit circle and generalized eigenfunctions of certain differential systems is used to obtain some new results in the spectral analysis of Sturm-Liouville operators. Some properties of Dirac-type differential systems are studied.

Robert Schrader

This article provides sufficient conditions for positive maps on the Schatten classes $\mathcal J_{p}, 1\le p<\infty$ of bounded operators on a separable Hilbert space such that a corresponding Perron-Frobenius theorem holds. With applications in quantum information theory in mind sufficient conditions are given for a trace preserving, positive map on $\math

Omar Mustafa, Maen Odeh

The energy levels of neutral atoms supported by Yukawa potential, $V(r)=-Z exp(-αr)/r$, are studied, using both dimensional and dimensionless quantities, via a new analytical methodical proposal (devised to solve for nonexactly solvable Schrodinger equation). Using dimensionless quantities, by scaling the radial Hamiltonian through $y=Zr$ and $α^{&#39;}=α/Z$

Bryan Clair, Shahriar Mokhtari-Sharghi

The $L^2$-zeta function of an infinite graph Y (defined previously in a ball around zero) has an analytic extension. For a tower of finite graphs covered by Y, the normalized zeta functions of the finite graphs converge to the $L^2$-zeta function of Y.

Ilya Kofman, Yongwu Rong

We find approximations by Vassiliev invariants for the coefficients of the Jones polynomial and all specializations of the HOMFLY and Kauffman polynomials. Consequently, we obtain approximations of some other link invariants arising from the homology of branched covers of links.

H. G. Kaper, H. Nordborg

The Ginzburg--Landau (GL) equations of superconductivity provide a computational model for the study of magnetic flux vortices in type-II superconductors. In this article we show through numerical examples and rigorous mathematical analysis that the GL model reduces to the frozen-field model when the charge of the Cooper pairs (the superconducting charge car

Barbara L. Osofsky

We show that, for a free abelian group $G$ and prime power $p^ν$, every direct sum decomposition of the group $G/p^νG$ lifts to a direct sum decomposition of $G$. This is the key result we use to show that, if $R$ is a commutative von Neumann regular ring, and $\mathcal{E}$ a set of idempotents in $R$, then the projective dimension of the ideal $\mathcal{E}

David R. Morrison

The geometric aspects of mirror symmetry are reviewed, with an eye towards future developments. Given a mirror pair (X,Y) of Calabi-Yau threefolds, the best-understood mirror statements relate certain small corners of the moduli spaces of X and of Y. We will indicate how one might go beyond such statements, and relate the moduli spaces more globally. In fact

Charles Livingston

For n >1, if the Seifert form of a knotted 2n-1 sphere K in S^{2n+1} has a metabolizer, then the knot is slice. Casson and Gordon proved that this is false in dimension three (n = 1). However, in the three dimensional case it is true that if the metabolizer has a basis represented by a strongly slice link then K is slice. The question has been asked as to wh

Peter A. Linnell

There has been interest recently concerning when a left ordered group is locally indicable. Bergman and Tararin have shown that not all left ordered groups are locally indicable, but all known examples contain a nonabelian free subgroup. We shall show for a large class of groups not containing a nonabelian free subgroup, that any left ordered group in this c

Tom H. Koornwinder, Nabila Touhami

This mainly tutorial paper is intended as a somewhat larger example for parts of the theory exposed in the Lectures on the dynamical Yang-Baxter equations by P. Etingof and O. Schiffmann, math.QA/9908064. We explicitly compute the matrix entries of the intertwining operator, fusion matrix and exchange matrix associated to sl(2,R) for q=1. We also consider th

T. Krasinski

Let X,Y be algebraic curves in P^n over C. We give an effective description of the join J(X,Y)\in P^n of X and Y in terms of local parametrizations of X and Y.

Jose Maria Ancochea-Bermudez, Otto Rutwig Campoamor-Stursberg

We construct large families of characteristically nilpotent Lie algebras by considering deformations of the Lie algebra g_{m,m-1}^{4} of type Q_{n},and which arises as a central extension fo the filiform Lie algebra L_{n}. By studying the graded cohomology spaces we obtain that the sill algebras are isomorphic to the nilradicals of solvable, complete Lie alg

Eckart Viehweg, Kang Zuo

Let Y be a projective non-singular curve of genus g, X a projective manifold, both defined over the field of complex numbers, and let f:X ---> Y be a surjective morphism with general fibre F. If the Kodaira dimension of X is non-negative, and if Y is the projective line we show that f has at least 3 singular fibres. In general, for non-isotrivial morphisms f

John H. Schwarz

I had the privilege of collaborating with Joel Scherk on three separate occasions: in 1970 at Princeton, in 1974 at Caltech, and in 1978-79 at the Ecole Normale Superieure. In this talk I give some reminiscences of these collaborations.

M. Garcia Perez, A. Gonzalez-Arroyo, C. Pena

We develop a perturbative expansion which allows the construction of non-abelian self-dual SU(2) Yang-Mills field configurations on the four-dimensional torus with topological charge 1/2. The expansion is performed around the constant field strength abelian solutions found by &#39;t Hooft. Next to leading order calculations are compared with numerical result

Jan Govaerts

New solutions to the abelian U(1) Higgs model, corresponding to vortices of integer and half-integer winding number bound onto the edges of domain walls and possibly surrounded by annular current flows, are described, based on a fine-grained analysis of the topology of such configurations in spacetime. The existence of these states, which saturate BPS bounds

G. Vlasov

We investigate superfluidity of the relativistic fermi-gas with gravitational interaction. The excitation spectrum is obtained within the linearized theory. While superfluidity may take place at a definite ratio of the Fermi momentum, rest mass and coupling constant, the metric coefficients play predominant role forming the gap of excitation spectrum.

Christos Kokorelis

We discuss supersymmetry breaking mechanism at the level of low energy N=1 effective superstring actions that exhibit $SL(2,Z)_T$ target space modular duality or $SL(2,Z)_S$ strong-weak coupling duality. The allowed superpotential forms use the assumption that the sourse of non-perturbative effects is not specified and as a result represent the most general

Gregory Mahlon

The McLerran-Venugopalan model provides a framework which allows one to compute the gluon distribution function of a very large nucleus from the equations of QCD, provided that the longitudinal momentum fraction, xF, is sufficiently small. The source of color charge for this computation may be thought of as a crepe moving along the z axis at the speed of lig

M. V. Garzelli, C. Giunti

We calculate with Monte Carlo the goodness of fit and the confidence level of the standard allowed regions for the neutrino oscillation parameters obtained from the fit of solar neutrino data. We show that the values of the goodness of fit and of the confidence level of the allowed regions are significantly smaller than the standard ones. Using Neyman&#39;s

V. Uleshchenko, A. Szczurek, J. Speth

We discuss the role of some nonpartonic effects which lead to $N_p^{π^+} \ne N_n^{π^+}$ and $N_p^{π^-} \ne N_n^{π^-}$ and may therefore modify the conclusionon the $\bar d - \bar u$ asymmetry extracted from semi-inclusive production of pions in DIS. Quantitative estimations for resolved photon and exclusive $ρ^0$ are given as examples. The results are discus

M. A. Braun, F. del Moral, C. Pajares

It is shown that different ways of interacting strings formed in high energy nucleus-nucleus collisions cause a different strength of the chaoticity parameter lambda of Bose-Einstein correlations. In particular, in the case of percolation of strings, lambda shows a peculiar dependence on the string density, very similar to the dependence of the fractional av

K. Fialkowski, R. Wit

We analyse the entropy properties in the proton-proton 1800 GeV events from the PYTHIA/JETSET Monte Carlo generator following a recent proposal concerning the measurement of entropy in multiparticle systems. The dependence on the number of bins and on the size of the phase-space region is investigated. Our results may serve as a reference sample for experime

A. V. Kuznetsov, N. V. Mikheev

The amplitude of a Compton-like process nu_i gamma^* -> nu_j gamma^* with virtual photons is calculated in the standard GWS theory with lepton mixing. The contribution of this process to the high energy neutrino scattering on the nucleus with single photon radiation nu N -> nu N gamma is discussed. The bremsspectrum and the total cross-section are estimated

J. Kontros, K. Kontros, A. Lengyel

Two models for the Pomeron, supplemented by exchange degenerate sub-leading Regge trajectories, are fitted to the forward scattering data for a number of reactions. By considering new Pomeron models, we extend the recent results of the COMPAS group, being consistent with our predecessors.

Frithjof Karsch, Sven Stickan

We analyze the critical behaviour of the three-dimensional, three-state Potts model in the presence of an external ordering field. From a finite size scaling analysis on lattices of size up to 70**3 we determine the critical endpoint of the line of first order phase transitions as (b_c, h_c) =(0.54938(2), 0.000775(10)). We determine the relevant temperature

P. Baringer

The D0 preshower detector consists of scintillator strips with embedded wavelength-shifting fibers, and a readout using Visible Light Photon Counters. The response to minimum ionizing particles has been tested with cosmic ray muons. We report results on the gain calibration and light-yield distributions. The spatial resolution is investigated taking into acc

S. Henrot-Versillé, F. Le Diberder

We advocate the use of an optimal variable to demontrate CP violation. This variable, named the Kin variable, provides a means to visualize graphically CP violation, to pin point the most statistically powerful events, and to combine several channels and experiments. For the B0->J/PSiKs channel, its use leads to a straightforward measurement of sin(2beta).

D. Singh, G. Papini

Spin-1/2 particles can be used to study inertial and gravitational effects by means of interferometers, particle accelerators, and ultimately quantum systems. These studies require, in general, knowledge of the Hamiltonian and of the inertial and gravitational quantum phases. The procedure followed gives both in the low- and high-energy approximations. The l

S. Capozziello, A. Feoli, G. Lambiase, G. Papini

We study the problem of quantization of thin shells in a Weyl-Dirac theory by deriving a Wheeler-DeWitt equation from the dynamics. Solutions are found which have interpretations in both cosmology and particle physics.

Michael A. Frumkin, Rob F. Van der Wijngaart

We derive tight bounds on cache misses for evaluation of explicit stencil operators on structured grids. Our lower bound is based on the isoperimetrical property of the discrete octahedron. Our upper bound is based on good surface to volume ratio of a parallelepiped spanned by a reduced basis of the inter- ference lattice of a grid. Measurements show that ou

Suhail Ansari, Ron Kohavi, Llew Mason, Zijian Zheng

We show that the e-commerce domain can provide all the right ingredients for successful data mining and claim that it is a killer domain for data mining. We describe an integrated architecture, based on our expe-rience at Blue Martini Software, for supporting this integration. The architecture can dramatically reduce the pre-processing, cleaning, and data un

Robert Givan, David McAllester

We consider the concept of a local set of inference rules. A local rule set can be automatically transformed into a rule set for which bottom-up evaluation terminates in polynomial time. The local-rule-set transformation gives polynomial-time evaluation strategies for a large variety of rule sets that cannot be given terminating evaluation strategies by any

Slava V. Rotkin, Robert A. Suris

The energetics of transformation of a planar fragment of a graphite monolayer into a spherical cluster is studied. The path considered is that a flat cluster rolls up into a segment of a spherical shell. The energy landscape of the process is presented. A simple model, formerly invented for calculating the carbon nanocluster formation energy, is used to eval

T. Valla, M. Kralj, A. Siber, M. Milun

The temperature dependence of peak widths in high resolution angle-resolved photoelectron spectroscopy from quantum well states in ultra thin Ag films on V(100) has been used to determine the electron-phonon coupling constant, lambda, for films of thickness 1-8 layers. A strong oscillatory variation in coupling strength is observed as a function of film thic

Primoz Ziherl, Randall D. Kamien

We propose a physical mechanism to explain the crystal symmetries found in macromolecular and supramolecular micellar materials. We argue that the packing entropy of the hard micellar cores is frustrated by the entropic interaction of their brush-like coronas. The latter interaction is treated as a surface effect between neighboring Voronoi cells. The observ

C. D. Ling, J. E. Millburn, J. F. Mitchell, D. N. Argyriou J. Linton

The crystallographic and magnetic phase diagram of the n=2 layered manganite La2-2xSr1+2xMn2O7 in the region x=>0.5 has been studied using temperature dependent neutron powder diffraction. The magnetic phase diagram reveals a progression of ordered magnetic structures generally paralleling that of 3-D perovskites with similar electronic doping: A (0.5<=x<=0.

F. Ronning, C. Kim, K. M. Shen, N. P. Armitage

The photon energy dependence of angle-resolved photoemission data on Ca_2CuO_2Cl_2 is presented, and the role of the matrix element is investigated. It is shown that despite strong variations in the matrix element, the loss in intensity as one crosses the antiferromagnetic zone boundary is a robust feature of the Mott insulator. As expected for a two dimensi

George Kastrinakis

Comment on the view of P.W. Anderson on the cuprates, as expressed in the Feb. &#39;00 issue of Physics Today.

S. H. Chun, Y. Lyanda-Geller, M. B. Salamon, R. Suryanarayanan

We report here a detailed study of AC/DC magnetization and longitudinal/transverse transport properties of La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ single crystals below $T_{c}$ = 121 K. We find that the resistivity upturn below 40 K is related to the reentrant spin glass phase at the same temperature, accompanied by additional anomalous Hall effects. The carrier

Ll. Balcells, J. Navarro, M. Bibes, A. Roig

The role of the synthesis conditions on the cationic Fe/Mo ordering in Sr2FeMoO6 double perovskite is addressed. It is shown that this ordering can be controlled and varied systematically. The Fe/Mo ordering has a profound impact on the saturation magnetization of the material. Using the appropriate synthesis protocol a record value of 3.7muB/f.u. has been o

E. Burgos, E. Halac, Ruben Weht, H. Bonadeo

We have explored new possible phases of 3D C60-based fullerites using semiempirical potentials and ab-initio density functional methods. We have found three closely related structures - two body centered orthorhombic and one body centered cubic - having 52, 56 and 60 tetracoordinated atoms per molecule. These 3D polymers result in semiconductors with bulk mo

O. N. Zhuravlev, A. E. Muryshev, P. O. Fedichev

We discuss the dissipative dynamics of vortex arrays in trapped Bose-condensed gases and analyze the lifetime of the vortices as a function of trap anisotropy and the temperature. In particular, we distinguish the two regimes of the dissipative dynamics, depending on the relative strength of the mutual friction between the vortices and the thermal component,

Tsunehiko Araki, Makoto Tsubota

Recently the Kelvin wave cascade process in superfluid $^4$He at very low temperatures was discussed. In this mechanism, the dynamics of the waves on the vortex lines plays an important role. In order to investigate this mechanism, we study numerically the dynamics of the waves on the reconnected vortex lines using the full Biot-Savart law. This work shows t

Iwan Jensen, Anthony J Guttmann

We have developed an improved algorithm that allows us to enumerate the number of site animals (polyominoes) on the square lattice up to size 46. Analysis of the resulting series yields an improved estimate, $τ= 4.062570(8)$, for the growth constant of lattice animals and confirms to a very high degree of certainty that the generating function has a logarith

Zheng Weihong, J. Oitmaa

We use linked cluster series expansion methods to estimate the values of various short distance correlation functions in $S=1/2$ Heisenberg antiferromagnets at T=0, for dimension $d=1,2,3$. The method incorporates the possibility of spontaneous symmetry breaking, which is manifest in $d=2,3$. The results are important in providing a test for approximate theo

Shaun Hendy

We consider the stability of a system of equations which are a singular perturbation of the incompressible rigid-plastic flow equations used to model granular flow. A linear stability analysis shows that solutions of these equations are unstable, in general, and that these instabilities may lead to ill-posedness. However, the analysis suggests that these equ

T. Valla, A. V. Fedorov, P. D. Johnson, Q. Li

For optimally doped Bi 2212, scattering rates in the normal state are found to have a linear temperature dependence over most of the Fermi surface. In the immediate vicinity of the (1,0) point, the scattering rates are nearly constant in the normal state, consistent with models in which scattering at this point determines the c-axis transport. In the superco

Gaurav Dar, Mahendra K. Verma, V. Eswaran

In an earlier paper (physics/0006012) we had developed a method for computing the effective energy transfer between any two Fourier modes in fluid or magnetohydrodynamic (MHD) flows. This method is applied to a pseudo-spectral, direct numerical simulation (DNS) study of energy transfer in the quasi-steady state of 2-D MHD turbulence with large scale kinetic

S. Winitzki, J. H. P. Wu

A description of CMB temperature fluctuations beyond the power spectrum is important for verifying models of structure formation, especially in view of forthcoming high-resolution observations. We argue that higher-order statistics of inter-scale correlations, because of their low cosmic variance, may be effective in detecting non-Gaussian features in the CM

Andreas Reisenegger, H. Quintana, Eleazar R. Carrasco, Jerónimo Maze

We present the first application of a spherical collapse model to a supercluster of galaxies. Positions and redshifts of $\sim 3000$ galaxies in the Shapley Supercluster (SSC) are used to define velocity caustics that limit the gravitationally collapsing structure in its central part. This is found to extend at least to $8 h^{-1}$ Mpc of the central cluster,

H. Quintana, Eleazar R. Carrasco, Andreas Reisenegger

We report 2868 new multi-object spectroscopic measurements of galaxy redshifts in an area roughly 12°$\times$ 6°(right ascension $\times$ declination) centered on the Shapley Supercluster (SSC). These correspond to 2627 different galaxies. Including other measurements reported in the literature, the total number of galaxies with measured redshifts in a 19°$\

Pasquale Blasi

While several arguments can be proposed against the existence of particles with energy in excess of $(3-5)\times 10^{19}$ eV in the cosmic ray spectrum, these particles are actually observed and their origin seeks for an explanation. After a description of the problems encountered in explaining these ultra-high energy cosmic rays (UHECRs) in the context of a

Pasquale Blasi

Some clusters of galaxies have been identified as powerful sources of non-thermal radiation, from the radio to X-ray wavelengths. The classical models proposed for the explanation of this radiation usually require large energy densities in cosmic rays in the intracluster medium and magnetic fields much lower that those measured using the Faraday rotation. We

R. Gilli

We will briefly examine the following three issues related to the AGN synthesis models for X-ray background: 1) the possibility that absorbed AGNs evolve faster than unabsorbed ones; 2) the existence of the still debated population of luminous absorbed AGNs, the so-called QSO2s; 3) the behavior of the AGN density at a redshift above ~3.

William H. Lee

We present a hydrodynamical study of the final stages of inspiral in a black hole-neutron star (NS) binary. We use a Newtonian 3D SPH code, and model the NS with a stiff (index G=3 and G=2.5) polytropic equation of state and the black hole as a Newtonian point mass. Our initial conditions correspond to irrotational binaries in equilibrium (approximating the

Mark A. Fardal, Neal Katz, Jeffrey P. Gardner, Lars Hernquist

We examine the cooling radiation from forming galaxies in hydrodynamic simulations of the LCDM model (cold dark matter with a cosmological constant), focusing on the Ly-alpha line luminosities of high-redshift systems. Primordial composition gas condenses within dark matter potential wells, forming objects with masses and sizes comparable to the luminous reg

L. C. Garcia de Andrade

The gravitational stability of Friedmann metric with respect to homogeneous and isotropic perturbations in Einstein-Cartan cosmology is used together with the COBE data to place a limit on the spin-torsion primordial density fluctuation.Cosmological perturbations in Bianchi type III models are shown to have no contributions from torsion at the early stages o

B. G. Elmegreen, M. Kaufman, C. Struck, D. M. Elmegreen

Hubble Space Telescope images of the galaxies NGC 2207 and IC 2163 show star formation and dust structures in a system that has experienced a recent grazing encounter. Tidal forces from NGC 2207 compressed and elongated the disk of IC 2163, forming an oval ridge of star formation. Gas flowing away from this ridge has thin parallel dust filaments transverse t

Rachel Bean, Joao Magueijo

Quintessence scenarios provide a simple explanation for the observed acceleration of the Universe. Yet, explaining why acceleration did not start a long time ago remains a challenge. The idea that the transition from radiation to matter domination played a dynamical role in triggering acceleration has been put forward in various guises. We propose a simple d